Abstract
We report on the effects associated with photonic nanojet (PNJ) formation under illumination of a metallic spherical particle with a focused light beam with polarization singularity. Owing to radial polarization, the strongly focused beam generates the on-axis localized structure of intensity in the shadow area of the metal scatterer of different sizes, from the Rayleigh particle to microbeads. Significant amplification factor, small transverse size, and zero magnetic component on the axis and longitudinal polarization of the electric field are the distinctive features of such structures.
Highlights
Focusing a light wave with a system of lenses cannot achieve the light spot in focus less than a half of the wavelength [1]
We present the results of numerical computations and make a comparison between plasmonic nanojet formation and the nanojets formed by dielectric spheres
Unlike the nanojets, which are generated by a scattering the plane wave or vortex-free Gaussian beam, the plasmonic nanojets do not split into two off-axis hot spots if the size of the scatterer is small
Summary
Focusing a light wave with a system of lenses cannot achieve the light spot in focus less than a half of the wavelength [1]. Multiphoton absorption of an illuminated sample is widely used [1, 2] Another way is to obtain a localization of the electromagnetic field in the near zone of the scatterer. Most of the studies in this area are directed to the formation of PNJ by light diffraction on dielectric microspheres [2,3,4,5,6,7,8,9,10,11,12,13,14] and on microcylinders [15,16,17]. The formation a nanojet by light scattering on full-metal micro particles has been not considered yet, except our brief remark about possibility of PNJ formation using strongly focused singular beams [24]. We pay attention to the case of a metallic spherical particles illuminated by a singular optical beam, i.e., carrying optical singularity in a form of an optical vortex with a helical phase front or radial or azimuthal polarization with undetermined state on the beam axis
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