Research And Design Of Metamaterials Based On Heavily Doped Semiconductors

The regulation of electromagnetic waves has always been a research direction that people cannot ignore.The method and application of perfect absorption of electromagnetic waves is one of the important problems in electromagnetic science and technology that need to be solved urgently.Electromagnetic absorbers play a vital role in many applications,such as solar energy collection,thermal-photovoltaic energy conversion,thermal imaging,and emissivity control.At the same time,many studies have shown that electromagnetic devices developed based on metamaterials have considerable application value in the microwave,terahertz,infrared and optical frequency ranges.With the progress and development of micro-nano processing technology,in the frequency range of the terahertz band,electromagnetic devices designed based on the concept of "metamaterials" have found a key breakthrough in the related research on the regulation of terahertz waves.Generally,due to the large number of free electrons on the surface of metal materials,it has become the material of choice for the design of metamaterial devices.However,due to the limitations of the metal itself,the resulting devices often have problems such as narrow working bandwidth,complicated processing,high precision,and uncontrollable response to electromagnetic waves once the device is formed.In response to the existing problems,we used heavily doped semiconductors to study and design the adjustable and broadband absorbers in the terahertz frequency band.The main research contents and progress of this paper are as follows:(1)Using the simple structure of dielectric-doped semiconductor,based on the method of impedance transformation,the dielectric constant of the doped semiconductor is adjusted by doping to achieve perfect absorption of terahertz waves.Based on this research,we designed a broadband absorber and a tunable absorber separately.A broadband absorber formed by a double-layer grating structure by superimposing a dielectric-doped semiconductor layer on top of the basic absorption structure,whose average absorption rate reaches 95% from 1.1 THz to 2 THz;A metal layer containing a geometric pattern pair is added on top,and the function of adjusting the carrier concentration of the semiconductor material is used to realize the function of adjusting the intensity of the absorber and switching the absorption mode.(2)To deal with the problem of narrow working bandwidth,we designed anultra-wideband polarization-insensitive terahertz absorber composed of only heavily doped semiconductors.Using transmission line theory and geometric evolution methods to achieve ultra-wideband absorption from 0.74 to 10 THz,the efficiency exceeds 90%.Analyze its working principle including surface plasmon polariton(SPP)and local surface plasmon resonance(LSP)tuned by non-uniform structure and cavity,and propose the corresponding preparation method.