High-order interior caustics produced in scattering of a diagonally incident plane wave by a circular cylinder

We examine scattering of a family of initially parallel diagonally incident rays by a dielectric circular cylinder and show that the interior and exterior caustics that occur are qualitatively identical to those produced at normal incidence. We find, however, that (1) varying the plane-wave tilt angle has the same effect on the caustics as varying the refractive index of the cylinder at normal incidence and (2) high-order interior caustics are visible because of larger internal-reflection Fresnel coefficients at diagonal incidence than at normal incidence. We also observe noncaustic ray trajectories produced by the sharp peaking of internal-reflection Fresnel coefficients at large ray impact parameters, as well as another class of internal caustics produced by scattering from inhomogeneities in our glass cylinder. (C) 1997 Optical Society of America.