Diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO4 laser with Cr4+:YAG saturable absorber

A diode-pumped passively Q-switched and mode-locked (QML) c-cut Nd:GdVO4 laser with Cr4+:YAG saturable absorber is realized in a V-type folded cavity. The mode-locked pulse inside the Q-switched pulse has a repetition rate of 14 MHz, and its average pulse width is estimated to be about 460 ps. About, 90% modulation depth for the mode-locked pulses has been obtained. Basing on a hyperbolic secant function method, a developed rate equation model for Q-switched and mode-locked lasers was introduced, in which not only the Gaussian distribution of the intracavity photon density and the influences of the continuous pump rate were considered, but the stimulated radiation lifetime of the active medium as well as the excited-state lifetime of the saturable absorber were taken into account. The numerical solutions of the equations are in good agreement with the experimental results.