Oral: Confined Exciton-Polaritons in CrSBr, a van der Waals magnet

In nanophotonics, high refractive index semiconductors play a pivotal role in downsizing optical components and systems, a fundamental requirement for creating compact and seamlessly integrated photonic circuits and devices. In this context, we explore the intriguing properties of CrSBr, an anisotropic van der Waals magnet with significantly varying refractive indices along the two in-plane crystal axes. Notably, CrSBr is a direct band gap semiconductor that emits near-infrared radiation (NIR) and displays magnetic order below 132 K in bulk form. Our investigation focuses on harnessing the contrasting refractive indices along the two in-plane axes to engender confined exciton-polariton states in a dielectric cavity. We demonstrate significant confinement of polaritons along the b-axis, even within micrometer-wide flakes, while simultaneously facilitating the free propagation of polaritons along the a-axis. We employ spectral filtering to capture real-space images of these confined polariton states and delve into their nonlinear behavior. Additionally, we highlight the efficient waveguiding capabilities of polaritons in CrSBr, showcasing their propagation over distances exceeding 20 micrometers. With further tunability of these confined polariton states with a magnetic field, our study underscores CrSBr as a promising platform for developing integrated magneto-photonic devices.