title: Highly efficient and ultra-broadband graphene oxide ultrathin lenses with three-dimensional subwavelength focusing.
abstract: Nanometric flat lenses with three-dimensional subwavelength focusing are indispensable in miniaturized optical systems. However, they are fundamentally challenging to achieve because of the difficulties in accurately controlling the optical wavefront by a film with nanometric thickness. Based on the unique and giant refractive index and absorption modulations of the sprayable graphene oxide thin film during its laser reduction process, we demonstrate a graphene oxide ultrathin (∼200 nm) flat lens that shows far-field three-dimensional subwavelength focusing (λ(3)/5) with an absolute focusing efficiency of >32% for a broad wavelength range from 400 to 1,500 nm. Our flexible graphene oxide lenses are mechanically robust and maintain excellent focusing properties under high stress. The simple and scalable fabrication approach enables wide potential applications in on-chip nanophotonics. The wavefront shaping concept opens up new avenues for easily accessible, highly precise and efficient optical beam manipulations with a flexible and integratable planar graphene oxide ultrathin film.
authors.affiliation: Centre for Micro-Photonics in Faculty of Science, Engineering and Technology at Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Centre for Micro-Photonics in Faculty of Science, Engineering and Technology at Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Baohua
authors.identifier: http://orcid.org/0000-0002-6703-477X
authors.initials: B
authors.lastname: Jia
authors.affiliation: Centre for Micro-Photonics in Faculty of Science, Engineering and Technology at Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Han
authors.initials: H
authors.lastname: Lin
authors.affiliation: Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Ling
authors.initials: L
authors.lastname: Qiu
authors.affiliation: Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Centre for Micro-Photonics in Faculty of Science, Engineering and Technology at Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Min
authors.initials: M
authors.lastname: Gu