Donut-like photonic nanojet with reverse energy flow

Photonic nanojets (PNJs) are subwavelength jet-like propagating waves generated by illuminating a dielectric microstruc-ture with an electromagnetic wave, conventionally a linearly polarized plane wave. Here, we study the donut-like PNJ produced when a circularly polarized vortex beam is used instead. This novel PNJ also has a reverse energy flow at the donut-like focal plane depending on both the optical vortex topological charge and microsphere size. Our tunable PNJ, which we investigate numerically and analytically, can find applications in optical micromanipulation and trapping.

Automated summary

Photonic nanojets (PNJs) are subwavelength jet-like propagating waves generated by illuminating a dielectric microstructure with an electromagnetic wave, conventionally a linearly polarized plane wave. When a circularly polarized vortex beam is used instead of a linearly polarized plane wave, a donut-like PNJ is produced with a reverse energy flow at the focal plane depending on both the optical vortex topological charge and microsphere size. This tunable PNJ can find applications in optical micromanipulation and trapping, and has been studied numerically and analytically in this research.