Simulation of solid-state lasers with temperature and wavelength dependent absorption and emission

Simulation of diode-pumped solid-state lasers (DPSSL) and amplifiers often do not account for the temperature and spectral dependencies of the absorption and emission cross sections of the gain medium. Typically, to track the pump absorption within the crystal, an average absorption coefficient is applied via a raytracing technique. The outcome, therefore, is an approximation of the pump absorption profile that is independent of the temperature profile within the gain medium. Here an iterative algorithm involving raytracing and Finite Element Analysis (FEA) is demonstrated in the simulation of neodymium(Nd) and ytterbium(Yb) doped yttrium aluminium garnet(YAG) single crystal fiber (SCF) gain media. The algorithm calculates the local temperature, associated absorption coefficient and hence temperature-dependent pump absorption. This allows for a more accurate determination of the distributions of the calculated population inversion and temperature in the crystal. The temperature dependence of the emission spectra can then be taken into account as well, which defines the achievable gain of the amplifying media. The resulting calculations’ influence on the simulated output beam quality and gain for these active media is presented.