1 research outputs found
Wideband Absorbers in the Visible with Ultrathin Plasmonic-Phase Change Material Nanogratings
The narrowband surface plasmon resonance
of metallic nanostructures
was once thought to limit the bandwidth of absorptance, yet recent
demonstrations show that it can be harnessed using mechanisms such
as multiple resonances, impedance matching, and slow-light modes to
create broadband absorptance. However, in the visible spectrum, realization
of absorbers based on patterned plasmonic nanostructures is challenging
due to strict fabrication tolerances. Here we experimentally compare
two different candidates for visible light broadband high absorptance.
The first candidate is planar thin film dual layers of Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> and aluminum (Al), while the second
structure employs ultrathin Al grating/Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> dual layers. In both cases, the absorbers yield a
measured absorptance greater than 78% in the visible. A remarkably
high-absorptance bandwidth of 120 nm was measured and associated with
the large imaginary part of Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> dielectric function. We find that the simple dual-layer planar structure
is an effective absorber in the near-infrared, but its absorptance
is less effective in the visible. However, for visible wavelengths
the grating structure can blue-shift the absorptance peak to 422 nm.
The simple geometries of the plasmonic absorbers facilitate fabrication
over large areas. It has practical applications in light harvesting,
sensing, and high-resolution color printing