Ultra-Fast All-Optical Half Subtractor Based on Photonic Crystal Ring Resonators

In this paper, we aim to design and propose a novel structure for all-opticalhalf subtractor based on the photonic crystal. The structure includes two optical switches,one power splitter, and one power combiner. The optical switches are made of theresonant rings which use the nonlinear rods for dropping operation. The footprint of thedesigned structure is about 602 μm2 that is more compact than one in most works.Furthermore, despite some works, the input signals are the same in the phase angle andthe optical power. Also, each input signal is applied to one port while this issue has notbeen considered in some works. Plane wave expansion and finite difference time domainmethods are used to calculate the band diagram and simulation of the optical wavepropagation throughout the structure, respectively. The maximum obtained rise time ofall states of the proposed device is just about 1.4 ps. Besides, the presented structure iscapable of working at the third communication window so it can be matched with opticalfiber transmission systems.