A tunable, high-efficiency circular dichroism enhancement device and its fabrication method

Abstract

This invention discloses a tunable, high-efficiency circular dichroism (CDI) enhancement device and its fabrication method, belonging to the fields of micro-nano optics, photoelectric detection, and imaging. The device comprises a chiral microstructure of a phase change material and a low-refractive-index material, with the chiral microstructure encapsulated by the low-refractive-index material. This invention breaks the mirror symmetry and inversion symmetry of the structure by geometrically altering rectangular phase change material rods. Furthermore, by flipping one of the rectangular phase change material rods to break the inversion symmetry, the continuum bound-in-continuum (BIC) state is transformed into a quasi-BIC. Simultaneously, rotating both rectangular phase change material rods transforms the quasi-BIC into a chiral quasi-BIC, achieving a high-efficiency CDI response. Moreover, ultra-high tuning depth of the CDI response can be achieved through heating. This invention possesses advantages such as simple structure, high-efficiency CDI response, and ultra-high modulation depth, showing promising application prospects in photoelectric detection, drug development, biosensing, optical imaging, and optical communication.

Description

Technical Field

[0001] This invention relates to a tunable, high-efficiency circular dichroism enhancement device and its fabrication method, belonging to the fields of micro-nano optics, photoelectric detection, and bio-optical detection. Background Technology

[0002] Chirality refers to the inability of a structure to coincide with itself through rotation or translation operations; these two non-coincident structures are called enantiomers. Circular dichroism is an important characteristic of chiral microstructures, manifested as the difference in reflectivity, transmittance, or absorptivity between right-handed circularly polarized light (RCP) and left-handed circularly polarized light (LCP). It is one of the most commonly used methods for detecting molecular chirality, primarily applied in biomedicine, chemical engineering, and photoelectric detection. However, due to the fundamental mismatch between molecular size and incident light wavelength, the circular dichroism response in natural materials is usually too weak to be detected. By designing artificial microstructures composed of elementary atoms lacking mirror symmetry, the chiral response can be significantly enhanced.

[0003] However, once a chiral microstructure composed of traditional elementary atoms is fabricated, its function is often fixed. In fact, in many applications such as chiral detection, and for chiral optical devices with switching or tuning functions, dynamic control of the circular dichroism (CCD) response is crucial. To achieve dynamic control of the CCD response, in recent years, researchers have introduced active materials (such as graphene and phase change materials) into chiral microstructures to achieve dynamic tuning of the CCD response. For example, for graphene microstructures, "chiral patterned graphene-dielectric" and "chiral patterned metal-graphene" micro / nanostructures are used, and the Fermi energy of graphene is adjusted by applying an external voltage, thereby achieving tunability of the CCD response. However, these devices typically have a small tuning depth, and the external excitation source is difficult to obtain, leading to complex fabrication processes and high manufacturing costs. Alternatively, using chiral microstructures based on phase change materials, such as vanadium dioxide (VO2) and Ge2Sb2Te5 (GST), dynamic tuning of the CCD response can be achieved by directly heating (such as resistance wire heating or laser irradiation) to change the material's refractive index. Compared to the applied voltage regulation of graphene, the direct heating method is simpler and more economical, and its modulation depth is much greater than that of graphene. However, previous circular dichroism responses achieved using phase change materials were based on metal plasmon nanostructures. Due to the high loss of metal materials in the optical band, it is difficult to obtain a high-efficiency circular dichroism response.

[0004] In summary, previous devices that used graphene chiral microstructures to achieve dynamic tuning of the circular dichroism response had a small tuning depth and were difficult to connect to an external excitation source, resulting in high fabrication difficulty and low application value. On the other hand, the tunable circular dichroism response obtained by using phase change material chiral microstructures is difficult to obtain with high efficiency because previous methods were based on metal plasmonic nanostructures, and metal materials have high losses in the optical band. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a tunable, high-efficiency circular dichroism enhancement device and its fabrication method, the technical solution of which is as follows:

[0006] The first objective of this invention is to provide a circular dichroism enhancement device, the circular dichroism enhancement device comprising: a chiral microstructure, the chiral microstructure being encapsulated by a low refractive index material;

[0007] The chiral microstructure is composed of a periodic array of phase change material nanorods with broken symmetry, and each period includes: a first nanorod and a second nanorod.

[0008] The length, width, and thickness of the first nanorod are l, w1, and t1, respectively, and the length, width, and thickness of the second nanorod are l, w2, and t2, respectively, where t1 = w2 and t2 = w1.

[0009] The length and width constitute the bottom surface. The bottom surfaces of the first nanorod and the second nanorod are on the same plane, and there is an angle between the length directions of the two nanorods formed by rotating about the thickness direction.

[0010] Optionally, the angle between the length directions of the first nanorod and the second nanorod is 18°.

[0011] Optionally, the low refractive index material is silicon dioxide (SiO2), calcium fluoride (CaF2), or magnesium fluoride (MgF2).

[0012] Optionally, the phase change material is vanadium dioxide (VO2) or GST.

[0013] Optionally, the periods of the symmetry-broken phase change material nanorods in the X and Y directions are respectively: P x =P y =2.0μm.

[0014] Optionally, the length of the nanorod is l = 1.0 μm, the thickness of the first nanorod and the width of the second nanorod are t1 = w2 = 0.51 μm, and the thickness of the second nanorod and the width of the first nanorod are t2 = w1 = 0.2 μm.

[0015] A second objective of this invention is to provide a method for fabricating a circular dichroism enhancement device, for fabricating the circular dichroism enhancement device described in any of the above claims, the method comprising:

[0016] Step 1: Prepare a phase change material thin film with a thickness ranging from 0.1 to 2 μm;

[0017] The phase change material thin film is deposited on a low refractive index material substrate using radio frequency magnetron sputtering or vacuum evaporation technology;

[0018] Step 2: Preparation of chiral microstructures:

[0019] Positive photoresist is spin-coated onto the phase change material film in step 1, followed by exposure and development. Then, electron beam lithography is used to pattern the nanostructure to form two non-chiral rectangular phase change material patterns of the same thickness. The patterns are then transferred to the phase change material layer by ion beam etching.

[0020] Next, after removing the positive photoresist, positive photoresist is spin-coated onto the non-chiral rectangular phase change material pattern, followed by exposure and development. Then, electron beam lithography is used again to pattern the nanostructure to form a single rectangular phase change material pattern. The pattern is transferred to the phase change material layer by ion beam etching to obtain chiral microstructure patterns of phase change material with varying thicknesses, thereby obtaining phase change material nanorods with broken symmetry.

[0021] Step 3: Prepare a low-refractive-index material thin film:

[0022] The low-refractive-index material is prepared on the chiral microstructure obtained in step 2 using atomic layer deposition, molecular beam epitaxy, or electron beam evaporation techniques, so that the chiral microstructure pattern is completely wrapped by the low-refractive-index material, thus realizing the chiral microstructure wrapped by the low-refractive-index material and completing the fabrication of the device.

[0023] Optionally, step 2 involves fabricating the chiral microstructure using 3D printing or two-photon lithography.

[0024] A third objective of the present invention is to provide a method for enhancing the circular dichroic response, wherein the circular dichroic response is enhanced using any of the aforementioned circular dichroic enhancement devices.

[0025] The fourth objective of this invention is to provide a method for achieving dynamic control and switching of circular dichroism, which utilizes the circular dichroism enhancement device described in any of the above claims to achieve phase change of the phase change material through heating, thereby obtaining a circular dichroism optical response with tunable or switchable functions.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention breaks all mirror symmetry and inversion symmetry by geometrically transforming rectangular phase change material rods. By flipping one of the rectangular phase change material rods to break the inversion symmetry, the bound state (BIC) in the continuum is transformed into a quasi-BIC. Then, by simultaneously rotating the two rectangular phase change material rods, the quasi-BIC is transformed into a chiral quasi-BIC. Theoretically, the maximum circular dichroism response is predicted and simulated to be 0.93.

[0028] 2. Simulation results demonstrate that by changing the volume fraction of the phase change material's crystal phase, this invention can achieve ultra-high depth tuning of the circular dichroic response under external heating conditions, and has great application prospects in fields such as photoelectric detection, drug development, biosensing, optical imaging, and optical communication.

[0029] 3. The tunable high-efficiency circular dichroism enhancement device of the present invention can be fabricated using conventional electron beam evaporation technology and radio frequency magnetron sputtering technology, and the fabrication process is mature.

[0030] 4. The materials selected in this invention can be conventional low-loss, low-refractive-index materials such as SiO2, CaF2 or MgF2, which effectively reduces the preparation cost compared with existing chiral microstructure circular dichroism enhancement devices such as graphene.

[0031] 5. The chiral patterning material selected in this invention can be the phase change material GST. Heating it achieves tunable, high-efficiency circular dichroism. Compared to existing technologies, this invention achieves superior circular dichroism response and ultra-high modulation depth, and the direct heating method is simpler and more cost-effective. Therefore, compared to existing tunable circular dichroism enhancement devices and methods, this invention significantly improves its application scope and value. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 Here are schematic diagrams, band diagrams, and transmission spectra of the chiral microstructure based on GST proposed in this invention;

[0034] Unless otherwise stated, GST is fixed in the amorphous phase in this invention. (a) Schematic diagram of the chiral microstructure of GST under LCP and RCP light irradiation. (b) Enlarged view of the unit cell of this microstructure, wherein the structural parameters are shown in the figure. The parameters are: P x =P y=2.0 μm, l = 1.0 μm, t1 = w2 = 0.51 μm and t2 = w1 = 0.2 μm. (c) Band diagram of the proposed GST chiral microstructure along X′-Г-X without breaking any symmetry. (d) Transmission spectrum under circularly polarized light incident as a function of the asymmetry parameter δ.

[0035] Figure 2 This is a flowchart of the fabrication method of a tunable high-efficiency circular dichroism enhancement device based on GST according to Embodiment 2 of the present invention.

[0036] Figure 3 The images show the transmission spectrum and circular dichroism response spectrum of the chiral microstructure based on GST in Embodiment 2 of the present invention.

[0037] The microstructure has broken the inversion symmetry, meaning that one of the rectangular GST rods has been flipped by 90 degrees; (a) and (b) are the transmission spectra of the GST chiral microstructure under circularly polarized light illumination when the rotation angles θ = 0° and θ = 18°, respectively; (c) is the circular dichroism response spectrum of the GST chiral microstructure when the rotation angle θ = 18°; (d) is the maximum circular dichroism response spectrum predicted by theory and simulated by the finite-difference time-domain method (FDTD).

[0038] Figure 4 The chiral coupling mode theory and FDTD simulation diagram of the tunable high-efficiency circular dichroism enhancement device of the present invention are shown. The FDTD simulation results and theoretical prediction results of the circular dichroism response when the rotation angle of the rectangular GST bar is θ = 18° are also shown.

[0039] Figure 5 The tunable circular dichroism response spectrum is achieved by the tunable high-efficiency circular dichroism enhancement device of the present invention.

[0040] (a) is a graph of the circular dichroism spectrum of the chiral microstructure as a function of the volume fraction f; (b) is a graph of the circular dichroism value as a function of the volume fraction f, and a graph of the peak position of the circular dichroism response as a function of the volume fraction f. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0042] Example 1:

[0043] This embodiment provides a circular dichroism enhancement device, including: a chiral microstructure, wherein the chiral microstructure is encapsulated by a low refractive index material;

[0044] The chiral microstructure is composed of a periodic array of phase change material nanorods with broken symmetry, and each period contains: a first nanorod and a second nanorod;

[0045] The length, width, and thickness of the first nanorod are l, w1, and t1, respectively, and the length, width, and thickness of the second nanorod are l, w2, and t2, respectively, where t1 = w2 and t2 = w1.

[0046] The length and width form the bottom surface. The bottom surfaces of the first nanorod and the second nanorod are on the same plane, and there is an angle between the length directions of the two nanorods formed by rotating about the thickness direction.

[0047] Example 2:

[0048] This embodiment provides a tunable, high-efficiency circular dichroism enhancement device, which designs a rectangular GST rod chiral microstructure that breaks the in-plane and out-of-plane symmetry to achieve a chiral quasi-BIC optical response.

[0049] The chiral microstructure proposed in this embodiment is as follows: Figure 1 As shown in (a), it consists of two symmetry-broken rectangular GST bar periodic arrays. Figure 1 (b) A schematic diagram of the unit structure of the microstructure is given, wherein the left rectangular bar is rotated 90° counterclockwise around the y-axis compared to the right rectangular bar, and the bottoms of the two rectangular bars are on the same plane. P x and P y These are the periods along the x and y axes, respectively; l is the length of the vertical bar of the rectangular GST rod (along the y-axis), and the two rectangular GST rods have the same length; the thickness and width of the left rectangular GST rod are t1 and w1, respectively; the thickness and width of the right rectangular GST rod are t2 and w2, respectively, where the thickness and width satisfy the following relationships: t1 = w2, t2 = w1. Detailed structural parameters are as follows... Figure 1 As shown, unless otherwise stated, they are fixed.

[0050] exist Figure 1 In (c), this embodiment plots the band structure of the chiral microstructure calculated using FDTD. The microstructure has no symmetry breakage, and the rectangular GST bars on the left and right sides are equal in size and have not been rotated. It can be seen from the figure that there are two bands in total. This embodiment calculates the first band 1, which represents the BIC resonance band. Figure 1 (d) is the transmission spectrum under circularly polarized light incident as a function of the asymmetry parameter δ. Note that... Figure 1 (d) and Figure 1(c) The simulated structural parameters are the same. Here, the invention defines the asymmetry parameter δ as being related to the thickness and width of the microstructure and expressed as: w1 = w2 - δ, t1 = t2 + δ. When the proposed microstructure is undisturbed (δ = 0), we obtain w1 = w2, t1 = t2, which means that the microstructure has both inversion and mirror symmetry. However, for non-zero δ, the width and thickness of the proposed chiral microstructure are different from each other.

[0051] When δ≠0, the microstructure breaks the inversion symmetry but retains the mirror symmetry about the xoz plane. For δ=0, the intrinsic modes are not coupled to the external far field. As the inversion asymmetry of the system increases with δ, the transmittance gradually increases and remains stable. Furthermore, it can be seen from the figure that the spectral width of the resonance mode increases with increasing δ value. These characteristics indicate that the excited polarization-dependent modes are a result of quasi-BIC caused by the breaking of inversion symmetry. This is also consistent with… Figure 1 It matches the band 1 resonance mode in (c).

[0052] Example 3:

[0053] This embodiment provides a method for fabricating a tunable high-efficiency circular dichroism enhancement device, used to fabricate the tunable high-efficiency circular dichroism enhancement device described in Embodiment 2. The flowchart of the fabrication method is as follows. Figure 2 As shown, the main steps include:

[0054] Step 1: Preparation of GST thin films, a phase change material:

[0055] A GST film of a certain thickness is deposited on a low-refractive-index CaF2 substrate using radio frequency magnetron sputtering or vacuum evaporation technology.

[0056] Step 2: Preparation of GST microstructures:

[0057] A certain thickness of positive photoresist is spin-coated onto the GST film in step 1, followed by exposure and development. Then, electron beam lithography is used to pattern the nanostructure to form two non-chiral rectangular GST patterns of the same thickness. The patterns are then transferred to the GST layer by ion beam etching.

[0058] Next, after removing the positive photoresist, a certain thickness of positive photoresist is spin-coated onto the non-chiral rectangular GST pattern. Then, exposure and development are performed, and electron beam lithography is used again to pattern the nanostructure to form a single rectangular GST pattern. The pattern is transferred to the GST layer by ion beam etching to obtain chiral GST microstructure patterns of varying thicknesses, thus obtaining a vertically placed and an inverted rectangular GST bar.

[0059] Step 3: Preparation of low-refractive-index CaF2 thin films:

[0060] In step 2, a low-refractive-index CaF2 thin film of a certain thickness is prepared on the GST microstructure using atomic layer deposition, molecular beam epitaxy, or electron beam evaporation techniques. This allows the chiral GST microstructure pattern to be completely encapsulated by the CaF2 material, ultimately realizing a CaF2-encapsulated chiral GST microstructure and completing the fabrication of the device.

[0061] Example 4:

[0062] This embodiment provides a method and theoretical prediction for achieving a super-strong circular dichroism response based on tunable high-efficiency circular dichroism. The method for achieving a super-strong circular dichroism response utilizes the aforementioned tunable high-efficiency circular dichroism enhancement device, breaks the mirror symmetry and inversion symmetry of the microstructure, and then compares the results with the simulation results through chiral coupled-mode theory.

[0063] Figure 3 The optical responses of the device proposed in this embodiment under RCP and LCP light irradiation are shown respectively. In the calculations, GST is fixed as amorphous unless otherwise specified. Figure 3 (a) and 3(b) are the transmission spectra of the GST chiral microstructures under circularly polarized light irradiation when the rotation angles are θ = 0° and θ = 18°, respectively. Figure 3 (c) and 3(d) are the polarization conversion and circular dichroic response spectra of the GST chiral microstructure when the rotation angle θ = 18°, respectively, as well as the maximum circular dichroic response spectra predicted by theory and simulated by the finite-difference time-domain method (FDTD).

[0064] from Figure 3 As shown in (a), in the wavelength range of interest (3.0-3.4 μm), when the rotation angle of the rectangular GST is 0°, the overall microstructure lacks chirality, the transmittance of LCP light is equal to that of RCP light, and a sharp resonance occurs at 3.27 μm. This is because the microstructure has broken the inversion symmetry of the system, transforming the BIC into a quasi-BIC. Figure 3 In (b), it can be seen that when the rotation angle of the rectangular GST is equal to 18°, the geometric properties of the microstructure break all inversion symmetry and mirror symmetry, and the quasi-BIC becomes a chiral quasi-BIC, isolating the RCP light from the quasi-BIC, making the RCP light almost perfectly transmitted, while the LCP light is strongly coupled with the chiral microstructure, making the transmission almost zero. Figure 3 As shown in (c), when the rotation angle of the rectangular GST is equal to 18°, circular dichroism is defined here as the difference between the transmittance of LCP and RCP. The figure shows that at the resonant wavelength of 3.23 μm, the maximum circular dichroism response is 0.93, and this high-efficiency circular dichroism response is attributed to the difference between the same polarization conversions. Figure 3(d) The accuracy of the maximum circular dichroism response theory was verified by scanning the rotation angle θ of the rectangular GST bar. It can be seen that as the rotation angle gradually increases, the maximum circular dichroism value first rises and then slowly decreases, reaching a maximum value of 0.93 at 18°. When k and d are substituted into the formula: m R ∝e ikd / 2 sin(θ-kd / 2), where mR is the circular polarization coupling coefficient, θ is the rotation angle, k is the wave vector, and d is the relative displacement of the rod's center of mass in the z-direction. The coupling parameter m is then calculated. R The maximum rotation angle θ equal to 0 is 17.2°, and the theoretical and simulation results are almost consistent, indicating the correctness of the theory.

[0065] Figure 4 The simulation and theoretical results of the circular dichroism response in a chiral microstructure with a rectangular GST bar rotated by an angle θ = 18° are shown. The formula for circular dichroism can be rewritten theoretically using the method described in this invention as follows:

[0066]

[0067] Where ω0 is the resonant frequency, γ0 is the total loss, and γ d This represents dissipative loss. It can be seen that compared to non-lossy chiral microstructures, the circular dichroism response of low-loss chiral microstructures can only approach 1, and cannot achieve a perfect circular dichroism response. Therefore, this invention only needs to determine γ0, γ... d The values ​​in the chiral response spectrum can be used to theoretically predict the values ​​of the maximum circular dichroism, and by introducing the resonant frequency range of interest, the spectrum across the entire frequency band can be obtained. Figure 4 As can be seen, the theoretical predictions are in good agreement with the FDTD simulations, with the maximum circular dichroism response reaching a maximum value of 0.93 at 3.23 μm. Therefore, this invention can serve as a general method for evaluating the circular dichroism response performance of chiral quasi-BICs caused by symmetry breaking.

[0068] In summary, the method of this embodiment, employing the tunable high-efficiency circular dichroism enhancement device described in Embodiment 1, can achieve the maximum circular dichroism response through theoretical guidance and optimization of the structural parameters of the chiral device. The superior circular dichroism response shows great promise for applications in photoelectric detection, drug development, biosensing, and optical communication.

[0069] Example 5:

[0070] This embodiment provides a tunable high-efficiency circular dichroism method to achieve dynamic tunability of the circular dichroism. The tunable high-efficiency circular dichroism method uses the above-mentioned device, and changes the temperature of the device by means of resistance wire heating or laser irradiation, so as to cause GST to change between the amorphous phase and the crystalline phase, thereby realizing dynamic control of the circular dichroism response.

[0071] Figure 5 The tunable circular dichroism of the proposed chiral microstructure is shown as the volume fraction of GST (c-GST) varies. The dielectric constants of GST with different volume fractions are calculated using the formula:

[0072]

[0073] Where ε a and ε c Let f represent the relative permittivity of amorphous GST (a-GST) and c-GST, respectively. Here, f is the volume fraction of GST. It is 0 when GST is entirely in the amorphous phase and 1 when it is entirely in the crystalline phase. Figure 5 As shown in (a), the circular dichroism (CBD) response increases with the volume fraction of c-GST. When GST is in the amorphous phase (f=0), the maximum CBD response is 0.93. When GST is in the crystalline phase (f=1), the CBD response is almost zero. This is because the large imaginary part of c-GST makes the chiral quasi-BIC loss uncharacterizable in the microstructure. The bandwidth of the CBD response gradually widens with increasing volume fraction. Note that in the mid-infrared region, because the refractive index of c-GST is greater than that of a-GST, the position of the CBD peak redshifts with increasing volume fraction. Figure 5 As shown in (b), the circular dichroism value exhibits a linear decreasing trend over a wide range as the volume fraction increases from 0 to 1, and possesses a large tuning range, making it suitable for thermal switching applications of circular dichroism devices. Furthermore, the resonant position also exhibits a linear redshift with increasing volume fraction. Therefore, in practical applications, the volume fraction of c-GST can be adjusted by temperature, which is beneficial for dynamically controlling the circular dichroism response based on GST microstructures.

[0074] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A circular dichromatic enhancement device, characterized in that, The circular dichroism enhancement device includes a chiral microstructure encapsulated by a low-refractive-index material. The chiral microstructure is composed of a periodic array of phase change material nanorods with broken symmetry, and each period includes: a first nanorod and a second nanorod. The length, width, and thickness of the first nanorod are as follows: l、w 1 and t 1. The length, width, and thickness of the second nanorod are as follows: l、w 2 and t 2 ， in, t 1 =w 2, t 2 =w 1; The length and width constitute the bottom surface. The bottom surfaces of the first nanorod and the second nanorod are on the same plane, and there is an angle between the length directions of the two nanorods formed by rotating about the thickness direction as an axis. The low refractive index material is silicon dioxide, calcium fluoride, or magnesium fluoride.

2. The circular dichroism enhancement device according to claim 1, characterized in that, The angle between the length directions of the first nanorod and the second nanorod is 18°.

3. The circular dichroism enhancement device according to claim 1, characterized in that, The phase change material is vanadium dioxide or GST.

4. The circular dichroism enhancement device according to claim 1, characterized in that, The periods of the symmetry-broken phase change material nanorods in the X and Y directions are as follows: P x = P y =2.0 μm.

5. The circular dichroism enhancement device according to claim 1, characterized in that, Length of nanorods l =1.0 μm, the thickness of the first nanorod and the width of the second nanorod t 1= w 2 = 0.51 μm, the thickness of the second nanorod and the width of the first nanorod t 2 =w 1 = 0.2 μm .

6. A method for preparing a circular dichroism enhancement device, characterized in that, The method for preparing the circular dichroism enhancement device according to any one of claims 1-5 comprises: Step 1: Prepare a phase change material thin film with a thickness ranging from 0.1 to 2 μm; The phase change material thin film is deposited on a low refractive index material substrate using radio frequency magnetron sputtering or vacuum evaporation technology; Step 2: Preparation of chiral microstructures: Positive photoresist is spin-coated onto the phase change material film in step 1, followed by exposure and development. Then, electron beam lithography is used to pattern the nanostructure to form two non-chiral rectangular phase change material patterns of the same thickness. The patterns are then transferred to the phase change material layer by ion beam etching. Next, after removing the positive photoresist, positive photoresist is spin-coated onto the non-chiral rectangular phase change material pattern, followed by exposure and development. Then, electron beam lithography is used again to pattern the nanostructure to form a single rectangular phase change material pattern. The pattern is transferred to the phase change material layer by ion beam etching to obtain chiral microstructure patterns of phase change material with varying thicknesses, thereby obtaining phase change material nanorods with broken symmetry. Step 3: Prepare a low-refractive-index material thin film: The low-refractive-index material is prepared on the chiral microstructure obtained in step 2 using atomic layer deposition, molecular beam epitaxy, or electron beam evaporation techniques, so that the chiral microstructure pattern is completely wrapped by the low-refractive-index material, thus realizing the chiral microstructure wrapped by the low-refractive-index material and completing the fabrication of the device.

7. The method for preparing a circular dichroism enhancement device according to claim 6, characterized in that, Step 2 involves fabricating the chiral microstructure using 3D printing or two-photon lithography.

8. A method for enhancing circular dichroism response, characterized in that, The circular dichroic response enhancement method uses the circular dichroic enhancement device described in any one of claims 1-5 to enhance the circular dichroic response.

9. A method for realizing dynamic control and switching of two circular colors, characterized in that, Using the circular dichroism enhancement device according to any one of claims 1-5, a phase change of the phase change material is achieved by heating, thereby obtaining a circular dichroism optical response with tunable or switchable functions.

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