WO2007083110A1 - High power short optical pulse source - Google Patents

High power short optical pulse source Download PDF

Info

Publication number
WO2007083110A1
WO2007083110A1 PCT/GB2007/000136 GB2007000136W WO2007083110A1 WO 2007083110 A1 WO2007083110 A1 WO 2007083110A1 GB 2007000136 W GB2007000136 W GB 2007000136W WO 2007083110 A1 WO2007083110 A1 WO 2007083110A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
high power
fibre
amplifier
pulse source
Prior art date
Application number
PCT/GB2007/000136
Other languages
French (fr)
Inventor
Anatoly Borisovich Grudinin
John Redvers Clowes
Ian Michael Godfrey
Kestutis Vysniauskas
Original Assignee
Fianium Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fianium Limited filed Critical Fianium Limited
Priority to JP2008550837A priority Critical patent/JP2009524232A/en
Priority to EP07700401.8A priority patent/EP1979997B1/en
Priority to US12/087,850 priority patent/US8379298B2/en
Publication of WO2007083110A1 publication Critical patent/WO2007083110A1/en
Priority to US13/523,723 priority patent/US8593726B2/en
Priority to US13/797,640 priority patent/US8902496B2/en
Priority to US13/797,665 priority patent/US8724215B2/en
Priority to US13/796,966 priority patent/US8767287B2/en
Priority to US14/556,746 priority patent/US9287677B2/en
Priority to US15/017,605 priority patent/US11038316B2/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/37—Non-linear optics for second-harmonic generation
    • G02F1/377—Non-linear optics for second-harmonic generation in an optical waveguide structure
    • G02F1/383—Non-linear optics for second-harmonic generation in an optical waveguide structure of the optical fibre type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H01S3/06758—Tandem amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2375—Hybrid lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S2301/00—Functional characteristics
    • H01S2301/03—Suppression of nonlinear conversion, e.g. specific design to suppress for example stimulated brillouin scattering [SBS], mainly in optical fibres in combination with multimode pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0064—Anti-reflection devices, e.g. optical isolaters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/0602—Crystal lasers or glass lasers
    • H01S3/061—Crystal lasers or glass lasers with elliptical or circular cross-section and elongated shape, e.g. rod
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06712—Polarising fibre; Polariser
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1618—Solid materials characterised by an active (lasing) ion rare earth ytterbium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA
    • H01S3/2316—Cascaded amplifiers

Definitions

  • the invention relates to a high power short optical pulse source.
  • the inspection tool In many applications such as semiconductor inspection, the inspection tool is just one of many instruments and machines used within the semiconductor manufacturing process, and space on the manufacturing floor - very often being in an expensive, clean-room environment - costs a premium. Therefore, reduction of the instrumentation footprint is highly beneficial.
  • the application environment can very often be noisy, dirty and a challenge to the operation of a laser source. In this application additional measures are often required to protect the laser and beam steering optics from the hostile working environment.
  • Fibre delivery of the laser beam is a clear and interesting option, enabling the laser source to be positioned remotely from the target space and enabling a compact optical beam delivery head (optical head) to be installed within the instrument, with the large laser source being positioned, along with any power supplies and cooling systems, outside an instrument and clean room environment.
  • fibre delivery involves launching of the laser output beam into an optical fibre. This is very difficult to achieve, especially in high-power laser applications. Most applications require a good beam quality of the laser, which requires a single mode fibre to deliver the beam. In reality, a single mode fibre has a core diameter of less than 15 ⁇ m, very often less than 10 ⁇ m, and efficient and stable launching of a beam into this aperture is difficult to achieve. Furthermore, in high-power applications, launching of such high intensities into a fibre will damage the fibre facet.
  • HCPCF's Hollow Core Photonic Crystal Fibres
  • HCPCF's have two benefits - they enable the propagation of UV radiation with relatively low loss and also reduced fibre nonlinearity by a factor of approximately 1000 in comparison to conventional glass-guided optical fibres.
  • Fibre lasers clearly have a significant advantage over conventional bulk lasers, since the optical beam is already within the fibre and no launching optics are required.
  • Most high-power fibre lasers particularly in the pulsed lasers, use a Master Oscillator Power Amplifier (MOPA) configuration, in which the output of a low-power fibre oscillator is amplified in a series of high-power fibre amplifiers.
  • MOPA Master Oscillator Power Amplifier
  • the output of a fibre laser or fibre amplifier can be delivered directly to the intended target through an output fibre.
  • Short optical pulses are generally defined (and defined herein) as pulses having a duration of less than 10ns (10 ⁇ 8 seconds). Reduction of fibre nonlinearity is a major challenge in any fibre-based system, particularly when short pulses are required at relatively high peak intensities.
  • HCPCF's reduce the nonlinearity by several orders of magnitude, where LMA fibres reduce the nonlinearity, scaling with the area of the core.
  • LMA fibres reduce the nonlinearity, scaling with the area of the core.
  • the use of LMA fibres for beam delivery in high-power pulsed applications is not a solution since even the largest single- mode core fibre (of 15-20 ⁇ m), results in significant nonlinear effects when high-peak power pulses are delivered.
  • CPA Chirped Pulse Amplification
  • One of the main problems with the CPA approach is that, in order to amplify pulses without significant nonlinear distortion, the pulse must be stretched to a duration of typically greater than 10ns. Therefore, to compress the stretched amplified pulse, a fairly long and complex compressor is required. Furthermore, in stretching and compressing the pulse, bulk optic components are typically required, preventing an all- fibre approach. This is difficult to make robust and involves significant loss which necessitates another stage of amplification in the MOPA. Furthermore, after amplification and fibre delivery, the compression stage also involves significant optical loss and, due to the relatively long pulse duration, the compressor itself is very large, meaning that the optical head itself has a large footprint. In general, the approach of CPA is not ideal and is also difficult to maintain in a compact, robust and lightweight form especially in a harsh operating environment.
  • a high power short optical pulse source comprising: an optical signal source operable to output short optical pulses; an optical pump light source provided at a first location; an optical head provided at a second location remote from the first location; high power optical fibre amplifier means having at least its optical output located within the optical head; an optical signal delivery fibre arranged to deliver optical pulses from the optical signal source to the high power optical fibre amplifier means; and a pump light delivery fibre arranged to deliver optical pump light to the high power optical fibre amplifier means, wherein short optical pulses of a first optical power are delivered to the high power optical fibre amplifier means and are amplified therein to a second, high optical power for output from the optical head.
  • the optical signal source preferably comprises a master oscillator optically coupled to an optical fibre preamplifier, comprising a preamplifier amplifier optical fibre and one or more preamplifier optical pump sources.
  • the preamplifier amplifier optical fibre preferably comprises a rare-earth doped optical fibre.
  • the optical signal source is preferably provided at the first location.
  • the master oscillator and the preamplifier amplifier optical fibre may be provided at a third location, intermediate the first and second locations, with the or each preamplifier optical pump source being provided at the first location and being coupled to the preamplifier amplifier optical fibre via a corresponding one or more preamplifier pump delivery fibres.
  • a plurality of optical pump light sources may be provided at the first location and a corresponding plurality of pump light delivery fibres.
  • the high power optical fibre amplifier means preferably comprises an amplifier optical fibre and one or more pump signal combiners.
  • the amplifier optical fibre preferably comprises a rare-earth doped optical fibre, and is most preferably of the same type of rare-earth doped optical fibre as the preamplifier amplifier optical fibre.
  • the high power short optical pulse source may comprise a plurality of high power optical fibre amplifier means optically coupled in series, at least the optical output of the final high power optical fibre amplifier means being located within the optical head.
  • the or each amplifier optical fibre is preferably located within the optical head.
  • the or each pump signal combiner may be located within the optical head.
  • the or each pump signal combiner may alternatively be located at the first location, with the high power optical fibre amplifier means additionally comprising a pump signal delivery fibre optically coupled between the or each pump signal combiner and the or each amplifier optical fibre.
  • the or each pump signal delivery fibre is preferably a double-clad optical fibre and is most preferably a polarisation maintaining optical fibre.
  • the amplifier optical fibre may be arranged to extend from the first location to the optical head.
  • the amplifier optical fibre preferably comprises a double-clad amplifier optical fibre.
  • the or a pump signal combiner may be provided at the first location, arranged to couple optical pulses and pump light into one end of the amplifier optical fibre.
  • the or a pump signal combiner may be provided within the optical head, arranged to couple pump light into the signal output end of the amplifier optical fibre.
  • the optical head preferably further comprises an optical isolator and optical collimator assembly optically coupled to the output of the high power optical fibre amplifier means.
  • the high power optical fibre amplifier means may further comprise a bulk optic amplifier element, most preferably a rod amplifier, optically coupled to the output end of the or the final amplifier optical fibre, said amplifier optical fibre being under-length such that a proportion of any pump light coupled into said amplifier optical fibre is unabsorbed by it, and serves to pump the bulk optic amplifier element.
  • the high power short optical pulse source may further comprise nonlinear optical frequency conversion means optically coupled to the output of the or the final high power optical fibre amplifier means.
  • the nonlinear optical frequency conversion means preferably comprises a nonlinear optical crystal.
  • the nonlinear optical frequency conversion means may comprise a plurality of nonlinear optical crystals arranged optically in series.
  • the nonlinear optical frequency conversion means may alternatively comprise a nonlinear optical fibre.
  • the high power short optical pulse source may alternatively or additionally comprise an optical pulse compressor optically coupled to the output of the or the final high power optical fibre amplifier means or the nonlinear optical frequency conversion means.
  • the optical pulse compressor may comprise a transmission grating pair or photonic crystal fibre having anomalous dispersion at the signal wavelength.
  • the high power short optical pulse source may further comprise a pulse picker operable to reduce the optical pulse frequency.
  • the pulse picker preferably comprises an optical gate, such as an acousto-optic modulator, driven at a synchronised gating frequency lower than the optical pulse frequency output from the optical signal source.
  • the high power short optical pulse source may further comprise optical monitoring means within the optical head.
  • the optical head may be movably mounted to enable accurate direction of generated high power short optical pulses onto a target or specimen under test.
  • the optical head is preferably mounted on a translation stage or a mechanical manipulator, such as a robotic arm.
  • Figure 1 is a schematic representation of a high power short optical pulse source according to a first embodiment of the invention
  • Figure 2 is a schematic representation of a high power short optical pulse source according to a second embodiment of the invention
  • Figure 3 is a schematic representation of a high power short optical pulse source according to a third embodiment of the invention
  • Figure 4 is a schematic representation of a high power short optical pulse source according to a fourth embodiment of the invention.
  • Figure 5 is a schematic representation of a high power short optical pulse source according to a fifth embodiment of the invention.
  • Figure 6 is a schematic representation of a high power short optical pulse source according to a sixth embodiment of the invention.
  • Figure 7 is a schematic representation of a high power short optical pulse source according to a seventh embodiment of the invention.
  • Figure 8 is a schematic representation of a high power short optical pulse source according to a eighth embodiment of the invention.
  • Figure 9 is a schematic representation of a high power short optical pulse source according to a ninth embodiment of the invention.
  • Figure 10 is a schematic representation of a high power short optical pulse source according to a tenth embodiment of the invention.
  • Figure 11 is a schematic representation of a high power short optical pulse source according to an eleventh embodiment of the invention.
  • a first embodiment of the invention provides a high power short optical pulse source 10 comprising an optical signal source in the form of a master oscillator 12 and an Ytterbium doped fibre amplifier (YDFA) preamplifier 14, a pump light source 16, an optical head 18, high power optical fibre amplifier means 20, an optical signal delivery fibre 22, a pump light delivery fibre 24, and a high power optical isolator 26.
  • YDFA Ytterbium doped fibre amplifier
  • the master oscillator 12 comprises a modelocked fibre oscillator operable to output 10ps pulses at a pulse frequency of 200MHz.
  • the preamplifier 14 amplifies the pulse average power to approximately 10OmW.
  • the master oscillator 12, preamplifier 14, and pump laser 16, together with their associated drive and control electronics, and cooling systems (not shown), are provided within a first enclosure 28 at a first location. Additional optical isolators 30, 32 are provided after the master oscillator 12 and the preamplifier 14 to protect them from back reflections.
  • the high power fibre amplifier means 20 comprises a im long single-mode, polarisation maintaining, large.mode area Ytterbium doped amplifier fibre and a pump signal combiner having a large mode area signal fibre.
  • the high power fibre amplifier means 20 and the high power optical isolator 26 are provided within the optical head 18, which is located at a second location, remote from the first location.
  • the short, relatively low power optical pulses output from the preamplifier 14 are delivered to the pump signal combiner of the high power fibre amplifier means 20 via the optical signal delivery fibre 22, which comprises a 5m long polarisation maintaining, single-mode optical fibre; the use of polarisation maintaining fibre prevents any environmental effects disturbing the signal.
  • the pump light source 16 comprises a fibre pig-tailed multi-emitter pump source operable to generate cw pump light at a wavelength of 915nm, and an optical power of between 20W and 4OW.
  • the pump light is delivered to the pump signal combiner of the high power optical fibre amplifier means 20 through the pump delivery fibre 24, which in this example is a 5m length of optical fibre having a 105 ⁇ m diameter core and a numerical aperture of 0.22.
  • the pump delivery fibre 24 is not sensitive to environmental effects but can, along with signal delivery fibre, be protected within an armoured jacket for industrial applications.
  • the high power optical fibre amplifier means 20 amplifies the received optical pulses to an average power of approximately 2OW, resulting in a pulse peak power of approximately 1OkW.
  • the overall low nonlinearity of the high power optical pulse source 10 ensures that spectral broadening of the optical pulses is minimised, and the pulses have a final spectral bandwidth of less than 0.5nm.
  • the optical head 18, containing the high power optical fibre amplifier means 20 and the isolator 26, has a small footprint and can be positioned at the intended target of the optical pulses.
  • the large, noisy elements of the high power short optical pulse source 10 are thereby provided away from the application site of the pulses, and only the smaller optical head need be located near the intended target.
  • FIG. 2 shows a high power short optical pulse source 40 according to a second embodiment of the invention.
  • the optical pulse source 40 of this embodiment is substantially the same as the optical pulse source 10 of the first embodiment, with the following modifications.
  • the same reference numbers are retained for corresponding features.
  • a second pump light source 42 is provided at the first location, within the first enclosure.
  • a second pump light delivery fibre 44 is also provided and delivers pump light from the second pump light source 42 to the pump signal combiner of the high power optical fibre amplifier means 20.
  • the high power optical fibre amplifier means 20 may alternatively comprise a two-stage amplifier having a series of two amplifier fibres and pump signal combiners, with an isolator provided between amplifier stages as necessary.
  • Each pump signal source 16, 42 would then pump a separate amplifier stage, the amplifier stages being cascaded to provide increasing signal with balanced gain throughout the cascade.
  • the high power optical fibre amplifier means 20 will only require a single amplifier fibre.
  • the number of amplifier fibres (and thus the number of pump light sources) will at least in part be determined by the power of the optical pulses output from the preamplifier 14, the length of signal delivery fibre 22, and the permitted amount of nonlinear effects as determined by the application of the high power short optical pulse source 10.
  • a high power short optical pulse source 50 according to a third embodiment of the invention is shown in Figure 3.
  • the pulse source 50 according to this embodiment is substantially the same as the pulse source 40 of the previous embodiment, with the following modifications.
  • the same reference numbers are retained for corresponding features.
  • the pump signal combiner 52 of the high power optical fibre amplifier means 20 is provided at the first location, within the first enclosure 28.
  • the pump delivery fibres 24, 44 and the signal delivery fibre 22 are also wholly contained within the first enclosure 28.
  • the high power optical fibre amplifier means 20 of this embodiment further comprises a pump signal delivery fibre 54, which comprises the output fibre of the pump signal combiner 52.
  • the pump signal delivery fibre 54 is a polarisation maintaining double clad optical fibre which has a signal-guiding core region and an inner cladding which guides the pump light from the pump sources 16, 42.
  • the pump signal delivery fibre 54 extends from the pump signal combiner 52, within the first enclosure 28, to the amplifier fibre 56, within the optical head 18.
  • the amplifier fibre 56 is therefore pumped in the co-propagating regime.
  • FIG. 4 shows a high power short optical pulse source 60 according to a fourth embodiment of the invention.
  • the pulse source 60 of this embodiment is substantially the same as the pulse source 50 of the previous embodiment, with the following modifications.
  • the amplifier fibre 62 comprises a polarisation maintaining double clad amplifier fibre and extends between the pump signal combiner 52 and the optical head 18.
  • the input end of the amplifier fibre 62 is coupled to the output of the pump signal combiner 52 and the output end of the amplifier fibre 62 is located in the optical head 18, where it is coupled to an optical isolator and collimating optics 64.
  • the amplifier fibre 62 therefore provides the dual functions of pulse amplification and pulse delivery to the optical head 18.
  • the amplifier fibre 62 will get warm during use. Heat dissipation may be achieved by using an armoured cable to protect the amplifier fibre 62; the void around the amplifier fibre 62 being filled with a suitable heat transfer fluid or paste to ensure good thermal contact between the amplifier fibre 62 and the cable inner surface.
  • a high power short optical pulse source 70 according to a fifth embodiment of the invention is shown in Figure 5.
  • the pulse source 70 of this embodiment is substantially the same as the pulse source 60 of the previous embodiment, with the following modifications.
  • the pump signal combiner 52 is provided in the optical head 18, so that a counter-propagating pump regime is used.
  • the pump delivery fibres 24, 44 extend from the pump sources 16, 42 in the first enclosure to the pump signal combiner 52 in the optical head 18.
  • a high power short optical pulse source 80 according to a sixth embodiment of the invention is shown in Figure 6.
  • the optical pulse source 80 is substantially the same as the pulse source 60 of Figure 4, with the following modifications.
  • the amplifier fibre 62 is made to be "under-length", such that quite a large portion of the pump light delivered to the amplifier fibre is not absorbed within the amplifier fibre, but propagates through to the fibre output, along with the signal pulses.
  • the high power optical fibre amplifier means 20 further comprises a rod amplifier 82, in the form of a Yttrium Aluminium Garnet (YAG) crystal rod, optically coupled to the output of the amplifier fibre 62, to form a hybrid amplifier device.
  • the YAG crystal rod 82 performs a second stage of amplification of the short optical pulses, in a very short piece of material, using the unabsorbed pump light to pump the YAG crystal rod 82.
  • the YAG crystal rod 82 can provide an additional gain of a few dB's while providing very little nonlinear distortion to the signal pulses.
  • the gain of the YAG crystal rod 82 is determined by the efficiency of the crystal, the divergence of pump light and the signal pulses, and the overlap of the pump light and the signal pulses through the YAG crystal rod 82.
  • both the output end of the amplifier fibre 62 and the YAG crystal rod 82 are coated with anti-reflection coatings.
  • the amplifier fibre 62 and the YAG crystal rod can be fused together. It will be appreciated that a rod amplifier such as the YAG crystal rod 82 may also be used with any of the embodiments described above.
  • FIG 7 shows a high power short optical pulse source 90 according to a seventh embodiment of the invention.
  • the optical pulse source 90 is based on the optical pulse source 40 of Figure 2, with the following modifications.
  • the same reference numbers are retained for corresponding features.
  • the high power short optical pulse source 90 further comprises nonlinear optical frequency conversion means 92, optically coupled to the output of the high power optical fibre amplifier means 20 and located within the optical head 18.
  • the nonlinear optical frequency conversion means 92 comprises (optically coupled in series) a set of phase plates 94, a first nonlinear crystal 96, which in this example is a Type I LBO crystal, a second nonlinear crystal 98, which in this example is a Type I BBO crystal, and a harmonic separator 100.
  • the pulses are then launched, using conventional collimation and focusing optics, into the LBO crystal 96, to convert the wavelength of the pulses to their second harmonic of 532nm, at an average power of 12W.
  • the frequency converted pulses output from the LBO crystal 96 are then launched into the BBO crystal 98, where the wavelength is converted to their fourth harmonic wavelength of 266nm, at an average power of 1.2W.
  • the output from the BBO crystal 98 is then passed through the harmonic separator 100, which transmits only the desired wavelength, in this case 266nm, as the output of the high power short optical pulse source 90 to the intended target.
  • the LBO and BBO crystals 96, 98 are respectively mounted within ovens, controlled by a temperature controller 102. Electrical power for the ovens and the temperature controller 102, and to a cooling fan (not shown) for the high power optical fibre amplifier means 20 is delivered to the optical head 18 through a power cable 104.
  • the nonlinear optical frequency conversion means 92 could alternatively use other combinations of crystals to generate 3 rd , 4 th or higher harmonics, for example periodically poled nonlinear crystals such as PPLN or PPKTP, or could use other combinations of conventional crystals such as LBO, BBO, BIBO, CLBO, and KTP.
  • the spectral bandwidth of the pulses must be maintained as narrow as possible.
  • the high power short optical pulse source 90 ensures that spectral distortion of the pulses is minimised and nonlinear optical conversion efficiency is thereby maximised.
  • the high power short optical pulse source 90 can therefore deliver UV light directly to an intended target whilst remotely positioning the bulky elements of the source 90 away from the intended target.
  • nonlinear optical frequency conversion means 92 may be included in any of the high power short optical pulse sources according to the previously described embodiments.
  • a high power short optical pulse source 110 according to an eighth embodiment of the invention is shown in Figure 8.
  • the pulse source 110 of this embodiment is based on the pulse source 10 of the first embodiment, with the following modifications, and is operable to generate ultrashort (femtosecond) optical pulses.
  • the same reference numbers are retained for corresponding features.
  • the optical pulse source 110 further comprises a pulse compressor 112 provided within the optical head 18 and optically coupled to the output of the high power optical fibre amplifier means 20.
  • the pulse compressor takes the form of a transmission grating pair 112 having a grating separation of less than 10cm.
  • the pulse compressor 112 could alternatively comprise a fibre pulse compressor based on Photonic Crystal Fibre with anomalous dispersion at the signal wavelength.
  • the master oscillator 12 generates optical pulses having a duration of approximately 10ps at a pulse frequency of 10MHz.
  • the pulses are then amplified by the optical fibre preamplifier 14 to an optical power of approximately 5OmW.
  • the signal pulses and 20W 975nm pump light from the pump light source 16 single are delivered over the signal delivery fibre 22 and the pump delivery fibre 24 respectively, each of which are 2m long in this example, to large mode area, polarisation maintaining, single-mode Ytterbium doped amplifier fibre within the high power optical fibre amplifier means 20.
  • the high power optical fibre amplifier means 20 amplifies the average pulse power to approximately 12W, resulting in a pulse energy of greater than 1 ⁇ J.
  • the pulses (which enter the high power optical fibre amplifier means with a duration of approximately 10ps) becomes linearly chirped due to the combination of positive fibre dispersion and self-phase modulation.
  • the amplified pulses are then passed through the transmission grating pair 112, which acts to compress the pulses to less than 500 femtoseconds duration, with an efficiency of greater than 80%, to produce pulses having an energy of approximately 1 ⁇ J and peak powers of 2 MW.
  • the high power ultrashort pulses can then be delivered from the head 18 which can be positioned directly at the intended target without the need for complex beam steering optics.
  • a pulse compressor 112 may be incorporated into any of the above described high power short optical pulse sources in order to generate ultrashort, femtosecond pulses.
  • FIG 9 shows a high power short optical pulse source 120 according to a ninth embodiment of the invention.
  • the pulse source 120 is substantially the same as the pulse source 40 of Figure 2, with the following modifications.
  • the same reference numbers are retained for corresponding features.
  • the pump light sources 16, 42 are provided within the first enclosure 28, at the first location, together with the pump sources 122, 124 for the preamplifier 14, and their associated electrical drive circuitry, cooling and heat dissipation elements (not shown).
  • the high power optical fibre amplifier means 20 and the optical isolator 26 are provided within the optical head 18, at a second location, remote from the first location.
  • the master oscillator 12 and the amplifier fibre and pump signal combiner of the optical fibre preamplifier 14, together with their associated isolators 30, 32, are provided within a second enclosure 126, at a third location intermediate the first and second locations.
  • the outputs of the preamplifier pump sources 122, 124 are delivered to the amplifier fibre of the optical fibre preamplifier 14 respectively via preamplifier pump delivery fibres 128, 130.
  • the master oscillator 12, preamplifier 14, and high power optical fibre amplifier means 20 can thus be enclosed in one or more separate enclosures positioned close to the application target area thus avoiding the need for beam steering optics.
  • FIG 10 shows a high power short optical pulse source 140 according to a tenth embodiment of the invention.
  • the pulse source 140 is substantially the same as the pulse source 10 of Figure 1 , with the following modifications.
  • the same reference numbers are retained for corresponding features.
  • the pulse source 140 further comprises a pulse picker 142 operable to reduce the optical pulse frequency.
  • the pulse picker 142 comprises an acousto- optic modulator driven at a synchronised gating frequency lower than the optical pulse frequency output from the master oscillator 12.
  • the pulse picker 142 is provided after the preamplifier 14, within the first enclosure 28.
  • the pulse picker 142 is located at a position within the pulse source 140 where the optical pulses have a low pulse energy. This is because the optical insertion loss into the acousto-optical modulator pulse picker 142 is high, so it is preferable for the pulses to be transmitted through the pulse picker 142 prior to amplifying them to their final high power.
  • a pulse picker 142 may be provided within any of the above described pulse sources, and that where the pulse source comprises high power optical fibre amplifier means having two or more amplifier stages the pulse picker may be provided after any one of the amplifier stages between the master oscillator the final high power amplifier stage.
  • a high power short optical pulse source 50 is shown in Figure 11.
  • the optical head 18 is movably mounted on a translation stage 152 which is operable to provide translation of the optical head 18 in one or more of the x-, y- and z-axes.
  • the controlled movement of the optical head 18 provided by the translation stage 152 enables accurate direction of the output high power short optical pulses onto a target or specimen under test.
  • the optical head 18 may alternatively be mounted on a mechanical manipulator such as a robotic arm.
  • optical heads 18 of any of the previously described embodiments may be similarly movably mounted.
  • the master oscillator could alternatively comprise any optical source operable to generate short optical pulses, such as a solid-state modelocked laser, for example a Neodynium Vanadate laser, or a gain-switched laser diode.
  • the amplifier fibres of the preamplifier and the high power optical fibre amplifier means may alternatively be doped with a different rare-earth dopant, such as Erbium, Thulium, or Neodynium.
  • the pump source/s will be a multi-mode pump source operating at a suitable wavelength to pump the rare-earth-doped amplifier fibre (eg 808nm, 915nm or 975nm).
  • a single fibre-pigtailed laser diode, diode bar or multi-emitter pump source such as the PUMA source commercially supplied by Fianium Ltd, which delivers between 20 and 40W within a single, 105 ⁇ m core, 0.22NA pump delivery fibre.
  • the pump signal combiner will typically include a conventional tapered bundle, such as those commercially available from OFS or Sifam Fibre Optics.
  • the pump signal combiner may be a tapered coupler, a side-pumping fibre configuration, or a distributed pump coupling fibre configuration such as that proposed in US 6,826,335.
  • the amplifier fibre typically comprises a double-clad fibre structure where the signal pulses are guided within a signal core and the pump light is guided within the fibre cladding.
  • the pump source/s can be a single mode pump source such as a fibre- pigtailed laser diode or a fibre laser.
  • the fibre laser can be a Raman fibre laser or could be a cladding pumped fibre laser generating cw or pulsed radiation at the wavelength required to pump the rare-earth-doped amplifier fibre.
  • the signal pulses and pump light from the one or more pump sources are combined using conventional WDM components such as fused WDM couplers or thin-film WDM couplers.
  • the amplifier fibre In the single-mode pump regime, the amplifier fibre has a conventional single clad geometry, where both the signal pulses and the pump light propagate within the core of the amplifier fibre. This has benefits in increasing the pump absorption and thus reducing amplifier length and hence nonlinearity.
  • the optical head of any of the high power short optical pulse sources described may also include a heat sink and integrated fan within the high power optical fibre amplifier means, to provide forced-air cooling of the amplifier fibre.
  • Optical monitoring means may also be provided within the optical head, with both electrical and optical communication to the first enclosure to monitor feedback and power levels, enabling interlocks and automatic fault detection.
  • the high power short optical pulse sources enable a short-length fibre amplifier system and post processing optics to be remotely located from the bulky, noisy heat producing elements of the pulse source, and thereby enable optical head to be very compact.
  • the optical head can therefore be positioned close to the application space, taking up minimal space and avoiding the need for complex and expensive beam steering optics.
  • the high power short optical pulse sources enable the delivery of ultrashort (femtosecond) optical pulses with high energy and narrow spectral bandwidth, without the use of complex chirped pulse amplification (CPA) methods.
  • CPA complex chirped pulse amplification
  • the high power short optical pulse sources incorporating a pulse compressor eliminate the need for CPA in fibre-delivered laser sources. Providing a high power ultrashort pulse source which is more robust, lower cost and easier to maintain and assemble than known ultrashort pulse sources using CPA pulse compression.
  • the high power short optical pulse sources further enable the delivery of UV optical pulses, efficiently generated within the optical head.
  • the high power short optical pulse sources also provide the advantage of beam delivery directly to the target without the use of complex beam steering optics.
  • the high power short optical pulse sources therefore offer improved mechanical robustness, reduced cost and weight, and ease of maintenance over known high power optical pulse sources.
  • the high power short optical pulse sources also allow for scalability in power because they can incorporate multiple pump light sources in the remote pump enclosure and the pump delivered over long lengths with very low loss to the amplifier system which is remotely located whether within or close to the output optical head.

Abstract

A high power short optical pulse source (10) comprising a master oscillator (12) and a Ytterbium doped fibre amplifier (YDFA) preamplifier (14), a pump light source (16), an optical head (18), high power optical fibre amplifier means (20), an optical signal delivery fibre (22), and a pump light delivery fibre (24). The master oscillator (12), preamplifier (14), and pump laser (16), together with their associated drive and control electronics, and cooling systems (not shown), are provided within a first enclosure (28) at a first location. The high power fibre amplifier means (20) comprises a Ytterbium doped amplifier fibre and a pump signal combiner. The high power fibre amplifier means (20) is provided within the optical head (18), which is located at a second location, remote from the first location. The optical head (18) has a small footprint and can be positioned at the intended target of the optical pulses. The large, noisy elements of the high power short optical pulse source (10) are thereby provided away from the application site of the pulses.

Description

High power short optical pulse source
The invention relates to a high power short optical pulse source.
There are many existing and emerging applications of high power lasers in industrial, medical and scientific processes. Conventionally, solid state and gas lasers, with bulk- optical cavities, are used in these applications, and the outputs of these lasers are generally free space, collimated beams. In most cases, the laser source can be very large, and often constitutes the largest single element of an instrument or machine. In using laser systems in industrial applications, it is often difficult to position the large laser very close to the intended target of the laser beam and therefore bulk-optic beam steering is required. Such beam steering includes specially designed, low loss, high reflective and high-damage threshold mirrors, mounted and positioned with precision and on a heavy and vibration-isolated surface to enable a robust, reliable performance. In many applications such as semiconductor inspection, the inspection tool is just one of many instruments and machines used within the semiconductor manufacturing process, and space on the manufacturing floor - very often being in an expensive, clean-room environment - costs a premium. Therefore, reduction of the instrumentation footprint is highly beneficial. In other industrial applications, such as laser materials processing, the application environment can very often be noisy, dirty and a challenge to the operation of a laser source. In this application additional measures are often required to protect the laser and beam steering optics from the hostile working environment.
Fibre delivery of the laser beam is a clear and interesting option, enabling the laser source to be positioned remotely from the target space and enabling a compact optical beam delivery head (optical head) to be installed within the instrument, with the large laser source being positioned, along with any power supplies and cooling systems, outside an instrument and clean room environment. With conventional bulk lasers, fibre delivery involves launching of the laser output beam into an optical fibre. This is very difficult to achieve, especially in high-power laser applications. Most applications require a good beam quality of the laser, which requires a single mode fibre to deliver the beam. In reality, a single mode fibre has a core diameter of less than 15μm, very often less than 10μm, and efficient and stable launching of a beam into this aperture is difficult to achieve. Furthermore, in high-power applications, launching of such high intensities into a fibre will damage the fibre facet.
In addition, applications of UV fibre lasers cannot use a conventional optical fibre to deliver the beam since the UV is absorbed by the fibre. One option that has been considered is to use Hollow Core Photonic Crystal Fibres (HCPCF's) in which the light is mostly guided within an air-core of the fibre. The use of HCPCF's does not solve the problem of launching the light into the fibre and avoiding facet damage at high powers. However, HCPCF's have two benefits - they enable the propagation of UV radiation with relatively low loss and also reduced fibre nonlinearity by a factor of approximately 1000 in comparison to conventional glass-guided optical fibres.
Fibre lasers clearly have a significant advantage over conventional bulk lasers, since the optical beam is already within the fibre and no launching optics are required. Most high-power fibre lasers, particularly in the pulsed lasers, use a Master Oscillator Power Amplifier (MOPA) configuration, in which the output of a low-power fibre oscillator is amplified in a series of high-power fibre amplifiers. In principle, the output of a fibre laser or fibre amplifier can be delivered directly to the intended target through an output fibre. However, in short pulse applications the nonlinear effects of the fibre and amplifier prevent this. Short optical pulses are generally defined (and defined herein) as pulses having a duration of less than 10ns (10~8 seconds). Reduction of fibre nonlinearity is a major challenge in any fibre-based system, particularly when short pulses are required at relatively high peak intensities.
In cw and long pulse applications, there is little issue with the use of additional lengths of fibre at the amplifier output, since nonlinear effects can often be neglected owing to relatively low peak powers. However, for short-pulse fibre delivery, the nonlinear effects within an optical fibre prevent the delivery of high power pulses due to degradation of the pulses' temporal and spectral characteristics due to high order nonlinear effects such as self-phase modulation, which causes spectral broadening, and Raman scattering, which causes both spectral and temporal broadening. HCPCF's and conventional optical fibres with larger core sizes (referred to as large- mode-area (LMA) fibres) have been used to reduce fibre nonlinearity. HCPCF's reduce the nonlinearity by several orders of magnitude, where LMA fibres reduce the nonlinearity, scaling with the area of the core. However, the use of LMA fibres for beam delivery in high-power pulsed applications is not a solution since even the largest single- mode core fibre (of 15-20 μm), results in significant nonlinear effects when high-peak power pulses are delivered.
The importance of reducing nonlinear effects can be illustrated by considering UV generation from a short-pulse source. The use of short pulses to generate visible and UV radiation is a common approach, since the high peak powers attainable from short pulses provide efficient frequency conversion in nonlinear materials such as LBO and BBO. However, efficient conversion within conventional nonlinear media, often requires that the spectral bandwidth of the pulse is as narrow as possible - preferably with the pulses transform limited. Any high order nonlinearity within a delivery fibre or a fibre amplifier will result in spectral broadening; a relatively low nonlinearity will double the spectral bandwidth of a pulse and hence significantly reduce the conversion efficiency of that pulse. It is therefore important in all stages of amplification of the pulse to avoid or reduce fibre nonlinear effects.
For amplifying short optical pulses, it is possible to use Chirped Pulse Amplification (CPA), a technique developed for bulk-laser systems, in which a short pulse from an oscillator is stretched in a fibre or bulk optic stretcher, amplified and then compressed. In this instance, the amplified, long pulses can also be delivered by an optical fibre to a remote probe where they are subsequently re-compressed, as described in US 6249630.
One of the main problems with the CPA approach is that, in order to amplify pulses without significant nonlinear distortion, the pulse must be stretched to a duration of typically greater than 10ns. Therefore, to compress the stretched amplified pulse, a fairly long and complex compressor is required. Furthermore, in stretching and compressing the pulse, bulk optic components are typically required, preventing an all- fibre approach. This is difficult to make robust and involves significant loss which necessitates another stage of amplification in the MOPA. Furthermore, after amplification and fibre delivery, the compression stage also involves significant optical loss and, due to the relatively long pulse duration, the compressor itself is very large, meaning that the optical head itself has a large footprint. In general, the approach of CPA is not ideal and is also difficult to maintain in a compact, robust and lightweight form especially in a harsh operating environment.
According to an aspect of the present invention there is provided a high power short optical pulse source comprising: an optical signal source operable to output short optical pulses; an optical pump light source provided at a first location; an optical head provided at a second location remote from the first location; high power optical fibre amplifier means having at least its optical output located within the optical head; an optical signal delivery fibre arranged to deliver optical pulses from the optical signal source to the high power optical fibre amplifier means; and a pump light delivery fibre arranged to deliver optical pump light to the high power optical fibre amplifier means, wherein short optical pulses of a first optical power are delivered to the high power optical fibre amplifier means and are amplified therein to a second, high optical power for output from the optical head.
The optical signal source preferably comprises a master oscillator optically coupled to an optical fibre preamplifier, comprising a preamplifier amplifier optical fibre and one or more preamplifier optical pump sources. The preamplifier amplifier optical fibre preferably comprises a rare-earth doped optical fibre. The optical signal source is preferably provided at the first location. Alternatively, the master oscillator and the preamplifier amplifier optical fibre may be provided at a third location, intermediate the first and second locations, with the or each preamplifier optical pump source being provided at the first location and being coupled to the preamplifier amplifier optical fibre via a corresponding one or more preamplifier pump delivery fibres.
A plurality of optical pump light sources may be provided at the first location and a corresponding plurality of pump light delivery fibres. The high power optical fibre amplifier means preferably comprises an amplifier optical fibre and one or more pump signal combiners. The amplifier optical fibre preferably comprises a rare-earth doped optical fibre, and is most preferably of the same type of rare-earth doped optical fibre as the preamplifier amplifier optical fibre.
The high power short optical pulse source may comprise a plurality of high power optical fibre amplifier means optically coupled in series, at least the optical output of the final high power optical fibre amplifier means being located within the optical head.
The or each amplifier optical fibre is preferably located within the optical head. The or each pump signal combiner may be located within the optical head. The or each pump signal combiner may alternatively be located at the first location, with the high power optical fibre amplifier means additionally comprising a pump signal delivery fibre optically coupled between the or each pump signal combiner and the or each amplifier optical fibre. The or each pump signal delivery fibre is preferably a double-clad optical fibre and is most preferably a polarisation maintaining optical fibre.
Alternatively, the amplifier optical fibre may be arranged to extend from the first location to the optical head. The amplifier optical fibre preferably comprises a double-clad amplifier optical fibre. The or a pump signal combiner may be provided at the first location, arranged to couple optical pulses and pump light into one end of the amplifier optical fibre. Alternatively or additionally, the or a pump signal combiner may be provided within the optical head, arranged to couple pump light into the signal output end of the amplifier optical fibre.
The optical head preferably further comprises an optical isolator and optical collimator assembly optically coupled to the output of the high power optical fibre amplifier means.
The high power optical fibre amplifier means may further comprise a bulk optic amplifier element, most preferably a rod amplifier, optically coupled to the output end of the or the final amplifier optical fibre, said amplifier optical fibre being under-length such that a proportion of any pump light coupled into said amplifier optical fibre is unabsorbed by it, and serves to pump the bulk optic amplifier element. The high power short optical pulse source may further comprise nonlinear optical frequency conversion means optically coupled to the output of the or the final high power optical fibre amplifier means. The nonlinear optical frequency conversion means preferably comprises a nonlinear optical crystal. The nonlinear optical frequency conversion means may comprise a plurality of nonlinear optical crystals arranged optically in series. The nonlinear optical frequency conversion means may alternatively comprise a nonlinear optical fibre.
The high power short optical pulse source may alternatively or additionally comprise an optical pulse compressor optically coupled to the output of the or the final high power optical fibre amplifier means or the nonlinear optical frequency conversion means. The optical pulse compressor may comprise a transmission grating pair or photonic crystal fibre having anomalous dispersion at the signal wavelength.
The high power short optical pulse source may further comprise a pulse picker operable to reduce the optical pulse frequency. The pulse picker preferably comprises an optical gate, such as an acousto-optic modulator, driven at a synchronised gating frequency lower than the optical pulse frequency output from the optical signal source.
The high power short optical pulse source may further comprise optical monitoring means within the optical head.
The optical head may be movably mounted to enable accurate direction of generated high power short optical pulses onto a target or specimen under test. The optical head is preferably mounted on a translation stage or a mechanical manipulator, such as a robotic arm.
Embodiments of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a high power short optical pulse source according to a first embodiment of the invention;
Figure 2 is a schematic representation of a high power short optical pulse source according to a second embodiment of the invention; Figure 3 is a schematic representation of a high power short optical pulse source according to a third embodiment of the invention;
Figure 4 is a schematic representation of a high power short optical pulse source according to a fourth embodiment of the invention;
Figure 5 is a schematic representation of a high power short optical pulse source according to a fifth embodiment of the invention;
Figure 6 is a schematic representation of a high power short optical pulse source according to a sixth embodiment of the invention;
Figure 7 is a schematic representation of a high power short optical pulse source according to a seventh embodiment of the invention;
Figure 8 is a schematic representation of a high power short optical pulse source according to a eighth embodiment of the invention;
Figure 9 is a schematic representation of a high power short optical pulse source according to a ninth embodiment of the invention;
Figure 10 is a schematic representation of a high power short optical pulse source according to a tenth embodiment of the invention; and
Figure 11 is a schematic representation of a high power short optical pulse source according to an eleventh embodiment of the invention.
Referring to Figure 1 , a first embodiment of the invention provides a high power short optical pulse source 10 comprising an optical signal source in the form of a master oscillator 12 and an Ytterbium doped fibre amplifier (YDFA) preamplifier 14, a pump light source 16, an optical head 18, high power optical fibre amplifier means 20, an optical signal delivery fibre 22, a pump light delivery fibre 24, and a high power optical isolator 26.
The master oscillator 12 comprises a modelocked fibre oscillator operable to output 10ps pulses at a pulse frequency of 200MHz. The preamplifier 14 amplifies the pulse average power to approximately 10OmW. In this example, the master oscillator 12, preamplifier 14, and pump laser 16, together with their associated drive and control electronics, and cooling systems (not shown), are provided within a first enclosure 28 at a first location. Additional optical isolators 30, 32 are provided after the master oscillator 12 and the preamplifier 14 to protect them from back reflections.
The high power fibre amplifier means 20 comprises a im long single-mode, polarisation maintaining, large.mode area Ytterbium doped amplifier fibre and a pump signal combiner having a large mode area signal fibre. The high power fibre amplifier means 20 and the high power optical isolator 26 are provided within the optical head 18, which is located at a second location, remote from the first location.
The short, relatively low power optical pulses output from the preamplifier 14 are delivered to the pump signal combiner of the high power fibre amplifier means 20 via the optical signal delivery fibre 22, which comprises a 5m long polarisation maintaining, single-mode optical fibre; the use of polarisation maintaining fibre prevents any environmental effects disturbing the signal.
The pump light source 16 comprises a fibre pig-tailed multi-emitter pump source operable to generate cw pump light at a wavelength of 915nm, and an optical power of between 20W and 4OW.
The pump light is delivered to the pump signal combiner of the high power optical fibre amplifier means 20 through the pump delivery fibre 24, which in this example is a 5m length of optical fibre having a 105μm diameter core and a numerical aperture of 0.22. The pump delivery fibre 24 is not sensitive to environmental effects but can, along with signal delivery fibre, be protected within an armoured jacket for industrial applications.
The high power optical fibre amplifier means 20 amplifies the received optical pulses to an average power of approximately 2OW, resulting in a pulse peak power of approximately 1OkW. The overall low nonlinearity of the high power optical pulse source 10 ensures that spectral broadening of the optical pulses is minimised, and the pulses have a final spectral bandwidth of less than 0.5nm. The optical head 18, containing the high power optical fibre amplifier means 20 and the isolator 26, has a small footprint and can be positioned at the intended target of the optical pulses. The large, noisy elements of the high power short optical pulse source 10 are thereby provided away from the application site of the pulses, and only the smaller optical head need be located near the intended target.
Figure 2 shows a high power short optical pulse source 40 according to a second embodiment of the invention. The optical pulse source 40 of this embodiment is substantially the same as the optical pulse source 10 of the first embodiment, with the following modifications. The same reference numbers are retained for corresponding features.
In this embodiment, a second pump light source 42 is provided at the first location, within the first enclosure. A second pump light delivery fibre 44 is also provided and delivers pump light from the second pump light source 42 to the pump signal combiner of the high power optical fibre amplifier means 20.
It will be appreciated that the high power optical fibre amplifier means 20 may alternatively comprise a two-stage amplifier having a series of two amplifier fibres and pump signal combiners, with an isolator provided between amplifier stages as necessary. Each pump signal source 16, 42 would then pump a separate amplifier stage, the amplifier stages being cascaded to provide increasing signal with balanced gain throughout the cascade.
In most applications, the high power optical fibre amplifier means 20 will only require a single amplifier fibre. However, the number of amplifier fibres (and thus the number of pump light sources) will at least in part be determined by the power of the optical pulses output from the preamplifier 14, the length of signal delivery fibre 22, and the permitted amount of nonlinear effects as determined by the application of the high power short optical pulse source 10.
A high power short optical pulse source 50 according to a third embodiment of the invention is shown in Figure 3. The pulse source 50 according to this embodiment is substantially the same as the pulse source 40 of the previous embodiment, with the following modifications. The same reference numbers are retained for corresponding features.
In this embodiment, the pump signal combiner 52 of the high power optical fibre amplifier means 20 is provided at the first location, within the first enclosure 28. The pump delivery fibres 24, 44 and the signal delivery fibre 22 are also wholly contained within the first enclosure 28.
The high power optical fibre amplifier means 20 of this embodiment further comprises a pump signal delivery fibre 54, which comprises the output fibre of the pump signal combiner 52. The pump signal delivery fibre 54 is a polarisation maintaining double clad optical fibre which has a signal-guiding core region and an inner cladding which guides the pump light from the pump sources 16, 42.
The pump signal delivery fibre 54 extends from the pump signal combiner 52, within the first enclosure 28, to the amplifier fibre 56, within the optical head 18. The amplifier fibre 56 is therefore pumped in the co-propagating regime.
Figure 4 shows a high power short optical pulse source 60 according to a fourth embodiment of the invention. The pulse source 60 of this embodiment is substantially the same as the pulse source 50 of the previous embodiment, with the following modifications.
In this embodiment, the amplifier fibre 62 comprises a polarisation maintaining double clad amplifier fibre and extends between the pump signal combiner 52 and the optical head 18. The input end of the amplifier fibre 62 is coupled to the output of the pump signal combiner 52 and the output end of the amplifier fibre 62 is located in the optical head 18, where it is coupled to an optical isolator and collimating optics 64. The amplifier fibre 62 therefore provides the dual functions of pulse amplification and pulse delivery to the optical head 18.
Since fibre amplifiers are not 100% efficient (typically 50 to 75% efficiency is achievable), the amplifier fibre 62 will get warm during use. Heat dissipation may be achieved by using an armoured cable to protect the amplifier fibre 62; the void around the amplifier fibre 62 being filled with a suitable heat transfer fluid or paste to ensure good thermal contact between the amplifier fibre 62 and the cable inner surface.
A high power short optical pulse source 70 according to a fifth embodiment of the invention is shown in Figure 5. The pulse source 70 of this embodiment is substantially the same as the pulse source 60 of the previous embodiment, with the following modifications.
In this example, the pump signal combiner 52 is provided in the optical head 18, so that a counter-propagating pump regime is used. The pump delivery fibres 24, 44 extend from the pump sources 16, 42 in the first enclosure to the pump signal combiner 52 in the optical head 18.
A high power short optical pulse source 80 according to a sixth embodiment of the invention is shown in Figure 6. The optical pulse source 80 is substantially the same as the pulse source 60 of Figure 4, with the following modifications.
In this example, the amplifier fibre 62 is made to be "under-length", such that quite a large portion of the pump light delivered to the amplifier fibre is not absorbed within the amplifier fibre, but propagates through to the fibre output, along with the signal pulses. The high power optical fibre amplifier means 20 further comprises a rod amplifier 82, in the form of a Yttrium Aluminium Garnet (YAG) crystal rod, optically coupled to the output of the amplifier fibre 62, to form a hybrid amplifier device. The YAG crystal rod 82 performs a second stage of amplification of the short optical pulses, in a very short piece of material, using the unabsorbed pump light to pump the YAG crystal rod 82. The YAG crystal rod 82 can provide an additional gain of a few dB's while providing very little nonlinear distortion to the signal pulses. The gain of the YAG crystal rod 82 is determined by the efficiency of the crystal, the divergence of pump light and the signal pulses, and the overlap of the pump light and the signal pulses through the YAG crystal rod 82.
In order to prevent optical feedback from the YAG crystal 82 into the amplifier fibre 62, both the output end of the amplifier fibre 62 and the YAG crystal rod 82 are coated with anti-reflection coatings. Alternatively, the amplifier fibre 62 and the YAG crystal rod can be fused together. It will be appreciated that a rod amplifier such as the YAG crystal rod 82 may also be used with any of the embodiments described above.
Figure 7 shows a high power short optical pulse source 90 according to a seventh embodiment of the invention. The optical pulse source 90 is based on the optical pulse source 40 of Figure 2, with the following modifications. The same reference numbers are retained for corresponding features.
In this example the high power short optical pulse source 90 further comprises nonlinear optical frequency conversion means 92, optically coupled to the output of the high power optical fibre amplifier means 20 and located within the optical head 18.
The nonlinear optical frequency conversion means 92 comprises (optically coupled in series) a set of phase plates 94, a first nonlinear crystal 96, which in this example is a Type I LBO crystal, a second nonlinear crystal 98, which in this example is a Type I BBO crystal, and a harmonic separator 100.
The output optical pulses from the high power optical fibre amplifier means 20, having a wavelength of 1064nm and an average power of approximately 2OW, pass through the phase plates 94, to set the optimum state of polarisation for the nonlinear frequency conversion. The pulses are then launched, using conventional collimation and focusing optics, into the LBO crystal 96, to convert the wavelength of the pulses to their second harmonic of 532nm, at an average power of 12W.
The frequency converted pulses output from the LBO crystal 96 are then launched into the BBO crystal 98, where the wavelength is converted to their fourth harmonic wavelength of 266nm, at an average power of 1.2W. The output from the BBO crystal 98 is then passed through the harmonic separator 100, which transmits only the desired wavelength, in this case 266nm, as the output of the high power short optical pulse source 90 to the intended target.
The LBO and BBO crystals 96, 98 are respectively mounted within ovens, controlled by a temperature controller 102. Electrical power for the ovens and the temperature controller 102, and to a cooling fan (not shown) for the high power optical fibre amplifier means 20 is delivered to the optical head 18 through a power cable 104. It will be appreciated that the nonlinear optical frequency conversion means 92 could alternatively use other combinations of crystals to generate 3rd, 4th or higher harmonics, for example periodically poled nonlinear crystals such as PPLN or PPKTP, or could use other combinations of conventional crystals such as LBO, BBO, BIBO, CLBO, and KTP.
For efficient frequency conversion the spectral bandwidth of the pulses must be maintained as narrow as possible. By transmitting the optical pulses through the greatest length of fibre before amplifying the pulses close to the nonlinear optical conversion means 92, the high power short optical pulse source 90 ensures that spectral distortion of the pulses is minimised and nonlinear optical conversion efficiency is thereby maximised.
The high power short optical pulse source 90 can therefore deliver UV light directly to an intended target whilst remotely positioning the bulky elements of the source 90 away from the intended target.
It will be appreciated that the nonlinear optical frequency conversion means 92 may be included in any of the high power short optical pulse sources according to the previously described embodiments.
A high power short optical pulse source 110 according to an eighth embodiment of the invention is shown in Figure 8. The pulse source 110 of this embodiment is based on the pulse source 10 of the first embodiment, with the following modifications, and is operable to generate ultrashort (femtosecond) optical pulses. The same reference numbers are retained for corresponding features.
The optical pulse source 110 further comprises a pulse compressor 112 provided within the optical head 18 and optically coupled to the output of the high power optical fibre amplifier means 20.
In this example the pulse compressor takes the form of a transmission grating pair 112 having a grating separation of less than 10cm. The pulse compressor 112 could alternatively comprise a fibre pulse compressor based on Photonic Crystal Fibre with anomalous dispersion at the signal wavelength. The master oscillator 12 generates optical pulses having a duration of approximately 10ps at a pulse frequency of 10MHz. The pulses are then amplified by the optical fibre preamplifier 14 to an optical power of approximately 5OmW. The signal pulses and 20W 975nm pump light from the pump light source 16 single are delivered over the signal delivery fibre 22 and the pump delivery fibre 24 respectively, each of which are 2m long in this example, to large mode area, polarisation maintaining, single-mode Ytterbium doped amplifier fibre within the high power optical fibre amplifier means 20. The high power optical fibre amplifier means 20 amplifies the average pulse power to approximately 12W, resulting in a pulse energy of greater than 1 μJ.
During amplification within the high power optical fibre amplifier means, the pulses (which enter the high power optical fibre amplifier means with a duration of approximately 10ps) becomes linearly chirped due to the combination of positive fibre dispersion and self-phase modulation.
The amplified pulses are then passed through the transmission grating pair 112, which acts to compress the pulses to less than 500 femtoseconds duration, with an efficiency of greater than 80%, to produce pulses having an energy of approximately 1 μJ and peak powers of 2 MW. The high power ultrashort pulses can then be delivered from the head 18 which can be positioned directly at the intended target without the need for complex beam steering optics.
It will be appreciated that a pulse compressor 112 may be incorporated into any of the above described high power short optical pulse sources in order to generate ultrashort, femtosecond pulses.
Figure 9 shows a high power short optical pulse source 120 according to a ninth embodiment of the invention. The pulse source 120 is substantially the same as the pulse source 40 of Figure 2, with the following modifications. The same reference numbers are retained for corresponding features.
In this embodiment the pump light sources 16, 42 are provided within the first enclosure 28, at the first location, together with the pump sources 122, 124 for the preamplifier 14, and their associated electrical drive circuitry, cooling and heat dissipation elements (not shown). The high power optical fibre amplifier means 20 and the optical isolator 26 are provided within the optical head 18, at a second location, remote from the first location.
The master oscillator 12 and the amplifier fibre and pump signal combiner of the optical fibre preamplifier 14, together with their associated isolators 30, 32, are provided within a second enclosure 126, at a third location intermediate the first and second locations. The outputs of the preamplifier pump sources 122, 124 are delivered to the amplifier fibre of the optical fibre preamplifier 14 respectively via preamplifier pump delivery fibres 128, 130.
The master oscillator 12, preamplifier 14, and high power optical fibre amplifier means 20 can thus be enclosed in one or more separate enclosures positioned close to the application target area thus avoiding the need for beam steering optics.
It will be appreciated that this arrangement can also be applied to any of the previously described embodiments, including those with nonlinear frequency conversion and pulse compression.
Figure 10 shows a high power short optical pulse source 140 according to a tenth embodiment of the invention. The pulse source 140 is substantially the same as the pulse source 10 of Figure 1 , with the following modifications. The same reference numbers are retained for corresponding features.
The pulse source 140 further comprises a pulse picker 142 operable to reduce the optical pulse frequency. In this example the pulse picker 142 comprises an acousto- optic modulator driven at a synchronised gating frequency lower than the optical pulse frequency output from the master oscillator 12. The pulse picker 142 is provided after the preamplifier 14, within the first enclosure 28. The pulse picker 142 is located at a position within the pulse source 140 where the optical pulses have a low pulse energy. This is because the optical insertion loss into the acousto-optical modulator pulse picker 142 is high, so it is preferable for the pulses to be transmitted through the pulse picker 142 prior to amplifying them to their final high power. The provision of a pulse picker also enables higher pulse energies to be achieved for a given average output power. It will be appreciated that a pulse picker 142 may be provided within any of the above described pulse sources, and that where the pulse source comprises high power optical fibre amplifier means having two or more amplifier stages the pulse picker may be provided after any one of the amplifier stages between the master oscillator the final high power amplifier stage.
A high power short optical pulse source 50 according to an eleventh embodiment of the invention is shown in Figure 11. In this example, the optical head 18 is movably mounted on a translation stage 152 which is operable to provide translation of the optical head 18 in one or more of the x-, y- and z-axes. The controlled movement of the optical head 18 provided by the translation stage 152 enables accurate direction of the output high power short optical pulses onto a target or specimen under test. The optical head 18 may alternatively be mounted on a mechanical manipulator such as a robotic arm.
It will be appreciated that the optical heads 18 of any of the previously described embodiments may be similarly movably mounted.
Various modifications may be made to the described embodiments without departing from the scope of the invention.
It will be appreciated that the master oscillator could alternatively comprise any optical source operable to generate short optical pulses, such as a solid-state modelocked laser, for example a Neodynium Vanadate laser, or a gain-switched laser diode. The amplifier fibres of the preamplifier and the high power optical fibre amplifier means may alternatively be doped with a different rare-earth dopant, such as Erbium, Thulium, or Neodynium.
In most applications, the pump source/s will be a multi-mode pump source operating at a suitable wavelength to pump the rare-earth-doped amplifier fibre (eg 808nm, 915nm or 975nm). For example, a single fibre-pigtailed laser diode, diode bar or multi-emitter pump source such as the PUMA source commercially supplied by Fianium Ltd, which delivers between 20 and 40W within a single, 105μm core, 0.22NA pump delivery fibre. Where multi-mode pump delivery fibres are used, the pump signal combiner will typically include a conventional tapered bundle, such as those commercially available from OFS or Sifam Fibre Optics. Alternatively, the pump signal combiner may be a tapered coupler, a side-pumping fibre configuration, or a distributed pump coupling fibre configuration such as that proposed in US 6,826,335. In the multi-mode pumping regime, the amplifier fibre typically comprises a double-clad fibre structure where the signal pulses are guided within a signal core and the pump light is guided within the fibre cladding.
Alternatively, the pump source/s can be a single mode pump source such as a fibre- pigtailed laser diode or a fibre laser. The fibre laser can be a Raman fibre laser or could be a cladding pumped fibre laser generating cw or pulsed radiation at the wavelength required to pump the rare-earth-doped amplifier fibre. In the single-mode pump regime, the signal pulses and pump light from the one or more pump sources are combined using conventional WDM components such as fused WDM couplers or thin-film WDM couplers.
In the single-mode pump regime, the amplifier fibre has a conventional single clad geometry, where both the signal pulses and the pump light propagate within the core of the amplifier fibre. This has benefits in increasing the pump absorption and thus reducing amplifier length and hence nonlinearity.
The optical head of any of the high power short optical pulse sources described may also include a heat sink and integrated fan within the high power optical fibre amplifier means, to provide forced-air cooling of the amplifier fibre. Optical monitoring means may also be provided within the optical head, with both electrical and optical communication to the first enclosure to monitor feedback and power levels, enabling interlocks and automatic fault detection.
The described embodiments provide various advantages, as follows.
The high power short optical pulse sources enable a short-length fibre amplifier system and post processing optics to be remotely located from the bulky, noisy heat producing elements of the pulse source, and thereby enable optical head to be very compact. The optical head can therefore be positioned close to the application space, taking up minimal space and avoiding the need for complex and expensive beam steering optics.
The high power short optical pulse sources enable the delivery of ultrashort (femtosecond) optical pulses with high energy and narrow spectral bandwidth, without the use of complex chirped pulse amplification (CPA) methods. In short optical pulse amplifier systems which don't incorporate CPA methods, it is essential that all fibre lengths which deliver or amplify pulses to high peak powers, are kept as short as physically possible; the structure and configuration of the high power short optical pulse sources ensures that this is achieved.
The high power short optical pulse sources incorporating a pulse compressor eliminate the need for CPA in fibre-delivered laser sources. Providing a high power ultrashort pulse source which is more robust, lower cost and easier to maintain and assemble than known ultrashort pulse sources using CPA pulse compression.
The high power short optical pulse sources further enable the delivery of UV optical pulses, efficiently generated within the optical head.
The high power short optical pulse sources also provide the advantage of beam delivery directly to the target without the use of complex beam steering optics. The high power short optical pulse sources therefore offer improved mechanical robustness, reduced cost and weight, and ease of maintenance over known high power optical pulse sources.
The high power short optical pulse sources also allow for scalability in power because they can incorporate multiple pump light sources in the remote pump enclosure and the pump delivered over long lengths with very low loss to the amplifier system which is remotely located whether within or close to the output optical head.

Claims

Claims
1. A high power short optical pulse source comprising: an optical signal source operable to output short optical pulses; an optical pump light source provided at a first location; an optical head provided at a second location remote from the first location; high power optical fibre amplifier means having at least its optical output located within the optical head; an optical signal delivery fibre arranged to deliver optical pulses from the optical signal source to the high power optical fibre amplifier means; and a pump light delivery fibre arranged to deliver optical pump light to the high power optical fibre amplifier means, wherein short optical pulses of a first optical power are delivered to the high power optical fibre amplifier means and are amplified therein to a second, high optical power for output from the optical head.
2. A high power short optical pulse source as claimed in claim 1 , wherein the optical signal source comprises a master oscillator optically coupled to an optical fibre preamplifier, comprising a preamplifier amplifier optical fibre and one or more preamplifier optical pump sources.
3. A high power short optical pulse source as claimed in claims 1 or 2, wherein the optical signal source is provided at the first location.
4. A high power short optical pulse source as claimed in claims 1 or 2, wherein the master oscillator and the preamplifier amplifier optical fibre are provided at a third location, intermediate the first and second locations, with the or each preamplifier optical pump source being provided at the first location and being coupled to the preamplifier amplifier optical fibre via a corresponding one or more preamplifier pump delivery fibres.
5. A high power short optical pulse source as claimed in any preceding claim, wherein a plurality of optical pump light sources are provided at the first location and a corresponding plurality of pump light delivery fibres.
6. A high power short optical pulse source as claimed in any preceding claim, wherein the high power optical fibre amplifier means comprises an amplifier optical fibre and one or more pump signal combiners.
7. A high power short optical pulse source as claimed in claim 6, wherein the high power short optical pulse source comprises a plurality of high power optical fibre amplifier means optically coupled in series, at least the optical output of the final high power optical fibre amplifier means being located within the optical head.
8. A high power short optical pulse source as claimed in claim 6 or 7, wherein the or each amplifier optical fibre is located within the optical head.
9. A high power short optical pulse source as claimed in claim 8, wherein the or each pump signal combiner is located within the optical head.
10. A high power short optical pulse source as claimed in claim 8, wherein the or each pump signal combiner is located at the first location, with the high power optical fibre amplifier means additionally comprising a pump signal delivery fibre optically coupled between the or each pump signal combiner and the or each amplifier optical fibre.
11. A high power short optical pulse source as claimed in claim 6, wherein the amplifier optical fibre is arranged to extend from the first location to the optical head and comprises a double-clad amplifier optical fibre.
12. A high power short optical pulse source as claimed in claim 11 , wherein the or a pump signal combiner is provided at the first location, arranged to couple optical pulses and pump light into one end of the amplifier optical fibre.
13. A high power short optical pulse source as claimed in claims 11 or 12, wherein the or a pump signal combiner is provided within the optical head, arranged to couple pump light into the signal output end of the amplifier optical fibre.
14. A high power short optical pulse source as claimed in any of claims 6 to 13, wherein the high power optical fibre amplifier means further comprises a bulk optic amplifier element optically coupled to the output end of the or the final amplifier optical fibre, said amplifier optical fibre being under-length such that a proportion of any pump light coupled into said amplifier optical fibre is unabsorbed by it, and serves to pump the bulk optic amplifier element.
15. A high power short optical pulse source as claimed in any preceding claim, wherein the high power short optical pulse source further comprises nonlinear optical frequency conversion means optically coupled to the output of the or the final high power optical fibre amplifier means.
16. A high power short optical pulse source as claimed in any preceding claim, wherein the high power short optical pulse source comprises an optical pulse compressor optically coupled to the output of the or the final high power optical fibre amplifier means or the nonlinear optical frequency conversion means.
17. A high power short optical pulse source as claimed in claim 16, wherein the optical pulse compressor comprises a transmission grating pair or photonic crystal fibre having anomalous dispersion at the signal wavelength.
18. A high power short optical pulse source as claimed in any preceding claim, wherein the high power short optical pulse source further comprises a pulse picker operable to reduce the optical pulse frequency.
19. A high power short optical pulse source as claimed in any preceding claim, wherein the high power short optical pulse source further comprises optical monitoring means within the optical head.
20. A high power short optical pulse source as claimed in any preceding claim, wherein the optical head is movably mounted to enable accurate direction of generated high power short optical pulses onto a target or specimen under test.
21. A high power short optical pulse source as claimed in claim 20, wherein the optical head is mounted on a translation stage or a mechanical manipulator, such as a robotic arm.
22. A high power short optical pulse source substantially as described above with reference to the accompanying drawings.
PCT/GB2007/000136 2006-01-20 2007-01-18 High power short optical pulse source WO2007083110A1 (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
JP2008550837A JP2009524232A (en) 2006-01-20 2007-01-18 High power short optical pulse source
EP07700401.8A EP1979997B1 (en) 2006-01-20 2007-01-18 High power short optical pulse source
US12/087,850 US8379298B2 (en) 2006-01-20 2007-01-18 High power short optical pulse source
US13/523,723 US8593726B2 (en) 2006-01-20 2012-06-14 Methods and apparatus for producing short optical pulses
US13/797,640 US8902496B2 (en) 2006-01-20 2013-03-12 Source of optical pulses
US13/797,665 US8724215B2 (en) 2006-01-20 2013-03-12 Optical pulse source
US13/796,966 US8767287B2 (en) 2006-01-20 2013-03-12 Optical pulse apparatus and method
US14/556,746 US9287677B2 (en) 2006-01-20 2014-12-01 Hybrid optical pulse source
US15/017,605 US11038316B2 (en) 2006-01-20 2016-02-06 Optical pulse source apparatus with nonlinear fibre and operable to reduce the optical pulse frequency of optical output pulses

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0601154A GB2434483A (en) 2006-01-20 2006-01-20 High-Power Short Optical Pulse Source
GB0601154.8 2006-01-20

Related Child Applications (2)

Application Number Title Priority Date Filing Date
US12/087,850 A-371-Of-International US8379298B2 (en) 2006-01-20 2007-01-18 High power short optical pulse source
US13/523,723 Continuation US8593726B2 (en) 2006-01-20 2012-06-14 Methods and apparatus for producing short optical pulses

Publications (1)

Publication Number Publication Date
WO2007083110A1 true WO2007083110A1 (en) 2007-07-26

Family

ID=36010652

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2007/000136 WO2007083110A1 (en) 2006-01-20 2007-01-18 High power short optical pulse source

Country Status (5)

Country Link
US (7) US8379298B2 (en)
EP (1) EP1979997B1 (en)
JP (2) JP2009524232A (en)
GB (1) GB2434483A (en)
WO (1) WO2007083110A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110122895A1 (en) * 2009-11-23 2011-05-26 Lockheed Martin Corporation Q-switched oscillator seed-source for mopa laser illuminator method and apparatus
EP2540434A1 (en) 2011-06-28 2013-01-02 Trumpf Laser Marking Systems AG Laser system with an electro-optical connection element
US9531153B2 (en) 2008-01-19 2016-12-27 Fianium Ltd. Apparatus and method for the generation of supercontinuum pulses
WO2023063415A1 (en) * 2021-10-14 2023-04-20 Atonarp Inc. System including a laser module

Families Citing this family (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2434483A (en) 2006-01-20 2007-07-25 Fianium Ltd High-Power Short Optical Pulse Source
AU2008268087B2 (en) * 2007-06-27 2012-09-06 Fujikura Ltd. Fiber laser having superior resistance to reflection light
US20110069376A1 (en) * 2009-09-23 2011-03-24 Coherent Inc. Fiber mopa with amplifying transport fiber
DE102009056092B4 (en) * 2009-11-30 2013-02-28 PicoQuant GmbH. Unternehmen für optoelektronische Forschung und Entwicklung Light source with a diode laser
US8351113B2 (en) * 2010-09-02 2013-01-08 Textron Systems Corporation High power fiber laser system
FR2971640B1 (en) * 2011-02-16 2014-04-04 Univ Bordeaux 1 OPTICAL PUMPING DEVICE.
JP6063875B2 (en) 2011-02-24 2017-01-18 エキシモ メディカル リミテッド Hybrid catheter for tissue resection
JP2012234978A (en) * 2011-05-02 2012-11-29 Omron Corp Laser irradiation device and laser machining device
EP2756562A4 (en) * 2011-09-14 2015-06-17 Fianium Inc Methods and apparatus pertaining to picosecond pulsed fiber based lasers
GB2511043B (en) * 2013-02-20 2016-03-23 Fianium Ltd A supercontinuum source
WO2014138433A1 (en) * 2013-03-06 2014-09-12 Ipg Photonics Corporation Ultra high power single mode fiber laser system with non-uniformly configured fiber-to-fiber rod multimode amplifier
US9806487B2 (en) * 2013-03-13 2017-10-31 Nufern Optical fiber system having a remote power module
DE102013102880B4 (en) 2013-03-21 2016-09-15 Laserline Gesellschaft für Entwicklung und Vertrieb von Diodenlasern mbH laser assembly
DE102013102891B4 (en) 2013-03-21 2016-09-15 Laserline Gesellschaft für Entwicklung und Vertrieb von Diodenlasern mbH laser assembly
EP3058628B1 (en) * 2013-10-14 2021-09-29 Ram Photonics, LLC Method and apparatus for generating high power laser light
CN103647211A (en) * 2013-12-24 2014-03-19 中国科学院半导体研究所 Optoelectronic oscillator based optical pulse generation device
FR3018144B1 (en) * 2014-02-28 2017-05-19 Thales Sa HYBRID OPTICAL AMPLIFICATION DEVICE
US20170079718A1 (en) 2014-05-18 2017-03-23 Eximo Medical Ltd. System for tissue ablation using pulsed laser
DK3266078T3 (en) * 2015-03-05 2022-03-07 Nufern PROCEDURE AND APPLIANCE FOR PROVIDING AMPLIFIED RADIATION
CN106159649A (en) * 2015-03-27 2016-11-23 深圳激扬光电有限公司 A kind of separation amplifying fiber Optical Maser System
CN109414292A (en) 2016-05-05 2019-03-01 爱克斯莫医疗有限公司 Device and method for cutting off and/or melting unwanted tissue
CN108493747A (en) * 2018-03-12 2018-09-04 中国科学院上海光学精密机械研究所 2 μm of high-energy pure-tone pulse lasers based on optical fiber solid Cascaded amplification
CN108957250B (en) * 2018-04-10 2021-05-25 西安理工大学 Multi-path diversity power line corona detection system and method carried by unmanned aerial vehicle
GB201913629D0 (en) * 2019-09-20 2019-11-06 Alltec Angewandte Laserlicht Tech Gmbh Electromagnetic radiation system
US20210305763A1 (en) * 2020-03-24 2021-09-30 David Stucker Composite fiber laser assembly
WO2024027938A1 (en) * 2022-08-03 2024-02-08 Das-Nano Tech, S.L. Delivering high-power laser pulses

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6275250B1 (en) * 1998-05-26 2001-08-14 Sdl, Inc. Fiber gain medium marking system pumped or seeded by a modulated laser diode source and method of energy control
US6373623B1 (en) * 1997-10-17 2002-04-16 Fujitsu Limited Optical amplifier for use in optical communications equipment
EP1564853A2 (en) * 2004-02-11 2005-08-17 FITEL USA CORPORATION (a Delaware Corporation) Fiber amplifier for generating femtosecond pulses in single mode fiber
WO2005081430A2 (en) * 2004-01-24 2005-09-01 Fianium Ltd Apparatus and method for the delivery of high-energy ultra-short optical pulses from a fibre amplifier

Family Cites Families (100)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4647330A (en) * 1985-10-01 1987-03-03 The United States Of America As Represented By The Secretary Of The Air Force Hybrid single crystal optic fibers by growth solution
US4784716A (en) * 1985-11-06 1988-11-15 The United States Of America As Represented By The Secretary Of The Air Force Hybrid single crystal optic fibers by embedding
GB8803450D0 (en) * 1988-02-15 1988-03-16 British Telecomm Optical frequency mixer
GB8927697D0 (en) * 1989-12-07 1990-02-07 British Telecomm Second harmonic generation in optical fibres
US5076658A (en) * 1990-04-30 1991-12-31 Unisys Corporation Non-linear optical polymeric fiber waveguides
JPH05104266A (en) * 1991-05-16 1993-04-27 Nikon Corp Laser beam machine
US5222181A (en) * 1992-07-01 1993-06-22 The United States Of America As Represented By The Secretary Of The Navy Fraunhofer line laser transmitting system
US5323404A (en) * 1993-11-02 1994-06-21 At&T Bell Laboratories Optical fiber laser or amplifier including high reflectivity gratings
JPH07142798A (en) * 1993-11-17 1995-06-02 Fujitsu Ltd Optical fiber amplifier
US5440576A (en) * 1994-04-18 1995-08-08 Sdl, Inc. Branched MOPA device with phased array of amplifiers
DE69634021T2 (en) 1995-02-24 2005-12-15 Nippon Telegraph And Telephone Corp. Coherent white light source and optical devices with the same
US5822486A (en) * 1995-11-02 1998-10-13 General Scanning, Inc. Scanned remote imaging method and system and method of determining optimum design characteristics of a filter for use therein
US5867305A (en) * 1996-01-19 1999-02-02 Sdl, Inc. Optical amplifier with high energy levels systems providing high peak powers
US5847863A (en) * 1996-04-25 1998-12-08 Imra America, Inc. Hybrid short-pulse amplifiers with phase-mismatch compensated pulse stretchers and compressors
US6249630B1 (en) * 1996-12-13 2001-06-19 Imra America, Inc. Apparatus and method for delivery of dispersion-compensated ultrashort optical pulses with high peak power
US5880877A (en) * 1997-01-28 1999-03-09 Imra America, Inc. Apparatus and method for the generation of high-power femtosecond pulses from a fiber amplifier
EP1658663A4 (en) * 1997-03-21 2009-11-11 Imra America Inc High energy optical fiber amplifier for picosecond-nanosecond pulses for advanced material processing applications
US6181463B1 (en) * 1997-03-21 2001-01-30 Imra America, Inc. Quasi-phase-matched parametric chirped pulse amplification systems
US6160568A (en) * 1997-05-27 2000-12-12 Sdl, Inc. Laser marking system and method of energy control
US6030398A (en) * 1997-05-30 2000-02-29 Summit Technology, Inc. Surgical microtomes
US5966391A (en) * 1997-06-27 1999-10-12 Mcdonnell Douglas Corporation Long cavity laser system including frequency doubling long cavity fiber optic laser system
US5946130A (en) * 1997-10-03 1999-08-31 Mcdonnell Douglas Corporation Optical fiber amplifier network having a coherently combined output and high-power laser amplifier containing same
US6049415A (en) * 1997-12-08 2000-04-11 Sdl, Inc. Polarization maintaining fiber lasers and amplifiers
CN100578876C (en) * 1998-03-11 2010-01-06 株式会社尼康 Ultraviolet laser apparatus, and exposure apparatus and mehtod using ultraviolet laser apparatus
US6620180B1 (en) * 1998-09-09 2003-09-16 Medtronic Xomed, Inc. Powered laryngeal cutting blade
JP3390755B2 (en) * 1998-09-29 2003-03-31 科学技術振興事業団 Wavelength tunable short pulse light generating apparatus and method
US6381391B1 (en) * 1999-02-19 2002-04-30 The Regents Of The University Of Michigan Method and system for generating a broadband spectral continuum and continuous wave-generating system utilizing same
JP2000261077A (en) * 1999-03-09 2000-09-22 Mitsubishi Electric Corp Optical circuit
JP3411852B2 (en) * 1999-05-31 2003-06-03 サンクス株式会社 Laser marking device
US6307667B1 (en) 1999-12-02 2001-10-23 Tycom (Us) Inc. Gain-clamped erbium-doped fiber amplifier with pulsed compensating laser signal
US6340806B1 (en) * 1999-12-28 2002-01-22 General Scanning Inc. Energy-efficient method and system for processing target material using an amplified, wavelength-shifted pulse train
US20040134894A1 (en) * 1999-12-28 2004-07-15 Bo Gu Laser-based system for memory link processing with picosecond lasers
JP5123456B2 (en) * 2000-01-10 2013-01-23 エレクトロ サイエンティフィック インダストリーズ インコーポレーテッド Laser cutting method and laser system for conductive link
US6690463B2 (en) 2000-02-10 2004-02-10 Evotec Biosystems Ag Fluorescence intensity and lifetime distribution analysis
US7394591B2 (en) 2000-05-23 2008-07-01 Imra America, Inc. Utilization of Yb: and Nd: mode-locked oscillators in solid-state short pulse laser systems
US7190705B2 (en) 2000-05-23 2007-03-13 Imra America. Inc. Pulsed laser sources
US6885683B1 (en) * 2000-05-23 2005-04-26 Imra America, Inc. Modular, high energy, widely-tunable ultrafast fiber source
JP2001347387A (en) * 2000-06-09 2001-12-18 Ishikawajima Harima Heavy Ind Co Ltd Laser beam machining head
DE20122782U1 (en) 2000-06-17 2007-11-15 Leica Microsystems Cms Gmbh lighting device
US6687000B1 (en) 2000-06-26 2004-02-03 Wisconsin Alumni Research Foundation Photon-sorting spectroscopic microscope system
US6490081B1 (en) * 2000-07-28 2002-12-03 The Board Of Trustees Of The Leland Stanford Junior University Method of amplifying optical signals using doped materials with extremely broad bandwidths
JP3761567B2 (en) * 2000-09-13 2006-03-29 浜松ホトニクス株式会社 Laser processing method
AU2002211459A1 (en) * 2000-10-06 2002-04-15 The Johns Hopkins University A compact, highly efficient and rugged uv source based on fiber laser
DE10100857B4 (en) * 2001-01-11 2006-05-18 Carl Zeiss Jena Gmbh Laser slit lamp with laser radiation source
JP2002229080A (en) * 2001-01-30 2002-08-14 Furukawa Electric Co Ltd:The Optical pulse waveform converter and optical pulse light source having the same
US6954575B2 (en) * 2001-03-16 2005-10-11 Imra America, Inc. Single-polarization high power fiber lasers and amplifiers
EP1288705A3 (en) * 2001-08-28 2005-03-02 Nippon Telegraph and Telephone Corporation Wavelength tunable light source and pulse light source
GB2385460B (en) 2002-02-18 2004-04-14 Univ Southampton "Pulsed light sources"
JP4021680B2 (en) * 2002-02-22 2007-12-12 サンクス株式会社 Laser processing equipment
DE10228374A1 (en) 2002-06-25 2004-01-15 Leica Microsystems Heidelberg Gmbh Microscopy method and microscope
JP4397567B2 (en) * 2002-07-05 2010-01-13 富士通株式会社 Optical AND gate and waveform shaping device
US6775447B2 (en) 2002-09-20 2004-08-10 Fitel Usa Corp. All fiber low noise supercontinuum source
US7103076B2 (en) * 2002-10-24 2006-09-05 Matsushita Electric Industrial Co., Ltd. Ultrashort pulsed laser and optical head using the same
DE10251345B4 (en) * 2002-11-05 2006-08-17 Leica Microsystems Cms Gmbh Method and device for examining layers of tissue in living animals with a microscope
US7046432B2 (en) * 2003-02-11 2006-05-16 Coherent, Inc. Optical fiber coupling arrangement
US7218443B2 (en) * 2003-02-25 2007-05-15 Toptica Photonics Ag Generation of tunable light pulses
US7224518B2 (en) * 2003-02-25 2007-05-29 Toptica Photonics Ag Fiber-optic amplification of light pulses
US6839489B2 (en) * 2003-03-11 2005-01-04 Advr, Inc. Micro-electrodes for electro-optic control of optical waveguides
JP4445217B2 (en) * 2003-03-14 2010-04-07 サンクス株式会社 Laser marking device
US7330301B2 (en) * 2003-05-14 2008-02-12 Imra America, Inc. Inexpensive variable rep-rate source for high-energy, ultrafast lasers
US7257302B2 (en) * 2003-06-03 2007-08-14 Imra America, Inc. In-line, high energy fiber chirped pulse amplification system
US7414780B2 (en) * 2003-06-30 2008-08-19 Imra America, Inc. All-fiber chirped pulse amplification systems
US20040252733A1 (en) * 2003-06-16 2004-12-16 Zhenguo Huang Apparatus and method for laser frequency doubler utilizing PPLN waveguide
DE10340964A1 (en) 2003-09-05 2005-03-31 Leica Microsystems Heidelberg Gmbh Light source with a microstructured optical element
GB0328370D0 (en) * 2003-12-05 2004-01-14 Southampton Photonics Ltd Apparatus for providing optical radiation
ATE499174T1 (en) * 2003-12-10 2011-03-15 Vietz Gmbh ORBITAL WELDING DEVICE FOR PIPELINE CONSTRUCTION
JP2005192046A (en) 2003-12-26 2005-07-14 Fujitsu Ltd Pulse generation apparatus and method
EP1812823A4 (en) 2004-03-25 2009-08-05 Imra America Inc Optical parametric amplification, optical parametric generation, and optical pumping in optical fibers systems
US7139294B2 (en) * 2004-05-14 2006-11-21 Electro Scientific Industries, Inc. Multi-output harmonic laser and methods employing same
US20050265407A1 (en) 2004-05-14 2005-12-01 Braun Alan M Compact semiconductor-based chirped-pulse amplifier system and method
US20050280892A1 (en) * 2004-05-28 2005-12-22 Nobuyuki Nagasawa Examination method and examination apparatus
JP2005347338A (en) 2004-05-31 2005-12-15 Sunx Ltd Laser beam machining device
WO2005119328A1 (en) 2004-06-03 2005-12-15 University Of Strathclyde Improved scanning microscope source
JP3920297B2 (en) * 2004-09-01 2007-05-30 富士通株式会社 Optical switch and optical waveform monitoring device using optical switch
US7508853B2 (en) 2004-12-07 2009-03-24 Imra, America, Inc. Yb: and Nd: mode-locked oscillators and fiber systems incorporated in solid-state short pulse laser systems
US7301981B2 (en) * 2004-12-09 2007-11-27 Electro Scientific Industries, Inc. Methods for synchronized pulse shape tailoring
EP1720223A1 (en) 2005-05-07 2006-11-08 Aarhus Universitet Environmentally stable self-starting mode-locked waveguide laser and a method of generating mode-locked laser pulses
US7787729B2 (en) * 2005-05-20 2010-08-31 Imra America, Inc. Single mode propagation in fibers and rods with large leakage channels
US7909817B2 (en) * 2005-06-08 2011-03-22 Innovaquartz, Inc. (AMS Research Corporation) Lateral laser fiber for high average power and peak pulse energy
GB2434483A (en) * 2006-01-20 2007-07-25 Fianium Ltd High-Power Short Optical Pulse Source
WO2007083660A1 (en) * 2006-01-20 2007-07-26 Sumitomo Electric Industries, Ltd. Light source device
US9130344B2 (en) * 2006-01-23 2015-09-08 Raydiance, Inc. Automated laser tuning
US7443903B2 (en) * 2006-04-19 2008-10-28 Mobius Photonics, Inc. Laser apparatus having multiple synchronous amplifiers tied to one master oscillator
US20070263680A1 (en) * 2006-05-15 2007-11-15 Andrei Starodoumov MOPA laser apparatus with two master oscillators for generating ultraviolet radiation
US7813035B2 (en) * 2006-05-18 2010-10-12 Polaronyx, Inc. Nonlinearity and dispersion management for pulse reshaping in high energy fiber amplifier
US20090185583A1 (en) * 2006-06-02 2009-07-23 Corning Incorporated UV and Visible Laser Systems
US7529281B2 (en) * 2006-07-11 2009-05-05 Mobius Photonics, Inc. Light source with precisely controlled wavelength-converted average power
US7469081B2 (en) * 2006-09-01 2008-12-23 Mobius Photonics, Inc. Reducing thermal load on optical head
US7773294B2 (en) * 2007-08-13 2010-08-10 Institut National D'optique Low-average-power parabolic pulse amplification
EP2223396B1 (en) * 2007-12-18 2018-09-12 NKT Photonics A/S Mode-locked fiber laser with improved life-time of saturable absorber
GB0800936D0 (en) 2008-01-19 2008-02-27 Fianium Ltd A source of optical supercontinuum generation having a selectable pulse repetition frequency
US20090273828A1 (en) * 2008-04-30 2009-11-05 Raydiance, Inc. High average power ultra-short pulsed laser based on an optical amplification system
EP2194621A3 (en) * 2008-11-15 2013-02-13 TOPTICA Photonics AG Generation of tunable light pulses
US8730570B2 (en) * 2009-07-01 2014-05-20 Calmar Optcom, Inc. Optical pulse compressing based on chirped fiber bragg gratings for pulse amplification and fiber lasers
US8830567B2 (en) * 2009-07-01 2014-09-09 Calmar Optcom, Inc. Fiber lasers for producing amplified laser pulses with reduced non-linearity
FR2950443B1 (en) * 2009-09-22 2011-11-18 Draka Comteq France OPTICAL FIBER FOR SUM FREQUENCY GENERATION AND METHOD FOR MANUFACTURING THE SAME
US20110069376A1 (en) * 2009-09-23 2011-03-24 Coherent Inc. Fiber mopa with amplifying transport fiber
US9166355B2 (en) * 2011-09-12 2015-10-20 Lawrence Livermore National Security, Llc Directly driven source of multi-gigahertz, sub-picosecond optical pulses
EP2756562A4 (en) * 2011-09-14 2015-06-17 Fianium Inc Methods and apparatus pertaining to picosecond pulsed fiber based lasers
EP2982012A2 (en) * 2013-04-02 2016-02-10 Electro Scientific Industries, Inc. Apparatus and method for generating ultrashort laser pulses

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6373623B1 (en) * 1997-10-17 2002-04-16 Fujitsu Limited Optical amplifier for use in optical communications equipment
US6275250B1 (en) * 1998-05-26 2001-08-14 Sdl, Inc. Fiber gain medium marking system pumped or seeded by a modulated laser diode source and method of energy control
WO2005081430A2 (en) * 2004-01-24 2005-09-01 Fianium Ltd Apparatus and method for the delivery of high-energy ultra-short optical pulses from a fibre amplifier
EP1564853A2 (en) * 2004-02-11 2005-08-17 FITEL USA CORPORATION (a Delaware Corporation) Fiber amplifier for generating femtosecond pulses in single mode fiber

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
LIMPERT J ET AL: "High-power femtosecond fiber laser systems", PROCEEDINGS OF THE SPIE, SPIE, BELLINGHAM, VA, US, vol. 4978, no. 1, 2003, pages 6 - 20, XP002361181, ISSN: 0277-786X *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9531153B2 (en) 2008-01-19 2016-12-27 Fianium Ltd. Apparatus and method for the generation of supercontinuum pulses
US9570878B2 (en) 2008-01-19 2017-02-14 Fianium Ltd. Method and apparatus for providing supercontinuum pulses
US10074957B2 (en) 2008-01-19 2018-09-11 Nkt Photonics A/S Variable repetition rate supercontinuum pulses
US20110122895A1 (en) * 2009-11-23 2011-05-26 Lockheed Martin Corporation Q-switched oscillator seed-source for mopa laser illuminator method and apparatus
US8934509B2 (en) * 2009-11-23 2015-01-13 Lockheed Martin Corporation Q-switched oscillator seed-source for MOPA laser illuminator method and apparatus
EP2540434A1 (en) 2011-06-28 2013-01-02 Trumpf Laser Marking Systems AG Laser system with an electro-optical connection element
WO2023063415A1 (en) * 2021-10-14 2023-04-20 Atonarp Inc. System including a laser module

Also Published As

Publication number Publication date
US11038316B2 (en) 2021-06-15
JP2014090196A (en) 2014-05-15
US8767287B2 (en) 2014-07-01
US8902496B2 (en) 2014-12-02
EP1979997B1 (en) 2015-06-17
GB0601154D0 (en) 2006-03-01
US9287677B2 (en) 2016-03-15
US8724215B2 (en) 2014-05-13
US20150131144A1 (en) 2015-05-14
US8593726B2 (en) 2013-11-26
EP1979997A1 (en) 2008-10-15
US20140092925A1 (en) 2014-04-03
JP2009524232A (en) 2009-06-25
US20130271824A1 (en) 2013-10-17
US8379298B2 (en) 2013-02-19
US20120268808A1 (en) 2012-10-25
US20100157419A1 (en) 2010-06-24
JP6014579B2 (en) 2016-10-25
GB2434483A (en) 2007-07-25
US20140104677A1 (en) 2014-04-17
US20160276800A1 (en) 2016-09-22

Similar Documents

Publication Publication Date Title
EP1979997B1 (en) High power short optical pulse source
US7537395B2 (en) Diode-laser-pump module with integrated signal ports for pumping amplifying fibers and method
JP5185929B2 (en) Fiber laser
EP2430716B1 (en) Cascaded raman fiber laser system based on filter fiber
US8369004B2 (en) MOPA light source
US9472919B2 (en) Generation of narrow line width high power optical pulses
US9667021B2 (en) Phosphate photonic crystal fiber and converter for efficient blue generation
Hemming et al. Development of resonantly cladding-pumped holmium-doped fibre lasers
JP5980909B2 (en) High power single mode fiber laser system operating in the 2μm range
WO2005081430A2 (en) Apparatus and method for the delivery of high-energy ultra-short optical pulses from a fibre amplifier
CN113258419A (en) Picosecond seed laser based on full-large mode field optical fiber
CN105896255A (en) Adjustable picosecond solid laser system
Paschotta High-power Fiber Lasers and Amplifiers
Lange et al. Fully integrated Q-switch for commercial high-power resonator with solitary XLMA-fiber
EP2517317A1 (en) Laser system for the marking of metallic and non-metallic materials
Gaida et al. Peak power scaling in Tm doped fiber lasers to MW-level
Di Teodoro et al. Multi-mJ energy, multi-MW peak-power photonic crystal fiber amplifiers with near-diffraction-limited output
Kadwani et al. CW and pulsed performance of Tm-doped photonic crystal fiber lasers
Madasamy et al. High peak power Yb-doped diode pumped fiber amplifier system
Kaczmarek et al. Universal all in fiber coherent light source at the wavelength 1550 nm and output power 5 W
Liu et al. Nanosecond pulse passively Q-switched Yb-doped fiber laser with Cr4+: YAG as saturable absorber

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application
WWE Wipo information: entry into national phase

Ref document number: 2008550837

Country of ref document: JP

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2007700401

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 12087850

Country of ref document: US