为了研究入射激光功率密度对等离子体冲击波力学效应的影响，利用波长1．06μm，脉冲能量42mJ～320mJ，脉宽10ns的Nd∶YAG激光作用在Al靶上，研究了冲量耦合系数C_m和激光功率密度I₀的关系。实验发现靶材在离焦度x不同时，C_m和I的变化关系相似，而对应的最佳功率密度明显不同。在功率密度由低慢慢升高过程中，冲量耦合系数先随功率密度升高而增加，升到最大值后随功率密度增加而减小。通过分析激光等离子体的吸收作用和离焦度不同时激光和靶相互作用机理的不同，认为C_m出现峰值主要是受等离子体屏蔽效应的影响，稀疏波的作用使得焦斑处最佳功率密度最大，而焦斑处空气击穿消耗能量导致焦后C_m峰值减小。

The dependence of the mechanics effect to the target induced by laser on laser intensity was reported. The experiments were performed by focusing output pulses of the Nd∶YAG laser(1Ons pulse width at 1.06 μm wavelength and 42mJ～320mJ pulse energy)on aluminum targets mounted on a ballistic pendulum. The data showed that there were different optimum intensities which gave a maximum C_m at different extant of depart from the focus(χ). And the impulse coupling coefficients(C_m)was determined by similar functions of intensity in the different χ. The C_m increases slowly with the increasing of laser intensity and decreases after it gets maximum quantity. According to the absorption of the plasma and the different laser-target interaction mechanisms at the differentχ,the results show that there is the maximum C_m because of the plasma shielding effect;the optimum intensity is largest at the focus because of the effect caused by the rare faction wave and the maximum C_m at χ > 0 is smaller than the others due to the energy consuming of the air breakdown at the focus.