High-Conversion Efficiency Pulse Compression by Stimulated Raman Scattering and Laser Induced Breakdown in Water

A novel temporal pulse compression technique, combining stimulated Raman scattering (SRS) and laser induced breakdown (LIB) principles was presented in this work, which employing an energy controllable dual-cell setup. As a novel type of plasma shutter, the 2
^nd
cell was used to transmit the high-power peak at the leading pulse edge and successfully block its low-power tail. The effect resulted in a 7 ns pulse duration from a Nd: YAG laser compressed into 330 ps, the pulse compression ratio was about 21×. The magnified optical power of the leading edge diminished the threshold of SRS and improved the beam quality of the output pulse. In addition, the output energy of Stokes was approximately 2 times than that of the 1
^st
cell process, and the 2
^nd
cell process increased the energy conversion efficiency from 4.2% to 15.8%. Thus, the 1
^st
-order Stokes SRS was greatly improved, and the 2
^nd
-order Stokes SRS was more easily generated. The method provided a simple but convenient way to generate a short pulse with a high energy conversion efficiency Raman laser.