A self-Q-switch regime based on the dual-frequency beat effect with a microchip crystal cavity is demonstrated. Unlike the microchip based passively Q-switched laser, the pulses are generated without a saturable absorber. It is the microchip's dual-crystal structure along with the beat effect that leads to the Q value's modulation and offers the possibility for generating Q-switched pulses. A Nd:YAG microchip and a $\mathrm{LiTa}{\mathrm{O}}_3$ microchip compose the laser cavity by the optical cement method. The stress and thermal induced anisotropy of the Nd:YAG crystal offers the dual-frequency component and the $\mathrm{LiTa}{\mathrm{O}}_3$ microchip offers polarization selection for the beat effect. The dual-frequency component experiences periodically changed loss with the variation of the two frequencies’ phase difference, due to the polarization selection by the $\mathrm{LiTa}{\mathrm{O}}_3$ chip. The principle of the beat effect based self-Q-switch regime is analyzed and Q-switched pulses with a repetition rate of around 1 MHz are achieved experimentally. This phenomenon gives us a way to obtain pulsed lasers and might be interesting to those conducting research on Q-switch lasers and light-borne microwave generation.

• Received 15 May 2018

DOI:https://doi.org/10.1103/PhysRevA.98.033831