Superenhanced photonic nanojet by core-shell microcylinders

The super-enhancement of photonic nanojets generated at the shadow side surfaces of core-shell microcylinders illuminated by a plane wave is reported. Using high resolution finite-difference time-domain simulation, the enhancements of photonic nanojet at resonance and off-resonance conditions of microcylinders are investigated. The intensity enhancement of photonic nanojet depends strongly on the thickness of metal shell. Under proper resonance condition, the photonic nanojet super-enhancement can be excited in the core-shell microcylinder. Even under off-resonance condition, the photonic nanojet from microcylinder is still strong enough. The results may provide a new technique to detect and image nanoscale objects below the diffraction limit. This could yield a new ultra-microscopy technique for using visible light to detecting nanoparticles, optical gratings, and single molecules. -- Highlights: ► We report the super-enhancement of photonic nanojets by core-shell microcylinders. ► Intensity enhancement of photonic nanojet depends on thickness of metallic shell. ► The results provide a new tool to detect nano-objects below the diffraction limit.