Mid-infrared tunable polarization-independent perfect absorber using a phase-change metamaterial

We present the design of a polarization-independent tunable absorbing metamaterial (MM) in the mid-infrared wavelength regime. Our structure is composed of an array of thin gold (Au) squares separated from a continuous Au film by a phase-change material (PCM) layer. It is shown that a 10% tuning of the absorbance peak can be obtained by switching the PCM between its amorphous and crystalline states. The strong absorbance shows a substantial overlap between TE and TM polarization states over a wide range of incident angles. The electric field, magnetic field, and current distributions in the absorber are investigated to further explain the physical origin of the absorption. The study provides a path toward the realization of tunable absorbers for applications, such as selective thermal emitters, sensors, and bolometers.