We recently setup a high energy, tunable, injection seeded Ti:Sapphire laser source whose implementation was reported in [Rev. Sci. Instrum. 78, 033102 (2007)]. The analysis of the spectral linewidth has demonstrated that the pulses were time Fourier-transform limited. The present paper reports on the modeling of this source with the aim of understanding the energy conversion in the injected as well as in the free run regimes. The experimental lasing threshold, output energy, slope efficiencies, buildup time, and pulse duration are compared to the analytical solution obtained by solving the laser rate equations. The developed model deals with the spatial dependence of the photon and population inversion densities, the physical properties of the Ti:Sa medium, and the unstable resonator (based on a super-Gaussian output coupler). The energy-related as well as the temporal features are discussed. The use of a squared asymmetrical hyperbolic secant function to describe the temporal pulse shapes is justified. The pulse durations exhibit a simple analytical shape when they are plotted versus the output pulse energy. The model is applied to experimental data obtained at different wavelengths by tuning the laser amplifier previously described. It can readily be applied to other pulsed Ti:Sapphire sources.

The use of CR-39, a solid state nuclear track detector, to detect the emission of energetic charged particles during Pd/D co-deposition is demonstrated. The pits observed in the CR-39 are attributed to the Pd/D cathode and are not due to radionuclide contamination in the cell components; nor to the impingement of D2 bubbles on the surface of the CR-39; nor to chemical attack by D2, O2, or Cl2. The features (i.e., optical contrast, shape, and bright spot in the center of the pit) of the pits generated during Pd/D co-deposition are consistent with those observed for pits that are of a nuclear origin.

The bulk lifetime $\tau _{n}$ and diffusion length Ln of minority carriers vary through the height of a cast multicrystalline silicon (mc-Si) block. This variation is due to the segregation of metallic impurities during the directional solidification and the native impurity concentrations increase from the bottom to the top of the ingot, which is solidified last, while the ingot bottom, which is solidified first, is contaminated by the contact with the crucible floor. It is of interest to verify if a correlation exists between the bulk lifetime $\tau $ of as cut wafers and the conversion efficiency $\eta $ of solar cells. In a very large ingot (>310 kg), it was found that $\tau_{0}$, in raw wafers, $\tau_{dif}$ in phosphorus diffused ones and Ln in diffused wafers are smaller in the top and in the bottom of the ingot. The same evolution is observed in solar cells, however the diffusion length values Lcel in the central part of the ingot are markedly higher than those found in diffused wafers, due to the in-diffusion of hydrogen from the SiN-H antireflection coating layer. The variations of $\eta $ and those of $\tau _{0}$, along the ingot height, are well correlated, suggesting that the evaluation of $\tau _{0}$ can predict the properties of the devices. In addition, segregation phenomena around the grain boundaries are observed at the bottom of the ingots, due to a marked contamination by the crucible floor, and at its top where impurities are accumulated. These phenomena are linked to the long duration of the solidification process and the large amount of imperfect silicon used to cast the ingot.

We report the influence of an exciton-blocking layer and/or an Al2O3 thin layer at the interface “organic acceptor/aluminium” on the efficiency of CuPc/C60 based photovoltaic cells. The presence, or not, of a thin Al2O3 layer depends on the encapsulating process of the devices. In the case of glass/ITO/CuPc/C60/Al cells, the presence of an Al2O3 thin layer at the interface “organic acceptor/aluminium” increases strongly the open circuit voltage of the cells but decreases slightly their short circuit current and fill factor. In the case of glass/ITO/CuPc/C60/Alq3/Al cells, the open circuit voltage is systematically higher than without Alq3. However, in that case, the presence of Al2O3 does not improve significantly the cell performances. All these results are discussed in terms of series and shunt resistance values related to possible oxygen contamination and organic covalent action with the Al films. The effectiveness of these different phenomena depends on the presence, or not, of Alq3 and/or Al2O3 layers.

An attempt was made to widen the photosensitivity spectral range of poly(3-hexylthiophene)-fullerene blend by adding an extra electron donor — a newly synthesized soluble phthalocyanine derivative (SnClPc) having the electron absorption band at 708 nm. As the electron acceptor, home-synthesised di(ethoxycarbonyl) methano-fullerene carboxylate (C61(CO2Et)2) was used, and as the hole transporter — the regioregular poly 3-hexylthiophene (P3HT). The sandwich-type samples were prepared on an ITO glass substrate by coating it with a 30–50 nm thick PEDOT:PSS layer followed by a ~100 nm thick P3HT:C61(CO2Et)2:SnClPc blend. For the top electrodes In or Au were used. Spectral dependences of the PV effect and of the influence of external magnetic field (0–3000 Oe) on it were studied in the 370–1000 nm spectral range in vacuum of ~10-6 Torr. Significant photosensitivity of the blend was observed in the 370–800 nm spectral range. However, the short-circuit photocurrent quantum efficiency evaluated for absorbed light was found to be 4 times higher for illumination in the P3HT absorption band as compared with that in the SnClPc band. The observed magnetic field effect shows that the low IPCE values may be explained by the space charge formation in the samples, leading to a strong geminate recombination of CP states.

In a normal and an abnormal ELCAD plasmas the density of electrons and positive ions were estimated from the earlier measured values of the cathodic current density, the cathode fall, the electric field, the length of cathode dark space, the kinetic energy, the last free path of positive ions hitting the cathode and the rate of secondary electron emission. In a normal ELCAD, the density of positive ions forming the space charge: $n_{sp}^{+}$ ≈ 5.7×1012 cm-3, the density of positive ions hitting the cathode: n+ ≈ 1.1×1012 cm-3, the electron density at the cathode: $n_{e,c}$ ≈ 3.7×1011 cm-3, the electron density at the end of cathode dark space: ne ≈ 5.7×1012 cm-3 and the multiplication of electron in cathode dark space M ≈ 15.3 were obtained. In an abnormal case, $n_{sp}^{+}$ ≈ 2.1×1013 cm-3, n+ ≈ 4.3×1012 cm-3, $ n_{e,c}$ ≈ 3.9×1012 cm-3, ne ≈ 2×1013 cm-3, M ≈ 5.17 were received.

A transmission type of experiment was set-up to investigate coherent light scattering on suspensions with scattering centers having a wider size distribution. For each sample the contrast, the average intensity and the average speckle size of the far interference field were calculated using an alternative simple algorithm that is presented in detail. The variation of the far field parameters with the scattering centers concentration is presented. A possible application in measuring the scattering centers concentration in the very small values range is suggested and the range is indicated.

In this paper, a new type PCF with three different air-hole diameters in cladding region is proposed and investigated by using a compact 2-D finite difference frequency domain (FDFD) method with anisotropic perfectly matched layers (PML) absorbing boundary conditions. Through numerical simulation we found that by optimizing the geometrical parameters, our proposed structure with fewer of air-hole rings greatly meets the performance criteria such as ultraflattened dispersion and low confinement loss, which is highly instructive for designing photonic crystal fibers.

An efficient method was proposed to determine the cross sections of charge exchange in ion-molecule collisions. The cross sections for charge exchange were derived by comparing the calculated ion transport parameters with the measured data. The computational procedure was presented by obtaining the cross sections of charge exchange for NO+ and CO+ ions in NO and CO gases, respectively. The present method is usable for providing the accurate cross sections of charge exchange in ion-molecule collisions with the particle modeling of plasma discharges.

An experimental study is presented involving the modelling of a concept which enables exterior dehydration of contaminating or fragile products. This concept is based upon the use of a ground-breaking film which is permeable exclusively to water vapour and semi-transparent to the sun's rays. The experimental results presented (derived from a campaign conducted with the help of a drying cell designed for this purpose) lead to the setting up of a simple model enabling the design and sizing of systems based on the use of this film to be considered.

We present results on the realization of a multicolour microspherical glass light source fabricated from the erbium doped fluoride glass ZBLALiP. Whispering gallery mode lasing and upconversion processes give rise to laser and fluorescent emissions at multiple wavelengths from the ultraviolet to the infrared. Thirteen discrete emissions ranging from 320 to 849 nm have been observed in the upconversion spectrum. A Judd-Ofelt analysis was performed to calculate the radiative properties of Er3+:ZBLALiP microspheres, including the radiative transition probabilities, the electric dipole strengths, the branching ratios and the radiative lifetimes of the transitions involved. We have also identified the primary processes responsible for the generation of the observed wavelengths and have shown that this material has an improved range of emissions over other erbium doped fluoride glasses.

The object of this work is to report a passive filter structure dedicated for power applications. The structure is based on a series combination of elementary notch filters resonating at harmonic frequencies of a base frequency (switching frequency of a converter). A calculation of values of the components used for a given performance is presented. In addition, energy study comparing the behavior of this new structure with that of a traditional LC filter shows that the same performances can be achieved with the 50% volume reduction.

In this paper the new approach is proposed to consider a large number of resonantly interacting internal waves in order to investigate the evolution of the energy spectrum in the ocean. The approach is based on a new method for deriving and solving the system of coupled differential equations that govern the evolution of the waves on the interaction time scale. All previous analytical models are based on studying of three resonant internal waves and under hydrostatic approximation. The case of eight resonant waves has been studied experimentally in [J. Fluid Mech. 30, 723 (1967)]. To study the oceanic energy spectrum, only statistical models has been used which are not precise enough to provide estimates of energy exchange in the ocean. The model reported in this paper, provides an illustrative example involving 140 000 resonant internal waves. In this model we don't need to assume the hydrostatic approximation. So our model involves internal waves with frequencies spanning the range of possible frequencies, i.e., between a maximum of the buoyancy frequency N to a minimum of the inertial frequency f. Periodic nature of the spectrum (which has never been reported in previous studies) is investigated. The possible application of this model to investigation of internal waves energy dissipation is discussed.

The purpose of this work is to study the formation of hydroxyapatite (Ca10 (PO4)6(OH)2) on the surface of glass 48S4 with chemical composition: SiO2: 48%, CaO: 30%, Na2O: 18% and P2O5: 4% in weight ratio. This selected composition presents phosphorus contributions lower than that in Bioglass® [Hench et al. J. Biomed. Mater. 36, 117 (1971)] developed by L. Hench. Comparison of the kinetic formation of hydroxyapatite on the glass surfaces of these two biomaterials was made. The Material was prepared by melting and rapid quenching. It shows a bioactive character. This phenomenon is confirmed by the “in vitro” formation of hydroxycarbonate apatite (HCA) layer on the surface of glass after immersion in the Simulated Body Fluid (SBF). Before immersion in SBF, The proposed composition of glass was analyzed using several physicochemical methods like XRD, FTIR, SEM, and EDS confirming the composition and its amorphous state well. The pellets were soaked in SBF for 2 h, 1, 3, 7 and 15 days at 37 °C. The analyses of SBF after each immersion time were carried out using ICP-OES method. Results show important exchanges of ions between the surface of glass and the SBF. They revealed the formation of an amorphous CaO-P2O5- rich layer on the surface of the specimens after 1 day in the solution and a crystalline HCA layer after 3 days immersion time as will be shown by XRD, EDS and FTIR analysis. The cristallinity increases with immersion time. After 15 days immersion in SBF liquid, the specimens are still fully covered by hydroxycarbonate apatite (HCA) layer.

We present the operating principle and a first experimental characterization of a holographic rangefinder, that couples a two wave mixing phase demodulation set-up with a frequency modulated laser source. In its first implementation, the system allows millimetre sensitivity on tens of meters measurement range with the ability to work with scattering surfaces.

In this work, we present an algorithm for the space vector pulse width modulation (SVPWM) applied to five-level diode clamped inverter. In this algorithm, the space vector diagram of the five-level inverter is decomposed into six space vector diagrams of three-level inverters. In turn, each of these six space vector diagrams of three-level inverter is decomposed into six space vector diagrams of two-level inverters. This idea allows us to generalize the two-level SVPWM algorithm into the case of five-level inverter.

Acoustic streaming patterns, velocity fields, which is induced by a cylindrical ultrasonic exciter vibrating at 28.4 kHz in an open physical boundaries, is analytically and experimentally investigated using Particle Imaging Velocimetry (PIV). Induced acoustic streaming patterns and velocity fields for the gaps of 18 mm at which the irrotational tangential velocity becomes a maximum, resulting in a substantial increase in the acoustic streaming velocity and pronounced visualization of streaming patterns between the vibrator and quiescent glass plate are presented. The overall air flow patterns at the gaps of 24, 30, 36 mm are similar to the gap of 18 mm but as the gap increases the frequency of occurrence and irregularity of vortices in the gap appear to increase. The symmetric definite steady circular flow with local vortices is observed. The maximum streaming velocity measured stands at 0.16 cm/s with a vibration amplitude of 50 micrometers. Theoretical analysis indicates that the pattern of air flow in the gap is determined by the top and bottom limiting velocities induced by acoustic streaming within the Stokes boundary layer and that the streaming pattern is symmetrical with respect to the center axis of the vibrator by reason of symmetry. The comparison between the experimental data and the theoretical estimation based on Nyborg and Jackson is performed.

In Tip-Enhanced Raman Spectroscopy (TERS) a metal (or metallized) sharp tip is used to enhance the electromagnetic field by a localized surface-plasmon excitation. Two different modes – atomic force mode (AFM) and scanning tunneling mode (STM) – together with their respective types of probe tips are used in TERS experiments. We have compared the efficiency in enhancing the Raman signal on a thin dye layer for metal-coated AFM tips as well as for electrochemically etched metal STM tips. A much higher enhancement factor and better reproducibility were found when using STM tips. The very different performance is mainly attributed to the more efficient plasmonic excitation when using bulk-metal tips and possibly to the morphological differences in the tip and apex shapes existing between the two tip types.

Structure, wetting, mechanical and electrical transport properties of tin- (2.5, 3.5, 5 and 10) wt.% silver alloys have been investigated. The results showed that, addition of silver to pure tin causes more precipitations of the intermetallic compound Ag3Sn. A new intermetallic compound Ag4Sn has been formed with adding Ag more than 3.5 wt.%. This compound causes continuous increase in the Young's modulus and electrical resistivity. While for the wetting measurements, additions of silver to pure tin up to 5 wt.% reduces the contact angle. Above that, the contact angle increases due to more precipitations of Ag–Sn compounds, which may tend to reduce the adhesive forces between molten alloys and the substrate.

In most organs, depending on the scale, the nature of the heart pump, the geometry and topology of the organ, some of the blood vessels tend to exhibit sinuous trajectories. We describe a part of this sinuous behavior, including partial biological and strong physical effects in a global physical framework. We will voluntarily focus on physical and topological effects. This study is performed on the vitelline membrane of the chicken embryo. Crossing angles, sinuosity, and the oscillation amplitude of the vascular system are analyzed. Surprisingly, the equation of river meandering dynamics is found to model the sinuosities in the vascular system, and an extension of this equation to non planar case is able to explain the effect of tissue global curvature on the vascular system. Results of this study could lead to a new understanding of the interplay between biological signaling and physical effects in determining the vascular pattern in different tissues.