Design and comparison of composite rod crystals for power scaling of diode end-pumped Nd:YAG lasers

A comparison of composite Nd:YAG laser rod crystals with one, two and three doped segments for high-power diode end-pumping is presented. An approach based on an expansion of the heat generation density and temperature distributions into a Fourier-Bessel basis set for solving the stationary heat conduction equation is used for choosing adequate segment lengths and dopant concentrations. A maximum laser output power of 167.5 W at an optical-to-optical efficiency of 53.6 % was achieved by longitudinal pumping a crystal with three doped segments with fibre-coupled laser diodes.