Ultrafast Laser Two‐Photon Lithography for Metasurface Engineering: Advances in Fabrication and Photonic Applications

ABSTRACT Ultrafast laser two‐photon lithography (TPL) has revolutionized micro/nanofabrication, enabling the creation of intricate 3D structures with sub‐diffraction‐limited resolution. The integration of TPL with metasurface engineering has unlocked new frontiers in photonic device design, offering unprecedented control over light‐matter interactions at the nanoscale. This review delves into the cutting‐edge advancements in TPL as applied to the fabrication of metasurfaces, which are thin, artificially structured materials with unique optical properties. We explore TPL's unparalleled precision of TPL, which allows the creation of complex metasurface geometries, facilitating breakthroughs in diverse applications, including high‐efficiency diffractive optics, next‐generation imaging systems, quantum optics, and dynamic tunable photonic devices. Key challenges, such as material limitations, process optimization, and scalability, are discussed along with promising solutions and future directions for overcoming these barriers. Furthermore, the potential of TPL to drive innovation in areas such as optical sensing, energy harvesting, and quantum information processing is critically analyzed. Through this comprehensive review, we highlight the transformative role of ultrafast laser two‐photon lithography in advancing metasurface technologies, positioning it as a cornerstone of the future of photonics.