Tunable Nanophotonic Devices and Cavities based on a Two-Dimensional Magnet

TL;DR

This paper demonstrates the fabrication of tunable nanophotonic devices using a two-dimensional magnetic semiconductor, enabling dynamic control of optical properties and strong light-matter interactions at near-visible and infrared wavelengths.

Contribution

It introduces a novel approach to dynamically tune photonic crystal resonances using a 2D magnetic material, CrSBr, with high Q-factors and strong excitonic coupling.

Findings

Achieved in situ optical tunability via external magnetic fields.

Demonstrated high Q-factors exceeding 500.

Observed intrinsic strong light-matter coupling with excitons.

Abstract

Central to the field of nanophotonics is the ability to engineer the flow of light through nanoscale structures. These structures often have permanent working spectral ranges and optical properties that are fixed during fabrication. Quantum materials, with their correlated and intertwined degrees of freedom, offer a promising avenue for dynamically controlling photonic devices without altering their physical structure. Here, we fabricate photonic crystal slabs from CrSBr, a van der Waals antiferromagnetic semiconductor, and demonstrate unprecedented in situ control over their optical properties. Leveraging the combination of the exceptionally large refractive index of CrSBr near its excitonic resonances and its tunability via external fields, we achieve precise manipulation of photonic modes at near-visible and infrared wavelengths, showcasing a new paradigm for nanophotonic device design. The resulting guided resonances of the photonic crystal are tightly packed in the spectrum with very small mode volumes, are highly tunable via external magnetic fields, and exhibit high Q-factors exceeding 500. These resonances self-hybridize with the excitonic degrees of freedom, resulting in intrinsic strong light-matter coupling. Our findings underscore the potential of quantum materials for developing in situ tunable photonic elements and cavities.