SCALING CW DIODE-END-PUMPED ND-YAG LASERS TO HIGH AVERAGE POWERS

We analyze the scaling limits of diode-end-pumped Nd:YAG lasers imposed by pumping geometry, thermal distortion, birefringence, and fracture. A scalable 15 W output power diode-end-pumped laser is demonstrated which achieves a 60% slope efficiency. Thermal distortion in this laser is reduced from 2.6 waves to less than 0.15 waves with an aspheric laser rod. Depolarization is reduced by 40x to less than 0.2% per pass using optical rotators. Modeling results, which accurately predict thermal distortion and birefringence, imply a thermal fracture-limited output power for short end-pumped rods less than 45 W. A dual rod design for an 80 W device is described. One of the four modules in this device has been assembled and tested, producing a CW output of 22.5 W.