Room-temperature operation of a nanoelectromechanical resonator embedded in a phase-locked loop

We describe the operation of a phase-locked loop (PLL) that tracks the high-frequency electromechanical resonance of a nanoscale beam resonator. The fundamental in-plane flexural resonance of the beam resonator embedded in the PLL is actuated electrostatically and detected optically. PLL operation is demonstrated by locking stably to the resonance frequency of the beam, and by tracking this resonance with high fidelity as the beam is mass loaded. Our analysis reproduces the observed locking behavior. Feedback control schemes for nanoelectromechanical resonators may offer prospects for miniature timekeeping devices and ultrasensitive sensors.