Design and numerical analysis of 4-inputs all-optical XOR gate in optical waveguides

In this article, a novel design of a 4-input all-optical XOR logic gate based on the principle of linear optics has been proposed. To design the proposed device, two-dimensional (2D) rods in air photonic crystal (PC) structure (where rods are arranged in a triangular lattice) has been chosen. A 340 mu m2 structure is taken where the radius of the silicon rods and the lattice constant of the structure have been selected as 120 nm and 600 nm respectively. To control the phase of the propagating optical waves through the waveguides, 3 Pi-phase shifters have been utilized within the waveguides. Plane-wave expansion (PWE) method and finite difference time domain (FDTD) algorithm have been utilized to analyze the energy band diagram of the basic structure and to observe the electric field propagation profile of the device respectively. However, in the absence of optical nonlinearity, the proposed XOR gate has the ability to function in low-power input signals and provides a high response time of 0.57 picoseconds and a data rate of 660 Gbps (in the worst-case scenario). Moreover, the on-off contrast ratio of the proposed device has also been measured as 14.84 dB. Owing to its simple structural design and high-performance metrics altogether proves the proposed device is suitable as a component of future optical arithmetic and logic units (ALUs).