Induced focusing and spatial wave breaking from cross-phase modulation in a self-defocusing medium.

The spatial effects of cross-phase modulation on a weak probe beam as it copropagates with an intense pump beam through a self-defocusing medium are investigated. Experimental results are presented that demonstrate induced focusing, beam deflection, and the spatial analog of optical wave breaking. The experimental results are in good qualitative agreement with theoretical predictions.

Two-beam-excited conical emission.

We describe a conical emission process that occurs when two beams of near-resonant light intersect as they pass through sodium vapor. The light is emitted on the surface of a circular cone that is centered on the bisector of the two applied beams and has an angular extent equal to the crossing angle of the two applied beams. We ascribe the origin of this effect to a perfectly phase-matched four-wave mixing process.