Impulse coupling coefficients from a 1.06 μm, 10 ns Nd: YAG pulsed-laser radiation to HgCdTe targets with different area were measured using the ballistic pendulum method in the laser power-density range from 4.0×10~8-5.0×10~9 Wcm~-2. In theory, a detonation model of the plasma was established and the expansion process of the plasma after the laser pulse end was described in detail. Moreover, impulse coupling coefficients from pulsed with different energy to HgCdTe with different area were calculated by using the model. It is found that the theoretical results agree well with the experimental data.