An investigation was made of the appearance of an ultra-violet absorption band, in crystalline quartz, that was produced by an intense fs laser pulse. By using a conventional pump-probe technique, measurements were made of absorptions at 219nm (5.66eV) and 240nm (5.16eV), at 10 and 300K. The rise-time of the absorption was found to be equal to 150fs. It was independent of the probe wavelength and the sample temperature. The absorption coefficients were similar for both probe wavelengths, and the values at room temperature were about twice those at 10K. The appearance of the absorption was attributed to the ultra-fast formation of self-trapped excitons. The latter recombined radiatively at low temperatures. A cumulative effect was observed at room temperature. This demonstrated that, at 300K, some of the self-trapped excitons were converted to permanent color centers which were tentatively identified as being neutral O vacancies.

S.Guizard, P.Martin, G.Petite, P.D’Oliveira, P.Meynadier: Journal of Physics - Condensed Matter, 1996, 8[9], 1281-90