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Jeremy Munday1

1, University of Maryland, College Park, Maryland, United States

Bulk metals are generally reflective and are therefore commonly overlooked as efficient absorbers; however, the fields of plasmonics and metasurfaces have given new insights into methods for turning reflective surfaces into absorbing ones. Another recent approach has been the use of subwavelength Fabry-Perot-like resonances in ultra-thin films, which has been used to achieve absorption above 70%, approaching the theoretical limit using traditional substrates. Here we take a different approach and show that near-perfect absorption is achievable provided that the ultra-thin metals are deposited on an index near zero (INZ) substrate. In this talk, I will present the various design considerations that allow for ultra-thin metal films on INZ substrates to obtain near-perfect absorption throughout the visible spectrum and into the near-infrared (NIR). We find that metals commonly used for plasmonics and hot carrier devices, such as Au and Ag, can obtain near-perfect absorption for near-ultraviolet and visible wavelengths, while metals such as Pd and Pt are efficient absorbers throughout the near-ultraviolet to near-infrared spectrum. Finally, I will present results where we use this mechanism to enhance the photocurrent of photodetectors based on hot carrier generation in thin metal films.

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