Tellurite and phospho-tellurite glasses: candidate materials for fiber Raman amplifiers

The necessity of materials innovation in the field of Raman amplification is reviewed. A new family of tellurite and phospho-tellurite glasses containing heavy metal oxides suitable for ultra-broadband Raman amplification was designed and fabricated. These glasses show enhanced properties than the silica based glasses studied so far for the Raman amplifier application. In addition to the bandwidth, the gain characteristics of these glasses were proved to be much higher than those of the silica based materials. The various structural units which contribute to the overall Raman band were unravelled. Accordingly Raman band engineering was used to tailormake glass compositions with wide continuous Raman bands. This chapter also details the enhanced thermal properties of these glasses suitable for fiber fabrication and the third order nonlinear optical properties which are essential for optical switching and other nonlinear optical effects

Emission from a bismuth doped chalcogenide glass spanning from 1µm to 2.7µm

We report emission from a bismuth doped chalcogenide glass with a full width half maximum of 850 nm. The quantum efficiency and lifetime were 32% and 175 µs. We report two new bismuth emission bands at 2000 and 2600 nm

Field-Induced Quasiparticle Excitation in Ca(Al0.5_{0.5}Si0.5_{0.5})2_2: Evidence for unconventional Superconductivity

The temperature ($T$) and magnetic field ($H$) dependence of the magnetic penetration depth, $\lambda(T,H)$, in Ca(Al$_{0.5}$Si$_{0.5}$)$_2$ exhibits significant deviation from that expected for conventional BCS superconductors. In particular, it is inferred from a field dependence of $\lambda(H)$ ($\propto H$) at 2.0 K that the quasiparticle excitation is strongly enhanced by the Doppler shift. This suggests that the superconducting order parameter in Ca(Al$_{0.5}$Si$_{0.5}$)$_2$ is characterized by a small energy scale $\Delta_S/k_B\le 2$ K originating either from anisotropy or multi-gap structure.Comment: 4 pages, 4 figures, submitted to J. Phys. Soc. Jp

Hybrid Optical Fiber Sensor And Artificial Neural Networks System For Bioethanol Quality Control And Productivity Enhancement

Bioethanol is produced by bio-chemical process that converts sugar or biomass feedstock into ethanol. After bio-chemical process, the solution is distilled under controlled conditions of pressure and temperature, in order to obtain an ethanol-water solution. However, the ethanol concentration analysis is generally performed off-line and, sometimes, a re-distillation process becomes necessary. In this research, an optical apparatus based on Fresnel reflection has been used in combination with artificial neural networks for determination of bioethanol concentration in hydro-alcoholic solution at any temperature. The volumetric concentration and temperature effect was investigated. This intelligent system can effectively detect and update in real-time the correction of distillation parameters to reduce losses of bioethanol and also to improve the quality in a production plant.7004Buggy, S.J., Murphy, R.P., James, S.W., Tatam, R.P., Cure monitoring of a UV cured epoxy resin using a long period grating Mach-Zehnder interferometer (2007) Proceedings of SPIE, 6619, pp. 66190VChehura, E., James, S.W., Tatam, R.P., Simultaneous, independent measurement of temperature and strain using a tilted fibre Bragg grating (2007) Proceedings of SPIE, 6619, pp. 66190IChong, J.H., Shum, P., Haryono, H., Yohana, A., Rao, M.K., Lu, C., Zhu, Y., Measurements of refractive index sensitivity using long-period grating refractometer (2004) Optics Communications, 229, pp. 65-69Su, H., Huang, X.G., Fresnel-reflection-based fiber sensor for on-line measurement of solute concentration in solutions (2007) Sensors and Actuators B: Chemical, 126 (2), pp. 579-582Meneghini, C., Caron, S., Proulx, A., Émond, F., Paradis, P., Paré, C., Fougères, A., Ethanol concentration measurement by Raman spectroscopy in liquid-core microstructured optical fiber (2007) Proceedings of SPIE, 6619, pp. 66191ULiang, W., Huang, Y., Xu, Y., Lee, R.K., Yariv, A., Highly sensitive fiber Bragg grating refractive index sensors (2005) Appl. Phys. Lett, 86, p. 151122Kheshgi, H.S., Prince, R.C., Sequestration of fermentation CO2 from ethanol production (2005) Energy, 30, pp. 1865-1871Olsson, L., Hahn-Hagerdal, B., Fermentation of lignocellulosic hydrolysates for ethanol production (1996) Enzyme and Microbial Technology, 18, pp. 312-331Natural Gas and Biofuel, ANP Resolution, (36 BRand 2005). , www.anp.gov, National Agency of PetroleumTakeishi, R.T., Gusken, E., de Souza, H.G.E., Meirelles, B.M., Suzuki, C.K., Study of the temperature effects in the alcohol-gasoline blend ratio determined by optical sensor (2007) 4th Brazilian Conference of R&D in Petroleum and Gas, , Proceedings, Campinas-SP, CD-RomBishop, C.M., (1995) Neural Networks for Pattern Recognition, , Oxford: Oxford University PressChen, S., Billings, S.A., Neural networks for nonlinear dynamic system modelling and identification (1992) International Journal of Control, 56 (2), pp. 319-346Dempsey, G.L., Alt, N.L., Olson, B.A., Alig, J.S., Control sensor linearization using a microcontroller-based neuralnetwork (1997) IEEE Intern. Conf. on Computational Cybernetics and Simulation, 4 (12-15), pp. 3078-3083. , PPLin, T.K., Chang, K.C., Lin, Y.B., Active Control with Optical Fiber Sensors and Neural Networks. II: Experimental Verification (2006) Journal of Structural Engineering, 132 (8), pp. 1304-1313Lin, T.K., Chang, K.C., Chung, L.L., Lin, Y.B., Active Control with Optical Fiber Sensors and Neural Networks. I: Theoretical Analysis (2006) Journal of Structural Engineering, 132 (8), pp. 1293-1303Rumelhart, D.E., Hinton, G., Willians, R., Learning Representation by Back-Propagation Errors (1986) Parallel Distributed Processing, 323 (9), pp. 533-536Kolodner, P., Williams, H., Moe, C., Optical measurement of the soret coefficient of ethanol/water solutions (1988) J. Chem. Phys, 88 (10), pp. 6512-6524Pan, S., Saghir, M.Z., Kawaji, M., Jiang, C.G., Yan, Y., Theoretical approach to evaluate thermodiffusion in aqueous alkanol solutions (2007) J. of Chemical Physics, 126, p. 014502González-Salgado, D., Nezbeda, I., Excess properties of aqueous mixtures of methanol: Simulation versus experiment (2006) Fluid Phase Equilibria, 240 (2), pp. 161-166. , PPPandey, J.D., Vyas, V., Jain, P., Dubey, G.P., Tripathi, N., Dey, R., Speed of sound, viscosity and R.I. of multicomponent systems: Theoretical predictions from the properties of pure components (1999) J. of Mol. Liq, 81, pp. 123-133C. K.Suzuki, E. Gusken, A. C. Mercado, E. Fujiwara, E. Ono, Fiber Optics Sensing System For Liquid Fuels, INPI Patent, Prot. 018070050521, 200

Atomic Carbon and CO Isotope Emission in the Vicinity of DR15

We present observations of the 3P1-3P0 fine structure transition of atomic carbon [CI], the J=3-2 transition of CO, as well as of the J=1-0 transitions of 13CO and C18O toward DR15, an HII region associated with two mid-infrared dark clouds (IRDCs). The 13CO and C18O J=1-0 emissions closely follow the dark patches seen in optical wavelength, showing two self-gravitating molecular cores with masses of 2000 Msun and 900 Msun, respectively, at the positions of the catalogued IRDCs. Our data show a rough spatial correlation between [CI] and 13CO J=1-0. Bright [CI] emission occurs in relatively cold gas behind the molecular cores, neither in highly excited gas traced by CO J=3-2 emission nor in HII region/molecular cloud interface. These results are inconsistent with those predicted by standard photodissociation region (PDR) models, suggesting an origin for interstellar atomic carbon unrelated to photodissociation processes.Comment: 11 pages Latex, 6 figures, Accepted for publication in The Astrophysical Journa

Observations of five molecular species in absorption towards Sagittarius B2

Seven diffuse molecular clouds have been detected in absorption, using the Sgr B2 star-formation region was used as a source of background continuum emission. Transitions were observed at frequencies around 49, 85 and 98 GHz, from CS, C34S, H13CN, H13CO+, SiO and C3H2. Clouds detected in absorption include the "nuclear disk", the 3 kpc expanding arm, spiral arms in the Galactic Plane, and two unidentified regions. The nuclear disk line profile was found to be inconsistent with homogeneous disk or bar models, instead suggesting irregular perturbations of the gas within a few hundred pc of the Galactic Centre. Absorption in CS was detected in two different rotational transitions, leading to reliable estimates of the physical parameters of the clouds. In particular, exitation temperaturers could be estimated, instead of assumed values being used, as was the case in previous studies. Results from an LTE analysis and from LVG modelling show that the absorption lines are mostly optically thin, with molecular column densities ~1012-14cm-2 per cloud. Excitation temperatures as high as 5K were found, inconsistent with heating by the 2.7K cosmic background radiation alone. Cloud densities were estimated at nH2~104cm-3, or less if the gas is highly subthermalised

Er-doped Tellurite glasses for planar waveguide power amplifier with extended gain bandwidth

Tellurite glass compositions doped with erbium and erbium/ytterbium optimised to support extended gain bandwidth with significant amplification have been fabricated, and their thermal, optical absorption, excitation and luminescence properties investigated. Each rare-earth dopant concentration was set at 1x1020/cm3. Broad emission cross-section bandwidths up to 50nm FWHM were observed, with fluorescence lifetimes of ~3ms. Collinear pump probe measurements on ~4mm thick bulk samples revealed peak gains of up to 2.1dB/cm at a wavelength of 1535nm in the co-doped material, with an incident pump intensity of only Iinc~8kW/cm2 at a wavelength of 974nm. At equivalent absorbed pump powers between co-doped and single doped materials the relative gain was 1.25dB/cm (Iinc~4kW/cm2) and 0.9dB/cm (Iinc~8kW/cm2) respectively, demonstrating efficient energy transfer from the ytterbium to erbium ions. Excited state absorption at longer wavelengths was observed and characterised and its implication on realising sufficient gain in the wavelength band of interest is discussed

Observation of the first gravitational microlensing event in a sparse stellar field : the Tago event

We report the observation of the first gravitational microlensing event in a sparse stellar field, involving the brightest (V=11.4 mag) andclosest (~ 1 kpc) source star to date. This event was discovered by an amateurastronomer, A. Tago, on 2006 October 31 as a transient brightening, by ~4.5 mag during a ~15 day period, of a normal A-type star (GSC 3656-1328) in the Cassiopeia constellation. Analysis of both spectroscopic observations and the light curve indicates that this event was caused by gravitational microlensing rather than an intrinsically variable star. Discovery of this single event over a 30 year period is roughly consistent with the expected microlensing rate for the whole sky down to V = 12 mag stars. However, the probability for finding events with such a high magnification (~ 50) is much smaller, by a factor ~1/50, which implies that the true event rate may be higher than expected. This discovery indicates the potential of all sky variability surveys, employing frequent sampling by telescopes with small apertures and wide fields of view, for finding such rare transient events, and using the observations to explore galactic disk structure and search for exo-planets.Comment: 13 pages, 2 tables, 3 figures, accepted by Ap

Effects of Disorder in FeSe : An Ab Initio Study

Using the coherent-potential approximation, we have studied the effects of excess Fe, Se-deficiency, and substitutions of S, Te on Se sub-lattice and Co, Ni and Cu on Fe sub-lattice in FeSe. Our results show that (i) a small amount of excess Fe substantially disorders the Fe-derived bands while Se-deficiency affects mainly the Se-derived bands, (ii) the substitution of S or Te enhances the possibility of Fermi surface nesting, specially in FeSe$_{0.5}$Te$_{0.5}$, in spite of disordering the Se-derived bands, (iii) the electron doping through Co, Ni or Cu disorders the system and pushes down the Fe-derived bands, thereby destroying the possibility of Fermi surface nesting. A comparison of these results with the rigid-band, virtual-crystal and supercell approximations reveals the importance of describing disorder with the coherent-potential approximation.Comment: Redone VCA calculations, and some minor changes. (Accepted for publication in Journal of Physics:Condensed Matter