<p>A novel all-optical U-shaped 4 × 2 encoder based on two-dimensional silicon photonic crystals is designed to achieve ultra-fast operation, compact size, and a high contrast ratio, targeting applications in computing and all-optical logic systems. The silicon encoder structure, composed of a U-shaped power splitter, a nanocavity, and biperiodic waveguides, significantly enhances performance by increasing the contrast ratio while minimizing power loss and return loss. The photonic crystal is formed by a periodic array of high-refractive-index silicon rods embedded in a low-index dielectric medium, providing strong light confinement and guiding capabilities. The photonic band structure is analyzed using the Plane Wave Expansion (PWE) method to ensure bandgap suitability for the targeted wavelength. Functional parameters such as response time, delay time, steady-state time, insertion loss, bit rate, contrast ratio, and extinction ratio are numerically estimated using the two-dimensional Finite-Difference Time-Domain (2D-FDTD) technique at an operational wavelength of 1550&#xa0;nm. To assess material impact, the proposed U-shaped silicon encoder is analyzed using different core materials, including Indium Phosphide (InP) and Gallium Arsenide (GaAs), in addition to silicon. The comparison reveals that the silicon-based encoder outperforms the others by achieving the maximum contrast ratio of 29.2&#xa0;dB, minimal crosstalk of -29.2&#xa0;dB, and an ultra-compact footprint of 246µm². The silicon encoder also demonstrates a high data rate of 2.083Tbps. These promising results indicate that the optimized silicon photonic crystal encoder is well-suited for compact, high-speed, and scalable integration in photonic logic and computing circuits.</p>