Kim, JongbumDutta, AveekNaik, Gururaj V.Giles, Alexander J.Bezares, Francisco J.Ellis, Chase T.Engheta, Nader2025-09-252025-09-2520162334-2536https://doi.org/10.1364/OPTICA.3.000339https://hdl.handle.net/20.500.12573/4592Kildishev, Alexander/0000-0002-8382-8422; Boltasseva, Alexandra/0000-0001-8905-2605; Caglayan, Humeyra/0000-0002-0656-614X; Caldwell, Joshua/0000-0003-0374-2168; Mahmoud, Ahmed/0000-0002-5784-9502; Tischler, Joseph/0000-0001-9517-0229; Giles, Alexander/0000-0001-6245-1913;Radiation patterns and the resonance wavelength of a plasmonic antenna are significantly influenced by its local environment, particularly its substrate. Here, we experimentally explore the role of dispersive substrates, such as aluminum-or gallium-doped zinc oxide in the near infrared and 4H-silicon carbide in the mid-infrared, upon Au plasmonic antennas, extending from dielectric to metal-like regimes, crossing through epsilon-near-zero (ENZ) conditions. We demonstrate that the vanishing index of refraction within this transition induces a "slowing down" of the rate of spectral shift for the antenna resonance frequency, resulting in an eventual "pinning" of the resonance near the ENZ frequency. This condition corresponds to a strong backward emission with near-constant phase. By comparing heavily doped semiconductors and undoped, polar dielectric substrates with ENZ conditions in the near- and mid-infrared, respectively, we also demonstrate the generality of the phenomenon using both surface plasmon and phonon polaritons, respectively. Furthermore, we also show that the redirected antenna radiation induces a Fano-like interference and an apparent stimulation of optic phonons within SiC. (C) 2016 Optical Society of Americaeninfo:eu-repo/semantics/openAccessArticle10.1364/OPTICA.3.0003392-s2.0-84962509286