Research On Femtosecond Laser Fabrication Technologies Based On Optics Modulation

With its ultra-short pulse width and ultra-high peak power,femtosecond laser has a wide range of applications in micro-nano manufacturing.The traditional two-photon polymerization fabrication technology is realized by single-point scanning,which has the advantages of high fabrication resolution and easy control of the processing.Limited by its low processing efficiency,it is difficult to be used in large-area and large-scale related applications.Computed holography can achieve arbitrary light field distribu-tion by laser wavefront phase modulation and is used for fabricating two-dimensional graphic structures.This kind of technology can improve the processing efficiency,but generally only applied to 2D planar fabrication.In order to solve the problem of the inefficiency of traditional processing technology and the two-dimensional limitation of holographic processing,this thesis proposes the spatial and temporal modulation tech-nology,introducing digital micromirrors devices and grating,which improves the pro-cessing resolution while improving the processing efficiency.Firstly,this thesis introduces the traditional femtosecond laser single-point scan-ning processing technology,which was used to modify the glass to improve the etching efficiency of hydrofluoric acid.Based on this method,a tunable microlens device was fabricated,and the relevant modulation parameters and modulation effects were ana-lyzed.Secondly,based on the Computed-Fourier-Holographic algorithm,this thesis presents a new method to simultaneously control the position and energy of the focal spot,which is based on liquid crystal on silicon spatial light modulator dynamic loading computer-generated-holograms.Taking advantage of this method,ring structures have been fabricated successfully,just as what have been expected,proving that this method is feasible in the field of femtosecond laser micro-nanofabrication.Finally,this thesis describes the femtosecond lasers spatial and temporal modula-tion technology in detail.With the digital micromirrors devices,arbitrary patterns can be realized.Based on the dispersion effect of the grating,the spectrum can be separated in space to broaden laser pulse.The collimated laser is focused by the objective on the back focal plane,then the spectra coincide and the pulse width is recompressed.The focusing process makes the spatial energy density of the laser reaching the maximum at the back focal plane of the objective,and the overlapping of the spectra on the back focal plane minimizes the pulse width at this position,so that the laser energy density reaches the maximum in the time domain.The two-photon excitation efficiency is highest at the back focal plane of the objective,and decreases rapidly when defocusing.Graphic processing can be realized based on this technique,and the superiority of the resolution of the technology in single-point and single-layer processing has been explored.