Plasmonic Coupled Modes in a Metal-Dielectric Periodic Nanostructure.

In this study we investigate the optical properties of a 2D-gap surface plasmon metasurface composed of gold nanoblocks (nanoantennas) arranged in a metal-dielectric configuration. This novel structure demonstrates the capability of generating simultaneous multi-plasmonic resonances and offers tunability within the near-infrared domain. Through finite difference time domain (FDTD) simulations, we analyze the metasurface's reflectance spectra for various lattice periods and identify two distinct dips with near-zero reflectance, indicative of resonant modes.

Integrated Optical Filters with Hyperbolic Metamaterials.

The growing development of nanotechnology requires the design of new devices that integrate different functionalities at a reduced scale. For on-chip applications such as optical communications or biosensing, it is necessary to selectively transmit a portion of the electromagnetic spectrum. This function is performed by the so-called band-pass filters.

Does the Use of Immunosuppressive Drugs Impact on SARS-CoV-2 Infection Outcome? Data From A National Cohort of Patients With Immune-Mediated Inflammatory Diseases (SAR-COVID Registry).

Background/objective: This study describes the impact of immunomodulatory and/or immunosuppressive (IM/IS) drugs in the outcomes of COVID-19 infection in a cohort of patients with immune-mediated inflammatory diseases (IMIDs).

Methods: Adult patients with IMIDs with a confirmed SARS-CoV-2 infection were included. Data were reported by the treating physician between August 13, 2020 and July 31, 2021.

[Myocardial infarction with non-obstructive coronary artery disease. Diagnostic value of intravascular imaging and cardiac resonance].

Background: Myocardial infarction with non-obstructive coronary artery disease (MINOCA) is common. Cardiac magnetic resonance (CMR) and intravascular imaging (IVI) may be useful for establishing its etiology.

Aim: To describe a population with MINOCA and its multi-image assessment using IVI or CMR.

Single function crystalline lens capable of mimicking ciliary body accommodation.

The lens is a complex optical component of the human eye because of its physiological structure: the surface is aspherical and the structural entities create a gradient refractive index (GRIN). Most existent models of the lens deal with its external shape independently of the refractive index and, subsequently, through optimization processes, adjust the imaging properties. In this paper, we propose a physiologically realistic GRIN model of the lens based on a single function for the whole lens that accurately describes different accommodative states simultaneously providing the corresponding refractive index distribution and the external shape of the lens by changing a single parameter that we associate with the function of the ciliary body.

Topographic synthesis of arbitrary surfaces with vortex Jinc functions.

When a circular aperture is uniformly illuminated, it is possible to observe in the far field an image of a bright circle surrounded by faint rings known as the Airy pattern or Airy disk. This pattern is described by the first-order Bessel function of the first type divided by its argument expressed in circular coordinates. We introduce the higher-order Bessel functions with a vortex azimuthal factor to propose a family of functions to generalize the function defining the Airy pattern.

Excitation of surface plasmon polaritons in a gold nanoslab on ion-exchanged waveguide technology.

Integrated metaphotonic devices has opened new horizons to control light-guiding properties at nanoscale; particularly interesting is the application of plasmonic nanostructures coupled to dielectric waveguides to reduce the inherent light propagation losses in metallic metamaterials. In this contribution, we show the feasibility of using ion-exchanged glass waveguides (IExWg) as a platform for the efficient excitation of surface plasmon polaritons (SPP). These IExWg provide high coupling efficiency and low butt-coupling with conventional dielectric optical waveguides and fibers, overcoming the hard fabrication tunability of commonly used CMOS-guiding platforms.

Plasmonic directional couplers using channel waveguides in random arrays of metal nanoparticles.

Plasmonic directional couplers based on channel waveguides embedded in random arrays of metal nanoparticles (NPs) operating in near-infrared are fabricated using electron-beam lithography and investigated experimentally characterizing their performance with leakage-radiation microscopy. The power exchange between coupled waveguides, its spatial period and efficiency, along with the overall power transmission, are determined in the wavelength range from 700 to 800 nm. We introduce a simple coupled-mode approach based on three coupled waveguides.

3D thickness map reconstruction of dielectric thin films using scattering of surface plasmon polaritons.

Thin films are key elements in the current development of nanotechnology, and their characterization has become an essential task. In this Letter, we report on a technique to reconstruct full 3D maps of dielectric thin films using the scattered light of decoupled surface plasmon polaritons. Patterned magnesium fluoride thin films were fabricated, and their 3D thickness map was fully reconstructed with high (<1  nm) precision.

Plasmonic channel waveguides in random arrays of metallic nanoparticles.

We report detailed characterization of surface plasmon-polariton guiding along 1-, 1.5- and 2-μm-wide channels in high-density (~75 μm) random arrays of gold 70-nm-high and 50-nm-wide nanoparticles fabricated on a 70-nm-thin gold film supported by a 170-μm-thick silica substrate. The mode propagation losses, effective index dispersion, and scattering parameters are characterized using leakage-radiation microscopy, in direct and Fourier planes, in the wavelength range of 740-840 nm.

Enhancement of two-photon photoluminescence and SERS for low-coverage gold films.

Electromagnetic field enhancement (FE) effects occurring in thin gold films 3-12-nm are investigated with two-photon photoluminescence (TPL) and Raman scanning optical microscopies. The samples are characterized using scanning electron microscopy images and linear optical spectroscopy. TPL images exhibit a strong increase in the level of TPL signals for films thicknesses 3-8-nm, near the percolation threshold.

Three-dimensional ray tracing in spherical and elliptical generalized Luneburg lenses for application in the human eye lens.

Ray tracing in spherical Luneburg lenses has always been represented in 2D. All propagation planes in a 3D spherical Luneburg lens generate the same ray tracing, due to its radial symmetry. A geometry without radial symmetry generates a different ray tracing.

Biosensing enhancement using passive mixing structures for microarray-based sensors.

The combination of microarray technologies with microfluidic sample delivery and real-time detection methods has the capability to simultaneously monitor 10-1000 s of biomolecular interactions in a single experiment. Despite the benefits that microfluidic systems provide, they typically operate in the laminar flow regime under mass transfer limitations, where large analyte depletion layers act as a resistance to analyte capture. By locally stirring the fluid and delivering fresh analyte to the capture spot, the use of passive mixing structures in a microarray environment can reduce the negative effects of these depletion layers and enhance the sensor performance.

Generation of diffraction-free plasmonic beams with one-dimensional Bessel profiles.

We demonstrate experimentally generation of diffraction-free plasmonic beams with zeroth- and first-order Bessel intensity profiles using axicon-like structures fabricated on gold film surfaces and designed to operate at a wavelength of 700 nm. The central beam features a very low divergence (~8π mrad) for a narrow waist of the order of one wavelength and the ability to self reconstruct, which are the main signatures of diffraction-free beams.

Partial loss compensation in dielectric-loaded plasmonic waveguides at near infra-red wavelengths.

We report on the fabrication and characterization of straight dielectric-loaded surface plasmon polaritons waveguides doped with lead-sulfide quantum dots as a near infra-red gain medium. A loss compensation of ~33% (an optical gain of ~143 cm⁻¹) was observed in the guided mode. The mode propagation, coupling efficiency and stimulated emission were characterized using leakage radiation microscopy.

Angle dependence of the interaction distance in the shear force technique.

We study the interaction distance in the lateral force detection, using a standard quartz tuning fork as a force transducer. That is the distance at which the interaction sample-probe starts to be detected. We study in particular the dependence on the approaching angle.

Direct observation of localized second-harmonic enhancement in random metal nanostructures.

Second harmonic (SH) scanning optical microscopy in reflection is used to image the gold film surface covered with randomly placed scatterers. SH images obtained with a tightly focused tunable (750-830 nm) laser beam show small (approximately 0.7 microm) and very bright (approximately 10(3) times the background) spots, whose locations depend on the wavelength and polarization of light.

Experimental statistics of near-field intensity distributions at nanostructured surfaces.

Scanning near-field optical microscopy is a technique in which the resolution is primarily determined by the size of a probe and not by the wavelength of illumination as in classical (far-field) microscopy. However, the relationship between a sample and its near-field optical image is usually rather complex. Typical factors responsible, at least partially, for such a complexity are the conditions of illumination and detection, sample characteristics (e.