RBS CHANNELING TO LOCATE ACTIVE IONS IN LASER MATERIALS - APPLICATIONTO RARE-EARTH ACTIVATED LINBO3/

The potentiality of Rutherford backscattering spectrometry, used in ch anneling mode, to locate ions in laser crystals is tested by studying the case of trivalent rare earth active ions in LiNbO3 crystals. It is shown that these active ions occupy Li+ sites but off-centered from t he regular lithium position by different amounts. These displacements are directly related to the ionic radii of the active ions. First evid ence of multicenter structure obtained by RBS/channeling is reported f or Pr3+ ions in LiNbO3. Taking advantage of this multicenter structure the crystal field parameter can be experimentally obtained for each c enter. Thus, it is shown how small variations of crystal field paramet ers, as a consequence of the non-equivalent centers, account for featu res observed in the optical spectra of Nd3+ ions in this crystal. (C) 1997 Elsevier Science B.V.