The detection of optical second harmonic generation from high Tc YBa/sub 2/Cu/sub 3/O/sub 7/ epitaxial thin films

We have attempted to measure the second harmonic generation (SHG) of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) epitaxial films grown on [001] MgO substrates by laser ablution. Since the structure of the film has inversion symmetry, the possibly SHG susceptibility can only be attributed to the antiferromagnetic dipoles and electric quadrupoles. The delicate and meticulous experiment shows that the angular dependence of the second harmonic susceptibility of the superconducting films can be fitted successfully by the time-dependent density functional approach.<>