  We report successful incorporation of an ensemble of G centers in
silicon-on-insulator (SOI) microrings using ion implantation and conventional
nanofabrication. The coupling between the emitters and the resonant modes of
the microrings is studied using continuous-wave and time-resolved
microphotoluminescence (PL) experiments. We observe the resonant modes of the
microrings on PL spectra, on the wide spectral range that is covered by G
centers emission. By finely tuning the size of the microrings, we match their
zero-phonon line at 1278 nm with a resonant mode of quality factor around 3000
and volume 7.2 (lambda over n)^3. The zero-phonon line intensity is enhanced by
a factor of 5, both in continuous-wave and time-resolved measurements. This is
attributed to the Purcell enhancement of zero-phonon spontaneous emission into
the resonant mode and quantitatively understood considering the distribution of
the G centers dipoles. Despite the enhancement of the zero-phonon emission, we
do not observe any sizeable decrease of the average lifetime of the G centers,
which points at a low radiative yield (<10%). We reveal the detrimental impact
of parasitic defects in heavily implanted silicon, and discuss the perspectives
for quantum electrodynamics experiments with individual color centers in
lightly implanted SOI rings. Our results provide key information for the
development of deterministic single photon sources for integrated quantum
photonics.
