CPM Seminar

New approaches for the investigation of confined hyperbolic polaritons in Van der Waals crystals

Sébastien Francoeur

Polytechnique Montréal

Strong coupling between an electromagnetic wave and a solid-state polar excitation yields hybrid quasiparticles known as polaritons. Owing to their mixed light-matter characteristics, polaritons express distinctive properties and enable a unique level of control over light, matter, and their interactions. Phonon-polaritons results from the coupling of polar transverse optical phonons with light. In strongly anisotropic nanostructures, they exhibit a hyperbolic dispersion relation from which high-momentum states become accessible, providing the means to achieve extreme energy confinement and a large density of states enhancements, thereby providing new functionalities for IR sensing, low-loss photonic circuits, and new regimes of light-matter interactions.

In this presentation, I will delve into the science of hyperbolic photon-polaritons, elucidating their significance and exploring some of their most promising applications. I will also describe why almost all advances in this field have been driven by a single measurement technique for the last two decades: scattering-type near-field microscopy.

Then, I will then undertake two key discussions that may play a role in accelerating developments in this field:

• I will experimentally demonstrate how Raman spectroscopy, a simple, convenient, and widely used technique can be a powerful tool to investigate phonon-polariton dispersion relations, strong confinement, and coupling to other solid-state excitations such as excitons.
• I will introduce a promising polaritonic material, GaSe, characterized by low-propagation losses and confinement factors matching or surpassing those reported for other Van der Waals crystals.