87,300 research outputs found
Upconversion rate in Nd-doped Ta<sub>2</sub>O<sub>5</sub> waveguides and influence on the cw laser performance
No full textThe non-linear upconversion processes in Nd-doped Ta2O5 waveguides have been investigated to determine the depopulation rate of the 4F3/2 laser level due to energy transfer upconversion (ETU). A rate-equation analysis has been used to obtain analytical expressions of the population and average lifetime of the 4F3/2 level under modulated cw excitation. The analysis of lifetime measurements as a function of excitation power yielded to an ETU rate of about 22 800 s-1. Equations for the four level cw laser performance have been obtained using a rate-equation approximation that includes ETU processes. The effect of upconversion on the laser performance has been estimated using the parameters obtained for the Nd-doped Ta2O5 waveguide lasers
Stability of syzygy bundles on abelian varieties
No full textWe prove that the kernel of the evaluation morphism of global sections -
namely the syzygy bundle - of a sufficiently ample line bundle on an abelian
variety is stable. This settles a conjecture of Ein-Lazarsfeld-Mustopa, in the
case of abelian varieties.Comment: Final version. To appear in Bull. Lond. Math. So
Optical gain in conjugated polymer hybrid structures based on porous silicon waveguides
No full textThe fabrication and optical characterization of a hybrid waveguide formed by a MDMO-PPV semiconductor layer deposited on a porous silicon cladding is reported. Evidence of amplified spontaneous emission is observed when the intensity of the excitation pump pulses is higher than a certain threshold. A net gain coefficient of about 50 ± 8 cm-1 is estimated, which is similar to those reported for other PPV derivate conjugated polymers. The demonstration of positive optical gain in these hetero-structures is very promising because new photonic structures could be envisaged due to the versatility of the porous silicon cladding
Data set on a study of gene expression in peripheral samples to identify biomarkers of severity of allergic and nonallergic asthma
No full textThis article contains information related to the research article entitled “Biomarkers associated with disease severity in allergic and nonallergic asthma” (S. Baos, D. Calzada, L. Cremades, J. Sastre, J. Quiralte, F. Florido, C. Lahoz, B. Cárdaba, In press). Specifically, the clinical criteria stablished for selecting the study population (n=104 subjects) are described. Moreover, this article describes the criteria for selecting the 94 genes to be analyzed in PBMCs (peripheral blood mononuclear cells), it is provided a description of these genes and a Table with the genes most differentially expressed by clinical phenotypes and, finally it is detailed the experimental methodology followed for studying the protein expression of MSR1 (macrophage scavenger receptor 1), one of the genes evaluated in the research
Efficient blue upconversion emission due to confined radiative energy transfer in Tm<sup>3+</sup>:Nd<sup>3+</sup> co-doped Ta<sub>2</sub>O<sub>5</sub> waveguides under infrared-laser excitation
No full textIntense blue upconversion emission at 480nm has been obtained at room temperature in Tm3+:Nd3+ co-doped Ta2O5 channel waveguides fabricated on a Si substrate, when the sample is excited with an infrared laser at 793nm. The upconversion mechanism is based on the radiative relaxation of the Nd3+ ions (4F3/2 to 4I11/2) at about 1064nm followed by the absorption of the emitted photons by Tm3+ ions in the 3H4 excited state. A coefficient of energy transfer rate as high as 3 × 10-16 cm3/s has been deduced using a rate equation analysis, which is the highest reported for Tm-Nd co-doped systems. The confinement of the 1064nm emitted radiation in the waveguide structure is the main reason of the high energy transfer probability between Nd3+ and Tm3+ ions
Room temperature infrared-laser-induced upconversion in Nd<sup>3+</sup> doped Ta<sub>2</sub>O<sub>5</sub> waveguides
No full textThe room temperature infrared to visible upconversion properties of Nd3+ doped Ta2O5 rib waveguides deposited on a silica substrate have been investigated in the 720-900 nm excitation range. Two possible upconversion mechanisms exist at different excitation wavelengths. The main one is due to energy transfer upconversion and results in the population of the 4G7/2 level. Radiative relaxations from this level to the 4I9/2, 4I11/2 and 4I13/2 multiplets produce visible emission bands in the green, orange and red regions. Excited state absorption from the 4F3/2 to the 2P1/2 state can also occur, giving rise to a blue emission band (2P1/2 to 4I9/2). A rate equation analyses supports the proposed mechanisms
EFFICACY OF RUE EXTRACT, SODIUM BICARBONATE AND FUNGICIDES AT REDUCED RATES TO CONTROL OF POWDERY MILDEW ON TOBACCO.
No full textNd:LaF<sub>3</sub> waveguide laser fabricated by molecular beam epitaxy
No full textWe describe the first demonstration of laser action in a dielectric waveguide grown by molecular beam epitaxy. Laser emission at 1.063µm is obtained from a Nd:LaF3 thin film grown on a CaF2 substrate
- …
