Intermediate infrared full-dielectric metasurface sensor

Abstract

The invention discloses a mid-infrared full-dielectric metasurface sensor, and relates to the field of infrared sensing. The sensor includes: a substrate; the dielectric metasurface resonance layer is arranged on the surface of the substrate and comprises a plurality of periodically arranged unit structures; and each unit structure is provided with a plurality of holes which are arranged periodically. Periodic disturbance can be carried out by changing the distance between the holes of the unit structure, so that a narrow-band harmonic peak is generated, and the problems that an existing metasurface based on symmetric breaking BIC is low in robustness and difficult to machine are solved.

Description

Technical Field

[0001] The present invention relates to the field of infrared sensing, and particularly to a mid-infrared all-dielectric metasurface sensor. Background Art

[0002] Mid-infrared spectroscopy technology can detect and identify the infrared spectral differences induced by various vibration modes of the microstructures of different types of materials, such as DNA, protein, and lipid molecules. Multispectral sensing can obtain information of multiple spectral bands simultaneously, and has higher detection and identification efficiency. Therefore, there is a strong demand for optical devices with multi-narrowband responses in applications such as biosensing and filters.

[0003] Metasurfaces use sub-wavelength micro-nano structures to control the wavefront of light. They have extremely strong manipulation capabilities for light waves, can achieve multi-narrowband and high-sensitivity optical responses, and have the advantages of being ultra-light, ultra-thin, and easy to integrate. It is expected to open up a new path for infrared optical sensing and ultra-miniature optoelectronic devices. Devices based on metasurfaces have the characteristic of label-free detection function. Therefore, devices of all-dielectric metasurfaces operating in the mid-infrared band range have broad application prospects in the fields of security inspection, biosensing, and environmental monitoring. In recent years, the research and development of metasurface sensor devices in the visible and near-infrared bands have been in good progress. However, due to the limitations of materials, processes, and other factors, the current research on dielectric metasurfaces in the mid-infrared band is still relatively less. Summary of the Invention

[0004] The object of the present invention is to provide a mid-infrared all-dielectric metasurface sensor, which can generate narrowband resonance peaks by periodically disturbing the distance between the holes of the unit structure, overcoming the problems of low robustness and difficult processing of the existing symmetry-breaking BIC metasurfaces.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One aspect of the present invention provides a mid-infrared all-dielectric metasurface sensor, comprising:

[0007] A substrate;

[0008] A dielectric metasurface resonance layer, disposed on the surface of the substrate, comprising a plurality of periodically arranged unit structures; a plurality of periodically arranged holes are provided on each of the unit structures.

[0009] According to an embodiment of the present invention, the holes on the unit structure are arranged in a first preset periodic arrangement manner; the plurality of unit structures are arranged in a second preset periodic arrangement manner, so that the dielectric metasurface resonance layer has a preset pattern.

[0010] According to an embodiment of the present invention, among multiple adjacent holes of the holes in the metasurface resonance layer, there is at least one target adjacent hole, and the distance between the hole and the target adjacent hole is different from the distance between the hole and other adjacent holes.

[0011] According to an embodiment of the present invention, the material of the substrate is a material with a mid-infrared wave absorption rate lower than a preset threshold.

[0012] According to an embodiment of the present invention, the material of the metasurface resonance layer is a material with a mid-infrared wave absorption rate lower than a preset threshold.

[0013] According to an embodiment of the present invention, materials with a mid-infrared wave absorption rate lower than a preset threshold include SiO2, Si, Si3N4, Ge, GaAs, ZnSe, ZnS, and GeS.

[0014] According to an embodiment of the present invention, the sizes and shapes of the holes are the same.

[0015] According to an embodiment of the present invention, the size of the hole is smaller than the working wavelength.

[0016] According to an embodiment of the present invention, the size range of the unit structure is from 6 microns to 10 microns.

[0017] According to an embodiment of the present invention, the thickness range of the metasurface resonance layer is from 0.5 microns to 1.5 microns.

[0018] According to a specific embodiment provided by the present invention, the present invention discloses the following technical effects:

[0019] 1. By performing periodic perturbation by changing the distance between the holes of the unit structure, a narrowband resonance peak is generated; the problems of low robustness and difficult processing of the existing symmetry-breaking BIC metasurface are solved.

[0020] 2. By periodic perturbation, the unit structures are coupled to each other to generate multi-mode resonance; the problem that the function of a single-resonance metasurface is limited in actual sensing applications is solved.

[0021] 3. The present invention uses dielectric materials. Compared with metal metasurfaces, the ohmic loss is low, and the problem of overheating of the device is not easily generated in practical applications; it can be integrated with Complementary Metal-Oxide-Semiconductor (CMOS) to achieve miniaturization and integration.

[0022] 4. By scaling the size of the unit structure proportionally, the resonance peak position can be flexibly adjusted, and the problem that it is difficult to adjust the resonance wavelength in the refractive index detection of traditional mode coupling, resulting in limited detection, is solved.

[0023] 5. Generation of sharp resonances based on bound states in the continuum. The electromagnetic fields overlap in the surface space of the confined structure, enabling a rapid and highly sensitive response to local refractive index changes caused by individual biomolecules. It has excellent sensing performance and can achieve label-free biosensing. Brief Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 Schematic diagram of the optical path of a mid-infrared all-dielectric metasurface sensor provided by the present invention;

[0026] Figure 2 Schematic diagram of the unit structure with different shapes provided by the present invention;

[0027] Figure 3 Schematic diagram of the sensor structure with circular holes in the unit structure provided by the present invention;

[0028] Figure 4 Schematic diagram of the direction for adjusting the position of the holes in the unit structure provided by the present invention;

[0029] Figure 5 Another schematic diagram of the sensor structure with circular holes in the unit structure provided by the present invention;

[0030] Figure 6 Schematic diagram of the reflection spectrum of the sensor with circular holes in the unit structure provided by the present invention;

[0031] Figure 7 Another schematic diagram of the reflection spectrum of the sensor with circular holes in the unit structure provided by the present invention;

[0032] Figure 8 Another schematic diagram of the refractive index sensing of the sensor with circular holes in the unit structure provided by the present invention. Detailed Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0034] All-dielectric metasurfaces with high quality factor (Q) have many excellent properties, such as greater slow-light dispersion. For refractive sensing of measuring spectral shifts, sharp spectra (i.e., high Q factor) are more conducive to high-resolution sensing and have good application prospects in optical sensors. In the early days, metals such as gold were often used to design metasurfaces. Due to the strong ohmic loss caused by the oscillation of free electrons in metal structures, the resonance linewidth increases, and then the figure of merit (FOM) and Q factor are reduced. Recently, researchers proposed the concept of bound states in the continuum (BIC) to achieve extremely sharp spectral resonance responses. Different from general bound states, although BIC is located in the radiative continuum, it is completely decoupled from the radiative continuum. Compared with plasmonics, dielectric nanoresonators have no inherent material absorption loss, and they can support BIC modes; in practice, BIC is converted into quasi-BIC (q-BIC) with extremely high but finite Q factor. Metasurfaces based on q-BIC generally need to slightly reduce, increase or change the angle of the structure to perturb the BICs. In actual processing, small size differences have a great impact on the device performance; while metasurfaces that break BICs through periodic perturbation have high robustness and are more conducive to actual processing; metasurfaces can be prepared with dielectric materials to reduce structural losses.

[0035] The purpose of the present invention is to provide a mid-infrared all-dielectric metasurface sensor, aiming to generate narrowband resonance peaks by periodically perturbing the distance between the holes of the unit structure, overcoming the problems of low robustness and difficult processing of the existing symmetry-breaking BIC metasurfaces.

[0036] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] As Figures 1 to 5 shown, the present invention provides a mid-infrared all-dielectric metasurface sensor, including: a substrate 2; a dielectric metasurface resonant layer 3 disposed on the surface of the substrate 2, including a plurality of periodically arranged unit structures 4; a plurality of periodically arranged holes are provided on each of the unit structures 4. After the incident light is regulated by the dielectric metasurface resonant layer 3, narrowband resonance peaks with different wavelength responses can be obtained.

[0038] As Figure 1 shown, the incident light irradiates the metasurface in the direction shown by the arrow in the figure. The beam propagation process incident on the mid-infrared all-dielectric metasurface sensor 1 is as follows: the beam reaches the dielectric metasurface resonant layer 3, and after the dielectric metasurface resonant layer 3 regulates the light, a reflection spectrum is obtained.

[0039] As a specific implementation manner, the holes on the unit structure 4 are arranged in a first preset periodic arrangement manner; a plurality of the unit structures 4 are arranged in a second preset periodic arrangement manner, so that the metasurface resonance layer 3 has a preset pattern.

[0040] As a specific implementation manner, among a plurality of adjacent holes of the holes of the metasurface resonance layer 3, at least one target adjacent hole and the distance between the hole and the hole are different from the distance between other adjacent holes and the hole.

[0041] As a specific implementation manner, the material of the substrate 2 is a material with a mid-infrared wave absorption rate lower than a preset threshold. The material of the metasurface resonance layer 3 is a material with a mid-infrared wave absorption rate lower than a preset threshold. Materials with a mid-infrared wave absorption rate lower than a preset threshold include Si, Si3N4, Ge, GaAs, ZnSe, ZnS, and GeS. That is to say, both the substrate 2 and the metasurface resonance layer 3 adopt high-transmittance materials in the mid-infrared band, such as silicon, germanium, etc., to minimize the loss of the device.

[0042] As a specific implementation manner, the sizes and shapes of the holes are the same. The size of the holes is smaller than the working wavelength. The size range of the unit structure is 6 micrometers to 10 micrometers. The thickness range of the metasurface resonance layer 3 is 0.5 micrometers to 1.5 micrometers.

[0043] In the same sensor, the size of the unit structure 4 of the metasurface resonance layer 3 is a fixed value; this size refers to the length, width, and height of the unit structure 4; by changing the interval between the holes of adjacent unit structures 4, an asymmetric perturbation is applied, and based on the Mie resonance, BIC, and Fano resonance induced by the metasurface resonance layer 3, etc., the intensity and position of the resonance peak can be regulated.

[0044] The unit period P of the dielectric metasurface resonant layer 3 is 6 to 10 micrometers; the thickness of the unit structure 4 is 0.5 to 1.5 micrometers; wherein, the metasurface resonant layer 3 is composed of a plurality of unit structures 4 arranged periodically along the length and width directions, and one period length refers to the length of the length or width of the unit structure 4. Here, it means that when the length and width are equal, the ranges of the length and width of the dielectric metasurface resonant layer 3 are both 6 to 10 micrometers. To further reduce the loss of the material, the unit structure 4 is a flat plate with a hole shape. When the shape of the hole is a cylindrical hole, the radius of the hole is 0.2 to 1 micrometer. The shape of the unit structure 4 can be a cuboid or a cube, and the center distance between adjacent unit structures 4 is 3 to 5 micrometers. Among them, the metasurface resonant layer includes an upper surface and a lower surface opposite to the upper surface, and the lower surface is the contact surface between the dielectric metasurface resonant layer 3 and the substrate 2. The center of the cross-sectional shape of the upper surface of the unit structure 4 of the metasurface resonant layer is used as the first center point, and the center of the cross-sectional shape of the upper surface of the adjacent unit structure 4 is used as the second center point, and the distance between the first center point and the second center point is the center distance.

[0045] Both the substrate 2 and the dielectric metasurface resonant layer 3 use high-transmittance materials in the mid-infrared band. For example, materials with a transmittance higher than 90%. The metasurfaces realized based on the bound states in the continuum (BIC) principle have complex shapes and small structural gaps, which lead to processing difficulties; metal metasurfaces choose high-cost materials such as gold, and are affected by temperature, humidity fluctuations and instrument inherent drifts, and the obtained spectra will show artificial offsets. Existing metasurface sensing has problems of low accuracy and reliability. The present invention realizes multi-wavelength narrowband resonance, the structure is robust to perturbations, the designed shape and size are conducive to processing, and low-cost dielectric materials are used, solving the problem of high manufacturing cost. Compared with metal metasurfaces based on the plasmonic effect, the energy loss is small and the sensing performance is higher.

[0046] The unit structure 4 is obtained by etching a periodic hole structure on a mid-infrared high-transmittance thin film. The shape of the hole can be Figure 2 shown cylindrical holes, elliptical holes, rectangular holes, polygonal holes, triangular holes, pentagram holes, fan-shaped holes, crescent-shaped holes, cross-shaped holes, circular ring holes, rhombic holes, semi-circular holes, etc. The above holes are all holes penetrating the dielectric metasurface resonant layer 3, and the holes can also be non-penetrating holes of the dielectric metasurface resonant layer 3, or Figure 2 other shaped holes shown in

[0047] Such as Figure 3As shown in the figure, taking the holes in the dielectric metasurface resonant layer 3 as circular holes as an example, the circular holes in the dielectric metasurface resonant layer 3 are evenly distributed, and the center distances between each hole and its adjacent hole are all equal. The circular holes all penetrate the dielectric metasurface resonant layer 3. When the holes in the dielectric metasurface resonant layer 3 are holes of other shapes, the center distance between each hole and its adjacent hole refers to the distance between the geometric centers of each hole.

[0048] In the dielectric metasurface resonant layer 3, a perturbation can be applied to the metasurface by changing the distance between the holes of two adjacent unit structures 4; as Figure 4 shown, taking the holes in the dielectric metasurface resonant layer 3 as circular holes as an example, four circular holes move towards the center position, thereby applying a perturbation to the structure; the center position can be understood as the geometric center of the unit structure 4; by changing the distance between the holes of two adjacent unit structures 4 based on principles such as Mie resonance, BIC, and Fano resonance, the regulation of the resonant peak intensity and wavelength is realized, thereby achieving multi-wavelength narrowband resonance.

[0049] As Figure 5 shown, another sensor provided by the present invention has the same layer distribution as the Figure 3 sensor structure shown, however, the center distance between adjacent circular holes of the unit structure 4 is different from that of the Figure 3 sensor shown, that is, the degree of perturbation applied to the Figure 5 unit structure 4 shown is different from that of the Figure 3 sensor shown.

[0050] As Figure 6 shown, the finite-difference time-domain method is used to perform numerical simulation operations on the Figure 3 mid-infrared all-dielectric metasurface with a circular-hole unit structure 4 shown, and the reflection spectrum corresponding to the center distance between adjacent circular holes is obtained. Figure 6 In it, the abscissa represents the wavelength of light, and the ordinate represents the relative intensity of the reflected light after the incident light is reflected by the metasurface. The results show that this structure has multiple narrowband resonant peaks, and the resonant peaks are located at 6.82 μm, 7.33 μm, and 7.46 μm respectively.

[0051] As Figure 7 shown, the finite-difference time-domain method is used to perform numerical simulation operations on the Figure 5 sensor shown, and the reflection spectrum corresponding to the center distance between adjacent circular holes is obtained. Figure 7 In it, the abscissa represents the wavelength of light, and the ordinate represents the relative intensity of the reflected light after the incident light is reflected by the metasurface. Compared with the Figure 6 reflection spectrum, Figure 7The number and reflectivity of the resonant peaks in the reflection spectrum have changed. The resonant peaks are located at 6.48μm, 6.82μm, 7.33μm, and 7.46μm respectively. The quality factor can reach up to 2199, and the present invention has effectiveness and superiority.

[0052] It should be noted that: the quality factor of the present invention is obtained according to the calculation formula Q = lambda / FWHM, where Q is the quality factor, lambda represents the reflection center wavelength, and FWHM represents the full width at half maximum.

[0053] The change in the distance between the centers of adjacent circular holes affects the resonant intensity and mode types of the structure. Through periodic perturbation, the present invention overcomes the problem of low robustness of the symmetry-breaking BIC metasurface. This structure has four-fold symmetry and is insensitive to the polarization angle of the incident light; the sensing mechanism of the present invention lies in the interaction between the substance to be measured and the electromagnetic field on the surface of the structure. The resonant wavelength of the structure is sensitive to the refractive index of the substance to be measured. An increase in the refractive index will cause the resonant wavelength to redshift. Therefore, the influence of the substance to be measured on the structure resonance is obtained through the position of the peak in the reflection spectrum.

[0054] As Figure 8 shown, the finite-difference time-domain method is used to perform numerical simulation operations on the Figure 5 sensor shown, and the refractive index sensing diagram of the structure of the Figure 5 sensor shown is demonstrated; as the environmental refractive index increases, all four resonant peak positions redshift, and the maximum sensitivity can reach 460nm / RIU. The present invention has good refractive index sensing ability. Figure 8 In it, the abscissa represents the wavelength of light, and the ordinate represents the relative intensity of the reflected light after the incident light is reflected by the metasurface.

[0055] The refractive index sensing performance can be defined by the following two parameters: sensitivity (S), figure of merit (FOM). Where S = Δn / Δλ, n represents the environmental refractive index; λ represents the resonant wavelength, FOM = S / FWHM, and FWHM represents the full width at half maximum of the resonant peak.

[0056] The mid-infrared all-dielectric metasurface is supported by a substrate 2 (a substrate 2 of a near-transparent material in the mid-infrared band). The dielectric metasurface resonant layer 3 has strong resonance; both the substrate 2 and the dielectric metasurface resonant layer 3 use materials with low absorption in the mid-infrared, and materials such as SiO2, Si, Si3N4, Ge, GaAs, ZnSe, ZnS, GeS, etc. can be used; the substrate 2 uses SiO2 material, and the dielectric metasurface resonant layer 3 uses Si material and is patterned by micro-nano processing, and its thickness is 0.5 microns to 5 microns; taking each unit structure 4 of the dielectric metasurface resonant layer 3 as a circular hole with the same radius size as an example, the radius of the circular hole is 0.2 microns to 1 micron; as Figure 3 and Figure 5The mid-infrared all-dielectric metasurface sensor shown has a unit structure 4 of the metasurface resonant layer 3 that is a cylindrical hole structure with the same height, the same diameter, and different positions. Each dimension of each unit structure 4 is less than the working wavelength λ and is approximately 6 to 10 micrometers. The working wavelength can be the wavelength of the incident light.

[0057] Based on Mie resonance, by changing the dimensions and shapes of various structures as Figure 2 shown, the regulation of resonance can be achieved. Multiple structures can be selected to achieve narrowband resonance, so as to achieve the same resonance effect at the incident wavelength in the mid-infrared band.

[0058] To solve the deficiencies of existing resonant metasurfaces in the mid-infrared band, the present invention proposes a mid-infrared all-dielectric metasurface. Based on the design concept of resonant metasurfaces, a series of dielectric artificial atoms with high refractive index and low loss are combined to realize the dielectric metasurface. The dielectric metasurface resonant layer highly concentrates the electromagnetic wave energy in the array structure, and a material with high transmittance in the mid-infrared band is selected as the substrate of the dielectric metasurface to reduce the energy loss in the substrate structure. The all-dielectric metasurface mid-infrared sensor of the present invention realizes mid-infrared multi-wavelength narrowband resonance and has the advantages of being ultra-light, ultra-thin, and easy to integrate. The present invention opens up a new path for biosensing and ultra-miniature optoelectronic devices. The present invention achieves high robustness, low radiation loss, low cost, batch processing, and simplicity.

[0059] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0060] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A mid-infrared all-dielectric metasurface sensor, characterized in that: include: substrate; A dielectric metasurface resonance layer is disposed on the surface of the substrate and includes a plurality of periodically arranged unit structures; Each of the unit structures is provided with a plurality of periodically arranged holes.

2. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: The holes on the unit structure are arranged according to a first preset periodic arrangement; and a plurality of the unit structures are arranged according to a second preset periodic arrangement so that the dielectric metasurface resonance layer has a preset pattern.

3. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: Among the multiple adjacent holes of the holes in the dielectric metasurface resonance layer, there is at least one target adjacent hole whose distance to the hole is different from the distances between the other adjacent holes and the hole.

4. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: The material of the substrate is a material whose mid-infrared wave absorption rate is lower than a preset threshold.

5. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: The material of the dielectric metasurface resonance layer is a material whose mid-infrared wave absorption rate is lower than a preset threshold.

6. The mid-infrared all-dielectric metasurface sensor according to claim 4 or 5, characterized in that: Materials with mid-infrared wave absorption rates below a preset threshold include SiO2, Si, Si3N4, Ge, GaAs, ZnSe, ZnS, and GeS.

7. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: The holes are of the same size and shape.

8. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: The size of the hole is smaller than the operating wavelength.

9. The mid-infrared all-dielectric metasurface sensor according to claim 8, characterized in that: The size of the unit structure ranges from 6 microns to 10 microns.

10. The mid-infrared all-dielectric metasurface sensor according to claim 1, characterized in that: The thickness of the dielectric metasurface resonant layer ranges from 0.5 microns to 1.5 microns.

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