CN117154420A - Three-band high Q value terahertz metamaterial absorber based on metal split ring - Google Patents
Three-band high Q value terahertz metamaterial absorber based on metal split ring Download PDFInfo
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- 239000002184 metal Substances 0.000 title claims abstract description 91
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 91
- 239000006096 absorbing agent Substances 0.000 title claims abstract description 82
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- 238000009413 insulation Methods 0.000 claims abstract description 4
- 238000001514 detection method Methods 0.000 claims description 23
- 229920002120 photoresistant polymer Polymers 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 12
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 11
- 229910052737 gold Inorganic materials 0.000 claims description 11
- 239000010931 gold Substances 0.000 claims description 11
- -1 polytetrafluoroethylene Polymers 0.000 claims description 9
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 9
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 9
- 238000005516 engineering process Methods 0.000 claims description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- 238000005530 etching Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 239000000758 substrate Substances 0.000 claims description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 239000010949 copper Substances 0.000 claims description 5
- 229910052709 silver Inorganic materials 0.000 claims description 5
- 239000004332 silver Substances 0.000 claims description 5
- 238000000034 method Methods 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000011161 development Methods 0.000 claims description 3
- 238000001704 evaporation Methods 0.000 claims description 3
- 238000010884 ion-beam technique Methods 0.000 claims description 3
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- 238000004528 spin coating Methods 0.000 claims description 3
- 238000002604 ultrasonography Methods 0.000 claims description 3
- 238000010521 absorption reaction Methods 0.000 description 25
- 239000012491 analyte Substances 0.000 description 14
- 229930006000 Sucrose Natural products 0.000 description 10
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 10
- 239000005720 sucrose Substances 0.000 description 10
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 8
- 230000005684 electric field Effects 0.000 description 8
- 239000008103 glucose Substances 0.000 description 8
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- 238000001328 terahertz time-domain spectroscopy Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0086—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
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Abstract
The invention discloses a three-band high Q value terahertz metamaterial absorber based on a metal split ring, which is formed by periodically arranging a plurality of metamaterial square periodic units, wherein gaps exist between adjacent metamaterial square periodic units; each metamaterial square periodic unit comprises a metal resonant layer, a middle insulating layer and a metal reflecting layer which are arranged from top to bottom; the metal reflecting layer is closely attached to the lower surface of the middle insulating layer, and the section size of the metal reflecting layer is consistent with that of the middle insulating layer; the metal resonance layer is closely arranged in the middle of the upper surface of the middle insulation layer and comprises two symmetrically arranged metal split resonators; the split metal resonator comprises two split square rings which are symmetrically arranged, the opening position of each split square ring is the middle part of a loop line of the split square ring, which is close to the symmetrical center line of the two split square rings, and the loop lines of the two split square rings, which are far away from the symmetrical center lines of the two split metal resonators, are integrally connected.
Description
Technical Field
The invention belongs to the field of metamaterial devices, and particularly relates to a three-band high-Q-value terahertz metamaterial absorber based on a metal split ring.
Background
Terahertz waves are electromagnetic waves with the frequency of 0.1-10THz, are located between infrared rays and microwaves, are regions of electronic-to-photonics transition, have low photon energy, are non-ionized in nature, cannot damage substances, and realize nondestructive detection; high penetrability, for substances with small and nonuniform structures, reducing scattering effect and increasing penetration depth of the substances; molecular fingerprint spectrum, the internal information of the substance can be detected. The terahertz waves become hot spots in the research world, and are successfully applied to the aspects of spectrum and imaging technology, communication technology, radar, safety inspection and the like; however, natural materials are not suitable for the terahertz wave band because they have a frequency of gigahertz, thereby impeding research and study of the terahertz wave band by researchers.
The metamaterial is a composite material which is designed manually and has a variable structure and a negative refractive index, overcomes the defects of natural materials, and can realize the functions of wave front regulation, wave back control and the like for terahertz waves. The terahertz metamaterial absorber can realize perfect absorption of incident terahertz waves, analyte refractive index sensing, analyte thickness sensing detection and the like, and has been widely studied in the fields of biomedicine, agricultural product/food safety and the like. The multiband terahertz metamaterial absorber has stable performance due to the characteristic of generating a plurality of resonance peaks, and can realize the functions of multipoint matching, high-precision sensing and detection of substance information when detecting analytes. The terahertz metamaterial is combined with a terahertz time-domain spectroscopy instrument, so that high-sensitivity detection of trace or trace substances is realized, national standards are achieved, and the detection lower limit of the trace substances is improved. Therefore, it is of great significance to design terahertz metamaterial absorbers with perfect absorption characteristics, multiband and high quality factor.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a three-band high-Q-value terahertz metamaterial absorber based on a metal split ring, which is near perfect to absorb and has high quality factor, and a preparation method of the terahertz metamaterial absorber, and also provides a high-sensitivity qualitative detection device based on the terahertz metamaterial absorber.
The invention provides a three-band high Q value terahertz metamaterial absorber based on a metal split ring, which is formed by periodically arranging a plurality of metamaterial square periodic units, wherein gaps exist between adjacent metamaterial square periodic units;
each metamaterial square periodic unit comprises a metal resonant layer, a middle insulating layer and a metal reflecting layer which are arranged from top to bottom;
the metal reflecting layer is closely attached to the lower surface of the middle insulating layer, and the section size of the metal reflecting layer is consistent with that of the middle insulating layer;
the metal resonance layer is closely arranged in the middle of the upper surface of the middle insulation layer and comprises two symmetrically arranged metal split resonators;
the split metal resonator comprises two split square rings which are symmetrically arranged, the opening position of each split square ring is the middle part of a loop line of the split square ring, which is close to the symmetrical center line of the two split square rings, and the loop lines of the two split square rings, which are far away from the symmetrical center lines of the two split metal resonators, are integrally connected.
Based on the above, the line width w of the open square ring is 1-3 μm, the length a is 76-82 μm, and the width b is 18-23 μm; the opening distance g1 of the opening square ring is 1-3 mu m; the distance g2 between two symmetrically arranged open square rings is 3-5 μm.
Based on the above, the material of the metal resonance layer and the metal reflection layer is one of gold, silver and copper, the thickness is 0.1-0.3 μm, and the conductivity is 4.561 ×10 7 S/m。
Based on the above, the metal resonance layer and the metal resonance layerThe metal reflecting layer is made of one of gold, silver and copper, has a thickness of 0.2 μm and an electrical conductivity of 4.561 ×10 7 S/m。
Based on the above, the line width w of the open square ring is 2 μm, the length a is 76-82 μm, and the width b is 18-23 μm; the opening distance g1 of the opening square ring is 2 mu m; the distance g2 between two symmetrically arranged open square rings is 4 μm.
Based on the above, the cross section of the middle insulating layer is consistent with that of the metamaterial square periodic unit, the side length is 120 μm, and the thickness t2 is 20 μm; the material of the middle insulating layer is polytetrafluoroethylene with a dielectric constant of 2.1 (1+i0.0002).
Based on the above, the terahertz metamaterial absorber generates resonance frequencies at f1=1.11 THz, f2= 2.256THz, and f3=2.64 THz.
Based on the above, the terahertz metamaterial absorber has a harp peak with a high Q value at both f2= 2.256THz and f3=2.64 THz.
The second aspect of the invention provides a preparation method of the three-band high Q value terahertz metamaterial absorber based on the metal split ring, which comprises the following steps:
firstly, preparing a polytetrafluoroethylene substrate with the frequency of 2 cm on high-resistance silicon, and evaporating a layer of metal film on the bottom and the top of the cleaned polytetrafluoroethylene substrate by utilizing a metal evaporation technology;
then spin coating a layer of uniform photoresist on the metal film on the top layer, carrying out ultraviolet exposure by using a positive mask, dissolving the photoresist sol in the shape of the metal resonance layer in a developing solution during development, and etching the gold layer of the area without photoresist protection by using an ion beam etching technology;
finally, the remaining photoresist is removed using alcohol and acetone ultrasound, leaving the absorber metal resonant layer structure.
The third aspect of the invention provides a high-sensitivity qualitative detection device, which adopts the three-band high-Q-value terahertz metamaterial absorber based on the metal split ring as a detection sensor of the high-sensitivity qualitative detection device to realize qualitative identification of trace or trace substances.
Compared with the prior art, the invention has the following characteristics:
1. the three-band high-Q-value terahertz metamaterial absorber based on the metal split ring provided by the invention is composed of a simple metal split square ring, and the metal split square ring is easy to interact with incident terahertz waves to realize efficient absorption, and has the characteristics of simple structure, easiness in processing, small volume and easiness in integration.
2. The structure of the invention has three resonance absorption peaks in 1-3THz, and the absorption rate is more than 96%, which is near perfect absorption.
3. The structure of the invention has two harp peaks at resonance, and the quality factor can reach 528.
4. The structure of the invention can realize insensitivity of x and y polarization due to symmetry of the unit structure.
Drawings
Fig. 1 (a) is a schematic structural view of the terahertz metamaterial absorber of the present invention.
FIG. 1 (b) is a schematic diagram of the front structure of a metamaterial square periodic unit in the present invention.
FIG. 1 (c) is a schematic side view of a metamaterial square periodic unit in accordance with the present invention.
Fig. 2 is an absorption characteristic simulation curve of the terahertz metamaterial absorber of the present invention.
Fig. 3 (a) is an absorption curve of different polarization angles (angle varying from 0 ° to 30 °) of the terahertz metamaterial absorber of the present invention.
Fig. 3 (b) is an absorption curve of the terahertz metamaterial absorber of the present invention at different incident angles (angle varying from 0 ° to 30 °).
Fig. 4 (a) is an electric field of the terahertz metamaterial absorber of the present invention at a resonance frequency f 1.
Fig. 4 (b) is a surface current of the terahertz metamaterial absorber of the present invention at a resonance frequency f 1.
Fig. 4 (c) is a bottom plate current of the terahertz metamaterial absorber of the present invention at a resonance frequency f 1.
Fig. 4 (d) is an electric field of the terahertz metamaterial absorber of the present invention at a resonance frequency f 2.
Fig. 4 (e) is the surface current of the terahertz metamaterial absorber of the present invention at the resonance frequency f 2.
Fig. 4 (f) is the bottom plate current of the terahertz metamaterial absorber of the present invention at a resonance frequency f 2.
Fig. 4 (g) is an electric field of the terahertz metamaterial absorber of the present invention at a resonance frequency f 3.
Fig. 4 (h) is the surface current of the terahertz metamaterial absorber of the present invention at a resonance frequency f 3.
Fig. 4 (i) is the bottom plate current of the terahertz metamaterial absorber of the present invention at a resonance frequency f 3.
Fig. 5 (a) is an absorption curve at a resonance frequency f1 when the terahertz metamaterial absorber of the present invention employs analytes of different refractive indices.
Fig. 5 (b) is an absorption curve at the resonance frequency f2 when the terahertz metamaterial absorber of the present invention employs analytes of different refractive indices.
Fig. 5 (c) is an absorption curve at the resonant frequency f3 when the terahertz metamaterial absorber of the present invention employs analytes of different refractive indices.
Fig. 5 (d) is the frequency shift at f1, f2, f3 resonance when the terahertz metamaterial absorber of the present invention employs analytes with refractive indices of 1.1-1.6.
Fig. 6 (a) is an absorption curve of different thicknesses when the terahertz metamaterial absorber of the present invention employs an analyte refractive index of 1.4.
FIG. 6 (b) is an absorption curve of analytes of different refractive indices when the thickness of the analytes used in the terahertz metamaterial absorber of the present invention is 20. Mu.m.
Fig. 7 is a flow chart of a method for manufacturing the terahertz metamaterial absorber.
Fig. 8 (a) shows simulated absorption curves of a terahertz metamaterial absorber at a resonance frequency f1 of a glucose solution, a granulated sugar solution and a sucrose solution.
Fig. 8 (b) shows simulated absorption curves of the terahertz metamaterial absorber at a resonance frequency f2 of a glucose solution, a granulated sugar solution and a sucrose solution.
Fig. 8 (c) shows simulated absorption curves of the terahertz metamaterial absorber at a resonance frequency f3 of a glucose solution, a granulated sugar solution and a sucrose solution.
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.
Example 1
As shown in fig. 1 (a) -1 (c), the present embodiment provides a three-band high Q terahertz metamaterial absorber based on a metal split ring, wherein the absorber is formed by periodically arranging a plurality of metamaterial square periodic units, and gaps exist between adjacent metamaterial square periodic units;
each metamaterial square periodic unit comprises a metal resonant layer, a middle insulating layer and a metal reflecting layer which are arranged from top to bottom;
the metal reflecting layer is closely attached to the lower surface of the middle insulating layer, and the section size of the metal reflecting layer is consistent with that of the middle insulating layer;
the metal resonance layer is closely arranged in the middle of the upper surface of the middle insulation layer and comprises two symmetrically arranged metal split resonators;
the split metal resonator comprises two split square rings which are symmetrically arranged, the opening position of each split square ring is the middle part of a loop line of the split square ring, which is close to the symmetrical center line of the two split square rings, and the loop lines of the two split square rings, which are far away from the symmetrical center lines of the two split metal resonators, are integrally connected.
Specifically, in the terahertz metamaterial absorber of the embodiment, the line width w of the open square ring is 1-3 μm, the length a is 76-82 μm, and the width b is 18-23 μm; the opening distance g1 of the opening square ring is 1-3 mu m; the distance g2 between two symmetrically arranged open square rings is 3-5 μm.
Specifically, the terahertz metamaterial absorber of the embodimentWherein the metal resonance layer and the metal reflection layer are made of one of gold, silver and copper, the thickness is 0.1-0.3 mu m, and the conductivity is 4.561 multiplied by 10 7 S/m。
Example 2
The embodiment provides specific structural parameters of a terahertz metamaterial absorber:
the terahertz metamaterial absorber is formed by periodically arranging a plurality of metamaterial square periodic units.
The metal resonance layer and the metal reflection layer are made of gold with thickness of 0.2 μm and conductivity of 4.561 ×10 7 S/m。
The line width w of the open square ring is 2 mu m, the length a is 80 mu m, and the width b is 20 mu m; the opening distance g1 of the opening square ring is 2 mu m; the distance g2 between two symmetrically arranged open square rings is 4 μm.
The cross section of the middle insulating layer is consistent with that of the metamaterial square periodic unit, the side length is 120 mu m, and the thickness t2 is 20 mu m; the material of the middle insulating layer is polytetrafluoroethylene with a dielectric constant of 2.1 (1+i0.0002).
Simulation test
For the structural parameters in this embodiment, full wave simulation calculations were performed using a CST Studio Suite 2020:
a periodic boundary is set in the x, y direction, an open boundary condition is set in the z direction, and terahertz waves polarized in the x direction are perpendicularly incident on the absorber. With the finite element integration method, the absorber generates three resonance frequencies at f1=1.11 THz, f2= 2.256THz, and f3=2.64 THz, as shown in fig. 2, according to the formula a (ω) =1-R (ω) -T (ω), a (ω) representing the absorptivity of the absorber, R (ω) representing the reflectivity, T (ω) representing the transmissivity, and since the thickness of gold is far greater than the skin depth, the terahertz wave is totally reflected when it irradiates the bottom gold layer of the absorber, so T (ω) is 0, and the resonance frequency and absorption coefficient of the absorber of this embodiment are calculated, and the absorptivity of the absorber at f1=1.11 THz, f2= 2.256THz, and f3=2.64 THz are 99.5%, 96.5%, and 99.8%, respectively. The quality factors Q of the absorber of the present embodiment at f1=1.11 THz, f2= 2.256THz and f3=2.64 THz are 18.4, 282, 528, respectively, according to the formula q=f/FWHM.
Angle analysis
In order to explore the sensitivity characteristics of the terahertz metamaterial absorber of the embodiment, simulation calculation is performed on the absorption rate at different polarization angles and incidence angles. FIG. 3 (a) shows the absorption curves of terahertz metamaterial absorbers with different polarization angles, and when the polarization angles are changed, three resonance peaks are not obviously shifted, because the absorber is of a symmetrical structure and is insensitive to polarization; FIG. 3 (b) shows the absorption curves of absorbers at different angles of incidence, showing that the resonance peak at low frequencies is unchanged, i.e. the f1 is insensitive to the angle of incidence; and f2 and f3 are sensitive to the incident angle, so in order to achieve multipoint matching of information during experimental detection, the terahertz waves should be kept vertically incident on the terahertz metamaterial absorber.
Resonance mechanism analysis
In order to deeply study the wave absorption mechanism and resonance characteristics of the absorber, the electric field and the surface current of the metal split ring when TE polarized waves are perpendicularly incident are analyzed;
fig. 4 (a) -4 (c) show that at the resonant frequency f1, the electric field is concentrated mainly at the horizontal metal arm and at the two openings, the corresponding two left split rings form a counter-clockwise surface current, the two right split rings form a clockwise surface current, and the charge is accumulated on the metal ring horizontal arm. The resonance on the horizontal metal arm belongs to the excitation of the four-level resonance and can be regarded as two magnetic dipoles with opposite directions.
Fig. 4 (d) -4 (f) show that at the resonance frequency f2, the electric field exists not only at the outer metal openings but also is distributed in the nonmetallic region, the surface current flows upward from the middle opening through the horizontal arms outside the left and right metals, and the electric field strength and the current distribution confirm that the resonance at f2 is jointly excited by the electric dipole and the surface lattice resonance. The reason is that the resonance response of the metal resonator is matched with the surface lattice resonance, the Q factor is effectively improved, the enhancement of local fields is effectively improved, the radiation and loss of electromagnetic waves are reduced, and accordingly resonance f2 with narrower line width is generated, narrow bands appear at the position of 2.25THz, and a harp peak value with high Q value is generated.
As shown in fig. 4 (g) -fig. 4 (i), at the resonant frequency f3, the electric field intensity is mainly distributed in the horizontal arm inside the square ring of the metal, the surface current flows downwards from the middle opening through the horizontal arm inside the metal, and currents with opposite directions are respectively formed between the two metal rings and are dipole resonance, and because of excitation of the magnetic dipole, a harp peak with high absorptivity and high Q value is generated at f 3.
Refractive index analysis of different analytes
The terahertz metamaterial absorber of the experimental example is used for analyzing the absorption conditions of different detection analyte refractive indexes and the response characteristics of substances to be detected, and is shown in fig. 5 (a) -5 (c). The real and imaginary parts of the analyte refractive index are defined as:wherein->For the relative permittivity of the analyte, +.>Is air relative permeability->Approximately 1. When the thickness of the analyte is 10 mu m, the refractive index is changed from 1.1 to 1.6, the three resonance frequencies are red shifted, wherein the absorption rate at f1 is still kept above 99%, and the calculation formula of the refractive index sensitivity is adopted: s is S f When the analyte thickness is 10 μm, =Δf/Δn, the frequency shift and sensitivity of the three resonance modes are respectively: Δf1=168 ghz, s f （f1）=336GHz/RIU；Δf2=162GHz，S f （f2）=324GHz/RIU；Δf3=198GHz，S f (f3) =396 GHz/RIU, as shown in fig. 5 (d).
The thickness of the analyte also affects the sensitivity of the absorber. FIG. 6 shows simulated resonance frequency shift patterns for different analyte thicknesses for three resonance modes for an analyte refractive index n of 1.4. The sensitivity was maximized at an analyte thickness of 20 μm, S f （f1）=360Hz/RIU，S f （f2）=570GHz/RIU，S f (f3) =766 GHz/RIU. In addition to the quality factor Q, the refractive index sensitivity S f The FOM value is also an important index for evaluating terahertz metamaterial absorbers. Calculation formula of FOM value:
FOM=S f FWHM, wherein FWHM is the full width half maximum at resonance frequency.
From the formula, it can be calculated that when the analyte thickness is 20 μm, the FOM values of the three resonance peaks are respectively: FOM (f 1) =6, FOM (f 2) =71.3, FOM (f 3) =153.2; the FOM is the reciprocal of the matching rate, and the smaller the value is, the better the matching degree is.
Example 3
The embodiment provides a method for preparing the three-band high Q terahertz metamaterial absorber based on a metal split ring in embodiment 2, as shown in fig. 7:
firstly, preparing a polytetrafluoroethylene substrate with the frequency of 2 cm on high-resistance silicon, and evaporating a layer of metal film on the bottom and the top of the cleaned polytetrafluoroethylene substrate by utilizing a metal evaporation technology;
then spin coating a layer of uniform photoresist on the metal film on the top layer, carrying out ultraviolet exposure by using a positive mask, dissolving the photoresist sol in the shape of the metal resonance layer in a developing solution during development, and etching the gold layer of the area without photoresist protection by using an ion beam etching technology;
finally, the remaining photoresist is removed using alcohol and acetone ultrasound, leaving the absorber metal resonant layer structure.
Example 4
The embodiment provides a high-sensitivity qualitative detection device, which adopts the three-band high-Q-value terahertz metamaterial absorber based on the metal split ring in embodiment 2 as a detection sensor of the high-sensitivity qualitative detection device, so as to realize qualitative identification of trace or trace substances.
In order to verify the detection performance of the high-sensitivity qualitative detection device based on the terahertz metamaterial absorber, the detection device is used for detecting and analyzing 25% of glucose solution, granulated sugar solution and sucrose solution.
Given that the refractive index of the glucose solution is 1.36, the refractive index of the sucrose solution is 1.45, and the refractive index of the sucrose solution is 1.78, fig. 8 shows simulated absorption curves of the detection device in the glucose solution, the sucrose solution, and the sucrose solution. When the glucose solution is detected, the frequency shift of the three resonance frequencies is 130GHz, 200GHz and 200GHz respectively; when the granulated sugar solution is detected, the frequency shift of the three resonance frequencies is 170GHz, 240GHz and 260GHz respectively; when the sucrose solution is detected, three resonance frequencies are 280GHz, 340GHz and 490GHz respectively; the result shows that the three resonance peaks are obviously red-shifted along with the increase of the refractive index, the absorptivity of the low frequency is maintained above 99%, and the absorptivity of the medium frequency is obviously reduced; the analyte is more sensitive at high frequencies, the sensitivity is not only higher than the low and medium frequencies, but the absorptivity remains at 99% without significant losses.
Therefore, the terahertz metamaterial absorber can be used as a detection sensor to distinguish three solutions of glucose, granulated sugar and sucrose, and can realize qualitative identification of trace or trace substances, so that the terahertz metamaterial absorber can be widely applied to high-sensitivity detection in the fields of biomedicine, agricultural product/food safety and the like.
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 (10)
1. A three-band high Q value terahertz metamaterial absorber based on a metal split ring is characterized in that: the absorber is formed by periodically arranging a plurality of metamaterial square periodic units, and gaps are reserved between adjacent metamaterial square periodic units;
each metamaterial square periodic unit comprises a metal resonant layer, a middle insulating layer and a metal reflecting layer which are arranged from top to bottom;
the metal reflecting layer is closely attached to the lower surface of the middle insulating layer, and the section size of the metal reflecting layer is consistent with that of the middle insulating layer;
the metal resonance layer is closely arranged in the middle of the upper surface of the middle insulation layer and comprises two symmetrically arranged metal split resonators;
the split metal resonator comprises two split square rings which are symmetrically arranged, the opening position of each split square ring is the middle part of a loop line of the split square ring, which is close to the symmetrical center line of the two split square rings, and the loop lines of the two split square rings, which are far away from the symmetrical center lines of the two split metal resonators, are integrally connected.
2. The three-band high-Q terahertz metamaterial absorber based on metal split rings according to claim 1, wherein: the line width w of the open square ring is 1-3 mu m, the length a is 76-82 mu m, and the width b is 18-23 mu m; the opening distance g1 of the opening square ring is 1-3 mu m; the distance g2 between two symmetrically arranged open square rings is 3-5 μm.
3. The three-band high-Q terahertz metamaterial absorber based on metal split rings according to claim 2, wherein: the metal resonance layer and the metal reflection layer are made of one of gold, silver and copper, and have a thickness of 0.1-0.3 μm and an electrical conductivity of 4.561 ×10 7 S/m。
4. The three-band high Q terahertz metamaterial absorber based on metal split rings as set forth in claim 3, wherein: the metal resonance layer and the metal reflection layer are made of one of gold, silver and copper, and have a thickness of 0.2 μm and an electrical conductivity of 4.561 ×10 7 S/m。
5. The three-band high-Q terahertz metamaterial absorber based on metal split rings as set forth in claim 4, wherein: the line width w of the open square ring is 2 mu m, the length a is 76-82 mu m, and the width b is 18-23 mu m; the opening distance g1 of the opening square ring is 2 mu m; the distance g2 between two symmetrically arranged open square rings is 4 μm.
6. The three-band high-Q terahertz metamaterial absorber based on metal split rings according to claim 5, wherein:
the cross section of the middle insulating layer is consistent with that of the metamaterial square periodic unit, the side length is 120 mu m, and the thickness t2 is 20 mu m; the material of the middle insulating layer is polytetrafluoroethylene with a dielectric constant of 2.1 (1+i0.0002).
7. The three-band high-Q terahertz metamaterial absorber based on metal split rings according to claim 6, wherein:
the terahertz metamaterial absorber generates resonant frequencies at f1=1.11 THz, f2= 2.256THz, and f3=2.64 THz.
8. The three-band high-Q terahertz metamaterial absorber based on metal split rings as set forth in claim 7, wherein:
the terahertz metamaterial absorber has a harp peak with a high Q value at f2= 2.256THz and f3=2.64 THz.
9. A method for preparing the three-band high Q terahertz metamaterial absorber based on metal split rings as set forth in any one of claims 1 to 6, which is characterized in that:
firstly, preparing a polytetrafluoroethylene substrate with the frequency of 2 cm on high-resistance silicon, and evaporating a layer of metal film on the bottom and the top of the cleaned polytetrafluoroethylene substrate by utilizing a metal evaporation technology;
then spin coating a layer of uniform photoresist on the metal film on the top layer, carrying out ultraviolet exposure by using a positive mask, dissolving the photoresist sol in the shape of the metal resonance layer in a developing solution during development, and etching the gold layer of the area without photoresist protection by using an ion beam etching technology;
finally, the remaining photoresist is removed using alcohol and acetone ultrasound, leaving the absorber metal resonant layer structure.
10. A high-sensitivity qualitative detection device is characterized in that: the three-band high Q value terahertz metamaterial absorber based on the metal split ring as claimed in any one of claims 1-6 is adopted as a detection sensor of the high-sensitivity qualitative detection device, so as to realize qualitative identification of trace or trace substances.
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