On-chip metasurface and multi-dimensional multiplexing holographic method based on on-chip metasurface

Abstract

The invention belongs to the technical field of micro-nano optics, and discloses an on-chip metasurface and a multi-dimensional multiplexing holographic method based on the on-chip metasurface. Firstly, a unit structure of the on-chip metasurface is constructed, the unit structure comprises a substrate layer, an optical waveguide layer and a nanometer structure layer which are sequentially arranged from bottom to top, and the nanometer structure layer comprises a nanometer brick of a rectangular structure; a plurality of nano bricks with the same size contained in the on-chip metasurface form a nano brick array; and then according to a plurality of set target holographic images, the arrangement of the position and the corner of each nano brick in the nano brick array is obtained by using the combined coding of the circuitous phase and the geometric phase, a final on-chip metasurface is obtained after the arrangement is completed, and the three-dimensional multiplexing holography of the incident angle, the wavelength and the polarization is realized by using the on-chip metasurface. According to the invention, not only is the limitation of incidence in the orthogonal direction overcome, but also the information storage capacity and the information security are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano optical technology, and more specifically, relates to an on-chip metasurface and a multi-dimensional multiplexing holographic method based on the on-chip metasurface. Background Art

[0002] Metasurfaces, a new type of planar optical device composed of precisely designed arrays of metaatoms (e.g., nanobrick arrays), exhibit remarkable capabilities in manipulating electromagnetic waves, enabling precise control of phase, amplitude, frequency, and polarization. These versatile modulation capabilities have promoted the widespread application of metasurfaces in diverse fields, including holographic displays and structured beam generation. Recently, the integration of metasurfaces with optical waveguides (referred to as on-chip metasurfaces) has further enhanced the ability to manipulate in-plane guided waves while significantly improving the compactness and integrability of optical systems. This advancement has enabled a range of on-chip functions such as beam steering, mode conversion, and optical computing. However, most existing research has focused on controlling a single optical dimension, which has limited storage capacity and information security.

[0003] Furthermore, in previous explorations of the multiplexing degrees of freedom enabled by on-chip metasurfaces, key optical parameters such as wavelength, polarization, intensity, and orthogonal illumination directions have been extensively studied. However, despite these advances, the exploitation of the azimuth angle of guided wave incidence as an independent multiplexing dimension for multidimensional encoding remains largely unaddressed. Previous studies on multidimensional optical multiplexing using on-chip metasurfaces have primarily relied on fixed orthogonal incidence directions, with insufficient exploitation of arbitrary in-plane incident angles (i.e., azimuth angles). This limitation stems from the fact that the circuitous phase modulation is initially patterned along orthogonal directions, which makes it challenging to extract meaningful phase profiles when the illumination deviates from these predefined directions.

[0004] In summary, how to overcome the limitation of only orthogonal incidence and improve information storage capacity and information security is a topic of concern and research in this field. Summary of the Invention

[0005] The present invention solves the problem in the prior art that the solution based on the on-chip metasurface relies on a fixed orthogonal incident direction and the storage capacity and information security need to be improved by providing an on-chip metasurface and a multi-dimensional multiplexing holographic method based on the on-chip metasurface.

[0006] The present invention provides a multi-dimensional multiplexing holographic method based on an on-chip metasurface, comprising the following steps: Constructing a unit structure of an on-chip metasurface, the unit structure comprising a substrate layer, an optical waveguide layer, and a nanostructure layer arranged in sequence from bottom to top, the nanostructure layer comprising a nanobrick having a rectangular structure; the on-chip metasurface comprising a plurality of nanobricks of uniform size forming a nanobrick array; According to the set multiple target holographic images, the combined encoding of the circuitous phase and geometric phase is used to obtain the arrangement of the position and rotation angle of each nanobrick in the nanobrick array. After the arrangement is completed, the final on-chip metasurface is obtained, and the on-chip metasurface is used to realize three-dimensional multiplexed holography of incident angle, wavelength and polarization.

[0007] Preferably, incident angle multiplexing is achieved by establishing a mapping relationship between a plurality of preset non-orthogonal incident angles and corresponding circuitous phase responses.

[0008] Preferably, the position arrangement of the nanobricks is calculated based on the circuitous phase; the circuitous phase of each nanobrick is the first circuitous component and the second circuitous component The sum of; to establish two mutually perpendicular sides parallel to the working surface of the optical waveguide layer xy Coordinate system, incident angle θ Defined as xy The incident light on the plane is y The angle between the axes; When the incident angle satisfies 0≤ θ When the angle is less than 90°, the first and second circuitous components are calculated using the following formulas:

[0009] When the incident angle satisfies 90≤ θ When the angle is less than 180°, the first and second circuitous components are calculated by the following formula:

[0010] Where, M is the column number of the unit structure on the left side of the unit structure to which the nanobrick belongs, N is the number of unit structure rows on the lower side of the unit structure to which the nanobrick belongs, T is the total number of rows / columns of unit structures contained in the on-chip metasurface, P is the period of the unit structure, is the displacement of the nanobrick along the x direction during the period, is the displacement of the nanobrick along the y direction during the period.

[0011] Preferably, the size of the target holographic image corresponding to each wavelength is adjusted by a scaling factor, and each scaled target holographic image is encoded into a specific position corresponding to its respective wavelength on the on-chip metasurface to achieve wavelength multiplexing.

[0012] Preferably, the scaling factor satisfies the following compensation conditions:

[0013] Where, For thei The scaling factor corresponding to the wavelength is For the i wavelength, C is a constant.

[0014] Preferably, the compensation condition is such that when the on-chip metasurface is illuminated by light of corresponding wavelength, the diffracted light generated by the target holographic image corresponding to all wavelengths is k The holographic images are pointed to the same predetermined position range in space, so that target holographic images corresponding to different wavelengths can be observed from the same observation angle in the imaging plane of real space.

[0015] Preferably, the k Pointing to the same predetermined position range in space k The value is in the range of -0.05 to 0.15.

[0016] Preferably, under circularly polarized light conditions, the geometric phase of the nanobrick is equal to twice the size of its corresponding rotation angle; under left-handed circular polarization and right-handed circular polarization, the geometric phase takes positive and negative values ​​respectively, realizing polarization multiplexing.

[0017] Preferably, based on inverse design, a gradient descent algorithm is used to perform phase optimization, and the position and rotation angle arrangement of each nanobrick in the nanobrick array is obtained according to the optimization result.

[0018] On the other hand, the present invention provides an on-chip metasurface for realizing the above-mentioned multi-dimensional multiplexing holographic method based on the on-chip metasurface, wherein the on-chip metasurface includes a substrate layer, an optical waveguide layer located on the substrate layer, and a nanobrick array arranged on the optical waveguide layer.

[0019] One or more technical solutions provided in the present invention have at least the following technical effects or advantages: The multi-dimensional multiplexing holographic method based on an on-chip metasurface provided by the present invention first constructs a unit structure of the on-chip metasurface. The unit structure includes a substrate layer, an optical waveguide layer, and a nanostructure layer arranged in sequence from bottom to top. The nanostructure layer includes a rectangular nanobrick. The on-chip metasurface includes a plurality of nanobricks of uniform size forming a nanobrick array. Then, based on multiple target holographic images, the position and rotation angle arrangement of each nanobrick in the nanobrick array is obtained by combining the circuitous phase and the geometric phase. After the arrangement is completed, the final on-chip metasurface is obtained, and the on-chip metasurface is used to realize three-dimensional multiplexing holography of incident angle, wavelength, and polarization. The present invention can effectively phase encode any plane incident angle and, combined with the wavelength and polarization dimensions, realizes the simultaneous multiplexing of the three-dimensional optical parameters of incident angle, wavelength, and polarization. The present invention not only overcomes the limitation of only orthogonal incidence, but also significantly improves the information storage capacity and information security, showing broad application prospects in virtual / augmented reality, data storage, and optical encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a multi-dimensional multiplexing holographic method based on an on-chip metasurface provided in Example 1 of the present invention.

[0021] Figure 2 is a schematic diagram of an on-chip metasurface in a multi-dimensional multiplexing holographic method based on an on-chip metasurface provided in Example 1 of the present invention; wherein, Figure 2 (a) is a schematic diagram of a light wave at a specific angle incident on the on-chip metasurface. Figure 2 (b) is a schematic diagram of the structure of the on-chip metasurface. Figure 2 (c) is a schematic diagram of the displacement and rotation angle of the nanobricks in the on-chip metasurface.

[0022] Figure 3 is a schematic diagram of a multi-dimensional multiplexed holographic method based on an on-chip metasurface that combines a circuitous phase with a geometric phase, as provided in Example 1 of the present invention; wherein, Figure 3 (a) is a schematic diagram of the principle of combining the circuitous phase with the geometric phase. Figure 3 (b) in the figure is the function relationship between the geometric phase and the wavelength and rotation angle.

[0023] Figure 4 : is a schematic diagram of the principle of wavelength multiplexing in a multi-dimensional multiplexing holographic method based on an on-chip metasurface provided in Example 1 of the present invention; wherein, Figure 4 (a) is a schematic diagram of wavelength multiplexing using dispersion engineering design. Figure 4 (b) in the equation is k Schematic diagram of image position design in space and target observation angle, Figure 4 (c) in the figure is the dispersion image after the design is completed.

[0024] Figure 5 : is a schematic diagram of the circuitous phase calculation principle at different incident angles in a multi-dimensional multiplexed holographic method based on an on-chip metasurface provided in Example 1 of the present invention; wherein, Figure 5 (a) is the circuitous phase calculation method under angle multiplexing. Figure 5 (b) is a schematic diagram of the circuitous phase change caused by displacement within the lattice.

[0025] Figure 6 This is a flowchart of a multi-dimensional multiplexed holographic image optimization algorithm in a multi-dimensional multiplexed holographic method based on an on-chip metasurface provided in Example 1 of the present invention.

[0026] Figure 7 It is the experimental measurement scene diagram of the present invention.

[0027] Figure 8 It is a diagram of experimental measurement results of the present invention. DETAILED DESCRIPTION

[0028] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0029] Example 1: Embodiment 1 provides a multi-dimensional multiplexing holographic method based on an on-chip metasurface, comprising the following steps: Constructing a unit structure of an on-chip metasurface, the unit structure comprising a substrate layer, an optical waveguide layer, and a nanostructure layer arranged in sequence from bottom to top, the nanostructure layer comprising a nanobrick having a rectangular structure; the on-chip metasurface comprising a plurality of nanobricks of uniform size forming a nanobrick array; According to the set multiple target holographic images, the combined encoding of the circuitous phase and geometric phase is used to obtain the arrangement of the position and rotation angle of each nanobrick in the nanobrick array. After the arrangement is completed, the final on-chip metasurface is obtained, and the on-chip metasurface is used to realize three-dimensional multiplexed holography of incident angle, wavelength and polarization.

[0030] Incident angle multiplexing is achieved by establishing a mapping relationship between multiple preset non-orthogonal incident angles and corresponding circuitous phase responses.

[0031] The position arrangement of nanobricks is calculated based on the circuitous phase; the circuitous phase of each nanobrick is the first circuitous component and the second circuitous component The sum of; to establish two mutually perpendicular sides parallel to the working surface of the optical waveguide layer xy Coordinate system, incident angle θ Defined as xy The incident light on the plane is y The guided wave propagates along the waveguide in TE0 mode and interacts with the meta-atoms (i.e., nanobricks). The nanobricks are rectangular in structure, and the sides of the rectangular nanobricks are parallel to the working surface of the optical waveguide layer.

[0032] That is, the positional arrangement of the nanobricks can be calculated by the detour phase principle; the total detour phase of each meta-atom can be calculated as the sum of two components: the distance between the unit cell of the meta-atom and the zero-phase reference plane. , and the relative displacement Δx or Δy caused by the meta-atoms in their unit cells .

[0033] When the incident angle satisfies 0≤ θ When the angle is less than 90°, the first and second circuitous components are calculated using the following formulas:

[0034] When the incident angle satisfies 90≤ θ When the angle is less than 180°, the first and second circuitous components are calculated by the following formula:

[0035] Where, M is the column number of the unit structure on the left side of the unit structure to which the nanobrick belongs, N is the number of unit structure rows on the lower side of the unit structure to which the nanobrick belongs, T is the total number of rows / columns of unit structures contained in the on-chip metasurface, P is the period of the unit structure, is the displacement of the nanobrick along the x direction during the period, is the displacement of the nanobrick along the y direction during the period.

[0036] The size of the target holographic image corresponding to each wavelength is adjusted by the scaling factor, and the scaled target holographic images are encoded into specific positions corresponding to their respective wavelengths on the on-chip metasurface to achieve wavelength multiplexing.

[0037] The scaling factor satisfies the following compensation conditions:

[0038] Where, For the i The scaling factor corresponding to the wavelength is For the i wavelength, C is a constant.

[0039] The compensation condition is such that when the on-chip metasurface is illuminated by light of corresponding wavelength, the diffracted light generated by the target holographic image corresponding to all wavelengths is k The holographic images are pointed to the same predetermined position range in space, so that target holographic images corresponding to different wavelengths can be observed from the same observation angle in the imaging plane of real space.

[0040] described k Pointing to the same predetermined position range in space k The value is in the range of -0.05 to 0.15.

[0041] Among them, under the condition of circularly polarized light, the geometric phase of the nanobrick is equal to twice the size of its corresponding rotation angle; under left-handed circular polarization and right-handed circular polarization, the geometric phase takes positive and negative values ​​respectively, realizing polarization multiplexing.

[0042] Example 1 can achieve holographic encoding under any in-plane azimuth illumination by precisely optimizing and encoding the detour phase and geometric phase, while simultaneously achieving polarization decoupling, thereby significantly improving the multiplexing capability.

[0043] In Example 1, based on inverse design, a gradient descent algorithm is used to perform phase optimization, and the position and rotation angle arrangement of each nanobrick in the nanobrick array are obtained according to the optimization results.

[0044] Example 1 utilizes arbitrary incident angles to effectively encode their corresponding phases, and combines this strategy with wavelength and polarization dimensions to propose a solution for advancing high-capacity and high-security optical multi-dimensional multiplexing technology. Example 1 can also be understood as providing a method for effective phase encoding at arbitrary angles, wavelengths, and polarizations based on metasurfaces.

[0045] Example 1 establishes a mathematical mapping relationship between multiple preset non-orthogonal incident angles and corresponding circuitous phase responses, and combines the optimization algorithm to perform global optimization of the phase distribution, thereby realizing efficient phase control of incident light at any spatial angle; on this basis, a multi-dimensional multiplexing holographic technology is constructed, which can generate and capture different holographic images based on multiple groups of incident parameter combinations within the same output viewing angle range; the reconstruction of the image depends on the accurate acquisition of three key optical parameters: incident angle, operating wavelength and polarization state. The lack of any parameter will result in the inability to correctly decode the holographic information. Therefore, Example 1 can effectively improve the system's information multiplexing capability and its security and reliability in the field of data encryption and storage.

[0046] The present invention is described below with reference to the parameters.

[0047] The present invention selects a well-designed nanobrick array to form a metasurface to achieve the effect of multi-dimensional multiplexed holography. Figure 1 Specifically, by combining the circuitous phase driven by the incident wave with the geometric phase and further tuning it through a deep optimization algorithm, the present invention can achieve efficient phase encoding of multi-dimensional light waves with non-orthogonal incident angles.

[0048] Figure 2 is a schematic diagram of an on-chip metasurface in a multi-dimensional multiplexing holographic method based on an on-chip metasurface provided by the present invention; wherein, Figure 2 (a) is a specific angle θ Schematic diagram of light waves incident on the on-chip metasurface, Figure 2 (b) is a schematic diagram of the structure of the on-chip metasurface. Figure 2 (c) is a schematic diagram of the displacement and rotation angle of the nanobricks in the on-chip metasurface. The nanostructure of the on-chip metasurface can be made of amorphous silicon nanobricks, and the optical waveguide layer can be made of silicon nitride (thickness of 220 nm). The waveguide refractive index is about 2.05. The substrate layer can be a silicon dioxide layer (thickness of about 500 μm), which is a silicon dioxide substrate. The nanobricks are rectangular, and the height of the nanobricks is about 100 μm. H is 360 nm, and the length and width of the nanobrick are L= 150 nm, W =60 nm, P is the period of the unit structure, and the period in the x and y directions is expressed as , and The nanobricks are x Direction and y Directional displacement, is the rotation angle in nanometers.

[0049] The positional arrangement of nanobricks can be calculated using the circuitous phase principle, and the phase distribution along any incident angle can be solved using the calculation formulas for the first circuitous component and the second circuitous component. Figure 3 The invention shows that the design of the invention makes comprehensive use of the circuitous phase and the geometric phase. Figure 3 (a) is a schematic diagram of the principle of combining the circuitous phase with the geometric phase. Figure 3 (b) in the figure is the function relationship between the geometric phase and the wavelength and rotation angle.

[0050] Figure 4 Schematic diagram of the principle of wavelength multiplexing in a multi-dimensional multiplexing holographic method based on an on-chip metasurface provided by the present invention; wherein, Figure 4 (a) is a schematic diagram of wavelength multiplexing achieved by dispersion engineering design, that is, wavelength multiplexing is achieved by dispersion; Figure 4 (b) in the equation is k Schematic diagram of image position design in space and target observation angle, Figure 4 (c) is the designed dispersion image. Under different wavelengths of incidence, we adjust the position of the target image to achieve the same dispersion at different wavelengths. k Spatial position emission.

[0051] In order to achieve multi-dimensional light field manipulation, the design strategy of the present invention realizes wavelength multiplexing of metasurfaces through dispersion engineering. By utilizing the inherent dispersion characteristics of periodic metaatoms, the present invention independently designs holographic images of different wavelengths to make them k The target images of different wavelengths occupy the same position in space, ensuring that they are diffracted from the same angle. This achieves effective wavelength multiplexing within the imaging plane. In order to ensure that target images of different wavelengths can be diffracted toward the same observation angle, we choose k = -0.05 to k =0.15 as the specified viewing direction of the image design. Within this range, holographic patterns of different sizes are accurately encoded at specific positions corresponding to their respective wavelengths. For example, the scaling factors of the red and green images are determined based on the following compensation conditions S R as well as S Gto ensure k Angular alignment in space: S R · λ R = S G · λ G Where, λ R and λ G are the wavelengths corresponding to the red and green images respectively.

[0052] Figure 5 This is a schematic diagram of the circuitous phase calculation principle at different incident angles in a multi-dimensional multiplexed holographic method based on an on-chip metasurface provided by the present invention; wherein, Figure 5 (a) in the figure illustrates the method for calculating the roundabout phase under angle multiplexing. Figure 5 (b) in the figure is the calculation of the circuitous phase change caused by displacement within the lattice (i.e., the unit structure to which the nanobrick belongs).

[0053] In order to assign meaningful phase distribution to each spatial light angle multiplexing scheme, we adopt the inverse design method and combine it with the gradient descent algorithm to optimize the phase, such as Figure 6 In the optimization process, for waves incident at any angle, we select three randomly generated phase matrices 、 and Start initialization, where and represent the initial detour phase along the x-axis and y-axis respectively, represents the initial geometric phase. Each incident angle encodes a unique holographic image. During the optimization process, we measure the quality of the hologram by calculating the root mean square error (RMSE) between the generated hologram and the ideal target, and minimize the RMSE as the loss function. As the iteration proceeds, and The algorithm continuously adjusts and eventually converges to the minimum value of the loss function, thereby outputting the optimized phase mask. Finally, based on the optimized phase matrix, the fast Fourier transform (FFT) is used to generate the holographic images of all channels.

[0054] To demonstrate the omnidirectional angular multiplexing metaholography strategy, we fabricated a metasurface hologram sample and measured holographic images from 24 channels. The fabrication process began with plasma-enhanced chemical vapor deposition (PECVD) on a fused silica substrate (500 μm thick) to form a 220 nm thick optical waveguide layer. Subsequently, a 360 nm thick amorphous silicon (α-Si) coating was applied to the Si3N4 waveguide using PECVD. To create the metasurface pattern, polymethyl methacrylate (PMMA) was spin-coated onto the α-Si layer and baked at 150°C for 3 minutes. The pattern was achieved using electron beam lithography (RaitheLine Plus, 20 kV) and developed for 80 seconds. A 20 nm chromium film was then deposited by thermal evaporation as an etch-resistant mask before removing the PMMA using acetone-based lift-off. The chromium pattern was transferred to the α-Si layer using reactive ion etching (RIE), and the chromium film was finally stripped using a chromium-specific etchant. The experiment produced 24 channels of holograms, each consisting of 1000 × 1000 pixels, containing 1000 × 1000 meta-atoms, and the overall sample size is The incident light has a wavelength of 560 nm / 640 nm and illuminates the fabricated metasurface at different incident angles. By changing the incident angle, we are able to capture different holographic images in the far field at the same output viewing angle.

[0055] The experimental setup of the sample is as follows Figure 7 To simplify the experimental measurement, we rotate the sample to change the incident angle, and change the polarization and wavelength to achieve the required conditions. Finally, the 24-channel holographic images obtained experimentally are highly consistent with the simulation results, as shown in Figure 8 In the experiment, the holographic images under different incident conditions can be clearly distinguished.

[0056] Example 1 expands the optimization space, improves the optimized image quality and capacity, and realizes the use of non-orthogonal incidence by thoroughly correlating and optimizing the detour phase and geometric phase at different incident angles. Example 1 overcomes the limitation of only orthogonal incidence. Considering that the optimization space of the detour phase alone is limited and the polarization dimension cannot be realized, Example 1 expands the optimization space and improves the optimized image quality and capacity by adding the regulation of the geometric phase. That is, Example 1 uses the combination of the detour phase and the geometric phase to achieve simultaneous multiplexing of the three dimensions of incident angle, wavelength, and polarization, greatly improving the information storage capacity. If the three decoded optical parameters cannot be accurately obtained, it is impossible to extract the correct holographic image, which enhances the information security of the meta-device; as a method verification, we successfully constructed three-dimensional multiplexed holography and captured different holographic images at up to 24 predefined arbitrary spatial angles within the same field of view. It can be seen that Example 1 greatly improves information security.

[0057] Example 2: Example 2 provides an on-chip metasurface for realizing the multi-dimensional multiplexing holographic method based on the on-chip metasurface as described in Example 1, wherein the on-chip metasurface includes a substrate layer, an optical waveguide layer located on the substrate layer, and a nanobrick array arranged on the optical waveguide layer.

[0058] That is, the on-chip metasurface includes a substrate layer, the optical waveguide layer, and a rectangular nanobrick structure array arranged in different positions and angles on the optical waveguide layer.

[0059] The length and width of the nanobricks are both sub-wavelength sizes, and all the nanobricks have the same size.

[0060] Since the on-chip metasurface provided in Example 2 is used to implement the multi-dimensional multiplexing holographic method based on the on-chip metasurface as described in Example 1, Example 2 can be understood by referring to the description of Example 1 and will not be repeated here.

[0061] In summary, the present invention provides a multidimensional holographic method based on an on-chip metasurface that effectively phase encodes arbitrary planar incident angles (azimuths) and combines wavelength and polarization for multiplexing. This method integrates a two-dimensional array metasurface composed of individual rectangular nanobricks onto a waveguide. Using a combined encoding strategy of detour phase and geometric phase, the positional displacement of each nanobrick is associated with incident light at a predefined arbitrary azimuth angle. By combining a gradient descent algorithm to optimize the detour phase and rotation angle of the structure, the method achieves simultaneous multiplexing of three-dimensional optical parameters: incident angle, wavelength, and polarization, significantly improving information capacity and security. As a validation, holographic images of 24 independent channels were successfully generated and recognized in experiments, demonstrating the method's superior performance in multidimensional information multiplexing and light field manipulation. This technology offers high capacity, robustness, and security, and holds broad application prospects in virtual / augmented reality, data storage, and optical encryption.

[0062] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-dimensional multiplexing holographic method based on an on-chip metasurface, characterized in that: The following steps are involved: Constructing a unit structure of an on-chip metasurface, the unit structure comprising a substrate layer, an optical waveguide layer, and a nanostructure layer arranged in sequence from bottom to top, the nanostructure layer comprising a nanobrick having a rectangular structure; the on-chip metasurface comprising a plurality of nanobricks of uniform size forming a nanobrick array; According to the set multiple target holographic images, the combined encoding of the circuitous phase and geometric phase is used to obtain the arrangement of the position and rotation angle of each nanobrick in the nanobrick array. After the arrangement is completed, the final on-chip metasurface is obtained, and the on-chip metasurface is used to realize three-dimensional multiplexed holography of incident angle, wavelength and polarization.

2. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 1, characterized in that: Incident angle multiplexing is achieved by establishing a mapping relationship between multiple preset non-orthogonal incident angles and corresponding circuitous phase responses.

3. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 2, characterized in that: The position arrangement of nanobricks is calculated based on the circuitous phase; the circuitous phase of each nanobrick is the first circuitous component and the second circuitous component The sum of; to establish two mutually perpendicular sides parallel to the working surface of the optical waveguide layer xy Coordinate system, incident angle θ Defined as xy The incident light on the plane is y The angle between the axes; When the incident angle satisfies 0≤ θ When the angle is less than 90°, the first and second circuitous components are calculated using the following formulas: When the incident angle satisfies 90≤ θ When the angle is less than 180°, the first and second circuitous components are calculated by the following formula: Where, M is the column number of the unit structure on the left side of the unit structure to which the nanobrick belongs, N is the number of unit structure rows on the lower side of the unit structure to which the nanobrick belongs, T is the total number of rows / columns of unit structures contained in the on-chip metasurface, P is the period of the unit structure, is the displacement of the nanobrick along the x direction during the period, is the displacement of the nanobrick along the y direction during the period.

4. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 1, characterized in that: The size of the target holographic image corresponding to each wavelength is adjusted by the scaling factor, and the scaled target holographic images are encoded into specific positions corresponding to their respective wavelengths on the on-chip metasurface to achieve wavelength multiplexing.

5. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 4, characterized in that: The scaling factor satisfies the following compensation conditions: Where, For the i The scaling factor corresponding to the wavelength is For the i wavelength, C is a constant.

6. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 5, characterized in that: The compensation condition is such that when the on-chip metasurface is illuminated by light of corresponding wavelength, the diffracted light generated by the target holographic image corresponding to all wavelengths is k The holographic images are pointed to the same predetermined position range in space, so that target holographic images corresponding to different wavelengths can be observed from the same observation angle in the imaging plane of real space.

7. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 6, characterized in that: described k Pointing to the same predetermined position range in space k The value is in the range of -0.05 to 0.

15.

8. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 1, characterized in that: Under circularly polarized light conditions, the geometric phase of the nanobrick is equal to twice the size of its corresponding rotation angle; under left-handed circular polarization and right-handed circular polarization, the geometric phase takes positive and negative values ​​respectively, realizing polarization multiplexing.

9. The multi-dimensional multiplexing holographic method based on on-chip metasurface according to claim 1, characterized in that: Based on inverse design, a gradient descent algorithm is used to perform phase optimization, and the position and rotation angle arrangement of each nanobrick in the nanobrick array are obtained according to the optimization results.

10. An on-chip metasurface, characterized in that: A multi-dimensional multiplexing holographic method based on an on-chip metasurface as described in any one of claims 1 to 9, wherein the on-chip metasurface includes a substrate layer, an optical waveguide layer located on the substrate layer, and a nanobrick array arranged on the optical waveguide layer.

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