1School of Physics, Sun Yat-sen University, Guangzhou 510275 2Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai 519082 3National Demonstration Center for Experimental Physics Education, Sun Yat-sen University, Guangzhou 510275
Abstract：We develop a two-stage end-pumped Nd:YVO$_{4}$ amplifier seeded by a passively Q-switched microchip laser. An average output power of 13.5 W with repetition rate up to 7 kHz and pulse duration of $\sim$1.24 ns is obtained, corresponding to a pump extraction efficiency of 16.1% (19.5% for the second stage) and peak power of $\sim $1.5 MW. The beam quality factors at maximum output power are measured to be $M_{x}^{2}=1.56$ and $M_{y}^{2}=1.48$. We introduce an analytical model to estimate gain and beam quality after amplification. This model focuses on the influence of ratio of seed spot radius to pump spot radius when designing an amplifier. Moreover, our experiments reveal that the re-imaging system in the double-pass configuration can be used to enhance the beam quality.
2019, Vol. 36 
