Wide-Dynamic-Range Cantilever Magnetometry Using a Fiber-Optic Interferometer and its Application to High-frequency Electron Spin Resonance Spectroscopy

TL;DR

This paper introduces a wavelength-tunable laser interferometry method to extend the dynamic range of cantilever displacement detection, enabling high-frequency electron spin resonance spectroscopy with improved background noise suppression.

Contribution

The novel use of wavelength-tunable laser control in fiber-optic interferometry significantly enhances displacement measurement range and stability in ESR spectroscopy.

Findings

Achieved measurement of displacements over 1 micrometer without sensitivity loss.

Successfully removed irregular background signals in ESR measurements.

Demonstrated applicability to high-frequency ESR spectroscopy.

Abstract

We present a method of broadening the dynamic range of optical interferometric detection of cantilever displacement. The key idea of this system is to use a wavelength-tunable laser source. The wavelength is subject to proportional-integral control, which is used to keep the cavity detuning constant during a measurement. Under this control, the change in wavelength is proportional to the cantilever displacement. Using this technique, we can measure large displacements ($>1\ \mathrm{\mu m}$) without degradation of sensitivity. We apply this technique to high-frequency electron spin resonance spectroscopy and succeed in removing an irregular background signal that arises from the constantly varying sensitivity of the interferometer.