Abstract The crystallization behaviour of two new stable glasses belonging to the BaO-K2O-Na2O-Nb2O5-SiO2 system, synthesized by the melt-quenching technique, was studied with the aim to obtain nanostructured glasses based on tungsten-bronze phases. Nanostructured samples with valuable SHG activity were obtained starting from 8BaO·15K2O·27Nb2O5·50SiO2 glass after suitable heat treatments performed in the glass transition range, by means of the bulk nucleation mechanism. The influence of the devitrification mechanism on the second harmonic generation (SHG) efficiency was clarified with particular reference to the effect of structural modifications on the transparency of the nanostructured glasses. These samples are formed by Ba2NaNb5O15 nanocrystals (about 15 nm in size) randomly dispersed in a phase-separated amorphous matrix. Their SHG efficiency is partially impaired by the Rayleigh scattering originated by the nanocrystals. These nanostructured glasses can be useful when the generation efficiency is not an issue, as in the diagnostics for ultrafast lasers, due to the independence of the second harmonic generation from the polarization state of the laser light and no need for preferential material orientation.
INFLUENCE OF THE DEVITRIFICATION MECHANISM ON SECOND HARMONIC GENERATION EFFICIENCY AND TRANSPARENCY IN Ba2NaNb5O15 NANOSTRUCTURES
ESPOSITO, Serena;
2012-01-01
Abstract
Abstract The crystallization behaviour of two new stable glasses belonging to the BaO-K2O-Na2O-Nb2O5-SiO2 system, synthesized by the melt-quenching technique, was studied with the aim to obtain nanostructured glasses based on tungsten-bronze phases. Nanostructured samples with valuable SHG activity were obtained starting from 8BaO·15K2O·27Nb2O5·50SiO2 glass after suitable heat treatments performed in the glass transition range, by means of the bulk nucleation mechanism. The influence of the devitrification mechanism on the second harmonic generation (SHG) efficiency was clarified with particular reference to the effect of structural modifications on the transparency of the nanostructured glasses. These samples are formed by Ba2NaNb5O15 nanocrystals (about 15 nm in size) randomly dispersed in a phase-separated amorphous matrix. Their SHG efficiency is partially impaired by the Rayleigh scattering originated by the nanocrystals. These nanostructured glasses can be useful when the generation efficiency is not an issue, as in the diagnostics for ultrafast lasers, due to the independence of the second harmonic generation from the polarization state of the laser light and no need for preferential material orientation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
