Development of a Domestic Supply of Large, High-performance LiNbO3 Crystals

Lithium niobate (LiNbO? or LN) is a cornerstone material in advanced photonic and quantum technologies, supporting applications ranging from optical modulators and nonlinear optics to integrated optical components and quantum sensors.Ý However, the U.S. faces critical supply chain vulnerabilities as nearly all LN crystals are sourced from foreign suppliers.Ý This SBIR proposal addresses the Navyís need to establish a robust domestic source for high-quality LN substrates by developing an innovative, scalable synthesis technique that meets or exceeds stringent optical quality specifications required for Department of Defense (DoD) applications.Czochralski (CZ) growth, the dominant method for LN production, presents several challenges, including point defects, compositional inhomogeneities, bubbles, and dislocations. ÝThese issues limit the optical uniformity and purity of LN crystals, particularly for large-diameter substrates needed in photonic integrated circuits (PICs) and quantum inertial sensors. ÝTo overcome these limitations, we propose a practical synthesis process leveraging precise thermal and compositional controls to achieve defect-minimized LN crystals with superior optical properties.In Phase I, we will conduct a feasibility study of this innovative approach, targeting uniform composition (+/- 0.01 mol% Li?O), Curie temperature uniformity (+/- 1∞C), refractive index uniformity (+/- 1e-4), and impurity levels below 1 ppm.Ý This effort will involve small-scale synthesis trials and a set of material characterization methods to achieve key results and inform the design of the crystal growth system.Ý While large single-crystal production is beyond Phase I, we will fabricate and characterize polycrystalline sections to validate the proposed technique.ÝPhase I results will significantly derisk the overall effort.In Phase II, we will produce large crystals and fabricate LN wafers (150 mm diameter, 1 mm thickness) with tight specifications on orientation, flatness, and optical quality.Ý Five prototype wafers will be delivered to the Navy to confirm key properties (e.g., crystallinity, surface quality, composition, optical properties).Ý By Phase IIís conclusion, the process will meet Navy specifications for high-quality LN substrates, enabling a secure domestic supply chain for critical DoD and commercial applications.The proposed work directly addresses the Navy's objectives by developing a reproducible, scalable crystal growth process ensuring high-quality LN substrates with fewer defects and superior uniformity.Ý Phase I results will demonstrate feasibility, while preparing the foundation for full-scale production in Phase II.Ý This initiative will support U.S. photonics and quantum technologies by eliminating reliance on foreign suppliers and establishing a sustainable domestic source for LN crystals.