The Hanle effect and level crossing spectroscopy in Rb vapour under strong laser excitation

We measure and simulate numerically the Hanle effect and non-zero field level crossing signals in Rb-85 and Rb-87 atoms in a magnetic field at room temperature. Diode laser radiation from 4 mW cm(-2) to 3.3 W cm(-2) tuned to the D-2 absorption line of each isotope excites atoms into all the excited-state hyperfine levels simultaneously inside the unresolved Doppler profile. Polarization fluorescence detection is used to observe dark and bright resonances, as well as non-zero field level crossing resonances, for several excitation lines. A broad spectral line excitation model is applied to analyse the measured signals. The non-linear Zeeman effect is included in the model for both ground and excited states. Although the applied magnetic field does not exceed 80 G, several hyperfine levels of the excited state show a substantial deviation from the linear Zeeman effect.