Non-resonant subwavelength imaging by dielectric microparticles

Reza Heydarian*, Constantin Simovski

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Recently a hypothesis explaining the non-resonant mechanism of subwavelength imaging granted by a dielectric microsphere has been suggested. In accordance to the hypothesis, the far-field image of a subwavelength scatterer strongly coupled to a microsphere by near fields is offered by the scatterer polarization normal to the sphere surface. The radiation of a closely located normally polarized dipole is shaped by the microsphere so that the transmitted wave beam has a practically flat phase front. Then this beam turns out to be imaging – keeping the subwavelength information about the dipole location. However, this mechanism of subwavelength imaging was only supposed in our previous paper. In this paper, we present a theoretical study which confirms this hypothesis and extends the underlying physics. In several scenarios of the imaging beam evolution either a flat or a slightly diverging phase front of the hollow wave beam formed by a microsphere enables the deeply subwavelength (0.1− 0.2λ) resolution of two dipole sources. We numerically simulate one of these scenarios – that one in which the focusing lens is located closer than the Rayleigh diffraction length to the beam-forming microsphere and represents a microsphere itself. In our simulations we replace a 3D microsphere by a 2D “sphere” (microcylinder) so that to use an available electromagnetic solver for dielectric microparticles of very large optical sizes. The physical mechanism of the imaging does not suffer of this replacement.

Original languageEnglish
Article number100950
Number of pages10
JournalPhotonics and Nanostructures - Fundamentals and Applications
Volume46
DOIs
Publication statusPublished - Sep 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • Diffraction free beam
  • Diffraction limit
  • Microsphere

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