Research On Terahertz Functional Devices Based On Metamaterials

Terahertz wave is an area of electromagnetic spectrum that has not yet been fully devel-oped,with good properties,such as high safety and low energy consumption.It also has wide application prospects in the fields of medicine,imaging,nondestructive testing,safety inspec-tion and communication.However,the terahertz functional device is developed slowly due to the lack of materials in nature that can provide direct electromagnetic responses to terahertz frequencies.Metamaterials are artificially designed materials with unique electromagnetic properties.By reasonably designing their structures,those properties that natural materials do not possess can be realized.The metamaterial brings hope for the research and development of terahertz functional devices as well.Based on the characteristics of metamaterials,we study the filters and modulators in terahertz functional devices in this paper.The main work is as follows:Based on traditional metamaterial resonant cells(Type U&T),we designed Single-band bandstop filter(Type U&T)on polyester substrates using metal-dielectric-metal structure.We use HFSS software to simulate and analyze the resonance principle and the influence of main parameters on transmission characteristics.On this basis,we combined the Type U and T to design dual-band bandstop filter(Type TU)and triple-band one(Type TUU).According to the actual needs,the structural size can be reasonably designed to achieve the filtering of the re-quired frequency band.In addition,the complementary structure of the above band-stop filter is analyzed separately.The results show that most complementary structures can achieve good performance of band-pass filters.Based on the U-shape metamaterial structure,combined with the Bimorph beam theory,a dynamic tunable terahertz filter is designed with the two vertical arms of the U-shape in-stalled as cantilever beam structure.The tuning range of resonant frequency of 0.22THz is realized by temperature control;Based on that,a double-sided dynamic tunable filter is de-signed,which improved the edge feature,stopband width,inner inhibiting capability,and thus optimizing the filtering effect compared with the single-sided filter.Moreover,the cantilever tunable structure has a good application prospect.A triple-band Terahertz modulator is designed,which is based on the horizontal asym-metric triple resonance unit with a simple structure.And the transmission coefficient at the resonance frequency is extremely small.Semiconductor silicon is filled inside unit gap and the modulation of the three bands can be achieved by light control.The modulation depths at the three resonance points can reach 88.7%,68.1%,and 86.0%,respectively;We improved the horizontal asymmetric structure and designed an improved triple-band modulator modula-tor which composed of three open rings of different sizes.Of the device,the modulation depth at the three resonant frequency points can reach 87.9%,90.0%and 83.3%respectively.In ad-dition,the independence between the three bands is better and the overall performance is im-proved.Filling the semiconductor silicon in the different gaps can achieve the modulation of triple-band to single or dual-band respectively.A modulator is designed with vertical coupling structure and the structure is constituted by two parts.Modulation of the resonant frequency and amplitude can be achieved by adjust-ing the distance between the two parts.The relevance of the distance and resonance frequency can be calculated by the analysis of its equivalent circuit,and thus the fitted curve is obtained with the fitted factor found.