title: Anomalous Light Scattering by Topological PT-symmetric Particle Arrays.
abstract: Robust topological edge modes may evolve into complex-frequency modes when a physical system becomes non-Hermitian. We show that, while having negligible forward optical extinction cross section, a conjugate pair of such complex topological edge modes in a non-Hermitian -symmetric system can give rise to an anomalous sideway scattering when they are simultaneously excited by a plane wave. We propose a realization of such scattering state in a linear array of subwavelength resonators coated with gain media. The prediction is based on an analytical two-band model and verified by rigorous numerical simulation using multiple-multipole scattering theory. The result suggests an extreme situation where leakage of classical information is unnoticeable to the transmitter and the receiver when such a -symmetric unit is inserted into the communication channel.
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: C W
authors.initials: CW
authors.lastname: Ling
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Ka Hei
authors.initials: KH
authors.lastname: Choi
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: T C
authors.initials: TC
authors.lastname: Mok
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Zhao-Qing
authors.initials: ZQ
authors.lastname: Zhang
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Kin Hung
authors.initials: KH
authors.lastname: Fung