Integrated optomechanical sensing

The interplay of light and motion in optical cavities is at the heart of the fascinating field of optomechanics and has promising applications in sensing. However, in typical experimental realizations the three key functionalities of actuation, optomechanical sensing and optical detection are implemented separately, which makes the sensing system bulky and limits its applicability. Here we report the experimental demonstration of a system, based on an electromechanical photonic crystal structure, where actuation, sensing and detection are fully integrated in a single physical system with micron-scale footprint. It allows the direct measurement of the intracavity photon number and its mechanically induced fluctuations and thereby enables spectral and displacement sensing at the picometer level, potentially opening the way to a new generation of fully-integrated optomechanical systems.