Nanostructured plasmonic thin films for enhanced optical properties

The unique optical properties of nano-structured plasmonic films have attracted great attention due to their potential applications in solar cells, photo-detectors, sensors, nano-imaging devices, thermal emitters and many more. Surface plasmon polaritons (SPPs) are surface electromagnetic waves that exist at the interface between a metal and a dielectric material. In this work, the significant role of the surface plasmons in understanding novel optical phenomena like enhanced transmission or enhanced absorption in nano-structured plasmonic thin films is investigated in detail. The extra-ordinary transmission of light through an array of holes in thin plasmonic films for use as conducting transparent electrodes is proposed. By experiments and simulations, these structured metallic electrodes are also shown to enhanced absorption for solar cell applications. Complementary layers of ladder-like plasmonic structures fabricated by laser interference lithography (LIL) are investigated for enhanced optical properties in the visible-IR bands. Possible applications as polarization dependent sensors at IR frequencies is also discussed. Enhanced absorption from a trilayer plasmonic system consisting of structured hole arrays in gold film separted from the bottom gold layer by dielectric spacer is reported. The fabrication by LIL and optical characterization of these samples are presented. A new approach to design dual band perfect absorber in the visible to the NIR region with top metallic patches on a SiO2 coated Si substrate is reported. A physical model for these absorbers is presented. A combined structuring of metallic disc and grating arrays on glass substrates that give rise to triple-band perfect absorption at visible frequencies is also reported. The physics behind these enhanced phenomena are discussed. The results have good potential for realizing low-cost large area
nanostructured plasmonic thin film devices for energy applications.

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