On-chip metasurface and design method thereof, method for realizing color routing based on on-chip metasurface

Abstract

This invention belongs to the field of micro-nano optics technology and discloses an on-chip metasurface and its design method, as well as a method for color routing based on the on-chip metasurface. The unit structure of the on-chip metasurface in this invention includes a nanostructure layer, an optical waveguide layer, and a dielectric substrate layer. The nanostructure layer is composed of diatomic nanobricks and exhibits geometric asymmetry. The on-chip metasurface contains several diatomic nanobricks that form one or more arrays of nanobricks. All diatomic nanobricks in each array have the same geometric dimensions, while arrays of different types contain diatomic nanobricks with different geometric dimensions. Each array is used for selective extraction of a narrow band spectrum, while arrays of different types are used for selective extraction of different spectral ranges. The geometric dimensions of the diatomic nanobricks are used as adjustment parameters to encode the color information of the image into the on-chip metasurface. This invention achieves wavelength-selective extraction and multi-color routing for image display based on the on-chip metasurface.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optical technology, and more specifically, relates to an on-chip metasurface and its design method, and a method for implementing color routing based on the on-chip metasurface. Background Technology

[0002] In the development of chip-integrated and miniaturized nanophotonic devices, the integration of metasurfaces into optical waveguides as a compact platform for manipulating and guiding planar light waves has attracted widespread attention from researchers. Recently, by carefully designing subwavelength nanostructures on waveguides, on-chip integrated metasurfaces can precisely control the amplitude, phase, and polarization of extracted light, enabling a variety of functions, including directional beam control, on-chip superlenses, vortex beam generators, metasurface holography, and screen displays. Due to its on-chip propagation scheme, this technology possesses unique advantages such as zero-order background interference, multi-stage cascading capability, and compatibility with other micro-on-chip devices, which can facilitate the creation of advanced chip-integrated metasurface optics.

[0003] On-chip metasurfaces have achieved considerable success in phase modulation, utilizing mechanisms such as resonant or detour phase manipulation for phase control; amplitude modulation is achieved through nanoscale structure size or interference between two metaatoms; polarization control utilizes geometric phase and other combined phase modulation mechanisms. Despite these advances, these methods offer limited control over the spectral characteristics of coupled light, failing to achieve wavelength-selective light extraction. Typically, when the guided wave is perturbed by on-chip metaatoms, the extracted light exhibits a broadband response, lacking wavelength selectivity. To date, no feasible strategy remains for achieving wavelength-selective extraction for on-chip integrated metasurfaces.

[0004] Wavelength modulation and selective extraction control on waveguide-integrated metasurface platforms are crucial for advancing integrated photonic applications such as wavelength division multiplexing and color routing. Therefore, unlocking the degrees of freedom for on-chip wavelength selective extraction is a key challenge in this field.

[0005] Furthermore, it is worth mentioning that although traditional free-space metasurfaces or multilayer thin films can achieve color filters and routing functions, these methods are based on spatial multiplexing and suffer from severe energy utilization efficiency (EUE) loss because a considerable portion of the incident light outside the wavelength filter passband is wasted. Summary of the Invention

[0006] This invention addresses the problem that wavelength-selective extraction cannot be achieved using on-chip metasurfaces in the prior art by providing an on-chip metasurface and its design method, as well as a method for color routing based on on-chip metasurfaces.

[0007] In a first aspect, the present invention provides a method for designing an on-chip metasurface, comprising the following steps:

[0008] A unit structure for an on-chip metasurface is constructed, comprising, from top to bottom, a nanostructure layer, an optical waveguide layer, and a dielectric substrate layer. The nanostructure layer is composed of diatomic nanobricks, which exhibit geometric asymmetry. The on-chip metasurface contains several of these diatomic nanobricks, forming one or more arrays of nanobricks. All diatomic nanobricks in each array have the same geometric dimensions, while arrays of different types contain diatomic nanobricks with different geometric dimensions. Each array of nanobricks is used for selective extraction of a specific narrowband spectrum, while arrays of different types are used for selective extraction of different spectral ranges.

[0009] The geometric dimensions of the biatomic nanobricks in each nanobrick array are used as adjustment parameters to encode the color information of the image into the on-chip metasurface.

[0010] Preferably, an xoy coordinate system is established with the two sides parallel to the working surface of the optical waveguide layer as the coordinates, and the rotation angles of the two nanobricks in the i-th group of nanobrick array about the y-axis are respectively θ. i 180°-θ i And 0° < θ i <90°; all diatomic nanobricks in each nanobrick array have the same rotation angle design.

[0011] Preferably, when the on-chip metasurface comprises several diatomic nanobricks forming multiple nanobrick arrays, the multiple nanobrick arrays of different types are horizontally cascaded, and the on-chip metasurface selectively extracts guided waves of different wavelengths from different spatial locations into free space for color routing.

[0012] Preferably, the diatomic nanobrick is composed of two rectangular nanobricks with the same geometric dimensions; the geometric dimensions of the diatomic nanobricks in the i-th group of nanobrick array are set as: L i =L0×S i W i =W0×S i P i =P x =P y =P0×S i Among them, L i Let W be the length of the diatomic nanobrick in the i-th nanobrick array. i Let P be the width of the two-atom nanobrick in the i-th nanobrick array. i Let P be the period of the diatomic nanobricks in the i-th group of nanobrick arrays. x and P yLet L0 be the period of the diatomic nanobrick along the x-axis and y-axis, respectively, and let W0 be the reference length, W0 be the reference width, P0 be the reference period, and S be the reference period. i S is the scaling factor for the i-th group of nanobrick arrays. i >0; different groups of nanobrick arrays have different scaling factors; the wavelength corresponding to the spectral peak extracted from the nanobrick array increases with the increase of the scaling factor; the geometric size of the diatomic nanobricks in each group of nanobrick arrays is determined based on the color information of the image.

[0013] Preferably, both the reference length and the reference width are subwavelength dimensions; the guided wave propagates along the x-axis, and the local displacement between the two-atom nanobricks along the x-axis is P. x / 2.

[0014] Preferably, the design method of the on-chip metasurface further includes: using the rotation angle of the diatomic nanobricks in each group of nanobrick arrays as an adjustment parameter to encode the intensity information of the image into the on-chip metasurface.

[0015] Preferably, the asymmetry factor α of the i-th group of nanobrick arrays is... i Defined as α i =sinθ i The spectral intensity extracted from the nanobrick array increases with the increase of the asymmetry factor; the rotation angle design of the diatomic nanobricks in each nanobrick array is determined based on the intensity information of the image.

[0016] Secondly, the present invention provides an on-chip metasurface, which is obtained by the above-described on-chip metasurface design method.

[0017] Thirdly, the present invention provides a method for color routing based on an on-chip metasurface. The method uses spatial mapping to encode the color information of an image into the on-chip metasurface. The on-chip metasurface contains several diatomic nanobricks that form multiple nanobrick arrays, and multiple nanobrick arrays of different types are horizontally cascaded. The on-chip metasurface is used to selectively extract guided waves of different wavelengths from different spatial locations into free space for color routing, thereby realizing multi-color routed image display.

[0018] Preferably, the color and intensity information of the image are encoded into the on-chip metasurface to achieve multi-color routing image display with controllable spectral intensity.

[0019] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0020] (1) The unit structure of the on-chip metasurface in this invention includes a nanostructure layer, an optical waveguide layer, and a dielectric substrate layer arranged sequentially from top to bottom. The nanostructure layer is composed of diatomic nanobricks, which have geometric asymmetry. The on-chip metasurface contains several diatomic nanobricks that form one or more arrays of nanobricks. All diatomic nanobricks in each array have the same geometric dimensions, while arrays of different types contain diatomic nanobricks with different geometric dimensions. Each array of nanobricks is used for selective extraction of a narrow band spectrum, while arrays of different types are used for selective extraction of different spectral ranges. This invention uses the geometric dimensions of the diatomic nanobricks in each array as an adjustment parameter to encode the color information of the image into the on-chip metasurface. The diatomic nanobricks in this invention have geometric asymmetry, which allows guided modes to leak into free space. By adjusting the geometric dimensions of the diatomic nanobricks, selective extraction of guided waves entering free space can be achieved, enabling selective extraction of a certain wavelength range or multiple wavelength ranges. That is, this invention achieves wavelength selective extraction based on an on-chip metasurface.

[0021] (2) Based on the above scheme, the rotation angle of the diatomic nanobrick can be adjusted to achieve wavelength selective extraction with adjustable intensity.

[0022] (3) When the on-chip metasurface provided by this invention comprises several diatomic nanobricks forming multiple nanobrick arrays, it yields an on-chip color router employing a cascaded multiplexing strategy, which can be applied to image display. All extracted energy is fully utilized to construct the corresponding wavelength channels. The design of this invention overcomes the limitations of spatial multiplexing efficiency, and no energy utilization efficiency loss occurs when propagation loss is negligible. Furthermore, due to the on-chip propagation mechanism, the generated image display can effectively suppress zero-order background light interference. The on-chip metasurface proposed in this invention has advantages in miniaturization and integration, and has great potential in applications such as next-generation wearable display devices, wavelength division multiplexing, and information routing in integrated photonic systems. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the unit structure of the on-chip metasurface constructed in this invention.

[0024] Figure 2 This is a schematic diagram of a diatomic nanobrick composed of two parallel and two tilted nanobricks, respectively, corresponding to the transition from BIC mode to quasi-BIC mode.

[0025] Figure 3 This is a schematic diagram of a nanobrick array.

[0026] Figure 4 This is a schematic diagram of a two-atom nanobrick. Among them, Figure 4 (a) and Figure 4 (b) shows the simulated electric field intensity distribution in the xy plane when the TE0 mode is incident from the x direction, under two cases with rotation angles of θ = 0° and θ = 20°. Figure 4 (c) shows the electric field distribution in the yz plane at rotation angles of θ = 0°, θ = 20°, and θ = 40°.

[0027] Figure 5 This is the extracted spectrum obtained through simulation. Among them, Figure 5 (a) shows the simulated extracted spectral profile of the nanobrick array when the rotation angle changes from 0° to 20°; Figure 5 (b) in the figure shows the simulated extraction spectrum of the nanobrick array when the length L changes from 120 nm to 180 nm; Figure 5 (c) in the figure shows the extracted spectral lines of the nanobrick array at rotation angles θ = 0°, θ = 10° and θ = 20°; Figure 5 (d) in the figure represents the extracted spectral lines of the nanobrick array when the scaling factor S changes from 0.85 to 1.

[0028] Figure 6 It involves extracting simulated electric field intensity distributions at different wavelengths from the waveguide. Figure 6 (a) in the figure shows the simulated electric field intensity distribution at a wavelength of 572 nm extracted from the waveguide; Figure 6 (b) in the figure shows the simulated electric field intensity distribution at a wavelength of 608 nm extracted from the waveguide; Figure 6 (c) in the figure represents the simulated electric field intensity distribution at a wavelength of 652 nm extracted from the waveguide.

[0029] Figure 7 This is a conceptual schematic diagram of an on-chip metasurface capable of color routing.

[0030] Figure 8 These are the extracted spectra of arrays of different sizes obtained through simulation. Figure 8 In the image (a), the extracted spectra are simulated for arrays of different sizes, with the number N along the propagation direction (x-axis) varying from 1 to 50; Figure 8 (b) in the middle is from Figure 8 Plot the line graph of maximum extraction efficiency in the spectrum of (a) in the figure.

[0031] Figure 9 These are the extraction spectra of different array samples obtained experimentally. Among them, Figure 9 (a) shows the experimentally extracted spectra of different arrays as the rotation angle θ changes from 0° to 30°; Figure 9 (b) shows the experimental extracted spectra of different arrays as the scaling factor S changes from 0.88 to 1.

[0032] Figure 10This is a conceptual diagram corresponding to a method for implementing color routing based on an on-chip metasurface provided by the present invention.

[0033] Figure 11 It is a measurement device and corresponding spectrum based on on-chip metasurfaces to achieve color routing. Figure 11 (a) shows the experimental measurement setup used to characterize on-chip near-field micro-image displays; Figure 11 (b) in the figure is a comparison of the extracted spectral profiles obtained by measuring the conventional grating coupler and the present invention.

[0034] Figure 12 This demonstrates the color routing functionality of the on-chip metasurface provided by this invention. Figure 12 (a) to (c) show the functional diagrams of the conventional grating coupler and the present invention when guided waves with wavelengths of 640 nm and 530 nm propagate simultaneously from the x-direction, as well as optical microscope images of the corresponding “R” and “G” letters. Figure 12 (d) to (f) show the functional diagrams of the conventional grating coupler and the present invention when a guided wave with a wavelength of 640 nm propagates from the x-direction, as well as optical microscope images of the corresponding “R” and “G” letters; Figure 12 Figures (g) to (i) show the functional diagrams of a conventional grating coupler and the present invention when a guided wave of wavelength 530 nm propagates from the x-direction, along with optical microscope images of the corresponding “R” and “G” letters.

[0035] Figure 13 This is an experimental demonstration of multicolor image display based on on-chip metasurfaces and color pixels. Among them, Figure 13 (a) shows a schematic diagram of designing metasurface patterns on a three-dimensional multicolor nanoprinted sheet to achieve simultaneous adjustment of color and brightness; Figure 13 (b) shows the captured stereoscopic “3D” optical image (Demonstration 1).

[0036] Figure 14 This is an experimental demonstration of the two-color grayscale image "red flowers and green leaves" based on an on-chip metasurface (Demonstration 2).

[0037] Among them, 1-nano brick, 2-optical waveguide layer, 3-dielectric substrate layer. Detailed Implementation

[0038] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0039] Example 1:

[0040] Example 1 provides a method for designing an on-chip metasurface, comprising the following steps:

[0041] Step 1: Construct the unit structure of the on-chip metasurface.

[0042] The unit structure includes a nanostructure layer, an optical waveguide layer, and a dielectric substrate layer arranged sequentially from top to bottom. The nanostructure layer is composed of diatomic nanobricks, which have geometric asymmetry.

[0043] The on-chip metasurface contains several diatomic nanobricks that form a nanobrick array. All the diatomic nanobricks in the array have the same geometric dimensions. This array is used to selectively extract a narrowband spectrum.

[0044] Step 2: Using the geometric dimensions of the biatomic nanobricks in the array of nanobricks as adjustment parameters, the color information of the image is encoded into the on-chip metasurface.

[0045] The diatomic nanobrick is composed of two rectangular nanobricks with identical geometric dimensions. An xoy coordinate system is established with the two sides parallel to the working surface of the optical waveguide layer as reference. The rotation angles of the two nanobricks in this array about the y-axis are θ and 180°-θ, respectively, where 0°<θ<90°. All diatomic nanobricks in this array have the same rotation angle design.

[0046] In a preferred embodiment, the method may further include: using the rotation angle of the diatomic nanobricks in the array of nanobricks as an adjustment parameter to encode the intensity information of the image into the on-chip metasurface.

[0047] Specifically, while keeping the geometric dimensions of the structure constant, the intensity of the extracted spectrum can be adjusted by changing the geometric asymmetry of the diatomic nanobricks, i.e., changing the rotation angle θ. For example, as the rotation angle θ increases from 0° to 20°, the extraction intensity increases accordingly.

[0048] The on-chip metasurface in Example 1 is a nonlocal on-chip metasurface that supports symmetry-protected bound states (BICs) in a continuum. When the rotation angle θ = 0° of the diatomic nanobrick, it is in an undisturbed symmetry-protected BIC mode with a large wave vector, confining the guided wave to propagate within the waveguide rather than extracting it into free space. As asymmetry gradually develops (θ > 0°), perturbation is applied to the dual metapairs, doubling the effective lattice period, thus causing the guided mode to leak into free space. The diatomic nanobricks (i.e., dual metapairs) in Example 1 have geometric asymmetry, 0° < θ < 90°, which allows the guided mode to leak into free space. By adjusting the geometry of the diatomic nanobricks, selective extraction of the guided wave into free space can be achieved, i.e., wavelength-selective light extraction. In a preferred scheme that also adjusts the rotation angle of the diatomic nanobricks, intensity-tunable narrowband spectral extraction can be achieved.

[0049] Example 2:

[0050] Example 2 provides a design method for an on-chip metasurface, including the following steps:

[0051] Step 1: Construct the unit structure of the on-chip metasurface.

[0052] The unit structure includes a nanostructure layer, an optical waveguide layer, and a dielectric substrate layer arranged sequentially from top to bottom. The nanostructure layer is composed of diatomic nanobricks, which have geometric asymmetry.

[0053] The on-chip metasurface contains several diatomic nanobricks that form multiple nanobrick arrays; all diatomic nanobricks in each nanobrick array have the same geometric size, while the diatomic nanobricks in different nanobrick arrays have different geometric sizes; each nanobrick array is used to selectively extract a certain narrowband spectrum, while different nanobrick arrays are used to selectively extract different spectral ranges.

[0054] Step 2: Using the geometric dimensions of the biatomic nanobricks in each nanobrick array as an adjustment parameter, the color information of the image is encoded into the on-chip metasurface.

[0055] In this process, multiple arrays of different types of nanobricks are horizontally cascaded, and the on-chip metasurface selectively extracts guided waves of different wavelengths from different spatial locations into free space for color routing.

[0056] The diatomic nanobricks are composed of two rectangular nanobricks with the same geometric dimensions; the geometric dimensions of the diatomic nanobricks in the i-th group of nanobrick arrays are set as: L i =L0×S i W i =W0×S i Pi =P x =P y =P0×S i Among them, L i Let W be the length of the diatomic nanobrick in the i-th nanobrick array. i Let P be the width of the two-atom nanobrick in the i-th nanobrick array. i Let P be the period of the diatomic nanobricks in the i-th group of nanobrick arrays. x and P y Let L0 be the period of the diatomic nanobrick along the x-axis and y-axis, respectively, and let W0 be the reference length, W0 be the reference width, P0 be the reference period, and S be the reference period. i S is the scaling factor for the i-th group of nanobrick arrays. i >0; different groups of nanobrick arrays have different scaling factors; the wavelength corresponding to the spectral peak extracted from the nanobrick array increases with the increase of the scaling factor; the geometric size of the diatomic nanobricks in each group of nanobrick arrays is determined based on the color information of the image.

[0057] By precisely adjusting the scaling factor of the nanobrick array, i.e., increasing or decreasing the period and size of the unit structure as a whole, wavelength selective extraction and routing of the output coupled light can be achieved, resulting in narrowband spectral extraction.

[0058] Both the reference length and the reference width are subwavelength dimensions; the guided wave propagates along the x-axis, and the local displacement between the diatomic nanobricks along the x-axis is P. x / 2.

[0059] In a preferred embodiment, the method may further include: using the rotation angle of the diatomic nanobricks in each nanobrick array as an adjustment parameter to encode the intensity information of the image into the on-chip metasurface.

[0060] The asymmetry factor α of the i-th group of nanobrick arrays i Defined as α i =sinθ i The spectral intensity extracted from the nanobrick array increases with the increase of the asymmetry factor; the rotation angle design of the diatomic nanobricks in each nanobrick array is determined based on the intensity information of the image.

[0061] The difference between Example 2 and Example 1 is that the on-chip metasurface of Example 2 contains several of the aforementioned two-atom nanobricks forming multiple nanobrick arrays. That is, Example 2 adopts cascaded multiplexing, which can realize wavelength-selective light extraction. The on-chip metasurface can also realize multi-color routing.

[0062] Example 2 demonstrates that by precisely adjusting the geometric asymmetry and scaling factor of the diatomic nanobricks in multiple nanobrick arrays, selective extraction and routing of guided waves into free space can be achieved, while simultaneously generating intensity-tunable narrowband spectral extraction.

[0063] Example 3:

[0064] Example 3 provides an on-chip metasurface, which is obtained using the on-chip metasurface design method as described in Example 1 or Example 2.

[0065] Example 4:

[0066] Example 4 provides a method for color routing based on an on-chip metasurface. It employs spatial mapping to encode the color information of an image into the on-chip metasurface described in Example 2. The on-chip metasurface contains several diatomic nanobricks forming multiple nanobrick arrays, with multiple arrays of different types horizontally cascaded. The on-chip metasurface selectively extracts guided waves of different wavelengths from different spatial locations into free space for color routing, thereby achieving multi-color routed image display.

[0067] Based on the above scheme, the intensity information of the image can also be encoded into the on-chip metasurface. That is, the preferred scheme is to encode the color information and intensity information of the image into the on-chip metasurface to realize multi-color routing image display with controllable spectral intensity.

[0068] The preferred approach encodes the color and intensity information of the image into dual superstructure atom pairs with different geometric dimensions and rotation angles, and demonstrates the implementation of multicolor routing image display by horizontally cascading pixels assisted by different BICs.

[0069] The present invention will be further described below with reference to the parameters.

[0070] See Figure 1 The unit structure of the on-chip metasurface (i.e., on-chip nonlocal metasurface) includes, from top to bottom, a nanostructure layer, an optical waveguide layer 2, and a dielectric substrate layer 3. The nanostructure layer is composed of diatomic nanobricks, for example, pairs of tilted amorphous silicon (α-Si) nanobricks 1. The major axis dimension (i.e., length) of each nanobrick 1 is L, the minor axis dimension (i.e., width) is W, and the height is H, where H can be 380 nm. θ is the tilt angle (i.e., rotation angle) of the major axis of one of the diatomic nanobricks relative to the y-axis. The periods along the x and y directions are represented by P, respectively. x and P y The optical waveguide layer 2 can be a Si3N4 planar waveguide with a thickness of 220 nm and a high effective refractive index (n is approximately 2.05). The dielectric substrate layer 3 can be a SiO2 substrate with a thickness of 500 μm.

[0071] The key working principle of the on-chip color routing metasurface (i.e., BIC-assisted router) provided by this invention is based on the concept of quasi-bound states (q-BIC) in a continuous medium. This is achieved by applying spatially varying perturbations to break the in-plane inversion symmetry of the dual metamaterial atom pairs (see...). Figure 2 It can convert guided wave mode (bound wave) into free space optical field mode (quasi-bound wave). Figure 2 In this context, θ represents the tilt angle of the BIC-assisted diatomic nanobricks, and the local displacement between the diatomic nanobricks along the x-direction is designed as P. x / 2. Specifically, the symmetry-protected BIC structure (θ = 0°) is in an undisturbed state and has a large wave vector, which confines the guided wave to propagate within the waveguide rather than extracting it into free space. As asymmetry gradually develops (θ > 0°), perturbations are applied to the double metacrystalline silicon atom pairs, doubling the effective lattice period, causing the guided mode to leak into free space due to the period-doubling perturbation.

[0072] Figure 3 A 3D schematic diagram of the q-BIC nanostructure array designed in this invention under TE0 mode incident conditions is shown. Then, we analyze the in-plane electric field intensity |E| of the dual metapairs. 2 The distributions are simulated, and the mode diagrams of BIC and q-BIC excited on the periodic array are shown respectively. Specifically, Figure 4 (a) and Figure 4 (b) represents the simulated electric field intensity (|E|) in the xy plane when the TE0 mode is incident from the x direction, under two cases: rotation angle θ = 0° and θ = 20°. 2 Distribution. The corresponding parameters are L = 130 nm, W = 65 nm, P x =P y =400nm and H=380nm. Figure 4 Figure (c) shows the electric field intensity distribution (|E|) in the yz plane at rotation angles θ = 0°, θ = 20°, and θ = 40°. 2 ).

[0073] The photon leakage behavior of symmetry-protected metasurfaces is fundamentally determined by the asymmetry factor α, defined as the sine of the rotation angle θ, i.e., α = sinθ. The asymmetry factor α controls the extracted light intensity, allowing the intensity of the spectrum to be adjusted by changing the rotation angle θ. The simulated electric field intensities (|E|) on the yz cross section at θ = 0°, 20°, and 40° are shown. 2 ) distribution, corresponding Figure 4 (c) shows a significant intensity change, indicating that the greater the asymmetry, the stronger the off-screen extraction intensity.

[0074] Figure 5In the image, (a) shows the extracted spectral profile of the simulated on-chip BIC dual meta-atom array as the rotation angle changes from 0° to 20°. Figure 5 (a) shows the simulated two-dimensional extracted spectrum as a function of θ, exhibiting a spike against a low-spectral background in the broadband visible light range.

[0075] Figure 5 (c) shows the detailed extraction spectrum, specifically the extraction spectrum of the BIC double meta-atom array at rotation angles θ = 0°, θ = 10° and θ = 20°. It can be seen that the extraction intensity increases accordingly as the rotation angle θ increases from 0° to 20°, confirming that the extraction spectrum intensity can be adjusted by adjusting the asymmetry parameter.

[0076] In addition to intensity control, wavelength-selective extraction of the output coupled light can also be achieved by adjusting the size of the double metapairs. Figure 5 (b) shows the simulated extraction spectrum of the BIC double metamorphic atomic array when the length L changes from 120 nm to 180 nm, with the corresponding parameters being W = 60 nm and P... x =P y =400nm and H=380nm. It can be seen that as the length L increases from 120nm to 180nm (with the width fixed at 60nm), the simulated extracted spectral peak position redshifts from 602nm to 680nm.

[0077] We further investigated numerically the dependence of the extracted spectrum on the cell size multiplied by the scaling factor S (given by L = L0 × S, W = W0 × S, P = P0 × S). Figure 5 In Figure (d), the extracted spectra of the BIC dual meta-atom array are obtained by varying the scaling factor S from 0.85 to 1, while keeping θ fixed at 20°. When S = 1, the corresponding parameters are L0 = 160 nm, W0 = 60 nm, and P0 = 400 nm. The results show that when θ = 20°, adjusting S from 0.85 to 1 shifts the spectral peak from 580 nm to 660 nm.

[0078] To illustrate the unique color routing function more intuitively, we predefine an array with a continuously gradient-varying length L of the dual metapairs, ranging from 95nm to 170nm (keeping W fixed at 60nm), and arranges BIC-assisted dual metapairs along the propagation direction (x-axis). Figure 6 The simulated electric field intensities (|E|) with wavelengths of 572 nm, 608 nm, and 652 nm extracted from the waveguide in this embodiment of the invention are... 2 ) distribution, among which, Figure 6 (a) in the figure shows the simulated electric field intensity distribution at a wavelength of 572 nm extracted from the waveguide; Figure 6(b) in the figure shows the simulated electric field intensity distribution at a wavelength of 608 nm extracted from the waveguide; Figure 6 In the diagram, (c) shows the simulated electric field intensity distribution at a wavelength of 652 nm extracted from the waveguide, with the black arrow indicating the propagation direction of the guided wave. The simulated electric field intensity |E| of the array on the xz cross section... 2 The distribution indicates that guided waves of different wavelengths will be strongly extracted into free space from their respective locations. Therefore, this on-chip cascade can selectively extract guided waves of different wavelengths from different spatial locations into free space for color routing.

[0079] Compared to free-space metasurfaces, the on-chip metasurface provided by this invention offers significant advantages in horizontally cascading multiple structures. This allows for the integration of periodic BIC-assisted arrays to selectively extract and route guided waves, such as... Figure 7 This is conceptually illustrated. When the broadband light guide encounters the red extraction array, light waves of other colors (such as yellow and green) continue to propagate without any loss of energy utilization efficiency. It is worth noting that the on-chip extraction efficiency itself is relatively low (less than about 7%); however, the emphasis here on no loss of energy utilization efficiency means that, due to the on-chip cascading strategy, all extracted energy is fully utilized to construct the corresponding wavelength channels, without energy blockage or waste caused by traditional spatial multiplexing schemes.

[0080] Furthermore, we conducted a numerical study on the extracted spectra of a BIC-assisted M×N cell periodic array, where N varied from 1 to 50. Here, M and N are the row number (y-direction) and column number (x-direction) of the array, respectively, where M approaches infinity due to the periodic boundary conditions in the y-direction. Specifically, Figure 8 In the image (a), the extracted spectra are simulated for arrays of different sizes, with the number N along the propagation direction (x-axis) varying from 1 to 50; Figure 8 (b) in the middle is from Figure 8 A line plot of the maximum extraction efficiency is shown in (a) of the spectrum. The spectra and maximum extraction efficiencies of these arrays show that the peak extraction efficiency increases as the array size N expands along the x-direction. Note that after N > 20, the peak extraction efficiency reaches saturation (approximately 0.5) and does not increase significantly even with further increases in array size.

[0081] To experimentally demonstrate narrowband wavelength selective extraction and intensity tuning in on-chip nonlocal metasurfaces, we fabricated designed samples using plasma-enhanced chemical vapor deposition (PECVD) and conventional electron beam lithography (EBL). A broadband polarized laser (500 nm to 800 nm) was coupled to a waveguide via an end face using an fiber collimator. For a fixed scaling factor (S = 1), as the asymmetry parameter increases, Figure 9Figure (a) shows the experimental extraction spectra of different arrays as the rotation angle θ changes from 0° to 30°, demonstrating that the extraction intensity increases simultaneously, thus experimentally verifying the continuous intensity adjustment achieved by introducing an asymmetric parameter. We further prepared another set of on-chip samples with a scaling factor S varying from 0.88 to 1 (keeping the rotation angle θ = 25° constant). Figure 9 Figure (b) shows the experimental extraction spectra of different arrays as the scaling factor S changes from 0.88 to 1. It can be seen that as the scaling factor increases, the measured extraction peak position redshifts from 570 nm to 630 nm, which is very consistent with the theoretical trend.

[0082] To further explore selective extraction and routing capabilities, we demonstrate their potential applications in micro-image display. Figure 10 The diagram schematically compares a conventional on-chip grating external coupler (GO) with the proposed BIC-assisted router (BIC-RO), highlighting the shift from broadband external coupling to narrowband wavelength-selective extraction. Using our designed on-chip BIC-assisted dual meta-atom array, we fabricated solid-color fonts of the letters "R" and "G," as well as "R" and "G" letters formed using conventional GO, for comparison. To evaluate the on-chip color routing display performance, we used an optical microscope with a 50x objective and a CCD camera to focus near the sample surface and capture the light intensity distribution extracted from the on-chip pattern. Figure 11 (a) shows the experimental measurement setup used to characterize on-chip near-field micro-image displays, which mainly includes a laser, a polarizer, a lens, an objective lens, and a CCD. Figure 11 Figure (b) shows the experimental extraction spectra of green and red RO for conventional GO and the BIC-assisted router proposed in this invention, confirming that BIC-RO achieves narrowband (approximately 20 nm) wavelength-selective extraction, while conventional GO is broadband (approximately 60 nm) with external coupling. GO composed of a single metaatomic pixel is intentionally used here for comparison because its extraction intensity at red and green wavelengths lacks contrast.

[0083] To further illustrate the actual selective extraction and routing capabilities of on-chip BIC-assisted metasurfaces Figure 12 The diagram schematically illustrates the extraction performance of conventional GO and the BIC-RO proposed in this invention under guided wave incidence with different wavelength combinations. When red (640 nm) and green (530 nm) guided waves are incident, the corresponding... Figure 12 In (a), traditional broadband GO extracts two wavelengths simultaneously without significant contrast, causing the letters "R" and "G" to appear yellow due to the mixing of red and green. Figure 12 In contrast, the BIC-RO proposed in this invention extracts only the red and green wavelengths separately, displaying different red and green colors respectively. Figure 12 (c) in the middle. Similarly, when only red (640nm) is present (see...). Figure 12 (d) shown in the middle) or green (530nm) (see Figure 12 When the guided wave (as shown in (g)) is incident, a conventional GO will non-selectively extract the corresponding color (see [reference]). Figure 12 (e) and Figure 12 (as shown in (h)), while BIC-RO can selectively extract red (see [reference]). Figure 12 (shown in middle (f)) and green (see Figure 12 As shown in (i) in the figure, this successfully confirmed the color routing in the micro-image display.

[0084] Next, by encoding color and brightness information (i.e., intensity information) into different dual-superstructure atom pairs with different geometric dimensions and tilt angles (i.e., rotation angles), we can create on-chip stereoscopic and multicolor nanoprinted images. First, we select a stereoscopic "3D" pattern as the target image; see [link to relevant documentation]. Figure 13 In (a), the image is pixelated using a parameter matching method, then segmented into different color and intensity channels, and each pixel is matched to the closest color and intensity with a BIC-assisted dual meta-atom array. In Demonstration 1, two different patterns were created, and the experiment yielded red and green stereoscopic "3D" images, as shown in [example 1]. Figure 13 As shown in (b) above. This highlights the differences in extracted color and intensity between BIC-assisted dual-superatoms under different tilt angles and scaling factors. Next, we present a display of the two-color (650nm and 560nm) grayscale images “Red Flower and Green Leaf” (i.e., Demonstration 2) (see [link]). Figure 14 The images all exhibit vibrant colors and smooth brightness transitions. Notably, thanks to the on-chip propagation scheme, the captured images are unaffected by zero-order background interference and do not require additional optical components such as a polarization analyzer.

[0085] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for designing an on-chip metasurface, characterized in that, Includes the following steps: A unit structure for constructing an on-chip metasurface is provided. The unit structure includes a nanostructure layer, an optical waveguide layer, and a dielectric substrate layer arranged sequentially from top to bottom. The nanostructure layer is composed of diatomic nanobricks, which have geometric asymmetry. The on-chip metasurface contains a plurality of the diatomic nanobricks that form multiple nanobrick arrays. Each group of nanobrick arrays contains all diatomic nanobricks with the same geometric dimensions, while different groups of nanobrick arrays contain diatomic nanobricks with different geometric dimensions. Each group of nanobrick arrays is used to selectively extract a certain narrow band spectrum, and different groups of nanobrick arrays are used to selectively extract different spectral ranges. The geometric dimensions of the biatomic nanobricks in each nanobrick array are used as adjustment parameters to encode the color information of the image into the on-chip metasurface. The on-chip metasurface contains several diatomic nanobricks that form multiple nanobrick arrays. Multiple nanobrick arrays of different types are horizontally cascaded. The on-chip metasurface selectively extracts guided waves of different wavelengths from different spatial locations into free space for color routing.

2. The design method for on-chip metasurfaces according to claim 1, characterized in that, Establish an xoy coordinate system with the two sides parallel to the working surface of the optical waveguide layer. The rotation angles of the two nanobricks in the i-th group of nanobrick array about the y-axis are θ and θ respectively. i 180°-θ i And 0° < θ i <90°; all diatomic nanobricks in each nanobrick array have the same rotation angle design.

3. The design method for on-chip metasurfaces according to claim 2, characterized in that, The diatomic nanobricks are composed of two rectangular nanobricks with the same geometric dimensions; the geometric dimensions of the diatomic nanobricks in the i-th group of nanobrick arrays are set as: L i = L0×S i W i = W0×S i P i = P x =P y =P0×S i Among them, L i Let W be the length of the diatomic nanobrick in the i-th nanobrick array. i Let P be the width of the two-atom nanobrick in the i-th nanobrick array. i Let P be the period of the diatomic nanobricks in the i-th group of nanobrick arrays. x and P y Let L0 be the period of the diatomic nanobrick along the x-axis and y-axis, respectively, and let W0 be the reference length, W0 be the reference width, P0 be the reference period, and S be the reference period. i S is the scaling factor for the i-th group of nanobrick arrays. i > 0; different groups of nanobrick arrays have different scaling factors; the wavelength corresponding to the spectral peak extracted from the nanobrick array increases with the increase of the scaling factor; the geometric size of the diatomic nanobricks in each group of nanobrick arrays is determined based on the color information of the image.

4. The design method for an on-chip metasurface according to claim 3, characterized in that, Both the reference length and the reference width are subwavelength dimensions; the guided wave propagates along the x-axis, and the local displacement between the diatomic nanobricks along the x-axis is P. x / 2.

5. The design method for an on-chip metasurface according to claim 2, characterized in that, Also includes: The rotation angle of the diatomic nanobricks in each nanobrick array is used as an adjustment parameter to encode the intensity information of the image into the on-chip metasurface.

6. The design method for an on-chip metasurface according to claim 5, characterized in that, The asymmetry factor α of the i-th group of nanobrick arrays i Defined as α i =sinθ i The spectral intensity extracted from the nanobrick array increases with the increase of the asymmetry factor; the rotation angle design of the diatomic nanobricks in each nanobrick array is determined based on the intensity information of the image.

7. An on-chip metasurface, characterized in that, It is obtained by using the design method of on-chip metasurface as described in any one of claims 1-6.

8. A method for implementing color routing based on an on-chip metasurface, characterized in that, The color information of the image is encoded into the on-chip metasurface as described in claim 7 by means of spatial mapping. The on-chip metasurface contains several diatomic nanobricks that form multiple nanobrick arrays, and multiple nanobrick arrays of different types are horizontally cascaded. The on-chip metasurface is used to selectively extract guided waves of different wavelengths from different spatial positions into free space for color routing, thereby realizing multi-color routing image display.

9. The method for implementing color routing based on on-chip metasurfaces according to claim 8, characterized in that, The color and intensity information of the image are encoded into the on-chip metasurface to achieve multi-color routing image display with controllable spectral intensity.

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