The tunable photonic nanojet achieved by core-shell microcylinder with nematic liquid crystal is reported. The core-shell microcylinder can be obtained by the infiltration of liquid crystals into the air core of microcylinder. The refractive indices of liquid crystals can be changed by rotating the directors of liquid crystals. Therefore, we can control the flow direction of photonic nanojet in two-dimensional core-shell microcylinder structures. Using high resolution finite-difference time-domain simulation, we demonstrated that the photonic nanojet can be continuously tuned in the core-shell microcylinder. The horizontal and vertical shifts of photonic nanojet depend strongly on the director of liquid crystals. Such a mechanism of nanojet adjustment should open up a new application for using visible light to detecting nanoparticles, optical gratings, and single molecules with subwavelength spatial resolution.
