扫描方向对金属和硅复合薄膜表面激光诱导自组织加工质量的影响(特邀)

Influence of Scanning Direction on the Quality of LIPSS onMetal-Si Hybrid Films( Invited)

激光诱导周期性表面结构的质量可通过调整激光参数、改善材料表面和优化扫描策略等手段来提高。研究了扫描方向对线偏振激光诱导金属/硅复合薄膜表面氧化LIPSS的影响。结果表明,当扫描方向垂直于激光偏振方向时,纳米结构会出现分叉、不连续等问题;当扫描方向平行于激光偏振方向时,纳米结构呈现短程有序,但在光斑拼接处存在扭曲;而当扫描方向与激光偏振方向存在一定夹角时,容易获得长程均匀有序的周期性纳米结构。数值仿真结果表明造成这些现象的原因是近场效应对自组织过程具有不可忽略的影响。

Laser-Induced Periodic Surface Structures(LIPSS)have emerged as a powerful tool in nanofabrication and nanophotonics due to their unique optical and surface properties.In recent years,the long-range uniformity of LIPSS formation have been a subject of extensive research,with efforts focused on optimizing laser parameters,material surfaces,and scanning strategies.In this study,we investigated the influence of scanning direction with respect to laser polarization on the regularity of LIPSS which was produced on metal/silicon hybrid thin films via femtosecond laser-induced surface oxidation.Our experimental findings revealed intriguing phenomena associated with LIPSS formation under different scanning directions relative to the laser polarization direction.When the scanning direction was perpendicular to the laser polarization,the nanometer-scale structures exhibited irregularities,such as branching and discontinuities.Conversely,when the scanning direction was parallel to the laser polarization,the structures demonstrated short-range order,but undesirable distortion occurred at the overlap of adjacent laser spots.Remarkably,when the scanning direction formed a certain angle with the laser polarization,long-range and uniform periodic nanostructures were readily obtained.To gain insights into the underlying mechanisms,Finite-Difference Time-Domain(FDTD)-based numerical simulations were conducted to elucidate the role of near-field enhancement and far-field interference during the laser-induced self-organization process.The simulations provided a comprehensive understanding of the interplay between the near-field and far-field effects,showing that near-field enhancements significantly impacted the spatial distribution of LIPSS.Consequently,we proposed an optimal scanning strategy that deviates from the conventional approach of perpendicular or parallel scanning relative to the laser polarization direction.By selecting an appropriate crossing angle between the scanning direction and the polarization direction,we effectively mitigated common issues like branching,discontinuities,and distortion,leading to the generation of high-quality and reproducible periodic nanostructures.Exploiting our new findings,we successfully fabricated one-dimensional periodic nanostructures on the surface of metal/silicon bilayer films by using single-beam femtosecond laser pulses.The quality and uniformity of the nanostructures were markedly improved by implementing the optimized scanning strategy.This breakthrough not only addresses the challenges associated with LIPSS formation but also opens up exciting opportunities for nanophotonics applications.The potential applications of periodic dielectric/semiconductor nanostructures on metal films in nanophotonics are vast and promising.These structures have demonstrated exceptional capabilities in refractive index sensing,nonlinear optical effects,photodetection,and structural coloring.Moreover,the low-cost and scalable nature of the proposed fabrication method offers great potential for widespread adoption in diverse applications.In conclusion,this research underscores the significance of optimizing scanning strategies for achieving high-quality and large-scale LIPSS.By considering the interplay of near-field and far-field effects during the self-organization process,we have demonstrated a novel approach to enhance the quality of LIPSS fabrication.Additionally,the applications of periodic nanostructures on metal films in nanophotonics hold promise for revolutionary advancements in various optical devices and technologies.The findings from this study lay the foundation for further exploration of LIPSS-based nanofabrication techniques,paving the way for a new era in nanophotonics and nanotechnology.Through continued research and innovation,LIPSS is poised to play a pivotal role in shaping the future of advanced nanophotonics and nanofabrication,impacting a wide range of scientific and technological domains.