Self-regulating nanostructuring of transparent materials via femtosecond laser irradiation

Ultrafast lasers have been widely exploited ever since the end of the last century for inscribing pristine, accurate and localised modifications in the bulk of transparent materials. Despite offering an enabling technique, this technology suffered from resolution limitations. Nonetheless, laser-inscribing arbitrary patterns with a sub-wavelength resolution in the bulk of transparent materials is of great importance for allowing reliable and versatile non-invasive nano-manufacturing. In this work, we focus on developing and investigating novel techniques for laser-based nanometric structuring in the bulk of fused silica. In particular, we explore two approaches: one to overcome the diffraction limit and another one to reduce it. The first one consists on a seeding-writing near-field enhancement based method for creating single nanoplanes at arbitrary locations with programmable length and curvature. The second one, in exploring the manufacturing potential of reducing the machining laser wavelength down to the UV range. As a result of the first method, we prove the possibility of generating nanoplanes characterised by an etching contrast, presenting a thickness of the order of tens of nanometers and having a different refractive index from the surrounding material. Incidentally, seed-less side planes are also produced under certain writing conditions. While defining ideal writing conditions for the single nanoplane inscription, we propose a model for the formation of the lateral ones. Thanks to the second approach, instead, we prove the capability of inscribing self-organised periodic patterns that we characterise and classify. We suggest a link between these features and the etching rate and we propose a phenomenological explanation for the self-organisation. Finally, we develop a model to assess the importance of stress-induced cumulative effects on the generation of these structures. Ultimately, in this thesis work we introduce new machining techniques, report novel regimes of modification, offer innovative characterisation approaches and advance original explanatory models. All these finally contribute to the understanding and the industrial implementation of laser nano-manufacturing in transparent materials.