The quadratic nonlinear optical coefficients of pure and MgO-doped lit
hium diborate (Li2B4O7) crystals grown by the Czochralski method have
been measured at the fundamental wavelength of 1064 nm. The effects of
MgO-doping in the lithium diborate crystals are discussed. By doping
1 mol% MgO in the lithium diborate crystals d(31) is increased by 40%
while d(33) is decreased.