Kharkiv Quantum Seminar: April 14, 11:00 EEST

Hyperbolic light

Alexey Nikitin (Donostia International Physics Center, Donostia-San Sebastian, Spain)

The propagation of light through various media has long been a subject of fundamental interest in physics. Optical phenomena such as diffraction, scattering, and emission are not only rich in physical content but also central to applications in information processing, imaging, security, and medicine—making research in optics both scientifically and socially relevant.

While most optical effects in conventional isotropic media are well understood, light behavior can change dramatically in strongly anisotropic materials, giving rise to surprising and less-explored phenomena. Notably, certain van der Waals crystals can support polaritons—electromagnetic waves coupled with dipolar excitations in matter. In these materials, the polariton dispersion relation (linking energy and momentum) can acquire a hyperbolic character.

This hyperbolic dispersion results in polaritons that propagate only along specific directions, exhibiting highly non-intuitive effects such as negative reflection and refraction, negative phase and group velocities, canalization (confined propagation along narrow angular sectors), and deep subwavelength focusing.

In this talk, we will introduce the field of hyperbolic nanooptics, explaining the fundamental physics behind hyperbolic polaritons and showcasing recent experimental advances. We will explore how these unusual light-matter interactions can be observed, interpreted, and potentially harnessed for novel optical functionalities. The presentation will conclude with a discussion of promising directions for future research.