Insitu microparticle diagnostics by stimulated Raman scattering

Abstract

A novel technique for the identification of the chemical composition of microdroplets has been developed. External seeding of stimulated Stokes Raman scattering (SSRS) has been applied to reduce the minimum detectable concentration of the minority species in multicomponent microdroplets. To avoid complications with polarizer and analyzer in remote sensing applications, we utilize the fact that the probed (seeded) SSRS band of the minority species (at ν_min) can efficiently pump SSRS of the majority species (at ν_maj). The Raman signal of the minority species appears at a shift of ν_min+maj, which can easily be distinguished from the elastically scattered light of the seed laser at the shift of ν_min. Furthermore, we investigated fluorescing microdroplets with stimulated anti-stokes Raman scattering (SARS).