  We demonstrate efficient generation of correlated photon pairs by spontaneous
four wave mixing in a 5 \mu m radius silicon ring resonator in the telecom band
around 1550 nm. By optically pumping our device with a 200 \mu W continuous
wave laser, we obtain a pair generation rate of 0.2 MHz and demonstrate photon
time correlations with a coincidence-to-accidental ratio as high as 250. The
results are in good agreement with theoretical predictions and show the
potential of silicon micro-ring resonators as room temperature sources for
integrated quantum optics applications.
