Design and simulation of all optical logic gates based on 2D photonic crystal fiber

Design and simulation of all optical NOT and XOR gates based on 2D photonic crystal with quasi-square ring cavity are reported in this paper. The designed 13µm×8µm photonic crystal has a square lattice of GaAs rods in air with refractive index of 3.40 at operating wavelength of 1.55 µm. The lattice constant, a = 0.540 µm and radius of rods, r = 0.185a µm are chosen so that a large band gap for a TE polarized wavelength range of 1.23 µm to 1.80 µm can be obtained. The Finite Difference Time Domain (FDTD) and Plane Wave Expansion (PWE) methods are used to analyze the behavior of the structure. At first the performance of NOT logic gate is realized using different amplitude concept showing maximum transmittance of 36% for logic High. Then the performance of the same NOT gate is realized using different phase concept for logic implementation. After applying different phase definitions, it is shown that 180° and 90° phase difference between port signals can offer maximum transmittance of 69% and 55% respectively for the designed structure. So 180° phase difference is chosen for the designed NOT and XOR gates to ensure maximum transmittance for logic High.