PubMed Health⌕ Search

Biomedical subjects

L Martín-Moreno

Publications and source records attributed to L Martín-Moreno.

At least 19 recordsLinked to original sources
PubMed2006

Terahertz surface plasmon-polariton propagation and focusing on periodically corrugated metal wires.

In this Letter, we show how the dispersion relation of surface plasmon polaritons (SPPs) propagating along a perfectly conducting wire can be tailored by corrugating its surface with a periodic array of radial grooves. In this way, highly localized SPPs can be sustained in the terahertz region of the electromagnetic spectrum. Importantly, the propagation characteristics of these spoof SPPs can be controlled by the surface geometry, opening the way to important applications such as energy concentration on cylindrical wires and superfocusing using conical structures.

Journal Article↗
PubMed2005

Resonant transmission of cold atoms through subwavelength apertures.

Recently, it has been observed that transmission of light through subwavelength apertures, which is usually negligible, can be significantly enhanced when surface plasmons are resonantly excited. Here we introduce the idea that similar effects can be expected for cold atoms in structures supporting surface matter waves. We show that surface matter waves are possible in properly designed structures, and then we theoretically demonstrate 100% transmission of rubidium atoms through an array of slits much narrower than the de Broglie wavelength of the atoms. Our results open up the possibility of using surface matter waves to control the flow of neutral atoms.

Journal Article↗
PubMed2005

Transmission of light through a single rectangular hole.

We show that a single rectangular hole in a metallic film exhibits transmission resonances that appear near the cutoff wavelength of the hole waveguide. For light polarized with the electric field pointing along the hole's short axis, it is shown that the normalized-to-area transmittance at resonance is proportional to the ratio between the long and short sides, and to the dielectric constant inside the hole. Importantly, this resonant transmission process is accompanied by a huge enhancement of the electric field at both entrance and exit interfaces of the hole.

Journal Article↗
PubMed2004

Resonant transmission of light through finite chains of subwavelength holes in a metallic film.

In this Letter we show that the extraordinary optical transmission phenomenon found before in 2D hole arrays is already present in a linear chain of subwavelength holes, which can be considered as the basic geometrical unit showing this property. In order to study this problem, we have developed a new theoretical framework, able to analyze the optical properties of finite collections of subwavelength apertures and/or dimples (of any shape and placed in arbitrary positions) drilled in a metallic film.

Journal Article↗
PubMed2004

Enhanced millimeter-wave transmission through subwavelength hole arrays.

We explore, both experimentally and theoretically, the existence in the millimeter-wave range of the phenomenon of extraordinary light transmission through arrays of subwavelength holes. We have measured the transmission spectra of several samples made on aluminum wafers by use of an AB Millimetre quasi-optical vector network analyzer in the wavelength range 4.2-6.5 mm. Clear signals of the existence of resonant light transmission at wavelengths close to the period of the array appear in the spectra.

Journal Article↗
PubMed2004

Mimicking surface plasmons with structured surfaces.

Metals such as silver support surface plasmons: electromagnetic surface excitations localized near the surface that originate from the free electrons of the metal. Surface modes are also observed on highly conducting surfaces perforated by holes. We establish a close connection between the two, showing that electromagnetic waves in both materials are governed by an effective permittivity of the same plasma form. The size and spacing of holes can readily be controlled on all relevant length scales, which allows the creation of designer surface plasmons with almost arbitrary dispersion in frequency and in space, opening new vistas in surface plasmon optics.

Journal Article↗
PubMed2004

Theory of plasmon-assisted transmission of entangled photons.

The recent surface plasmon entanglement experiment [Nature (London) 418, 304 (2002)]] is theoretically analyzed. The entanglement preservation upon transmission in the nonfocused case is found to provide information about the interaction of the biphoton and the metallic film. The entanglement degradation in the focused case is explained in the framework of a fully multimode model. This phenomenon is a consequence of the polarization-selective filtering behavior of the metallic nanostructured film. It is shown that the "which-way" labels that degrade entanglement are not located in the degrees of freedom of the metallic film but rather in the spatial degrees of freedom of the photon field.

Journal Article↗
PubMed2004

Transmission properties of a single metallic slit: from the subwavelength regime to the geometrical-optics limit.

In this work we explore the transmission properties of a single slit in a metallic screen. We analyze the dependence of these properties on both slit width and angle of incident radiation. We study in detail the crossover between the subwavelength regime and the geometrical-optics limit. In the subwavelength regime, resonant transmission linked to the excitation of waveguide resonances is analyzed. Linewidth of these resonances and their associated electric-field intensities are controlled by just the width of the slit. More complex transmission spectra appear when the wavelength of light is comparable to the slit width. Rapid oscillations associated with the emergence of different propagating modes inside the slit are the main features appearing in this regime.

Journal Article↗
PubMed2003

Multiple paths to enhance optical transmission through a single subwavelength slit.

In this Letter, we explore transmission properties of a single subwavelength slit flanked by a finite array of grooves made on a thick metallic film. We identify three main mechanisms that can enhance optical transmission: groove cavity mode excitation (controlled by the depth of the grooves), in-phase groove reemission (controlled by the period of the groove array), and slit waveguide mode (controlled by the thickness of the metal film). By tuning these geometrical parameters, enhancements of transmission of light by up to 2 orders of magnitude can be achieved when all three mechanisms coincide. Experimental verification of these findings is also shown for structured silver films fabricated by focused-ion-beam milling.

Journal Article↗
PubMed2003

Theory of highly directional emission from a single subwavelength aperture surrounded by surface corrugations.

We present a theoretical foundation for the beaming of light displayed by a single subwavelength aperture in an appropriately corrugated metal film [H. J. Lezec, Science 297, 820 (2002)]]. Good agreement is found between calculations and experimental data. We show that beaming is due to the formation of electromagnetic surface resonances and that the beam direction, width, and wavelength at which it occurs can be selected by tuning geometrical parameters of the structure.

Journal Article↗
PubMed2001

Theory of extraordinary optical transmission through subwavelength hole arrays.

We present a fully three-dimensional theoretical study of the extraordinary transmission of light through subwavelength hole arrays in optically thick metal films. Good agreement is obtained with experimental data. An analytical minimal model is also developed, which conclusively shows that the enhancement of transmission is due to tunneling through surface plasmons formed on each metal-dielectric interface. Different regimes of tunneling (resonant through a "surface plasmon molecule," or sequential through two isolated surface plasmons) are found depending on the geometrical parameters defining the system.

Journal Article↗
PubMed1997

[Clinical significance of the isolation of rapidly growing mycobacteria].

BACKGROUND: To assess the clinical significance of the isolates of rapid-growing mycobacteria in a Universitary hospital from Madrid (Spain). PATIENTS AND METHODS: Review of medical records from patients with isolates of rapid-growing mycobacteria identified between 1979 and 1996 in the Microbiology department of the Fundación Jiménèz Díaz (Madrid, Spain). RESULTS: Rapid-growing mycobacteria were isolated from 28 patients during the study period (13 M. chelonae, 10 M. fortuitum, 2 M. mucogenicum, 1 M. marinum, 1 M. smegmatis and 1 M. flavascens). Clinical records of 26 patients were reviewed, being the isolate significative in 10 cases (5 soft tissue infections, 2 peritonitis in patients undergoing Continuous Ambulatory Peritoneal Dialysis [CAPD], 1 urinary tract infection, 1 osteomyelitis and 1 catheter-related soft-tissue infection). No patient was HIV+. All infections cured except 2 of them (the urinary tract infection and the osteomyelitis). Catheter withdrawal was needed in 3 cases (peritonitis in CAPD and catheter-related soft-tissue infection), apart from proper antimicrobial therapy. CONCLUSION: The most frequent rapid-growing mycobacteria isolated were those of the M. fortuitum complex. In our experience, isolation of rapid-growing mycobacteria from skin and soft-tissue samples was usually clinically significant, while isolates from respiratory tract, gut and blood cultures are always nonsignificant.

Adult↗
PubMed1995

The effect of completeness of medical records on the determination of appropriateness of hospital days.

Although the Appropriateness Evaluation Protocol (AEP) has been widely used during the past decade, several methodological concerns have not yet been properly resolved, including the possible influence of low completeness of the medical records on the results yielded by the AEP in retrospective studies. We examined medical records for a random sample of 345 patient-days with the AEP, according to a protocol that included several variables potentially related to inappropriateness. The completeness of physician and nursing notes was also assessed. The proportion of inappropriate days of hospitalization was 36.2%. In the crude analysis, significantly higher proportions of inappropriateness were found for lower values of completeness. Factors related to the inappropriateness of stay were summer season, elective admission, no previous admissions, surgical and medical-surgical service in charge, and the day sampled falling within the last third of the hospital stay. Adjustment for the completeness level of medical records did not substantially change the strength of the association between these factors and the inappropriateness of hospital stay. Completeness level itself did not show any significant association with the proportion of inappropriate days in the adjusted analysis.

Bias↗