Research On Broadband Terahertz Absorber

Terahertz(THz)technology has shown its distinctive application in materials,chemistry,biomedicine,security and other fields.However,these applications are severely restricted due to the lack of effective THz detectors.An effective way to realize broadband THz detector with high sensitivity and fast response is ultra-thin broadband THz absorber.But it still faces many challenges to obtain ultra-thin broadband THz absorber.To realize the goal of ultra-thin broadband THz absorber,my research work focuses on the following aspects:(1)Participated in the research on broadband THz time-domain spectroscopy(THz-TDS)system used to measure and characterize the THz functional materials such as THz absorbers and THz modulators.Generation of THz wave is optimized by single-shot TDS detection technique and a broadband THz-TDS system is established.Based on air coherent detection technique,this system reaches the wavelength response range of 0.1-10 THz with the peak SNR of over 40 dB.(2)A ultra-thin broadband THz absorber based on a structure of periodic array of nickel pillars combined with silicon.is designed and simulated.By optimizing the parameters of the structure,an absorber with thickness less than 15 ?m and more than 80% absorption in the 2.4-10 THz range is obtained;(3)On the basis of above THz absorber,another ultra-thin broadband THz absorber based on the periodic array structure of nickel-silicon laminated pillars.is further designed and simulated.By optimizing the parameters of the structure,the absorber with thickness less than 17 ?m and more than 80% average absorption in the 1.45-7.92 THz range is achieved;(4)A photoinduced fast active THz wave modulator based on vanadium dioxide film combined with metamaterial is designed and simulated.It is found that the modulated THz frequency can be adjusted by changing the parameters of periodic structure.Two photoinduced modulators were proposed,one with modulation depth of 56% and 71% at 2.93 and 3.28 THz respectively,the other with modulation depth of 82% and 71% at 2 and 2.69 THz,respectively.These modulators combining with high sensitivity THz detectors based on broadband THz absorbers with high absorption efficiency,can be used in fast active THz wave detection.(5)To overcome the fabrication difficulty of the cross-scale functional materials between nanometer and submillimeter with high depth-to-width ratio in THz band by existing dry or wet etching techniques,a photolithography based on micro-lens array focusing femtosecond laser beam is proposed.The system is designed and is being established.The system is expected to be used for the subsequent fabrication of cross-scale THz functional materials and devices including the THz absorbers and modulators.