A novel design of all-optical half adder using a linear defect in a square lattice rod-based photonic crystal microstructure

In this paper, we propose an all-optical high-speed half adder based on linear defects in a photonic crystal (PhC) structure composed of silicon rods. The proper design of half adder results in no need to increase the intensity of the input optical signal for the appearance of the nonlinear Kerr effect, which leads to diverting the incoming light toward the desired output. The proposed device consists of four optical waveguides and a defect in a square lattice PhC. Two famous plane wave expansion and finite difference time domain methods are used to study and analyze photonic band structure and light propagation inside the PhC, respectively. The presented structure, the ON-OFF contrast ratios for Sum and Carry, are 16dB and 14dB, respectively. Our simulation results reveal the proposed half adder has a maximum delay time of 0.7 ps with a total footprint of 158 um2. Due to very low delay time, high contrast ratio, and small footprint that they are more crucial in modern optoelectronic technologies, this structure can be used in the next generation of all-optical high-speed central processing units.