  Photonic crystal (PhC) nanocavities with high quality (Q) factors have
attracted much attention because of their strong spatial and temporal light
confinement capability. The resulting enhanced light-matter interactions are
beneficial for diverse photonic applications, ranging from on-chip optical
communications to sensing. However, currently achievable Q factors for active
PhC nanocavities, which embed active emitters inside, are much lower than those
of the passive structures because of large optical loss, presumably originating
from light scattering by structural imperfections and/or optical absorptions.
Here, we demonstrate a significant improvement of Q factors up to ~160,000 in
GaAs active PhC nanocavities using a sulfur-based surface passivation
technique. This value is the highest ever reported for any active PhC
nanocavities with semiconductor quantum dots. The surface-passivated cavities
also exhibit reduced variation in both Q factors and cavity resonant
wavelengths. We find that the improvement in the cavity performance presumably
arises from suppressed light absorption at the surface of the PhC's host
material by performing a set of PL measurements in spectral and time domains.
With the surface passivation technique, we also demonstrate a strongly-coupled
single quantum dot-cavity system based on a PhC nanocavity with a high Q factor
of ~100,000. These results will pave the way for advanced quantum dot-based
cavity quantum electrodynamics and for GaAs micro/nanophotonic applications
containing active emitters.
