Holder for aligning optical end caps connected to optical fibers

Abstract

A holder for aligning optical end caps each connected to an optical fiber, the holder comprising a body including at least one row of bores each sized to receive a single optical end cap, at least one adhesive channel intersecting the at least one row of bores and configured to supply and retain an adhesive material for securing each optical end cap to a corresponding bore, and an array of cooling channels connected to at least one inlet and at least one outlet for circulating a cooling fluid, the cooling channel arranged to surround at least a portion of an outer wall of each bore.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is a PCT application claiming the benefit of priority to Israel Patent Application No. 300635, entitled "Holder for Aligning Optical End Caps Connected to Optical Fibers," filed February 14, 2023, the contents of which are incorporated by reference in their entirety as if fully set forth herein.

[0002] The present invention relates generally to the alignment of optical fibers, and more particularly to a holder for aligning an optical end cap connected to an optical fiber for a high power laser. [Background technology]

[0003] Creating high-power lasers requires combining multiple laser beams. For effective combination, all beams must be precisely aligned and positioned. The beams also need to be aligned within a small structure.

[0004] Operating at high laser powers results in extremely high power densities within the fiber core. To allow the laser beam to exit the fiber into the free-space environment, a power density reduction must occur. End caps are glass windows with a diameter significantly larger than the fiber core, expanding the beam through the fiber numerical aperture, allowing for a larger beam and lower power density.

[0005] The length and diameter of the end caps correspond to the required power density reduction and are limited by the pitch between the end caps and the structural features that hold all the end caps together.

[0006] Internal reflections within the end caps can transfer light to the surrounding mechanisms, generating heat that can lead to misalignment of the holders. The absorptivity of the glass can also lead to heating of the end caps and surrounding mechanisms. Stray light within the system can also lead to heating of the surrounding mechanisms. Heating can also create temperature gradients, which can potentially lead to loss of laser efficiency.

[0007] Several attempts have been made to overcome the heating and alignment shortcomings.

[0008] Examples include V-groove arrays, which are machined plates with a precise single row of V-grooves milled into them. End caps are attached to the V-grooves, aligning them parallel to each other with the appropriate spacing. This method is only used for one-dimensional (1D) arrays.

[0009] Therefore, a different approach is needed that allows for precise alignment of a two-dimensional (2D) array of end caps while significantly reducing thermal effects such as thermal expansion and distortion. Summary of the Invention

[0010] Some aspects of the present invention may be directed to a holder for aligning optical end caps each connected to an optical fiber, the holder comprising: a body having at least one row of bores, each dimensioned to receive a single optical end cap; at least one adhesive channel intersecting the at least one row of bores and configured to supply and retain an adhesive material for securing each optical end cap to a corresponding bore; and an array of cooling channels connected to at least one inlet and at least one outlet for circulating a cooling fluid, the array of cooling channels being arranged to surround at least a portion of an outer wall of each bore.

[0011] In some embodiments, each bore is sized to receive a single optical end cap with a diameter tolerance of up to 50 microns. In some embodiments, each row of bores comprises at least two bores. In some embodiments, the central axes of all bores 122 deviate from parallelism to the reference optical axis by up to 0.05°. In some embodiments, the positions of the central axes of all bores deviate from a reference point on the body by up to 0.007 mm.

[0012] In some embodiments, the body is made from an alloy selected from aluminum alloys, copper, titanium alloys, tungsten-based metal composites, and carbon-based composites.

[0013] In some embodiments, the array of cooling channels is arranged to surround at least a portion of an outer wall of each bore such that direct contact between the end cap and the cooling fluid is avoided. In some embodiments, the holder may further include at least one pump in fluid communication with the at least one inlet and the at least one outlet for circulating the cooling fluid. In some embodiments, the cooling fluid is selected to be a fluid between -40°C and +70°C.

[0014] Some additional aspects of the invention may be directed to an optical system comprising a holder according to any one of the embodiments disclosed herein and an array of optical fibers each welded to an end cap, in some embodiments, each end cap being inserted into a corresponding bore in the holder and secured using an adhesive.

[0015] In some embodiments, all of the end caps are aligned in the same plane on the holder, hi some embodiments, all of the optical fibers and end caps are aligned to provide the same polarization.

[0016] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification, however the invention, both as to organization and method of operation, together with its objects, features, and advantages, may best be understood by reference to the following detailed description read in connection with the accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1A] FIG. 1 is a rear perspective view of an optical system including a holder for holding and aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 1B] 1 is a front perspective view of an optical system including a holder for holding and aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. FIG. [Figure 2A] 1A-1C are diagrams of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 2B] 1A-1C are diagrams of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 2C] 1A-1C are diagrams of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 2D] 1A-1C are diagrams of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 2E] 1 is a cross-sectional view of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 2F] 1 is a cross-sectional view of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 2G]1 is a cross-sectional view of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. [Figure 3A] 10A-10C are diagrams of adhesive channels intersecting at least one row of bores in a holder, according to some embodiments of the present invention. [Figure 3B] 10A-10C are diagrams of adhesive channels intersecting at least one row of bores in a holder, according to some embodiments of the present invention. [Figure 3C] 10A-10C are diagrams of adhesive channels intersecting at least one row of bores in a holder, according to some embodiments of the present invention. [Figure 3D] 10A-10C are diagrams of adhesive channels intersecting at least one row of bores in a holder, according to some embodiments of the present invention. [Figure 4A] 1A-1C are diagrams of several flow regimes in various cooling channel arrays within a holder, according to some embodiments of the present invention. [Figure 4B] 1A-1C are diagrams of several flow regimes in various cooling channel arrays within a holder, according to some embodiments of the present invention. [Figure 4C] 1A-1C are diagrams of several flow regimes in various cooling channel arrays within a holder, according to some embodiments of the present invention. [Figure 5] FIG. 10 is a perspective view of another optical system including a holder for holding and aligning a 2D array of optical end caps, according to some embodiments of the present invention. [Figure 6] FIG. 10 is a perspective view of another optical system including a holder for holding and aligning a 1D array of optical end caps, according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] It should be understood that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Furthermore, where appropriate, reference numerals may be repeated among the figures to indicate corresponding or similar elements.

[0019] Those skilled in the art will understand that the present invention may be embodied in other specific forms without departing from its spirit and essential characteristics. Accordingly, the above-described embodiments are to be considered in all respects as illustrative rather than limiting the invention described herein. The scope of the present invention is therefore indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

[0020] Aspects of the present invention relate to providing a holder for holding and aligning a 2D or 1D array of optical end caps, each welded to an optical fiber. The holder, according to embodiments of the present invention, can provide precise alignment of all the end caps in the array and a cooling mechanism for extracting heat generated in the end caps during operation of the laser.

[0021] 1A and 1B, which are front and rear perspective views of an optical system including a holder for holding and aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. The optical system 1000 may include a holder 100 that holds a 2D array of end caps 10, each welded to an optical fiber 15. In some embodiments, both the end caps 10 and the optical fibers 15 are made of optical-grade glass.

[0022] In the non-limiting example of holder 100 shown in Figures 1A-1B and 2A-2B, the 2D array is a hexagonal array, although one skilled in the art will understand that the present invention is not limited to 2D arrays or this particular geometric shape. Examples of alternative holders showing additional 2D and 1D arrays are illustrated and described below with respect to Figures 3 and 4.

[0023] 2A, 2B, 2C, 2D, 2F, and 2G, which illustrate various views and cross-sectional views of a holder for aligning optical end caps each connected to an optical fiber, according to some embodiments of the present invention. The holder 100 may include a body 110 made of any suitable thermally conductive material, such as, but not limited to, a copper alloy, an aluminum alloy, a titanium alloy, a tungsten-based metal composite, a carbon-based composite, or the like.

[0024] Body 110 may be manufactured using any suitable technique capable of forming high precision (optical standard) shapes and cavities, such as additive manufacturing powder bed fusion using a laser beam, laser ablation, high precision machining, electroetching, electrical discharge machining, etc. In some embodiments, the manufacturing process may require one or more thermal (e.g., heating) treatments depending on the material selected. In some embodiments, portions of the surface of body 110 may be coated and / or provided with a surface treatment.

[0025] The body 110 may include at least one row 120 or bore 122, each sized to receive a single optical endcap 10. In some embodiments, the body 110 may include only one row 120, as shown in Figure 6, or multiple rows 120, e.g., 2, 3, 4, 5, 6, 7, 8, 10, 15, 20, or more, as shown in Figures 2A-2F (e.g., seven rows 120) and 4 (e.g., seven rows). In some embodiments, each row 120 may include at least two, e.g., 2-50, 4-40, 5-20, 5-10, or any number in between, of bores 122.

[0026] In some embodiments, the bore 122 can have a circular cross-section, a hexagonal cross-section, a rectangular cross-section, etc. In some embodiments, the bore 122 can be characterized by a diameter of the circular cross-section or a diameter of an inscribed circle inscribed in the hexagonal or rectangular cross-section that is between 0.5 and 20 mm, e.g., 0.7 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 7 mm, 8 mm, 10 mm, 15 mm, 20 mm, or any value therebetween.

[0027] In some embodiments, the bore 122 is sized to receive a single optical end cap with a diameter tolerance of up to +50 microns, e.g., +40 microns, +30 microns, +25 microns, +20 microns, +15 microns, +10 microns, +5 microns, +1 micron, and any value therebetween. For example, if the end cap and corresponding bore are cylindrical, the diameter of the bore may be up to 50 microns larger than the diameter of the end cap. As yet another example, if the end cap and corresponding bore are hexagonal prisms, the diameter of the inscribed circle inscribed in the hexagonal cross section of the bore may be up to 50 microns larger than the diameter of the inscribed circle inscribed in the end cap.

[0028] In some embodiments, the central axes of all bores 122 deviate from parallelism to the reference optical axis by up to 1°, 0.5°, 0.1°, 0.05°, or 0.01°. In some embodiments, a reference optical axis is defined. In some embodiments, the positions of the central axes of all bores 122 deviate from a reference point on body 110 by up to ±0.5 mm, ±0.1 mm, ±0.05 mm, ±0.01 mm, 0.007 mm, or ±0.001 mm. For example, the reference point is defined as the central axis of first bore 122a and first line 120a shown in FIG. 2C . In yet another example, the reference point is defined as a reference pin, reference key, or the like, attached to or included in body 110.

[0029] In some embodiments, the outer end faces of all end caps held within holder 100 are aligned on the same plane, for example, outer surface 112 shown in Figures 1A and 2D. Thus, the front and / or rear faces of all end caps 10 are substantially aligned with each other and with a reference plane, such as plane 112, to within 0.01, 0.02, 0.05, 0.06, 0.1, 0.2, 0.03, 0.5, 0.7, 0.8, 1 mm, and any value therebetween.

[0030] In some embodiments, all end caps 10 are optically aligned to provide a laser beam with the same polarization, in which case each end cap can be adjusted (by rotation) to a predetermined polarization before being secured with adhesive.

[0031] In some embodiments, the body 110 may further include at least one adhesive channel 130 intersecting at least one row of bores 120 and configured to supply and retain adhesive material for securing each optical end cap 10 to a corresponding bore 122, as shown in FIG. 2D and described in more detail below with respect to FIGS. 3A and 3B.

[0032] In a non-limiting example, the adhesive channels 130 may have a diameter 0.5 to 1 mm that of the bore 122; for example, if the bore 122 has a diameter of 2 mm, the adhesive channels 130 may have a diameter of 1.6 mm. In some embodiments, the adhesive material is selected from ultraviolet (UV) epoxy, silicone-based adhesives, and the like. The adhesive material may be injected into the adhesive channels 130 after inserting and aligning the end caps 10 into the bores 122. For example, the alignment and fixation process may be performed row by row so that all end caps inserted in a single row 120 have the same polarization and the same front / rear faces of the end caps are substantially aligned with each other and with a reference plane. After the alignment process is complete, adhesive material may be injected into the corresponding adhesive channels 130 to fix the end caps to the bores in the aligned positions.

[0033] In some embodiments, the adhesive material may be selected to have sufficient flowability within the adhesive channel 130 while providing good wetting and adhesion between the adhesive channel 130 and the end cap 10. Accordingly, the viscosity of the adhesive material may be selected to be between 500K and 20K cP, e.g., between 500K and 100K cP, between 400 and 50 cP, between 200 and 75 cP, and any value therebetween. In some embodiments, the adhesive material may further be selected to have a thermal coefficient (after curing) as close as possible to the thermal coefficient of the body 110 and / or the end cap 10. The thermal coefficient is selected to minimize the formation of thermal stresses in the end cap 10. Accordingly, the thermal coefficient (CTE) of the adhesive material may be between 1 and 200 ppm°C (and any value therebetween), and the thermal conductivity of the adhesive material may be between 0.1 and 2.5 W / m 2 K]. Some non-limiting examples of optional adhesive materials are shown in Table 1.

[0034] [Table 1]

[0035] In some embodiments, the body 110 may further include an array 140 of cooling channels 142 connected to at least one inlet 144 and at least one outlet 146 for circulating a cooling fluid, the array 140 of cooling channels 142 being positioned to surround at least a portion of the outer wall of each bore 122, as shown in FIG. 2F . In some embodiments, the array 140 of cooling channels 142 is positioned to surround at least a portion of the outer wall of each bore 122 so as to avoid direct contact of the end cap 10 with the cooling fluid. Some non-limiting examples of optional cooling channel arrays and flow patterns are illustrated and described below with respect to FIGS. 4A, 4B, and 4C.

[0036] In some embodiments, the holder 100 may further include at least one pump 150 fluidly connected to the at least one inlet 144 and the at least one outlet 146, for example, to circulate a cooling fluid between the array 140 and the chiller 160. The pump 150 and the chiller 160 may be any commercially available component. In some embodiments, the pump 150 and the chiller 160 may be included in a single device or may be two separate devices fluidly connected by a set of pipes. In some embodiments, the cooling fluid is selected to be a fluid between −40° C. and +70° C. In some embodiments, the cooling fluid may be in a gas phase or a liquid phase. Some non-limiting examples of cooling fluids may include demineralized water, water with ethylene glycol, ethylene glycol, oil, etc.

[0037] 3A, 3B, 3C, and 3D, which are diagrams of an adhesive channel intersecting at least one row of bores 120 in a holder, according to some embodiments of the present invention. In some embodiments, adhesive material may be introduced into adhesive channel 130 via adhesive inlet 132, for example, by any injection means. For example, the nozzle of an adhesive gun (also known in the art as an injection gun or glue gun) may be attached / inserted into inlet 132 to form proper contact between the nozzle and inlet 132 prior to injecting the adhesive material.

[0038] In some embodiments, each intersection 134 (marked by a dashed oval in FIG. 3B , a dashed circle in FIG. 3C , and shown in FIG. 3D ) between any adhesive channel 130 and any bore 122 in the holder 100 may have substantially the same area / size, so that substantially the same amount of adhesive may contact each end cap 10. In some embodiments, the adhesive channel 130 may intersect a portion of the circumference of the bore 122. For example, the portion may be about 15% of the circumference of the bore 122 as shown. In other examples, the portion may be about 5% of the circumference of the bore 122, about 10% of the circumference of the bore 122, about 20% of the circumference of the bore 122, about 30% of the circumference of the bore 122, about 40% of the circumference of the bore 122, about 50% of the circumference of the bore 122, or any value therebetween.

[0039] In some embodiments, each bore may be intersected by two adhesive channels 130, for example, each of the upper and lower 10% of the circumference of the bore 122 may be intersected by a respective adhesive channel 130.

[0040] Reference is now made to Figures 4A, 4B, and 4C, which are illustrations of several flow regimes in various cooling channel arrays within a holder, according to some embodiments of the present invention. Each of the cooling channel arrays has a different number and different arrangement of cooling fluid inlets and outlets. As one skilled in the art will appreciate, Figures 4A, 4B, and 4C are shown by way of example only, and the overall invention is not limited to these particular designs.

[0041] In some embodiments, the design of the array of cooling channels 140, inlet(s) 144, and outlet(s) 146 is made to ensure uniform temperature distribution in all bores 122 within the holder 100 and minimize any thermal stresses added to the end caps 10. This design may ensure that all bores 122 are exposed to substantially the same temperature (e.g., the temperature difference between different end caps 10 is no more than 10°C, e.g., a difference of 0.1-10°C, and any value therebetween), which adds negligible thermal stress to the end caps 10.

[0042] The holder 100 in Figure 4A includes a single inlet 144 and a single outlet 146. The inlet flow is indicated by the dark gray arrows, and the outlet flow is indicated by the light gray arrows. This arrangement can result in thorough fluid mixing and ensure uniform temperature distribution.

[0043] 4B includes three inlets 144, 144A, and 144B and three outlets 146, 146A, and 146B in a mirror-symmetric arrangement, which ensures thorough internal fluid mixing in each channel 142 of the array 140.

[0044] 4C includes three inlets 144, 144A, and 144B and three outlets 146, 146A, and 146B, with the central inlet 144 located between the two side outlets 146A and 146B and the central outlet 146 located between the two side inlets 144A and 144B. Such an arrangement ensures immediate thermal uniformity.

[0045] Reference is now made to Figures 5 and 6, which are perspective views of two optical systems each comprising a holder for holding and aligning optical end caps each connected to an optical fiber, in accordance with some embodiments of the present invention.

[0046] 5 may include a holder 200 that holds a 2D array of end caps 10 each welded to an optical fiber 15. The optical system 3000 shown in FIG. 4 may include a holder 300 that holds a 2D array of end caps 10 each welded to an optical fiber 15.

[0047] Holders 200 and 300 may include substantially the same elements and components as holder 100 described above. Holders 200 and 300 differ from holder 100 in the geometric arrangement of the bores 122. In holder 200, all of the bores 122 are arranged in a cubic 2D array, while in holder 300, all of the bores 122 are arranged in a 1D array comprising a single row 120. As those skilled in the art will appreciate, the 7×7 bore array shown in FIG. 5 and the seven bore rows shown in FIG. 6 are merely examples, and the present invention is not limited to this configuration. In some embodiments, a rectangular 2D array may include any number n×m of bores 122, where n and m are integers.

[0048] In some embodiments, all end caps in systems 1000, 2000, and 3000 are aligned in the same plane, eg, outer surface 112, of the holder.

[0049] In some embodiments, all optical fibers 15 and end caps 10 of systems 1000, 2000, and 3000 are aligned to provide the same polarization.

[0050] Unless expressly stated, the method embodiments described herein are not limited to a particular order or sequence. Furthermore, all methods described herein are intended as examples only, and other or different methods may be used. Also, some of the described method embodiments or elements thereof may occur or be performed at the same time.

[0051] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0052] Various embodiments have been presented, each of which may of course include features of the other presented embodiments, and embodiments not specifically described may include various features described herein.

Claims

1. A holder for aligning optical end caps each connected to an optical fiber, comprising: The main body is at least one row of bores, each dimensioned to receive a single optical end cap; at least one adhesive channel intersecting the at least one row of bores and configured to supply and retain an adhesive material for securing each optical end cap to a corresponding bore; an array of cooling channels connected to at least one inlet and at least one outlet for circulating a cooling fluid, said array of cooling channels being disposed to surround at least a portion of an outer wall of each bore; A main body A holder comprising:

2. 10. The holder of claim 1, wherein each bore is sized to receive the single optical end cap with a maximum diameter tolerance of 50 microns.

3. 3. A holder according to claim 1 or claim 2, wherein each row of bores comprises at least two bores.

4. A holder according to any one of claims 1 to 3, wherein the central axis of each bore deviates from parallelism to the reference optical axis by a maximum of 0.05°.

5. A holder according to any one of claims 1 to 4, wherein the position of the central axis of each bore deviates from a reference point on the body by a maximum of 0.007 mm.

6. A holder according to any one of claims 1 to 5, wherein the body is made of an alloy selected from the group consisting of an aluminium alloy, copper, titanium alloy, tungsten-based metal composite, and carbon-based composite.

7. A holder as described in any one of claims 1 to 6, wherein the array of cooling channels is arranged to surround at least a portion of the outer wall of each of the bores so as to avoid direct contact between the end cap and the cooling fluid.

8. The holder of any one of claims 1 to 7, further comprising at least one pump in fluid communication with the at least one inlet and at least one outlet for circulating the cooling fluid.

9. A holder according to any one of the preceding claims, wherein the cooling fluid is selected to be a fluid between -40°C and +70°C.

10. 1. An optical system comprising: A holder according to any one of claims 1 to 9; an array of optical fibers each welded to an end cap; An optical system comprising: Each end cap is inserted into a corresponding bore in the holder and secured using an adhesive.

11. The optical system of claim 10 , wherein all of the end caps are aligned in the same plane on the holder.

12. 11. The optical system of claim 9 or claim 10, wherein all of the optical fibers and the end caps are aligned to provide the same polarization.

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