Measurement of third-order nonlinear susceptibilities by non-phase matched third-harmonic generation

The third-order susceptibilities χ _xxxx ⁽³⁾ (?ω₃;ω₁,ω₁,ω₁) of some liquids, solids and air are determined by third-harmonic generation. The samples are placed behind the focal region of a laser beam in an evacuated environment to avoid third-harmonic generation of the surroundings. For fluid media the sample cell is made out of two thin fused quartz plates and oriented to an angle of zero net third-harmonic production in each window (minimum Maker fringe position).