All-optical 8-QAM signal demodulator based on 2D photonic crystals

Abstract

This paper proposes a novel two-dimensional photonic crystal-based 8-QAM signal demodulator with a unique combination of nonlinear cavities and line defects. It consists of chalcogenide cylinders arranged in a square lattice against an air background. The proposed structure enables 8-QAM signal demodulation in an all-optical environment. Instead of the photoelectric conversion process, the structure converts the communication signal into the corresponding optical logic signal by distinguishing the intensity and phase differences of the incident light. The performances are analyzed and calculated by using the finite difference time-domain method and the plane wave expansion method. Simulation results illustrate that the maximum response time of the demodulator is 1.067 ps, and the minimum light contrast ratio is 4.39 dB.