Effect of linear polarizers on highly focused spirally polarized fields

•Linear polarizers do not act as a projector when a high focused field impinges on it.•Fresnel coefficients plays a key role in the description of polarizers on highly focused fields.•Pure-transverse beam display a non-negligible longitudinal component after polarizer.

Linear polarizers are commonly used for projecting the direction of the electric field of a transverse paraxial beam on the direction of the polarizer axis. However, the use of these devices with highly convergent field poses a practical problem because the non transversal character of electric field. In this article, we discuss the behavior of highly focused beams with spiral polarization when they pass through a polarizer. Interestingly, beams with azimuthal polarization display a non negligible irradiance in the direction of propagation after passing through a polarizer. On top of that, we found that the irradiance of a highly focused radially polarized beam after a polarizer is notably different from the projection of the field on the direction of the polarizer axis.