We developed a Gd<sub><i>x</i></sub>Y<sub>1-<i>x</i></sub>Ca<sub>4</sub>O(BO<sub>3</sub>)<sub>3</sub> (GdYCOB) crystal for control of optical birefringence. GdYCOB crystals were successfully used to generate noncritical phase-matched (NCPM) second and third harmonics of 1064-nm lights. However, we observed degradation of third-harmonic-generation (THG) output power and distortion of the beam pattern as a result of photoinduced damage and thermal dephasing. The photoinduced damage was classified into two types. One was gray-track and the other was photorefractive damage. It seems that these types of damage were similar to the types of damage that occurred with KTiOPO<sub>4</sub> and LiNbO<sub>3</sub> crystals. We tried to circumvent this problem by crystal heating. Photoinduced damage of GdYCOB was overcome by elevation of the crystal temperature, and NCPM THG (355-nm) output power from heated GdYCOB increased to 9 mW (62.5 kHz).
© 2000 Optical Society of America
H. Furuya, H. Nakao, I. Yamada, Y. F. Ruan, Y. K. Yap, M. Yoshimura, Y. Mori, and T. Sasaki, "Alleviation of photoinduced damage in GdxY1-xCa4O(BO3)3 at elevated crystal temperature for noncritically phase-matched 355-nm generation," Opt. Lett. 25, 1588-1590 (2000)