Thermochemical model of optical discharges in glasses

An experimental determination was made of the threshold temperatures for the excitation of optical discharges in silicate glasses under the action of millisecond laser pulses. At normal pressure the discharges on glass surfaces appeared at a temperature of ~2000 K. In the interior of the glasses, where the pressure as a result of local heating increased to ~10⁴ atm, the discharges appeared at ~2500 K. A theoretical analysis was made of spontaneous decomposition of the main glass-forming oxide (silica) and it was found that the proposed model describes satisfactorily the pressure dependence of the threshold temperature. A quantitative agreement was established between the calculated thermal characteristics of the decomposition process and the experimentally determined threshold temperatures for the onset of optical discharges.