All optical half-adder/subtractor using photonic-crystal-based nonlinear cavities

Abstract

In this paper, we aim to design a compact structure that can work both as an optical adder and subtractor. Also, as far as we know, one of the main disadvantages of previous optical adders or subtractors is that, inside a single structure, the levels of optical intensity for logic 1 at different output ports are different. In this work, we aim to solve this issue, too. For this purpose, two separate structures were designed for the half-adder and half-subtractor. The final structure was realized by combining these structures and adding an extra control port. When the control port is 0, the structure can work as an optical half-adder; however, when the control port is 1, the proposed structure can work as an all optical half-subtractor. The simulation results show that the rise time and ON/OFF contrast ratio are about 1.5 ps and 18.3 dB, respectively. Also the simulation results prove that the output levels for logic at all the output ports are at similar levels.