Tunable and ultra-elongated photonic nanojet generated by a liquid-immersed core-shell dielectric microsphere

摘要

A three-dimensional (3D) photonic nanojet (PNJ) emerging from a liquid-immersed core-shell dielectric microsphere is numerically investigated by the finite-difference time-domain (FDTD) method. An ultra-elongated PNJ with an effective length larger than 57 wavelengths while retaining a high intensity and a large working distance is obtained from the simulation. In particular, PNJ properties, including intensity enhancement, working distance, effective length, and full width at half maximum (FWHM), can be well tuned and controlled by varying the refractive index of the immersed liquid. We believe that this design is applicable to many fields, such as material science, nanophotonics, and biomedicine.