We harness non-volatile, amorphous-crystalline transitions in the chalcogenide phase-change medium germanium antimony telluride (GST) to realize optically-switchable, all-dielectric metamaterials. Nanostructured, subwavelength-thickness films of GST present high-quality resonances that are spectrally shifted by laser-induced structural transitions, providing reflectivity and transmission switching contrast ratios of up to 5:1 (7 dB) at visible/near-infrared wavelengths selected by design.Comment: 8 pages, 8 figure
Chalcogenides-alloys based on group-16 'chalcogen' elements (sulfur, selenium, and tellurium) covalently bound to 'network formers' such as arsenic, germanium, antimony, and gallium-have a variety of technologically useful properties, including infrared transparency, high optical nonlinearity, photorefractivity and readily induced, reversible, non-volatile structural phase switching. Such phase-change materials are of enormous interest in the fields of plasmonics and nanophotonics. However, in such applications, the fact that some chalcogenides accrue plasmonic properties in the transition from an amorphous to a crystalline state, i.e., the real part of their relative permittivity becomes negative, has gone somewhat unnoticed. Indeed, one of the most commercially important chalcogenide compounds, germanium antimony telluride (Ge 2 :Sb 2 :Te 5 or GST), which is widely used in rewritable optical and electronic data storage technologies, presents this behavior at wavelengths in the near-ultraviolet to visible spectral range. In this work, we show that the phase transition-induced emergence of plasmonic properties in the crystalline state can markedly change the optical properties of sub-wavelength-thickness, nanostructured GST films, allowing for the realization of non-volatile, reconfigurable (e.g., color-tunable) chalcogenide metasurfaces operating at visible frequencies and creating opportunities for developments in non-volatile optical memory, solid state displays and alloptical switching devices.
Demonstration of a nearly ideal wavelength-selective optical mirror using a metamaterial-enabled dielectric coating Appl.
Photonic materials with tuneable and switchable ultraviolet (UV) to high-energy-visible (HEV) optical properties would benefit applications in sensing, high-density optical memory, beam-steering, adaptive optics and light modulation. Here, for the first time, we demonstrate a non-volatile switchable dielectric metamaterial operating in the UV-HEV spectral range. Nano-grating metamaterials in a layered composite of low-loss ZnS/SiO2 and the chalcogenide phase-change medium germanium antimony telluride (Ge2Sb2Te5) exhibit reflection resonances at UV-HEV wavelengths that are substantially modified by light-induced (amorphous-crystalline) phase transitions in the chalcogenide layer. Despite the presence of the lossy GST, resonance quality factors up to Q~15 are ensured by the transparency (low losses) of ZnS/SiO2 in the UV-HEV spectral range and values of Q increase as the refractive index of Ge2Sb2Te5 decreases, upon crystallization. Notably however, this switching leaves resonance spectral positions unchanged.
Barium titanate (BaTiO3) is a synthetic crystal used in electromechanical transducers and multilayer ceramic capacitors. Since it is not available in nature, a variety of growth methods has been employed to produce in large scale, with high quality and low‐cost. BaTiO3, as a metal oxide meets practical requirements such as physical hardness, stability and tunable optoelectronic properties. The plethora of characteristics renders it functional in diverse fields of applications from energy harvesting to biophotonics. Related to optical properties, it is a dielectric material from the near ultraviolet to the near‐infrared part of the spectrum with low optical losses and relatively high refractive index. The strong second‐order nonlinear response has resulted in several breakthroughs in bioimaging, while its intrinsic electrooptic response is among the highest within the existing materials. The properties of the BaTiO3 may also be modified by doping or hybridization with other materials. This review presents the basic optoelectronic properties of BaTiO3, reports on the recent advances in BaTiO3 nanostructures and thin films related to photonic applications, and oversees photonic technologies that may benefit from this material platform in the near future.
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