Modal "self-coupling" as a sensitive probe for nanomechanical detection

TL;DR

This paper introduces a highly sensitive nanomechanical detection method based on mode coupling and frequency shifts, enabling precise measurement of nanobeam resonances through nonlinear effects and two-tone excitation.

Contribution

It presents a novel dispersive mode-coupling technique and a two-tone excitation scheme for enhanced nanomechanical sensing, supported by a theory matching experimental data without free parameters.

Findings

Mode coupling causes measurable resonance shifts.

Two-tone excitation enables amplitude-to-frequency transduction.

Theoretical model accurately reproduces experimental results.

Abstract

We present a high-sensitivity measurement technique for mechanical nanoresonators. Due to intrinsic nonlinear effects, different flexural modes of a nanobeam can be coupled while driving each of them on resonance. This mode-coupling scheme is dispersive and one mode resonance shifts with respect to the motional amplitude of the other. The same idea can be implemented on a {\it single} mode, exciting it with two slightly detuned signals. This two-tone scheme is used here to measure the resonance lineshape of one mode through a frequency shift in the response of the device. The method acts as an amplitude-to-frequency transduction which ultimately suffers only from phase noise of the local oscillator used and of the nanomechanical device itself. We also present a theory which reproduces the data without free parameters.