Diffractive optics based two-color six-wave mixing: phase contrast heterodyne detection of the fifth order Raman response of liquids

Fifth order Raman scattering is extremely sensitive to anharmonicities and nonlinear polarizabilities and thus provides a unique probe of the many-bod y potential of Liquids. The weak signals from this high order, chi((5)), pr ocess are complicated by cascaded lower-order chi((3)) processes. A new app roach has reduced the beam delivery to a single diffractive optic that gene rates the beam pattern for phase-matched six-wave mixing, and passively pha se Locks all six fields. Heterodyne detection introduces signal amplificati on and phase contrast against lower-order nonlinearities. The findings prov ide new Insight into the nature of the direct chi((5)) nonlinear response f unction and two-time correlation of liquids. (C) 2000 Elsevier Science B.V. All rights reserved.