Experimental verification of twin photonic nanojets from a dielectric microcylinder

In this Letter, the direct generation of twin photonic nanojets (PNJs) through two coherent illuminations of a microcylinder is investigated theoretically and experimentally. The dielectric microcylinder (polydimethylsiloxane) with 5 μm diameter and 6 μm height is employed to generate symmetric twin PNJs. The finite-difference time-domain calculation is used to simulate the electric field distributions inside and outside the microcylinder. The scanning optical microscope system is performed for experimental verification of twin photonic nanojets. In both theory and in practice, the intensity null of electric field creates two separate PNJs. Compared to a single PNJ, twin PNJs have a smaller subwavelength waist and more complex intensity distribution. The focal distance, interval, and full width at half-maximum of twin PNJs are a function of the offset angle. The twin PNJs will provide novel applications in nanolithography, optical trapping, biophotonic sensing, and therapy.