Femtosecond laser-induced periodic surface structure and its applications

In recent years, femtosecond laser micro/nano fabrication has attracted much interest. With ultrahigh power intensities and ultrashort irradiation periods, femtosecond laser presents unique advantages over conventional laser. Femtosecond laser machining can greatly reduce the heat-affected zone, microcracks and recast layer when it interacts with materials, which changes the physical and chemical mechanisms of laser-material interaction basically. Almost all materials can be manufactured by femtosecond laser via a noncontact and nonthermal process. In addition, femtosecond laser machining can break through the optical diffraction limit as a result of the nonlinear multi-photon effect occurred when it processes materials, which improves the precision significantly. Both sub-micron structures and three dimensional complex structures can be fabricated by femtosecond laser high-precision low-energy-consumption processing. In short, femtosecond laser presents unique advantages in the field of micro/nano manufacturing. The pulse width of femtosecond laser is usually shorter than or equal to the characteristic time of most of the physical/chemical processes, so that a series of interesting phenomena are induced through controlling the local transient electrons dynamics during the processing. Periodic surface micro/nano structures, which have significant effects on the surface properties of the materials, have been observed on almost all materials including metals, dielectrics, semiconductors and so on during femtosecond laser machining. Many researchers have carried out theoretical and experimental studies on femtosecond laser-induced periodic surface structures (LIPSS), such as ripples, quasi-periodic conical structures, regularly arranged nano-column structures and so on, due to their great applied potentialities in national defense, medical treatment, top-end manufacture and other fields. In this paper, we summarized the distinct advantages of femtosecond laser micro/nano machining and made main contents on the femtosecond laser-induced periodic surface structures (LIPSS) as follows. Above all, we briefly elaborated the fundamental characteristics of femtosecond laser and its distinct advantages in machining in the introduction. Additionally, we brought forward LIPSS and expounded its great applied potentialities in the field of manufacture and other kinds of researches. Then in the first part of the main body, we summarized the theoretical and experimental results on LIPSS since ripple was discovered by Birnbaum firstly. In the aspect of theoretical research, we summarized some representative results relevant to ripple mainly. And in the second part, we showed some representative results about the interesting surface properties improvement caused by periodic surface micro/nano structures in the past decades, such as wettability, optical properties and surface-enhanced Raman scattering (SERS). In the end, the future research directions of femtosecond laser-induced surface micro/nano structures were prospected. The combination of experimental research and theoretical analysis has become a trend in these years. With the improvement of femtosecond laser micro/nano fabrication and the development of research on the periodic surface micro/nano structures, in the near future, LIPSS will be widely applied in the practical industrial fields including national defense, automotive, medical, aerospace, top-end manufacture and so on.