Toward Large-Scale Photonic Chips Using Low-Anisotropy Thin-Film Lithium-Tantalate.

Photonic manipulation of large-capacity data with the advantages of high speed and low power consumption is a promising solution for explosive growth demands in the era of post-Moore. A well-developed lithium-niobate-on-insulator (LNOI) platform has been widely explored for high-performance electro-optic (EO) modulators to bridge electrical and optical signals. However, the photonic waveguides on the x-cut LNOI platform suffer serious polarization-mode conversion/coupling issues because of strong birefringence, making it hard to realize large-scale integration. Here, low-birefringence photonic integrated circuits (PICs) based on lithium-tantalate-on-insulator (LTOI) are proposed and demonstrated, which enables high-performance passive photonic devices as well as EO modulators, showing great potential for large-scale photonic chips. Analysis of mode conversion and evolution behaviors with both low- and high-birefringence shows undesired mode hybridizations can be effectively suppressed. A simple and universal fabrication process is developed and various representative passive photonic devices are demonstrated with impressive performances. Finally, a wavelength-division-multiplexed optical transmitter is developed with a data rate of 1.6 Tbps by monolithically integrating 8 EO modulators and an 8-channel arrayed waveguide grating. Therefore, the demonstrated low-birefringence LTOI platform shows strong ability in both passively and actively controlling photon behaviors on a chip, indicating great potential for ultrafast processing and communicating large-capacity data.