  We have developed a computational method to describe the nonlinear light
propagation of an intense and ultrashort pulse at oblique incidence on a flat
surface. In the method, coupled equations of macroscopic light propagation and
microscopic electron dynamics are simultaneously solved using a multiscale
modeling. The microscopic electronic motion is described by first-principles
time-dependent density functional theory. The macroscopic Maxwell equations
that describe oblique light propagation are transformed into one-dimensional
wave equations. As an illustration of the method, light propagation at oblique
incidence on a silicon thin film is presented.
