Detection of sharp absorption lines in thin NdF_3 films

Abstract
We report the use of a sensitive spectrometer system for studying sharp optical absorption lines that are due to transitions between 4ƒ3 crystal-field levels of Nd3+ in epitaxial NdF3 films. Films as thin as 50 Å on GaAs substrates displayed absorption lines with asymmetric line shapes. Samples with an antireflecting LaF3 buffer between the NdF3 layer and the substrate permitted observation of absorption lines in thinner films.