Temperature dependence of the absorption coefficient of optical glasses exposed to laser radiation

Results are presented of an interferometric investigation of the refractive index variations of K8 and L47 glasses and laser glasses under the action of neodymium laser radiation. Thermal instability, found in the laser glasses, is associated with the thermal excitation of the ions to the ⁴I_11/2 level and with the existence of a nonradiative decay channel for the metastable level via the higher ²G_9/2 level. The cross section of the ⁴F_3/2→²G_9/2 transition is determined.