L Journal of Alloys and Compounds 300–301 (2000) 395–397 www.elsevier.com / locate / jallcom Colour centers in doped Gd Ga O and Y Al O laser crystals 3 5 12 3 5 12 a,b, c b a d e * A. Matkovskii , D. Sugak , S. Melnyk , P. Potera , A. Suchocki , Z. Frukacz a Institute of Physics, HPS, 16 Rejtana St. 35-310 Rzeszow, Poland b State University «Lvivska Politechnika», 290646 Lviv, Ukraine c Institute of Materials, SRC «Carat», 202 Stryjska St. 290031 Lviv, Ukraine d Institute of Physics, PAS, 32 /46 Al. Lotnikow 02-668 Warsaw, Poland e Institute of Electronic Materials Technology, 133 Wolczynska st. Warsaw, Poland Abstract The influence of rare earth and 3d impurities on the process of ionizing recharge of genetic defects under gamma-irradiation in 31 31 Gd Ga O and Y Al O laser crystals has been studied by absorption spectroscopy. Impurities with stable trivalent states (Nd , Er , 3 5 12 3 5 12 31 Sm , etc) do not change the character of absorption spectra of the colour centers formed during gamma-irradiation. Impurities (Cr, Fe, Ce) which can easily change valency during irradiation, compete with growth defects in trapping of the charge carriers generated by irradiation.  2000 Elsevier Science S.A. All rights reserved. Keywords: Colour centers; Gd Ga O ; Y Al O ; Radiation defects 3 5 12 3 5 12 1. Introduction (0.2%); YAG-Cr (0.0017%), Mg (0.01%); YAG-V (0.7%); Gd Sc Ga O (GSGG); GGG-In (0.1%); GGG-Ca 3 2 3 12 Gadolinium gallium garnet Gd Ga O (GGG) and (0.01%); GGG-Mg (0.01%); GSGG-Co (0.01%); GSGG- 3 5 12 yttrium aluminium garnet Y Al O (YAG) single crystals Fe (0.01%); Nd Ga O (NGG); Sm Ga O (SGG)) 3 5 12 3 5 12 3 5 12 31 31 31 31 were grown by Czochralski method from iridium crucibles doped with rare earth ions (Nd , Er , Tm , Ho , 31 31 41 31 21 31 in Ar or Ar1O atmosphere. Samples for the inves- Pr , Ce ) or with 3d-ions (Cr , Cr , Co ,V ) are 2 tigations of crystal optical properties were made in the the most prospective materials for laser engineering [1,2]. form of plane-parallel polished plates of 0.5–2 mm Irradiation with UV light and ionizing radiation (IR) often thickness. The transmission spectra were recorded with a worsens the crystal optical and lasing properties since it spectrophotometer SPECORD M 40 (Carl Zeiss, Ger- creates stable or transient colour centers with additional many). The AA values were determined as: absorption (AA) bands both in the UV and visible spectrum range [3,4]. The radiation-stimulated changes of the garnet T 1 1 crystals properties are associated with two main processes: ] ] DK 5 ln , d T 2 ionizing recharging of growth defects and formation of radiation defects through the impact mechanism [3]. The where d is the sample thickness, T and T , the crystal 1 2 first process prevails in the case of UV, gamma and transmission before and after irradiation influence, respec- 7 electron irradiation at absorbed doses up to 10 Gy. In this tively. work the results of investigation of the influence of The samples were irradiated with gamma-quanta from a 60 7 impurities on the process of ionizing recharge of growth Co source with average energy of 1.25 MeVup to 10 Gy defects under the gamma-irradiation are presented. absorbed doses. 3. Results and discussion 2. Samples and experimental methods 2 7 After irradiation by gamma-quanta with doses 10 –10 The examined crystals (GGG; YAG; YAG-Nd (1%); Gy, the AA wide band in the range of 35 000–11 000 GGG-Nd (1%); (Y Er ) Al O (YAG-Er); YAG-Ce 21 21 0.5 0.5 3 5 12 cm with maxima at 32 000, 25 000 and 16 000 cm *Corresponding author. arise in YAG crystal spectra. The same shape and position 0925-8388 / 00 / $ – see front matter  2000 Elsevier Science S.A. All rights reserved. PII: S0925-8388(99)00771-9