Wafer-Scale Thin Film Lithium Niobate (TFLN) Substrate Solution for Integrated Photonics and RF Acoustic Filters

Lithium niobate (LN) is a crystal with unique optical and electrical properties, making it useful for optical communication systems and microwave photonics. Compared to bulk LN, thin film LN (TFLN) is an enabling material for a wide range of defense and non-defense applications, driven by its superior electro-optic, nonlinear optical, and acousto-optic properties. In defense applications, TFLN plays a critical role in high-speed optical communication systems, where its low optical loss and high modulation efficiency enables secure, high-bandwidth signal transmission for military and aerospace communications.Additionally, the increasing demand for higher data rates in 4G and 5G wireless communication has led to the development of new technologies like bulk acoustic wave (BAW) filters. These filters, based on piezoelectric Aluminum Nitride (AlN), offer high Q factors for better filtering but are limited by material properties. To address these needs, next-generation RF filter technologies using engineered materials like TFLN are being considered. This includes combining the benefits of surface acoustic wave (SAW) and BAW technologies on unconventional engineered materials platforms. There is a limited global supply of TFLN substrates, mainly from companies in Asia, which are critical for RF filter and integrated photonics applications. Also most of these TFLN providers rely on Smart Cut based layer transfer approach. Therefore, on-shoring this capability for US supply chain and investigating alternative strategies for the fabrication of TFLN substrates are warranted. This Phase I STTR program aims to develop a method for fabricating TFLN engineered substrates as an alternative to the traditional Smart-Cut™ ion-implantation approach. Our proposed backside wafer grinding and polishing method offers key advantages, including independence from lithium niobate (LN) crystallographic orientation and compatibility with various handle substrates, enabling precise thickness control from 0.3 µm to several microns. This effort will establish a scalable, cost-effective domestic production pathway for TFLN substrates, enabling high-performance integrated photonic and RF applications while reducing reliance on foreign supply chains.