A multiphysics model for high frequency optomechanical sensors optically actuated and detected in the oscillating mode

Optomechanical systems combine extreme sensitivity and bandwidth in the control of mechanical motion, of interest for various applications. Integrated on a chip, actuated and detected all-optically by a single laser, they could disrupt sensing technologies. We introduce here a multiphysics model that describes their operation in the oscillating mode, under sinusoidal modulation of the laser, when both photothermal forces and radiation pressure are present, and when nonlinear absorption occurs in the device. The model is validated by systematic experiments on ultra-high frequency optomechanical disk resonators and leads to a quantitative assessment of the amplitude and phase of the demodulated output signal, which carries the sensing information.