Research On Terahertz Absorber Based On Silicon Material

Terahertz technology is widely used in wireless communication,biochemical sensing and nondestructive imaging.A major research direction is the construction of compact and practical terahertz systems,which rely on the development of miniaturized components such as signal sources,detectors,modulators,switches and absorbers.Advances in electromagnetic metamaterials have greatly improved our ability to manipulate terahertz waves,which provides a significant opportunity to build practical terahertz devices.The terahertz metamaterial perfect absorber has attracted a great deal of interest for its potential applications in physics,medicine,materials science and chemistry.In recent years,silicon-based semiconductor materials that can be regulated by infrared light have been introduced into the absorber design for the construction of metamaterial absorbers using single materials and three-dimensional geometry.This paper takes terahertz absorbers as the research object,proposes three kinds of metamaterial absorbers based on silicon materials,and analyzes the absorption performance of the structures.The main research contents are as follows:1.An inverted conical hole broadband absorber based on doped silicon is proposed.The structure is composed of an inverted conical hole array etched on the doped silicon substrate and silicon dioxide（Si O₂）covered on the top layer.With a relatively simple all-medium structure,high absorptivity of over 90%in the range of1.38-4.00 THz is achieved.In this paper,the absorption properties of the structure are described in detail,and the absorption mechanism is analyzed.2.An Optically switchable ultra-broadband terahertz perfect absorption in doped superlattice photonic-crystal silicon is proposed.By superimposing different lattice constants to support different cavity modes,the absorption frequency band is widened to achieve ultra-broadband absorption between 1.03-5.00 THz.The mechanism of ultra-broadband absorption was analyzed from the perspective of photonic crystal structure,the contribution of each part to the absorption,the resonance mode at the absorption peak and the optimization process of structural parameters were analyzed.The influence of infrared light on the carrier concentration in doped silicon was modeled,and the absorption under different optical pumps was simulated.With a modulation depth of more than 70%in the frequency range of 1.03THz-1.65THz,the switch of the absorption on and off is realized.3.A tunable and switchable terahertz absorber based on photoconductive silicon and vanadium dioxide（VO₂）is proposed.The difunctional modulation of absorption switch and bandwidth conversion is realized by using silicon-based semiconductor as the resonant cell material.The absorption spectra of silicon excited by different pump light and at different temperatures are simulated.By means of the electromagnetic field distribution of the absorption peak and valley values,combined with the theory of relative impedance and the theory of multiple interference,the conversion of the harmonic absorption bandwidth of the absorption efficiency is analyzed,and the compatibility of the structure to the polarization mode and the Angle of incident wave is explored.