Faraday-rotation fluctuation spectroscopy with static and oscillating magnetic fields

TL;DR

This paper models Faraday-rotation fluctuation spectroscopy to measure spin noise, exploring static and oscillating magnetic fields to improve detection precision and observe multi-photon processes.

Contribution

It introduces a theoretical model for spin noise measurement under static and oscillating magnetic fields, highlighting new methods to enhance measurement accuracy and observe multi-photon absorption.

Findings

Resonance line reveals Larmor frequency and spin coherence time in static fields.

Oscillating fields enable observation of multi-photon absorption processes.

Oscillating fields can reduce line broadening, improving measurement precision.

Abstract

By Faraday-rotation fluctuation spectroscopy one measures the spin noise via Faraday-induced fluctuations of the polarization plane of a laser transmitting the sample. In the fist part of this paper, we present a theoretical model of recent experiments on alkali gas vapors and semiconductors, done in the presence of a {\em static} magnetic field. In a static field, the spin noise shows a resonance line, revealing the Larmor frequency and the spin coherence time $T_2$ of the electrons. Second, we discuss the possibility to use an {\em oscillating} magnetic field in the Faraday setup. With an oscillating field applied, one can observe multi-photon absorption processes in the spin noise. Furthermore an oscillating field could also help to avoid line broadening due to structural or chemical inhomogeneities in the sample, and thereby increase the precision of the spin-coherence time measurement.