Visualising strongly focused 3D light fields in an atomic vapour

Intensity measurements visualising the spectrally and spatially dependent absorption of the longitudinal polarisation component by atoms in the hyperfine Paschen-Back regime. Beams with varying degrees and distributions of initially radial polarisation components are strongly focussed into a vapour cell of Rb-87 under a longitudinal magnetic field of 1.5 T. For certain wavelengths, the atoms were predicted and are observed to exclusively absorb the longitudinal polarisation component generated by the focusing of radially polarised light. The transmitted light is collimated and measured with a photodiode at two cell temperatures, and an additional spatial measurement was taken with a camera.