Applied Nanophotonics, Liquid Crystals and Biomedical Optics

Light induced transformations have been studied as a function of the irradiation time by the Raman scattering technique on the chalcogenide alloy glass As₂Se₃. As a function of the laser intensity we observe: (i) For very low laser intensities there are no detectable changes in the Raman spectra; (ii) For intermediate laser intensities the spectrum exhibits oscillatory changes as a function of the irradiation time; (iii) For high laser intensities crystallization starts after some time of irradiation, which depends on the power level. Our explanations are based on the assumption that the radiation pumps the material from the glassy state towards the crystalline state, through the formation of submicrocrystalline clusters, which can coalesce to form large clusters attaining microcrystalline size at high power levels.