A 2 in. diam single crystal of lithium tetraborate(Li2B4O7)was successfully grown by the Czochralski method. The crystal was free from macrodefects and had a dislocation density as low as100/cm2.It had an excellent homogeneity of the refractive index and a wide transparency down to 170 nm. The optical damage threshold was 40GW/cm2.Second-harmonic generation and sum frequency generation were investigated in association with the generation of the fourth and fifth harmonics of aQ-switched Nd:YAG laser. The conversion efficiency of the second-harmonic generation from the green (532 nm) light was 20&percent;. ©1997 American Institute of Physics.