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One fundamental aspect of photonic technology has always been the quest for the perfect light-guiding system, which would
exhibit, over a large frequency bandwidth, subwavelength modes of controllable (with special interest lately on small [1]) group
velocity and small attenuation, both devoid of frequency dispersion [2]. If this were possible, a temporally and spatially tiny
wavepacket would basically propagate without changing shape but only with slowly uniformly decreasing size. Such a system is
yet not known to exist in nature, as none of the existing material platforms can achieve simultaneously all of the above attributes,
but at most only a subset. All-dielectric structures [3] cannot support highly-subwavelength light propagation, which can be attained
by exploiting (bulk or surface) polaritons in plasmonic [4-14] or other resonant-material (e.g. atomic, excitonic, phononic
[15, 16]) waveguiding structures, which typically suffer though from high absorption losses. The one problem, however, that
is commonly shared among all existing photonic systems is modal dispersion. In particular, for slow- [17-25] and stopped-
[26-28] light systems, dispersion is the major reason there is a limitation on their achievable so-called 'bandwidth-delay product'
[29-34]. This fact has thus motivated the recent invention of a few advanced dispersion-cancellation schemes, which make
use of coupled geometric [35] or gain-material [36] resonances or a fine balance of dispersion with nonlinearities [37]. It was
also pointed out recently [38] that layered axially-uniform plasmonic-dielectric-hybrid waveguiding systems can guide broadband
slow and subwavelength light, but the proposed systems were still dispersion-limited. In this Article, we show that such
multilayered Surface-PlasmonoDielectric-Polaritonic (SPDP) systems allow for a new physical mechanism, which enables their
inherently-single-polarization surface-polaritonic modes to additionally have - for small positive, negative or zero group-velocity - the dispersion coefficients of simultaneously both the group velocity and the attenuation systematically cancelled to unusually high orders, thus leading to the first linear passive system in nature, known to us, that essentially is dispersionless and breaks the 'bandwidth-delay product' limitation. By arguing [38] that, in the absence of disorder, attenuation may also, in principle,
be reducible by cooling, these material systems approach the ideal slow-light-guiding system. Furthermore, they can also be
tailored to invent a variety of novel intricate dispersion relations with multiple points of zero group velocity. The applications of
this class of guiding systems in the technological realm of nanophotonics could be substantial.
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