Chiral Flat-Band Optical Cavity with Atomically Thin Mirrors

TL;DR

This paper introduces a novel sub-wavelength 2D nano-cavity using atomically thin transition metal dichalcogenide mirrors, demonstrating flat bands, tunable chiral modes, and electrical control, advancing light confinement and spin-photon applications.

Contribution

It presents the first experimental realization of a chiral flat-band optical cavity with atomically thin mirrors, enabling tunable and chiral light-matter interactions.

Findings

Demonstrated a flat band in a 2D nano-cavity

Achieved tunable chiral optical modes with magnetic fields

Showed electrical tunability of confined light modes

Abstract

A fundamental requirement for photonic technologies is the ability to control the confinement and propagation of light. Widely utilized platforms include two-dimensional (2D) optical microcavities in which electromagnetic waves are confined between either metallic or distributed Bragg reflectors. Recently, transition metal dichalcogenides hosting tightly bound excitons with high optical quality have emerged as promising atomically thin mirrors. In this work, we propose and experimentally demonstrate a sub-wavelength 2D nano-cavity using two atomically thin mirrors with degenerate resonances. Angle-resolved measurements show a flat band, which sets this system apart from conventional photonic cavities. Remarkably, we demonstrate how the excitonic nature of the mirrors enables the formation of chiral and tunable optical modes upon the application of an external magnetic field. Moreover, we show the electrical tunability of the confined mode. Our work demonstrates a mechanism for confining light with high-quality excitonic materials, opening perspectives for spin-photon interfaces, and chiral cavity electrodynamics.