Terahertz-band metasurface circular dichroic device based on liquid crystal elastomers, and preparation method therefor

Abstract

A terahertz-band metasurface circular dichroic device based on liquid crystal elastomers, and a preparation method therefor. The metasurface circular dichroic device comprises a dielectric layer (1), a plurality of movable structural main bodies (2) and a plurality of liquid crystal elastomers (3), wherein the movable structural main bodies (2) are periodically attached onto the dielectric layer (1); the liquid crystal elastomers (3) are attached to a part of each movable structural main body (2); and the response of the metasurface circular dichroic device can be adjusted by means of structural changes in the movable structural main bodies (2). Circular dichroism values are flexible and adjustable at different frequencies by means of the different bending degrees of microstructural metal sheets (22) inside the movable structural main bodies (2). By means of the attachment of the liquid crystal elastomers (3), the response performance and the flexibility of the metasurface circular dichroic device are further improved, thereby further improving the usage flexibility of detection while simplifying the structure of the circular dichroic device, and facilitating the detection on chiral molecules.

Description

A terahertz band metasurface circular dichroist based on liquid crystal elastomer and its preparation method

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on February 23, 2024, with application number 202410202469.7 and invention name “A metasurface circular dichroic device based on liquid crystal elastomer in the terahertz band and its preparation method”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates to the technical field of metasurface devices, and in particular to a terahertz band metasurface circular dichroist based on liquid crystal elastomer and a preparation method thereof. Background Art

[0003] Chirality is a ubiquitous phenomenon in nature, whereby a mirror image of a structure cannot be superimposed upon its original structure through translation or rotation. Most biomolecules are chiral, and chirality is a fundamental characteristic of life processes, present in humans, animals, plants, and microorganisms.

[0004] Molecular chirality can be manifested through interactions with chiral electromagnetic fields. Circular dichroism (CD) has been extensively studied due to its differential absorption of left-handed and right-handed circularly polarized light. Distinguishing different chiralities by measuring the absorption difference between left-handed and right-handed circularly polarized light is of great significance for improving properties such as the absorption of circularly polarized light and circular dichroism.

[0005] Metasurfaces, due to their ability to enhance local electric fields through artificial design, are widely used in the design of circular dichroism (CD) devices or for detecting the CD spectra of chiral substances. However, existing CD devices, after fabrication, can only detect one chiral electromagnetic wave, with their chirality and operating frequency fixed, making dynamic control impossible and limiting their flexibility.

[0006] Summary of the Invention

[0007] The present invention provides a terahertz band metasurface circular dichroist based on liquid crystal elastomer and a preparation method thereof, which solves the technical problem that the existing metasurface circular dichroist can only detect one chiral electromagnetic wave after processing and manufacturing, and its chirality and operating frequency band are fixed, resulting in the inability to achieve dynamic regulation and low flexibility of use.

[0008] The present invention provides a terahertz band metasurface circular dichroist based on liquid crystal elastomer, comprising a dielectric layer, a plurality of movable structural bodies and a plurality of liquid crystal elastomers;

[0009] Each of the movable structural bodies is periodically attached to the dielectric layer;

[0010] The liquid crystal elastomer is partially attached to each of the movable structural bodies, so as to adjust the response of the metasurface circular dichroism through the structural change of the movable structural body.

[0011] Optionally, the movable structural body includes a rectangular metal frame and a microstructured metal sheet;

[0012] The liquid crystal elastomer is attached to the microstructured metal sheet, and the rectangular metal frame is attached to the dielectric layer;

[0013] The connecting end of the microstructured metal sheet is connected to the rectangular metal frame, and the microstructured metal sheet can be bent to different degrees to adjust the response of the metasurface circular dichroic device.

[0014] Optionally, the microstructured metal sheet includes a first metal sheet and a second metal sheet;

[0015] The shapes of the first metal sheet and the second metal sheet are both asymmetrical;

[0016] The connecting end of the first metal sheet and the connecting end of the second metal sheet are connected through a rectangular metal frame and are arranged in a mirror-symmetrical manner along the central axis of the rectangular metal frame.

[0017] Optionally, the microstructured metal sheet has a length ranging from 50 μm to 200 μm, a width ranging from 50 μm to 200 μm, and a thickness ranging from 0.05 μm to 5 μm.

[0018] Optionally, the side length of the rectangular metal frame ranges from 200 μm to 500 μm;

[0019] The rectangular metal frame has a frame width ranging from 10 μm to 50 μm, and a frame thickness ranging from 0.05 μm to 5 μm; wherein the frame thickness is smaller than the thickness of the dielectric layer.

[0020] Optionally, the rectangular metal frame and the microstructured metal sheet are both made of metal materials that have conductive properties and conduct electricity through circulating current.

[0021] Optionally, the liquid crystal elastomer comprises a liquid crystal monomer, a cross-linking agent and a polymer;

[0022] The liquid crystal elastomer is attached to the first metal sheet and the second metal sheet respectively, and the polymers are different to provide different stimulus responses under light of different frequencies;

[0023] Wherein, the polymer is a near-infrared organic dye.

[0024] Optionally, the material of the dielectric layer is polyimide, silicon dioxide or silicon with different dielectric constants and dielectric losses; wherein the dielectric constant ranges from 2 to 6;

[0025] The thickness of the dielectric layer ranges from 3 μm to 1000 μm.

[0026] Optionally, the movable structural bodies are arranged at the same interval, and the number of the movable structural bodies is m×n, where m≥10, n≥10, and m and n are integers.

[0027] The present invention also provides a method for preparing a metasurface circular dichroic device based on a liquid crystal elastomer in the terahertz band, which is used to prepare any of the metasurface circular dichroic devices described above, and the method comprises:

[0028] attaching an initial structural body of the same size to the dielectric layer;

[0029] Processing the initial structural body according to preset parameters to obtain a plurality of movable structural bodies;

[0030] A liquid crystal elastomer is partially attached to each movable structural body to obtain a supersurface circular dichroic device.

[0031] It can be seen from the above technical solutions that the present invention has the following advantages:

[0032] The present invention provides a terahertz-band metasurface circular dichroist based on liquid crystal elastomers, comprising a dielectric layer, multiple movable structural bodies, and multiple liquid crystal elastomers; each movable structural body is periodically attached to the dielectric layer; and each movable structural body is partially attached with a liquid crystal elastomer, so that the response of the metasurface circular dichroist can be adjusted by structural changes of the movable structural body. By varying the degree of bending of the microstructured metal sheet within the movable structural body, the circular dichroism values ​​at different frequencies can be flexibly adjusted. Furthermore, the attachment of the liquid crystal elastomers further improves the response performance and flexibility of the metasurface circular dichroist, thereby simplifying the circular dichroist structure and further enhancing the flexibility of detection, making it easier to use for the detection of chiral molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] FIG1 is a schematic structural diagram of a terahertz-band metasurface circular dichroist based on a liquid crystal elastomer provided by an embodiment of the present invention;

[0035] FIG2 is a schematic diagram of different circular dichroism responses of a single movable structural body in an embodiment of the present invention;

[0036] FIG3 is a circular dichroism spectrum corresponding to a terahertz-band metasurface circular dichroist in an embodiment of the present application;

[0037] FIG4 is a schematic diagram showing the adjustable results of a terahertz band metasurface circular dichroic device based on liquid crystal elastomer in the first terahertz band provided by an embodiment of the present invention;

[0038] FIG5 is another schematic structural diagram of a terahertz band metasurface circular dichroist based on liquid crystal elastomer provided by an embodiment of the present invention;

[0039] FIG6 is a schematic diagram of different circular dichroism responses of another structure of a single movable structural body provided by an embodiment of the present invention;

[0040] FIG7 is a circular dichroism spectrum of another structure of a liquid crystal elastomer-based metasurface circular dichroist in the terahertz band provided by an embodiment of the present invention;

[0041] FIG8 shows an adjustable result of another structure of a terahertz band metasurface circular dichroic device based on liquid crystal elastomer provided by an embodiment of the present invention;

[0042] FIG9 is a flowchart showing the steps of a method for preparing a terahertz band metasurface circular dichroist based on liquid crystal elastomer provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] Molecular chirality can be expressed through interaction with chiral electromagnetic fields. The most effective technique is circular dichroism (CD), which distinguishes different chiralities by measuring the difference in absorption between left and right circularly polarized light. Therefore, improving the absorption of circularly polarized light and circular dichroism is of great significance.

[0044] To this end, an embodiment of the present invention provides a terahertz band metasurface circular dichroist based on liquid crystal elastomer and a preparation method thereof, which is used to solve the technical problem that the existing metasurface circular dichroist can only detect one chiral electromagnetic wave after processing and manufacturing, and its chirality and operating frequency band are fixed, resulting in the inability to achieve dynamic regulation and low flexibility of use.

[0045] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] Please refer to FIG1 , which is a schematic structural diagram of a liquid crystal elastomer-based metasurface circular dichroist in the terahertz band provided by an embodiment of the present invention.

[0047] The present invention provides a metasurface circular dichroic device based on a liquid crystal elastomer 3, comprising a dielectric layer 1, a plurality of movable structural bodies 2 and a plurality of liquid crystal elastomers 3;

[0048] Each movable structural body 2 is periodically attached to the dielectric layer 1;

[0049] A liquid crystal elastomer 3 is partially attached to each movable structural body 2 so as to adjust the response of the metasurface circular dichroism by changing the structure of the movable structural body 2 .

[0050] Circular dichroism refers to the dichroism of circularly polarized light, specifically the differential absorption of left-handed and right-handed light. Left-handed and right-handed circularly polarized light represent the two possible spin angular momentum states of a photon, so circular dichroism is also called the dichroism of spin angular momentum.

[0051] In this embodiment, in order to achieve the ability to absorb different circularly polarized waves separately in a simple structure and adjust the circular dichroism of the metasurface circular dichroist, a metasurface circular dichroist based on a liquid crystal elastomer 3 (hereinafter referred to as a metasurface circular dichroist) is provided. The metasurface circular dichroist comprises a dielectric layer 1, multiple movable structural bodies 2, and multiple liquid crystal elastomers 3 stacked in sequence from bottom to top.

[0052] Specifically, thin metal films or metal plates, such as 200 nm thick, are periodically attached to a dielectric layer 1 as movable structural bodies 2. Each movable structural body 2 is then processed according to a preset shape, such as by electron beam etching, mask printing, or photolithography. This process divides each movable structural body 2 into a rectangular metal frame 21 fixed to the dielectric layer 1 and a microstructured metal sheet 22 movable at one end. Furthermore, a liquid crystal elastomer 3 is attached to each microstructured metal sheet 22. By varying the degree of bending of the microstructured metal sheet 22 within the movable structural body 2, the circular dichroism of the metasurface circular dichroist can be adjusted.

[0053] Among them, the dielectric layer 1 can be made of materials with different dielectric constants and dielectric losses, with a layer thickness of 3μm to 1000μm and a dielectric constant range of 2 to 6. The material can be polyimide, silicon dioxide or silicon, etc., and its shape specifications can be regular squares or polygons. It can be cut according to technical parameter requirements, the number and shape of the movable structural body 2, and the embodiment of the present application does not limit this.

[0054] In one example of the present application, the movable structural body 2 includes a rectangular metal frame 21 and a microstructured metal sheet 22;

[0055] The liquid crystal elastomer 3 is attached to the microstructured metal sheet 22, and the rectangular metal frame 21 is attached to the dielectric layer 1;

[0056] The connection end of the microstructured metal sheet 22 is connected to the rectangular metal frame 21 . The microstructured metal sheet can be bent to different degrees to adjust the response of the metasurface circular dichroic device.

[0057] In one example of the present application, the cross-sectional shape of the dielectric layer 1 is a regular polygon;

[0058] The material of the dielectric layer 1 is polyimide, silicon dioxide or silicon with different dielectric constants and dielectric loss; wherein the dielectric constant ranges from 2 to 6;

[0059] The thickness of the dielectric layer 1 ranges from 3 μm to 1000 μm.

[0060] For example, the side length of a single dielectric layer 1 attached to the movable structural body 2 can be in the range of 200 to 500 μm, such as 20 μm, 50 μm, 260 μm, etc., and the dielectric constant range is 2 to 6, such as 3.4, 4.41, etc. The appropriate dielectric material is selected according to the required operating frequency band of the design. The periods of the periodic unit in the x-direction and y-direction are P respectively. x and P y The length of the first period in the x direction is P x , the length is 200 to 500 μm, which can be 200 μm, 300 μm, 350 μm, etc. The second period length in the y direction is P y , the length is 200-500 μm, which can be 200 μm, 300 μm, 350 μm, etc. For example, the material of the dielectric layer 1 is silicon dioxide, with a thickness of 220 μm and a dielectric constant of 4.41. The first period length P x = second period length P y =300μm.

[0061] It should be noted that the cross-sectional shape of the metasurface circular dichroic device is rectangular, and the movable structural bodies 2 are arranged horizontally and vertically at the same intervals. The number of movable structural bodies 2 is m×n, where m≥10, n≥10, and m and n are integers.

[0062] If each dielectric layer 1 unit is a polygon, the number of periods can be expressed in other ways.

[0063] Please refer to FIG. 2 , which is a schematic diagram of different circular dichroism responses of a single movable structural body 2 in an embodiment of the present invention.

[0064] In this embodiment, the movable structural body 2 comprises a rectangular metal frame 21 and a microstructured metal sheet 22. The microstructured metal sheet 22 is bendable. The degree of bending of the microstructured metal sheet 22 can affect the frequency shift of a frequency point or produce corresponding changes in the spectral waveform, thereby adjusting the circular dichroism of the metasurface circular dichroist. In a specific implementation, the degree of bending increases with the increase in illumination time within a certain period of time. The change in bending degree further affects the frequency shift of a frequency point or changes in the spectral waveform.

[0065] It should be noted that the rectangular metal frame 21 and the microstructured metal sheet 22 are both made of conductive metal materials that conduct current. Such metal materials include, but are not limited to, gold, silver, aluminum, copper, and other metal materials that have good electrical conductivity and can conduct the generated current. The specific types of these materials are not limited in this embodiment of the present application.

[0066] Furthermore, the microstructured metal sheet 22 includes a first metal sheet 221 and a second metal sheet 222 ;

[0067] The shapes of the first metal sheet 221 and the second metal sheet 222 are both asymmetrical;

[0068] The connecting end of the first metal sheet 221 and the connecting end of the second metal sheet 222 are connected through the rectangular metal frame 21 and are arranged in mirror symmetry along the central axis of the rectangular metal frame 21 .

[0069] As shown in Figure 2, the first metal sheet 221 and the second metal sheet 222 within the microstructured metal sheet 22 can be arranged in mirror symmetry with respect to the central axis of the rectangular metal frame 21, such as the y-axis. The shapes of the first metal sheet 221 and the second metal sheet 222 can each be regular or irregular, but each is asymmetrical. Furthermore, the first metal sheet 221 and the second metal sheet 222 are connected at their connecting ends by the rectangular metal frame 21, while the remaining portions are separated and non-contacting.

[0070] The length of the microstructured metal sheet 22 is in the range of 50 μm to 200 μm, the width is in the range of 50 μm to 200 μm, and the thickness is in the range of 0.05 μm to 5 μm.

[0071] In one example of the present application, the side length of the rectangular metal frame 21 ranges from 200 μm to 500 μm;

[0072] The rectangular metal frame 21 has a frame width ranging from 10 μm to 50 μm, and a frame thickness ranging from 0.05 μm to 5 μm; wherein the frame thickness is smaller than the thickness of the dielectric layer 1 .

[0073] In this embodiment, the cross-sectional shape of the rectangular metal frame 21 may include various shapes, such as regular polygons, regular rectangles, etc., which can be processed according to user needs, and the embodiment of the present application does not limit this.

[0074] Optionally, the liquid crystal elastomer 3 includes a liquid crystal monomer, a cross-linking agent and a polymer;

[0075] The liquid crystal elastomer 3 is attached to the first metal sheet 221 and the second metal sheet 222 respectively, and has different polymers to provide different stimulus responses under different frequencies of light;

[0076] Wherein, the polymer is a near-infrared organic dye.

[0077] In the embodiment of the present application, the liquid crystal elastomer 3 includes a liquid crystal monomer, a crosslinker, and a polymer. The polymer may include, but is not limited to, near-infrared organic dyes (YHD796, Dye1002, DisperseRed1, etc.), single-arm carbon nanotubes, metal nanoparticles, azobenzene groups and their derivatives. The liquid crystal monomer may include polymerizable liquid crystals C6M, RM23, RM105, etc. The crosslinker may be selected from cyclic siloxane, dichloromethane, pentaerythritol tetrakis-3-mercaptopropionate, etc. By utilizing the different responses of different liquid crystal elastomers 3 to different stimuli (light stimulation, thermal stimulation, chemical stimulation, etc.), the dynamic adjustment of the metasurface circular dichroism can be flexibly achieved.

[0078] Taking azobenzene groups as an example, azobenzene mesogens form an ordered arrangement on the microscopic level, but appear disordered on the macroscopic level. Because the absorption of linearly polarized light by the rod-shaped azobenzene mesogens is largely dependent on the polarization direction of the light, when the liquid crystal elastomer 3 film is illuminated by linearly polarized ultraviolet light, the mesogens aligned with the linearly polarized light undergo photoinduced contraction, causing the entire film to bend along the polarization direction of the light. Precise control of the film's bending direction can be achieved simply by changing the polarization direction of the incident light.

[0079] In an embodiment of the present application, referring to FIG. 2 , a first liquid crystal elastomer 31 is attached to a first metal sheet 221, and a second liquid crystal elastomer 32 is attached to a second metal sheet 222. The first liquid crystal elastomer 31 and the second liquid crystal elastomer 32 have different responses under illumination of different frequencies. The first liquid crystal elastomer is doped with a near-infrared dye, Dye1002, and the illumination frequency is 520 nm. The second liquid crystal elastomer is doped with a near-infrared dye, YHD796, and the illumination frequency is 808 nm.

[0080] For example, referring to FIG1 and FIG2, the dielectric layer is made of silicon dioxide, and the microstructured metal sheet can be made of gold, with a conductivity of 4.56×10 7 The rectangular metal frame microstructured metal sheet has a first length L1 of 20 μm, a second length L2 of 160 μm, and a third length L3 of 160 μm. The first width W1 is 48 μm, the second width W2 is equal to the third width W3, and the thickness is 0.2 μm. The width S of the rectangular metal frame ranges from 10 μm to 50 μm, with S being 40 μm by way of example.

[0081] Please refer to FIG3 , which shows a circular dichroism spectrum corresponding to a metasurface circular dichroist in an embodiment of the present application.

[0082] In this embodiment, a metasurface circular dichroist (MCD) using the structure illustrated in Figures 1 and 2 can be simulated using the commercial 3D electromagnetic field simulation software CST. A unit-period simulation model of the design was established within the CST microwave and millimeter-wave laboratory. Periodic boundary conditions were set in the x and y directions to simulate m×n periods. A terahertz circularly polarized wave was incident perpendicularly on the structure's surface along the -z direction. The +z and -z directions were set as open boundary conditions, serving as the terahertz wave's entrance and exit ports. Further simulation revealed the circular dichroism (CD) spectra generated by the periodic structure's differential absorption of left-handed and right-handed circularly polarized waves, as shown in Figure 3. The horizontal axis represents frequency, and the vertical axis represents CD values. The solid and dashed lines correspond to the CD spectra of the two terahertz CDs, respectively. The spectral lines of the two terahertz metasurface CDs exhibited completely opposite trends, indicating that the different responses of the liquid crystal elastomer to illumination of different frequencies result in opposite transmission effects for left-handed and right-handed circularly polarized waves within the corresponding frequency ranges.

[0083] Please refer to Figure 4, which illustrates the tunable results of a terahertz-band liquid crystal elastomer-based metasurface circular dichroism (CD) device in an embodiment of the present invention. As can be seen, by varying the duration of illumination and the degree of bending of the microstructured metal sheet attached to the CD, flexible adjustment of CD values ​​at different frequencies can be achieved. For example, if YHD796 is selected as the near-infrared dye, the initial response time for irradiation with light at a frequency of 808nm is approximately 10 seconds, reaching the maximum response time at approximately 25 seconds. If DisperseRed1 is selected as the near-infrared dye, the initial response time for irradiation with light at a frequency of 980nm is approximately 8 seconds, reaching the maximum response time at approximately 30 seconds.

[0084] Figure 5 is another structural schematic diagram of a terahertz band metasurface circular dichroist based on liquid crystal elastomer provided by an embodiment of the present invention, which is specifically a periodic unit structure diagram and side view of the second terahertz band metasurface circular dichroist based on liquid crystal elastomer.

[0085] The metasurface circular dichroic device of this embodiment includes a dielectric layer 4, a movable structural body 5, and a liquid crystal elastomer 6. The structure, from top to bottom, along the second order, is the liquid crystal elastomer 6, the movable structural body 5, and the dielectric layer 4. The movable structural body 5 includes a rectangular metal ring 51 and a microstructured metal sheet 52. The metal microstructures 5 are periodically attached to the surface of the dielectric layer 4, and the liquid crystal elastomer 6 is attached to the third microstructured metal sheet 521 (i.e., the first metal sheet) and the fourth microstructured metal sheet 522 (i.e., the second metal sheet).

[0086] FIG6 is a schematic diagram showing different circular dichroism responses of a single movable structural body in another structure according to an embodiment of the present invention.

[0087] The movable structural body 5 includes a rectangular metal frame 51, a third microstructured metal sheet 521, and a fourth microstructured metal sheet 522. The thickness of the movable structural body 5 is less than that of the dielectric layer 4. The third microstructured metal sheet 521 and the fourth microstructured metal sheet 522 are asymmetric structures. The third microstructured metal sheet 521 and the fourth microstructured metal sheet 522 are mirror images relative to the y-axis, with a microstructured metal sheet length of a fourth length L and a third width W. The rectangular metal sheet can have a length range of 50 μm to 200 μm, and a width range of 50 μm to 200 μm; for example, the length can be 80 μm, 100 μm, or 160 μm, and the width can be 50 μm, 70 μm, or 90 μm. The movable structural body 5 is arranged in rows and columns with equal spacing, thereby forming a periodic arrangement of metal sheet units. The metal sheets can also have other regular or irregular shapes. The dielectric and metal materials in this embodiment are consistent with the parameters of a terahertz-band liquid crystal elastomer-based metasurface circular dichroist provided in the embodiment. In the actual processing process, the actual number of periods of the periodic unit contained in the device is m×n, generally m≥10, n≥10. If each dielectric layer unit is a polygon, the number of periods can be expressed in other ways. For example, the material of the dielectric layer 4 is selected as silicon dioxide, with a thickness of 220μm and a dielectric constant of 4.41. The third period length Px1 = the fourth period length Py1 = 300μm. The fourth length L of the rectangular metal frame microstructure metal sheet is set to 120μm, the fourth width W = 140μm, and the thickness is 0.2μm.

[0088] Figure 7 shows the circular dichroism (CD) spectrum of another structure of a terahertz-band liquid crystal elastomer-based metasurface CD device, provided by an embodiment of the present invention. The solid and dashed lines correspond to the CD spectra of the two THz CD devices, respectively. The spectra of the two THz CD devices exhibit completely opposite trends, indicating that the different responses of the liquid crystal elastomer under illumination of different frequencies result in opposite transmission effects for left- and right-handed circularly polarized waves within the corresponding frequency ranges.

[0089] Figure 8 shows the circular dichroism spectra of another structure of a liquid crystal elastomer-based metasurface circular dichroist in the terahertz band provided by an embodiment of the present invention at different bending degrees. By applying different illumination times, the degree of bending of the micro-junction metal sheet attached with the liquid crystal elastomer is different, and flexible adjustment of different circular dichroism values ​​at different frequency points can be achieved. Among them, the three structures are distinguished by ellipticity. The ellipticity of structure A in Figure 8 is 1 / 4, the ellipticity of structure B is 1 / 8, and the ellipticity of structure C is 0. As the ellipticity decreases, the circular dichroism spectrum near 0.33THz gradually moves toward the low-frequency direction, and the amplitude gradually decreases. The frequency of the circular dichroism spectrum at the beginning of 0.45THz does not have an obvious offset but the amplitude gradually increases. And when the ellipticity is 0, there will be an obvious trough with an amplitude of -0.28 at 0.5THz.

[0090] In an embodiment of the present application, a terahertz-band metasurface circular dichroist based on a liquid crystal elastomer is provided, comprising a dielectric layer, multiple movable structural bodies, and multiple liquid crystal elastomers; each movable structural body is periodically attached to the dielectric layer; and each movable structural body is partially attached with a liquid crystal elastomer, so that the response of the metasurface circular dichroist can be adjusted by structural changes of the movable structural body. By varying the degree of bending of the microstructured metal sheet within the movable structural body, the circular dichroism values ​​at different frequencies can be flexibly adjusted. Furthermore, the attachment of the liquid crystal elastomer further improves the response performance and flexibility of the metasurface circular dichroist, thereby simplifying the circular dichroist structure and further improving the flexibility of detection, making it easier to detect chiral molecules.

[0091] Please refer to FIG9 , which shows a flowchart of the steps of a method for preparing a metasurface circular dichroist based on liquid crystal elastomer in the terahertz band in an embodiment of the present application.

[0092] An embodiment of the present invention provides a method for preparing a terahertz-band metasurface circular dichroic device based on a liquid crystal elastomer, which is used to prepare the metasurface circular dichroic device of any embodiment, comprising:

[0093] Step 901: attaching an initial structure body of the same size to a dielectric layer;

[0094] Step 902: Processing the initial structural body according to preset parameters to obtain multiple movable structural bodies;

[0095] Step 903: partially attaching a liquid crystal elastomer to each movable structural body to obtain a metasurface circular dichroic device.

[0096] In the embodiment of the present application, before preparation, the dielectric layer or dielectric substrate is generally cut into a suitable size according to user needs or product needs. The thickness range is 20μm to 1000μm, and the shape and side length can be set according to product requirements, which is not limited in this embodiment.

[0097] When fabricating a metasurface circular dichroist, an initial structural body of the same size as the dielectric layer can be directly attached to the dielectric layer. Specifically, a selected metal dielectric film or plate with a thickness ranging from 0.05 μm to 5 μm can be attached to the dielectric layer. The initial structural body is then etched according to preset parameters, such as the shape, length, and width of the rectangular metal frame, first metal sheet, and second metal sheet within the movable structural body to be fabricated. This produces multiple movable structural bodies attached to the dielectric layer. A liquid crystal elastomer is then attached to the first and second metal sheets of each movable structural body, thereby producing a metasurface circular dichroist.

[0098] There is a same interval between each movable structural body, and the liquid crystal elastomer can be prepared uniformly before preparing the circular dichroist.

[0099] In the embodiments of this application, initial structural bodies of identical dimensions are attached to a dielectric layer and processed according to preset parameters, such as by electron beam etching, mask printing, or photolithography, to obtain multiple movable structural bodies. A liquid crystal elastomer is partially attached to each movable structural body to form a metasurface circular dichroist. This simplifies the circular dichroist structure and further enhances its detection flexibility, facilitating its application in the detection of chiral molecules.

[0100] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the module division is merely a logical function division. In actual implementation, other division methods may be used, such as combining or integrating multiple modules or components into another system, or ignoring or not implementing certain features.

[0101] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A terahertz band metasurface circular dichroic device based on liquid crystal elastomer, characterized in that: It includes a dielectric layer, a plurality of movable structural bodies and a plurality of liquid crystal elastomers; Each of the movable structural bodies is periodically attached to the dielectric layer; The liquid crystal elastomer is partially attached to each of the movable structural bodies, so as to adjust the response of the metasurface circular dichroism through the structural change of the movable structural body.

2. The metasurface circular dichroic device according to claim 1, characterized in that: The movable structural body includes a rectangular metal frame and a microstructured metal sheet; The liquid crystal elastomer is attached to the microstructured metal sheet, and the rectangular metal frame is attached to the dielectric layer; The connecting end of the microstructured metal sheet is connected to the rectangular metal frame, and the microstructured metal sheet can be bent to different degrees to adjust the response of the metasurface circular dichroic device.

3. The metasurface circular dichroic device according to claim 2, characterized in that: The microstructured metal sheet includes a first metal sheet and a second metal sheet; The shapes of the first metal sheet and the second metal sheet are both asymmetrical; The connecting end of the first metal sheet and the connecting end of the second metal sheet are connected through a rectangular metal frame and are arranged in a mirror-symmetrical manner along the central axis of the rectangular metal frame.

4. The metasurface circular dichroic device according to claim 2, wherein: The length of the microstructured metal sheet ranges from 50 μm to 200 μm, the width ranges from 50 μm to 200 μm, and the thickness ranges from 0.05 μm to 5 μm.

5. The metasurface circular dichroic device according to claim 2, characterized in that: The side length of the rectangular metal frame ranges from 200 μm to 500 μm; The rectangular metal frame has a frame width ranging from 10 μm to 50 μm, and a frame thickness ranging from 0.05 μm to 5 μm; wherein the frame thickness is smaller than the thickness of the dielectric layer.

6. The metasurface circular dichroic device according to claim 2, characterized in that: The rectangular metal frame and the microstructured metal sheet are both made of metal materials that have conductive properties and conduct electricity through circulating current.

7. The metasurface circular dichroic device according to claim 3, characterized in that: The liquid crystal elastomer includes a liquid crystal monomer, a cross-linking agent and a polymer; The liquid crystal elastomer is attached to the first metal sheet and the second metal sheet respectively, and the polymers are different so as to provide different stimulus responses under light of different frequencies.

8. The metasurface circular dichroic device according to claim 1, wherein: The material of the dielectric layer is polyimide, silicon dioxide or silicon with different dielectric constants and dielectric loss; wherein the dielectric constant ranges from 2 to 6; The thickness of the dielectric layer ranges from 3 μm to 1000 μm.

9. The metasurface circular dichroic device according to claim 1, characterized in that: The movable structural bodies are arranged at the same intervals, and the number of the movable structural bodies is m×n, where m≥10, n≥10, and m and n are integers.

10. A method for preparing a terahertz band metasurface circular dichroic device based on liquid crystal elastomer, characterized in that: A method for preparing the metasurface circular dichroic device according to any one of claims 1 to 9 comprises: attaching an initial structural body of the same size to the dielectric layer; Processing the initial structural body according to preset parameters to obtain a plurality of movable structural bodies; A liquid crystal elastomer is partially attached to each movable structural body to obtain a supersurface circular dichroic device.

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