Observation of Zeeman shift in the rubidium D2 line using an optical nanofiber in vapor

TL;DR

This paper demonstrates the observation of Zeeman shifts in rubidium D2 lines using an optical nanofiber, revealing magnetic field effects on atomic absorption and enabling potential laser stabilization techniques.

Contribution

It presents the first measurement of Zeeman shifts in rubidium D2 lines via an optical nanofiber, including a method for laser frequency stabilization based on differential absorption spectra.

Findings

Zeeman shifts of ~100 MHz observed in rubidium D2 lines.

Linear shift rates of 1.6 MHz/G and -2.0 MHz/G measured.

Dichroic atomic vapor laser lock demonstrated.

Abstract

We report on the observation of a Zeeman shift (order of 100 MHz) of the Doppler-broadened D2 transition of both 85Rb and 87Rb isotopes via transmission through a tapered optical nanofiber in the presence of a DC magnetic field. Linearly-polarized light propagating in the nanofiber is analyzed as a superposition of two orthogonally circularly-polarized orientations, {\sigma}+ and {\sigma}-. In the absence of the magnetic field, the absorption of these polarizations by the atomic vapor, via the evanescent field at the waist of the nanofiber, is degenerate. When a weak magnetic field is applied parallel to the propagating light, this degeneracy is lifted and relative shifts in the resonance frequencies are detected. Typical linear shift rates of 1.6 MHz/G and -2.0 MHz/G were observed. We also demonstrate a dichroic atomic vapor laser lock line shape by monitoring the real-time subtraction of the two magnetically-shifted absorption spectra. This is particularly interesting for magneto-optical experiments as it could be directly implemented for diode laser frequency-stabilization.