Confocal polarization tomography of dielectric nanocavities

TL;DR

This paper uses polarization tomography in a confocal setup to analyze dielectric nanocavities, revealing polarization-dependent Fano lineshapes, a new resonance, and modal features even in symmetry-forbidden polarizations.

Contribution

It introduces a novel polarization tomography method to characterize nanocavity modes and uncovers previously unreported resonances and polarization effects.

Findings

Fano lineshape depends strongly on polarization

A Lorentzian-like peak can be achieved at specific polarization

Discovery of a new resonance in dielectric nanocavities

Abstract

We employ polarization tomography to characterize the modal properties of a dielectric nanocavity with sub-wavelength mode confinement. Our analysis of reflection spectra shows that the Fano-lineshape depends strongly on the polarization in a confocal configuration, and that the lineshape can be transformed into a Lorentzian-like peak for a certain polarization. For this polarization setting, the background is almost fully suppressed in a finite range of frequencies. This enables us to identify another resonance that has not yet been experimentally reported for these nanocavities. Lastly, we use symmetry-forbidden polarizations and show that, surprisingly, the modal resonance features of the system remain visible.