为了研究大气条件下，正焦移距离对冲量耦合系数的影响，采用能量为15.7×(1±6%)J的激光脉冲聚焦于铝靶前端，通过改变激光焦点距离靶面的位置，获得了冲量耦合系数与正焦移距离的对应关系。结果表明脉冲激光在与大气环境中的铝靶相互作用时，靶面通过能量转移获得的冲量耦合系数与激光焦点距离靶面的位置呈非单调性变化。焦移距离在从0~20 mm之间变化时，获得的冲量耦合系数从4.48×10^-5 N?s/J连续下降到1.68×10^-5 N?s/J，随着焦移距离的进一步增大，冲量耦合系数在20~35 mm间呈缓慢上升趋势，在35 mm处升至2.21×10^-5 N?s/J后转而下降，在45 mm处降至1.91×10^-5 N?s/J。文中采用大气中激光支持爆轰波与固体靶面相互作用的二维模型对上述物理过程进行理论计算，获得了与实验结果较为一致的结论。

To study the effects of the positive focal shift on the impulse coupling coefficients about the CO2 pulse laser focus on the aluminium target at air ambient. By changing the distance from the focus to the target, the relation between the positive focal shift and the impulse coupling coefficients is achieved. The experimental result indicates that coupling coefficients declined from 4.48×10^-5 N?s/J to 1.68×10^-5 N?s/J, when the focal shift changes from 0 to 20 mm.While the focal shift increase between the 20 mm and 35 mm,the coupling coefficients rise and reach 2.21×10^-5 N?s/J, then decrease to 1.91×10^-5 N?s/J at the 45 mm.The two-dimensional model theory of laser supported detonation wave interacting with solid target was used to calculate the coupling coefficients. The trends of theory and experiment are same.