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Semifree As2S3glass flakes undergo submm scale anisotropic deformation upon illumination of linearlypolarized cw bandgap light. The mechanism has been ascribed to photoinduced birefringence, optical torque, and photoinduced fluidity. Quantitative measurements demonstrate that generated optical torque is ∼10–20Nm under a light intensity of 1 mW. This value combined with measured deformation rates for As2S3cantilevers suggests a related photoinduced fluidity of 10–1P–1, which is much more fluidal ∼ten orders than that reported in the conventional photoinduced fluidity. Reasons for this discrepancy are discussed. © 2009 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim

We fabricated glass-ceramics composed of emissive nanocrystals that show variation in photoluminescence coloration. The change in emission color is based on the amorphous-to-crystalline phase transformation in a Mn-containing zincogermanate glass. The transformation occurred at a 50 degC temperature range (538-588 degC), resulting in a change in photoluminescence color from orange to white to green. The color change is attributed to the co-crystallization of emissive nanophases and a change in the coordination state of Mn2+. Using laser-induced crystallization, we also achieved the space-selective arrangement of the different photoluminescence colors, indicating that photoluminescence coloration can be tuned in this Mn-doped glass.

We assessed the photoluminescence performance characteristics of Mn4+-doped tetragermanate and silicogermanate phases with a benitoite-type structure. We observed a visible red emission based on the 2E ? 4A2transition in the doped benitoite-type tetragermanate. The partial substitution of Si for Ge, resulting in SrGe3.495Mn0.005Si0.5O9, improved the internal quantum efficiency and thermal stability of the red emission. A possible explanation of the substitution effect was reasonably presented on the basis of the connectivity of luminescent polyhedral units and the decrease in the Franck-Condon off-set value in the benitoite structure.

Photoluminescence and electron-spin resonance in nano-structured GeO2-GeS2glasses have been studied. With an increase in the GeO2content from 0 to 80 mol %, a luminescence peak blue-shifts from 1.3 to 2.1 eV in photon energy, which is more prominent than an increase in the optical gap from 3.4 to 3.6 eV. Dark and photoinduced electron-spin signals become maximal at around an intermediate composition 50GeO2-50GeS2. It is difficult to interpret these composition variations using the charged defect model proposed for chalcogenide glasses.