Resources of polarimetric sensitivity in spin noise spectroscopy

TL;DR

This paper demonstrates that polarimetric sensitivity in spin noise spectroscopy can be significantly enhanced using high-extinction polarization geometries, enabling more sensitive measurements at low photon flux levels and opening new research opportunities.

Contribution

The study introduces high-extinction polarization geometries that boost sensitivity by over an order of magnitude without increasing photon flux, improving spin noise spectroscopy techniques.

Findings

Enhanced sensitivity by more than tenfold using high-extinction geometries.

Demonstrated measurements on bulk n:GaAs in the 835-918 nm range.

Sensitivity gain allows for studying nonlinear light-spin interactions.

Abstract

We attract attention to the fact that the ultimate (shot-noise-limited) polarimetric sensitivity can be enhanced by orders of magnitude leaving the photon flux incident onto the photodetector on the same low level. This opportunity is of crucial importance for present-day spin noise spectroscopy, where a direct increase of sensitivity by increasing the probe beam power is strongly restricted by the admissible input power of the broadband photodetectors. The gain in sensitivity is achieved by replacing the 45-deg polarization geometry commonly used in conventional schemes with balanced detectors by geometries with stronger polarization extinction. The efficiency of these high-extinction polarization geometries with enhancement of the detected signal by more than an order of magnitude is demonstrated by measurements of the spin noise spectra of bulk n:GaAs in the spectral range 835-918 nm. It is shown that the inevitable growth of the probe beam power with the sensitivity gain makes spin noise spectroscopy much more perturbative, but, at the same time, opens up fresh opportunities for studying nonlinear interactions of strong light fields with spin ensembles.