Double resonance interference in third-order light mixing

Abstract The first observation of interference effects between two sharp resonant contributions to the third-order nonlinear susceptibility χ(3) (ω3=ω0+ω1−ω2) is reported. Using two tunable near ir frequencies, ω0=ω1 and ω2, the was seen in crystalline CuCl when 2ω1 and ω1−ω2 were close to the sharp Z3 exciton at 3.21 eV and the 210 cm-1 Raman line, respectively. Three different tunable visible frequencies were used to observe similar interference effects in a benzene-cyclohexane mixture when ω0−ω2 and ω1−ω2 were close to the 992 cm-1 Raman line of benzene and the 801 cm-1 Raman line of cyclohexane, respectively.