Absolute absorption and dispersion of a rubidium vapour in the hyperfine Paschen-Back regime

Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure Rb-87 vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions have different magnitudes, and show that we enter the hyperfine Paschen-Back regime for fields greater than 0.33 T on the Rb D-2 line. The experiment uses a compact 1 mm(3) microfabricated vapour cell that makes it easy to maintain a uniform and large magnetic field with a small and inexpensive magnet. We find excellent agreement between the experimental results and numerical calculations of the weak probe susceptibility where the line positions and strengths are calculated by matrix diagonalization.