Design and Simulation of Photonic Crystal Based Optical Filter of Specified Flat-top Pass Bandwidth

Abstract

In this paper, the bandwidth of a photonic crystal (PhC) based band pass filter is tailored to accommodate a carrier wavelength in presence of maximum shifts specified for a coarse wavelength division multiplexing (CWDM) system. For desired tailoring we introduce defects, whose distribution is crucial in determining flatness of the filter pass band. To analyze filter performance, transfer matrix method is employed, and a condition guiding distribution of defects within the structure is derived. Design parameters of proposed model are optimized through simulation using MATLAB. To validate the MATLAB simulation results for practical implementation, the filter is further simulated by CST MW Studio. Both simulation results show close agreement with each other. According to ITU-T Recommendation G.694.2 for a CWDM system, a channel wavelength may undergo a maximum shift of ±(6–7) nm. The flat top pass band of our proposed filter can support such channels. The most striking feature of the filter is that it is expected to perform satisfactorily, even if during fabrication, the dimension of individual unit cell deviates from its estimated value. The choice of silicon and silicon dioxide as PhC materials provides easy realization of integrated filter structure.