Growth and optical properties of Na3Gd2(BO3)3 crystal

► A Na3Gd2(BO3)3 crystal with dimensions of 25 × 15 × 10 mm3 is successfully grown from the NaBO2-NaF flux. ► Refractive indices are measured and the Sellmeier equations construct. ► Nonlinear optical coefficients are determined. ► d31 coefficient is about six times as large as d36(KDP).