Fast optical source for quantum key distribution based on semiconductor optical amplifiers.

A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as 1.14×10⁻² while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

Carvedilol stability in paediatric oral liquid formulations.

OBJECTIVE: Two carvedilol aqueous solutions and one carvedilol aqueous suspension for paediatric oral use (1mg/ml) were studied to determine their stability. METHOD: All samples were stored at 4, 25 and 40°C. Carvedilol content of each of the three formulations was tested using high performance liquid chromatography (HPLC). Each sample was analysed in triplicate at 0, 3, 7, 14, 28 and 56 days. RESULTS: Carvedilol stayed stable in the acidic aqueous solution at the three different temperatures during the 56 days of the study. In the alkaline solution, carvedilol was stable during 56 days at 25°C, but only 28 days at 4 and 40°C. In the aqueous suspension, carvedilol was stable during 56 days at 4 and 25°C, but only 28 days at 40°C. CONCLUSIONS: All the formulations that were tested can be stored at 25°C for at least 56 days.

Hemispheric laterality and dissociative tendencies: differences in emotional processing in a dichotic listening task.

The present work investigates whether the hemispheric processing of both verbal and emotional stimuli, studied by means of a dichotic listening task, differs between normal high and low dissociators as assessed by the Dissociative Experiences Scale (DES; Bernstein & Putnam (1986). Development, reliability and validity of a dissociation scale. Journal of Nervous and Mental Disease, 174(2), 727-735). Two groups of subjects (50 high and 50 low dissociators), participated in the experiment. The task consisted in identifying both verbal and emotional stimulus-targets, respectively, on successive sessions. Reaction time and response accuracy were registered and analysed using ANOVA (Analysis of Variance). The interaction between stimuli (verbal, emotional), channel (right ear, left ear), and dissociation level (high, low) reached statistical significance in terms of accuracy measures (d': F(1,98)=4.75; p<.05). Both high and low dissociators exhibited the expected right ear advantage (REA effect) on verbal targets. On the other hand, whereas low dissociators exhibited the expected left ear advantage (LEA effect) on emotional targets, high dissociators failed to follow this typical pattern of hemispheric asymmetry: both hemispheres exhibited similar performances. These results confirm the hypothesis that dissociation is related to changes in hemispheric processing, specifically of emotional information.

Characterization of 5-HT receptors on human pulmonary artery and vein: functional and binding studies.

1. This study aimed to investigate the 5-hydroxytryptamine (5-HT) receptors mediating contraction of ring preparations isolated from human pulmonary arteries and veins. In functional studies, the responses to 5-HT, sumatriptan, ergotamine, serotonin-O-carboxymethyl-glycyl-tyrosinamide (SCMGT), alpha-methyl 5-HT (alpha-Me) and 2-methyl 5-HT (2-Me) were studied with WAY100635, GR127935, ritanserin, zacopride and SB204070 as antagonists. 2. All agonists produced concentration-dependent contractions of human pulmonary artery and vein preparations. The order of potency (-log ECS0 values) was ergotamine (6.88) > 5-HT (6.41) > or = SCMGT (6.20) = sumatriptan (6.19) > or = alpha-Me (6.04) in the artery, and ergotamine (7.84) > 5-HT (6.96) > sumatriptan (6.60) = alpha-Me (6.56) > SCMGT (6.09) in the vein. The potency of each agonist, except for SCMGT, was greater in vein than in artery preparations. Contractile responses to 5-HT were similar in intact and endothelium-denuded preparations but responses to sumatriptan were enhanced in artery rings without endothelium. 3. GR127935 (1 nM to 0.5 microM) produced an unsurmountable antagonism of the response to 5-HT, sumatriptan, ergotamine and SCMGT. Ritanserin (1 nM to 1 microM) also reduced the maximum contractile responses to 5-HT, ergotamine and alpha-Me in artery and vein preparations without affecting those to sumatriptan and SCMGT. In endothelium-denuded preparations, surmountable antagonism of sumatriptan by GR127935 (in the presence of ritanserin) and of alpha-Me by ritanserin (in the presence of GR127935) allowed for the calculation of the apparent pK(B) values of GR127935 (9.17+/-0.11 in artery and 9.11+/-0.05 in vein) and ritanserin (8.82+/-0.09 in artery and 8.98+/-0.12 in vein). 4. WAY100635 (1 nM to 1 microM), zacopride (1 nM to 1 microM), or SB204070 (1 nM) did not significantly alter the concentration-response curves for 5-HT, sumatriptan, ergotamine, SCMGT or 2-Me in human pulmonary artery or vein thus indicating that 5-HT1A, 5-HT3 and 5-HT4 receptors are presumably not involved in the contractile response to these agonists. 5. Binding studies using selective radioligands for different 5-HT receptors could not detect the presence of 5-HT1A receptor binding in human pulmonary blood vessels whereas the 5-HT(1B/1D) radioligand [3H]-5CT significantly labelled a population of specific binding sites in both vessel types. The presence of 5-HT2A receptors could also be inferred from the level of binding of [3H]-ketanserin to membranes obtained from human pulmonary vessels, although significance could not be reached for arteries. 5-HT4 specific receptor binding was scarce in veins and absent in the case of arteries. 6. These findings indicate that the human pulmonary artery and vein have a mixed functional population of 5-HT(1B/1D) and 5-HT2A receptors mediating the contractile response to 5-HT which is consistent with results of the binding studies.

Enhancement of surface inspection by Moiré interferometry using flexible reference gratings.

We have extended the use of shadow Moiré technique to be implemented in simple curved surfaces by using a flexible grating. Dynamic visual inspection of surface micro-damages is significantly favored by the use of well adapted pliable gratings compared to the use of flat reference gratings. The experimental set-up consists of a plastic foil with a printed Ronchi grating stretched between three points which adapts to any cylindrical or conical convex surface independently of the relative orientation grating/surface. Static quantification of defects profiles is also possible with an attached CCD camera. Visual detection of defects in the range of ~30 microm in depth is obtainable.

Generalized grating imaging using an extended monochromatic light source

It is a well-known fact that one grating can act as an imaging element for another grating when the first is illuminated with an extended monochromatic light source. The conditions for image formation in such a system are studied when the finite size and position of the broad light source are considered. From the presented analysis, expressions for the location and the depth of focus of such images can be derived.

Estimation of the standard deviation in three-dimensional microscopy by spatial statistics.

Usually, the calibration process for three-dimensional microscopy involves the use of a reference flat surface. The random fluctuations of the topographic image for this reference surface are used for determining the uncertainty of the microscope. When the sample material or the measuring conditions of the microscope are modified (such as the objective used in a confocal microscope, or the tip in an atomic force microscope), the measuring conditions vary and thus a new calibration is required. In this work, a technique based on spatial statistics methods (more specifically, the variogram function) is proposed to determine accurately the standard deviation for three-dimensional microscopy that does not require a reference flat surface and therefore eliminates the need for a previous calibration process of this parameter.

ABCD matrix for weakly apertured Gaussian beams in the far field.

When a Gaussian beam is weakly diffracted by a circular aperture it can be approximated by another Gaussian beam with slightly different properties in the far field. In this Technical Note, using the relationship between these two Gaussian beams, before and after the aperture, an ABCD matrix is defined for cascaded laser systems.

ABCD matrix for apertured spherical waves.

An ABCD matrix for describing the hard aperture under a large Fresnel number is defined in this Technical Note based on Li and Wolf's formula. It is useful for analyzing focal shifts of complicated optical systems with hard apertures.

Moiré signal distortion caused by phase and amplitude nonuniformities of light beams.

The distortion suffered by the amplitude and phase of a moiré signal when the illuminating beam is not a coherent and monochromatic plane wave has been measured by using different kinds of illuminating sources and a phase-sensitive intensity subtraction technique. A phenomenological model is proposed that explains these effects in terms of an irregular amplitude distribution and a phase evolution of the moiré signal with a grating gap. These effects are of great interest in all the measurement techniques related to the moiré effect, especially when compact light sources such as light-emitting diodes and incandescent lamps are used.

Automatic three-dimensional spectrogoniometer for determination of optical properties and surface parameters.

An automatic three-dimensional spectrogoniometer is presented. The wavelength of ligth and angles of incidence and observation are variable, making it capable of performing different optical characterizations in an integrated way.

Phase-unwrapping algorithm for noisy phase-map processing.

Automated fringe-pattern processing is important in a great number of industrial applications, such as optical data testing and quality control. One of the main problems that arises with these processes is the automated phase unwrapping of the phase map associated with the fringe pattern. Usually the phase map presents problems such as noise, and low-modulation areas. A new phase-unwrapping algorithm with high noise immunity is presented. The algorithm is easily implemented and can process arbitrary shapes. The main features of this algorithm are the use of a queue for the processing of arbitrary shapes and a selection criterion that determines which pixels are going to be processed.

Reflection optical encoders as three-grating moiré systems.

Reflection optical encoders are studied as three-grating moiré systems. An analysis is made of the differences that may appear between it and the standard case in which an optical encoder is regarded as a two-grating system.

Retroreflective properties of a hemispherical surface.

A dielectric hemisphere and a reflective hemisphere are presented as a new type of retroreflector. The conditions that create this property and potential applications are discussed.

Planar optical array with a spatial-integration feature.

A planar optical array is presented that provides a selective concentration of the light incident upon the system onto a given area. Several alternative designs are analyzed and explained geometrically. The photometric calculation is presented for three different levels of approximation. A prototype of the proposed system is tested, showing good accordance with the theoretical predictions.

Influence of coating thickness on the performance of a Fabry-Perot interferometer.

The effects of the coating thickness on the physical performance of a Fabry-erot interferometer (FP) are investigated. The FP is modeled as three media separated by two thin films and not merely by two interfaces. We show that the transmitted intensity obeys an Airy function, but not the reflected intensity because of the appearance of a complex factor accounting for the coupling between the reflected waves in the coatings. The Stokes relations are generalized for this model. We study the dependence of the phase lag of reflection in the coatings on the angle of incidence, which causes a shift in the position of the intensity maxima. We discuss as well the properties of the FP with an absorbing medium in the cavity, defining a merit function that optimizes the compromise between peak transmission and finesse.

Polycrystalline materials for magneto-optical devices.

The replacement of single-crystal compounds by polycrystalline compounds in some magneto-optical devices is proposed. For this purpose a characterized polycrystalline, Cd(0.55)Mn(0.45) Te, has been manufactured. Its Verdet constant and cutoff wavelength are identical to those of single crystals of the same composition. Optical transmission is lower in polycrystals because they have larger light-scattering coefficients; hence they are not well suited for applications such as isolators but are adequate for magnetometers, modulators, and similar devices.

Complex beam parameter and ABCD law for non-Gaussian and nonspherical light beams.

We define the width, divergence, and curvature radius for non-Gaussian and nonspherical light beams. A complex beam parameter is also defined as a function of the three previous ones. We then prove that the ABCD law remains valid for transforming the new complex beam parameter when a non-Gaussian and nonspherical, orthogonal, or cylindrical symmetric laser beam passes through a real ABCD optical system. The product of the minimum width multiplied by the divergence of the beam is invariant under ABCD transformations. Some examples are given.

Colorimetric matching by minimum-square-error fitting.

Least-squares approximation can be used in image-based colorimetry once the set of sampling functions is selected. We discuss the accuracy obtained in earlier research, and we compare it with a better calculation method.

Local dioptric power matrix in a progressive addition lens.

In this paper we use the formalism of the Dioptric Power Matrix to visualise and characterise the properties of a Progressive Addition Lens. For progressive addition lenses, the dioptric power matrix is point-dependent, and we have measured its elements over the lens surface by means of an automatic focimeter. We show the obtained contour plots corresponding to the matrix elements, and we compare them with the traditional sphere and cylinder graphs. Although the two representations give the same information, the advantages and disadvantages between them are analysed. The dioptric power matrix method turns out to be specially useful for the computation of prismatic effects along the lens surface.