Analysis of output characteristics of the actively Q-switched intracavity optical parametric oscillator considering Gaussian distribution of intracavity photon densities

By considering the Gaussian spatial distribution of the initial population-inversion density and the intracavity photon densities of the fundamental, the signal and the idle lights, the rate equations of a LD-pumped actively Q-switched intracavity optical parametric oscillator (IOPO) are derived. The influence of the pump rate, the thermal effect in the gain medium and the change of the photon density along the cavity axis have also been taken account in the equations. By numerically solving these coupled equations, the dependences of pulse width, pulse energy and peak power on incident pump power for the generated-signal light are obtained. In the experiment, a laser-diode-pumped actively Q-switched Nd:GdVO4/KTP IOPO with an acousto-optic (AO) modulator is realized and the experimental results agree with the theoretical calculations.