Beam quality improvement by population-dynamic-coupled combined guiding effect in end-pumped Nd:YVO4 laser oscillator

Beam quality improvement with pump power increasing in an end-pumped laser oscillator is experimentally realized for the first time, to the best of our knowledge. The phenomenon is caused by the population-dynamic-coupled combined guiding effect, a comprehensive theoretical model of which has been well established, in agreement with the experimental results. Based on an 888 nm in-band dual-end-pumped oscillator using four tandem Nd:YVO4 crystals, the output beam quality of M-2 = 1.1/1.1 at the pump power of 25 W is degraded to M-2 = 2.5/1.8 at 75 W pumping and then improved to M-2 = 1.8/1.3 at 150 W pumping. The near-TEM00 mode is obtained with the highest continuous-wave output power of 72.1 W and the optical-to-optical efficiency of 48.1%. This work demonstrates great potential to further scale the output power of end-pumped laser oscillator while keeping good beam quality.