Fourier-Tailored Light-Matter Coupling in van der Waals Heterostructures

TL;DR

This paper demonstrates enhanced light-matter coupling in van der Waals heterostructures by Fourier-tailoring the dielectric surface, enabling strong exciton-photon interactions with potential applications in quantum optoelectronics.

Contribution

The authors introduce a novel Fourier surface fabrication technique to optimize light-matter coupling in WS$_2$-hBN heterostructures, achieving near-strong coupling conditions.

Findings

Observation of exciton-polaritons with Rabi splitting

Successful fabrication of sinusoidal Fourier surfaces with nanometer precision

Enhanced optical mode overlap in vdW heterostructures

Abstract

Dielectric structures can support low-absorption optical modes, which are attractive for engineering light-matter interactions with excitonic resonances in two-dimensional (2D) materials. However, the coupling strength is often limited by the electromagnetic field being confined inside the dielectric, reducing spatial overlap with the active excitonic material. Here, we demonstrate a scheme for enhanced light-matter coupling by embedding excitonic tungsten disulfide (WS$_2$) within dielectric hexagonal boron nitride (hBN), forming a van der Waals (vdW) heterostructure that optimizes the field overlap and alignment between excitons and optical waveguide modes. To tailor diffractive coupling between free-space light and the waveguide modes in the vdW heterostructure, we fabricate Fourier surfaces in the top hBN layer using thermal scanning-probe lithography and etching, producing sinusoidal topographic landscapes with nanometer precision. We observe the formation of exciton-polaritons with a Rabi splitting indicating that the system is at the onset of strong coupling. These results demonstrate the potential of Fourier-tailored vdW heterostructures for exploring advanced optoelectronic and quantum devices.