Casimir probe based upon metallized high Q SiN nanomembrane resonator

TL;DR

This paper introduces a highly sensitive Casimir force measurement method using a metallized high Q silicon nitride nanomembrane resonator, capable of precise force detection and surface potential imaging.

Contribution

The work presents a novel instrumentation combining a high Q nanomembrane resonator with a fiber interferometer and phase-locked loop for enhanced Casimir force measurement and surface potential imaging.

Findings

Achieved force gradient resolution of 3 μN/m.

Demonstrated stable resonance frequency tracking with 2×10^{-9} resolution.

Enabled simultaneous Casimir force and Kelvin probe measurements.

Abstract

We present the instrumentation and measurement scheme of a new Casimir force probe that bridges Casimir force measurements at microscale and macroscale. A metallized high Q silicon nitride nanomembrane resonator is employed as a sensitive force probe. The high tensile stress present in the nanomembrane not only enhances the quality factor but also maintains high flatness over large area serving as the bottom electrode in a sphere-plane configuration. A fiber interferometer is used to readout the oscillation of the nanomembrane and a phase-locked loop scheme is applied to track the change of the resonance frequency. Because of the high quality factor of the nanomembrane and the high stability of the setup, a frequency resolution down to $2\times10^{-9}$ and a corresponding force gradient resolution of 3 $\mu$N/m is achieved. Besides sensitive measurement of Casimir force, our measurement technique simultaneously offers Kelvin probe measurement capability that allows in situ imaging of the surface potentials.