Influence of thermal effect on output power optimization in fiber-coupled laser-diode end-pumped lasers

A general model has been developed for the output power optimization of fiber-coupled laser-diode end-pumped lasers by including the thermal effect into the analysis. The optical path difference (OPD) distribution has been derived as a function 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. With the derived OPD, the diffraction losses arising from thermal-induced spherical aberration have been estimated by the Strehl intensity ratio. The practical example of an Nd:YVO ₄ laser pumped by a 1.2-W fiber-coupled laser diode is considered to illustrate the utility of the present model. Experimental results have shown a fairly good agreement with the theoretical predictions.