Abstract
We succeeded in obtaining propulsion of an aluminum bullet by a gigawatt nanosecond pulse Nd:glass laser, in which we demonstrated the effectiveness of a simple double-confined structure that consists of a thin black-paint coat covered with a glass board as a transparent overlay. The black-paint coat not only serves as a substitute for the target to be ablated, but also improves the absorbency of the incident laser energy. Another main feature of this structure is that it can lead to the enhancement of the coupling coefficient due to plasma confinement and impedance mismatch. Adopting this simple double-confined structure, a coupling coefficient up to 160 dyne/W was achieved, which was enhanced by about 20 times with respect to direct ablation.