Diffraction Resonances in Thin Refractive Fibers

The resonant phenomena arising from the incidence of electromagnetic radiation on the cylinder are investigated. The case when a plane wave is incident on an infinitely long circular cylinder is considered. Resonances arise at certain ratios between the cylinder diameter $D$ and the radiation wavelength $\lambda$. In thick refractive cylinders with absorption $(D >> \lambda)$ resonances are associated with the appearance of a wave that propagates along the surface of the cylinder, but at some points passes inside it. Scattering and absorption increase at resonance. Fano resonances arise in thin cylinders with a high refractive index. At some values of the cylinder diameter, its interaction with the wave is enhanced (resonance), at other values, the “anti-resonance” is weakened. The distribution of the field in the cylinder and its vicinity and the scattering diagram in these cases are calculated. It is the same as that of a dipole at resonance. With “anti-resonance” the shape of the scattering diagram is close to circular, and the intensity of the scattered radiation is hundreds of times less. The cylinder becomes invisible.