  The continuous growth of global data traffic over the past three decades,
along with advances in disaggregated computing architectures, presents
significant challenges for optical transceivers in communication networks and
high-performance computing systems. Specifically, there is a growing need to
significantly increase data rates while reducing energy consumption and cost.
High-performance optical modulators based on materials such as InP, thin-film
lithium niobate (LiNbO3), or plasmonics have been developed, with LiNbO3
excelling in high-speed and low-voltage modulation. Nonetheless, the widespread
industrial adoption of thin film LiNbO3 remains compounded by the rather high
cost of the underlying 'on insulator' substrates -- in sharp contrast to
silicon photonics, which can benefit from strong synergies with high-volume
applications in conventional microelectronics. Here, we demonstrate an
integrated 110 GHz modulator using thin-film lithium tantalate (LiTaO3) -- a
material platform that is already commercially used for millimeter-wave filters
and that can hence build upon technological and economic synergies with
existing high-volume applications to offer scalable low-cost manufacturing. We
show that the LiTaO3 photonic integrated circuit based modulator can support
176 GBd PAM8 transmission at net data rates exceeding 400 Gbit/s, while
exhibiting a lower bias drift compared to LiNbO3. Moreover, we show that using
silver electrodes can reduce microwave losses compared to previously employed
gold electrodes. Our demonstration positions LiTaO3 modulator as a novel and
highly promising integration platform for next-generation high-speed,
energy-efficient, and cost-effective transceivers.
