Induced scattering of light by light in a vacuum

The energy scattered from three intense, circularly polarized laser beams into a fourth beam due to vacuum-polarization effects is calculated for general angles between the beams. A semiclassical WKB technique is used which allows an accurate treatment of the geometry of the interaction region. The effects of incoherence and optical phase errors are estimated. Both the center-of-momentum and tetrahedrally symmetric cases are examined explicitly, and the results indicate that light-light scattering may be observable using laser systems of the size needed for laser-fusion studies.