  Multi-element cavity optomechanics constitutes a direction to observe novel
effects with mechanical resonators. Several exciting ideas include
superradiance, increased optomechanical coupling, and quantum effects between
distinct mechanical modes among others. Realizing these experiments has so far
been difficult, because of the need for extremely precise positioning of the
elements relative to one another due to the high-reflectivity required for each
element. Here we overcome this challenge and present the fabrication of
monolithic arrays of two highly reflective mechanical resonators in a single
chip. We characterize the optical spectra and losses of these 200 $\mu$m-long
Fabry-P\'{e}rot interferometers, measuring finesse values of up to 220. In
addition, we observe an enhancement of the coupling rate between the cavity
field and the mechanical center-of-mass mode compared to the single membrane
case. Further enhancements in coupling with these devices are predicted,
potentially reaching the single-photon strong coupling regime, giving these
integrated structures an exciting prospect for future multi-mode quantum
experiments.
