We report a novel type of fully integrated optomechanical sensor and demonstrate high sensitivity mechanical displacement measurements on chip. We sense the motion of micro and nano-mechanical devices by near field coupling them to high quality factor optical microdisk resonators. In a first geometry, we sense the position of a dielectric ring moved by a micromechanical actuator. Tunable optomechanical coupling of up to g_OM/2π = 4.8 GHz/nm results in the photodetector-limited displacement sensitivity of 4.3x10^-15 m/√Hz with optical excitation power below 20 uW. In a second geometry, we sense the thermal motion of a nanoscale cantilever probe. Transduction of the cantilevers MHz frequency vibration is achieved with a displacement sensitivity of 4.4x10-16 m/√Hz and a mechanical quality factor of 6000 is measured in vacuum.
Proceedings Title: Transducers 2011
Conference Dates: June 5-9, 2011
Conference Location: Beijing, -1
Pub Type: Conferences
cavity optomechanics, MEMS, NEMS, interferometric sensing, optical position measurement