Ring solid-state laser with self-pumping waves and an antiresonant acoustooptic diffraction feedback

A new method for creating self-pumping waves in a solid-state laser with a YAG:Nd³⁺ active element was based on the use of an antiresonant acoustooptic diffraction feedback, acting under conditions of mode locking in a laser with a (in an acoustooptic switch) resonator axis self-intersecting at an angle close to twice the Bragg angle. The acoustooptic feedback and self-diffraction, in the active medium, of counterpropagating waves and of self-pumping waves (generated by diffraction of the counterpropagating waves in the acoustooptic switch) ensured an effective stabilization of the mode locking parameters, of the parameters of ultrashort output pulses, and of bidirectional lasing generating counterpropagating waves with different frequencies. In a symmetric ring solid-state laser a double passage of the counterpropagating waves through the switch suppressed completely the nonreciprocal acoustooptic effects resulting from the Bragg diffraction of these waves in a conventional ring laser. An asymmetry of the ring resonator and suppression of the interaction between the counterpropagating and self-pumping waves in the active medium revealed optical bistability of ultrashort pulses, particularly when the difference between the counterpropagating wave frequencies or the power or frequency of an ultrasonic wave in the acoustooptic switch were varied.