Four-photon parametric light scattering of ultrashort laser pulses in water in case of weak self-phase modulation

The hyper-Raman scattering (HRS) of light in water is detected reliably by the active spectroscopy method of coherent light scattering, in particular, by the method of four-photon parametric light scattering in a medium in which HRS is a "signal" wave in the parametric process involving simultaneously two high-power laser photons and IR photons of an "idler" wave. Hyper-Raman scattering by libration vibrations of water molecules, which virtually cannot be detected by conventional methods of Raman scattering, was observed.