Self-sustaining MoS2 nanomechanical oscillators and feedback cooling

Abstract

We report on the experimental demonstration of self-sustaining feedback oscillators referenced to ultrathin molybdenum disulfide (MoS2) nanomechanical resonators vibrating in the ∼10 to 20 MHz range. Based on comprehensive open-loop characterization of MoS2 resonators with dynamic ranges up to 85 dB, self-sustaining oscillators are constructed by incorporating the MoS2 resonators into an optoelectronic feedback circuitry. The prototyped MoS2 self-sustaining oscillators generate stable radio frequency waveforms with frequency stability (measured in Allan deviation) down to ∼2 × 10−5 and phase noise mainly limited by electronic thermal noise. Beyond self-sustaining oscillations, we demonstrate feedback cooling of thermomechanical motion of a bilayer (2L) MoS2 resonator from 300 K to 255 K by tuning the phase in the feedback, suppressing or “squashing” the noise level of the system.