Infrared photoluminescence of Nd3+ multicenters in KTiOPO4 crystals

The infrared photoluminiscence and optical absorption of Nd3+ in KTP single crystals and in those co-doped with Al, Na and W have been studied. Characteristic emission band sets in 1030-1150 and 1300-1500 nm corresponding to the F-4(3/2) --> I-4(11/2) and F-4(3/2) --> I-4(13/2) transitions, respectively, have been observed. The excitation spectra of these bands show the splitting of the F-4(3/2) multiplet in two sublevels. The excitation spectrum of Nd in KTP only shows the contribution of one type of Nd center, the energy difference between the F-4(3/2) sublevels of this center is 183 cm(-1). Nd3+ in the two slightly different titanium lattice sites is likely contributing to this spectrum. In crystals co-doped with Al the F-4(3/2) splitting is larger, namely 202 cm(-1) but still a single center is observed. The co-doping with Na or W induces the presence of additional new centers as well as new emission bands. It is inferred that Na-Nd and W-Nd pairs have been formed. W enhances the optical absorption cross section of Nd3+ in KTP. (C) 1998 Elsevier Science B.V. All rights reserved.