典型激光波长对纳秒激光烧蚀铝靶冲量耦合特性的影响

Effects of Typical Laser Wavelength on Impulse Coupling Characteristics Ablated by Nanosecond Pulsed Laser with Al Target

关键词:  激光烧蚀  冲量耦合  等离子体屏蔽  光学性质  热物理性质  铝

Key words:  Laser ablation  Impulse coupling  Plasma shielding  Optical property  Thermal property  

摘要:

为研究532nm和1064nm两种典型激光波长对纳秒脉冲激光烧蚀铝靶冲量耦合特性的影响，在建立的热传导模型和羽流膨胀流体动力学模型基础上，加入了在激光烧蚀过程中靶材吸收系数、热导率和反射率等光学和热物理参数的变化，考虑了形成的等离子体羽流对入射激光的屏蔽作用因素影响，从而建立了一个复杂的一维纳秒激光烧蚀铝靶冲量耦合物理模型。通过计算，获得了两种激光波长辐照下，烧蚀过程中烧蚀参数和物理参数的变化，分析等离子体羽流对入射激光的屏蔽效应，进一步分析得到对冲量耦合特性的影响。结果表明:短波长激光不仅有利于激光与靶材的能量耦合，同时，短波长激光辐照下形成的等离子体羽流对短波长入射激光吸收率也较低，有利于提高靶的冲量耦合；在等离子体形成初期，即等离子体吸收率较低时，分别达到两种激光波长辐照下的最优冲量耦合。

Abstract:

To study the effects of two typical laser wavelength of 532nm and 1064nm on impulse coupling characteristics by nanosecond pulsed laser with Al target，a comprehensive nanosecond laser ablation Al target impulse coupling physical model including one-dimensional heat conduct and plume expansion fluid dynamics was developed. The model added the change of absorption coefficient，thermal conductivity and reflectivity during the process of laser ablation. In addition，the model also includes the plasma shielding effects during the plasma plume expansion process. According to the computing，the changes of ablation parameters and physical parameters were obtained under the condition of two laser wavelength. The shielding effects on the incoming laser by plasma plume were analyzed. Further more，the final impulse coupling characteristics were studied. The results show that，respecting to ablation in the wavelength of 532nm and 1064nm，it is not only advantageous for the energy coupling between laser and Al target irradiated by shorter laser wavelength，but also favorable for promoting the impulse coupling because of the lower incoming laser absorption in plasma plume with shorter laser wavelength. The optimum impulse coupling coefficient is obtained under the condition of ablation by the two typical laser wavelength when the plasma forms at the early stage，which is the circumstance of the absorption rate when the plasma is relatively lower.