Broadband mid-infrared second harmonic generation using epitaxial polydomain barium titanate thin films

The mid-infrared (mid-IR) second-order optical nonlinearity of the barium titanate (BTO) thin films was characterized by second harmonic generation (SHG). The epitaxial BTO thin films were grown on strontium titanate substrates by pulsed-laser deposition. From the azimuthal-dependent polarized SHG measurements, the tensorial optical nonlinear coefficients, d(ij), and ferroelectric domain fraction ratio, delta A(Y)/delta A(z), were resolved. Strong SHG signals were obtained at the pumping laser wavelength lambda between 3.0 and 3.6 mu m. The SHG intensity was linearly dependent upon the square of the pumping laser power. The broadband mid-IR optical nonlinearity enables BTO thin films for applications in chip-scale quantum optics and nonlinear integrated photonic circuits. (C) 2019 Chinese Laser Press