Linear and nonlinear magneto-optical rotation on the narrow strontium intercombination line

TL;DR

This paper investigates both linear and nonlinear magneto-optical rotation in cold strontium gas, demonstrating high sensitivity to magnetic fields on a narrow intercombination line and highlighting differences from broader alkali transitions.

Contribution

It presents the first experimental observation of nonlinear magneto-optical rotation on a narrow strontium intercombination line, showing insensitivity to Doppler broadening and enhanced magnetic sensitivity.

Findings

Nonlinear rotation is insensitive to Doppler broadening.

Sensitivity to magnetic fields is three orders of magnitude higher than in alkali transitions.

Both linear and nonlinear regimes are observed by varying temperature.

Abstract

In the presence of an external static magnetic field, an atomic gas becomes optically active, showing magneto-optical rotation. In the saturated regime, the coherences among the excited substates give a nonlinear contribution to the rotation of the light polarization. In contrast with the linear magneto-optical rotation, the nonlinear counterpart is insensitive to Doppler broadening. By varying the temperature of a cold strontium gas, we observe both regimes by driving the $J=0\rightarrow J=1$ transition on the intercombination line. For this narrow transition, the sensitivity to the static magnetic field is typically three orders of magnitude larger than for a standard broad alkali transition.