OPTIMIZATION IN SCALING FIBER-COUPLED LASER-DIODE END-PUMPED LASERS TO HIGHER POWER - INFLUENCE OF THERMAL EFFECT

The optimum mode-to-pump ratio in scaling fiber-coupled laser-diode en d-pumped lasers to higher power has been investigated by including the thermal effect into the space-dependent rate equation analysis. The o ptical path difference (OPD) distribution has been derived as a functi on of the pump-beam quality, focus position of pumping light, and pump radius at the focal plane under the assumption that the end faces of the crystal are thermally insulated. The diffraction losses arising fr om thermally induced spherical aberration have been estimated by the S trehi intensity ratio, The present results for the optimum node-to-pum p ratio is markedly different from the previous results In which therm al effects are neglected and the optimum mode-to-pump ratio is an incr easing function of input pump power, It is seen that the optimum mode- to-pump ratio a decreasing function of input pump power, Also, the opt imum mode-to-pump ratio is less than unity in the ease of a slightly h igh pump power. The practical example of a Nd:YAG laser pumped by a 13 -W fiber-coupled laser diode is considered to confirm our physical ana lysis.