Evidence of Mie scattering at terahertz frequencies in powder materials

We present experimental results as well as modelling concerning terahertz (THz) wave scattering by powder materials with grain size of the order of the wavelength. The studied material is a mixture of high density polyethylene and fructose powders, whose grain size is varied from a sample to another one while the volume concentration is kept constant. Experimental data are recorded with a THz time-domain spectroscopy set up. The scattering contribution to the total propagation loss in such powders shows a resonant behaviour for grain size roughly equal to the THz wavelength, for which it reaches 80%–90% of the total loss. Modelling using Mie theory allows us to well describe the absorption and scattering phenomena.