Repetition rate control in continuous-wave-pumped, passively Q-switched solid-state lasers

We describe a technique for the adjustment and control of repetition rates in continuous-wave-pumped, passively Q-switched solid-state lasers. The method uses a movable intracavity lens to modify the mode matching and hence the gain of the laser beam per pass. The technique was applied to a diode-pumped Nd3+: YVO4 laser passively Q-switched with a Cr4+: YAG saturable absorber at 1064 nm. At a fixed pump power of 5.4 W, we were able to continuously adjust the repetition rate between 13.8 and 25 kHz by translating an intracavity converging lens. We also demonstrate that by adjusting the lens position, the repetition rate can be kept at a desired value as the pump power varies. In particular, as the pump power was increased from 3.95 to 5.9 W, the lens position was varied by 0.91 cm to keep the repetition rate constant at 13.8 kHz. Rate-equation formalism was used to investigate the variation of the repetition rate as a function of lens position, and very good agreement was obtained between experiment and theory. (c) 2007 Society of Photo-Optical Instrumentation Engineers.