Unveiling the Zero-Phonon Line of the Boron Vacancy Center by Cavity-Enhanced Emission
Chenjiang Qian, Viviana Villafañe, Martin Schalk, G. V. Astakhov, Ulrich Kentsch, M. Helm, Pedro Soubelet, Nathan P. Wilson, Roberto Rizzato, Stephan Mohr, Alexander W. Holleitner, Dominik Bucher, Andreas V. Stier, Jonathan J. Finley
Abstract
Negatively charged boron vacancies (VB–) in hexagonal boron nitride (hBN) exhibit a broad emission spectrum due to strong electron–phonon coupling and Jahn–Teller mixing of electronic states. As such, the direct measurement of the zero-phonon line (ZPL) of VB– has remained elusive. Here, we measure the room-temperature ZPL wavelength to be 773 ± 2 nm by coupling the hBN layer to the high-Q nanobeam cavity. As the wavelength of cavity mode is tuned, we observe a pronounced intensity resonance, indicating the coupling to VB–. Our observations are consistent with the spatial redistribution of VB– emission. Spatially resolved measurements show a clear Purcell effect maximum at the midpoint of the nanobeam, in accord with the optical field distribution of the cavity mode. Our results are in good agreement with theoretical calculations, opening the way to using VB– as cavity spin–photon interfaces.