Optically detected magnetic resonance of Cu, Fe and Mn defects inLiNbO3

Abstract

The optical absorptions of Cu2+, Fe3+ and Mn2+ in LiNbO3 are investigated using optically detected magnetic resonance (ODMR). Themethod is based on the changes of the magnetic circular dichroism (MCD)bands of the ions, caused by the magnetic resonances of the paramagneticground states of these ions. All transitions reached from the ground state ofCu2+ lie between 1180 and 860 nm. Three bands are observed, resulting from combined spin–orbitand trigonal field splitting of the first excited crystal field states. All features resulting fromFe3+ have to be ascribed to the forbidden transitions from the6A tothe 4G cubic precursor states. Their weak and narrow optical transitionsare superimposed on the wide and strong intervalence absorption ofFe2+. This ion leads to a diamagnetic contribution to the MCD, resultingfrom the Zeeman admixture of the first excited spin state ofFe2+ to its diamagnetic ground state. The MCD ofMn2+ is caused by an intervalence transition to the conduction band. ODMR allows us to detectthese bands, lying near 400 nm, which in plain optical absorption are coveredby strong precursor absorptions before the onset of the fundamental transition.