Fully vectorial highly nonparaxial beam close to the waist

Abstract

I use the angular spectrum representation to compute exactly the Gaussian beam close to the waist (w(0)) in the case of a highly nonparaxial field (w(0)<lambda). The computation is done in the vectorial case for a polarized Gaussian beam. In the area of the waist, the contribution of the propagating and evanescent waves is discussed. Moreover, the Gaussian wave is developed in terms of a series, which permits one to get analytical expressions for both propagating and evanescent waves when the observation is close to the waist.