Narrowband quantum emitters over large spectral range with Fourier-limited linewidth in hexagonal boron nitride

TL;DR

This study demonstrates narrowband, Fourier-limited quantum emitters in hexagonal boron nitride with stable, tunable spectral properties over a large range, suitable for quantum photonics applications.

Contribution

It reports the first observation of Fourier-transform limited linewidths in hBN quantum emitters and their stability upon transfer to photonic platforms.

Findings

Achieved Fourier-limited linewidths of ~50 MHz in hBN emitters

Distributed zero-phonon lines over 580-800 nm with high polarization contrast

Emitters remain stable after transfer to a silver mirror platform

Abstract

Single defect centers in layered hexagonal boron nitride (hBN) are promising candidates as single photon sources for quantum optics and nanophotonics applications. However, until today spectral instability hinders many applications. Here, we perform resonant excitation measurements and observe Fourier-Transform limited (FL) linewidths down to $\approx 50$ MHz. We investigate optical properties of more than 600 quantum emitters (QE) in hBN. The QEs exhibit narrow zero-phonon lines (ZPL) distributed over a spectral range from 580 nm to 800 nm and with dipole-like emission with high polarization contrast. The emission frequencies can be divided into four main regions indicating distinct families or crystallographic structures of the QEs, in accord with ab-initio calculations. Finally, the emitters withstand transfer to a foreign photonic platform - namely a silver mirror, which makes them compatible with photonic devices such as optical resonators and paves the way to quantum photonics applications including quantum commmunications and quantum repeaters.