Angular distribution of coherent Raman emission in degenerate four-wave mixing with pumping by a single diffraction coupled laser beam: configurations for high spatial resolution.

This paper contains a discussion of the relation between the angular distributions of the coherently emitted radiation and the angular distribution of the incident beams in a degenerate four-wave mixing experiment, when two of the input beams are derived from the same laser source. The objective of the discussion is to obtain beam configurations that permit the use of such spectroscopic techniques when good spatial resolution is required so that the conventional collinear phase matching geometry is inappropriate. Two different configurations are indeed obtained and experimentally demonstrated that have, in the worst direction (longitudinal), spatial resolution of the order of 1 mm, with beam apertures comparable with those used in the standard collinear experiments and without the complicating requirement of two distinct pump beams.