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Simultaneous measurement of the degree of circular polarization and intensity of a laser beam is essential in advanced photonic applications. However, it is not feasible with conventional helicity dependent detectors where an additional detector is needed to measure the intensity. Here, we report the development of a spin-optoelectronic detector that can measure the degree of circular polarization and the intensity of a laser beam simultaneously. The principle of operation of device is based on the two independent fundamental phenomena occurring in Au/InP hybrid structures, namely, Inverse Spin Hall Effect (ISHE) and the Photo-Voltaic (PV) Effect. The magnitude of ISHE and PV signals is simultaneously measured across the two pairs of contacts that are made on the top of device. No cross talk is observed between the two detectors made on the same chip. The all-electronic compact device is fast, operates at room temperature, and opens up the possibility of many applications in an integrated optoelectronic platform. [ABSTRACT FROM AUTHOR]

Photodetectors hold a critical position in optoelectronic integrated circuits, and they convert light into electricity. Over the past decades, high-performance photodetectors (PDs) have been aggressively pursued to enable high-speed, large-bandwidth, and low-noise communication applications. Various material systems have been explored and different structures designed to improve photodetection capability as well as compatibility with CMOS circuits. In this paper, we review state-of-theart photodetection technologies in the telecommunications spectrum based on different material systems, including traditional semiconductors such as InGaAs, Si, Ge and HgCdTe, as well as recently developed systems such as low-dimensional materials (e.g. graphene, carbon nanotube, etc.) and noble metal plasmons. The corresponding material properties, fundamental mechanisms, fabrication, theoretical modelling and performance of the typical PDs are presented, including the emerging directions and perspectives of the PDs for optoelectronic integration applications are discussed. [ABSTRACT FROM AUTHOR]

The main objective of this study is to optimize an optical component considered as an essential building block in wavelength division multiplexing applications. The work presented here focuses on the design of an optimum 1 x 8 compact splitter based on a two-dimensional (2-D) photonic crystal (PhC) in triangular unit cells exhibiting high transmission. It generates a contribution to the 2-D planar PhCs in the integrated optics field. These new materials may prohibit the propagation of light in certain directions and energies. We also optimize the splitter topologies in order to integrate them in optoelectronic systems as division components. To do so, the 2-D finite-difference time-domain method is employed to characterize the transmission properties. Simulation results show that total transmissions of about 86%, 78%, and 86% for the 1 x 2, 1 x 4, and 1 x 8 Y splitters, respectively, at output ports are obtained around the wavelength 1.55 µm widely used in optical telecommunications. It is demonstrated numerically that the corresponding total insertion losses for the three splitters are, respectively, about 0.65, 1.08, and 0.65 dB. The simulation results are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study in physiological monitoring between a wearable opto-electronic patch sensor (OEPS) comprising a three-axis Microelectromechanical systems (MEMs) accelerometer (3MA) and commercial devices. The study aims to effectively capture critical physiological parameters, for instance, oxygen saturation, heart rate, respiration rate and heart rate variability, as extracted from the pulsatile waveforms captured by OEPS against motion artefacts when using the commercial probe. The protocol involved 16 healthy subjects and was designed to test the features of OEPS, with emphasis on the effective reduction of motion artefacts through the utilization of a 3MA as a movement reference. The results show significant agreement between the heart rates from the reference measurements and the recovered signals. Significance of standard deviation and error of mean yield values of 2.27 and 0.65 beats per minute, respectively; and a high correlation (0.97) between the results of the commercial sensor and OEPS. T, Wilcoxon and Bland-Altman with 95% limit of agreement tests were also applied in the comparison of heart rates extracted from these sensors, yielding a mean difference (MD: 0.08). The outcome of the present work incites the prospects of OEPS on physiological monitoring during physical activities. [ABSTRACT FROM AUTHOR]

We present a microfluidic optoelectronic sensor for saliva diagnostics with a potential application for non-invasive early diagnosis of stomach cancer. Stomach cancer is the second most common cause of cancer-related deaths in the world. The primary identified cause is infection by a gram-negative bacterium Helicobacter pylori . These bacteria secrete the enzyme urease that converts urea into carbon dioxide (CO 2 ) and ammonia (NH 3 ), leading to their elevated levels in breath and body fluids. The proposed optoelectronic sensor will detect clinically relevant levels of CO 2 and NH 3 in saliva that can potentially be used for early diagnosis of stomach cancer. The sensor is composed of the embedded in a microfluidic device array of microwells filled with ion-exchange polymer microbeads doped with various organic dyes. The optical response of this unique highly diverse sensor is monitored over a broad spectrum, which provides a platform for cross-reactive sensitivity and allows detection of CO 2 and NH 3 in saliva at ppm levels. [ABSTRACT FROM AUTHOR]

Electrical detection of spins is an essential tool for understanding the dynamics of spins, with applications ranging from optoelectronics and spintronics, to quantum information processing. For electron spins bound to donors in silicon, bulk electrically detected magnetic resonance has relied on coupling to spin readout partners such as paramagnetic defects or conduction electrons, which fundamentally limits spin coherence times. Here we demonstrate electrical detection of donor electron spin resonance in an ensemble by transport through a silicon device, using optically driven donor-bound exciton transitions. We measure electron spin Rabi oscillations, and obtain long electron spin coherence times, limited only by the donor concentration. We also experimentally address critical issues such as non-resonant excitation, strain, and electric fields, laying the foundations for realizing a single-spin readout method with relaxed magnetic field and temperature requirements compared with spin-dependent tunnelling, enabling donor-based technologies such as quantum sensing. [ABSTRACT FROM AUTHOR]

Single crystalline copper selenide (Cu2−xSe) nanocrystals (NCs) with well-defined octahedral morphology are successfully synthesized by a colloidal hot-solution injection method from the reaction of anhydrous CuCl with Ph2Se2 under argon flow, in which 1-octadecene (ODE) and oleylamine (OAm) are used as solvent and surfactant, respectively. The Cu2−xSe octahedral nanostructures are characterized by XRD, SEM, TEM, HRTEM, SAED, EDS, FT-IR and XPS and it is found that they are in the cubic phase with high quality. The growth process of the nanostructures is investigated and it is noted that reaction temperature, reaction time and capping surfactant OAm play significant roles in controlling the morphologies of the final products. Meanwhile, the current–voltage (I–V) behavior of the as-prepared octahedral Cu2−xSe nanostructures is explored for the first time and it is found that the Cu2−xSe octahedral nanostructures are promising candidates for application in photodetection and related areas. [ABSTRACT FROM AUTHOR]

Enologists usually rely on spectrophotometers to perform the chromatic characterization of red wines. This work reports an optoelectronic instrument based on absorbance measurements aiming not only at the assessment of the chromatic characteristics of finished red wines, but at the supervision of the gradual maceration of fermenting grape musts as well. Maceration is a chemical process that takes place during the early stages of the fermentation that finally results in red wine. It is through maceration that wine acquires its distinctive chromatic features. Key issues related to the selection of optoelectronic components, the system design and its final validation using diluted wine samples are thoroughly discussed. Resolution figures lie in the range of one thousandth of an absorbance unit. Maceration has been successfully monitored with the proposed instrument using grape must samples extracted during the first three days from two different fermentations. [ABSTRACT FROM AUTHOR]

An integrated Sequential Injection (SI)/Flow Injection (FI) system furnished with a miniaturized LED-based fluorometric detector is presented in this work for expedient bioaccessibility tests of orthophosphate in soils. Equipped with a microcolumn of conical shape containing 50 mg of soil, the hybrid flow system was resorted to on-line dynamic leaching and real-time quantification of pools of mobilizable orthophosphate using a bi-directional syringe pump and multiposition valve. The flexibility of the flow manifold was harnessed to explore both bi-directional and uni-directional flow extraction modes with the added degree of freedom of on-line dilution of extracts whenever needed. Bioaccessible orthophosphate was split in three fractions, the so-called NH 4 Cl fraction containing labile exchangeable phosphates, the alkaline fraction with Fe and Al-bound phosphates and the acidic fraction containing Ca-bound phosphates. The prevailing molybdenum blue photometric detection method is replaced by spectrofluorometric detection based on the ion pair formation between the phosphomolybdate heteropolyacid and rhodamine B with the subsequent quenching of the dye fluorescence. The dedicated optoelectronic detector was integrated in a secondary FI manifold and operated according to the fluorometric paired emitter–detector diode (FPEDD) principle involving two light emitting diodes as fluorescence inductors and one as detector of LED-induced fluorescence. Demonstrated with the analysis of a standard reference material (SRM 2711) and a real agricultural soil, the developed FI/SI fractionation system with FPEDD detection is proven reliable against the standard molybdenum blue method ( p >0.05), and useful for investigation of the leaching kinetics of orthophosphate in bioaccessibility tests through in-line recording of the extraction profiles. [ABSTRACT FROM AUTHOR]

Activation of aromatic CH bonds by a transition metal catalyst has received significant attention in the synthetic chemistry community. In recent years, rapid and site-selective extension of π-electron systems by C-H activation has emerged as an ideal methodology for preparing organic materials with extended π-systems. This Review focuses on recently reported π-extending C-H activation reactions directed toward new optoelectronic conjugated materials. [ABSTRACT FROM AUTHOR]

Certain insects affect cultivations in a detrimental way. A notable case is the olive fruit fly (Bactrocera oleae (Rossi)), that in Europe alone causes billions of euros in crop-loss/per year. Pests can be controlled with aerial and ground bait pesticide sprays, the efficiency of which depends on knowing the time and location of insect infestations as early as possible. The inspection of traps is currently carried out manually. Automatic monitoring traps can enhance efficient monitoring of flying pests by identifying and counting targeted pests as they enter the trap. This work deals with the hardware setup of an insect trap with an embedded optoelectronic sensor that automatically records insects as they fly in the trap. The sensor responsible for detecting the insect is an array of phototransistors receiving light from an infrared LED. The wing-beat recording is based on the interruption of the emitted light due to the partial occlusion from insect's wings as they fly in the trap. We show that the recordings are of high quality paving the way for automatic recognition and transmission of insect detections from the field to a smartphone. This work emphasizes the hardware implementation of the sensor and the detection/counting module giving all necessary implementation details needed to construct it. [ABSTRACT FROM AUTHOR]

This paper describes two different optoelectronic detection techniques: cavity-enhanced absorption spectroscopy and photoacoustic spectroscopy. These techniques are designed to perform a sensitive analysis of trace gas species in exhaled human breath for medical applications. With such systems, the detection of pathogenic changes at the molecular level can be achieved. The presence of certain gases (biomarkers), at increased concentration levels, indicates numerous human diseases. Diagnosis of a disease in its early stage would significantly increase chances for effective therapy. Non-invasive, real-time measurements, and high sensitivity and selectivity, capable of minimum discomfort for patients, are the main advantages of human breath analysis. At present, monitoring of volatile biomarkers in breath is commonly useful for diagnostic screening, treatment for specific conditions, therapy monitoring, control of exogenous gases (such as bacterial and poisonous emissions), as well as for analysis of metabolic gases. [ABSTRACT FROM AUTHOR]

This paper reports the development of a novel force/torque sensor for robotic applications. Optoelectronic components have been used as sensible elements, allowing a relatively simple and quite reliable implementation of the sensor. These properties allow an easier integration of the sensor in a number of different robotic systems, such as in the fingers of robotic hands or in industrial grippers. The basic working principle and the design of the sensor are presented, and experimental data are reported and discussed to illustrate its theoretical model and its main features. Finally, the implementation of a sensor prototype is shown, and its use as an intrinsic tactile sensor is investigated and experimentally validated. [ABSTRACT FROM AUTHOR]

When clouds cannot be detected by a radiometry approach, the O2-A absorption band, located around 762 nm, can be used under clear sky conditions to perform this task. We present in this article a 5S-like formalism for the O2band, based on single scattering approximation, aiming to isolate the aerosol contribution. The apparent pressure of the aerosols layer, derived from this new formalism, is used in the processing chain for the Medium Resolution Imaging Spectrometer (MERIS; on-board the ENVISAT platform) third processing to detect the presence of cirrus clouds over water. This formalism can be used as well over land to correct surface pressure, derived from the O2-A band, from the influence of the atmosphere. [ABSTRACT FROM PUBLISHER]

The preparation and characterization of hexylated, brominated, and 5-hexyl-2-thienyl-substituted tetrathienoacridine (TTAc) is described. Comparative electrochemical, optical, computational, and solid-state studies with their thienoanthracene (TTAn) analogs demonstrate that replacement of CH with nitrogen leads to an overall lowering of the frontier molecular energy levels and decrease in the HOMO-LUMO energy gap. While the brominated TTAc and TTAn derivatives are isostructural, as indicated by X-ray diffraction studies, the lower sublimation temperature and thermochromic behaviour exhibited by bromo-TTAc is attributed to an additional dipole−dipole interaction resulting from the dipole moment afforded by carbon/nitrogen substitution in the core aromatic ring. This work represents a fundamental study of heteroatom substitution in 2-D conjugated small molecules and investigates how inclusion of an electron deficient aromatic ring into the molecular framework (i.e., acridine versus anthracene) can influence the physical properties. [ABSTRACT FROM AUTHOR]

We demonstrate dissolved ammonia (NH3) sensing in complex mixtures using an optoelectronic sensor comprising a composite sensing material based on a metalloporphyrin zinc tetraphenylporphyrin (ZnTPP) and spectroscopic detection. The metalloporphyrin dye is incorporated within ion-exchange polymeric microbeads arranged in a microfluidic array. Spectroscopic analysis at multiple wavelengths allows sensitive detection in complex backgrounds. The sensor shows preferential sensitivity to ppm levels of concentrations of NH3 dissolved in water, as well as in human saliva, making it relevant for medical diagnostic applications (e.g. detection of stomach bacterial infections). The microfluidic platform and a miniaturized optical arrangement provide a potential for the development of a portable low-power sensor for detection of dissolved ammonia for a variety of applications. [ABSTRACT FROM AUTHOR]

The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability. [ABSTRACT FROM AUTHOR]

This article reports the synthesis and characterisation of Barium titanate (BaTiO3) nanocomposite and its application as opto-electronic humidity sensor. Titanium tetrachloride and barium hydroxide were mixed in molar ratio 1 : 1 in deionised water under continuous stirring at room temperature. Later, sodium hydroxide solution was added to above solution with continuous stirring. Finally, BaTiO3gel was obtained. The synthesised nano-composite material was characterised using a scanning electron microscope, X-ray diffraction (XRD) and UV-Visible spectrophotometer. SEM image of the composite film shows that the film is porous having uniform grains. From XRD the minimum crystallite size of BaTiO3was found to be 8 nm using Debye–Scherer formula. UV-Visible absorption spectroscopy was used for optical characterisation of the film. It was found that the optical band gap of the composite material was 3.50 eV. Barium titanate thin film was deposited on the base of an equilateral prism using sol–gel spin coating process at 4000 rpm. The humidity sensing properties of the film was investigated at different angles of incidence. It was observed that the intensity of reflected light increased with an increase in relative humidity (%RH) in the range 5–95% at a particular angle of incidence. Sensing element has maximum sensitivity ∼6 µW/%RH, which is quite significant for sensor fabrication purposes. [ABSTRACT FROM AUTHOR]

We review recent work on THz frequency combs generated by femtosecond lasers. An overview about the underlying theory and application examples for the analysis of THz signals are given. Using different optoelectronic detection methods, spatially resolved measurements of frequency, phase, and amplitude of GHz and THz emitters are presented. The measurement setup allows for high-precision measurements of the frequency (accuracy of 9 · 10within a 10 s measurement interval), relative amplitude (standard deviation of the mean 0.1 %) and phase (standard deviation of the mean 0.2°). Moreover, the accuracy and invasiveness of different optoelectronic techniques are compared. The large spectral coverage provided by THz frequency combs is demonstrated by simultaneously measuring signals at 16 GHz and 28 THz. [ABSTRACT FROM AUTHOR]

Abstract: A thin, flat and single crystal membrane on which to mount sensors is generally required for integration with electronics through standard silicon processing technology. We present an approach to producing single crystal membranes of germanium with in-built tensile strain, which serves to keep the membrane flat and ripple free, and demonstrate a 600nm thick, free-standing 1mm2 Ge membrane. We convert the fabrication technique into an integrated-circuit compatible wafer scale process to produce 60nm thin membranes with large areas of 3.5mm2. The single crystal Ge membrane provides an excellent platform for further epitaxial growth or deposition of materials. [Copyright &y& Elsevier]

The optoelectronic performance of the mid-wavelength HgCdTe infrared focal plane array (IRFPA) with refractive microlenses integrated on its CdZnTe substrate has been numerically simulated. A reduced light-distribution model based on scalar Kirchhoff diffraction theory was adopted to reveal the true behavior of IRFPAs operating in an optical system under imaging conditions. The pixel crosstalk obtained and the energy-gathering characteristics demonstrated that the microlenses can delay the rise in crosstalk when the image point shifts toward pixel boundaries, and can restrict the major optical absorption process in any case within a narrow region around the pixel center. The dependence of the microlenses' effects on the system's properties was also analyzed; this showed that intermediate relative aperture and small microlens radius are required for optimized device performance. Simulation results also indicated that for detectors farther from the center of the field of view, the efficacy of microlenses in crosstalk suppression and energy gathering is still maintained, except for a negligible difference in the lateral magnification from an ordinary array without microlenses. [ABSTRACT FROM AUTHOR]

Localized structures have been observed in many spatially extended systems of either biological, chemical, or physical nature. Here, we study experimentally front pinning and dissipative localized structures in a delayed optical system based on a bistable semiconductor laser with optoelectronic feedback. We observe that many of the concepts known to apply to spatially localized structures also apply in this context, with specificities related to the lack of reversibility symmetry. Numerical simulations based on purely prototypical modeling reproduce very well the experimental findings, which indicates that the results do not depend on the specific physical system under consideration, but are, on the contrary, very generic features of time delayed systems. [ABSTRACT FROM AUTHOR]

The work deals with modeling an optoelectronic fire smoke alarm detector at the functional diagram level by means of MATLAB tools. The developed model makes it possible to estimate the ability of a logic unit to distinguish between fire signals and noise. [ABSTRACT FROM AUTHOR]

In this study, we report the development of a phosphate sensor by exploiting phosphate-binding capability ofAcinetobactersp. biopolymer. An engineered strain ofAcinetobactersp. overproducing biopolymer was selected by Tn5 mutagenesis. The mutant showed a five-fold increase in biopolymer production and an increase in expression of intracellular biopolymer synthetic enzymes, phosphoglucomutase and glucosyl transferase. Physical and chemical analysis of biopolymer revealed a porous, compact surface morphology and a polysaccharide structure with predominance of uronic acid residues. Cellulose acetate membranes precoated with purified biopolymer were exposed to phosphate solutions and membrane-bound phosphate was determined by stannous chloride method. The colored membranes were analyzed by a LED (690 nm)/photodiode detection system. The phosphate concentration was estimated by converting the amperometric signal to phosphate concentrations from a standard plot. In conclusion, we anticipate that the developed sensor could be used for on-site phosphate analysis due to its compactness, portability, low detection levels (1 μg L−1), and low power consumption. [ABSTRACT FROM PUBLISHER]

The design, fabrication and validation of an optoelectronic sensor implemented in an easy-to-use portable device for the selective and sensitive detection of CO in air is reported herein. The system is based on the colour changes observed in the binuclear rhodium complex of formula [Rh2[(C6H4)P(C6H5)2]2(O2CCF3)2] (CF3CO2H)2 (1) upon coordinating CO molecules in axial positions. Complex 1 is used supported on cellulose chromatography paper. In this support, colour changes to the naked eye are observed for CO concentrations above 50ppm. The probe is also implemented in a simple portable optoelectronic device. The cellulose support containing probe 1 in this device is placed inside a small dark chamber, is illuminated with a tricolour LED emitting at 624, 525 and 470nm, respectively corresponding to red (R), green (G) and blue (B) light, and reflected light is detected by a photodiode. With a transimpedance amplifier, the current generated by the photodiode is transformed into a voltage compatible with the 10-bit analogue-to-digital converter (ADC) port. Colour changes are measured as the distance d between the R, G and B data of the blank (probe without CO) and that for a certain CO concentration. Typical calibration curves are fitted using a bi-exponential equation. This system offers a typical response time of a few minutes (ca. 7min) and a limit of detection of 11ppm. The probe in the cellulose supports is also highly reversible. The optoelectronic device is portable (dimensions 14×8.5×3.5cm; weighs approximately 270g) and is powered by AA batteries. In addition, no variations in experimental parameter d upon exposure to CO2, N2, O2, Ar, water-saturated air and vapours of chloroform, hexane, ethanol, acetone, methane, toluene or formaldehyde are observed. Besides, colour changes are found for acetonitrile vapour, NO and NO2, but only at high concentrations. For validation purposes, the device was used to determine the CO present in the 4-shed accumulated smoke of two cigarette types after passing smokers’ lungs. [ABSTRACT FROM AUTHOR]

The proposed colorimetric sensor of ammonia for the confined animal feeding industry uses the method of optoelectronic spectroscopic measurement of the reversible change of the color of a nanocomposite reagent film in response to ammonia. The film is made of a gold nanocolloid in a polymer matrix with an ammonia-sensitive indicator dye additive. The response of the indicator dye (increase of the optical absorption between 550 and 650 nm) is enhanced by the nanoparticles (~8 nm in size) in two ways: (a) concentration of the optical field near the nanoparticle due to the plasmon resonance and (b) catalytic acceleration of the chemical reaction of deprotonization of the indicator dye in the presence of ammonia and water vapor. This enhancement helps to miniaturize the sensing element without compromising its sensitivity of <1 parts per million (ppm) for the range 0 to 100 ppm. The sensor underwent field tests in commercial poultry farms in Georgia and Arkansas and was compared against a scientific-grade photoacoustic gas analyzer. The coefficient of correlation between the sensor and the photoacoustic data for several weeks of continuous side-by-side operation in a commercial poultry house was ~0.9 and the linear regression slope was 1.0. The conclusions on the necessary improvements were made. [ABSTRACT FROM AUTHOR]

The monitoring of ammonia gas concentrations by means of an optoelectronic gas sensor is described in this paper. An optoelectronic gas sensor based on interferometric, gasochromic nanostructures contains Cu-phthalocyanine (CuPc) thin films and palladium (Pd) thin film. The optical changes (interferometric colour changes) that occur Pd/CuPc or CuPc are due to being exposed to different relative humidites (RH) or various ammonia concentrations (at 70°C). The CuPc films were deposited by thermal evaporation. Additionally, to enhance the sensing performance of these CuPc thin films, the surfaces of CuPc were coated with an ultra-thin film of palladium. This metallic Pd film can act as catalyst that increasing the efficiency of dissociation of the molecular ammonia gas to its more reactive atomic form in order to enhance the surface reaction during the gas sensing. The thin films of Pd were obtained also by means of the vacuum-thermal method. When a physical–chemical interaction between the sensing structure and ammonia gas is taking place (on the sensing window of the measuring channel), the interferential colour of the sensing element (nanostructure) changes and colour coordinates the measuring optical signal will also change. The colour sensor TCS230 detecting the intensity and change of the colour coordinates RGB of the optical signal resulting from the exposure sensing structure to ammonia gas. An optical ammonia gas sensor displays a very fast response time and a fast regeneration time at low temperature (70°C) in a dry and humid gaseous environment. [ABSTRACT FROM AUTHOR]

A novel method for assessing the accuracy of inertial/magnetic sensors is presented. The method, referred to as the "residual matrix" method, is advantageous because it decouples the sensor's error with respect to Earth's gravity vector (attitude residual error: pitch and roll) from the sensor's error with respect to magnetic north (heading residual error), while remaining insensitive to singularity problems when the second Euler rotation is close to + 90°. As a demonstration, the accuracy of an inertial/ magnetic sensor mounted to a participant's forearm was evaluated during a reaching task in a laboratory. Sensor orientation was measured internally (by the inertial/magnetic sensor) and externally using an optoelectronic measurement system with a marker cluster rigidly attached to the sensor's enclosure. Roll, pitch and heading residuals were calculated using the proposed novel method, as well as using a common orientation assessment method where the residuals are defined as the difference between the Euler angles measured by the inertial sensor and those measured by the optoelectronic system. Using the proposed residual matrix method, the roll and pitch residuals remained less than 1° and, as expected, no statistically significant difference between these two measures of attitude accuracy was found; the heading residuals were significantly larger than the attitude residuals but remained below 2°. Using the direct Euler angle comparison method, the residuals were in general larger due to singularity issues, and the expected significant difference between inertial/magnetic sensor attitude and heading accuracy was not present. [ABSTRACT FROM AUTHOR]

An automated laboratory based X-ray beamline with a multi-capillary sample chamber capable of undertaking small angle X-ray scattering measurements on a maximum of 104 samples at a time as a function of temperature between 5 and 85 °C has been developed. The modular format of the system enables the user to simultaneously equilibrate samples at eight different temperatures with an accuracy of ±0.005 °C. This system couples a rotating anode generator and 2D optoelectronic detector with Franks X-ray optics, leading to typical exposure times of less than 5 min for lyotropic liquid crystalline samples. Beamline control including sample exchange and data acquisition has been fully automated via a custom designed LabVIEW framework. [ABSTRACT FROM AUTHOR]

Abstract: We introduce and test an original approach for the optical assessment of road conditions due to various atmospheric perturbations such as the presence of ice, wet surfaces and rain. The technique is based on measuring diffused and reflected light under near infrared illumination, extracting the polarization contrast after reflection. Several tests, carried out on various types of asphalt and various thicknesses of water and ice layers, demonstrate that the system exhibits selectivity and robustness to allow the recognition of dry asphalt, water-layered, wet asphalt and asphalt with ice. [Copyright &y& Elsevier]

Abstract: In this paper, we present an uncalibrated phase read-out circuit for the detection of chemical substances through optoelectronic devices such as photodiodes and image sensors. The system, based on an automatic analogue circuit operating a phase-to-voltage conversion, shows the following main characteristics: high sensitivity and resolution, high accuracy and precision, low noise, reduced circuitry complexity (minimum required silicon area for the integration on chip), good linearity, capability of phase sign detection, independence from input signal amplitudes and waveforms, setting and zeroing of the output voltage offset and autocalibration. For these reasons, since several sensor applications need an array management performed by a single chip, the developed read-out analogue circuit can be easily integrated on a single chip together with optoelectronic devices, so it can be considered as a suitable solution for signal detection portable systems. Experimental measurements, conducted through the fabricated prototype PCB and employing a single commercial photodiode as light power sensor, have shown a high circuit sensitivity and resolution, in the three considered phase full-scales equal to ±10°, ±1° and ±0.1°, confirming the very good performances of the proposed system to reveal also very small phase shifts. The complete measurement system has been utilised to detect and quantify variations of the molar concentration of methylene blue diluted in distilled water by employing a suitable optical set-up that allowed to achieve resolutions lower than 44pM. [Copyright &y& Elsevier]

We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant'Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is completely modular and scalable, allowing one to cover areas of any sizes and shapes, and to measure different pressure ranges. In this work we present the main application areas for this technology. A first generation of the system was used to monitor human-robot interaction in upper- (NEUROExos; Scuola Superiore Sant'Anna) and lower-limb (LOPES; University of Twente) exoskeletons for rehabilitation. A second generation, with increased resolution and wireless connection, was used to develop a pressure-sensitive foot insole and an improved human-robot interaction measurement systems. The experimental characterization of the latter system along with its validation on three healthy subjects is presented here for the first time. A perspective on future uses and development of the technology is finally drafted. [ABSTRACT FROM AUTHOR]

The generation of a current by light is a key process in optoelectronic and photovoltaic devices. In band semiconductors, depletion fields associated with interfaces separate long-lived photo-induced carriers. However, in systems with strong electron-electron and electron-phonon correlations it is unclear what physics will dominate the photoresponse. Here, we investigate photocurrent in VO2, an exemplary strongly correlated material known for its dramatic metal-insulator transition at Tc ? 68 °C, which could be useful for optoelectronic detection and switching up to ultraviolet wavelengths. Using scanning photocurrent microscopy on individual suspended VO2 nanobeams we observe a photoresponse peaked at the metal-insulator boundary but extending throughout both insulating and metallic phases. We determine that the response is photothermal, implying efficient carrier relaxation to a local equilibrium in a manner consistent with strong correlations. Temperature-dependent measurements reveal subtle phase changes within the insulating state. We further demonstrate switching of the photocurrent by optical control of the metal-insulator boundary arrangement. Our work shows the value of applying scanning photocurrent microscopy to nanoscale crystals in the investigation of strongly correlated materials, and the results are relevant for designing and controlling optoelectronic devices employing such materials. [ABSTRACT FROM AUTHOR]

Abstract: A simple multicommutated flow system based on optoelectronic detector, three valves and peristaltic pump only has been developed for photometric determination of alkaline phosphatase activity in human serum. A miniaturized, compact flow-through detector dedicated to selective photometric detection of product formed in the course of the enzyme assay has been constructed using two paired light emitting diodes. The proposed analytical procedure based on kinetic methodology of enzyme activity detection and stopped-flow methodology of two-point measurements eliminates interferences caused by intense color of real samples and impurities present in commercial reagents. After optimization the system allows reproducible, mechanized analysis of human serum in relatively short time (8–9 samples per hour). Volume of serum required for single determination is 0.05mL only. The system validated with real clinical samples is useful for determination of enzyme activity in human serum at physiological and pathological levels. [Copyright &y& Elsevier]

Abstract: Two miniature, fibreless, compact and highly integrated flow-through optoelectronic detectors dedicated for photometric and fluorimetric determination of proteins have been developed. Both detectors operating according to paired-emitter-detector-diode methodology are constructed only of light emitting diodes and therefore their total cost is extremely low. The photometric detector is dedicated for protein determination according to Bradford method based on detection of protein adduct with Coomassie Brilliant Blue. The fluorimetric detector allows determination of proteins after reaction with fluorescamine. Both developed detectors have been incorporated into economic flow systems constructed of microsolenoid valves and pumps. The resulting multicommutated/multipumping flow analysis systems enable detection of albumins and globulins at ppm levels, thus they are useful for protein determination in diluted samples of physiological fluids. [Copyright &y& Elsevier]

The photoresponse of a TiO2 thin film was significantly improved due to the decrease in the Schottky barrier height between Au and TiO2via the formation of interface dipoles, which was caused by electrostatically self-assembled PEI on the surface of the TiO2 film. [ABSTRACT FROM AUTHOR]

The recent reports of various photodetectors based on molybdenum disulfide (MoS2) field effect transistors showed that it was difficult to obtain optoelectronic performances in the broad detection range [visible–infrared (IR)] applicable to various fields. Here, by forming a mono-/multi-layer nano-bridge multi-heterojunction structure (more than > 300 junctions with 25 nm intervals) through the selective layer control of multi-layer MoS2, a photodetector with ultrasensitive optoelectronic performances in a broad spectral range (photoresponsivity of 2.67 × 106 A/W at λ = 520 nm and 1.65 × 104 A/W at λ = 1064 nm) superior to the previously reported MoS2-based photodetectors could be successfully fabricated. The nano-bridge multi-heterojunction is believed to be an important device technology that can be applied to broadband light sensing, highly sensitive fluorescence imaging, ultrasensitive biomedical diagnostics, and ultrafast optoelectronic integrated circuits through the formation of a nanoscale serial multi-heterojunction, just by adding a selective layer control process. Fabrication of photodetector devices by selective etching of 2D materials can enable broadband detection. Here, the authors design mono- and multi-layer nano-bridge multi-heterojunction photodetectors based on MoS2 with high responsivities of 2.67 × 106 A/W and 1.65 × 104 A/W in the visible–infrared wavelength range and fast photoresponse. [ABSTRACT FROM AUTHOR]

Fruit flies (Diptera: Tephritidae) cause losses to world fruit growing. For a fast and effective control of the pest, it is necessary to identify the species and their populations. Thus, we developed an infrared optoelectronic sensor using phototransistors to capture the signal of the partial occlusion of the infrared light caused by the beating of the fly wings. Laboratory experiments were conducted using the sensor to capture the wing beat signal of A. fraterculus and C. capitata. The captured signals were used to obtain the characteristics of the flies' wing beats frequency and for a production of a dataset made available as one of the results of this work. For the passage detection, we developed the algorithm of detection of events of passage (PEDA) that uses the root mean square (RMS) value of a sliding window applied to the signal compared to a threshold value. We developed the algorithm of detection of events of passage (CAEC) that uses the techniques of autocorrelation and Fourier transform for the extraction of the characteristics of the wings' beat signal. The results demonstrate that it is possible to use the sensor for the development of an intelligent trap with detection and classification in real time for A. fraterculus and C. capitata using the wing beat frequency obtained by the developed sensor. [ABSTRACT FROM AUTHOR]

Objective The critical action for gait initiation involves lifting of the swing leg while shifting the centre of mass (CoM) of the body over the stance leg. This action is made possible by the initial displacement of the centre of pressure (CoP) in the direction of the swing leg. We hypothesised that the CoP displacement requires a coordinated action of the swing-leg abductor muscles and of the dorsiflexor muscles of the stance leg. Material/patients and methods Nine subjects initiated gait starting from three different initial stance widths (small, medium, wide). Optoelectronic, force platform and EMG measurements (ankle dorsi- and plantarflexors, and hip abductor muscles) were performed. The initial CoP and CoM displacements in opposite direction were accompanied by an early and moderate knee flexion of the stance leg. A linear relationship was found across stance widths between this knee flexion and CoP displacement. The concurrent dorsiflexor muscle activity of the stance leg was also greater with increasing step-width. This activity was almost simultaneous with that of the hip abductors of the swing leg. Results We propose that the early CoP displacement in the direction of the swing leg during the preparation phase of gait initiation is caused not only by abduction of the swing leg. The flexion of the stance knee, favoured by the foot dorsiflexor muscles of the stance leg, also contributes to the unloading of the stance leg and the loading of the other, thereby producing the torque for CoM displacement toward the stance leg. Discussion–conclusion We suggest to monitor the activity of both hip abductor muscles and foot dorsiflexor muscles whenever gait initiation is impaired by brain injury or movement disorders, which may particularly affect the fine coordination between these muscles in their combined effect on to the mediolateral displacement of the CoP. [ABSTRACT FROM AUTHOR]

Review: 374 refs. [ABSTRACT FROM AUTHOR]

(GaIn)(AsBi) layers were grown on a GaAs substrate. Their alloy composition, structural characteristics as well as the optical and electrical parameters were determined. It was found that by incorporating Bi and In into the lattice of GaAs, the energy bandgaps can be as narrow as 0.6 eV. These epitaxial layers of quaternary bismide alloys have shorter than a one picosecond carrier lifetime and a relatively large dark resistivity, demonstrating that this material is a good candidate for ultrafast optoelectronics applications. Thick quaternary bismide layers were used for the fabrication of photoconductive antenna type THz radiation detectors activated by femtosecond laser pulses. The performance of THz detectors manufactured from (GaIn)(AsBi) layers was comparable to that of previously reported Ga(AsBi) devices, but the range of optical wavelengths at which the detectors can be activated was considerably wider, covering the technologically important 1.55 μm wavelength range. [ABSTRACT FROM AUTHOR]

We investigate optical field enhancement for a wide mid-infrared range, originating from the excitation of graphene plasmons, by introducing a graded dielectric grating of varying period underneath a graphene monolayer. Excitation of the plasmonic mode can be achieved by illuminating a normal-incidence plane wave on the gratings due to guided-mode resonance. The gratings of varying period enable the excitation of the plasmonic mode with a very high field enhancement factor (to the order of magnitude of 1000) within a wide spectral band, which leads to the frequency-dependent spatially separated localization of the infrared spectrum modes. We also demonstrate that the excitation position of the plasmonic mode can be freely tuned by varying the thickness of the interlayer as well as the chemical potential of the graphene monolayer. This structure enables the design of two-dimensional plasmonic photonic circuits and metamaterials targeted towards numerous potential applications including optoelectronic detectors, light-harvest devices, on-chip optical interconnects, biosensors, and light-matter interactions. [ABSTRACT FROM AUTHOR]