title: Catenary optics for achromatic generation of perfect optical angular momentum.
abstract: The catenary is the curve that a free-hanging chain assumes under its own weight, and thought to be a "true mathematical and mechanical form" in architecture by Robert Hooke in the 1670s, with nevertheless no significant phenomena observed in optics. We show that the optical catenary can serve as a unique building block of metasurfaces to produce continuous and linear phase shift covering [0, 2π], a mission that is extremely difficult if not impossible for state-of-the-art technology. Via catenary arrays, planar optical devices are designed and experimentally characterized to generate various kinds of beams carrying orbital angular momentum (OAM). These devices can operate in an ultra-broadband spectrum because the anisotropic modes associated with the spin-orbit interaction are almost independent of the incident light frequency. By combining the optical and topological characteristics, our approach would allow the complete control of photons within a single nanometric layer.
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Mingbo
authors.initials: M
authors.lastname: Pu
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Xiong
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Yanqin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Zeyu
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Changtao
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Chenggang
authors.initials: C
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Huang
authors.affiliation: Centre for Micro-Photonics and CUDOS (Centre for Ultrahigh Bandwidth Devices for Optical Systems), Faculty of Science, Engineering and Technology, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Haoran
authors.initials: H
authors.lastname: Ren
authors.affiliation: Centre for Micro-Photonics and CUDOS (Centre for Ultrahigh Bandwidth Devices for Optical Systems), Faculty of Science, Engineering and Technology, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Xiangping
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Electrical & Computer Engineering, National University of Singapore, Engineering Drive 3, Singapore 117576, Singapore.
authors.forename: Fei
authors.initials: F
authors.lastname: Qin
authors.affiliation: Department of Electrical & Computer Engineering, National University of Singapore, Engineering Drive 3, Singapore 117576, Singapore.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: Centre for Micro-Photonics and CUDOS (Centre for Ultrahigh Bandwidth Devices for Optical Systems), Faculty of Science, Engineering and Technology, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Min
authors.initials: M
authors.lastname: Gu
authors.affiliation: Department of Electrical & Computer Engineering, National University of Singapore, Engineering Drive 3, Singapore 117576, Singapore.
authors.forename: Minghui
authors.initials: M
authors.lastname: Hong
authors.affiliation: State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Xiangang
authors.initials: X
authors.lastname: Luo
keywords: geometric phase; metasurface; nanostructure; orbital angular momentum; phase modulation; spin angular momentum