Effects of typical laser wavelength on impulse coupling characteristics ablated by nanosecond pulsed laser with Al target

To study the effects of two typical laser wavelength of 532 nm and 1064 nm 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 532 nm and 1064 nm, 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. © 2015, Journal of Propulsion Technology. All right reserved.