End face coupler, preparation method and communication system

Abstract

The embodiment of the invention discloses an end face coupler, a preparation method and a communication system.The end face coupler comprises a substrate, a waveguide structure located on the substrate and a wrapping layer wrapping the waveguide structure, the waveguide structure comprises a gradient refractive index lens, a first waveguide and a second waveguide, the first side of the gradient refractive index lens is used for being connected with an optical fiber, and the second side of the gradient refractive index lens is used for being connected with an optical fiber; the first waveguide is in contact with the second side of the gradient refractive index lens, the first waveguide is in contact with the second waveguide, and the second waveguide is used for being connected with an optical waveguide in the optoelectronic chip. On the basis, the end face of the optical fiber can be connected with the end face of the optical waveguide in the photoelectron chip through the end face coupler, and in the optical signal transmission process, the spot size of an optical signal can be gradually reduced through the gradient refractive index lens, the first waveguide and the second waveguide; the size of the spot size of the optical signal output by the end face coupler can be better matched with the size of the spot size in the optical waveguide, and the coupling loss of the optical signal from the optical fiber to the photoelectron chip is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of optoelectronic devices, and in particular to an end coupler, a preparation method and a communication system. Background Art

[0002] With the rapid development of optical communication technology, the integration of optoelectronic devices is getting higher and higher. In optical communication systems, when light is transmitted in optical fibers, the end face size of the optical fibers is often hundreds of microns, and the size of the mode spot in the optical fibers is also often several to ten microns. When light is transmitted in the optical waveguide in the optoelectronic chip, the end face size of the optical waveguide is generally hundreds of nanometers, and the size of the mode spot in the optical waveguide is also often hundreds of nanometers. Therefore, there is a large size mismatch between the mode spot in the optical fiber and the mode spot in the optical waveguide. If the optical fiber and the optical waveguide are directly connected, a large mode field mismatch problem will occur, resulting in large coupling loss. Therefore, how to reduce the coupling loss between the optical fiber and the optoelectronic chip is a technical problem that needs to be solved urgently. Summary of the invention

[0003] The embodiments of the present application provide an end coupler, a preparation method and a communication system for reducing the coupling loss between an optical fiber and an optoelectronic chip.

[0004] In the first aspect, an embodiment of the present application provides an end coupler, comprising: a substrate, a waveguide structure located on the substrate, and a cladding covering the waveguide structure, wherein the waveguide structure comprises: a gradient refractive index lens, a first waveguide, and a second waveguide. The refractive index of the first waveguide is less than the refractive index of the second waveguide, so that the optical signal in the first waveguide can be coupled to the second waveguide and light leakage can be avoided through the cladding. In addition, the gradient refractive index lens has a first side and a second side arranged opposite to each other in a first direction, the first side of the gradient refractive index lens is used to connect to the optical fiber, and the first waveguide is located on the second side of the gradient refractive index lens and contacts the second side of the gradient refractive index lens. Based on this, the optical signal input by the optical fiber can be reduced in the vertical direction (i.e., the direction perpendicular to the substrate) through the gradient refractive index lens, and coupled to the first waveguide. Since the second waveguide is located on the second side of the gradient refractive index lens and contacts the first waveguide, the first waveguide extends along the first direction, the second waveguide also extends along the first direction, and the area of ​​the cross section of the first waveguide gradually decreases in the direction from the gradient refractive index lens to the first waveguide. And, since the side of the second waveguide away from the gradient refractive index lens is used to connect with the optical waveguide in the optoelectronic chip, and the area of ​​the cross section of the second waveguide gradually increases in the direction along the gradient refractive index lens pointing to the first waveguide. Based on this, in combination with the first waveguide and the second waveguide, the optical signal is reduced in the horizontal direction (the horizontal direction is perpendicular to the vertical direction, and the horizontal direction is perpendicular to the first direction) and is coupled to the optical waveguide through the second waveguide. In summary, by setting the first waveguide, the mode spot size of the optical signal output by the gradient refractive index lens is first reduced through the first waveguide and then coupled to the second waveguide, which can reduce the coupling loss of the optical signal directly coupled to the second waveguide by the gradient refractive index lens. Therefore, during the transmission of the optical signal, the mode spot size of the optical signal can be gradually reduced in the horizontal and vertical directions by the gradient refractive index lens, the first waveguide and the second waveguide, so that the mode spot size of the optical signal output by the end coupler can be better matched with the mode spot size in the optical waveguide, thereby reducing the coupling loss of the optical signal from the optical fiber to the optoelectronic chip.

[0005] In some examples, the first waveguide covers the second waveguide, and the length of the first waveguide in the first direction is the same as the length of the second waveguide in the vertical direction, that is, the orthographic projection of the first waveguide on the substrate covers the orthographic projection of the second waveguide on the substrate. With this arrangement, the first waveguide and the second waveguide can be combined to reduce the mode spot size of the optical signal in the horizontal direction and the vertical direction respectively. Exemplarily, the first waveguide has a first side and a second side arranged oppositely in the first direction, the first side of the first waveguide contacts the gradient refractive index lens, the second waveguide has a first side and a second side arranged oppositely in the first direction, and the first side of the second waveguide can be aligned with the first side of the first waveguide in the first direction, and the second side of the second waveguide can be aligned with the second side of the first waveguide in the first direction.

[0006] In some examples, the second waveguide is located on the side of the first waveguide away from the gradient refractive index lens, and the second waveguide is in contact with the side of the first waveguide away from the gradient refractive index lens, that is, the orthographic projection of the first waveguide on the substrate does not overlap with the orthographic projection of the second waveguide on the substrate, but the orthographic projection of the first waveguide on the substrate abuts with the orthographic projection of the second waveguide on the substrate. With this arrangement, the first waveguide can reduce the mode spot size of the optical signal in the horizontal direction before coupling to the second waveguide. Exemplarily, the first side of the second waveguide can also be aligned with the second side of the first waveguide in the first direction.

[0007] In order to further transmit the light directionally into the optical waveguide, the waveguide structure also includes a third waveguide extending along the first direction, the third waveguide is in contact with the side of the second waveguide away from the gradient refractive index lens, and the side of the third waveguide away from the gradient refractive index lens is used to connect to the optical waveguide in the optoelectronic chip, so that the second waveguide is connected to the optical waveguide through the third waveguide. In addition, in the direction along the gradient refractive index lens pointing to the first waveguide, the area of ​​the cross section of the third waveguide is made the same, so that the light output by the second waveguide is directionally transmitted into the optical waveguide through the third waveguide. Exemplarily, the refractive index of the third waveguide is the same as the refractive index of the second waveguide, and the cladding also covers the third waveguide to prevent light from leaking from the third waveguide. In addition, the cross section of the third waveguide can also be made to match the size of the optical waveguide in the optoelectronic chip to further improve the reliability of optical signal transmission.

[0008] In order to further reduce the transmission loss, the third waveguide also has a first side and a second side that are arranged opposite to each other in the first direction, and the cross-section of the third waveguide has the same shape in the direction from the first side of the third waveguide to the second side of the third waveguide. In addition, the cross-section of the first side of the third waveguide can be made the same in area and shape as the cross-section of the second side of the second waveguide, so as to further reduce the coupling loss between the second waveguide and the third waveguide. Also, the cross-section of the third waveguide has the same area and shape as the cross-section of the optical waveguide, so as to further reduce the coupling loss between the third waveguide and the optical waveguide.

[0009] In some examples, in order to further reduce light leakage, the waveguide structure further includes a fourth waveguide extending along the first direction, and the fourth waveguide contacts the side of the first waveguide away from the gradient refractive index lens. When the first waveguide covers the second waveguide, the fourth waveguide covers the third waveguide, that is, the orthographic projection of the fourth waveguide on the substrate covers the orthographic projection of the third waveguide on the substrate, further reducing light leakage. Exemplarily, the refractive index of the fourth waveguide is the same as the refractive index of the first waveguide, and the cladding also covers the fourth waveguide. Based on this, the light is confined in the third waveguide by the fourth waveguide and the cladding to avoid light leakage.

[0010] In some other examples, in order to further reduce light leakage, the waveguide structure further includes a fourth waveguide extending along the first direction, and the fourth waveguide contacts the side of the first waveguide away from the gradient refractive index lens. Wherein, when the second waveguide is located on the side of the first waveguide away from the gradient refractive index lens, the fourth waveguide covers the second waveguide and the third waveguide, that is, the orthographic projection of the fourth waveguide on the substrate covers the orthographic projection of the second waveguide and the third waveguide on the substrate, further reducing light leakage. Exemplarily, the refractive index of the fourth waveguide is the same as the refractive index of the first waveguide, and the cladding also covers the fourth waveguide. Based on this, the light is confined in the third waveguide by the fourth waveguide and the cladding to avoid light leakage.

[0011] Exemplarily, in a direction along the gradient refractive index lens pointing toward the first waveguide, the areas of the cross sections of the fourth waveguide are made the same.

[0012] In order to reduce the coupling loss between the second waveguide and the third waveguide, the third waveguide can be made of the same material as the second waveguide, and the third waveguide and the second waveguide can be formed into an integral structure. Based on this, the second waveguide and the third waveguide can be formed using the same patterning process, reducing the number of steps in the preparation process.

[0013] In order to reduce the number of steps in the manufacturing process, the fourth waveguide is made of the same material as the first waveguide, and the fourth waveguide and the first waveguide are formed as an integral structure. Based on this, the fourth waveguide and the first waveguide can be formed using the same patterning process, reducing the number of steps in the manufacturing process.

[0014] In some examples, the first waveguide includes, but is not limited to, being a tapered waveguide, ie, the first waveguide is a positive tapered waveguide.

[0015] In some examples, the second waveguide includes, but is not limited to, being a tapered waveguide, ie, the second waveguide is an inverted tapered waveguide.

[0016] In some examples, the third waveguide includes, but is not limited to, being a rectangular waveguide.

[0017] In some examples, the fourth waveguide includes, but is not limited to, being a rectangular waveguide.

[0018] In some examples, the gradient refractive index lens includes: a plurality of light-transmitting layers stacked on a substrate, and the refractive index of the plurality of light-transmitting layers decreases in sequence in the direction from the substrate to the gradient refractive index lens. Moreover, the first side surface of the plurality of light-transmitting layers in the first direction serves as the first side of the gradient refractive index lens, and the second side surface in the first direction serves as the second side of the gradient refractive index lens. With this arrangement, the mode spot size of the optical signal at the end face of the optical fiber can be reduced in the vertical direction.

[0019] In addition, the first waveguide is in contact with the second side surface of the light-transmitting layer in the gradient refractive index lens that is in contact with the substrate, and the refractive index of the first waveguide is the same as the refractive index of the light-transmitting layer in the gradient refractive index lens that is in contact with the substrate. In this way, the mode spot size of the optical signal at the end face of the optical fiber can be reduced in the vertical direction through the gradient refractive index lens, and the optical signal can be coupled to the first waveguide through the light-transmitting layer in contact with the substrate, thereby reducing the coupling loss.

[0020] Exemplarily, the first waveguide and the light-transmitting layer in the gradient refractive index lens that is in contact with the substrate are an integrally formed structure and are made of the same material.

[0021] In order to reduce light leakage, the cladding further covers the gradient refractive index lens, and the cladding exposes the first side of the gradient refractive index lens so that the first side of the gradient refractive index lens can be connected to the optical fiber.

[0022] Furthermore, the thicknesses of the plurality of light-transmitting layers in the vertical direction may be the same or different to meet process requirements.

[0023] In some examples, the material of the first waveguide includes but is not limited to oxynitride. For example, the material of the first waveguide is silicon oxynitride, so that the first waveguide is a positive-tapered silicon oxynitride waveguide.

[0024] In some examples, the material of the second waveguide includes, but is not limited to, silicon, so that the second waveguide is an inverted tapered silicon waveguide.

[0025] In some examples, the material of the light-transmitting layer in the gradient refractive index lens includes but is not limited to nitride oxide. For example, the material of the light-transmitting layer is silicon oxynitride, so that the gradient refractive index lens is a silicon oxynitride gradient refractive index lens.

[0026] In some examples, the material of the cladding includes, but is not limited to, oxide. For example, the material of the cladding is silicon dioxide, so that the cladding is a silicon dioxide cladding.

[0027] In a specific implementation, the substrate may include a stacked oxide layer and a semiconductor layer, and the waveguide structure and the cladding are located on the side of the oxide layer away from the semiconductor layer. Alternatively, the substrate may also be an oxide layer, that is, no semiconductor layer is provided. In addition, the material of the oxide layer may be the same as that of the cladding to prevent light from leaking from one side of the substrate.

[0028] In a second aspect, the present application also provides a method for preparing an end coupler, including the following contents:

[0029] A second waveguide is formed on the substrate, wherein the second waveguide extends along a first direction, and in the first direction, the cross-sectional area of ​​the second waveguide gradually increases; the second waveguide is used to connect with the optical waveguide in the optoelectronic chip, and the first direction is parallel to the substrate;

[0030] A gradient refractive index lens and a first waveguide are formed on the substrate, wherein the gradient refractive index lens has a first side and a second side arranged opposite to each other in a first direction, the first side of the gradient refractive index lens is used to connect with an optical fiber, the second waveguide contacts the first waveguide, the first waveguide contacts the second side of the gradient refractive index lens, the second waveguide extends along the first direction, and the cross-sectional area of ​​the second waveguide gradually decreases in the first direction;

[0031] A cladding is deposited on the substrate, wherein the cladding covers the gradient refractive index lens, the first waveguide, and the second waveguide.

[0032] In order to further transmit light in a directionally directed manner into the optical waveguide, the method further includes: forming a third waveguide when forming the second waveguide, the third waveguide extending along the first direction, the third waveguide being in contact with a side of the second waveguide away from the gradient refractive index lens, and the side of the third waveguide away from the gradient refractive index lens being used to connect with an optical waveguide in an optoelectronic chip; in a direction along the gradient refractive index lens pointing to the first waveguide, the cross-sectional area of ​​the third waveguide is the same. Furthermore, the cladding also covers the third waveguide.

[0033] In order to further reduce light leakage, the preparation method further includes: forming a fourth waveguide when forming the first waveguide, the fourth waveguide extending along the first direction, and the fourth waveguide contacting the side of the first waveguide away from the gradient refractive index lens; wherein, when the first waveguide covers the second waveguide, the fourth waveguide covers the third waveguide; or, when the second waveguide is located on the side of the first waveguide away from the gradient refractive index lens, the fourth waveguide covers the second waveguide and the third waveguide. In addition, the cladding also covers the fourth waveguide.

[0034] In a specific implementation, a silicon on insulator (SOI) substrate is used to form an end coupler. Exemplarily, the preparation method includes the following process: providing an SOI substrate, the SOI substrate includes a bottom silicon, a buried oxide layer and a top silicon. The top silicon is patterned and etched to form a second waveguide. And, for forming a gradient refractive index lens and a first waveguide on the substrate, the following process is included: depositing a plurality of silicon oxynitride film layers on the buried oxide layer on which the second waveguide is formed, and making the refractive index of the plurality of silicon oxynitride film layers decrease in sequence in the direction from the bottom silicon to the buried oxide layer. Thereafter, patterning the remaining silicon oxynitride film layers in the plurality of silicon oxynitride film layers, and etching to form the remaining light-transmitting layers in the gradient refractive index lens, the remaining silicon oxynitride film layers being the silicon oxynitride film layers in the plurality of silicon oxynitride film layers except the silicon oxynitride film layers in contact with the buried oxide layer. Afterwards, the silicon oxynitride film layer in contact with the buried oxide layer is patterned, and etching is performed to form a light-transmitting layer and a first waveguide in contact with the buried oxide layer in the gradient refractive index lens.

[0035] In the third aspect, the embodiment of the present application also provides a communication system, which includes an optical fiber, an optoelectronic chip and an end coupler. Among them, the end face of the optical fiber is connected to the first side of the gradient refractive index lens in the end coupler, and the second side of the second waveguide in the end coupler is connected to the end face of the optical waveguide in the optoelectronic chip, so that the mode spot size of the end face of the optical fiber is reduced by the end coupler and then coupled to the optical waveguide, thereby reducing the coupling loss. In addition, the end coupler is an end coupler as in the first aspect or various possible designs of the first aspect. Since the coupling loss of the above-mentioned end coupler is low, the coupling loss of the communication system including the above-mentioned end coupler is also low. In addition, the principle of solving the problem by the communication system is similar to the principle that the aforementioned end coupler can solve the problem. Therefore, the technical effect of the communication system can refer to the technical effect of the aforementioned end coupler, and the repeated parts will not be repeated. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the three-dimensional structure of an end face coupler in one embodiment of the present application;

[0037] Figure 2 for Figure 1 A schematic diagram of the top view structure of the end face coupler in FIG.

[0038] Figure 3 for Figure 2 A schematic diagram of the cross-sectional structure along the AA' dashed line;

[0039] Figures 4a to 4e They are respectively partial structural schematic diagrams of an end face coupler in an embodiment of the present application;

[0040] Figure 5a to Figure 5cThey are respectively schematic diagrams of simulation results in one embodiment of the present application;

[0041] Figure 6 A flowchart of a preparation method in an embodiment of the present application;

[0042] Figures 7a to 7e They are schematic diagrams of structures in the process of preparing an end face coupler in one embodiment of the present application;

[0043] Figure 8 This is a schematic diagram of the three-dimensional structure of an end face coupler in another embodiment of the present application;

[0044] Fig. 9 for Figure 8 A schematic diagram of the top view structure of the end face coupler in FIG.

[0045] Fig.10 for Fig. 9 A schematic diagram of the cross-sectional structure along the AA' dashed line;

[0046] Fig.11 This is a schematic diagram of the three-dimensional structure of an end face coupler in another embodiment of the present application;

[0047] Fig.12 for Fig.11 A schematic diagram of the top view structure of the end face coupler in FIG.

[0048] Fig.13 for Fig.12 A schematic diagram of the cross-sectional structure along the AA' dashed line;

[0049] Figures 14a to 14c They are respectively schematic diagrams of simulation results in yet another embodiment of the present application;

[0050] Fig.15 This is a schematic diagram of the three-dimensional structure of an end face coupler in another embodiment of the present application;

[0051] Fig.16 for Fig.15 A schematic diagram of the top view structure of the end face coupler in FIG.

[0052] Fig.17 for Fig.16 Schematic diagram of the cross-sectional structure along the AA' dashed line.

[0053] Reference numerals:

[0054] 100-substrate; 110-oxide layer; 120-semiconductor layer; 200-gradient refractive index lens; 210 / 220 / 230 / 240 / 250-light-transmitting layer; 210a / 220a / 230a / 240a / 250a-silicon oxynitride film layer; 310-second waveguide; 320-first waveguide; 330-third waveguide; 340-fourth waveguide; 400-cladding; 500-optical fiber, X-first direction; Y-horizontal direction; Z-vertical direction; d1 / d2 / d3 / d4-length; h0 / h1 / h2 / h3 / h4-thickness; S01 / S11 / S21 / S31 / S41-first side; S02 / S12 / S22 / S32 / S42-second side; TW tip width. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The reference "one embodiment" or "some embodiments" described in this specification means that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in the differences in this specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways. In addition, the words "first", "second", etc. involved in this specification are only used to distinguish the purpose of description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0056] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "an", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context.

[0057] The end coupler provided in the embodiment of the present application is connected between the end face of the optical fiber and the end face of the optical waveguide of the optoelectronic chip, and is used to reduce the mode spot size of the optical signal transmitted by the optical fiber and couple it into the optical waveguide. The end coupler provided in the embodiment of the present application can be widely used in communication systems based on the coupling of optoelectronic chips and optical fibers, such as access networks, transmission networks, data centers, routers and other communication systems that require the use of optical modules. In addition, the above-mentioned optical fiber includes but is not limited to single-mode optical fiber, and the above-mentioned optoelectronic chip includes but is not limited to silicon-based optoelectronic chips. It is understandable that the end coupler in the embodiment of the present application is intended to include but is not limited to application in these and any other suitable types of equipment.

[0058] Figure 1 is a schematic diagram of the three-dimensional structure of an end face coupler in an embodiment of the present application, Figure 2 for Figure 1 Schematic diagram of the top view of the end coupler in the figure. Figure 3 for Figure 2 The schematic diagram of the cross-sectional structure along the AA' dashed line in the figure. Figures 4a to 4e They are partial structural schematic diagrams of an end face coupler in an embodiment of the present application. Figures 1 to 4eThe end coupler may include: a substrate 100, a waveguide structure located on the substrate 100, and a cladding 400 covering the waveguide structure, wherein the waveguide structure includes a gradient refractive index lens (GRIN lens) 200 formed on the substrate 100, a second waveguide 310, and a first waveguide 320. The first waveguide 320 is located on the side of the second waveguide 310 away from the substrate 100, and the first waveguide 320 covers the second waveguide 310, that is, the orthographic projection of the first waveguide 320 on the substrate 100 covers the orthographic projection of the second waveguide 310 on the substrate 100, and the cladding 400 is located on the side of the first waveguide 320 away from the substrate 100, and the cladding 400 covers the first waveguide 320, that is, the orthographic projection of the cladding 400 on the substrate 100 covers the orthographic projection of the first waveguide 320 on the substrate 100. Furthermore, the refractive index of the first waveguide 320 is smaller than that of the second waveguide 310, so that the optical signal in the first waveguide 320 can be coupled to the second waveguide 310. The refractive index of the cladding 400 is smaller than that of the first waveguide 320, so as to prevent light leakage through the cladding 400. Furthermore, the gradient index lens 200 has a first side S01 and a second side S02 arranged opposite to each other in the first direction X, the second waveguide 310 has a first side S11 and a second side S12 arranged opposite to each other in the first direction X, and the first waveguide 320 has a first side S21 and a second side S22 in the first direction X. The first side S01 of the gradient index lens 200 is used to connect to an optical fiber, the first side S21 of the first waveguide 320 contacts the second side S02 of the gradient index lens 200, the first waveguide 320 contacts the second waveguide 310, and the second side S22 of the second waveguide 310 is used to connect to an optical waveguide in an optoelectronic chip. Based on this, the optical fiber 500 is connected to the end face of the optical waveguide in the optoelectronic chip through the end face coupler, that is, the end face of the optical fiber 500 is connected to the first side S01 of the gradient refractive index lens 200, and the second side S12 of the second waveguide 310 is connected to the end face of the optical waveguide. During the optical signal transmission process, the mode spot size of the optical signal in the end face of the optical fiber 500 is reduced in the vertical direction Z by the gradient refractive index lens 200 and then coupled to the first waveguide 320 and the second waveguide 310. For the second waveguide 310 and the first waveguide 320, the area of ​​the cross section of the first waveguide 320 perpendicular to the first direction X gradually decreases in the direction along the gradient refractive index lens 200 pointing to the first waveguide 320 (i.e., the direction indicated by the arrow in the first direction X), and the area of ​​the cross section of the second waveguide 310 perpendicular to the first direction X gradually increases in the direction along the gradient refractive index lens 200 pointing to the first waveguide 320 (i.e., the direction indicated by the arrow in the first direction X). Based on this, the first waveguide 320 and the second waveguide 310 are combined with each other, and the optical signal coupled to the gradient refractive index lens 200 is subjected to pattern spot size reduction in the horizontal direction Y and the vertical direction Z, and is coupled to the optical waveguide through the second waveguide 310 to achieve pattern spot size reduction, and then the optical signal with reduced pattern spot size is coupled to the optical waveguide.In summary, by providing the first waveguide 320, the mode spot size of the optical signal output by the gradient refractive index lens 200 is first reduced by the first waveguide 320 and then coupled to the second waveguide 310, so that the coupling loss of the optical signal directly coupled from the gradient refractive index lens 200 to the second waveguide 310 can be reduced. Therefore, during the transmission of the optical signal, the mode spot size is gradually reduced by the gradient refractive index lens 200, the first waveguide 320 and the second waveguide 310, so that the mode spot size of the optical signal output by the end face coupler can be better matched with the mode spot size in the optical waveguide, thereby reducing the coupling loss of the optical signal from the optical fiber to the optoelectronic chip.

[0059] In addition, the first direction X and the horizontal direction Y are both parallel to the substrate 100 , and the first direction X is perpendicular to the horizontal direction Y, and the vertical direction Z is also perpendicular to the first direction X. Furthermore, the vertical direction Z is perpendicular to the substrate 100 .

[0060] Continue to refer to Figures 1 to 4e , the orthographic projection of the first waveguide 320 on the substrate 100 may cover the orthographic projection of the second waveguide 310 on the substrate 100, that is, the first waveguide 320 is located on the side of the second waveguide 310 away from the substrate 100, and the first waveguide 320 is arranged to cover the second waveguide 310. Exemplarily, the first side S11 of the second waveguide 310 may be aligned with the first side S21 of the first waveguide 320 in the first direction X, and the second side S12 of the second waveguide 310 may be aligned with the second side S22 of the first waveguide 320 in the first direction X. In this way, the length d1 of the second waveguide 310 along the first direction X and the length d2 of the first waveguide 320 along the first direction X may be the same. In addition, the first side S11 and the second side S12 of the second waveguide 310 are arranged in parallel, and the first side S21 and the second side S22 of the first waveguide 320 are also arranged in parallel.

[0061] To further direct the light into the optical waveguide, refer to Figures 1 to 3 , Figure 4b and Figure 4dThe waveguide structure further includes a third waveguide 330 extending along the first direction X. The refractive index of the third waveguide 330 is the same as that of the second waveguide 310. The cladding 400 also covers the third waveguide 330, that is, the orthographic projection of the cladding 400 on the substrate 100 also covers the orthographic projection of the third waveguide 330 on the substrate 100, so as to prevent light from leaking from the third waveguide 330. In addition, the third waveguide 330 has a first side S31 and a second side S32 that are arranged opposite to each other in the first direction X. The first side S31 of the third waveguide 330 contacts the second side S12 of the second waveguide 310, that is, the third waveguide 330 contacts the side of the second waveguide 310 that is away from the gradient refractive index lens 200. The side of the third waveguide 330 that is away from the gradient refractive index lens 200 is used to connect with the optical waveguide in the optoelectronic chip, that is, the second side S32 of the third waveguide 330 is used to connect with the optical waveguide in the optoelectronic chip. Furthermore, the cladding 400 exposes the second side S32 of the third waveguide 330 so that the second side S32 of the third waveguide 330 can be connected to the optical waveguide. With this configuration, the second waveguide 310 can be connected to the optical waveguide through the third waveguide 330 to match the size of the optical waveguide in the optoelectronic chip. Furthermore, the area of ​​the cross section of the third waveguide 330 perpendicular to the first direction X is the same in the direction from the gradient refractive index lens 200 to the first waveguide 320 (i.e., the direction indicated by the arrow of the first direction X), so that the light output from the second waveguide 310 is transmitted to the optical waveguide in a directionally manner through the third waveguide 330.

[0062] Further, in order to reduce the transmission loss, the shape of the cross section of the third waveguide 330 perpendicular to the first direction X can be made the same in the direction along the gradient index lens 200 pointing to the first waveguide 320 (i.e., the direction indicated by the arrow of the first direction X). In addition, the cross section of the first side S31 of the third waveguide 330 perpendicular to the first direction X can be made the same in area and shape as the cross section of the second side S12 of the second waveguide 310 perpendicular to the first direction X, so as to further reduce the coupling loss between the second waveguide 310 and the third waveguide 330. In addition, the cross section of the third waveguide 330 perpendicular to the first direction X has the same area and shape as the cross section of the optical waveguide perpendicular to the first direction X, so as to further reduce the coupling loss between the third waveguide 330 and the optical waveguide. In addition, the first side S31 and the second side S32 of the third waveguide 330 are arranged in parallel.

[0063] To further reduce light leakage, refer to Figures 1 to 3 and Figure 4b to Figure 4eThe end coupler further includes a fourth waveguide 340 extending along the first direction X, the refractive index of the fourth waveguide 340 is the same as the refractive index of the first waveguide 320, and the cladding 400 further covers the fourth waveguide 340, that is, the orthographic projection of the cladding 400 on the substrate 100 also covers the orthographic projection of the fourth waveguide 340 on the substrate 100. The fourth waveguide 340 further covers the third waveguide 330, that is, the orthographic projection of the fourth waveguide 340 on the substrate 100 covers the orthographic projection of the third waveguide 330 on the substrate 100, and the fourth waveguide 340 contacts the side of the first waveguide 320 away from the gradient refractive index lens 200, for example, the fourth waveguide 340 has a first side S41 and a second side S42 arranged opposite to each other in the first direction X, and the first side S41 of the fourth waveguide 340 contacts the second side S22 of the first waveguide 320. The second side S42 of the fourth waveguide 340 and the second side S32 of the third waveguide 330 may be aligned in the first direction X, and in the direction from the gradient refractive index lens 200 to the first waveguide 320 (i.e., the direction indicated by the arrow of the first direction X), the areas of the cross sections of the fourth waveguide 340 perpendicular to the first direction X are the same. Based on this, the light is confined in the third waveguide 330 by the fourth waveguide 340 to avoid light leakage. In addition, the cross section of the first side S41 of the fourth waveguide 340 perpendicular to the first direction X and the cross section of the second side S22 of the first waveguide 320 perpendicular to the first direction X have the same area and shape, and the shape of the cross section of the fourth waveguide 340 perpendicular to the first direction X may also be the same in the direction from the first side S41 of the fourth waveguide 340 to the second side S42 of the fourth waveguide 340 (i.e., the direction indicated by the arrow of the first direction X).

[0064] Continue to refer to Figure 1 and Figure 2 , the second side S12 of the second waveguide 310, the second side S22 of the first waveguide 320, the first side S31 of the third waveguide 330, and the first side S41 of the fourth waveguide 340 are aligned in the first direction X, and the second side S32 of the third waveguide 330 and the second side S42 of the fourth waveguide 340 are aligned in the first direction X, so that the length d3 of the third waveguide 330 along the first direction X is the same as the length d4 of the fourth waveguide 340 along the first direction X, further avoiding light leakage.

[0065] Continue to refer to Figure 1 and Figure 2The end face coupler has a center line (e.g., AA' dashed line) extending along the first direction X, and the orthographic projection of the gradient refractive index lens 200 on the substrate 100 can be symmetrically arranged about the AA' dashed line. Exemplarily, the gradient refractive index lens 200 includes: light-transmitting layers 210 to 250 stacked and arranged on the substrate 100, and in the direction from the substrate 100 to the gradient refractive index lens 200 (i.e., the direction indicated by the arrow perpendicular to the direction Z), the refractive index n of the light-transmitting layer 210 is 210 , the refractive index n of the light-transmitting layer 220 220 , the refractive index n of the light-transmitting layer 230 230 , the refractive index n of the light-transmitting layer 240 240 , the refractive index n of the light-transmitting layer 250 250 becomes smaller successively, that is, n 210 >n 220 >n 230 >n 240 >n 250 . And, the first side surface of the light-transmitting layer 210-250 in the first direction X serves as the first side S01 of the gradient refractive index lens 200, and the second side surface in the first direction X serves as the second side S02 of the gradient refractive index lens 200. And, the first side S21 of the first waveguide 320 contacts the second side surface of the light-transmitting layer 210 in the gradient refractive index lens 200 that contacts the substrate 100, and the refractive index of the first waveguide 320 is the same as the refractive index of the contacted light-transmitting layer 210. With this arrangement, the mode spot size of the optical signal at the end face of the optical fiber can be reduced in the vertical direction Z through the light-transmitting layers 210-250, and the optical signal can be coupled to the first waveguide 320 through the light-transmitting layer 210, thereby reducing the coupling loss.

[0066] Furthermore, the thickness of the light-transmitting layers 210 to 250 in the vertical direction Z can be made the same or different to meet the process requirements. In addition, the present application does not limit the material of the light-transmitting layer. Optionally, the material of the light-transmitting layer includes nitride oxide, for example, the material of the light-transmitting layer is silicon oxynitride, so that the gradient refractive index lens is a silicon oxynitride gradient refractive index lens. It is understandable that the present application uses the gradient refractive index lens 200 having 5 light-transmitting layers as an example for illustration. In actual applications, the specific number of light-transmitting layers in the gradient refractive index lens 200 can be determined according to the needs of the actual application to meet the process requirements.

[0067] Continue to refer to Figure 1 and Figure 2 , the orthographic projection of the second waveguide 310 on the substrate 100 may be symmetrically arranged about the AA' dashed line. Exemplarily, the second waveguide 310 includes, but is not limited to, a tapered waveguide. Moreover, the present application does not limit the material of the second waveguide 310. For example, the material of the second waveguide 310 includes silicon, so that the second waveguide 310 is an inverted tapered silicon waveguide.

[0068] Continue to refer to Figure 1 and Figure 2 , the orthographic projection of the third waveguide 330 on the substrate 100 may be symmetrically arranged about the AA' dashed line. Exemplarily, the third waveguide 330 includes but is not limited to being a rectangular waveguide. Moreover, the present application does not limit the material of the third waveguide 330. Further, the second waveguide 310 and the third waveguide 330 may be made of the same material, that is, the material of the third waveguide 330 includes silicon, so that the third waveguide 330 is a rectangular silicon waveguide.

[0069] Exemplarily, the third waveguide 330 and the second waveguide 310 are configured as an integrally formed structure, and the third waveguide 330 and the second waveguide 310 are made of the same material. In this way, the third waveguide 330 and the second waveguide 310 can be configured in the same layer, so that the thickness h1 of the second waveguide 310 in the vertical direction Z is the same as the thickness h3 of the third waveguide 330 in the vertical direction Z, thereby further reducing the coupling loss of the optical signal from the second waveguide 310 to the third waveguide 330, and the second waveguide 310 and the third waveguide 330 can also be prepared by the same patterning process, thereby reducing the number of steps in the preparation process.

[0070] Continue to refer to Figure 1 and Figure 2 , the orthographic projection of the first waveguide 320 on the substrate 100 may be symmetrically arranged about the AA' dashed line. Exemplarily, the first waveguide 320 includes, but is not limited to, a tapered waveguide. In addition, the present application does not limit the material of the first waveguide 320. For example, the material of the first waveguide 320 includes nitride oxide, for example, the material of the first waveguide 320 is silicon oxynitride, so that the first waveguide 320 is a positive tapered silicon oxynitride waveguide.

[0071] Furthermore, the material of the first waveguide 320 is the same as that of the light-transmitting layer in the gradient refractive index lens 200, so as to reduce the coupling loss of light from the light-transmitting layer to the first waveguide 320. In addition, the first waveguide 320 and the light-transmitting layer 210 in the gradient refractive index lens 200 that contacts the substrate 100 are an integrally formed structure, so that the first waveguide 320 and the light-transmitting layer 210 can be prepared by the same patterning process, thereby reducing the number of steps in the preparation process.

[0072] Continue to refer to Figure 1 and Figure 2 , the orthographic projection of the fourth waveguide 340 on the substrate 100 may be symmetrically arranged about the AA' dashed line. Exemplarily, the fourth waveguide 340 includes, but is not limited to, a rectangular waveguide. In addition, the present application does not limit the material of the fourth waveguide 340. Optionally, the material of the fourth waveguide 340 includes nitride oxide, for example, the material of the fourth waveguide 340 is silicon oxynitride, so that the fourth waveguide 340 is a rectangular silicon oxynitride waveguide.

[0073] Furthermore, the materials of the first waveguide 320, the fourth waveguide 340 and the light-transmitting layer 210 are the same, and the first waveguide 320, the fourth waveguide 340 and the light-transmitting layer 210 are an integrally formed structure, so that the thickness h2 of the first waveguide 320 in the vertical direction Z, the thickness h4 of the fourth waveguide 340 in the vertical direction Z, and the thickness h0 of the light-transmitting layer 210 in the vertical direction Z are the same, so that the first waveguide 320, the fourth waveguide 340 and the light-transmitting layer 210 can be prepared by the same patterning process, thereby reducing the steps of the preparation process.

[0074] It is understandable that the Figure 1 and Figure 2 In the figure, the cladding 400 covering the second side of the light-transmitting layer 220-250 in the gradient refractive index lens 200 is taken as an example for illustration. In practical applications, the orthographic projection of the cladding 400 on the substrate 100 can also cover the orthographic projection of the gradient refractive index lens 200 on the substrate, that is, the cladding 400 also covers the upper surface of the gradient refractive index lens 200 facing away from the substrate 100 and the two side surfaces of the gradient refractive index lens 200 in the horizontal direction Y. In addition, the cladding 400 exposes the first side S01 of the gradient refractive index lens 200 so that the first side S01 of the gradient refractive index lens 200 can be connected to the optical fiber. In addition, the present application does not limit the material of the cladding 400. For example, the material of the cladding 400 includes but is not limited to oxides. For example, the material of the cladding is silicon dioxide, so that the cladding is a silicon dioxide cladding.

[0075] Continue to refer to Figure 1 and Figure 2 , the substrate 100 includes a stacked oxide layer 110 and a semiconductor layer 120, and the gradient refractive index lens 200, the second waveguide 310, the first waveguide 320, the third waveguide 330, the fourth waveguide 340 and the cladding 400 are located on the side of the oxide layer 110 away from the semiconductor layer 120. Alternatively, the substrate 100 may also be an oxide layer, that is, no semiconductor layer is provided. In addition, the material of the oxide layer 110 may be the same as that of the cladding 400 to prevent light from leaking from one side of the substrate 100.

[0076] This application is Figure 1The structure of the end face coupler shown in the figure and the simulation are performed by taking the mode spot size of the optical signal of the end face of the optical fiber 500 as 10 microns as an example. Through the simulation, it can be known that the mode spot size can be reduced from 10 microns to approximately several microns (for example, 3 microns) in the vertical direction Z through the gradient refractive index lens 200, and it is not reduced in the horizontal direction Y, and the optical signal after the mode spot is reduced is coupled to the first waveguide 320 and the second waveguide 310 through the light-transmitting layer 210. The first waveguide 320 and the second waveguide 310 are combined with each other to reduce the mode spot size of the optical signal to several hundred nanometers (for example, 300 nanometers) in the horizontal direction Y and the vertical direction Z, respectively, and transmit it to the optical waveguide through the third waveguide 330. Based on this, the conversion process of reducing the mode spot size from 10 microns to several hundred nanometers can be realized.

[0077] This application also Figure 1 Taking the structure of the end coupler shown in the figure, and the materials of the second waveguide 310 and the third waveguide 330 are silicon, and the materials of the light-transmitting layer, the first waveguide 320 and the fourth waveguide 340 are silicon oxynitride as an example, the coupling loss of the end coupler is simulated. Among them, the coupling loss of the end coupler mainly includes: the first loss Loss1 and the second loss Loss2. Among them, the first loss Loss1 represents the total loss of the optical signal from the optical fiber through the gradient refractive index lens 200 to the first waveguide 320 (the total loss mainly includes: the Fresnel reflection loss between the optical fiber and the gradient refractive index lens 200, the mode spot conversion loss of the gradient refractive index lens 200, and the Fresnel reflection loss between the gradient refractive index lens 200 and the first waveguide 320 and the cladding 400). The second loss Loss2 represents the transmission loss of the optical signal from the first waveguide 320 to the third waveguide 330. As for the transmission losses inherent in each structure, these transmission losses include material absorption loss, scattering loss caused by sidewall roughness, radiation loss caused by waveguide bending, etc. Due to the limitations of material properties and simulation, the transmission losses can be ignored. Among them, for the first loss Loss1: its key influencing factor is the performance of the gradient refractive index lens 200. Based on this, a physical model of the end face coupler is established in the 2DFDTD module of the simulation software for simulation, and the influence curve of the refractive index change of the light-transmitting layer in contact with the substrate 100 in the gradient refractive index lens 200 on the first loss Loss1 is obtained, as shown in FIG. Figure 5a As shown, the horizontal axis IB represents the refractive index of the light-transmitting layer in contact with the substrate 100 in the gradient refractive index lens 200, the vertical axis Loss1 represents the first loss, and different line types represent the first loss Loss1 of the TE mode respectively. TE and the first loss of TM mode Loss1 TM . Reference Figure 5a , when IB=1.5, Loss1 TE =-0.039dB, Loss1 TM=-0.052dB. And, for the second loss Loss2: its key influencing factors are the length d1 of the second waveguide 310, the length d2 of the first waveguide 320 (d1=d2) and the tip width TW of the second waveguide 310. Based on this, a physical model of the end face coupler is established in the MODE module of the simulation software for simulation, and the influence curve of the length d1 of the second waveguide 310 and the length d2 of the first waveguide 320 on the second loss Loss2 is obtained, as shown in FIG. Figure 5b As shown, the horizontal axis LE represents the length d1 of the second waveguide 310 and the length d2 of the first waveguide 320, the vertical axis Loss2 represents the second loss, and different line types represent the second loss Loss2 of the TE mode respectively. TE and the second loss of TM mode Loss2 TM . Reference Figure 5b , when d1=d2=700μm, Loss2 TE =-0.014dB, Loss2 TM =-0.012dB. In addition, taking d1=d2=700μm as an example, the second loss Loss2 is optimized by changing the tip width TW of the second waveguide 310, as shown in FIG. Figure 5c As shown, the horizontal axis TW represents the tip width of the second waveguide 310, the vertical axis Loss2 represents the second loss, and different line types represent the second loss Loss2 of the TE mode respectively. TE and the second loss of TM mode Loss2 TM When the tip width TW of the second waveguide 310 is 40 nm, Loss2 TE and Loss2 TM Minimum, close to 0. In summary, the coupling loss Loss of the end coupler corresponding to the TE mode is obtained through simulation. TE =Loss1 TE +Loss2 TE =-0.053dB, and the corresponding TM mode coupling loss Loss TM =Loss1 TM +Loss2 TM =-0.064dB. It can be understood that when IB=1.5, d1 (or d2)=700μm, and the tip width TW of the second waveguide 310=40nm, the corresponding coupling loss is the lowest loss of the current structure.

[0078] Figure 6 Flow chart of the preparation method in one embodiment of the present application. Figure 6 , the preparation method may include the following steps:

[0079] S10, etching to form a second waveguide and a third waveguide on the substrate.

[0080] by Figure 2 As an example, step S10 may include the following process: Figure 7a , a silicon on insulator (SOI) substrate 100 may be used, and the SOI substrate 100 includes a bottom silicon, a buried oxide layer, and a top silicon. The top silicon is patterned and etched to form the second waveguide 310 and the third waveguide 330, so that the buried oxide layer serves as the oxide layer 110 of the substrate 100 in the end coupler, and the bottom silicon serves as the semiconductor layer 120 of the substrate 100 in the end coupler. Alternatively, a semiconductor layer, an oxide layer, and a silicon layer may be epitaxially grown in sequence, and the silicon layer may be patterned and etched to form the second waveguide and the third waveguide.

[0081] S20, etching on the substrate to form a gradient refractive index lens, a first waveguide and a fourth waveguide.

[0082] by Figure 2 As an example, step S20 may include the following process: first, referring to Figure 7b , depositing five silicon oxynitride film layers 210a-250a on the oxide layer 110, and adjusting the refractive index and thickness of the five silicon oxynitride film layers 210a-250a so that the refractive index and thickness of the five silicon oxynitride film layers 210a-250a meet the process requirements. Figure 7c , the silicon oxynitride film layers 220a-250a are patterned and etched to form the light-transmitting layers 220-250 in the gradient refractive index lens 200. Figure 7d The silicon oxynitride film layer 210 a is patterned and etched to form the light-transmitting layer 210 , the first waveguide 320 and the fourth waveguide 340 in the gradient refractive index lens 200 , and the first waveguide 320 covers the second waveguide 310 , and the fourth waveguide 340 covers the first waveguide 320 .

[0083] S30, depositing a cladding layer on the substrate.

[0084] by Figure 2 As an example, step S30 may include the following process: Figure 7e, a silica cladding 400 is deposited on the substrate 100, and the silica cladding 400 covers the side surfaces of the first waveguide 320, the fourth waveguide 340 and the light-transmitting layers 220 to 250. Exemplarily, the cladding 400 is also in contact with the second side surfaces of the light-transmitting layers 220 to 250 in the gradient refractive index lens 200, so as to further prevent light leakage. Further, the orthographic projection of the cladding 400 on the substrate 100 also covers the orthographic projection of the gradient refractive index lens 200 on the substrate, that is, the cladding 400 also covers the upper surface of the gradient refractive index lens 200 away from the substrate 100 and the two side surfaces of the gradient refractive index lens 200 in the horizontal direction Y. Furthermore, the cladding 400 exposes the first side S01 of the gradient refractive index lens 200 so that the first side S01 of the gradient refractive index lens 200 can be connected to the optical fiber. Furthermore, the present application does not limit the material of the cladding 400, for example, the material of the cladding 400 includes but is not limited to oxides (such as silica).

[0085] Figure 8 is a schematic diagram of a three-dimensional structure of an end face coupler in another embodiment of the present application, Fig. 9 for Figure 8 Schematic diagram of the top view of the end coupler in the figure. Fig.10 for Fig. 9 The cross-sectional structure diagram along the AA' dashed line. Figures 8 to 10 The end coupler may include: a substrate 100 and a gradient refractive index lens 200, a second waveguide 310, a first waveguide 320 and a cladding 400 located on the substrate 100. Figure 1 The difference of the embodiment shown is that the third waveguide 330 and the fourth waveguide 340 are not provided, that is, the second side S12 of the second waveguide 310 is directly connected to the optical waveguide in the optoelectronic chip, so that light is directly coupled from the second waveguide 310 to the optical waveguide. The rest of the contents of this embodiment can be compared with Figure 1 The contents in the illustrated embodiments are substantially the same and will not be described in detail herein.

[0086] To prepare Figure 8 As an example, the structure of the end face coupler shown in FIG. 1 is used as an example, and the flowchart of the corresponding preparation method can be referred to Figure 6 In step S10, the third waveguide 330 does not need to be etched. In step S20, the fourth waveguide 340 does not need to be etched. The rest of the preparation process can refer to the description of the above preparation method, which will not be described in detail here.

[0087] Fig.11 is a schematic diagram of a three-dimensional structure of an end face coupler in another embodiment of the present application, Fig.12 for Fig.11 Schematic diagram of the top view of the end coupler in the figure. Fig.13 for Fig.12The cross-sectional structure diagram along the AA' dashed line. Figures 11 to 13 The end coupler may include: a substrate 100 and a gradient index lens 200, a second waveguide 310, a first waveguide 320, a third waveguide 330, a fourth waveguide 340 and a cladding 400 located on the substrate 100. The second waveguide 310 is located on the side of the first waveguide 320 away from the gradient index lens 200, and the second waveguide 310 is in contact with the side of the first waveguide 320 away from the gradient index lens 200, that is, the orthographic projection of the first waveguide 320 on the substrate 100 does not overlap with the orthographic projection of the second waveguide 310 on the substrate 100, and the first side S11 of the second waveguide 310 is in contact with the second side S22 of the first waveguide 320, so that the orthographic projection of the first waveguide 320 on the substrate 100 is located between the orthographic projection of the second waveguide 310 on the substrate 100 and the gradient index lens 200. According to this configuration, the optical signal can be coupled to the second waveguide 310 after the optical spot is reduced in the horizontal direction Y through the first waveguide 320. In addition, the fourth waveguide 340 covers the second waveguide 310 and the third waveguide 330, that is, the orthographic projection of the fourth waveguide 340 on the substrate 100 covers the orthographic projection of the second waveguide 310 on the substrate 100 and the orthographic projection of the third waveguide 330 on the substrate 100, and the fourth waveguide 340 prevents light leakage in the second waveguide 310 and the third waveguide 330. In addition, the first side S11 of the second waveguide 310, the second side S22 of the first waveguide 320, and the first side S41 of the fourth waveguide 340 are aligned in the first direction X, and the second side S32 of the third waveguide 330 and the second side S42 of the fourth waveguide 340 are aligned in the first direction X. In addition, the sum of the length d1 of the second waveguide 310 and the length d3 of the third waveguide 330 can be made the same as the length d4 of the fourth waveguide 340. The rest of the content in this embodiment can be Figure 1 The contents in the illustrated embodiments are substantially the same and will not be described in detail herein.

[0088] To prepare Fig.11 As an example, the structure of the end face coupler shown in FIG. 1 is used as an example, and the flowchart of the corresponding preparation method can be referred to Figure 6 In step S20, the second waveguide 310 and the first waveguide 320 formed by etching need to be disposed between the oxide layer 110 and the fourth waveguide 340, and the fourth waveguide 340 covers the second waveguide 310 and the first waveguide 320. The rest of the preparation process can refer to the description of the above preparation method and will not be described in detail here.

[0089] This application is Fig.11The structure of the end face coupler shown in FIG. 1 and the mode spot size of the optical signal at the end face of the optical fiber 500 is 10 microns as an example for simulation. It can be seen from the simulation that the mode spot size can be reduced from 10 microns to approximately several microns (e.g., 3 microns) in the vertical direction Z by the gradient refractive index lens 200, and it is not reduced in the horizontal direction Y, and the optical signal with the reduced mode spot is coupled to the first waveguide 320 through the light-transmitting layer 210. The first waveguide 320 can reduce the mode spot size of the optical signal from 10 microns to several microns (e.g., 3 microns) in the horizontal direction Y, and it is not reduced in the vertical direction Z, and is coupled to the second waveguide 310. Then, the mode spot size of the light coupled to the second waveguide 310 is approximately several microns (e.g., 3 microns) in the vertical direction Z, and is also approximately several microns (e.g., 3 microns) in the horizontal direction Y. The second waveguide 310 can reduce the spot size of the input light from several microns to several hundred nanometers (e.g., 300 nanometers) in the horizontal direction Y, and also reduce it from several microns to several hundred nanometers (e.g., 300 nanometers) in the vertical direction Z, and couple it to the optical waveguide. Based on this, a conversion process can be achieved in which the spot size can be reduced from 10 microns to several hundred nanometers.

[0090] This application also Fig.11 Taking the structure of the end coupler shown in the figure, and the second waveguide 310 and the third waveguide 330 being made of silicon, and the light-transmitting layer, the first waveguide 320 and the fourth waveguide 340 being made of silicon oxynitride as an example, the coupling loss of the end coupler is simulated. For the first loss Loss1: Figure 5a , when IB=1.5, Loss1 TE =-0.039dB, Loss1 TM =-0.052dB. And, for the second loss Loss2: a physical model of the end face coupler is established in the MODE module of the simulation software for simulation, and the influence curve of the length d2 of the first waveguide 320 on the transmission loss of the first waveguide is obtained, as shown in FIG. Fig.14a As shown, the horizontal axis LE represents the length d2 of the first waveguide 320, the vertical axis Loss2_1 represents the transmission loss of the first waveguide, and different line types represent the transmission loss Loss2_1 of the first waveguide of the TE mode respectively. TE The transmission loss of the first waveguide of the TM mode is Loss2_1 TM .based on Fig.14a d2 can be set to 300 μm, and the tip width TW = 40 nm is given for simulation to obtain the influence curve of the length d1 of the second waveguide 310 on the second loss, as shown in FIG. Fig.14b As shown, the horizontal axis LE represents the length d1 of the second waveguide 310, the vertical axis Loss2 represents the second loss, and different line types represent the second loss Loss2 of the TE mode respectively. TE and the second loss of TM mode Loss2 TM. Reference Fig.14b , when d1=400μm, Loss2 TE =-0.038dB, Loss2 TM =-0.028dB. In addition, taking d1=400μm and d2=300μm as an example, the second loss Loss2 is optimized by changing the tip width TW of the second waveguide 310, as shown in FIG. Fig.14c As shown, the horizontal axis TW represents the tip width of the second waveguide 310, the vertical axis Loss2 represents the second loss, and different line types represent the second loss Loss2 of the TE mode respectively. TE and the second loss of TM mode Loss2 TM In summary, when d2 = 300 μm, the tip width TW of the second waveguide 310 = 40 nm, and d1 = 400 μm, the coupling loss Loss of the end coupler corresponding to the TE mode is obtained through simulation. TE =Loss1 TE +Loss2 TE =-0.077dB, and the corresponding TM mode coupling loss Loss TM =Loss1 TM +Loss2 TM =-0.080 dB. It can be understood that when IB=1.5, d1=400 μm, d2=300 μm, and the tip width TW of the second waveguide 310=40 nm, the corresponding coupling loss is the lowest loss of the current structure.

[0091] Fig.15 is a schematic diagram of a three-dimensional structure of an end face coupler in another embodiment of the present application, Fig.16 for Fig.15 Schematic diagram of the top view of the end coupler in the figure. Fig.17 for Fig.16 The cross-sectional structure diagram along the AA' dashed line. Figures 15 to 17 The end coupler may include: a substrate 100 and a gradient refractive index lens 200, a second waveguide 310, a first waveguide 320 and a cladding 400 located on the substrate 100. Fig.11 The difference of the embodiment shown is that the third waveguide 330 and the fourth waveguide 340 are not provided, that is, the second side S12 of the second waveguide 310 is directly connected to the optical waveguide in the optoelectronic chip, so that the optical signal is directly coupled from the second waveguide 310 to the optical waveguide. The rest of the contents of this embodiment can be compared with Fig.11 The contents in the illustrated embodiments are substantially the same and will not be described in detail herein.

[0092] To prepare Fig.15 As an example, the structure of the end face coupler shown in FIG. 1 is used as an example, and the flowchart of the corresponding preparation method can be referred to Figure 6In step S10, the third waveguide 330 does not need to be etched. In step S20, the fourth waveguide 340 does not need to be etched. The rest of the preparation process can refer to the description of the above preparation method, which will not be described in detail here.

[0093] The embodiment of the present application also provides a communication system, which includes an optical fiber, an optoelectronic chip, and an end coupler provided in the embodiment of the present application. The end face of the optical fiber is connected to the first side of the gradient refractive index lens in the end face coupler, and the second waveguide in the end face coupler is connected to the end face of the optical waveguide in the optoelectronic chip, so that the mode spot size of the end face of the optical fiber is reduced by the end face coupler and then coupled to the optical waveguide. Since the coupling loss of the above-mentioned end face coupler is low, the coupling loss of the communication system including the above-mentioned end face coupler is also low. In addition, the principle of solving the problem by the communication system is similar to the principle that the above-mentioned end face coupler can solve the problem, so the technical effect of the communication system can refer to the technical effect of the above-mentioned end face coupler, and the repeated parts will not be repeated.

[0094] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. An end coupler, characterized in that: include: A substrate, a waveguide structure located on the substrate, and a cladding covering the waveguide structure, wherein the waveguide structure comprises: a gradient refractive index lens, a first waveguide, and a second waveguide; The gradient refractive index lens has a first side and a second side arranged opposite to each other in a first direction, the first side of the gradient refractive index lens is used to connect to the optical fiber, and the first direction is parallel to the substrate; The first waveguide is located at a second side of the gradient refractive index lens and contacts the second side of the gradient refractive index lens, the first waveguide extends along the first direction, and an area of ​​a cross section of the first waveguide gradually decreases in a direction along the gradient refractive index lens pointing to the first waveguide; The second waveguide is located at a second side of the gradient refractive index lens and contacts the first waveguide, the second waveguide extends along the first direction, and the cross-sectional area of ​​the second waveguide gradually increases in a direction along the gradient refractive index lens pointing to the first waveguide, the side of the second waveguide away from the gradient refractive index lens is used to connect with an optical waveguide in an optoelectronic chip, and the refractive index of the first waveguide is smaller than that of the second waveguide.

2. The end coupler according to claim 1, characterized in that: The first waveguide covers the second waveguide, and a length of the first waveguide in the first direction is the same as a length of the second waveguide in the perpendicular direction.

3. The end coupler according to claim 1, characterized in that: The second waveguide is located on a side of the first waveguide away from the gradient refractive index lens, and the second waveguide is in contact with a side of the first waveguide away from the gradient refractive index lens.

4. The end coupler according to claim 1 or 2, characterized in that: The waveguide structure further includes: a third waveguide extending along the first direction, the third waveguide being in contact with a side of the second waveguide away from the gradient refractive index lens, and the side of the third waveguide away from the gradient refractive index lens being used to connect with an optical waveguide in an optoelectronic chip; In a direction along the gradient refractive index lens pointing toward the first waveguide, the cross-sectional areas of the third waveguide are the same.

5. The end coupler according to claim 4, characterized in that: The waveguide structure further includes: a fourth waveguide extending along the first direction, the fourth waveguide being in contact with a side of the first waveguide facing away from the gradient refractive index lens; Wherein, when the first waveguide covers the second waveguide, the fourth waveguide covers the third waveguide; or, When the second waveguide is located on a side of the first waveguide away from the gradient refractive index lens, the fourth waveguide covers the second waveguide and the third waveguide.

6. The end coupler according to claim 5, characterized in that: In a direction along the gradient refractive index lens pointing toward the first waveguide, the cross-sectional areas of the fourth waveguide are the same.

7. The end coupler according to any one of claims 4 to 6, characterized in that: The third waveguide and the second waveguide are integrally formed and made of the same material; and / or, The fourth waveguide and the first waveguide are integrally formed and made of the same material.

8. The end coupler according to any one of claims 1 to 7, characterized in that: The first waveguide comprises: a tapered waveguide; and / or, The second waveguide comprises: a tapered waveguide; and / or, The third waveguide comprises: a rectangular waveguide; and / or, The fourth waveguide includes: a rectangular waveguide.

9. The end coupler according to any one of claims 1 to 8, characterized in that: The gradient refractive index lens comprises: a plurality of light-transmitting layers stacked on the substrate, wherein the refractive indexes of the plurality of light-transmitting layers decrease in sequence in a direction from the substrate to the gradient refractive index lens; The first side surfaces of the plurality of light-transmitting layers in the first direction serve as the first side of the gradient refractive index lens, and the second side surfaces of the plurality of light-transmitting layers in the first direction serve as the second side of the gradient refractive index lens.

10. The end coupler according to claim 9, characterized in that: The first waveguide is in contact with a light-transmitting layer in the gradient index lens that is in contact with the substrate, and a refractive index of the first waveguide is the same as a refractive index of the light-transmitting layer in the gradient index lens that is in contact with the substrate.

11. The end coupler according to claim 10, characterized in that: The first waveguide and the light-transmitting layer in the gradient refractive index lens that is in contact with the substrate are an integrally formed structure and are made of the same material.

12. The end coupler according to any one of claims 1 to 11, characterized in that: The material of the first waveguide includes oxynitride; The material of the second waveguide includes silicon; The material of the cladding layer includes oxide; The material of the light-transmitting layer in the gradient refractive index lens includes oxynitride.

13. A method for preparing an end coupler, characterized in that: include: A second waveguide is formed on the substrate, wherein the second waveguide extends along a first direction, and in the first direction, the cross-sectional area of ​​the second waveguide gradually increases; the second waveguide is used to connect with the optical waveguide in the optoelectronic chip, and the first direction is parallel to the substrate; A gradient refractive index lens and a first waveguide are formed on the substrate, wherein the gradient refractive index lens has a first side and a second side arranged opposite to each other in a first direction, the first side of the gradient refractive index lens is used to connect with an optical fiber, the second waveguide contacts the first waveguide, the first waveguide contacts the second side of the gradient refractive index lens, the second waveguide extends along the first direction, and the cross-sectional area of ​​the second waveguide gradually decreases in the first direction; A cladding is deposited on the substrate, wherein the cladding covers the gradient refractive index lens, the first waveguide, and the second waveguide.

14. The preparation method according to claim 13, characterized in that: Also includes: A third waveguide is formed when the second waveguide is formed, the third waveguide extends along the first direction, the third waveguide is in contact with a side of the second waveguide away from the gradient refractive index lens, and the side of the third waveguide away from the gradient refractive index lens is used to connect with an optical waveguide in an optoelectronic chip; in a direction along the gradient refractive index lens pointing to the first waveguide, the cross-sectional area of ​​the third waveguide is the same; The cladding also covers the third waveguide.

15. The preparation method according to claim 14, characterized in that: The preparation method further includes: forming a fourth waveguide when forming the first waveguide, the fourth waveguide extending along the first direction, and the fourth waveguide contacting a side of the first waveguide away from the gradient refractive index lens; wherein when the first waveguide covers the second waveguide, the fourth waveguide covers the third waveguide; or when the second waveguide is located on a side of the first waveguide away from the gradient refractive index lens, the fourth waveguide covers the second waveguide and the third waveguide; The cladding also covers the fourth waveguide.

16. The preparation method according to any one of claims 13 to 15, characterized in that: The preparation method comprises: Providing a silicon-on-insulator substrate, the silicon-on-insulator substrate comprising bottom silicon, a buried oxide layer and top silicon; Patterning the top silicon and etching to form the second waveguide; The step of forming a gradient refractive index lens and a first waveguide on the substrate comprises: Depositing a plurality of silicon oxynitride film layers on the buried oxide layer on which the second waveguide is formed, wherein the refractive indexes of the plurality of silicon oxynitride film layers gradually decrease in a direction from the bottom silicon to the buried oxide layer; Patterning the remaining silicon oxynitride film layers among the plurality of silicon oxynitride film layers, and etching to form the remaining light-transmitting layers in the gradient refractive index lens, wherein the remaining silicon oxynitride film layers are the silicon oxynitride film layers among the plurality of silicon oxynitride film layers except the silicon oxynitride film layers in contact with the buried oxide layer; The silicon oxynitride film layer in contact with the buried oxide layer is patterned, and is etched to form a light-transmitting layer in contact with the buried oxide layer and the first waveguide in the gradient refractive index lens.

17. A communication system, characterized in that: Comprising an optical fiber, an optoelectronic chip and an end coupler as claimed in any one of claims 1 to 12; The end face of the optical fiber is connected to the first side of the gradient refractive index lens in the end face coupler, and the second waveguide in the end face coupler is connected to the end face of the optical waveguide in the optoelectronic chip.

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