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 repl ace 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. T his results in a faster and much simpler measurement procedure. The ac curacy of the femtosecond hyper-Rayleigh scattering set-up was checked by measuring the first hyperpolarizability beta of the octopolar mole cule crystal violet in methanol [(450+/-100)X10(-30) esu at 800 nm]. T he sensitivity of the instrument allows concentration-dependence studi es, down to the pure solvent.