title: Polarisers in the focal domain: Theoretical model and experimental validation.
abstract: Polarisers are one of the most widely used devices in optical set-ups. They are commonly used with paraxial beams that propagate in the normal direction of the polariser plane. Nevertheless, the conventional projection character of these devices may change when the beam impinges a polariser with a certain angle of incidence. This effect is more noticeable if polarisers are used in optical systems with a high numerical aperture, because multiple angles of incidence have to be taken into account. Moreover, the non-transverse character of highly focused beams makes the problem more complex and strictly speaking, the Malus' law does not apply. In this paper we develop a theoretical framework to explain how ideal polarisers affect the behavior of highly focused fields. In this model, the polarisers are considered as birefringent plates, and the vector behaviour of focused fields is described using the plane-wave angular spectrum approach. Experiments involving focused fields were conducted to verify the theoretical model and a satisfactory agreement between theoretical and experimental results was found.
authors.affiliation: Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Martínez-Herrero
authors.affiliation: Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Maluenda
authors.affiliation: Universitat de Barcelona (UB), Facultat de Física, Departament de Física Aplicada, Martí i Franquès 1, 08028 Barcelona, Spain.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Juvells
authors.affiliation: Universitat de Barcelona (UB), Facultat de Física, Departament de Física Aplicada, Martí i Franquès 1, 08028 Barcelona, Spain.
authors.forename: Artur
authors.initials: A
authors.lastname: Carnicer