A high-resolution microchip optomechanical accelerometer

Abstract

The monitoring of acceleration is essential for a variety of applications ranging from inertial navigation to consumer electronics1,2. Typical accelerometer operation involves the sensitive displacement measurement of a flexibly mounted test mass, which can be realized using capacitive3,4, piezo-electric5, tunnel-current6,7 or optical8,9,10,11 methods. Although optical detection provides superior displacement resolution8, resilience to electromagnetic interference and long-range readout7, current optical accelerometers either do not allow for chip-scale integration or utilize relatively bulky test mass sensors of low bandwidth8,9,10. Here, we demonstrate an optomechanical accelerometer that makes use of ultrasensitive displacement readout using a photonic-crystal nanocavity12 monolithically integrated with a nanotethered test mass of high mechanical Q-factor13. This device achieves an acceleration resolution of 10 µg Hz−1/2 with submilliwatt optical power, bandwidth greater than 20 kHz and a dynamic range of greater than 40 dB. Moreover, the nanogram test masses used here allow for strong optomechanical backaction14,15,16,17, setting the stage for a new class of motional sensors.