Refractive index engineering of metal-dielectric nanocomposite thin films for optical super absorber

Using metal-dielectric nanocomposite materials, we developed thin-film resonant and nonresonant absorbers with tunable absorption band. A compact double-side vertically graded metal-dielectric nanocomposite absorber was fabricated by gradually varying metal-dielectric nanocomposite ratios. The optical impedance of this metal-dielectric nanocomposite structure can be engineered to realize the antireflection characteristics. A broad-band and angle-insensitive super absorption over 81% was obtained in visible to near-infrared spectral region (i.e., 400 nm to 1100 nm), which is broader than recently reported plasmonic metamaterial absorbers in the similar spectral region.