Tunable broadband, wide angle and lithography-free absorber in the near-infrared using an ultrathin VO2 film.

We demonstrate a tunable broadband near-infrared absorber composed of VO₂ /Al₂O₃/ITO layers with a facile lithography-free method. Simulated and experimental spectra show that absorption bands with above 90% absorptance can be tuned from 1.62 ∼ 2.42 μm to 1.2 ∼ 1.5 μm by thermally induced VO₂ phase transition. Furthermore, the absorber with VO₂ in the intermediate state can yield a broadband perfect absorption over the wavelength range of 1.2 ∼ 2.5 μm. Besides high absorption performance can still be remained at the incident up to 70° for both polarizations due to the presence of ultrathin layer of VO₂ (λ/52) in the absorber. [ABSTRACT FROM AUTHOR]