Research On Femtosecond Laser Precise Polishing Of Complex Optical Elements

With the continuous development of optical system,higher requirements are put forward for the manufacturing technology of optical components.After a long period of development,more and more technology methods have been applied to this process.With the development of laser technology and laser manufacturing technology,ultrashort pulse laser processing has been applied to process transparent optical materials.By summarizing and comparing the development and research status of polishing technology applied to spherical and aspheric free-form surface,it can be concluded that the ultra short pulse laser polishing technology has unique advantages.In this paper,the key theory and technology of ultra short laser processing transparent dielectric optical materials are studied(1)The mechanism of ultra fast laser pulse removing transparent dielectric optical materials,the photoionization process and avalanche ionization process inside the materials are analyzed in detail.Combining k.k.thornber avalanche ionization equation with simplified Keldysh photoionization equation,the whole ionization process of ultrafast laser pulse interacting with dielectric optical transparent materials is analyzed.(2)According to the ionization process of materials irradiated by femtosecond laser,the analytical model of material removal depth and laser energy density was deduced.According to the principle of laser,combining with the calculation model of laser pulse energy distribution and material incubation effect,a practical physical model of optical material surface removal is established.(3)Based on the physical model of material removal and the geometric model of material surface,the calculation method of material surface morphology after ultrashort laser pulse static and dynamic acting on material surface is proposed.With this method,a program is written to simulate the polishing process of optical materials by femtosecond laser under different processing parameters.The influence of different processing parameters on the polishing surface quality is analyzed based on the numerical results,and the optimal processing parameters combination of femtosecond laser polishing glass-ceramic material is selected according to the calculation results.(4)The experimental system of femtosecond laser polishing optical material surface is built,and the process experiment of femtosecond laser polishing glass-ceramic material is carried out.What’s more,the relevant conclusions of numerical model calculation are verified...