POLARIZATION-ROTATION AND THERMAL-MOTION STUDIES VIA RESONANT DEGENERATE 4-WAVE MIXING

We report experimental observation of polarization rotation in resonant degenerate four-wave mixing (DFWM) arising from the third-order coupling of the electric fields. This effect allows investigation of molecular motion and its effect on the efficiency of the DFWM. By controlling the pulse width and therefore γ=T0/τp (where T 0≡λ/vth) we show quantitative agreement with a third-order density matrix perturbation calculation. In particular, using a CO2 laser at 10.6 μm and SF6 as the nonlinear medium, we show that for γ≫1 (stationary limit) we see no molecular motion and for γ≈1, we see a significant washout" of one third-order polarization."