Design methodology for enhanced nonlinear wavelength conversion efficiency using periodically poled single-domain thin-film barium titanate

Barium titanate (BTO) is renowned for its exceptionally high electro-optic coefficient, which is orders of magnitude larger than that of lithium niobate (LN). Exploiting BTO's large nonlinearity to miniaturize the nonlinear wavelength converters is thus highly desired, yet progress remains limited. In this work, we focus on the design methodology of periodically poled barium titanate. We qualitatively analyze the benefit introduced by single-domain engineering, quantitatively evaluate the propagation-loss-dependent conversion efficiency from the TE mode at the fundamental harmonic to the TM mode at the second harmonic, and identify the operating regime where its performance outperforms LN at a footprint in millimeter to centimeter scale. The periodic poling technique is also presented.