Abstract

The phase conjugate reflectivity of a solution of chínese tea¹in ethanol, at different concentrations, was measured, using degenerate four wave mixing of a Nd:YAG laser beam at 532 nm. A reflectivity ≅ 7% was obtained at a concentration of 3.6 × 10^-4g/cm³, The square root of the reflectivity versus the pump intensities $\left(\sqrt{I_1{I}_2}\right)$ was plotted. The slope, of the straight line obtained, was used to estimate the value of the third order non-linear susceptibility, χ⁽³⁾≅ 1.1 × 10⁻⁷esu, assuming that absoprtion is the dominant mechanism for phase conjugation. At a higher concentration of 3.7 × 10⁻³g/cm³, χ⁽³⁾is 1.4 × 10⁻⁶esu. χ⁽³⁾was also estimated from the critical power P_cfor self trapping of a CW ar+ laser beam at 514.5 nm. χ⁽³⁾is linear at low concentrations, and saturates at the optical density (O.D.) = 0.5. At this O.D., χ⁽³⁾= 1.2 × 10^-6esu, which is comparable to that obtained from DFWM. Other self-action effects, such as self-defocussing, spatial self-phase modulation and beam fanning, were also observed. Further investigations are in progress.

© 1990 Optical Society of America