SOI纳米光波导激光熔凝光整加工温度场的数值模拟及分析

摘要

激光表面熔凝技术可有效降低纳米光波导侧壁粗糙度进而减小光传输的散射损耗.为明确波导侧壁在KrF准分子激光表面熔凝过程的温度场演化规律,考虑材料参数随温度变化和相变潜热的影响,建立了纳米光波导侧壁激光熔凝的二维有限元数值模型,研究了熔池边界的推进行为与不同工艺参数的映射关系.结果表明:熔池形成于波导上表面与迎光侧壁夹角处;激光入射角度一定时,熔池熔深与平均能量密度正相关;熔池形貌受控于激光入射角度,随着入射角度的减小,熔池形貌由单边U形过渡为单边V形最终呈带钝角单边V形.分析表明,较大激光入射角对应的熔池形貌更有利于波导侧壁的光整加工;据此提出先确定激光入射角度以优化熔池形貌,再选取合适平均能量密度以获得足够熔化深度的工艺方法.%Laser surface melting technology can effectively reduce nano optical waveguide sidewall roughness for scattering loss reduction.To clarify the temperature field evolution law of KrF excimer laser surface melting on waveguide sidewall,a two dimensional finite element numerical model is established,which has taken into account the effects of temperature dependences of material parameters and latent heat.Several investigations have been made about the relationships between the carry behavior forward of melting pool boundary and different processing parameters.Simulation results indicate that melting pool begins developing in the corner between the upper surface of waveguide and the laser-facing sidewall surface.At a given laser incidence angle,the depth of melting pool is correlated positively with the average energy density.Melting pool shape is mainly controlled by laser incident angle:with the decreasing incidence angle,the melting pool appears firstly single-edge U-shaped,then single-edge V-shaped,and finally single-edge V-shaped with an obtuse angle.Analysis shows that melting pool shape induced by a larger laser incidence angle is more favourable to the finishing process of waveguide sidewall.On this basis,a new process method is proposed for determinating laser incident angle to optimize the shapes of melting pool and then selecting the appropriate laser energy density to obtain sufficient melting depth.