Characteristics And Application Of All-dielectric Metasurface Terahertz Absorber

Artificial electromagnetic metamaterials have great application value in military,medical,imaging and other fields because of their ability to achieve electromagnetic response characteristics that are not achievable by ordinary materials in nature.They have attracted widespread attention.The singular characteristics of metamaterial absorbers are obtained from artificially designed structures rather than directly from their constituent materials.At present,most metamaterial absorbers composed of metaldielectric-metal three-dimensional structures have single-band or multi-band absorption performance by designing different structures on the upper metal,which have the characteristics of narrow bandwidth and high quality factor.However,the characteristics of metal itself are easy to oxidize,corrode,and have high loss,which limits its application.As a new research hotspot,the all-dielectric metasurface absorber has a simpler two-dimensional structure,more stable performance,and smaller ohmic losses value.This paper uses all-dielectric silicon materials to design three metasurface absorbers with different structures to achieve single-band,dual-band,and broadband absorption in the terahertz band,respectively.All three types of absorbers are made of N-type highly doped silicon through lithography and dry etching processes to achieve perfect absorption in the terahertz band.The experimental and simulation results show that the absorption of single-band,dual-band and broadband can reach more than 99%.The perfect absorption mechanism of the absorber is explained by the surface plasmon theory.Further research on the modulation effect of geometric parameters on the absorber shows that as the geometric parameters of the absorber change,the resonance position and amplitude of the absorber change significantly.At the same time,according to the characteristics of the absorber being more sensitive to the external environment,the absorption spectrum changes of the absorber under light conditions are studied.The results show that as the power of the pump light increases,the absorber exhibits regular changes in amplitude and resonance frequency position.When the power of the pump light is higher,the absorption amplitude of the absorber is lower,and the resonance frequency is red-shifted accordingly.In order to prove the application value of all-dielectric absorber in sensing,two types pesticides,which have different concentrations of chlorpyrifos and herbicide(2,4-Dichlorophenoxyacetic acid),were deposited on the absorber.The change of the amplitude and frequency position analyzes the change of its concentration.The obtained results show that the narrower the absorption bandwidth of the absorber,the higher the corresponding Q value,and the more sensitive the absorber can detect the change of pesticide concentration.It is confirmed that the all-dielectric metasurface absorber proposed in this paper has important application value in biochemical detection and other aspects.