Anomalous scattering from dielectric bispheres in the specular direction

Resonant scattering from dielectric bispheres in the specular direction (the so-called specular resonance), previously known only in the microwave range, has been observed at the optical wavelength. Systematic experiments with micrometer-sized dielectric bispheres assembled by micromanipulation, together with rigorous numerical calculations, reveal that this scattering is a precursor of the classical rainbow and is a general phenomenon observed in the wide range of size parameters (>5 for n = 1.59) for various refractive indices. (C) 2002 Optical Society of America.