Fig. 2: Optical loss measurements.

a Photograph of a 3-inch LiNbO₃ wafer fully bonded to a 4-inch photonic Si₃N₄ Damascene wafer. b Photograph of an integrated photonic chip (5 mm × 5 mm size) with electrodes. c Broadband transmission measurements of a ring resonator with a FSR of 100 GHz showing flat coupling of resonances for wavelengths from 1260 nm to 1630 nm. d Extracted integrated dispersion of the ring resonator. The inset shows an expanded view of one of the modes at 184 THz with amplitude modulation sidebands at 500 MHz and the corresponding fitting curve. e Wafer map with average linewidth indicated for the ring resonators with a FSR of 21 GHz used as a reference. f Simulated optical mode confinement in LiNbO₃ as a function of optical frequency. Insets show typical mode profiles. The grey-shaded area represents the range measured. g Loaded (red), intrinsic (green), and external coupling (blue) linewidth of a 21-GHz microring (F6, see Supplementary Informaton). h The measured linewidth of three types of devices on the wafer accumulated over a measurement bandwidth of 55 THz.