Examination of classical coupling of laser light to thin, dense plasma layers

Classical absorption, i.e., inverse bremsstrahlung, is examined in the context of two different models of the radiation field and the plasma. One model is developed by approximations starting from Maxwell's equations plus a hydrodynamic description of the plasma. The other is based upon a model of photon transport. It is shown that the laser-plasma coupling implied by these models appears (at least qualitatively) to be quite different. According to the Maxwell-hydrodynamic model, thin but dense plasma layers are strongly reflecting whereas the photon transport model seems to imply that they are strongly absorptive. This discrepancy is not a paradox but a consequence of different kinds of approximations implicit in the two computational approaches. However, it is not clear at this point that this predicted differences in laser-plasma coupling can readily be clarified analytically. (auth)