Optical mount

Abstract

An optical mount and a method of alignment of an optical element on an optical bench using the optical mount. The optical mount comprises: a main body configured to support an optical element; and two holes for receiving respective mounting screws for securing the optical mount on an optical bench; wherein the two holes are configured to allow adjustment of a position of the optical mount relative to the optical bench by movement of the two holes relative to the respective screws in at least one degree of horizontal freedom relative to the optical bench.

Description

[0001] OPTICAL MOUNT

[0002] FIELD OF INVENTION

[0003] The present invention relates broadly an optical mount and to a method of aligning an optical element on an optical bench, in particular for space applications.

[0004] BACKGROUND

[0005] Any mention and / or discussion of prior art throughout the specification should not be considered, in any way, as an admission that this prior art is well known or forms part of common general knowledge in the field.

[0006] In a global quantum-secure network using Quantum Key Distribution (QKD) and other quantum-safe key distribution methods, satellites designed for space-to-ground optical communications communicate with optical ground stations (OGS") to receive signals and use them to derive shared symmetric keys which form a backbone to a global network for sharing quantum-safe keys between any two end users.

[0007] A key part in quantum satellite system applications are quantum sources of light. While these sources focus on the generation of quantum light, efficiently capturing these light particles is also a crucial aspect. Whether it is using integrated photonics or bulk optics, once the quantum light is generated, it needs to be efficiently delivered to the next immediate node / user / target. If this delivery is performed in free-space, usually this presents a constraint in that the point of quantum light generation and quantum light delivery are stringently linked via free space optics, making it challenging for low-SWaP (size, weight and power) systems to implement such an optical scheme. On the other hand, if light delivery is implemented via optical fibres, once the quantum light particles are fibre-coupled, the fibre is free to be routed in the most spatially-optimal way to complete that light delivery.

[0008] Quantum sources of light typically involve laser diodes in the generation of quantum light. While there are several types of laser diodes (i.e. fibre coupled, module-based), free-space, TO- can diodes are widely popular for their higher optical power levels and convenience of use. There is a drawback, however, in that the rays of light emitted from free-space laser diodes will always come with a directional offset, making these light rays not co-aligned with respect to the optical assembly’s mechanical axis. For satellite quantum systems where the volume allocated for optical devices is limited, these optical beam deviations can be a problem. Adding extra optical elements in the path of the laser light to correct such deviations is possible (i.e. using prism pairs), but typically this can compromise optical power transmission and, ultimately, adds more complexity to the system. Embodiments of the present invention seek to address one or more of the abovementioned problems.

[0009] SUMMARY

[0010] In accordance with a first aspect of the present invention, there is provided an optical mount comprising: a main body configured to support an optical element; and two holes for receiving respective mounting screws for securing the optical mount on an optical bench; wherein the two holes are configured to allow adjustment of a position of the optical mount relative to the optical bench by movement of the two holes relative to the respective screws in at least one degree of horizontal freedom relative to the optical bench.

[0011] In accordance with a second aspect of the present invention, there is provided method of alignment of an optical element on an optical bench using the optical mount of the first aspect.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:

[0014] FIG. 1 shows a schematic drawing illustrating the optical layout of the collection scheme for coupling between free-space and fibre-based light propagation, in low-SWaP assemblies for space applications according to example embodiments

[0015] FIG. 2A shows a schematic drawing illustrating a lens base of a two-part lens mounting assembly according to an example embodiment.

[0016] FIG. 2B shows a schematic drawing illustrating a two-part lens mounting assembly according to an example embodiment without screws in elongated holes on the lens mount, here for degree of freedom in x.

[0017] FIG. 2C shows a schematic drawing illustrating a two-part lens mounting assembly according to an example embodiment with screws in elongated holes on the lens mount 206, here for degree of freedom in x.

[0018] FIG. 3A shows a schematic drawing illustrating a lens base of a two-part lens mounting assembly according to another example embodiment. FIG. 3B shows a schematic drawing illustrating a two-part lens mounting assembly according to another example embodiment with screws in elongated holes on the lens base, here for degree of freedom in y.

[0019] FIG. 4 shows a schematic drawing illustrating a collimator mounting assembly according to an example embodiment.

[0020] FIG. 5 shows a schematic drawing illustrating a two-part laser mounting assembly according to an example embodiment.

[0021] FIG. 6A shows a schematic drawing illustrating a base of a two-part laser mounting assembly according to an example embodiment.

[0022] FIG. 6B shows another schematic drawing illustrating a base of a two-part laser mounting assembly according to an example embodiment.

[0023] FIG. 6C shows another schematic drawing illustrating a two-part laser mounting assembly according to an example embodiment.

[0024] FIG. 7 shows a cross-sectional schematic drawing illustrating a two-part laser mounting assembly according to an example embodiment.

[0025] DETAILED DESCRIPTION

[0026] An example embodiment provides a three-part mechanical solution to couple single photons of light into single-mode fibres. When compared to other solutions, an example embodiment mitigates single-mode fibre coupling tolerance issues in low-SWaP assemblies for space applications. At the same time, an example embodiment provides a solution for filtering out ambient light without the need for aggressive spectral filtering. An example embodiment is also adaptable to different optical schemes and can enable quantum light systems to tailor their light delivery methods when resources are limited.

[0027] It has been recognised by the present inventors that for space applications, i.e. low-SWaP assemblies (with mechanical footprints around several square centimeters), optical components (for example collimator, lens, laser diode) cannot move once they are fixed in place, and their machining tolerances need to be accounted for when aligning them prior to launch. The solution provided in various example embodiments for accommodating the machining tolerances during pre-launch assembly and alignment is to elongate screw holes (for example + / - 0.5 mm, but not limited thereto) and / or to relax the screw hole machining tolerances (for example hundreds of micrometres instead of tens of micrometres, but not limited thereto) on, for example, the lens mount(s), collimator mount(s), and / or laser diode mount(s) to provide an alignment degree of freedom in x (horizontal relative to the optical bench / support) or in the y-direction (i.e. in the direction of light propagation). Additionally, or alternatively, a mounting assembly is provided in an example embodiment, comprising a base and, for example, the lens mount supported on the base. The base (e.g. a rectangular work piece) can be manufactured with different heights, so that a z (vertical relative to the optical bench / support) alignment degree of freedom is provided. A two-part collimator mount, and / or two-part laser diode mount can similarly be provided according to example embodiments.

[0028] It is noted that in different example embodiments, the base may additionally be configured with elongated holes for providing an additional alignment degree of freedom, for example in y, if the mount, for example a lens mount, is configured for alignment degree of freedom in x, or in x, if the mount, for example a lens mount, is configured for alignment degree of freedom in y.

[0029] While in different example embodiments, degree of freedom in x and y may be provided by way of generally enlarged holes, it has been found by the inventors that, in practice, too many degrees of freedom can lead to inaccuracies in the positioning of the mount or mounting assembly. Hence, in preferred embodiments, each mount or mounting assembly provides degree of freedom in either x or y, and optionally in z (i.e. height of base). On the other hand, if the alignment degree of freedom is provided by relaxed screw hole machining tolerances, then accuracy in the position may be maintained due to the more limited alignment magnitudes in such embodiments, compared to elongated / generally enlarged holes.

[0030] FIG. 1 shows the optical layout of the collection scheme for coupling between free-space and fibre-based light propagation, in low-SWaP assemblies for space applications according to example embodiments. A collimated free-space beam 100 is focused down by a single lens 102. The diameter of the free-space collimated beam 100 and the focal length of the lens 102 are two parameters to be determined based on the diameter of the focused / collimated beam for coupling into the fibre (not shown).

[0031] FIGs. 2A-C show the assembly of a two-part lens mounting assembly 200 according to an example embodiment. FIG. 2A: Base 202. FIG. 2B: Full assembly 200 without screws in elongated holes 208, 210 on the lens mount 206, here for degree of freedom in x. FIG. 2C: Full assembly 200 with screws 212, 214 in elongated holes 208, 210 on the lens mount 206, here for degree of freedom in x. The screws 212, 214 are threadedly received in holes 216, 218 on the base 202. Screws 220, 222 are used to secure the base 2026 on the optical bench (not shown) via fitted holes (hidden). While the base 202 can be manufactured with different thicknesses to adjust the height of the lens 204 vertically, the lens mount 206 features two mounting points with the elongated holes 208, 210 and screws 212, 214 so that the lens 204 position can be adjusted horizontally. The lens 204 is received in a cavity of the lens mount 206 and secured with adhesive materials on the outer areas of a flat face of the lens 204.

[0032] FIGs. 3A-B show the assembly of a two-part lens mounting assembly 300 according to another example embodiment. FIG. 3 A: Base 302. FIG. 3B: Full assembly 300 with screws 312, 314 in holes (hidden) on the lens mount 306, for threaded engagement in holes 309, 311 on the lens base 302. The base 302 can be manufactured with different thicknesses to adjust the height of the lens 304 vertically. Additionally, the base 302 in this example embodiment features two mounting points with elongated holes 316, 318 and screws 320, 322 so that the base 302, and hence the two-part lens mounting assembly 300, position can be adjusted horizontally, here for degree of freedom in y. The lens 304 is received in a cavity of the lens mount 306 and secured with adhesive materials on the outer areas of a flat face of the lens 304.

[0033] FIG. 4 shows a collimator mounting assembly 400 according to an example embodiment with a fibre optic collimator 402. The collimator mount 405 features two mounting points with screws 406, 408 received in holes (hidden) fabricated with relaxed machining tolerances that allows the collimator 402 to be adjusted horizontally, i.e. small adjustment with degree of freedom in x and y. In this example embodiment, the collimator 402 is a standard Fibre Connector / Physical Contact (FC / PC) connected tube with a front threading engaging a corresponding threading in the collimator mount 405, such that the collimator mount 405 accepts the front threading. In the example embodiment in FIG. 4, the collimator mounting assembly 400 advantageously implements a baffle / pinhole 410 approach to remove background light noise at the entry to the collimator 402. The collimator assembly 400 may be secured to an optical bench 401 with or without a base that can be manufactured with different thicknesses to adjust the height of the collimator 402 vertically (compare bases 202, 302 in FIGs. 2 and 3).

[0034] Another example embodiment provides a mechanical solution to mechanically secure and optically align TO-can, free-space laser diodes. When compared to other solutions, this solution can mitigate laser beam directional offsets in low-SWaP assemblies for space applications. Advantageously, an example embodiment also allows temperature controlling the laser diode, as one of the mechanical parts acts as an oven. Example embodiments are preferably adaptable to all types of TO-can lasers and can enable streamlined alignment procedures for quantum light sources while advantageously reducing the number of optical elements in the optical assembly.

[0035] FIG. 5 shows the full assembly of a two-part laser mounting assembly 500 according to an example embodiment. The base 502 can be manufactured with different thicknesses to adjust the height of the laser diode 504 vertically. The laser mount 506, is secured onto the base 502 via two mounting points with screws 528, 530 received in fitted holes 508, 510, and the base 502 is secured to an optical bench 501.

[0036] FIGs. 6A and B show details of the base 502, including ridges 512, 514 to guide the placement of a thermoelectric cooler (TEC) 516 (FIG. 5 and FIG. 6C) sandwiched between the base 502 and the laser mount 506 (Fig. 5 and FIG. 6C), threaded holes 518, 520 for mounting the laser mount 506 (FIG. 5 and FIG. 6C) to the base 502, and screws 524, 526 passing through respective though holes 532, 534 for mounting of the base 502 to an optical bench (not shown). The holes 532, 534 are fabricated with relaxed machining tolerances so that the laser diode 504 position can be adjusted horizontally, i.e. small adjustment with degree of freedom in x and y. A thermistor 535 is provided in a channel 537 for temperature measurement.

[0037] FIG. 7 shows a cross-sectional view of the full assembly of the two-part laser mounting assembly 500. The laser diode 504 is mechanically secured in a cavity of the laser mount 506. Thermal paste provides better contact area between the diode 504 and the cavity walls. The TEC 516 is sandwiched between the laser mount 506 and the base 502, for good thermal contact and control of the laser mount 506 functioning as an oven for temperature control of the laser diode 504.

[0038] In one embodiment, an optical mount is provided, comprising a main body configured to support an optical element; and two holes for receiving respective mounting screws for securing the optical mount on an optical bench; wherein the two holes are configured to allow adjustment of a position of the optical mount relative to the optical bench by movement of the two holes relative to the respective screws in at least one degree of horizontal freedom relative to the optical bench.

[0039] The two holes may be elongated in an x-direction relative to the optical bench.

[0040] The two holes may be elongated in an y-direction relative to the optical bench.

[0041] The two holes may be fabricated with relaxed machining tolerances for movement of the two holes relative to the respective screws in two degrees of horizontal freedom relative to the optical bench.

[0042] The optical element may comprise one of a group consisting of a lens, a collimator, and a laser diode.

[0043] The optical element may comprise a collimator, and the main body is configured to have the collimator attached thereto on one side and to comprise a pinhole on another side opposite to the collimator for light filtering. The collimator may be attached to the main body by threaded engagement.

[0044] The optical element may comprise a laser diode or a lens, and the main body is configured to have the laser diode or lens attached thereto in a cavity of the main body.

[0045] The optical mount may comprise a base configured to have the main body attached thereto using the two screws and to be mounted to the optical bench.

[0046] The optical mount may be in the form of a base configured for supporting the optical element in a holder element attached to the base.

[0047] A height of the base may be selected or adjustment of the position of the optical element vertically relative to the optical bench.

[0048] The base may comprise two other holes for receiving respective other mounting screws for securing the base on an optical bench. The two other holes may be configured to allow adjustment of a position of the base relative to the optical bench by movement of the two other holes relative to the respective screws in at least one degree of horizontal freedom relative to the optical bench. The movement of the two other holes in the base relative to the respective other screws may be in the other degree of horizontal freedom relative to the optical bench, as compared to the movement of the two holes in the main body relative to the respective screws. The optical element comprises a laser diode, and the optical mount comprises a thermoelectric controller sandwiched between the base and the main body.

[0049] In one embodiment, a method of alignment of an optical element on an optical bench is provided, using the optical mount according to an example embodiment described herein.

[0050] It will be appreciated by a person skilled in the art that numerous variations and / or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. Also, the invention includes any combination of features described for different embodiments, including in the summary section, even if the feature or combination of features is not explicitly specified in the claims or the detailed description of the present embodiments.

[0051] In general, in the following claims, the terms used should not be construed to limit the systems and methods to the specific embodiments disclosed in the specification and the claims, but should be construed to include all processing systems that operate under the claims. Accordingly, the systems and methods are not limited by the disclosure, but instead the scope of the systems and methods is to be determined entirely by the claims.

[0052] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "hereunder," "above," "below," and words of similar import refer to this application as a whole and not to any particular portions of this application. When the word "or" is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list.

Claims

CLAIMS1. An optical mount comprising: a main body configured to support an optical element; and two holes for receiving respective mounting screws for securing the optical mount on an optical bench; wherein the two holes are configured to allow adjustment of a position of the optical mount relative to the optical bench by movement of the two holes relative to the respective screws in at least one degree of horizontal freedom relative to the optical bench.

2. The optical mount of claim 1, wherein the two holes are elongated in an x-direction relative to the optical bench.

3. The optical mount of claims 1 or 2, wherein the two holes are elongated in an y-direction relative to the optical bench.

4. The optical mount of claim 1, wherein the two holes are fabricated with relaxed machining tolerances for movement of the two holes relative to the respective screws in two degrees of horizontal freedom relative to the optical bench.

5. The optical mount of any one of the preceding claims, wherein the optical element comprises one of a group consisting of a lens, a collimator, and a laser diode.

6. The optical mount of claim 5, wherein the optical element comprises a collimator, and the main body is configured to have the collimator attached thereto on one side and to comprise a pinhole on another side opposite to the collimator for light filtering.

7. The optical mount of claim 6, wherein the collimator is attached to the main body by threaded engagement.

8. The optical mount of claim 5, wherein the optical element comprises a laser diode or a lens, and the main body is configured to have the laser diode or lens attached thereto in a cavity of the main body.

9. The optical mount of any one of the preceding claims, comprising a base configured to have the main body attached thereto using the two screws and to be mounted to the optical bench.

10. The optical mount of any one of claims 1 to 8, in the form of a base configured for supporting the optical element in a holder element attached to the base.

11. The optical mount of claims 9 or 10, wherein a height of the base is selected or adjustment of the position of the optical element vertically relative to the optical bench.

12. The optical mount of any one of claims 9 to 11, wherein the base comprises two other holes for receiving respective other mounting screws for securing the base on an optical bench.

13. The optical mount of claim 12, wherein the two other holes are configured to allow adjustment of a position of the base relative to the optical bench by movement of the two other holes relative to the respective screws in at least one degree of horizontal freedom relative to the optical bench.

14. The optical mount of claim 13, wherein the movement of the two other holes in the base relative to the respective other screws is in the other degree of horizontal freedom relative to the optical bench, as compared to the movement of the two holes in the main body relative to the respective screws.

15. The optical mount of any one of claims 9 to 14, wherein the optical element comprises a laser diode, and the optical mount comprises a thermoelectric controller sandwiched between the base and the main body.

16. A method of alignment of an optical element on an optical bench using the optical mount of any one of the preceding claims.

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