0000000000424072
AUTHOR
David Pastor
Single-Polarization Double Refraction in Plasmonic Crystals: Considerations on Energy Flow
We examined the optical properties of nanolayered metal-dielectric lattices. At subwavelength regimes, the periodic array of metallic nanofilms demonstrates nonlocality-induced double refraction, conventional positive and as well as negative. In particular, we report on energy-flow considerations concerning both refractive behaviors concurrently. Numerical simulations provide transmittance of individual beams in Ag-TiO2 metamaterials under different configurations. In regimes of the effective-medium theory predicting elliptic dispersion, negative refraction may be stronger than the expected positive refraction. This research was funded by the Spanish Ministry of Economy and Competitiveness …
Plasmon-driven Bessel beams
We report on subwavelength diffraction-free beams with grazing propagation in metal-dielectric devices. The nondiffracting beams are resonantly transmitted through the nanostructured medium leading to light confinement and wave amplification around the beam axis.
Plasmon-driven nondiffracting surface beaming
We introduce diffraction-free plasmonic waves in metal-dielectric surfaces which are the analogue to nondiffracting Bessel beams in free space. By interfering multiple converging plane waves with controlled phase matching, we generate a subwavelength transverse spot located at the boundaries of a 1D plasmonic lattice. The diffraction-free beam is resonantly transmitted through the stratiform medium leading not only to light confinement but also to wave enhancement assisted by surface plasmons polaritons. To conclude, we briefly analyze other types of localized surface modes which were proposed recently.
Subwavelength surface waves with zero diffraction
We identified nanostructured devices sustaining out-of-plane nondiffracting beams with near-grazing propagation and a transverse beamwidth clearly surpassing the diffraction limit of half a wavelength. This type of device consists of a planar multilayered metal-dielectric structure with a finite number of films deposited on a solid transparent substrate. We assumed that the nondiffracting beam is launched from the substrate. The construction of the subwavelength diffraction-free beam is attended by plane waves which are resonantly transmitted through the stratified medium. Therefore, light confinement and wave amplification occurs simultaneously. We performed an optimization process concern…
Uniaxial epsilon-near-zero metamaterials: from superlensing to double refraction
We investigated optical properties of nanostructured metal-dielectric multilayered lattices under the conditions of epsilon-near-zero (ENZ), a concept derived from the effective-medium approach (EMA). We theoretically found that the periodic array of metallic nanolayers may exhibit either superlensing driven by broadband canalization from point emitters or single-polarization double refraction, and conventional positive as well as negative, even at subwavelength regimes. For the latter case, we formulated a modified EMA, and subsequently a generalized refraction law, that describes both refractive behaviors concurrently. The modal coupling of plasmonic lattice resonances, and nonlocality in…
Three-dimensional point spread function of multilayered flat lenses and its application to extreme subwavelength resolution
The three-dimensional (3D) point spread function (PSF) of multilayered flat lenses was proposed in order to characterize the diffractive behavior of these subwavelength image formers. We computed the polarization-dependent scalar 3D PSF for a wide range of slab widths and for different dissipative metamaterials. In terms similar to the Rayleigh criterion we determined unambiguously the limit of resolution featuring this type of image-forming device. We investigated the significant reduction of the limit of resolution by increasing the number of layers, which may drop nearly 1 order of magnitude. However, this super-resolving effect is obtained in detriment of reducing the depth of field. Li…
Nondiffracting Bessel plasmons.
We report on the existence of nondiffracting Bessel surface plasmon polaritons (SPPs), advancing at either superluminal or subluminal phase velocities. These wave fields feature deep subwavelength FWHM, but are supported by high-order homogeneous SPPs of a metal/dielectric (MD) superlattice. The beam axis can be relocated to any MD interface, by interfering multiple converging SPPs with controlled phase matching. Dissipative effects in metals lead to a diffraction-free regime that is limited by the energy attenuation length. However, the ultra-localization of the diffracted wave field might still be maintained by more than one order of magnitude. This research was funded by the Spanish Mini…
Plasmonic stratified devices for superlensing in the self-focusing regime
We show that diffraction-management of subwavelength scattered fields assisted by metallodielectric heterostructures leads to superresolving imaging. An accurate design of a passive multilayered compound provides nearly aberration-free images with subwavelength resolution out of the canalization regime even using optical paths longer than a wavelength.
Diffraction-managed superlensing using plasmonic lattices
Abstract We show that subwavelength diffracted wave fields may be managed inside multilayered plasmonic devices to achieve ultra-resolving lensing. For that purpose we first transform both homogeneous waves and a broad band of evanescent waves into propagating Bloch modes by means of a metal/dielectric (MD) superlattice. Beam spreading is subsequently compensated by means of negative refraction in a plasmon-induced anisotropic medium that is cemented behind. A precise design of the superlens doublet may lead to nearly aberration-free images with subwavelength resolution in spite of using optical paths longer than a wavelength.
Some considerations on the transmissivity of trirefringent metamaterials
Nonlocal effects in metal–dielectric (MD) periodic nanostructures may typically be observed when the plasmonic particles and gaps are on the scale of a few tens of nanometers, enabling under certain conditions (succinctly for epsilon near zero) a collimated beam to split into three refracted signals. We developed a method for precisely evaluating the categorized transmissivity in an air/trirefringent metamaterial interface, which uses a fast one-dimensional Fourier transform and finite element solvers of Maxwell’s equations. In periodic arrays of MD nanofilms, it is proved a tunable transmissivity switch of the multirefracted beams under varying angle of incidence and wavelength, while keep…
Considerations on the electromagnetic flow in Airy beams based on the Gouy phase
We reexamine the Gouy phase in ballistic Airy beams (AiBs). A physical interpretation of our analysis is derived in terms of the local phase velocity and the Poynting vector streamlines. Recent experiments employing AiBs are consistent with our results. We provide an approach which potentially applies to any finite-energy paraxial wave field that lacks a beam axis. This research was funded by the Spanish Ministry of Economy and Competitiveness under the project TEC2009-11635.
Metamaterial coatings for subwavelength-resolution imaging
Coating lenses are membranes made of materials exhibiting negative index of refraction and deposited on other media with high dielectric constant e 3 . Unfortunately far-field imaging suffers from centrosymmetric aberrations. We propose a simple procedure to compensate partially deviations from ray-tracing perfect imaging in asymmetric metamaterial lenses. We also show that, under some circumstances, coating superlens may recover subwavelength information transmitted in a relative spatial spectrum ranging from 1 to √e 3 .
Three-dimensional point spread function and generalized amplitude transfer function of near-field flat lenses.
We derive a nonsingular, polarization-dependent, 3D impulse response that provides unambiguously the wave field scattered by a negative-refractive-index layered lens and distributed in its image volume. By means of a 3D Fourier transform, we introduce the generalized amplitude transfer function in order to gain a deep insight into the resolution power of the optical element. In the near-field regime, fine details containing some depth information may be transmitted through the lens. We show that metamaterials with moderate absorption are appropriate for subwavelength resolution keeping a limited degree of depth discrimination.
Metasurfaces for colour printing
We present a theoretical analysis and experimental evidences of metasurfaces based on particle resonators that achieve bright-field colour prints. We created pixels that support individual colours, miniaturized and juxtaposed at the optical diffraction limit. Different strategies are followed to offer the flexibility of using both transmitting and epi (reflective) white light sources. We discuss their potential applications in large-volume colour printing via nanoimprint lithography.
Left-handed metamaterial coatings for subwavelength-resolution imaging
We report on a procedure to improve the resolution of far-field imaging by using a neighboring high-index medium that is coated with a left-handed metamaterial. The resulting plot can also exhibit an enhanced transmission by considering proper conditions to retract backscattering. Based on negative refraction, geometrical aberrations are considered in detail since they may cause a great impact in this sort of diffraction-unlimited imaging by reducing its resolution power. We employ a standard aberration analysis to refine the asymmetric configuration of metamaterial superlenses. We demonstrate that low-order centrosymmetric aberrations can be fully corrected for a given object plane. For su…
Diffraction-managed superlensing using metallodielectric heterostructures
We show that subwavelength diffracted wave fields may be managed inside multilayered plasmonic devices to achieve ultra-resolving lensing. For that purpose we first transform both homogeneous waves and a broad band of evanescent waves into propagating Bloch modes by means of a metal/dielectric (MD) superlattice. Beam spreading is subsequently compensated by means of negative refraction in a plasmon-induced anisotropic effective-medium that is cemented behind. A precise design of the superlens doublet may lead to nearly aberration-free images with subwavelength resolution in spite of using optical paths longer than a wavelength. This research was funded by the Spanish Ministry of Economy and…