Plasmonic-Dielectric Systems for High-Order Dispersionless Slow or Stopped Subwavelength Light

Abstract

A material platform of multilayered surface-plasmon-dielectric-polariton systems is introduced, along with a new physical mechanism enabling simultaneous cancellation of group-velocity and attenuation dispersion to extremely high orders for subwavelength light of any small positive, negative, or zero group velocity. These dispersion-free systems could have significant impact on the development of nanophotonics, e.g., in the design of efficient and very compact delay lines and active devices. The same dispersion-manipulation mechanism can be employed to tailor at will exotic slow-light dispersion relations. DOI: 10.1103/PhysRevLett.103.043906 PACS numbers: 42.82.Et, 73.20.Mf A fundamental quest of modern photonic technology is for the perfect slow-light guiding system, which would exhibit, over a large frequency bandwidth, subwavelength modes of very small group velocity and small attenuation, both devoid of frequency dispersion. Achieving all of these attributes simultaneously appears to be physically impossible. Dielectric structures [1] cannot support highly subwavelength light propagation, polaritons in dispersive (e.g., plasmonic [2]) materials typically suffer from high absorption losses, and, most importantly, all existing slowor stopped-light systems [3-6] commonly suffer from modal dispersion. In fact, this has been proven as the major reason for the limitation on their achievable so-called ''bandwidth-delay product'' [7][8][9], motivating thus the recent invention of a few advanced dispersion-cancellation schemes, using coupled geometric [10] or gain-material [11] resonances or nonlinearities [12]. In this Letter, we demonstrate a new physical mechanism, employing a fine balance of both geometric and material dispersion, present in a multilayered axially uniform hybrid plasmonicdielectric system that enables subwavelength surfacepolaritonic modes-for small positive, negative, or zero group velocity-to exhibit cancellation, to unusually high orders, of the dispersion coefficients for both the group velocity and the attenuation simultaneously. Therefore, this is the first, to our knowledge, linear passive system in nature that essentially is dispersionless, breaks the bandwidth-delay product limitation, and displays extraordinarily high densities of states. With the last obstacle the attenuation losses, this material system approaches the ideal slow-light guiding system. Moreover, it can be tailored to a variety of novel intricate dispersion relations with multiple points of zero group velocity.Surface-plasmon polaritons (SPPs) [2] are electromagnetic waves that propagate along the interface between a plasmonic (e.g., metallic) and a dielectric material of permittivities p and . A SPP exists only for TM polarization (H-field parallel to the interface), and its !ðkÞ dispersion

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