Metasurface structure, laser array, optical imaging chip and preparation method

Abstract

The application discloses a metasurface structure, a laser array, an optical imaging chip and a preparation method, the metasurface structure is arranged on a substrate layer of a VCSEL laser array, and comprises a phase compensation metasurface structure and a holographic phase metasurface structure; the phase compensation metasurface structure is used for compensating a spherical wave front of the laser array reaching a surface of the substrate layer; and the holographic phase metasurface structure is used for generating a far-field light spot pattern. According to the application, the metasurface structure is directly designed on the substrate material of the VCSEL laser array, and the phase compensation of each laser in the laser array and the holographic phase of the required projection pattern design are simultaneously realized.

Description

Technical Field

[0001] This invention belongs to the field of vertical cavity surface-emitting laser (VCSEL) chip and metasurface imaging technology, specifically relating to a metasurface structure, laser array, optical imaging chip and its fabrication method. Background Technology

[0002] The growing demand for sensing and reconstructing information about real-world objects has spurred a variety of applications in various market segments based on structured light, such as facial recognition, light detection and ranging, and 3D imaging. Whether it's the generation of structured light, beamforming and beam control, or 3D display, all require the manipulation of the light field.

[0003] Metasurfaces have emerged as a new type of subwavelength two-dimensional optical element, exhibiting excellent phase, intensity, and polarization controllability in the optical field. Meanwhile, vertical cavity surface-emitting lasers (VCSELs) have the characteristics of low power consumption, low packaging cost, and ease of fabrication into wafer-level arrays, making them a suitable laser source for 3D imaging.

[0004] In existing technologies, light generation or imaging devices are usually external devices. The light is modulated by the external device and then imaged in the far field. Such external structured light generation or imaging devices will increase the size of the overall system on the one hand, and the alignment problem between the laser array and the external device will also greatly increase the cost on the other hand.

[0005] Alternatively, in some embodiments, a high-temperature bonding process is used to add structured light generating or imaging devices to the VCSEL laser array to reduce the size, but the collimation problem still exists, and the high-temperature bonding process also complicates the fabrication process. Summary of the Invention

[0006] In view of this, the main objective of the present invention is to provide a metasurface structure, a laser array, an optical imaging chip, and a method for fabricating it.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] This invention provides a metasurface structure disposed on the substrate of a VCSEL laser array, and includes a phase-compensating metasurface structure and a holographic phase metasurface structure.

[0009] The phase-compensating metasurface structure is used to compensate for the spherical wavefront of the laser array reaching the substrate surface; the holographic phase metasurface structure is used to generate far-field spot patterns.

[0010] In the above scheme, the phase value of the phase-compensated metasurface structure satisfies the expression k(x) 2 +y 2) / (2R(z)), where λ is the wavenumber of the laser emitted by the laser array on the substrate, n1 is the refractive index of the substrate material, λ is the laser wavelength, R(z) is the radius of curvature of the laser emitted by the laser array when it reaches the substrate surface, and z is the thickness of the substrate.

[0011] In the above scheme, the phase value of the holographic phase metasurface structure is generated by the Gerchberg-Saxton algorithm or the gradient descent algorithm.

[0012] In the above scheme, the size of the phase-compensated metasurface structure is determined according to the beam width when the laser propagates to the surface U1 of the substrate layer.

[0013] In the above scheme, the size of the holographic phase metasurface structure is matched with the size of the VCSEL laser array.

[0014] In the above scheme, the substrate layer is made of gallium arsenide (GaAs), indium phosphide (InP), or gallium nitride (GaN).

[0015] This invention also provides a method for preparing a metasurface structure as described in any of the above embodiments, the method comprising:

[0016] Determine the total phase of the metasurface structure

[0017] According to the total phase Determine the phase value required at each location on the surface U1 of the substrate layer.

[0018] According to the phase value Determine the etching method for each location;

[0019] Etching is performed at each location according to the etching method to obtain a metasurface structure.

[0020] In the above scheme, the step of basing the phase value The etching method for each location is determined specifically by: based on the phase value. The etching depth formula determines the required etching depth at each location, or the structure at each location can be modified to adjust to the desired phase value.

[0021] This invention also provides a laser array, including a substrate layer, a plurality of light-emitting holes disposed on the substrate layer, and a metasurface structure as described in any of the above embodiments disposed on each light-emitting hole.

[0022] This invention also provides an optical imaging chip, including a laser array as described in the above embodiments.

[0023] Compared with existing technologies, this invention designs metasurface structures directly on the substrate material of VCSEL laser arrays, thereby achieving phase compensation for each laser in the laser array and holographic phase design for the desired projection pattern. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and, together with their descriptions, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0025] Figure 1 This is a schematic diagram of a metasurface structure provided in Embodiment 1 of the present invention;

[0026] Figure 2 This is a flowchart illustrating how the phase value of a holographic phase metasurface structure in a metasurface structure is generated using the Gerchberg-Saxton algorithm, as provided in Embodiment 1 of the present invention.

[0027] Figure 3 This is a flowchart illustrating how the phase value of a holographic phase metasurface structure is generated using a gradient descent algorithm in Embodiment 1 of the present invention.

[0028] Figure 4 This is a flowchart of a method for preparing a metasurface structure according to Embodiment 2 of the present invention;

[0029] Figure 5 This is a schematic diagram of the structure prepared by etching different depths on a substrate material in a method for preparing a metasurface structure according to Embodiment 2 of the present invention.

[0030] Figure 6 This is a schematic diagram of the structure of the metasurface structure preparation method provided in Embodiment 2 of the present invention, which involves etching different shapes (radius, length and width) on a substrate material to prepare the desired structure.

[0031] Figure 7 This is a schematic diagram of the structure of the metasurface structure preparation method provided in Embodiment 2 of the present invention, in which other materials are first deposited and then photolithography is used to prepare the desired structure;

[0032] Figure 8 This is a schematic diagram of the structure of a laser array provided in Embodiment 3 of the present invention;

[0033] Figure 9 This is a schematic diagram of the structure of a back-emitting optical imaging chip provided in Embodiment 4 of the present invention;

[0034] Figure 10 This is a schematic diagram of the phase values ​​of a back-emitting optical imaging chip provided in Embodiment 4 of the present invention;

[0035] Figure 11 This is a schematic diagram of far-field imaging of a back-emitting optical imaging chip provided in Embodiment 4 of the present invention;

[0036] Figure 12 for Figure 11 A schematic diagram of the x-direction distribution in structured light imaging;

[0037] Figure 13 for Figure 11 A schematic diagram of the y-direction distribution in structured light imaging;

[0038] Figure 14 This is a schematic diagram of a far-field imaging Tai Chi pattern provided in Embodiment 4 of the present invention for a back-emitting optical imaging chip. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0041] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0042] Embodiment 1 of the present invention provides a metasurface structure, such as Figure 1 As shown, the structure is disposed on the substrate layer of the VCSEL laser array and includes a phase-compensated metasurface structure and a holographic phase metasurface structure.

[0043] The phase-compensating metasurface structure is used to compensate for the spherical wavefront of the laser array reaching the substrate surface; the holographic phase metasurface structure is used to generate far-field spot patterns.

[0044] The phase-compensating metasurface structure and the holographic phase metasurface structure are a unified whole, and the phase compensation is... Holographic phase is The two values ​​need to be added together to get the result.

[0045] The metasurface structure can achieve phase changes in the range of -π to +π.

[0046] After determining the phase of all points, the phase value corresponding to each point is achieved by modifying the metasurface structure. In this embodiment, the phase value of the point is achieved by modifying the etching depth.

[0047] The phase value of the phase-compensating metasurface structure satisfies the expression k(x) 2 +y 2 ) / (2R(z)), where λ is the wavenumber of the laser emitted by the laser array on the substrate, n1 is the refractive index of the substrate material, λ is the laser wavelength, R(z) is the radius of curvature of the laser emitted by the laser array when it reaches the substrate surface, and z is the thickness of the substrate.

[0048] In this embodiment, each phase-compensated metasurface structure The size is approximately 20 μm, determined by the beam width when the laser propagates to the surface U1 of the substrate.

[0049] The phase value of the holographic phase metasurface structure is generated using the Gerchberg-Saxton algorithm.

[0050] Specifically, such as Figure 2 As shown, the phase value of the holographic phase metasurface structure is generated using the Gerchberg-Saxton algorithm, which is achieved through the following steps:

[0051] S1: Set the number of iterations and the error threshold, and initialize the number of iterations and the error;

[0052] S2: Determine the target far-field pattern (Target) and the near-field light source (Source);

[0053] S3: Randomly initialize the far-field phase Target = Target * exp(i * randomPhase);

[0054] S4: Calculate the near-field distribution A = IFT(Target) using the inverse Fourier transform;

[0055] S5: If the error between the far-field distribution C and the far-field target pattern Target is less than the threshold condition, or the number of iterations has exceeded the set number of iterations, then proceed to S7; otherwise, proceed to step S6.

[0056] S6: Multiply the extracted near-field distribution phase (A) with the near-field light source amplitude (Source) to obtain the updated near-field distribution B; determine the far-field distribution C using the updated near-field distribution B; determine the error between the far-field distribution C and the far-field target pattern (Target); then, multiply the extracted far-field distribution phase (C) with the target amplitude (Target) to obtain the updated far-field distribution D; process the far-field distribution D using inverse Fourier transform to obtain the near-field distribution A; then return to S5.

[0057] S7: Extract the holographic phase Phase(A) from the near-field distribution A.

[0058] Optionally, the phase value of the holographic phase metasurface structure is generated using a gradient descent algorithm.

[0059] Specifically, such as Figure 3 As shown, the full gradient descent algorithm is generated through the following steps:

[0060] S1: Set the number of iterations and the error threshold for the loss function, and initialize the number of iterations and the error threshold.

[0061] S1: Determine the target far-field pattern (Target) and the near-field light source (Source);

[0062] S2: Randomly initialize the far-field phase Target = Target * exp(i * randomPhase);

[0063] S3: Calculate the near-field distribution A = IFT(Target) using inverse Fourier transform;

[0064] S4: Obtain the initial holographic phase theta = Phase(A);

[0065] S5: If the loss function Error of the far-field distribution C and the far-field target pattern Target is less than the threshold condition, or the number of iterations has exceeded the set number of iterations, then proceed to S7; otherwise, proceed to step S6.

[0066] S6: Multiply the holographic phase theta by the near-field source amplitude Amplitude (Source) to obtain the updated near-field distribution B; determine the far-field distribution C using the updated near-field distribution B; determine the loss function Error between the far-field distribution C and the far-field target phase Target, and determine the gradient Δtheta = θError / θtheta using the loss function Error; update the holographic phase theta = theta - η * Δtheta with a step size η; then return to S5.

[0067] S7: Extract the holographic phase theta.

[0068] Optionally, the phase value of the holographic phase metasurface structure can also be determined using various variations of the gradient descent algorithm, such as stochastic gradient descent, Newton's method, etc.; it can also be determined using a genetic algorithm; or by reverse design using FDTD software.

[0069] The dimensions of the phase-compensated metasurface structure are determined based on the beam width when the laser propagates to the surface U1 of the substrate.

[0070] Specifically, the distribution of the laser light emitted by a laser generally satisfies the formula Among them, the beam width For focal depth, Where n is the wavenumber of the laser in the substrate material, W0 is the laser beam waist radius, n1 is the refractive index of the substrate material, and z substrate λ represents the substrate thickness, and λ represents the laser wavelength.

[0071] In this embodiment, W0 = 3µm, n1 = 3.552, z substrate =150um, λ=940nm. Based on this formula, the intensity distribution of the laser propagating to the substrate surface U1 is calculated. It can be confirmed that the beam width is about 20um when the intensity drops to the peak value of 0.0001. Therefore, setting the size of the phase-compensated metasurface structure to 20um can reasonably cover the laser emitted from the entire light-emitting aperture.

[0072] The size of the holographic phase metasurface structure is matched to the size of the VCSEL laser array.

[0073] In this embodiment, a holographic phase metasurface structure It measures 650um*650um and covers the entire VCSEL laser array.

[0074] The substrate layer is made of gallium arsenide (GaAs), indium phosphide (InP), or gallium nitride (GaN).

[0075] In some embodiments, the substrate is made of gallium arsenide (GaAs) with a thickness of 150 μm and a refractive index n1 of 3.552.

[0076] It should be noted that the thickness of the substrate material can be achieved by means including but not limited to grinding, and the materials include but are not limited to gallium arsenide (GaAs), indium phosphide (InP), or gallium nitride (GaN).

[0077] A laser beam with wavelength λ emitted from the active region travels at a wavenumber in a substrate material with a refractive index of n1. The beam propagates at a divergence angle of θ0. When it propagates to the surface U1 of the substrate layer, its beam width will be broadened to a certain size.

[0078] In this embodiment, the beam width is approximately 20 μm (the range where the intensity drops to the peak value of 0.0001).

[0079] It should be noted that the beam width reaching the substrate surface U1 is affected by the beam waist radius W0 and the substrate thickness z. substrate The beam width is influenced by factors such as the refractive index n1 of the substrate material. In other embodiments, the beam width can be other values ​​that can be controlled and changed as needed.

[0080] Example 2 of this invention provides a method for preparing a metasurface structure, such as... Figure 4 As shown, the method includes:

[0081] Step 201: Determine the total phase of the metasurface structure

[0082] Specifically, the total phase value is

[0083] Step 202: Based on the total phase Determine the phase value required at each location on the surface U1 of the substrate layer.

[0084] Step 203: Based on the phase value Determine the etching method for each location;

[0085] Specifically, in some embodiments, such as Figure 5 As shown, based on the phase value The etching depth formula determines the etching depth required at each location; based on the etching depth formula s=λ / [2(n1-1)], the etching depth required at each location is confirmed.

[0086] In some embodiments, such as Figure 6 As shown, the phase value can also be adjusted to the required value by modifying the structure of each position (such as radius, length, width, etc.) based on the phase value of each position (each point).

[0087] In some embodiments, such as Figure 7 As shown, alternatively, other materials, such as silicon nitride (Si3N4), silicon (Si), or silicon dioxide (SiO2), can be deposited on the substrate first. Then, based on the phase value at each location (each point), the structure at each location (such as radius, length, and width) can be modified to achieve the desired phase value.

[0088] Step 204: Etch according to the etching method at each location to obtain a metasurface structure.

[0089] Specifically, in some embodiments, etching is performed according to the required etching depth at each location to obtain a metasurface structure; in some embodiments, etching can also be performed on the substrate layer according to the required structure (such as radius, length and width) at each location to obtain a metasurface structure.

[0090] In some embodiments, other materials may be deposited on the substrate first, and then etched according to the required structure (such as radius, length and width) at each location to obtain a metasurface structure.

[0091] Embodiment 3 of the present invention provides a laser array, such as Figure 8 As shown, it includes a substrate layer, on which a plurality of light-emitting holes are disposed, and on each light-emitting hole a metasurface structure is disposed.

[0092] The metasurface structures include phase-compensated metasurface structures and holographic phase metasurface structures;

[0093] The phase-compensating metasurface structure is used to compensate for the spherical wavefront of the laser array reaching the substrate surface; the holographic phase metasurface structure is used to generate far-field spot patterns.

[0094] The metasurface structure can achieve phase changes in the range of -π to +π by changing its shape.

[0095] The phase value of the phase-compensating metasurface structure satisfies the expression k(x) 2 +y 2 ) / (2R(z)), where λ is the wavenumber of the laser emitted by the laser array on the substrate, n1 is the refractive index of the substrate material, λ is the laser wavelength, R(z) is the radius of curvature of the laser emitted by the laser array when it reaches the substrate surface, and z is the thickness of the substrate.

[0096] In this embodiment, each phase-compensated metasurface structure The size is approximately 20 μm, determined by the beam width when the laser propagates to the surface U1 of the substrate.

[0097] The phase value of the holographic phase metasurface structure is generated using the Gerchberg-Saxton algorithm.

[0098] The dimensions of the phase-compensated metasurface structure are determined based on the beam width when the laser propagates to the surface U1 of the substrate.

[0099] The size of the holographic phase metasurface structure is matched to the size of the VCSEL laser array.

[0100] In this embodiment, a holographic phase metasurface structure It measures 650um*650um and covers the entire VCSEL laser array.

[0101] The substrate is made of gallium arsenide (GaAs) with a thickness of 150 μm and a refractive index n1 of 3.552.

[0102] It should be noted that the thickness of the substrate material can be achieved by means including but not limited to grinding, and the materials include but are not limited to gallium arsenide (GaAs).

[0103] A laser beam with wavelength λ emitted from the active region travels at a wavenumber in a substrate material with a refractive index of n1. The beam propagates at a divergence angle of θ0. When it propagates to the surface U1 of the substrate layer, its beam width will be broadened to a certain size.

[0104] In this embodiment, the beam width is approximately 20 μm (the range where the intensity drops to the peak value of 0.0001).

[0105] It should be noted that the beam width reaching the substrate surface U1 is affected by the beam waist radius W0 and the substrate thickness z. substrate The beam width is influenced by factors such as the refractive index n1 of the substrate material. In other embodiments, the beam width can be other values ​​that can be controlled and changed as needed.

[0106] This invention enables the direct realization of a metasurface structure for structured light generation or imaging on the surface U1 of a VCSEL laser array substrate, comprising a phase-compensated metasurface structure for each laser in the laser array. Holographic phase metasurface structure designed for the desired projection pattern It eliminates the need for alignment of external components, reduces the overall size, and eliminates the need for high-temperature bonding processes to add structured light generation or imaging devices to the VCSEL array.

[0107] like Figure 8 As shown, this is a top view, i.e., an xy-plane diagram, taken from the direction of the substrate, where the intensity has been normalized.

[0108] Optionally, it includes 332 emission apertures confined by an oxide layer, representing a total of 332 lasers arranged in an alternating odd-even row configuration, with an overall size ranging from 650µm to 650µm. The laser wavelength λ emitted from the active region of the laser is 940nm, and its beam width is approximately 20µm when it reaches the substrate surface.

[0109] It should be noted that the number of lasers in this embodiment is 332, arranged in an alternating pattern of odd and even rows, but this is not a limitation of this disclosure.

[0110] In other embodiments, other numbers of lasers may be used, and / or the arrangement may be a regular arrangement of m*1, n*1, and m*n (where m is the number of lasers in the x-direction and n is the number of lasers in the y-direction), or a random, irregular arrangement. Similarly, the operating wavelength of the lasers may also be other wavelengths.

[0111] After being modulated by the metasurface structure on the U1 plane, the laser enters the n2 space to propagate. The laser propagates a distance d in the n2 space and will present the desired structured light or pattern on the far-field imaging surface U2.

[0112] In this embodiment, n2 space is free space, i.e., n2 = 1, the propagation distance d = 0.65m, the laser is modulated by the metasurface structure on the substrate surface U1, and then propagates in free space n2 for a distance d = 0.65m, and finally presents a structured light spot with a field of view of 15°*43° on the far-field imaging surface U2.

[0113] It should be noted that the structured light or pattern presented on the far-field imaging plane U2 is the sum of the effects of all lasers in the VCSEL laser array.

[0114] Embodiment 4 of the present invention provides a back-emitting optical imaging chip, such as Figure 9 As shown, it includes a VCSEL laser array, and a metasurface structure is formed on the substrate layer of the VCSEL laser array.

[0115] By monolithically integrating the metasurface structure and VCSEL laser array in a back-emitting manner, the desired pattern can be directly projected into the far field in a more compact manner. Compared with existing technologies, this eliminates the alignment process of external devices, reduces the overall size, and eliminates the need for high-temperature bonding processes to add structured light generation or imaging devices to the VCSEL array. Furthermore, it provides an accurate phase compensation formula and maintains excellent far-field brightness and uniformity compared with existing technologies.

[0116] The metasurface structures include phase-compensated metasurface structures and holographic phase metasurface structures;

[0117] The phase-compensating metasurface structure is used to compensate for the spherical wavefront of the laser array reaching the substrate surface; the holographic phase metasurface structure is used to generate far-field spot patterns.

[0118] The metasurface structure can achieve phase changes in the range of -π to +π by changing its shape.

[0119] The phase value of the phase-compensating metasurface structure satisfies the expression k(x) 2 +y 2 ) / (2R(z)), where λ is the wavenumber of the laser emitted by the laser array on the substrate, n1 is the refractive index of the substrate material, λ is the laser wavelength, R(z) is the radius of curvature of the laser emitted by the laser array when it reaches the substrate surface, and z is the thickness of the substrate.

[0120] In this embodiment, each phase-compensated metasurface structure The size is approximately 20 μm, determined by the beam width when the laser propagates to the surface U1 of the substrate.

[0121] The phase value of the holographic phase metasurface structure is generated using the Gerchberg-Saxton algorithm.

[0122] The dimensions of the phase-compensated metasurface structure are determined based on the beam width when the laser propagates to the surface U1 of the substrate.

[0123] The size of the holographic phase metasurface structure is matched to the size of the VCSEL laser array.

[0124] In this embodiment, a holographic phase metasurface structure It measures 650um*650um and covers the entire VCSEL laser array.

[0125] The substrate is made of gallium arsenide (GaAs) with a thickness of 150 μm and a refractive index n1 of 3.552.

[0126] It should be noted that the thickness of the substrate material can be achieved by means including but not limited to grinding, and the materials include but are not limited to gallium arsenide (GaAs).

[0127] A laser beam with wavelength λ emitted from the active region travels at a wavenumber in a substrate material with a refractive index of n1. The beam propagates at a divergence angle of θ0. When it propagates to the surface U1 of the substrate layer, its beam width will be broadened to a certain size.

[0128] In this embodiment, the beam width is approximately 20 μm (the range where the intensity drops to the peak value of 0.0001).

[0129] It should be noted that the beam width reaching the substrate surface U1 is affected by the beam waist radius W0 and the substrate thickness z. substrate The beam width is influenced by factors such as the refractive index n1 of the substrate material. In other embodiments, the beam width can be other values ​​that can be controlled and changed as needed.

[0130] This invention enables the direct realization of a metasurface structure for structured light generation or imaging on the surface U1 of a VCSEL laser array substrate, comprising a phase-compensated metasurface structure for each laser in the laser array. Holographic phase metasurface structure designed for the desired projection pattern It eliminates the need for alignment of external components, reduces the overall size, and eliminates the need for high-temperature bonding processes to add structured light generation or imaging devices to the VCSEL array.

[0131] like Figure 8 As shown, this is a top view, i.e., an xy-plane diagram, taken from the direction of the substrate, where the intensity has been normalized.

[0132] Optionally, it includes 332 emission apertures confined by an oxide layer, representing a total of 332 lasers arranged in an alternating odd-even row configuration, with an overall size ranging from 650µm to 650µm. The laser wavelength λ emitted from the active region of the laser is 940nm, and its beam width is approximately 20µm when it reaches the substrate surface.

[0133] It should be noted that the number of lasers in this embodiment is 332, arranged in an alternating pattern of odd and even rows, but this is not a limitation of this disclosure.

[0134] In other embodiments, other numbers of lasers may be used, and / or the arrangement may be a regular arrangement of m*1, n*1, and m*n (where m is the number of lasers in the x-direction and n is the number of lasers in the y-direction), or a random, irregular arrangement. Similarly, the operating wavelength of the lasers may also be other wavelengths.

[0135] After being modulated by the metasurface structure on the U1 plane, the laser enters the n2 space to propagate. The laser propagates a distance d in the n2 space and will present the desired structured light or pattern on the far-field imaging surface U2.

[0136] In this embodiment, n2 space is free space, i.e., n2 = 1, the propagation distance d = 0.65m, the laser is modulated by the metasurface structure on the substrate surface U1, and then propagates in free space n2 for a distance d = 0.65m, and finally presents a structured light spot with a field of view of 15°*43° on the far-field imaging surface U2.

[0137] It should be noted that the structured light or pattern presented on the far-field imaging plane U2 is the sum of the effects of all lasers in the VCSEL laser array.

[0138] like Figure 9 As shown, it is displayed as a two-dimensional planar diagram in the yz direction, but the actual structure is a three-dimensional structure in the xyz direction.

[0139] First, let's explain the variables in the diagram:

[0140] U0 is the active region (beam waist) plane of the VCSEL laser array, W0 is the VCSEL beam waist radius, θ0 is the VCSEL divergence angle, n1 is the refractive index of the substrate material, and z substrate U1 is the substrate thickness, and U2 is the surface area of ​​the VCSEL laser array substrate. For phase compensation metasurface structures for each laser in a laser array, The holographic phase metasurface structure designed for the desired projection pattern is defined as follows: U2 is the far-field imaging surface, n2 is the refractive index of the propagation space before the laser reaches the far field, and d is the propagation distance of the laser before reaching the far field.

[0141] To better illustrate the structure and operation of the optical imaging chip provided by this invention:

[0142] Wherein, U0 is the active region (waist) plane of the VCSEL array, with n emission apertures constrained by the oxide layer in the y direction, and similarly, m emission apertures constrained by the oxide layer in the x direction (not shown in the figure). Once the size of the emission apertures is constrained, the waist radius W0 is also determined; in this embodiment, W0 is 3 μm.

[0143] like Figure 10 As shown, the substrate surface U1 contains (Corresponding position for each laser) and (Covering the entire VCSEL laser array). The overall phase value of the metasurface is... The value ranges from -π to +π.

[0144] like Figure 11 As shown, this embodiment uses the Gerchberg-Saxton iterative algorithm to calculate the required... Then according to Modify the overall phase value of the metasurface. The laser beam is modulated by the metasurface structure on the substrate surface U1, then propagates a distance d = 0.65m in free space n2, and finally appears as a structured light spot with a field of view of 15°*43° on the far-field imaging surface U2.

[0145] like Figure 12 and 13 As shown, it demonstrates Figure 11The intensity distribution of far-field structured light imaging in the x=0 and y=0 directions, where the intensity has been normalized.

[0146] like Figure 14 As shown, this embodiment uses the Gerchberg-Saxton iterative algorithm to calculate the new... Then according to Modify the overall phase value of the metasurface.

[0147] The laser is modulated by the metasurface structure on the substrate surface U1, then propagates a distance d = 0.65m in free space n2, and finally presents the designed Tai Chi pattern on the far-field imaging surface U2.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A metasurface structure, characterized in that, The structure is disposed on the substrate of the VCSEL laser array and includes a phase-compensated metasurface structure and a holographic phase metasurface structure. The phase-compensating metasurface structure is used to compensate for the spherical wavefront of the laser array reaching the substrate surface; the holographic phase metasurface structure is used to generate far-field spot patterns. The phase value of the phase-compensating metasurface structure satisfies the expression k(x) 2 +y 2 ) / (2R(z)), where λ is the wavenumber of the laser emitted by the laser array on the substrate, n1 is the refractive index of the substrate material, λ is the laser wavelength, R(z) is the radius of curvature of the laser emitted by the laser array when it reaches the substrate surface, and z is the thickness of the substrate.

2. The metasurface structure according to claim 1, characterized in that, The phase value of the holographic phase metasurface structure is generated by the Gerchberg-Saxton algorithm or the gradient descent algorithm.

3. The metasurface structure according to claim 2, characterized in that, The dimensions of the phase-compensated metasurface structure are determined based on the beam width when the laser propagates to the surface U1 of the substrate.

4. The metasurface structure according to claim 3, characterized in that, The size of the holographic phase metasurface structure is matched to the size of the VCSEL laser array.

5. The metasurface structure according to claim 4, characterized in that, The substrate layer is made of gallium arsenide (GaAs), indium phosphide (InP), or gallium nitride (GaN).

6. A method for preparing a metasurface structure as described in any one of claims 1-5, characterized in that, The method includes: Determine the total phase of the metasurface structure According to the total phase Determine the phase value required at each location on the surface U1 of the substrate layer. According to the phase value Determine the etching method for each location; Etching is performed at each location according to the etching method to obtain a metasurface structure.

7. The method for preparing the metasurface structure according to claim 6, characterized in that, According to the phase value The etching method for each location is determined specifically by: based on the phase value. The etching depth formula determines the required etching depth at each location, or the structure at each location can be modified to adjust to the desired phase value.

8. A laser array, characterized in that, It includes a substrate layer, on which a plurality of light-emitting holes are disposed, and on each light-emitting hole a metasurface structure as described in any one of claims 1-5 is disposed.

9. An optical imaging chip, characterized in that, Includes the laser array as described in claim 8.

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