Mie scattering based measurements of the optical size of single spherical dielectric microparticles

[EN] The scattering of light by dielectric particles has significant implications for fields such as atmospheric science, optical sensing, and material characterization. We present an experimental study of the backscattered spectra of different dielectric materials, employing tightly focused Laguerre-Gaussian beams as incident light. Analysis of the experimental data allows us to determine the optical size of the measured spheres. Due to the extended wavelength range used in the experiments, the influence of the dispersion of the refractive index is also studied, unveiling that the oscillatory behavior of the spectra is related to the group velocity of the material. Circularly polarized Laguerre-Gaussian beams with different topological charges are also employed to probe the scattering process. We evaluated the limitations of the method depending on the particle sizes. We also compare some similarities of our analysis with the theory of cavities.