CN116859522B - Grating coupler, optical chip system and preparation method of grating coupler - Google Patents
Grating coupler, optical chip system and preparation method of grating coupler Download PDFInfo
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- CN116859522B CN116859522B CN202311107122.6A CN202311107122A CN116859522B CN 116859522 B CN116859522 B CN 116859522B CN 202311107122 A CN202311107122 A CN 202311107122A CN 116859522 B CN116859522 B CN 116859522B
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 27
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 9
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 4
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- 239000004431 polycarbonate resin Substances 0.000 claims description 4
- 229920000647 polyepoxide Polymers 0.000 claims description 4
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
- G02B6/29325—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide of the slab or planar or plate like form, i.e. confinement in a single transverse dimension only
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/34—Optical coupling means utilising prism or grating
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
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- Microelectronics & Electronic Packaging (AREA)
- Optical Integrated Circuits (AREA)
- Optical Couplings Of Light Guides (AREA)
Abstract
The application relates to a grating coupler, an optical chip system and a preparation method of the grating coupler. Wherein, the grating coupler includes: a substrate and a coupling waveguide. The coupling waveguide is located on the substrate. The coupling waveguide comprises a grating waveguide part and a cladding part, wherein the grating waveguide part is positioned in the cladding part. The grating waveguide part comprises grating teeth, and the opening direction of the grating teeth faces away from the substrate. The substrate comprises a substrate part, a light guide part and an isolation groove. The substrate is arranged on the plane of the substrate, the substrate part is adjacent to the isolation groove, the isolation groove is adjacent to the light guide part, the isolation groove is arranged between the light guide part and the substrate part, the substrate part surrounds the isolation groove, and the isolation groove surrounds the light guide part. The light guide part is used for guiding the light incident to the light guide part to the grating teeth in a non-divergent mode. According to the embodiment of the application, the coupling efficiency of the grating coupler can be improved on the premise of having the advantages of simple preparation process and low preparation cost and avoiding great influence on the substrate strength.
Description
Technical Field
The application relates to the technical field of silicon-based optoelectronic chips, in particular to a grating coupler, an optical chip system and a preparation method of the grating coupler.
Background
In the related art, the coupling in and the coupling out of optical signals are critical to the operation of a silicon-based optoelectronic chip. In order to overcome the problem of low coupling efficiency caused by mismatching of the on-chip waveguide mode spot and the optical fiber mode spot, on-chip optical coupler technology is developed, and the on-chip optical coupler technology can be mainly divided into an end face coupler and a grating coupler at present. The grating coupler has the advantages of large alignment tolerance, convenience in wafer level test, free placement position and the like, and is one of the on-chip optical couplers which are commonly used at present.
The grating coupler further comprises a forward grating coupler and a back grating coupler. Wherein when back coupling is performed with a back grating coupler, light diffuses during the passage through the substrate layer. Therefore, it is still a problem to be solved.
Disclosure of Invention
According to a first aspect of embodiments of the present application, there is provided a grating coupler comprising: a substrate and a coupling waveguide;
the coupling waveguide is positioned on the substrate; the coupling waveguide comprises a grating waveguide part and a cladding part, and the grating waveguide part is positioned in the cladding part; the grating waveguide part comprises grating teeth, and the opening direction of the grating teeth is opposite to the substrate;
the substrate comprises a substrate part, a light guide part and an isolation groove; the substrate part is adjacent to the isolation groove on the plane where the substrate is located, the isolation groove is adjacent to the light guide part, the isolation groove is located between the light guide part and the substrate part, the substrate part surrounds the isolation groove, and the isolation groove surrounds the light guide part; the light guide part is used for guiding the light incident to the light guide part to the grating teeth in a non-divergent mode.
According to the embodiment of the application, the isolation groove surrounding the light guide part is arranged, so that air enters the isolation groove and surrounds the light guide part. Because the refractive index of the gas is lower than that of the solid, after one side of the light guide part far away from the coupling waveguide is in butt joint with the light input structure, the light incident to the light guide part can generate total reflection on the interface between the light guide part and the isolation groove, so that the light guide part can form a waveguide structure to realize the effect of guiding the light incident to the light guide part to the grating teeth in a non-divergent mode through the light guide part, and further, the diffusion degree of the light incident to the grating coupler can be reduced, and the coupling efficiency of the grating coupler is improved.
In addition, the isolation groove is only required to be arranged on the substrate, so that the preparation process of the light guide part is simple and the preparation cost is low.
Meanwhile, the substrate is not required to be thinned when the isolation groove is formed, so that the strength of the substrate can be prevented from being greatly influenced. Furthermore, by arranging the isolation groove surrounding the light guide part, the degree of light diffusion incident to the grating coupler can be reduced on the premise of having the advantages of simple preparation process and low preparation cost and avoiding great influence on the strength of the substrate, so that the coupling efficiency of the grating coupler is improved.
In some embodiments, further comprising: a filling part;
the refractive index of the filling part is smaller than that of the light guide part; the filling part is positioned in the isolation groove.
In some embodiments, the filling portion is further located at a side of the substrate away from the coupling waveguide, and the filling portion wraps around the light guiding portion.
In some embodiments, the material of the substrate portion and the light guide portion comprises silicon or silicon dioxide; the material of the grating waveguide part comprises silicon, silicon dioxide, silicon nitride or lithium niobate; the material of the filling part comprises silicon dioxide, polymethyl methacrylate, polystyrene, polycarbonate or epoxy resin.
In some embodiments, the angle between the light guided by the light guiding part and the normal line of the grating waveguide part is a coupling angle, and the coupling angle is 0 degree;
when the coupling angle is 0 degree, the grating teeth satisfy the formula: q/Λ=n eff /λ；
Wherein q is the diffraction order of the grating teeth, Λ is the period of the grating teeth, n eff In order to achieve an effective refractive index of a transverse wave mode of light propagating through the grating waveguide, λ is a wavelength of light incident on the grating teeth.
In some embodiments, the fundamental mode field supported by the light guide is the same as the incident mode field of light incident to the light guide.
In some embodiments, the substrate has a thickness of 700 microns or greater.
In some embodiments, the projections of the grating teeth on the substrate are located within the isolation grooves and the light guide.
According to a second aspect of embodiments of the present application, there is provided an optical chip system comprising any one of the grating couplers described above.
According to a third aspect of embodiments of the present application, there is provided a method for manufacturing a grating coupler, for manufacturing any one of the above-mentioned grating couplers, including: providing a substrate, and forming the coupling waveguide on the substrate to form a first intermediate structure; after the first intermediate structure is formed, the first intermediate structure is turned over, and an etching process is performed from one side of the substrate away from the coupling waveguide, so as to form the light guide part, the isolation groove and the substrate part.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
Fig. 1 is a top view of a grating coupler according to an embodiment of the present application.
Fig. 2 is a cross-sectional view along section line AA in fig. 1, shown in accordance with an embodiment of the present application.
Fig. 3 is a top view of another grating coupler according to an embodiment of the present application.
Fig. 4 is a cross-sectional view along section line BB in fig. 3, shown in accordance with an embodiment of the present application.
Fig. 5 is a cross-sectional view of another grating coupler according to an embodiment of the present application.
Fig. 6 is a schematic structural diagram of an optical chip system according to an embodiment of the present application.
Fig. 7 is an intermediate structure in the fabrication of a grating coupler according to an embodiment of the present application.
Fig. 8 is another intermediate structure in the fabrication of a grating coupler according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples are not representative of all implementations consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present application as detailed in the accompanying claims.
When the grating coupler is used for carrying out mode spot coupling, light incident to the grating coupler passes through a substrate of the grating coupler before reaching the grating of the grating coupler. And diffusion occurs as the incident light passes through the substrate. The extent to which the incident light diffuses increases with increasing substrate thickness. Once the incident light is diffused, only the component perpendicular to the grating structure of the grating coupler diffracts the diffused light when it passes through the grating of the grating coupler, but not all the light, thereby resulting in a decrease in coupling efficiency of the grating coupler.
In order to solve the problem of light incident on the grating coupler diffusing as it passes through the substrate, some solutions choose to thin the thickness of the substrate. However, the reduction of the substrate thickness of the grating coupler reduces the diffusion of incident light, and simultaneously leads to the reduction of the overall strength of the grating coupler, so that the grating coupler is more easily damaged. Other alternatives have been to fabricate a lens structure in the substrate of the grating coupler to focus the incident light. However, fabricating the lens structure in the substrate of the grating coupler increases the process difficulty and manufacturing cost of fabricating the grating coupler.
Embodiments of the present application provide a grating coupler 10. Fig. 1 shows a top view of the grating coupler 10, and fig. 2 shows a cross-sectional view along the sectional line AA in fig. 1. As shown in fig. 1 and 2, the grating coupler 10 includes: a substrate 110 and a coupling waveguide 120.
The coupling waveguide 120 is located on the substrate 110. The coupling waveguide 120 includes a grating waveguide portion 121 and a cladding portion 122, and the grating waveguide portion 121 is located in the cladding portion 122. The grating waveguide 121 includes grating teeth 1211, and an opening direction of the grating teeth 1211 faces away from the substrate 110.
Specifically, cladding 122 may include an upper cladding 1221 and a lower cladding 1222. Wherein the upper cladding 1221 is located on a side of the grating waveguide portion 121 remote from the substrate 110, and the lower cladding 1222 is located between the grating waveguide portion 121 and the substrate 110. The grating waveguide 121 is located within the cladding 122, i.e. the grating waveguide 121 is located between the upper cladding 1221 and the lower cladding 1222.
After light is incident on the coupling waveguide 120 from the substrate 110, diffraction occurs at the grating teeth 1211 of the grating waveguide portion 121, so that energy of the incident light is converted to the grating waveguide portion 121 and transmitted along the extending direction of the grating waveguide portion 121. Wherein, the diffracted light at the grating teeth 1211 is totally reflected at the interface of the grating waveguide portion 121 and the cladding portion 122, so as to realize the transmission of the diffracted light in the grating waveguide portion 121.
The substrate 110 includes a substrate portion 111, a light guide portion 112, and an isolation trench 113. On the plane of the substrate 110, the substrate portion 111 is adjacent to the isolation groove 113, the isolation groove 113 is adjacent to the light guide portion 112, the isolation groove 113 is located between the light guide portion 112 and the substrate portion 111, the substrate portion 111 surrounds the isolation groove 113, and the isolation groove 113 surrounds the light guide portion 112. The light guide 112 is for guiding light incident to the light guide 112 to the grating teeth 1211 in a non-divergent manner.
Specifically, on the plane of the substrate 110, that is, in the first direction X shown in fig. 2, the substrate portion 111 is adjacent to the isolation groove 113, the isolation groove 113 is adjacent to the light guide portion 112, the isolation groove 113 is located between the light guide portion 112 and the substrate portion 111, the substrate portion 111 surrounds the isolation groove 113, and the isolation groove 113 surrounds the light guide portion 112.
Further, since the light guide 112 needs to be adapted to the mode field of the incident light, the incident light is generally transmitted through the optical fiber. Therefore, the cross-sectional shape of the light guide 112 is preferably circular in order to match the mode field of light transmitted within the optical fiber.
By providing the isolation groove 113 surrounding the light guide 112, air is made to enter the isolation groove and surround the light guide 112. Since the refractive index of the gas is lower than that of the solid, after the light guide 112 is abutted against the light input structure at a side far from the coupling waveguide 120, the light incident to the light guide 112 is totally reflected at the interface between the light guide 112 and the isolation groove 113, so that the light guide 112 can be formed into a waveguide structure, the effect of guiding the light incident to the light guide 112 to the grating teeth 1211 in a non-divergent manner through the light guide 112 can be achieved, and the degree of diffusion of the light incident to the grating coupler 10 can be reduced, thereby improving the coupling efficiency of the grating coupler 10.
Also, since only the isolation groove 113 needs to be provided on the substrate 110, the manufacturing process of the light guide 112 is simple and the manufacturing cost is low.
Meanwhile, since the isolation trench 113 is formed without thinning the substrate 110, a large influence on the strength of the substrate 110 can be avoided. Furthermore, by providing the isolation groove 113 surrounding the light guide 112, the degree of diffusion of light incident to the grating coupler 10 can be reduced to enhance the coupling efficiency of the grating coupler 10 on the premise of having the advantages of simple manufacturing process and low manufacturing cost and avoiding a large influence on the strength of the substrate 110.
In some embodiments, as shown in fig. 2, the grating coupler 10 further comprises: a reflective layer 123.
The reflective layer 123 is located on a side of the cladding 122 away from the substrate 110, i.e., the reflective layer 123 is located on a side of the upper cladding 1221 away from the lower cladding 1222. The material of the reflective layer 123 is a metal material.
After the incident light enters the coupling waveguide 120 from the light guide 112, the incident light enters the grating teeth 1211 of the grating waveguide 121 in the second direction Z. The light is diffracted when passing through the grating teeth 1211, so that the light transmitted in the second direction Z can be coupled into the grating waveguide 121 through the grating teeth 1211 of the grating waveguide 121 and transmitted in the first direction X, that is, so that the energy of the incident light is converted to the grating waveguide 121 and transmitted in the extending direction of the grating waveguide 121, thereby coupling the incident light through the grating waveguide 121.
For light incident on the grating teeth 1211, part or all of the energy thereof is converted to the grating waveguide portion 121 and transmitted along the extending direction of the grating waveguide portion 121, and light in which no conversion occurs exits the grating waveguide portion 121 in the direction of incidence on the grating teeth 1211 and passes through the upper cladding layer 1221 after exiting the grating waveguide portion 121 to reach the reflective layer 123. Since the material of the reflective layer 123 is a metal material, after reaching the reflective layer 123, a part of the light is reflected and reflected to the grating teeth 1211 of the grating waveguide 121, and at this time, the part of the light which passes through the grating teeth 1211 for the first time and is not energy-converted passes through the grating teeth 1211 again and is diffracted. By the energy conversion process of the grating teeth 1211 twice, it is ensured that substantially all light is coupled by the grating teeth 1211 of the grating waveguide 121, and thus, the coupling efficiency of the grating coupler 10 can be improved.
In some embodiments, fig. 3 shows a top view of another grating coupler 10, and fig. 4 shows a cross-sectional view of fig. 3 along section line BB. As shown in fig. 3 and 4, the grating coupler 10 further includes: and a filling portion 130.
The refractive index of the filling portion 130 is smaller than that of the light guide portion 112. The filling portion 130 is located in the isolation groove 113.
Since the refractive index of the filling portion 130 is smaller than that of the light guide portion 112, after the filling portion 130 is filled into the isolation groove 113, it is still possible to ensure that light incident to the light guide portion 112 is totally reflected at the interface between the light guide portion 112 and the isolation groove 113, that is, to ensure that light incident to the light guide portion 112 is totally reflected at the interface between the light guide portion 112 and the filling portion 130, so that the light guide portion 112 can be formed into a waveguide structure, to achieve the effect of guiding light incident to the light guide portion 112 to the grating teeth 1211 in a non-divergent manner through the light guide portion 112, and further, the degree of diffusion of light incident to the grating coupler 10 can be reduced, to improve the coupling efficiency of the grating coupler 10.
Also, the filling portion 130 is provided to fill the isolation groove 113, so that a gap is prevented from being left on the substrate 110, and further, the strength of the substrate 110 can be improved to improve the strength of the grating coupler 10. Accordingly, by providing the filling portion 130, the strength of the substrate 110 can be increased to increase the strength of the grating coupler 10 while ensuring that the degree of diffusion of light incident to the grating coupler 10 is reduced to increase the coupling efficiency of the grating coupler 10.
In some embodiments, fig. 5 shows a cross-sectional view of another grating coupler 10, with reference to fig. 3 for a top view, based on the filling portion 130 being located in the isolation trench 113. As shown in fig. 5, the filling portion 130 is further located on a side of the substrate 110 away from the coupling waveguide 120, and the filling portion 130 encapsulates the light guiding portion 112. The partially filled portion 130 is the same material as the filled portion 130 located within the isolation trench 113.
By having the filling portion 130 also located on the side of the substrate 110 away from the coupling waveguide 120, the strength of the substrate 110 can be further increased by the filling portion 130 located on the side of the substrate 110 away from the coupling waveguide 120, so as to further increase the strength of the grating coupler 10. Therefore, by having the filling portion 130 also located at a side of the substrate 110 away from the coupling waveguide 120, it is possible to further enhance the strength of the substrate 110 to further enhance the strength of the grating coupler 10 while ensuring that the degree of diffusion of light incident to the grating coupler 10 is reduced to enhance the coupling efficiency of the grating coupler 10.
In some embodiments, the material of the substrate portion 111 and the light guide portion 112 includes silicon or silicon dioxide. The material of the grating waveguide 121 includes silicon, silicon dioxide, silicon nitride, or lithium niobate. The material of the filling part 130 includes silicon dioxide, polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC), or epoxy.
In some embodiments, the light guided by the light guiding portion 112 and the normal line of the grating waveguide portion 121 form a coupling angle, and the coupling angle is 0 degrees.
At a coupling angle of 0 degrees, grating teeth 1211 satisfyThe formula: q/Λ=n eff /λ。
Where q is the diffraction order of grating teeth 1211, Λ is the period of grating teeth 1211, n eff In order to achieve the effective refractive index of the transverse wave mode of the light propagating through the grating waveguide 121, λ is the wavelength of the light incident on the grating tooth 1211. Where the period of grating tooth 1211 is the distance between the corresponding sides of two adjacent grating teeth within grating tooth 1211, i.e., distance Λ1 shown in fig. 2.
By setting in this way, the coupling angle is ensured to be 0 degrees by the grating teeth 1211 satisfying the above formula, and the light guided to the grating teeth 1211 of the grating waveguide portion 121 by the light guide portion 112 has no component in other directions, so that the coupling loss of the light when coupled through the grating teeth 1211 of the grating waveguide portion 121 can be reduced, and further, the coupling efficiency of the grating coupler 10 can be improved.
In some embodiments, the fundamental mode field supported by the light guide 112 is the same as the incident mode field of light incident to the light guide 112.
By this arrangement, the loss due to the mismatch between the incident mode field and the fundamental mode field when light is incident on the light guide 112, that is, when light is incident on the grating coupler 10 can be reduced, and thus, the light successfully incident on the light guide 112 can be increased, and further, the coupling efficiency of the grating coupler 10 as a whole can be further improved.
In some embodiments, the thickness of the substrate 110 is 700 microns or greater.
When the thickness of the substrate 110 is 700 μm or more, the strength of the substrate 110 is good, and at this time, if the light guide 112 and the isolation groove 113 are not provided, significant scattering occurs when light passes through the substrate 110. Therefore, the substrate is set to 700 μm or more, and it is ensured that the light incident to the light guide 112 is guided to the grating in a non-divergent manner by the arrangement of the light guide 112 and the isolation groove 113 while ensuring that the substrate 110 has better strength, so that the strength of the substrate 110 can be further improved while ensuring that the coupling efficiency of the grating coupler 10 is improved.
In addition, the substrate layer thickness of the wafer is typically greater than 700 microns. Therefore, the grating coupler 10 can be adapted to more wafers by making the thickness of the substrate 110 equal to or greater than 700 μm, thereby expanding the application range of the grating coupler 10.
In some embodiments, the projections of grating teeth 1211 onto substrate 110 are located within isolation trenches 113 and light guide 112.
By providing such a configuration, it is possible to ensure that all of the light guided by the light guide 112 to the grating teeth 1211 of the grating waveguide 121 can pass through the grating teeth 1211, and thus, the amount of light passing through the grating teeth 1211 can be increased, and further, the coupling efficiency of the grating coupler 10 as a whole can be further improved.
The application also provides a light chip system. The optical chip system includes any of the grating couplers 10 described above. Fig. 6 shows a schematic structural diagram of an optical chip system. As shown in fig. 6, the optical chip system includes: a grating coupler 10, an optical chip 20 and an optical fiber 30.
The optical chip 20 and the coupling waveguide 120 are connected to each other in the extending direction of the cladding 122. The optical fiber 30 is connected to a side of the substrate 110 away from the coupling waveguide 120, and the optical fiber 30 corresponds to the light guide 112. Wherein, the optical fiber 30 includes an optical fiber inner core 31 and an outer cladding 32 surrounding the optical fiber inner core 31, and the optical fiber 30 corresponds to the light guiding portion 112, that is, the mode field of the light transmitted in the optical fiber inner core 31 is similar to the mode field of the light transmitted in the light guiding portion 112. The similarity between the mode field of the light transmitted in the optical fiber core 31 and the mode field of the light transmitted in the light guide 112 is 90% or more, and is considered to be similar.
By arranging the isolation groove 113 around the light guide part 112, the coupling efficiency of the grating coupler 10 can be improved by reducing the diffusion degree of light incident to the grating coupler 10 on the premise of having the advantages of simple preparation process and low preparation cost and avoiding great influence on the intensity of the substrate 110.
The present application also provides a method of making the grating coupler 10. The method of making the grating coupler 10 is used to make any of the grating couplers 10 described above. The preparation method comprises the following steps: a substrate 110 is provided and a coupling waveguide 120 is formed on the substrate 110 to form a first intermediate structure.
The first intermediate structure 40 may refer to what is shown in fig. 7, specifically, forming the coupling waveguide 120 on the substrate 110 may include: a lower cladding layer 1222 is deposited over the substrate 110. Specifically, the lower cladding 1222 may be formed by depositing a material such as silicon dioxide or a polymer. Wherein the polymer comprises polymethyl methacrylate, polystyrene, polycarbonate or epoxy resin.
Silicon, silicon oxide, silicon nitride or lithium niobate is deposited on the side of the lower cladding layer 1222 remote from the substrate 110, and a photoresist is coated on the side of the layer remote from the substrate 110, and the grating waveguide 121 is formed by etching through a photolithography process after the photoresist is coated.
After forming the grating waveguide 121, excess photoresist is removed, and an upper cladding layer 1221 covering the grating waveguide 121 is deposited on a side of the grating waveguide 121 remote from the lower cladding layer 1222, such that the grating waveguide 121 is positioned between the upper cladding layer 1221 and the lower cladding layer 1222. Specifically, the upper cladding layer 1221 is the same as the lower cladding layer 1222, and the upper cladding layer 1221 may be formed by depositing a material such as silicon dioxide or a polymer, but is not limited thereto. Wherein the polymer comprises polymethyl methacrylate, polystyrene, polycarbonate or epoxy resin.
The reflective layer 123 is deposited on the side of the upper cladding layer 1221 away from the grating waveguide portion 121, and the intermediate structure after the reflective layer 123 is formed is the first intermediate structure 40. Specifically, the reflective layer 123 may be formed by depositing a metal film, and the specific metal film to be deposited may be flexibly selected according to the design criteria of the actual grating coupler 10.
After the first intermediate structure 40 is formed, the first intermediate structure 40 is turned over, and an etching process is performed from a side of the substrate 110 away from the coupling waveguide 120, so as to form the light guide portion 112, the isolation trench 113, and the substrate portion 111.
The structure of this step may be as shown in fig. 8, and in particular, in this step, the etching process may be an electron beam etching process, a laser direct writing process, or a photolithography process, but is not limited thereto.
Wherein, if a photolithography process is used, after inverting the first intermediate structure 40, it further comprises: a photoresist is coated on the side of the substrate 110 remote from the coupling waveguide 120. After the photoresist is coated, a photolithography process is performed on the substrate 110 to etch the isolation trench 113, and after the isolation trench 113 is etched, the substrate 110 is then isolated from the substrate portion 111 and the light guide portion 112 by the isolation trench 113. After the etching is completed, the photoresist remaining on the substrate 110 is washed away.
Through the above steps, the light guide part 112, the isolation groove 113 and the substrate part 111 may be formed on the substrate 110, so that the light guide part 112 may be formed into a waveguide structure to achieve the effect of guiding the light incident to the light guide part 112 to the grating teeth 1211 in a non-divergent manner through the light guide part 112, and further, the degree of diffusion of the light incident to the grating coupler 10 may be reduced to improve the coupling efficiency of the grating coupler 10.
In some embodiments, after etching to form isolation trenches 113, further comprising: a filling portion 130 is deposited in the isolation trench 113. Specifically, the filling portion 130 may be formed by depositing silicon dioxide in the isolation trench 113 to deposit in the isolation trench 113, but is not limited thereto.
By forming the filling portion 130, the strength of the substrate 110 can be increased to increase the strength of the grating coupler 10 while ensuring that the degree of diffusion of light incident to the grating coupler 10 is reduced to increase the coupling efficiency of the grating coupler 10.
In some embodiments, after depositing the filling portion 130 in the isolation trench 113, it further includes: a filling portion 130 is formed on a side of the substrate 110 away from the coupling waveguide 120 by deposition, such that the filling portion 130 covers the light guide portion 112, and the filling portion 130 is made of the same material as the filling portion 130 located in the isolation trench 113. In particular, the portion of the filling part 130 may be formed by depositing silicon dioxide on a side of the substrate 110 remote from the coupling waveguide 120, but is not limited thereto.
By forming the filling portion 130 at a side of the substrate 110 away from the coupling waveguide 120, the strength of the substrate 110 can be further increased by the filling portion 130 at a side of the substrate 110 away from the coupling waveguide 120, so as to further increase the strength of the grating coupler 10. Therefore, forming the filling portion 130 at a side of the substrate 110 away from the coupling waveguide 120 can further enhance the strength of the substrate 110 to further enhance the strength of the grating coupler 10 while ensuring that the degree of diffusion of light incident to the grating coupler 10 is reduced to enhance the coupling efficiency of the grating coupler 10.
The above embodiments of the present application may be complementary to each other without conflict.
It is noted that in the drawings, the size of layers and regions may be exaggerated for clarity of illustration. Moreover, it will be understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element or intervening layers may be present. In addition, it will be understood that when an element or layer is referred to as being "under" another element or layer, it can be directly under the other element or intervening layers or elements may be present. In addition, it will be understood that when a layer or element is referred to as being "between" two layers or elements, it can be the only layer between the two layers or elements, or more than one intervening layer or element may also be present. Like reference numerals refer to like elements throughout.
The term "plurality" refers to two or more, unless explicitly defined otherwise.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It is to be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (9)
1. A grating coupler, comprising: a substrate and a coupling waveguide;
the coupling waveguide is positioned on the substrate; the coupling waveguide comprises a grating waveguide part and a cladding part, and the grating waveguide part is positioned in the cladding part; the grating waveguide part comprises grating teeth, and the opening direction of the grating teeth is opposite to the substrate;
the substrate comprises a substrate part, a light guide part and an isolation groove; the substrate part is adjacent to the isolation groove on the plane where the substrate is located, the isolation groove is adjacent to the light guide part, the isolation groove is located between the light guide part and the substrate part, the substrate part surrounds the isolation groove, and the isolation groove surrounds the light guide part; the light guide part is used for guiding the light incident to the light guide part to the grating teeth in a non-divergent mode;
the grating coupler further comprises: a filling part;
the refractive index of the filling part is smaller than that of the light guide part; the filling part is positioned in the isolation groove.
2. The grating coupler of claim 1, wherein the filler is further located on a side of the substrate remote from the coupling waveguide, and wherein the filler encapsulates the light guide.
3. The grating coupler of claim 2, wherein the material of the substrate portion and the light guide portion comprises silicon or silicon dioxide; the material of the grating waveguide part comprises silicon, silicon dioxide, silicon nitride or lithium niobate; the material of the filling part comprises silicon dioxide, polymethyl methacrylate, polystyrene, polycarbonate or epoxy resin.
4. The grating coupler according to claim 1, wherein an angle between the light guided into the grating waveguide by the light guide and a normal line of the grating waveguide is a coupling angle, and the coupling angle is 0 degrees;
when the coupling angle is 0 degree, the grating teeth meet the common requirementThe formula: q/Λ=n eff /λ；
Wherein q is the diffraction order of the grating teeth, Λ is the period of the grating teeth, n eff In order to achieve an effective refractive index of a transverse wave mode of light propagating through the grating waveguide, λ is a wavelength of light incident on the grating teeth.
5. The grating coupler of claim 1, wherein the fundamental mode field supported by the light guide is the same as the incident mode field of light incident to the light guide.
6. The grating coupler of claim 1, wherein the substrate has a thickness of 700 microns or greater.
7. The grating coupler of claim 1, wherein a projection of the grating teeth onto the substrate is located within the isolation trenches and the light guide.
8. A photo chip system comprising a grating coupler according to any one of claims 1 to 7.
9. A method of manufacturing a grating coupler according to any one of claims 1 to 7, comprising: providing a substrate, and forming the coupling waveguide on the substrate to form a first intermediate structure; after the first intermediate structure is formed, the first intermediate structure is turned over, and an etching process is performed from one side of the substrate away from the coupling waveguide, so as to form the light guide part, the isolation groove and the substrate part.
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