Plasma formation when CO2 laser radiation passes through transparent dielectrics

The dynamics of plasma development at the surfaces of transparent plates, placed in a converging pulsed laser beam, was examined. Variations in the shape of the plasmas formed and the spectral composition of their emitted radiation were explained on the basis of an optical detonation plasma-propagation mechanism. A comparison was made with the results of experiments in which plasma formation was accompanied by cracking of transparent dielectrics. Localized radiation was observed inside a specimen at subthreshold laser intensities. The data obtained confirmed the formation of a luminous surface discharge.