CN116087138B - Terahertz metamaterial sensor with interdigital structure - Google Patents
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- 239000000463 material Substances 0.000 claims description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 7
- 239000005350 fused silica glass Substances 0.000 claims description 7
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 239000010931 gold Substances 0.000 claims description 6
- -1 polymethylpentane Substances 0.000 claims description 5
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
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- G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
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Abstract
The invention discloses a terahertz metamaterial sensor with an interdigital structure, and belongs to the technical field of terahertz sensors. The sensor comprises: a dielectric substrate and a metal double-split resonant ring periodically arranged on the dielectric substrate; one of the openings of the metal double-opening resonant ring comprises one or more metal interdigital structures; when the metal double-opening resonant ring is a square ring, the double openings are respectively positioned on two arms parallel to the electric field direction of the electromagnetic wave; when the metal double-opening resonant ring is a circular ring, the double openings are respectively positioned on the upper semicircle and the lower semicircle of the circular ring, and the shortest arc angle between the double openings is more than 90 degrees, and the tangential direction of the opening comprising one or more metal cross finger-shaped structures is parallel to the electric field direction of electromagnetic waves. By introducing a metal interdigital structure at one opening of the double-opening resonant ring structure, the sensor provided by the invention has high resonant intensity, sensitivity S and sensitivity value FOM, and is particularly suitable for trace substance detection.
Description
Technical Field
The invention belongs to the technical field of terahertz sensors, and particularly relates to a terahertz metamaterial sensor with an interdigital structure.
Background
Terahertz radiation is an electromagnetic wave with the frequency of 0.1THz-10THz, has the advantages of low photon energy and no ionization damage compared with X-rays, and has high penetrability for non-metal and nonpolar materials. In the biomedical field, the rotation and vibration energy levels of a plurality of biomacromolecules are located in a terahertz frequency band, so-called fingerprint spectrum characteristics exist, and the application of the terahertz technology in the biomedical field has the characteristics of safety, no need of marking, no damage and the like.
The terahertz metamaterial is an artificially prepared material with sub-wavelength size and periodic arrangement, and has special and adjustable electromagnetic characteristics which are not possessed by natural materials in the terahertz frequency band. Terahertz metamaterials have strong electric field enhancement factors (compared with an incident electric field) and electric field space limitation capability, have strong interaction with analytes (analysis), and have wide application in the aspects of real-time, label-free and high-sensitivity sensors. The most typical metallic terahertz metamaterials are single split ring resonators (split ring resonator, SRR) and asymmetric double split resonators (asymmetric double split ring resonator, asrr), where the latter have a higher quality factor (Q-factor) or a narrower bandwidth (full width at half maximum, FWHM).
Terahertz sensors enable the measurement of analytes by inducing changes in the resonant frequency caused by analytes of different types (having different refractive indices) or different thicknesses in the region of strong electric fields, so that the frequency shift caused by changes in the unit refractive index or the unit thickness of the analyte is an important parameter for measuring the performance of the sensor, also known as sensitivity (S). The overall measure of sensor performance is the sensing sensitivity value (FOM), which is the sensitivity divided by the bandwidth. An ideal sensor would have a high quality factor, sensitivity and sensitivity value at the same time, but in practice these performance parameters would need to be taken into account in a compromise.
However, the current terahertz sensor has the defect of low sensitivity and low sensitivity value in the aspect of trace substance detection, and limits the practical application of the terahertz sensor in the biomedical field, in particular to the sensing analysis of liquid materials containing very low concentration biomolecules or smaller volumes and very thin medium materials.
Disclosure of Invention
Aiming at the defects and improvement demands of the prior art, the invention provides a terahertz metamaterial sensor with an interdigital structure, and aims to solve the technical problems of low sensitivity and low sensitivity value of the conventional terahertz sensor in trace substance detection.
To achieve the above object, the present invention provides a terahertz metamaterial sensor with an interdigital structure, comprising:
a dielectric substrate and a metal double-split resonant ring periodically arranged on the dielectric substrate; one of the openings of the metal double-opening resonant ring comprises one or more metal interdigital structures;
when the metal double-opening resonant ring is a square ring, the double openings are respectively positioned on two arms parallel to the electric field direction of the electromagnetic wave;
when the metal double-opening resonant ring is a circular ring, the double openings are respectively positioned on the upper semicircle and the lower semicircle of the circular ring, and the shortest arc angle between the double openings is more than 90 degrees, and the tangential direction of the opening comprising one or more metal cross finger-shaped structures is parallel to the electric field direction of electromagnetic waves.
Further, the material of the medium substrate is any one of fused quartz, high-resistance silicon, polyimide, polymethylpentane TPX, polyethylene PE and polytetrafluoroethylene PTFE.
Further, the thickness of the medium substrate is d=0.1 to 1 mm; when the material of the dielectric substrate is fused silica, the relative dielectric constant of the dielectric substrate is 3.75+j0.0015.
Further, the metal double-opening resonant ring is made of any one of gold, silver, copper, aluminum, nickel, chromium and titanium.
Further, the metal thickness of the metal double-opening resonant ring is 100-500 nanometers; when the material of the metal double-split resonant ring is gold, the conductivity of the metal is 4.561 ×107S/m.
Further, the unit structure of the terahertz metamaterial sensor has a period of px=py=100-500 micrometers in the x-axis direction and the y-axis direction;
when the metal double-opening resonance ring is a square ring, the length of the metal double-opening resonance ring in the x-axis direction and the y-axis direction is nx=ny=50-300 micrometers, and the metal line width is U=2-20 micrometers; the opening size is g1=g2=2 to 20 micrometers, and the centers of the two openings are offset by a=0 to 20 micrometers.
Further, the unit structure of the terahertz metamaterial sensor has a period of px=py=240 micrometers in the x-axis direction and the y-axis direction;
when the metal double-split resonant ring is a square ring, the length of the metal double-split resonant ring in the x-axis direction and the y-axis direction is nx=ny=130 micrometers, and the metal line width is u=13.8 micrometers; the opening size is g1=g2=12 micrometers, the centers of the two openings being offset a=10 micrometers relative to each other.
Further, the finger length of the metal interdigital structure is l=2-20 micrometers, the finger width is w=0.1-1 micrometers, and the inter-finger gap m=0.1-1 micrometers.
Still further, the metal interdigital structure has a finger length l=11 micrometers, a finger width w=0.6 micrometers, and an inter-finger gap m=0.6 micrometers.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
when the direction of the electric field of the incident electromagnetic wave is perpendicular to the metal arm where the opening is located, the terahertz metamaterial sensor of the existing metal asymmetric double-opening resonator (aDSRR) structure shows an asymmetric Fano resonance phenomenon, and the resonance has a Q value higher than that of LC resonance in the SRR structure, so that the position of a resonance frequency point and tiny frequency shift can be accurately distinguished in the experimental measurement process. On the basis of the invention, by introducing the metal interdigital structure at one opening of the double-opening resonator structure, when the direction of the electric field of the incident electromagnetic wave is parallel to the metal arm where the opening of the metal interdigital structure is introduced, the symmetrical resonant mode is shown, and the Q value is slightly lower than the Fano resonance in the aDSRR structure, but the metal metamaterial disclosed by the invention has extremely strong surface current density, inter-finger electric field and extremely small mode volume during resonance, so that the metal metamaterial has high resonant intensity, sensitivity S and sensitivity FOM, and is particularly suitable for trace substance detection.
Drawings
Fig. 1 is a schematic three-dimensional structure of a unit structure of a terahertz metamaterial sensor with an interdigital structure in accordance with an embodiment of the present invention;
FIG. 2 is a two-dimensional structural schematic of a cell structure of a terahertz metamaterial sensor with an interdigital structure in accordance with an embodiment of the present invention;
FIG. 3 is a schematic two-dimensional structure of a metallic double-split resonant ring according to an embodiment of the present invention, wherein (a) to (d) are square rings and (e) to (h) are circular rings;
FIG. 4 is a simulated graph of a terahertz metamaterial sensor power transmission spectrum in accordance with an embodiment of the present invention;
FIG. 5 is a simulated graph of a two-dimensional distribution of surface current density at resonance for a terahertz metamaterial sensor in accordance with an embodiment of the present invention;
FIG. 6 is a simulated graph of two-dimensional distribution of electric field amplitude at resonance for a terahertz metamaterial sensor in accordance with an embodiment of the present invention;
FIG. 7 is a simulated plot of the resonant frequency shift of a terahertz metamaterial sensor in accordance with an embodiment of the present invention when placing analytes of different refractive indices;
FIG. 8 is a simulated plot of the resonant frequency shift of a terahertz metamaterial sensor in accordance with an embodiment of the present invention when placing analytes of different thicknesses.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. Additional advantages and features of the present invention will become readily apparent to those skilled in the art from the present disclosure, as illustrated and described herein, by the following detailed description of the embodiments of the present invention. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. The drawings provided in the present embodiment merely illustrate the basic idea of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings, not according to the number, shape and size of the components in actual implementation, the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated. The structures, proportions, sizes, etc. shown in the drawings attached hereto are for illustration purposes only and are not intended to limit the scope of the invention, which is defined by the claims, but rather by the claims. Also, the terms such as "upper," "lower," "left," "right," "middle," and "a" and the like recited in the present specification are merely for descriptive purposes and are not intended to limit the scope of the invention, but are intended to provide relative positional changes or modifications without materially altering the technical context in which the invention may be practiced.
The invention provides a terahertz metamaterial sensor with an interdigital structure, which comprises a medium substrate and a metal double-opening resonant ring which is periodically arranged on the medium substrate; one of the openings of the metal double-opening resonant ring comprises one or more metal interdigital structures; when the metal double-opening resonant ring is a square ring, the double openings are respectively positioned on two arms parallel to the electric field direction of the electromagnetic wave; when the metal double-opening resonant ring is a circular ring, the double openings are respectively positioned on the upper semicircle and the lower semicircle of the circular ring, and the shortest arc angle between the double openings is more than 90 degrees, and the tangential direction of the opening comprising one or more metal cross finger-shaped structures is parallel to the electric field direction of electromagnetic waves.
It should be noted that, for the existing metal asymmetric double-split resonant ring, the double-split must be asymmetric, otherwise, the ring cannot have Fano resonance. The dual openings of the resonant ring to which the sensor of the present invention relates may be either symmetrical or asymmetrical, and may have the same or different opening widths.
Fig. 1 and 2 show a three-dimensional structure schematic view and a two-dimensional plan schematic view of a unit structure of a terahertz metamaterial sensor with an interdigital structure in accordance with an embodiment of the present invention, respectively. Wherein the substrate is fused quartz, a square ring made of gold is arranged on the substrate, the upper arm and the lower arm of the square ring are respectively provided with an opening, and the upper opening contains a periodic structure made of interdigital gold. The specific parameters are as follows: the unit period is px=py=100-500 micrometers, the square ring length is nx=ny=50-300 micrometers, the metal line width is u=2-20 micrometers, the square ring opening size is g1=g2=2-20 micrometers, the relative offset a of the two opening centers is 0-20 micrometers, the finger length of the metal interdigital structure is l=2-20 micrometers, the finger width is w=0.1-1 micrometers, the inter-finger gap m=0.1-1 micrometers, the thickness of the fused quartz substrate is d=0.1-1 millimeter, the relative dielectric constant of the substrate is 3.75+j 0.0015, the metal thickness is 100-500 nanometers, and the conductivity of the metal is 4.561 ×10+7s/M.
In some embodiments of the present invention, the metallic double-split resonant ring may be a double-split square ring or a double-split circular ring. In the following, taking fig. 3 as an example, several structures are specifically listed: as shown in fig. 3 (a), a double-opening square ring structure is provided, wherein two openings are positioned on the upper arm and the lower arm, the two openings have the same opening size, but the centers of the two openings have a certain displacement in the horizontal direction, and an interdigital structure is positioned in the opening of the upper arm; as shown in fig. 3 (b), there is a double-opening square ring structure in which two openings are provided in the upper and lower arms, the two openings have the same opening size, but the centers of the two openings are not displaced in the horizontal direction, and the interdigital structure is provided in the opening of the upper arm; as shown in fig. 3 (c), a double-opening square ring structure is provided, wherein two openings are positioned on the upper and lower arms, the two openings have different opening sizes, but the centers of the two openings have a certain displacement in the horizontal direction, and the interdigital structure is positioned in the opening of the upper arm; as shown in fig. 3 (d), a double-opening square ring structure is provided, wherein two openings are positioned on the upper arm and the lower arm, the two openings have the same opening size, but the centers of the two openings have a certain displacement in the horizontal direction, and the interdigital structure is positioned in the opening of the lower arm; as shown in fig. 3 (e), the ring structure is a double-opening circular ring structure, wherein two openings are positioned on the upper semicircle and the lower semicircle, the two openings have the same opening angle, the central lines of the two openings are coincident, and the arc-shaped interdigital structure is positioned in the upper semicircle opening; as shown in fig. 3 (f), a double-opening circular ring structure is provided, wherein two openings are positioned on the upper semicircle and the lower semicircle, the two openings have different opening angles, the central lines of the two openings coincide, and an arc-shaped interdigital structure is positioned in the upper semicircle opening; as shown in fig. 3 (g), the ring structure is a double-opening circular ring structure, wherein two openings are positioned on the upper semicircle and the lower semicircle, the two openings have the same opening angle, the central lines of the two openings have a certain included angle, and the arc-shaped interdigital structure is positioned in the upper semicircle opening; as shown in fig. 3 (h), a double-opening circular ring structure is provided, wherein two openings are positioned on the upper semicircle and the lower semicircle, the two openings have the same opening angle, the central lines of the two openings coincide, and an arc-shaped interdigital structure is positioned in the lower semicircle.
A frequency domain solver using CST MWS software simulated the dual-open square ring metamaterial sensor shown in fig. 3 (a). In the simulation, the structural parameters involved are: the unit period is px=py=240 micrometers, the square ring length is nx=ny=130 micrometers, the metal line width is u=13.8 micrometers, the square ring opening size is g1=g2=12 micrometers, the relative offset a of the centers of the two openings is=10 micrometers, the finger length of the metal interdigital structure is l=11 micrometers, the finger width is w=0.6 micrometers, the inter-finger gap m=0.6 micrometers, the thickness of the fused quartz substrate is d=150 micrometers, the relative dielectric constant of the substrate is 3.75+j0.0015, the metal thickness is 200 nanometers, the conductivity of the metal is 4.561 ×10≡7s/M, and the change relation of the power transmittance with the frequency is shown in fig. 4. For an asymmetric dual-opening terahertz metamaterial sensor (reference sensor) without an interdigital structure, when electromagnetic waves are perpendicularly incident and the electric field direction is perpendicular to a metal arm where an opening is located, the structure has two resonance peaks, namely asymmetric Fano resonance with lower frequency and higher Q value (73.5) and lower resonance intensity, namely symmetric electric dipole resonance with higher frequency and 380GHz, the resonance has larger bandwidth and lower Q value (less than 10) due to radiation loss, and the resonance intensity is larger. It should be noted that, in order to ensure that the resonant frequency of the reference sensor Fano is close to the resonant frequency of the sensor of the present invention and to facilitate comparison of performance parameters, the length of the square ring of the reference sensor is increased to nx=ny=173 micrometers in the simulation, and other parameters remain unchanged. For a double-opening terahertz metamaterial sensor (sensor provided by the invention) with an interdigital structure, the structure has only one symmetrical resonance in a simulated frequency range of 200-400 GHz and has stronger resonance intensity than Fano resonance, the fundamental mode resonance frequency is 297.3GHz, the quality factor Q is 33.1, and the Q value is far higher than the Q value corresponding to electric dipole resonance. The electric dipole resonance frequency of the structure (the sensor of the present invention) is located at a higher frequency outside the simulation interval.
The distribution of the current density of the metal surface of the sensor is shown in figure 5 when the sensor is at the fundamental mode resonance frequency, the left arm and the right arm have currents with the same magnitude and opposite directions, and the current density is 1.3 times of the current density when the sensor does not contain Fano resonance corresponding to the double-opening terahertz metamaterial sensor (reference sensor) with the interdigital structure. FIG. 6 shows the distribution of the electric field amplitude in the plane of the upper surface of the metal at the fundamental mode resonant frequency of the sensor of the present invention, wherein the electric field at the opening with the interdigital structure above is stronger and more concentrated in a smaller space, i.e., the inter-finger gap, except for the strong electric field distribution at the opening below. The maximum electric field intensity of the structure is 3.9 times of the maximum electric field intensity of Fano resonance corresponding to the double-opening terahertz metamaterial sensor (reference sensor) without the interdigital structure, so that the unique structural design of the terahertz sensor has strong resonance amplitude, current density and electric field intensity, and is more suitable for realizing the terahertz sensor with high sensitivity.
When analytes of different types and thicknesses are placed on the metamaterial metal surface, the resonant frequency of the metamaterial structure can be subjected to red shift, and the shift amount of the resonant frequency is related to the types and the thicknesses of the analytes. Fig. 7 compares the shift in resonant frequency of a sensor of the present invention with a reference sensor having a fundamental mode resonance when different refractive index materials (n= 1.2,1.4,1.6,1.8 and 2.0) are placed on a metal surface, wherein the analyte material has a thickness of 100 nm. The slope of the line obtained by fitting with a linear function is the sensitivity of the sensor at an analyte thickness of 100 nm, and the values are s=1.7 GHz/RIU (reference sensor) and 8.6GHz/RIU (sensor of the present invention), respectively, where RIU is the refractive index unit (refractive index unit). Thus, the sensitivity of the sensor of the present invention is 5.1 times that of the reference sensor. Meanwhile, the Q value of the sensor is 33.1, the Q value of the reference sensor is 73.5, and the sensing sensitivity values can be calculated to be FOM=0.43/RIU (reference sensor) and 0.96/RIU respectively, so that the sensitivity value of the sensor is 2.2 times that of the reference sensor. The sensor has the advantages of high sensitivity and sensing sensitivity value.
FIG. 8 compares the shift in resonant frequency of a sensor of the present invention with a reference sensor having a relative permittivity of 2.6+j 0.0026, the resonance of the reference sensor being Fano resonance, and the sensor of the present invention having a fundamental mode resonance, when materials of different thicknesses (0.02,0.05,0.08,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1,2,3,4,5,6,7,8,9 and 10 microns) are placed on a metal surface. The resonance frequency shift is nonlinear with the analyte thickness, and as the analyte thickness increases, the frequency shift increases rapidly, then slowly, and finally tends to saturate. Because the electric field value at resonance of the inventive sensor is large and the strong field is localized in a small spatial region from the interface of the metal and the substrate, the inventive sensor has a larger resonant frequency shift than the reference sensor when the thickness of the analyte material is small, thereby having a higher sensitivity. When the thickness of the analyte is 0.1 micrometers, the resonant frequency of the reference sensor is reduced by 1.1GHz, while the resonant frequency of the sensor is reduced by 4.9GHz, which is 4.5 times that of the reference sensor; when the thickness of the analyte is 1 micrometer, the resonance frequency of the reference sensor is reduced by 6.6GHz, and the resonance frequency of the sensor is reduced by 14.9GHz, which is 2.3 times that of the reference sensor; the resonant frequency of the reference sensor is reduced by 19.1GHz at an analyte thickness of 5 microns, and the resonant frequency of the sensor of the present invention is reduced by 23.9GHz, which is close to the reference sensor. The result shows that the sensor has sensitivity far higher than that of a reference sensor when detecting extremely thin materials, and the sensitivity is obviously improved when the thickness is thinner, especially for materials with the thickness of 1 micrometer or less, so the sensor is particularly suitable for high-sensitivity sensing of trace substances.
TABLE 1 sensor performance parameters of the invention
Furthermore, as shown in table 1, the ratio of finger width to inter-finger gap of the interdigital structure was kept constant (W/m=1), the resonant frequency and quality factor of the inventive sensor were changed when m=0.2 micrometers and m=1 micrometers, and the sensitivity and sensitivity value of the inventive sensor were still superior to those of the reference sensor when the analyte thickness was 100 nanometers. The calculations indicate that as the value of M increases, the resonant frequency and quality factor increase, and that structures with m=0.2 microns have high sensitivity when the analyte thickness is less than 100 nm, but generally require electron beam etching, which is complex to implement, long in time and expensive. Both m=0.6 micron and m=1 micron structures can be realized by a simple well-established photolithography process, with the former having a higher sensitivity. Thus, a terahertz sensor with m=0.6 μm is a preferred structure from the standpoint of achieving both process and performance parameters.
In summary, the present invention provides a terahertz metamaterial sensor with an interdigital structure, which includes a dielectric substrate and a metal double-split resonant ring periodically arranged on the dielectric substrate; one of the openings of the metal double-opening resonant ring comprises one or more metal interdigital structures; when the metal double-opening resonant ring is a square ring, the double openings are respectively positioned on two arms parallel to the electric field direction of the electromagnetic wave; when the metal double-opening resonant ring is a circular ring, the double openings are respectively positioned on the upper semicircle and the lower semicircle of the circular ring, and the shortest arc angle between the double openings is more than 90 degrees, and the tangential direction of the opening comprising one or more metal cross finger-shaped structures is parallel to the electric field direction of electromagnetic waves. Due to the adoption of the special structure, the sensor can generate strong resonance with incident terahertz waves, is easy to observe in simulation and experimental measurement, and can concentrate near a metal surface, and when an analyte is placed on the metal surface, the sensor shows extremely high sensitivity and sensitivity values, particularly the analyte with the thickness of less than 1 micrometer. Compared with a terahertz metamaterial sensor without an interdigital structure, the terahertz metamaterial sensor has the advantages that the sensing performance is greatly improved, the sensor is particularly suitable for high-sensitivity sensing of trace substances, viruses, DNA, biomolecules and the like, is easy to manufacture and measure, and has great industrial application value.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (8)
1. A terahertz metamaterial sensor with an interdigital structure, comprising:
a dielectric substrate and a metal double-split resonant ring periodically arranged on the dielectric substrate; one of the openings of the metal double-opening resonant ring comprises one or more metal interdigital structures; the metal double-opening resonant ring is a square ring or a circular ring; the finger length of the metal interdigital structure is L=2-20 micrometers, the finger width is W=0.1-1 micrometers, and the inter-finger gap M=0.1-1 micrometers;
when the metal double-opening resonant ring is a square ring, the double openings are respectively positioned on two arms parallel to the electric field direction of the electromagnetic wave;
when the metal double-opening resonant ring is a circular ring, the double openings are respectively positioned on the upper semicircle and the lower semicircle of the circular ring, and the shortest arc angle between the double openings is more than 90 degrees, and the tangential direction of the opening comprising one or more metal cross finger-shaped structures is parallel to the electric field direction of the electromagnetic wave.
2. The terahertz metamaterial sensor with an interdigital structure according to claim 1, wherein the material of the dielectric substrate is any one of fused quartz, high-resistance silicon, polyimide, polymethylpentane, polyethylene and polytetrafluoroethylene.
3. The terahertz metamaterial sensor with an interdigital structure according to claim 2, wherein the thickness of the dielectric substrate is d=0.1 to 1 millimeter; when the material of the dielectric substrate is fused silica, the relative dielectric constant of the dielectric substrate is 3.75+j0.0015.
4. The terahertz metamaterial sensor with an interdigital structure according to claim 1, wherein the material of the metallic double-split resonant ring is any one of gold, silver, copper, aluminum, nickel, chromium, and titanium.
5. The terahertz metamaterial sensor with an interdigital structure according to claim 4, wherein the metal thickness of the metal double-split resonant ring is 100-500 nanometers; when the material of the metal double-split resonant ring is gold, the conductivity of the metal is 4.561 ×10 7 S/m。
6. The terahertz metamaterial sensor with the interdigital structure according to claim 1, wherein the unit structure of the terahertz metamaterial sensor has a period of px=py=100 to 500 micrometers in the x-axis direction and the y-axis direction;
when the metal double-opening resonant ring is a square ring, the length of the square ring in the x-axis direction and the y-axis direction is nx=ny=50-300 micrometers, and the metal line width is U=2-20 micrometers; the opening size is G1=G2=2-20 micrometers, and the centers of the two openings are offset by A=0-20 micrometers.
7. The terahertz metamaterial sensor with an interdigital structure according to claim 6, wherein the cell structure of the terahertz metamaterial sensor has a period of px=py=240 μm in the x-axis direction and the y-axis direction;
when the metal double-opening resonant ring is a square ring, the length of the square ring in the x-axis direction and the y-axis direction is nx=ny=130 micrometers, and the metal line width is u=13.8 micrometers; the opening size is g1=g2=12 micrometers, the centers of the two openings being offset a=10 micrometers relative to each other.
8. The terahertz metamaterial sensor with an interdigital structure according to claim 1, wherein the metal interdigital structure has a finger length l=11 micrometers, a finger width w=0.6 micrometers, and an inter-finger gap m=0.6 micrometers.
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