Research On Femtosecond Laser Nano-fabrication By Nano-Sphere Near Field Effect

With the development of nanoscale machining technology,the requirement of machining precision is increasing day by day.Nanoscale processing with spatial resolution beyond the diffraction limit can be achieved by controlling the interaction between femtosecond and nanospheres through localizing the laser energy.The gold(Au)nanoparticles and polystyrene(PS)nanoparticles assisted femtosecond laser nano-fabrication were studied systematically.The main research contents and results are as follows:In the Au nanospheres assisted femtosecond laser nanoscale processing,the near-field enhancement of Au nanospheres with different diameters was simulated by FDTD,and the different intensity of near-field enhancement was obtained.Based on the simulation results,nanoholes beyond diffraction limit was processed,and it was found that the laser polarization(linear polarization and circular polarization)can significantly affect the variation of the nanohole shape with the laser energy density.This is because the different effect(near-field effect and thermal effect)of Au nanospheres on the formation of nanoholes under different energy density laser irradiation.Furthermore,the introduction of dielectric layer on the surface that the Au nanoparticles were located.After laser irradiation,the substrate can generate butterfly-like and double loop-like nanostructures that was different from the typical nanoholes.The research results can enrich the regulation methods for the production of nanostructures.These studies were important for the research and development of super diffraction limited nanostructures on silicon(Si)substrate surface through laser preparation.In PS nanosphere assisted femtosecond laser nanoholes processing.The near field enhancement of PS nanoparticles with different diameters was numerically simulated by FDTD method.The effect of PS nanoparticles with different diameters on the near field enhancement was obtained.The PS nanoparticles on the surface of Si substrate were irradiated by femtosecond laser with different wavelength and polarization,and the shape and size of the nanoholes were processed.The preparation of Si substrate surface array nanoholes was realized by the array of PS nanoparticles.This research should have certain significance to the engineering transformation of nanospheres assisted femtosecond laser nanoholes processing.Based on the ultrafast physical phenomenon that femtosecond laser pulse can induce dielectric environment of substrate to change,the optimized preparation of nanoholes based on the near-field effect of PS nanospheres through two-color femtosecond double-pulse irradiation was studied.Firstly,the effects of substrate dielectric parameters on that near field enhancement of PS nanospheres were studied by numerical simulation.Furthermore,the PS nanoparticles on surface of Si substrate were irradiated with two-color femtosecond double-pulse irradiation,and the effective optimization of the nanoholes size between 180nm-240 nm was achieved by changing the time delay.