Optical fiber and optical waveguide coupling structure and coupling method

Abstract

This invention relates to an optical fiber and optical waveguide coupling structure and method. The coupling structure includes an optical fiber and an optical waveguide. The front end of the optical fiber is tapered to form a micro / nano fiber, which is fixed to the optical waveguide by a refractive index matching adhesive B. The outer periphery of the micro / nano fiber is coated with a refractive index matching adhesive A, and a graphene layer is provided on one side of the outer periphery of the refractive index matching adhesive A coating. When light passes through the optical fiber, the micro / nano fiber bends towards the graphene layer. In this invention, the surface of the micro / nano fiber is coated with a refractive index matching adhesive, and one side of the refractive index matching adhesive has a graphene layer. In the light-transmitting state, the micro / nano fiber remains bent under the action of the refractive index matching adhesive and the graphene layer. In this state, the micro / nano fiber has a certain strength and can overcome the adsorption force of the optical waveguide or a chip with an optical waveguide, thereby enabling it to move smoothly and accurately to the corresponding position, achieving precise and efficient coupling between the optical fiber and the optical waveguide.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic chip technology, specifically relating to an optical fiber and optical waveguide coupling structure and coupling method. Background Technology

[0002] Optoelectronic chips are rapidly developing and have shown great potential in fields such as communication, sensing, and computing. However, a core challenge in integrating optoelectronic chips into practical systems is how to efficiently, stably, and cost-effectively couple optical signals into and out of the chip. Currently, optical signal coupling into and out of optical chips is generally achieved through optical fibers. The mode field size of conventional single-mode fiber is approximately 9 micrometers, and the significant difference between the mode field of the optical waveguide and the single-mode fiber is one of the important sources of insertion loss in optoelectronic devices. To reduce insertion loss in optoelectronic devices, a structure is needed to achieve efficient coupling between optical fibers and optical waveguides. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a novel optical fiber-waveguide coupling structure and a coupling method thereof. This structure involves coating the outer periphery of a micro / nano fiber formed by tapering the fiber's front end with a refractive index matching adhesive A coating layer, and then coating one side of this adhesive A layer with a graphene layer. This allows the micro / nano fiber to maintain a bent state while transmitting light, thereby enabling precise positional movement and achieving efficient coupling with the optical waveguide.

[0004] The objective of this invention and the technical problem it solves are achieved by the following technical solution. According to this invention, an optical fiber and optical waveguide coupling structure includes an optical fiber 101 and an optical waveguide 201. The front end of the optical fiber 101 is tapered to form a micro / nano optical fiber 1021, which is fixed to the optical waveguide 201 by a refractive index matching adhesive B. The outer periphery of the micro / nano optical fiber 1021 is coated with a refractive index matching adhesive A coating layer 1022, and a graphene layer 1023 is provided on one side of the outer periphery of the refractive index matching adhesive A coating layer 1022. When light passes through the optical fiber 101, the micro / nano optical fiber 1021 bends towards the graphene layer 1023. Maintaining its bent state, the micro / nano optical fiber 1021 can overcome the floating and adsorption phenomenon caused by its small size, thereby enabling it to be moved to the corresponding position on the optical waveguide.

[0005] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0006] In the aforementioned optical fiber and optical waveguide coupling structure, the graphene layer 1023 covers 40% to 60% of the circumferential area of ​​the refractive index matching adhesive A coating layer 1022, thereby ensuring the bending of the micro-nano optical fiber 1021 during light transmission.

[0007] In the aforementioned optical fiber and optical waveguide coupling structure, there is also a transition section 102 with a gradually decreasing outer diameter between the micro / nano optical fiber 1021 and the optical fiber 101. This transition section 102 is suspended to prevent it from affecting the coupling effect.

[0008] In the aforementioned optical fiber and optical waveguide coupling structure, the length of the micro / nano optical fiber 1021 is not less than 2 mm.

[0009] In the aforementioned optical fiber and optical waveguide coupling structure, the optical waveguide 201 is located on an optical chip that allows light to enter and exit in a horizontally coupled manner. The optical chip includes an optical chip functional area 202, and at least one side of the optical chip functional area 202 is connected to the optical waveguide 201.

[0010] In the aforementioned optical fiber and optical waveguide coupling structure, the optical chip is a thin-film lithium niobate modulator chip, a silicon photonic chip, or a waveguide optical detector chip.

[0011] The objectives of this invention and the technical problems it solves are also achieved by the following technical solutions. The coupling method of the optical fiber and optical waveguide coupling structure proposed in this invention includes the following steps: 1) Tapering the front end of the optical fiber 101 to form a micro / nano optical fiber 1021, coating the outer periphery of the micro / nano optical fiber 1021 with a refractive index matching adhesive A coating layer 1022, and then coating one side of the outer periphery of the refractive index matching adhesive A coating layer 1022 with a graphene layer 1023; 2) Passing light through the optical fiber 101, causing the micro / nano optical fiber 1021 to bend towards the graphene layer 1023 and maintaining this bent state; 3) Moving the bent micro / nano optical fiber 1021 to a position above the optical waveguide and adjusting the bending direction of the micro / nano optical fiber to bend upward; 4) Bringing the micro / nano optical fiber 1021 close to the optical waveguide 201, and then stopping the light transmission through the optical fiber 101, causing the micro / nano optical fiber to return to a flexible, non-bent state and automatically adsorb onto the optical waveguide 201; 5) Dropping refractive index matching adhesive B onto the micro / nano optical fiber 1021 and the optical waveguide 201 to couple and fix them.

[0012] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0013] In the aforementioned coupling method of the optical fiber and optical waveguide coupling structure, in step 5), after the micro-nano optical fiber 1021 is close to the optical waveguide 201, the optical power entering the optical fiber 101 is gradually reduced to allow the micro-nano optical fiber 1021 to gradually return to a non-bent state. Then, the light transmission to the optical fiber 101 is stopped so that the micro-nano optical fiber 1021 gradually returns to a non-bent state. During the process of the micro-nano optical fiber 1021 returning to a non-bent state, the position of the micro-nano optical fiber 1021 can be observed and adjusted to ensure the precise coupling between the micro-nano optical fiber 1021 and the optical waveguide.

[0014] In the aforementioned coupling method of optical fiber and optical waveguide coupling structure, in step 3), the micro-nano optical fiber is bent directly upward or obliquely upward, and its projection on the plane where the optical waveguide 201 is located falls completely on the optical waveguide 201, so that after the light transmission is stopped, the micro-nano optical fiber can be smoothly adsorbed on the surface of the optical waveguide.

[0015] In the aforementioned coupling method of optical fiber and optical waveguide coupling structure, in step 3), the bending direction adjustment of micro / nano optical fiber 1021 is achieved through a six-dimensional adjustment frame.

[0016] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, this invention achieves considerable technological advancement and practicality, and has broad industrial application value, possessing at least the following advantages:

[0017] The micro / nano fiber of this invention has a refractive index matching adhesive coated on its surface, and a graphene layer on one side of the adhesive. In the light-transmitting state, the micro / nano fiber remains bent under the action of the adhesive and the graphene layer. In this state, the micro / nano fiber possesses a certain strength and can overcome the adsorption forces of optical waveguides or chips equipped with optical waveguides, thereby enabling it to move smoothly and accurately to the corresponding position. This invention overcomes the problem that existing micro / nano fibers, due to their small diameter, are prone to floating and easily adsorbed when near other objects, making them difficult to control and move precisely. Furthermore, when placed on a waveguide, the adhesion forces make it difficult to reach the target position.

[0018] This invention employs a submicron fiber coupling structure, enabling evanescent field coupling between the fiber and waveguide to connect optoelectronic chips in application systems. Compared to submicron waveguides fabricated by etching, the submicron fiber and waveguide surfaces are smoother, eliminating the need for auxiliary processing of the optoelectronic chip surface. This allows for direct coupling between the fiber and waveguide, resulting in simple fabrication and low loss. Furthermore, the bending and non-bending states of the micro / nano fiber are controlled by optical power, facilitating coupling operations. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the optical fiber and optical waveguide coupling structure of the present invention;

[0020] Figure 2 This is a schematic diagram of the cross-section of the micro / nano fiber of the present invention;

[0021] Figure 3 This is a schematic diagram of the micro / nano fiber of the present invention when no light is transmitted;

[0022] Figure 4 This is a schematic diagram of the micro / nano fiber transmitting light according to the present invention;

[0023] Figure 5 This is a schematic diagram of the optoelectronic chip according to an embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of an optoelectronic chip according to another embodiment of the present invention.

[0025] [Explanation of Key Component Symbols]

[0026] 101-Single-mode optical fiber; 102-Transition section; 200-Optical chip; 201-Optical waveguide; 202-Optical chip functional area; 1021-Micro-nano optical fiber; 1022-Refractive index matching adhesive A coating layer; 1023-Graphene layer. Detailed Implementation

[0027] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, describes the specific implementation, structure, features, and effects of the optical fiber and optical waveguide coupling structure proposed according to the present invention.

[0028] Please see Figure 1-4 This is a schematic diagram of the various components of the optical fiber and optical waveguide coupling structure of the present invention. The coupling structure includes an optical fiber 101 and an optical waveguide 201. The front end of the optical fiber 101 is tapered to form a micro / nano fiber 1021 with a substantially constant outer diameter. The micro / nano fiber 1021 has a refractive index matching adhesive A coating layer 1022 on its outer periphery, and a graphene layer 1023 is provided on one side of the outer periphery of the refractive index matching adhesive A coating layer 1022. This allows the micro / nano fiber 1021 to bend towards the graphene layer 1023 when light is transmitted and maintain this bent state. After the light is cut off, it returns to a non-bent state. The micro / nano fiber 1021 is fixed to the optical waveguide 201 by a refractive index matching adhesive B, achieving stable coupling between the two.

[0029] When the optical fiber 101 is coupled to the optical waveguide in this invention, the front end of the optical fiber 101 is first tapered to form a micro / nano fiber 1021. A transition section 102 connects the micro / nano fiber 1021 to the optical fiber 101. This transition section 102 is tapered, with its outer diameter gradually decreasing from large to small. The maximum outer diameter of the transition section 102 is the same as the outer diameter of the optical fiber 101, and the minimum outer diameter is the same as the outer diameter of the micro / nano fiber 1021. The extension length of the micro / nano fiber 1021 is not less than 2 mm to achieve stable and reliable coupling with the optical waveguide 201. When the micro / nano fiber 1021 is coupled to the optical waveguide 201, the transition section 102 is suspended.

[0030] When the optical fiber 101 is coupled to the optical waveguide 201, light is passed through the optical fiber 101, keeping the micro-nano optical fiber 1021 at its front end in a bent state. The bending direction of the micro-nano optical fiber 1021 is adjusted to keep it bent upwards, and it is moved to a position above the optical waveguide and close to the optical waveguide 201. Then, light is stopped from passing through the optical fiber 101, so that the micro-nano optical fiber 1021 returns to a soft, non-bent state and automatically adheres to the optical waveguide 201. Finally, refractive index matching adhesive B is dropped onto the micro-nano optical fiber 1021 and the optical waveguide 201 to fix the micro-nano optical fiber 1021 on the optical waveguide 201.

[0031] When the micro-nano fiber 1021 in the present invention moves close to the optical waveguide 201, it gradually returns to a non-bent state by gradually reducing the power of the light passing through the fiber 1021. When the micro-nano fiber 1021 has basically returned to a non-bent state, the light transmission is stopped.

[0032] In this embodiment of the invention, when the micro / nano fiber 1021 moves to a position close to the optical waveguide 201, the bent micro / nano fiber 1021 tilts upwards or diagonally upwards, so that its horizontal projection falls entirely on the optical waveguide 201. This prevents the micro / nano fiber 1021 from being attracted to the portion outside the optical waveguide 201 on the optical chip 200 when it returns to its non-bent state. The bending direction of the micro / nano fiber 1021 can be adjusted using a six-dimensional adjustment frame.

[0033] The degree of bending of the micro-nano optical fiber 1021 of the present invention can be controlled by the type and power of the light introduced. In this embodiment, the light introduced into the optical fiber 101 is high-power red light, so that the micro-nano optical fiber 1021 can be bent and deformed quickly and maintain the bent shape.

[0034] In this embodiment of the invention, the optical waveguide 201 is a 600 nm thin-film lithium niobate single-mode optical waveguide, and the outer diameter of the micro / nano fiber 1021 coupled to the optical waveguide 201 is 300~1000 nm. When the size of the optical waveguide 201 changes, the outer diameter of the micro / nano fiber 1021 will also change accordingly.

[0035] In this embodiment of the invention, the graphene layer 1023 extends circumferentially along the micro / nano optical fiber 1021 for 40% to 60% of the size of the refractive index matching adhesive A coating layer 1022 on the outer periphery of the micro / nano optical fiber 1021. That is, 40% to 60% of the area of ​​the refractive index matching adhesive A coating layer 1022 on the outer periphery of the micro / nano optical fiber 1021 is covered with the graphene layer 1023. This results in a different heat absorption rate on the side covered with the graphene layer 1023 and the side without the graphene layer when light is transmitted, thereby causing the micro / nano optical fiber 1021 to bend towards the side covered with the graphene layer 1023. Preferably, the length of the graphene layer 1023 extending circumferentially along the micro / nano optical fiber 1021 is 50% of the outer periphery of the refractive index matching adhesive A coating layer 1022. That is, after the refractive index matching adhesive A coating layer 1022 is coated on the outer periphery of the micro / nano optical fiber 1021, the graphene layer 1022 is coated at half the position of the outer periphery of the refractive index matching adhesive A coating layer 1022.

[0036] In this embodiment of the invention, the optical fiber 101 is a single-mode optical fiber.

[0037] Please see Figure 5 and Figure 6 The optical waveguide 201 of the present invention can be located on any optical chip 200 that transmits and receives light through horizontal coupling, such as a thin-film lithium niobate modulator chip, a silicon photonic chip, or a waveguide photodetector chip. The optical chip 200 includes a central optical chip functional area 202 and optical waveguides 201 connected to one or both sides of the optical chip functional area 202. The optical waveguides 201 can be coupled to the micro / nano optical fiber 1021 in accordance with the above method to form a coupling structure.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A fiber-to-waveguide coupling structure comprising a fiber and a waveguide, characterized by: The front end of the optical fiber is tapered to form a micro / nano fiber, which is fixed to the optical waveguide by refractive index matching adhesive B. The outer periphery of the micro / nano fiber is coated with a refractive index matching adhesive A coating layer, and a graphene layer is provided on one side of the outer periphery of the refractive index matching adhesive A coating layer, so that when the optical fiber transmits light, the micro / nano fiber bends towards the graphene layer side.

2. The optical fiber and optical waveguide coupling structure of claim 1, wherein: The graphene layer covers a circumferential area of ​​40% to 60% of the refractive index matching adhesive A coating layer.

3. The optical fiber and optical waveguide coupling structure of claim 1, wherein: The micro-nano optical fibers also have a transition section with a gradually decreasing outer diameter between them, and this transition section is suspended.

4. The optical fiber and optical waveguide coupling structure of claim 3, wherein: The length of the micro / nano optical fiber is not less than 2 mm.

5. The optical fiber and optical waveguide coupling structure of any of claims 1-4, wherein: The optical waveguide is located on an optical chip that allows light to enter and exit in a horizontally coupled manner. The optical chip includes an optical chip functional area, and at least one side of the optical chip functional area is connected to the optical waveguide.

6. The optical fiber and optical waveguide coupling structure of claim 5, wherein: The optical chip is a thin-film lithium niobate modulator chip, a silicon photonic chip, or a waveguide photodetector chip.

7. The method of coupling a fiber to an optical waveguide coupler structure according to any one of claims 1-6, wherein, Includes the following steps: 1) Taper the front end of the optical fiber to form a micro / nano fiber. Coat the outer periphery of the micro / nano fiber with a refractive index matching adhesive A coating layer. Then coat one side of the outer periphery of the refractive index matching adhesive A coating layer with a graphene layer. 2) Light is passed through the optical fiber, causing the micro / nano fiber to bend towards the graphene layer and maintain this bent state; 3) Move the bent micro / nano fiber to a position above the optical waveguide and adjust the bending direction of the micro / nano fiber so that it bends upward; 4) Bring the aforementioned micro / nano fiber close to the optical waveguide, then stop transmitting light through the fiber, allowing the micro / nano fiber to return to its flexible, non-bending state and automatically adhere to the optical waveguide. 5) Apply refractive index matching adhesive B to the micro / nano optical fiber and the optical waveguide to couple and fix them.

8. The coupling method of the optical fiber and optical waveguide coupling structure according to claim 7, characterized in that, In step 4), after the micro-nano fiber is close to the optical waveguide, the optical power entering the fiber is gradually reduced to allow the micro-nano fiber to gradually return to a non-bent state, and then the transmission of light into the fiber is stopped.

9. The coupling method of the optical fiber and optical waveguide coupling structure according to claim 7, characterized in that, In step 3), the micro-nano fiber bends upward or diagonally upward, and its projection on the plane of the optical waveguide falls completely on the optical waveguide.

10. The coupling method of the optical fiber and optical waveguide coupling structure according to claim 7, characterized in that, In step 3), the bending direction of the micro-nano fiber is adjusted by a six-dimensional adjustment frame.

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