The Design And Study On Characteristics Of Dual-wavelength THz Filter Based On Compound Lattice Photonic Crystals

As the blank band in the electromagnetic spectrum, THz wave has immense developingpotential and will be extensively used in high speed and ultra wide band wireless communicationsystem in the future. THz filter is one of the key devices in the THz communication system, thecombination of THz technology and photogenic crystal technology provides a solid theoreticalfoundation for the design of the THz filter. With the rapid development of DWDM communicationsystem, the study on THz multi-wavelength filter will have important significance.A new kind of THz dual-wavelength filter （DWF）based on compound square lattice isproposed in this paper. The principles of the photonic crystals filter are firstly analyzed; then theTHz dual-wavelength frequency-selecting filter is designed by combining the point defects and linedefects, the nonlinear material gallium arsenide is filled in the point defect; on this basis, the defectmodes in the point defect of the filter,the transmission spectrum of main waveguide and filteringwaveguide are simulated by using FDTD method; At last, the best optical structural parameters ofthe THz DWF are determined, the various performance indexes of the filter are analyzed. Thesimulation results show that the photonic crystals based on compound square lattice has a broadphotonic band gap, of which the structure can realize two defect modes by one point defect, theTHz DWF designed can select the wavelength62.511μmand65.925μm at the same time, whosefiltering efficiency can reach97.62%, channel isolation is22.57dB, insert loss is0.08dB, the overallresponse time of filter is64ps.On the basis of the THz DWF, by introducing third order nonlinear optical organic materialspolystyrene doped benzofuran in the point defect and controlling the intensity of the pump lightworking for the point defect, a tunable THz dual-wavelength frequency-selecting filter is designed,of which center frequency is adaptively changeable, and then the tunable range of the filter isanalyzed. The simulation results reveal that the filter can realize the function of filteringdual-wavelength, the dynamic tunable range is41.534~41.834μm and74.264~75.164μm, themaximum dynamic migration of the filter is0.9μm, the wavelength filtered out is taper and sheer,the bandwidth is narrow, the study lays a theoretical foundation for the fabrication of tunablenarrow-band DWF with good performance. At last, the application of the THz dual-wavelengthfrequency-selecting filter in the future is discussed.