Theoretical Study of Brillouin Light Scattering by Spherical Particles

Postgraduate Thesis uoadl:1317966 119 Read counter

Κατεύθυνση Φυσική των Υλικών (ΒΑΣΙΚΗ ΦΥΣΙΚΗ)
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Ζδάγκας Απόστολος
Supervisors info:
Νικόλαος Στεφάνου Καθηγητής (Επιβλέπων), Μαρία Καλαμιώτου Αναπλ. Καθηγήτρια, Εμμανουήλ Συσκάκης Επίκ. Καθηγητής
Original Title:
Θεωρητική Μελέτη της Σκέδασης Brillouin από Σφαιρικά Σωματίδια
Translated title:
Theoretical Study of Brillouin Light Scattering by Spherical Particles
Brillouin light scattering is the inelastic light scattering due to the spatial
and temporal
variations of the refractive index of a material. These variations are due to
collective oscil-
lations of a quantity in the material which, in our case, are the collective
lattice oscillations
(phonons). These oscillations are in the GHz frequency range and this is why
the deve-
lopment of lasers and the invention of the multi-pass tandem Fabry-Perot
was needed in order to use the eff ect as a spectroscopic technique. This
technique has
already been used for the characterization of the elastic properties of solids
and liquids
but with the advent of meso-scale periodic structures, in which the dominant
are in the GHz range, it soon became apparent that the technique could be used
for the
characterization of phononic microstructures. In the last decade, a lot of e
ffort has been
devoted in order to explain the Brillouin spectrum of such periodic
microstructures of
spherical particles. The eff ort was focused on indirect explanations either by
the eigenmodes, the scattering cross section and the density of states of the
particles or the frequency band structure of the phononic crystal, as well as
using group
theory. It became clear that only a detailed theoretical study, which takes
into account
the interaction of light with the elastic field, can give the correct relative
intensities of the
scattered light. Such a theoretical approach of the Brillouin light scattering
by a spherical
particle, based on Green's functions, is attempted in the present thesis. Using
the work of
T. Still et al., J. Phys. Chem. Lett. 1, 2440-2444 (2010) as a starting point,
we improve
the computation time and the accuracy of the calculations and establish the
foundations for a thorough description of the e ffect as well as the extension
of Brillouin
light scattering calculations to periodic structures.
Brillouin scattering, Inellastic light scattering, Eigen-modes of a spherical particle, Photo-elastic effect
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