HYPER-RAYLEIGH SCATTERING IN SOLUTION WITH TUNABLE FEMTOSECOND CONTINUOUS-WAVE LASER SOURCE

Hyper-Rayleigh scattering has been developed as a generally applicable technique for the determination of the first hyperpolarizability beta of a wide class of molecules [Clays and Persoons, Rev. Sci. Instrum. 63, 3285 (1992)]. In this article, we show that it is possible to replace the low repetition rate, nanosecond pulse, Q-switched laser source and fast gated electronics by a self-mode-locked, femtosecond pulse, broadly tunable continuous-wave laser and phase-sensitive detection. This results in a faster and much simpler measurement procedure. The accuracy of the femtosecond hyper-Rayleigh scattering set-up was checked by measuring the first hyperpolarizability beta of the octopolar molecule crystal violet in methanol [(450+/-100)X10(-30) esu at 800 nm]. The sensitivity of the instrument allows concentration-dependence studies, down to the pure solvent.