Autostochastic operation of a solid-state ring laser with low-frequency periodic loss modulation

An experimental investigation was made of a single-frequency solid-state (YAG:Nd³⁺) travelingwave ring laser subjected to sinusoidal loss modulation. At a fixed modulation frequency an increase in the depth of modulation first resulted in nonlinear distortions of the laser response and then caused an abrupt change to pulsed operation at a repetition frequency equal to the loss modulation frequency. A further increase of the modulation depth resulted in complicated lasing, bifurcated increase in the period, and eventually emission characterized by a random variation of the amplitude and of the interval between the pulses. At the maximum experimentally attainable depths of modulation this random or autostochastic lasing changed to regular pulsing at a repetition frequency equal to half the loss modulation frequency. The dependence of the laser response on the depth of modulation exhibited a hysteresis. All the experimental results, including the autostochastic lasing regime, were in good agreement with the results obtained by numerical solution of the equations describing a solid-state ring laser.