Spatial Fano resonance of a dielectric microsphere impinged by a Bessel beam

TL;DR

This paper demonstrates the existence of spatial Fano resonance in a dielectric microsphere illuminated by a Bessel beam, revealing a giant electric field jump and potential for submicron optical trapping.

Contribution

It introduces the concept of spatial Fano resonance in space and analyzes its occurrence using Bessel beam illumination on dielectric microspheres, which is a novel approach.

Findings

Identification of spatial Fano resonance in dielectric microspheres

Observation of a giant electric field jump due to resonance interference

Potential application in submicron optical trapping

Abstract

General concept of Fano resonance is considered so that to show the possibility of this resonance in space. Using a recently found solution for a Bessel wave beam impinging a dielectric sphere, we analyze the electromagnetic fields near a microsphere with different optical size and permittivity values. We theoretically reveal a spatial Fano resonance when a resonant mode of the sphere interferes with {an amount of } non-resonant modes. This resonance results in a giant jump of the electric field behind the sphere impinged by the first-order Bessel beam. The local minimum of the electromagnetic field turns out to be noticeably distanced from the rear edge of the microsphere. However, this is a near-field effect and we prove it. We also show that this effect can be utilized for engineering a submicron optical trap with unusual and useful properties.