Transmission and reflection of a Gaussian beam at oblique incidence on a dielectric slab

The reflection and the transmission of a gaussian beam normally incident on a dielectric slab are investigated. The reflected and the transmitted field are expanded in a series of beam-mode functions. From the expansion coefficients, the relation between the wave theory and the complex beam parameters is made clear. The reflected and transmitted power are calculated as functions of the thickness of the slab. The thicker the slab, the smaller becomes the variation of these powers, which differs from the phenomena known in the case of plane-wave incidence.