Chiral super-structure surface and dynamic regulation and control method of circular dichroism of chiral super-structure surface

Abstract

The invention provides a chiral super-structure surface and a dynamic regulation and control method for circular dichroism of the chiral super-structure surface, and belongs to the technical field of micro-nano optics. The chiral metasurface can perform differential absorption on vertically incident left-handed circularly polarized light and right-handed circularly polarized light. The chiral metasurface comprises: a substrate layer; the optical waveguide layer is arranged on the substrate layer; the nano structure layer is arranged on the optical waveguide layer and comprises a plurality of Z-shaped nano units which are periodically arranged in a square shape; and the hydrogel layer is arranged on the optical waveguide layer and the plurality of Z-shaped nano units and is used for dynamically regulating and controlling the circular dichroism of the chiral super-structure surface when the environment humidity changes. Under the condition that high circular dichroism of the chiral super-structure surface is achieved, the circular dichroism of the chiral super-structure surface is made to move when the environment humidity changes, and therefore the circular dichroism of the chiral super-structure surface is dynamically regulated and controlled.

Description

Technical Field

[0001] The present disclosure relates to the field of micro-nano optical technology, and in particular to a chiral metasurface and a method for dynamically controlling circular dichroism thereof. Background Art

[0002] In recent years, chiral metasurfaces have become a research hotspot for the next generation of chiral optical devices due to their superior optical control capabilities. In particular, within a single-layer structure, they achieve spin-selective modulation of left-handed and right-handed circularly polarized (LCP / RCP) light by coupling multidimensional optical field parameters such as amplitude, polarization, and orbital angular momentum.

[0003] However, this single-layer static system still faces challenges, mainly because existing materials are insufficient in optical performance, stability, reliability and control precision. These factors together make it difficult to effectively achieve chiral dynamic control. Summary of the Invention

[0004] This disclosure provides a chiral metasurface and a method for dynamically controlling its circular dichroism. This method can achieve high circular dichroism on the chiral metasurface while shifting the circular dichroism spectrum of the chiral metasurface when the ambient humidity changes, thereby dynamically controlling the circular dichroism of the chiral metasurface. The technical solution includes at least the following: On the one hand, a chiral metasurface is provided, which can differentially absorb vertically incident left-handed circularly polarized light and right-handed circularly polarized light. The chiral metasurface includes: a substrate layer; an optical waveguide layer, disposed on the substrate layer; a nanostructure layer, disposed on the optical waveguide layer, including a plurality of Z-shaped nanounits arranged in a square periodic pattern; and a hydrogel layer, disposed on the optical waveguide layer and the plurality of Z-shaped nanounits, for dynamically regulating the circular dichroism of the chiral metasurface when the ambient humidity changes.

[0005] Optionally, the thickness of the hydrogel layer may dynamically change with the ambient humidity, and the thickness of the hydrogel layer is 400 nm to 700 nm.

[0006] Optionally, the material of the hydrogel layer includes polyvinyl alcohol.

[0007] Optionally, the Z-shaped nanounit includes a first rectangular nanoarm, a central nanobrick and a second nanoarm connected in sequence, the long axis of the first nanoarm is perpendicular to the long axis of the central nanobrick, the long axis of the central nanobrick is perpendicular to the long axis of the second nanoarm, and the long axis of the first nanoarm is parallel to the long axis of the second nanoarm.

[0008] Optionally, the length of the central nanobrick is 360nm to 380nm, the width of the central nanobrick is 190nm to 210nm, the first nanoarm and the second nanoarm have the same size, the length of the first nanoarm and the second nanoarm is 110nm to 130nm, and the width of the first nanoarm and the second nanoarm is 90nm to 110nm.

[0009] Optionally, the arrangement period of the Z-shaped nano-units is 490 nm to 510 nm.

[0010] Optionally, the Z-shaped nanometer unit has a thickness of 370 nm to 390 nm.

[0011] Optionally, the maximum circular dichroism of the chiral metasurface is 0.9 to 0.95.

[0012] Optionally, under the same incident wavelength conditions, the maximum variation of the circular dichroism of the chiral metasurface under different ambient humidity conditions is 0.5 to 0.6.

[0013] On the other hand, a method for dynamically controlling the circular dichroism of a chiral metasurface is provided, wherein the chiral metasurface is any of the aforementioned chiral metasurfaces, and the method comprises: controlling the circular dichroism of the chiral metasurface by changing the ambient humidity.

[0014] The beneficial effects of the technical solutions provided by the embodiments of the present disclosure include at least: In the disclosed embodiments, by configuring the nanostructure layer with multiple Z-shaped nanounits arranged in a square periodic pattern, Mie resonance can be combined to achieve chiral optical response, enhancing the circular dichroism of the chiral metasurface. By providing a hydrogel layer over the optical waveguide layer and the multiple Z-shaped nanounits, and leveraging the hydrogel's transparent optical properties, as well as its ability to dynamically change its thickness and refractive index with changes in ambient humidity, the hydrogel layer and nanostructure layer can achieve high circular dichroism on the chiral metasurface while shifting the circular dichroism spectrum of the chiral metasurface as the ambient humidity changes, thereby dynamically controlling the circular dichroism of the chiral metasurface. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0016] Figure 1 Schematic diagram of the structure of a chiral metasurface provided by an embodiment of the present disclosure; Figure 2 Schematic diagram of the changes in the hydrogel layer of the chiral metasurface under dry and wet environments provided by an embodiment of the present disclosure; Figure 3 is a schematic diagram of a partial cross-sectional structure of a chiral metasurface provided by an embodiment of the present disclosure; Figure 4 is a partial top view of a chiral metasurface provided by an embodiment of the present disclosure; Figure 5 Schematic diagram of the simulation effect of circular dichroism distribution of the Z-shaped nanometer unit scanning size provided by the embodiment of the present disclosure; Figure 6 Schematic diagram of the transmittance of left-handed / right-handed circularly polarized light of the chiral metasurface provided by an embodiment of the present disclosure under dry conditions; Figure 7 Schematic diagram of the simulation effect of circular dichroism of the chiral metasurface provided by the embodiment of the present disclosure under different arrangement periods of Z-shaped nanounits; Figure 8 Schematic diagram of plane electric field simulation effect of Z-shaped nanounits provided by an embodiment of the present disclosure under different circularly polarized light incidences; Figure 9 1 is a schematic diagram of a thickness curve of a hydrogel layer at different humidity levels provided by an embodiment of the present disclosure; Figure 10 Schematic diagram of the transmittance of left-handed / right-handed circularly polarized light of the chiral metasurface provided by an embodiment of the present disclosure under wet conditions; Figure 11 Schematic diagram of the simulation effect of circular dichroism spectra of the chiral metasurface under different humidity conditions provided by the embodiment of the present disclosure; Figure 12 Schematic diagram of the simulation effect of circular dichroism spectra of chiral metasurfaces with different nanoarm lengths under different humidity conditions provided by an embodiment of the present disclosure; Figure 13 Schematic diagram of the simulation effect of circular dichroism spectra of chiral metasurfaces with different nano-arm widths under different humidity conditions provided by an embodiment of the present disclosure; Figure 14 Schematic diagram of the simulation effect of circular dichroism spectra of chiral metasurfaces with different central nanobrick lengths under different humidity conditions provided by an embodiment of the present disclosure; Figure 15 Schematic diagram of the simulation effect of circular dichroism spectra of chiral metasurfaces with different central nanobrick widths under different humidity conditions provided by an embodiment of the present disclosure.

[0017] Reference numerals: 10: substrate layer; 20: optical waveguide layer; 30: nanostructure layer; 31: Z-shaped nanounit; 311: first nanoarm; 312: second nanoarm; 313: central nanobrick; 40: hydrogel layer. DETAILED DESCRIPTION

[0018] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by a person of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," "third," and similar terms used in the patent specification and claims of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish between different components. Similarly, terms such as "a" or "an" do not indicate a quantitative limitation, but rather indicate the presence of at least one. Terms such as "include" or "comprising" mean that the elements or objects preceding "include" or "comprising" encompass the elements or objects listed after "include" or "comprising," and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. "A and / or B" indicates three situations: A, B, and A and B.

[0019] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0020] Figure 1 Schematic diagram of the structure of the chiral metasurface provided by the embodiment of the present disclosure. Figure 1 As shown in Figure 2, the chiral metasurface can differentially absorb perpendicularly incident left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP). That is, when left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP) of different chiralities are incident perpendicularly to the working surface of the chiral metasurface, the absorptivity and transmittance of the chiral metasurface for the left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP) differ. Figure 1 The neutral chiral metasurface has a higher absorptivity and a lower transmittance for left-handed circularly polarized light (LCP), and a lower absorptivity and a higher transmittance for right-handed circularly polarized light (RCP).

[0021] Figure 2 Schematic diagram of the changes in the hydrogel layer of the chiral metasurface provided by the embodiment of the present disclosure under dry and wet environments. Figure 3 Schematic diagram of a local cross-sectional structure of a chiral metasurface provided by an embodiment of the present disclosure. Figure 4 : is a partial top view of the chiral metasurface provided by the embodiment of the present disclosure. Figures 1 to 4The chiral metasurface includes: a substrate layer 10; an optical waveguide layer 20 disposed on the substrate layer 10; a nanostructure layer 30 disposed on the optical waveguide layer 20 and including a plurality of Z-shaped nanounits 31 arranged in a square periodic pattern; and a hydrogel layer 40 disposed on the optical waveguide layer 20 and the plurality of Z-shaped nanounits 31, for dynamically regulating the circular dichroism (CD) of the chiral metasurface when the ambient humidity changes.

[0022] In the disclosed embodiment, by configuring the nanostructure layer 30 with a plurality of Z-shaped nanounits 31 arranged in a square periodic pattern, a chiral optical response can be achieved in conjunction with Mie resonance, thereby enhancing the circular dichroism of the chiral metasurface. By disposing a hydrogel layer 40 on the optical waveguide layer 20 and the plurality of Z-shaped nanounits 31, and leveraging the hydrogel's transparent optical properties, as well as its ability to dynamically change its thickness and refractive index with changes in ambient humidity, the hydrogel layer 40 and the nanostructure layer 30 can achieve high circular dichroism while shifting the circular dichroism spectrum of the chiral metasurface in response to changes in ambient humidity, thereby dynamically controlling the circular dichroism of the chiral metasurface. This chiral metasurface combines chiral light field response with humidity-induced refractive index changes, enhancing electric field excitation efficiency and inheriting polarization-selective properties, providing a promising approach for polarization-sensitive optical sensing systems and environmentally responsive biomedical detection.

[0023] Figure 2 The thickness of the hydrogel layer 40 under dry conditions is significantly smaller than the thickness of the hydrogel layer 40 under humidified conditions, that is, the thickness of the hydrogel layer 40 can dynamically change with the ambient humidity.

[0024] Optionally, the material of the substrate layer 10 includes silicon dioxide.

[0025] See also Figures 1 to 4 The thickness H1 of the substrate layer 10 is 900 nm to 1100 nm. For example, the thickness H1 of the substrate layer 10 can be 1000 nm. This ensures a high transmittance of the substrate layer 10.

[0026] Optionally, the material of the optical waveguide layer 20 includes silicon nitride.

[0027] Optionally, the thickness H2 of the optical waveguide layer 20 is 360 nm to 400 nm. For example, the thickness H2 of the optical waveguide layer 20 may be 380 nm. In this way, the optical waveguide layer 20 can be better used for phase matching.

[0028] Optionally, the material of the nanostructure layer 30 includes silicon.

[0029] Optionally, the thickness H3 of the Z-shaped nanometer unit 31 is 370 nm to 390 nm.

[0030] For example, the thickness H3 of the Z-shaped nanometer unit 31 may be 370 nm, 380 nm, or 390 nm.

[0031] Optionally, the Z-shaped nanounit 31 includes a first cuboid nanoarm 311, a central nanobrick 313, and a second nanoarm 312, all connected in sequence. The long axis of the first nanoarm 311 is perpendicular to the long axis of the central nanobrick 313, the long axis of the central nanobrick 313 is perpendicular to the long axis of the second nanoarm 312, and the long axis of the first nanoarm 311 is parallel to the long axis of the second nanoarm 312. This design of the Z-shaped nanounit 31 facilitates chiral resonance and improves the circular dichroism of the chiral metasurface.

[0032] Optionally, the length L1 of the central nanobrick 313 is 360 nm to 380 nm, and the width W1 of the central nanobrick 313 is 190 nm to 210 nm.

[0033] For example, the length L1 of the central nanobrick 313 may be 360 ​​nm, 370 nm, or 380 nm, and the width W1 of the central nanobrick 313 may be 190 nm, 200 nm, or 210 nm, for example.

[0034] Optionally, the first nano-arm 311 and the second nano-arm 312 have the same size, a length L2 of the first nano-arm 311 and the second nano-arm 312 is 110 nm to 130 nm, and a width W2 of the first nano-arm 311 and the second nano-arm 312 is 90 nm to 110 nm.

[0035] For example, the length L2 of the first nano-arm 311 and the second nano-arm 312 may be 110 nm, 120 nm, or 130 nm, and the width W2 of the first nano-arm 311 and the second nano-arm 312 may be 90 nm, 100 nm, or 110 nm, etc.

[0036] By designing the dimensions of each part of the Z-shaped nanounit 31, a nanounit with two-fold symmetry (C2) can be formed, allowing chiral light to be selectively coupled. The change in circular dichroism spectral resonance supported by the Z-shaped nanounit 31 is conducive to achieving high circular dichroism of the chiral metasurface in the visible light range.

[0037] Optionally, the maximum value of the circular dichroism of the chiral metasurface is 0.9 to 0.95.

[0038] For example, the maximum value of the circular dichroism of the chiral metasurface can be 0.9, 0.93, or 0.95, etc.

[0039] Figure 5 : is a schematic diagram of the simulation effect of the circular dichroism distribution of the Z-shaped nanometer unit scanning size provided by the embodiment of the present disclosure, Figure 5This is the CD distribution simulation effect diagram at the resonant wavelength. Figure 6 Schematic diagram of the transmittance of left-handed / right-handed circularly polarized light of the chiral metasurface provided by the embodiment of the present disclosure under dry conditions. Figure 5 and Figure 6 Scanning L1, W1, L2, and W2 in 10nm steps, the CD value reaches a maximum of approximately 0.95 at L1 = 370nm, W1 = 200nm, L2 = 120nm, and W2 = 100nm. Under dry conditions, the transmittance of the chiral metasurface for left-handed circularly polarized light (LCP) at a wavelength of 735nm is only 0.02, while the transmittance for right-handed circularly polarized light (RCP) is higher, resulting in the observed CD maximum at this wavelength.

[0040] See also Figures 1 to 4 The arrangement period P of the Z-shaped nano-units 31 is 490 nm to 510 nm. In this embodiment, each Z-shaped nano-unit 31 is located at the center of a square area on the optical waveguide layer 20, and the arrangement period P of the Z-shaped nano-units 31 is also the side length of the square area.

[0041] For example, the arrangement period P of the Z-shaped nano-units 31 may be 490 nm, 500 nm, or 510 nm.

[0042] Figure 7 Schematic diagram of the simulation effect of circular dichroism spectrum of the chiral metasurface provided by the embodiment of the present disclosure under different arrangement periods of Z-shaped nanounits. Figure 7 As shown in Figure 3, when P is 490nm, 495nm, 500nm, 505nm and 510nm, the circular dichroism spectrum of the chiral metasurface red-shifts with the increase of P.

[0043] For example, the bandwidth of the circular dichroism spectrum of the chiral metasurface is about 10 nm, which can support narrow-bandwidth chiral resonances.

[0044] It should be noted that the selection of materials, thickness and size of each film layer in this embodiment is only an example. In other embodiments, the selection of materials, thickness and size of each film layer can be adjusted according to actual needs, and this disclosure does not limit this.

[0045] The principle of the Z-shaped nanounit in this embodiment is explained below. The chiral optical response of a chiral metasurface refers to the specific optical response exhibited by the chiral metasurface when interacting with light. These responses are mainly reflected in the differences in the absorption, transmission, and reflection of circularly polarized light of different chiralities. The chiral optical response of a chiral metasurface can be described by circular dichroism. Circular dichroism can be calculated using the following formula (1): (1) Among them, CDK is circular dichroism, K LCP and K RCP are the coefficients corresponding to left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP), respectively. K can be A, T, or R, where A represents absorptivity, T represents transmittance, and R represents reflectivity. To construct a structure with high circular dichroism, the Jones matrix can be used for calculations.

[0046] Figure 8 This is a schematic diagram of the plane electric field simulation effect of the Z-shaped nanounit provided by the embodiment of the present disclosure under different circularly polarized light incidences. Figure 8 Part (a) shows the schematic diagram of the plane electric field simulation effect under the incidence of left-handed circularly polarized light LCP. Figure 8 Part (b) shows the schematic diagram of the plane electric field simulation effect under the incidence of right-handed circularly polarized light RCP. Figure 8 As shown, the Z-shaped nanounits selectively couple light of different handednesses. When left-handed circularly polarized light (LCP) is incident, a helical electric field with opposite handedness is generated in the center of the Z-shaped nanounit, with the electric field intensity primarily concentrated at the interface between the Z-shaped nanounit and the air. However, when right-handed circularly polarized light (RCP) is incident, the electric field intensity is primarily concentrated between adjacent Z-shaped nanounits due to a resonance effect caused by the small distance between the Z-shaped nanounits. The overall electric field variation is concentrated at the interface between the Z-shaped nanounit and the air interface. Therefore, by placing a hydrogel layer on the Z-shaped nanounits and varying the refractive index of the hydrogel by changing the ambient humidity, dynamic control of high circular dichroism can be achieved.

[0047] See also Figures 1 to 4 The thickness H4 of the hydrogel layer 40 is 400 nm to 700 nm. Here, the thickness H4 of the hydrogel layer 40 refers to the maximum thickness of the hydrogel layer 40 disposed on the optical waveguide layer 20. Dynamic variations in the thickness H4 of the hydrogel layer 40 within this range under varying ambient humidity facilitate precise control of the circular dichroism of the chiral metasurface.

[0048] For example, the thickness H4 of the hydrogel layer 40 may be 450 nm, 500 nm, 600 nm, or 670 nm.

[0049] Optionally, the material of the hydrogel layer 40 includes polyvinyl alcohol.

[0050] Figure 9 1 is a schematic diagram of a thickness curve of a hydrogel layer at different humidity levels provided by an embodiment of the present disclosure. Figure 10 Schematic diagram of the transmittance of the chiral metasurface provided by the embodiment of the present disclosure to left / right circularly polarized light under wet conditions. Figure 11 Schematic diagram of the simulation effect of circular dichroism spectrum of the chiral metasurface provided by the embodiment of the present disclosure under different humidity conditions. Figure 3 and Figures 9 to 11 As the relative humidity (RH) of the environment increases, the thickness H4 of the hydrogel layer 40 also increases. Under low relative humidity (LRH) conditions (approximately 20%), i.e., dry conditions, the thickness H4 of the hydrogel layer 40 can be designed to be 450 nm, at which point the refractive index of the hydrogel layer 40 is 1.51. When the RH is increased to high relative humidity (HRH) conditions (approximately 80%), i.e., wet conditions, the thickness H4 of the hydrogel layer 40 dynamically increases to 672 nm, at which point the refractive index of the hydrogel layer 40 decreases to 1.43, and the transmittance of the chiral metasurface to LCP and RCP changes. Because the designed circular dichroism resonant wavelength is highly dependent on the refractive index difference between the chiral metasurface and the surrounding medium, the refractive index change caused by changes in the thickness H4 of the hydrogel layer 40 can cause a continuous blue shift in the resonant wavelength, thereby achieving active modulation of the circular dichroism of the chiral metasurface in the visible spectrum.

[0051] Optionally, the maximum change in circular dichroism of the chiral metasurface under different ambient humidity conditions is 0.5 to 0.6.

[0052] For example, the maximum change in the circular dichroism of the chiral metasurface under different ambient humidity conditions can be 0.5, 0.55, or 0.6, etc.

[0053] Figure 12 This is a schematic diagram of the simulation effect of the circular dichroism spectra of the chiral metasurface with different nanoarm lengths under different humidity conditions provided by an embodiment of the present disclosure. Figure 13 Schematic diagram of the simulation effect of circular dichroism spectra of the chiral metasurface with different nano-arm widths under different humidity conditions provided by an embodiment of the present disclosure. Figure 14 Schematic diagram of the simulation effect of circular dichroism spectra of the chiral metasurface with different central nanobrick lengths under different humidity conditions provided by an embodiment of the present disclosure. Figure 15 Schematic diagram of the simulation effect of circular dichroism spectrum of chiral metasurface with different central nanobrick widths under different humidity conditions provided by the embodiment of the present disclosure. Figure 4 and Figures 12 to 15 , you can select the low relative humidity LRH condition of about 20% RH and the high relative humidity HRH condition of about 80% RH for simulation, and scan with a step size of 5nm in the range of L2 from 110nm to 130nm, W2 from 90nm to 110nm, L1 from 360nm to 380nm, and W1 from 190nm to 200nm, respectively. Figures 12 to 15 Both have high circular dichroism peaks and humidity control characteristics, and the maximum change of circular dichroism under LRH conditions and HRH conditions can reach 0.55.

[0054] In the disclosed embodiments, the chiral metasurface can achieve high circular dichroism and active high-precision control of circular dichroism. At the same time, when the size of the Z-shaped nanounit 31 produces size perturbation fluctuations due to factors such as processing accuracy, the chiral metasurface can also maintain the peak stability of high circular dichroism and excellent dynamic control performance. It has high robustness, greatly improving the preparation feasibility and reliability of the chiral metasurface.

[0055] The present disclosure also provides a method for dynamically controlling the circular dichroism of a chiral metasurface, wherein the chiral metasurface is any of the aforementioned chiral metasurfaces, and the method comprises: controlling the circular dichroism of the chiral metasurface by changing the ambient humidity.

[0056] The above description is merely an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A chiral metasurface, characterized in that: The chiral metasurface can differentially absorb vertically incident left-handed circularly polarized light and right-handed circularly polarized light, and the chiral metasurface comprises: substrate layer; an optical waveguide layer, disposed on the substrate layer; a nanostructure layer, disposed on the optical waveguide layer, comprising a plurality of Z-shaped nanounits arranged in a square periodic pattern; A hydrogel layer is disposed on the optical waveguide layer and the plurality of Z-shaped nanounits, and is used to dynamically control the circular dichroism of the chiral metasurface when the ambient humidity changes.

2. The chiral metasurface according to claim 1, wherein The thickness of the hydrogel layer can dynamically change with the ambient humidity, and the thickness of the hydrogel layer is 400 nm to 700 nm.

3. The chiral metasurface according to claim 2, wherein: The material of the hydrogel layer includes polyvinyl alcohol.

4. The chiral metasurface according to any one of claims 1 to 3, wherein: The Z-shaped nanounit includes a first rectangular nanoarm, a central nanobrick and a second nanoarm connected in sequence, the long axis of the first nanoarm is perpendicular to the long axis of the central nanobrick, the long axis of the central nanobrick is perpendicular to the long axis of the second nanoarm, and the long axis of the first nanoarm is parallel to the long axis of the second nanoarm.

5. The chiral metasurface according to claim 4, wherein: The length of the central nanobrick is 360nm to 380nm, the width of the central nanobrick is 190nm to 210nm, the first nanoarm and the second nanoarm have the same size, the length of the first nanoarm and the second nanoarm is 110nm to 130nm, and the width of the first nanoarm and the second nanoarm is 90nm to 110nm.

6. The chiral metasurface according to claim 4, wherein: The arrangement period of the Z-shaped nanometer units is 490 nm to 510 nm.

7. The chiral metasurface according to claim 4, wherein: The thickness of the Z-shaped nanounit is 370 nm to 390 nm.

8. The chiral metasurface according to any one of claims 1 to 3 and claims 5 to 7, characterized in that: The maximum circular dichroism of the chiral metasurface is 0.9 to 0.

95.

9. The chiral metasurface according to claim 8, wherein: Under the same incident wavelength conditions, the maximum change in the circular dichroism of the chiral metasurface under different ambient humidity conditions is 0.5 to 0.

6.

10. A method for dynamically controlling circular dichroism of a chiral metasurface, characterized in that: The chiral metasurface is the chiral metasurface according to any one of claims 1 to 9, and the method comprises: regulating the circular dichroism of the chiral metasurface by changing the ambient humidity.

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