Photonic nanojet enhancement of dielectric microcylinders with metallic coating

The detailed analysis of localized photonic nanojets generated at the shadow side surfaces of dielectric microcylinders with different metallic coatings illuminated by a plane wave is reported. Using high resolution finite-difference time-domain simulation, we have found that the photonic nanojets have waists smaller than the diffraction limit and power modulation by metallic coatings. The intensity enhancement of nanojets depends on the thickness of different metallic coatings. We have further analyzed the effect of refractive index and diameter upon the focal length of photonic nanojets. The results may provide a new ultra-microscopy technique of using visible light to detect and image nanoscale objectives such as nanoparticles, optical gratings, and single molecules.