Gaussian beam without approximation

We use the angular spectrum representation to compute exactly the Gaussian beam close to the waist (w₀) in the case of highly nonparaxial field (w₀<λ). 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 series, which permits to get analytical expressions for both propagating and evanescent waves when the observation is close to the waist.

• Link (25 Apr 2021)