title: High efficiency multilevel phase-type fractal zone plates.
abstract: Three kinds of high efficiency phase-type fractal zone plates were rapidly (in tens of minutes) fabricated by femtosecond laser two-photon photopolymerization. Their theoretical maximal diffractive efficiencies of 24.5%, 12.52%, and 18.76% were predicted both by numerical simulation and analytical deduction and were verified by the measured values of 20.5%, 9.1%, and 13%, respectively. The characteristic of multifoci and the improved imaging ability for phase-type fractal lens was also demonstrated. Moreover, to further enhance the diffractive efficiency, a four-level fractal phase lens, whose diffraction efficiency reached as high as 37.6%, was proposed and realized.
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Wu
authors.forename: Li-Gang
authors.initials: LG
authors.lastname: Niu
authors.forename: Qi-Dai
authors.initials: QD
authors.lastname: Chen
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Sun