Ultralow switching threshold optical bistable devices based on epsilon-near-zero Ga<sub>2</sub>O<sub>3</sub>-SiC-Ag multilayer structures

Abstract

Optical bistability has attracted much attention due to its enormous potential applications in all-optical operation and signal processing. However, the weak nonlinear responses typically require huge pump power to reach the threshold of the optical bistability, thus hindering the real applications. In this study, we propose an efficient optical bistable metamaterial, which is composed of multilayer Ga<sub>2</sub>O<sub>3</sub>-SiC-Ag metal-dielectric nanostructures. We not only use the epsilon-near-zero (ENZ) with SiC-Ag thin layers to enhance the substantial field, but also incorporate the SiC material to increase its significant optical nonlinear coefficient. In the structural design, the introduction of Ga<sub>2</sub>O<sub>3</sub> layer facilitates the light field concentration, contributing to the further reduction in threshold power for optical bistability, and also conducing to the improvement of 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 by 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<sup>–6</sup> W/cm<sup>2</sup> in the telecommunication band. Comparing with the previously reported optical bistability based on ENZ mechanism, the threshold shows a significant reduction by 9 orders of magnitude, demonstrating great application potential in the fields of semiconductor devices and photonic integrated circuits.