Research On Terahertz Filters Based On Metal Micro-structures

As one of the most important functional devices in a terahertz system,terahertz filters have been widely used in terahertz communication systems andterahertz detection systems. Because of the presence of all kind of impact factors inapplied environment such as noise, the overall performance of these terahertz systemsneed to be improved through filtering the useless frequency and noise, leaving onlyuseful terahertz signals by employing terahertz filters. Therefore, researches onterahertz filters gradually attract more and more scientists and scholars all over theworld. In this paper, international and domestic researches on terahertz filters aredescribed at first, then the design of five terahertz filters based on metalmicro-structure are presented and the filtering performance of all these five designedfilters has been analyzed in details.A novel terahertz filter using a kind of flexible materials made from polyimide(PI) as the substrate is proposed. This is a band-pass filter with doublepass-bands, designed on the basis of periodic metal micro-structure, and can becharacterized by its flexibility, light weight and very thin thickness. After simulating,processing and testing this terahertz filter, the obtained results show that the centerfrequency of its first band is0.485THz, the band-pass range is0.435-0.529THz, thebandwidth is94GHz, the simulation result and the experimental result of themaximum transmission coefficient of the filter are88.7%and66.8%, respectively;the center frequency of its second band is0.741THz, the band range is0.703-0.782THz with a bandwidth of79GHz, the simulation result and theexperimental result of the maximum transmission coefficient of the filter are89.2%and59.7%, respectively. The simulation and experimental results meet well.A non-substrate terahertz filter using copper as the material is proposed, withsquare pierced holes arranged in hexagonal plum-shape. The theoretical calculationresult of this terahertz filter shows that its center frequency is0.989THz, theband-pass range is0.826-1.158THz with a3dB band width of0.332THz, and thehighest transmittance coefficient is99.99%; the simulation result of this terahertzfilter obtained by CST software shows that its center frequency is0.985THz, theband-pass range is0.833-1.159THz with a3dB band width of0.326THz, and thehighest transmittance coefficient is99.99%. The theoretical calculation result agrees with the simulation result.A non-substrate terahertz filter using copper as the material is proposed, withsquare pierced holes arranged in hexagonal plum-shape. The theoretical calculationresult of this terahertz filter shows that its center frequency is1.2THz, the band-passrange is1.035-1.334THz with a3dB band width of0.299THz, and the highesttransmittance coefficient is99.99%; the simulation result of this terahertz filterobtained by CST software shows that its center frequency is1.2THz, the band-passrange is1.029-1.324THz with a3dB band width of0.295THz, and the highesttransmittance coefficient is99.99%. The theoretical calculation result agrees with thesimulation result.A non-substrate terahertz filter using copper as the material is proposed, withcircular pierced holes arranged in regular quadrilateral. This terahertz filter has apass-band, the theoretical calculation result shows that its center frequency is0.922THz, the band-pass range is0.831-0.976THz with a3dB band width of0.145THz, and the highest transmittance coefficient is99.99%; the simulation resultof this terahertz filter obtained by CST software shows that its center frequency is0.92THz, the band-pass range is0.832-0.975THz with a3dB band width of0.143THz,and the highest transmittance coefficient is98.37%. The theoretical calculation resultagrees with the simulation result.A non-substrate band-pass terahertz filter using copper as the material isproposed, with square pierced holes arranged in regular quadrilateral. The theoreticalcalculation result of this terahertz filter shows that its center frequency is1.21THz,the band-pass range is1.102-1.318THz with a3dB band width of0.216THz, and thehighest transmittance coefficient is99.99%; the simulation result of this terahertzfilter obtained by CST software shows that its center frequency is1.207THz, theband-pass range is1.090-1.309THz with a3dB band width of0.219THz, and thehighest transmittance coefficient is99.03%. The theoretical calculation result agreeswith the simulation result.Contrast to conventional terahertz filters with hardboard, a terahertz filter basedon metal micro-structure with flexible substrate is proposed. This filter ischaracterized by its small-sized and bendable properties. The proposed fournon-substrate terahertz filters based on metal micro-structure are designed with high transmission coefficient, which can be up to99.99%.