Collimating fiber array and optical mode multiplexer
A high-precision collimating optical fiber array with a waveguide array processed by a three-dimensional femtosecond laser system addresses low positioning accuracy issues, enhancing alignment and reducing loss for improved performance in mode multiplexers.
Patent Information
- Application Number
- CN202420607245.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-25
- Publication Date
- 2024-12-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing collimation methods for optical fiber arrays in optical mode multiplexers suffer from low positioning accuracy, leading to excessive loss and inability to meet high-precision demands, particularly in mode multiplexers.
A collimating optical fiber array is designed with a waveguide array processed by a three-dimensional femtosecond laser direct writing system, combined with a microlens array, achieving high positioning accuracy and reducing loss through precise alignment of single-mode optical fibers and waveguide channels.
The proposed solution significantly improves positioning accuracy and reduces loss by 20-25%, enabling effective use in high-precision scenarios like mode multiplexers, while reducing manufacturing costs and time.
Smart Images
Figure CN222189512U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of optical communication, in particular to a collimated optical fiber array and an optical mode multiplexer. Background Art
[0002] Multiple discrete phase planes form an optical mode multiplexer called MPLC (Multi-Plane Light Converter).
[0003] The optical mode multiplexer consists of three parts: the input end, the modulation structure and the output end. The input end is a collimated fiber array, the modulation structure is composed of a gold-plated phase plate and a reflector, and the output end is a few-mode fiber integrated with a gradient refractive index lens.
[0004] In an optical mode multiplexer, light input is achieved by a collimated fiber array. At present, the maximum positioning accuracy of the collimated fiber array introduces an offset in the packaging stress, which is far from the optimal accuracy required by the modulation structure. This will bring a large amount of additional loss to the optical mode multiplexer. When the loss is too large, the beneficial effect of the exponentially increased transmission capacity of the optical mode multiplexer will be offset by the exponentially attenuated power, resulting in poor use of the optical mode multiplexer.
[0005] The existing collimating fiber array has the problem of low positioning accuracy and cannot be applied to scenarios with high requirements for positioning accuracy, such as mode multiplexers. Therefore, designing a collimating fiber array with high positioning accuracy is an urgent problem to be solved. Utility Model Content
[0006] Based on this, it is necessary to propose a collimating fiber array and an optical mode multiplexer to address the above problems in order to achieve a collimating fiber array with high positioning accuracy.
[0007] The first aspect of the utility model provides a collimating optical fiber array, the collimating optical fiber array comprising:
[0008] Optical fiber arrays, waveguide arrays and microlens arrays;
[0009] The optical fiber array is composed of a plurality of single-mode optical fiber ferrules, which are used to transmit laser light and input the laser light into the waveguide array;
[0010] The waveguide array is composed of a plurality of waveguide channels in parallel whose positioning accuracy meets the preset high positioning accuracy requirement, and the positions of the single-mode optical fibers in the optical fiber array correspond one-to-one to the positions of the waveguide channels in the waveguide array, and the laser output by the single-mode optical fibers is incident on the waveguide channels at the corresponding positions;
[0011] The microlens array is composed of a plurality of lenses arranged in combination, and the positions of the waveguide channels in the waveguide array correspond one-to-one to the positions of the lenses in the microlens array. The laser output by the waveguide channels is incident on the lenses at the corresponding positions to achieve beam collimation.
[0012] Furthermore, the waveguide array is processed on a sample using a three-dimensional femtosecond laser direct writing system.
[0013] Furthermore, the sample is a glass substrate.
[0014] Furthermore, the preset high positioning accuracy requirement is less than 0.5um.
[0015] Furthermore, an anti-reflection coating is provided on a side of the microlens array facing the waveguide array.
[0016] Furthermore, the three-dimensional femtosecond laser direct writing system includes: a femtosecond laser, a first reflector, a concave lens, a cylindrical lens, a mechanical slit, an objective lens, a beam splitter and a translation stage;
[0017] The femtosecond laser is used to output a laser beam, and the laser beam is incident on the concave lens through the first reflector;
[0018] The concave lens is used to amplify the laser beam, and the amplified laser beam is incident on the cylindrical lens;
[0019] The cylindrical lens is used to compress the incident laser light speed, and the compressed laser beam is incident on the mechanical slit;
[0020] The mechanical slit is used to modulate the incident laser beam, and the modulated laser beam is incident on the objective lens through the beam splitter;
[0021] The objective lens is used to focus the incident laser beam, and the focused laser beam hits the sample on the displacement stage, and the sample is processed to obtain the waveguide array.
[0022] Furthermore, the three-dimensional femtosecond laser direct writing system further includes: a second reflector and a camera;
[0023] After the focused laser beam hits the sample on the translation stage, a reflected beam is generated. The reflected beam passes through the beam splitter and is incident on the second reflector. The second reflector is used to reflect the reflected beam to the camera. The camera is used to form an image based on the reflected beam.
[0024] Furthermore, the three-dimensional femtosecond laser direct writing system supports the processing of three-dimensional waveguides within a maximum spatial range of 100*100*20mm.
[0025] Furthermore, the three-dimensional femtosecond laser direct writing system supports the processing of waveguide channels with a maximum length of 100 mm.
[0026] A second aspect of the present invention provides an optical mode multiplexer, which includes: a collimating optical fiber array as described in any one of the first aspects, and also includes a modulation structure and an output end.
[0027] The following beneficial effects are achieved by using the embodiments of the present invention:
[0028] The present application provides a collimating optical fiber array, which includes: an optical fiber array, a waveguide array and a microlens array, wherein the optical fiber array is composed of a plurality of single-mode optical fiber ferrules for transmitting laser light, and the laser light is input into the waveguide array, the waveguide array is composed of a plurality of waveguide channels in parallel whose positioning accuracy meets the preset high positioning accuracy requirement, and the position of the single-mode optical fiber in the optical fiber array corresponds one-to-one to the position of the waveguide channel in the waveguide array, and the laser light outputted by the single-mode optical fiber is incident on the waveguide channel at the corresponding position, and the microlens array is composed of a plurality of lens combinations and arrangements, and the position of the waveguide channel in the waveguide array corresponds one-to-one to the position of the lens in the microlens array, and the laser light outputted by the waveguide channel is incident on the lens at the corresponding position to achieve light beam collimation, and by setting a waveguide array whose positioning accuracy meets the preset high positioning accuracy requirement, the collimating optical fiber array can also meet the high positioning accuracy requirement, thereby effectively improving the positioning accuracy of the collimating optical fiber array. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0030] in:
[0031] Figure 1 is a structural diagram of a collimating optical fiber array in an embodiment of the utility model;
[0032] Figure 2 An angle offset mode conversion loss diagram in an embodiment of the present utility model;
[0033] Figure 3 It is a structural diagram of a three-dimensional femtosecond laser direct writing system in an embodiment of the utility model. DETAILED DESCRIPTION
[0034] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0035] In the existing collimation device, collimation is achieved through microlens array + fiber array packaging. In this device, the method to obtain the collimated fiber array is: combine the microlens array with the collimated fiber array and package it. In theory, the fiber position and lens position on the two arrays correspond one to one. The light output horizontally from the fiber diverges and hits the center of the corresponding lens, generating horizontal light that continues to move along the optical axis to achieve collimation. However, the positioning accuracy (single-fiber tolerance 2μm, multi-fiber maximum error 4μm) and pointing accuracy of the fiber array are too low (offset exceeds 1°), resulting in overall coupling difficulties due to the one-to-one correspondence. There is a situation where the output light quality at one position is acceptable, but the output light at the surrounding positions is offset. The output light collimation accuracy is low and cannot be used in high-precision demand scenarios.
[0036] In addition, there are also ways to achieve alignment by integrating double-sided components with microlens arrays and fiber arrays. For example, an integrated component has a core hole etched out on one side of the silicon substrate by semiconductor lithography and plasma, and a lens array is prepared on the other side using semiconductor double-sided exposure technology. The optical fiber is inserted into the core hole to achieve alignment. However, this method is too expensive and demanding, and it is expensive. It not only requires semiconductor lithography (the market price of a three-inch lithography mask is about 3,000 yuan per time) and plasma etching (three-inch silicon-based single-sided etching is about 5,000 yuan), but also requires semiconductor double-sided exposure processing, and its difficulty and price will increase exponentially. In addition, the manufacturing process involves the use of a variety of toxic gases and large instruments, and it cannot be miniaturized and used in the laboratory.
[0037] Based on this, the utility model proposes a collimated fiber array to achieve the purpose of obtaining a high-precision collimated fiber array. For details, please refer to Figure 1 , Figure 1 The structure diagram of the collimating optical fiber array of the utility model includes:
[0038] Fiber array 102, waveguide array 103 and microlens array 104; the fiber array is composed of multiple single-mode optical fibers 101 cores, which are used to transmit lasers and input lasers into the waveguide array 103; the waveguide array 103 is composed of multiple parallel waveguide channels whose positioning accuracy meets the preset high positioning accuracy requirements, and the positions of the single-mode optical fibers 101 in the fiber array 102 correspond to the positions of the waveguide channels in the waveguide array 103, and the laser output by the single-mode optical fibers 101 is incident on the waveguide channels at the corresponding positions; the microlens array 104 is composed of a plurality of lenses 105 arranged in combination, and the positions of the waveguide channels in the waveguide array 103 correspond to the positions of the lenses 105 in the microlens array 104, and the laser output by the waveguide channels is incident on the lenses 105 at the corresponding positions to achieve beam collimation.
[0039] Specifically, Figure 1 As shown, the optical fiber is generally a single-mode optical fiber, and other types of optical fibers can also be used. All single-mode optical fibers are inserted into the core in parallel at preset intervals to form an optical fiber array. An optical fiber array refers to a component in which multiple optical fibers are arranged in parallel and fixed with a substrate or other means. The core refers to the manufacturing method used in existing two-dimensional optical fiber arrays: a plastic substrate with multiple pre-through holes, multiple optical fibers are inserted into it in parallel, and glued together.
[0040] Since the existing through-hole positioning tolerance is about 2μm, the maximum error between two adjacent columns is 4μm. In comparison, the core diameter of a single-mode optical fiber is only 9μm. The huge error that may exist may cause uneven light intensity and non-circular light spots when the light enters the lens array after being emitted. Figure 2 , Figure 2 is the angle offset mode transformation loss diagram, given by Figure 2 It can be seen that when the optical fiber is offset from the parallel position by 0.1 degrees, the overall loss of the mode multiplexer increases by 1.3dB, accounting for about 19% of the total loss of the device. In fact, the actual offset of the existing optical fiber array can be up to 1 degree, which will bring a large amount of additional loss to the mode multiplexer. When the loss is too large, the beneficial effect of the device's exponentially increased transmission capacity will be offset by the exponentially attenuated power. Therefore, a good collimated fiber array is necessary to bring out the advantages of the mode multiplexer. Because the optical fiber is deflected during the gluing process, its emitted light often also produces an offset. Therefore, whether it is the positioning error or the existence of the normal offset angle, the existing collimated fiber array cannot be applied to high-precision usage scenarios such as mode multiplexers, and a new fiber array collimation method is urgently needed.
[0041] Therefore, in order to solve the above-mentioned large offset problem, the utility model sets a waveguide array 103, which is composed of multiple high-precision waveguides in parallel, and the position of the single-mode optical fiber 101 in the optical fiber array corresponds one-to-one to the position of the waveguide channel in the waveguide array 103. The waveguide array 103 can be processed inside the glass by a three-dimensional femtosecond laser direct writing system. The microlens array 104 is composed of a plurality of lenses 105 arranged in combination, and its arrangement corresponds one-to-one to the position of the waveguide channel in the waveguide array 103. The laser output by the single-mode optical fiber 101 of the optical fiber array 102 is incident on the waveguide channel at the corresponding position, and then the laser output by the waveguide channel is incident on the lens 105 at the corresponding position, thereby realizing the collimation of the light beam.
[0042] The collimated fiber array proposed by the utility model adds a waveguide array 103 between the fiber array 102 and the microlens array 104 to form a fiber array 102-two-dimensional straight waveguide 103-microlens array 104 structure. Since the waveguide array 103 can achieve high positioning accuracy and high pointing accuracy, the collimation effect of the fiber array is effectively improved. In addition, the loss of the device using the collimated light array input is reduced. Taking the MPLC mode multiplexer as an example, the mode multiplexer loss using a low-precision collimated fiber array is about 4-5dB, while the actual loss of the high-precision collimated light array device in the present invention is about 3-4dB. Reduced by 20-25%.
[0043] In a feasible embodiment of the present invention, the waveguide array is processed on a sample using a three-dimensional femtosecond laser direct writing system.
[0044] In a feasible embodiment of the present invention, the sample is a glass substrate.
[0045] The utility model proposes a specific structure of a three-dimensional femtosecond laser direct writing system. Figure 3 , Figure 3 The structural diagram of the three-dimensional femtosecond laser direct writing system in the embodiment of the utility model, the specific three-dimensional femtosecond laser direct writing system includes: a femtosecond laser 301, a first reflecting mirror 302, a concave lens 303, a cylindrical lens 304, a mechanical slit 305, an objective lens 306, a beam splitter 307 and a translation stage 308.
[0046] Specifically, the femtosecond laser 301 is used to output a laser beam, and the laser beam is incident on the concave lens 303 through the first reflector 302; the concave lens 303 is used to amplify the laser beam, and the amplified laser beam is incident on the cylindrical lens 304; the cylindrical lens 304 is used to compress the incident laser light speed, and the compressed laser beam is incident on the mechanical slit 305; the mechanical slit 305 is used to modulate the incident laser beam, and the modulated laser beam is incident on the objective lens 307 through the beam splitter 306; the objective lens 307 is used to focus the incident laser beam, and the focused laser beam hits the sample on the displacement stage 308, and the sample is processed to obtain the waveguide array 103.
[0047] The utility model outputs a laser beam from a femtosecond laser 301, which is reflected, amplified by a concave lens 303, compressed by a cylindrical lens 304, modulated by a mechanical slit 305, and focused by an objective lens 307. Finally, the laser beam is processed on a sample on a displacement stage 308 to obtain a waveguide array with high positioning accuracy and high pointing accuracy. The femtosecond laser 301 and the displacement stage 308 are uniformly controlled by a computer.
[0048] The utility model greatly reduces the processing cost. Compared with the existing higher-precision alignment solutions, the processing cost of semiconductor lithography and double-sided etching of three-inch silicon-based substrates alone requires more than 10,000 yuan, and the related equipment is huge and difficult to use in the laboratory. The present embodiment adopts a self-built three-dimensional femtosecond laser direct writing system. The whole system only requires a meter level, can be placed on the laboratory desktop, and can be moved as a whole. In addition, the system also greatly improves the processing speed. Compared with the existing higher-precision alignment solutions, the silicon-based processing process is long and complicated, and the commercial processing cycle is generally 1-2 months. The actual processing process of this embodiment is a few minutes, and the combined overall packaging time can also be completed quickly within 1-2 hours.
[0049] In a feasible embodiment of the present invention, the three-dimensional femtosecond laser direct writing system further includes: a second reflecting mirror 309 and a camera 310 .
[0050] Specifically, after the focused laser beam hits the sample on the translation stage 308, a reflected beam is generated. The reflected beam passes through the beam splitter 306 and is incident on the second reflector 309. The second reflector 309 is used to reflect the reflected beam to the camera 310. The camera 310 is used to form an image based on the reflected beam.
[0051] The reflected light beam generated by the interface processed on the translation stage 308 is directed upward from the objective lens 307, hits the second reflector 309 through the beam splitter 306, and is reflected to the camera 310 for imaging, which can be used to monitor the state of the processing interface in real time.
[0052] In a feasible embodiment of the present invention, the three-dimensional femtosecond laser direct writing system supports the processing of three-dimensional waveguides within a maximum spatial range of 100*100*20mm.
[0053] Specifically, the waveguide array 103 is processed by a three-dimensional femtosecond laser direct writing system. The three-dimensional femtosecond laser direct writing system constructed in the embodiment of the utility model supports any number of waveguide channels in a three-dimensional space of 100mm*100mm*20mm. For example, if two layers are processed at an interval of 250μm, theoretically up to 320,000 waveguide channels can be processed.
[0054] In a feasible embodiment of the present invention, the three-dimensional femtosecond laser direct writing system supports the processing of waveguide channels with a maximum length of 100 mm.
[0055] In the embodiment of the utility model, the diameter width can be changed by repeated scanning, changing the scanning speed and power, etc. In the experiment, various diameter waveguides within 9-30μm have been realized. In addition, in this embodiment, a maximum length of 100mm waveguide can be realized, and its length can be cut arbitrarily according to actual needs.
[0056] Conventional optical fiber arrays usually use commercial standard products with a spacing of 27 μm and 250 μm. Since the three-dimensional femtosecond laser direct writing system of the waveguide array 2 in the utility model supports arbitrary waveguide array spatial customization, the utility model can support optical fiber arrays with arbitrary spacing.
[0057] In a feasible embodiment of the present invention, the preset high positioning accuracy requirement is less than 0.5um.
[0058] In order to achieve high positioning accuracy and high pointing accuracy of optical fiber array alignment, a high-precision waveguide array is processed inside the glass by a three-dimensional femtosecond laser direct writing system. After packaging the optical fiber array and microlens array, the actual positioning accuracy is <0.5μm and the pointing accuracy is <0.5°.
[0059] In a feasible embodiment of the present invention, an anti-reflection coating is provided on the side of the microlens array facing the waveguide array, wherein the radius of curvature of the microlens array is determined based on not passing through the optical fiber core.
[0060] The embodiment of the utility model also provides an optical mode multiplexer, which includes the collimating optical fiber array provided above, and also includes a modulation structure and an output end, so as to achieve high-precision collimation of the optical fiber array.
[0061] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope covered by the present invention.
Claims
1. A collimating optical fiber array, characterized in that: The collimating optical fiber array comprises: Optical fiber arrays, waveguide arrays and microlens arrays; The optical fiber array is composed of a plurality of single-mode optical fiber ferrules, which are used to transmit laser light and input the laser light into the waveguide array; The waveguide array is composed of a plurality of waveguide channels in parallel whose positioning accuracy meets the preset high positioning accuracy requirement, and the positions of the single-mode optical fibers in the optical fiber array correspond one-to-one to the positions of the waveguide channels in the waveguide array, and the laser output by the single-mode optical fibers is incident on the waveguide channels at the corresponding positions; The microlens array is composed of a plurality of lenses arranged in combination, and the positions of the waveguide channels in the waveguide array correspond one-to-one to the positions of the lenses in the microlens array. The laser output by the waveguide channels is incident on the lenses at the corresponding positions to achieve beam collimation.
2. The collimating optical fiber array according to claim 1, characterized in that: The waveguide array is processed on a sample by using a three-dimensional femtosecond laser direct writing system.
3. The collimating optical fiber array according to claim 2, characterized in that: The sample is a glass substrate.
4. The collimating optical fiber array according to claim 1, characterized in that: The preset high positioning accuracy requirement is less than 0.5um.
5. The collimating optical fiber array according to claim 1, characterized in that: An anti-reflection coating is provided on a side of the microlens array facing the waveguide array.
6. The collimating optical fiber array according to claim 2, characterized in that: The three-dimensional femtosecond laser direct writing system comprises: a femtosecond laser, a first reflecting mirror, a concave lens, a cylindrical lens, a mechanical slit, an objective lens, a beam splitter and a translation stage; The femtosecond laser is used to output a laser beam, and the laser beam is incident on the concave lens through the first reflector; The concave lens is used to amplify the laser beam, and the amplified laser beam is incident on the cylindrical lens; The cylindrical lens is used to compress the incident laser light speed, and the compressed laser beam is incident on the mechanical slit; The mechanical slit is used to modulate the incident laser beam, and the modulated laser beam is incident on the objective lens through the beam splitter; The objective lens is used to focus the incident laser beam, and the focused laser beam hits the sample on the displacement stage, and the sample is processed to obtain the waveguide array.
7. The collimating optical fiber array according to claim 6, characterized in that: The three-dimensional femtosecond laser direct writing system also includes: a second reflector and a camera; After the focused laser beam hits the sample on the translation stage, a reflected beam is generated. The reflected beam passes through the beam splitter and is incident on the second reflector. The second reflector is used to reflect the reflected beam to the camera. The camera is used to form an image based on the reflected beam.
8. The collimating optical fiber array according to claim 6, characterized in that: The three-dimensional femtosecond laser direct writing system supports the processing of three-dimensional waveguides within a maximum spatial range of 100*100*20mm.
9. The collimating optical fiber array according to claim 6, characterized in that: The three-dimensional femtosecond laser direct writing system supports the processing of waveguide channels with a maximum length of 100 mm.
10. An optical mode multiplexer, characterized in that: The optical mode multiplexer comprises: the collimating optical fiber array according to any one of claims 1 to 9, and also comprises a modulation structure and an output end.