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Thermal expansion of synthetic fused silica as a function of OH content and fictive temperature
(2009)
A matrix of synthetic fused silica samples with OH contents from 30 to 1300 ppm and of a fictive temperature from 1000 to 1300 °C has been characterized regarding their thermal expansion with high precision. The thermal expansion increases with fictive temperature and drops with OH content. Although fictive temperature and OH are coupled due to the influence of OH on the relaxation of the network, an independent influence of the OH content on thermal expansion has been observed. This may provide a deeper insight into the impact of impurities incorporated into the fused silica network.
Structural relaxation phenomena in binary and multicomponent lithium silicate glasses were studied upon irradiation with femtosecond (fs) laser pulses (800 nm central wavelength, 130 fs pulse duration) and subsequent thermal annealing experiments. Depending on the annealing temperature, micro-Raman spectroscopy analyses evidenced different relaxation behaviours, associated to bridging and non-bridging oxygen structures present in the glass network. The results indicate that the mobility of lithium ions is an important factor during the glass modification with fs-laser pulses. Quantitative phase contrast imaging (spatial light interference microscopy) revealed that these fs-laser induced structural modifications are closely related to local changes in the refractive index of the material. The results establish a promising strategy for tailoring fs-laser sensitivity of glasses through structural mobility.