The doped nonlinear optical (NLO) crystal Yb:GdCa4O(BO3)(3) (Yb:GdCOB) has been grown by using the Czochralski method, with large sizes and good optical quality, The polarized absorption and fluorescence spectra have been measured and analyzed according to the Judd-Ofelt theory. The ground-state energy-level splitting is 1002 cm(-1). The spectral parameters of the crystal such as the emission lifetime, the absorption cross-section. and the peak emission cross-section have been calculated. In comparison with established laser crystals the results suggest that this crystal has potential as an efficient self-frequency-doubling (SFD) laser operation in the green. (C) 2002 Published by Elsevier Science B.V.