Tunable perfect absorber in the short-wave infrared band based on ITO nonlinear metasurface with enhanced optical response

A polarization-sensitive nonlinear metasurface of antenna-indium tin oxide (ITO) coupled structure has been meticulously designed to enhance the nonlinear response with strong coupling between the localized surface plasmon resonance (LSPR) of gold nanoantenna and the epsilon-near-zero (ENZ) mode of the ITO film. This metasurface exhibits a broadband spectrum (similar to 730 nm) and a large nonlinear index coefficient n2 of 1.41 cm2/GW, which is approximately 520 times greater than that of a single-layer ITO film. Additionally, we have engineered a perfect absorber using an ITO nonlinear metasurface, with a 38 nm absorption bandwidth ranging from 1085 nm to 1123 nm, achieving near-perfect absorption, with a maximum absorption rate of up to 94% in the short-wave infrared band. These findings offer a promising foundation for the development of ultra-compact and large nonlinear optical devices.