Abstract

We describe results of experiments that evaluate the ability of a transient Raman amplifier to preserve the wavefronts of both aberrated and unaberrated incident Stokes beams. The experimental measurements were made using 40-ps pulses produced by a mode-locked Nd:YAG laser doubled to 532 nm. The incident Stokes was produced in a self-generator cell filled with hydrogen gas at 25 atm. A Mach-Zehnder interferometer that had a 1-m amplifier cell in one arm was used to measure distortions in the wavefront of the Stokes beam that were introduced by the transient Raman amplifier. In addition, aberrations could be imposed onto the incident Stokes beam by using a small gas jet. Near-and far-field intensity distributions and power-in-the-bucket energy measurements were also made of the unaberrated beam. Power-in-the-bucket measurements show a very minor degradation of a good quality incident Stokes beam. Preliminary near-and far-field results indicate that a good quality Stokes beam may undergo spatial gain narrowing in unsaturated conditions and can show other spatial effects in saturated conditions. Far-field results are presented and compared with calculated results. Interferometer measurements show little distortion of weakly aberrated beams but more significant distortion for larger initial aberrations.

© 1987 Optical Society of America