Properties, mechanisms, and perspectives of ultrafast laser modifications in silicate glass volume

Abstract Ultrafast laser irradiation of glass enables highly localized structural transformations within the material's bulk, unlocking diverse applications in photonics, data storage, and microfabrication. Here, we provide a concise yet comprehensive overview of the main types of femtosecond laser‐induced modifications in silica‐based glasses (Types I, II, III, X, and related crystalline transformations), highlighting their distinct features and underlying thermal‐ and pressure‐driven mechanisms. This review offers a current state‐of‐the‐art perspective on various modifications, while also presenting new nanoscale insights through advanced scattering scanning near‐field optical microscopy and nano‐Fourier transform infrared spectroscopy, discussing the densification mechanisms behind. Finally, we outline broader perspectives, from fundamental research directions to industry developments, to inspire future advances in next‐generation optical technologies.