12 research outputs found
Transparent Conducting Oxides for Epsilon-Near-Zero Nanophotonics
Epsilon-near-zero materials are an emerging class of nanophotonic materials which engender electromagnetic field enhancement and small phase variation due to their approximate zero permittivity. These quasi-static fields facilitate a number of unique optical properties such as supercoupling, subwavelength confinement, and enhanced light-matter interactions, which has made epsilon-near-zero media a rapidly expanding field of optical physics. Contemporary methods of realizing a system with zero permittivity rely on microwave cavities/waveguides or complex metal-dielectric metamaterials; however, both techniques require advanced fabrication and their operational wavelength is fixed relative to their geometric and optical parameters. It remains an open and substantial challenge to realize an epsilon-near-zero material at pertinent wavelengths, particularly near- and mid-infrared, with tunable/dynamic properties. The focus of this thesis is the exploration of transparent conducting oxides for the development of epsilon-near-zero nanophotonic phenomena and applications. Transparent conducting oxides have an inherent low permittivity, in addition to simple fabrication and tunable optical properties, making them exceptionally promising. Application of transparent conducting oxide films for highly confined modes, nonlinear/ultrafast optics, and strongly coupled systems are discussed
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Enhanced Graphene Photodetector with Fractal Metasurface.
Graphene has been demonstrated to be a promising photodetection material because of its ultrabroadband optical absorption, compatibility with CMOS technology, and dynamic tunability in optical and electrical properties. However, being a single atomic layer thick, graphene has intrinsically small optical absorption, which hinders its incorporation with modern photodetecting systems. In this work, we propose a gold snowflake-like fractal metasurface design to realize broadband and polarization-insensitive plasmonic enhancement in graphene photodetector. We experimentally obtain an enhanced photovoltage from the fractal metasurface that is an order of magnitude greater than that generated at a plain gold-graphene edge and such an enhancement in the photovoltage sustains over the entire visible spectrum. We also observed a relatively constant photoresponse with respect to polarization angles of incident light, as a result of the combination of two orthogonally oriented concentric hexagonal fractal geometries in one metasurface
Enhanced Graphene Photodetector with Fractal Metasurface
Graphene has been demonstrated to
be a promising photodetection material because of its ultrabroadband
optical absorption, compatibility with CMOS technology, and dynamic
tunability in optical and electrical properties. However, being a
single atomic layer thick, graphene has intrinsically small optical
absorption, which hinders its incorporation with modern photodetecting
systems. In this work, we propose a gold snowflake-like fractal metasurface
design to realize broadband and polarization-insensitive plasmonic
enhancement in graphene photodetector. We experimentally obtain an
enhanced photovoltage from the fractal metasurface that is an order
of magnitude greater than that generated at a plain gold–graphene
edge and such an enhancement in the photovoltage sustains over the
entire visible spectrum. We also observed a relatively constant photoresponse
with respect to polarization angles of incident light, as a result
of the combination of two orthogonally oriented concentric hexagonal
fractal geometries in one metasurface