Resonance enhancement stimulated Raman scattering of O-H stretching vibration in water molecule

Stimulated Raman scattering (SRS) of water molecules excited by 532 nm laser is greatly enhanced by the application of CW(continuous-wave) seeding laser with 650 nm. When the CW laser power is 1 mW, the normalized SRS intensity of O-H stretching vibration at 3405 cm(-1) is increased by ten orders of magnitude. Two new lower frequency shoulder peaks are also observed after adding CW seeding laser, which shift to the low-wavenumber due to the pulse heating of water molecules in the laser focused volume. The CW seeding laser not only lowers the threshold of SRS, but also increases the intensity of SRS. The mechanism of enhancement is attributed to the frequency difference between pump laser (532 nm) and CW seeding laser (650 nm) matching the O-H stretching vibrational frequency of water molecule, which provides the possibility of using resonance methods to enhance weak Raman vibration modes. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study found that the stimulated Raman scattering of water molecules excited by 532 nm laser can be greatly enhanced by introducing a 650 nm continuous-wave seeding laser, which not only increases the intensity but also reduces the threshold of SRS. This opens up new possibilities for enhancing weak Raman vibrational modes using resonance methods.