Photonic nanojet as a result of a focused near-field diffraction

In this paper, we present the formation of the photonic nanojet as a result of focused near-field diffraction. The dielectric structure responsible for the observation of the photonic nanojet effect plays the role of a diffracting slit and a focusing lens at the same time. We show numerically, for the first time to our knowledge, that it is possible to observe photonic nanojets by replacing the dielectric structure and incident plane wave with a diffracting slit and Gaussian beam, respectively. We find that one might control the most important features of the photonic nanojet, namely, the width and length, by varying the focusing parameters of the dielectric structure.