CN104070731B - A kind of artificial Terahertz absorbing material of high-performance broadband and method for designing thereof - Google Patents
A kind of artificial Terahertz absorbing material of high-performance broadband and method for designing thereof Download PDFInfo
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- CN104070731B CN104070731B CN201410294724.1A CN201410294724A CN104070731B CN 104070731 B CN104070731 B CN 104070731B CN 201410294724 A CN201410294724 A CN 201410294724A CN 104070731 B CN104070731 B CN 104070731B
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Abstract
The invention discloses the artificial Terahertz absorbing material of a kind of high-performance broadband and method for designing thereof. The present invention is made up of multiple material cell, and each material cell comprises chromium and photoresist SU-8; Concrete: in substrate, be provided with layer of metal chromium film, this layer of crome metal film is as anti-transmission layer; On crome metal film, the square array of photoresist SU-8 and chromium alternately superposes and forms pyramid shape from bottom to top; The square array of described chromium has five layers, and the thickness of every layer is 200nm, its square array length of side regular dwindling successively from bottom to top, from bottom to top successively: 70 μ m, 66 μ m, 62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μ m; The material cell cycle is 95 μ m; The present invention has realized the large bandwidth assimilation effect of terahertz wave band; Break through the process limitations that traditional super material is made, completed the designing and making of the three-dimensional artificial special medium of terahertz wave band.
Description
Technical field
The invention belongs to terahertz wave band wireless energy transfer field, relate in particular to the artificial Terahertz of a kind of high-performance broadbandAbsorbing material and method for designing thereof.
Background technology
THz wave refer to frequency at 0.1THz to the electromagnetic wave within the scope of 10THz, wavelength about 0.03mm to 3mm itBetween, between microwave and infrared waves. THz ripple has the feature that a lot of microwaves and light wave do not possess, for example THz photon energyLow, only have several electron-volts, can not damage detection material; Most nonmetal non-polar material is to THz radiation absorptionLess, make it can be for detection of material internal information; THz clock only comprises the electromagnetic viscosimeter in several cycles, singleThe frequency band of pulse can cover the scope of GHz to tens THz, and vibration and the rotational energy level of a lot of large biological molecules, are partly led at dielectricThe phonon vibration energy level of body, superconductor etc. is all in the wavelength band of THz. At present mostly by thinking that dry Detection Techniques obtainThe realtime power of THz because THz pulse has very high peak power, has very high signal to noise ratio in time-domain spectroscopy system. ByIn possessing above-mentioned advantage, Terahertz Technology can be brought into play huge effect in fields such as safety check, sensing and imagings, has been subject in recent yearsResearchers show great attention to, and many new units that are operated in terahertz wave band also arise at the historic moment.
Absorbing material is the material that can have to a certain frequency or frequency range electromagnetic wave strong absorption, can adopt for solar energyCollect or shield a certain specific wavelength or wave band, having wide range of applications. There is scientist to design and utilized super material at terahertzThe material that hereby the efficient arrowband of wave band multi-angle absorbs, but be limited to the manufacture difficulty of three-dimensional super material, and two-dimentional super material can onlyRealize arrowband and absorb, cannot realize the effect of broadband suction ripple.
Summary of the invention
The object of the invention is can not realize for current material the defect of the large wide band absorption of terahertz wave band, provide a kind ofThe artificial Terahertz absorbing material of high-performance broadband and method for designing thereof.
The artificial Terahertz absorbing material of a kind of high-performance broadband, is made up of multiple material cell, and each material cell comprisesChromium and photoresist SU-8; Concrete: in substrate, be provided with layer of metal chromium film, this layer of crome metal film is as anti-transmission layer; ?On crome metal film, the square array of photoresist SU-8 and chromium alternately superposes and forms pyramid shape from bottom to top; The side of described chromiumBlock array has five layers, and the thickness of every layer is 200nm, its square array length of side regular dwindling successively from bottom to top, from lower andOn successively: 70 μ m, 66 μ m, 62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μ m; Material cell weekPhase is 95 μ m;
Near the dielectric coefficient of described photoresist photoresist SU8 1THz frequency is about 2.79-0.31i, metal materialMagnetic conductivity σ=8 × 10 of chromium (chromium)6s/m。
A method for designing for the artificial Terahertz absorbing material of high-performance broadband, specifically comprises the steps:
Step 1. is according to Effective medium theory: Metamaterials(MMs) performance by magnetic conductivity μ and dielectric coefficient ε certainlyFixed, and reflectivity R (ω) and transmissivity T (ω) depend on refractive index n and wave impedance Ω, all with magnetic conductivity μ and dielectric coefficient εRelevant. Therefore, can obtain needed transmission and reflecting effect by the magnetic conductivity μ and the dielectric coefficient ε that regulate MMs.
By the S parameter of analog computation material, compriseWithThereby, calculate transmission parametersAnd reflection parameters; Wherein
，
Absorption parameterObtain by following formula:
。
And having under the condition of the anti-transmission layer of metal transmission coefficientBe 0, that is:
。
Therefore, absorption coefficientCan be by regulating magnetic conductivity μ and dielectric coefficient ε to modulate. MetamaterialsCan be by regulating the shape and size of micro-structural to determine its magnetic conductivity μ and dielectric coefficient ε under certain frequency, therefore oneDetermine can realize absorption coefficient under frequencyModulation.
Step 2. is made material, specific as follows:
Sputter layer of metal chromium film in substrate, this layer of crome metal film is as anti-transmission layer; On crome metal film, photoresistThe square array of SU-8 and chromium film alternately superposes and forms pyramid shape from bottom to top; Every layer photoetching glue SU-8 make by spin coating andBe heating and curing, the square array of every layer of chromium film has been peeled off by photoetching and sputter; The square array of described chromium film hasFive layers, and the thickness of every layer is 200nm, its square array length of side regular dwindling successively from bottom to top, from bottom to top successively:70 μ m, 66 μ m, 62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μ m;
Have and experiment showed, that the metal film structures of individual layer can realize the height absorption of some frequencies, by regulating metalThe size of membrane structure and cycle can be modulated the frequency of absorption, and the pyramidal metal film structures in board design from top to bottomSize gradual change, their absorption frequency is contiguous, and stack can realize the efficient absorption in large broadband.
Beneficial effect of the present invention is as follows:
(1) the present invention can realize the large wide band absorption under terahertz wave band. The absorbing material of terahertz wave band was normal in the pastBe often arrowband, at present the full width at half maximum (FWHM) coefficient (FWHM) of the best broadband absorbing material of effect also only has 55%, and the present invention is to thisOne parameter has been done very large raising, and its full width at half maximum (FWHM) coefficient (FWHM) has exceeded 100%.
(2) method for designing in the present invention can realize adjustable wide band absorption effect. By regulating the size of micro-structuralAnd the cycle, absorption frequency corresponding to each structure also can change, and according to method for designing of the present invention, can design differenceWide band absorption material under frequency.
(3) absorbing material designing in the present invention has ultra-thin feature. The electromagnetic wavelength of 1THz is about 300 μ m, andThe absorbing material gross thickness designing in the present invention is about 21 μ m, and its thickness is less than 1/10th of corresponding wavelength.
Brief description of the drawings
Fig. 1 is the simulation top view (2*2 cell schematics) of Terahertz broadband absorbing material.
Fig. 2 is the profile of single Terahertz absorbing material unit, and wherein black part is divided into metal structure, between metal structureWhite portion be photoresist SU-8.
Fig. 3 is material cell TE pattern mould under different incidence angles in simulation softward (CSTMicrowavestudio)Intend absorption spectra.
Fig. 4 is material cell TM pattern mould under different incidence angles in simulation softward (CSTMicrowavestudio)Intend absorption spectra.
Fig. 5 is the absorbing state of single-layer metal structure to a certain fixed frequency (0.8THz), and red line and blue line represent respectivelyThe absorptivity of simulation and actual measurement.
Fig. 6 is in simulation under different frequency, the distribution schematic diagram of Electric and magnetic fields in cellular construction.
Fig. 7 is the absorption spectra of laboratory sample under different incidence angles degree.
Fig. 8 is sample observation figure under the microscope, and wherein right figure is respectively focal plane up and down at top level structure and bottom knotImage when structure.
Detailed description of the invention
Below in conjunction with drawings and Examples, the invention will be further described.
As shown in Figure 1 and Figure 2, the artificial Terahertz absorbing material of a kind of high-performance broadband, is made up of multiple material cell, everyIndividual material cell comprises chromium and photoresist SU-8; Concrete: in substrate, be provided with layer of metal chromium film, this layer of crome metal film doneFor anti-transmission layer; On crome metal film, the square array of photoresist SU-8 and chromium alternately superposes and forms pyramid shape from bottom to top;The square array of described chromium has five layers, and the thickness of every layer is 200nm, and its square array length of side is regular successively from bottom to topDwindle, from bottom to top successively: 70 μ m, 66 μ m, 62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μM; The material cell cycle is 95 μ m;
Near the dielectric coefficient of described photoresist photoresist SU-8 1THz frequency is about 2.79-0.31i, metal materialMagnetic conductivity σ=8 × 10 of chromium (chromium)6s/m。
A method for designing for the artificial Terahertz absorbing material of high-performance broadband, specifically comprises the steps:
Step 1. is according to Effective medium theory: Metamaterials(MMs) performance by magnetic conductivity μ and dielectric coefficient ε certainlyFixed, and reflectivity R (ω) and transmissivity T (ω) depend on refractive index n and wave impedance Ω, all with magnetic conductivity μ and dielectric coefficient εRelevant. Therefore, can obtain needed transmission and reflecting effect by the magnetic conductivity μ and the dielectric coefficient ε that regulate MMs.
By the S parameter of analog computation material, compriseWithThereby, calculate transmission parametersAnd reflection parameters; Wherein
，
Absorption parameterObtain by following formula:
。
And having under the condition of the anti-transmission layer of metal transmission coefficientBe 0, that is:
。
Therefore, absorption coefficientCan be by regulating magnetic conductivity μ and dielectric coefficient ε to modulate. MetamaterialsCan be by regulating the shape and size of micro-structural to determine its magnetic conductivity μ and dielectric coefficient ε under certain frequency, therefore oneDetermine can realize absorption coefficient under frequencyModulation.
Step 2. is made material, specific as follows:
Sputter layer of metal chromium film in substrate, this layer of crome metal film is as anti-transmission layer; On crome metal film, photoresistThe square array of SU-8 and chromium alternately superposes and forms pyramid shape from bottom to top; Every layer photoetching glue SU-8 makes by spin coating and addsHeat cure completes, and the square array of every layer of chromium has been peeled off by photoetching and sputter; The square array of described chromium has five layers, andThe thickness of every layer is 200nm, its square array length of side regular dwindling successively from bottom to top, from bottom to top successively: 70 μ m,66 μ m, 62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μ m;
Have and experiment showed, that the metal film structures of individual layer can realize the height absorption of some frequencies, by regulating metalThe size of membrane structure and cycle can be modulated the frequency of absorption, and the pyramidal metal film structures in board design from top to bottomSize gradual change, their absorption frequency is contiguous, and stack can realize the efficient absorption in large broadband. As shown in accompanying drawing 3, Fig. 4, individual layerMetal film structures at simulation softward CSTmicrowavestudio Imitating, can realize between 0.9 to 1.6THz and reachingTo more than 80% absorptivity.
Referring to accompanying drawing 3, Fig. 4, contrast TE and TM ripple absorption intensity in the time of multi-angle incident, can find, in the present invention, establishesThe absorbent structure of meter does not rely on incident angle and pattern, when maximum incident angle reaches 70 degree, still can keep high and absorbRate and large bandwidth.
Laboratory sample above completes by spin-on dielectrics and making metal micro structure at silicon chip (transparent at terahertz wave band), materialMaterial thickness approximately 21 μ m, be less than 1THz frequency electromagnetic wavelength (300 μ m) 1/10th.
Actual measured results: in centre wavelength, reflectivity when vertical incidence≤-15dB, absorption spectra when vertical incidenceFWHM(full width at half maximum (FWHM)) reach 100%(with respect to centre wavelength), realize more than 80% to the frequency range of 2.3THz at 0.7THzAbsorb. Be limited to taking measurement of an angle of terahertz time-domain system, the oblique incidence Optical thin film of sample only proceeds to 40 degree, arrives 0Under the different angles condition of incidence of 40 degree, sample has all kept very high Absorber Bandwidth, and absorption when different angles oblique incidenceRate and vertical incidence are suitable.
The broadband absorbing material of terahertz wave band has also successfully been made in experimental design, has not only obtained in design large broadbandWave-absorbing effect, also broken through the bottleneck of MMs micro-nano processing technology, realized the preparation of the three-dimensional MMs of terahertz wave band.
Embodiment 1
The wave-absorbing effect of the artificial Terahertz absorbing material of high-performance broadband
According to above-mentioned method for designing, on silicon chip, complete the making of sample, referring to accompanying drawing 6, Fig. 7 and Fig. 8, alignment precisionBetter, by regulating microscopical focal length can find out that the metal structure of different size is positioned at different height, and layer with layerStructure is in same position substantially, substantially can reach the pyramidal effect in design.
The absorbing property test result of sample under terahertz time-domain system (TDSZomega-Z3) be as illustration 5,0.7THz has realized more than 80% absorption to the frequency range of 2.3THz, in centre wavelength, and reflectivity when vertical incidence≤-15dB,The FWHM(full width at half maximum (FWHM) of absorption spectra when vertical incidence) reach 100%(with respect to centre wavelength), under the incidence angle of 0 to 40 degreeCan keep very high Absorber Bandwidth, performance and vertical incidence are suitable.
In addition,, by changing the size of unit cycle and metal structure, corresponding absorption frequency also can be adjusted. AlsoIn other words, the method for designing in the present invention not only can realize the existing large bandwidth assimilation effect of sample, can also be by changingParameter obtains the electromagnetic high-performance broadband of other frequencies and absorbs.
Claims (2)
1. the artificial Terahertz absorbing material of high-performance broadband, is characterized in that being made up of multiple material cell each materialUnit comprises chromium and photoresist SU-8; Concrete: in substrate, be provided with layer of metal chromium film, this layer of crome metal film is as permeation-proofPenetrate layer; On crome metal film, the square array of photoresist SU-8 and chromium alternately superposes and forms pyramid shape from bottom to top; DescribedThe square array of chromium has five layers, and the thickness of every layer is 200nm, its square array length of side regular dwindling successively from bottom to top,From bottom to top successively: 70 μ m, 66 μ m, 62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μ m; MaterialThe unit cycle is 95 μ m; Near the dielectric coefficient of described photoresist SU-8 1THz frequency is 2.79-0.31, metal material chromiumMagnetic conductivity σ=8 × 106s/m。
2. the method for designing of the artificial Terahertz absorbing material of a kind of high-performance broadband as claimed in claim 1, is characterized in thatComprise the steps:
Step 1. is determined by magnetic conductivity μ and dielectric coefficient ε according to the performance of Effective medium theory: Metamaterials, and reflectsParameters R (ω) and transmission parameters T (ω) depend on refractive index n and wave impedance Ω, all relevant with dielectric coefficient ε to magnetic conductivity μ; CauseThis, can obtain needed transmission and reflecting effect by the magnetic conductivity μ and the dielectric coefficient ε that regulate Metamaterials;
By the S parameter of analog computation material, S parameter comprises S21 (ω) and S11 (ω), thereby calculates transmission parameters T (ω)With reflection parameters R (ω); Wherein
T(ω)＝|S21(ω)|2,R(ω)＝|S11(ω)|2；
Absorption parameter A (ω) obtains by following formula:
T(ω)+R(ω)+A(ω)＝1；
And having under the condition of the anti-transmission layer of metal, transmission parameters T (ω) is 0, that is:
A(ω)＝1-R(ω)＝1-|S11(ω)|2；
Absorption parameter A (ω) can be by regulating magnetic conductivity μ and dielectric coefficient ε to modulate; Metamaterials can be by regulatingThe shape and size of micro-structural are determined its magnetic conductivity μ and dielectric coefficient ε under certain frequency;
Step 2. is made material, specific as follows:
Sputter layer of metal chromium film in substrate, this layer of crome metal film is as anti-transmission layer; On crome metal film, photoresist SU-8Alternately superpose and form pyramid shape from bottom to top with the square array of chromium; Every layer photoetching glue SU-8 makes by spin coating and adds thermosettingChange completes, and the square array of every layer of chromium has been peeled off by photoetching and sputter; The square array of described chromium has five layers, and every layerThickness be 200nm, its square array length of side regular dwindling successively from bottom to top, from bottom to top successively: 70 μ m, 66 μ m,62 μ m, 58 μ m and 54 μ m; The thickness of described every layer photoetching glue SU-8 is 4 μ m.
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| CN104466427A (en) * | 2014-12-24 | 2015-03-25 | 中国计量学院 | Efficient broadband terahertz wave absorption device based on highly-doped silicon materials |
| CN104714218B (en) * | 2015-02-10 | 2017-05-10 | 枣庄学院 | Terahertz code metasurface for wide-frequency-band radar scattering cross section reduction |
| CN104774472A (en) * | 2015-04-10 | 2015-07-15 | 大连东信微波技术有限公司 | Ultra-wideband terahertz wave-absorbing material |
| CN104767012A (en) * | 2015-04-24 | 2015-07-08 | 江苏科技大学 | Frequency selective surface |
| CN105629463B (en) * | 2016-01-20 | 2017-11-24 | 浙江大学 | A kind of design method for the circularly polarized light separator for surpassing surface based on artificial micro-structure |
| CN106785468B (en) * | 2017-01-11 | 2019-10-18 | 中国人民解放军空军工程大学 | A kind of suction wave-wave transparent integration Meta Materials |
| CN110081826B (en) * | 2019-04-29 | 2021-03-02 | 中国矿业大学 | Terahertz technology-based thermal barrier coating ceramic layer thickness measurement method |
| CN111585034B (en) * | 2020-06-02 | 2021-09-07 | 中国人民解放军军事科学院国防科技创新研究院 | Design method of impedance matching type metamaterial |
| CN112255715B (en) * | 2020-10-23 | 2021-12-03 | 江南大学 | Method for realizing broadband light absorption enhancement based on ultrathin metal film and wave absorbing device |
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