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The title compound was prepared from 1-phenyl-5-thione-1,2,3,4-tetrazole and triphenyltin(IV) hydroxide and its crystal structure was determined by X-ray diffraction. The lattice is formed by discrete molecules that contain the tin atom coordinated to three phenyl groups and to the tetrazole via the deprotonated -SH group in a distorted tetrahedral coordination polyhedron. There is evidence of a very weak intramolecular interaction between N(4) of the tetrazole and the Sn atom. 13C and 15N NMR studies (CDCl3) suggest that in solution the tetrazole is also in the deprotonated thiol form, and binds to the tin via its S atom.

Nanoscale metallic barriers embedded in terahertz (THz) slot antennas are shown to provide unprecedented control of the transition state arising at the crossover between the full- and half-wavelength resonant modes of such antennas. We demonstrate strong near-field coupling between two paired THz slot antennas separated by a 5 nm wide nanobarrier, almost fully inducing the shift to the resonance of the double-length slot antenna. This increases by a factor of 50 the length-scale needed to observe similar coupling strengths in conventional air-gap antennas (around 0.1 nm), making the transition state readily accessible to experiment. Our measurements are in good agreement with a quantitative theoretical modeling, which also provides a simple physical picture of our observations. © 2011 American Chemical Society.

We show that sub-skin depth nanoscale barriers separating two vertically aligned slot antennas can strongly modulate their resonance features. Our findings have fundamental implications for the sensitive nano-particle detections using long wavelength light.

Laparoscopic gastric plication, a new bariatric procedure: report of one case Bariatric surgery is an effective treatment for morbid obesity. Various techniques have been developed with different outcomes and complications. A new technique with promising results recently described in the literature: the gastric plication, which would not have the complications of using mechanical suture and would imply a reduction of costs. We report the fi rst case in Chile under this technique.

We report on the experimental observation of speckle formation from a transparent crystal formed by a random distribution of nonlinear domains. The angular distribution of second-harmonic light generated by a transparent strontium barium niobate crystal is measured for different diameters of the fundamental beam and crystal thicknesses. Distinct manifestations of speckle pattern formation are found in these experiments. By using a theoretical Green’s function formalism, we explain the reported observations as a result of the linear interference among the second-harmonic waves generated in all directions by each of the nonlinear domains forming the nonlinear crystal.

4 páginas, 3 figuras.-- PACS numbers: 41.20.Jb, 42.25.Fx, 42.79.Ag.-- et al., We investigate band formation in one-dimensional periodic arrays of rectangular holes which have a nanoscale width but a length of 100 μm. These holes are tailored to work as resonators in the terahertz frequency regime. We study the evolution of the electromagnetic response with the period of the array, showing that this dependence is not monotonic due to both the oscillating behavior of the coupling between holes and its long-range character., The experimental work was supported by the Korea Science and Engineering Foundation (KOSEF) (SRC, No. R11-2008-095-01000-0), the Korea Research Foundation (KRF), KICOS (GRL, K20815000003), Hi Seoul Science/Humanities grant funded by the Korea government (MEST) (No. 2009-0071309), the Seoul R&BD Program (10543), and Seoul Scholarship Foundation. The theory work was funded by the Spanish Ministry of Science and Innovation under Projects No. MAT2008- 06609-C02, No. CSD2007-046-NanoLight.es, and by Grant No. RyC-2009-05489.

We show that the weak second harmonic light generated from a random distribution of nonlinear domains of transparent Strontium Barium Niobate crystals can display a particularly intense generation in the forward direction. By using a theoretical model able to analyze the optical response of arbitrary distributions of three-dimensional nonlinear volumes of any shape, we found that the physical origin of this observation can be explained in terms of the scattering of light by a single nonlinear domain.

[Cp(*)RhCl(PTA)(2)]X (PTA = 7-phospha-1,3,5-triazaadamantane) undergoes an H/D exchange process between the methyl groups of Cp(*) and D(2)O whose rate depends on the coordinating ability of the counterion X(-). Kinetic studies and DFT calculations indicate that deuteration involves the abstraction of a Me-Cp(*) proton by a coordinated OH(-); the formation of the latter seems to be facilitated by the presence of the N-basic centers of PTA.

The second-harmonic generation from transparent strontium-barium niobate crystals is experimentally studied and explained from the emission patterns of randomly scattered nonlinear domains and the far field interference of the light generated from such domains.

A family of cationic and neutral highly water-soluble rhodium complexes [Cp∗Rh(PTA) 3 ]Cl 2 ( 1 ), [Cp∗RhCl 2 (THP)] ( 2 ), [Cp∗RhCl(THP) 2 ]Cl ( 3 ), and [Cp∗RhCl(PTA)(THP)]Cl ( 4 ) have been synthesised and fully characterised [PTA = 1,3,5-triaza-7-phosphaadamantane; THP = tris(hydroxymethyl)phosphine]. Their water-solubility increases as the number of the phosphines coordinated to the metal centre is increased. The X-ray crystal structure of compound 2 was obtained and shows the presence of intermolecular hydrogen bonding. NMR speciation studies of [Cp∗RhCl 2 (PTA)] in deuterated water show the existence of several equilibria involving substitution processes in which the water molecules can substitute both chloride and PTA ligands.

We propose a scheme for efficient cavity-enhanced nonlinear THz generation via difference-frequency generation (DFG) processes using a triply resonant system based on photonic crystal cavities. We show that high nonlinear overlap can be achieved by coupling a THz cavity to a doubly-resonant, dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam cavity, allowing the mixing of three mutually orthogonal fundamental cavity modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory that complete depletion of the pump frequency - i.e., quantum-limited conversion - is possible in an experimentally feasible geometry, with the operating output power at the point of optimal total conversion efficiency adjustable by varying the mode quality (Q) factors.

Background In March 2009, public health surveillance detected increased numbers of influenza-like illness presenting to hospitals in Mexico City. The aetiological agent was subsequently determined to be a novel influenza A (H1N1) triple reassortant, which has spread worldwide. As a consequence the World Health Organisation has declared the first Influenza pandemic of the 21st century. Objectives To describe clinically and molecularly the first outbreak of influenza A pH1N1 (2009) during 1–5 May to establish a baseline of epidemiological data for pH1N1. Also, to monitor for the emergence of antiviral resistance, and mutations affecting virulence and transmissibility. Study design Samples were collected from 751 patients with influenza-like symptoms throughout Mexico City and were tested for influenza A pH1N1 (2009) using real-time PCR. In the samples that were positive for influenza A pH1N1 (2009) fragments from the haemagglutinin (H1) and neuraminidase (N1) genes were sequenced. Results A total of 203/751 (27%) patients were positive for the pandemic H1N1 (2009) virus (53% male and 47% female). The 0–12-year-old group was the most affected 85/751 (42%). Sequence analysis showed five new variants of the pandemic H1N1 (2009) virus for NA: G249E (GQ292900), M269I (GQ292892), Y274H (GQ292913), T332A (GQ292933), N344K (GQ292882), and four variants for HA: N461K (GQ293006), K505R (GQ292989), I435V (GQ292995), I527N (GQ292997). Conclusions We have provided a baseline of epidemiological data from the first outbreak of influenza A pH1N1 (2009) during 1–5 May in Mexico City. The sequencing of partial fragments of the HA and NA genes did not show the presence of previously described mutations affecting known sites of antiviral resistance in seasonal influenza A such as the H275Y (oseltamivir resistance), R293 or N295 etc.

Hydrido complexes [MnH(CO)3L1–3] [L1 = 1,2-bis-(diphenylphosphanoxy)-ethane (1); L2 = 1,2-bis-(diisopropylphosphanoxy)ethane (2); L3 = 1,3-bis-(diphenylphosphanoxy)-propane (3)] were prepared by treating [MnH(CO)5] with the appropriate bidentate ligand by heating to reflux. Photoirradiation of a toluene solution of complexes 1 and 2 in the presence of PPhn(OR)3–n (n = 0, 1; R = Me, Et) leads to the replacement of a CO ligand by the corresponding monodentate phosphite or phosphonite ligand to give new hydrido compounds of formula [MnH(CO)2(L1–2)(L)] [L = P(OMe)3 (1a–2a); P(OEt)3 (1b–2b); PPh(OMe)2 (1c–2c); PPh(OEt)2 (1d–2d)]. All complexes were characterized by IR, 1H, 13C and 31P NMR spectroscopy. In case of compounds 2 and 3, suitable crystals for X-ray diffraction studies were isolated.

Achieving efficient terahertz (THz) generation using compact turn-key sources operating at room temperature and modest power levels represents one of the critical challeges that must be overcome to realize truly practical applications based on THz. Up to now, the most efficient approaches to THz generation at room temperature -- relying mainly on optical rectification schemes -- require intricate phase-matching set-ups and powerful lasers. Here we show how the unique light-confining properties of triply-resonant photonic resonators can be tailored to enable dramatic enhancements of the conversion efficiency of THz generation via nonlinear frequency down-conversion processes. We predict that this approach can be used to reduce up to three orders of magnitude the pump powers required to reach quantum-limited conversion efficiency of THz generation in nonlinear optical material systems. Furthermore, we propose a realistic design readily accesible experimentally, both for fabrication and demonstration of optimal THz conversion efficiency at sub-W power levels.

"En una primera parte se ofrece una distinción teórica entre la comunicación social y gubernamental, para posteriormente hacer una descripción de la comunicación gubernamental durante el sexenio de Vicente Fox. El artículo remata con el uso que la administración foxista hizo de los tiempos oficiales y el gasto sexenal en comunicación gubernamental."

We develop a theoretical framework for second-order nonlinear difference frequency generation in triply resonant wavelength-scale cavities, demonstrating stable CW conversion with quantum-limited efficiency. We propose a scheme for efficient THz generation based on this framework.

[TpRuCl(PTA)(PPh3)] (1; PTA = l,3,5-triaza-7-phosphaadamantane) reacts with phenylacetylene, yielding the alkynyl complex [TpRu(C≡CPh) (PTA)(PPh3)] (2) or the neutral vinylidene complex [TpRuCl{C=C(H)Ph}(PTA)] (4), depending on the solvent and the reaction conditions (Tp = hydrotris(pyrazolyl)borate). Protonation of 2 with HOTf(OTf = OSO2CF3) in CH2Cl2 yields the dicationic vinylidene compound [TpRu{C=C(H)Ph}{PTAH}(PPh3)](OTf) 2 (3), bearing a N-protonated PTA ligand. Reaction of 1 with 1,1-diphenyl-2-propyn-l-ol affords the new cationic compound [TpRu(C=C=CPh 2)(PTA)(PPh3)]PF6 (5) or neutral allenylidene compound [TpRuCl(C=C = CPh2)(PTA)] (6), depending on the reaction solvent (MeOH or toluene, respectively). The reactivity of complexes 5 and 6 toward tertiary phosphines (PTA and PPh2Me) has been investigated. Remarkably, both the cationic and the neutral allenylidene compounds undergo regioselective nucleophilic attack at the allenylidene Ca position to give the cr-allenyl-phosphonium complexes [TpRu{C(L)=C=CPh2}(PTA)(PPh 3)]PF6 (L = PPh2Me (8), PTA (9)) and [TpRuCl{C(L)= C=CPh2)(PTA)] (L = PTA (10), PPh2Me (11)), respectively. Noticeably, the reaction goes to completion in the case of the neutral allenylidene complex 6, whereas an equilibrium between the phosphonioallenyl adduct and the educt species is observed in the case of the cationic allenylidene compound 5. The thermodynamic parameters for such an equilibrium have been determined by NMR methods at different temperatures. Finally, the hydrolysis of the neutral allenylidene 6 has been briefly considered, showing the formation of the carbonyl compound [TpRuCl(CO)(PTA)] (7). © 2009 American Chemical Society., We obtained financial support from the Xunta de Galicia (Project CITE08PXIB314206PR) and the Spanish MCINN (Project Consolider Ingenio CSD2007-00006).

In this letter we theoretically demonstrate that by dramatically enhancing two-photon absorption, all-silicon optical microresonators can act as efficient photodetectors for light at telecom wavelengths. We illustrate this approach with two specific designs based on a ring resonator and a photonic crystal cavity. The proposed scheme is fully compatible with standard silicon complementary metal-oxide-semiconductor processing technology, and thus, could contribute to the development of chip-scale integrated photodetectors based exclusively on silicon.

We investigate transmission efficiency and finite size effects for the subwavelength hole arrays. Experiments and simulations show how the finite size effects depend strongly on the hole diameter. The transmission efficiency reaches an asymptotic upper value when the array is larger than the surface plasmon propagation length on the corrugated surface. By comparing the transmission of arrays with that of the corresponding single holes, the relative enhancement is found to increase as the hole diameter decreases. In the conditions of the experiments the enhancement is one to two orders of magnitude but there is no fundamental upper limit to this value.

Esta tecnica no tuvo el exitoesperado inicialmente por ser un procedimientocomplejo que tiene una larga curva de aprendizaje,un mayor tiempo operatorio, instrumentacion cos-tosa y necesidad de incisiones para la extraccionde la pieza operatoria. Ademas, existian dudasacerca de la laparoscopia como procedimientooncologicamente seguro y efectivo

The self-aggregation tendency of RAPTA complexes {[Ru(?6-p-cymene){PTA(-R)}Cl2]X, R ) H (1BPh4 and 1PF6) and Me (2BPh4 and 2OTf), and [Ru(?6-p-cymene)(PTA)2Cl]X (3BPh4 and 3BF4)} in acetone-d6 was inVestigated by means of diffusion NMR spectroscopy. On increasing the concentration, the protonated species (1X) undergoes intercationic self aggregation driVen by hydrogen bonding that leads to the formation of 12 2+ dications and a small amount of 12X+ ion triples

The reaction between 1-boranyl-1,3,5-triaza-7-phosphaadamantane ligand N – B –PTA(BH 3 ) and [Cp ∗ RhCl(μ-Cl)] 2 affords [Cp ∗ Rh{ N – B –PTA(BH 3 )}Cl 2 ] ( 3 ) or [Cp ∗ Rh{ N – B –PTA(BH 3 )} 2 Cl]Cl ( 5 ) containing one or two P-bonded boronated PTA ligands. The hydride [Cp ∗ Rh{ N – B –PTA(BH 3 )}H 2 ] ( 8 ) was also obtained by reaction of 3 with NaBH 4 and alternatively by direct hydroboration of [Cp ∗ Rh(PTA)Cl 2 ] with excess NaBH 4 . Moderately slow hydrolysis of the N-boranyl rhodium complexes affords dihydrogen, H 3 BO 3 and the corresponding PTA derivatives, including the water-soluble dihydride [Cp ∗ Rh(PTA)H 2 ] ( 9 ). Finally, the reaction of 8 with electron poor alkynes gives the alkene complexes [Cp ∗ Rh{ N – B –PTA(BH 3 )}(η 2 -CH 2 = CHR)] (R = Ph, 10 ; C(O)OEt, 11 ) as a mixture of rotamers η 2 -coordinated to rhodium without affecting the N–BH 3 moiety. The X-ray crystal structures of 3 and 10 were also obtained and are here discussed.

By using a theoretical formalism able to work in both real and k-spaces, the physical origin of the phenomenon of extraordinary transmission of light through quasi-periodic arrays of holes is revealed. Long-range order present in a quasiperiodic array selects the wavevector(s) of the surface electromagnetic mode(s) that allows an efficient transmission of light through subwavelength holes., 4 pages, 4 figures

We show that Weyl points can be realized in all-dielectric superlattices based on three-dimensional (3D) layered photonic crystals. Our approach is based on creating an inversion-breaking array of weakly-coupled planar defects embedded in a periodic layered structure with a large omnidirectional photonic band gap. Using detailed band structure calculations and tight-binding theory arguments, we demonstrate that this class of layered systems can be tailored to display 3D linear point degeneracies between two photonic bands, without breaking time-reversal symmetry and using a configuration that is readily-accessible experimentally. These results open new prospects for the observation of Weyl points in the near-infrared and optical regimes and for the application of Weyl-physics in integrated photonic devices., Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (W911NF-13-D-0001), United States. Dept. of Energy. Office of Basic Energy Sciences (DE- SC0001299), National Science Foundation (U.S.) (DMR-1419807

The theoretical fundamentals of the so called zero velocity Mössbauer spectroscopy is presented to measure the nuclear resonance thickness at zero velocity and total area for nuclear resonance absorption of a given sample in the transmission mode. The methodology to take and analyze the experimental data is presented, including instrumental parameters and the uncertainty in the results, using triangular and sinusoidal signals., Se presenta la base teórica que sustenta la denominada espectroscopia Mössbauer de velocidad cero para medir el espesor resonante nuclear a velocidad cero y el área total para absorción resonante nuclear de una muestra dada en la modalidad de transmisión. Se presenta la metodología para tomar y analizar los datos experimentales, incluyendo parámetros instrumentales y la incertidumbre en los resultados, utilizando señales de forma triangular y sinusoidal.

4 pages, 4 figures.-- et al., The extraordinary optical transmission through periodic arrays of subwavelength holes has been studied extensively since it was first reported in 1998, owing to both its fundamental implications and its technological potential. The picture of the underlying mechanism that emerges from most of the theoretical studies is a resonant process assisted by surface electromagnetic modes, such as surface plasmons. However, these studies consider an infinite array of holes. By combining experiment and theory, we have analysed the influence of the inherent finite size of the arrays and report here the unexpected spatial distribution of light as it emerges from the arrays. This distribution is strongly anisotropic and extremely sensitive to the angle of incidence of the impinging light. The behaviour can be explained by a model that takes into account the asymmetry induced by the array edges, and the effects this has on the emission pattern across the array., Financial support by the EC under Project Nos. FP6-NMP4-CT-2003-505699 (Surface Plasmon Photonics) and FP6-2002-IST-1-507879 (Plasmo-Nano-Devices) is gratefully acknowledged.

Surface plasmons (SPs) have long been known to be able to guide light on the surface of a metal and to concentrate light in subwavelength volumes. But another functionality of SPs was added to the previous list in 1998, when Ebbesen and coworkers found that SPs could enhance the transmission of light passing through subwavelength holes. Seminal paper reported that, when a metal film is perforated with subwavelength holes and these are arranged in a two-dimensional (2D) periodic array, the transmission of light is greatly enhanced at some particular wavelengths. The experimental spectral location of transmission peaks was found to be related to the dispersion relation of SPs modes running on the metal surface. This chapter establishes a close connection between the extraordinary optical transmission (EOT) and the excitation of SPs. Since 1998, several experimental and theoretical groups around the world have reproduced the main features present in the first set of experiments. The influence of the metal forming the structure and the dependence of EOT with the lattice symmetry (square or triangular), hole shape (circular, elliptical, square, or rectangular) and frequency regime (optical, THz, or microwave) have been thoroughly analyzed. This chapter summarizes the theoretical results on the EOT (in both 2D hole arrays and single apertures) and beaming from single apertures, concentrating on the basic physics behind these phenomena.

Hydroxylamine and O-methylhydroxylamine complexes [M(NH 2 OH)(CO) n P 5-n ]BPh 4 and [M(NH 2 OCH 3 )(CO) n P 5-n ]-BPh 4 [M = Mn, Re; n = 1, 2, 3; P = P(OEt) 3 , PPh(OEt) 2 , PPh 2 OEt] were prepared by allowing hydrides MH(CO) n -P 5-n to react first with triflic acid and then with an excess of hydroxylamine. Bidentate phosphane and phosphite can also be used to prepare both NH 2 OH and NH 2 OCH 3 complexes of manganese and rhenium of the [M(NH 2 OR)(CO) 2 (P-P)-{P(OEt) 3 }]BPh 4 and [M(NH 2 OR)(CO) 3 (P-P)]BPh 4 [R = H, CH 3 ; P-P = Ph 2 POCH 2 CH 2 OPPh 2 , Ph 2 PO(CH 2 ) 3 OPPh 2 , Ph 2 PN-(CH 3 )CH 2 CH 2 N(CH 3 )PPh 2 ] types with the use of MH(CO) 2 -(P-P)(P(OEt) 3 } and MH(CO) 3 (P-P) as precursors. The complexes were characterized spectroscopically and by the X-ray crystal-structure determination of [Re(NH 2 OCH 3 )(CO) 2 -{PPh(OEt) 2 } 3 ]BPh 4 and [Re(NH 2 OCH 3 )(CO) 3 {Ph 2 PO(CH 2 ) 3 -OPPh 2 }]BPh 4 . Oxidation of the hydroxylamine complexes with Pb(OAc) 4 was studied at -40 °C and led to an unstable compound tentatively characterized as a nitroxyl [M]- N(H)=O derivative.

7 pages, 5 figures., In this paper, we study how extraordinary transmission through an array of holes in a metallic film appears as a function of the number of holes and their distribution. We have used a theoretical formalism able to analyze the optical properties of finite collections of apertures placed at arbitrary positions in a metallic film. First, we describe how the total transmission in a hexagonal two-dimensional hole array evolves as the number of holes in the array is increased. Second, we study the extraordinary transmission appearing in a single one-dimensional chain of holes. We find that the transmission through this structure is very sensitive to the incident polarization. Third, we show that a single hole flanked symmetrically by two finite chains of dimples can also present extraordinary transmission properties., This work was supported in part by the Spanish MCyT under Grant BES-2003-0374, Contract MAT2002-01534, and Contract MAT2002-00139, and in part by the European Commission (EC) under Project FP6-2002-IST-1-507879 and Project FP6-NMP4-CT-2003-505699.

In this work, we study how extraordinary electromagnetic transmission through an array of holes in a metallic film appears as a function of the number of holes and their distribution. In order to do that, we have used a theoretical formalism able to analyze the optical properties of finite collections of apertures placed at arbitrary positions in a metallic film. First, we analyze how the total transmission in a hexagonal 2D hole array evolves as the number of holes in the array is increased. Secondly, we study what is the minimal system showing extraordinary electromagnetic transmission. We find numerically that a linear chain of holes can be considered as the basic entity with extraordinary transmission properties.

Lattice surface plasmons enable large-area unidirectional emission of coherent light generated at deep subwavelength scales.

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.

In this paper we explore the transmission properties of single subwavelength apertures perforated in thin metallic films flanked by asymmetric configurations of periodic arrays of indentations. It is shown how the corrugation in the input side can be used to transmit selectively only two different wavelengths. Also, by tuning the geometrical parameters defining the corrugation of the output side, these two chosen wavelengths can emerge from the structure as two very narrow beams propagating at well-defined directions. This new ability of structured metals can be used as a base to build micron-sized wavelength de-multiplexers., Comment: Accepted for publication in Photonics and Nanostructures

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 to the emergence of different propagating modes inside the slit are the main features appearing in this regime., Comment: Accepted for publication in Phys. Rev. E

In this letter we explore, both experimentally and theoretically, the existence in the millimeter wave range of the phenomenon of extraordinary light transmission though arrays of subwavelength holes. We have measured the transmission spectra of several samples made on aluminum wafers by using an AB Millimetre Quasioptical Vector Network Analyzer in the wavelength range between 4.2mm to 6.5mm. Clear signals of the existence of resonant light transmission at wavelengths close to the period of the array appear in the spectra., Comment: To be published in Optics Letters

When rows of cylinders are periodically removed from a hexagonal array of dielectric cylinders, a new two-dimensional (2D) photonic crystal (PC) arises. The new structure consists of a lattice of vacancies embedded in the initial hexagonal lattice. We called it Suzuki Phase because it remains similar structures discovered in the 60's by K. Suzuki studying alkali halides. A plane-wave algorithm as well as a 2D finite difference-time-domain method has been employed to study the photonic properties of this PC as a function of the filling fraction (f) in the case of high dielectric cylinders ((epsilon) equals 13.6) in air. For TM- modes, it is shown that in a certain range of f an isolated miniband appears in the gap of the initial hexagonal lattice. The miniband, which is created by the coupling of defect states, is described by a tight-binding formalism with two parameters. Also, the frequencies of the two possible vacancy defects in the SP have been obtained and their symmetry analyzed.

Transmission of light through linear defects in two-dimensional (2D) photonic crystals has been already successfully demonstrated in two ways: numerical simulations and experimental measurements. Recently, novel waveguides have been proposed in which the propagation of photons is performed via hopping due to overlapping between nearest-neighbors defect cavities. These waveguides are commonly referred to as coupled-cavity waveguides (CCW). In this work, we present a comprehensive analysis of the light transmission (TM modes) in CCW's created in hexagonal 2D photonic crystals made of high-index dielectric rods. Numerical simulations of the transmission are performed using a 2D Finite-Difference Time-Domain method. A plane wave algorithm and a simple one-dimensional (1D) tight-binding model are employed to describe the miniband which allows the light transport. It is shown that modifying the individual cavities along the CCW one can control the average frequency and the dispersion relation of the miniband. The results also show that this novel guiding method can be used to develop 1310nm/1550nm Coarse-WDM optical demultiplexers employing bended waveguides.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this Letter we introduce a novel route for achieving negative-group-velocity waveguiding at deep-subwavelength scales. Our scheme is based on the strong electromagnetic coupling between two conformal surface plasmon structures. Using symmetry arguments and detailed numerical simulations, we show that the coupled system can be geometrically tailored to yield negative-index dispersion. A high degree of subwavelength modal confinement, of λ/10 in the transversal dimensions, is also demonstrated. These results can assist in the development of ultrathin surface circuitry for the low-frequency region (microwave and terahertz regimes) of the electromagnetic spectrum.

Organic dye molecules offer significant potential as gain media in the emerging field of optical amplification and lasing at subwavelength scales. Here, we investigate the laser dynamics in systems comprising subwavelength-structured cavities that incorporate organic dyes. To this end, we have developed a comprehensive theoretical framework able to accurately describe the interaction of organic molecules with any arbitrary photonic structure to produce single-mode lasing. The model provides explicit analytic expressions of the threshold and slope efficiency that characterize this class of lasers, and also the duration over which lasing action can be sustained before the dye photobleaches. Both the physical properties of the dyes and the optical properties of the cavities are considered. We also systematically studied the feasibility of achieving lasing action under continuous-wave excitation in optically pumped monolithic organic dye lasers. This study suggests routes to realize an organic laser that can potentially lase with a threshold of only a few W cm⁻². Our work puts forward a theoretical formalism that could enable the advancement of nanostructured organic-based light emitting and sensing devices., National Science Foundation (U.S.) (DMR-0819762), Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (W911NF-13-D-0001), Solid-State Solar-Thermal Energy Conversion Center (DE-SC0001299)

Diffusive random lasers, whose mechanism has been elusive, are now explained by a general theory that encompasses conventional lasers.

Photonic crystal resonators present unique properties for confining light in volumes much smaller than the wavelength. The ultrafast dynamic change of these properties is an important step towards the complete control of light.