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Ambrosio, Antonio

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Ambrosio

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Antonio

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Ambrosio, Antonio

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2016 - 20182

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Author's Publications: search.filters.isAuthorOfPublication.1dfe389c-a6a6-4be5-81b2-2d43f697e1db

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    Ultra-confined mid-infrared resonant phonon polaritons in van der Waals nanostructures
    (American Association for the Advancement of Science, 2018) Tamagnone, Michele; Ambrosio, Antonio; Chaudhary, Kundan; Jauregui, Luis A.; Kim, Philip; Wilson, William; Capasso, Federico
    Hexagonal boron nitride has been proposed as an excellent candidate to achieve subwavelength infrared light manipulation owing to its polar lattice structure, enabling excitation of low-loss phonon polaritons with hyperbolic dispersion. We show that strongly subwavelength hexagonal boron nitride planar nanostructures can exhibit ultra-confined resonances and local field enhancement. We investigate strong light-matter interaction in these nanoscale structures via photo-induced force microscopy, scattering-type scanning near-field optical microscopy, and Fourier transform infrared spectroscopy, with excellent agreement with numerical simulations. We design optical nano-dipole antennas and directly image the fields when bright- or dark-mode resonances are excited. These modes are deep subwavelength, and strikingly, they can be supported by arbitrarily small structures. We believe that phonon polaritons in hexagonal boron nitride can play for infrared light a role similar to that of plasmons in noble metals at visible frequency, paving the way for a new class of efficient and highly miniaturized nanophotonic devices.
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    Broadband and chiral binary dielectric meta-holograms
    (American Association for the Advancement of Science (AAAS), 2016) Khorasaninejad, Mohammadreza; Ambrosio, Antonio; Kanhaiya, Pritpal; Capasso, Federico
    Subwavelength structured surfaces, known as meta-surfaces, hold promise for future compact and optically thin devices with versatile functionalities. By revisiting the concept of detour phase, we demonstrate high-efficiency holograms with broadband and chiral imaging functionalities. In our devices, the apertures of binary holograms are replaced by subwavelength structured microgratings. We achieve broadband operation from the visible to the near infrared and efficiency as high as 75% in the 1.0 to 1.4 mm range by compensating for the inherent dispersion of the detour phase with that of the subwavelength structure. In addition, we demonstrate chiral holograms that project different images depending on the handedness of the reference beam by incorporating a geometric phase. Our de- vices’ compactness, lightness, and ability to produce images even at large angles have significant potential for impor- tant emerging applications such as wearable optics.