Intrinsically chiral metasurface and preparation method and application thereof

Abstract

This invention discloses an intrinsically chiral metasurface, its preparation method, and its applications, relating to the field of electromagnetic materials technology. The intrinsically chiral metasurface is based on satisfying… C 2. A symmetrical "+" shaped BIC structure, by adjusting the relative positions of the rectangles on both sides of the structure, simultaneously disrupts the mirror symmetry of the structure. C 2. Symmetry, so that the corresponding circularly polarized C The point forms at the Γ point in wave vector space, achieving chiral resonance in the vertical direction of real space. The intrinsic chiral metasurface of this invention requires only simple planar geometry adjustments, reducing the requirements for manufacturing technology and facilitating large-scale fabrication. Furthermore, the intrinsic chiral metasurface of this invention can theoretically achieve over 99% circular polarization without additional optical components, which is beneficial for integrated applications. Further, when the intrinsic chiral metasurface of this invention is integrated with a gain material such as perovskite, it realizes chiral laser emission in the vertical direction, demonstrating its application potential in the field of chiral light sources.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic materials technology, and in particular to an intrinsically chiral metasurface, its preparation method, and its applications. Background Technology

[0002] Metasurfaces are a class of artificially designed electromagnetic materials that can be constructed on demand within a two-dimensional plane at subwavelength scales, thereby achieving extraordinary physical properties not found in natural materials, such as negative refractive index, electromagnetic wave invisibility, and the anti-Doppler effect. Among them, chiral metasurfaces, due to their different response characteristics to left-handed and right-handed circularly polarized light, are widely used in fields such as biosensing, optical encryption, and quantum information processing.

[0003] Among the various optical modes supported by metasurfaces, bound states in the continuous domain (BIC) have attracted widespread attention from researchers both domestically and internationally in recent years due to their high quality factor and excellent polarization control capabilities, and have been used to excite chiral resonances. The core of BIC-based chiral resonance excitation lies in disrupting the structure. C 2. Symmetry (i.e., in-plane 180° rotational symmetry) splits the polarization singularity at the BIC position in wave vector space into two circularly polarized points corresponding to left-handed and right-handed polarization, respectively. C point.

[0004] The method to achieve this goal is usually to make the original satisfaction C 2. Symmetrical structures (such as circles, squares, etc.) are changed to asymmetrical shapes (such as trapezoids, triangles, etc.) or asymmetrical arrangements are adopted. This structural adjustment will create two circularly polarized poles near the Γ point in wave vector space, corresponding to left-handed and right-handed polarization respectively. C In real space, this chirality manifests as chiral resonance radiating along a tilted direction. It is noteworthy that this type of chirality is extrinsic chirality; its chiral signal does not originate from the intrinsic chirality of the structure itself, but rather depends on the tilt of the probe direction or incident angle. Furthermore, the quality factor of this type of chiral resonance is typically subject to significant limitations.

[0005] In order to [determine the wave vector space] CTo achieve high-quality intrinsic chirality resonance in the vertical direction of real space by moving the point to the Γ point, researchers propose that the out-of-plane mirror symmetry of the metasurface structure needs to be disrupted. Achieving this typically requires angle-dependent tilting etching techniques to fabricate tilted resonant metasurfaces, or using grayscale lithography, multi-step lithography, or even twisted stacking of multilayer resonant structures to construct resonant unit arrangements of different heights. These methods place high demands on fabrication precision, such as requiring accurate overlay alignment, and the overall process is relatively complex, making it difficult to achieve simple, controllable, large-scale fabrication.

[0006] Therefore, existing technologies still need improvement and development. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide an intrinsically chiral metasurface, its preparation method and application, aiming to overcome the problems of complex process, high precision requirements and difficulty in large-scale preparation caused by the need to destroy the external mirror symmetry of the metasurface structure in order to achieve BIC-based intrinsic chiral resonance.

[0008] The technical solution of the present invention is as follows: In a first aspect, an intrinsically chiral metasurface is provided, the intrinsically chiral metasurface being composed of periodically arranged units, each unit comprising: a substrate layer and a chiral layer loaded on the substrate layer; The base layer has a square planar shape with periodic sides. p ; The chiral layer has a chiral structure, which is composed of three cuboids: a first cuboid, a second cuboid, and a third cuboid. The first, second, and third cuboids have the same height H and are located in the same plane; The base layer is established with one corner of a square as the origin, one side as the x-axis, another side perpendicular to the x-axis as the y-axis, and the z-axis perpendicular to the base layer, forming a spatial coordinate system upwards. The center coordinates of the base layer are ( ). p / 2, p / 2, 0), the geometric center coordinates of the first cuboid are ( p / 2, p / 2, H / 2); From a top-down perspective, the first cuboid, the second cuboid, and the third cuboid are respectively a first rectangle, a second rectangle, and a third rectangle; The longer side of the first rectangle is parallel to the y-axis; The shorter side of the second rectangle closest to the y-axis overlaps with the longer side of the first rectangle furthest from the y-axis. The perpendicular distance between the longer side of the second rectangle closest to the x-axis and the shorter side of the first rectangle closest to the x-axis is [missing information]. Δ ; The short side of the third rectangle away from the y-axis overlaps with the long side of the first rectangle close to the y-axis, and the vertical distance between the long side of the third rectangle away from the x-axis and the short side of the first rectangle away from the x-axis is 0.

[0009] The preferred technical solution, the p = 450~550 nm.

[0010] In a preferred technical solution, the longer side of the first rectangle l 1 = 300~350 nm, with the shorter side being w 1 = 90~110 nm.

[0011] In the preferred technical solution, the longer side of the second rectangle l 2 = 90~110 nm, with the shorter side being w 2 = 75~90 nm.

[0012] In the preferred technical solution, the long side of the third rectangle l 3 = 90~110 nm, with the shorter side being w 3 = 75~90 nm.

[0013] The preferred technical solution, the Δ = 20~80 nm.

[0014] A further preferred technical solution, the p = 460 nm.

[0015] A further preferred technical solution is that the long side of the first rectangle l 1 = 322 nm, with the shorter side being w 1 = 98 nm.

[0016] A further preferred technical solution is that the long side of the second rectangle l 2 = 98 nm, with the shorter side being w 2 = 83 nm.

[0017] A further preferred technical solution is that the long side of the third rectangle l 3 = 94 nm, the shorter side is w 3 = 83 nm.

[0018] A further preferred technical solution, the Δ = 56 nm.

[0019] In a preferred embodiment, the material of the chiral structure includes one or more of silicon dioxide, silicon nitride, titanium dioxide, amorphous silicon, polycrystalline silicon, and monocrystalline silicon.

[0020] In a preferred embodiment, the substrate layer is made of one or more of silicon dioxide, silicon nitride, titanium dioxide, sapphire, amorphous silicon, polycrystalline silicon, and monocrystalline silicon.

[0021] In a preferred embodiment, the intrinsic chiral metasurface further includes a gain material filling the spaces between the chiral structures of the chiral layer.

[0022] In a further preferred embodiment, the gain material is selected from perovskite, colloidal quantum dots, or organic dyes.

[0023] In a further preferred embodiment, the perovskite is selected from MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3, CsPbCl3, MASnI3, FASnI3, CsSnI3, MASnBr3, FASnBr3, CsSnBr3, MASnCl3, FASnCl3, CsSnCl3, PEA2MA n-1 Pb n Br 3n+1 PEA2Cs n-1 Pb n Br 3n+1 BA2MA n-1 Pb n I 3n+1 and PEA2FA n-1 Sn n I 3n+1 One or more of the following, where n represents an integer.

[0024] In a further preferred embodiment, the colloidal quantum dots are selected from one or more of PbS, PbSe, CdSe, InP, and ZnSe.

[0025] In a further preferred embodiment, the organic dye is selected from one or more of the following: IR-140, IR-808, IR-825, Cy7, iFluor 800, IR-900, IR-950, FD-1080, IR-1048, IR-1061, DCM dye, PM597, and the Rhodamine series.

[0026] Secondly, a method for preparing the intrinsically chiral metasurface described in the first aspect is provided, comprising the steps of: A substrate is provided, the substrate comprising a base layer and a chiral material layer loaded on the base layer; A photoresist layer is prepared on the chiral material layer, and the chiral structure is exposed and developed to obtain a chiral material layer with photoresist masking. A chromium thin film is deposited on the chiral material layer with photoresist masking, and then the photoresist layer is removed to obtain a chiral material layer with chromium masking. The chiral material layer with chromium masking is etched, and then the chromium film is removed to form a chiral layer with a chiral structure, thus obtaining the intrinsic chiral metasurface.

[0027] In a preferred embodiment, the substrate is an SOI silicon wafer; The SOI silicon wafer consists of a substrate silicon layer, a silicon dioxide layer, and a single-crystal silicon layer from bottom to top; the single-crystal silicon layer is a chiral material layer.

[0028] Thirdly, the application of the intrinsic chiral metasurface described in the first aspect in chiral light sources is provided.

[0029] Compared with the prior art, the advantages of the technical solution of the present invention include: (1) Compared with the complex process of destroying the external mirror symmetry of the metasurface structure in order to achieve BIC intrinsic chiral resonance in the prior art, the intrinsic chiral metasurface of the present invention can achieve BIC intrinsic chiral resonance by simply adjusting the planar geometry, which greatly reduces the requirements for manufacturing technology and makes it easier to achieve large-scale preparation and application.

[0030] (2) The intrinsic chiral metasurface of the present invention can theoretically achieve a circular polarization degree of more than 99% without additional optical elements (such as waveplates, liquid crystal layers, etc.), which is beneficial for integrated applications.

[0031] (3) The intrinsic chiral metasurface of the present invention, after being integrated with a gain material such as perovskite, realizes chiral laser emitted in the vertical direction, demonstrating its application potential in the field of chiral light sources.

[0032] (4) Compared with the metasurface structures commonly used for luminescence research, which are constructed on glass and quartz substrates, the intrinsic chiral metasurface of this invention and its integration with gain materials can be directly completed on SOI silicon wafers. The substrate has better thermal conductivity, and the sample preparation is more compatible with Si-based chip manufacturing processes, which is expected to promote the development of on-chip chiral light sources. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the design scheme of the intrinsic chiral metasurface of the present invention.

[0034] Figure 2 This is the simulated circularly polarized reflection spectrum of the type ① metasurface in the vertical direction in Example 1.

[0035] Figure 3This is the simulated circularly polarized reflection spectrum of the type ② metasurface in the vertical direction in Example 2.

[0036] Figure 4 This is the simulated circularly polarized reflection spectrum of the type ③ metasurface in the vertical direction in Example 3.

[0037] Figure 5 This is a schematic diagram of the optimized type ③ metasurface structure unit in Example 4.

[0038] Figure 6 This is the simulated circularly polarized reflection spectrum of the optimized type ③ metasurface in the vertical direction in Example 4.

[0039] Figure 7 It is the simulated circular polarization spectrum of the optimized type ③ metasurface in the vertical direction in Example 4.

[0040] Figure 8 These are scanning electron microscope images of the intrinsically chiral metasurface prepared in Example 5.

[0041] Figure 9 It is the circularly polarized reflection spectrum in the vertical direction of the intrinsic chiral metasurface prepared in Example 5.

[0042] Figure 10 It is the circular polarization spectrum of the intrinsic chiral metasurface prepared in Example 5 in the vertical direction.

[0043] Figure 11 The image shows the angle-resolved right-handed circularly polarized emission spectrum of the integrated perovskite intrinsic chiral metasurface prepared in Example 5.

[0044] Figure 12 The image shows the angle-resolved left-handed circularly polarized emission spectrum of the integrated perovskite intrinsic chiral metasurface prepared in Example 5. Detailed Implementation

[0045] This invention provides an intrinsically chiral metasurface, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below.

[0046] In existing technologies, to achieve intrinsic chiral resonance based on BIC, it is necessary to destroy the external mirror symmetry of the metasurface structure, which brings problems such as complex processes, high precision requirements, and difficulty in large-scale fabrication.

[0047] Based on this, embodiments of the present invention provide an intrinsic chiral metasurface, wherein the intrinsic chiral metasurface is composed of periodically arranged units, and each unit includes: a substrate layer and a chiral layer loaded on the substrate layer; The base layer has a square planar shape with periodic sides. p ; The chiral layer has a chiral structure, which is composed of three cuboids: a first cuboid, a second cuboid, and a third cuboid. The first, second, and third cuboids have the same height H and are located in the same plane; The base layer is established with one corner of a square as the origin, one side as the x-axis, another side perpendicular to the x-axis as the y-axis, and the z-axis perpendicular to the base layer, forming a spatial coordinate system upwards. The center coordinates of the base layer are ( ). p / 2, p / 2, 0), the geometric center coordinates of the first cuboid are ( p / 2, p / 2, H / 2); From a top-down perspective, the first cuboid, the second cuboid, and the third cuboid are respectively a first rectangle, a second rectangle, and a third rectangle; The longer side of the first rectangle is parallel to the y-axis; The shorter side of the second rectangle closest to the y-axis overlaps with the longer side of the first rectangle furthest from the y-axis. The perpendicular distance between the longer side of the second rectangle closest to the x-axis and the shorter side of the first rectangle closest to the x-axis is [missing information]. Δ ; The short side of the third rectangle away from the y-axis overlaps with the long side of the first rectangle close to the y-axis, and the vertical distance between the long side of the third rectangle away from the x-axis and the short side of the first rectangle away from the x-axis is 0.

[0048] Specifically, this invention designs an intrinsic chiral metasurface structure based on BIC (Bipolar Instinct). By manipulating the in-plane geometry of the metasurface, intrinsic chiral resonance in the vertical direction can be achieved. This intrinsic chiral metasurface structure is based on satisfying... C 2. A symmetrical "+" shaped BIC structure, by adjusting the relative positions of the rectangles on both sides of the structure, simultaneously disrupts the mirror symmetry of the structure. C 2. Symmetry, so that the corresponding circularly polarized C The point is formed at the Γ point in the wave vector space, and chiral resonance is achieved in the vertical direction of the real space.

[0049] The design process of this intrinsically chiral metasurface structure is as follows: An infinitely thick Si substrate with a 350 nm thick SiO2 planar substrate is constructed in optical simulation software, and a 200 nm thick Si metasurface structure with a period of 450 nm is then constructed on top of it. The metasurface structure unit is as follows: Figure 1 ① It has a "+" shaped structure, and the width of each side is... w 1. Set the wavelength to 100 nm; 2. Adjust the "+" shaped structure to a "z" shaped structure; 3. Move the rectangular area at the lower right corner of the "z" shaped structure upwards. Δ distance, Δ= 30 nm. Solve the vertical reflection spectra of the three types of metasurface structures to determine their intrinsic chiral resonance characteristics. Finally, optimize the geometric parameters of structure ③ to obtain the maximum circular polarization degree, and obtain the final intrinsic chiral metasurface structure.

[0050] In some embodiments, the p = 450~550 nm, but not limited to this.

[0051] In some embodiments, the longer side of the first rectangle l 1 = 300~350 nm, with the shorter side being w 1 = 90~110nm, but not limited to this.

[0052] In some embodiments, the longer side of the second rectangle l 2 = 90~110 nm, with the shorter side being w 2 = 75~90 nm, but not limited to this.

[0053] In some embodiments, the longer side of the third rectangle l 3 = 90~110 nm, with the shorter side being w 3 = 75~90 nm, but not limited to this.

[0054] In some embodiments, the Δ = 20~80 nm, but not limited to this.

[0055] In some embodiments, H = 100~300 nm, but is not limited thereto.

[0056] In some more specific embodiments, the p = 460 nm, but not limited to this.

[0057] In some more specific embodiments, the longer side of the first rectangle l 1 = 322 nm, with the shorter side being w 1 = 98nm, but not limited to this.

[0058] In some more specific embodiments, the longer side of the second rectangle l 2 = 98 nm, with the shorter side being w 2 = 83nm, but not limited to this.

[0059] In some more specific embodiments, the long side of the third rectangle l 3 = 94 nm, the shorter side is w 3 = 83nm, but not limited to this.

[0060] In some more specific embodiments, the Δ = 56 nm, but not limited to this.

[0061] In some more specific embodiments, H = 200 nm, but is not limited thereto.

[0062] In some embodiments, the material of the chiral structure includes one or more of silicon dioxide, silicon nitride, titanium dioxide, amorphous silicon, polycrystalline silicon, and monocrystalline silicon, but is not limited thereto.

[0063] In some embodiments, the substrate layer is made of one or more of silicon dioxide, silicon nitride, titanium dioxide, sapphire, amorphous silicon, polycrystalline silicon, and monocrystalline silicon, but is not limited thereto.

[0064] In some embodiments, the intrinsic chiral metasurface further includes, but is not limited to, a gain material filling the spaces between the chiral structures of the chiral layer.

[0065] Specifically, this invention, based on the designed intrinsic chiral metasurface, further combines it with gain materials to achieve effective control of chiral luminescence and explore its application potential in chiral lasers, thus providing a new technical path for high-performance, easily integrated on-chip chiral light sources.

[0066] In some more specific embodiments, the gain material is selected from perovskite, colloidal quantum dots, or organic dyes, but is not limited thereto.

[0067] In some more specific embodiments, the perovskite is selected from MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3, CsPbCl3, MASnI3, FASnI3, CsSnI3, MASnBr3, FASnBr3, CsSnBr3, MASnCl3, FASnCl3, CsSnCl3, PEA2MA n-1 Pb n Br 3n+1 PEA2Cs n-1 Pb n Br 3n+1 BA2MA n- 1Pb n I 3n+1 and PEA2FA n-1 Sn n I 3n+1One or more of the following, but not limited to, where n represents an integer. Specifically, these perovskites share the common characteristics of being room-temperature, solution-processable, and easily integrated with metasurfaces via spin coating. The intrinsically chiral metasurfaces prepared in the following specific embodiments of the present invention operate at a wavelength of around 800 nm, so FAPbI3 and MAPbI3 with emission bands in this range can be used as gain materials; simultaneously, through structural design, the operating wavelength of the intrinsically chiral metasurface can be extended to a longer wavelength range, so CsSnI3 and MASnI3 with longer emission bands can also be used as gain materials. In addition, when the material of the chiral structure is silicon nitride or titanium dioxide, the operating wavelength of the intrinsically chiral metasurface prepared in this embodiment is in the visible light range, so MAPbBr3, CsPbBr3, and FAPbBr3 with emission bands in the visible light range can be used as gain materials. Based on this, by controlling the size and material of the chiral structure, the intrinsically chiral metasurface prepared in this embodiment can also use other conventional perovskites or quasi-two-dimensional perovskites as gain materials, which will not be elaborated here.

[0068] In some more specific embodiments, the colloidal quantum dots are selected from one or more of PbS, PbSe, CdSe, InP, and ZnSe, but are not limited thereto. Specifically, these colloidal quantum dots share the common characteristics of being room temperature, solution-processable, and easily integrated with metasurfaces via spin coating. The intrinsically chiral metasurfaces prepared in the following specific embodiments of the present invention operate at a wavelength of approximately 800 nm, so PbS, with its emission band in this vicinity, can be used as a gain material. When the material of the chiral structure is silicon nitride or titanium dioxide, the operating wavelength of the intrinsically chiral metasurface prepared in this embodiment is in the visible light range, so CdSe and ZnSe, with their emission bands in the visible light range, can be used as gain materials. Based on this, by controlling the size and material of the chiral structure, the intrinsically chiral metasurface prepared in this embodiment can also use other colloidal quantum dots as gain materials, which will not be elaborated here.

[0069] In some more specific embodiments, the organic dye is selected from one or more of IR-140, IR-808, IR-825, Cy7, iFluor 800, IR-900, IR-950, FD-1080, IR-1048, IR-1061, DCM dyes, PM597, and the Rhodamine series, but is not limited thereto. Specifically, these organic dyes share the common characteristics of being room temperature, solution-processable, and easily integrated with metasurfaces via spin coating. The intrinsically chiral metasurfaces prepared in the following specific embodiments of the present invention operate at a wavelength of around 800 nm, therefore, IR-140, IR-808, IR-825, Cy7, and iFluor 800, with emission bands in this vicinity, can be used as gain materials; simultaneously, through structural design, the operating wavelength of the intrinsically chiral metasurface can be extended to a longer band, therefore, IR-900, IR-950, FD-1080, IR-1048, and IR-1061, with longer emission bands, can also be used as gain materials. When the chiral structure is made of silicon nitride or titanium dioxide, the intrinsically chiral metasurface prepared in this embodiment operates within the visible light range. Therefore, DCM dyes, PM597, and the Rhodamine series, whose emission bands are within the visible light range, can be used as gain materials. Furthermore, by controlling the size and material of the chiral structure, other organic dyes can also be used as gain materials for the intrinsically chiral metasurface prepared in this embodiment; these will not be elaborated upon here.

[0070] This invention provides a method for preparing the intrinsically chiral metasurface as described above, comprising the following steps: A substrate is provided, the substrate comprising a base layer and a chiral material layer loaded on the base layer; A photoresist layer is prepared on the chiral material layer, and the chiral structure is exposed and developed to obtain a chiral material layer with photoresist masking. A chromium thin film is deposited on the chiral material layer with photoresist masking, and then the photoresist layer is removed to obtain a chiral material layer with chromium masking. The chiral material layer with chromium masking is etched, and then the chromium film is removed to form a chiral layer with a chiral structure, thus obtaining the intrinsic chiral metasurface.

[0071] In some embodiments, after the step of forming a chiral layer with chiral structures, the step further includes filling the spaces between the chiral structures of the chiral layer with a gain material, but is not limited thereto.

[0072] In some embodiments, the substrate is an SOI silicon wafer; the SOI silicon wafer consists of a substrate silicon layer, a silicon dioxide layer and a single crystal silicon layer from bottom to top; wherein the single crystal silicon layer is a chiral material layer, but is not limited thereto.

[0073] In some more specific embodiments, when the substrate is an SOI silicon wafer, the method for preparing the intrinsically chiral metasurface includes the following steps: An SOI silicon wafer is provided, wherein the SOI silicon wafer consists of a substrate silicon layer, a silicon dioxide layer and a single crystal silicon layer from bottom to top; A photoresist layer is prepared on the single-crystal silicon layer of the SOI silicon wafer, and chiral structure exposure and development are performed to obtain a single-crystal silicon layer with photoresist masking. A chromium thin film is deposited on the single-crystal silicon layer with photoresist masking, and then the photoresist layer is removed to obtain a single-crystal silicon layer with chromium masking. The chromium-masked single-crystal silicon layer is etched, and then the chromium film is removed to form a single-crystal silicon layer with a chiral structure, thus obtaining the intrinsic chiral metasurface.

[0074] In some more specific embodiments, the thickness of the substrate silicon layer is 500~1000 µm, the thickness of the silicon dioxide layer is 300~400 nm, and the thickness of the single crystal silicon layer is 150~250 nm; preferably, the thickness of the substrate silicon layer is 675 µm, the thickness of the silicon dioxide layer is 350 nm, and the thickness of the single crystal silicon layer is 200 µm, but not limited thereto.

[0075] In some more specific embodiments, the thickness of the photoresist layer is 60-100 nm, preferably 80 nm, but not limited thereto. Specifically, the photoresist layer can be prepared from PMMA A2 positive electron beam resist, with a chiral structure as shown in the figure. Figure 5 As shown, exposure is achieved via electron beam, but is not limited to this.

[0076] In some more specific embodiments, the developing step is carried out by immersion in a mixed solution of methyl isobutyl ketone (MIBK) and isopropanol (IPA) (mixing ratio 1:3); preferably, the immersion time is 1 to 3 minutes, but not limited thereto.

[0077] In some more specific embodiments, the thickness of the chromium film is 30-70 nm, preferably 50 nm, but not limited thereto.

[0078] In some more specific embodiments, the step of removing the photoresist layer is performed by ultrasonic treatment in acetone; preferably, the ultrasonic treatment time is 40 to 80 minutes, but not limited thereto.

[0079] In some more specific embodiments, the etching step is carried out using a mixture of sulfur hexafluoride (SF6) and trifluoromethane (CHF3), but is not limited thereto.

[0080] In some more specific embodiments, the step of removing the chromium film is carried out by immersion in a chromium etchant; wherein the chromium etchant is a cerium ammonium nitrate system (such as Sigma-Aldrich, part number: 651826), but is not limited thereto.

[0081] In some more specific embodiments, after the step of forming the single-crystal silicon layer with a chiral structure, the method further includes filling the spaces between the chiral structures of the single-crystal silicon layer with a gain material, but is not limited thereto. Preferably, the gain material is perovskite; more preferably, the perovskite is FAPbI3, but is not limited thereto.

[0082] The embodiments of the present invention provide the application of the intrinsically chiral metasurface described above in a chiral light source.

[0083] The present invention will be further described below through specific embodiments.

[0084] Example 1 1) Metasurface Model Construction: A 3D model was constructed in COMSOL Multiphysics software. The bottom layer consisted of a 1 μm thick Si layer, upon which a 350 nm thick SiO2 layer was built. A 200 nm thick type ① Si structure was then constructed on top of the SiO2. Finally, a 1 μm thick air layer was placed over the type ① Si structure. The mesh was set to extremely fine. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) z A 500 nm perfectly matched layer is constructed on the top air layer and under the bottom Si layer in the direction. x , y All directions are set to Floquet periodic boundary conditions with a period of 450 nm. An excitation port is placed in the model air layer, and its electric model field follows either left-handed or right-handed circular polarization, with the propagation direction along - z Direction. An additional unexcited port is placed below the excitation port in the air layer to collect the reflected signal.

[0085] 2) Calculation of Circularly Polarized Reflection Spectra: Using electromagnetic waves and a wavelength-domain preset in the frequency domain physical field, a wavelength scanning range is added and calculations are performed. After the calculations are completed, the reflection spectra of left-handed and right-handed circularly polarized incident light in the vertical direction of the type ① Si metasurface can be obtained by comparing the reflected power collected at the unexcited port with the input power at the excitation port. The results are as follows: Figure 2 .

[0086] Example 2 1) Metasurface Model Construction: A 3D model was constructed in COMSOL Multiphysics software. The bottom layer consisted of a 1 μm thick Si layer, upon which a 350 nm thick SiO2 layer was built. A 200 nm thick type II Si structure was then constructed on top of the SiO2. Finally, a 1 μm thick air layer was placed over the type II Si structure. The mesh was set to extremely fine. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) z A 500 nm perfectly matched layer is constructed on the top air layer and under the bottom Si layer in the direction. x , y All directions are set to Floquet periodic boundary conditions with a period of 450 nm. An excitation port is placed in the model air layer, and its electric model field follows either left-handed or right-handed circular polarization, with the propagation direction along - z Direction. An additional unexcited port is placed below the excitation port in the air layer to collect the reflected signal.

[0087] 2) Calculation of Circularly Polarized Reflection Spectra: Using electromagnetic waves and a wavelength-domain preset in the frequency domain physical field, a wavelength scanning range is added and calculations are performed. After the calculations are completed, the reflection spectra of left-handed and right-handed circularly polarized incident light in the vertical direction of the type ② Si structure metasurface can be obtained by comparing the reflected power collected at the unexcited port with the input power at the excitation port. The results are as follows: Figure 3 .

[0088] Example 3 1) Metasurface Model Construction: A 3D model was constructed in COMSOL Multiphysics software. The bottom layer consisted of a 1 μm thick Si layer, upon which a 350 nm thick SiO2 layer was built. A 200 nm thick type ③ Si structure was then constructed on top of the SiO2. Finally, a 1 μm thick air layer was placed over the type ③ Si structure. The mesh was set to extremely fine. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) z A 500 nm perfectly matched layer is constructed on the top air layer and under the bottom Si layer in the direction. x , y All directions are set to Floquet periodic boundary conditions with a period of 450 nm. An excitation port is placed in the model air layer, and its electric model field follows either left-handed or right-handed circular polarization, with the propagation direction along - z Direction. An additional unexcited port is placed below the excitation port in the air layer to collect the reflected signal.

[0089] 2) Calculation of Circularly Polarized Reflection Spectra: Using electromagnetic waves and a wavelength-domain preset in the frequency domain physical field, a wavelength scanning range is added and calculations are performed. After the calculations are completed, the reflection spectra of left-handed and right-handed circularly polarized incident light in the vertical direction of the type ③ Si metasurface can be obtained by comparing the reflected power collected at the unexcited port with the input power at the excitation port. The results are as follows: Figure 4 .

[0090] Example 4 1) Metasurface Model Construction: A 3D model was constructed in COMSOL Multiphysics software. The bottom layer consisted of a 1 μm thick Si layer, upon which a 350 nm thick SiO2 layer was built. A 200 nm thick type ③ Si structure was then constructed on top of the SiO2. Finally, a 1 μm thick air layer was placed over the type ③ Si structure. The mesh was set to extremely fine. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) z A 500 nm perfectly matched layer is constructed on the top air layer and under the bottom Si layer in the direction. x , y All directions are set to Floquet periodic boundary conditions with a period of 450 nm. An excitation port is placed in the model air layer, and its electric model field follows either left-handed or right-handed circular polarization, with the propagation direction along - z Direction. An additional unexcited port is placed below the excitation port in the air layer to collect the reflected signal.

[0091] 2) Calculation of circularly polarized reflection spectrum: Using electromagnetic waves, wavelength domain preset research in the frequency domain physical field is conducted, a wavelength scanning range is added, and calculations are performed. After the calculation is completed, the reflection spectrum of left-handed and right-handed circularly polarized incident light in the vertical direction of the type ③ Si structure metasurface can be obtained by comparing the reflected power collected at the unexcited port with the input power at the excitation port.

[0092] 3) Metasurface Structure Optimization: The degree of circular polarization of the metasurface is calculated using the formula (left-handed circular polarization reflectance - right-handed circular polarization reflectance) / (left-handed circular polarization reflectance + right-handed circular polarization reflectance). The geometric parameters of the type ③ Si structure are continuously adjusted to maximize the degree of circular polarization. The optimized geometric structure is shown below. Figure 5 ( p x = p y = 460 nm, w 1= l 2 = 98 nm l 3 = 94 nm l 1 = 322 nm w 2= w 3 = 83 nm Δ = 56 nm), circularly polarized reflectance spectrum as Figure 6 Circular polarization spectrum such as Figure 7 .

[0093] Example 5 1) Metasurface Preparation: The SOI silicon wafer was ultrasonically cleaned sequentially with acetone, isopropanol, and deionized water for 15 minutes, and then dried with a nitrogen gun. The cleaned SOI silicon wafer was then treated with ultraviolet ozone for 10 minutes. 30 µL of PMMA A2 positive electron beam resist was dropped onto the top surface of the treated SOI silicon wafer (bottom Si thickness 675 µm, middle SiO2 thickness 350 nm, top Si thickness 200 nm), and spin-coated at 4000 rpm for 40 seconds, followed by annealing at 160 °C for 5 minutes, resulting in a PMMA A2 positive electron beam resist thickness of 80 nm. The annealed SOI silicon wafer was then exposed to the top Si using EBL to create an optimized type ③ structure (i.e., the optimized metasurface structure in step 3 of Example 4) for 100 cycles. The accelerating voltage was 30 keV, the beam current was 20 pA, the working distance was 6 mm, the write field size was 120 µm, the exposure step size was 8 nm, and the exposure dose was 240 µC cm⁻¹. -2 After exposure, the exposed SOI silicon wafer was immersed and developed using a mixed solution of methyl isobutyl ketone (MIBK) and isopropanol (IPA) (mixing ratio 1:3). After immersion for 2 minutes, it was removed, rinsed with IPA, and dried with a nitrogen gun. A 50 nm chromium (Cr) film was deposited on the sample surface using electron beam evaporation, and residual PMMA A2 adhesive on the silicon wafer was removed by ultrasonic cleaning with acetone for 1 hour. After ultrasonic cleaning, it was rinsed with IPA and dried with a nitrogen gun. The cleaned silicon wafer was placed in an ICP-RIE etching machine with the following etching parameters: temperature 20 °C, vacuum 5 mTorr, ICP power 150 W, RIE power 50 W, sulfur hexafluoride (SF6) gas flow rate 10 sccm, trifluoromethane (CHF3) gas flow rate 70 sccm, and etching time 110 seconds. After etching, the sample is immersed in a chromium etchant (Sigma-Aldrich, catalog number: 651826) for 5 minutes, then removed, rinsed with IPA, and dried with a nitrogen gun to obtain the desired planar intrinsically chiral metasurface. See [link to microstructure]. Figure 8 The circularly polarized reflectance spectra obtained from the test are shown in [reference needed]. Figure 9 The circular polarization spectrum obtained from the test is shown in [reference needed]. Figure 10 .

[0094] 2) Preparation of perovskite precursor solution: Three 5 mL reagent bottles were ultrasonically cleaned sequentially with acetone, isopropanol, and deionized water for 15 minutes each. After cleaning, they were dried in a 60 °C oven. 172 mg of formamidinium hydroiodate (FAI) and 461 mg of lead iodide (PbI2) were weighed into the first cleaned 5 mL reagent bottle in a nitrogen-atmosphere glove box. 2.4 mL of DMF solution and 0.3 mL of DMSO solution were added to the second cleaned 5 mL reagent bottle and stirred for 1 hour. 2.11 mL of the mixed solution from the second reagent bottle was added to the first reagent bottle. The first reagent bottle was allowed to stand until the solution became clear. The solution was then filtered into the third cleaned 5 mL reagent bottle to obtain the desired perovskite precursor solution.

[0095] 3) Integration of Perovskite and Metasurface: The prepared planar intrinsically chiral metasurface substrate was treated with ultraviolet ozone for 10 minutes, and then transferred to a nitrogen-atmospheric glove box. 30 µL of perovskite precursor solution was dropped onto the metasurface substrate and spin-coated at 3000 rpm for 45 seconds, with 200 µL of chlorobenzene added during the spin-coating process. After spin-coating, the sample was sequentially placed on hot stages at 110 ℃, 130 ℃, and 150 ℃ for 5 minutes, 5 minutes, and 10 minutes respectively, and then removed. After the sample cooled to room temperature, 30 µL of PMMA A2 adhesive was dropped onto the sample surface and spin-coated at 2000 rpm for 40 seconds, thus completing the integration of the gain material (using perovskite as an example) with the prepared chiral metasurface.

[0096] 4) Chiral luminescence application testing: A 400 nm femtosecond pulsed laser (pulse width 50 fs, pulse frequency 1 kHz, spot diameter 20 μm) was used as the pump source, and the chiral luminescence performance of the integrated perovskite intrinsic chiral metasurface was tested using a back focal plane array. At the pump power density where left-handed circularly polarized lasers were observed, the right-handed and left-handed circularly polarized emission spectra are shown below. Figure 11 and Figure 12 .

[0097] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An intrinsically chiral metasurface, characterized in that, The intrinsic chiral metasurface is composed of periodically arranged units, each unit comprising: a substrate layer and a chiral layer loaded on the substrate layer; The base layer has a square planar shape with periodic sides. p ; The chiral layer has a chiral structure, which is composed of three cuboids: a first cuboid, a second cuboid, and a third cuboid. The first, second, and third cuboids have the same height H and are located in the same plane; The base layer is established with one corner of a square as the origin, one side as the x-axis, another side perpendicular to the x-axis as the y-axis, and the z-axis perpendicular to the base layer, forming a spatial coordinate system upwards. The center coordinates of the base layer are ( ). p / 2, p / 2, 0), the geometric center coordinates of the first cuboid are ( p / 2, p / 2, H / 2); From a top-down perspective, the first cuboid, the second cuboid, and the third cuboid are respectively a first rectangle, a second rectangle, and a third rectangle; The longer side of the first rectangle is parallel to the y-axis; The shorter side of the second rectangle closest to the y-axis overlaps with the longer side of the first rectangle furthest from the y-axis. The perpendicular distance between the longer side of the second rectangle closest to the x-axis and the shorter side of the first rectangle closest to the x-axis is [missing information]. Δ ; The short side of the third rectangle away from the y-axis overlaps with the long side of the first rectangle close to the y-axis, and the vertical distance between the long side of the third rectangle away from the x-axis and the short side of the first rectangle away from the x-axis is 0.

2. The intrinsically chiral metasurface according to claim 1, characterized in that, The p = 450~550 nm; The long side of the first rectangle l 1 = 300~350 nm, with the shorter side being w 1 = 90~110 nm; The longer side of the second rectangle l 2 = 90~110 nm, with the shorter side being w 2 = 75~90 nm; The long side of the third rectangle l 3 = 90~110 nm, with the shorter side being w 3 = 75~90 nm; The Δ = 20~80 nm.

3. The intrinsically chiral metasurface according to claim 1, characterized in that, The p = 460 nm; The long side of the first rectangle l 1 = 322 nm, the shorter side is w 1 = 98 nm; The longer side of the second rectangle l 2 = 98 nm, the shorter side is w 2 = 83 nm; The long side of the third rectangle l 3 = 94 nm, with the shorter side being w 3 = 83 nm; The Δ = 56 nm.

4. The intrinsically chiral metasurface according to claim 1, characterized in that, The material of the chiral structure includes one or more of silicon dioxide, silicon nitride, titanium dioxide, amorphous silicon, polycrystalline silicon, and monocrystalline silicon; The substrate layer is made of one or more of the following materials: silicon dioxide, silicon nitride, titanium dioxide, sapphire, amorphous silicon, polycrystalline silicon, and monocrystalline silicon.

5. The intrinsically chiral metasurface according to claim 1, characterized in that, The intrinsic chiral metasurface further includes a gain material filling the spaces between the chiral structures of the chiral layer.

6. The intrinsically chiral metasurface according to claim 5, characterized in that, The gain material is selected from perovskite, colloidal quantum dots, or organic dyes.

7. The intrinsically chiral metasurface according to claim 6, characterized in that, The perovskite is selected from MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3, CsPbCl3, MASnI3, FASnI3, CsSnI3, MASnBr3, FASnBr3, CsSnBr3, MASnCl3, FASnCl3, CsSnCl3, PEA2MA n-1 Pb n Br 3n+1 PEA2Cs n- 1Pb n Br 3n+1 BA2MA n-1 Pb n I 3n+1 and PEA2FA n-1 Sn n I 3n+1 One or more of the following, where n represents an integer; The colloidal quantum dots are selected from one or more of PbS, PbSe, CdSe, InP, and ZnSe; The organic dye is selected from one or more of the following: IR-140, IR-808, IR-825, Cy7, iFluor 800, IR-900, IR-950, FD-1080, IR-1048, IR-1061, DCM dye, PM597, and the Rhodamine series.

8. A method for preparing an intrinsically chiral metasurface according to any one of claims 1 to 7, characterized in that, Including the following steps: A substrate is provided, the substrate comprising a base layer and a chiral material layer loaded on the base layer; A photoresist layer is prepared on the chiral material layer, and the chiral structure is exposed and developed to obtain a chiral material layer with photoresist masking. A chromium thin film is deposited on the chiral material layer with photoresist masking, and then the photoresist layer is removed to obtain a chiral material layer with chromium masking. The chiral material layer with chromium masking is etched, and then the chromium film is removed to form a chiral layer with a chiral structure, thus obtaining the intrinsic chiral metasurface.

9. The method for preparing an intrinsically chiral metasurface according to claim 8, characterized in that, The substrate is an SOI silicon wafer; The SOI silicon wafer consists of a substrate silicon layer, a silicon dioxide layer, and a single-crystal silicon layer from bottom to top; wherein the single-crystal silicon layer is a chiral material layer.

10. The application of the intrinsic chiral metasurface according to any one of claims 1-7 in a chiral light source.

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