| Quartz glass has excellent properties such as low thermal expansion coefficient,high electrical insulation,wear resistance and oxidation resistance,which makes it one of the most promising optical materials in this century and has been widely used in photonic devices,power sources,photovoltaic,optical fiber communication and other fields.However,due to the'brittle'and'hard'characteristics of quartz glass,the surface roughness after processing is large and the large-scale processing is uneven,which is difficult to directly meet the growing industrial needs.Aiming at the difficulty of fine processing of quartz glass materials,femtosecond laser with the inherent ultra-short pulse width and peak intensity provide the advantages for'cold processing'and'ultra-fine'in the micro-nano scale processing of quartz glass.Therefore,this thesis takes quartz glass as experimental material and femtosecond laser processing platform as experimental means to systematically study the preparation process of quartz glass,explore its application in various fields and improve the processing quality of microstructure.The main research contents include the following parts:(1)Based on solid band theory and energy conservation law,the participation of multiphoton ionization and collision ionization in femtosecond laser etching of quartz glass is analyzed,and the physical mechanism of femtosecond laser etching of quartz glass is described.The variation of multi-photon ionization rate and avalanche ionization rate under different laser energy densities are calculated by Matlab software.Through numerical calculation,the damage threshold during femtosecond laser etching of quartz glass is10.23J/cm~2.(2)The Gaussian distribution characteristics of laser pulse energy density are analyzed and discussed.Based on the area estimation method,the single pulse damage threshold of quartz glass is 10.61J/cm~2 by fitting the experimental measurement data.Then,the change of laser parameters is controlled by single-line etching,and the influence of laser single pulse energy,scanning speed and scanning times on the depth-width ratio of microgrooves is analyzed in detail.The depth-width ratio of microgrooves is increased by the spiral ring cutting method.Finally,on the basis of micro-groove etching experiment,the preparation process of functional microstructures such as transmission grating and microfluidic channel was preliminarily explored.(3)A single laser pulse is used to etched pits on the surface of quartz glass.Based on the beam propagation method,the temporal and spatial distribution characteristics of the incident laser intensity propagating inside the material are deduced.Then,the Beer Lambert law is used as the estimation formula of the pit depth in the single pulse etching experiment to simulate the pit etching depth under different energy densities.At the same time,the measured values of the pit depth obtained by the experiment are in good agreement with the quartz glass etching depth model.(4)In the experiment of femtosecond laser etching quartz glass via array,the effects of laser pulse energy,scanning speed and defocusing amount on the experimental results are analyzed,In the quartz glass through-hole array experiment,the effects of laser single pulse energy,scanning speed and defocus amount on the experimental results are analyzed,and the micro-through-hole array with aperture smaller than the spot diameter is prepared(the aperture is about 10?m,and the ratio of depth to diameter is 25:1).The applicability of processing parameters in the etching of quartz glass through-hole arrays with different specifications was verified,and the through-hole array with minimum taper of 0.57°was prepared.Finally,the preparation process of large-scale micro-concave lens array template was preliminarily explored.In summary,in this thesis,the physical mechanism of femtosecond laser etching of quartz glass is summarized to solve the process problems existing in the microstructure of quartz glass.Through the experiments of femtosecond laser etching microgrooves and micropores,the mechanism of laser parameters on the preparation of microstructure is systematically studied,and the process parameters are experimentally optimized.Based on the fabrication of microgrooves and micropores,functional microstructure devices such as transmission gratings,microfluid channels,and microconcave lens array templates are prepared. |
PDF Full Text Request