Comment on “Functional dielectric microstructure for photonic nanojet generation in reflection mode” by Aleksandr Sergeev and Ksenia Sergeeva, Optical Materials 110 (2020) 110503

This work addresses the shortcomings of the recent paper by A. Sergeev and K. Sergeeva [Optical Materials 110 (2020) 110503], in which the authors attempted to analyze the extended photonic nanojet generated in reflection mode by an array of aluminum oxide hemispheres. In this contribution we show the nature and parameters of photonic nanojet in reflection mode obtained in simulations, do not correspond to the experimental conditions and contradict the physics of the phenomenon, and this is worth discussing. In fact, the authors of above cited work observed in simulations a formation of the photonic nanojet in reflection mode, but the interaction with the incident field was not taken into account, which led to the absence of modulation of the photonic nanojet by a standing wave, which does not correspond to the physics of the process. Therefore, the results of the simulations presented in Figure 3 are not reliable.