Modeling of active and passive Q-switched intracavity frequency-doubled solid state lasers

We present a model of high-power continuous-wave laser-diode pumped actively Q-switched intracavity frequency-doubled green laser, in which the energy transfer up-conversion effect was taken into account. Our theoretical analysis showed that the overall laser performance is affected by both pulse repetition rate and energy transfer up-conversion effect. The energy transfer up-conversion effect increase greatly and seriously degrade the laser performance especially when operating at high pumping power and low pulse repetition rate. The good agreement with the experimental measurements reported in previous paper demonstrates that energy transfer up-conversion effect have to be considered to predict the laser operational characteristics accurately. We also first derived the second threshold condition for passively Q-switched intracavity frequency doubled solid state laser by including the effect of excited state absorption of saturable absorber into this model. A simple, and very clear formula was obtained.