| In recent years,quartz glass,as a transparent material with high hardness,high transmittance and excellent chemical stability,has become an promising material in cutting edge technologies used in biomedical microstructures,optical devices,space exploration,atomic energy industry,national defense equipment,automation systems,optical fiber communications,etc.It is also one of the indispensable excellent materials in other fields.Due to it’s high brittleness,easy fracture and other characteristics,the quartz glass is difficult to be processed with traditional methods,in addtion to the usually low yield-The precise fabrication of micro-scale devices and micro-nano structures on glass materials,therefore,has become one of the hot research topics in recent years.Femtosecond laser delivers ultra-short pulses with ultra-high peak intensity,which can inhibit the diffusion of heat-affected zone.The femtosecond laser beam can also be focused into a small spot,which can even break through the diffraction limit.It is one of the ideal laser processing methods for transparent and brittle materials.Based on the above background,we are in this thesis going to explore the process of femtosecond laser etching of quartz glass,systematically analyze and study the microstructure processing technology with the femtosecond laser,and hopefully to lay a foundation for the application research of quartz glass with functional microstructures.The main research contents of this thesis are as follows:1.The basic physical mechanism of femtosecond laser processing of transparent and brittle materials is analyzed,and a theoretical model is established based on keldysh parameters to distinguish the multi-photon ionization mechanism and the tunnel ionization mechanism in the nonlinear effect.Combined with the multi-photon ionization,Joule heating effect and avalanche ionization mechanism involved in the interaction between femtosecond laser and transparent brittle materials,the mathematical model is established by using the Fokker-Planck dynamic formula,and the characterization and deduction are based on the dynamic equation of the electron distribution function.The electron number changes with time during the processing of quartz glass.2.The transmission grating is prepared by femtosecond laser etching of quartz glass,and the etching mechanism and influence rule of femtosecond laser etching of transmission quartz glass grating are studied.Using the laser direct writing scanning method,the galvanometer is digitally controlled to control the focus on the surface of the sample for scanning and etching,and the laser-related parameters such as average laser power,scanning speed,and repeated scanning times are adjusted.The effect of trace width,depth and morphology.In addition,a grating diffraction efficiency optical path test system was built to test the diffraction efficiency of the etched quartz glass grating,and then optimize the process parameters of the femtosecond laser to prepare the quartz glass grating structure.When the laser repetition frequency is 100 k Hz,the number of repeated scans is N=10,the average laser power is P=442m W,the scanning speed is v=380mm/s,and the period is 8μm,the 0-level,-1-level and +1-level of the transmissive quartz glass grating are measured The diffraction efficiencies are 24.98%,31.8% and 31.04%,respectively.3.Micro-lenses were fabricated on the surface of quartz glass by single-pulse femtosecond laser.Through experimental and theoretical analysis,the relationship between the radius of the micro-concave lens and the laser energy was fitted.The fit is high.According to the theoretical fitting result of the logarithm ln of the femtosecond laser pulse energy and the measured value of the ablation radius,the laser processing parameters are adjusted to control the radius and duty cycle of the micro-concave lens on the quartz glass surface.The speed is 1818mm/s,and a large-area microlens array with a radius of 5.31μm can be prepared in a single scan.4.Using femtosecond laser to prepare microfluidic channels on quartz glass,including the preparation of serpentine and linear microfluidic channels.Among them,in the microfluidic channel with a total length of 3507.38μm,the widest part is 38.621μm,the narrowest part is36.396μm,the deepest part is 6.03μm,and the shallowest part is 5.09μm.The average flow rate of unidirectional liquid in the microfluidic channel is about 14799.07 μm/s,of which the flow rate of the U-shaped curved microchannel is 16145.71μm/s,the flow rate of the vertical straight microchannel is 13333.33μm/s,and the flow rate of the horizontal straight microchannel is12682.92μm/s.In addition,the process of preparing micro-nano structures on the surface of the fiber core by femtosecond laser is studied,including the preparation of tapered holes and rectangular micro-grooves in the fiber core.27。;the depth of the micro-grooves on the surface of the fiber core reaches about 10 μm,which is widely used in the fields of optical sensing and optical imaging of the micro-structure of the optical fiber surface.To sum up,this paper focuses on the processing of functionalized micro-nano structures on quartz glass by femtosecond laser,and studies the mechanism of femtosecond laser directly etching quartz glass,and summarizes the rules to prepare surface microstructures,including microscale gratings,Microfluidic channels,micro-concave lens arrays,and extended to the preparation of micro-conical holes and micro-grooves on the surface of the fiber core,provide a practical technical solution for the preparation of commercial functionalized micro-nano devices。... |
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