Specific features of thermal regimes in rectangular laser slabs under steady-state pumping

We continue to investigate the phenomena related to smoothing of temperature profiles in rectangular laser slabs and to an increase in the thresholds of their breakdown under optical pumping with variations in the slab optical density [the effect of smoothing of thermooptical inhomogeneities (STOI effect)]. It is found that the STOI effect is observed not only with increasing but also with decreasing optical density if this occurs due to a decrease in the sample thickness. The dependence of the maximum temperature difference inside the slab on its optical density at the instant of its thermal breakdown is calculated. It is shown that the variations in the optical density caused by variations in both the absorption coefficient and geometric dimensions of the slab differently affect the order of occurrence of two undesirable events — destruction of the slab or boiling of cooling water — with increasing pump power. The calculated relationships reveal two optical density regions corresponding to different orders of occurrence of these events. The maximum allowable temperatures in each region are determined.