Magnetic trapping of an ultracold $^{39}$K-$^{40}$K mixture with a versatile potassium laser system

TL;DR

This paper demonstrates magnetic trapping and cooling of a $^{39}$K-$^{40}$K mixture using a novel versatile laser system capable of rapid isotope switching, enabling efficient preparation of ultracold potassium gases.

Contribution

Development of a versatile laser system for rapid isotope selection and sub-Doppler cooling, facilitating magnetic trapping of potassium isotopes in a single setup.

Findings

Successfully trapped over 2.2×10^5 fermions and 1.4×10^7 bosons with >1.2 s lifetime.

Achieved rapid isotope switching (~1 μs) without mechanical adjustments.

Demonstrated sub-Doppler cooling of $^{41}$K.

Abstract

We present a dual isotope magneto-optical trap (MOT), simultaneous sub-Doppler laser cooling, and magnetic trapping of a spin-polarized $^{39}$K-$^{40}$K Bose-Fermi mixture realized in a single-chamber setup with an unenriched potassium dispenser as the source of atoms. We are able to magnetically confine more than $2.2\times10^5$ fermions ($F=9/2\,m_F=9/2$) and $1.4\times10^7$ bosons ($F=2\,m_F=2$) with a lifetime exceeding 1.2 s. For this work, we have developed a versatile laser tailored for sub-Doppler cooling of all naturally occurring potassium isotopes and their mixtures. This laser system incorporates innovative features, such as the capability to select an isotope by activating or deactivating specific acousto-optic modulators that control the light seeding tapered amplifiers. Switching between isotopes takes $\sim$1 $\mathrm{\mu}$s without any mechanical adjustment of the components. As a final step in characterizing the laser system, we demonstrate sub-Doppler cooling of $^{41}$K.