Design of a Rocket-Shaped 2D Photonic Crystal Coupler for Ultra-Compact 4x2 Encoder

There is a growing need for computers and mobile devices to analyze and transmit data more quickly, driving a growing interest in utilizing photonic crystals to develop advanced all-optical processors and communication systems. This study presents an all-optical $4 \times 2$ encoder designed with a triangular lattice photonic crystal structure. The encoder comprises four input waveguides and two output waveguides. The frequency modes and overall design were examined using the plane wave expansion (PWE) method. Numerical analysis, simulations, and optimizations were performed using the finite-difference time-domain (FDTD) technique. Operating at 1550 nm, the proposed encoder supports operations where only one input port is active at a time. It boasts a compact footprint of $129.6 \mu \mathbf{m}^{2}$, a rapid response time of 209 fs, and a high contrast ratio of $30.6 \mathbf{d B}$.