Chalcogenide glass

Summary

Chalcogenide glass (pronounced hard ch as in chemistry) is a glass containing one or more chalcogens (sulfur, selenium and tellurium, but excluding oxygen). Such glasses are covalently bonded materials and may be classified as covalent network solids. Polonium is also a chalcogen but is not used because of its strong radioactivity. Chalcogenide materials behave rather differently from oxides, in particular their lower band gaps contribute to very dissimilar optical and electrical properties. The classical chalcogenide glasses (mainly sulfur-based ones such as As-S or Ge-S) are strong glass-formers and possess glasses within large concentration regions. Glass-forming abilities decrease with increasing molar weight of constituent elements; i.e., S > Se > Te. Chalcogenide compounds such as AgInSbTe and GeSbTe are used in rewritable optical disks and phase-change memory devices. They are fragile glass-formers: by controlling heating and annealing (cooling), they can be switched between a

Official source

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Glass-in-glass infiltration for 3D micro-optical composite components

Yves Bellouard, Mathieu Bertrand, Luciano Borasi, Enrico Casamenti, Jérôme Faist, Andreas Mortensen, Gözden Torun

Chalcogenide glass exhibits a wide transmission window in the infrared range, a high refractive index, and nonlinear optical properties; however, due to its poor mechanical properties and low chemical and environmental stability, producing three-dimensional microstructures of chalcogenide glass remains a challenge. Here, we combine the fabrication of arbitrarily shaped three-dimensional cavities within fused silica molds by means of femtosecond laser-assisted chemical etching with the pressure-assisted infiltration of a chalcogenide glass into the resulting carved silica mold structures. This process enables the fabrication of 3D, geometrically complex, chalcogenide-silica micro-glass composites. The resulting products feature a high refractive index contrast that enables total-internal-reflection guiding and an optical quality roughness level suited for applications in the infrared.

2022

Ultrafast Laser Direct-Writing of Self-Organized Microstructures in Ge-Sb-S Chalcogenide Glass

Yves Bellouard, Gözden Torun

The structuring of mid-IR materials, such as chalcogenide glass (ChG), at the micro and nano scales, is of high interest for the fabrication of photonic devices in general, and for spectroscopy applications in particular. One efficient method for producing regular patterns with a sub-micron to micron length scale is through self-organization processes occurring during femtosecond laser exposure. These processes occur in a broad set of materials, where such self-organized patterns can be found not only on the surface but also within the material volume. This study specifically investigates the case of chalcogenide glass (Ge23Sb7S70) exposed to femtosecond laser pulses, inducing pulse-to-pulse nanostructure formation that is correlated to the glass network structural evolution using Raman spectroscopy as well as morphological and elemental microscopy analysis.

2022

Novel Insights into Thin Film Instabilities: From Fundamentals to Metamaterial Applications

Louis Marie Philippe Martin-Monier

The advent of metamaterials, e.g. artificially structured materials with physical properties significantly distinct from their bulk counterparts, has ushered in new perspectives in materials science and photonics, and constitutes today a new research frontier. Tailored order at the micro- or nanoscale has unlocked a host of novel opportunities in fields such as harmonic generation, wavefront shaping, and biochemical detection and analysis. Recent progress in dynamic tuning of metamaterial properties (active metamaterials) further promise to demultiply their impact, radically redefining functionality in modern optical devices. This progress has heavily relied on thin films, which consti-tutes fundamental building blocks for many micro- and nanoscale devices today. As dimensions of devices has shrunk, the question of thin film stability has become critical in numerous systems, given that their intrinsic high surface to volume ratio makes them particularly subject to instabilities. Such instabilities are potentially responsible for loss of percolation and disordered geometries, hence threatening both metamaterial integrity and functionality. In this thesis, we propose to investigate the stability of thin optically functional films for application in passive and active 2D-metamaterials (metasurfaces) along two complementary persepectives. In a first perspective, we investigate the possibility to guide pre-defined (or templated) instabilities in thin chalcogenide films to induce prescribed order at the micro and nanoscale through a diverse set of original processes, effectively providing a novel frame for scalable yet high performance metasurfaces. In a second perspective, thin film instabilities are supressed in highly unstable liquid metal thin films, opening up novel perspectives for electronic and optical nanostructures.

EPFL2021