Fabrication Of Antireflective Micro Nano Structure On 2A12 Aluminum Alloy Surface By Femtosecond Laser

With the increasing demand for high-precision detectors,infrared seeker,space attitude sensors and other applications in China,space cameras need to be updated.To further improve the accuracy of space camera,it is necessary to suppress stray light.Stray light is produced by external radiation and self-reflection of internal instrument surface.It is a kind of non-imaging light,which is an interference signal for imaging optical system.In order to suppress the interference of stray light,an extinction coating or an extinction paint is usually added to the interior of a space camera.It is of great significance to suppress stray light by femtosecond laser processing micro nano structure on aluminum alloy surface.This kind of in-situ processing functional micro structure has outstanding anti reflection performance.The main contents and conclusions of this paper are as follows :(1)optical simulation is carried out by using FDTD to simulate the response of 2A12 aluminum alloy surface with different morphologies to incident electromagnetic waves,and the results of surface wide spectral reflectance are obtained,so as to find out the morphology with the best anti reflection performance.A suitable physical model of microstructure was designed,and a series of univariate simulation experiments were carried out to optimize the structural parameters.Finally,a conical structure model with height of 30 ? m,transverse size of 12 ? m and duty cycle of 1 was obtained.(2)The effect of femtosecond laser processing parameters on the surface microstructure of 2A12 aluminum alloy was studied by using femtosecond laser direct writing processing technology,including femtosecond laser power,defocusing amount,scanning distance,scanning speed,repetition rate,scanning times and other main parameters.Finally,the optimized laser processing parameters are: laser pulse width: < 600fs;focal length: 56mm;laser wavelength: 1064nm;focal spot: 9 ? m;laser power: 0.8W;scanning speed: 1500 mm / S;scanning spacing: 12 ? m;repetition rate: 500KHz;scanning times: 200.Under this parameter,the microstructure morphology obtained is very similar to that of the simulation design,and has good uniformity and consistency.(3)The influence of femtosecond laser processing parameters on the surface reflectance of 2A12 aluminum alloy was studied,and the contribution of micro nano structures with different scales to anti reflection was analyzed.The transformation of 2A12 aluminum alloy from bright surface to anti reflection surface was realized.The results show that the composite structure can promote the wide spectrum antireflection performance,and the average reflectivity is reduced to 9.83% in the range of 400nm-2500 nm,and 2.20% in the range of 2.5? M-15 ? M.