  We develop a stoichiometric SiN membrane-based optoelectromechanical system,
in which the properties of the mechanical resonator can be dynamically
controlled by the piezoelectric actuation. The mode splitting is observed in
the mechanical response spectra of a phase-sensitive degenerate parametric
amplifier. In addition, the quality factor Q of the membrane oscillator in this
process is signicantly enhanced by more than two orders of magnitude due to the
coherent amplication, reaching a Q factor of ~ 3*10^8 and a f*Q product of ~
8*10^14 at room temperature. The thermomechanical noise squeezing close to -3
dB limitation is also achieved. This system integrates the electrical, optical
and mechanical degrees of freedom without compromising the exceptional material
properties of SiN membranes, and can be a useful platform for studying cavity
optoelectromechanics.
