Lithium tantalate photonic integrated circuits for volume manufacturing.

Abstract

Electro-optical photonic integrated circuits (PICs) based on lithium niobate (LiNbO₃) have demonstrated the vast capabilities of materials with a high Pockels coefficient^1,2. They enable linear and high-speed modulators operating at complementary metal-oxide-semiconductor voltage levels³ to be used in applications including data-centre communications⁴, high-performance computing and photonic accelerators for AI⁵. However, industrial use of this technology is hindered by the high cost per wafer and the limited wafer size. The high cost results from the lack of existing high-volume applications in other domains of the sort that accelerated the adoption of silicon-on-insulator (SOI) photonics, which was driven by vast investment in microelectronics. Here we report low-loss PICs made of lithium tantalate (LiTaO₃), a material that has already been adopted commercially for 5G radiofrequency filters⁶ and therefore enables scalable manufacturing at low cost, and it has equal, and in some cases superior, properties to LiNbO₃. We show that LiTaO₃ can be etched to create low-loss (5.6 dB m^-1) PICs using a deep ultraviolet (DUV) stepper-based manufacturing process⁷. We demonstrate a LiTaO₃ Mach-Zehnder modulator (MZM) with a half-wave voltage-length product of 1.9 V cm and an electro-optic bandwidth of up to 40 GHz. In comparison with LiNbO₃, LiTaO₃ exhibits a much lower birefringence, enabling high-density circuits and broadband operation over all telecommunication bands. Moreover, the platform supports the generation of soliton microcombs. Our work paves the way for the scalable manufacture of low-cost and large-volume next-generation electro-optical PICs.