We show a new approach for achieving precise control over the internal structure of phase-change materials (PCMs) using the glancing angle deposition (GLAD) technique, which offers a foundry-friendly bottom-up growth alternative to commonly used lithography or chemical modification methods that introduce unwanted defects and impurities. We show that by adjusting deposition angle and rotation speed during growth, GLAD can enable a precise and unprecedented engineering of refractive index and extinction coefficient, in both amorphous and crystalline phases of commonly used GeTe and GST PCM films, without the need to alter their chemical composition.
Previous approaches for achieving asymmetric transmission (AT) of light rely on nonreciprocal systems, which are limited to having external bias or high input powers. We show AT from a metasurface comprising dielectric nanogratings on two sides of a silicon nitride membrane. The proposed metagrating provides wideband AT over multiple operational windows, and we demonstrate that such metasurfaces can be realized using both noble plasmonic metals and chalcogenide phase change materials to achieve reconfigurable AT. The proposed structure has various applications, from enhancing efficiencies in photovoltaic systems to tunable isolators and electromagnetic shielding.
Alloys of sulphur, selenium and tellurium, often referred to as chalcogenide semiconductors offer a highly versatile, compositionally-controllable material platform for reconfigurable metamaterial applications. They present various high- and low-index dielectric, low-epsilon and plasmonic properties across ultra-violet (UV), visible and infrared frequencies, in addition to an ultra-fast, non-volatile, electrically-/optically-induced switching capability between phase states with markedly different electromagnetic properties. We show that by integrating chalcogenide metasurfaces on the tip and side of optical fibers as well as silicon photonic waveguide platforms a range of wavelength-tunable modulators for telecommunication networks and synaptic weights for emerging neuromorphic computing applications can be realized.
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