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Atmospheric and Oceanic Optics

Inelastic linear scattering of light by spherical microparticles with active molecules

A. D. Bulygin, Yu. É. Geints, Aleksandr A. Zemlyanov

Published Apr 1, 2009• 0 citations
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Abstract

Based on the theory of open resonators, we investigate the fluorescence and Raman scattering of light by active molecules from a spherical microparticle in stationary and nonstationary excitation regimes using methods of statistical physics. Temporal and spectral energy characteristics of the resonator’s internal optical field at the Stokes frequency have been found. Expressions for the differential and total cross sections for inelastic scattering by a water droplet have been derived.

DOI
10.1134/s102485600902002x

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Based on the theory of open resonators, we investigate the fluorescence and Raman scattering of light by active molecules from a spherical microparticle in stationary and nonstationary excitation regimes using methods of statistical physics. Temporal and spectral energy characteristics of the resonator’s internal optical field at the Stokes frequency have been found. Expressions for the differential and total cross sections for inelastic scattering by a water droplet have been derived.
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The problem about two-photon induced fluorescence of organic dye active molecules located in spherical transparent microparticles at the ultrashort laser pulses influence was theoretically investigated. The system of kinetic equations for laser generation was written taking into account stimulation transitions. Generation regimes of stimulated radiation were found. Resonator properties of spherical microparticles were theoretically investigated using the method of expanding optical fields into series of eigenfunctions. The breakdown of the beginning of stimulated radiation in the microparticle was determined. It was shown that stimulated radiation intensity depends on degree of its spatial overlap with all other modes of the pump radiation. The interpretation of experimental data of two-photon induced fluorescence in the particles with organic dye was carried out.
The total cross section for fluorescent scattering by a spherical particle uniformly filled with fluorescent scatters is computed using a model for fluorescent scattering formulated earlier. Results are given for an arbitrary incident beam and for a linearly polarized plane wave normalized to the cross section for the same number of scatterers in bulk medium. The cross section has a form which clearly shows the possibility of resonance peaks when either the incident or the fluorescent frequency (or both) coincides with eigenfrequencies of the particle.
The spontaneous Raman scattering from liquid samples of C6{\mathrm{C}}_{6}C6​H6{\mathrm{H}}_{6}H6​ is investigated in the Casimir topology of a microscopic optical Fabry-P\'erot cavity terminated by Bragg reflectors tuned at the emitted Stokes wavelength. The given general quantum scattering theory is based on a complete set of mode functions describing the cavity-confined field in its vacuum state. The coupling of the field with the normal CH ring stretching mode at \ensuremath{\Delta}\ensuremath{\nu}=3062 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (totally symmetric species A1g{\mathit{A}}_{1\mathit{g}}A1g​) of the benzene molecule is given via the related Raman tensor, which leads to the appropriate form of the coupling Hamiltonian. A detailed experimental investigation of the spontaneous Raman scattering for the mode is then reported. The results confirm the relevant predictions of the scattering theory, namely, the effect of the vacuum confinement on the enhancement and inhibition of the total and differential cross sections, on the angular distribution of the scattered radiation, and on the molecular depolarization ratio. \textcopyright{} 1996 The American Physical Society.