arXiv subjects

F. J. Valdivia-Valero

Publications and source records attributed to F. J. Valdivia-Valero.

4 recordsLinked to original sources

arXiv2012

Optical forces on cylinders near subwavelength slits illuminated by a photonic nanojet

We discuss optical forces exerted on particles, either dielectric or metallic, near a subwavelength slit illuminated by a photonic nanojet. We compare those cases in which the Mie resonances are or are not excited. The configurations on study are 2D, hence those particles are infinite cylinders and, in order to obtain extraordinary transmission, the illuminating beam is p-polarized. We show the different effects of these particle resonances on the optical forces: while whispering gallery modes under those illumination conditions weaken the force strength, this latter is enhanced by localized plasmon excitation. Also, illuminating the slit with a nanojet enhances the optical forces on the particle at the exit of the aperture by a factor between 3 and 10 compared with illumination of the slit with a Gausian beam. In addition, the pulling force that such a small resonant metallic particle suffers on direct illumination by a nanojet, can change by the presence of the slit, so that it may become repulsive at certain lateral positions of the particle.

physics.optics↗

arXiv2012

Composites of resonant dielectric rods: A test of their behavior as metamaterial refractive elements

We report numerical experiments of optical wave propagation in composites of high refractive index dielectric rods at frequencies where their first electric and magnetic Mie resonances are excited. The arrays of these particles have been extensively studied and proposed as non-absorbing and isotropic metamaterials. We show that negative refraction, observed in ordered particle arrays, is due to diffraction and that an effective medium theory yields constitutive parameters that do not reproduce the observations in these composites, whose transmission also depends on the sample shape. This is further confirmed by disordering the arrays, a case in which large transmission losses appear due to extinction by resonant scattering from the particles. Therefore, these composites although little absorbing have large extinction due to scattering.

physics.optics↗

arXiv2011

Propagation of localized surface plasmons in sets of metallic nanocylinders at the exit of subwavelength slits

We analyze, by means of numerical simulations, transmission enhancements through sub- wavelength slits due to the presence of sets of plasmonic nanocylinders, placed near the exit of these apertures. Further, we extend this study to photonic crystals of dipolar plasmonic particles in front of an array of extraordinarily transmitting slits practiced in a metallic slab.

physics.optics↗

arXiv2011

Enhanced transmission through subwavelength apertures by excitation of particle localized plasmons and nanojets

We study, and illustrate with numerical calculations, transmission enhancement by subwavelength 2D slits due to the dominant role played by the excitation of the eigenmodes of plasmonic cylinders when they are placed at the aperture entrance; and also due to reinforced and highly localized energy in the slit as a consequence of the formation of a nanojet. We show that, providing the illumination is chosen such that an aperture transmitting eigenmode is generated, the phenomenon is independent of whether or not the slit alone produces extraordinary transmission; although in the former case this enhancement will add to this slit supertransmission. We address several particle sizes, and emphasize the universality of this phenomenon with different materials.

physics.optics↗