Omnidirectional Absorption Research Articles

Omnidirectional, polarization-insensitive and broadband thin absorber in the terahertz regime

A nearly omnidirectional THz absorber for both transverse electric (TE) and transverse magnetic (TM) polarizations is proposed. Through the excitation of the magnetic polariton in a metal-dielectric layer, the incident light is perfectly absorbed in a thin thickness that is about 25 times smaller than the resonance wavelength. By simply stacking several such structural layers with different geometrical dimensions, the bandwidth of this strong absorption can be effectively enhanced due to the hybridization of magnetic polaritons in different layers.

Metamaterial-induced band-gap of surface plasmon propagation

Surface plasmon propagation along a periodically corrugated metallic–air interface can be completely suppressed due to the formation of an equivalent dielectric metamaterial layer with a large real part of its effective refractive index. The effect can be explained by the transformation of the surface plasmon excitation conditions into a Brewster effect. This phenomenon leads to a high absorption of the incident light over a very wide range of incidence. One-dimensional periodicity (classical grating) leads to a single-polarization absorption, while two-dimensional periodicity (crossed grating) results in omnidirectional absorption in unpolarized light.

Optical black hole: Broadband omnidirectional light absorber

We develop an approach to broad-band omnidirectional light absorption, based on light propagation in a metamaterial structure forming an effective “black hole.” The proposed system does not rely on magnetic response, is nonresonant, and can be fabricated from existing materials.

Omnidirectional absorption in nanostructured metal surfaces

Light absorbers available at present provide far from optimal black-body performance. The need for more efficient absorbers is particularly acute on the microscale, where they can play a significant role in preventing crosstalk between optical interconnects, and also as thermal light-emitting sources. Several efforts have been made in this context to achieve near-total but directionally dependent absorption using periodic grating structures1,2,3,4,5,6,7. However, the ability to absorb light completely for any incident direction of light remains a challenge. Here we show that total omnidirectional absorption of light can be achieved in nanostructured metal surfaces that sustain localized optical excitations. The effect is realized over a full range of incident angles and can be tuned throughout the visible and near-infrared regimes by scaling the nanostructure dimensions. We suggest that surfaces displaying omnidirectional absorption will play a key role in devising efficient photovoltaic cells in which the absorbed light leads to electron–hole pair production. Light absorbers are not 100% efficient, and it is a challenge to absorb light completely for any direction of incidence. Using nanostructured metal surfaces, de Abajo and colleagues show that such omnidirectional absorption is now possible, potentially leading to more efficient solar cells.