Highly efficient continuous-wave operation of a Nd:YAG rod laser that is side pumped by p-polarized diode laser bars

We report on the performance of highly efficient, high-power continuous-wave (CW) Nd:YAG lasers that are side pumped by p-polarized diode laser beams. In this configuration pump light is directly coupled into the Nd:YAG rod through a threefold symmetric gold-coated flow tube. The polarization direction of our pump diode bars is perpendicular to the rod's axis (p-polarized). In a closed coupled resonator, a maximum output power of 195 W in multimode operation is obtained for a pump power of 423 W, which corresponds to an optical-to-optical efficiency of 46% and an electrical-to-optical efficiency of 23%. This is, to the best of our knowledge, the highest electrical-to-optical efficiency reported for a CW diode side-pumped Nd:YAG laser. By the pump-power leakage analysis method, we measured the pumping efficiency to be approximately 94%. The high efficiency of the system can be attributed to wing pumping, which results in uniform pump-light distribution and better pumping efficiency because of the use of p-polarized pump beams.