title: Multilevel phase-type diffractive lenses in silica glass induced by filamentation of femtosecond laser pulses.
abstract: Multilevel phase-type diffractive lenses were fabricated by translating a filament of a femtosecond laser pulse into three-dimensional space inside synthesized silica. The profile of the lenses was designed by use of a multi-level approximation to a kinoform lens. Two-level diffractive lenses with multiple layers along the optical axis provided a maximum efficiency of 37.6% at a wavelength of 632.8 nm. A four-level diffractive lens provided a maximum efficiency of 56.9%. The lenses fabricated with filamentation were free from birefringence.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamada
authors.forename: Wataru
authors.initials: W
authors.lastname: Watanabe
authors.forename: Yudong
authors.initials: Y
authors.lastname: Li
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Itoh
authors.forename: Junji
authors.initials: J
authors.lastname: Nishii