Cryst. Res. Technol. 36 2001 11 1223–1229 © WILEY- VCH Verlag Berlin GmbH, 13086 Berlin, 2001 0232-1300/01/1111-1223 $ 17.50+.50/0 The results on optical absorption, photoluminescence and thermoluminescence of YAP-Tm crystals of 1 at.% and 4 at.% of Tm are presented as well as influence of UV-, γ-radiation and thermal treatments on optical and luminescence properties of the crystals. The blue-green luminescence of defect centers was observed in YAP-Tm crystals at Ar + -laser excitation. The possibility of energy transfer processes between defect centers and Tm 3+ ions was shown. Keywords: YAlO 3 -Tm, optical absorption, luminescence, color centers (Received March 2, 2001; Accepted July 2, 2001) 1. Introduction Yttrium aluminum perovskite crystals YAlO 3 doped with thulium (YAP-Tm) in recent years are of interest as materials for 2 μm lasers at 4-5 at.% concentration of thulium and up- conversion visible lasers at ~1 at.% of thulium (ELDER et al., 1996; ELDER et al., 1998; GUY et al., 1998). Though YAP-Tm crystals are of much interest, the problem of obtaining of large, structurally perfect and optically qualitative (free from cloudiness and parasitic absorption) crystals is not solved finally. The influence of point defects on YAP-Tm optical properties remains scanty studied. The purpose of the paper is investigation of influence of UV-, γ- radiation and thermal treatments on optical and luminescence properties of YAP-Tm crystals. 2. Experimental procedure The YAP-Tm crystals were grown by the Czochralski technique with an automatic diameter control and radio frequency induction heating from iridium crucibles in argon atmosphere. The crystals were pulled in the [010] direction in Pbnm setting. The YAP-Tm (4 at.%) crystals (50 mm in diameter and more than 100 mm in length) and YAP-Tm (1 at.%) crystals (25×50 mm) were grown by the technologies described in detail by SAVITSKII et al., 2000 and NEUROTH et al., 1999 respectively. The optical transmission spectra of investigated crystals were measured in visible and IR region at room temperature using UV-VIS LAMBDA 2, BECKMAN ACTA MVII, FT-IR D. SUGAK 1,2 , A. DURYGIN 3 , A. MATKOVSKII 2,4 , A. SUCHOCKI 3 , I. SOLSKII 1 , D. SAVITSKII 2 , YA. ZHYDACHEVSKII 2 , F. WALLRAFEN 5 , K. KOPCZYNSKI 6 1 SRC “Carat”, Lviv, Ukraine 2 National University “Lviv Polytechnic”, Lviv, Ukraine 3 Institute of Physics PAS, Warsaw, Poland 4 Institute of Physics, Pedagogical University, Rzeszow, Poland 5 Bonn University, Bonn, Germany 6 MUT, Institute of Optoelectronics, Warsaw, Poland Optical and Luminescence Properties of YAlO 3 -Tm Crystals