Low-drift Zeeman shifted atomic frequency reference

D J Reed,N Šibalić,D J Whiting,J M Kondo,C S Adams,K J Weatherill

doi:10.1364/osac.1.000004

Abstract

We present a simple method for producing a low-drift atomic frequency reference based upon the Zeeman effect. Our Zeeman Shifted Atomic Reference `ZSAR' is demonstrated to have tens of GHz tuning range, limited only by the strength of the applied field. ZSAR uses Doppler-free laser spectroscopy in a thermal vapor where the vapor is situated in a large, static and controllable magnetic field. We use a heated $^{85}$Rb vapor cell between a pair of position-adjustable permanent magnets capable of applying magnetic fields up to 1 T. To demonstrate the frequency reference we use a spectral feature from the Zeeman shifted D1 line in $^{85}$Rb at 795 nm to stabilize a laser to the 7S$_{1/2}$ $\longrightarrow$ 23P$_{1/2}$ transition in atomic cesium, which is detuned by approximately 19 GHz from the unperturbed Rb transition. We place an upper bound on the stability of the technique by measuring a 2.5 MHz RMS frequency difference between the two spectral features over a 24 hour period. This versatile method could be adapted easily for use with other atomic species and the tuning range readily increased by applying larger magnetic fields.

Highlights

The frequency stabilization or ‘locking’ of narrow linewidth lasers to atomic transitions is a common requirement in atomic and molecular physics experiments [1,2,3]
One can perform a beat measurement between the slave and reference lasers and stabilize the frequency difference between them [16, 17] or apply a sideband to the light using an electro-optic modulator (EOM) and seed the slave with the sideband [18, 19]
We can infer that Zeeman Shifted Atomic Reference’ (ZSAR) is highly robust to local perturbations as, in order to induce a shift of this magnitude, either the laboratory ambient field would have to fluctuate by ±1.8 Gauss or the magnets themselves move by ∼ 200 μm

Summary

Introduction

The frequency stabilization or ‘locking’ of narrow linewidth lasers to atomic transitions is a common requirement in atomic and molecular physics experiments [1,2,3]. It is desirable to stabilize a laser to a transition between two excited atomic states [20], in which case it is necessary to have additional lasers to first couple the ground state population to the lower of the excited states. An example of this is in the study of Rydberg systems where it is typical to use two [21] or more [22, 23] lasers. [33] uses a 40 μm vapor cell [34] placed between permanent magnets to stabilize a laser to an atomic resonance shifted by > 5 GHz or Ref. Because the Zeeman shifts are greater than the typical Doppler broadening, the method is useful for simplifying atomic spectra into more cleanly defined systems and for precision measurements and quantum optics in thermal vapors [36,37,38,39]

Modeling

Experiment

Discussion

Conclusion