A simple 2 W continuous-wave laser system for trapping ultracold metastable helium atoms at the 319.8 nm magic wavelength

TL;DR

This paper presents a simple, high-power 2 W continuous-wave laser system at 319.8 nm for trapping ultracold helium atoms at the magic wavelength, enabling high-precision spectroscopy with reduced ac-Stark shift.

Contribution

The authors developed a cost-effective, reliable laser system at the magic wavelength using commercial components, achieving over 2 W power for ultracold helium trapping.

Findings

Successfully trapped ultracold helium atoms at 319.8 nm

Achieved trap lifetimes of several seconds

Demonstrated trapping of both thermal and BEC helium atoms

Abstract

High precision spectroscopy on the $2 \ ^3 S \rightarrow 2 \ ^1 S$ transition is possible in ultracold optically trapped helium but the accuracy is limited by the ac-Stark shift induced by the optical dipole trap. To overcome this problem, we have built a trapping laser system at the predicted magic wavelength of 319.8 nm. Our system is based on frequency conversion using commercially available components and produces over 2 W of power at this wavelength. With this system, we show trapping of ultracold atoms, both thermal ($\sim0.2 \ \mathrm{\mu K}$) and in a Bose-Einstein condensate, with a trap lifetime of several seconds, mainly limited by off-resonant scattering.