The intensity spectrum of modulated noisy light on optical microwave signal processing and on conversion of FM noise to intensity noise in optical links is investigated theoretically and experimentally with a good agreement. We have applied a model that uses a 1550 nm distributed feedback (DFB) laser and an unbalanced Mach-Zehnder interferometer (UMZI) considering the external phase modulator. Numerical calculations show the influence of the phase modulation index, modulation frequency, and interferometric delay in the phase-to-intensity noise conversion by lowest-order group-velocity dispersion in optical fiber. The results can be employed to estimate the influence of the chromatic dispersion in phase-to-intensity noise conversion, which use either self-delayed interferences or interferometers.

In image processing, the Wavelet Transform (WT) is largely used. However, time requirements for large two-dimensional image transforms are hard to meet with sequential implementations. Parallel implementation decreases the processing time and allows to reach a real-time operation in image coding. Unfortunately, this parallel coding increases the hardware complexity. We propose an optical implementation of the JPEG2000 compression using a special implementation of the WT. Special attention is paid to propose a simple all optical setup carrying out the optical implementation of JPEG2000 compression for gray-level images. Finally, an adaptation of our technique to colored images is proposed. Wb

Molecular dynamics simulations with Tersoff potentials were used to study the tensile and compressive mechanical behavior of SiC nanowires with torsion strain. The simulation results show that small torsion strain does not affect the mechanical behavior of SiC nanowires. However, large torsion strain induces the decrease of the critical stress. With large torsion strain, the collapse occurs in the nanowires before tensile failure and compressive buckling, and deformation zone occurs in the collapsed part.

A general vector approach to the polarization mode dispersion (PMD) and polarization dependent loss (PDL) calculation in a cascade of optical components with each component having both PMD and PDL is presented. By using the formalism, the PMD-PDL coupling effect is quantitatively described and its implications are discussed. In particular, it is shown that the presence of PDL in the components is a second-order effect in the PMD of the cascade. As an illustration of the formalism, a statistical estimation of PMD and PDL in a practical optical device is performed. The accuracy and the computational advantage of the vector approach are demonstrated.

The formation of crystalline silicon nanoparticles was investigated by means of Raman spectroscopy. SiOx (x = 1 and x = 1.5) films deposited by electron-gun evaporation onto silica substrates were submitted to post-deposition thermal treatments at 1000 and 1100 °C for various times. From lineshape analysis of the Raman band, it appeared that the crystalline volume fraction never excessed 30% for annealing at 1000 °C, while the mean diameter remained almost constant. Complete crystallisation was achieved after annealing at 1100 °C, accompanied by an increase of the nanoparticle size. Mean diameters of the nanoparticles obtained from Raman spectra analysis along the two main confinement models, Richter et al., Campbell, Fauchet model and bond-polarizability model, were discussed and compared to values deduced from transmission electron microscopy measurements.

Hysteresis behavior of magnetic force versus gap between a high-Tc superconductor and a magnet, in static and dynamic cases, is studied numerically. Differing from the previous methods, based on macro electromagnetic constitutive relation of superconductors and Maxwell equations, a numerical method with the finite element method (FEM) is established. After numerical code is examined by comparing between numerical and experimental results of the relation of magnetic force-gap, the hysteresis curves of magnetic force-gap including major and minor loops in static case are simulated, and furthermore the dependences of major loop on main parameters including the critical current density and the thickness of superconductor, the residual magnetic field of magnet, and the diameter ratio of superconductor to magnet are studied numerically. In the case of free vibration, by investigating dynamic response of levitated body at different levitation/suspension positions in this magnetic levitation system, we obtain the corresponding results of the variation of magnetic force with gap. All the numerical results of the relation between magnetic force and gap show the strongly nonlinear and highly hysteretic behavior.

The methods to control the pulse width of a laser-diode end-pumped doubly Q-switched Nd:YVO4/YVO4 composite crystal laser with acoustic-optic (AO) and GaAs saturable absorber has been theoretically and experimentally studied. By varying the laser beam radius in the Q-switchers and the pump beam radius in the gain medium, we provide efficient means to control the pulse duration. The coupled rate equations are used to analyze the process of the laser. The experimental results are consistent with the theoretical results.

The efficiency of iron-catalysts in hydrocarbon decomposition, aimed at growth of carbon nanotubes by chemical vapour deposition (CVD), is systematically investigated. The synthesis reaction is carried out at different temperatures (873–1123 K), for various durations (0.5–6.0 h), using diverse precursor gases (C2H6 or C4H10) and catalyst supports (SiO2 or Al2O3). A large variety of experimental conditions is explored by varying amount (0.5–2.0 g), metal load (20 wt.% and 29 wt.%) and annealing temperature (723–973 K) of the catalysts and by considering different gas flowing setups, namely, by changing flow rate (100–240 cc/min) and composition (H2/precursor/He, with He at 0–63%) of the gas mixture, flow-rates and flow-ratio of reactant gases (H2: 0–120 cc/min; Precursor Gas: 15–120 cc/min; H2/PG: 0–3). Iron catalysts encapsulation is shown to be the main factor limiting C yields in the cases considered, and its changes to be responsible for the broad yield variations (20–910 wt.%) observed. The results of analyses, carried out by Raman spectroscopy (RS) and complementary diagnostics techniques, demonstrate the need of accurately tuning the manifold growth parameters, in order to fully benefit of the advantages potentially deriving from a proper choice of precursor gas and catalyst-support material.

The effect of thickness and heat treatment on the structural and optical properties of Sb2Te3 thin films fabricated by using flash evaporation technique were investigated. The as-deposited films were found to be stoichiometric. For the as-deposited and annealed samples of thickness in the range of 20.7–120.5 nm, large variations in transmittance and reflectance were observed for wavelength below 2000 nm due to strong absorption, while slight variations were observed above 2000 nm. The optical constants, n and k, measured in the range of 500–4000 nm, increased slightly by annealing the samples at 573 K for 2 h in air and a red shift was observed. Allowed indirect transitions were observed for the as-deposited and the annealed samples. The results showed two energy gaps for these transitions varied from 0.28 to 0.31 eV for the as-deposited samples and from 0.56 to 0.54 eV for the annealed films. The spectral distribution of the real part of the dielectric constant ε′ showed a maximum at 0.73 eV for the as-deposited films decreased to 0.65 eV by annealing.

Photoinduced changes in a Sudan I doped PMMA thin film were investigated. The dependence of photoinduced birefringence of the thin film on light intensity was studied, with a continuous wave (CW) 532 nm laser as pump light and a CW 650 nm laser as probe light. For all the light intensities (100–1000 mW/cm2), the thin film possessed large photoinduced birefringence (Δn ~ 10−4). With a CW 532 nm laser at relatively low light intensity, a reversible polarization hologram has been recorded in the thin film. Moreover, Z-scan measurements showed that the thin film possessed large nonlinear refractive index (−7.93 × 10−5  cm 2/W) and nonlinear absorption coefficient (−5.50 W/cm) under a CW 532 nm excitation.

We present electromagnetic invisible cloaks and concentrators which are composed of inhomogeneous and anisotropic metamaterials with a square-shaped outer boundary and a circular-shaped inner boundary. Using the technique of coordinate transformation, closed-form formulations of the permittivity and permeability tensors have been derived for the metamaterials to realize the invisible cloaking and to concentrate electromagnetic waves. Full-wave simulation results are given to validate the non-rotationally invariant cloaks and concentrators.

Analysis of the optical generation of three bands of continuously tunable millimeter-wave signals using an optical phase modulator (OPM) and an optical notch filter is presented. Three bands of millimeter-wave signals are tuned by using an optical phase modulator and a polarization state rotation filter (PSRF) as optical notch filter. The effect of the chromatic dispersion on wide-band continuously tunable millimeter-wave signal which using an OPM and a PSRF is investigated. The spectrum of the generated millimeter-wave signal after transmission over a 25 km standard single-mode fiber (SSMF) is obtained.

A dispersion compensating fiber exhibiting low losses is used to study the phase to amplitude noise and amplitude to phase noise conversion mechanisms with a very good signal-to-noise ratio over a 20 GHz bandwidth. It is shown that the large frequency noise of semiconductor lasers and the losses in the fiber restrain this technique from efficiently reducing the relative intensity noise to improve the dynamic range of opto-microwave links. However, these properties are proved to be useful to precisely characterize the laser phase noise over a large bandwidth.

High-k (Zr,Sn)TiO4 films were grown on glass substrate by DC magnetron sputtering at ambient temperature using elemental, all metallic targets. Films were polycrystalline irrespective of the oxygen partial pressure. The refractive index and optical bandgap of the films were in the range 1.79–1.59 at 600 nm and 3.27–3.39 eV, respectively. Highest value of microwave dielectric constant exhibited was 33 and lowest loss tangent was 0.001 at 10 GHz. Films prepared at 40% oxygen mixing percentage (OMP) gave minimum strain and the same film gave minimum dielectric loss with highest dielectric constant. A correlation between strain values and dielectric loss was observed. The grain sizes as observed from atomic force microscope images are found to be triangular in nature.

A recent claim [Eur. Phys. J. Appl. Phys. 40, 293 (2007)] demonstrating a nuclear process triggered by electrolysis is challenged. An analysis, based on relative diameters, is used to demonstrate that predominant pits could not possibly be attributed to alpha particles, or to less massive nuclear projectiles. This conclusion is supported not only by positive results from a replication experiment, but also by results from the experiment on which the original claim was based. While the numerous SPAWAR-type pits seem to be highly reproducible, their interpretation is not yet clear.

The mechanical and structural properties were studied at room temperature for Al-2wt.%Ag and Al-2wt.%Ag-1wt.%Sn alloys 503 K–583 K. The variation in the internal friction, Q−1, dynamic Young's modulus, Y, Vickers hardness, Hv, and X-ray diffraction patterns were obtained. For 533 K the internal friction showed abrupt increase while Young's modulus and Vickers hardness showed minima. The results showed a remarkable dependence of the measured parameters on both Sn addition and the heat treatment regime.

Earlier we reported, in this journal, that the pits generated in CR-39 detectors during Pd/D co-deposition experiments are consistent with those observed for pits that are of a nuclear origin. Recently, that interpretation has been challenged. In this communication, additional experimental data and further analysis of our earlier results are provided that support our original conclusions.

In the French watt balance experiment, in order to have a single point of application of a weight and an electromagnetic force balancing this weight, a system of double gimbals with flexure pivots was made out of copper-beryllium alloy. This allows the articulation of the suspension devices of the mass (generating the weight) and coil (on which the electromagnetic force acts) around four coplanar axes which intersect at one point (equivalent to a virtual centre of rotation). The study of the free dynamic behaviour under vacuum of this device dealt with resonance, damping due to internal friction of the material and coupling between the two systems of gimbals. The results obtained show that this novel device presents suitable characteristics for concentrating two different forces at a single point and aligning them around a common vertical axis. It can be used not only for watt balance experiments but also for any other mechanical applications where alignment and concentration of two forces are necessary.

In this paper, we describe the design of a permanent magnet actuator that can make linear and rotary movements independently or simultaneously. Special attention has been placed on the simplicity of the structure and its dynamic behavior. First, we compare the different approaches to perform a linked movement and a structure is chosen. Then, we detail the magnetic conversion used through a rotary machine and a linear actuator. In a last part, the actuator designed is presented and studied using the 3D finite element approach. Results concerning the flux linkages and forces are given and discussed.

It is theoretically shown that an attractive effective potential is generated via optical phonon exchange between two quasi-free, different particles in deuterated Pd which, in turn, enhances the probability of their nuclear fusion reaction. Mechanisms, that may be responsible for extra heat production and nuclear isomer formation, are also discussed. Creation of 4He pairs due to the significantly increased probability of the p + 7Li $\rightarrow$ 24He + 17.35 MeV and d + 6Li $\rightarrow$ 24He + 22.37 MeV nuclear reactions is predicted. Some of the basic questions of fusion reactions in solids seem to be successfully explained.