Design method of on-chip metasurface and full-color holographic display system

Abstract

The invention belongs to the field of integrated photonics, and discloses a design method of an on-chip metasurface and a full-color holographic display system.The on-chip metasurface of a double-atom structure is designed at first, linear polarized light in one polarization direction is extracted through each kind of nano bricks to conduct respective independent imaging display, and then the full-color holographic display system is obtained; in the process of designing the nano brick with the on-chip super-structure surface, through dispersion compensation optimization, red, green and blue three-primary-color light is diffracted and then overlaid in a far field for high-quality full-color display imaging; after the on-chip metasurface of the structure, a light source, a polarizer and a polarization analyzer form a display system, display images can be rapidly switched, high-precision phase regulation and control of a red channel, a green channel and a blue channel are achieved at the same time in the visible light range, and high-fidelity reconstruction of full-color images is supported; and meanwhile, the system also has the advantages of high integration, miniaturization, high image fidelity and the like, and is suitable for next-generation on-chip AR display equipment.

Description

Technical Field

[0001] The present invention belongs to the field of integrated photonics and relates to a metasurface imaging technology, and in particular to a design method of an on-chip metasurface and a full-color holographic display system. Background Art

[0002] In recent years, on-chip metasurfaces have become a research hotspot for the next generation of nano-optical display and control devices due to their extraordinary control capabilities over light fields and excellent on-chip integration potential. In particular, in the field of holographic displays, on-chip metasurfaces, with their subwavelength-scale precision structural design, enable highly flexible control of light wavefront, polarization state, and phase information, laying the foundation for high-resolution, highly compact optical displays. However, existing metaholographic devices still have limitations in terms of display realism, color reproduction, and dynamic interactivity, making it difficult to meet the comprehensive requirements of augmented reality (AR) displays for high fidelity, full color, and miniaturization.

[0003] To achieve more realistic and vivid image reconstruction, full-color holographic display has become one of the important research directions. However, due to the difficulty of dispersion control and the complexity of multi-wavelength holographic encoding, traditional optical equipment systems often suffer from large system size, severe color crosstalk, and complex manufacturing, which limits their practical application in portable AR terminals.

[0004] On-chip metasurfaces, integrated on a chip, offer a novel solution to these challenges. Through precise nanostructure design, on-chip metasurfaces not only enable simultaneous manipulation of multi-wavelength light field information, but also boast exceptionally compact design, system scalability, and the ability to avoid zero-order background interference, making them an ideal platform for miniaturized, low-power AR holographic displays. Furthermore, leveraging high-refractive-index materials and advanced nanofabrication techniques, on-chip metasurfaces can encode multicolor information within a single layer, enabling the reconstruction of rich, crisp holograms.

[0005] While some on-chip holographic display solutions have been demonstrated, achieving both high resolution and dynamic interactivity, particularly effectively controlling chromatic aberration and image stability in full-color display, remains a key challenge in this field. This paper, based on an on-chip metasurface, proposes a full-color holographic display solution with a novel structure and excellent optical performance, which can be integrated into augmented reality systems. This approach aims to promote the practical implementation and application of holographic display technology in the AR field. Summary of the Invention

[0006] In response to the shortcomings of existing full-color holographic display systems in color reproduction, integration, and augmented reality (AR) adaptability, the present invention provides a design method for an on-chip metasurface. The on-chip metasurface obtained by the design method of the present invention can quickly switch between monochrome imaging and full-color high-quality imaging.

[0007] In order to solve the above problems, the technical solutions adopted by the present invention are as follows: In a first aspect, the present invention provides a method for designing an on-chip metasurface for holographic full-color display switching, comprising the following steps: According to the number of images to be switched, the number of nanobrick types in the nanostructure unit of the on-chip metasurface is selected, and each nanobrick extracts linear polarization of a polarization state to independently image an image; Select the polarization direction of the linear polarization of each polarization state; The rotation angle of each nanobrick is determined according to the polarization direction of the linear polarized light; According to the principle of three primary colors, the incident light is divided into three primary colors: red, green and blue. Perform three-color light diffraction compensation on each image distribution that needs to be displayed to obtain the compensated target light intensity distribution; The far-field target phase distribution of each image is obtained by using a phase recovery algorithm based on the target light intensity distribution; According to the far-field target phase distribution, the circuitous phase principle is used to calculate the position of each nanobrick in each nanostructure unit to complete the design of the on-chip metasurface.

[0008] Furthermore, the nanostructure unit includes nanobricks of two sizes, the long axes of the first nanobrick and the second nanobrick are perpendicular to each other, and linear polarized light in two directions is extracted respectively for display imaging.

[0009] Furthermore, the nanobrick is a nanobrick with birefringence properties.

[0010] Furthermore, the on-chip metasurface includes a waveguide layer and nanostructure units located on the waveguide layer, and each nanostructure unit has a plurality of nanobricks.

[0011] Furthermore, performing three-color light diffraction compensation on each image distribution to be displayed includes the following steps: The wavelengths of the three primary colors of red, green, and blue are used as the working wavelengths, and the diffraction angle at each working wavelength is calculated based on the diffraction principle; Select a target diffraction angle and calculate the phase gradients at three working wavelengths based on the target diffraction angle; Taking one of the operating wavelengths as a reference wavelength, the pixel coordinates in the far-field image at the reference wavelength are calculated; Calculate the pixel shift for the other two operating wavelengths; The target image is decomposed into images under the red, green and blue channels, and the images under the red, green and blue channels and their corresponding pixel coordinates are combined into a picture to obtain the light intensity distribution of the combined image as the target light intensity distribution after compensation.

[0012] Furthermore, the far-field phase distribution of each image is obtained by a phase recovery algorithm according to the target light intensity distribution, including the following steps: Initialize the far-field phase distribution, and combine the initialized far-field phase distribution with the target light intensity distribution to obtain the initial complex amplitude of the far field; Perform inverse Fourier transform on the far-field complex amplitude to obtain the near-field complex amplitude, set the amplitude of the near-field complex amplitude to a constant, retain its phase, and obtain a new near-field complex amplitude; According to the new near-field complex amplitude, a new far-field complex amplitude is obtained by Fourier transform; Replace the amplitude in the far-field complex amplitude with the target light intensity distribution, keep the far-field phase unchanged, and update the far-field complex amplitude; The calculation is repeated until convergence; the far-field phase distribution of the last iteration is used as the far-field target phase distribution.

[0013] Furthermore, the method for calculating the position of each nanobrick in each nanostructure unit using the circuitous phase principle is as follows: Fold the far-field target phase distribution to Range: The folded phase distribution is mapped to the displacement of nanobricks on the on-chip metasurface.

[0014] Furthermore, in the calculation process using the detour phase principle, only the displacement of the incident direction of the linearly polarized light is modulated.

[0015] Furthermore, the on-chip metasurface includes a waveguide layer and periodically arranged nanostructure units arranged on the waveguide layer, and the nanostructure units include a plurality of nanobricks.

[0016] In a second aspect, the present invention provides a full-color holographic display system based on an on-chip integrated metasurface with switchable images, comprising: A light source for emitting three primary colors of light: red, green, and blue; The on-chip metasurface is designed using the above-mentioned design method; A polarizer, disposed between the light source and the on-chip metasurface, for polarizing the red, green, and blue primary colors of light and coupling them into the waveguide of the on-chip metasurface; and The polarizer is arranged on the observation direction side of the on-chip metasurface and is used to select the image to be observed.

[0017] This invention utilizes a single-layer metasurface and precisely designed diatomic nanoantenna arrays to achieve control of the three primary colors of light (RGB) and two orthogonal polarization states. Subwavelength-scale nanostructures are fabricated on an on-chip silicon dioxide substrate and silicon nitride waveguides through processes such as electron beam lithography and plasma etching, forming an on-chip metasurface capable of multi-band, high-efficiency light field control.

[0018] The on-chip metasurface structure features a subwavelength periodic arrangement, enabling simultaneous manipulation of the phase information of red, green, and blue wavelengths in orthogonal polarization states, thereby achieving high-fidelity color holographic images within a single layer. Compared to traditional full-color on-chip metasurface structures based on multi-layer stacking or multiple exposures, this solution offers the advantages of simplified manufacturing, minimal alignment errors, and high integration.

[0019] The metasurface structure of this invention can be integrated into transparent substrates or waveguide-coupled optical systems to construct a new lightweight, transparent AR display module. Its micro-nanostructure does not affect the human eye's perspective observation of the real environment, while reconstructing virtual color images within a specific viewing angle, achieving a naturally integrated augmented reality visual experience.

[0020] Due to the highly compact and adaptable structure employed, the system is widely applicable to terminal devices such as head-mounted displays (HMDs) and AR glasses. Further control of the incident angle and polarization state can also enable dynamic image display and interactive visual feedback, meeting the performance requirements of holographic AR displays in complex scenarios.

[0021] The invention solves the key problems of traditional full-color holographic display systems, such as large size, unrealistic colors, and difficulty in integration with AR devices, and provides a new technical solution for building the next generation of full-color, lightweight, on-chip integrated augmented reality display terminals.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. The on-chip metasurface structure proposed in this paper achieves high-precision phase control of the red, green, and blue color channels simultaneously within the visible light range, enabling high-fidelity reconstruction of full-color images. Compared to traditional single-band or low-color separation precision holographic devices, this invention overcomes the limitations of dispersion control and phase consistency, providing an effective solution for generating high-quality full-color holographic images.

[0023] 2. By incorporating polarization-sensitive nanostructures into an on-chip metasurface structure, this invention enables the device to reconstruct distinct holographic patterns under incident light of varying polarization states (e.g., linear polarization and circular polarization). This polarization multiplexing mechanism not only significantly improves information throughput and image encoding density but also enables the realization of multifunctional information displays and encrypted holograms. Compared to traditional single-polarization channel holographic devices, this polarization multiplexing strategy significantly expands the functional scope of holographic displays and is suitable for augmented reality systems with multi-level information interaction.

[0024] 3. The on-chip metasurface design employed in this invention boasts exceptionally compact structure and system compatibility. The associated devices can be directly integrated onto silicon or nitride substrates and are highly compatible with established microelectronics manufacturing processes such as CMOS, facilitating collaborative packaging with other optoelectronic functional modules (such as waveguides, modulators, and light sources). Compared to traditional bulk optical systems, this invention significantly reduces the size and power consumption of display systems, making it suitable for applications such as wearable devices and AR glasses that require lightweight and low power consumption. It represents an ideal technical path for the next generation of miniaturized, low-cost, mass-produced augmented reality display solutions.

[0025] 4. The present invention can achieve image switching by changing the polarization direction of the analyzer, has the function of rapid imaging switching, and expands the application scenarios of holographic imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a flow chart of the design method of the on-chip metasurface for holographic full-color display switching in the present invention.

[0028] Figure 2 This is a schematic diagram of the on-chip metasurface structure designed in Example 1 of the present invention.

[0029] Figure 3 Schematic diagram of the diatomic structure on the on-chip metasurface in Example 1 of the present invention.

[0030] Figure 4 This is a schematic diagram of phase control of a diatomic structure using a circuitous phase in Example 1 of the present invention.

[0031] Figure 5 Schematic diagram of the polarization extraction structure and electric field simulation diagram in Example 1 of the present invention.

[0032] Figure 6 Schematic diagram of the polarization multiplexing principle in Example 1 of the present invention.

[0033] Figure 7 Schematic diagram of the full-color image dispersion design in Example 1 of the present invention.

[0034] Figure 8 This is an overall flow chart of the design of holographic image dispersion pre-compensation in Example 1 of the present invention.

[0035] Figure 9 Schematic diagram of the structure of a full-color holographic display system based on on-chip integrated metasurface switchable images in Example 2 of the present invention.

[0036] Figure 10 These are simulation and experimental renderings of the holographic image in Example 2 of the present invention.

[0037] Figure 11 This is an experimental rendering of augmented reality display using the full-color holographic display system in Example 2 of the present invention.

[0038] 100-substrate, 200-waveguide layer, 300-nanostructure unit, 310-first type of nanobrick, 320-second type of nanobrick, 400-incident light, 500-polarizer, 600-light source, 700-analyzer, 800-camera. DETAILED DESCRIPTION

[0039] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0040] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0042] Example 1: Figure 1 As shown, this embodiment provides a design method for an on-chip metasurface for holographic full-color display switching, comprising the following steps: S100, selecting the type and quantity of nanobricks in the nanostructure unit of the on-chip metasurface according to the number of images to be switched, and extracting linear polarization of a polarization state from each nanobrick to independently image an image; S200, selecting the polarization direction of the linear polarization in each polarization state; S300, determining the rotation angle of each nanobrick according to the polarization direction of the linear polarized light; S400, according to the principle of three primary colors, dividing the incident light into three primary colors of red, green, and blue; S500, performing three-color light diffraction compensation on each image distribution to be displayed to obtain a compensated target light intensity distribution; S600, obtaining the far-field target phase distribution of each image by a phase recovery algorithm according to the target light intensity distribution; S700. Based on the far-field target phase distribution, the circuitous phase principle is used to calculate the position of each nanobrick within each nanostructure unit to complete the design of the on-chip metasurface.

[0043] In this embodiment, for the convenience of calculation and explanation, Figure 2 As shown, the on-chip metasurface includes a waveguide layer 200 and periodically arranged nanostructure units 300 on the waveguide layer 200. The nanostructure units 300 include a variety of nanobricks. An XY coordinate system is established with two adjacent vertical working edges of the on-chip metasurface as the X and Y axes respectively. The position of each nanobrick on the waveguide layer 200 is defined as the position of the nanobrick center (or center of mass). In the XY coordinate system, it can be expressed as Each nanobrick is a nanostructure with a roughly rectangular cross-section, with the major axis denoted as L, the minor axis denoted as W, the height denoted as H, and the rotation angle of the nanobrick denoted as the angle with the X-axis. .

[0044] like Figure 2The waveguide layer 200 is prepared on a substrate 100. In the present invention, the substrate 100 can be any substrate material in the prior art, such as a silicon substrate, a silicon-on-insulator (SOI) substrate, a gallium arsenide (GaAs) substrate, an indium phosphide (InP), a sapphire (Al2O3) / quartz (SiO2) substrate, a silicon nitride substrate, a silicon dioxide (SiO2) substrate, etc. Exemplarily, the present invention uses a silicon dioxide substrate. Common materials for the waveguide layer 200 include crystalline silicon (c-Si), silicon nitride (Si3N4), titanium dioxide (TiO2), tantalum oxide (Ta2O5) / hafnium oxide (HfO2), polymers (SU-8, PMMA), silicon phosphide (a-Si), etc. Exemplarily, the waveguide layer 200 of the present invention is silicon nitride.

[0045] Common nanobrick materials are silicon (Si), silicon nitride (Si3N4), titanium dioxide (TiO2), gallium arsenide (GaAs), germanium (Ge), and metal-dielectric mixtures (such as Au / SiO2 core-shell); illustratively, the present invention is amorphous silicon (α-Si).

[0046] Taking the display of two images of badminton and volleyball as an example, the on-chip metasurface design process is explained in detail.

[0047] In S100, in order to switch between the two images of badminton and volleyball, two types of nanobricks are required to extract polarized light in two polarization directions for independent imaging; for example, Figure 2 As shown, each nanostructure unit 300 has two nanobricks, namely a first nanobrick 310 and a second nanobrick 320, forming a nanostructure unit with a diatomic structure. Figure 5 As shown in a, all the first type nanobricks 310 on the waveguide layer 200 have the same rotation angle, which is denoted as , the rotation angles of all the second type nanobricks 320 are also the same, denoted as ; The period P of the nanostructure unit 300 is 400nm, and all nanobricks have the same size, with a major axis L=120nm, a minor axis W=60nm, and a height H=380nm; the above dimensions and the number of nanobricks in each nanostructure unit 300 are only exemplary and do not mean that only the above values can be used.

[0048] In step S200, since two images of badminton and volleyball need to be displayed, two directions are selected as the polarization directions of the polarized light, namely the first state polarized light parallel to the X-axis and the second state polarized light parallel to the Y-axis. By setting the directions of the two polarization states perpendicularly, the mutual interference of the imaging is minimized to the greatest extent, ensuring high-quality independent imaging in the two polarization states.

[0049] In step S300, the method for determining the rotation angle of the nanobrick is as follows: For incident linearly polarized light, when the incident polarization direction is neither parallel nor perpendicular to the long axis of the nanobrick, it can be decomposed into two components along the long axis (slow axis) and the short axis (fast axis). When the two components are equal in size, the modulation efficiency can be improved. Taking the first type of nanobrick 310 to adjust the first state polarized light as an example, when the angle between the long axis of the first type of nanobrick and the X axis is 45 degrees, the two components along the long axis (slow axis) and the short axis (fast axis) are equal, so the rotation angle of the first type of nanobrick 310 is determined. =45 degrees, the second type of nano brick 320 degrees of rotation =135.

[0050] In step S300, after determining the rotation angle of each nanobrick, the size of the nanobrick is optimized. The specific method is as follows: For the first type of nanobrick 310, fixed angle (e.g. 45 degrees), and then scan the length L and width W of the nanobrick so that at the target wavelength, the two orthogonal polarization components (along the long and short axes) of the reflection produce a specific phase difference (e.g. 0 to 2π) and the amplitude is as high as possible, that is, the phase difference needs to cover 0 to 2π, for example, for the selected working wavelength When the length L of the nanobrick is changed (keeping the width W unchanged), the phase difference (i.e., the phase difference between the slow axis and the fast axis) will change with L. It is necessary to find the L and W parameter ranges in which the phase difference δ changes continuously in the range of 0 to 2π when L is changed, select a value from them, and ensure that the phase difference δ changes continuously in the range of 0 to 2π at all operating wavelengths; for example, for the period P = 400nm, the major axis L = 120nm, the minor axis W = 60nm, and the height H = 380nm for the nanostructure unit 300; since all nanobricks have the same size, there is no need to determine the size of the second nanobrick 320.

[0051] In S500, in order to ensure that the images formed by the three wavelengths of red, green and blue (480nm, 550nm, 645nm) are coherently superimposed in the far field to achieve full-color imaging; therefore, dispersion pre-compensation is required, such as Figure 7 and Figure 8 The specific method is as follows: S510, calculating the diffraction angle at each operating wavelength according to the diffraction angle calculation formula; The formula for calculating the diffraction angle is as follows:

[0052] in, is the diffraction angle, is the equivalent refractive index, which is a constant with the materials of the waveguide layer 200 and the nanobricks; m represents the diffraction order. Considering the incident wavelengths of 480 nm, 550 nm, and 645 nm, the zero-order beam is confined in the waveguide, and the m = -1 order diffraction angle can be expressed as:

[0053]

[0054]

[0055] 、 、 are the diffraction angles of red light, green light, and blue light, respectively. 、 、 are the wavelengths of red, green, and blue light, respectively. 、 、 The phase gradient required for the on-chip metasurface when red light, green light, and blue light are used as the working wavelengths, respectively.

[0056] S520, select the target diffraction angle, calculate the phase gradients at three working wavelengths according to the diffraction angles at three working wavelengths, and select As the target diffraction angle, Can be 、 、 One of the three, or the average of the three;

[0057]

[0058]

[0059] S530: Using one of the operating wavelengths as a reference wavelength, calculate the pixel coordinates in the far-field image at the reference wavelength. ; S540. Calculate the pixel offsets (X-axis offsets) of the other two operating wavelengths, using the green wavelength as a reference. The formula is as follows:

[0060]

[0061] In the above formula, 、 are the pixel coordinate offsets of the far field under red light and blue light respectively; S550. Calculate the pixel coordinates at the other two operating wavelengths based on the pixel offset. The formula is as follows:

[0062]

[0063] 、 are the far-field pixel coordinates respectively.

[0064] S560 , superimposing and combining the images under the red, green, and blue channels and their corresponding pixel coordinates into a single image, and obtaining the light intensity distribution of the combined image as the target light intensity distribution after compensation.

[0065] In S600, the Gerchberg-Saxton (GS) algorithm is used to perform phase recovery calculations to obtain the far-field target phase distribution of each image as follows: S610, initialize far-field phase distribution , and the initial complex amplitude of the far field is obtained ; S620, perform inverse Fourier transform on the far-field complex amplitude to obtain the near-field complex amplitude , the near-field complex amplitude The amplitude is set to a constant (such as 1), and its phase is preserved ( ), and obtain the new near-field complex amplitude ; S630, based on the new near-field complex amplitude The new far-field complex amplitude is obtained by Fourier transform ; S640, the far field complex amplitude The amplitude in is replaced by the target light intensity distribution , preserving the far-field phase unchanged, update the far-field complex amplitude; S650, repeat the calculation steps S620-S640 until convergence (for example, reaching the maximum number of iterations or the error is less than the threshold); the far-field phase distribution of the last iteration As the far-field target phase distribution .

[0066] The error is less than the threshold value, which can be used to obtain a new far-field complex amplitude in step S640. Medium amplitude and target light intensity distribution Is the difference less than the threshold?

[0067] In S700, the method for calculating the position of each nanobrick in each nanostructure unit using the circuitous phase principle is as follows: S710, phase folding processing Since the displacement modulation range is limited to , the target phase needs to be folded to Range:

[0068] represents the phase distribution after folding, and mod represents the phase folding mapping calculation.

[0069] S720, displacement calculation The folded phase is mapped to the displacement according to the far-field target phase distribution calculation formula:

[0070] is the displacement of the nanobrick in the X direction, that is or ; Determine the X-direction displacement of all nanobricks of each nanobrick type using the above formula 、 .

[0071] The on-chip metasurface structure obtained by the above method is as follows Figure 2 As shown, Figure 5 The polarization response principle of the diatomic structure is shown. Each nanostructure unit 300 is composed of two nanobricks with orthogonal orientations, each responding to different linear polarization directions. When the light wave is coupled into the waveguide and propagates through the on-chip metasurface array, the two nanobrick structures extract the two polarization states of light respectively, such as Figure 6 shown. Figure 4 The principle of phase modulation of the diatomic structure is demonstrated. By precisely designing its spatial arrangement and introducing a circuitous phase, independent phase encoding of two orthogonal polarization channels is achieved, thereby reconstructing different holographic patterns under different polarization incidences.

[0072] Example 2: Figure 9As shown, this embodiment provides a full-color holographic display system based on an on-chip integrated metasurface with switchable images. Based on the on-chip metasurface designed in Example 1, it also includes a light source 600 (continuous spectrum laser), a polarizer 500 and an analyzer 700. The polarizer 500 is arranged between the light source and the on-chip metasurface, and is used to polarize the three primary colors of red, green and blue and couple them into the waveguide of the on-chip metasurface; the analyzer 700 is arranged on the observation direction side of the on-chip metasurface (for example, between the metasurface and the camera 800), and is used to select the image to be observed; for example, there are two states of linearly polarized light, the polarization direction of the first linearly polarized light is parallel to the X-axis Parallel, the polarization direction of the second linear polarized light is parallel to the Y axis, when the polarization direction of the analyzer 700 is parallel to the first polarized light, the first image (such as badminton) can be seen through the analyzer 700, and when the analyzer 700 is parallel to the second polarized light, the second image (such as volleyball) can be seen through the analyzer 700; the switching of the displayed image is realized; if the polarizer is set to two, the polarization direction of the first analyzer is parallel to the first polarized light, and the second analyzer is parallel to the second polarized light, the first analyzer and the second analyzer are installed on the two frames of the glasses, after wearing the glasses, the left and right eyes of a person can see different images respectively.

[0073] The simulation results during design and the actual measurement results are as follows Figure 10 As shown, it can be seen that the imaged volleyball and badminton can be switched quickly and have high imaging quality.

[0074] Finally, to demonstrate full-color holographic display with dynamic polarization control, the designed on-chip metasurface was integrated into an on-chip platform for actual experimental measurements. Figure 9 As shown in the figure, a continuous spectrum laser is used as the light source, and three wavelength lasers are emitted simultaneously. After being polarized by a polarizer, they are coupled into the waveguide of the upper metasurface in an end-incident manner. A polarizer is added between the upper metasurface and the camera. The polarizer is rotated to filter light of different polarization states, thereby switching to display different full-color holographic patterns (such as "badminton" and "volleyball" patterns) in real time. These patterns are seamlessly integrated with the real background in actual AR scenes, and the image colors are bright and the contrast is high. Figure 11 As shown, the powerful potential of the present invention in augmented reality display is verified; through this experiment, it can be seen that the present invention basically has no zero-order diffraction light, eliminating the influence of zero-order light on imaging.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A design method for an on-chip metasurface for holographic full-color display switching, characterized in that: The following steps are involved: According to the number of images to be switched, the number of nanobrick types in the nanostructure unit of the on-chip metasurface is selected, and each nanobrick extracts linear polarization of a polarization state to independently image an image; Select the polarization direction of the linear polarization of each polarization state; The rotation angle of each nanobrick is determined according to the polarization direction of the linear polarized light; According to the principle of three primary colors, the incident light is divided into three primary colors: red, green and blue. Perform three-color light diffraction compensation on each image distribution that needs to be displayed to obtain the compensated target light intensity distribution; The far-field target phase distribution of each image is obtained by using a phase recovery algorithm based on the target light intensity distribution; According to the far-field target phase distribution, the circuitous phase principle is used to calculate the position of each nanobrick in each nanostructure unit to complete the design of the on-chip metasurface.

2. The design method of an on-chip metasurface for holographic full-color display switching according to claim 1, characterized in that: The nanostructure unit includes nanobricks of two sizes. The long axes of the first nanobrick and the second nanobrick are perpendicular to each other, and linear polarized light in two directions is extracted respectively for display imaging.

3. The design method of an on-chip metasurface for holographic full-color display switching according to claim 1, characterized in that: The nanobrick is a nanobrick with birefringence.

4. The design method of an on-chip metasurface for holographic full-color display switching according to claim 1, characterized in that: The on-chip metasurface includes a waveguide layer and nanostructure units located on the waveguide layer, and each nanostructure unit has a plurality of nanobricks.

5. The design method of an on-chip metasurface for holographic full-color display switching according to claim 1, characterized in that: Performing three-color light diffraction compensation for each image distribution to be displayed includes the following steps: The wavelengths of the three primary colors of red, green, and blue are used as the working wavelengths, and the diffraction angle at each working wavelength is calculated based on the diffraction principle; Select a target diffraction angle and calculate the phase gradients at three working wavelengths based on the target diffraction angle; Taking one of the operating wavelengths as a reference wavelength, the pixel coordinates in the far-field image at the reference wavelength are calculated; Calculate the pixel shift for the other two operating wavelengths; The target image is decomposed into images under the red, green and blue channels, and the images under the red, green and blue channels and their corresponding pixel coordinates are combined into a picture to obtain the light intensity distribution of the combined image as the target light intensity distribution after compensation.

6. The design method of an on-chip metasurface for holographic full-color display switching according to claim 5, characterized in that: The far-field phase distribution of each image is obtained by a phase recovery algorithm based on the target light intensity distribution, including the following steps: Initialize the far-field phase distribution, and combine the initialized far-field phase distribution with the target light intensity distribution to obtain the initial complex amplitude of the far field; Perform inverse Fourier transform on the far-field complex amplitude to obtain the near-field complex amplitude, set the amplitude of the near-field complex amplitude to a constant, retain its phase, and obtain a new near-field complex amplitude; According to the new near-field complex amplitude, a new far-field complex amplitude is obtained by Fourier transform; Replace the amplitude in the far-field complex amplitude with the target light intensity distribution, keep the far-field phase unchanged, and update the far-field complex amplitude; The calculation is repeated until convergence; the far-field phase distribution of the last iteration is used as the far-field target phase distribution.

7. The design method of an on-chip metasurface for holographic full-color display switching according to claim 5, characterized in that: The method for calculating the position of each nanobrick within each nanostructure unit using the circuitous phase principle is as follows: Fold the far-field target phase distribution to Range: The folded phase distribution is mapped to the displacement of nanobricks on the on-chip metasurface.

8. The design method of an on-chip metasurface for holographic full-color display switching according to claim 1, characterized in that: In the calculation process using the detour phase principle, only the displacement of the incident direction of the linear polarization is modulated.

9. The design method of an on-chip metasurface for holographic full-color display switching according to claim 1, characterized in that: The on-chip metasurface includes a waveguide layer and periodically arranged nanostructure units arranged on the waveguide layer, wherein the nanostructure units include a plurality of nanobricks.

10. A full-color holographic display system based on an on-chip integrated metasurface with switchable images, characterized in that: include: A light source for emitting three primary colors of light: red, green, and blue; An on-chip metasurface designed using the design method according to any one of claims 1 to 9; A polarizer, disposed between the light source and the on-chip metasurface, for polarizing the red, green, and blue primary colors of light and coupling them into the waveguide of the on-chip metasurface; and The polarizer is arranged on the observation direction side of the on-chip metasurface and is used to select the image to be observed.

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