During femtosecond laser fabrication,photons are mainly absorbed by electrons,and the subsequent energy transfer from electrons to ions is of picosecond order.Hence,lattice motion is negligible within the femtosecond pulse duration,whereas femtosecond photon-electron interactions dominate the entire fabrication process.Therefore,femtosecond laser fabrication must be improved by controlling localized transient electron dynamics,which poses a challenge for measuring and controlling at the electron level during fabrication processes.Pump-probe spectroscopy presents a viable solution,which can be used to observe electron dynamics during a chemical reaction.In fact,femtosecond pulse durations are shorter than many physical/chemical characteristic times,which permits manipulating,adjusting,or interfering with electron dynamics.Hence,we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses,and further to modify localized transient materials properties,and then to adjust material phase change,and eventually to implement a novel fabrication method.This review covers our progresses over the past decade regarding electrons dynamics control(EDC)by shaping femtosecond laser pulses in micro/nanomanufacturing:(1)Theoretical models were developed to prove EDC feasibility and reveal its mechanisms;(2)on the basis of the theoretical predictions,many experiments are conducted to validate our EDC-based femtosecond laser fabrication method.Seven examples are reported,which proves that the proposed method can significantly improve fabrication precision,quality,throughput and repeatability and effectively control micro/nanoscale structures;(3)a multiscale measurement system was proposed and developed to study the fundamentals of EDC from the femtosecond scale to the nanosecond scale and to the millisecond scale;and(4)As an example of practical applications,our method was employed to fabricate some key structures in one of the 16 Chinese National S&T Major Projects,for which elec
Lan JiangAn-Dong WangBo LiTian-Hong CuiYong-Feng Lu
Modern three-dimensional nanofabrication requires both additive and subtractive processes.However,both processes are largely isolated and generally regarded as incompatible with each other.In this study,we developed simultaneous additive and subtractive fabrication processes using two-photon polymerization followed by femtosecond(fs)laser multiphoton ablation.To demonstrate the new capability,submicrometer polymer fibers containing periodic holes of 500-nm diameter and microfluidic channels of 1-mm diameter were successfully fabricated.This method combining both two-photon polymerization and fs laser ablation improves the nanofabrication efficiency and enables the fabrication of complex three-dimensional micro-/nanostructures,promising for a wide range of applications in integrated optics,microfluidics and microelectromechanical systems.
Wei XiongYun Shen ZhouXiang Nan HeYang GaoMasoud Mahjouri-SamaniLan JiangTommaso BaldacchiniYong Feng Lu
