A self-calibrating optomechanical force sensor with femtonewton resolution
John T. Melcher, Julian Stirling, Felipe Guzman, Jon R. Pratt, Gordon A. Shaw
We report the development of an ultrasensitive optomechanical sensor designed to improve the accuracy and precision of force measurements with atomic force microscopy. The sensors achieve quality factors of 4.3x10^6 (a 100-fold improvement over quartz tuning forks) and force resolution on the femtonewton scale. Self-calibration of the sensor is accomplished using the photon momentum force exerted by photons reflecting from the sensor surface. This property enables in situ calibration of the sensor at cryogenic ultra-high vacuum.