Highly efficient broadband second harmonic generation using polydomain epitaxial barium titanate thin film waveguides

摘要

Broad band second harmonic generation (SHG) over the spectral range of 530-700 nm is reported using an epitaxial barium titanate (BaTiO_3) thin film waveguide. The epitaxial layers are multidomain consisting of both a and c domain variants. The SHG conversion efficiency is nearly independent of wavelength over the visible spectra range. An enhanced broadband conversion efficiency was observed that is attributed to random quasi-phase matching in the polydomain epitaxial layers. In contrast to theory of SHG for disordered nonlinear media, the observed SHG shows a quadratic dependence on pump power.