Gerard Gouesbet
CORIA
website
A story of analytical light scattering theories.
Abstract:We shall provide a story of generalized Lorenz-Mie theories which are analytical light scattering theories describing the scattering of arbitrary shaped beams by scatterers under the proviso that Maxwellís equations can be solved by using a method of separation of variables. Motivated by the need of mea- suring simultaneously velocities and sizes of individual particles in multiphase áows, the generalized Lorenz-Mie theory, stricto sensu, deals with the case when the scatterer is a homogeneous sphere, and was Örst published, for on-axis illu- mination in 1982. Several other theories for other kinds of scatterers not only in spherical coordinates but as well in circular and elliptical cylindrical coor- dinates and in spheroidal coordinates have afterward been developed. These theories have been applied to optical particle characterizations, mechanical ef- fects of light (forces, torques), internal resonances, among other topics. Recent studies demonstrated that the arsenal gained during more than four decades in electromagnetism can be transferred to the Öeld of acoustics. We shall pro- vide particular discussions (with videos) concerning the failure of the optical theorem, the unexpected fact that photons in structured beams in free space can propagate slower than the speed of light, and that internal hot spots inside scatterers can propagate at a velocity higher than the speed of light. We shall Önally discuss a few unsolved problems of interest. For overviews, see a textbook [1] and a recent review [2].
References
[1] G. Gouesbet and G.GrÈhan. Generalized Lorenz-Mie theories, 3rd edition. Springer, 2023.
[2] G. Gouesbet. T-matrix methods for electromagnetic structured beams: A commented reference database for the period 2019-2023. Journal of Quan- titative Spectroscopy and Radiative Transfer, 322:Article 109015, 2024.
