On May 8th, the research team led by Dr. Ou Xin from the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, in collaboration with Tobias Kippenberg's team from the Swiss Federal Institute of Technology in Lausanne, made a breakthrough in the field of lithium tantalate heterogeneous integrated wafers and high-performance photonic chips. The related achievements were published in "Nature".
Lithium tantalate, known as "optical silicon", has attracted widespread attention in recent years. Foreign research institutions such as Harvard University have even proposed a plan to build a new generation of "lithium tantalate valley" following the "Silicon Valley" model. Dr. Ou Xin's team and their collaborators found that compared to lithium tantalate, single-crystal lithium tantalate films exhibit similar excellent electro-optic conversion characteristics and have advantages in birefringence, transparent window range, light bending resistance, and frequency comb generation. Additionally, lithium tantalate films can achieve low-cost and large-scale manufacturing, making them highly valuable for applications.
Dr. Ou Xin's team utilized heterogeneous integration technology based on the "universal ion knife" to prepare high-quality silicon-based lithium tantalate single-crystal film heterogeneous wafers through hydrogen ion implantation combined with wafer bonding. Furthermore, in collaboration with the partner team, they jointly developed a super-low-loss lithium tantalate photonic device microfabrication method, with the optical losses of the corresponding devices generally lower than the reported waveguide losses of lithium tantalate at the wafer level.
The lithium tantalate photonic chip demonstrates comparable electro-optic modulation efficiency to lithium tantalate films. Moreover, the research team successfully generated a soliton optical frequency comb for the first time in an X-cut electro-optic platform. With its electro-optic tunability, it is expected to find applications in laser radar, precision measurement, and other fields. It is worth mentioning that the research team has already tackled the 8-inch wafer preparation technology, laying the foundation for the development of larger-scale domestically produced optoelectronic integrated chips and mobile terminal RF filter chips.
Schematic diagram of lithium tantalate hetero-integrated wafer and high-performance photonic chip. Image source: Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences.
Ou Xin explained: "Compared to lithium niobate thin films, lithium tantalate thin films are easier to prepare and have higher preparation efficiency. At the same time, lithium tantalate thin films have a wider transparent window, strong electro-optic modulation, weak birefringence, and stronger anti-light-induced refractive index change characteristics. These inherent material advantages greatly expand the optical design freedom of the lithium tantalate platform."
Related paper information: https://doi.org/10.1038/s41586-024-07369-1
