NONLINEAR REFRACTIVE-INDEX NEAR POINTS OF ZERO ABSORPTION AND IN THE DEAD ZONE

Cross focusing (defocusing), determined by the probe Kerr coefficient, which is defined as the derivative of the probe refractive index with respect to the pump intensity, is studied at points of probe nonabsor ption and in the dead zone. Spatial control of the probe can be achiev ed not only by the probe Kerr coefficient itself but also by its stron g variation with pump intensity at points of probe nonabsorption. This strong variation allows the pump beam to be used as a waveguide for t he probe.