Ultrabroadband strong light absorption based on thin multilayered metamaterials

Abstract

Light absorbers have drawn intensive attention as crucial components for solar-energy harvesting, thermal emission tailoring, modulators, etc. However, achievement of light absorbers with wide bandwidth remains a challenge thus far. Here, a thin, unprecedentedly ultrabroadband strong light absorber is proposed and experimentally demonstrated, which consists of periodic taper arrays constructed by an alumina-chrome multilayered metamaterial (MM) on a gold substrate. This MM can change from a hyperbolic material to an anisotropic dielectric material at different frequency ranges and the special material features are the fundamental origins of the ultrabroadband absorption. The absorber is quite insensitive to the incident angle, and can be insensitive to the polarization. One two-dimensional periodic array of 400-nm height MM tapers is fabricated. The measured absorption is over 90% over almost the entire solar spectrum, reaching an average level of 96%, and remains high (above 85%) even in the longer-wavelength range till 4 μm. The proposed absorbers open up a new avenue to realize broadband thin light-harvesting structures.

Angle and Polarization Selective Spontaneous Emission in Dye‐Doped Metal/Insulator/Metal Nanocavities

“…Modes with purely plasmonic nature, mixed photonic/plasmonic and purely photonic properties have been theoretically predicted, and experimentally studied . Thanks to their straightforward fabrication, metal/insulator/metal (MIM) cavities of various geometries have been investigated, with applications in a plethora of fields, from superabsorption to high‐resolution color printing . More recently, MIM cavity resonances have been attributed to resonant tunneling epsilon‐near‐zero (ENZ) modes that can be excited without the need of momentum matching techniques .…”

Broadband near-infrared metamaterial absorbers utilizing highly lossy metals

“…Thus the bandwidth broadening is still limited and the experimentally measured absorption efficiency is not very high. In addition to this, there have been other methods addressing this issue, such as adiabatic nanofocusing of gap surface plasmon modes excited by the scattering off subwavelength-sized wedges2324 and the excitation of slow-wave modes in tapered alternating metal-dielectric multiple thin films25262728.…”

An ultra-broadband polarization-independent perfect absorber for the solar spectrum

“…For example, Aydin et al demonstrated an ultra-thin plasmonic super absorber consisting of a metal-insulator-metal stack with crossed trapezoidal top arrays. Such an absorber exhibits broadband and polarization independent light absorption over the entire visible spectrum with an average measured absorption of 0.71 and simulated absorption of 0.85 10 15 . However, the slight dimension variations of these broadband absorbers are hard to distinguish, which requires a sophisticated fabrication process and precision.…”