Near-field infrared nano-spectroscopy of surface phonon-polariton resonances

TL;DR

This paper combines experimental and numerical methods to analyze near-field infrared nano-spectroscopy of surface phonon-polariton resonances, revealing detailed tip effects and discovering a strong resonance in SrTiO3.

Contribution

It introduces detailed tip geometry in numerical simulations of near-field spectroscopy without free parameters, matching experimental spectral shapes and absolute scattering amplitudes.

Findings

Numerical simulations match experimental spectral shapes.

Verified published absolute scattering amplitudes.

Discovered a strong SPhP resonance in SrTiO3 at 24 micrometers.

Abstract

We present combined experimental and numerical work on light-matter interactions at nanometer length scales. We report novel numerical simulations of near-field infrared nanospectroscopy that consider, for the first time, detailed tip geometry and have no free parameters. Our results match published spectral shapes of amplitude and phase measurements even for strongly resonant surface phonon-polariton (SPhP) modes. They also verify published absolute scattering amplitudes for the first time. A novel, ultrabroadband light source enables near-field amplitude and phase acquisition into the far-infrared spectral range. This allowed us to discover a strong SPhP resonance in the polar dielectric SrTiO3 (STO) at approximately 24 micrometer wavelength of incident light.