Enhancement of second-harmonic generation inBaTiO3/SrTiO3superlattices

Second-harmonic generation (SHG) of a 1.064-μm incident beam was investigated on ${\mathrm{BaTiO}}_3{/\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ superlattices prepared by laser molecular-beam epitaxy. The incidence angle and the polarization angle dependence of the SHG coefficients were measured. The SHG coefficients were greatly enhanced by the superlattice structure with the maximum value of $d_{33}=156.5\mathrm{}\mathrm{p}\mathrm{m}/\mathrm{V}$ being more than one order of magnitude larger than that of bulk ${\mathrm{BaTiO}}_3$ crystal. The mechanism of SHG enhancement was discussed.