title: On-chip discrimination of orbital angular momentum of light with plasmonic nanoslits.
abstract: The orbital angular momentum (OAM) of light can be taken as an independent and orthogonal degree of freedom for multiplexing in an optical communication system, potentially improving the system capacity to hundreds of Tbits per second. The high compactness and miniaturization of devices required for optical communications impose strict requirements on discriminating OAM modes of light at a small (micro- or even nano-meter) scale for demultiplexing; these requirements represent a challenge for traditional OAM sorting strategies. Here, we propose a semi-ring plasmonic nanoslit to directly and spatially sort various OAM modes of light into ∼120 nm-spaced mode intervals on the metallic surface. Making use of the constructive interference of a helical-phase modulated surface wave excited by a vortex beam, this on-chip interval can be stably demonstrated both theoretically and experimentally with a quasi-linear dependence on the plasmonic wavelength. Furthermore, its immunity to semi-ring geometry (i.e., the radius and number of rings) is verified by simulations. As a result, OAM discriminating is guaranteed by this stable sorting function. This technique shows a viable solution to discriminate the OAM of light at the nano-scale and might lead to broad benefits across the fields of optical communications, plasmonic physics and singular optics.
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore. chengwei.qiu@nus.edu.sg and Graduate School for Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences (CeLS), #05-01, 28 Medical Drive, Singapore 117456, Singapore.
authors.forename: Shengtao
authors.initials: S
authors.lastname: Mei
authors.affiliation: Institute of Materials Research and Engineering Agency for Science, Technology and Research (A*STAR), #08-03, 2 Fusionopolis Way, Innovis, Singapore 138634.
authors.forename: Kun
authors.initials: K
authors.lastname: Huang
authors.affiliation: Institute of Materials Research and Engineering Agency for Science, Technology and Research (A*STAR), #08-03, 2 Fusionopolis Way, Innovis, Singapore 138634.
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore. chengwei.qiu@nus.edu.sg.
authors.forename: Fei
authors.initials: F
authors.lastname: Qin
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore. chengwei.qiu@nus.edu.sg.
authors.forename: Muhammad Q
authors.initials: MQ
authors.lastname: Mehmood
authors.affiliation: Nanophotonics Laboratory, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: Zhengji
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore. chengwei.qiu@nus.edu.sg.
authors.forename: Minghui
authors.initials: M
authors.lastname: Hong
authors.affiliation: Nanophotonics Laboratory, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: Daohua
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Institute of Materials Research and Engineering Agency for Science, Technology and Research (A*STAR), #08-03, 2 Fusionopolis Way, Innovis, Singapore 138634.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Teng
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore. chengwei.qiu@nus.edu.sg.
authors.forename: Aaron
authors.initials: A
authors.lastname: Danner
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore. chengwei.qiu@nus.edu.sg and Graduate School for Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences (CeLS), #05-01, 28 Medical Drive, Singapore 117456, Singapore.
authors.forename: Cheng-Wei
authors.initials: CW
authors.lastname: Qiu