Bulk plasmon-polaritons in hyperbolic nanorod metamaterial waveguides

• Published in: Laser & photonics reviews 2015-05, Vol.9 (3), p.345-353
• Main Authors: Vasilantonakis, Nikolaos, Nasir, Mazhar E., Dickson, Wayne, Wurtz, Gregory A., Zayats, Anatoly V.
• Format: Article
• Language: English
• Subjects: Hyperbolic; Metamaterials; Original Papers; Plasmonics; waveguides
• ISSN: 1863-8880; 1863-8899
• DOI: 10.1002/lpor.201400457

Hyperbolic metamaterials comprised of an array of plasmonic nanorods provide a unique platform for designing optical sensors and integrating nonlinear and active nanophotonic functionalities. In this work, the waveguiding properties and mode structure of planar anisotropic metamaterial waveguides are characterized experimentally and theoretically. While ordinary modes are the typical guided modes of the highly anisotropic waveguides, extraordinary modes, below the effective plasma frequency, exist in a hyperbolic metamaterial slab in the form of bulk plasmon‐polaritons, in analogy to planar‐cavity exciton‐polaritons in semiconductors. They may have very low or negative group velocity with high effective refractive indices (up to 10) and have an unusual cut‐off from the high‐frequency side, providing deep‐subwavelength (λ0/6–λ0/8 waveguide thickness) single‐mode guiding. These properties, dictated by the hyperbolic anisotropy of the metamaterial, may be tuned by altering the geometrical parameters of the nanorod composite. The waveguiding properties and mode structure of planar anisotropic metamaterial waveguides are characterized experimentally and theoretically. The extraordinary modes, originating from bulk plasmon polaritons of the metamaterial with hyperbolic dispersion, are shown to exhibit low or negative group velocity and high effective refractive indices (up to 10), allowing a deep‐subwavelength‐size single mode waveguides. The results are important for understanding of the enhanced nonlinear, sensing and Purcell properties of such metamaterials.