A microelectromechanically controlled cavity optomechanical sensing system

Abstract

Microelectromechanical systems (MEMS) have been applied to many measurement\nproblems in physics, chemistry, biology and medicine. In parallel, cavity\noptomechanical systems have achieved quantum-limited displacement sensitivity\nand ground state cooling of nanoscale objects. By integrating a novel cavity\noptomechanical structure into an actuated MEMS sensing platform, we demonstrate\na system with high quality-factor interferometric readout, electrical tuning of\nthe optomechanical coupling by two orders of magnitude, and a mechanical\ntransfer function adjustable via feedback. The platform separates optical and\nmechanical components, allowing flexible customization for specific scientific\nand commercial applications. We achieve displacement sensitivity of 4.6\nfm/Hz^1/2 and force sensitivity of 53 aN/Hz^1/2 with only 250 nW optical power\nlaunched into the sensor. Cold-damping feedback is used to reduce the thermal\nmechanical vibration of the sensor by 3 orders of magnitude and to broaden the\nsensor bandwidth by approximately the same factor, to above twice the\nfundamental frequency of \\approx 40 kHz. The readout sensitivity approaching\nthe standard quantum limit is combined with MEMS actuation in a fully\nintegrated, compact, low power, stable system compatible with Si batch\nfabrication and electronics integration.\n