Edge coupler and preparation method therefor

Abstract

An edge coupler (1), comprising: a substrate (10); and a coupling end portion (100) and a spot size converter (200) which are located on the same surface of the substrate (10) and are connected to one another. The coupling end portion (100) comprises a first stack layer (20), a second stack layer (30), and a third stack layer (40) which are sequentially stacked on the substrate (10). The second stack layer (30) is a ridge-shaped structure or a strip-shaped structure. The refractive index of the first stack layer (20) is less than the refractive index of the second stack layer (30), and the refractive index of the third stack layer (40) is less than the refractive index of the second stack layer (30). The spot size converter (200) comprises a first waveguide core layer (240) and a cover layer disposed on the substrate (10). The first waveguide core layer (240) is located in the cover layer, so that a mode field in a silicon optical chip matches a mode field in an optical fiber, thereby achieving coupling at low insertion loss. Also provided is a preparation method for an edge coupler (1).

Description

Edge coupler and method of manufacturing the same

[0001] This application claims priority to the Chinese patent application No. 202411117027.9, filed on August 14, 2024, and entitled "Edge coupler and method of manufacturing the same", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of optical communication, in particular to an edge coupler and a method of manufacturing the same. BACKGROUND

[0003] With the development of the Internet, the emergence of massive content, and the deployment and application of 5G networks, the requirements for communication rate and communication capacity are increasing, and the performance and cost of optical communication modules are also becoming higher and higher. Chips, such as silicon optical chips, gradually replace traditional discrete devices in optical devices and optical modules, further improving the integration of optical communication modules, reducing the size of optical communication modules, reducing the power consumption of optical communication modules, and reducing the production and assembly costs of optical communication modules.

[0004] The coupler, as an optical bridge connecting the optical fiber and the silicon optical chip, is one of the most important structures in the optical communication module. With the increasing of the communication rate of the optical communication module, the requirements for the link budget and the performance of the device are becoming higher and higher, which requires the silicon optical chip to have lower loss. The current mainstream edge coupler has an insertion loss of 1.5dB~2dB for single coupling, and this coupling loss is the main loss of the entire silicon optical chip.

[0005] In addition, due to the large difference between the mode field size (usually 0.1μm 2 ) in the silicon optical chip and the mode field size (usually 100μm 2 ) in the single-mode optical fiber, it is difficult to match the two mode fields. There are currently two solutions: one method is to use a lens fiber or a high numerical aperture fiber (High-NA fiber) to reduce the mode field at the fiber end, but this will increase the coupling difficulty and packaging cost; the other method is to hollow out the substrate part that affects the mode field when manufacturing the edge coupler, forming a cantilever part, to expand the mode field at the chip end, but this also increases the process difficulty of the silicon optical chip, increases the requirements for the back-end process and subsequent packaging process, and reduces the reliability of the silicon optical chip. SUMMARY

[0006] Therefore, it is necessary to provide an edge coupler that can match the mode field in the silicon optical chip with the mode field in the optical fiber to achieve low-insertion-loss coupling.

[0007] In addition, it is necessary to provide a preparation method of the edge coupler.

[0008] The edge coupler comprises a substrate, a coupling end and a mode spot converter which are located on the same surface of the substrate and are connected, the coupling end comprises a first layer, a second layer and a third layer which are sequentially stacked on the substrate, the second layer is a ridge structure or a strip structure; the refractive index of the first layer is less than the refractive index of the second layer, and the refractive index of the third layer is less than the refractive index of the second layer; the mode spot converter comprises a first waveguide core layer and a cover layer which are located on the substrate, and the first waveguide core layer is located in the cover layer.

[0009] In some embodiments, the material of the first layer comprises at least one of silicon dioxide and silicon oxynitride.

[0010] In some embodiments, the material of the second layer comprises at least one of silicon dioxide, silicon oxynitride, silicon nitride and lithium niobate.

[0011] In some embodiments, the edge coupler comprises any one of (1)-(5) below:

[0012] (1) defining a direction from the first layer to the second layer as a preset direction, the second layer comprises a first body and a first protruding part which is formed by a part of the surface of the first body protruding towards the preset direction, and the third layer covers the first body and the first protruding part;

[0013] (2) the third layer and the first layer jointly cover the second layer;

[0014] (3) defining a direction from the first layer to the second layer as a preset direction, the first layer comprises a second body and a second protruding part which is formed by a part of the surface of the second body protruding towards the preset direction, the second layer is located on the second protruding part, and the first layer and the third layer jointly cover the second layer;

[0015] (4) the third layer and the substrate jointly cover the first layer and the second layer;

[0016] (5) defining a direction from the first layer to the second layer as a preset direction, the substrate comprises a third body and a third protruding part which is formed by a part of the surface of the third body protruding towards the preset direction, the first layer is located on the third protruding part, and the substrate and the third layer jointly cover the first layer and the second layer.

[0017] In some embodiments, the cover layer comprises a first cover layer and a second cover layer which are arranged in sequence; the first cover layer has a refractive index less than that of the second cover layer.

[0018] In some embodiments, the first waveguide core layer is located in the first cover layer; or

[0019] the first waveguide core layer is located in the second cover layer; or

[0020] a part of the first waveguide core layer is located in the first cover layer, and another part of the first waveguide core layer is located in the second cover layer.

[0021] In some embodiments, a direction from the first cover layer to the second cover layer is defined as a preset direction, the second cover layer comprises a main body and an extension part extending from a part of the surface of the main body in the preset direction; and / or

[0022] the material of the first cover layer comprises silicon dioxide; and / or

[0023] the material of the second cover layer comprises at least one of silicon dioxide, silicon oxynitride and silicon nitride; and / or

[0024] the second cover layer is a ridge structure or a strip structure; and / or

[0025] the material of the first waveguide core layer comprises at least one of silicon nitride and lithium niobate.

[0026] In some embodiments, the cover layer further comprises a third cover layer, the third cover layer is located on the surface of the second cover layer away from the first cover layer, and the third cover layer has a refractive index less than that of the second cover layer.

[0027] In some embodiments, the coupling end further comprises a fourth stack, the fourth stack is located between the second stack and the first stack, and the fourth stack has a refractive index less than that of the second stack.

[0028] In some embodiments, a direction from the first stack to the second stack is defined as a preset direction, the fourth stack comprises a fourth body and a fourth protrusion part protruding from a part of the surface of the fourth body in the preset direction, and the second stack covers the fourth body and the fourth protrusion part; and / or

[0029] the material of the fourth stack comprises at least one of silicon dioxide, silicon oxynitride and silicon nitride.

[0030] In some embodiments, the cover layer further comprises a fourth cover layer, the fourth cover layer is located between the second cover layer and the first cover layer, and the refractive index of the fourth cover layer is less than the refractive index of the second cover layer.

[0031] In some embodiments, the first waveguide core layer is located in a fourth cover layer.

[0032] In some embodiments, the coupling end further comprises a fifth stack layer, the fifth stack layer is located on the third stack layer, and the refractive index of the fifth stack layer is less than the refractive index of the second stack layer; and / or

[0033] The material of the third stack layer comprises at least one of silicon oxynitride and silicon dioxide.

[0034] In some embodiments, a direction from the first stack layer to the second stack layer is a preset direction, the second stack layer comprises a fifth body and a fifth protruding part protruding from a part of the surface of the fifth body in the preset direction, and the third stack layer covers the fifth body and the fifth protruding part; and / or

[0035] The material of the third stack layer comprises at least one of silicon oxynitride and silicon dioxide.

[0036] In some embodiments, the cover layer further comprises a fifth cover layer, the fifth cover layer is located on the third cover layer, and the refractive index of the fifth cover layer is less than the refractive index of the second cover layer.

[0037] A preparation method of the edge coupler, comprising the following steps: preparing the coupling end and the mode spot converter on one surface of the substrate.

[0038] The coupling end in the edge coupler provided by the application generates mode field confinement in the up-down direction through the high-low difference between the refractive index of the first stack layer and the third stack layer which has a lower refractive index and the refractive index of the second stack layer which has a higher refractive index, and generates mode field confinement in the left-right direction through the third stack layer which has a lower refractive index and the second stack layer which has a higher refractive index and the ridge or strip structure of the second stack layer, so as to realize the matching of the mode field in the silicon optical chip and the mode field in the optical fiber, thereby realizing high-efficiency and low-insertion-loss coupling.

[0039] The application optimizes the design through the lower refractive index difference between the first stack layer and the third stack layer and the second stack layer, so that most of the mode field is confined inside the second stack layer, the mode field has less interaction with the substrate, and therefore, a coupler with good performance can be realized without removing the substrate.

[0040] In addition, the etching process of the semiconductor processing technology produces relatively rough waveguide sidewalls, the traditional material and design adopt a material with a high refractive index as a waveguide core layer, the mode field is strong at the waveguide sidewall, the rough sidewall has a strong reflection effect on light, which enhances the reflection of the edge coupler; the lower refractive index difference between the first stack and the third stack and the second stack weakens the mode field at the edge of the second stack, and the reflection effect on light is also weak, thus improving the reflection performance compared with the traditional design. BRIEF DESCRIPTION OF DRAWINGS

[0041] Fig. 1 is a cross-sectional view of an edge coupler provided by a first embodiment of the present application in a direction parallel to a coupling end portion to a mode spot converter;

[0042] Fig. 2 is a cross-sectional view of the coupling end portion in the edge coupler provided by the first embodiment of the present application in an A-A direction;

[0043] Fig. 3 is a cross-sectional view of the coupling end portion in the edge coupler provided by a second embodiment of the present application in an A-A direction;

[0044] Fig. 4 is a cross-sectional view of the coupling end portion in the edge coupler provided by a third embodiment of the present application in an A-A direction;

[0045] Fig. 5 is a cross-sectional view of the coupling end portion in the edge coupler provided by a fourth embodiment of the present application in an A-A direction;

[0046] Fig. 6 is a cross-sectional view of the coupling end portion in the edge coupler provided by a fifth embodiment of the present application in an A-A direction;

[0047] Fig. 7 is a cross-sectional view of the coupling end portion in the edge coupler provided by a sixth embodiment of the present application in an A-A direction;

[0048] Fig. 8 is a cross-sectional view of the coupling end portion in the edge coupler provided by a seventh embodiment of the present application in an A-A direction;

[0049] Fig. 9 is a cross-sectional view of the coupling end portion in the edge coupler provided by an eighth embodiment of the present application in an A-A direction;

[0050] Fig. 10 is a cross-sectional view of the mode spot converter in the edge coupler provided by the first embodiment of the present application in a B-B direction;

[0051] Fig. 11 is a cross-sectional view of an alternative structure of the mode spot converter in the edge coupler provided by the first embodiment of the present application in a B-B direction;

[0052] Fig. 12 is a cross-sectional view of an alternative structure of the mode spot converter in the edge coupler provided by the first embodiment of the present application in a B-B direction;

[0053] Fig. 13 is a sectional view of the mode spot converter in the alternative structure of the edge coupler according to the first embodiment of the present application in the direction of B-B;

[0054] Fig. 14 is a sectional view of the mode spot converter in the alternative structure of the edge coupler according to the first embodiment of the present application in the direction of B-B;

[0055] Fig. 15 is a sectional view of the mode spot converter in the alternative structure of the edge coupler according to the first embodiment of the present application in the direction of B-B;

[0056] Fig. 16 is a sectional view of the second substrate and the first cladding layer according to the present application;

[0057] Fig. 17 is a sectional view of the first cladding layer in Fig. 16 after the second cladding layer is prepared thereon;

[0058] Fig. 18 is a sectional view of the second cladding layer in Fig. 17 after the waveguide core layer material is prepared thereon;

[0059] Fig. 19 is a sectional view of the waveguide core layer material in Fig. 18 after etching;

[0060] Fig. 20 is a sectional view of the second cladding layer in Fig. 19 after thickening;

[0061] Fig. 21 is a sectional view of the second cladding layer in Fig. 20 after etching;

[0062] Fig. 22 is a sectional view of the mode spot converter after the third cladding layer is prepared on the second cladding layer in Fig. 21.

[0063] Reference numerals: 1, edge coupler; 100, 110, 120, 130, 140, 150, 160, 170, coupling end; 10, substrate; 101, third body; 102, third protrusion; 20, 21, 22, first stack; 211, second body; 212, second protrusion; 30, 31, 32, 33, second stack; 301, first body; 302, first protrusion; 331, fifth body; 332, fifth protrusion; 40, 41, 42, 43, 44, 45, third stack; 50, fourth stack; 501, fourth body; 502, fourth protrusion; 60, fifth stack; 200, 300, 400, 500, 600, 700, mode spot converter; 210, first cladding layer; 220, second cladding layer; 2201, body; 2202, extension; 230, third cladding layer; 240, first waveguide core layer; 241, waveguide core layer material; 250, second waveguide core layer. DETAILED DESCRIPTION

[0064] For the purposes of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings. The embodiments shown are intended to be illustrative only and not limiting of the present application. The present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The embodiments are presented for the best mode contemplated for carrying out the application in the aspects described herein.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for describing particular embodiments only and is not intended to be limiting of the application. The use herein of the terms "including", "comprising", "having" and the like are meant to encompass the items listed thereafter as well as other items.

[0066] Referring to FIG. 1 and FIG. 2, FIG. 1 shows a cross-sectional view of an edge coupler provided by a first embodiment of the present application in a direction parallel to a coupling end portion to a mode field transformer. FIG. 2 shows a cross-sectional view of the coupling end portion 100 in the edge coupler provided by the first embodiment of FIG. 1 in a direction of A-A.

[0067] The edge coupler 1 includes a substrate 10, and a coupling end portion 100 and a mode field transformer 200 connected to the substrate 10 and located on the same surface of the substrate 10. The coupling end portion 100 includes a first layer 20, a second layer 30 and a third layer 40 sequentially stacked on the substrate 10. The second layer 30 is in a ridge structure or a strip structure. The first layer 20 has a refractive index less than that of the second layer 30, and the third layer 40 has a refractive index less than that of the second layer 30. The mode field transformer 200 includes a first waveguide core layer 240 and a cladding layer disposed on the substrate 10, and the first waveguide core layer 240 is located in the cladding layer.

[0068] In some embodiments, the material of the first layer 20 includes at least one of silicon dioxide and silicon oxynitride. The material of the second layer 20 includes at least one of silicon dioxide, silicon oxynitride, silicon nitride and lithium niobate. The material of the substrate 10 includes silicon (Si).

[0069] Referring to FIG. 2, a direction from the first layer 20 to the second layer 30 is defined as a preset direction. In the first embodiment, the second layer 30 includes a first body 301 and a first protruding portion 302 protruding from a part of the surface of the first body 301 in the preset direction. That is, the structure of the second layer 30 is approximately inverted "T" shaped. Optionally, the material of the second layer 30 includes at least one of silicon dioxide, silicon oxynitride and silicon nitride.

[0070] In the first embodiment, the third stack 40 covers the first body 301 and the first protrusion 302. The refractive index of the third stack 40 is less than the refractive index of the second stack 30. Optionally, the material of the third stack 40 includes at least one of photoresist and silicon dioxide. As shown in FIG. 2, the third stack 40 is located on the surface of the first body 301 and the top surface and the side surface of the first protrusion 302.

[0071] Optionally, the cover layer includes a first cover layer 210 and a second cover layer 220 which are sequentially stacked; the refractive index of the first cover layer 210 is less than the refractive index of the second cover layer 220. The first waveguide core layer 240 is located in the first cover layer 210, or the first waveguide core layer 240 is located in the second cover layer 220, or a part of the first waveguide core layer 240 is located in the first cover layer 210 and another part of the first waveguide core layer 240 is located in the second cover layer 220.

[0072] Optionally, a direction from the first cover layer 210 to the second cover layer 220 is defined as a preset direction, and the second cover layer 220 includes a main body 2201 and an extension 2202 which is formed by extending part of the surface of the main body 2201 in the preset direction. Further optionally, the material of the first cover layer 210 includes silicon dioxide. The material of the second cover layer 220 includes at least one of silicon dioxide, silicon oxynitride and silicon nitride. The material of the first waveguide core layer 240 includes at least one of silicon nitride and lithium niobate.

[0073] Optionally, the thickness of the first cover layer 210 is equal to the thickness of the first stack 20, and the thickness of the second cover layer 220 is equal to the thickness of the second stack 30.

[0074] Optionally, the first cover layer 210 and the first stack 20 are integrally formed, and the second cover layer 220 and the second stack 30 are integrally formed.

[0075] Optionally, the shape of the first cover layer 210 is the same as the shape of the first stack 20, and the shape of the second cover layer 220 is the same as the shape of the second stack 30. It can be understood that the shape of the first cover layer 210 being the same as the shape of the first stack 20 means that the outer contour shape of the first cover layer 210 is the same as the outer contour shape of the first stack 20. The shape of the second cover layer 220 being the same as the shape of the second stack 30 means that the outer contour shape of the second cover layer 220 is the same as the outer contour shape of the second stack 30. For example, the second cover layer 220 is a ridge structure or a strip structure.

[0076] Optionally, the first cladding layer 210 and the first stack 20 can be the same layer, the first stack 20 is located at the coupling end region 100, and the first cladding layer 210 is located at the mode field transformer 200 region. Optionally, the first cladding layer 210 and the first stack 20 can be prepared synchronously when the edge coupler is prepared.

[0077] Optionally, the second cladding layer 220 and the second stack 30 can be the same layer, the second stack 30 is located at the coupling end region 100, and the second cladding layer 220 is located at the mode field transformer 200 region. Optionally, the second cladding layer 220 and the second stack 30 can be prepared synchronously when the edge coupler is prepared.

[0078] Optionally, the cladding layer further comprises a third cladding layer 230, the third cladding layer 230 is located at a surface of the second cladding layer 220 away from the first cladding layer 210. The third cladding layer 230 has a refractive index less than that of the second cladding layer 220.

[0079] Optionally, the material of the third cladding layer 230 comprises at least one of photoresist and silicon dioxide.

[0080] Optionally, the thickness of the third cladding layer 230 is equal to the thickness of the third stack 40.

[0081] Optionally, the third cladding layer 230 and the third stack 40 are integrally formed.

[0082] Optionally, the third cladding layer 230 has the same shape as the third stack 40. It can be understood that the third cladding layer 230 has the same shape as the third stack 40 means that the third cladding layer 230 has the same outer contour shape as the third stack 40.

[0083] Optionally, the third cladding layer 230 and the third stack 40 can be the same layer, the third stack 40 is located at the coupling end region 100, and the third cladding layer 230 is located at the mode field transformer 200 region. Optionally, the third cladding layer 230 and the third stack 40 can be prepared synchronously when the edge coupler is prepared.

[0084] Please refer to FIG. 10, which shows a sectional view of the mode field transformer 200 in the edge coupler 1 provided by the first embodiment of the present application in the B-B direction. In the figure,

[0085] The direction from the first cladding layer 210 to the second cladding layer 220 is defined as the preset direction. In the first embodiment, the second cladding layer 220 comprises a main body 2201 and an extension 2202 extending from a part of the surface of the main body 2201 in the preset direction. That is, the structure of the second cladding layer 220 is roughly inverted “T” type. Optionally, the material of the second cladding layer 220 comprises at least one of silicon dioxide, silicon oxynitride and silicon nitride.

[0086] In the first embodiment, the third cladding layer 230 covers the main body 2201 and the extension 2202. The material of the third cladding layer 230 includes at least one of photoresist and silicon dioxide. As shown in FIG. 10, the third cladding layer 230 is located on the surface of the main body 2201 and the top surface and the side surface of the extension 2202.

[0087] In the first embodiment, the first waveguide core layer 240 is completely located in the second cladding layer 220. The material of the first waveguide core layer 240 includes at least one of silicon nitride (Si3N4) and lithium niobate (LiNbO3).

[0088] Referring to FIG. 11, a cross-sectional view of the alternative mode field transformer 200 in the edge coupler provided by the first embodiment in the B-B direction, i.e., the mode field transformer 300, is shown. The mode field transformer 300 is different from the mode field transformer 200 in that the first waveguide core layer 240 is located in the second cladding layer 220, and the first waveguide core layer 240 is in contact with the first cladding layer 210.

[0089] Referring to FIG. 12, a cross-sectional view of the alternative mode field transformer 200 in the edge coupler provided by the first embodiment in the B-B direction, i.e., the mode field transformer 400, is shown. The mode field transformer 400 is different from the mode field transformer 200 in that one part of the first waveguide core layer 240 is located in the first cladding layer 210, and another part of the first waveguide core layer 240 is located in the second cladding layer 220.

[0090] Referring to FIG. 13, a cross-sectional view of the alternative mode field transformer 200 in the edge coupler provided by the first embodiment in the B-B direction, i.e., the mode field transformer 500, is shown. The mode field transformer 500 is different from the mode field transformer 200 in that the first waveguide core layer 240 is located in the first cladding layer 210, and the first waveguide core layer 240 is in contact with the second cladding layer 220.

[0091] Referring to FIG. 14, a cross-sectional view of the alternative mode field transformer 200 in the edge coupler provided by the first embodiment in the B-B direction, i.e., the mode field transformer 600, is shown. The mode field transformer 600 is different from the mode field transformer 200 in that the first waveguide core layer 240 is completely located in the first cladding layer 210.

[0092] Please refer to FIG. 15, which shows a cross-sectional view of the replaceable mode converter 200 in the edge coupler provided by the first embodiment in the B-B direction, i.e., the mode converter 700. The mode converter 700 is different from the mode converter 200 in that the first waveguide core layer 240 is located in the first cladding layer 210, and the first waveguide core layer 240 is in contact with the second cladding layer 220. The mode converter 700 further includes a second waveguide core layer 250. The material of the second waveguide core layer 250 includes silicon (Si). The second waveguide core layer 250 is entirely located in the first cladding layer 210, and the second waveguide core layer 250 is spaced apart from the first waveguide core layer 240.

[0093] Please refer to FIG. 3, which shows a cross-sectional view of the coupling end portion 110 in the edge coupler provided by the second embodiment of the present application in the A-A direction. The coupling end portion 110 is different from the coupling end portion 100 provided by the first embodiment in that the second stack 31 does not include the first body 301, and the third stack 41 and the first stack 20 jointly cover the second stack 31. As shown in FIG. 3, the third stack 41 is located on the top surface of the first stack 20, and on the top surface and the side surface of the second stack 31.

[0094] Please refer to FIG. 4, which shows a cross-sectional view of the coupling end portion 120 in the edge coupler provided by the third embodiment of the present application in the A-A direction. The coupling end portion 120 is different from the coupling end portion 110 provided by the second embodiment in that the direction from the first stack 21 to the second stack 31 is defined as a preset direction, the first stack 21 includes a second body 211 and a second protruding portion 212 protruding from a part of the surface of the second body 211 in the preset direction. The second stack 31 is located on the second protruding portion 212, and the first stack 21 and the third stack 42 jointly cover the second stack 31. As shown in FIG. 4, the third stack 42 is located on the top surface of the second body 211, the side surface of the second protruding portion 212, and the top surface and the side surface of the second stack 31.

[0095] Please refer to FIG. 5, which shows a cross-sectional view of the coupling end portion 130 in the edge coupler provided by the fourth embodiment of the present application in the A-A direction. The coupling end portion 130 is different from the coupling end portion 110 provided by the second embodiment in that the first stack 22 is located on a part of the surface of the substrate 10, and the third stack 43 and the substrate 10 jointly cover the first stack 22 and the second stack 31. As shown in FIG. 5, the third stack 43 is located on the top surface of the substrate 10, the side surface of the first stack 22, and the top surface and the side surface of the second stack 31.

[0096] Referring to FIG. 6, a cross-sectional view of the coupling end 140 in the A-A direction of the edge coupler provided by the fifth embodiment of the present application is shown. The coupling end 140 differs from the coupling end 130 provided by the fourth embodiment in that the substrate 10 includes a third body 101 and a third protrusion 102 protruding from a partial surface of the third body 101 in a predetermined direction. The first cladding layer 22 is located on the third protrusion 112, and the substrate 10 and the third cladding layer 44 collectively cover the first cladding layer 22 and the second cladding layer 31. As shown in FIG. 6, the third cladding layer 44 is located on the top surface of the third body 101, the side surface of the third protrusion 102, the side surface of the first cladding layer 22, and the top surface and the side surface of the second cladding layer 31.

[0097] Optionally, the coupling end further includes a fourth cladding layer (not shown in the figure), the fourth cladding layer is located between the second cladding layer and the first cladding layer, and the refractive index of the fourth cladding layer is less than the refractive index of the second cladding layer.

[0098] Optionally, a direction from the first cladding layer to the second cladding layer is defined as the predetermined direction, the fourth cladding layer includes a fourth body and a fourth protrusion protruding from a partial surface of the fourth body in the predetermined direction, and the second cladding layer covers the fourth body and the fourth protrusion. The material of the fourth cladding layer includes at least one of silicon oxynitride and silicon dioxide. The material of the third cladding layer includes photoresist.

[0099] Optionally, the cover layer further includes a fourth cover layer, the fourth cover layer is located between the second cover layer and the first cover layer, and the refractive index of the fourth cover layer is less than the refractive index of the second cover layer.

[0100] Optionally, the first waveguide core layer is located in the fourth cover layer.

[0101] Optionally, the material of the fourth cover layer includes at least one of silicon dioxide, silicon oxynitride, and silicon nitride.

[0102] Optionally, the thickness of the fourth cover layer is equal to the thickness of the fourth cladding layer.

[0103] Optionally, the fourth cover layer and the fourth cladding layer are integrally formed.

[0104] Optionally, the shape of the fourth cover layer is the same as the shape of the fourth cladding layer. It can be understood that the shape of the fourth cover layer being the same as the shape of the fourth cladding layer means that the outer contour shape of the fourth cover layer is the same as the outer contour shape of the fourth cladding layer.

[0105] Optionally, the fourth cover layer and the fourth cladding layer can be the same layer, the fourth cladding layer is located in the coupling end region 100, and the fourth cover layer is located in the mode spot converter 200 region. Optionally, the fourth cover layer and the fourth cladding layer can be prepared synchronously when the edge coupler is prepared.

[0106] Referring to FIG. 7, a cross-sectional view of the coupling end 150 in the sixth embodiment of the present application is shown in the A-A direction. The coupling end 150 includes the substrate 10, the first stack 20, the fourth stack 50, the second stack 32, and the third stack 45, which are sequentially stacked.

[0107] In the sixth embodiment, the material of the substrate 10 includes silicon (Si).

[0108] The refractive index of the first stack 20 is less than the refractive index of the second stack 32. In the sixth embodiment, the material of the first stack 20 includes silicon dioxide.

[0109] The direction from the first stack 20 to the second stack 32 is defined as a preset direction. In the sixth embodiment, the fourth stack 50 includes a fourth body 501 and a fourth protrusion 502 protruding from a partial surface of the fourth body 501 in the preset direction. That is, the fourth stack 50 has a structure of approximately inverted "T" shape.

[0110] The refractive index of the fourth stack 50 is less than the refractive index of the second stack 32. As shown in FIG. 7, the second stack 32 covers the fourth body 501 and the fourth protrusion 502. The second stack 32 is located on the top surface of the fourth body 501, and on the top surface and the side surface of the fourth protrusion 502. In the sixth embodiment, the material of the fourth stack 50 includes at least one of silicon dioxide, silicon oxynitride, and silicon nitride.

[0111] The refractive index of the third stack 45 is less than the refractive index of the second stack 32. In the sixth embodiment, the material of the third stack 45 includes photoresist.

[0112] Optionally, the coupling end further includes a fifth stack, which is located on the third stack, and the refractive index of the fifth stack is less than the refractive index of the second stack. The material of the fifth stack includes at least one of silicon dioxide and silicon oxynitride. The material of the third stack includes photoresist.

[0113] Optionally, the direction from the first stack to the second stack is defined as a preset direction, the second stack includes a fifth body and a fifth protrusion protruding from a partial surface of the fifth body in the preset direction, and the third stack covers the fifth body and the fifth protrusion. The material of the third stack includes at least one of silicon dioxide and silicon oxynitride.

[0114] Optionally, the cover layer further includes a fifth cover layer (not shown in the figure), which is located on the third cover layer, and the refractive index of the fifth cover layer is less than the refractive index of the second cover layer.

[0115] Optionally, the material of the fifth cover layer includes photoresist.

[0116] Optionally, the fifth cover layer has a thickness equal to a thickness of the fifth stack.

[0117] Optionally, the fifth cover layer is integrally formed with the fifth stack.

[0118] Optionally, the fifth cover layer has a shape identical to a shape of the fifth stack. It is understood that the shape of the fifth cover layer identical to the shape of the fifth stack means that the outer contour shape of the fifth cover layer is identical to the outer contour shape of the fifth stack.

[0119] Optionally, the fifth cover layer and the fifth stack can be the same layer, the fifth stack is located in the coupling end region 100, and the fifth cover layer is located in the mode spot converter 200 region. Optionally, the fifth cover layer and the fifth stack can be prepared synchronously when the edge coupler is prepared.

[0120] Referring to FIG. 8, a cross-sectional view of the coupling end 160 in the edge coupler provided by the seventh embodiment of the present application in the A-A direction is shown. The coupling end 160 is different from the coupling end 100 provided by the first embodiment in that the coupling end 160 further includes a fifth stack 60 located on the third stack 40. The refractive index of the fifth stack 60 is less than the refractive index of the second stack 33. The material of the third stack 40 includes at least one of silicon oxynitride and silicon dioxide. The material of the fifth stack 60 includes a photoresist having a refractive index less than the second stack 33. A direction from the first stack 20 to the second stack 33 is defined as a preset direction, and the second stack 33 includes a fifth body 331 and a fifth protruding portion 332 protruding from a partial surface of the fifth body 331 in the preset direction, and the third stack 40 covers the fifth body 331 and the fifth protruding portion 332. The material of the third stack 40 includes at least one of silicon oxynitride and silicon dioxide.

[0121] Referring to FIG. 9, a cross-sectional view of the coupling end 170 in the edge coupler provided by the eighth embodiment of the present application in the A-A direction is shown. The coupling end 170 is different from the coupling end 100 provided by the first embodiment in that the coupling end 180 does not include the third stack 40.

[0122] Each of the mode spot converters provided by the present application can convert the mode field in the second cover layer 230 into the mode field in the first waveguide core layer 250 or the second waveguide core layer 260 through the evanescent wave coupling effect, and then realize subsequent transmission in the first waveguide core layer 250 or the second waveguide core layer 260.

[0123] The coupling end portion in the edge coupler can be selected from any one of the coupling end portions in the first embodiment to the eighth embodiment. The mode field transformer can be selected from any one of the mode field transformers shown in the first embodiment and various alternative mode field transformers thereof. The coupling end portion and the mode field transformer are directly connected or connected by glue.

[0124] The application further provides a preparation method of an edge coupler, comprising the following steps: preparing a coupling end portion and a mode field transformer on one surface of a substrate 10.

[0125] Optionally, the preparation method of the edge coupler comprises the following steps:

[0126] Step S11, a coupling end portion and a mode field transformer are prepared.

[0127] Specifically, the preparation of the mode field transformer comprises the following steps:

[0128] Step 111, referring to FIG. 16, a substrate 10 is provided. Optionally, the material of the substrate 10 comprises silicon (Si).

[0129] Step S112, a first cladding layer 210 is prepared on the substrate 10.

[0130] Specifically, the first cladding layer 210 can be prepared on the substrate 10 by means of growth deposition. Optionally, the material of the first cladding layer 210 comprises silicon dioxide.

[0131] Step S113, referring to FIG. 17, a second cladding layer 220 is prepared on the first cladding layer 210.

[0132] Specifically, the second cladding layer 220 can be prepared on the first cladding layer 210 by means of growth deposition. Optionally, the material of the second cladding layer 220 comprises at least one of silicon dioxide, silicon oxynitride and silicon nitride.

[0133] Step S114, referring to FIG. 18, a waveguide core layer material 241 is prepared on the second cladding layer 220.

[0134] Specifically, the waveguide core layer material 241 can be prepared on the second cladding layer 220 by means of growth deposition. Optionally, the waveguide core layer material 241 comprises at least one of silicon nitride (Si3N4) and lithium niobate (LiNbO3).

[0135] Step S115, referring to FIG. 19, part of the waveguide core layer material 241 is etched to obtain a first waveguide core layer 240.

[0136] Optionally, the material of the first waveguide core layer 240 comprises at least one of silicon nitride (Si3N4) and lithium niobate (LiNbO3).

[0137] Step S116, referring to Fig. 20, the second cladding layer 220 is thickened so as to cover the first waveguide core layer 240.

[0138] Specifically, the second cladding layer 220 can be thickened by growth deposition.

[0139] Step S117, referring to Fig. 21, the second cladding layer 220 is etched so as to include a main body 2201 and an extension 2202 extending from a part of the surface of the main body 2201 in a preset direction (the direction from the first cladding layer 210 to the second cladding layer 220 is defined as the preset direction).

[0140] That is, the structure of the second cladding layer 220 is approximately inverted "T" shaped.

[0141] Step S118, referring to Fig. 22, a third cladding layer 230 is prepared on the second cladding layer 220 to obtain a mode spot converter.

[0142] Specifically, the third cladding layer 230 can be prepared on the second cladding layer 220 by growth deposition or coating to obtain the mode spot converter.

[0143] Optionally, the third cladding layer 230 covers the main body 2201 and the extension 2202. Optionally, the material of the third cladding layer 230 includes at least one of photoresist and silicon dioxide. As shown in Fig. 22, the third cladding layer 230 is located on the top surface of the main body 2201 and the top surface and the side surface of the extension 2202.

[0144] Step S12, the coupling end portion is connected with the mode spot converter to obtain an edge coupler.

[0145] The coupling end portion in the edge coupler provided by the application guides light in an optical fiber into a silicon optical chip, and the mode spot converter in the edge coupler converts the light guided into the silicon optical chip into light in a silicon optical waveguide and transmits the light. The optical waveguide forms a mode field confinement on the light by the waveguide cladding layer with low refractive index and the waveguide core layer with high refractive index, so that the light is transmitted in the optical waveguide with low loss. The coupling end portion in the edge coupler provided by the application generates a mode field confinement in the up-down direction by the high-low difference between the refractive index of the first stack and the third stack with lower refractive index and the refractive index of the second stack with higher refractive index, and generates a mode field confinement in the left-right direction by the third stack with lower refractive index and the second stack with higher refractive index and the ridge or strip structure of the second stack, so as to realize the matching of the mode field in the silicon optical chip and the mode field in the optical fiber, thereby realizing high-efficiency and low-insertion-loss coupling.

[0146] In addition, the application also has the following characteristics:

[0147] The mode field area in the application has a certain distance from the substrate, the substrate has a smaller influence on the mode field, a cantilever beam structure does not need to be formed by a substrate hollowing-out process, high-efficiency fiber-chip coupling can be realized, the process difficulty of the silicon optical chip is reduced, the process limitation requirement for the back-end process and subsequent packaging is reduced, and the reliability of the silicon optical chip is enhanced.

[0148] The evanescent wave coupling effect generated by the buried waveguide structure composed of the waveguide core layer and the first cover layer or the second cover layer in the mode spot converter is used to realize the conversion of the mode field from the coupling end to the silicon optical waveguide.

[0149] The preparation method of the edge coupler provided by the application can be realized based on the current standard silicon optical chip processing technology, and a new process development is not needed.

[0150] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0151] The above-described embodiments only express several implementation manners of the application, the description is more specific and detailed, but it should not be understood as the limitation of the patent scope of the application. It should be pointed out that, for ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the application, and these all belong to the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. An edge coupler characterized by, The edge coupler comprises a substrate, a coupling end and a mode field converter located on the same surface of the substrate and connected with each other, the coupling end comprises a first stack, a second stack and a third stack which are sequentially stacked on the substrate, the second stack is in a ridge type structure or a strip type structure; the refractive index of the first stack is less than the refractive index of the second stack, and the refractive index of the third stack is less than the refractive index of the second stack; the mode field converter comprises a first waveguide core layer and a cover layer arranged on the substrate, and the first waveguide core layer is located in the cover layer.

2. The edge coupler of claim 1, wherein, The material of the first stack comprises at least one of silicon dioxide and silicon oxynitride; and / or The material of the second stack comprises at least one of silicon dioxide, silicon oxynitride, silicon nitride and lithium niobate.

3. The edge coupler of claim 1, wherein, The edge coupler comprises any one of (1) to (5) as follows: (1) defining a direction from the first stack to the second stack as a preset direction, the second stack comprises a first body and a first protruding part protruding from a part of the surface of the first body to the preset direction, and the third stack covers the first body and the first protruding part; (2) the third stack and the first stack collectively cover the second stack; (3) defining a direction from the first stack to the second stack as a preset direction, the first stack comprises a second body and a second protruding part protruding from a part of the surface of the second body to the preset direction, the second stack is located on the second protruding part, and the first stack and the third stack collectively cover the second stack; (4) the third stack and the substrate collectively cover the first stack and the second stack; (5) defining a direction from the first stack to the second stack as a preset direction, the substrate comprises a third body and a third protruding part protruding from a part of the surface of the third body to the preset direction, the first stack is located on the third protruding part, and the substrate and the third stack collectively cover the first stack and the second stack.

4. The edge coupler of any one of claims 1-3, wherein, The cover layer comprises a first cover layer and a second cover layer which are sequentially stacked; the refractive index of the first cover layer is less than the refractive index of the second cover layer.

5. The edge coupler of claim 4, wherein, The first waveguide core layer is located in the first cover layer; or The first waveguide core layer is located in the second cover layer; or Part of the first waveguide core layer is located in the first cover layer, and another part of the first waveguide core layer is located in the second cover layer.

6. The edge coupler of claim 4, wherein, Defining a direction from the first cover layer to the second cover layer as a preset direction, the second cover layer comprises a main body and an extension part extending from a part of the surface of the main body to the preset direction; and / or The material of the first cover layer comprises silicon dioxide; and / or The material of the second cover layer comprises at least one of silicon dioxide, silicon oxynitride and silicon nitride; and / or The second cover layer is in a ridge type structure or a strip type structure; and / or The material of the first waveguide core layer comprises at least one of silicon nitride and lithium niobate.

7. The edge coupler of claim 4, wherein, The cover layer further comprises a third cover layer, the third cover layer is located on a surface of the second cover layer away from the first cover layer, and a refractive index of the third cover layer is less than a refractive index of the second cover layer.

8. The edge coupler of claim 4, wherein, The coupling end further comprises a fourth stack layer, the fourth stack layer is located between the second stack layer and the first stack layer, and a refractive index of the fourth stack layer is less than a refractive index of the second stack layer.

9. The edge coupler of claim 8, wherein, A direction from the first stack layer to the second stack layer is defined as a preset direction, the fourth stack layer comprises a fourth body and a fourth protruding part protruding from a part of a surface of the fourth body in the preset direction, and the second stack layer covers the fourth body and the fourth protruding part; and / or A material of the fourth stack layer comprises at least one of silicon dioxide, silicon oxynitride and silicon nitride.

10. The edge coupler of claim 8, wherein, The cover layer further comprises a fourth cover layer, the fourth cover layer is located between the second cover layer and the first cover layer, and a refractive index of the fourth cover layer is less than a refractive index of the second cover layer.

11. The edge coupler of claim 10, wherein, The first waveguide core layer is located in the fourth cover layer.

12. The edge coupler of claim 7, wherein, The coupling end further comprises a fifth stack layer, the fifth stack layer is located on the third stack layer, and a refractive index of the fifth stack layer is less than a refractive index of the second stack layer; and / or A material of the third stack layer comprises at least one of silicon dioxide and silicon oxynitride.

13. The edge coupler of claim 12, wherein, A direction from the first stack layer to the second stack layer is defined as a preset direction, the second stack layer comprises a fifth body and a fifth protruding part protruding from a part of a surface of the fifth body in the preset direction, and the third stack layer covers the fifth body and the fifth protruding part; and / or A material of the third stack layer comprises at least one of silicon dioxide and silicon oxynitride.

14. The edge coupler of claim 12, wherein, The cover layer further comprises a fifth cover layer, the fifth cover layer is located on the third cover layer, and a refractive index of the fifth cover layer is less than a refractive index of the second cover layer.

15. A method of manufacturing an edge coupler as claimed in any one of claims 1 to 14, characterised in that, The method comprises the following steps: The coupling end and the mode field transformer are prepared on one surface of the substrate. The coupling end and the mode field transformer are prepared on one surface of the substrate.

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