THE EFFECTS OF COLLISIONAL QUENCHING ON DEGENERATE 4-WAVE-MIXING

We report a theoretical and experimental investigation of the effects of collisional quenching on resonant degenerate four-wave mixing (DFWM). Using single-mode laser radiation, peak signal intensity measurements were performed on an isolated line in the A-X transition of NO. By using appropriate mixtures of N2 and CO2 as buffer gases, we varied the collisional quenching rate over several orders of magnitude while maintaining a fixed total collisional dephasing rate. The mixtures had approximately 100 Torr total pressure and were at room temperature. For I/I(sat) approximately equal to 0.02, DFWM intensities were found to be less affected by variations in quench rate than were laser-induced fluorescence (LIF) intensities (I and I(sat) are the pump laser and one-photon saturation intensities, respectively). Moreover, for I/I(sat) roughly equal to 0.5, DFWM intensities were observed to be nearly independent of quench rate. The results are compared to two theoretical predictions, with good agreement observed. Both theories indicate that the minimum sensitivity of DFWM to quenching occurs near I/I(sat) almost-equal-to 1.