Detection of sharp absorption lines in thin NdF₃ films

We report the use of a sensitive spectrometer system for studying sharp optical absorption lines that are dueto transitions between 4f3 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 LaF2 buffer between the NdF3 layer and the substrate permitted observation ofabsorption lines in thinner films. © 1991 Optical Society of America.