Extreme light confinement mediated by the transverse Kerker effect

TL;DR

This paper introduces a novel approach to achieve extreme light confinement using the transverse Kerker effect in dielectric metasurfaces, enabling polarization-independent bound states in the continuum with high quality factors.

Contribution

It demonstrates the first experimental realization of polarization-independent bound states in the continuum without symmetry breaking or Brillouin-zone folding.

Findings

Achieved polarization-independent bound states in the continuum in the visible spectrum.

Modes maintain large quality factors over broad momentum space regions.

Enabled ultranarrow resonances without standard BIC constraints.

Abstract

Dielectric nanoparticles can be engineered to scatter light predominantly in the transverse direction, a phenomenon known as the transverse Kerker effect. Although complete cancelation of forward scattering from a single object is forbidden by the optical theorem, we show that a single photonic mode can nonetheless realize an ideal transverse Kerker effect. The mode remains dark under normal incidence but evolves into an accidental bound state in the continuum when the nanoparticles are arranged in metasurfaces. This enables a new route to polarization-independent quasi-bound states in the continuum whose quality factors are tunable without symmetry breaking. We experimentally demonstrate our concept in the visible, achieving the first polarization-independent bound state in the continuum without the need for Brillouin-zone folding. Furthermore, we show that our modes maintain large quality factors over a substantially broader region of momentum space than conventional bound states in the continuum. Our results establish a platform for realizing ultranarrow resonances free of the constraints for designs with standard bound states in the continuum.