Thin‐Film Lithium Niobate Modulators with Ultra‐High Modulation Efficiency

Abstract Thin‐film lithium niobate (TFLN)‐based electro‐optic modulators have extensive applications in broadband optical communications due to their broad bandwidth, high extinction ratio, and low optical loss. However, compared with their silicon and indium‐phosphide (InP)‐based counterparts, TFLN exhibits lower modulation efficiency. Simultaneously achieving low driving voltage and a wide modulating bandwidth poses a significant challenge. To address this limitation, this paper proposes a transparent conductive oxide film into the device, resulting in an ultra‐high modulation efficiency of 1.02 V cm. The fabricated composite electrode not only attains high modulation efficiency but also sustains a high electro‐optic bandwidth, as evidenced by the 3 dB roll‐off at 108 GHz and the transmission of PAM‐4 signals at 224 Gbit s −1 . The fabricated device offers novel solutions for low‐cost, high‐performance modulators, thereby facilitating the downsizing of TFLN‐based multichannel optical transmitter chips.