Mechanical model of giant photoexpansion in a chalcogenide glass and the role of photofluidity

Abstract

Abstract. An analytical model is developed to describe the phenomenon of giant photoexpansion in chalcogenide glasses. The proposed micro-mechanical model is based on the description of photoexpansion as a new type of eigenstrain, i.e. a deformation analogous to thermal expansion induced without external forces. In this framework, it is the viscoelastic flow induced by photofluidity which enable the conversion of the self-equilibrated stress into giant photoexpansion. This simple approach yields good fits to experimental data and demonstrates, for the first time, that the photoinduced viscous flow actually enhances the giant photoexpansion or the giant photocontraction as it has been suggested in the literature. Moreover, it highlights that the shear relaxation time due to photofluidity controls the expansion kinetic. This model is the first step towards describing giant photoexpansion from the point of view of mechanics and it provides the framework for investigating this phenomenon via numerical simulations.

Optically trapped delayed elasticity in germanium selenide glass fibers

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Dielectric spectroscopic investigation of reversible photo-induced changes in amorphous Ge2Sb2Se5 thin films

“…Chalcogenide glasses, essentially semiconducting alloys, exhibit a wide range of photo-induced phenomena such as photo-induced darkening/bleaching, photo-fluidity, structural relaxation, expansion, and contraction. [1][2][3] Understanding and control of such photo-induced phenomena are technologically important for many applications, including waveguide writing, in-memory computing and information storage, 4,5 chiroptical switches, 6 photonic trimming, and chiral metamaterials. 7 Such light-induced structural changes are either isotropic or anisotropic depending on the pumping light's polarization and can be partially or fully reversed by the application of external stimuli (e.g., by changing the temperature or the wavelength of the incident light).…”