Kinetics of the stimulated emission of a CaF2:Dy2+ laser with a hemispherical resonator

Experimental investigation was made of the kinetics of the stimulated emission of a CaF₂:Dy²⁺ laser with a resonator formed by a plane mirror evaporated directly on the end of the fluoride crystal and an external spherical mirror. When the resonator geometry was sufficiently far from the stability limit, the pulsed emission of the laser was in the form of a transient spiking, decaying to a quasisteady-state level. The rate of decay depended strongly only on the aperture parameter of the resonator, which governed the number of the transverse modes which were excited, but was independent of the ratio of the resonator length to the radius of curvature of the spherical mirror in a fairly wide range of both these parameters. When the resonator geometry was close to the stability limit, the laser emitted random spikes. A large number of transverse modes were emitted in the continuous regime, which was characterized by a constant emission level with a slight spiking. A strong selection of the transverse modes under continuous pumping conditions resulted in the generation of regular undamped spikes.