Fig. 2

Schematic of CO₂ laser setup and measured beam profile. a The CO₂ laser is linearly polarized parallel to the z-axis. Motorized stages position the beam in the yz-plane (see Methods). The optical power is monitored after the vacuum chamber by a thermal detector. The magnetic field is rotated in the yz-plane to form an angle ϕ with respect to the fixed laser polarisation \(\vec {\cal E}\) || z. A π-polarized 646 nm state preparation laser counter-propagates to the CO₂ laser with the aid of a dichroic mirror. b Spatial profile of the laser at the ion’s position measured via the light shift. Black points indicate measurement positions and the surface plot is a cubic spline interpolation of these measurements