A continuous domain bound state sensor based on composite prismatic all-dielectric metasurface

Abstract

The present invention discloses a continuous domain bound state sensor based on a composite prism all-dielectric metasurface, which is composed of a periodically arranged unit structure, wherein the unit structure includes a barium fluoride substrate layer and a group of silicon structure layers stacked on the barium fluoride substrate layer; the silicon structure layer includes two first composite prisms arranged along a main diagonal and two second composite prisms arranged along a secondary diagonal, wherein the main diagonal and the secondary diagonal are in a crossed state; the tips of the two first composite prisms and the tips of the two second composite prisms are arranged in opposite directions, and the first composite prisms and the second composite prisms are asymmetric structures; when polarized light is incident vertically, a resonant response of a ring dipole is excited to form two Fano resonance peaks; the sensor has ultrahigh sensitivity and quality factor in the mid-infrared band, and can be applied to gas sensing and detection of various blood components.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous domain bound state sensors, and in particular to a continuous domain bound state sensor based on a composite prism all-dielectric metasurface. Background Art

[0002] Metasurfaces, as a two-dimensional manifestation of metamaterials, are a type of artificial periodic structure that operates at the subwavelength scale. Compared to traditional artificial materials, metasurfaces have unique advantages in electromagnetic wave manipulation. By constructing specific surface structures, the amplitude, phase, and polarization state of the incident electromagnetic wave can be precisely controlled to meet the application requirements of different scenarios. In recent years, based on these advantages, metasurfaces have been widely used in fields such as superlenses, absorbers, sensors, filters, and slow-light devices. These applications mostly rely on the resonant interaction between metasurfaces and electromagnetic waves, among which achieving high-Q resonance with extremely narrow linewidth is crucial to improving device performance.

[0003] Thanks to advances in surface plasmon theory, sensing technologies based on metallic materials, such as surface plasmon resonance and localized surface plasmon resonance, have been widely studied. However, metasurfaces constructed from metallic materials such as gold, silver, and copper exhibit inherent ohmic losses, resulting in low efficiency and limited Q, which compromises sensing performance. In contrast, all-dielectric metasurfaces effectively circumvent ohmic losses by replacing conduction current with displacement current, enabling resonances with higher Q values ​​(Wang K, Coatings. 2022, 12, 7, 970). As a key parameter characterizing resonant energy storage capacity, Q has become a key research focus in micro-nanooptics. The introduction of continuum bound states offers new insights into the design of high-Q optical devices. By combining all-dielectric metasurfaces with continuum bound states and introducing specific perturbation elements, continuum bound state modes with theoretically infinite Q values ​​can be converted into quasi-continuum bound state modes that maintain ultrahigh Q values. Furthermore, all-dielectric metasurfaces can excite Mie resonances and support electric dipole, magnetic dipole, and high-order multipole resonances, providing a versatile platform for light-matter interactions.

[0004] Refractive index sensing technology is an important tool in fields such as biochemical testing, food safety, industrial manufacturing, and clinical diagnosis. However, traditional sensors face challenges such as limited detection range, low sensitivity, slow response speed, and complex manufacturing processes. All-dielectric metasurfaces provide a high-performance, low-cost, and versatile solution for refractive index measurement (Liye Li, Photonics Research. 2023, 11, 12, 2210). Their response characteristics are closely related to the refractive index of the surrounding medium and the analyte, and they can convert refractive index changes into resonance shifts, which manifest as frequency shifts of resonant peaks in transmission, reflection, or absorption spectra. In addition, mid-infrared spectroscopy plays a key role in non-destructive and label-free sensing, expanding the application of near-infrared metasurface refractive index detection.

[0005] The mid-infrared band can identify a variety of biomacromolecules by using molecular absorption fingerprints generated by the intrinsic vibrational modes of chemical bonds. Therefore, achieving high-Q-factor resonance in the mid-infrared band has become a promising research direction, with wide applications in biomedical diagnostics, environmental monitoring, food safety testing, and other fields (Wenwen Sun, Optics & Laser Technology. 2024, 174, 110631). However, the performance of current continuum bound-state sensors operating in the mid-infrared band is low, and further research is needed to develop continuum bound-state sensors with ultrahigh sensitivity and quality factors. Summary of the Invention

[0006] (1) Technical issues

[0007] The purpose of the present invention is to provide a continuous domain bound state sensor based on a composite prismatic all-dielectric metasurface, which has ultra-high sensitivity and quality factor in the mid-infrared band and can be applied to gas sensing and detection of various blood components.

[0008] (2) Technical solution

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A continuous domain bound state sensor based on a composite prism all-dielectric metasurface is composed of a periodically arranged unit structure, wherein the unit structure includes a barium fluoride substrate layer and a group of silicon structure layers stacked on the barium fluoride substrate layer; the silicon structure layer includes two first composite prisms arranged along a main diagonal and two second composite prisms arranged along a secondary diagonal, wherein the main diagonal and the secondary diagonal are in a crossed state; the tips of the two first composite prisms and the tips of the two second composite prisms are arranged in opposite directions, and the first composite prisms and the second composite prisms have an asymmetric structure; when polarized light is incident vertically, a resonant response of a ring dipole is excited, forming two Fano resonance peaks.

[0011] Preferably, the first composite prism includes a first rectangular prism and a first triangular prism formed as one piece, and the second composite prism includes a second rectangular prism and a second triangular prism formed as one piece, the first rectangular prism and the second rectangular prism have the same size, and the cross-sections of the first triangular prism and the second triangular prism are both isosceles triangles.

[0012] Preferably, the long side lengths of the first rectangular column and the second rectangular column are a , the short side length is b , a =1900 nm, b= 480 nm.

[0013] Preferably, the distance from the top angle to the bottom edge of the first triangular prism is h 2, h 2=1420 nm; the distance from the vertex to the bottom edge of the second triangular prism is h 1, h 1=1680 nm.

[0014] Preferably, the asymmetry parameter of the silicon structure layer is h , h = h 1- h 2.

[0015] Preferably, the distance between adjacent first triangular prisms and second triangular prisms is g , g =1200 nm.

[0016] Preferably, the thickness of the barium fluoride substrate layer is ts , ts =380 nm; the thickness of the silicon structure layer is tm , tm =120 nm.

[0017] Preferably, the dielectric constant of the silicon structure layer is 11.71.

[0018] Preferably, the unit structure is along x The cycle length of the direction is P x ,along y The cycle length of the direction is P y , P x = P y =6200 nm.

[0019] (3) Beneficial effects

[0020] Multiple groups of silicon structure layers are periodically stacked on a barium fluoride substrate layer. The first composite prisms arranged on the main diagonal of the silicon structure layer and the second composite prisms arranged on the secondary diagonal present an asymmetric structure. By breaking the structural symmetry, a radiation channel is established between the free space continuous domain and the non-radiative bound state, and the original non-radiative mode is converted into a weak radiation mode, thereby exciting a quasi-continuous domain bound state mode with a high Q value. Two Fano resonance peaks appear in the transmission spectrum, which makes the continuous domain bound state sensor have ultra-high sensitivity and quality factor, and can be used for gas sensing and detection of various blood components.

[0021] The optimized continuous domain bound-state metasurface can be applied to mid-infrared sensing. Mid-infrared spectroscopy plays a key role in nondestructive and label-free sensing, expanding the application of near-infrared metasurface refractive index detection. The mid-infrared band can generate molecular absorption fingerprints through the inherent vibrational modes of chemical bonds, enabling the identification of a variety of biomacromolecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the top view size parameter structure of an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the side-view dimensional parameter structure in an embodiment of the present invention;

[0025] Figure 4 The embodiment of the present invention is asymmetric parameter h Transmission spectrum in the range of 0~650 nm;

[0026] Figure 5 The embodiment of the present invention is asymmetric parameter h Transmission curve of Fano fitting (mode 1) at 260 nm;

[0027] Figure 6 The Q factor and asymmetry parameter of the Fano resonance peak (mode 1) of the embodiment of the present invention are h relationship diagram;

[0028] Figure 7 This is a transmission spectrum diagram of an embodiment of the present invention when the gas refractive index is in the range of 1.01 to 1.09;

[0029] Figure 8 is a graph showing the relationship between the resonant wavelength and the gas refractive index according to an embodiment of the present invention;

[0030] Figure 9 is a graph showing the relationship between the quality factor and the gas refractive index according to an embodiment of the present invention;

[0031] Figure 10 This is a transmission spectrum diagram of different blood components detected by an embodiment of the present invention;

[0032] Figure 11 is a graph showing the relationship between the resonance wavelength and the refractive index of different blood components according to an embodiment of the present invention;

[0033] Figure 12 is a graph showing the relationship between the quality factor and the refractive index of different blood components according to an embodiment of the present invention;

[0034] exist Figures 1 to 12In the figure, the corresponding relationship between the component names or lines and the figure numbers is as follows:

[0035] Silicon structure layer 1, barium fluoride substrate layer 2, first composite prism 3, first rectangular prism 31, first triangular prism 32, second composite prism 4, second rectangular prism 41, second triangular prism 42, main diagonal line 5, and sub-diagonal line 6. DETAILED DESCRIPTION

[0036] 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 described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0037] See also Figure 1-Figure 3 As shown, an embodiment of the present invention proposes a continuous domain bound state sensor based on a composite prism all-dielectric metasurface, which is composed of a periodically arranged unit structure, wherein the unit structure includes a barium fluoride substrate layer 2 and a group of silicon structure layers 1 stacked on the barium fluoride substrate layer 2; the silicon structure layer 1 includes two first composite prisms 3 arranged along a main diagonal 5 and two second composite prisms 4 arranged along a secondary diagonal 6, wherein the main diagonal 5 and the secondary diagonal 6 are in a cross state, wherein the tips of the two first composite prisms 3 and the tips of the two second composite prisms 4 are arranged in opposite directions, and the first composite prisms 3 and the second composite prisms 4 are asymmetric structures; by breaking the structural symmetry, a radiation channel is established between the free space continuous domain and the non-radiative bound state, converting the original non-radiative mode into a weak radiation mode, thereby exciting a quasi-continuous domain bound state mode with a high Q value, and two Fano resonance peaks appear in the transmission spectrum, so that the continuous domain bound state sensor has ultra-high sensitivity and quality factor, and can be applied to gas sensing and detection of various blood components;

[0038] The optimized continuous domain bound-state metasurface can be applied to mid-infrared sensing. Mid-infrared spectroscopy plays a key role in nondestructive and label-free sensing, expanding the application of near-infrared metasurface refractive index detection. The mid-infrared band can generate molecular absorption fingerprints through the inherent vibrational modes of chemical bonds, enabling the identification of a variety of biomacromolecules.

[0039] Among them, the structural forms of the first composite prism 3 and the second composite prism 4 are similar, but there are certain differences. Specifically, the first composite prism 3 includes an integrally formed first rectangular prism 31 and a first triangular prism 32, and the second composite prism 4 includes an integrally formed second rectangular prism 41 and a second triangular prism 42. The first rectangular prism 31 and the second rectangular prism 41 have the same size, and the cross-sections of the first triangular prism 32 and the second triangular prism 42 are both isosceles triangles, but the cross-sectional dimensions of the first triangular prism 32 and the second triangular prism 42 are different.

[0040] Based on the above structure, in order to ensure the detection results, the structural parameters are optimized. Among them, the long side lengths of the first rectangular column 31 and the second rectangular column 41 are a , the short side length is b , a =1900 nm, b= 480 nm. The distance from the top corner to the bottom edge of the first triangular prism 32 is h 2, h 2=1420 nm; the distance from the top corner to the bottom edge of the second triangular prism 42 is h 1, h 1=1680 nm.

[0041] Among them, the asymmetry parameter of the silicon structure layer is h , h = h 1- h 2. By changing the asymmetry parameter h The structural symmetry can be broken, so that a radiation channel can be established between the free space continuous domain and the non-radiative bound state, converting the original non-radiative mode into a weak radiation mode, thereby exciting the quasi-continuous domain bound state mode with a high Q value, resulting in the appearance of two Fano resonance peaks in the transmission spectrum.

[0042] Furthermore, the spacing between the adjacent first triangular prisms 32 and the second triangular prisms 42 is g , g =1200 nm. At the same time, the thickness of the barium fluoride substrate layer 2 is ts , ts =380 nm; the thickness of the silicon structure layer 1 is tm , tm =120 nm. The dielectric constant of the silicon structure layer 1 is 11.71.

[0043] In order to control the size of the entire sensor, the unit structure is arranged along x The cycle length of the direction is P x ,along y The cycle length of the direction is P y , P x = P y =6200 nm.

[0044] Therefore, the structural dimensions of the continuous domain bound state sensor are further optimized through the above parameters, thereby ensuring the accuracy of the detection results.

[0045] When polarized light is incident perpendicularly, the designed continuum bound-state sensor can excite a resonant response of the ring dipole in the mid-infrared band, forming two Fano resonance peaks, labeled Mode 1 and Mode 2. By changing the asymmetry parameters and breaking the symmetry of the first and second composite prisms 3 and 4, a new mode can be excited, transforming the continuum bound-state resonance into a quasi-continuum bound-state resonance with a high Q value.

[0046] In order to further verify the performance of the continuous domain bound state sensor in this embodiment, verification was performed before and after the asymmetry parameter was changed. At the same time, the gas sensing and blood component detection results of the asymmetric structure in the mid-infrared band were verified.

[0047] When the asymmetric parameter h When the diameter is 0 nm, the silicon structure layer 1 is completely symmetrical. Only Fano resonance peak mode 2 exists in the transmission spectrum, which means that the Q factor is infinite and appears as a continuum domain bound state mode. With the introduction of the asymmetric parameter, a new Fano resonance peak mode 1 is generated in the continuum domain bound state. By breaking the symmetry of the structure, a radiation channel is established between the free space continuum domain and the non-radiative bound state. Figure 4 , when the asymmetric parameter h When the asymmetry parameter is 0 nm, mode 1 does not exist, indicating that the radiation channel is closed and there is no energy leakage; h As the value increases, the line widths of the two resonance peaks gradually increase.

[0048] When the asymmetric parameter h When the wavelength is 260 nm, the transmission spectrum of the continuous domain bound state sensor shows Fano resonance peak mode 1 at 6629.3 nm and Fano resonance peak mode 2 at 6629.3 nm. Figure 5 , the transmission spectrum is fitted using the Fano formula: ;

[0049] in a 1. a 2. b are all constants, j is the imaginary unit, Indicates frequency, represents the resonant frequency, γ It can be seen that the Fano fitting results are consistent with the transmission spectrum obtained by simulation results. The Q values ​​of Fano resonances under different asymmetry parameters can be obtained. Figure 6 , when the asymmetric parameter h At 260 nm, the Q factor is 1.3×10 5 ; When the asymmetric parameter hAt 65 nm, the Q factor can reach 10 6 With the asymmetric parameter h As the value increases, the Q factor decreases, resulting in more energy being radiated from the quasi-continuum bound state mode. The Q value follows an inverse quadratic relationship with the asymmetry parameter.

[0050] The resonance phenomenon in metasurfaces has been widely used in the field of refractive index sensing. and quality factor To evaluate the sensing performance, is the change in the resonance peak wavelength, It represents the change in refractive index, and FWHM is the full width at half maximum of the resonance peak.

[0051] The two resonant wavelengths of the metasurface depend on the surrounding background medium, which has great potential for gas sensing applications. Increasing the gas refractive index from 1.01 to 1.09 causes the resonant wavelength to redshift. The results are shown in Figure 7 The linear fit of mode 1 and mode 2 can be found in Figure 8 The slope represents the sensitivity of the sensor, reaching 5348 nm / RIU and 5338 nm / RIU respectively. The quality factor of mode 1 and mode 2 varies with the gas refractive index. Figure 9 , with the increase of refractive index, the quality factor of mode 1 and mode 2 gradually increases and reaches the maximum value when the refractive index is 1.5 and Since the bandwidth of mode 1 is extremely narrow, its quality factor generally reaches 10 5 .

[0052] To further analyze the performance of the continuous domain bound state sensor, we coated its surface with analytes of different blood components with refractive indices ranging from 1.33 to 1.40: water ( n water =1.33), plasma ( n plasma =1.35)、white blood cells( n WBC =1.36), hemoglobin ( n Hb =1.38) and red blood cells ( n RBC =1.40). See Figure 10 Increasing the refractive index of the analyte from 1.33 to 1.40 causes the resonance wavelength to red-shift. The linear fit of mode 1 and mode 2 can be found in Figure 11 , and their sensitivities reached 3419 nm / RIU and 3403 nm / RIU respectively. The quality factors of mode 1 and mode 2 vary with the refractive index. Figure 12, with the increase of refractive index, the quality factor of mode 1 and mode 2 gradually increases and reaches the maximum value when the refractive index is 1.4 and , the quality factor of mode 1 generally reaches 10 5 .

[0053] Therefore, we can conclude that the continuous domain bound state sensor produces double Fano resonance in the mid-infrared band, breaking the structural symmetry and showing a high sensitivity of up to 1.3×10 5 When the refractive index changes from 1.01 to 1.09, gas sensing can be achieved, with the maximum sensitivity and quality factor being 5348 nm / RIU and When the refractive index changes from 1.33 to 1.40, specific detection of blood components can be achieved, with the maximum sensitivity and quality factor being 3419nm / RIU and .

[0054] Through the above verification, the continuous domain bound state sensor proposed in this embodiment can be applied to gas sensing and detection of various blood components and has good detection result accuracy.

[0055] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0056] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is typically placed when in use. These terms are intended solely to facilitate and simplify the description of the present invention and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," etc., etc., are used solely for distinction and should not be construed as indicating or implying relative importance.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A continuous domain bound-state sensor based on a composite prismatic all-dielectric metasurface, characterized by: The invention is composed of a periodically arranged unit structure, wherein the unit structure comprises a barium fluoride substrate layer (2) and a group of silicon structure layers (1) stacked on the barium fluoride substrate layer (2); the silicon structure layer (1) comprises two first composite prisms (3) arranged along a main diagonal line (5) and two second composite prisms (4) arranged along a secondary diagonal line (6), wherein the main diagonal line (5) and the secondary diagonal line (6) are in a cross state; The tips of the two first composite prisms (3) and the tips of the two second composite prisms (4) are arranged in opposite directions, and the first composite prism (3) and the second composite prism (4) are asymmetrical structures; When polarized light is incident vertically, the continuous domain bound state sensor excites the resonance response of the ring dipole in the mid-infrared band, forming two Fano resonance peaks; The first composite prism (3) comprises an integrally formed first rectangular prism (31) and a first triangular prism (32); the second composite prism (4) comprises an integrally formed second rectangular prism (41) and a second triangular prism (42); the first rectangular prism (31) and the second rectangular prism (41) have the same size; the first triangular prism (32) and the second triangular prism (42) both have isosceles triangle cross-sections; and the first triangular prism (32) and the second triangular prism (42) have different cross-sectional sizes; The distance from the top angle to the bottom edge of the first triangular prism (32) is h 2. The distance from the top angle to the bottom edge of the second triangular prism (42) is h 1. The asymmetric parameter of the silicon structure layer (1) is h , h = h 1- h 2. By changing the asymmetry parameter h Breaking the symmetry of the first and second composite prisms establishes a radiation channel between the free-space continuous domain and the non-radiative bound state, converting the original non-radiative mode into a weak radiation mode, thereby exciting the quasi-continuous domain bound state mode with a high Q value, resulting in the appearance of two Fano resonance peaks in the transmission spectrum.

2. The continuous domain bound state sensor based on a composite prism all-dielectric metasurface according to claim 1, characterized in that: The long side lengths of the first rectangular column (31) and the second rectangular column (41) are a , the short side length is b , a =1900nm, b= 480 nm.

3. The continuous domain bound state sensor based on a composite prism all-dielectric metasurface according to claim 2, characterized in that: h 2=1420 nm; h 1=1680 nm.

4. The continuous domain bound state sensor based on a composite prism all-dielectric metasurface according to claim 3, characterized in that: The spacing between adjacent first triangular prisms (32) and second triangular prisms (42) is g , g=1200 nm.

5. The continuous domain bound state sensor based on a composite prism all-dielectric metasurface according to claim 4, characterized in that: The thickness of the barium fluoride substrate layer (2) is ts, ts=380 nm; the thickness of the silicon structure layer (1) is tm, tm=120 nm.

6. The continuous domain bound state sensor based on a composite prism all-dielectric metasurface according to claim 5, characterized in that: The dielectric constant of the silicon structure layer (1) is 11.

71.

7. A continuous domain bound state sensor based on a composite prism all-dielectric metasurface according to any one of claims 1 to 6, characterized in that: The period length of the unit structure along the x direction is Px, and the period length along the y direction is Py, where Px=Py=6200 nm.

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