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1.
Nat Commun ; 15(1): 2696, 2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38538588

RESUMO

Polariton canalization is characterized by intrinsic collimation of energy flow along a single crystalline axis. This optical phenomenon has been experimentally demonstrated at the nanoscale by stacking and twisting van der Waals (vdW) layers of α-MoO3, by combining α-MoO3 and graphene, or by fabricating an h-BN metasurface. However, these material platforms have significant drawbacks, such as complex fabrication and high optical losses in the case of metasurfaces. Ideally, it would be possible to canalize polaritons "naturally" in a single pristine layer. Here, we theoretically predict and experimentally demonstrate naturally canalized phonon polaritons (PhPs) in a single thin layer of the vdW crystal LiV2O5. In addition to canalization, PhPs in LiV2O5 exhibit strong field confinement ( λ p ~ λ 0 27 ), slow group velocity (0.0015c), and ultra-low losses (lifetimes of 2 ps). Our findings are promising for the implementation of low-loss optical nanodevices where strongly directional light propagation is needed, such as waveguides or optical routers.

2.
J Phys Chem C Nanomater Interfaces ; 124(28): 15434-15439, 2020 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-32704340

RESUMO

The development of broadband and ultracompact optoelectronic devices relies on the possibility of fabricating bright and tunable emitters at the nanoscale. Here, we show emission from EuO x (1 ≤ x < 1.4) thin films on silicon formed by nanocrystals with average sizes in the range of 5 nm. The photoluminescence emission of the nano-EuO x films is tunable as a function of the oxygen concentration changing from a green broadband Eu2+-related emission to a narrow red Eu3+-related emission. To reach these results has been instrumental through the use of a new methodology specially designed to achieve high-quality europium oxide films whose compositional properties are controlled by the growth base pressure and preserved thanks to a chemically stable and transparent cover layer of Al2O3. Our findings confirm the outstanding potential of nanostructured EuO x films as "one-compound" optical elements with tunable emission properties for their implementation in integrated silicon-based devices.

3.
Sci Rep ; 7: 42697, 2017 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-28198432

RESUMO

Since the technological breakthrough prompted by the inception of light emitting diodes based on III-nitrides, these material systems have emerged as strategic semiconductors not only for the lighting of the future, but also for the new generation of high-power electronic and spintronic devices. While III-nitride optoelectronics in the visible and ultraviolet spectral range is widely established, all-nitride efficient devices in the near-infrared (NIR) are still wanted. Here, through a comprehensive protocol of design, modeling, epitaxial growth and in-depth characterization, we develop AlxGa1-xN:Mn/GaN NIR distributed Bragg reflectors and we show their efficiency in combination with GaN:(Mn,Mg) layers containing Mn-Mgk complexes optically active in the near-infrared range of wavelengths.

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