Tm, Ho-codoped LiYF4 (Tm,Ho:YLF) and Tm, Ho-codoped LiLuF4 (Tm,Ho:LLF) single crystals with extended diameter were grown by the Czochralski method under CF4 atmosphere. The growth conditions were optimized for the growth of Tm,Ho:YLF and Tm,Ho:LLF single crystals with 3-in diameters. The crystallinity was studied using X-ray rocking curve analysis. Color center formation in the ultraviolet and visible spectral regions was investigated with the induced absorption study using X-ray irradiation. (C) 2003 Elsevier Science B.V. All rights reserved.