Laser performance of LD side-pumped Er: YSGG crystal rods with different diameters

Abstract

We demonstrate comparatively the laser performance of 970 nm laser diode (LD) side-pumped Er:YSGG crystals with a length of 85 mm and diameters of 2, 3, and 4 mm. The maximum average powers of 25.18, 25.74, and 20.41 W are achieved at 150 Hz and 200 μs, corresponding to the slope efficiencies of 30.01%, 31.47%, and 24.38%, respectively. The experimental results show that the Er:YSGG crystal rod with a diameter of 2 mm has no obvious advantage in laser output at low frequency and low pump power because the gain volume is small and the pump power cannot be fully absorbed, resulting in the gain saturation phenomenon. However, it exhibits the best laser output under high repetition rate and high pump power. The average power of 16.47 W obtained at 500 Hz is still not saturated. The beam quality factors M² in the x and y direction are determined to be 3.15/3.12, respectively, which is significantly better than those of the rods with diameters of 3 and 4 mm. All the results indicate that the crystal rod with a smaller diameter has better thermal management due to its larger specific surface area and better cooling ability, which is conducive to improving laser performance under the high repetition rate and high pump power operation.