Growth twins in self-frequency doubling laser crystal YbxY1-xAl3(BO3)4

Using chemical etching method, the growth twins in self-frequency doubling laser crystal YbxY1-xAl3(BO3)(4) have been observed. The etching pits on both sides of growth twin boundaries in the (<10(1)over bar 1>) slice are of the triangles with different orientations. The structure of growth twins is investigated by transmission synchrotron topography. In the transmission synchrotron topograph, the growth twins are visible not by 'domain contrast' but by 'boundary contrast', i.e. the twins appear in the topograph in form of X-ray kinematical diffraction contrast due to the lattice strain stemming from the impurity incorporation in the boundaries. The growth twins in YbxY1-xAl3(BO3)(4) crystal are of inversion types, since no domain contrast was observed.