The designs of 4×2 encoder based on photonic crystals

All-optical logic gate is a basic and crucial element for optical signal processing. In this paper, we propose a 4×2 encoder based on two dimensional triangular lattice photonic crystals composed of cylindrical silicon rods. The main structure of the device is a combination of both line defect Y branch and coupler photonic crystal waveguides. The computational simulation is carried out by using a finite-difference time-domain (FDTD) method. The simulation results show that the proposed all-optical photonic crystal waveguide structure could really function as a 4×2 encoder logic gate. In addition, the distance between coupler photonic crystal waveguides, the length of coupler waveguides and the distance between line defect Y branch waveguide structure are optimized for achieving the optimal performance for the proposed encoder logic gates. This device is potentially applicable for photonic integrated circuits.