We derive a new model to simulate passively Q-switched intracavity frequency-doubling solid-state laser. By
introducing a nonlinear loss term caused by frequency-doubling crystal into the rate equations ,we can express the
effect of second-harmonic generation (SHG). We apply a finite volume discretization on gain medium, saturable
absorber and frequency-doubling crystal. "Dynamic Multimode Analysis (DMA)" and several Gaussian modes
are utilized. At the end, numerical results of passively Q-switched intracavity frequency-doubling solid-state
laser are presented. In the case of large pump radius,chaoic phenomenon can be observed numerically. In order
to realize the 3D simulation, we mainly use two technics: One is that common rate equations are extended to a
set of 3D multimode rate equations, which calculate photon number for different modes separately. The other is
to take into account a finite volume discretization.
Passive Q-switched lasers are constructed using saturable absorbers (SA). One characteristic of these lasers is
that they are built with small dimensions. There are difficulties in designing lasers with a given pulse repetition
rate or pulse energy using saturable absorbers. Numerical simulation of Q-switches facilitates the design and
production of such lasers and helps to reduce development time and cost. This paper presents a new simulation
method which calculates beam quality, maximal output power, pulse-width and pulse energy.