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.
“Influence of an edge height on the diffracted EM field distribution“, Bobin Varghese, Oksana Shramkova, Valter Drazic, Valérie Allié, Laurent Blondé*, International Conference on Transparent Optical Networks, 9-13 July 2019, Angers, France.
In this contribution we reveal how the step-like topology of a microstructure can contribute to the formation of a single high-intensity nanojet (NJ) beam located on its axis of symmetry. The proposed method for generating condensed optical NJ beams relies on the complex electromagnetic phenomenon associated with the light diffraction on the edges of step-like dielectric microstructures embedded in a host medium with lower refractive index. The possibility of NJ beam intensification in the near zone of such microstructure illuminated by a plane wave is demonstrated and explained by the recombination of multiple NJ beams associated with different edges or edge segments of the step-like microlens. We demonstrate that by changing materials of the layers we can intensify the NJ beam. We examine the dependence of the generated beam on the step size, shape and material.
“Localized photonic jets generated by step-like dielectric microstructures“, O. Shramkova, V. Drazic, M. Damghanian, A. Boriskin, V. Allié, L. Blondé, International Conference on Transparent Optical Networks, 1-5 July 2018, Bucharest, Romania.