Heterogeneously integrated photonic terahertz transmitter on thin-film lithium niobate

Terahertz (THz) communication unlocks massive capacity for future data-intensive networks. While photonics-based THz systems offer broad bandwidths, their reliance on discrete optical assemblies dictates substantial coupling losses and bulky footprints. Achieving complete on-chip integration without degrading the bandwidth or efficiency of discrete optoelectronic components remains a central challenge. Here, we demonstrate an integrated photonic THz transmitter by heterogeneously bonding an InP-based uni-traveling-carrier photodiode (UTC-PD) to a thin-film lithium niobate (TFLN) modulator chip. This architecture successfully merges TFLN's excellent electro-optic response with robust III-V THz generation, featuring an integrated photodiode with a benchmark 3-dB bandwidth of 240 GHz and 0.67 A/W internal responsivity. In sub-THz wireless links, the transmitter delivers 40 Gbit/s at 150 GHz and 32 Gbit/s at 200 GHz using NRZ or PAM4 formats, establishing a scalable pathway for next-generation wireless interconnects.