超短激光脉冲与烈性炸药的相互作用

Ultrashort laser pulses can be focused to get ultrahigh power density of 1020～1022 W／cm2. The interaction between laser pulses and materials reveals multiphoton absorption mechanism, and this can be used to ablate any kinds of materials without heat transfer because of nonlinear multiphoton absorption and acquire ultrafine “clod machining”. This project will demonstrate the determination of the critical pulse width of the interaction between ultrashort laser pulses and high explosives by means of the kinetic model of laser ablation of dielectric materials. The safety and possibility of machining explosives with ultrashort laser pulses are demonstrated through simulation and experiment. The group will record and analyze the transient process of the interaction between ultrashort laser pulses and explosives by means of time resolved pump-probe technique and femtosecond digital holography in order to figure out the critical impact pressure and the critical impact trmperature as well as the corresponding laser parameters. Systemic experimental study of the interaction between ultrashort laser pulse and TNT & PETN is carried to realize precise cutting and punching. The PI expects to realize machining miniature weapons including explosives, metal, fuse, and organic materials safely and precisely, and obtain the corresponding green security key techniques. Significances of this research are developing new theories of the femtosecond laser-matter interaction, grasp the fs laser ultrafine machining techniques for high explosives and miniature arms control with independent intellectual property rights, filling the domestic vacancy, and making contributions to Chinese military industry.

超短脉冲激光经过透镜聚焦可以实现超强的功率密度（1020～1022 W／cm2），其与各种物质的相互作用是多光子非线性吸收的物理机制，可对任何材料实现无热传递的微细加工。本课题提出从理论上利用超短脉冲与介质材料相互作用的动力学模型来确定超短激光脉冲与烈性炸药相互作用过程中的临界脉冲宽度，通过计算机仿真论证超短脉冲激光加工烈性炸药的安全性；借助超短脉冲激光时间分辨泵浦探测技术和数字全息术，记录激光脉冲与炸药相互作用的瞬态过程阴影图和全息图，提取安全加工的临界冲击压强和临界冲击温度，给出相应的激光参数；从实验上系统研究超短激光脉冲与TNT（梯恩梯）和PETN（太安）两种烈性炸药的相互作用，实现对压片式TNT和PETN的精密打孔和切割。研究意义在于发展超短脉冲激光与物质相互作用的新理论，掌握具有自主知识产权的烈性炸药及小型武器的超短脉冲激光精细冷加工技术，填补国内空白，为我国军工科技事业做贡献。

本课题从理论上利用超短脉冲与介质材料相互作用的动力学模型来确定超短激光脉冲与烈性炸药相互作用过程中的临界脉冲宽度，通过计算机仿真论证了超短脉冲激光加工烈性炸药的安全性；借助超短脉冲激光时间分辨泵浦探测技术和数字全息术，记录激光脉冲与炸药相互作用的瞬态过程阴影图和全息图，提取了安全加工的临界冲击压强和临界冲击温度，给出相应的激光参数；从理论上研究了超短激光脉冲与TNT（梯恩梯）和PETN（太安）两种烈性炸药的相互作用机理，探索了利用飞秒激光对烈性炸药实现安全的“冷加工”的可行性，并对之前设计和加工的飞秒激光加工炸药的安全防护实验装置进行了改进。通过对点火药的实验研究，估算出飞秒激光加工点火药的加工阈值为 0.23 J/cm2，并给出了飞秒激光加工点火药的点火阈值为2.35 J/cm2，表明飞秒激光加工过程的“冷加工”、“热加工”可以依赖激光参数实现转换。以三维热传导模型为基础，利用 ANSYS 有限元分析方法，模拟了单脉冲飞秒激光作用后，点火药样品表面轴向和径向的温度分布情况，并分析得出单脉冲飞秒激光加工点火药的热影响区半径约为4 μm，烧蚀深度约为0.6 μm。利用飞秒激光对红磷样品进行划线实验，在控制重复频率和脉冲重叠个数的条件下，得到了激光通量在5.04 J/cm2以下为飞秒激光加工红磷的安全激光通量范围；脉冲重叠个数为1时的烧蚀宽度为14.67 μm。在控制其它变量的情况下，得到脉冲重叠个数为100时的烧蚀阈值为0.0121 J/cm2，飞秒激光加工红磷的脉冲累积因子为1.0014。本课题研究意义在于发展超短脉冲激光与物质相互作用的新理论，掌握具有自主知识产权的烈性炸药及小型武器的超短脉冲激光精细冷加工技术，填补国内空白，为我国军工科技事业做贡献。