Actively $Q$ -switched and Mode-Locked Diode-Pumped ${\hbox {Nd:GdVO}}_{4}{\hbox {--KTP}}$ Laser

By using a comparative simple configuration and a short cavity length, a diode-pumped actively $Q$-switched and mode-locked intracavity frequency doubled ${\hbox {Nd:GdVO}}_{4}{\hbox {--KTP}}$ green laser with the modulation depth 100% was realized, from which the great average output power, the high efficiency were obtained and the mode-locked pulse inside the $Q$-switched pulse has a repetition rate of 476 MHz. Using the hyperbolic secant function methods and by considering the Gaussian distribution of the intracavity photon density, the influences of continuous pump rate, the upper state lifetime of the active medium and the turnoff time of the acousto-optic $Q$-switch, we proposed a developed rate equation model for actively $Q$-switched and mode-locked green lasers. With this developed model, the theoretical calculations are in good agreement with the experimental results and the width of the mode-locked green pulse is estimated to be about 185 ps.