Dual-band and spectrally selective infrared absorbers based on hybrid gold-graphene metasurfaces.

In this paper, we propose a dual-band and spectrally selective infrared (IR) absorber based on a hybrid structure comprising a patterned graphene monolayer and cross-shaped gold resonators within a metasurface. Rooted in full-wave numerical simulations, our study shows that the fundamental absorption mode of the gold metasurface hybridizes with the graphene pattern, leading to a second absorptive mode whose properties depend on graphene's electrical properties and physical geometry. Specifically, the central operation band of the absorber is defined by the gold resonators whereas the relative absorption level and spectral separation between the two modes can be controlled by graphene's chemical potential and its pattern, respectively. We analyze this platform using coupled-mode theory to understand the coupling mechanism between these modes and to elucidate the emergence and tuning of the dual band response. The proposed dual-band device can operate at different bands across the IR spectrum and may open new possibilities for tailored sensing applications in spectroscopy, thermal imaging, and environmental monitoring.

Tunable optical traps over nonreciprocal surfaces.

We propose engineering optical traps over plasmonic surfaces and precisely controlling the trap position with an external bias by inducing in-plane nonreciprocity on the surface. The platform employs an incident Gaussian beam to polarize targeted nanoparticles, and exploits the interplay between nonreciprocal and spin-orbit lateral recoil forces to construct stable optical traps and manipulate their position within the surface. To model this process, we develop a theoretical framework based on the Lorentz force combined with nonreciprocal Green's functions and apply it to calculate the trapping potential. Rooted on this formalism, we explore the exciting possibilities offered by graphene to engineer stable optical traps using low-power laser beams in the mid-IR and to manipulate the trap position in a continuous manner by applying a longitudinal drift bias. Nonreciprocal metasurfaces may open new possibilities to trap, assemble and manipulate nanoparticles and overcome many challenges faced by conventional optical tweezers while dealing with nanoscale objects.

Slow light mediated by mode topological transitions in hyperbolic waveguides.

We show that slow light in hyperbolic waveguides is linked to topological transitions in the dispersion diagram as the film thickness changes. The effect appears in symmetric planar structures with type II films, whose optical axis (OA) lies parallel to the waveguide interfaces. The transitions are mediated by elliptical mode branches that coalesce along the OA with anomalously ordered hyperbolic mode branches, resulting in a saddle point. When the thickness of the film increases further, the merged branch starts a transition to hyperbolic normally ordered modes propagating orthogonally to the OA. In this process, the saddle point transforms into a branch point featuring slow light for a broad range of thicknesses, and a new branch of ghost waves appears.

Nonlocal response of hyperbolic metasurfaces.

We analyze and model the nonlocal response of ultrathin hyperbolic metasurfaces (HMTSs) by applying an effective medium approach. We show that the intrinsic spatial dispersion in the materials employed to realize the metasurfaces imposes a wavenumber cutoff on the hyperbolic isofrequency contour, inversely proportional to the Fermi velocity, and we compare it with the cutoff arising from the structure granularity. In the particular case of HTMSs implemented by an array of graphene nanostrips, we find that graphene nonlocality can become the dominant mechanism that closes the hyperbolic contour - imposing a wavenumber cutoff at around 300k(0) - in realistic configurations with periodicity L<π/(300k(0)), thus providing a practical design rule to implement HMTSs at THz and infrared frequencies. In contrast, more common plasmonic materials, such as noble metals, operate at much higher frequencies, and therefore their intrinsic nonlocal response is mainly relevant in hyperbolic metasurfaces and metamaterials with periodicity below a few nm, being very weak in practical scenarios. In addition, we investigate how spatial dispersion affects the spontaneous emission rate of emitters located close to HMTSs. Our results establish an upper bound set by nonlocality to the maximum field confinement and light-matter interactions achievable in practical HMTSs, and may find application in the practical development of hyperlenses, sensors and on-chip networks.

Gradient Nonlinear Pancharatnam-Berry Metasurfaces.

We apply the Pancharatnam-Berry phase approach to plasmonic metasurfaces loaded by highly nonlinear multiquantum-well substrates, establishing a platform to control the nonlinear wave front at will based on giant localized nonlinear effects. We apply this approach to design flat nonlinear metasurfaces for efficient second-harmonic radiation, including beam steering, focusing, and polarization manipulation. Our findings open a new direction for nonlinear optics, in which phase matching issues are relaxed, and an unprecedented level of local wave front control is achieved over thin devices with giant nonlinear responses.

Hyperbolic Plasmons and Topological Transitions Over Uniaxial Metasurfaces.

We explore the unusual electromagnetic response of ultrathin anisotropic σ-near-zero uniaxial metasurfaces, demonstrating extreme topological transitions--from closed elliptical to open hyperbolic--for surface plasmon propagation, associated with a dramatic tailoring of the local density of states. The proposed metasurfaces may be implemented using nanostructured graphene monolayers and open unprecedented venues for extreme light confinement and unusual propagation and guidance, combined with large tunability via electric bias.

Self-biased reconfigurable graphene stacks for terahertz plasmonics.

The gate-controllable complex conductivity of graphene offers unprecedented opportunities for reconfigurable plasmonics at terahertz and mid-infrared frequencies. However, the requirement of a gating electrode close to graphene and the single 'control knob' that this approach offers limits the practical implementation and performance of these devices. Here we report on graphene stacks composed of two or more graphene monolayers separated by electrically thin dielectrics and present a simple and rigorous theoretical framework for their characterization. In a first implementation, two graphene layers gate each other, thereby behaving as a controllable single equivalent layer but without any additional gating structure. Second, we show that adding an additional gate allows independent control of the complex conductivity of each layer within the stack and provides enhanced control on the stack equivalent complex conductivity. These results are very promising for the development of THz and mid-infrared plasmonic devices with enhanced performance and reconfiguration capabilities.

Plane wave excitation-detection of non-resonant plasmons along finite-width graphene strips.

An approach to couple free-space waves and non-resonant plasmons propagating along graphene strips is proposed based on the periodic modulation of the graphene strip width. The solution is technologically very simple, scalable in frequency, and provides customized coupling angle and intensity. Moreover, the coupling properties can be dynamically controlled at a fixed frequency via the graphene electrical field effect, enabling advanced and flexible plasmon excitation-detection strategies. We combine a previously derived scaling law for graphene strips with leaky-wave theory borrowed from microwaves to achieve rigorous and efficient modeling and design of the structure. In particular we analytically derive its dispersion, predict its coupling efficiency and radiated field structure, and design strip configurations able to fulfill specific coupling requirements. The proposed approach and developed methods are essential to the recent and fundamental problem of the excitation-detection of non-resonant plasmons propagating along a continuous graphene strip, and could pave the way to smart all-graphene sensors and transceivers.

Graphene-based plasmonic switches at near infrared frequencies.

The concept, analysis, and design of series switches for graphene-strip plasmonic waveguides at near infrared frequencies are presented. Switching is achieved by using graphene's field effect to selectively enable or forbid propagation on a section of the graphene strip waveguide, thereby allowing good transmission or high isolation, respectively. The electromagnetic modeling of the proposed structure is performed using full-wave simulations and a transmission line model combined with a matrix-transfer approach, which takes into account the characteristics of the plasmons supported by the different graphene-strip waveguide sections of the device. The performance of the switch is evaluated versus different parameters of the structure, including surrounding dielectric media, electrostatic gating and waveguide dimensions.

Zygosaccharomyces bailii inactivation by means of UV light and low-frequency ultrasound treatments.

Zygosaccharomyces bailii inactivation suspended in apple juice was evaluated under the effects of selected treatments: short-wave UV light (UVC, using one or two lamps), or low-frequency ultrasound (US), or their simultaneous combination. US treatments (20 kHz, 120-µm wave amplitude) were performed at 35°C in a double-wall vessel by using a 13-mm probe. The UVC device consists of two 90-cm-long stainless steel tubes with 40-W UVC lamps covered with quartz tubes, each one inside a stainless steel tube (annular inside diameter of 2.6 cm) connected to a peristaltic pump. Inoculated systems were recirculated through individual or simultaneous US and UVC treatments, samples were taken periodically, and yeast survivors were determined by the plate-count technique. Yeast survival curves demonstrated that UVC alone or in combination with US produced higher inactivation than US alone. Survival curves were appropriately described by the Weibull distribution of resistances model, obtaining model parameter values that adequately reflected the effect of the studied treatments. For every tested case, the distribution of resistances model revealed an absence of mode, while mean values and variances decreased when simultaneous UVC irradiation with two lamps and US were applied, reaching a 7-log cycle reduction after 40 min of treatment. Combined treatment was more effective than individual US or UVC treatments.

Varón con hipertensión arterial, lesión cutánea y nódulos esplénicos / No disponible

No disponible

[Idiopathic myelofibrosis with cutaneous extramedullary hematopoiesis]. / Mielofibrosis idiopática con hematopoyesis extramedular cutánea.

Idiopathic myelofibrosis is a chronic myeloproliferative syndrome characterized by the proliferation of the three hemopoietic series and the marrow connective tissue and the development of extramedullary hemopoiesis in the liver and spleen. Cutaneous extramedullary hemopoiesis is and uncommon finding, and only thirteen cases have been reported up to now. We report the first case in the Spanish literature. The patient was a 78-year-old male in whom skin lesions preceded the diagnosis of myelofibrosis. These lesions, consisting of violet coloured maculae and papulae, contained elements from the three hemopoietic series. Therapy with hydroxyurea was started, but the patient died because of cardiorespiratory complications.

[Amyloid arthropathy associated with multiple myeloma]. / Artropatía amiloide asociada a mieloma múltiple.

Amyloidosis as a complication of patients afflicted with multiple myeloma only arose in 15% of the cases. The articular localization is particularly rare, the clinical findings being similar to rheumatoid arthritis. A case of amyloid arthritis associated to Bence-Jones myeloma, kappa type, is presented and the literature is reviewed.