Non-uniform polarized beams: Applications to optical encryption

Recently, a variety of applications requiring the use of non-uniformly polarized beams have been described. Moreover, digital holography using liquid crystal displays has provided a way of implementing in practice such beams. In particular, in the field of optical security, this type of beams has become very important since information can be encrypted using polarization keys. Moreover, focusing a non uniform polarized beam using a high numerical aperture lens provides a way of encoding information in the longitudinal component of the field. Security can be improved when the system works in low light illumination conditions.