Onset of strong coupling in site-controlled high C3v-symmetric InGaAs QD-nanocavity on the (111)B-oriented GaAs membrane

Precise positioning of single site-controlled InGaAs QD embedded in the (111)B-oriented GaAs PhC cavity, which enables high C3v symmetries of QD with nanometer-scale accuracy offers great promise for on-chip photonic quantum information processing. However, achieving the strong coupling regime in this geometry is rarely reported due to the increase in cavity loss. Here, we reveal the onset of phonon-mediated coherent exciton-photon interaction on our tailored device. Our results present a Rabi-like oscillation of luminescence intensity between excitonic and photonic components correlated with their oscillatory energy splitting. Such Rabi-like oscillation is well reproduced by modeling the coherent exchange of the exciton-photon population. The modeling further reveals an oscillatory two-time covariance at QD-cavity resonance, which indicates the system operates at the onset of the strong coupling regime. Moreover, by using the cavity mode as a probe of the virtual state of QD induced by phonon scattering, it reveals an increase in phonon scattering rates near the QD-cavity resonance, which can result in the onset of the strong coupling regime disguised with a singlet spectral feature.