Observation of O₂ inside voids formed in Geo₂ glass by tightly-focused fs-laser pulses

Unusual generation of molecular oxygen confined in a void inside the bulk of GeO₂ glass is observed with the Raman spectroscopy. The voids are formed by single tightly-focussed femtosecond laser pulses, converting a host glass material into a high temperature plasma, which explodes creating a void and inducing unexpected phase transformations. The intensity of the 1556 cm^-1 Raman line, that is a signature of molecular oxygen, increases with pulse energy. The mechanism of O₂ formation and material synthesis in plasma is presented and its relevance to fundamental problems of matter at high-pressure and temperature conditions and subject to geo-physical sciences is discussed.