Characterization of low-loss 6-inch wafers of lithium niobate thin film

Thin-film lithium niobate stands out as a versatile platform for integrated photonics due to its favorable electro-optic, acousto-optic, and nonlinear properties, coupled with its low propagation loss and broad transparency range. While it is an established material platform, the large-scale production of high-quality lithium niobate on insulator (LNOI) wafers is still limited to only a handful of producers worldwide. Here, we report the characterization of 6-inch X-cut LNOI wafers fabricated at CEA-Leti using the Smart Cut technique. The wafers exhibit sub-nanometer surface-level roughness (<1 nm), exceptional thickness uniformity (3-5%), and high crystalline quality. Furthermore, we demonstrate typical low propagation losses (<0.5 dB/cm -1 ) and high electro-optic efficiencies (Vπ•L = 2.38 ± 0.06 V•cm at 1550 nm) for ridge waveguides fabricated on this platform. To the best of our knowledge, these wafers are the first 6” LNOI wafers reaching such a high-quality standard to be fabricated in Europe.