  Aluminum nitride (AlN) has been widely used in microeletromechanical
resonators for its excellent electromechanical properties. Here we demonstrate
the use of AlN as an optomechanical material that simultaneously offer low
optical and mechanical loss. Integrated AlN microring resonators in the shape
of suspended rings exhibit high optical quality factor (Q) with loaded Q up to
125,000. Optomechanical transduction of the Brownian motion of a GHz contour
mode yields a displacement sensitivity of 6.2\times10^(-18)m/Hz^(1/2) in
ambient air.
