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arXiv · 2501.18473

Absorption loss and Kerr nonlinearity in barium titanate waveguides

Annina Riedhauser·Charles Möhl·Johannes Schading·Daniele Caimi·David I. Indolese·Thomas M. Karg·Paul Seidler
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Abstract

Because of its exceptionally large Pockels coefficient, barium titanate (BaTiO$_3$) is a promising material for various photonic applications at both room and cryogenic temperatures, including electro-optic modulation, frequency comb generation, and microwave-optical transduction. These applications rely on devices with low optical loss to achieve high efficiency. Material absorption sets a lower limit to optical loss and is thus a crucial property to determine, particularly for integrated photonic devices. Using cavity-enhanced photothermal spectroscopy, we measure the absorption loss of BaTiO$_3$ ridge waveguides at wavelengths near 1550~nm to be $α_{\mathrm{abs}} = 10.9$~{\raisebox{0.5ex}{\tiny$^{+5.8}_{-0.4}$}} dB~m$^{-1}$, well below the propagation losses due to other sources, such as scattering. We simultaneously determine that BaTiO$_3$ has a large Kerr nonlinear refractive index of $n_{\mathrm{2,BaTiO_3}}$ = 1.8 {\raisebox{0.5ex}{\tiny$^{+0.3}_{-0.3}$}} $\times$ 10$^{-18}$ m$^2$ W$^{-1}$. Considering these results, photonic integrated circuits utilizing BaTiO$_3$ have the potential to achieve significantly higher efficiency than demonstrated to date and are especially interesting for applications exploiting the combination of Pockels and Kerr effects.

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Annina Riedhauser, Charles Möhl, Johannes Schading, Daniele Caimi, David I. Indolese, Thomas M. Karg, Paul Seidler. 2025-01-30. Absorption loss and Kerr nonlinearity in barium titanate waveguides. https://doi.org/10.1063/5.0228990

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