The Study On Four-wavelength THz Wave Modulator Base On Compound Lattice Photonic Crystal

THz communication has important application in high speed and ultra broadband wireless access network. It has been the international hot research area. THz wave modulator is one of the key devices in THz communication system, photonic crystal has some important characteristics, such as photonic band gap and the photon local area, so the application of the photonic crystal technology to the THz wave modulator has an obvious superiority. WDM can expand THz communication system’s capacity, therefore, the study on the multi-wavelength modulator has a significance value.The modulating theory of photonic crystal THz wave modulator is analyzed primarily in the paper, namely photonic band gap migration and the defect mode change. Then a kind of compound lattice photonic crystal four-wavelength THz wave modulator is designed. Compound lattice photonic crystal is used in modulator where a line defect and two point defects have been introduced. The two points defects are circular point defect and square point defect respectively. The light-controlled modulator is designed through introducing GaAs as the material being filled in the point defect, and one point defect should have two different defect modes in compound lattice photonic crystal. Therefore, we can use two point defects to achieve the four-wavelength THz wave modulation. Three kinds of structure of the compound lattice photonic crystal modulator have been simulated respectively through taking advantage of FULL WAVE software. With incidence of single wavelength, double wavelengths and four wavelengths, the performance parameters have been discussed respective, including on-off state of time domain response, steady state modulus energy distribution, extinction ratio and curing rate. The simulating results show that insertion loss is about0.2dB and extinction ratio is about28dB under the circumstances of single wavelength incident; insertion loss is about0.23dB and extinction ratio is about15dB under the circumstances of double wavelength incident; insertion loss is about0.18dB and extinction ratio is about15dB under the circumstances of four wavelength incident. Finally, the application of four wavelength THz wave modulator in the THz wave communication system is discussed.