Structures responsible for quasisynchronism in second-harmonic generation in BaTiO3 : Fe

Second harmonic generation (SHG) of light in iron-doped BaTiO3 crystals occ urs primarily at an angle of about 7 degrees to incident lambda = 1.06 mu m radiation. It is shown that the quasisynchronism is accounted for by a 90 degrees domain structure with a spatial wave vector q parallel to[011] and a spatial period of about 3 mu m. This result may serve as a basis for inte rpretation of the anomalous SHG enhancement near the phase transition. (C) 1999 American Institute of Physics. [S1063-7834(99)03206-2].