Electro-optic integration

Nat. Mater. https://doi.org/gfh3qg (2018)

Silicon is a popular material for constructing nanoscale optical devices, but has the drawback of not having an electro-optic Pockels effect due to its centrosymmetric crystalline structure. Now, Stefan Abel and co-workers from Switzerland, the USA and Spain have developed a fabrication process to allow materials with a large Pockels effect to be integrated with nanoscale silicon photonic devices. The team epitaxially grew single-crystalline BaTiO₃ on a silicon substrate. Then, a 5- to 10-nm-thick Al₂O₃ layer was deposited on the BaTiO₃ layer in order to bond the BaTiO₃ layer and another silicon wafer covered with SiO₂. Using these multilayers, optical waveguides and plasmonic phase modulators were fabricated supporting data modulation up to 50 Gbit s^–1. The scientists experimentally measured that the Pockels coefficients in the structures were r₄₂ = 923 ± 215 pm V^–1 and r₃₃ = 342 ± 93 pm V^–1.