Frequency characteristics of a mode-locked solid-state ring laser with self-pumping waves

An efficient method for suppressing the competition between counterpropagating waves and stabilizing the beats was developed for a rotating solid-state ring laser with a homogeneously broadened gain profile of the active medium. Use was made of self-pumping waves created under the conditions of steady-state mode locking using a diffraction acoustooptic feedback loop. Experimental and theoretical investigations were made of the influence of such self-pumping waves, of the laser parameters, and of the nonreciprocal acoustooptic effects on the amplitude-frequency characteristics of a YAG:Nd³⁺ ring laser. Considerable distortions of the frequency characteristics of this laser observed under transient mode locking conditions were due to the appearance of frequency modulation of ultrashort pulses. Weakening of the coupling between the counterpropagating waves, optimization of the parameters of the acoustooptic feedback loop, and detuning of the modulation frequency from the intermode value established a stable beat regime characterized by slight distortions of the frequency characteristics even near the interval of locking of the counterpropagating wave frequencies.