Journal of Crystal Growth 237–239 (2002) 641–644 Influence of Ca 4 GdO(BO 3 ) 3 doping on its properties T. Lukasiewicz a, *, I.V. Kityk b , M. Makowska-Janusik b , A. Majchrowski c , Z. Ga" ) azka a , H. Kaddouri d , Z. Mierczyk e a Institute of Electronic Materials Technology, 133 Wolczynska Str., 01-919 Warsaw, Poland b Solid State Department, WSP Czestochowa, 1/144 Gombrowicza Str., 42-217 Czestochowa, Poland c Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland d Laboratoire LP2A, Universit ! e du Perpignan, 66680 Perpignan, France e Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland Abstract CzochralskigrowthofCa 4 GdO(BO 3 ) 3 (GdCOB)singlecrystals,pureanddopedwithseveralrareearthions(Nd 3+ , Pr 3+ ,Tm 3+ ,andSm 3+ ), has been carried out. As-grown single crystals free from inclusions, bubbles and cracks were 20mm in diameter and up to 60mm in length. Optical absorption spectra of 6 at% thulium and samarium doped calcium gadolinium oxoborate were measured and presented. It was found that introduction of Pr 3+ and Tm 3+ ions leads to an increase of second-order photoinduced effects in GdCOB. The second harmonic generation shows an increase of at least 35% under the influence of photoinducing nitrogen laser (l ¼ 377nm) power. r 2002 Elsevier Science B.V. All rights reserved. PACS: 81.10.Fq; 42.70.Mp Keywords: A2. Czochralski method; B1. Borates; B2. Nonlinear optic materials 1. Introduction The discovery of b-barium borate (BBO) and lithium triborate (LBO) triggered intensive inves- tigations of crystalline borates for optoelectronic applications. As a result numerous new borates have been discovered (SBBO, CLBO, KAB) [1–3]. Special interest arise crystalline borates containing heavy ions due to possibility of appearance of strong nonlinear optical effects in such materials. Our group investigates some borates containing heavyions,namelyYAl 3 (BO 3 ) 4 (YAB)[4],BiB3O 6 (BiBO) [5], and GdCOB [6], which show good nonlinear optical properties. This in connection with proper doping may create materials used in self-frequency doubling (SFD) lasers, optical parametric oscillators (OPOs) and other optoelec- tronic devices. This paper describes crystallisation of GdCOB and influence of doping on optoelectronic proper- ties of this single crystal. The material was first reported by Dirksen et al. [7] to be a good host lattice for luminescent materials. First GdCOB single crystals were obtained by Aka et al. [8] and since that time intensive investigations of this material have been done. GdCOB single crystals describedinthispaperweregrownbymeansofthe Czochralski technique. Pure and doped GdCOB *Corresponding author. Tel.: +48-22-834-9949; fax: +48- 22-834-9003. E-mail address: lukasi t@sp.itme.edu.pl (T. Lukasiewicz). 0022-0248/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0022-0248(01)02017-6