  We report on the realization of a liquid-filled optical microcavity and
demonstrate photon-pair generation by spontaneous four-wave mixing. The
bandwidth of the emitted photons is $\sim 300$ MHz and we demonstrate tuning of
the emission wavelength between 770 and 800 nm. Moreover, by employing a liquid
as the nonlinear optical medium completely filling the microcavity, we observe
more than a factor $10^3$ increase of the pair correlation rate per unit pump
power and a factor of 1.7 improvement in the coincidence/accidental ratio as
compared to our previous measurements.
