Broadband thermomechanically limited sensing with an optomechanical accelerometer

Acceleration measurement is widely used in commercial, scientific, and defense applications, but the resolution and accuracy achievable for demanding applications is limited by the current technology used to build and calibrate accelerometers. We report an optomechanical accelerometer based on a Fabry–Perot microcavity in a silicon chip that is extremely precise, field deployable, and can self-calibrate. The measured acceleration resolution is the highest reported to date for a microfabricated optomechanical accelerometer and is achieved over a wide frequency range ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>314</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mo>⋅</mml:mo> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:mo stretchy="false">√</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">H</mml:mi> <mml:mi mathvariant="normal">z</mml:mi> </mml:mrow> </mml:math> over 6.8 kHz). The combination of a single vibrational mode in the mechanical spectrum and the broadband thermally limited resolution enables accurate conversion from sensor displacement to acceleration. This also allows measurement of acceleration directly in terms of the laser wavelength, making it possible for sensors to calibrate internally and serve as intrinsic standards. This sensing platform is applicable to a range of measurements from industrial accelerometry and inertial navigation to gravimetry and fundamental physics.