Fabricació de nanoestructures plasmòniques tridimensionals

En aquest article es demostra l'ús de la deposició induïda per un feix d'electrons focalitzat (FEBID) per a la fabricació de nanoestructures d'or per a aplicacions d'òptica de plasmons. S'investiguen els efectes del material del substrat i dels paràmetres de deposició, com ara el corrent del feix i la pressió de vapor d'aigua, sobre el ritme de creixement i la puresa de l'or. S'ha emprat una recuita ex situ de la mostra com a mètode de millora de la puresa del material dipositat. Les mesures òptiques de dispersió sobre les estructures purificades evidencien que suporten plasmons de superfície localitzats. Aquest mètode de fabricació permet el creixement d'estructures plasmòniques amb una elevada relació d'aspecte i facilita l'escriptura en superfícies no planes

Tunable optical sorting and manipulation of nanoparticles via plasmon excitation

We numerically investigate the optical forces exerted by an incident light beam on Rayleigh metallic particles over a dielectric substrate. In analogy with atom manipulation, we identify two different trapping regimes depending on whether the illumination is performed within the plasmon band or out of it. By adjusting the incident wavelength, the particles can be selectively guided, or immobilized, at the substrate interface. © 2006 Optical Society of America OCIS codes: 140.7010, 240.5420, 260.3910, 240.0240. Due to their potential confinement down to subwavelength volumes, evanescent fields bound at interfaces open novel opportunities for efficient manipulation of nano-objects. 1-4 Lately, we have shown both theoretically and experimentally that plasmon fields at a metal/dielectric interface can be used to dramatically enhance the optical forces on a dielectric object. We consider a metal sphere immersed in water ͑n water = 1.33͒, floating at 15 nm from the surface of a heavy flint glass prism ͑n flint = 1.8͒. The illumination is performed from the glass under total internal reflection (TIR) by either a plane wave or a tightly focused three-dimensional Gaussian beam [see 9 This formalism accounts for multipolar contributions, which cannot be neglected for metal particles of diameter larger than a few tens of nanometers. Due to their dispersion, the optical forces that experience metal nanoparticles under illumination are susceptible to dramatic variations with the incident wavelength. For a small dielectric particle, using a dipolar approximation, the total force combines a gradient contribution that attracts the particle towards the highest field value and a scattering component that tends to push it along the incident wave vector. In the case of absorbing particles, an absorption force is added to the scattering component. The evolution with the incident wavelength of the X and Z components of the total force exerted on an 80 nm diameter gold sphere is shown i

Fabricació de nanoestructures plasmòniques tridimensionals

En aquest article es demostra l'ús de la deposició induïda per un feix d'electrons focalitzat (FEBID) per a la fabricació de nanoestructures d'or per a aplicacions d'òptica de plasmons. S'investiguen els efectes del material del substrat i dels paràmetres de deposició, com ara el corrent del feix i la pressió de vapor d'aigua, sobre el ritme de creixement i la puresa de l'or. S'ha emprat una recuita ex situ de la mostra com a mètode de millora de la puresa del material dipositat. Les mesures òptiques de dispersió sobre les estructures purificades evidencien que suporten plasmons de superfície localitzats. Aquest mètode de fabricació permet el creixement d'estructures plasmòniques amb una elevada relació d'aspecte i facilita l'escriptura en superfícies no planes

Localized surface plasmon resonance effects on the magneto-optical activity of continuous Au/Co/Au trilayers

We study how the magneto-optical activity in polar configuration of continuous Au/Co/Au trilayers is affected by the excitation of localized plasmon resonances of an array of Au nanodiscs fabricated on top of them over a dielectric SiO2 spacer. We show that the effect of the nanodiscs array is twofold. First, it optimizes the absorption of light at specific photon energies corresponding to the localized surface plasmon excitation of the array, modifying the reflectivity of the system (we define this effect as the purely optical contribution). Second, upon localized plasmon resonance excitation, the electromagnetic field in the whole system is redistributed, and an enhanced magneto-optical activity occurs at those energies where the electromagnetic field in the magnetic layer is increased (this effect is identified as the purely magneto-optical contribution of the nanodiscs array).This research was carried out with the financial support of the Spanish Ministry of Science and Education (NAN2004-09195-C04 and MAT2005-05524-C02-01), Comunidad de Madrid (S-0505/MAT/0194 NANOMAGNET) and the European Commission through the NoE PHOREMOST (FP6/2003/IST/2-511616). M. U. G. thanks the Spanish Ministry of Education for funding through the “Ramón y Cajal” program.Peer reviewe

Highly Sensitive Sensors Based on Photonic Crystal Fiber Modal Interferometers

We review the research on photonic crystal fiber modal interferometers with emphasis placed on the characteristics that make them attractive for different sensing applications. The fabrication of such interferometers is carried out with different post-processing techniques such as grating inscription, tapering or cleaving, and splicing. In general photonic crystal fiber interferometers exhibit low thermal sensitivity while their applications range from sensing strain or temperature to refractive index and volatile organic compounds