Fig. 1: Heterogeneously integrated LiNbO3 photonic circuits based on wafer scale bonding.
From: A heterogeneously integrated lithium niobate-on-silicon nitride photonic platform
a Conventional approaches to LiNbO3 photonics consisting of traditional Ti- or proton-exchange-based waveguides and the recently emerged integrated photonics based on etching of thin-film LNOI (mostly to create ridge waveguides). b The hybrid approach presented in this work, involving heterogeneous integration of thin-film LiNbO3 onto Si3N4 wafers with integrated photonic circuits. c Schematic showing our approach of bonding a 4 inch (100 mm) thin-film LiNbO3 wafer onto planarized low-loss Si3N4 photonic integrated circuits. d AFM image of the Si3N4 Damascene wafer before bonding showing 400 pm RMS roughness over an area 5 μm by 5 μm. e Long-range profilometry scan of the Si3N4 Damascene wafer before bonding. f False-colored scanning electron micrograph of a cross-section of the hybrid structure. g Optical microscope image of a hybrid waveguide with gold electrodes. h Half-wave voltage measurements for phase modulators with 4 mm length using a Mach-Zehnder interferometer. i FEM simulations of the hybrid optical mode profile for a waveguide with 38% optical mode participation in lithium niobate and 6 μm separation between electrodes.
