Light Absorber with an Ultra-Broad Flat Band Based on Multi-Sized Slow-Wave Hyperbolic Metamaterial Thin-Films

Here we realize a broadband absorber by using a hyperbolic metamaterial composed of alternating aluminum-alumina thin films based on superposition of multiple slow-wave modes. Our super absorber ensures broadband and polarization-insensitive light absorption over almost the entire solar spectrum, near-infrared and short-wavelength infrared regime (500-2500 nm) with a simulated absorption of over 90%. The designed structure is fabricated and the measured results are given. This absorber yields an average measured absorption of 85% in the spectrum ranging from 500 nm to 2300 nm. The proposed absorbers open an avenue towards realizing thermal emission and energy-harvesting materials.