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

摘要

We present a method of broadening the dynamic range of opticalinterferometric detection of cantilever displacement. The key idea of thissystem is to use a wavelength-tunable laser source. The wavelength is subjectto proportional-integral control, which is used to keep the cavity detuningconstant during a measurement. Under this control, the change in wavelength isproportional to the cantilever displacement. Using this technique, we canmeasure large displacements ($>1\ \mathrm{\mu m}$) without degradation ofsensitivity. We apply this technique to high-frequency electron spin resonancespectroscopy and succeed in removing an irregular background signal that arisesfrom the constantly varying sensitivity of the interferometer.