Large-area broadband near-perfect absorption from a thin chalcogenide film coupled to gold nanoparticles.

Perfect absorbers that can efficiently absorb electromagnetic wave over a broad spectral range are crucial for energy harvesting, light detection, and optical camouflage. Recently, perfect absorbers based on the metasurface have attracted intensive attention. However, high performance metasurface absorbers in the visible spectrum require strict fabrication tolerances, and this is a formidable challenge. Moreover, fabricating sub-wavelength meta-atoms requires a top-down approach thus limiting their scalability and limiting their spectral applicability. Here, we introduce a plasmonic near perfect absorber that exhibits a measured polarization-insensitive absorbance of ~92% across the spectral region from 400 nm to 1000 nm. The absorber is realised via a one-step self-assembly deposition of 50 nm gold (Au) nanoparticle (NP) clusters onto a 35 nm thick Ge2Sb2Te5 (GST225) chalcogenide film. An excellent agreement between the measured and theoretically simulated absorption was found. The coalescence of the lossy GST225 dielectric layer and high density of localized surface plasmon resonance modes induced by the randomly distributed Au NPs plays a vital role in obtaining the nearly perfect absorptance. The exceptionally high absorption together with the large-area high-throughput self-assembly fabrication demonstrates their potential for industrial scale manufacturability, and consequential widespread applications in thermophotovoltaics, photodetection, and sensing.