Coupling of non-normally incident pulsed laser flux to metal surfaces in an air environment

It is shown that the early-time plasma model for normal incidence of laser flux on a highly reflective metal surface in air is adaptable to nonnormal incidence by multiplying the laser intensity, and dividing the laser absorption coefficient, by the cosine of the incidence angle. The description of plasma development includes separate relaxation times to be used for the major and minor axes of the elliptical laser spot. Planar, spherical, and cylindrical relaxation laws for plasma pressure and thickness are used for later times. Thermal and impulse coupling to the surface are calculated for representative laser fluxes and incidence angles, and compared with available data.