Influence of an Edge Height on the Diffracted EM Field Distribution

The diffraction of light from a right-angled, lossless dielectric step, illuminated by a plane wave, forms a tilted focused beam. Its deviation angle depends on the index ratio between the structure material and host medium. This paper will demonstrate the existence of a critical height of a wavelength sized edge. This edge diffracts the incident light energy inside the higher index medium, as a specific field distribution. The analysis, done for optical frequencies, identifies lobes in the resulting field distribution. The lobes repartition is driven by a critical height and its multiples. These EM patterns are evaluated in relation with the photonic nanojet phenomenon.