title: Omnidirectional optical attractor in structured gap-surface plasmon waveguide.
abstract: An optical attractor based on a simple and easy to fabricate structured metal-dielectric-metal (SMDM) waveguide is proposed. The structured waveguide has a variable thickness in the vicinity of an embedded microsphere and allow for adiabatic nano-focusing of gap-surface plasmon polaritons (GSPPs). We show that the proposed system acts as an omnidirectional absorber across a broad spectral range. The geometrical optics approximation is used to provide a description of the ray trajectories in the system and identify the singularity of the deflection angle at the photon sphere. The analytical theory is validated by full-wave numerical simulations demonstrating adiabatic, deep sub-wavelength focusing of GSPPs and high local field enhancement. The proposed structured waveguide is an ideal candidate for the demonstration of reflection free omnidirectional absorption of GSPP in the optical and infrared frequency ranges.
authors.affiliation: National Laboratory of Solid State Microstructures &School of Physics, Collaborative Innovation Center of Advanced Microstructures, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China.
authors.forename: Chong
authors.initials: C
authors.lastname: Sheng
authors.affiliation: National Laboratory of Solid State Microstructures &School of Physics, Collaborative Innovation Center of Advanced Microstructures, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: National Laboratory of Solid State Microstructures &School of Physics, Collaborative Innovation Center of Advanced Microstructures, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China.
authors.forename: Shining
authors.initials: S
authors.lastname: Zhu
authors.affiliation: College of Engineering and Science, Louisiana Tech University, Ruston, Louisiana 71270, USA.
authors.forename: Dentcho A
authors.initials: DA
authors.lastname: Genov