Comparative optical characterization of various Nd3+: YVO4 single crystals

Nd:YVO4 single crystals were grown by using the Laser Heated Pedestal Growt h (LHPG) and flux techniques. These crystals are compared with other Nd:YVO 4 crystals grown by using different techniques and/or having different orig ins in order to investigate their intrinsic as well as their extrinsic opti cal properties. Both W-visible absorption and time resolved site selective infrared excitation and emission spectra were thus recorded. The former ind icate that the UV-blue absorption (340-400 nm responsible for the coloratio n of the crystals is directly linked, at least in part, to color centers in duced by oxygen vacancies, and the latter show a reproducible typical site structure found in all the crystals, at least in all those having about the same dopant concentration, which can be assigned to Nd3+ ions in regular u nperturbed and perturbed sites of D-2d symmetry and also to Nd3+ ions in on e or two other kinds of sites corresponding to very particular situations. On the other hand, this low temperature multisite structure strongly depend s on the dopant concentration, which is tentatively interpreted in terms of Nd3+ centers perturbed by nearby Nd3+ ions at various distances. Some of t hese spectra were also analysed and followed up to room temperature first t o determine the inhomogeneous or homogeneous character of the Nd3+ absorpti on line around 800 nm which is important for the diode laser pumping applic ation, then the phonon contribution to the observed spectral profiles and f inally to derive some important multiphonon deexcitation rates. (C) 1999 El sevier Science B.V. All rights reserved.