Aspects of Raman Scattering
Abstract
Aspects of stimulated Raman scattering are investigated to better understand the propagation of intense light beams through the atmosphere. In addition, a new unstable resonator cavities was developed for the long pulse excimer laser used in the Raman beam-cleanup experiments and have made preliminary measurements on an anti-Stokes Raman laser which operates in the vacuum ultra violet region of the spectrum. Experiments demonstrate the Raman gain suppression observed on-axis, or at very small angles, for rotational Raman gain using linearly polarized beams in hydrogen and deuterium. The reduction in vibrational Raman gain at the phase matching angle is noted in hydrogen and deuterium. The normal exponential gain observed in the transient limit has been modeled to fit our experiment. The theory had to take account of the actual beam shapes, both spatially and temporally, as well as the self-phase modulation, in order to correctly predict the observed gain functions. Experiments were made on the beam quality and gain dependence of the 2nd Stokes. In particular, a study of the seeding mechanism responsible for generating the 2nd Stokes through the threshold level, has required statistical, spectral, beam profile and gain parameter studies. The far field pattern was then compared with the Fourier transform of the near field pattern to give a measure of the beam quality. Pulse energy statistics of the self-generated Stokes as well as of amplified and saturated Stokes have been studied from the point of view of Raman beam control. Such studies have mainly been restricted to Fresnel number 1 systems although larger Fresnel number 10 systems have been studied by the control exerted over the spatial patterns.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 25, 1989
- Accession Number
- ADA213926
Entities
People
- David G. Cooper
- James L. Dexter
- Rita Mahon