Population hole burning on the [formula omitted] zero-phonon transition in MBE films of CaF 2:Eu 2 +

Abstract

Spectral holes due to the redistribution of population among the ground state hyperfine levels have been detected on the 413 nm zero-phonon transition in CaF 2:Eu 2 + MBE films grown on Si(1 1 1), in magnetic fields in excess of 3 T. These are the first long-lived (up to minutes) population holes reported for a paramagnetic ion. The hole lifetime results from phonon-induced transitions among hyperfine levels of the Eu 2 + ground electron spin states. The central hole linewidth of 40 MHz is probably determined by the EuF superhyperfine interaction which leads to spectral diffusion due to F nuclear spin flips. The hole pattern contains a narrow central hole (40 MHz) and side holes and antiholes which result from the hyperfine splittings in the ground and excited states.