Doppler-free frequency modulation spectroscopy of atomic erbium in a hollow cathode discharge cell

TL;DR

This paper demonstrates Doppler-free frequency modulation spectroscopy of atomic erbium in a hollow cathode discharge cell, enabling precise laser frequency stabilization for erbium cooling transitions, which is crucial for Bose-Einstein condensate experiments.

Contribution

It introduces a Doppler-free saturation spectroscopy method using frequency modulation in a hollow cathode cell to stabilize laser frequency on erbium's cooling transition.

Findings

Successful laser frequency stabilization on erbium's 400.91 nm transition.

Generation of a zero-crossing error signal for laser locking.

Enhanced precision for erbium laser cooling applications.

Abstract

The erbium atomic system is a promising candidate for an atomic Bose-Einstein condensate of atoms with a non-vanishing orbital angular momentum ($L \neq 0$) of the electronic ground state. In this paper we report on the frequency stabilization of a blue external cavity diode laser system on the 400.91 $nm$ laser cooling transition of atomic erbium. Doppler-free saturation spectroscopy is applied within a hollow cathode discharge tube to the corresponding electronic transition of several of the erbium isotopes. Using the technique of frequency modulation spectroscopy, a zero-crossing error signal is produced to lock the diode laser frequency on the atomic erbium resonance. The latter is taken as a reference laser to which a second main laser system, used for laser cooling of atomic erbium, is frequency stabilized.