  Rare-earth ions doped into desired locations of optical crystals might enable
a range of novel integrated photonic devices for quantum applications. With
this aim, we have investigated the production yield of cerium and praseodymium
by means of ion implantation. As a measure, the collected fluorescence
intensity from both, implanted samples and single centers was used. With a
tailored annealing procedure for cerium, a yield up to 53% was estimated.
Praseodymium yield amounts up to 91%.
