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Cavity quantum electrodynamics describes coupled systems comprising of optically active emitters with atom-like transitions, such as single-photon emitters (SPEs), and optical cavities that underlies various fundamental quantum properties. In the strong coupling regime, SPEs and cavity photons coherently exchange energy leading to two new hybrid states that significantly modify the optical responses of the originally uncoupled or weakly coupled states. As a result, various intriguing effects could be realized such as Rabi oscillations, nonlinearities, photon blockade when the system is in strong coupling conditions.
To achieve strong coupling between SPEs and photonic cavities, SPE transition energies have to coincide with cavity resonances (spectral overlapping), SPEs are precisely positioned at the electric field antinodes (spatial overlapping) and SPE emission decay is slower than coupling strength (narrow linewidth). Such stringent conditions impose serious challenges for experimental realization of SPE-cavity strong coupling particularly at room temperature due to the lack of stable single-photon sources with high color purity at high temperatures and controllability on positioning SPE in cavity. Strong coupling has been reported for single semiconducting quantum-dots and photonic crystal cavities at cryogenic temperature1,2 and for single molecules and plasmonics cavities at room temperature.3 Here, we introduce a new approach using point-defects purposely created in a two-dimensional few-layer-thick hexagonal boron nitride (hBN) film as single-photon emitters and a robust photonic cavity with arbitrarily high quality-factor based on bound-state-in-the-continuum (BIC) concept.4 We observe, at room temperature and in ambient conditions, strong coupling between SPEs and BIC photons characterized by a Rabi splitting of ∼7 meV. The coupling strength can be tuned by varying detuning energy that is strongly supported by theoretical calculation. Our findings unveil new opportunities for exploiting the BIC cavity to realize the long-sought strong coupling with SPEs, ultimately for the development of quantum-based devices operating at ambient conditions.
1Reithmaier, J. P. et al. Nature 432, 197-200 (2004)
2Yoshie, T. et al. Nature 432, 200-203 (2004)
3Chikkaraddy, R. et al. Nature 535, 127-130 (2016)
4Do, T. T. H. et al., manuscript in preparation (2022)
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