Bridgman growth and characterization of nonlinear optical single crystals Ca4GdO(BO3)3

Nonlinear optical single crystals Ca4GdO(BO3)3 (GdCOB) have been grown by the vertical Bridgman method. Bubble-free, twin-free and crack-free GdCOB single crystals 25 mm in diameter and 65 mm in length were obtained. The average thermal expansion coefficients along a-, b- and c-axes from 293 to 1273 K are 10.35×10−6 K−1, 7.78×10−6 K−1 and 13.10×10−6 K−1, respectively. The bulk damage threshold is 130 GW cm−2 for a single pulse of a mode-locked Nd:YAG laser with 35 ps pulse duration. The effective nonlinear coefficient (deff) in the phase matching directions of (θ, φ)=(66.8°, 132.6°) is 1.51 pm V−1.