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-optical half 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 the resonant rings which use the nonlinear rods for dropping operation. The footprint of the designed 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 and the optical power. Also, each input signal is applied to one port while this issue has not been considered in some works. Plane wave expansion and finite difference time domain methods are used to calculate the band diagram and simulation of the optical wave propagation throughout the structure, respectively. The maximum obtained rise time of all states of the proposed device is just about 1.4 ps. Besides, the presented structure is capable of working at the third communication window so it can be matched with optical fiber transmission systems.