Designing sensors with tensioned silicon nitride micromechanical resonators

Abstract: Mechanical resonators based on stressed silicon nitride have both exemplary optical and mechanical properties. Through targeted shaping of the resonator geometry, the dissipative properties of these resonators can be enhanced, yielding micromechanical devices that maintain coherence for up to billions of oscillation periods. Such coherence can be leveraged for a variety of sensing paradigms, ranging from magnetism, acceleration, thermal radiation, and gravity. We present developments of specific design criteria pertaining to force sensors based on phononic crystal resonators. We also develop a generalized formalism to understand the effects of a general, spatially varying, thermal environment on the sensing performance of such devices. By experimentally testing this formalism on a phononic crystal membrane device, we identify a generalized figure of merit for optomechanical devices exposed to spatially varying thermal baths, giving rise to a new design paradigm for future optomechanical devices.