Scanning optical homodyne detection of high-frequency picoscale resonances in cantilever and tuning fork sensors

TL;DR

This paper demonstrates high-frequency harmonic detection in nanoscale cantilevers and quartz tuning forks using a custom optical homodyne interferometer, revealing enhanced mass sensing capabilities through higher mode operation.

Contribution

It introduces a novel scanning optical homodyne method for detecting and mapping high-frequency resonances in nanoscale sensors, achieving significant sensitivity improvements.

Findings

Detected picometer-scale harmonic motion in resonators.

Mapped eigenmodes of tuning forks using optical detection.

Achieved over 6x sensitivity enhancement in mass sensing.

Abstract

Higher harmonic modes in nanoscale silicon cantilevers and microscale quartz tuning forks are detected and characterized using a custom scanning optical homodyne interferometer. Capable of both mass and force sensing, these resonators exhibit high-frequency harmonic motion content with picometer-scale amplitudes detected in a 2.5 MHz bandwidth, driven by ambient thermal radiation. Quartz tuning forks additionally display both in-plane and out-of-plane harmonics. The first six electronically detected resonances are matched to optically detected and mapped fork eigenmodes. Mass sensing experiments utilizing higher tuning fork modes indicate >6x sensitivity enhancement over fundamental mode operation.