Nd3+ photoluminescence in lithium niobate thin films

The F-4(3/2)-->I-4(11/2) photoluminescence of Nd3+ incorporated in LiNbO3 f ilms prepared by pulsed laser deposition on R-cut sapphire substrates has b een characterised. By using Rutherford backscattering spectrometry, it has been found that the neodymium concentration in the film is congruent with t he composition of the target. However, an incorporation upper limit of abou t 10% with regard to niobium is found for the Nd incorporation. This limit is due to the nucleation of LiNb3O8 phase for higher neodymium concentratio ns. The excitation and emission spectra of Nd3+ in the films is very simila r to that found in congruent LiNbO3 single crystals doped with 3% of Nd, be ing the main difference the broader character of the bands in the spectra c orresponding to films. Films prepared using targets with a [Li]/[Nb]= 3 com position, show an additional luminescence with a much narrower splitting of the F-4(3/2) multiplet. The latter is most likely related to an amorphous phase with composition LiNdNb2O7.