High-resolution material structuring using ultrafast laser non-diffractive beams

ABSTRACT Scales in the 100 nm range represent a generic cornerstone for laser material processing, enabling novel size-dependent functions on surfaces and in the bulk and thus a new range of technological applications. On these scales, the processed material acquires optical, transport or contact properties that do not only rely on local effects on singular topographic features but involve increasingly collective behaviors. Rapid access to sub-100 nm features with intense coherent light represents nevertheless a challenge in laser structuring in view of the optical diffraction limit. Ultrafast non-diffractive beams with controllable time envelopes can overcome this limit and achieve super-resolved processing, a prerequisite for the next generation of flexible and precise material processing tools. They show a remarkable capacity of structuring transparent materials with high degree of accuracy and exceptional aspect ratio. This capacity relies on triggering fast hydrodynamic and material fracture effects with characteristic spatial scales in the nm range. Reviewing the present achievements and technical potential, we discuss from a dynamic viewpoint the physical mechanisms enabling structural features beyond diffraction limit achieved using ultrafast Bessel beams and indicate applications of high technical relevance. Abbreviations: PCM: phase contrast microscopy; SEM: scanning electron microscopy; NBOHC: non-bridging oxygen hole cente