Pumping beam shaping for optimized performance of Q-Switched Nd:YAG/V:YAG microchip laser emitting at $$1.44\,\upmu$$m

Abstract We present a longitudinally diode-pumped Q-switched Nd:YAG/V:YAG microchip laser emitting at $$1.44\,\upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>1.44</mml:mn> <mml:mspace/> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> m and the optimization of its output parameters in terms of pulse energy and peak power maximization. Optimization was achieved by modifying the size of the pumping beam with four compact focusing systems, each consisting of an aspheric collimator and one of four aspheric focusing lenses. The laser’s emission spectrum, average power, pulse duration, and spatial beam profile were measured for pumping repetition frequencies ranging from 10 to 715 Hz. Using different focusing systems, it was possible to increase the maximum pulse energy and peak power up to $$91\,\upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>91</mml:mn> <mml:mspace/> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> J and 14.8 kW, respectively. Thermal effects due to pumping influenced both the laser operation and the parameters of the V:YAG saturable absorber, leading to a decrease in pulse duration from 9.6 to 4.9 ns.