title: Visible and near-infrared characterization and modeling of nanosized holographic-polymer-dispersed liquid crystal gratings.
abstract: We have studied the electro-optical and angular behavior of holographic-polymer-dispersed liquid crystal gratings at different wavelengths, in the visible and in the near-infrared range. As usual in these kinds of materials, a strong polarization dependent behavior was observed. Our samples showed very high diffraction efficiency for p-polarized radiation at 1.55 microm, which is very interesting for many possible applications in the telecom field. However, we also observed a very unusual behavior for visible p-polarized light and we try to suggest some explanation for that. By analyzing the angular dependence of the diffraction efficiency, we could measure the components of the permittivity modulation tensor and infer important information about the main parameters involved in the grating structure: the degree of phase separation and the anisotropy in the liquid crystal droplet distribution. In our opinion, this simple and nondestructive methodology can be very useful for studying these kinds of materials and getting information on their morphology, in view of optimizing their properties. Finally, we discuss the role of the refractive index optical dispersion in order to describe the behavior of these materials at different wavelengths. These remarks are especially important when properties in the infrared range are extrapolated from measurements in the visible.
authors.affiliation: INFM Coherentia and Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Monte S. Angelo, Naples, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Vita
authors.forename: Antigone
authors.initials: A
authors.lastname: Marino
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Tkachenko
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Abbate
authors.forename: Daniele E
authors.initials: DE
authors.lastname: Lucchetta
authors.forename: Luigi
authors.initials: L
authors.lastname: Criante
authors.forename: Francesco
authors.initials: F
authors.lastname: Simoni