Pulse Fluctuations Caused by the Thermal Lens Effect in a Passively Q-Switched Laser System

Abstract

We study theoretically and experimentally pulse fluctuations in a passively Q-switched laser caused by the thermal lens effect and design a special thermally insensitive cavity for an end-pumped passively Qswitched laser system with a composite crystal. We show experimentally that using a suitable cavity and maintaining the laser-system operation in the fundamental mode reduce the pulse fluctuations effectively. Under a pump power of 8 W, relative fluctuations of the pulse width and the repetition rate of this system are 2.3% and 3.5%, respectively.

Diode-end-pumped passively Q-switched blue laser with Nd:YAG/YAG/Cr4+:YAG/YAG composite crystal

“…When the thermal lens changed, the size of pumped light spot on the saturable absorber changed. It means the system needs different time to bleach the saturable absorber as well, which would lead to different pulse widths and repetition rates [12]. Second, since the spot size of the pumped laser in the composite laser rod is larger than that of fundamental laser, it tended to multimodes operation at high pump power.…”