Hanle effect in spectrally broadened light

The Hanle effect has been studied both experimentally and theoretically for the case where the exciting light has a large range of intensities and varying spectral width. The Hanle effect is the simplest example of a multilevel atomic transition and thus serves as a prototype for the effect of laser bandwidth on the coherence between sublevels. Solution of the equations shows that the lowest-order term is equivalent to monochromatic light, whereas the second term represents the effects of uncorrelated random phase jumps. The results of some sample calculations are shown. Hanle signals from Yb excited by low-intensity monochromatic light were observed. Raising the laser light intensity to several times the saturation level (a few mW/cm²) power broadened the coherence dip near the zero magnetic field as predicted. When the high-intensity laser light was made spectrally wider by noise modulation, the power broadening of the Hanle dip was appreciably reduced.