title: Birefringent Fresnel zone plates in silica fabricated by femtosecond laser machining.
abstract: We demonstrate maskless, single-step fabrication of strongly birefringent Fresnel zone plates by focusing of femtosecond laser pulses deep within silica substrates. The process allows us to produce alternate zone rings directly by inducing a local refractive-index modification of the order of n~10(-2) . The embedded zone plates shown in this Letter exhibit efficiencies that vary by as much as a factor of ~6 for orthogonal polarizations. Focal lengths of primary and secondary foci are shown to compare well with theory.
authors.forename: Erica
authors.initials: E
authors.lastname: Bricchi
authors.forename: John D
authors.initials: JD
authors.lastname: Mills
authors.forename: Peter G
authors.initials: PG
authors.lastname: Kazansky
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Klappauf
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Baumberg