Grating coupler

Abstract

The invention discloses a grating coupler, and relates to the technical field of grating couplers, the grating coupler comprises a waveguide core layer and a substrate layer, the waveguide core layer is provided with a grating part, and the grating part is used for receiving light coupled by an external optical fiber, so that the light is coupled into the waveguide core layer and transmitted through the waveguide core layer; the substrate layer is arranged on the side, away from the external optical fiber, of the waveguide core layer, the substrate layer is provided with a reflection structure, and the reflection structure is arranged opposite to the grating part and used for reflecting light scattered to the substrate layer from the waveguide core layer so that the light can be coupled into the waveguide core through the grating part. According to the technical scheme, the coupling efficiency of the grating coupler can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of grating couplers, and in particular to a grating coupler. Background Art

[0002] In the related art, the grating coupler is an optical device that connects the optical fiber and the waveguide, and can realize the mutual coupling between the optical fiber and the waveguide. At present, after the light emitted from the optical fiber is coupled into the waveguide core layer of the grating coupler, part of the light is transmitted along the waveguide core layer, and part of the light is scattered to the substrate of the grating coupler, resulting in light energy loss, which will affect the coupling efficiency of the grating coupler. Summary of the invention

[0003] The main purpose of the present invention is to provide a grating coupler, aiming to improve the coupling efficiency of the grating coupler.

[0004] To achieve the above object, the grating coupler proposed in the present invention comprises: A waveguide core layer is provided with a grating portion, wherein the grating portion is used to receive light coupled into the external optical fiber so that the light is coupled into the waveguide core layer and transmitted through the waveguide core layer; and The substrate layer is arranged on a side of the waveguide core layer away from the external optical fiber, and the substrate layer is provided with a reflection structure, which is arranged opposite to the grating part and is used to reflect the light scattered from the waveguide core layer to the substrate layer, so that the light is coupled into the waveguide core layer through the grating part.

[0005] In one embodiment, the substrate layer comprises: a substrate portion, which is disposed on a side of the waveguide core layer away from the external optical fiber and is spaced apart from the waveguide core layer, wherein the reflective structure is disposed on one side of the substrate portion; and The oxide buried portion is provided between the substrate portion and the waveguide core layer.

[0006] In one embodiment, the reflective structure is provided on a side of the substrate portion facing the oxide buried portion.

[0007] In one embodiment, a concave structure is provided on a side of the reflective structure facing the waveguide core layer, so that the light received by the reflective structure converges toward the grating portion.

[0008] In one embodiment, a plurality of the concave structures are provided, and the plurality of the concave structures are arranged side by side along the periodic direction of the grating portion.

[0009] In one embodiment, the waveguide core layer further comprises a waveguide portion, and the grating portion comprises: A base structure, the base structure is sequentially connected to the waveguide part and is arranged relatively and spaced apart from the reflection structure; A first grating structure, the first grating structure is located at a side of the base structure facing the substrate layer, and is used to receive and couple light reflected by the reflective structure; and The second grating structure is located at a side of the base structure away from the substrate layer and is used for receiving and coupling light coupled from an external optical fiber.

[0010] In one embodiment, the waveguide core layer further comprises a photoresist portion, the photoresist portion is stacked on one side of the substrate layer, and the base structure is stacked on a side of the photoresist portion away from the substrate layer; A grating groove is arranged on the side of the photoresist portion facing away from the substrate layer, and the grating groove and the first grating structure are arranged in a conformal manner.

[0011] In one embodiment, the first grating structure and the second grating structure are symmetrically arranged on opposite sides of the base structure.

[0012] In one embodiment, the first grating structure and / or the second grating structure is an apodized grating, and a period of the apodized grating is gradually reduced along a direction from the grating portion to the waveguide portion.

[0013] In one embodiment, the grating coupler further includes a cladding layer, wherein the cladding layer covers a side of the waveguide core layer facing away from the substrate layer.

[0014] The grating coupler of the technical solution of the present invention comprises a waveguide core layer and a substrate layer which are stacked, wherein the waveguide core layer is provided with a grating portion for receiving light coupled by an external optical fiber, and the substrate layer is provided with a reflective structure arranged opposite to the grating portion. When light is coupled into the waveguide core layer of the grating coupler by the external optical fiber, part of the light will be scattered to the reflective structure of the substrate layer, at which time, the reflective structure can reflect the part of the light back to the grating portion of the waveguide core layer, so that the light scattered into the substrate layer can be re-coupled into the waveguide core layer through the grating portion, thereby effectively reducing the light energy loss of the grating coupler caused by the light scattering into the substrate layer, and improving the coupling efficiency of the grating coupler. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 A schematic structural diagram of a first embodiment of a grating coupler provided by the present invention; Figure 2 A schematic structural diagram of a second embodiment of a grating coupler provided by the present invention; Figure 3 A schematic structural diagram of a third embodiment of a grating coupler provided by the present invention; Figure 4 A schematic structural diagram of a waveguide core layer of a grating coupler provided by the present invention; Figure 5 Another schematic structural diagram of the waveguide core layer of the grating coupler provided by the present invention; Figure 6 for Figure 5 Schematic diagram of the preparation of the waveguide core layer of the grating coupler.

[0017] Description of Figure Numbers: 100, grating coupler; 10, waveguide core layer; 11, grating part; 111, first grating structure; 112, second grating structure; 113, base structure; 12, waveguide part; 13, photoresist part; 20, substrate layer; 21, substrate part; 211, reflection structure; 211a, concave structure; 22, oxide buried part; 30, cladding.

[0018] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0021] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] In the related art, the grating coupler is an optical device that connects the optical fiber and the waveguide, which can realize the mutual coupling between the optical fiber and the waveguide. At present, after the light emitted from the optical fiber is coupled into the waveguide core layer of the grating coupler, part of the light is transmitted along the waveguide core layer, and part of the light will be scattered to the substrate of the grating coupler, resulting in light energy loss. When the wavelength of the light emitted from the optical fiber is 1550nm, the proportion of light scattered to the substrate of the grating coupler is about 25%. At this time, the insertion loss of the grating coupler mainly comes from the light scattered to the substrate of the grating coupler, resulting in a large insertion loss of the grating coupler.

[0023] To this end, the present invention proposes a grating coupler 100, which provides a reflective structure 211 in the substrate layer 20 of the grating coupler 100. The reflective structure 211 can be used to reflect the light scattered from the waveguide core layer 10 of the grating coupler 100 to the substrate layer 20 back to the waveguide core layer 10, so that the part of the light can be re-coupled into the waveguide core layer 10 and transmitted along the waveguide core layer 10, thereby effectively reducing the insertion loss caused by the light scattered to the substrate of the grating coupler 100.

[0024] See also Figures 1 to 6 In one embodiment of the present invention, the grating coupler 100 includes a waveguide core layer 10 and a substrate layer 20. The waveguide core layer 10 is provided with a grating portion 11. The grating portion 11 is used to receive light coupled from an external optical fiber 200 so that the light is coupled into the waveguide core layer 10 and transmitted through the waveguide core layer 10. The substrate layer 20 is arranged on a side of the waveguide core layer 10 away from the external optical fiber 200. The substrate layer 20 is provided with a reflection structure 211. The reflection structure 211 is arranged opposite to the grating portion 11 and is used to reflect the light scattered from the waveguide core layer 10 to the substrate layer 20 so that the light is coupled into the waveguide core layer 10 through the grating portion 11.

[0025] Specifically, the waveguide core layer 10 and the substrate layer 20 are generally planar, and the two are stacked. The substrate layer 20 can serve as the bearing base of the waveguide core layer 10. The waveguide core layer 10 covers a side surface of the substrate layer 20 and includes a grating portion 11 and a waveguide portion 12 connected in sequence in the light transmission direction. The grating portion 11 is arranged opposite to the external optical fiber 200 to receive and couple the light output by the external light. Optionally, the material of the waveguide core layer 10 can be specifically configured as Si, Si3N4, TFLN, etc., which is not limited here.

[0026] When the optical fiber 200 emitted from the external optical fiber 200 is transmitted to the grating portion 11 of the waveguide core layer 10, it can be coupled into the waveguide core layer 10 through the grating portion 11 of the waveguide core layer 10, wherein a portion of the light can be transmitted from the grating portion 11 to the waveguide portion 12 in the waveguide core layer 10, and another portion of the light will be scattered from the waveguide core layer 10 to the substrate layer 20. Further, the substrate layer 20 is provided with a reflection structure 211 arranged opposite to the grating portion 11, and the reflection structure 211 has a reflection surface arranged toward the waveguide core layer 10. When part of the light coupled into the waveguide core layer 10 is scattered from the waveguide core layer 10 to the substrate layer 20 and transmitted to the reflection surface of the reflection structure 211, the part of the light can be re-reflected by the reflection surface back to the grating portion 11 of the waveguide core layer 10, so as to be re-coupled into the waveguide core layer 10 through the grating portion 11. Optionally, the reflection structure 211 can be configured as a metal material, specifically, it can be set to gold, silver, copper, aluminum, etc., which is not limited here.

[0027] It can be understood that the technical solution of the present invention, by setting a reflective structure 211 in the substrate layer 20 so that the light scattered into the substrate layer 20 can be re-coupled into the waveguide core layer 10 through the grating portion 11, can effectively reduce the light energy loss of the grating coupler 100 caused by the scattering of light into the substrate layer 20, thereby improving the coupling efficiency of the grating coupler 100.

[0028] See also Figures 1 to 5 In an embodiment of the present invention, the substrate layer 20 includes a substrate portion 21 and an oxide embedded portion 22. The substrate portion 21 is disposed on a side of the waveguide core layer 10 away from the external optical fiber 200 and is spaced apart from the waveguide core layer 10. A reflective structure 211 is disposed on one side of the substrate portion 21; the oxide embedded portion 22 is disposed between the substrate portion 21 and the waveguide core layer 10.

[0029] Specifically, the substrate portion 21 and the oxide buried portion 22 are both arranged in a planar shape. The substrate portion 21 can serve as a supporting base for the substrate layer 20, and is used to stack the oxide buried portion 22 or the reflective structure 211 on its surface. Among them, the reflective structure 211 can be deposited on one side of the substrate portion 21 facing or away from the oxide buried portion 22. The waveguide core layer 10 is used to cover the side of the oxide buried portion 22 away from the substrate portion 21, and the grating portion 11 of the waveguide core layer 10 is in contact with the surface of the oxide buried portion 22.

[0030] With such a configuration, the light coupled into the waveguide core layer 10 can be partially scattered into the oxide buried portion 22, and transmitted to the substrate portion 21 through the oxide buried portion 22, so as to be reflected into the oxide buried portion 22 by the reflective structure 211 on the substrate portion 21, and further transmitted to the grating portion 11 of the waveguide core layer 10. The grating portion 11 in the waveguide core layer 10 can couple the light in the oxide buried portion 22 back into the waveguide core layer 10. Optionally, the substrate portion 21 can be specifically configured as a silicon substrate, and the material of the oxide buried portion 22 can be specifically configured as silicon dioxide, and its refractive index can be set to 1.44.

[0031] See also Figures 1 to 5 In the embodiment of the present invention, the reflective structure 211 is disposed on the side of the substrate portion 21 facing the oxide buried portion 22. In this way, the reflective structure 211 can be formed between the substrate portion 21 and the oxide buried portion 22, thereby facilitating the protection performance of the substrate layer 20 for the reflective structure 211.

[0032] See also Figure 1 In one embodiment of the present invention, the side of the reflective structure 211 facing the waveguide core layer 10 can be set as a plane, that is, the reflective surface of the reflective structure 211 facing the waveguide core layer 10 is a plane.

[0033] See also Figure 2 In another embodiment of the present invention, a concave structure 211a is provided on the side of the reflective structure 211 facing the waveguide core layer 10, so that the light received by the reflective structure 211 converges toward the grating portion 11. It can be understood that by providing the concave structure 211a on the side of the reflective structure 211 facing the waveguide core layer 10, the concave structure 211a can be used to further converge the reflected light of the reflective structure 211 to the grating portion 11 of the waveguide core layer 10, thereby facilitating further increasing the coupling efficiency of the grating portion 11.

[0034] Optionally, in an embodiment of the present invention, a plurality of concave structures 211 a are provided, and the plurality of concave structures 211 a are arranged side by side along the periodic direction of the grating portion 11 .

[0035] Among them, a plurality of arc-shaped grooves may be provided on the side of the reflective structure 211 facing the waveguide core layer 10, and the inner wall of each arc-shaped groove forms a concave structure 211a. In this way, the light transmitted from the substrate layer 20 to the reflective structure 211 can be evenly reflected back to the plurality of grating units of the grating part 11 through the plurality of concave structures 211a, thereby facilitating further ensuring the coupling efficiency of the grating part 11.

[0036] Of course, the technical solution of the present invention is not limited thereto. In other embodiments, the reflective structure 211 may be arranged to be concave on one side facing the waveguide core layer 10 as a whole, which is not limited here.

[0037] See also Figures 1 to 5 In an embodiment of the present invention, the waveguide core layer 10 further includes a waveguide portion 12, and the grating portion 11 includes a base structure 113, a first grating structure 111, and a second grating structure 112; the base structure 113 is sequentially connected to the waveguide portion 12, and is arranged relative to the reflective structure 211 at an interval; the first grating structure 111 is located on a side of the base structure 113 facing the substrate layer 20, and is used to receive and couple light reflected by the reflective structure 211; the second grating structure 112 is located on a side of the base structure 113 away from the substrate layer 20, and is used to receive and couple light coupled by the external optical fiber 200.

[0038] See also Figure 5 In one embodiment of the present invention, the first grating structure 111 and the second grating structure 112 are symmetrically arranged on opposite sides of the base structure 113. Such an arrangement is conducive to reducing the difficulty of manufacturing the grating part 11.

[0039] Of course, the technical solution of the present invention is not limited thereto. In another embodiment of the present invention, the first grating structure 111 and the second grating structure 112 may also be arranged asymmetrically up and down. In this way, the grating period, comb height and other parameters of the two may be optimized and designed according to the characteristics of the light used to couple in the first grating structure 111 and the second grating structure 112. The specific implementation method may be set according to actual needs and is not limited here.

[0040] See also Figures 1 to 3 In an embodiment of the present invention, the waveguide core layer 10 further includes a photoresist portion 13, the photoresist portion 13 is stacked on one side of the substrate layer 20, and the base structure 113 is stacked on the side of the photoresist portion 13 away from the substrate layer 20; a grating groove is provided on the side of the photoresist portion 13 away from the substrate layer 20, and the grating groove and the first grating structure 111 are arranged in a conformal manner.

[0041] The shape of the first grating structure 111 is mainly formed by grating grooves on the photoresist part 13. Optionally, the material of the photoresist part 13 can be specifically configured as negative electron beam photoresist, sulfur-containing polymer, high refractive index acrylic polymer, high refractive index polymer based on cyclotriphosphazene, lead bismuth titanate, etc.

[0042] Specifically, when preparing the waveguide core layer 10, the material corresponding to the photoresist portion 13 can be first covered on one side of the substrate layer 20 and pre-baked, and then, the grating pattern corresponding to the first grating structure 111 can be written on the photoresist portion 13 using an electron beam lithography system to form grating grooves that are arranged in the same shape as the first grating structure 111 on the side of the photoresist portion 13 away from the substrate layer 20. Then, the photoresist portion 13 is developed and rinsed in a developer, and the first grating structure 111, the base structure 113, and the second grating structure 112 are sequentially deposited on the side of the photoresist portion 13 where the grating grooves are provided, thereby preparing the waveguide core layer 10 on one side of the substrate layer 20.

[0043] Of course, the technical solution of the present invention is not limited to this. In other embodiments, after the photoresist portion 13 is developed and rinsed in a developer, a first grating structure 111, a base structure 113 and a deposition structure with a redundant volume can be sequentially deposited on one side of the photoresist portion 13 where a grating groove is provided, and then, photolithography and reactive ion etching are performed on the part of the deposition structure to prepare a second grating structure 112 on the side of the base structure 113 away from the first grating structure 111.

[0044] See also Figures 1 to 5 In an embodiment of the present invention, the first grating structure 111 and / or the second grating structure 112 is an apodized grating, and the period of the apodized grating is gradually reduced along the direction from the grating portion 11 to the waveguide portion 12.

[0045] Specifically, the waveguide core layer 10 has a coupling section for arranging the grating part 11 and a waveguide section for transmitting light, and the coupling section and the waveguide section are sequentially connected in a straight line direction. After the light emitted from the external optical fiber 200 enters the coupling section of the waveguide core layer 10 through the grating part 11, part of the light can be transmitted to the waveguide section through the grating section of the waveguide core layer 10. When the first grating structure 111 and / or the second grating structure 112 are apodized gratings, the spacing between two adjacent grating units can be set to gradually decrease along the light transmission direction of the waveguide core layer 10.

[0046] In some embodiments, when the first grating structure 111 and the second grating structure 112 are symmetrically arranged on opposite sides of the substrate, the first grating structure 111 and the second grating structure 112 may both be arranged as apodized gratings, and their periodic variation functions are the same.

[0047] In other embodiments, when the first grating structure 111 and the second grating structure 112 are asymmetrically arranged with respect to the base, the first grating structure 111 and the second grating structure 112 may also be both arranged as apodization gratings, and the periodic variation functions of the two apodization gratings are different, and at least parts of the two apodization gratings are staggered with each other.

[0048] See also Figures 1 to 5 In an embodiment of the present invention, the grating coupler 100 further includes a cladding 30, and the cladding 30 covers the side of the waveguide core layer 10 away from the substrate layer 20. The light emitted by the external optical fiber 200 can be transmitted to the grating portion 11 of the waveguide core layer 10 through the cladding 30, so as to be coupled into the waveguide core layer 10 through the grating portion 11. By making the cladding 30 cover the side of the waveguide core layer 10 away from the substrate layer 20, the protection performance of the waveguide core layer 10 can be improved. Optionally, the material of the cladding 30 can be specifically configured as silicon dioxide, and its refractive index is 1.44.

[0049] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A grating coupler, characterized in that: include: The waveguide core layer is provided with a grating portion, wherein the grating portion is used to receive light coupled into the waveguide from an external optical fiber so that the light is transmitted through the waveguide core layer; and The substrate layer is arranged on a side of the waveguide core layer away from the external optical fiber, and the substrate layer is provided with a reflection structure, which is arranged opposite to the grating part and is used to reflect the light scattered from the waveguide core layer to the substrate layer, so that the light is coupled into the waveguide core layer through the grating part.

2. The grating coupler according to claim 1, characterized in that The substrate layer comprises: a substrate portion, which is disposed on a side of the waveguide core layer away from the external optical fiber and is spaced apart from the waveguide core layer, wherein the reflective structure is disposed on one side of the substrate portion; and The oxide buried portion is provided between the substrate portion and the waveguide core layer.

3. The grating coupler according to claim 2, characterized in that The reflective structure is disposed on a side of the substrate portion facing the oxide embedded portion.

4. The grating coupler according to claim 1, characterized in that A concave structure is provided on a side of the reflective structure facing the waveguide core layer so as to converge the light received by the reflective structure toward the grating portion.

5. The grating coupler according to claim 4, characterized in that There are a plurality of concave structures, and the plurality of concave structures are arranged side by side along the periodic direction of the grating portion.

6. The grating coupler according to any one of claims 1 to 5, characterized in that: The waveguide core layer further includes a waveguide portion, and the grating portion includes: A base structure, the base structure is sequentially connected to the waveguide part and is arranged relatively and spaced apart from the reflection structure; A first grating structure, the first grating structure is located at a side of the base structure facing the substrate layer, and is used to receive and couple light reflected by the reflective structure; and The second grating structure is located at a side of the base structure away from the substrate layer and is used for receiving and coupling light coupled from an external optical fiber.

7. The grating coupler according to claim 6, characterized in that The waveguide core layer further comprises a photoresist portion, the photoresist portion is stacked on one side of the substrate layer, and the base structure is stacked on a side of the photoresist portion away from the substrate layer; A grating groove is arranged on the side of the photoresist portion facing away from the substrate layer, and the grating groove and the first grating structure are arranged in a conformal manner.

8. The grating coupler according to claim 6, characterized in that The first grating structure and the second grating structure are symmetrically arranged on opposite sides of the base structure.

9. The grating coupler according to claim 6, characterized in that The first grating structure and / or the second grating structure is an apodized grating, and a period of the apodized grating is gradually reduced along a direction from the grating portion to the waveguide portion.

10. The grating coupler according to any one of claims 1 to 5, characterized in that: The grating coupler further includes a cladding layer, which covers a side of the waveguide core layer away from the substrate layer.

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