New Piperazine Derivatives Synthesized from Thio-Substituted Polyhalogeno-2-nitro-1,3-butadienes

It is known that polyhalogeno-nitro-1,3-butadienes are important starting materials for the synthesis of polyfunctionalized bioactive heterocycles. Novel N,S-substituted nitrobutadienes (4a-j) were synthesized from the reaction of the monothio-substituted nitrodiene derivatives (2a) and (2b) with some piperazine derivatives. These new compounds are stable and the structures of these products were characterized by spectroscopic data. The structure of the novel N,S-substituted nitrodiene compound (4g) synthesized in this study was also elucidated by single crystal x-ray analysis

Grating based plasmonic band gap cavities

Cataloged from PDF version of article.We report on a comparative study of grating based plasmonic band gap cavities. Numerically, we calculate the quality factors of the cavities based on three types of grating surfaces; uniform, biharmonic and Moiré surfaces. We show that for biharmonic band gap cavities, the radiation loss can be suppressed by removing the additional grating component in the cavity region. Due to the gradual change of the surface profile in the cavity region, Moiré type surfaces support cavity modes with higher quality factors. Experimentally, we demonstrate the existence of plasmonic cavities based on uniform gratings. Effective index perturbation and cavity geometries are obtained by additional dielectric loading. Quality factor of 85 is obtained from the measured band structure of the cavity. © 2009 Optical Society of America

Critical coupling in plasmonic resonator arrays

Cataloged from PDF version of article.We report critical coupling of electromagnetic waves to plasmonic cavity arrays fabricated on Moire surfaces. Dark field plasmon microscopy imaging and polarization dependent spectroscopic reflection measurements reveal the critical coupling conditions of the cavities. The critical coupling conditions depend on the superperiod of the Moire surface, which also defines the coupling between the cavities. Complete transfer of the incident power can be achieved for traveling wave plasmonic resonators, which have a relatively short superperiod. When the superperiod of the resonators increases, the coupled resonators become isolated standing wave resonators in which complete transfer of the incident power is not possible. Analytical and finite difference time domain calculations support the experimental observations. (C) 2011 Optical Society of Americ

XPS investigation of thin SiOx and SiOxNy overlayers

Cataloged from PDF version of article.Angle-resolved XPS is used to determine the thickness and the uniformity of the chemical composition with respect to oxygen and nitrogen of the very thin silicon oxide and oxynitride overlayers grown on silicon. (C) 1999 Elsevier Science B.V. All rights reserved

Trap levels in layered semiconductor Ga2SeS

Cataloged from PDF version of article.Trap levels in nominally undoped Ga2SeS layered crystals have been characterized by thermally stimulated current (TSC) measurements. During the measurements, current was allowed to flow along the c-axis of the crystals in the temperature range of 10-300 K. Two distinct TSC peaks were observed in the spectra, deconvolution of which yielded three peaks. The results are analyzed by curve fitting, peak shape and initial rise methods. They all seem to be in good agreement with each other. The activation energies of three trapping centers in Ga2SeS are found to be 72, 100 and 150 meV. The capture cross section of these traps are 6.7 x 10(-23), 1.8 x 10(-23) and 2.8 x 10(-22) cm(2) with concentrations of 1.3 x 10(12), 5.4 x 10(12) and 4.2 x 10(12) cm(-3), respectively. (C) 2004 Elsevier Ltd. All rights reserved

Infrared luminescence of annealed germanosilicate layers

Cataloged from PDF version of article.In the light of growing importance of semiconductor nanocrystals for photonics, we report on the growth and characterization of annealed germanosilicate layers used for Ge nanocrystal formation. The films are grown using plasma enhanced chemical vapor deposition (PECVD) and post-annealed in nitrogen at temperatures between 600 and 1200 degrees C for as long as 2 h. Transmission electron microscopy (TEM), Raman scattering and photoluminescence spectroscopy (PL) has been used to characterize the samples both structurally and optically. Formation of Ge precipitates in the germanosilicate layers have been observed using Raman spectroscopy for a variety of PECVD growth parameters, annealing temperatures and times. Ge-Ge mode at similar to 300 cm(-1) is clearly observed at temperatures as low as 700 degrees C for annealing durations for 45 min. Raman results indicate that upon annealing for extended periods of time at temperatures above 900 degrees C; nanocrystals of few tens of nanometers in diameter inside the oxide matrix and precipitation and interdiffusion of Ge, forming SiGe alloy at the silicon and oxide interface take place. Low temperature PL spectroscopy has been used to observe luminescence from these samples in the vicinity of 1550 nm, an important wavelength for telecommunications. Observed luminescence quenches at 140 K. The photoluminescence data displays three peaks closely interrelated at approximately 1490,, 1530 and 1610 nm. PL spectra persist even after removing the oxide layer indicating that the origin of the infrared luminescent centers are not related to the Ge nanocrystals in the oxide layer. (C) 2013 Elsevier B.V. All rights reserved

Effect of Composition on the Spontaneous Emission Probabilities, simulated Emission Cross Sections and Local Environment of Tm+3, in Teo2-Wo3 Glass'

Cataloged from PDF version of article.Effect of composition on the structure, spontaneous and stimulated emission probabilities of various 1.0 mol% Tm2O3 doped (1 - x)TeO2 + (x)WO3 glasses were investigated using Raman spectroscopy, ultraviolet-visible-near-infrared (UV/VIS/NIR) absorption and luminescence measurements. Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f-4f transitions of Tm3+ ions. Six absorption bands corresponding to the absorption of the (1)G(4), F-3(2), F-3(3) and F-3(4), H-3(5) and H-3(4) levels from the H-3(6) ground level were observed. Integrated absorption cross-section of each band except that of H-3(5) level was found to vary with the glass composition. Luminescence spectra of the samples were measured upon 457.9 nm excitation. Three emission bands centered at 476 nm ((1)G(4) --> H-3(6) transition), 651 nm ((1)G(4) --> H-3(4) transition) and 800 nm ((1)G(4) --> H-3(5) transition) were observed. Spontaneous emission cross-sections together with the luminescence spectra measured upon 457.9 nm excitation were used to determine the stimulated emission cross-sections of these emissions. The effect of glass composition on the Judd-Ofelt parameters and therefore on the spontaneous and the stimulated emission cross-sections for the metastable levels of Tm3+ ions were discussed in detail. The effect of temperature on the stimulated emission cross-sections for the emissions observed upon 457.9 nm excitation was also discussed. (C) 2002 Elsevier Science B.V. All rights reserved

Slowing surface plasmon polaritons on plasmonic coupled cavities by tuning grating grooves

Cataloged from PDF version of article.We investigate slow surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by coupled plasmonic cavities on Moire surfaces. We demonstrate controlling the group velocity and dispersion of the SPPs by varying the depth of the plasmonic Bragg grating groove. Changing the grating depth results in modification of coupling coefficients between the cavities and hence the SPPs group velocity is altered. Variation in the group velocity and dispersion of SPPs can be measured with polarization dependent spectroscopic reflection measurements. Dispersion of SPPs has been calculated by finite-difference time-domain method in agreement with the experimental data. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3495781

Localization of Surface Plasmon Polaritons in Hexagonal Arrays of Moire Cavities

Cataloged from PDF version of article.In view of the progress on the confinement of light, we report on the dispersion characteristics of surface plasmon polaritons (SPPs) on two-dimensional Moire surfaces in the visible part of the electromagnetic spectrum. Polarization dependent spectroscopic reflection measurements show omnidirectional confinement of SPPs. The resonance wavelength of SPP cavity modes can be adjusted by tuning the propagation direction of SPPs. The results may have an impact on the control of spontaneous emission and absorption with applications in light emitting diodes and solar cells, as well as in quantum electrodynamics experiments. (C) 2011 American Institute of Physics. [doi:10.1063/1.3529469

Plexcitonic crystals: a tunable platform for light-matter interactions

Cataloged from PDF version of article.Coupled states of surface plasmon polaritons (SPPs) and excitons are collectively called plexcitons [Nano Lett. 8, 3481 (2008)]. Plexcitonics is an emerging field of research aiming to control light-matter interaction at the nanometer length scale using coupled pairs of surface-plasmons and excitons. Ability to control the interaction between localized excitons and propagating surface-plasmons is important for realization of new photonic devices. In this letter, we report plexcitonic crystals that yield direction-dependent plasmon-exciton coupling. We have fabricated one- and two-dimensional plexcitonic crystals on periodically corrugated silver surfaces, which are loaded with J-aggregate complexes. We show that plasmon-exciton coupling is blocked for some crystal directions when exciton energy falls inside the plasmonic band gap of the periodically corrugated metallic surface. (C) 2014 Optical Society of Americ