Analysis of tunable multiple-filtering property in a photonic crystal containing strongly extrinsic semiconductor

In this work, we analyze the tunable multiple-filtering property at infrared frequency in a finite semiconductor-dielectric photonic crystal (SDPC), (AB) ^P A, where A is a strongly extrinsic semiconductor, n-type germanium (n-Ge). B is a dielectric material, and P is the number of periods. It is found that multiple filtering phenomenon can be obtained in the region where the permittivity of n-Ge is negative. The number of resonant peaks is found to be equal to P. With the permittivity of n-Ge being concentration-dependent, these resonant peaks can be shifted as a function of impurity concentration. The analysis indicates that such an SDPC can work as a tunable multichannel filter which is of technical use for the semiconductor applications in optical communications.