Optically addressable spin defects coupled to bound states in the continuum metasurfaces

TL;DR

This paper demonstrates a scalable integration of spin defects in hBN with metasurfaces using quasi-bound states in the continuum, significantly enhancing photoluminescence and spectral control for quantum nanophotonics.

Contribution

It introduces a novel method to couple spin defects in hBN with high-Q resonances in metasurfaces, achieving substantial emission enhancement and spectral narrowing.

Findings

25-fold increase in photoluminescence intensity

Spectral linewidth narrowed below 4 nm

Q factors exceeding 100

Abstract

Van der Waals (vdW) materials, including hexagonal boron nitride (hBN), are layered crystalline solids with appealing properties for investigating light-matter interactions at the nanoscale. hBN has emerged as a versatile building block for nanophotonic structures, and the recent identification of native optically addressable spin defects has opened up exciting possibilities in quantum technologies. However, these defects exhibit relatively low quantum efficiencies and a broad emission spectrum, limiting potential applications. Optical metasurfaces present a novel approach to boost light emission efficiency, offering remarkable control over light-matter coupling at the sub-wavelength regime. Here, we propose and realise a monolithic scalable integration between intrinsic spin defects in hBN metasurfaces and high quality (Q) factor resonances leveraging quasi-bound states in the continuum (qBICs). Coupling between spin defect ensembles and qBIC resonances delivers a 25-fold increase in photoluminescence intensity, accompanied by spectral narrowing to below 4 nm linewidth facilitated by Q factors exceeding $10^2$. Our findings demonstrate a new class of spin based metasurfaces and pave the way towards vdW-based nanophotonic devices with enhanced efficiency and sensitivity for quantum applications in imaging, sensing, and light emission.