Ultralow Switching Threshold Optical Bistable Devices based on Epsilon-near-zero Ga₂O₃-SiC-Ag Multilayer Structures

Abstract

Optical bistability has attracted much attention due to its enormous potentials in all-optical operation and signal processing. However, the weak nonlinear responses typically require huge pump power to fulfill the threshold of the optical bistability, thus hindering the real applications. In this study, we propose an efficient optical bistable metamaterial that composes multi-layered Ga₂O₃-SiC-Ag metal-dielectric nanostructures. We not only achieve the substantial field enhancement by utilizing the epsilon – near - zero (ENZ) with SiC-Ag thin layers, but also incorporate the SiC material leveraging its significant optical nonlinear coefficient. In the structural design, the introduction of Ga₂O₃ layers facilitate the light field concentration, contributing to the further reduction in threshold power for optical bistability, and also help to improve the physical and chemical stability of the device. The influences of the thickness and length of the ENZ layer on the optical bistability are systematically investigated using the finite element method. The results demonstrate that optical bistability becomes more pronounced with the increase of the thickness and length of ENZ layer, exhibiting a bistability switching threshold as low as~10^-6 W/cm² in the telecommunication band. Compared with the previously reported optical bistability based on ENZ mechanism, it shows a significant reduction by 9 orders of magnitude, demonstrating great application potentials in the fields of semiconductor devices, and photonic integrated circuits.