Study On Enhanced Terahertz Wave Absorption Of Microbolometer Array By Periodic Antenna Structure

Terahertz(THz)wave is an electromagnetic wave between microwave and infrared light with the wavelength between 3mm-0.03?m.THz wave has a variety of unique properties,such as instantaneity,broadband,low energy,penetration,spectral characteristic absorption,etc.THz wave detection technology is one of the key technologies of terahertz wave research and application,which determines the development of terahertz science and technology.Uncooled infrared detectors based on microbolometers can be extended for terahertz wave detection,but the micro-bridge structures of traditional infrared microbolometers have weak absorption in the THz band,resulting in low response and signal-to-noise ratio.Therefore,the micro-bridge structure of the microbolometer needs to be optimized to enhance its absorption of terahertz waves.Surface plasma metamaterials are artificially designed sub-wavelength periodic arrays with adjustable electromagnetic parameters that can achieve perfect absorption in certain specific bands and can be used to improve the absorption of microbolometers in THz band.This paper aims to improve the absorption rate and increase the absorption bandwidth of the micro-bridge structure in the low-frequency THz band.Based on the small-size micro-bridge detection unit of 35×35?m~2,a variety of sub-wavelength periodic metal array structures are designed and integrated.The rigorous coupled wave analysis(RCWA)method and CST software are used for modeling simulation and parameter optimization,and the fabrication and test verification of the detection structures are completed.The absorption characteristics of the surface plasma metamaterial coupled microbridge structures in the THz band are studied.First,a titanium(Ti)disc periodic array antenna is designed and integrated in the microbolometer microbridge array structure.Based on the RCWA method,absorption structure models with different structures of Ti disc array are established,and the THz absorption characteristics are studied.The periodic Ti disc array structure reduces the surface plasmon frequency of metal,excites spoof Surface Plasmons Polaritons in the THz band and achieves resonance enhanced absorption.The resonance absorption frequency is determined by the structural parameters of the Ti disc array such as period and diameter.The thickness of the disc has an important effect on the terahertz wave absorption rate.The resonant cavity structure in the micro-bridge structure can reduce the resonance frequency and enhance the coupling efficiency.The designed micro-bridge detection structure achieves a THz wave constraint that breaks through the diffraction limit with a small Ti disk array period(37?m),and achieves a terahertz wave absorption rate close to 90%at 3.5 THz(wavelength 85.7?m).In the experiment,the sub-wavelength Ti disc periodic array absorption structures with different diameters and periods are prepared.Fourier infrared spectrometer is used to test the THz wave absorption characteristics to verify the theoretical calculation results.The difference between the experimental and theoretical calculation results is compared and analyzed.In addition,this paper integrates periodic antenna absorbing structures based on metal split-rings in the microbolometer micro-bridge structures,and uses CST software for modeling and simulation.The THz wave absorption characteristics of metal split-ring arrays with different coupling structures in microbridge structures are studied.The metal split-ring array with four openings in each ring has the characteristic of polarization insensitivity and significantly reduces the plasma frequency of the absorption structure.The resonance absorption frequency is determined by parameters such as the size of the openings and the width of the metal ring.The use of multiple metal split-rings or a combination of metal split-rings and metal discs can couple absorption peaks to achieve broadband absorption.The absorption structure coupled with the two metal split-rings and a disc forms a broadband absorption band within 4-7 THz,the highest absorption rate in the absorption band reaches 90%,and the lowest absorption rate is 40%.