Experimental Demonstration of Collective Photonic Nanojet Generated by Densely Packed Arrays of Dielectric Microstructures

Abstract Uncovering new ways for light localization at the micro‐ and nanoscale is essential for the development of state‐of‐the‐art photonic devices. Nowadays the most advances in this area are achieved using near‐field resonators, providing extreme light confinement in nanoscale volume. However, the boosting of device performance in some practical applications, for example, luminescent sensing, optical tweezing, and super‐resolution optical microscopy require light localization at distances beyond near‐field range. This issue can be addressed by employing dielectric microstructures that produce photonic nanojets (PNJs), representing an intermediate state between near‐field localization and geometric optics. Despite the promising benefits of PNJ implementation in various optical applications, their practical studies are scarce and mostly limited to numerical simulations. Here, a new type of PNJ is introduced and studied both numerically and experimentally. Contrary to the conventional case, wherein PNJ is generated by a single microstructure, the reported PNJ is produced through collective effects in a densely packed array of dielectric microstructures. The studies reveal that these collective PNJs can reach an unprecedented length of >60 λ, while maintaining a high localization intensity. Under certain configurations of the array, collective PNJ can enhance the electromagnetic field by up to sevenfold, being a versatile tool for various photonic applications.