Optical and spectroscopic characterisation of permanently densified GeO 2 glasses

Optical and spectroscopic characterization was carried out on densified vitreous germania glasses retrieved from pressures in the range 2–6 GPa. The density of the obtained glasses increased with applied pressure. Ultrasonic and Brillouin measurements revealed an increase of the longitudinal and shear sound velocity, in agreement with the hardening of the elastic medium. Raman measurements allowed the structural modification of the system to be studied as a function of its density and showed the evolution of the boson peak, which shifts towards higher frequencies and decreases in intensity.