Mass Sensing With Optomechanical Oscillation

We demonstrate the application of an optomechanical oscillator (OMO) as a high-resolution mass sensor. The coupling between high-Q optical and mechanical modes of a single optical microcavity results in narrow linewidth mechanical oscillation driven by the radiation pressure of the circulating optical power. The oscillation frequency can be monitored upon detection of the modulated transmitted optical power. Therefore the optical wave plays a dual role as both the driving power and a sensitive probe. The narrow oscillation linewidth, combined with the sensitivity of the mechanical resonance to mass changes, makes OMO an excellent candidate for all-optical mass sensing. Experimental results and theoretical analysis show that OMO can function as a compact, low-power mass sensor with sub-pg sensitivity.