A heterogeneously integrated lithium niobate-on-silicon nitride photonic platform
Mikhail Churaev, Rui Ning Wang, Annina Riedhauser, Viacheslav Snigirev, Terence Blésin, Charles Möhl, Miles Anderson, Anat Siddharth, Youri Popoff, Ute Drechsler, Daniele Caimi, Simon Hönl, Johann Riemensberger, Junqiu Liu, Paul Seidler, Tobias J. Kippenberg
Abstract
Abstract The availability of thin-film lithium niobate on insulator (LNOI) and advances in processing have led to the emergence of fully integrated LiNbO 3 electro-optic devices. Yet to date, LiNbO 3 photonic integrated circuits have mostly been fabricated using non-standard etching techniques and partially etched waveguides, that lack the reproducibility achieved in silicon photonics. Widespread application of thin-film LiNbO 3 requires a reliable solution with precise lithographic control. Here we demonstrate a heterogeneously integrated LiNbO 3 photonic platform employing wafer-scale bonding of thin-film LiNbO 3 to silicon nitride (Si 3 N 4 ) photonic integrated circuits. The platform maintains the low propagation loss ( < 0.1 dB/cm) and efficient fiber-to-chip coupling (<2.5 dB per facet) of the Si 3 N 4 waveguides and provides a link between passive Si 3 N 4 circuits and electro-optic components with adiabatic mode converters experiencing insertion losses below 0.1 dB. Using this approach we demonstrate several key applications, thus providing a scalable, foundry-ready solution to complex LiNbO 3 integrated photonic circuits.