Design of ultra-compact all optical half subtracter based on self-collimation in the two-dimensional photonic crystals

In the paper, a novel all optical half subtracter by two-dimensional photonic crystals is proposed. Based on the two light beams interference theory and self-collimation, a simple all optical half subtracter is simply realized and the electric field distribution is plotted by the finite-difference time-domain (FDTD) method, meanwhile, the higher light contrast ratio between logic state “1” and “0” is also obtained. The realization of the half subtracter is valuable in photonic device integration and compactness.