Short-Pulse Nd:YAG/Cr:YAG Microchip Laser With Pulse Duration of < 200 ps

A passively Q-switched Nd:YAG/Cr:YAG microchip laser with the pulse duration of < 200 ps has been developed. To obtain such short pulses from Nd:YAG/Cr:YAG microchip lasers, a numerical model based on rate equations was introduced and a design strategy of microchips was discussed. Since the pump bleaching effect in Cr:YAG leads to an increase of output pulse duration, a method of small-spot pumping was employed to reduce the effect and shorten the pulse duration. In the experiments, 1064-nm laser pulses with the duration of 153 ps and the energy of 18 $\mu \text{J}$ at 4.5 kHz was achieved. A good beam quality of $M^{2} =1.15$ was also measured.