New Two Dimensional Photonic Filters With A Circular Resonant Cavity

Optical filters,which play a vital role in acquiring,transmitting, processing and switching signals,are key components to access signals on a particular channel or multiple channels in wavelength division multiplexed optical communication system. However,the classic filters whose size varies from a few millimeters to a few centimeters have difficulties to achieve intensive,integrated WDM system.But because of its unique properties,the appearance of photonic crystals provide a new solution to achieve such intensive,high Q realization of photonic devices. So far, although we have achieved a wide range of various photonic crystal filters, these photonic crystal filters still have some deficiencies such as wavelength adjusting weak, low transmittance.It needs deeply study to design highly effective, tunable and multi-channel optical crystal filters. In this paper, novel ring resonator filters have been designed to make up these deficiencies, and they are not only adjustable, but also the transmittance can be up to 90%, which would have a broader application in wavelength division multiplexing system.Firstly,based on the research of the composed elements of photonic crystal including the lattice structure,the radius and refractive index of the dielectric cylinder,the radius of the air column and the refractive index of the matrix,a new ring resonator structure is designed in the two dimension triangular lattice circle rods PC.Secondly,by using Finite Difference Time Domain (FDTD) method,our numerical results of the multi-channel filter who is based on a single ring resonator,show that backward dropping of the photonic crystal filters can be achieved in the multi-channel filter in the condition of the output efficiency reaches 96%. Meanwhile, the effects of the scattering media column, the radius of the coupling rods, the dielectric constant of the overall rods and the internal rods on the transmission characteristics of the filter are also discussed. The results show that scattering media column is conducive to improving the transmission efficiency and the others help the filter achieves tuning. The method provides a very good reference for design and manufacture highly efficient, tunable multi-channel photonic crystal filter.Finally, this paper takes advantage of the new type of ring resonator to designe two bicyclic multi-channel filters. One structure is that the two ring resonators are placed parallelly in the vertical direction.And the other is the two rings are at a distance of 2a in the x-axis direction.On the other hand, each output port normalized transmission spectra of the multi-channel filter is obtained by simulation. Forward dropping of the photonic crystal filters can be achieved in the bicyclic multi-channel filters in the condition of the output efficiency are 91.6% and 98.6% respectively. And the design of the ring structure is easy to get the different wavelengths of light by changing the symmetry of the two rings. This provides a new method for obtaining different wavelengths of light.