title: Fabrication and testing of l = 2 optical vortex phase masks for coronography.
abstract: In this paper we present the fabrication process and tests of two different types of l = 2 spiral phase plates (SPPs), designed for an Optical Vortex Coronagraph (OVC) in the visible wavelength regime. Each phase mask is realized dividing the spirals area in sectors respectively of 8 and 512 of levels using lithographic nanofabrication approach. The SPPs produces different optical vortices (OVs) with topological charge l that depends on the number of steps and on the wavelength. We found that the residual light in the central dark region of the OV tends to zero as the number of steps increases.
authors.affiliation: CISAS G Colombo, University of Padua, Via Venezia 15 35131, Padova, Italy. elettra.mari@unipd.it
authors.forename: Elettra
authors.initials: E
authors.lastname: Mari
authors.forename: Gabriele
authors.initials: G
authors.lastname: Anzolin
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Tamburini
authors.forename: Mauro
authors.initials: M
authors.lastname: Prasciolu
authors.forename: Gabriele
authors.initials: G
authors.lastname: Umbriaco
authors.forename: Antonio
authors.initials: A
authors.lastname: Bianchini
authors.forename: Cesare
authors.initials: C
authors.lastname: Barbieri
authors.forename: Filippo
authors.initials: F
authors.lastname: Romanato