Abstract

Since fully 80% of the value of the total integrated intensity of a focused Gaussian beam occurs within three Raleigh ranges on either side of the focal point, it is common to refer to the interaction length for stimulated Brillouin scattering (SBS) in a focused geometry as being approximately three confocal parameters. However, there is evidence that regions that are significantly away from the focal point are significant in SBS.^1–3 We have investigated both experimentally and theoretically the energy present in the Stokes beam as a function of distance from the focal point, and we find that even in the regime of small SBS reflectivity, most of the energy in the Stokes beam is derived from tegions that are significantly removed from the focal region.

© 1993 Optical Society of America