Simulations have to accurately model thermal lensing in order to help improving resonator design of diode pumped
solid state lasers. To this end, a precise description of the pump light absorption is an important prerequisite. In
this paper, we discuss the frequency dependency of the pump light absorption in the laser crystal and its influence
on the simulated laser performance. The results show that the pump light absorption has to include the spectral
overlap of the emitting pump source and the absorbing laser material. This information can either be used for a
fully frequency dependent absorption model or, at least in the shown examples, to compute an effective value for
an exponential Beer-Lambert law of absorption. This is particularly significant at pump wavelengths coinciding
with a peak of absorption. Consequences for laser stability and performance are analyzed for different pump
wavelengths in a Nd:YAG laser.
The complex behavior of the optical wave in laser resonators requires a comprehensive model of thermal lensing
and the dynamic, 3-dimensional behavior of the laser beam. To this end, we perform a combined finite element
analysis (FEA) of the optical wave and of thermal lensing. Here, the simulation of the optical wave is the most
challenging task. Therefore, we also discuss another method, Dynamic Multimode Analysis, which is suitable
for a wide range of lasers. Finally, we present a complex heat model in order to analyze the interaction of heat
generation, thermal lensing, laser dynamics, and the beam profile.
The complex physical optics behavior in modern solid state lasers can only approximately be described using
common simulation techniques, such as a Gaussian mode analysis or beam propagation methods. For this reason
we present a new 3-dimensional, time-dependent method to model the laser beam in a resonator in a more
comprehensive way. We transform the wave equation by a special ansatz and solve the resulting equation, which
is similar to a Schroedinger equation, by a finite element analysis. In this paper we explain our new approach
and present first numerical results for a simple laser cavity. The results are compared with those of a dynamic
multimode analysis using Gaussian eigenmodes.
In order to improve the resonator design of solid state lasers, we provide a new simulation tool to calculate the
output power of the outgoing laser beam and its beam quality in terms of the <i>M</i><sup>2</sup>-factor. Furthermore, the
application of our method to actively Q-switched lasers provides detailed information about the pulse shape.
Using a time-dependent 3D simulation with Gaussian modes and Finite Elements, we take into account different
pumping types, thermal lensing effects, and the gain process in the crystal as well as optical apertures in
the resonator. Therefore, our model, which we call 'Incoherent-Multimode-Analysis' (IMMA), combines the
simulation of resonator optics with the computation of structural mechanics and a modified set of rate equations
in the crystal to describe complex effects like mode competition.
The optimization of output power and beam quality of a diode pumped solid state laser is a difficult task. In
this paper, we present a method to calculate approximate values of the beam quality factor M<sup>2</sup> and the output
power of a laser. Our method is based on the well-known Gauss mode analysis combined with rate equations.
As an application we analyze the beam quality of a Q-switched solid state laser.