Resonance structures in elastic and Raman scattering from microspheres

Abstract

To study the interactions between Mie scattering and Raman emissions of spherical particles, we measured the Raman spectra together with the elastically scattered light of the excitation source of an evaporating

Cavity enhanced droplet spectroscopy: Principles, perspectives and prospects

“…As in cavity enhanced fluorescence, the WGM orders were often lower than in elastic scattering, with the low mode orders necessarily trapped in high-Q modes, minimising elastic scattering but maximising SRS signal. 83 Experiments with a mode-locked Nd:YAG laser delivering 100 ps pulses in a pulse train led to similar conclusions on low mode orders. 12 Input modes of low order (l ¼ 2-4) were found to dominate; l ¼ 1 modes were not observed, presumably because output coupling of this high-Q mode is low.…”

Morphology-dependent stimulated Raman scattering imaging. I. Theoretical aspects

“…Accurate identification of MDRs can be made by comparing the experimentally measured ⌬a with that calculated. This has been verified by Chan et al 34 When the elastic scattering is monitored simultaneous with MDSRS generation, it becomes possible to precisely, and instantaneously, specify the green MDR accessed in the experiment, and identify not only the region inside the aerosol from which the MDSRS signal arises, but also the position of the external laser source, with respect to the aerosol center.…”

Single-particle Raman spectroscopy for studying physical and chemical processes of atmospheric particles

“…Furthermore, Raman emissions from spherical particles (e.g., levitated droplets) can be complicated by resonance modes at discrete wavelengths triggered by cavity-enhanced Raman scattering (CERS) (Miles et al, 2012) or so-called size parameters in the spectra. These resonant modes are often called morphology-dependent resonance (MDR) or whispering gallery modes (WGMs) (Chan et al, 1991;Krieger et al, 2012). They can be used to accurately determine size with a resolution down to ∼ 5 nm, refractive index, and even shell-core morphology of the mixed organic-inorganic particles based on the Mie theory (Gorkowski et al, 2017(Gorkowski et al, , 2020Rafferty and Preston, 2018;Sullivan et al, 2020).…”

“…The optical effects complicate the Raman measurements for chemical analysis, although they provide additional information for the sizing and refractive index of the particles based on Mie theory. We refer readers to the references for the interactions between Mie scattering and Raman spectroscopy (Chan et al, 1991;Krieger et al, 2012;Nadler et al, 2019). Micro-Raman is a combined system that uses an optical microscope for guiding the laser to analyte particles and collect Raman scattering from the same microscope connected to a spectrometer.…”