Efficient generation of multi-order Raman radiation in aqueous solutions derived from -CH and -NH vibrations via cascaded four-wave mixing and Stokes processes.

Multiple coherent radiations are achieved in a water-3-aminopropanol (3AP) mixed solution through cascaded four-wave mixing (C-FWM) and cascaded Stokes (C-Stokes) processes, both driven by stimulated Raman scattering (SRS) in this work. The O-H vibration peak from water is replaced by the emergence of the -NH symmetric stretching Raman peaks from 3AP, with intensity approaching that of the -CH symmetric stretching peak. The dual-wavelength SRS signals for the -NH and -CH stretching vibrations have a relatively small frequency interval of about 400 cm (16 nm). By varying the 3AP concentration and pump energy, these two peaks from 3AP act as new pump sources, enabling the successful generation of up to 16th-order Stokes and 5th-order anti-Stokes radiation through C-FWM and C-Stokes processes. The resulting spectrum spans a broad wavenumber range from -3318 to 6629 cm (452 to 822 nm), offering a new approach for broadband coherent light sources and multi-order Raman spectra in liquid media.