Nonlinear optical properties of Gd2(MoO4)3 and Tb2(MoO4)3

The magnitudes and absolute signs of the nonlinear optical coefficients that describe second harmonic generation (SHG) in β-Gd2 MoO4)3 and β-Tb2(MoO4)3 have been determined using a 1.06μ Nd: YAG laser. In marked contrast to the usual situation with ferroelectric crystals, nonphase-matched SHG with these two ferroelastic-ferroelectric materials is, for certain easily achieved conditions, insensitive to antiparallel domains. The vector part of the δ-form of their nonlinearities is in each case in agreement both in magnitude and absolute sign with the recent formulation due to Jerphagnon.