With the purpose to increase the light confinement and the efficiency of silicon solar cells, the reflection of the surface emitter needs to be minimized and the minority carrier collection improved. This improvement is currently achieved by the application of the chemical vapor etching (CVE) technique. In this paper, we investigate the effects of CVE on surface texturing and silicon grooving. CVE-based porous silicon (PS) was found to be a good antireflection and passivation layer for multicrystalline Si (mc-Si) solar cells. As a result, the reflectivity of the mc-Si solar cell decreases by about 60% of its initial value in the 650–950 nm spectral range and the internal quantum efficiency improves by 30% after PS application in the 400–700 nm spectral range. CVE can be used for surface texturing of single or mc-Si Si wafer leading to lower surface reflectivity and reduction of the dead layer. The chemical vapor etching techniques enabled realize buried metallic contacts by grooving mc-Si silicon wafers. The spectral response of mc-Si solar cells was found to enhance of about 12% in the long wavelength range when a rear buried metallic contacts is achieved, while a significant increase of about 35% was observed at short wavelengths (400–650 nm spectral range) subsequent front grid buried metallic contacts realization.

Double-channeled omnidirectional filtering properties are found in the sandwich structure composed of a ε-negative layer and a μ-negative layer separated by another single-negative layer with either dielectric permittivity or magnetic permeability described by Lorentz model. The twin tunneling interface modes are generated by the excitation of surface polaritons. It is shown that the two tunneling modes are insensitive to the incidence angles and the polarizations. Furthermore, the tunneling frequency and the frequency interval of the two modes can be tuned by changing the resonance frequency and the thickness of the center layer respectively. The characteristics can be utilized to design double-channeled tunable omnidirectional filters using in microwave and optical engineering.

Composite films containing silver nanoparticles embedded in diamond-like carbon (DLC) matrix were deposited on glass substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition techninique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of methane of a gas mixture of methane + argon in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and FTIR studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was associated with the increase in volume fraction of metal particles. The experimental results have been discussed in light of the existing Mie theory.

In this study the influence of morphology of vertically oriented titanium oxide nanotube arrays (TNTAs) on their photocatalytic activities was investigated. To obtain nanotubes with different morphologies, they were prepared at different anodization voltages. The size of TNTAs were measured using SEM images and also determined based on a non-destructive optical method; We demonstrate how the tubular geometry of the TNTAs can be used to adjust the optical and also the wetting properties of them and how these properties affect the performance of the nanostructure in further applications as a photocatalyst. To investigate their potentials for environmental applications, the photocatalytic activity of TNTAs in methylene blue (MB) aqueous solution was evaluated and compared to the behavior of porous TiO2 layers; we have found that the nanotubular TiO2 electrodes have considerably better photocatalytic performance in comparison with porous samples and the photocatalytic activity of TNTA was strongly dependent on the crystallographic structure and morphology.

Nucleation of a gold catalyst on a (100) oriented silicon substrate was extensively investigated. An anomalous mechanism of nucleation was observed in the grain formation of gold nanoislands. The chemical vapour deposition method was employed to grow zinc oxide nanowires. Zinc powder and oxygen gas were used as reaction sources for the growth. Different shaped ZnO nanowires were obtained for different nucleation mechanisms. The nucleation mechanism and growth evolution were monitored by scanning electron microscopy and atomic force microscopy.

We measured the single-photon detection efficiency of NbN superconducting single-photon detectors as a function of the polarization state of the incident light for different wavelengths in the range from 488 nm to 1550 nm. The polarization contrast varies from ~5% at 488 nm to ~30% at 1550 nm, in good agreement with numerical calculations. We use an optical-impedance model to describe the absorption for polarization parallel to the wires of the detector. For the extremely lossy NbN material, the absorption can be kept constant by keeping the product of layer thickness and filling factor constant. As a consequence, the maximum possible absorption is independent of filling factor. By illuminating the detector through the substrate, an absorption efficiency of ~70% can be reached for a detector on Si or GaAs, without the need for an optical cavity.

Several important errors and misinterpretations present in a recent publication by Khan et al. [Eur. Phys. J. Appl. Phys. 45, 11002 (2009)] are pointed out and discussed. In particular, it is shown that the method used to calculate the rate coefficients for the electron impact excitation of 3p 54p and 3p 55p states of argon is incorrect and leads to unrealistically high rate coefficients.

Embedded electric HVDC distribution network are facingdifficult issues on quality and stability concerns. In order to helpto resolve those problems, this paper proposes to develop ananalytical model of an electric drive. This self-contained modelincludes an inverter, its regulation loops and the PMSM. Aftercomparing the model with its equivalent (abc) full model, the studyfocuses on frequency analysis. The association with an input filterhelps in expressing stability of the whole assembly by means ofRouth-Hurtwitz criterion.

In this article, we report on the simulation and realization of a magnetic circuit allowing to apply an axial magnetic field higher than 1 T. The proposed electromagnet is used to investigate the influence of a magnetic field on the polarization behavior of a vertical-cavity-surface-emitting laser (VCSEL). A non-linear polarization behavior can be experimentally observed for currents as low as the threshold current, provided that the magnetic field is strong enough.

We obtain the approximate solutions for the steady temperatureprofiles of materials with a temperature-dependent thermalabsorptivity inside a microannulus with wavy-rough surfacesconsidering a quasilinear partial differential equation by theboundary perturbation approach. Our numerical results show thatthe wave number as well as the small amplitude of the wavyroughness will influence the net temperature significantlyespecially near the inner wall of a microannulus. Meanwhile weobserved that the critical Frank-Kamanestkii parameter depends onthe small-amplitude wavy-roughness for specific power-law ofthermal absorptivity. Our results could be applied to the relevantfields in MicroElectroMechanical System (MEMS).

Everyone knows the importance of sensors in our society and the huge attempt to improve their properties in order to obtain better sensitivity and selectivity. In this paper, we are more particularly focused on gas sensors based on surface acoustic waves (SAW) device. In a previous work, we have developed and studied a structure composed of a 90° rotated ST quartz crystal covered with a ZnO layer. By developing inter-digital transducers (IDT) on this structure, we can generate different types of acoustic waves. Love waves which are confined near the surface are known to be very sensitives to fluids (liquids or gases). The aim of this work is to present the way we have developed this optimal structure and to test it with a specific polymer. This polymer is polyaniline (PANI). Its main advantage is that it should be deposited by cold pulsed plasma process.

The optimal sinusoidal excitation of an ultrasonic transducer requests a knowledge of the frequency and the impedance of the used ceramic. These parameters, that vary during the application, depend on the characteristics of the transducer but also on the acoustic load of the propagation medium. In the search for an adaptive excitation, we propose the design of a digital generator assuring the functions of automatic tuning and impedance matching. The design uses the Butterworth-Van Dycke model of pizoelectric ceramics.The method of determination and identification of the model parameters is presented and applied on three different transducers.The negative feedback of the generator is carried out by the signal measured on the transducers. The dynamic voltage being very variable, the output resistor of the driver is controlled by transducer impedance.This feedback control allows the stability of the output voltage to a constant value whatever the frequency and the medium is.A Simulink® model of the regulation loop shows that the frequency tuning could be realized by exploiting the command signal of the driver resistance. The precision and the stability of the feedback system are tested for frequencies between 1 to 3 MHz.

Since the detection of nanoparticles is a major issue in nano sciences, we have developed two instruments for the fast imaging of individual nano objects. The first one is based on a spatial modulation of the sample using an incoherent dark field illumination and a multiplexed lock in detection.The second instrument uses digital heterodyne holography. Both instruments make it possible to achieve a high signal-to-noise ratio and therefore to detect very low signal.

The permanent operation of a 3 axes SQUID magnetometer in the LSBB below 550 m of calcite rock is a unique system of magnetic observation: a rejection rate better than 3 fT/ $\surd $ Hz over 40 Hz. The observation of magneto-ionosphere responses to P wave emissions both at the epicentre and at their arrival at LSBB for earthquakes of magnitude larger than 3 is reported. A simple model predicts the starting time of these events. These results are compared with those provided by Doppler sounders for ionosphere responses to Rayleigh waves.

This paper describes optical instrumentation devoted to vibration analysis. Two strategies based on digital Fresnel holography are presented. The first, called time-averaging consists in the numerical reconstruction of the hologram after recording with an exposure time much greater than the vibration period. Thus, the holograms are amplitude modulated by a Bessel function. The last strategy, using a pulsed regime, allows the reconstruction of the full movement of the vibration, even if it exhibits very high amplitude. Experimental results presented in this paper concern the study of the vibrations of a clarinet reed under free and forced oscillation regimes.

This paper deals with the development and application of in vivo spatially-resolved bimodal spectroscopy(AutoFluorescence AF and Diffuse Reflectance DR), to discriminate various stages of skin precancer in a preclinicalmodel (UV-irradiated mouse): Compensatory Hyperplasia CH, Atypical Hyperplasia AH and Dysplasia D. A programmableinstrumentation was developed for acquiring AF emission spectra using 7 excitation wavelengths:360, 368, 390, 400, 410, 420 and 430 nm, and DR spectra in the 390–720 nm wavelength range. After various steps of intensityspectra preprocessing (filtering, spectral correction and intensity normalization), several sets of spectralcharacteristics were extracted and selected based on their discrimination power statistically tested forevery pair-wise comparison of histological classes. Data reduction with Principal Components Analysis (PCA)was performed and 3 classification methods were implemented (k-NN, LDA and SVM), in order to compare diagnosticperformance of each method. Diagnostic performance was studied and assessed in terms of sensitivity (Se) andspecificity (Sp) as a function of the selected features, of the combinations of 3 different inter-fibers distances and of thenumbers of principal components, such that: Se and Sp≈ 100% when discriminating CH vs. others; Sp≈ 100% and Se> 95% when discriminating Healthy vs. AH or D; Sp≈ 74% and Se≈ 63% for AH vs. D.