CRYSTAL-GROWTH AND OPTICAL CHARACTERIZATION OF NOVEL 3D(2) ION LASER HOSTS

This paper reports the Czochralski growth of large single crystals of Cr4+:Ca-10(PO4)(6)F-2 (CFAP), Mn5+:Sr-10(VO4)(6)F-2(SVAP), and Cr4+:Sr GdGa3O7(SGGM) crystals in radio-frequency heated induction furnaces op erating at temperatures in the range 1873-1923 K. Crystals having exce llent optical quality were produced using growth rates of 2.8-11.2 mu m/s and rotation rates between pi/2 and pi rad/s. The optical absorpti on spectra confirm that the 3d(2)-configuration ions reside at distort ed (VO4), (PO4) and (GaO4) tetrahedra in SVAP, CFAP and SGGM, respecti vely, at which transition probabilities are enhanced by the odd-parity terms at the C-s site symmetry in the crystal field expansion. The ne ar-infrared luminescence is broadened by structural disorder and is st rongly dependent upon both the crystal held strength and temperature. Although the luminescence in Cr4+:CFAP and Cr4+:SGGM occur as broadban ds in the near infrared region, the intensity is weak at 300 K as a co nsequence of nonradiative decay. In contrast, the effects of nonradiat ive decay in Mn5+:SVAP are weak and strong zero-phonon lines are obser ved even at room temperature. (C) 1998 Elsevier Science B.V. All right s reserved.