SCATTERING OF LIGHT BY POLYDISPERSE, RANDOMLY ORIENTED, FINITE CIRCULAR-CYLINDERS

We use the T-matrix method, as described by Mishchenko [Appl. Opt. 32, 4652 (1993)], to compute rigorously light scattering by finite circul ar cylinders in random orientation. First we discuss numerical aspects of T-matrix computations specific for finite cylinders and present re sults of benchmark computations for a simple cylinder model. Then we r eport results of extensive computations for polydisperse, randomly ori ented cylinders with a refractive index of 1.53 + 0.008i, diameter-to- length ratios of 1/2, 1/1.4, 1, 1.4, and 2, and effective size paramet ers ranging from 0 to 25. These computations parallel our recent study of Light scattering by polydisperse, randomly oriented spheroids and are used to compare scattering properties of the two classes of simple convex particles. Despite the significant difference in shape between the two particle types (entirely smooth surface for spheroids and sha rp rectangular edges for cylinders), the comparison shows rather small differences in the integral photometric characteristics (total optica l cross sections, single-scattering albedo, and asymmetry parameter of the phase function) and the phase function. The general patterns of t he other elements of the scattering matrix for cylinders and aspect-ra tio-equivalent spheroids are also qualitatively similar, although noti ceable quantitative differences can be found in some particular cases. In general, cylinders demonstrate much less shape dependence of the e lements of the scattering matrix than do spheroids. Our computations s how that, like spheroids and bispheres, cylinders with surface-equival ent radii smaller than a wavelength can strongly depolarize backscatte red light, thus suggesting that backscattering depolarization for nons pherical particles cannot be universally explained by using only geome tric-optics considerations. (C) 1996 Optical Society of America