Scattering asymmetry in in-situ Mie polarimetry diagnostic of nanodust clouds

Abstract

Imaging Mie polarimetry is key to determining spatially resolved information about the properties, i.e., refractive index and grain size, of particle clouds, such as during the growth process in reactive particle producing plasmas. Asymmetries in the intensity maps of the different Stokes parameters resulting from the anisotropic scattering of polarized laser light complicate the analysis and require the use of radiative transfer simulations.
 We use radiative transfer simulations to investigate the asymmetric scattering behaviour based on a model of a typical reactive argon-acetylene plasma. We address possible misinterpretations and explore the potential for analysing particle properties. We find that the asymmetric pattern of the intensity distributions is highly dependent on the refractive index, providing the potential to determine the refractive index and grain size at any time during the growth process.

Analyzing dust particle size and size distribution on extracted particles by SEM and comparing with light scattering techniques

“…In addition, the model deviates for particles with a radius of above 200 nm. This has been explored [ 24,46 ] and attempts have been made to utilize Radiative Transfer Simulations [ 47,48 ] as a diagnostic tool. But so far it is not certain if this deviation occurs due to the influence of multiple light scattering, a change in the refractive index of the particles or a surface modification, which could require a core–shell description.…”