Quantitatively accurate numerical modeling of amplitude and phase contrast in broadband near-field infrared spectroscopy*

Proper modeling of near field infrared spectroscopy data is critical to extracting useful material properties. Current analytical models make underlying assumptions about the probe geometry that makes their use applicable in only limited situations. When strong coupling between probe and sample exists, a more robust solution method must be used. A full-wave numerical method for calculating broadband demodulated near-field amplitude and phase contrast will be presented. Our method captures the probe geometry accurately and is thus essential for obtaining quantitative results free of underlying assumptions and tunable parameters. We will present simulation results on SiO₂ and SrTiO₃, both of which exhibit surface phonon-polariton modes, and will compare the simulation results to experimental data.