Asymptotic solutions for optical properties of large particles with strongabsorption

The transverse wave condition is not applicable to the refracted electromag netic wave within the context of geometrical optics when absorption is invo lved. Either the TM or the TE wave condition can be assumed for the wave to locally satisfy the electromagnetic boundary condition in a ray-tracing ca lculation. The assumed wave mode affects both the reflection and the refrac tion coefficients. As a result, nonunique solutions for these coefficients are inevitable. In this study the appropriate solutions for the Fresnel ref lection-refraction coefficients are identified in light-scattering calculat ions based on the ray-tracing technique. In particular, a 3 x 2 refraction or transmission matrix is derived to account for the inhomogeneity of the r efracted wave in an absorbing medium. An asymptotic solution that completel y includes the effect of medium absorption on Fresnel coefficients is obtai ned for the scattering properties of a general polyhedral particle. Numeric al results are presented for hexagonal plates and columns with both preferr ed and random orientations. (C) 2001 Optical Society of America.