WO2012044290A1

WO2012044290A1 - Method and system for encapsulating optical components

Info

Publication number: WO2012044290A1
Application number: PCT/US2010/050718
Authority: WO
Inventors: Valentin Gapontsev; Victor Ilyashenko; Karina Barseguian
Original assignee: Ipg Photonics Corporation
Priority date: 2010-09-29
Filing date: 2010-09-29
Publication date: 2012-04-05

Abstract

The disclosure is a method and system for encapsulating components of a fiber laser system. Optical components are placed in a housing, such as a fiber laser block (FB). The housing is filled with a polymerizing encapsulant optionally including a filler. The housing is placed in a vacuum chamber to cause a degassing of interstices created during a filling step. A vacuum is created at a rating level determined by the viscosity of the encapsulant system and the vacuum is released at a rapid rate sufficient to drive the encapsulant into the set of interstices filling the same.

Description

METHOD AND SYSTEM FOR ENCAPSULATING OPTICAL

COMPONENTS

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

[0001] The present disclosure relates to the encapsulation of optical components in a fiber laser system. More specifically, the present disclosure relates to the method and system for encapsulating optical fibers, optical components, optical elements, including those within a fiber laser block (FB) assembly, so as to minimize the effects of environmental stress.

2. Description of the Related Art

[0002] The utilization of fiber laser blocks (FB) as a critical component of any laser system since it is configured to generate radiation at the desired wavelengths. Depending on the environmental conditions, the fiber laser block (FB) may be exposed to elevated temperatures, mechanical stresses, pressure differentials and the like.

[0003] To prevent unfavorable conditions from affecting the functionality of the FB, its housing, which encloses a plurality of fiber components, is provided with potting material. The latter is poured onto fiber components, which are mounted on a support surface, and tends to solidify curing thus the entire stmcture. Potting material is known in the electronic arts for securing electronic components in the manner described.

[0004] Due to a variety of factors, including impurities, gases, and high viscosity, the potting material may stop penetrating before it reaches the bottom of the housing and all component surfaces. Accordingly, the entire structure within the housing may remain unprotected from environmental factors. This is a particular concern in fiber blocks where voids lead to local mechanical stresses and damaging local overheating and failure.

[0005] Accordingly, there is a need for an improved method and system for encapsulating the optical components used in a fiber laser system, including a fiber laser block.

ASPECTS AND SUMMARY OF THE DISCLOSURE

[0006] An aspect of the present disclosure is to provide an improved method and system for encapsulating the optical components that comprise a fiber laser block used in a fiber laser system.

[0007] Another aspect of the present disclosure is to provide a method for degassing an interstice created with the addition of a filler/encapsulant to the housing of the fiber block.

[0008] The present disclosure relates to a method and system for encapsulating the components of a fiber laser block in a laser system. A set of optical components is placed within the housing of the fiber block which is configured in a generally round, rectangular or ellipsoidal shape, although other regular and non-regular shapes. The housing is filled with a polymerizing material for use as an encapsulant. An additive can be added to the encapsulate material so as to improve resistance to heat, thermal conductivity , or moisture. The encapsulant, thus, as used in this disclosure is a fluid media pure or filled with various additives that are capable of turning into elastomers or solids by means of chemical polymerization or curing or thermal solidification upon cooling (molten media).

[0009] The filled housing is placed in a vacuum chamber and a vacuum is created to cause a degassing of the interstices and encapsulant created during the filling step. The vacuum is created at a rating level dictated by the viscosity of the encapsulant material. The degassing occurs through the encapsulant as the gas vacates the intestacy. The vacuum is released either rapidly or gradually and the change in pressure creates a high pressure differential within the housing sufficient enough to drive the encapsulant through and into the interstices providing complete contact to all components.

[00010] The method begins with establishing a set of optical components (i.e., fiber) within a bounded housing member, for a non-limiting example a fiber laser block. By way of example, the housing is configured in an ellipsoidal shape having a short axis direction and a long axis direction, and so as to have a relatively large radius along the short axis direction, and a relatively long straight stretches parallel to the long axis direction; and, wherein the housing comprises a bottom; the bottom supporting a plurality of fiber combiners. The plurality of fiber combiners is configured from a plurality of input pump-light delivery fibers. A plurality of output fibers of the respective combiners are coupled together into a single delivery fiber; the single delivery fiber running parallel to an active fiber.

[00011] After configuration of the housing components, the housing is then filled with any suitable curing or polymerizing material for use as an encapsulant. An additive or filler can be added to the polymerizing filler/encapsulant so as to improve resistance to heat, moisture, or to improve, for example, thermal capacity, thermal conductivity or other reason.

[00012] The filled housing is placed in a vacuum chamber and a vacuum is created to cause a degassing of a set of interstices created during the filling step. The vacuum is created at a rating level determined by the viscosity of the polymerizing filler; generally within the range of 1-100 torr.

[00013] The degassing occurs through the encapsulant as the gas vacates the interstice for a suitable time period. After a suitable time period, depending upon the viscosity of the selected filler, the vacuum is released. The change in pressure thus creates a high pressure differential within the housing sufficient enough to drive the encapsulant through the interstices.

[00014] The above, and other aspects, features and advantages of the present disclosure will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[00015] FIG. 1 is a flowchart of the method of the present disclosure.

[00016] FIG. 2 is an illustrative fiber laser block (FB) of the present disclosure.

[00017] FIG. 3 is a cross section view of FIG. 2 along line 3-3.

[00018] FIG. 4 is an illustrative schematic of a fiber laser block (FB) linked with other optical components.

[00019] FIG. 5 is an illustrative arrangement noting the butt splicing alignment of active and passive fibers for coating using the proposed method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[00020] Reference will now be made in detail to embodiments of the disclosure that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form. For purposes of convenience only, directional terms may be used with respect to the drawings. These and similar terms should not be construed to limit the scope of the disclosure.

[00021] Turning first to FIG. 1, there is shown a flowchart of the method of the present disclosure.

[00022] The method begins with the selection of exemplary fiber laser optical components for encapsulation; here a fiber laser block (FB) subsystem is selected at step 100. From step 100, the flow advances to step 102 where a set of optical components (i.e., fibers or other components) are laid down within the housing of the fiber block. In this non-limiting example, the housing is configured in an elliptical shape having a short axis and a long axis, and so as to have a relatively large radius along the short axis, and a relatively long straight stretches parallel to the long axis. The housing comprises a bottom; the bottom supporting a plurality of fiber combiners. The plurality of fiber combiners is configured from a plurality of input pump-light delivery fibers. The configuration of the housing (shown later) allows for minimal bending stresses, which are detrimental to the integrity of the fiber. A plurality of output fibers are coupled together into a single delivery fiber; the single delivery fiber running parallel to an active fiber. (All not shown here, but discussed later.) [00023] After configuration of the housing components, a polymerizing material is selected as an encapsulant at step 104. The method then advances to the query at step 106 which asks if an additive is to be added to the material. If the response to the query is "YES", then the flow advances to step 108 where an additive or other filler is selected based upon the conditions desired. From step 108, the flow advances to step 110 where the combined encapsulant is prepared. The encapsulant is thus configured as a fluid media pure or filled with various additives that are capable of turning into elastomers or solids by means of chemical polymerization or curing or thermal solidification upon cooling (molten media). The additives may include without any limitation low temperature metals and alloys such as wood, rose and etc.

[00024] Returning to the query at step 106, if the response to the query is "NO", then the flow advances directly to step 1 10.

[00025] The housing is then filled, at step 1 12, with a curable encapsulant for use as a 'potting' material. The polymerizing filler/encapsulant is selected from any suitable encapsulant. For example, the group comprising: Dow Coming's SYLGARD® 527; SYLGARD® 182; SILGEL® 612; and SYLGARD® Q3- 3600; Wacker's SILGEL® 612; or any other encapsulating epoxy; polyurethane; polyurea; or acrylic. A filler can be added to the polymerizing material/encapsulant so as to improve resistance to heat and/or moisture or to aid the uniformity of thermal transfer and conductivity. This effort to aid uniform heat removal from all optical fibers and elements leads to more stable and uniform temperatures inside a fiber block which in turn leads to a lower probability of thermal failure and higher potential optical power output of such devices. The filler additive may be selected from any suitable inorganic material including: boron nitride; copper powder; calcium carbonate; fumed silica; magnesium carbonate; ceramic powder such as aluminum oxide (alumina) powder, silica powders, zirconia related powders, and quartz powders. The filler materials may also aid cosmetic, mechanical, adhesion, or other factors in the encapsulant system.

[00026] The method flow then advances to step 114 where the filled housing is placed in a vacuum chamber and a vacuum is created at step 116 within the chamber so as to cause a degassing, at step 118, of a set of interstices created during the filling step. The vacuum is created at a rating level determined by the viscosity of the polymerizing encapsulant material and is maintained generally within the range of 1-100 torr for a duration of potentially five to sixty minutes.

[00027] The degassing occurs through the filler as the gas vacates the intestacy. After degassing, and the time depends upon the viscosity of the selected material (for a non-limited example, a viscosity of from 2 to approximately 50,000 centipoise (cP) may be used, although the viscosity varies depending upon the encapsulant), the vacuum is released at step 120 over a time from approximately 0.5 seconds to 60 minutes. The change in pressure thus creates a high pressure differential within the chamber sufficient enough to drive the encapsulant into the interstices at step 122. From step 122, the method queries, at step 124, as to whether or not another housing is to be filled. If the response to the query is "NO", then the process is terminated. If the response to the query at step 124 is "YES", then the flow returns to step 100 to initiate the encapsulation sequence for the next fiber block.

[00028] Turning next to FIGs. 2 and 3, there is shown an illustrative embodiment of the of the present disclosure provided as a fiber laser block (FB) 200 provided as a bounded ovoidal shape discussed above having a plurality of open sided guides 201 (See Fig. 3) for guiding of fibers or fiber components 202. In fiber block 200 (in FIG. 2) the lines generally illustrate fibers, here with the two lines running along an outer perimeter region of block 200 being active and passive pump light delivery fibers 203 and 204 respectively and the straight lines in the middle being fiber couplers 205. It will be understood that the optical components and geometry are provided for illustration only but denote a plurality of guides for fibers or fibers components that require enhanced and reliable encapsulation.

[00029] Referring now to FIG. 4 an illustrative schematic of an exemplary fiber block and component system that may be employed with the present disclosure using well known fiber laser arrangements as known in US 5, 442,897 and US 5,774,484 (both by Wyatt), the entire contents of which are herein incorporated fully by reference. As shown in the schematic a fiber block 215 is provided with a combiner 220 (shown as FC-7/1) for the outputs of seven laser diodes and a combiner 221 similarly (shown as FC-19/1) for 19 diodes. The pumping direction is irrelevant and can be directed in opposite directions, as shown. SP1 and SP2 are also combiners at the input and output of the fiber block. SP1 combines single mode input passive fiber (PFi), delivery fiber, and active fiber (AF) 215; whereas SP2 combines the opposite end of AF 215, output passive (PFo) and delivery fibers, respectively. The illustrated block is a fiber amplifier, but could be easily reconfigured in a fiber laser by adding FBGs typically written in respective input and output fibers. The geometry of the cores of respective SM passive input, output and active fibers illustrated is substantially uniform and most importantly, the mode filled diameters of the respective fibers substantially match one another as illustrated by FIG. 5.

[00030] FIG. 5 provides an instructive illustration of the arrangement of an active fiber (AF) 228 having a doped multimode core provided with respective butt splices 225, 225 to respective SM input passive fiber (PFi) 226 and output passive fiber (PFo) 227. Due to substantially uniform mode field diameters of respective fused SM and MM fibers, the SM launched through splice 225 into the MM core of active fiber 228 excites substantially only a single, fundamental mode in the latter. Accordingly, the illustrated block is characterized by high power radiation in a substantially fundamental mode..

[00031] Having described at least one of the preferred embodiments of the present disclosure with reference to the accompanying drawings, it is to be understood that the disclosure is not limited to those precise embodiments, and that various changes, modifications, and adaptations may be effected therein by one skilled in the art without departing from the scope or spirit of the disclosure as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method for encapsulating optical components in a fiber laser system, said method comprising the steps of:

(a) establishing a plurality of components within a bounded housing;

(b) filling said bounded housing with a polymerizing media for use as an encapsulant resulting in interstices proximate at least one said component;

(c) placing said encapsulant filled bounded housing in a vacuum environment;

(d) creating a vacuum so as to cause a degassing of said interstices, created during said filling step;

(e) releasing said vacuum, thereby creating a high pressure differential proximate said at least one component sufficient enough to drive said encapsulant into said interstices; and

(f) curing the encapsulant.

2. The method of claim 1, wherein:

said vacuum level is set within a range of 1-100 torr for a period of 5-60 minutes.

3. The method of claim 2, wherein:

said step of releasing said vacuum occurs within the range of 0.10 seconds to minutes.

4. The method of claim 1, wherein:

said encapsulant is selected from the group comprising: SYLGARD® 527, SYLGARD® 182, SILGEL® 612, SYLGARD® Q3- 3600, SILGARD 612, an epoxy, a polyurethane, a polyurea, and an acrylic.

5 The method of claim 1 , further comprising the step of:

adding an additive material to said encapsulant so as to reduce a thermal failure of said optical components;

said additive material selected from a group of inorganic materials comprising: boron nitride; copper powder; calcium carbonate; fumed silica; magnesium carbonate; ceramic powders, aluminum oxide (alumina) powder, silica powders, zirconia powders, and quartz powders.

6. The method of claim 1, wherein:

said bounded housing is configured so as to provide a relatively large bending radii for said components where said components are fiber laser components.

7. The method of claim 6, wherein:

said fiber laser components include fibers coupled together into a single delivery fiber, said single delivery fiber running parallel to an active fiber.

8. The method of claim 1, wherein said vacuum is created at a rating level determined by the viscosity of said polymerizing material.

9. A laser component encapsulation system, said system comprising:

(a) a bounded housing member;

(b) an operative vacuum environment including means to apply and release a vacuum during a use thereof;

(b) a set of components within said housing, and wherein said components are encapsulated within said housing member by a polymerizing encapsulant, said polymerizing encapsulant having been:

(i) filled into said housing so as to cover said set of components;

(ii) first subjected to a vacuum in said operative vacuum environment so as to cause a degassing of interstices proximate said components, created during said filling step, and

(iii) second subjected to a rapid release of said vacuum from said operative vacuum environment, thereby creating a high pressure differential within said housing sufficient enough to drive said encapsulant into said interstices.

10. The system of claim 9, wherein:

said polymerizing encapsulant is selected from the group comprising: SYLGARD® 527, SYLGARD® 182, SILGEL® 612, SYLGARD® Q3- 3600, SILGARD 612, an epoxy, a polyurethane, a olyurea, and an acrylic.

11. The system of claim 9, further comprising:

an additive material in said polymerizing encapsulant, and

12. The system of claim 9, wherein the set of components includes an active fiber with a multimode core configured to support substantially a fundamental mode at a given wavelength, and single mode passive input and output fibers butt- spliced to respective opposite ends of the active fiber, the active and passive fibers being configured with a substantially uniform mode filed diameter mode so as to provide laser radiation emitted from the output fiber substantially in the fundamental mode.