WO1995029277A1

WO1995029277A1 - Process for producing micro-optical elements or a fibre end in the form of a micro-optical element, and the use of such elements

Info

Publication number: WO1995029277A1
Application number: PCT/EP1995/001560
Authority: WO
Inventors: Lukas KÜPPER; Leonid Butvina
Original assignee: Kuepper Lukas; Leonid Butvina
Priority date: 1994-04-26
Filing date: 1995-04-25
Publication date: 1995-11-02
Also published as: DE4414552C2; DE4414552A1; AU2407795A

Abstract

The invention concerns a process for producing micro-optical elements or a fibre end in the form of a micro-optical element, a base material being shaped to form the required micro-optical element. As a process by which elements can be produced and reproduced in larger batches, are transparent with low loss levels over a greater (i.e. wider band) spectral range than prior art elements, are not restricted in their possible surface geometry and are inexpensive to manufacture, a crystalline or polycrystalline fibre or section thereof which is substantially absorption-free in the spectral range 0.4 - 30 νm and is produced from a base material of a solid solution, is shaped to produce micro-optical elements with that spectral range. The invention also concerns advantageous uses and applications of the disclosed micro-optical elements.

Description

P a t e n t a n m e l d n n

"Process for the production of micro-optical elements or a fiber end in the form of a micro-optical element and use of such elements"

The present invention relates to methods for producing micro-optical elements or a fiber end in the form of a micro-optical element, a starting material being brought into a shape of the micro-optical element. The invention further relates to the use of such elements.

A method of the type described above is specified in EP-AI 0567896. This patent application describes, inter alia, the production of a micro-optical element, wherein a carrier made of a ceramic-metal composite material is first provided, on one side of which a layer is applied which has a negative shape with respect to one half of the lens to be produced. This layer is then coated on its upper side with various alloy layers and with a final protective layer, which is said to have the property not to bond with glass. According to the microlens to be manufactured, for example a Fresnel lens, a second, negative one Mold half are made, which is used to form the other half of the lens. These two forms are then clamped in a press arrangement. A thin glass plate is inserted into the mold, then the glass plate is heated above its softening temperature and the pressure mold halves are moved toward one another under pressure, so that the glass fills the cavity of the mold. After cooling, the glass lens is removed from the mold. An essential problem that this document deals with is the avoidance of the glass sticking to the press mold, for which purpose various intermediate and protective layers are applied to the molds in each case. These protective layers are made, for example, from an alloy of the platinum group. By applying the protective layers, the method is complex, moreover it cannot be avoided that the material of the protective layer nevertheless connects to the lens material or adheres to the pressed lens. Glasses are used as the starting material. Their transparency is restricted to a narrower spectral range than the transparency of crystalline materials. Furthermore, transparent glasses in the far infrared have a very low softening temperature and crystallize very easily when heated by, for example, laser radiation, which destroys their optical transparency. Eg Ge ₀ As ₅₀ Te ₄₀ glass is transparent in the spectral range 1.6 / 25 / Um and has a freezing temperature of only 170 ^β C (see: E. Hartouni; F. Huldermann and T. Guiton, SPIE Proceedings 505 (1984 ), Pages 131-140). Crystalline Csl, on the other hand, is transparent in the spectral range 0.25 ... 80 µm and has a melting point of 62TC (see: AL Gentile, M. Braunstein, DA Pinnow, JA Harrongton "Infrared Fiber Optical Materials" in Fiber Optics : Advances in Research and Development, ed. By B. Bendow and SS Mitra, Plemun Publishing, NY (1979) pages 105-108).

Furthermore, US Pat. No. 5,080,706 describes a method for producing cylindrical microlenses with an elliptical or hyperbolic cross-sectional shape. According to this method, a glass preform is first produced, the cross-sectional contours of which correspond to the cross-sectional contour of the microlens to be produced. This preform is then heated until it becomes viscous. Then from this preform stripped thin fibers, the cross-sectional shape of the stripped fibers correlating directly to the cross-sectional shape of the preform. The drawn fiber is then divided into individual, cylindrical microlenses. The material used for the lenses is one which has a sufficient viscosity so that the fiber with a reduced, congruent cross section can be removed from the preform. No further statements are made about the starting material to be used for the production of this lens. By pulling off the preform, only individual cylindrical lenses can be produced. Furthermore, microlenses which are produced directly from drawn glass fibers by dividing them into individual sections are severely restricted in their radiation transparency compared to crystalline fibers.

In general, various crystalline lenses, prisms, windows, etc. that are transparent in the infrared are available on the market. These optical components are made of materials such as ZnSe, ZnS, Al-O- ,, CdTe, Si, BaF ₂ , KRS-6, KRS-5, Csl, AgCl, AgBr, NaCl, NaI, KCL, KBr, CsCl, KI and CsBr made in the form of plates or blocks. Such materials are offered, for example, by the product information "Precision Optical Components" from LOT GmbH. Plano-convex, biconvex or biconcave, plano-concave and meniscus lenses with diameters in the range of at least 10 mm are available from the above materials.

It has been shown that the reproducible quality of the known lenses decreases sharply as the diameter becomes smaller.

Furthermore, processes for the production of microlenses based on Si and S ^ have also become established in recent years, in which etching techniques or photolithographic techniques are used. The transparency of these lenses made of crystalline SiO ₂ quartz is limited to the narrow spectral range from 0.15 to 4 µm and for pure Si to the narrow spectral range from approximately 1.2 to 8.5 µm and to spherical geometries. Si microlens arrays in particular are used as thermographic systems. Microlens systems with transparency in the spectral A range above 8.5 µm is required for sensors in the room temperature range and below.

On the basis of the prior art specified above, the present invention is based on the object of specifying a method for producing micro-optical elements or a fiber end in the form of a micro-optical element, with which elements can be produced which can also be reproduced in large batches which are transparent over a larger or broadband spectral range compared to the prior art with low losses, which are not limited in their surface geometry and which are inexpensive to produce. Furthermore, the invention is concerned with advantageous uses of the micro-optical elements.

The above objects are achieved according to the method of the invention, starting from the prior art specified at the outset, in that for the production of micro-optical elements with a spectral range from 0.4 to 30, around a crystalline or polycrystalline fiber or a Portion thereof, which is substantially absorption-free in this spectral range, which is made of a solid solution raw material, is molded. The fact that, according to the method, crystalline or polycrystalline fibers are provided, which are then divided into individual sections before or after a shaping process step in order to produce the micro-optical elements, reproducible results can be achieved with regard to their transparency between the individual micro-optical elements produced. This is due in particular to the fact that the starting material is first transformed into a fiber and a starting material is obtained which contains non-aligned microcrystallites whose size is approximately in the range from 0.1 .mu.m to 0.5 .mu.m lie. In contrast to crystalline or polycrystalline material in the form of blocks or plates, a large number of additional dislocation lines with an isotropic orientation are generated via the manufacturing process of the fiber or the fiber section or via the shaping process the small size of the microcrystallites is responsible. Due to the very fine microcrystallite structure with a large number of isotropically distributed dislocation lines in the fiber or the fiber section, the starting material is dynamically recrystallized on a length scale of less than 0.1 .mu.m when it is shaped into the micro-optical element. This results in reproducible, optical surfaces whose roughness is one to two orders of magnitude lower than surfaces which are produced with the same shaping process on block or plate-shaped starting material. The scattering of the radiation on the surface of the micro-optical element made of crystalline or polycrystalline fibers or fiber sections is therefore much smaller, which in turn means lower radiation losses and a broad spectral transparency of the micro-optical elements between 0.4 .mu.m and 30 to bring with it.

The fact that reproducible results can be achieved with the individual microlenses produced, which are produced in accordance with the method according to the invention, makes it possible to meet high quality requirements, so that, for example, final checks are not necessary as part of a quality assurance which would otherwise be necessary to sort out lenses that do not meet the specified specification. Furthermore, by providing fibers as the starting material for the production of micro-optical elements, process engineering advantages such as e.g. a high production rate, lower material losses and fewer work steps can be achieved. Furthermore, the material used in the process is suitable for being processed both in the pressing process and in machining.

For example, the following values can be achieved with the specified fibers to be used according to the method, for example from a solid AgBr-Agl solution:

Spectral pass band of a fiber with a diameter of 0.7 mm and a length of 4 m: 3 - 30 »um Spectral pass band of a fiber section with a diameter of 0.7 mm and a length of 5 cm: 0.4 - 30 µm attenuation at 10.6 µm: 0.1 - 0.5 dB / m attenuation at 5-6 µm: <0.7 dB / m

A solid solution with a cubic crystal structure is preferably brought into the mold as the starting material. Such solid solutions with a cubic crystal structure are characterized by the fact that these materials are optically isotropic, i.e. the refractive index is the same in all directions.

Furthermore, the use of solid solutions improves the mechanical properties, such as flexibility, strength or sensitivity to corrosion of the fiber, and extends the spectral transmission. For example, by increasing the concentration of AgI in a solid solution of AgBr-Agl, the transmission in the visible spectral range is improved and the UV sensitivity is reduced.

Fibers or fiber sections with a diameter between 50 .mu.m and 3 mm are preferably provided, depending on the dimensions of the micro-optical component to be produced.

The method according to the invention preferably provides fibers or fiber sections made of a single-crystalline material in the form of a solid solution with an elliptical cross section or a rectangular cross section. Fiber sections with an elliptical cross section can be adapted in their cross-sectional shape to be produced to the cylindrical lens, so that the individual cylindrical lenses are produced by dividing the fibers. A fiber with a rectangular or square cross-section is particularly suitable for a subsequent pressing process perpendicular to the axis of the fiber, since the fiber can be inserted flat into the pressing mold with a flat outside.

During the pressurization in the course of the pressing process, the in the Fiber material present, non-aligned orientation of the dislocation lines are subjected to dynamic recrystallization. As a result, the crystalline material can change its shape in very small units, ie less than 0.1 μm, during the pressing process. This enables optical surfaces and reproducible properties of the micro-optical elements produced.

In connection with these micro-optical components, the method is preferably carried out in such a way that the fiber or the fiber section is subjected to pressure parallel or perpendicular to the axis of the fiber or the fiber section. Due to this special alignment of the fiber or the fiber section when pressurized during the pressing process, high production rates with a minimum number of work steps and low material losses as well as reproducible results can be achieved or the properties of the micro-optical elements produced in this way can still be achieved continue to be aligned. Of the two preferred orientations, the orientation of the fiber or of the fiber section, in which the fiber axis is perpendicular to the direction of the pressurization, is particularly noteworthy, since in particular microlens arrays or row or field arrangements can be produced from one piece of fiber, so that the individual microlenses within the array have the same optical properties.

The pressurization parallel to the fiber axis is used in particular for the production of micro-optical elements at the fiber end.

In order to achieve a soft, ie stress-free deformation, the starting material for its deformation should be heated. A temperature is preferably selected which corresponds at most to 0.8 times and at least 0.3 times the melting point of the starting material. The temperature should preferably be in the range of 0.5 times the melting point of the starting material. The exact temperature setting is also highly dependent on the size or diameter of the micro-optical component to be produced. For example, it was found that for deforming fiber pieces with a diameter of 2 mm, the temperature between 0.7 and 0.8 times and for deforming fibers with a very small diameter, the temperature between 0.2 and 0.3 -fold the melting point of the starting material. In addition, with the crystalline or polycrystalline fibers used as the starting material in the form of a solid solution, micro-optical elements can be pressed directly onto the end of the fiber pieces as the radiation entry and / or radiation exit surface, with the suitable temperature range during the deformation of fibers the diameter 2 mm between 0.7 and 0.8 times and for the deformation of fibers with a very small diameter should be between 0.2 and 0.3 times the melting point of the starting material.

As a further process parameter, the compression pressure used when shaping the fiber or the fiber section should be less than the tensile strength, but greater than the deformation resistance of the fiber. Depending on the material used, the maximum pressures to be used are between 20 MPa and 170 MPa. The deformation resistance is about 0.21 of the tensile strength of the fiber used in the invention.

In order to avoid contamination of the microlens, an ambient atmosphere is maintained during the shaping which is inert to the fiber material at the shaping temperature.

Furthermore, the pressurization should preferably be carried out in such a way that the rate of deformation of the fiber or the fiber section during the pressurization is less than 0.1 times the speed of sound in the fiber material. If such a process parameter is not adhered to, this can lead to microcracks and microgaps. In addition, larger crystallites can arise, as a result of which the light scattering in the micro-optical element is increased. If this rate of deformation is maintained, the dislocations moving under the pressure can form a microcrystalline structure similar to that of the fiber material before pressing. For the material of the mold, especially for the application of the method according to the invention, Ti compounds, Ge and monocrystals made from A1 ₂ 0 ₃ , Zr0 _{2 have} proven to be preferred. Such a mold has the advantage that it is sufficiently stable, does not react with the starting material at the process temperature or combines with it, and mechanical processing with surface roughness <0.05 .mu.m can take place, which in turn leads to an optical quality of the microlens surface with a Roughness <0.05. In connection with crystalline or polycrystalline starting material, the use of crystalline materials for the mold results in a surface roughness which is reduced by a factor of 3 compared to other, non-crystalline mold materials.

For the production of flat surfaces, processing the starting material with a polished knife has proven to be preferred. Such processing has the advantage that defective fiber sections can be separated in one operation with the creation of the new micro-optical element. The surface produced with a polished knife also achieves optical quality with a roughness of less than 0.05 μm.

For the material of the knife and / or cutting tool, especially for the applications of the method according to the invention, Ti compounds, Ge and monocrystals made of A1 ₂ 0 ₃ and Zr0 _{3 have} proven to be preferred. Such a knife and / or cutting tool has sufficient hardness and is inert to the starting material.

The starting material used to manufacture the micro-optical elements is preferably specified as follows, in particular in order to achieve the specified advantageous properties of the micro-optical elements:

- _j : AgCl in a concentration (0-1001) x ₂ : AgBr in a concentration (0-1001) x ₃ : AgI in a concentration (0-101) in the following combination: with x, + x ₂ + x ₃ - 1001.

There is a solid solution with a cubic crystal structure within the limits specified above. Due to a higher concentration of AgCl, the minimal absorption is shifted to the short-wave spectral range. A higher concentration of AgBr shifts the maximum transparency into the long-wave spectral range. Pure AgBr has a transparency of 0.48 - 34 .um, while the transparent spectral range of AgCl comprises 0.42 - 23 .um. In addition, the refractive index is varied between 1.98 and 2.3. Stabilization of the microcrystallites prevents aging. This is achieved by adding a few percent AgI in solid AgCl-AgBr solutions. A higher concentration of AgI, 101 and higher, is associated with a crystallographic transformation into a non-cubic crystal structure and the difficulty of growing a dense crystal and should therefore be avoided. On the other hand, AgI increases the photochemical stability, in particular with regard to incident sunlight, increases the mechanical stability and reduces surface corrosion in moist air by a factor of 10, so that a small proportion of AgI is advantageous.

ZnSe, KRS-5, Csl, KC1, BaF ₂ , A1 ₂ 0 ₃ , CaF ₂ , NaCl, KBr, TIBr and CsBr can also be used as preferred starting materials. The starting materials specified above each have specific properties or advantages, as follows:

ZnSe: ZnSe is water-insoluble, very hard and has a relatively high refractive index of 2.43.

TIBr: TIBr has a wide spectral range, but is not mechanically as robust as KRS-5.

KRS-5: KRS-5 is water-insoluble, toxic, has a relatively high level

Refractive index of 2.38 and a high Knoop hardness, which means it is very robust. KRS-5 is used in the area of C0 ₂ -High- power lasers use. KRS-5 fibers allow

2 drove a transmission of up to 30 kW / cm. This value is about twice that of silver halide fibers.

NaCl, KC1, Csl, KC1 and KBr have low transmission losses and a high water solubility. Their high melting temperature makes them particularly suitable for laser applications.

BaF ₂ , CaF ₂ , A1 ₂ 0 ₃ are very hard compared to the above materials and have a refractive index of approximately 1.5. The range of maximum transmission is shorter-wave than in the materials listed above. Due to their great hardness, they are used for the following lasers:

- RF laser (2.7 ^ µm),

- YAG: He ³⁺ (2.94 ₇ µm),

- DF laser (3.8 ^ um)

- CO laser (5.3-6.2 um)

- C0 ₂ laser (10 ^ m).

In order to use the lenses for applications in connection with lasers, in particular in connection with CO ₂ lasers, an anti-reflection coating is applied in a further process step to the micro-optical element removed from the mold after the pressing process. Such an antireflection coating preferably consists of PbF ₂ (for a wavelength of 10 .mu.m), which is applied to the beam entry and exit sides of the micro-optical element by means of a vapor deposition process.

The broadband, spectral transparency means that the micro-optical components, such as, for example, microlenses, or fibers with attached microlenses, are particularly suitable for beam guidance and beam focusing IR laser and FTIR spectroscopy (FTIR - Fourier Transform Infrared), where the beam guidance and focusing systems currently still consist of mirrors. In contrast to IR laser spectroscopy, FTIR spectroscopy uses a broadband IR spectrum. The transmitted, reflected or absorbed sample spectrum is calculated using a Fourier transformation of the measured variable, the so-called interferogram.

Furthermore, the broadband, spectral transparency of the micro-optical elements extends the detectable temperature range below the room temperature range. Due to the small diameter of the focused radiation, the micro-optical elements can be linked particularly effectively with detector elements whose sensitive detector areas correspond approximately to the focus diameter and which therefore have a significantly higher sensitivity than large-area detector elements.

Another preferred area of application of the micro-optical elements produced by the method according to the invention is the use as optical components in an infrared spectrometer. In order, in particular, to carry out transmission or reflection examinations on samples outside the spectrometer in positions that are difficult to access, e.g. within closed systems, microlenses with the same radii of curvature are applied to the end of the illumination and detection fiber. Without the use of additional collection optics, all of the radiation reflected or transmitted on the sample reaches the detector.

Another preferred area of application of the micro-optical elements produced by the method according to the invention is the use as a focusing component in an IR microscope. In contrast to the Cassegrain mirror systems usually used in IR microscopy, the microlenses are transparent over the entire aperture angle. Furthermore, the microlens focus is of the order of the wavelength. Additional diaphragms delimiting the measuring spot are no longer required. Furthermore, a microlens microscope is much smaller due to the short, optical paths. Its size is only determined by the dimensions of the positioner and detector.

With the procedure according to the invention or the material used, micro-optical lattice elements, micro-Fresnel lenses or cylindrical lenses can be produced by preparing the corresponding molds.

It has been shown that, in particular, spherical, parabolic and hyperbolic shaped micro-optical elements, the surfaces of which are at a distance from one another which is greater than 0.1 times the fiber diameter, can be produced using the specified method. Since fibers are used as the starting material, micro-optical elements, the thickness of which is only limited by the maximum fiber length, can be produced on both fiber ends.

A preferred micro-optical element is manufactured in the form of a cylinder with two optical surfaces which extend at an angle C> arctan n, where D is the angle between the plane of the surface and the fiber axis and where the refractive index of the starting material is n. This micro-optical component is particularly suitable for the reflection-free transmission of radiation polarized in the incident plane in the spectral range from 0.4 to 30 μm, in particular of infrared radiation. The radiation enters the micro-optical element at an angle i 2 arctan (n) - Jt / 2 to the fiber axis and leaves the component at the same angle.

A micro-optical element which has at least one flat surface which intersects the axis of the fiber at an angle of 45 ° is particularly suitable for coupling diode laser radiation into a fiber end or for coupling out those deflected at the fiber end and focused over the fiber cladding Radiation. Furthermore, a micro-optical element is preferred with at least one surface which is designed as a depression, specifically for deflecting and coupling radiation into a fiber end or for coupling radiation out of the fiber end. With such a geometry at the end of the micro-optical element, radiation from a plurality of radiation sources, in particular from diode lasers, which are arranged on a circular ring, can be coupled into such an end via the surfaces of this conical depression or seen in the opposite direction of radiation , ring-shaped from such an end, are coupled out; If the surface of the conical depression is less than 45 "to the axis, the radiation is coupled out and focused along a circular ring perpendicular to the axis of the fiber. With regard to the coupling in of radiation, such a micro-optical component can be advantageous for laser spectroscopy, since then around a cylindrical lens with such a micro-optical element at its end a geometry is shown which makes it possible to arrange different lasers of different wavelengths around the axis of the fiber (there is sufficient space for this) to emit radiation of different wavelengths into this micro-optical To couple fiber end.

If only two such coupling surfaces or coupling surfaces are required, for example in order to couple the radiation from the end into two partial beams or to couple radiation from the outside into the fiber end from two lasers, the depression can be divided into at least two or more flat surfaces. In order to obtain different radiation intensities, in particular with regard to coupling out radiation and partial beams, such partial areas are selected in different sizes.

A preferred, micro-optical component is provided by a cylindrical fiber section which has a fiber end with a cone arranged rotationally symmetrically to the optical axis of the cylindrical fiber section and / or a plurality of concentrically arranged cone rings. Such an end of the fiber can be used to totally reflect the radiation coupled in via the other end at an angle of the conical surface to the axis of 45 ° or less. Another preferred area of application of the micro-optical elements produced by the method according to the invention is the use of such elements as components for micro-objectives, consisting of at least two microlenses, which should be transparent in particular over a wide spectral range.

Further details and features of the invention result from the following description of exemplary embodiments with reference to the drawings.

Fig. 1 shows a sectional view of an example for the production of a mold for a linear arrangement of microlenses with a spherical curvature;

Fig. 2 shows schematically in a sectional view the manufacture of a linear arrangement of biconvex microlenses with the press molds produced in Figure 1, the arrangement being shown open with an inserted fiber blank.

Fig. 3 shows schematically in section an arrangement for producing a spherical fiber end.

4a) to 4h) show examples of different geometries of micro-optical elements and micro-optical elements at the fiber end, which can be produced, for example, with the arrangement according to FIG. 2 or 3.

5a shows a schematic representation of an arrangement for determining the beam focus diameter that can be achieved with a microlens according to the invention.

5b shows two spectra, which are recorded with an arrangement according to FIG. 5a with a measurement spot of 60 .mu.m (dashed) or 100 .mu.m (solid). 6a shows a mirror spectrum (solid line) in comparison to a spectrum which is recorded using the microlenses produced according to the invention (dashed line).

FIG. 6b shows a spectrum which is recorded with a spherical microlens at the end of a 4 m long polycrystalline AgBr-Agl fiber.

7 schematically shows the use of the microlens produced according to the invention in a conventional infrared mirror microscope.

8 shows the use of a microlens produced by the method according to the invention in fixed connection with a detector.

9 shows a micro-objective in a section, which is constructed from micro-lenses according to the invention.

10a schematically shows in section an embodiment of a

Infrared emission microscope using micro-optical components, which are manufactured according to the inventive method.

10b shows in section an embodiment of an infrared reflection / transmission microscope using micro-optical components which are produced in accordance with the method according to the invention.

Fig. 11 schematically shows an example of a flexible section

Illumination and detection optics for reflection measurements with an infrared spectro eter using crystalline or polycrystalline fibers with pressed-on micro-optical components according to the invention. Fig. 12 schematically shows an example of a flexible section

Illumination and detection optics for transmission measurements with an infrared spectrometer using crystalline or polycrystalline fibers with pressed-on micro-optical components according to the invention.

13a and 13b show a longitudinal and cross section through a flat, 45 ° shaped fiber end produced according to the invention for coupling in diode laser radiation.

14a and 14b show a longitudinal and cross-section through a conical tip of a fiber with a half angle of 45.degree. For total reflection of radiation at the fiber end.

15a and 15b show a longitudinal and cross-section through a conical tip of a fiber with an outer cone ring, which is also suitable for the total reflection of radiation at the fiber end.

16 shows a longitudinal section through a micro-optical element for the reflection-free transmission of light polarized in the plane of incidence, which is incident at an angle i to the fiber axis.

17a and 17b show a cross-section and a longitudinal section through a conical depression with a half-angle O - 45 °, for coupling radiation from several diode lasers into the fiber end.

18a, 18b, 18c and 18d each show top views of a fiber end with a view in the direction of the fiber axis, namely divided into two, three and four flat surfaces, for coupling two, three or four diode lasers into one fiber end.

FIG. 19 shows the use of the fiber end from FIG. 18 as a beam splitter, specifically in a top view from the front and in a side top view. In order to produce a micro-optical element or a fiber end in the form of a micro-optical element, it is first necessary to create a press mold which represents a negative form of the micro-optical element, for example a spherical microlens. Such micro-optical elements can be created as individual elements or as linear row arrangements or surface arrangements or arrays. 1 shows an arrangement for producing a press mold for four linearly arranged, spherical microlenses, the press mold produced according to FIG. 1 then being able to be used in a press arrangement as shown in FIG. 2. The arrangement as shown in FIG. 1 comprises a linear positioner 101 with a base body 102, in which a die blank 103 is held. In a pin 104, which is held with its axis perpendicular to the plane of the die blank 103, a ball bearing ball 105 carries at its end in a corresponding trough, the ball bearing ball 105 being glued into the trough of the cylindrical pin 104. In the exemplary embodiment shown, the diameter of the ball 105 is 2 mm. The pin 104 is guided in a disk 106 made of stainless steel, which rests flat on the upper side of the die blank 103 or on a support surface 107 of the base body 102. Both the pin 104 and the washer 106 are guided in a carrier 108 which is guided horizontally between a spring element 109 on one side and a micro-positioning screw 110 on the other side. The micro-positioning screw 110 is used to polish the pin 104 with the ball 105 over the press blank, which consists, for example, of crystalline ZrO ₂ , by the pin 104 using a suitable drive about its axis and thus the Ball 105 is rotated. The stainless steel disc 106 serves as a guide for the pin 104 and the ball 105. Diamond paste with a grain size of 25 μm to 0.15 μm is used as the polishing agent. A cylindrical ring 112, which is placed on the pin 104 and set back from the end of the pin 104 or the end of the ball 105, serves as a depth stop for the penetration of the ball 105 into the die blank 103. This stop can be achieved by suitable means , setting means, not shown, can be moved in the axial direction of the pin 104 and the depth of insertion of the ball 105 into the blank 103 can thus be reproduced - 19 -

can be set. After a first spherical press mold recess 111, which is adapted to the shape of the ball 105, is formed, the carrier 108 is moved in the X direction via the micro positioning screw 110, as is indicated by the arrow in FIG. 1, against the counterpressure of the spring element 109, in order to then introduce a further depression into the blank 103 following the depression 111, as is shown in FIG. 1. One after the other, four such spherical depressions 111 can be formed in a linear arrangement in the illustrated die blank 103, as shown in FIG. 2. According to the illustration in FIG. 1, a further positioning device, not shown, can be provided in order to move the carrier 108 together with the pin 104 and the ball 105 in the Y direction, in order to arrange an array or a field arrangement of spherical depressions 111 form. In order to obtain identical, spherical depressions, it is possible in a simple manner to replace the ball bearing ball 105 with a new, unused ball during the processing of the die blank 103. It has been shown that the surface roughness can be reduced to less than 0.1 .mu.m with the diamond paste as the grain size decreases during grinding. Depending on the depth of penetration of the ball 105, the diameter of the spherical depression can be 1 mm, for example. Adjacent depressions 111 can be arranged with their edge areas at a distance of 0.2 mm from one another. Microlens arrays with 10 x 10 microlenses can be produced with the arrangement according to FIG. 1 without any problems.

Press molds which are produced from the press mold blanks 103 of FIG. 1 are then inserted into a press arrangement 201, as is shown in FIG. 2. In order to manufacture biconvex lenses, a press mold 202 and 203 is inserted into a holder 204 and 205, which are positioned opposite one another. Each bracket 204, 205 is equipped with integrated heaters 206 and 207. One or more thermocouples, not shown, measure the temperature of the press molds 202, 203. For pressing biconvex microlenses or microlens array arrangements, the end of a 1 mm thick, up to 10 m long, polycrystalline AgBr-Agl fiber 208 guided over a sleeve-shaped guide 209 between the two molds 202, 203. In the example shown, the AgBr-Agl fiber 208 has an AgI content of 51. In the position shown in FIG. 2, the two brackets 204, 205 are heated via the heating device 206, 207 and the molds 202, 203 are moved toward one another, for which purpose the upper mold is held on a piston 210. In order to limit the pressing depth, stops 211 are provided on the piston 210, while the lower holder 204 is held by a height-adjustable frame 212. In order to ensure correct alignment of the upper die 203 to the lower die 202, a positioning sensor 213 is provided on the piston 210. When the two holders 204, 205 or the two press molds 202, 203 are moved towards one another, the pressed fiber section 214 is simultaneously cut off along the line 215 with a knife 216. The knife is a polished cutting edge made of crystalline zirconium oxide in order to avoid a reaction with the fiber material. Furthermore, a zirconium oxide cutting edge is very hard, so that it is not damaged by the cutting process.

The pressing pressure for the fiber with the arrangement shown in Fig. 2 is about 80 MPa; the rate of deformation during the pressurization is less than 1 mm / s. The pressing process is carried out in a nitrogen-filled atmosphere within the housing 209 of the pressing arrangement 201. The pressed and separated from the fiber 208 fiber sections 214 are then transported in the direction of arrow 218 after opening the holder 204 and 205 and then the end of the fiber 208 is advanced in the direction of arrow 218 to the next fiber section between the dies 202, 203th bring to. The respective length of the fiber sections is approximately 6 mm in the embodiment shown.

3, a press assembly 301 is shown to form a spherical fiber end on the end of a fiber 302. The press arrangement corresponds essentially to the structure of the press arrangement 201 of FIG. 2 in Reference to the upper bracket 303, the mold 304, the heating device 305 in the bracket 303, the piston 306 on which the bracket 303 is guided, the stops 307 and the positioning sensor 308. Instead of the lower bracket 204 and the 3, a sleeve-shaped guide 309 is arranged on the housing 310 in the arrangement of FIG. 3, in which a fiber 311 is guided. The fiber 311 in this embodiment has a diameter of 1 mm and is made of AgBr-Agl as a solid solution with an iodine content of 51. The compression mold 304 has a single, spherical depression 312, which is introduced into the compression mold 304, for example, with an arrangement as shown in FIG. 1. The fiber end of the fiber 311 is protruding over the end of the sleeve-shaped guide 309. To press a spherical fiber end onto the fiber 311, the holder 303 is heated to about 200 ^° C. by means of the heating device 305 and then the piston 306 is moved downward onto the end of the fiber 311. The spherical recess 312 is pressed onto the fiber end with a pressing pressure of approximately 80 MPa, then the piston 306 is moved up again and the fiber is pulled out of the sleeve-shaped guide 309.

4a to 4h show various micro-optical elements which can be produced as individual, micro-optical elements or which can be pressed onto a fiber end, with arrangements as shown in FIGS. 2 and 3 and described above.

The diameters and radii of curvature of the microlenses shown in FIGS. 4a and 4b are 0.5 mm, while the individual microlens of the microlens array shown in FIG. 4c have a diameter of 0.35 mm with a radius of curvature of 0.25 mm. 4d shows a micro Fresnel lens produced by the method according to the invention, which has a convexly curved surface on the opposite side. The lens of FIG. 4e has a flat lens surface opposite the micro grating. Because of the broad, spectral transparency of the starting material used according to the invention in the form of a crystalline one or polycrystalline fiber or a fiber section of a fiber with a spectral passband from 0.4 .mu.m to 30 .mu.m, which are made from a starting material of a solid solution, there is a wide range of possible uses of the microlenses and micro grids or the fibers of FIG 4f, 4g and 4h with differently shaped fiber ends, both in the visible and in the infrared spectral range. The fibers with the spherical, parabolic or hyperbolic fiber ends shown in FIGS. 4f to 4h are particularly suitable for flexible focusing optics and are used in particular in laser medicine, laser material processing and spectroscopy. For example, with the hyperbolic fiber end, as shown in FIG. 4h, the diameter of the focused radiation can be reduced by a factor of 1.8 compared to the spherical fiber end, as shown in FIG. 4f.

5a shows a method or a schematic arrangement with which the focus diameter of a microlens 501 produced according to the invention can be determined. For this purpose, the microlens 501, which is a microlens with a spherical beam entry surface and a flat beam exit surface, is illuminated with a parallel beam 502. The focus of the microlens 501 is determined via the two Cassegrain mirror optics 503, 504 with the aid of the adjusting optics 505 and a field diaphragm 506 in the beam path between the two mirror optics 503 and 504 and a positioner 507 on which the microlens 501 in the X -, Y- and Z-direction is kept adjustable, is mapped to an MCT detector element 508 (MCT: Hg, Cd, Te are the elements that make up the detector element).

FIG. 5 b shows two spectra, which are recorded with the arrangement according to FIG. 5 a, namely the intensity as a function of the wavelength that is transmitted through the microlens 501. The spectrum plotted in a solid line represents a measurement spot on the detector element 508 with a diameter of 100 .mu.m, while the spectrum plotted with a broken line represents a measurement spot on the Detector element 508 with a diameter of 60 µm shows. A comparison of these two spectra shows that more than 951 of the focused intensity lie within a recorded area with a diameter of 60 .mu.m. Furthermore, these spectra show that the microlens has good transparency in the wavelength range between 2 and 18 μm. Radiation with wavelengths greater than 18 µm can not be detected with the HgCdTe element used here. In FIG. 6a, a spectrum that is recorded with a microlens according to the invention (dashed curve) is compared with a spectrum that is recorded without a microlens according to the invention (solid curve). Both spectra were measured with a structure as shown in Fig. 5a. Analogous to the spectrum that was taken without a microlens, the microlens spectrum shows no scatter losses in the short-wave range. This is an indication of a very fine, microcrystalline structure of the starting material and of the optical quality of the surfaces of the microlens which are achieved with the material used according to the invention or with the manufacturing method according to the invention. In addition, the absence of additional absorption bands in the spectrum is typical of the crystalline IR fiber, which is produced from a starting material in the form of a solid solution, specifically for the production of micro-optical elements.

FIG. 6b shows the transmission spectrum of a 4 m long, polycrystalline AgBrI fiber with a spherical fiber end, as produced, for example, with the arrangement in FIG. 3 and shown in FIG. 4f. The broad, absorption-free, spectral transparency of the fiber in the range from 4 to 18 .mu.m enables applications, in particular in spectroscopy, which are otherwise restricted with conventional glass fibers in that the absorption-free spectral range is considerably narrower and only little spectral information is available stands. The spherical end, which is pressed directly onto the fiber, replaces focusing optics, reduces radiation losses at transition areas between a fiber end and a lens optic, and thereby makes the fiber much more flexible. 7 schematically shows the use of the microlens produced according to the invention in the project plane of a conventional mirror microscope. In this IR microscope, which has a classic structure, a spherical microlens 701 is used to improve the spatial resolution. Because of the large wavelengths (up to 20 .mu.m), diffraction effects are very noticeable in IR microscopy. They can lead to misinterpretation of the measurement results as well as to strong, spectrally dependent loss of intensity. The microlens 71, as a continuous lens, with a diameter and a radius of curvature of 0.5 mm and a thickness of 0.75 mm, introduces the strongly diffracted beams 702 into the objective 703. It reduces the spectrally dependent intensity losses due to the high refractive index of the lens material (n - 2.2) and improves the diffraction-related resolution by a factor of n.

The effect of the spherical microlens 801, which is shown in FIG. 8 and is fixedly connected to a detector 802, is similar. The microlens 801 is attached to a detector contact 804 by means of an adhesive intermediate layer 803. Due to the broad spectral transparency of the immersion microlens 801 produced according to the invention, the signal-to-noise ratio of an HgCdTe detector element 805, which is arranged on a carrier body 806, is improved, which in turn shortens measurement times and improves the IR microspectroscopy, for example Spatial resolution enables.

FIG. 9 shows a further possibility of using a combined microlens arrangement in the form of a micro objective 901, which consists of a biconvex lens 902 and a meniscus lens 903, which are held at their edge in a carrier structure 904. This lens combination reduces the focus diameter of a single, flat convex lens by a factor of 1.7. Because of the wide, spectral transparency of the starting material, which is in the range from 0.4 to 30 .mu.m, this objective can be used both in the visible spectral range and in the infrared spectral range, for which it is transparent. 10a, 10b, 11 and 12 show further possible uses for the use of microlenses which are produced with the corresponding materials by the method according to the invention and which are permeable in a spectral range from 0.4 to 30 .mu.m .

10a shows an embodiment of an infrared emission microscope. For example, a microelectronic component 1001 based on silicon is examined as sample 1001. Because of the transparency of the microlenses produced according to the invention, in particular in the long-wave spectral range (up to 30 .mu.m), very small, local temperature increases can be detected. The desired measuring spot is selected on the sample 1001 using microscope optics. The sample 1001 is then pivoted into the focus of the microlens system 1003 on a heatable, XYZ positioner 1002. The microlens system 1003 consists of four identical, spherical microlenses with a radius of curvature and a diameter of 1 mm and a thickness of 0.35 mm. The desired spot size is set via a field aperture 1004. The measurement is carried out by heating the sample 1001 via the XYZ positioner 1002 and scanning the set measurement spot. So that the emitted IR radiation can be detected with sufficient sensitivity by a nitrogen-cooled HgCdTe detector element 1005, it is modulated with a chopper 1006. If thicker microlenses are used in such an arrangement, a better spatial resolution is achieved due to the higher numerical aperture. At the same time, however, the distance to the sample is reduced. The highest resolution is provided by an arrangement in which the microlens sits directly on the sample.

10b shows the structure of a reflection / transmission IR microscope. This arrangement can be used to determine the optical properties such as reflection, transmission and absorption of samples 1001 with an inhomogeneity on the scale of a few micrometers, for which purpose either a reflection element 1007 or a transmission element 1008 is used. The sample 1001 is in turn, according to FIG. 10a, on an XYZ positioner 1002. The desired measurement spot on the sample 1001 is selected with a microscope. Subsequently, the sample 1001 is pivoted into the microlens system 1003 and readjusted in the vertical direction to the maximum intensity at a detector element 1005 using the IR interfering radiation coupled in via reflection beam 1007 via a beam splitter 1009. Analogously to the IR emission microscope of FIG. 10a, the desired measuring range is scanned and a reflection and / or transmission spectrum is recorded in every position. In contrast to conventional mirror microscopes, no diaphragms are required to limit the measuring spot. The number of optical components is limited to three microlenses and a beam splitter 1009, as can be seen in FIG. 10b. The size of the IR microlens microscope is only determined by the dimension of the positioner 1002 or the nitrogen-cooled detector 1005. This and the high numerical aperture improve the light conductance. The high light conductance and the sensitivity of the detector element 1005, which is adapted to the size of the measurement spot, enable the microlens microscope to be operated with a parallel beam 1007, 1008.

Figures 11 and 12 show lighting and detection optics for flexible reflection measurements (Fig. 11) and transmission measurements (Fig. 12) in an infrared spectrometer. These arrangements enable infrared spectroscopic and infrared microscopic examinations in environments in which conventional beam guidance systems cannot be used due to the size of their sensitive optics.

As shown in FIG. 11, in the arrangement oriented towards reflection measurements, the parallel IR interferometer beam 1101 is coupled into the illumination fiber 1103 (diameter 0.7 mm) via a plano-convex lens 1102 with an aperture angle of 20 ° and with a spherical or aspherical fiber end 1104 focused on the sample 1105. The reflected light is detected by a detection fiber 1106, onto which a micro-optical coupling element 1107 with an arrangement corresponding to FIG. 3 is also pressed, and on a detector element 1108 on the other end of the detection fiber 1106 bundled. The opening angle with which the sample is illuminated and the reflected light is collected can be set via the curvature of the fiber end 1104 or the corresponding pressed-on micro-optical element. For microscopic measurements with parabolic fiber ends 1104, the aperture angle is, for example, 60 ° and the focus diameter is 40 µm. If fibers with a smaller diameter are used, the focus diameter can be reduced further. For microscopic examinations, the combination of an illumination fiber 1103 with a small diameter (for example 0.3 mm) and a detection fiber 1106 with a larger diameter (for example 1 mm) is to be regarded as preferred. The large detection fiber 1106 collects a larger proportion of the radiation diffracted at the sample 1105, whereby a higher resolution is obtained. Spherical fiber ends with a radius of curvature of 1.5 mm at the fiber end 1104 of the illumination fiber 1103, diameter 0.7 mm, focus the radiation with an opening angle of 15 °. The focus diameter is then 500 µm.

11 can be applied analogously to the transmission arrangement in an infrared spectrometer of FIG. 12. In this case too, the interferometer beam 1101 is coupled into an illumination fiber 1103 via a plano-convex lens 1102 and focused on the sample 1105. The sample is illuminated and the transmitted light is tapped via a detection fiber 1106 and fed to the detector element 1108. In this case too, the fiber ends 1104 and 1107 in the form of micro-optical elements are pressed directly onto the ends of the fibers 1103 and 1106.

In embodiments 11 and 12, there is the possibility of indicating the detection fiber by an angle) indicated by arrow 1109 in FIG. 12 in order to rotate the measurement spot. In this way, for example, the scattering properties of samples 1105 can be examined.

13 to 18 show further micro-optical components which are molded onto the end of a fiber. 13a and 13b show the coupling of radiation 1303, which emanates from a laser diode 1304, into the end 1305 of a fiber 1302, the fiber axis being indicated by the reference symbol 1301 in the top view of FIG. 13a and the longitudinal sectional view of FIG. 13b is. The fiber end 1305 or the coupling surface is cut at an angle <% of 45 ° to the fiber axis 1301. Typically, the radiation divergence of a radiation 130340 ° to 80 ° in one direction or 10 ° to 15 ° in the direction perpendicular to it, emanating from a laser diode 1304, as shown in the two representations from different directions in FIGS. 13a and 13a 13b can be seen. The length and the thickness of the active laser layer of the laser diode 1304 is 200 μm in one direction and 1 μm in the direction perpendicular thereto. The cylindrical surface of the fiber 1302 and the fiber end 1305 cut at 45 ° transform the divergent laser radiation into almost parallel light within the fiber 1302. Furthermore, a fiber end 1305 shaped in this way prevents the feedback of reflected light into the active layer of the laser diode 1304; such feedback would otherwise destroy the mode and frequency of the light emitted. The broad, permeable spectral range of the fiber 1302 produced according to the invention is also advantageous in this application.

14a and 14b show a similar application to FIGS. 13a and 13b with a top view of the fiber end 1405 and a sectional view through the fiber 1402 along the fiber axis 1401. The fiber end 1405 is designed in the form of a conical tip, like the sectional view 14b shows. If the half opening angle of the conical fiber end 1405 is less than or equal to L-3174, a micro-optical element shaped in this way can be used as the totally reflecting fiber end 1405, as indicated by the beam path 1403 in FIG. 14b. Such an optical element would be suitable, for example, for extending the optical path in ATR fiber sensors (ATR - Attenated Total Reflection - attenuated total reflection). A multiple arrangement of concentric cone rings is shown in FIGS. 15a and 15b, again with half the opening angle of the conical fiber end 1505 of the fiber 1502 at an opening angle zu to the fiber axis 1501 less than. YES, so that different rays 1503 are totally reflected at the cone rings 1504 and reflected back into the fiber 1502.

A micro-optical fiber element 1602 is cut at its fiber end 1605 at an angle 00 to the fiber axis 1601 both on the input side and on the output side of the radiation 1603. Radiation 1603 polarized in the plane of incidence is incident on the oblique fiber end 1605 at an angle i-2 arctan n-3T / 2 to the fiber axis 1601, the fiber end 1605 being incident at an angle of k% arctan n to the fiber axis 1601 ¬ is cut. In this arrangement, the light polarized in the plane of incidence is coupled into and out of the fiber 1602 without reflection. Such an application is also advantageous with a fiber 1602 produced according to the invention if a broadband, spectral passband, i.e. a pass range between 0.4 to 30 .mu.m is required.

17a and 17b show an arrangement for the simultaneous coupling of radiation 1703 which is emitted by a plurality of laser diodes 1704 which are arranged radially to the axis 1701 of a fiber 1702. The fiber end 1705 of the fiber 1702 has a conical recess or depression, which is shown with an opening angle A of 45 ° to the fiber axis 1701. The individual laser diodes 1704 can emit radiation 1703 with different wavelengths, which are coupled into the interior of the fiber 1702 via the totally reflecting fiber end 1705. The strongly diverging radiation from the laser diodes 1704 runs almost parallel in the fiber 1702, owing to the deformation on the cylindrical fiber surface, as indicated schematically by the rays 1703 in the interior of the fiber 1702. Such an arrangement is particularly important for laser spectroscopy. 18a to 18b show various radiation-dividing, plane fiber ends 1805, similar to the embodiment of FIGS. 17a and 17b, into which the radiation 1803 of individual laser diodes 1804 are coupled. In the opposite direction, fiber ends shaped in this way can also be used as beam splitters. 18d represents a beam splitter with unevenly divided, coupled out radiation intensities. The coupling out of spectral broadband radiation on detectors with different levels of sensitivity is a further possible application of the fiber ends shown in FIGS. 18a to 18d.

Another application is shown in Fig. 19; it shows the coupling of two fibers 1901 and 1902 to a fiber end 1903 of a fiber 1902. The two-part depression 1904, which runs symmetrically to the fiber axis 1905, serves as a respective reflecting surface in order to couple the radiation 1906 into the respective fibers 1901 and 1902.

Claims

Patent application "Process for the production of micro-optical elements or a fiber end in the form of a micro-optical element and use of such elements" claims

1. A process for the production of micro-optical elements or a fiber end in the form of a micro-optical element, a starting material being brought into a form of the micro-optical element, characterized in that for the production of micro-optical elements with a spectral range of 0 , 4 to 30. Around a crystalline or polycrystalline fiber or a section thereof, which is essentially absorption-free in this spectral range and which is produced from a starting material of a solid solution, is brought into the mold.

2. The method according to claim 1, characterized in that a solid solution with a cubic crystal structure is brought into the mold as the starting material.

3. The method according to claim 1 or 2, characterized in that fibers or fiber sections with a diameter between 50 .um and 3 mm are provided.

4. The method according to any one of claims 1 to 3, characterized in that fibers or fiber sections with an elliptical cross section are provided.

5. The method according to any one of claims 1 to 3, characterized in that fibers or fiber sections are provided with a square or rectangular cross section.

6. The method according to any one of claims 1 to 5, characterized in that the starting material is placed in a mold and brought into its shape under pressure.

7. The method according to claim 6, characterized in that the Druck¬ applied parallel and / or perpendicular to the axis of the fiber or the fiber section.

8. The method according to claim 7, characterized in that the starting material is subjected to a heat treatment during pressing.

9. The method according to any one of claims 6 to 8, characterized in that a compression pressure less than the tensile strength of the fibers is applied.

10. The method according to any one of claims 6 to 9, characterized in that a compression pressure greater than the deformation resistance of the fiber is applied.

11. The method according to any one of claims 6 to 10, characterized in that an ambient atmosphere is maintained during the pressing, which is inert to the fiber material at the deformation temperature.

12. The method according to any one of claims 6 to 11, characterized in that the pressurization is carried out in such a way that the Defor¬ tion speed during the pressurization on the fiber or the fiber section is less than 0.1 times the speed of sound in the fiber material is.

13. The method according to any one of claims 6 to 12, characterized in that the fibers or fiber sections are used in a press mold which is inert to the starting material at the processing temperature and which is not deformed when the press pressure is applied.

14. The method according to any one of claims 1 to 5, characterized in that the starting material is brought into its shape with a knife and / or a Zerspanungs¬ tool.

15. The method according to claim 13, characterized in that a material is used as a knife and / or cutting tool, which is inert towards the starting material and is not deformed during processing of the starting material.

16. The method according to any one of claims 1 to 15, characterized in that the starting material is a solid solutions of: x,: AgCl in a concentration (0-1001) x ₂ : AgBr in a concentration (0-1001) x ₃ : AgI in a concentration (0- 101)

with x- + x ₂ + x ₃ - 1001

is used.

17. The method according to any one of claims 1 to 16, characterized in that as the starting material ZnSe, KRS-5, Csl, BaF ₂ , A1 ₂ 0 ₃ , CaF ₂ ,

NaCl, KC1, KBr, TIBr and / or CsBr is used.

18. The method according to any one of claims 1 to 17, characterized in that an antireflection coating is applied to the shaped, micro-optical element.

19. The method according to any one of claims 1 to 18, characterized in that a micro-optical element is produced in the form of a grating.

20. The method according to any one of claims 1 to 18, characterized in that a micro-optical element in the form of a micro Fresnel lens is manufactured.

21. The method according to any one of claims 1 to 18, characterized in that a micro-optical element is manufactured in the form of a cylindrical lens.

22. The method according to any one of claims 1 to 18, characterized in that a micro-optical element in the form of a cylinder with a first, spherical, parabolic, hyperbolic or multiple arrangement of spherical and / or parabolic and / or hyper¬ bolical optical Surfaces and a second, planar, spherical, parabolic, hyperbolic or multiple arrangement of spherical and / or parabolic and / or hyperbolic optical surface is produced, the first and second surfaces being at a distance from one another which is greater than the 0th Is 1 times the diameter of the fiber or fiber section used.

23. The method according to claim 22, characterized in that the first and the second optical surface is formed at an angle of Oi - arctan n, extending to the optical axis, where 06- is the angle between the plane of the surface and the fiber axis and wherein n is the refractive index of the fiber material.

24. The method according to claim 22, characterized in that the first and / or the second optical surface at an angle of

0. ■ 45 ° to the optical axis is formed, with Λ. is the angle between the plane of the surface and the fiber axis.

25. The method according to claim 22, characterized in that the first and / or the second optical surface is formed as a recess and is divided into at least two flat surfaces.

26. The method according to claim 22, characterized in that the first and / or the second optical surface is formed with a conical recess, the half angle of which is less than or equal to X / 4.

27. The method according to claim 22, characterized in that the one surface is formed with a conical tip and / or a plurality of concentrically arranged cone rings, the half angles of which are less than or equal to # 74.

28. Use of a micro-optical element produced by the method according to one of claims 20 to 22 for focusing laser and spectral broadband radiation.

29. Use of a micro-optical element produced by the method according to one of claims 20 to 22 as an optical component for micro-objectives.

30. Use of a micro-optical element produced by the method according to one of claims 20 to 22 as a component in an infrared spectrometer.

31. Use of a micro-optical element produced by the method according to one of claims 1 to 22 as an optical component in an infrared microscope.

32. Use of a micro-optical element produced by the method according to claim 23 for the reflection-free transmission of light which is polarized in the plane of incidence and is incident on the micro-optical element at an angle i 2 arctan (n) - 31/2 to the fiber axis.

33. Use of a micro-optical element produced by the method according to one of claims 24 to 26 for deflecting and coupling or decoupling laser radiation or spectral broadband radiation into or from a fiber end.

34. Use of a micro-optical element produced by the method according to claim 27 for internal reflection of laser radiation or spectral broadband radiation which is transported in the fiber.