Direct observation of high-order optical susceptibilities via angularly-resolved multiwave mixing

A new method of monitoring specific high-order optical susceptibilities of nonlinear media via angularly-resolved emission in a phase-matched multiwave mixing configuration is presented. This technique, which can be viewed as the creation by two optical beams of a strongly anharmonic absorption or index grating, and the simultaneous exploration of higher Bragg-diffraction orders by a third wave, is demonstrated here in the case of gas media near optical resonance.