Thermally insensitive and polarization tunable metamaterial absorbers enabled by one-dimensional saline-water gratings

A simple liquid-based metamaterial absorber, featuring a one-dimensional subwavelength grating incorporated with the saline water, has been proposed and investigated. Numerical simulations and experiments show that highly efficient (>85%) and wideband (∼98% relative bandwidth) microwave absorption can be achieved. Due to the robust dielectric loss of the saline water, remarkable thermal insensitivity of the absorber was revealed, significantly outperforming the pure-water-based designs. In addition, owing to the inherent anisotropy of the one-dimensional structure, the absorber displays a distinct polarization-dependent characteristic, thus providing an efficient degree of freedom for modulating the absorption. The results are useful for developing thermally insensitive and polarization tunable metamaterial absorbers.