Twin photonic nanojets generated from coherent illumination of microscale sphere and cylinder.

Photonic nanojets, highly focused beams of light created by planar illumination of a microsphere, have been shown to produce narrow subwavelength beams over distances of several wavelengths in the near field. In this work, we investigate the generation of twin photonic nanojets through the illumination of a microsphere or cylinder from two coherent sources with relative phase shift. Under these conditions, symmetric twin nanojets separated by an intensity null can be generated. Compared to a photonic nanojet, the twin nanojets can achieve an even smaller subwavelength beam, and have the added advantage of having more complex intensity profiles that can be controlled by multiple parameters. Using both finite-difference time-domain and Mie theory models, the width, length, and intensity enhancement factor of the nanojet geometry are found to be functions of the phase, angle offsets, and particle geometry. Such twin photonic nanojets can find applications in optical trapping, manipulation, nanolithography, and enhancement of nonlinear optical properties.