Medium metasurface structure capable of tuning circular dichroism peak value and chiral inversion
By designing a dielectric metasurface with a specific structure, the problems of low circular dichroism peak and difficult chirality reversal are solved, and a strong chiral response and continuous tuning of the CD peak are achieved, which is suitable for polarization conversion, imaging and biomedical sensing.
Patent Information
- Application Number
- CN202510713844.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-09-23
AI Technical Summary
The existing technology has the problem that the circular dichroism peak is low and the chirality reversal cannot be achieved.
A dielectric metasurface structure is designed, including a metasurface unit structure, a metal reflective layer and a substrate. The metasurface unit structure is composed of a specific geometric shape and material, and continuous tuning of chirality inversion and CD peak can be achieved by changing the structural parameters.
Strong chiral response and tuning of CD peaks are achieved in reflective chiral metasurfaces, which have the potential to modulate device spectra and polarization in different environments and are suitable for polarization conversion, imaging and biomedical sensing.
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Figure CN120686485A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of metamaterials and metasurfaces, and in particular to a dielectric metasurface structure capable of tunable circular dichroism peak value and chirality inversion. Background Art
[0002] Chirality is a ubiquitous phenomenon in nature. The chirality of a material refers to a geometric characteristic of its structure, whereby translation or in-plane rotation cannot be aligned with its mirror image. Optical chirality manifests as a medium's different responses to left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light, measured by circular dichroism (CD). The chiral response in natural materials is typically very weak, limiting their applications. Metasurfaces, due to their superior light field manipulation and localization capabilities, can achieve large CD responses. Under conditions of perpendicular incidence, chiral metasurfaces can achieve spin-selective reflection of incident light. Compared to mechanically rotated waveplates, chiral metasurfaces not only significantly improve the detection efficiency of circularly polarized signals, but also offer the advantages of being ultrathin, lightweight, and easily integrated. This makes them a significant advantage in dynamic, high-resolution imaging scenarios. Furthermore, chiral metasurfaces possess broad spectral adaptability. By designing nanostructures of varying scales and shapes, they can cover a wide spectral range from the visible to the infrared.
[0003] See the article "Meta-Atom Coupling Induced Chiral Hotspot in Silicon Nitride Staggered Nanorods Meta-Surface" published by Shen Chao et al. in the Journal of Physical Chemistry Letters. This technical solution is a chiral metasurface composed of achiral silicon nitride rectangular nanorods. Two nanorods are placed parallel to each other on a substrate. The coupling between the staggered nanorods is used to generate a chiral electric field hotspot in the gap, achieving different responses to left-handed and right-handed circularly polarized light. By varying the overlap length of the nanorods, the CD peak wavelength can be continuously tuned within a certain wavelength range. However, the CD peak is low and chirality reversal cannot be achieved. Summary of the Invention
[0004] In order to solve the problem of low CD peak and inability to achieve chirality reversal, the present invention provides a dielectric metasurface structure with tunable circular dichroism peak and chirality reversal.
[0005] The technical solution of the present invention to solve the technical problem is:
[0006] A dielectric metasurface structure with tunable circular dichroism peak and chirality inversion comprises: a metasurface unit structure, a metal reflective layer and a substrate, wherein the metal reflective layer is fixed on the substrate, and the metasurface unit structure is arranged on the metal reflective layer; the metasurface unit structure comprises a first component, a second component, a third component, a fourth component, a fifth component, a sixth component and a seventh component, wherein the first component and the seventh component are arranged in parallel, the second component connects the first component and the third component, the first component and the third component are perpendicular to each other, the third component and the fifth component are separated by the fourth component, the sixth component connects the fifth component and the seventh component, and the sixth component and the seventh component are perpendicular to each other; the first component, the second component and the third component are an integrally formed structure; the fifth component, the sixth component and the seventh component are also an integrally formed structure.
[0007] The present invention has the following beneficial effects:
[0008] The dielectric metasurface with tunable circular dichroism peak and chirality reversal provided by this invention exhibits a strong chiral response among reflective chiral metasurfaces. Chirality reversal can be achieved by simply changing the metasurface structure, and continuous tuning of the CD peak can be achieved by simply changing the structural parameters. High CD values are maintained within a certain wavelength range, offering the potential for modulating device spectra and polarization as needed in different environments. It has broad applications in polarization conversion, imaging, and biomedical sensing. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 Schematic diagram of the dielectric metasurface structure with tunable circular dichroism peak and chirality inversion provided by this embodiment Figure 1 (a) Forehand metasurface structure Figure 1 (b) Backhand metasurface structure diagram;
[0010] Figure 2 1 is a front view of a dielectric metasurface structure with tunable circular dichroism peak and chirality inversion provided by this embodiment;
[0011] Figure 3 1 is a top view of a dielectric metasurface structure with tunable circular dichroism peak and chirality inversion provided by this embodiment;
[0012] Figure 4 is a graph of the positive-handed CD curve of the dielectric metasurface structure with tunable circular dichroism peak and chirality reversal provided in this embodiment;
[0013] Figure 5 is a backhand CD curve diagram of the dielectric metasurface structure with tunable circular dichroism peak and chirality reversal provided in this embodiment;
[0014] Figure 63. This is a comparison diagram of the forward and backhand CD curves of the dielectric metasurface structure with tunable circular dichroism peak and chirality reversal provided in this embodiment;
[0015] Figure 7 7(a) is a functional verification result diagram of the positive-handed simulation experiment of the dielectric metasurface structure with tunable circular dichroism peak and chirality reversal provided in this embodiment. 7(b) is the electric field intensity distribution diagram on the structural plane at 690nm when the LCP wave (left-handed polarized light) is incident, and 7(a) is the electric field intensity distribution diagram on the structural plane at 690nm when the RCP wave (right-handed polarized light) is incident.
[0016] Figure 8 This is a CD spectrum diagram of the dielectric metasurface structure with tunable circular dichroism peak and chirality inversion provided by this embodiment. DETAILED DESCRIPTION
[0017] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings.
[0018] like Figure 1 As shown in Figure (a), a dielectric metasurface structure with tunable circular dichroism peak and chirality inversion comprises a metasurface unit structure 1, a metal reflective layer 2, and a substrate 3. The metal reflective layer 2 is fixed to the substrate 3, and the metasurface unit structure 1 is disposed on the metal reflective layer 2. The metasurface unit structure 1 comprises a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, a sixth component 16, and a seventh component 17. The first component 11 and the seventh component 17 are arranged in parallel. The second component 12 connects the first component 11 and the third component 13, and the first component 11 and the third component 13 are perpendicular to each other. The third component 13 and the fifth component 15 are separated by the fourth component 14. The sixth component 16 connects the fifth component 15 and the seventh component 17, and the sixth component 16 and the seventh component 17 are perpendicular to each other. The first component 11, the second component 12, and the third component 13 are integrally formed. The fifth component 15, the sixth component 16, and the seventh component 17 are also integrally formed.
[0019] The material of the super surface unit structure 1 is silicon nitride (Si3N4).
[0020] The material of the metal reflective layer 2 is aluminum (Al).
[0021] The substrate 3 is made of silicon dioxide (SiO2).
[0022] The first component 11 , the third component 13 , the fifth component 15 and the seventh component 17 are all cuboids and have the same size.
[0023] The fourth component 14 is a rectangular groove.
[0024] The second component 12 and the sixth component 16 are both cubes and have the same size.
[0025] The first component 11 is moved to the other end of the second component 12, the seventh component 17 is moved to the other end of the sixth component 16, and the other components remain unchanged, thereby achieving chirality reversal.
[0026] When the lengths a of the first component 11 , the third component 13 , the fifth component 15 and the seventh component 17 are changed while the parameters of the other components remain unchanged, the peak position of the CD spectrum can be continuously adjusted.
[0027] Example:
[0028] Finite-difference time-domain (FDTD) simulation software was used to establish a dielectric metasurface structure model with tunable circular dichroism peaks and chirality inversion. The thickness of the metasurface unit structure was defined as h1, the thickness of the metal layer as h2, and the thickness of the substrate as h3. In the metasurface unit structure, the first, third, fifth, and seventh components were all rectangular parallelepipeds of equal size, with a length a and a width b. The second and sixth components were both cubes of equal size, with a side length b. The fourth component was a rectangular groove with a width w. The longitudinal period of the metasurface was P1, and the transverse period was P2.
[0029] like Figure 2 、 3 As shown, the structural parameters are input into the FDTD software. The implementation steps are as follows:
[0030] S1. Set substrate 3, select silicon dioxide as the material, and set the thickness to h3 = 0.9 um.
[0031] S2. Add a metal reflective layer 2 on the substrate 3. The material is selected as aluminum and the thickness is set to h2 = 0.1 um.
[0032] S3. Add a metasurface unit structure 1 above the metal reflective layer 2. The first component 11, the third component 13, the fifth component 15 and the seventh component 17 are all rectangular and equal in size, with a length of a = 0.16um and a width of b = 0.185um. The second component 12 and the sixth component 16 are both cubes and equal in size, with a side length of b = 0.185um. The fourth component 14 is a rectangular groove with a width of w = 0.031um. The thickness of all metasurface components is h1 = 0.17um. The material of the first component 11, the second component 12, the third component 13, the fifth component 15, the sixth component 16 and the seventh component 17 is set to silicon nitride.
[0033] S4. Set the simulation area, set the longitudinal period to P1 = 0.69 μm, and the transverse period to P2 = 0.906 μm. Set the boundary conditions in the X and Y directions to periodic boundary conditions, and the Z direction to a perfectly matched layer (PML) boundary condition.
[0034] S5. Perform simulation and use formula Calculate the CD value. Where: R RCP is the reflectivity of right-handed circularly polarized light incident on the metasurface, R LCP is the reflectivity of left-handed circularly polarized light incident on the metasurface.
[0035] Based on the present invention, the chiral response results in the forehand case are as follows: Figure 4 As shown in the figure, at 690nm, the metasurface resonates and strongly absorbs left-handed circularly polarized light, causing its reflectivity to drop rapidly, while there is no absorption of right-handed circularly polarized light. This huge reflection difference reflects the strong chiral response of the metasurface. It can be seen in the figure that the CD value reaches the band peak of 0.8. The structure diagram of the chirality inversion based on the above metasurface is shown in the figure. Figure 1 As shown in (b), Figure 1 In the metasurface (a), the first component 11 is moved vertically to the other end of the second component 12, the seventh component 17 is moved to the other end of the sixth component 16, and the other components remain unchanged. After the movement, the new metasurface structure is still an integrated structure. The simulation is repeated, and the chiral response results in the reverse hand case are as follows: Figure 5 As shown, the CD value at 690nm reaches -0.8, which is consistent with Figure 4 The result is just the opposite, reflecting the chirality inversion phenomenon. Figure 6 Comparing the CD values of the positive and negative chirality, it can be seen that the positive and negative CD curves are symmetrical about the X-axis. The metasurface of the present invention has the chirality reversal function through a simple structural change.
[0036] Depend on Figure 7 As can be seen from (a) and (b), when left-handed circularly polarized light is incident on the designed metasurface structure, strong resonant absorption occurs at the middle groove of the "Z"-shaped structure, so that only a small amount of left-handed circularly polarized light is reflected. However, when right-handed circularly polarized light is incident on the designed metasurface structure, no strong resonance phenomenon occurs, and a large amount of right-handed circularly polarized light is reflected. This phenomenon shows that the structure has a strong chiral response, which is consistent with the designed function, thereby proving the effectiveness of the present invention.
[0037] When the lengths a of the first component 11, the third component 13, the fifth component 15, and the seventh component 17 are changed, and the parameters of the other components remain unchanged, the longitudinal period of the simulation area is calculated according to P1=2a+2b, and the transverse period is calculated according to P2=2a+3b+w, and the calculations are input into the software respectively, as shown in the following example: Figure 8As shown, the length a of the first component 11, the third component 13, the fifth component 15 and the seventh component 17 is changed from 40 nm to 240 nm with an interval of 40 nm. It can be seen that the CD peak moves monotonically from 525 nm to 780 nm, thereby proving that the peak position of the CD spectrum of the present invention can be continuously adjusted.
Claims
1. A dielectric metasurface structure with tunable circular dichroism peak and chirality inversion, characterized by: It comprises a super surface unit structure (1), a metal reflective layer (2) and a substrate (3); the metal reflective layer (2) is fixed on the substrate (3), and the super surface unit structure (1) is arranged on the metal reflective layer (2); The metasurface unit structure (1) comprises a first component (11), a second component (12), a third component (13), a fourth component (14), a fifth component (15), a sixth component (16) and a seventh component (17); the first component (11) and the seventh component (17) are arranged in parallel; the second component (12) connects the first component (11) and the third component (13); the first component (11) and the third component (13) are perpendicular to each other; the third component (13) and the fifth component (15) are separated by the fourth component (14); the sixth component (16) connects the fifth component (15) and the seventh component (17); the sixth component (16) and the seventh component (17) are perpendicular to each other; the first component (11), the second component (12) and the third component (13) are an integrated structure; the fifth component (15), the sixth component (16) and the seventh component (17) are also an integrated structure.
2. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: The material of the supersurface unit structure (1) is silicon nitride.
3. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: The material of the metal reflective layer (2) is aluminum.
4. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: The substrate (3) is made of silicon dioxide.
5. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: The first component (11), the third component (13), the fifth component (15) and the seventh component (17) are all rectangular parallelepipeds and have the same size.
6. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: The second component (12) and the sixth component (16) are both cubes and have the same size.
7. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: The first component (11) is moved to the other end of the second component (12), the seventh component (17) is moved to the other end of the sixth component (16), and the other components are not changed, so that chirality reversal can be achieved.
8. The dielectric metasurface structure with tunable circular dichroism peak and chirality inversion according to claim 1, characterized in that: When the lengths of the first component (11), the third component (13), the fifth component (15) and the seventh component (17) are changed and the parameters of the other components remain unchanged, the peak position of the CD spectrum can be continuously adjusted.