Monolithic lithium niobate photonic chip for efficient terahertz-optic modulation and terahertz generation.

Zhang, Yiwen; Yang, Jingwei; Zeng, Yuansong; Chen, Zhaoxi; Feng, Hanke; Zhu, Sha; Shum, Kam-Man; Chan, Chi Hou et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The terahertz (THz) range, bridging microwave and infrared frequencies, enables advanced imaging, sensing, communications, and spectroscopy. Analogous to microwave photonics, terahertz photonics offers a promising optical solution to critical THz challenges-THz-optical interfacing, including THz-optic modulation and optical generation of THz waves. We address these with a monolithic integrated photonic chip enabling efficient THz-optical bidirectional interaction. Leveraging strong second-order optical nonlinearity and optical/THz confinement in thin-film lithium niobate on quartz, the chip supports efficient THz-optic modulation and continuous THz generation up to 500 GHz. The measured continuous wave THz generation efficiency of 4.8 × 10<sup>-6</sup>/W at 500 GHz also marks a tenfold improvement over existing lithium niobate-based tunable THz generation devices. We further leverage the coherent nature of the optical THz generation process and on-chip modulators to realize 65 GHz high-speed electro-THz modulation. The chip-scale THz-photonic platform enables more compact, efficient, and cost-effective THz systems for communications, sensing, and spectroscopy.