VLS induced magnetic field gradient as a function of trapping beam polarisation

Magnetic field gradient induced by the vector light shift from the z’-oriented dipole beam (circles) and x’-beam (squares), for variable polarisation circularity. The VLS magnetic field difference is < 1 milligauss at two locations of each dipole beam (separated vertically by 41.7 microns) are probed using differential interferometry. Rotating a quarter-wave plate placed in the path of each beam changes the vector light shift and thus the light-induced field gradient.