Optical antenna, optical chip and laser radar
By alternately setting the grating substructure with gradually changing characteristic parameters in the waveguide grating of the optical antenna, the problems of inconsistent directionality and uneven luminescence of the optical antenna are solved, and the uniformity of the effective luminous diameter and radiation energy are improved.
Patent Information
- Application Number
- CN202311810744.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-26
- Publication Date
- 2025-07-04
AI Technical Summary
The directionality of existing optical antennas is inconsistent and the light emission is uneven, resulting in a reduction in the effective light emission diameter.
By setting the first grating substructure and the second grating substructure alternately arranged in the waveguide grating, the characteristic parameters gradually change along the light wave transmission direction, and adjust the energy of the light signal in each grating period to maintain consistent direction and uniform luminescence.
The effective luminous diameter of the optical antenna is improved, and uniform radiation of light waves is achieved while maintaining a high directional level.
Smart Images
Figure CN120255069A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of integrated optical technologies, and particularly to optical antennas, optical chips, and lidars. Background Art
[0002] Optical antennas have been widely used in the fields of lidar detection and optical communication technologies. An optical antenna can radiate the electromagnetic waves in the optical frequency band that are confined to propagate in a waveguide outward, and combined with an optical phased array, it can emit optical signals directionally.
[0003] The waveguide grating in an optical antenna generally includes multiple arranged grating periods, and the parameters of the waveguide within each grating period are the same. During the process of the input optical wave propagating along the direction in which multiple grating periods are arranged, the energy of the optical signal will exponentially decay, resulting in different energy magnitudes of the optical signals emitted from each grating period, and the non-uniform light emission reduces the effective light-emitting aperture of the optical antenna.
[0004] In the prior art, although a tapered optical antenna can be used to gradually increase the perturbation intensity to make the antenna emit light uniformly, it will gradually reduce the ratio of the energy radiated by the antenna into free space to the energy radiated in all directions, resulting in the gradual deterioration of the directivity of the antenna, and the gradual deterioration of the directivity will also reduce the energy radiated by the antenna outward and shorten the effective aperture of the antenna. Therefore, how to make the local directivity of the optical antenna remain consistent while emitting light uniformly is an urgent problem to be solved. Summary of the Invention
[0005] The embodiments of this application provide an optical antenna, an optical chip, and a lidar, which can solve the problems of inconsistent directivity and non-uniform light emission of the optical antenna.
[0006] In a first aspect, the embodiments of this application provide an optical antenna, including: a substrate and at least one waveguide grating disposed on the substrate; the waveguide grating includes M arranged grating units, each grating unit includes a first grating sub-structure and a second grating sub-structure, and M is a positive integer; the first characteristic parameters of the M first grating sub-structures in the waveguide grating gradually change along the propagation direction of the optical wave in the waveguide grating, and / or the second characteristic parameters of the M second grating sub-structures in the waveguide grating gradually change along the propagation direction of the optical wave in the waveguide grating.
[0007] Based on the optical antenna provided by this application, the first characteristic parameters of the first grating sub-structures and / or the second characteristic parameters of the second grating sub-structures in the waveguide grating gradually change along the propagation direction of the optical wave in the waveguide grating, making the structural characteristics of the M grating units in the waveguide grating not completely the same, enhancing the perturbation intensity of the waveguide grating, which can not only maintain a relatively high level of the directivity of the waveguide grating, but also enable the optical wave to uniformly radiate energy outward when propagating in the waveguide grating, thereby increasing the effective light-emitting aperture.
[0008] In a possible implementation of the first aspect, the first grating sub-structure and the second grating sub-structure are arranged alternately on the substrate; the first grating sub-structure has K layers in the direction perpendicular to the substrate surface, and the second grating sub-structure has N layers in the direction perpendicular to the substrate surface, where both K and N are positive integers.
[0009] In a possible implementation of the first aspect, the materials of the K-layer structure are the same or different.
[0010] In a possible implementation of the first aspect, the materials of the N-layer structure are the same or different.
[0011] In a possible implementation of the first aspect, the first grating sub-structure has 1 layer in the direction perpendicular to the substrate surface, and the second grating sub-structure has 1 layer in the direction perpendicular to the substrate surface; the material of the first grating sub-structure is the same as that of the second grating sub-structure.
[0012] In a possible implementation of the first aspect, the first characteristic parameter includes width, thickness, and / or refractive index; the second characteristic parameter includes width, thickness, and / or refractive index.
[0013] In a possible implementation of the first aspect, both the first characteristic parameter and the second characteristic parameter are width, and the width of the first grating sub-structure in the same grating unit is greater than that of the second grating sub-structure; the widths of the M first grating sub-structures in the waveguide grating gradually increase along the light wave transmission direction in the waveguide grating, and the widths of the M second grating sub-structures in the waveguide grating gradually decrease along the light wave transmission direction in the waveguide grating.
[0014] Based on this possible implementation, when the waveguide grating is composed of alternately arranged first grating sub-structures and second grating sub-structures, increasing the width of the first grating sub-structure while decreasing the width of the second grating sub-structure can make the depth of the perturbation structures on both side walls of the waveguide grating gradually increase along the light wave transmission direction, and gradually increase the grating width of the waveguide grating, adjust the energy of the optical signal emitted in each grating period, improve the effective light-emitting aperture of the optical antenna and the proportion of the energy radiated by the waveguide grating into space, so that the directivity of the waveguide grating is basically consistent, and the waveguide grating emits light uniformly during the light wave transmission process.
[0015] In a possible implementation of the first aspect, the first grating sub-structure has K layers in the direction perpendicular to the substrate surface, and the second grating sub-structure has N layers in the direction perpendicular to the substrate surface; both K and N are positive integers, and at least one of K and N is greater than or equal to 2.
[0016] In a possible implementation of the first aspect, the first characteristic parameter includes width, thickness, refractive index, number of layers, and / or layer spacing; the second characteristic parameter includes width, thickness, refractive index, number of layers, and / or layer spacing.
[0017] Based on this possible implementation, in the case where the waveguide grating is composed of a first grating sub-structure and a second grating sub-structure arranged one above the other, along the optical wave transmission direction, increasing or decreasing the width, thickness, refractive index, number of layers of the first grating sub-structure, and / or the width, thickness, refractive index, number of layers of the second grating sub-structure, and / or the spacing between the first grating sub-structure and the second grating sub-structure, can adjust the energy magnitude of the optical signal emitted by each grating period, improve the effective light-emitting aperture of the optical antenna and the proportion of the energy radiated by the waveguide grating into space, so as to keep the directivity of the waveguide grating consistent and make the waveguide grating emit light uniformly during the optical wave transmission process.
[0018] In a possible implementation of the first aspect, the material of the first grating sub-structure is silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride, or lithium niobate; the material of the second grating sub-structure is silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride, or lithium niobate.
[0019] In a second aspect, an embodiment of the present application provides an optical chip, including the optical antenna in any of the possible implementations in the first aspect.
[0020] In a third aspect, an embodiment of the present application provides a lidar, including the optical chip in the second aspect, and the optical chip is a transmitting chip and / or a receiving chip.
[0021] It can be understood that the beneficial effects of the above second aspect and third aspect can refer to the relevant descriptions in the above first aspect, and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0023] Figure 1 is a schematic structural diagram of an existing optical antenna;
[0024] Figure 2 is a schematic diagram of the energy radiated by the optical wave in different directions in the grating period provided by the present application;
[0025] Figure 3 is a schematic structural diagram of an optical antenna provided by the present application;
[0026] Figure 4 is a schematic cross-sectional view of an optical antenna provided by this application;
[0027] Figure 5 is a top view of a waveguide grating provided by this application Figure 1 ;
[0028] Figure 6 is a top view of a waveguide grating provided by this application Figure 2 ;
[0029] Figure 7 is a schematic diagram showing the variation of the grating width of a waveguide grating along the grating length direction provided by this application;
[0030] Figure 8 is a schematic diagram showing the variation of the depth of a perturbation structure along the grating length of a waveguide grating provided by this application;
[0031] Figure 9 is a schematic cross-sectional view of an optical antenna along the y direction provided by this application;
[0032] Figure 10 is a schematic cross-sectional view of an optical antenna along the x direction provided by this application;
[0033] Figure 11 is a top view of another waveguide grating provided by this application Figure 1 ;
[0034] Figure 12 is a schematic cross-sectional view of another optical antenna along the x direction provided by this application Figure 1 ;
[0035] Figure 13 is a schematic cross-sectional view of another optical antenna along the x direction provided by this application Figure 2 ;
[0036] Figure 14 is a top view of another waveguide grating provided by this application Figure 2 ;
[0037] Figure 15 is a schematic cross-sectional view of another optical antenna along the x direction provided by this application Figure 3 ;
[0038] Figure 16 is a schematic cross-sectional view of another optical antenna along the x direction provided by this application Figure 4 ;
[0039] Figure 17 is a top view of another waveguide grating provided by this application Figure 3 ;
[0040] Figure 18 Another cross-sectional view along the x-direction of the optical antenna provided by the present application Figure 5 ;
[0041] Figure 19 The top view of another waveguide grating provided by the present application Figure 4 ;
[0042] Figure 20 Schematic structural block diagram of a transmitting chip provided by the present application;
[0043] Figure 21 Schematic structural block diagram of a receiving chip provided by the present application;
[0044] Figure 22 Schematic structural block diagram of a lidar provided by the present application;
[0045] Figure 23 Schematic structural block diagram of an optical communication system provided by the present application. Detailed implementation manners
[0046] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are set forth in order to provide a thorough understanding of the embodiments of the present application. However, those skilled in the art should understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary details.
[0047] References to "one embodiment" or "some embodiments" etc. described in the present application mean that specific features, structures, or characteristics described in conjunction with that embodiment are included in one or more embodiments of the present application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments" etc. that appear in different places 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 another way. The terms "include", "comprise", "have" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in another way.
[0048] Optical antennas have been widely used in the fields of lidar detection and optical communication technologies. An optical antenna can convert the radiation of electromagnetic waves in the free-propagating optical frequency band into local energy, so as to emit optical signals directionally.
[0049] Figure 1 Structural schematic diagram of an existing optical antenna provided for an embodiment of the present application, as Figure 1As shown, the optical antenna includes a substrate and one or more waveguide gratings disposed on the substrate ( Figure 1 only one waveguide grating is shown). The transmission direction of the light wave in the waveguide grating is the x direction. A plurality of perturbation structures are respectively disposed on the two sidewalls of the waveguide grating along the x direction, and the depths d of the perturbation structures on the two sidewalls are equal, so as to form a plurality of grating periods arranged in sequence. The transmission direction of the light wave in the waveguide grating is the direction in which the plurality of grating periods in the waveguide grating are arranged.
[0050] Refer to Figure 1 , in the existing waveguide gratings, the structures of the plurality of grating periods are the same. Specifically, each grating period includes two waveguides with different widths (i.e., Figure 1 waveguide 1 and waveguide 2 in
[0051] Refer to Figure 2 ). The width of waveguide 1 is greater than the width of waveguide 2. The width of waveguide 1 is w1, and the width of waveguide 2 is w2. The depth d of the perturbation structure in each grating period can be (w1 - w2) / 2. In the existing waveguide gratings, the widths of waveguide 1 and waveguide 2 in each grating period are equal, that is, the grating width of the waveguide grating remains unchanged along the transmission direction of the light wave in the waveguide grating, and the depth of the perturbation structure also remains unchanged. up , the energy of the light wave radiated downward is P down , and the total energy of the light waves radiated to the left and right sides is P side . Then the local directivity D of the waveguide can be expressed as the ratio of the energy of the light wave radiated upward to the total radiated energy in the four directions, that is, D = P up / (P up + P down + P side ).
[0052] In a waveguide grating, the light wave radiates a certain amount of energy every time it passes through a grating period in the waveguide grating. The energy ratio of the light wave input to the next grating period after passing through a grating period is T, that is, the energy transmittance of each grating period is T, and the energy ratio radiated outward by each grating period is (1 - T). If the parameters such as the length and width of the waveguides in all grating periods in the waveguide grating are exactly the same, then for the input light wave with an energy of S0 input to the waveguide grating, after passing through n grating periods, the energy S input to the (n + 1)-th grating period is S = S0T n , and the energy S1 radiated outward by the (n + 1)-th grating period is S1 = S0T n(1 - T). It can be seen from this that when the structures of all grating periods in the waveguide grating are exactly the same, the energy of the optical signal radiated outward by each grating period will exponentially decay along with the arrangement direction of the grating periods, resulting in uneven light emission of the optical antenna and reducing the effective aperture of the optical antenna.
[0053] In the prior art, although a tapered optical antenna can be adopted to keep the width of waveguide 1 in each grating period of the waveguide grating unchanged, and gradually reduce the width of waveguide 2 along the transmission direction of light waves in the waveguide grating, or keep the width of waveguide 2 in each grating period of the waveguide grating unchanged, and gradually increase the width of waveguide 1 along the transmission direction of light waves in the waveguide grating, so as to make the antenna emit light evenly and improve the effective aperture of the antenna by gradually increasing the depth of the perturbation structure. However, the gradual change of the waveguide width leads to the gradual deterioration of the local directivity of the antenna.
[0054] To solve the above technical problems, the embodiments of the present application provide an optical antenna, an optical chip and a lidar. Along the transmission direction of light waves in the waveguide grating of the optical antenna, by changing the first characteristic parameter of the first grating sub-structure and / or the second characteristic parameter of the second grating sub-structure in each grating unit, the directivity of the optical antenna can be kept consistent, and the optical antenna can emit light evenly, improving the effective light-emitting aperture of the optical antenna.
[0055] Next, in conjunction with the accompanying drawings, the technical solutions of the present application will be described in detail. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and should not be construed as a limitation to the present application.
[0056] In a possible implementation manner, referring to Figure 3 the schematic structural diagram of an optical antenna shown in Figure 4 and the schematic cross-sectional diagram of an optical antenna shown in
[0057] it should be noted that Figure 3 any two of the x-direction, y-direction and z-direction shown in
[0058] are perpendicular to each other, where the x-direction is the direction in which light waves are transmitted from the light input end to the tail end in the waveguide grating, and the z-direction is the thickness direction or the vertical direction of the substrate.
[0059] In an embodiment of the present application, each waveguide grating in the optical antenna may include M grating units arranged in an array, where M is a positive integer, and each grating unit may include a first grating sub-structure and a second grating sub-structure.
[0060] In different types of optical antennas, along the transmission direction of light waves in the waveguide grating, by changing at least one characteristic parameter of the first grating sub-structure and / or changing at least one characteristic parameter of the second grating sub-structure, the structural characteristics of the M grating units in each waveguide grating can be made not completely the same and continuously change along the transmission direction of light waves in the waveguide grating. This can not only maintain a relatively high level of directivity of the waveguide grating but also enable the light waves to radiate energy outward uniformly when transmitting in the waveguide grating, thereby increasing the effective light-emitting aperture.
[0061] The following will specifically describe different ways of changing the characteristic parameters of the first grating sub-structure and the second grating sub-structure in different types of optical antennas through different embodiments in combination with different drawings.
[0062] Embodiment 1
[0063] In a possible implementation manner, the waveguide grating in the optical antenna is composed of a first grating sub-structure and a second grating sub-structure alternately arranged on a substrate. The first grating sub-structure has a single-layer structure in the direction perpendicular to the substrate surface, and the second grating sub-structure has a single-layer structure in the direction perpendicular to the substrate surface. The materials of the first grating sub-structure and the second grating sub-structure are the same. Exemplarily, the materials of the first grating sub-structure and the second grating sub-structure can be any one or more of silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride, or lithium niobate.
[0064] Specifically, referring to Figure 5 the top view of a waveguide grating shown Figure 1 , this waveguide grating includes M grating units arranged along the transmission direction of light waves in the waveguide grating ( Figure 5 only four grating units are shown), and perturbation structures are provided on both sidewalls along the transmission direction of light waves in the waveguide grating. The width of the first grating sub-structure in the same grating unit is greater than the width of the second grating sub-structure.
[0065] It should be noted that each waveguide grating in the optical antenna includes a light input end and a tail end. When light waves transmit in the waveguide grating, each grating unit in the waveguide grating can radiate light waves in all directions. Figure 5 The x direction in
[0066] The width of the first grating sub-structure in each grating unit is the side length of the first grating sub-structure along the y direction, and the width of the second grating sub-structure is the side length of the second grating sub-structure along the y direction. The centers of the first grating sub-structure and the second grating sub-structure in each grating unit correspond to each other along the x direction. Therefore, the depths of the two perturbation structures located on both sides of the second grating sub-structure in the same grating unit are equal, and the depth of the perturbation structure is equal to half of the difference between the width of the first grating sub-structure and the width of the second grating sub-structure in the grating unit to which the perturbation structure belongs.
[0067] Exemplarily, referring to Figure 5 , in grating unit 1 of the waveguide grating, the width of the first grating sub-structure is w1 and the length of the first grating sub-structure is l1, the width of the second grating sub-structure in grating unit 1 is w2 and the length of the second grating sub-structure is l1, and the depth d of the perturbation structure in grating unit 1 is (w1 - w2) / 2.
[0068] In the optical antenna of the first embodiment, the first characteristic parameter of the M first grating sub-structures in the waveguide grating can gradually change along the transmission direction of the light wave in the waveguide grating. At the same time, the second characteristic parameter of the M second grating sub-structures in the waveguide grating can also gradually change along the transmission direction of the light wave in the waveguide grating, so that the grating width of the waveguide grating and the depth of the perturbation structure both gradually increase along the transmission direction of the light wave in the waveguide grating, thereby increasing the perturbation intensity of the waveguide grating, enabling the directivity of the waveguide grating to maintain a relatively high level, and enabling the light wave to uniformly radiate energy outward when transmitting in the waveguide grating, thereby increasing the effective light-emitting aperture.
[0069] Specifically, in one embodiment, both the first characteristic parameter of the first grating sub-structure and the second characteristic parameter of the second grating sub-structure can be the width. The widths of the M first grating sub-structures in the waveguide grating gradually increase along the transmission direction of the light wave in the waveguide grating, and the widths of the M second grating sub-structures in the waveguide grating gradually decrease along the transmission direction of the light wave in the waveguide grating.
[0070] It should be noted that the term "gradually increase" described in the embodiments of the present application refers to increasing in sequence or in a stepped manner, and the term "gradually decrease" refers to decreasing in sequence or in a stepped manner.
[0071] In one example, referring to Figure 5 the shown waveguide grating, which includes grating unit 1, grating unit 2, grating unit 3, and grating unit 4 arranged in sequence along the x direction. The widths of the four first grating sub-structures in the waveguide grating gradually increase along the x direction, and the widths of the four second grating sub-structures in the waveguide grating gradually decrease along the x direction.
[0072] Specifically, asFigure 5 As shown, along the x direction, the width of the first grating sub-structure in grating unit 2 is greater than that in grating unit 1, the width of the second grating sub-structure in grating unit 2 is less than that in grating unit 1, and the depth of the perturbation structure in grating unit 2 is greater than that in grating unit 1; the width of the first grating sub-structure in grating unit 3 is greater than that in grating unit 2, the width of the second grating sub-structure in grating unit 3 is less than that in grating unit 2, and the depth of the perturbation structure in grating unit 3 is greater than that in grating unit 2; the width of the first grating sub-structure in grating unit 4 is greater than that in grating unit 3, the width of the second grating sub-structure in grating unit 4 is less than that in grating unit 3, and the depth of the perturbation structure in grating unit 4 is greater than that in grating unit 3.
[0073] In another example, refer to Figure 6 The top view of another waveguide grating shown, which includes six arranged grating units. The six grating units are sequentially grating unit 1, grating unit 2, grating unit 3, grating unit 4, grating unit 5, and grating unit 6 in the arrangement order along the x direction. The widths of the six first grating sub-structures in this waveguide grating increase step by step along the x direction, and the widths of the six second grating sub-structures in this waveguide grating also increase step by step along the x direction.
[0074] Specifically, as Figure 6 shown, along the x direction, the widths of the first grating sub-structure and the second grating sub-structure in grating unit 1 and grating unit 2 are equal. The widths of the first grating sub-structure and the second grating sub-structure in grating unit 3 and grating unit 4 are equal, and the widths of the first grating sub-structure in grating unit 3 and grating unit 4 are greater than those in grating unit 2 and grating unit 1, and at the same time, the widths of the second grating sub-structure in grating unit 3 and grating unit 4 are less than those in grating unit 2 and grating unit 1. The widths of the first grating sub-structure and the second grating sub-structure in grating unit 5 and grating unit 6 are equal, and the widths of the first grating sub-structure in grating unit 5 and grating unit 6 are greater than those in grating unit 4 and grating unit 3, and at the same time, the widths of the second grating sub-structure in grating unit 5 and grating unit 6 are less than those in grating unit 4 and grating unit 3.
[0075] It should be noted that in the case where the width of the first grating sub-structure in the waveguide grating increases stepwise along the x direction and the width of the second grating sub-structure decreases stepwise along the x direction, Figure 6 in the waveguide grating shown in Figure 6 , the number of adjacent grating units with the same characteristic parameters is two, and the characteristics include the width of the first grating sub-structure, the width of the second grating sub-structure, and the depth of the perturbation structure. However, in other embodiments, the number of adjacent grating units with the same characteristic parameters in the waveguide grating can be greater than two. For example, the characteristic parameters of grating unit 1, grating unit 2, and grating unit 3 are the same, the characteristic parameters of grating unit 4 and grating unit 5 are the same, the width of the first grating sub-structure of grating unit 4 is greater than the width of the first grating sub-structure in grating units 1 to 3, and the width of the second grating sub-structure of grating unit 4 is less than the width of the second grating sub-structure in grating units 1 to 3. The width of the first grating sub-structure of grating unit 6 is greater than the width of the first grating sub-structure in grating units 4 and 5, and the width of the second grating sub-structure of grating unit 6 is less than the width of the second grating sub-structure in grating units 4 and 5.
[0076] In each embodiment of the present application, there is no limitation on the number of waveguide gratings in the optical antenna and the number of grating units in each waveguide grating.
[0077] Furthermore, in one embodiment, the amplitude of increase in the width of the first grating sub-structure in the waveguide grating each time along the transmission direction of the light wave in the waveguide grating can be the same or the amplitude of increase can increase exponentially. The amplitude of decrease in the width of the second grating sub-structure in the waveguide grating each time along the transmission direction of the light wave in the waveguide grating can be the same or the amplitude of increase can increase exponentially.
[0078] Exemplarily, if the waveguide grating includes grating unit 1, grating unit 2, and grating unit 3 arranged along the x direction, then the increase in the width of the first grating sub-structure in grating unit 2 relative to the width of the first grating sub-structure in grating unit 1 is equal to the increase in the width of the first grating sub-structure in grating unit 3 relative to the width of the first grating sub-structure in grating unit 2; the decrease in the width of the first grating sub-structure in grating unit 2 relative to the width of the first grating sub-structure in grating unit 1 is equal to the decrease in the width of the first grating sub-structure in grating unit 3 relative to the width of the first grating sub-structure in grating unit 2.
[0079] Exemplarily, assuming the structure of the waveguide grating is as Figure 5 shown in Figure 5 , the widths of the four first grating sub-structures increase sequentially along the x direction, and the widths of the four second grating sub-structures decrease sequentially along the x direction. Then, referring to Figure 7 a schematic diagram showing the change of a grating width along the grating length direction of the waveguide grating, andFigure 8 Schematic diagram of the variation of the depth of a perturbation structure with the grating length of a waveguide grating. The grating length of the waveguide grating is 490 μm. The widths of the four first grating sub-structures in the waveguide grating can increase from 604 nm to 700 nm along the grating length direction, and the depth of the perturbation structure can increase from 35 nm to 144 nm along the grating length direction. Moreover, the widths of the first grating sub-structures and the depth of the perturbation structure both increase exponentially. Herein, the grating length of the waveguide grating is the sum of the lengths of all the first grating sub-structures and all the second grating sub-structures in the waveguide grating.
[0080] Embodiment 2
[0081] In a possible implementation, referring to Figure 9 Schematic cross-sectional view of an optical antenna along the y direction. The optical antenna includes a waveguide grating array composed of a plurality of double-layer waveguide gratings arranged at intervals. Each double-layer waveguide grating includes two identical waveguide gratings arranged at intervals up and down. Each waveguide grating includes a first grating sub-structure and a second grating sub-structure arranged along the x direction. The width of the first grating sub-structure in the same grating unit of the waveguide grating is greater than the width of the second grating sub-structure. A filling structure is arranged on the periphery of the waveguide grating.
[0082] It can be understood that in the optical antenna in Embodiment 2, the first grating sub-structure in each double-layer waveguide grating has K-layer structures in the direction perpendicular to the substrate surface, and the second grating sub-structure has N-layer structures in the direction perpendicular to the substrate surface, and both K and N can be positive integers greater than or equal to 2.
[0083] Exemplarily, the structure of each waveguide grating in the double-layer waveguide grating can be the waveguide grating shown in Figure 5 or the waveguide grating shown in Figure 6 The material of the filling structure can be silicon dioxide.
[0084] Furthermore, as shown in Figure 10 Schematic cross-sectional view of the optical antenna along the x direction Figure 1 , an input waveguide is arranged at the input end of each waveguide grating. The two waveguide gratings arranged up and down are displaced by a distance L0 along the x direction, thus breaking the symmetry in the vertical direction and further improving the antenna directivity. Assume that the grating period of the first grating unit connected to the input waveguide in the waveguide grating is Λ, then 0.01Λ ≤ L0 ≤ 0.99Λ.
[0085] Since the two waveguide gratings stacked in each double-layer waveguide grating are exactly the same, the corresponding first grating sub-structures are exactly the same and the second grating sub-structures are also exactly the same. For each waveguide grating in the double-layer waveguide grating, the first characteristic parameter of the first grating sub-structure and the second characteristic parameter of the second grating sub-structure in the waveguide grating are both widths. The widths of the M first grating sub-structures in the waveguide grating gradually increase along the transmission direction of the light wave in the waveguide grating, and the widths of the M second grating sub-structures in the waveguide grating gradually decrease along the transmission direction of the light wave in the waveguide grating.
[0086] Exemplarily, the material of the first grating sub-structure can be silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride or lithium niobate. The material of the second grating sub-structure can be silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride or lithium niobate.
[0087] Embodiment III
[0088] In a possible implementation, the waveguide grating includes M grating units, and each grating unit includes a first grating sub-structure and a second grating sub-structure, that is, the first grating sub-structure and the second grating sub-structure are arranged alternately on the substrate of the optical antenna. The first grating sub-structure has K layers in the direction perpendicular to the substrate surface (i.e., the z direction), and the second grating sub-structure has N layers in the direction perpendicular to the substrate surface, where K and N are both positive integers, and at least one of K and N is a positive integer greater than or equal to 2. The materials of the K-layer structure can be the same or different. The materials of the N-layer structure can be the same or different. There are filling structures between the K-layer structures and between the N-layer structures, and the material of the filling structure can be silicon dioxide.
[0089] Exemplarily, referring to Figure 11 the top view of another waveguide grating shown in Figure 1 and Figure 12 the cross-sectional schematic of another optical antenna along the x direction shown in Figure 1 , Figure 11 and Figure 12 show 5 grating units. The first grating sub-structure in each grating unit has a single layer structure in the z direction. The material of this layer structure can be silicon, the width is denoted as w1 and the thickness is denoted as h1. The second grating sub-structure in each grating unit has a two-layer structure in the z direction, and the materials of the two layers are different. Among them, the material of the upper layer structure can be silicon nitride, the width of the upper layer structure is denoted as w2 and the thickness is denoted as h2, and the material of the lower layer structure can be silicon. The width of the lower layer structure is denoted as w3 ( Figure 11 not shown in and the thickness is denoted as h3. The single layer structure in the first grating sub-structure and the lower layer structure in the second grating sub-structure are at the same height, and there is a certain interval between the upper layer structures of two adjacent second grating sub-structures.
[0090] It should be noted that in the Figures 11 to 18 optical antenna shown, only 5 grating units are shown, but this does not limit the number of grating units in the waveguide grating. In other embodiments, the optical antenna may include more or fewer grating units than shown.
[0091] In the third embodiment, the first characteristic parameter of the first grating sub-structure may include the width, thickness, refractive index, number of stacked layers K, and / or the layer spacing between the K layers of any one or more layers of the first grating sub-structure. The second characteristic parameter of the second grating sub-structure may include the width, thickness, refractive index, number of stacked layers N, and / or the layer spacing between the N layers of any one or more layers of the second grating sub-structure. By changing any one or more of the characteristic parameters of the first grating sub-structure and / or changing any one or more of the characteristic parameters of the second grating sub-structure, the perturbation intensity can be increased.
[0092] The following provides exemplary descriptions of different variation methods of different characteristic parameters of the first grating sub-structure and the second grating sub-structure through different examples.
[0093] In one example, assume that the first grating sub-structure has one layer in the z direction and the material is silicon, and the second grating sub-structure has two layers in the z direction, and the materials of the two layers are different. The material of the upper layer structure can be silicon nitride, and the material of the lower layer structure can be silicon. Based on this, referring to Figure 11 the waveguide grating shown, the second characteristic parameter that changes along the propagation direction of the optical wave in the waveguide grating (i.e., the x direction) of M second grating sub-structures ( Figure 11 only 5 second grating sub-structures are shown) can be the width of the silicon nitride in the second grating sub-structure, and the width of the silicon nitride in the M second grating sub-structures gradually increases along the x direction. The widths of the M first grating sub-structures remain unchanged, and the perturbation gradually increases. Therefore, when the optical wave propagates in the waveguide grating, it can uniformly radiate energy outward, thereby increasing the effective light-emitting aperture. For such an antenna composed of silicon material and silicon nitride material, even if the width of the silicon nitride is greatly increased, the directivity of the antenna will not deteriorate.
[0094] It should be noted that in the Figure 12 optical antenna shown, since the refractive index of silicon is significantly greater than that of silicon nitride, most of the energy of the optical signal is confined within the silicon structure, and the silicon nitride structure constitutes a perturbation to radiate the optical signal within the silicon structure into free space. Due to the too large refractive index difference between the two materials, the antenna perturbation intensity is not high, and it is difficult to form a truly uniform light-emitting antenna. To further increase the perturbation intensity, Figure 12The materials of the silicon structure in the first grating substructure and the silicon structure in the second grating substructure are replaced with silicon nitride, thereby obtaining Figure 13 The optical antenna shown in .
[0095] In other examples, in order to improve the structural strength of the silicon nitride structure in the second grating substructure and improve the manufacturability of the optical antenna, the silicon nitride structures in the M second grating substructures can be connected in series using a first waveguide with a narrower width.
[0096] For details, see Figure 14 Top view of the waveguide grating shown in Figure 2 Each of the first grating substructure and the second grating substructure in the waveguide grating has an upper and lower two-layer structure. The upper layer structure in the first grating substructure is Figure 14 In the first waveguide shown in , the material of the upper structure can be silicon nitride and the material of the lower structure can be silicon. The material of the upper structure in the second grating substructure can be silicon nitride and the material of the lower structure can be silicon. The first waveguide in the first grating substructure and the silicon nitride structure in the second grating substructure are at the same height, and the two silicon nitride structures in two adjacent second grating substructures can be connected in series through the first waveguide, and the width of the first waveguide can be smaller than the width of the silicon structure in the first grating substructure.
[0097] In other examples, the antenna perturbation strength is not high because the refractive index of silicon is too different from that of silicon nitride. The refractive index of silicon nitride can be changed by adjusting the ratio of silicon and nitrogen atoms in the silicon nitride material. Figure 15 The cross section of the optical antenna along the x direction is shown Figure 3 The first grating substructure has a layer structure and the material is silicon, the material of the upper layer structure in the second grating substructure can be silicon nitride, and the material of the lower layer structure can be silicon, Figure 15 Silicon nitride with different color depths has different refractive indices, and the darker the color, the higher the refractive index of silicon nitride. Figure 15 In the embodiment, the refractive index of the silicon nitride structure in the M second grating substructures can gradually increase along the transmission direction of the light wave in the waveguide grating (ie, the x direction), thereby making the perturbation intensity higher.
[0098] For other examples, see Figure 16 The cross section of the optical antenna along the x direction is shown Figure 4, the first grating sub-structure has a single-layer structure and the material can be silicon, and the second grating sub-structure has a two-layer structure where the material of the upper layer structure can be silicon nitride and the material of the lower layer structure can be silicon. Based on this, along the light wave propagation direction in the waveguide grating (i.e., the x-direction), by reducing the spacing H between the silicon nitride structure and the silicon structure in the vertical direction (i.e., the z-direction) in the M second grating sub-waveguides, the perturbation intensity can also be gradually increased. Here, the spacing H represents the distance between the bottom surface of the silicon nitride structure in the upper layer and the top surface of the silicon structure in the lower layer within the same second grating sub-structure.
[0099] In other examples, refer to Figure 17 the top view of the waveguide grating shown Figure 3 , the first grating sub-structure has a single-layer structure and the material can be silicon, and the second grating sub-structure has a two-layer structure where the material of the upper layer structure can be silicon nitride and the material of the lower layer structure can be silicon. Based on this, along the light wave propagation direction in the waveguide grating (i.e., the x-direction), the widths of the silicon structures in the first grating sub-structure and the second grating sub-structure can be gradually reduced, and the width of the silicon nitride structure in the second grating sub-structure can be kept unchanged, thereby gradually increasing the perturbation intensity. Alternatively, along the light wave propagation direction in the waveguide grating, the widths of the silicon structures in the waveguide grating can also be reduced step by step.
[0100] In other examples, refer to Figure 18 the cross-sectional schematic of the optical antenna shown along the x-direction Figure 5 , the first grating sub-structure has a single-layer structure and the material can be silicon, and the second grating sub-structure has a two-layer structure where the material of the upper layer structure can be silicon nitride and the material of the lower layer structure can be silicon. Along the light wave propagation direction in the waveguide grating (i.e., the x-direction), the thicknesses of the silicon structures in the M first grating sub-structures and the M second grating sub-structures can be gradually reduced, and the thickness of the silicon nitride structure in the second grating sub-structure can be kept unchanged, thereby gradually increasing the perturbation intensity. Alternatively, along the light wave propagation direction in the waveguide grating, the thicknesses of the silicon structures in the waveguide grating can also be reduced step by step.
[0101] In other examples, the perturbation of the optical antenna composed of the materials silicon and silicon nitride is small. In order to make the antenna emit light uniformly, the perturbation intensity of one or more grating units near the antenna tail end needs to be very high. Therefore, one or more grating units near the antenna tail end can be of a single-layer structure.
[0102] Specifically, refer to Figure 19For the waveguide grating shown in [description], the first three grating units near the antenna tail end are single-layer structures, that is, the first grating sub-structure and the second grating sub-structure in the first three grating units near the antenna tail end are arranged alternately along the x direction and both have single-layer structures. Any one or more sub-structures of the first grating sub-structure and the second grating sub-structure in the four grating units near the antenna input end can have multi-layer structures, and the materials of the multi-layer structures can be the same or different. Exemplarily, the materials of the first grating sub-structure and the second grating sub-structure in the first three grating units near the antenna tail end can both be silicon.
[0103] Based on the optical antenna provided in the above embodiments, an optical chip is further provided in an embodiment of the present application. It can be understood that the optical chip can be a transmitting chip, a receiving chip, or an optical chip integrated with transmitting and receiving functions.
[0104] Figure 20 It is a schematic structural block diagram of a transmitting chip provided in an embodiment of the present application. The transmitting chip includes the optical antenna in any of the above embodiments. The transmitting chip is used to emit the transmitted light into space through the optical antenna. Optionally, the transmitting chip may further include a first modulator, a beam splitter, and a coupler connected to the optical antenna in sequence. Among them, the coupler is used to couple and input the transmitted light and transmit it to the beam splitter for beam splitting. After the first modulator adjusts the amplitude and / or phase of the transmitted light, the transmitted light is emitted into space through the optical antenna to detect a target in space.
[0105] Figure 21 It is a schematic structural block diagram of a receiving chip provided in an embodiment of the present application. The receiving chip includes the optical antenna in any of the above embodiments. The receiving chip is used to receive the reflected light signal of a target in space into the chip through the optical antenna. Optionally, the receiving chip may further include a second modulator, a combiner, and a detector connected to the optical antenna in sequence. Among them, after the second modulator adjusts the amplitude and / or phase of the reflected light received by the optical antenna, the received multiple optical signals are combined by the combiner and then input to the detector to detect a target in space.
[0106] An embodiment of the present application further provides a lidar. Refer to Figure 22 The schematic structural block diagram of a lidar shown in [description]. The lidar includes a receiving chip provided with the optical antenna provided in the above embodiments of the present application and a transmitting chip provided with the optical antenna provided in the above embodiments of the present application. Among them, the transmitting chip can emit the transmitted light into space through the optical antenna, and the receiving chip can receive the diffuse reflected return light formed on a target in space, so as to detect a target in space.
[0107] The embodiment of the present application also provides an optical communication system, which can be a free-space optical communication system using laser light waves as the carrier and the atmosphere as the transmission medium. Refer to Figure 23 The schematic structural block diagram of an optical communication system shown in the figure. The optical communication system may include a first communication end and a second communication end. The first communication end may include a transmitting chip and / or a receiving chip provided with the optical antenna provided in the above embodiment of the present application. The second communication end may also include a transmitting chip and / or a receiving chip provided with the optical antenna provided in the above embodiment of the present application. Specifically, both the first communication end and the second communication end in the optical communication system can make the laser emit light through the power drive circuit for the modulated signal, so that the laser carrying the voice signal or data signal is transmitted to the opposite end through the transmitting chip, and the laser pulse signal transmitted by the other party is received and demodulated through the receiving chip, so as to achieve duplex communication.
[0108] It can be understood that the structure schematically shown in the embodiment of the present application does not constitute a specific limitation on the transmitting chip, the receiving chip, the lidar and the optical communication system. In other embodiments of the present application, the transmitting chip, the receiving chip, the lidar and the optical communication system may include more or fewer components than those shown in the figure.
[0109] In the description of the present application, it should be understood that the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features.
[0110] In the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected, or indirectly connected through an intermediate medium. It may be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
[0111] In the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature is at a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature is at a lower horizontal height than the second feature.
[0112] In the description of the present application, it should be understood that the orientations indicated by the terms "inner", "outer", "upper", "bottom", "front", "rear", etc. are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.
[0113] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. An optical antenna, characterized in that, Comprising: a substrate and at least one waveguide grating disposed on the substrate; The waveguide grating includes M grating units arranged in sequence, each of the grating units includes a first grating sub-structure and a second grating sub-structure, and M is a positive integer; A first characteristic parameter of the M first grating sub-structures in the waveguide grating gradually changes along the light wave transmission direction in the waveguide grating, and / or a second characteristic parameter of the M second grating sub-structures in the waveguide grating gradually changes along the light wave transmission direction in the waveguide grating.
2. The optical antenna according to claim 1, characterized in that, The first grating sub-structure and the second grating sub-structure are alternately arranged on the substrate; The first grating sub-structure has a K-layer structure in a direction perpendicular to the substrate surface, and the second grating sub-structure has an N-layer structure in a direction perpendicular to the substrate surface, and both K and N are positive integers.
3. The optical antenna according to claim 2, characterized in that, The materials of the K-layer structure are the same or different.
4. The optical antenna according to claim 2, wherein The materials of the N-layer structure are the same or different.
5. The optical antenna according to claim 2, characterized in that, The first grating sub-structure has a single-layer structure in a direction perpendicular to the substrate surface, and the second grating sub-structure has a single-layer structure in a direction perpendicular to the substrate surface; The material of the first grating sub-structure is the same as the material of the second grating sub-structure.
6. The optical antenna according to claim 5, wherein The first characteristic parameter includes width, thickness, and / or refractive index; The second characteristic parameter includes width, thickness, and / or refractive index.
7. The optical antenna according to claim 5, characterized in that, The first characteristic parameter and the second characteristic parameter are both width, and the width of the first grating sub-structure in the same grating unit is greater than the width of the second grating sub-structure; The widths of the M first grating sub-structures in the waveguide grating gradually increase along the light wave transmission direction in the waveguide grating, and the widths of the M second grating sub-structures in the waveguide grating gradually decrease along the light wave transmission direction in the waveguide grating.
8. The optical antenna according to claim 1, wherein The first grating sub-structure has a K-layer structure in a direction perpendicular to the substrate surface, and the second grating sub-structure has an N-layer structure in a direction perpendicular to the substrate surface; Both K and N are positive integers, and at least one of K and N is greater than or equal to 2.
9. The optical antenna according to claim 8, characterized in that, The first characteristic parameter includes width, thickness, refractive index, number of stacked layers, and / or layer spacing; The second characteristic parameter includes width, thickness, refractive index, number of stacked layers, and / or layer spacing.
10. The optical antenna according to any one of claims 1 to 9, characterized in that, The material of the first grating sub-structure is one or more of silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride, or lithium niobate; The material of the second grating sub-structure is one or more of silicon, silicon nitride, silicon dioxide, silicon carbide, gallium nitride, or lithium niobate.
11. An optical chip, characterized in that, Comprising the optical antenna according to any one of claims 1 to 10.
12. A lidar, characterized in that, Comprising the optical chip according to claim 11, wherein the optical chip is a transmitting chip and / or a receiving chip.