Study of Transient Thermal Effects in a Nd :YAG Laser Under Quasi-Continuous Laser-Diode End Pumping

We develop a quasi-steady-state thermal model to analyze transient thermal effects in a Nd :YAG laser rod under quasi-continuous laser-diode (LD) end pumping. Included is a quasi-adiabatic model for pump durations and a quasi-steady-state heat dissipation model for pump-free durations. We give an approximate expression of the transient temperature-difference distribution function of the crystal under quasi-continuous pumping. The method for calculating the transient thermal focal length is also presented. On this basis, the temperature distribution variation in the crystal with time and the variation range of the transient thermal focal length are quantitatively analyzed. For 50 W, 200 μs pulse-width, and 50 Hz pumping, the temperature at the center of the Nd:YAG rod has a range of 304.52 – 306.28 K, and the thermal focal length varied over 1612.8 – 310.43 mm. Both have saw-tooth periodic distributions. This study provides a theoretical reference for the design of laser-diode-pumped thermal Q-switched Nd :YAG lasers.