Ultra-Broadband and Polarization-Insensitive Tunable Metasurface Absorber

We propose two designs of tunable metasurface absorber (TMA), which are TMA with single- and dual-layer metasurfaces. They are denoted as TMA-I and TMA-2 for TMA with single- and dual-layer metasurfaces, respectively. Two devices show ultra-broadband and polarization-insensitive characteristics. The tuning ranges are 145 nm and 95 nm by tailoring the radius of metasurface disk for two designs. TMA-I exhibits the resonant bandwidth of 80 nm while TMA-2 can be improved 4-fold which exhibits the resonant bandwidth of 20 nm. By changing the gap between two metasurface layers of TMA-2. The tuning range of resonance could be spanned the whole visible wavelength range. It opens an avenue to a possibility for high-efficiency wavelength-selective devices in visible spectral range.