Method for forming a quasi-bic all-dielectric super surface based on u-shaped nanopillars

Abstract

The application belongs to the technical field of optical super surface, and particularly relates to a forming method and application of a full dielectric quasi-BIC super surface based on U-shaped nanorods. The U-shaped nanorod at the upper left corner of a symmetric BIC super surface is individually scaled in proportion; the symmetric BIC super surface is composed of a plurality of square lattices, each square lattice is composed of a nanosubstrate and a U-shaped nanorod tetramer deposited on the nanosubstrate, and the tetramer is composed of four first U-shaped nanorods, second U-shaped nanorods, third U-shaped nanorods and fourth U-shaped nanorods which are of the same size. When the incident light is x-polarized, the first U-shaped nanorod is individually scaled in proportion, an asymmetric disturbance is introduced, and an asymmetric square lattice is formed. The super surface is applied to bidirectional optical switch equipment and liquid sensors. The Q value of the super surface is high, the intensity and waveform of the transmission spectrum can be flexibly modulated by adjusting the relevant structure parameters of the super surface, and the super surface is widely applied.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical metasurfaces, and particularly relates to a forming method and application of a full-dielectric quasi-BIC metasurface based on U-shaped nanocolumns. BACKGROUND

[0002] The refractive index (RI) is an inherent property of a material and is often used for material identification, quality control, chemical analysis, optical design, and environmental monitoring. Metasurfaces are discrete subwavelength structures composed of artificial meta-atoms. Due to their sensitivity to the refractive index of the neighborhood, RI sensors based on metasurfaces have a wide range of applications in sensors, optical switches, surface wave couplers, and filters. For example, as an RI sensor, metasurfaces use resonant characteristics to detect small changes in refractive index, thereby improving the accuracy of chemical analysis and environmental monitoring. In these applications, the quality factor (Q factor) and the figure of merit (FOM) are key parameters that reflect the efficiency of the metasurface. Metal metasurfaces produce a large amount of radiation loss due to the oscillation of free electrons, resulting in a low Q value at the resonance point. In contrast, the resonance peak of a full-dielectric metasurface is sharper, and the FOM and Q factor are larger. Structures with bound states in the continuum (BIC) in a continuum are natural high-Q resonators because, in an ideal case, the radiation Q value is equal to infinity. This indicates a correlation between high-Q metasurfaces and BIC.

[0003] BIC optical modes provide a destructive interference mechanism that can achieve high-Q resonance and strong field localization. Ideally, BIC is a dark mode with infinite Q radiation, which cannot be directly excited by incident light and cannot appear in the spectrum. By breaking the symmetry of the unit cell, the original symmetric mode is broken, allowing it to couple with the external continuum and transform into a QBIC mode with a finite Q factor and a non-zero line width. To enhance the QBIC mode excitation, the symmetry of the full-dielectric metasurface can be broken by modifying certain parameters of the metasurface and changing the shape and orientation of the dielectric material on the metasurface.

[0004] The generation of quasi-BIC metasurfaces generally requires the symmetry of the structure to be broken, and most symmetric BICs are polarization-sensitive. In the prior art, there are methods of exciting quasi-BIC resonance by adding or cutting a small number of asymmetric rectangular or circular blocks; there are methods of exciting quasi-BIC resonance by converting the rotational symmetry of a simple lattice into the C4v rotational symmetry of a superlattice; and there are methods of exciting quasi-BIC resonance by combining the collective perturbation of C4v symmetric tetramers and specific displacements, however these methods have certain limitations for actual flexible applications. SUMMARY

[0005] In order to solve the above technical problems, the application provides a forming method and application of a full-dielectric quasi-BIC super surface based on a U-shaped nanocolumn. The structural symmetry can be destroyed by changing the structural size of the U-shaped nanorod to excite quasi-BIC resonance. When a U-shaped nanorod is scaled, the tetramer cannot coincide with itself after rotating by a certain angle (0°-360°). Therefore, the structure is non-rotationally symmetric, which is a very simple and effective method, realizing the conversion of a symmetry-protected BIC super surface into a quasi-BIC super surface with a very high Q value, which is of great significance for improving the sensitivity of optical sensing. The Q value of the super surface is high, and the intensity and waveform of the transmission spectrum can be flexibly modulated by adjusting the related structural parameters of the super surface, and the application is wide.

[0006] The technical scheme adopted by the application is as follows: a forming method of a full-dielectric quasi-BIC super surface based on a U-shaped nanocolumn, the forming method is:

[0007] The U-shaped nanorod at the upper left corner of the symmetric BIC super surface is individually scaled at a constant ratio; the symmetric BIC super surface is composed of a plurality of square lattices, each square lattice is composed of a nanosubstrate and a U-shaped nanorod tetramer deposited on the nanosubstrate, the U-shaped nanorod tetramer is composed of four first U-shaped nanorods, second U-shaped nanorods, third U-shaped nanorods and fourth U-shaped nanorods which are of the same size; the first U-shaped nanorod, the second U-shaped nanorod, the third U-shaped nanorod and the fourth U-shaped nanorod are symmetrically arranged in the x-axis direction and the y-axis direction;

[0008] When the incident light is x-polarized, the first U-shaped nanorod at the upper left corner in the U-shaped nanorod tetramer in the xy-plane is individually scaled at a constant ratio, and an asymmetric disturbance is introduced; the size and position of the second U-shaped nanorod, the third U-shaped nanorod and the fourth U-shaped nanorod remain unchanged, and an asymmetric square lattice is formed;

[0009] The above asymmetric square lattice is a full-dielectric quasi-BIC super surface based on a U-shaped nanocolumn;

[0010] The scaling ratio of the first U-shaped nanorod is 0.7, 0.8, 0.9, 1.1 or 1.2, respectively.

[0011] Further, the incident light is a plane wave, the wave vector of which is parallel to the z-axis direction, and the polarization angle is 0°-90°.

[0012] Further, when the quasi-BIC metasurface is excited by x-polarized incident light, the environmental refractive index is 1.319-1.36, the period of the quasi-BIC metasurface is 1000 nm; the polarization angle of the incident light is described by the angle between the incident electric field and the x-axis, and the polarization angle of the incident light is 0°-90°.

[0013] Further, the nanosubstrate is a nanocube with a thickness of 940-1060 nm, preferably a thickness of 1000 nm, and is made of silicon dioxide with a refractive index of 1.48; the material of the U-shaped nanorod tetramer is silicon.

[0014] Further, the first U-shaped nanorod, the second U-shaped nanorod, the third U-shaped nanorod and the fourth U-shaped nanorod of the symmetric BIC metasurface are all composed of a nanohalf-cylinder and a rectangular block, wherein the diameter of the nanohalf-cylinder and the length of the rectangular block are both 200 nm, the width of the rectangular block is 134-140 nm, and the height of the four U-shaped nanorods is 350-550 nm, wherein the distance between the centers of the U-shaped nanorods in the x-axis direction is 560 nm, and the distance between the centers of the U-shaped nanorods in the y-axis direction is 500 nm.

[0015] Further, the height of the four U-shaped nanorods is 450 nm.

[0016] Further, the prepared U-shaped nanocolumn-based all-dielectric quasi-BIC metasurface is applied to a bidirectional optical switch device.

[0017] Further, the prepared U-shaped nanocolumn-based all-dielectric quasi-BIC metasurface is applied to a liquid sensor.

[0018] Further, the silicon nanoparticles can be assembled with plasmonic nanostructures, combining the advantages of both to produce unique scattering behavior and coupling with the Fabry-Perot mode to achieve spectral tailoring. Design and optimization by designing silicon nanostructures are crucial for improving the performance of nanophotonics and optoelectronics. As the most common low-refractive all-dielectric material, silica has been widely used in the manufacture of photonic crystals. Although the refractive index is low, the near-zero absorption rate makes silica an ideal material in the field of optical communication. On the basis of ensuring low loss of dielectric materials, the output characteristics are efficiently expressed by promoting the coupling between different structures, so silicon and silica are selected in practical application. Different structures produce different optical phenomena; different structural parameters produce different optical properties; and different materials (refractive index) of structures dominate the trend of optical phenomena and optical properties. The above two materials are selected after a large number of calculation simulations.

[0019] The application discloses a forming method and application of a quasi-BIC super surface based on a U-shaped nanocolumn. 4 4 -1 The application discloses a forming method and application of a quasi-BIC super surface based on a U-shaped nanocolumn. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of a cubic structure of a square lattice of the symmetric BIC super surface in embodiment one;

[0021] Figure 2 is a schematic diagram of a cubic structure of a square lattice of the symmetric BIC super surface in embodiment one;

[0022] Figure 3 is a schematic diagram of a cubic structure of a square lattice of the symmetric BIC super surface in embodiment one;

[0023] Figure 4 is a schematic diagram of a cubic structure of a square lattice of the symmetric BIC super surface in embodiment one;

[0024] Figure 5 is a schematic diagram of a cubic structure of a square lattice of the symmetric BIC super surface in embodiment one;

[0025] Figure 6 is a schematic diagram of a cubic structure of a square lattice of the symmetric BIC super surface in embodiment one;

[0026] Figure 7 ​​is the multipole decomposition of FR2 of quasi-BIC metasurface of Example 1 in Test Example 2, ED-electric dipole; EQ-electric quadrupole; MD-magnetic dipole; MQ-magnetic quadrupole; TD-toroidal dipole;

[0027] Figure 8 is the electric field distribution of FR2 of quasi-BIC metasurface of Example 1 in Test Example 2;

[0028] Figure 9 is the magnetic field distribution of FR2 of quasi-BIC metasurface of Example 1 in Test Example 2;

[0029] Figure 10 is the schematic diagram of the polarization angle of incident light in Test Example 3;

[0030] Figure 11 is the transmission spectrum diagram of quasi-BIC metasurface of Example 1 in Test Example 3 under different polarization angles;

[0031] Figure 12 is the curve diagram of the transmission spectrum of quasi-BIC metasurface of Example 1 in Test Example 4 under x-polarized light with the change of background refractive index;

[0032] Figure 13 is the diagram of the resonance wavelength of FR1 and FR2 of quasi-BIC metasurface of Example 1 in Test Example 5 under x-polarized light with the change of square lattice period;

[0033] Figure 14 is the curve diagram of the transmission spectrum of quasi-BIC metasurface of Example 1 in Test Example 6 under x-polarized light with the change of substrate thickness;

[0034] Figure 15 is the broken line diagram of the transmission linewidth of FR1 and FR2 of quasi-BIC metasurface of Example 1 in Test Example 7 under x-polarized light with the change of rectangular width. DETAILED DESCRIPTION Embodiment

[0035] A forming method of a full-dielectric quasi-BIC metasurface based on U-shaped nanorods, the forming method is:

[0036] The U-shaped nanorod at the upper left corner of the symmetric BIC metasurface is individually scaled by a constant ratio; the symmetric BIC metasurface is composed of a plurality of square lattices and incident light (the polarization angle is between 0° and 90°). For example Figure 1As shown, each square lattice consists of a nano-substrate 1 and U-shaped nanorod tetramers 2 deposited on the nano-substrate. Each U-shaped nanorod tetramer consists of four U-shaped nanorods of the same size: a first U-shaped nanorod 3, a second U-shaped nanorod 4, a third U-shaped nanorod 5, and a fourth U-shaped nanorod 6. The first U-shaped nanorods, the second U-shaped nanorods, the third U-shaped nanorods, and the fourth U-shaped nanorods are arranged symmetrically in pairs along the x-axis and y-axis directions.

[0037] The nanosubstrate is a nanocube with a thickness H of 1000 nm, made of silicon dioxide with a refractive index of 1.48; the U-shaped nanorod tetramers are made of silicon. The first, second, third, and fourth U-shaped nanorods of the symmetrical BIC metasurface are all composed of nano-semi-cylinders and rectangular blocks. The diameter 2r of the nano-semi-cylinders and the length of the rectangular blocks are both 200 nm, and the width of the rectangular blocks is 134 nm. The height h1 of the four U-shaped nanorods is 450 nm. The distance between the centers of two U-shaped nanorods symmetrically arranged along the x-axis is 560 nm, and the distance between the centers of two U-shaped nanorods symmetrically arranged along the y-axis is 500 nm.

[0038] like Figure 2 As shown, the incident light is a plane wave with its wave vector parallel to the z-axis and its polarization parallel to the x-axis, with a polarization angle of 0° to 90°. In the xy-plane, the first U-shaped nanorod located in the upper left corner of the U-shaped nanorod tetramer is scaled proportionally by a scaling factor N of 0.9, introducing an asymmetric perturbation. The size and position of the second, third, and fourth U-shaped nanorods remain unchanged, forming an asymmetric square lattice. This asymmetric square lattice is a fully dielectric quasi-BIC metasurface based on U-shaped nanorods, with an ambient refractive index of 1.319–1.3, and a period of 1000 nm for the 6quasi-BIC metasurface. Example

[0039] Based on the technical solution of Embodiment 1, only the scaling ratio N of the first U-shaped nanorod is changed, and the rest of the operation is the same as in Embodiment 1. The first U-shaped nanorod is scaled proportionally, and its scaling ratio N is 0.8, introducing an asymmetric perturbation. Example

[0040] Based on the technical solution of Embodiment 1, only the scaling ratio N of the first U-shaped nanorod is changed, and the rest of the operation is the same as in Embodiment 1. The first U-shaped nanorod is scaled proportionally, and its scaling ratio N is 0.7, introducing an asymmetric perturbation. Example

[0041] On the basis of the technical scheme of the embodiment, only the scaling ratio N of the first U-shaped nanorod is changed, and the remaining operations are the same as those of the embodiment. The first U-shaped nanorod is scaled in proportion, and the scaling ratio N is 1.1, and an asymmetric disturbance is introduced. Embodiment

[0042] On the basis of the technical scheme of the embodiment, only the scaling ratio N of the first U-shaped nanorod is changed, and the remaining operations are the same as those of the embodiment. The first U-shaped nanorod is scaled in proportion, and the scaling ratio N is 1.2, and an asymmetric disturbance is introduced.

[0043] Comparative Example 1

[0044] The quasi-BIC metasurface a of the present comparative example is different from that of the embodiment 1 in that the size of the first U-shaped nanorod in the present comparative example has not changed, that is, the scaling ratio N is 1, and no asymmetric disturbance is introduced, which is a symmetric BIC metasurface.

[0045] Test Example

[0046] 1. Transmission spectrum tests were performed on the quasi-BIC metasurfaces of embodiments 1 to 5 and comparative example 1, and the results are shown in Figure 3 When the scaling ratio N of the first U-shaped nanorod is 1, the transmission spectrum is almost horizontal in the wavelength range of 1350 nm to 1480 nm, that is, it shows a BIC with an infinite high Q factor. This is a typical symmetric protection type BIC, which is characterized by extremely high transmittance and invisibility in the transmission spectrum.

[0047] When the scaling ratio N of the first U-shaped nanorod is 0.9 (embodiment 1), two sharp resonance modes (denoted as FR1 and FR2) are observed at wavelengths of 1388.2 nm and 1419.8 nm. The reason for this phenomenon is that breaking the structural symmetry enhances the coupling between the ideal symmetric protection type BIC and the radiation mode, thereby making it a quasi-BIC.

[0048] When the scaling ratio N of the first U-shaped nanorod is reduced from 0.9 to 0.7 and increased from 1.1 to 1.2 (the scaling ratios of embodiments 2, 3, 4 and 5 are 0.8, 0.7, 1.1 and 1.2, respectively), the line width of the two resonance modes gradually increases, of which FR1 is particularly significant.

[0049] 2. The multipole decomposition of FR1 and FR2 of the quasi-BIC metasurface of embodiment 1 was tested, and the results are shown in Figures 4-9 Figure 4 and Figure 7 Figures Figure 5 , respectively, show the multipole decomposition diagrams of FR1 and FR2 of the quasi-BIC metasurface of embodiment 1 (scaling ratio N = 0.9),​Figure 6 , Figure 8 and Figure 9 show the electric and magnetic field distribution of FR1 and FR2, respectively.

[0050] Figure 4 It is shown that the TD (ring dipole) dominates in the multipole contributions of FR1, while the MQ (magnetic quadrupole) has a small contribution. Figure 7 It is shown that the MD (magnetic dipole) and MQ (magnetic quadrupole) have a small contribution to FR2, while the EQ has the largest contribution. It can be clearly seen from the displacement current and field distribution that Figure 5 It is shown that the electric field direction arrows are connected head to tail to form a loop. On the left nanorod cross-section, the electric field arrows rotate clockwise along the Z direction. On the contrary, on the right nanorod, the circulation direction of the electric field arrows is exactly the opposite. It is obvious that the TD response dominates in these modes; Figure 6 It is shown that since a pair of isotropic magnetic dipoles induces TD and MQ, the subsequent contribution is MQ. It can be seen that the near-field electric and magnetic field distributions of FR1 are consistent with the multipole decomposition results in Figure 4 . Figure 8 and Figure 9 It is shown that the electric field distribution of FR2 is between the outside of the tetramer and the gap, and the eddy current of the displacement current proves the existence of EQ in the xy plane; the magnetic field is mainly located inside the structure. The magnetic vector obviously shows the prominent feature of MD.

[0051] 3、Test the changes of FR1 and FR2 of the quasi-BIC metasurface of Example 1 under different incident light polarization angles. The polarization angle of the incident light is described by the angle between the electric field of the incident light and the x-axis, defined as θ, as shown in Figure 11 . Set the polarization angle θ of Example 1 to 0°, 15°, 30°, 45°, 60°, 75° and 90°, respectively, as shown in Figure 10 . Observe the changes of FR1 and FR2 of the quasi-BIC metasurface of Example 1 under different polarization angles, and the results are shown in Figure 11 . As the polarization angle θ increases, the modulation depth of FR1 and FR2 gradually decreases. When the polarization angle changes from 0° to 90°, not only the original FR1 and FR2 disappear, but also new resonance peaks appear at wavelengths of 1382 nm and 1412.2 nm, defined as FR3 and FR4. It shows that as the incident light changes from x-axis polarization to y-axis polarization, the switching state changes from (0, 1, 0, 1) to (1, 0, 1, 0).

[0052] 4、Test the influence of the background refractive index on the transmission spectrum, the resonance wavelength of FR1 and FR2 of the quasi-BIC metasurface of Example 1 under x polarization, and the results are shown in Figure 12As shown, increasing the background refractive index causes a redshift in both FR1 and FR2, with different redshift amounts. The resonant wavelength of FR1 changes from 1454.11 nm to 1469.99 nm, while that of FR2 changes from 1538.56 nm to 1567.56 nm, with the redshift of FR2 being more significant. Further calculations yielded sensitivities S of FR1 and FR2 of 386.8 nm / RIU and 707 nm / RIU, respectively, with corresponding quality factors FOMs of 2767.3 RIU. -1 and 2314.2RIU -1 .

[0053] 5. The effect of the square lattice period of the quasi-BIC metasurface in Example 1 on the transmission spectrum and the resonant wavelengths of FR1 and FR2 under x-polarization was tested. The results are as follows: Figure 13 As shown, with the increase of the square lattice period, FR1 and FR2 undergo a redshift, and the redshift amounts of FR1 and FR2 are different. The resonant wavelength of FR1 changes from 1365.23 nm to 1411.43 nm, while the resonant wavelength of FR2 changes from 1395.07 nm to 1444.56 nm. Further calculations show that the redshift of FR2 is slightly higher than that of FR1.

[0054] 6. The effect of substrate thickness on the transmission spectrum and the resonant wavelengths of FR1 and FR2 under x-polarization of the quasi-BIC metasurface in Example 1 was tested. The results are as follows: Figure 14 As shown, increasing substrate thickness causes a redshift in FR1 and FR2. Furthermore, the transmittance of FR1 does not exhibit a linear relationship with substrate thickness. Firstly, when the substrate thickness is less than 1000 nm, the transmittance increases with increasing substrate thickness. However, when the substrate thickness exceeds 1000 nm, the transmittance decreases with increasing substrate thickness.

[0055] 7. The effect of the rectangular width of the quasi-BIC metasurface in Example 1 on the transmission spectrum and the resonant wavelengths of FR1 and FR2 under x-polarization was tested. The results are as follows: Figure 15 As shown, increasing substrate thickness causes a redshift in FR1 and FR2. Furthermore, the figure shows that the linewidth of the transmission valley is proportional to the width of the rectangle.

[0056] The symmetric BIC metasurface is numerically simulated by COMSOL Multiphysics, and the symmetric BIC metasurface is converted into an asymmetric quasi-BIC metasurface by destroying the geometric symmetry of the symmetric BIC metasurface. The first U-shaped nanorod is scaled by a certain ratio, and an asymmetric disturbance is introduced. The bound state is coupled from the continuous spectrum to the radiation channel, and the radiation channel becomes the resonance mode of leakage and radiation. At this time, the symmetric BIC metasurface is converted into an asymmetric quasi-BIC metasurface, and the increase of the scaling ratio difference will widen the linewidth of the resonance peaks FR1 and FR2.

[0057] The application discloses a full-dielectric quasi-BIC metasurface based on a U-shaped nanorod and a forming method and application thereof. The first U-shaped nanorod is scaled by a certain ratio, and an asymmetric square lattice is introduced; and a plurality of asymmetric square lattices form a quasi-BIC metasurface. The asymmetric peak of the quasi-BIC metasurface presents Fano resonance characteristics, and the application of the formed metasurface in a bidirectional optical switch device and a liquid sensor is disclosed. The metasurface has a high Q value, the intensity and waveform of the transmission spectrum can be flexibly modulated by adjusting the related structure parameters of the metasurface, and the metasurface has a wide application.

Claims

1. A method for forming a U-shaped nanopillar-based all-dielectric quasi-BIC metasurface, characterized in that: The forming method is: The upper left corner U-shaped nanorod in the symmetric BIC metasurface is individually scaled in proportion; the symmetric BIC metasurface is composed of a plurality of square lattices, each square lattice is composed of a nanosubstrate and a U-shaped nanorod tetramer deposited on the nanosubstrate, the U-shaped nanorod tetramer is composed of four first U-shaped nanorods, second U-shaped nanorods, third U-shaped nanorods and fourth U-shaped nanorods of the same size; the first U-shaped nanorods, the second U-shaped nanorods, the third U-shaped nanorods and the fourth U-shaped nanorods are symmetrically arranged in the x-axis direction and the y-axis direction; When the incident light is x-polarized, the first U-shaped nanorod at the upper left corner in the U-shaped nanorod tetramer in the xy-plane is individually scaled in proportion to introduce an asymmetric disturbance; the size and position of the second U-shaped nanorod, the third U-shaped nanorod and the fourth U-shaped nanorod remain unchanged to form an asymmetric square lattice; The above asymmetric square lattice is a U-shaped nanocolumn-based all-dielectric quasi-BIC metasurface; The scaling ratio of the first U-shaped nanorod is 0.7, 0.8, 0.9, 1.1 or 1.2, respectively. 2.The method for forming a U-shaped nanopillar-based all-dielectric quasi-BIC metasurface according to claim 1, wherein: The incident light is a plane wave, the wave vector of which is parallel to the z-axis direction, and the polarization angle is 0°-90°.

3. The method of claim 1, wherein the U-shaped nanopillar-based all-dielectric quasi-BIC metasurface is formed by: When the quasi-BIC metasurface is excited by x-polarized incident light, the environmental refractive index is 1.319-1.36, and the period of the quasi-BIC metasurface is 1000nm. 4.The method of claim 1, wherein: The nanosubstrate is a nanocube with a thickness of 940-1060nm, and the material thereof is silicon dioxide with a refractive index of 1.48; the material of the U-shaped nanorod tetramer is silicon. 5.The method of claim 1, wherein: The first U-shaped nanorod, the second U-shaped nanorod, the third U-shaped nanorod and the fourth U-shaped nanorod of the symmetric BIC metasurface are all composed of a nanohalf-cylinder and a rectangular block, wherein the diameter of the nanohalf-cylinder and the length of the rectangular block are both 200nm, the width of the rectangular block is 134-140nm, and the height of the four U-shaped nanorods is 350-550nm, wherein the distance between the centers of the U-shaped nanorods in the x-axis direction is 560nm, and the distance between the centers of the U-shaped nanorods in the y-axis direction is 500nm. 6.The method of claim 5, wherein: The height of the four U-shaped nanorods is 450nm.

7. The method of forming a U-shaped nanopillar based all-dielectric quasi-BIC metasurface according to any one of claims 1-6, wherein: The prepared U-shaped nanocolumn-based all-dielectric quasi-BIC metasurface is applied to a bidirectional optical switch device.

8. The method of forming a U-shaped nanopillar based all-dielectric quasi-BIC metasurface according to any one of claims 1-6, wherein: The prepared U-shaped nanocolumn-based all-dielectric quasi-BIC metasurface is applied to a liquid sensor.

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