Ultrafast laser micro and nano processing of transparent materials—From fundamentals to applications

Abstract

The distinctive features of ultrafast lasers, such as the extremely high peak intensity associated with their ultrashort pulse duration, enable the machining of materials whose band gaps are larger than the photon energies of the laser due to the nonlinear nature of photon absorption by matter. As a result, processing of transparent materials at micro and nanoscale levels can be achieved using ultrafast lasers, which is a matter of particular relevance in the fields of electronics, healthcare, photonics, and energy harvesting. By using ultrafast laser beams that possess a standard Gaussian spatial profile, and by exploiting nonlinear light-matter interaction confinement schemes, fabrication resolutions have declined to just a few tens of nanometers on the surface, and a few hundreds of nanometers inside most transparent materials. However, it is difficult to maintain such fabrication resolutions, especially at nanoscale levels, when forming high aspect ratio (length over diameter) structures inside transparent materials. This issue can be addressed using novel focusing strategies and spatiotemporal beam shaping techniques. In this chapter, we will begin by reviewing the basic concepts of, and experimental methodologies related to, laser machining techniques. Then, machining strategies that have been adopted to facilitate high fabrication resolutions and long fabrication lengths using standard Gaussian laser beams are discussed, along with other competent techniques, thereby highlighting the underlying fundamental mechanisms and their applicability for material processing such as for drilling and cutting. Furthermore, the impact of spatiotemporal beam shaping on material processing is discussed, with a special focus on applications of non-diffractive optical beams for fast and flexible material processing. Finally, we provide a futuristic viewpoint on the potential for achieving super-resolution, yet high-aspect-ratio, material fabrication.