Optical measurements of spin noise as a high resolution spectroscopic tool

TL;DR

This paper introduces a novel optical spin noise spectroscopy technique that uses wavelength-tunable probes to uncover detailed spin and optical properties, including linewidths and transition overlaps, inaccessible by traditional methods.

Contribution

It demonstrates that wavelength-dependent spin noise measurements can reveal homogeneous linewidths and resolve overlapping transitions, advancing spectroscopic capabilities.

Findings

Wavelength-tunable spin noise detects homogeneous linewidths.

It resolves overlapping optical transitions.

The method works on atomic vapors and quantum dots.

Abstract

The intrinsic fluctuations of electron spins in semiconductors and atomic vapors generate a small, randomly-varying "spin noise" that can be detected by sensitive optical methods such as Faraday rotation. Recent studies have demonstrated that the frequency, linewidth, and lineshape of this spin noise directly reveals dynamical spin properties such as dephasing times, relaxation mechanisms and g-factors without perturbing the spins away from equilibrium. Here we demonstrate that spin noise measurements using wavelength-tunable probe light forms the basis of a powerful and novel spectroscopic tool to provide unique information that is fundamentally inaccessible via conventional linear optics. In particular, the wavelength dependence of the detected spin noise power can reveal homogeneous linewidths buried within inhomogeneously-broadened optical spectra, and can resolve overlapping optical transitions belonging to different spin systems. These new possibilities are explored both theoretically and via experiments on spin systems in opposite limits of inhomogeneous broadening (alkali atom vapors and semiconductor quantum dots).