Laser directional emission system and its reverse design method

Abstract

The present invention provides a laser directional emission system and a reverse design method thereof. The method carries out the design according to the technical indicator input of the laser directional emission system, simplifies the process of traditional forward design with the technical indicator as the starting point, and provides a minimalist design method for the design of the laser directional emission system. By selecting a metasurface with the ability to precisely control the incident wavefront as a technical platform, a mechanical electric micro-displacement device is combined to realize the joint control of the incident wavefront, and the technical indicators of the laser directional emission system are decomposed into structural parameters of optical elements based on the metasurface through a reverse design method, thereby achieving wide-area precise pointing control of the emitted laser while ensuring the integration and lightweight of the laser directional emission system, and the laser directional emission system designed through this reverse design scheme has a higher angle coverage range and higher control accuracy.

Description

Technical Field

[0001] The present invention relates to the field of information optics technology, and in particular to a laser directional emission system and a reverse design method thereof. Background Art

[0002] Laser directional emission has always been one of the key research directions in the laser field. It is widely used in many fields such as laser communication, laser radar, laser manufacturing, etc., covering all aspects of national defense security, enterprise production, and social life. Therefore, it has extremely important research significance. At present, laser directional emission systems usually use mechanical beam deflectors such as theodolites, inertial turntables combined with fast tilt mirrors to achieve precise pointing and tracking of laser beams. However, mechanical beam control devices will inevitably introduce mechanical jitter in practical applications, resulting in problems such as large mass, large inertia, and easy wear in the laser system.

[0003] In view of the technical difficulties faced in the integrated and lightweight development of laser directional emission systems, the research focus in the field of laser directional emission has shifted from traditional mechanical beam control technology to non-mechanical beam control technology based on optical phased arrays. A series of non-mechanical beam control devices have emerged, such as liquid crystal optical phased arrays, liquid crystal prisms, electro-optical deflectors, microlens arrays, etc., each with unique performance and advantages. Through active control units, phase control is performed to achieve phase compensation of the outgoing light field, thereby realizing laser directional emission. With the continuous development and popularization of laser systems, higher requirements are placed on the pointing coverage and beam control accuracy of laser directional emission. The dielectric material properties, the number of phase control units, and the spatial resolution of the device in the above non-mechanical beam control technology have become limiting factors for further improving the pointing coverage and control accuracy of laser directional emission systems. Therefore, innovation and revolution of new concepts, new principles, and new technologies are urgently needed.

[0004] In view of this, it is necessary to design a laser directional emission system and its reverse design method to solve the above problems. Summary of the invention

[0005] In view of the defects of the above-mentioned prior art, the purpose of the present invention is to address the problems of large mass, large inertia and easy wear in the current mechanical beam control system, as well as the technical difficulties faced in the integration and lightweight development of non-mechanical laser directional emission systems. A metasurface with the ability to precisely control the incident wavefront is selected as a technical platform, and a mechanical electric micro-displacement device is combined to achieve joint control of the incident wavefront. The technical indicators of the laser directional emission system are decomposed into structural parameters of optical elements based on the metasurface through a reverse design method, so as to achieve wide-area precise pointing control of the emitted laser while ensuring the integration and lightweight of the laser directional emission system.

[0006] To achieve the above object, the present invention provides a reverse design method of a laser directional emission system, comprising the following steps:

[0007] S1. Determine the technical indicators of the laser directional emission system

[0008] The technical indicators of the laser directional emission system include angle coverage β cover , Angle control accuracy β pre , wavelength of incident light λ inc , the radius of the incident light r inc ;

[0009] S2. Determine the arrangement pattern of the metasurface array

[0010] The metasurface array includes a plurality of nanostructure units of uniform size arranged in a two-dimensional periodic pattern;

[0011] S3. Optimizing the structural parameters of nanostructure units

[0012] According to the wavelength of the incident light selected in the laser directional emission system λ inc Carry out the design of nanostructure units of metasurfaces, and then use simulation software to simulate and optimize the nanostructure units in the metasurface array based on circularly polarized light to obtain the structural parameters of the optimized nanostructure units;

[0013] S4. Design of the focal length of the lens based on the metasurface in the laser directional emission system

[0014] According to the structural parameters of the nanostructure unit optimized by simulation in step S3 and the angle control accuracy in step S1 β pre , calculate the focal length of the lens based on the metasurface f ;

[0015] S5. Design the size of the metasurface array in the laser directional emission system

[0016] The focal length of the lens calculated in step S4 f And the angle coverage in step S1 β cover , the radius of the incident light r inc , calculate the size of the metasurface array L meta , the calculation formula is: ;

[0017] S6. Design of phase distribution of metasurface array in laser directional emission system

[0018] The focal length of the lens calculated in step S4 f and the size of the metasurface array calculated in step S5 L meta , calculate the phase distribution of the metasurface array ;

[0019] S7: Determine the steering angle arrangement of the metasurface array

[0020] According to the phase distribution of the metasurface array calculated in step S6, the steering angle of each nanostructure unit in the geometric phase metasurface array is calculated. α Arrangement situation.

[0021] Furthermore, in step S2, the nanostructure unit includes a base workbench and nanobricks arranged on the surface of the base workbench.

[0022] Furthermore, the directions parallel to the two sides of the table surface of the substrate workbench are respectively set as x Axis and y Axis, perpendicular to x Axis and y The direction of the axis is set to z Axis, build xyz Coordinate system; wherein the period refers to the geometric centers of two adjacent nanostructure units. x Axis and y The distance between the nanobrick and the center of the substrate workbench is x o y In step S3, the structural parameters of the nanostructure unit include the parameters of the nanobrick and the parameters of the substrate workbench; the parameters of the nanobrick include the height perpendicular to the table of the substrate workbench. H , and the high H Vertical long axis L and short axis W ; The parameters of the substrate workbench include the side length of the table C ; The turning angle of the nanostructure unit is the long axis of the nanobrick in the nanostructure unit L and x The counterclockwise rotation angle of the axis.

[0023] Furthermore, in step S3, the simulation optimization process includes: using an electromagnetic simulation tool, when left-handed circularly polarized light is vertically incident on the nanostructure unit in the metasurface array, the conversion efficiency of the outgoing right-handed circularly polarized light is optimized to obtain the structural parameters of the nanostructure unit with the highest cross-polarization conversion efficiency and the lowest co-polarization conversion efficiency.

[0024] Furthermore, the metasurface array is composed of metasurface nanostructure units that are arranged in a two-dimensional periodic manner.

[0025] Furthermore, in step S4, the focal length of the lens based on the metasurface f The calculation formula is:

[0026] .

[0027] Furthermore, in step S6, the calculation formula of the phase distribution of the metasurface array is:

[0028] ;

[0029] Where, the position coordinates in the metasurface array are x The value range is , location coordinates y The value range is .

[0030] Furthermore, in step S7, the steering angle α The calculation formula is:

[0031] The present invention also provides a laser directional emission system obtained according to the above method.

[0032] Furthermore, the laser directional emission system is combined with a mechanical electric micro-displacement device, which dynamically changes the spatial position of the incident light after passing through the circular polarizer and incident on the metasurface array, thereby achieving wide-area precise pointing control of the outgoing light.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention provides a reverse design method for a laser directional emission system. The design is carried out according to the technical indicator input of the laser directional emission system. The traditional forward design process is simplified by taking the technical indicator as the starting point, and a minimalist design method is provided for the design of the laser directional emission system. In addition, the laser directional emission system designed by this reverse design scheme has a higher angle coverage range and higher control accuracy.

[0035] 2. A laser directional emission system provided by the present invention aims to solve the problems of large mass, large inertia and easy wear in the current mechanical beam control system and the technical difficulties faced by the integration and lightweight development process of non-mechanical laser directional emission systems. By selecting a metasurface with the ability to precisely control the incident wavefront as a technical platform, combined with a mechanical electric micro-displacement device, the incident wavefront can be jointly controlled. The technical indicators of the laser directional emission system are decomposed into structural parameters of optical elements based on the metasurface through a reverse design method, thereby achieving wide-area precise pointing control of the emitted laser while ensuring the integration and lightweight of the laser directional emission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the arrangement of the metasurface array in the present invention;

[0037] Figure 2 Schematic diagram of the structure of the nanostructure unit in the metasurface array of the present invention;

[0038] Figure 3 The scanning optimization result of the structural parameters of the nanostructure unit in the embodiment of the present invention;

[0039] Figure 4 Schematic diagram of lens phase distribution based on a metasurface array in an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the laser directional emission control of the metasurface array in an embodiment of the present invention;

[0041] Figure 6 The metasurface array in the embodiment of the present invention is x Schematic diagram of the change of the light spot on the image plane when the direction is displaced.

[0042] Reference numerals

[0043] 1. Nanobrick; 2. Base working surface. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0046] like Figure 1~2As shown, a reverse design method of a laser directional emission system includes the following steps:

[0047] S1. Determine the technical indicators of the laser directional emission system

[0048] The technical indicators of the laser directional emission system include angle coverage β cover , Angle control accuracy β pre , wavelength of incident light λ inc , the radius of the incident light r inc ;

[0049] S2. Determine the arrangement pattern of the metasurface array

[0050] The metasurface array includes a plurality of nanostructure units of the same size arranged in a two-dimensional periodic manner, wherein the nanostructure unit includes a base workbench, nanobricks arranged on the surface of the base workbench; and nanostructure units are respectively arranged in directions parallel to two sides of the surface of the base workbench. x Axis and y Axis, perpendicular to x Axis and y The direction of the axis is set to z Axis, build xyz Coordinate system; wherein the period refers to the geometric centers of two adjacent nanostructure units. x Axis and y The distance between the nanobrick and the center of the substrate workbench is x o y The projections of the planes coincide;

[0051] S3. Optimizing the structural parameters of nanostructure units

[0052] According to the wavelength of the incident light selected in the laser directional emission system λ inc The nanostructure unit design of the metasurface is carried out; then the material of the nanostructure unit is selected, and the nanostructure unit in the metasurface array based on circularly polarized light is simulated and optimized using electromagnetic simulation tools to obtain the structural parameters of the optimized nanostructure unit.

[0053] The structural parameters of the nanostructure unit include the parameters of the nanobrick and the parameters of the substrate workbench; the parameters of the nanobrick include the height perpendicular to the surface of the substrate workbench. H , and the high H Vertical long axis L and short axis W ; The long axis L With short axisW Not equal; the parameters of the substrate workbench include the side length of the table C .

[0054] The simulation optimization process includes: when left-handed circularly polarized light is vertically incident on the nanostructure unit in the metasurface array, the conversion efficiency of the outgoing right-handed circularly polarized light is optimized (or when right-handed circularly polarized light is vertically incident on the nanostructure unit in the metasurface array, the conversion efficiency of the outgoing left-handed circularly polarized light is optimized), and the structural parameters of the nanostructure unit with the highest cross-polarization conversion efficiency and the lowest co-polarization conversion efficiency are obtained;

[0055] S4. Design of the focal length of the lens based on the metasurface in the laser directional emission system

[0056] According to the structural parameters of the nanostructure unit optimized by simulation in step S3, the side length of the substrate working surface C and the angle control accuracy in step S1 β pre , calculate the focal length of the lens based on the metasurface f , the calculation formula is: ;

[0057] S5. Design the size of the metasurface array in the laser directional emission system

[0058] The focal length of the lens calculated in step S4 f And the angle coverage in step S1 β cover , the radius of the incident light r inc , calculate the size of the metasurface array L meta , the calculation formula is: ;

[0059] S6. Design of phase distribution of metasurface array in laser directional emission system

[0060] The focal length of the lens calculated in step S4 f and the size of the metasurface array calculated in step S5 L meta , calculate the phase distribution of the metasurface array , the calculation formula of the phase distribution of the metasurface array is: ;

[0061] Where, the position coordinates in the metasurface array are x The value range is , location coordinates y The value range is ;

[0062] S7: Determine the steering angle arrangement of the metasurface array

[0063] According to the phase distribution of the metasurface array calculated in step S6, the steering angle of each nanostructure unit in the geometric phase metasurface array is calculated. α The calculation formula is: .

[0064] The metasurface array is composed of metasurface nanostructure units that are arranged in a two-dimensional periodic manner.

[0065] Wherein, the steering angle of the nanostructure unit is the long axis of the nanobrick in the nanostructure unit L and x The counterclockwise rotation angle of the axis.

[0066] In this way, the design is carried out according to the technical indicators of the laser directional emission system. This reverse design scheme simplifies the traditional forward design process with technical indicators as the starting point, and provides a minimalist design method for the design of the laser directional emission system. In addition, the laser directional emission system designed by this reverse design scheme has a higher angle coverage range and higher control accuracy.

[0067] Specifically, in some embodiments of the present invention, the nanobrick 1 is made of silicon, and the substrate workbench is made of silicon.

[0068] The present invention also provides a laser directional emission system (or metasurface device) obtained by adopting the above-mentioned design method.

[0069] Specifically, in some embodiments of the present invention, the laser directional emission system is combined with a mechanical electric micro-displacement device, which dynamically changes the spatial position of the incident light after passing through the circular polarizer and incident on the metasurface array, thereby achieving wide-area precise pointing control of the outgoing light.

[0070] In this way, by selecting the metasurface with the ability to precisely control the incident wavefront as the technical platform, the mechanical electric micro-displacement device is combined to achieve joint control of the incident wavefront, and the technical indicators of the laser directional emission system are decomposed into the structural parameters of optical elements based on the metasurface through the inverse design method, thereby achieving wide-area precise pointing control of the outgoing laser while ensuring the integration and lightweight of the laser directional emission system.

[0071] The following is an explanation of the working mode of a laser directional emission system and its reverse design method provided by the present invention:

[0072] Example

[0073] This embodiment provides a reverse design method for a laser directional emission system, comprising the following steps:

[0074] S1. Determine the technical indicators of the laser directional emission system

[0075] The technical indicators of the laser directional emission system are: angle coverage β cover =120°, angle control accuracy β pre No more than 0.1°, wavelength of incident light λ inc =1550nm, radius of incident light r inc = 60 μm;

[0076] S2. Determine the arrangement pattern of the metasurface array

[0077] The metasurface array includes a plurality of nanostructure units of the same size arranged in a two-dimensional periodic manner, wherein the nanostructure unit includes a substrate workbench and nanobricks arranged on the surface of the substrate workbench; the metasurface array in this embodiment is as follows Figure 1 As shown;

[0078] The nanostructure units in this embodiment are as follows Figure 2 As shown; the directions parallel to the two sides of the table surface of the substrate workbench are respectively set as x Axis and y Axis, perpendicular to x Axis and y The direction of the axis is set to z Axis, build xyz Coordinate system; wherein the period refers to the geometric centers of two adjacent nanostructure units. x Axis and y The distance between the nanobrick and the center of the substrate workbench is x o y The projections of the planes coincide;

[0079] S3. Optimizing the structural parameters of nanostructure units

[0080] According to the wavelength of the incident light selected in the laser directional emission system λ incThe nanostructure unit design of the metasurface is carried out; then the material of the nanostructure unit is selected, and the nanostructure unit in the metasurface array based on circularly polarized light is simulated and optimized by using electromagnetic simulation software tools to obtain the structural parameters of the optimized nanostructure unit; in this embodiment, the working band of the nanostructure unit of the metasurface based on circularly polarized light is selected as the near-infrared band, and the λ inc =1550nm is the main wavelength; the material of the nanostructure unit is silicon;

[0081] Specifically, when a beam of linearly polarized light is incident vertically on a nanostructure unit, the phase delay of the transmitted light in the long axis and short axis directions of the nanostructure unit is , and the amplitude remains consistent, that is to say, the nanostructure unit can be equivalent to a miniature half-wave plate. And because the half-wave plate has a phase control function, when the incident light is converted from linearly polarized light to circularly polarized light, the nanostructure unit can achieve the control of the phase of the transmitted light by changing the steering angle of the nanostructure unit. Specifically, when a beam of circularly polarized light passes through a nanostructure unit with a steering angle of α and its function is equivalent to a half-wave plate, it will be modulated by the nanostructure unit to become circularly polarized light with the opposite rotation direction, and a phase delay is added. This is the phase control principle of the metasurface based on circularly polarized light in the present invention, where the sign of the phase delay is determined by the rotation direction of the incident circularly polarized light. In this embodiment, the incident light is left-handed circularly polarized light, and the corresponding phase delay sign is positive.

[0082] The structural parameters of the nanostructure unit are: H =920nm, the long axis of the nanobrick L and the short axis of the nanobrick W , the side length of the table top of the base workbench C =600nm.

[0083] The simulation optimization process includes: when left-handed circularly polarized light is vertically incident on the nanostructure unit in the metasurface array, the conversion efficiency of the outgoing right-handed circularly polarized light is optimized to obtain the structural parameters of the nanostructure unit with the highest cross-polarization conversion efficiency and the lowest co-polarization conversion efficiency;

[0084] Selecting the long axis of nanobricks in metasurfaces L and the short axis of the nanobrick W As the independent variable of the structural parameter scanning in electromagnetic simulation, the optimization results of the structural parameter scanning are as follows Figure 3 As shown ( Figure 3 The “width” and “length” in the figure correspond to the “minor axis” and “major axis” in the nanobrick, respectively).

[0085] S4. Design of the focal length of the lens based on the metasurface in the laser directional emission system

[0086] According to the structural parameters of the nanostructure unit optimized by simulation in step S3, the side length of the substrate working surface C and the angle control accuracy in step S1 β pre , calculate the focal length of the lens based on the metasurface ;

[0087] S5. Design the size of the metasurface array in the laser directional emission system

[0088] The focal length of the lens calculated in step S4 f And the angle coverage in step S1 β cover , the radius of the incident light r inc , calculate the size of the metasurface array ;

[0089] S6. Design of phase distribution of metasurface array in laser directional emission system

[0090] The focal length of the lens calculated in step S4 f and the size of the metasurface array calculated in step S5 L meta , calculate the phase distribution of the metasurface array , the calculation formula of the phase distribution of the metasurface array is:

[0091] ;

[0092] Where, the position coordinates in the metasurface array are x The value range is , location coordinates y The value range is ;

[0093] The phase distribution of the metasurface array is shown in Figure 2. Figure 4 shown.

[0094] S7: Determine the steering angle arrangement of the metasurface array

[0095] According to the phase distribution of the metasurface array calculated in step S6, the steering angle of each nanostructure unit in the geometric phase metasurface array is calculated. α The calculation formula is: .

[0096] The metasurface array is composed of metasurface nanostructure units that are arranged in a two-dimensional periodic manner.

[0097] Wherein, the steering angle of the nanostructure unit is the long axis of the nanobrick in the nanostructure unit L and x The counterclockwise rotation angle of the axis.

[0098] Finally, the laser directional emission system obtained by the above design method is combined with a mechanical electric micro-displacement device, such as Figure 5 As shown in the figure, the spatial position of the incident light after the circular polarizer incident on the metasurface array is dynamically changed by a mechanical electric micro-displacement device, so as to achieve wide-area precise pointing control of the outgoing light. The results are shown in Figure 6 shown.

[0099] In summary, the present invention provides a reverse design method for a laser directional emission system, which carries out the design according to the technical indicator input of the laser directional emission system, simplifies the process of the traditional forward design by taking the technical indicator as the starting point, and provides a minimalist design method for the design of the laser directional emission system; in addition, the laser directional emission system designed by this reverse design scheme has a higher angle coverage range and higher control accuracy. The laser directional emission system provided by the present invention aims at the problems of large mass, large inertia and easy wear in the current mechanical beam control system and the technical difficulties faced by the integration and lightweight development process of the non-mechanical laser directional emission system. By selecting a metasurface with the ability to precisely control the incident wavefront as a technical platform, the mechanical electric micro-displacement device is combined to realize the joint control of the incident wavefront, and the technical indicators of the laser directional emission system are decomposed into the structural parameters of the optical element based on the metasurface through the reverse design method, so as to achieve the wide-area precise pointing control of the emitted laser under the premise of ensuring the integration and lightweight of the laser directional emission system.

[0100] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A reverse design method for a laser directional emission system, characterized in that: The following steps are involved: S1. Determine the technical indicators of the laser directional emission system The technical indicators of the laser directional emission system include angle coverage β cover , Angle control accuracy β pre , wavelength of incident light λ inc , the radius of the incident light r inc ; S2. Determine the arrangement pattern of the metasurface array The metasurface array includes a plurality of nanostructure units of uniform size arranged in a two-dimensional periodic pattern; S3. Optimizing the structural parameters of nanostructure units According to the wavelength of the incident light selected in the laser directional emission system λ inc Conduct the design of nanostructure units of metasurfaces, and then use simulation software to simulate and optimize the nanostructure units in the metasurface array based on circularly polarized light to obtain the structural parameters of the optimized nanostructure units; S4. Design of the focal length of the lens based on the metasurface in the laser directional emission system According to the structural parameters of the nanostructure unit optimized by simulation in step S3 and the angle control accuracy in step S1 β pre , calculate the focal length of the lens based on the metasurface f ; S5. Design the size of the metasurface array in the laser directional emission system The focal length of the lens calculated in step S4 f And the angle coverage in step S1 β cover , the radius of the incident light r inc , calculate the size of the metasurface array L meta , the calculation formula is: ; S6. Design of phase distribution of metasurface array in laser directional emission system The focal length of the lens calculated in step S4 f and the size of the metasurface array calculated in step S5 L meta , calculate the phase distribution of the metasurface array ; S7: Determine the steering angle arrangement of the metasurface array According to the phase distribution of the metasurface array calculated in step S6, the steering angle of each nanostructure unit in the geometric phase metasurface array is calculated. α Arrangement situation.

2. The reverse design method of the laser directional emission system according to claim 1, characterized in that: In step S2, the nanostructure unit includes a base workbench and nanobricks arranged on the surface of the base workbench.

3. The reverse design method of the laser directional emission system according to claim 2, characterized in that: The directions parallel to the two sides of the table surface of the substrate workbench are respectively set as x Axis and y Axis, perpendicular to x Axis and y The direction of the axis is set to z Axis, build xyz Coordinate system; wherein the period refers to the geometric centers of two adjacent nanostructure units. x Axis and y The distance between the nanobrick and the center of the substrate workbench is x o y In step S3, the structural parameters of the nanostructure unit include the parameters of the nanobrick and the parameters of the substrate workbench; the parameters of the nanobrick include the height perpendicular to the table of the substrate workbench. H , and the high H Vertical long axis L and short axis W ; The parameters of the substrate workbench include the side length of the table C ; The turning angle of the nanostructure unit is the long axis of the nanobrick in the nanostructure unit L and x The counterclockwise rotation angle of the axis.

4. The reverse design method of the laser directional emission system according to claim 1, characterized in that: In step S3, the simulation optimization process includes: using electromagnetic simulation tools, when left-handed circularly polarized light is vertically incident on the nanostructure unit in the metasurface array, the conversion efficiency of the outgoing right-handed circularly polarized light is optimized to obtain the structural parameters of the nanostructure unit with the highest cross-polarization conversion efficiency and the lowest co-polarization conversion efficiency.

5. The reverse design method of the laser directional emission system according to claim 3, characterized in that: In step S4, the focal length of the lens based on the metasurface f The calculation formula is: 。 6. The reverse design method of the laser directional emission system according to claim 1, characterized in that: In step S6, the calculation formula of the phase distribution of the metasurface array is: ； Where, the position coordinates in the metasurface array are x The value range is , location coordinates y The value range is .

7. The reverse design method of the laser directional emission system according to claim 1, characterized in that: In step S7, the steering angle α The calculation formula is: .

8. A laser directional emission system, characterized in that: The laser directional emission system is obtained by using the reverse design method of the laser directional emission system as described in any one of claims 1-7.

9. A laser directional emission system according to claim 8, characterized in that: The laser directional emission system is combined with a mechanical electric micro-displacement device, which dynamically changes the spatial position of the incident light after passing through the circular polarizer and incident on the metasurface array, thereby achieving wide-area precise directional control of the outgoing light.

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