Efficient generation of multi-order Raman radiation in aqueous solutions derived from -CH2 and -NH2 vibrations via cascaded four-wave mixing and Stokes processes.

Abstract

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 -NH₂ symmetric stretching Raman peaks from 3AP, with intensity approaching that of the -CH₂ symmetric stretching peak. The dual-wavelength SRS signals for the -NH₂ and -CH₂ stretching vibrations have a relatively small frequency interval of about 400 cm^-1 (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^-1 (452 to 822 nm), offering a new approach for broadband coherent light sources and multi-order Raman spectra in liquid media.