title: Hybrid refractive-diffractive-gradient-index superresolving focusing device.
abstract: The focusing properties and resolving power of a device consisting of a tapered gradient-index (GRIN) lens with spherical input and output faces are investigated through the use of the ABCD formalism to achieve minimization of the Airy radius for the device. Diffractive elements, such as zone plates, can, with an appropriate choice of their parameters, increase the resolution of an imaging system compared with a conventional lens. We demonstrate that by combining both elements a hybrid refractive-diffractive-GRIN device can be designed that exhibits improved superresolution characteristics.
authors.affiliation: E.T.S. Ingenieros de Telecomunicación, Universidad Politécnica de Madrid, Avenida Complutense, S/N, Ciudad Universitaria, E28040 Madrid, Spain.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Rivas-Moscoso
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Fernández-Pousa
authors.forename: Carlos
authors.initials: C
authors.lastname: Gómez-Reino