The transverse Zeeman effect in calcium fluoride crystals containing erbium

A detailed study has been made of the optical transverse Zeeman effect for trivalent erbium ions at sites of tetragonal C 4v symmetry in crystals of calcium fluoride with magnetic fields of up to 6T. Interpretation of the optical absorption spectrum is complicated by the presence of magnetically non-equivalent C 4v sites and Er 3+ sites of other point symmetries, but selective excitation of fluorescence with a tunable dye laser has been used to isolate the spectrum of ions in the required transverse C 4v sites. Selective laser excitation spectroscopy has also been used to locate several previously undetected Er 3+ crystal-field energy levels for the C 4v site. A crystal-field analysis has successfully accounted for the observed transverse Zeeman patterns, including the variation in these patterns as a function of orientation of the magnetic field in the (100) crystal plane and as a function of magnetic field strength.