The Detection of Optical Second Harmonic Generation from High Tc YBa2Cu307 Epitaxial Thin Films

Abstract- We have attempted to measure the second har-monic generation (SHG) of YBa2Cu30,-6 (YBCO) epitaxial films grown on (001) MgO substrates by laser ablation. Since the structure of the film has inversion symmetry, the possi-bly SHG susceptibility can only be attributed to the antifer-romagnetic 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. HE DISCOVERY OF high Tc superconductors (HTSC) T invokes many research activities in optical measurements in attempt to find whether the Cooper pairing mechanism is mediated by excitons [ 1 I, polaritons [ 2] , bipolarons [31, plasmons 131, or magnons [4]. The crucial prospects are polaritons and phonons can be detected by Raman Scatter