OPTICAL SPECTROSCOPY OF HO3-CRYSTALS( AND TM3+ IONS IN KTIOPO4 SINGLE)

KTiOPO4 single crystals doped with Ho3+ or Tm3+ ions have been grown b y the top seeded solution growth (TSSG) slow cooling technique using a 49.8K(2)O:33.2P(2)O(5):16.32TiO(2):0.68RE(2)O(3) (RE = Ho, Tm) flux. The holmium and thulium concentrations obtained in the crystal are [Ho ] = 340 ppm and [Tm] = 500 ppm, and the corresponding distribution coe fficients K-Ho = 2.7 X 10(-3) and K-Tm = 5.1 X 10(-3). Sharp optical a bsorption bands corresponding to Ho3+ and Tm3+ ions have been measured at 4.2 K. For both ions the optical absorption shows a dichroic chara cter, generally being more intense when the polarization of the light is parallel to the c-axis of the crystal and weakest when the light is polarized parallel to the a-axis. Photoluminescence has been excited at room temperature in KTP:Tm crystals by using the 476 nm light of an Ar laser. (C) 1998 Elsevier Science B.V.