arXiv subjects

Mario Agio

Publications and source records attributed to Mario Agio.

27 records · Page 2Linked to original sources

arXiv2010

Fluorescence enhancement with the optical (bi-) conical antenna

We investigate the properties of finite gold nanocones as optical antennas for enhancing molecular fluorescence. We compute the modification of the excitation rate, spontaneous emission rate, and quantum efficiency as a function of the nanocone base and length, showing that the maximum field and fluorescence enhancements do not occur for the same nanocone parameters. We compare the results with those for nanorods and nanospheroids and find that nanocones perform better.

physics.chem-ph↗

arXiv2009

Magnetic metamaterials in the blue range using aluminum nanostructures

We report an experimental and theoretical study of the optical properties of two-dimensional arrays of aluminum nanoparticle in-tandem pairs. Plasmon resonances and effective optical constants of these structures are investigated and strong magnetic response as well as negative permeability are observed down to 400 nm wavelength. Theoretical calculations based on the finite-difference time-domain method are performed for various particle dimensions and lattice parameters, and are found to be in good agreement with the experimental results. The results show that metamaterials operating across the whole visible wavelength range are feasible.

physics.optics↗

arXiv2009

Highly efficient interfacing of guided plasmons and photons in nanowires

Successful exploitations of strongly confined surface plasmon-polaritons critically rely on their efficient and rapid conversion to lossless channels. We demonstrate a simple, robust, and broad-band butt-coupling technique for connecting a metallic nanowire and a dielectric nanofiber. Conversion efficiencies above 95% in the visible and close to 100% in the near infrared can be achieved with realistic parameters. Moreover, by combining butt-coupling with nanofocusing, we propose a broad-band high-throughput near-field optical microscope.

quant-ph↗

arXiv2009

Light scattering by an oscillating dipole in a focused beam

The interaction between a focused beam and a single classical oscillating dipole or a two-level system located at the focal spot is investigated. In particular, the ratio of the scattered to incident power is studied in terms of the oscillator's scattering cross section and the effective focal area. Debye diffraction integrals are applied to calculate it and results are reported for a directional dipolar wave. Multipole expansion of the incident beam is then considered and the equivalence between this and the Debye diffraction approach is discussed. Finally, the phase change of the electric field upon the interaction with a single oscillator is studied.

quant-ph↗

arXiv2009

Metal nanoparticles in strongly confined beams: transmission, reflection and absorption

We investigate the interaction of tightly focused light with the surface-plasmon-polariton resonances of metal nanospheres. In particular, we compute the scattering and absorption ratios as well as transmission and reflection coefficients. Inspired by our previous work in Ref. [1], we discuss how well a metal nanoparticle approximates a point-like dipolar radiator. We find that a 100 nm silver nanosphere is very close to such an ideal oscillator. Our results have immediate implications for single nanoparticle spectroscopy and microscopy as well as plasmonics.

physics.optics↗

arXiv2009

Tailoring the excitation of localized surface plasmon-polariton resonances by focusing radially-polarized beams

We study the interaction of focused radially-polarized light with metal nanospheres. By expanding the electromagnetic field in terms of multipoles, we gain insight on the excitation of localized surface plasmon-polariton resonances in the nanoparticle. We show that focused radially-polarized beams offer more opportunities than a focused plane wave or a Gaussian beam for tuning the near- and far-field system response. These results find applications in nano-optics, optical tweezers, and optical data storage.

physics.optics↗

arXiv2008

Gold, copper, silver and aluminum nanoantennas to enhance spontaneous emission

We compute the decay rates of emitters coupled to spheroidal nanoantennas made of gold, copper, silver, and aluminum. The spectral position of the localized surface plasmon-polariton resonance, the enhancement factors and the quantum efficiency are investigated as a function of the aspect ratio, background index and the metal composing the nanoantenna. While copper yields results similar to gold, silver and aluminum exhibit different performances. Our results show that with a careful choice of the parameters these nanoantennas can enhance emitters ranging from the UV to the near-IR spectrum.

physics.chem-ph↗

arXiv2007

Plasmon spectra of nanospheres under a tightly focused beam

We study the modification of the far-field cross sections and the near-field enhancement for gold and silver nanospheres illuminated by a tightly focused beam. Using a multipole-expansion approach we obtain an analytical solution to the scattering problem and provide insight on the effects of focusing on the optical response. Large differences with respect to Mie theory are found especially when the nanoparticle supports quadrupole or higher-order resonances.

physics.optics↗

arXiv2001

Mini-stop bands in single-defect photonic crystal waveguides

We numerically study single-defect photonic crystal waveguides obtained from a triangular lattice of air holes in a dielectric background. It is found that, for medium-high air filling ratios, the transmission has very small values in narrow frequency regions lying inside the photonic band gap - the so-called mini-stop bands. Two types of mini-stop bands are shown to exist; one of which is due to the multimode nature of the waveguide. Their dependence on the length of the waveguide and on the air filling ratio is presented.

physics.class-ph↗