Low-power all-optical switch based on the epsilon-near-zero material-coupled grating structure

The grating-based resonant structure can enable strong control of light–matter interaction at the subwavelength level. By incorporating different emerging nonlinear materials within the resonant structure, we can achieve a fast all-optical switch, which can provide significant opportunities for future all-optical communication technologies. In this study, we numerically propose, to our knowledge, a novel work on a low-powered, femtosecond all-optical switch by using an epsilon-near-zero (ENZ) material coupled with a metal-grating structure. We numerically demonstrate an all-optical switch at 1530 nm wavelength using indium-doped cadmium oxide (ICO), which shows large nonlinearity owing to its ENZ behavior around this wavelength. The nonlinearity is responsible for the change in refractive index in the ICO layer and shifts the resonance dip to achieve the ON/OFF switching state. The results demonstrate that the proposed all-optical switch leads to a good modulation depth of about 0.96 at 1530 nm wavelength within the communication band. The large nonlinearity in the ENZ region leads to switching between the ON/OFF states with a low pump fluence of 15µJ/cm 2 along with a fast response time of 700 fs. The proposed switch has the potential for advancing optical information processing for future all-optical networks.