Nd3+incorporation in CaF2layers grown by molecular‐beam epitaxy on CaF2substrates is investigated by making use of the photoluminescence lines associated with Nd3+centers involving one or several Nd3+ions. It is shown that the substrate crystal orientation has no effect on the aggregation state of Nd3+while the growth temperature greatly influences the formation of Nd3+aggregate centers. An optimum growth temperature around 500 °C is determined, leading to CaF2layers of good crystal quality in which the main emission, related to single Nd3+centers, is optimized. The results have been obtained for Nd3+concentrations as high as 3.6 wt % Nd and growth rates in the range of 0.2–1 &mgr;m/h.