Threshold conditions for a random laser mode

摘要

Stimulated emission in Nd_(0.5)La_(0.5)Al_3(BO_3)_4 ceramic random laser was studied at different diameters of the pumped spot d. The developed heuristic model adequately describes the dependence of threshold pumping energy density versus d at d ≥ 150 μm . At small pumping beam diameter (< 100 μm), very bright and strongly localized emission spot was observed in the center of the pumped area. The spectrum of the bright-spot emission appeared to be similar to that of "continuum wave" light sources.