All-Optical Switching Based on Symmetric Hybrid Microcavities of Whispering-Gallery and Nanobeam Modes

Abstract

Conventional all-optical switches rely on nonlinear effects that require high pump intensities, limiting their efficiency and integration potential. Here, we propose theoretically and demonstrate numerically a linear all-optical switch utilizing hybrid symmetry in a system with whispering-gallery modes (WGMs) coupled to a nanobeam cavity. Through phase-controlled selective excitation of symmetric or antisymmetric WGMs, we can control the coupling of these modes with the nanobeam cavity, enabling light emission or inhibition. Temporal coupled mode theory and Finite-Difference Time-Domain (FDTD) simulations confirm multifunctional logic gate operations and ultrafast switching with arbitrarily low energy consumption, high contrast, and picosecond switching times. Moreover, the switching time can be dynamically tuned by adjusting the control light's pulse duration. Interestingly, reducing the mode quality factor accelerates the switching speed, which eases experimental implementation. The proposed architecture offers a simplified, energy-efficient and flexible solution for integrated photonic circuits, combining robust performance with experimental feasibility through relaxed fabrication tolerances.

Keywords: All-optical switch, Logic gates, Optical microcavity, Whispering-gallery mode, Nanobeam cavity