Study On Terahertz Metamaterial Devices Based On Dielectric Resonator

Terahertz wave has a wide application prospect in the fields of terahertz imaging and sensing,material characterization,space science and communication due to its special physical properties in the electromagnetic spectrum,such as large bandwidth,low photon energy,good penetration and high spectral resolution.The terahertz technology with many advantages has greatly promoted the development of many terahertz devices,such as filters,absorbers,antennas,modulators,phase shifters,etc.Dielectric resonators can be used in the research of terahertz devices based on dielectric resonators because of their unique advantages,such as small size,easy excitation,good commercial performance,etc.At present,there are not many researches in this area,but with the development of terahertz technology,the frequency is more and more concentrated,and the future terahertz devices tend to develop in the direction of dielectric devices.Therefore,this dissertation carries out the research of terahertz filter and absorber based on dielectric resonator.The main contents are as follows:(1)An all-dielectric multi-band tunable terahertz filter was proposed by filling liquid crystal in hollow cylindrical calcium titanate resonator with flexible polymethylsiloxane as substrate and using multiple resonators.The transmission spectrum of the filter is studied by changing the structure parameters.At the same time,the filtering mechanism is studied from two aspects of effective medium theory and resonator theory.In addition,it is found that resonant frequency can be dynamically adjusted globally or locally by changing the dielectric constant of nematic liquid crystal globally or locally.(2)On the basis of the above work,Based on the above work,a terahertz tunable absorber based on dielectric resonator is proposed.On the basis of the above filter structure,an ideal conductive body layer is added to the device to prevent transmission,and photosensitive silicon layer is constructed between the resonator and the substrate.As the electrical conductivity of photosensitive silicon increases with the increase of light intensity,the absorption rate of the absorber can be tuned under different light conditions.It is found that when the conductivity of photosensitive silicon reaches 1.5×10~4S/m,the wave absorption effect is the best.At the same time,the factors affecting the absorption rate and the absorption mechanism are analyzed and discussed.(3)A flexible and optically transparent all-dielectric broadband metamaterial absorber is realized by combining a water resonator and polyimide container with high dielectric loss.The structure symmetry of the absorber makes it insensitive to the polarization of the incident wave.Moreover,the absorber has a large tolerance to the incident angle of the incident wave for TE and TM polarization modes.Furthermore,the influence of structure shape and geometry size on the absorption performance is studied in detail,and the absorption mechanism of the absorber is discussed from the perspectives of impedance matching and resonator theory.