A high-speed heterogeneous lithium tantalate silicon photonics platform

Abstract

The rapid expansion of cloud computing and artificial intelligence has driven the demand for faster optical components in data centres to unprecedented levels. A key advancement in this field is the integration of multiple photonic components onto a single chip, enhancing the performance of optical transceivers. Here silicon photonics, benefiting from mature fabrication processes, has gained prominence in both academic research and industrial applications. The platform combines modulators, switches, photodetectors and low-loss waveguides on a single chip. However, emerging telecommunication standards require modulation speeds that exceed the capabilities of silicon-based modulators. To address these limitations, thin-film lithium niobate has been proposed as an alternative to silicon photonics, offering a low voltage–length product and exceptional high-speed modulation properties. More recently, the first demonstrations of thin-film lithium tantalate circuits have emerged, potentially addressing some of the disadvantages of lithium niobate, enabling a reduced bias drift and enhanced resistance to optical damage. As such, this material arises as a promising candidate for next-generation photonic platforms. However, a persistent drawback of such platforms is the lithium contamination, which complicates integration with CMOS fabrication processes. Here we present for the first time the integration of lithium tantalate onto a silicon photonics chip. This integration is achieved without modifying the standard silicon photonics process design kit. Our device achieves low half-wave voltage (3.5 V), low insertion loss (2.9 dB) and high-speed operation (>70 GHz), paving the way for next-generation applications. By minimizing lithium tantalate material use, our approach reduces costs while leveraging existing silicon photonics technology advancements, in particular supporting ultra-fast monolithic germanium photodetectors and established process design kits.