Near-field Hyperspectral Imaging of Resonant Mie Modes in a Dielectric Island

TL;DR

This paper uses hyperspectral imaging to map and analyze Mie resonances in a dielectric silicon island at the sub-wavelength scale, revealing detailed spatial and spectral features relevant for light management and emitter coupling.

Contribution

It introduces a combined experimental and theoretical approach for spatially resolving multiple Mie resonant modes in dielectric structures at the nanoscale.

Findings

Detection of small features as tiny as 200 nm

Spectral splitting of quadrupolar modes observed

Agreement between experimental data and FDTD simulations

Abstract

All-dielectric, sub-micrometric particles have been successfully exploited for light management in a plethora of applications at visible and near-infrared frequency. However, the investigation of the intricacies of the Mie resonances at the sub-wavelength scale has been hampered by the limitation of conventional near-field methods. Here we address spatial and spectral mapping of multi-polar modes of a Si island by hyper-spectral imaging. The simultaneous detection of several resonant modes allows to clarify the role of substrate and incidence angle of the impinging light, highlighting spectral splitting of the quadrupolar mode and resulting in different spatial features of the field intensity. We explore theoretically and experimentally such spatial features. Details as small as 200 nm can be detected and are in agreement with simulations based on a Finite Difference Time Domain method. Our results are relevant to near-field imaging of dielectric structures, to the comprehension of the photophysics of resonant Mie structures, to beam steering and to the resonant coupling with light emitters. Our analysis paves the way for a novel approach to control the spatial overlap of a single emitter with localized electric field maxima.