The Design And Study On Characteristics Of A Four-wavelength THz Filter Based On Photonic Crystal Ring Resonator

As the last frequency window which is not completely understood and used, THz wave is the electromagnetic wave whose frequency ranges from 0.1THz to 10 THz. It is a good broadband information carrier. THz wave has a large bandwidth which can meet the need of ultra wide band communication in the future and it has great developing potential in the field of wireless communication. Photonic crystal has characteristics of photonic band gap and photonic localization and it will must has obvious advantages to use the photonic crystal technology to produce THz wave filter. As one of the basic components of the development of THz technology, THz wave filter has the effect of filtering noise, wavelength selection and gain equalization. So it is significant for the development of THz technology to study the photonic crystal THz filter.A novel type of four-wavelength THz photonic crystal filter based on resonance coupling is proposed in this paper, which contains a square dielectric cylinder in each ring resonator, four scattering dielectric cylinders in each side of the ring resonator and a row of coupling dielectric cylinder in each ring resonator’s up and down. And then, the effect of different structures of ring cavity towards the performance of the filter is analyzed by using the software RSoft7.0. By changing the side length of the internal square dielectric cylinder, the radius of the scattering dielectric cylinder and the radius of the coupling dielectric cylinder, it can filter different wavelengths of THz wave.After a series of optimization, the simulation results show that the bandgap of simple square lattice photonic crystal is larger, the corresponding wavelength is 65.304μm~99.901μm. The fourwavelength THz photonic crystal filter based on resonance coupling can filter four wavelengths.They are 74.813μm( the frequency of 4.001THz), 76.98μm(the frequency of 3.897), 78.168μm(the frequency of 3.809THz) and 78.883μm(the frequency of 3.803THz). The corresponding frequency band width is: 0.0016 THz, 0.00177 THz, 0.00178 THz and 0.0010 THz. The filtering efficiency of the filter is almost above 90%. Insertion loss is very low. Channel isolation is close to 20 d B. Quality factor is all above 200. The frequency band width is about 0.001 THz. Response time is around 2ns.The performance of this filter is excellent. This filter has important meaning for THz technology application.