Broadband tunable perfect absorber based on dielectric/Vanadium dioxide multilayer films in the mid-infrared frequency

Abstract

We present a lithography-free, wide-angle, polarization-insensitive, and tunable broadband absorber based on a multilayer thin-film architecture composed of five pairs of vanadium dioxide (VO${}_2$) and dielectric layers deposited on a glass substrate. The optical performance of the proposed structure is analyzed using the transfer matrix method (TMM). The numerical results demonstrate that, when VO${}_2$ is in its metallic phase, the absorptivity exceeds 99% under normal incidence over the wavelength range of $4\mu m$ to $15\mu m$. In contrast, nearly zero absorption is obtained when VO${}_2$ transitions to its dielectric phase, highlighting the strong phase-dependent tunability of the design. The influence of incident angle and polarization on the absorption response is systematically investigated, confirming robust wide-angle operation and polarization-insensitive behaviour. Field distribution analyses of the electric and magnetic components at representative wavelengths reveal that the enhanced absorption primarily originates from constructive interference and resonant electromagnetic confinement within the multilayer stack. Owing to its excellent tunable mid-infrared absorption characteristics, the proposed structure is a promising candidate for thermovoltaics and infrared imaging as well as other applications operating in the visible–infrared spectral regime.