Microwave analog experiments on optically soft spheroidal scatterers with weak electromagnetic signature

Abstract : Light scattering by optically soft particles is being theoretically investigated in many radiative studies. An interest is growing up to develop approximate methods when the resolution of Maxwell's equations is impractical due to time and/or memory size problems with objects of complex geometries. The participation of experimental studies is important to assess novel approximations when no reference solution is available. The microwave analogy represents an efficient solution to perform such electromagnetic measurements in controlled conditions. In this paper, we take advantage of the particular features of our microwave device to present an extensive experimental study on the electromagnetic scattering by spheroidal particles analogs with low refractive indices, as a first step toward the assessment of micro-organisms with low refractive index and heterogeneities. The spheroidal analogs are machined from a low density material and they mimic soft particles of interest to the light scattering community. The measurements are confronted to simulations obtained with Finite Element Method and T-Matrix method. A good agreement is obtained even with refractive index as low as 1.13. Scattered signals of low intensities are correctly measured and the position of the targets is precisely controlled. The forward scattering measurements show high sensitivity to noise and require careful extraction. The configuration of the measurement device reveals different technical requirements between forward and backward scattering directions. The results open interesting perspectives about novel measurement procedures as well as about the use of high prototyping technologies to manufacture analogs of precise refractive indices and shapes.
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Submitted on : Wednesday, August 30, 2017 - 5:13:58 PM
Last modification on : Monday, March 4, 2019 - 2:04:24 PM

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Hassan Saleh, Julien Charon, Jérémi Dauchet, Hervé Tortel, Jean-Michel Geffrin. Microwave analog experiments on optically soft spheroidal scatterers with weak electromagnetic signature. Journal of Quantitative Spectroscopy and Radiative Transfer, Elsevier, 2017, 196, pp.1 - 9. ⟨10.1016/j.jqsrt.2017.03.024⟩. ⟨hal-01579249⟩

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