Iaroslav Gnilitskyi

High-speed manufacturing of highly regular femtosecond laser-induced periodic surface structures: physical origin of regularity

Highly regular laser-induced periodic surface structures (HR-LIPSS) have been fabricated on surfaces of Mo, steel alloy and Ti at a record processing speed on large areas and with a record regularity in the obtained sub-wavelength structures. The physical mechanisms governing LIPSS regularity are identified and linked with the decay length (i.e. the mean free path) of the excited surface electromagnetic waves (SEWs). The dispersion of the LIPSS orientation angle well correlates with the SEWs decay length: the shorter this length, the more regular are the LIPSS. A material dependent criterion for obtaining HR-LIPSS is proposed for a large variety of metallic materials. It has been found that decreasing the spot size close to the SEW decay length is a key for covering several cm2 of material surface by HR-LIPSS in a few seconds. Theoretical predictions suggest that reducing the laser wavelength can provide the possibility of HR-LIPSS production on principally any metal. This new achievement in the unprecedented level of control over the laser-induced periodic structure formation makes this laser-writing technology to be flexible, robust and, hence, highly competitive for advanced industrial applications based on surface nanostructuring.

Mechanisms of high-regularity periodic structuring of silicon surface by sub-MHz repetition rate ultrashort laser pulses

Silicon is one of the most abundant materials which is used in many areas of modern research and technology. A variety of those applications require surface nanopatterning with minimum structure defects. However, the high-quality nanostructuring of large areas of silicon surface at industrially acceptable speed is still a challenge. Here, we report a rapid formation of highly regular laser-induced periodic surface structures (HR-LIPSS) in the regime of strong ablation by infrared femtosecond laser pulses at sub-MHz repetition rate. Parameters of the laser-surface interactions and obtained experimental results suggest an important role of electrostatically assisted bond softening in initiating the HR-LIPSS formation.

Nonlinear laser lithography for enhanced tribological properties

This paper investigates a new field for application of femtosecond laser-induced periodic surface structures (LIPSS). We designed an innovative solution to reduce coefficient of friction of mechanical parts by using the nonlinear laser lithography technique (NLL).

Highly-regular laser-induced periodic surface structures: Experiment and atomistic modelling

Surface nano- and microstructuring with additive and subtractive lithography techniques are commonly used in nanotechnology and photonics, while nanoimprint lithography and nanosphere lithography are used for creating periodic structures for plasmonics applications. Single step, maskless optical patterning techniques also exist, notably multi-beam interference based techniques and Laser Induced Periodic Surface Structures (LIPSS). LIPSS have been demonstrated on metals, semiconductors, dielectric surfaces, polymers, and have been used in various applications including solar cells, plasmonics, colorizing metals, wettability and tribology applications. Until recently these optical techniques lacked the long-range periodicity required for some of the applications. Moreover, conventional optical lithography techniques require complex masks, while e-beam lithography and ion-beam lithography require expensive equipment. Recently, a method for direct writing of highly-regular LIPSS (HR-LIPSS) was developed for creating uniform approach overcoming all aforementioned lithography problems [1].

Highly regular LIPSS on silicon decorated with gold nanoparticles for plasmonic applications

Plasmonic properties of gold nanoparticles self-assembled on silicon surfaces are significantly enhanced by a periodic surface ripples induced by ultrashort laser pulses. The nanostructured surfaces open new perspectives for production of photonic and plasmonic-sensor elements.

Cell and tissue response to modified by laser-induced periodic surface structures biocompatible materials for dental implants

The use of femtosecond laser-induced periodic surface structures (LIPSS) for dental implants surface modification for improving cell adhesion and proliferation is reported. Results demonstrated higher response of cells on modified surface compared to untreated ones.

Laser Nanopatterning for Wettability Applications

We report on periodic, homogenous nanoripples fabricated on stainless steel (SS), copper (Cu) and aluminium (Al) substrates using an ytterbium pulsed femtosecond laser. These structures called Laser Induced Periodic Surface Structures (LIPSS) are processed at a relatively high-speed allowing us to fabricate quasi regular nanoripples in a short time over large areas. This paper investigates the effect of LIPSS on wettability behavior of SS, Cu and Al surfaces. It is shown that nanoripples significantly influenced the wettability character of these metals turning them from hydrophilic to hydrophobic behavior. The most notable behavioral change is observed for SS and Al, where strong hydrophobicity is observed after the generation of LIPSS.Copyright