Light transmission through a subwavelength microstructured aperture: electromagnetic theory and applications

A differential theory of diffraction by apertures and/or objects described in cylindrical coordinates is outlined. It projects the electromagnetic field on a Fourier-Bessel basis and uses correct rules to express the components of the electric displacement D on that basis which is truncated in view of numerical computation. Maxwell equations are then reduced to a finite first order differential set which provides a fast convergence of the results when the truncation order is increased. We apply the theory to the study of the transmission of a circular aperture inside a metallic screen connected with a tapered fiber. Coaxial devices can be studied as well.