Ultra-compact and efficient standing-wave electro-optic modulator in lithium niobate

Journal article, 2026

Electro-optic (EO) modulators are fundamental building blocks in photonic systems, with broad applications in optical communications, computing, sensing, and quantum information processing. Thin-film lithium niobate (LN) has emerged as a leading platform for EO modulators owing to its strong Pockels effect and its potential for low-power, scalable, and cost-effective integrated photonic systems. To achieve low driving voltage at high modulation speeds, traveling wave (TW) electrodes are widely employed to extend the interaction length. However, the voltage-length product of TW LN modulators remains intrinsically limited and cannot be straightforwardly enhanced, resulting in device footprints on the order of several centimeters. To overcome this limitation, we propose a high-Q micro-structured standing-wave (SW) electrode design that significantly enhances intrinsic modulation efficiency, and as a result, can drastically reduce the electrode length. We experimentally demonstrate a single-drive SW LN phase modulator with a voltage-length product of Vπ · L = 1 V · cm (corresponding to 0.5 V · cm in a push-pull configuration) using a total electrode length of only 1 mm. Our device exhibits a 5.6-fold improvement in intrinsic modulation efficiency and a 20-fold reduction in footprint compared with a typical TW modulator. In addition to its compactness and high efficiency, the proposed SW modulator, to our knowledge, offers several unique advantages, including impedance-loading-free operation, relaxed velocity-matching requirements, and high reciprocity. These attributes make the SW modulator a promising building block for ultra-efficient and densely integrated EO circuits, such as EO frequency combs, optical switches, and microwave-photonics systems.