Degenerate Four-Wave Mixing for Quantitative Diagnostic Measurements

We report theoretical and experimental studies of the effects of collisional quenching and the contributions of thermal gratings in degenerate four-wave mixing (DFWM).1 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 varying quenching rate also had the effect of varying the heat released by population gratings to form thermal gratings, permitting detailed comparisons of signal intensities from both mechanisms.