Abstract
Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20 nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing.
Highlights
Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures
We propose and demonstrate experimentally realizable planar layered thin film broadband absorbers (BBA) that are capable of tuning the absorption in the mid-wavelength infrared (MWIR) spectrum based on VO2 phase transition
Spectral reflection measurements were carried out using an IR microscope which is coupled to a Fourier transform infrared (FTIR) spectrometer (Bruker Vertex 70) equipped with liquid nitrogen cooled mercury cadmium telluride (HgCdTe) detector
Summary
Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Resonant metamaterial and plasmonic absorbers have been demonstrated to enable either narrow or broadband absorption over microwave[1], terahertz[1], infrared[2,3,4,5], and visible[6,7] bands of electromagnetic spectrum. Electrical[23], optical[24], and thermal[25] tunability were demonstrated as the main active tuning mechanisms Tunable materials, such as vanadium dioxide (VO2) and niobium dioxide (NbO2) are called thermochromic materials, which change their optical properties as a function of temperature[26]. Opposite thermal behavior has negative dynamic range that is suitable for smart windows and space applications[26]
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