Three-Wave Optical-Mixing Effects in Wedge-Shaped Cells

The optical-mixing process in which the light at the frequency of 2ω1–ω2 is generated from two incident beams at ω1 and ω2 through the polarization of the third order in the electric field, is studied in several kinds of liquid using a sample cell with nonparallel windows. The dependence of the output light intensity at 2ω1–ω2 on the optical thickness z and the angle α of parallelism of the cell is obtained. For small α, the output intensity oscillates as z is changed except C6H6, in which a different behavior is observed under the same condition. For large α, this oscillatory behavior is observed fairly small. In these experiments, the optical path length z is 10∼15 times as long as the coherence length. The third-order nonlinear susceptibilities have been estimated to be of the order of 10-12∼10-14 cm3 erg-1.