Design and modelling of photonic crystal waveguide-based compact multifunctional optical logic gates with decoder

This paper presents the design and simulation of a reconfigurable, compact, multifunctional optical logic gate composed of a two-dimensional photonic crystal (PhC) structure with a square lattice of silicon rods in an air host. The design features 30 columns and 15 rows of dielectric rods (with a reduced index of refraction of 3.46) in an air matrix, providing strong light confinement and compact integration. Six basic operations-AND, OR, NOR, NAND, NOT, and 1 × 2 Decoder-are facilitated by strategic defect engineering and input signal modulation. A Gaussian light source excites the structure, and the Finite-Difference Time-Domain (FDTD) method simulates light propagation and evaluates logic performance. The device operates efficiently at a central wavelength of 1600 nm with negligible crosstalk, a data rate of 1.75 Tbps, a signal contrast ratio of 16.18 dB, and a compact footprint of 450 µm², making it highly suitable for photonic integrated circuits (PICs) and next-generation all-optical computing systems.