RESUMO
We apply the technique of far-field interferometry to measure the properties of surface waves generated by two-dimensional (2D) single subwavelength slit-groove structures on gold films. The effective surface index of refraction n(surf) measured for the surface wave propagating over a distance of more than 12 mum is determined to be n(surf) = 1.016+/-0.004, to within experimental uncertainty close to the expected bound surface plasmon-polariton (SPP) value for a Au/Air interface of n (spp) = 1.018. We compare these measurements to finite-difference-time-domain (FDTD) numerical simulations of the optical field transmission through these devices. We find excellent agreement between the measurements and the simulations for n(surf). The measurements also show that the surface wave propagation parameter k(surf) exhibits transient behavior close to the slit, evolving smoothly from greater values asymptotically toward k (spp) over the first 2-3 mum of slit-groove distance x(sg). This behavior is confirmed by the FDTD simulations.
RESUMO
We analyze the physical-chemical surface properties of single-slit, single-groove subwavelength-structured silver films with high-resolution transmission electron microscopy and calculate exact solutions to Maxwell's equations corresponding to recent far-field interferometry experiments using these structures. Contrary to a recent suggestion the surface analysis shows that the silver films are free of detectable contaminants. The finite-difference time-domain calculations, in excellent agreement with experiment, show a rapid fringe amplitude decrease in the near zone (slit-groove distance out to 3-4 wavelengths). Extrapolation to slit-groove distances beyond the near zone shows that the surface wave evolves to the expected bound surface plasmon polariton (SPP). Fourier analysis of these results indicates the presence of a distribution of transient, evanescent modes around the SPP that dephase and dissipate as the surface wave evolves from the near to the far zone.
RESUMO
We characterize the loading, containment and optical properties of all-optical atom traps implemented by diffractive focusing with one-dimensional (1D) microstructures milled on gold films. These on-chip Fresnel lenses with focal lengths of the order of a few hundred microns produce optical-gradient-dipole traps. Cold atoms are loaded from a mirror magneto-optical trap (MMOT) centered a few hundred microns above the gold mirror surface. Details of loading optimization are reported and perspectives for future development of these structures are discussed.
RESUMO
Transmission spectra of metallic films or membranes perforated by arrays of subwavelength slits or holes have been widely interpreted as resonance absorption by surface plasmon polaritons. Alternative interpretations involving evanescent waves diffracted on the surface have also been proposed. These two approaches lead to divergent predictions for some surface wave properties. Using far-field interferometry, we have carried out a series of measurements on elementary one-dimensional subwavelength structures with the aim of testing key properties of the surface waves and comparing them to predictions of these two points of view.
RESUMO
Lasing has been observed in optically pumped 4-dicyanomethylene-2-methyl-6-( p-dimethylaminostyrl)-4H-pyran-doped poly(methyl methacrylate) square-shaped micropillars that allow four-bounce closed and open ray orbits with internal incident angle theta(inc) > theta(c) (the critical angle for total internal reflection) and with the associated surface waves that emit at the four corners. We also detect strongly TE-polarized and spatially varying emission from the square sidewalls that is due to leaky open ray orbits with theta(inc) near but less than theta(c) for two of the four bounces. By selectively pumping the square microcavity with a stripe-shaped beam, we excite different four-bounce ray orbits.