Integrated lithium niobate electro-optic modulators: when performance meets scalability

TLDR

Electro‑optic modulators convert electrical signals to optical ones and are central to communication, signal processing, sensing, and quantum technologies; next‑generation devices demand high‑density integration, low cost, and high performance, which thin‑film lithium niobate can provide with its high EO efficiency, robust performance, and scalable fabrication, yielding smaller footprints, wider bandwidths, and lower power consumption. This mini‑review explains the principles and technical advances that enable state‑of‑the‑art lithium‑niobate modulators and outlines future opportunities for large‑scale EO circuits beyond single components. The authors discuss multiple design approaches, their advantages and challenges, and propose pathways to further improve performance, offering a perspective on the potential future capabilities of lithium‑niobate modulators. Thin‑film lithium‑niobate modulators already match or surpass the performance of mature silicon and indium phosphide platforms, demonstrating comparable or superior bandwidth, efficiency, and power consumption.

Abstract

Electro-optic modulators (EOMs) convert signals from the electrical to the optical domain. They are at the heart of optical communication, microwave signal processing, sensing, and quantum technologies. Next-generation EOMs require high-density integration, low cost, and high performance simultaneously, which are difficult to achieve with established integrated photonics platforms. Thin-film lithium niobate (LN) has recently emerged as a strong contender owing to its high intrinsic electro-optic (EO) efficiency, industry-proven performance, robustness, and, importantly, the rapid development of scalable fabrication techniques. The thin-film LN platform inherits nearly all the material advantages from the legacy bulk LN devices and amplifies them with a smaller footprint, wider bandwidths, and lower power consumption. Since the first adoption of commercial thin-film LN wafers only a few years ago, the overall performance of thin-film LN modulators is already comparable with, if not exceeding, the performance of the best alternatives based on mature platforms such as silicon and indium phosphide, which have benefited from many decades of research and development. In this mini-review, we explain the principles and technical advances that have enabled state-of-the-art LN modulator demonstrations. We discuss several approaches, their advantages and challenges. We also outline the paths to follow if LN modulators are to improve further, and we provide a perspective on what we believe their performance could become in the future. Finally, as the integrated LN modulator is a key subcomponent of more complex photonic functionalities, we look forward to exciting opportunities for larger-scale LN EO circuits beyond single components.