Numerical Calculation Of The Thermal Action Of Combined Pulsed Laser Induced Single Crystal Silicon

A millisecond pulse laser and nanosecond dual-pulse laser are combined in order to improve the coupling efficiency between the laser energy and single crystal silicon material in laser processing.The effects of the delay time of the millisecond pulse laser and nanosecond dual-pulse laser beams in the combined pulses laser are studied,and the optimized delay time can be obtained.The effects of the respective energy density of the millisecond pulse laser and nanosecond dual-pulse laser beams in the combined pulses laser are also studied.Based on the thermal elastic-plastic theory,a two-dimensional axisymmetric finite element method was used to study the interaction between the combined pulses laser and silicon material.The temperature field distribution respectively induced by single millisecond pulse laser,nanosecond dual-pulse laser and the combined pulses laser is computed in this thesis.The thermal stress field distribution and variation induced by the combined pulses laser can be further obtained,which will provide a basis for the following analysis.Furthermore,the damage effect of the silicon material induced by the combined pulse laser is simulated based on two aspects:the delay time and the energy ratio of millisecond pulse laser and nanosecond dual-pulse laser beams in the combined pulses laser.The influence of changing the energy ratio of millisecond pulse laser and nanosecond dual-pulse laser beams on the optimal delay time is also analyzed.The results show that under certain conditions,the delay time can significantly affect the effect of the combined laser,and the optimized delay time can be found.Increasing the millisecond or nanosecond pulses laser energy in the combined pulses laser will lead to the smaller optimal delay time.We find that when the proportion of millisecond laser energy in combined pulses laser is lower,the advantage of combined laser is more obvious.With increase of the millisecond laser energy proportion,the effect of combined pulses laser and single millisecond laser tends to be the same.In a certain range,the increase of the nanosecond laser energy proportion can improve the effect of the combined pulses laser.The research results in this thesis can provide a theoretical and experimental basis for studying the thermad stress properties of silicon material,which will promote the developing of laser fabrication technology.