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1.
ACS Nano ; 18(35): 24550-24557, 2024 Sep 03.
Artículo en Inglés | MEDLINE | ID: mdl-39167712

RESUMEN

Nanomechanical resonators can serve as ultrasensitive, miniaturized force probes. While vertical structures such as nanopillars are ideal for this purpose, transducing their motion is challenging. Pillar-based photonic crystals (PhCs) offer a potential solution by integrating optical transduction within the pillars. However, achieving high-quality PhCs is hindered by inefficient vertical light confinement. Here, we present a full-silicon photonic crystal cavity based on nanopillars as a platform for applications in force sensing and biosensing areas. Its unit cell consists of a silicon pillar with a larger diameter at its top portion than at the bottom, which allows vertical light confinement and an energy band gap in the near-infrared range for transverse-magnetic polarization. We experimentally demonstrate optical cavities with Q factors exceeding 103, constructed by inserting a defect within a periodic arrangement of this type of pillars. Each nanopillar naturally behaves as a nanomechanical cantilever, making the fabricated geometries excellent optomechanical (OM) photonic crystal cavities in which the mechanical motion of each nanopillar composing the cavity can be optically transduced. These geometries display enhanced mechanical properties, cost-effectiveness, integration possibilities, and scalability. They also present an alternative in front of the widely used suspended Si beam OM cavities made on silicon-on-insulator substrates.

2.
Nanoscale ; 14(37): 13428-13451, 2022 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-36082529

RESUMEN

Phonons play a key role in the physical properties of materials, and have long been a topic of study in physics. While the effects of phonons had historically been considered to be a hindrance, modern research has shown that phonons can be exploited due to their ability to couple to other excitations and consequently affect the thermal, dielectric, and electronic properties of solid state systems, greatly motivating the engineering of phononic structures. Advances in nanofabrication have allowed for structuring and phonon confinement even down to the nanoscale, drastically changing material properties. Despite developments in fabricating such nanoscale devices, the proper manipulation and characterization of phonons continues to be challenging. However, a fundamental understanding of these processes could enable the realization of key applications in diverse fields such as topological phononics, information technologies, sensing, and quantum electrodynamics, especially when integrated with existing electronic and photonic devices. Here, we highlight seven of the available methods for the excitation and detection of acoustic phonons and vibrations in solid materials, as well as advantages, disadvantages, and additional considerations related to their application. We then provide perspectives towards open challenges in nanophononics and how the additional understanding granted by these techniques could serve to enable the next generation of phononic technological applications.

3.
Nano Lett ; 20(10): 7627-7634, 2020 10 14.
Artículo en Inglés | MEDLINE | ID: mdl-32936659

RESUMEN

Optical forces on nanostructures are usually characterized by their interaction with the electric field component of the light wave, given that most materials present negligible magnetic response at optical frequencies. This is not the case however of a high-refractive-index dielectric nanoantenna, which has been recently shown to efficiently support both electric and magnetic optical modes. In this work, we use a photoinduced force microscopy configuration to measure optically induced forces produced by a germanium nanoantenna on a surrounding silicon near-field probe. We reveal the spatial distribution, character, and magnitude of the generated forces when exciting the nanoantenna at its anapole state condition. We retrieve optical force maps showing values of up to 20 pN, which are found to be mainly magnetic in nature, according to our numerical simulations. The results of this investigation open new pathways for the study, detection, and generation of magnetic light forces at the nanometer scale.

4.
Photochem Photobiol ; 94(5): 829-833, 2018 09.
Artículo en Inglés | MEDLINE | ID: mdl-29315606

RESUMEN

The photostability and photophysical properties of the dimethyl ester of the mycosporine-like amino acid shinorine have been experimentally evaluated in aqueous solution and in the presence of direct micelles prepared with a cationic or an anionic detergent, respectively. In comparison with shinorine, the ester molecule increases the photostability, the fluorescence quantum yield and the fluorescence lifetime in water as well as in the micellar solutions. The effects are more pronounced in sodium dodecyl sulfate solutions and suggest that the electrostatic attractions with the micellar interface contribute to limit the movement of the molecules and influence the relative rate of their deactivation channels. However, the predominance of the nonradiative decay is maintained together with the UV photoprotective ability of this atypical mycosporine species.

5.
Phys Rev Lett ; 121(25): 253902, 2018 Dec 21.
Artículo en Inglés | MEDLINE | ID: mdl-30608776

RESUMEN

The optical properties of small metallic particles allow us to bridge the gap between the myriad of subdiffraction local phenomena and macroscopic optical elements. The optomechanical coupling between mechanical vibrations of Au nanoparticles and their optical response due to collective electronic oscillations leads to the emission and the detection of surface acoustic waves (SAWs) by single metallic nanoantennas. We take two Au nanoparticles, one acting as a source and the other as a receptor of SAWs and, even though these antennas are separated by distances orders of magnitude larger than the characteristic subnanometric displacements of vibrations, we probe the frequency content, wave speed, and amplitude decay of SAWs originating from the damping of coherent mechanical modes of the source. Two-color pump-probe experiments and numerical methods reveal the characteristic Rayleigh wave behavior of emitted SAWs, and show that the SAW-induced optical modulation of the receptor antenna allows us to accurately probe the frequency of the source, even when the eigenmodes of source and receptor are detuned.

7.
Nano Lett ; 16(2): 1428-34, 2016 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-26814800

RESUMEN

Ultrashort laser pulses impinging on a plasmonic nanostructure trigger a highly dynamic scenario in the interplay of electronic relaxation with lattice vibrations, which can be experimentally probed via the generation of coherent phonons. In this Letter, we present studies of hypersound generation in the range of a few to tens of gigahertz on single gold plasmonic nanoantennas, which have additionally been subjected to predesigned mechanical constraints via silica bridges. Using these hybrid gold/silica nanoantennas, we demonstrate experimentally and via numerical simulations how mechanical constraints allow control over their vibrational mode spectrum. Degenerate pump-probe techniques with double modulation are performed in order to detect the small changes produced in the probe transmission by the mechanical oscillations of these single nanoantennas.

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