Advances in Thin-Film Lithium Niobate High-Speed Electro-Optic Modulators

Abstract

The thin-film lithium niobate (TFLN) platform, with high refractive-index contrast and a strong linear electro- optic effect, offers a viable pathway to overcoming the performance limitations of conventional bulk-material electro-optic modulators. This paper systematically reviews key technological advances in TFLN high -speed electro-optic modulators. In terms of synergistic optimization of modulation efficiency and electro -optic bandwidth, three technical routes are summarized: microstructured electrode design, waveguide mode engineering, and velocity -matching strategies, encompassing periodically capacitively loaded T -electrodes, slow-wave electrodes, buried dual-capacitor structures, slot waveguides, and high-permittivity cladding. These approaches have reduced the half -wave voltage-length product (VπL) to 1 –2.5 V· cm and pushed the 3 dB electro-optic bandwidth beyond 140 GHz. In terms of functional expansion and heterogeneous integration, polarization-independent modulation, Si/SiN, and chalcogenide glass heterogeneous integration technologies are reviewed, along with application -specific designs for ultrashort pulse generation, laser ranging, and fully packaged devices. Different technical routes exhibit distinct performance trade -offs: microstructured electrodes and optical mode engineering can significantly enhance modulation efficiency but at the cost of increased fabrication complexity, higher coupling loss, and enhanced high -frequency dispersion; heterogeneous integration offers advantages in bandw idth extension and functional convergence, yet faces challenges in thermal management, interfacial defects, and material compatibility. Currently, the development of TFLN modulators is transitioning from single-parameter performance enhancement toward comprehensive optimization of efficiency, bandwidth, loss, and manufacturability. Multi -objective co -design and optoelectronic co-packaging will represent important future directions.