Pr3+-doped CaF2 layers on CaF2(111) substrates were grown by molecular beam epitaxy. The effect of Pr concentration on spectroscopic properties and waveguide characteristics of the thin films was investigated and the existence of clustering of the tripositive praseodyme ions in CaF2 was put forward to explain certain optical results. Photoluminescence spectra were obtained in the wavelength range 590-650 nm for P-3(0) --> F-3(2) and (3)p(0), H-3(6) transitions of pr(3+) ions, and a P-3(0) level lifetime of the order of 100 mu s was measured. This work demonstrates that active optical waveguides, useful for integrated optoelectronic devices, can be produced by growing Pr-doped CaF2 epitaxiaI layers.