Ultra-broadband near- to mid-infrared electro-optic modulator on thin-film lithium niobate

The escalating capacity limitations of conventional near-infrared telecommunication bands have spurred urgent investigations into wide-band optical communication systems spanning from the near-infrared to mid-infrared regimes. This has motivated the development of optical components combining broadband bandwidth with high-speed operation. The state-of-the-art modulators face challenges in achieving broad operational bandwidth due to waveguide dispersion and velocity mismatch. Here we demonstrate a thin-film lithium niobate (TFLN) electro-optic (EO) modulator with an unprecedented 800-nm operational bandwidth, covering the full O-U telecom bands and extending into the 2-μm regime. The TFLN modulator exhibits >67 GHz EO bandwidth across O-U bands (~100 GHz at O-/S-/C-/L-bands) and >50 GHz at 2-μm band. It enables single-lane exceeding 240 Gbps PAM-4 transmission across O-U bands and a record 170 Gbps PAM-4 transmission at 2-μm band. This breakthrough establishes TFLN as a compelling platform for multispectral photonics, bridging conventional telecom infrastructure with emerging 2-μm technologies for next-generation optical communications. This work demonstrates a thin-film lithium niobate modulator with an 800-nm operational bandwidth covering from near- to mid-infrared region, enabling single-lane 240 Gbps and 170 Gbps PAM-4 transmission at all O-U bands and 2-μm band, respectively.