Portion Of Light Research Articles

Effect of Ti Doping on the Photoelectrochemical Water Splitting Efficiency of WO3 Photoanode

Photocatalytic/photo-electrochemical (PEC) water splitting is a process whereby H2O is split into H2 and O2 using sunlight. This solar to chemical conversion (specifically, solar-energy-driven H2 production) is an ambitious yet crucial objective for futuristic production of eco-friendly energy that is storable and transportable and can be efficiently converted into electricity using fuel cells whenever necessary. Most importantly, this process is believed to lay the foundation for a sustainable hydrogen-based energy economy, which represents a carbon-neutral approach for producing hydrogen gas using the most abundant renewable resources: water and sunlight. WO3, an n-type semiconductor, has been extensively studied as a photoanode for PEC water splitting because of its advantages such as non-toxicity, low cost, and chemical stability in acidic aqueous media. Furthermore, WO3 has a moderate hole diffusion length (~150 nm) compared to other oxides such as Fe2O3 (2–4 nm) and TiO2 (~100 nm), with inherently good electron transport properties. After absorbing a portion of the visible light during illumination, WO3 generates electron–hole pairs and its valence band edge can provide enough potential for the oxidation of water since it is located at approximately 3.0 eV versus NHE. Several strategies have been implemented to enhance the photocatalytic properties of WO3, such as morphological control, transition metal doping, noble metal loading, surface sensitization, and formation of composite materials. In particular, doping and co-doping are possible ways of tailoring the electronic band structure as well as the PEC properties of WO3. Therefore, photo-electrochemical properties of tungsten oxide (WO3) can be tailored by doping foreign atoms from which conduction band (CB)/valence band (VB) edge positions can be altered. Band edge engineering for WO3 is essential since VB maximum of WO3 is more positive more the photo-oxidation potential of H2O but CB minimum of WO3 is lower than the reduction potential of H2O to limit spontaneous solar water reduction. In view of this, here we propose a simple, single step and efficient strategy for band edge tailoring of WO3 by Ti doping for efficient solar water splitting. The physical properties of synthesized Ti doped WO3 thin films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), UV-Vis absorption spectra and X-ray photoelectron spectroscopy (XPS). The incorporation of Ti into WO3 reduces the crystallinity and increases the band gap of WO3. From XPS valence band analysis, we confirm that, substitution Ti into WO3 leads to slight shift up the CB maximum upwards more closed to the H+/H2 redox potential without any change in VB maximum. Compared to un-doped WO3, Ti doped WO3 exhibited an unprecedented photocurrent of 1.6 mA cm-2 (at 0.8 V vs Ag/AgCl) under simulated 1.5 AM sunlight without an added water oxidation catalyst due to the improved electrical conductivity and reaction kinetics after Ti doping. The method presented here, demonstrates a simple but systematic and efficient approach for the design and fabrication of band edge tailored WO3 photoanodes via Ti doping efficient for photo-electrochemical water splitting. Figure 1

Self-assembled antireflection coatings for light trapping based on SiGe random metasurfaces

We demonstrate a simple self-assembly method based on solid state dewetting of ultrathin silicon films and germanium deposition for the fabrication of efficient antireflection coatings on silicon for light trapping. We fabricate SiGe islands with a high surface density, randomly positioned and broadly varied in size. This allows one to reduce the reflectance to low values in a broad spectral range (from 500 nm to 2500 nm) and a broad angle (up to ${55}^{\ensuremath{\circ}})$ and to trap within the wafer a large portion of the impinging light $(\ensuremath{\sim}40%)$ also below the band gap, where the Si substrate is nonabsorbing. Theoretical simulations agree with the experimental results, showing that the efficient light coupling into the substrate is mediated by Mie resonances formed within the SiGe islands. This lithography-free method can be implemented on arbitrarily thick or thin ${\mathrm{SiO}}_{2}$ layers and its duration only depends on the sample thickness and on the annealing temperature.

Synthesis, characterization and application of Co doped TiO2 multilayer thin films

Abstract To use the visible portion of solar light, 2% cobalt doped TiO2 (Co: TiO2) multilayer thin films having 1, 2, 3 and 4 stacked layers have been deposited on FTO substrates using spray pyrolysis technique. XRD results show that 1 and 2 layers of films have anatase phase. Brookite phase has been appeared at the 3 and 4 layered films. The average grain size of 1, 2, 3 and 4 layers of films are 14.4, 23.5, 29.7 and 33.6 nm respectively. UV–Vis results show that 4th layer film has high absorption in the visible region. The calculated Eg of 1, 2, 3 and 4 layers is 3.54, 3.42, 3.30 and 3.03 eV respectively. The calculated average sheet resistivity of 1, 2, 3 and 4 layers of films is 7.68 × 104, 4.54 × 104, 8.85 × 103 and 7.95 × 102 (ohm-m) respectively, according to four point probe technique. Solar simulator results show that highest solar conversion efficiency (5.6%) has been obtained by using 3 stacked layers photoanode. This new structure in the form of stack layers provides a way to improve the efficiency of optoelectronic devices.

Role of MoSe2 on nanostructures WO3-CNT performance for photocatalytic hydrogen evolution

Exploration of highly-efficient photocatalysts for H2 evolution is a great concern for fabricating sustainable green energy systems. In this contribution, unique and architectural nanostructured WO3-CNT @MoSe2 composites were developed through facile hydrothermal and wet-chemical co-precipitation method. Structural, morphological and optical properties were investigated using XRD, SEM, EDX, BET, UV–vis and PL spectroscopy. Experimental results demonstrate that photocatalytic activity increases with increasing coupling contents of MoSe2 upto 4% and for CNT-WO3 with 2at%. However, the further increment in content above this optimal level lessened the photocatalytic performance of composites. Higher photocatalytic activity towards hydrogen evolution is accredited to extended region of visible portion of solar light, large surface area and suppresses the charge carrier's recombination by synergistic effect between MoSe2 and WO3-CNT. Consequently, the as-prepared photocatalyst empowers potential applications for green hydrogen evolution.

Out-of-Range Stray Light Characterization of Single-Monochromator Brewer Spectrophotometers

ABSTRACTStray light in single-monochromator Brewer instruments increases the uncertainty of solar ultraviolet spectral irradiance measurements and ozone retrievals. To study how spectral irradiance within and outside the measurement ranges of the instruments affects stray light, two Brewer MKII instruments were characterized for the level of in- and out-of-range stray light at multiple laser wavelengths. In addition, several solar-blind filters utilized in single-monochromator Brewers to limit out-of-range stray light were characterized for spectral and spatial transmittances. Finally, the measurement results were used to simulate the effect of stray light and stray light correction on spectral irradiance and ozone measurements at different wavelength regions. The effect of stray light from wavelengths above 340 nm was found to be negligible compared with other sources of uncertainty. On the other hand, contributions from wavelengths between 325 and 340 nm can form a significant portion of the overall stray light of the instrument, with 325 nm being the upper limit of the nominal measurement range of the instrument.

Cascaded PLC-VLC Channel: An Indoor Measurements Campaign

Recently, power-line communication (PLC) technology has been associated with the emerging visible light communication (VLC) technology. PLC technology is matured and has gained from tremendous research contributions over the past years. VLC technology, relatively new, utilizes light-emitting diodes (LEDs) to transmit information through the visible light portion of the electromagnetic spectrum. Their hybrid systems are attractive in their ubiquitousness for providing power delivery, illumination, and data transmission. Furthermore, such a hybrid system is cost effective due to its infrastructure already being used for other means. In this paper, we report on channel frequency measurement of a hybrid cascaded PLC-VLC channel. These measurements performed in a laboratory environment demonstrate the influence of power-line activities and the LED supply on the hybrid PLC-VLC channel response. Based on the previous models and the observed behaviors, we present simulation results of a PLC-VLC channel model. In our obtained results, the effect of the LED supply on both channels is emphasized and also considered in the proposed model. Finally, this paper provides an overall characterization, model, and spectral analysis for hybrid PLC-VLC channels, which is critical for effective promotion and mass production of hybrid PLC-VLC systems.

Intramuscular variations of proteome and muscle fiber type distribution in semimembranosus and semitendinosus muscles associated with pork quality

Proteome analysis was performed to understand intramuscular variations in muscle fiber distribution in semimembranosus (SM) and semitendinosus (ST) muscles associated with pork quality. Fifteen SM and ST muscles were separated into dark and light portions. The relative area of oxidative fiber was higher (P < .0001) in dark portion than that in light portion, while glycolytic fiber types were distributed primarily (P < .01) in light portions regardless of muscle types. Myosin-1, myosin-4, troponin complex (fast), myosin light chains, and metabolic enzymes responsible for fast-twitch glycolytic types were overexpressed in light portions (P < .05). However, myosin-2, myosin-7, myoglobin, and mitochondrial oxidative metabolic enzymes were closely related to slow-twitch oxidative fibers. These resulted in high pH, redness, and tenderness but low lightness and drip loss of pork quality. In conclusion, differentially expressed muscle proteins are associated with fiber type (oxidative vs. glycolytic) distribution, resulting in intramuscular variations of pork quality.

Dielectric and optical properties of graphitic carbon nitride–titanium dioxide nanocomposite with enhanced charge seperation

Graphitic carbon nitride (g-C3N4) a polymeric semiconductor material is appealing research topic because of enhanced absorption capability in visible region. g-C3N4–TiO2 composite material was prepared with varying composition (g-C3N4: TiO2) in the range of 0.25:1–2:1 and studied using various characterization techniques including X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) and FTIR spectroscopy for structural and morphological analysis. Optical properties were studied using UV–Vis, and photoluminescence (PL) spectroscopic techniques and dielectric properties were studied using impedance analyser. UV–visible spectra show a shift toward the higher wavelength region in composite owing to the decrease in the band gap value of g-C3N4–TiO2 composites. The dielectric constant was found increased with increasing content of g-C3N4 till the composition of 1.5:1 and decreased for higher content. The optimum composition based on above studies was found to be 1:1 and 1.5:1 with optical absorption in the range of 280–420 nm covering UV and small portion of visible light, and recombination of photogenerated charge carriers were also reduced compared to g-C3N4.

Influence of l-carnitine and l-arginine on protein synthesis and maturation of the semitendinosus muscle of lightweight piglets.

Lightweight (LW) piglets from large litters display impaired growth performance compared with heavier littermates. This study investigated the growth performance and muscle development of early-weaned LW piglets (birthweight <1.2kg) from large litters (17.3±3.0 total born per litter), fed ad libitum a milk replacer supplemented with either l-carnitine (CAR) or l-arginine (ARG) from day 7 to day 28 of age. In total, 36 female and entire male Swiss Large White piglets, weaned on day 7 of age, were artificially reared in pairs in rescue decks. They were allocated to one of three dietary treatments: unsupplemented control (CON), 0.48g l-carnitine·piglet-1 ·day-1 (CAR) or 1.20g l-arginine·kg body weight-1 ·day-1 (ARG). Milk replacer was prepared daily in a 1:4 powder-to-water ratio and fed ad libitum. Piglets were weighed at birth and on days 7, 14, 21 and 28. Feed intake was assessed daily. Piglets were euthanized on day 28. The entire semitendinosus muscle (STM) was collected, and organs were weighed. Subsequently, the STM was divided into the light (STMl ) and dark (STMd ) portion, and contractile and metabolic traits were analysed by ATP histochemistry, enzyme activities and gene expression. No differences in growth performance, organ and STM weight and on contractile traits were found between groups. A tendency (p<.10) for an elevated lipid oxidation enzyme activity in the STMl and STMd and greater (p<.05) phosphorylation of the mammalian target of rapamycin pathway in the STMl of CAR compared with CON piglets was found. Despite these metabolic responses, the lack of effect of CAR and ARG supplementation on growth performance suggests that providing the milk replacer ad libitum in combination with added CAR and ARG is insufficient for eliciting faster growth of LW piglets.

Nanostructured antireflective in-plane solar harvester.

In this work, we demonstrate a two-dimensional nano-hole array that can reduce reflection losses while passively trapping and harvesting incident light. The surface structure is designed to scavenge a small portion of incident light that would typically be lost due to Fresnel reflection, while the majority of light transmits unobstructed like a regular window. The trapping mechanism is dependent on angle and wavelength, and can be designed to selectively trap narrow wavelength bands using the constructed theoretical models. We demonstrate that structures with periods of 275 nm and 325 nm can trap different wavelength range within the visible spectrum, while simultaneously suppressing reflection losses. The trapping effect can be observed visually, and can be converted to a current output using a photovoltaic (PV) cell on the glass edge. The fabrication of such materials employs a simple replication process, and can be readily scaled up for large-scale manufacturing. The demonstrated solar harvester can be potentially be widely deployed in residential and commercial buildings as multifunctional windows for solar energy harvesting, scavenging, spectra splitting, and anti-glare properties.

Impact of dietary l-arginine supply during early gestation on myofiber development in newborn pigs exposed to intra-uterine crowding

Intra-uterine crowding (IUC) observed in hyperprolific sows impairs myofiber hyperplasia and overall fetal growth. Arginine supplementation (ARG) in gestation diets has been shown to positively affect litter and muscle development. The study objective was to assess whether the effect of ARG on offspring characteristics, with special emphasis on myofiber hyperplasia, differs under IUC conditions from these responses, because in that situation growth retardation is particularly prevalent due to reduced fetal nutrient supply. Unilateral oviduct ligation (OL) was used as a model for an uncrowded and hyperprolificacy (IN) as a model for a crowded intra-uterine environment. Five OL and five IN sows were fed a diet supplemented daily with either 43 g l-alanine (Ctrl) or 25 g l-arginine from d 14 to 28 of gestation in a cross-over design (two periods: 5th and 6th parity). At farrowing, two male and two female offspring, respectively, with a low and intermediate birth weight (BtW) were selected. After euthanization, the Semitendinosus muscle (STM) was removed and weighed, and the light and dark portions (STMd and STMl) were prepared for myofiber histochemistry using ATPase staining and the entire STM for gene expression analysis of myogenesis-related genes using RT-qPCR. In addition, various organs were removed and weighed. Data were analyzed using the MIXED model in SYSTAT. No effect of either IUC or dietary treatment was found in litter characteristics. Offspring of ARG sows displayed a greater muscle area in STM (P < 0.01) as a result of the greater myofiber hyperplasia (P < 0.01). The increase was more distinct in the STMl (P < 0.05) than in the STMd (P = 0.131). Offspring of OL sows were heavier at birth (P < 0.01), had a heavier STM (P < 0.05), liver (P < 0.01) and kidney (P < 0.05), but when expressed relative to birth weight, these differences were absent. In addition, IUC had an effect (P < 0.05) on the expression of one of the myogenesis-related genes investigated. Independent from the extent of IUC, ARG improved BtW, muscle and organ weights and myofiber hyperplasia in offspring.

Multiwavelength Light-Responsive Au/B-TiO2 Janus Micromotors.

Conventional photocatalytic micromotors are limited to the use of specific wavelengths of light due to their narrow light absorption spectrum, which limits their effectiveness for applications in biomedicine and environmental remediation. We present a multiwavelength light-responsive Janus micromotor consisting of a black TiO2 microsphere asymmetrically coated with a thin Au layer. The black TiO2 microspheres exhibit absorption ranges between 300 and 800 nm. The Janus micromotors are propelled by light, both in H2O2 solutions and in pure H2O over a broad range of wavelengths including UV, blue, cyan, green, and red light. An analysis of the particles' motion shows that the motor speed decreases with increasing wavelength, which has not been previously realized. A significant increase in motor speed is observed when exploiting the entire visible light spectrum (>400 nm), suggesting a potential use of solar energy, which contains a great portion of visible light. Finally, stop-go motion is also demonstrated by controlling the visible light illumination, a necessary feature for the steerability of micro- and nanomachines.

Wavelength-Dependent Ultrafast Charge Carrier Separation in the WO3/BiVO4 Coupled System

Due to its ∼2.4 eV band gap, BiVO4 is a very promising photoanode material for harvesting the blue portion of the solar light for photoelectrochemical (PEC) water splitting applications. In WO3/BiVO4 heterojunction films, the electrons photoexcited in BiVO4 are injected into WO3, overcoming the lower charge carriers’ diffusion properties limiting the PEC performance of BiVO4 photoanodes. Here, we investigate by ultrafast transient absorption spectroscopy the charge carrier interactions occurring at the interface between the two oxides in heterojunction systems to directly unveil their wavelength dependence. Under selective BiVO4 excitation, a favorable electron transfer from photoexcited BiVO4 to WO3 occurs immediately after excitation and leads to an increase of the trapped holes’ lifetime in BiVO4. However, a recombination channel opens when both oxides are simultaneously excited, evidenced by a shorter lifetime of trapped holes in BiVO4. PEC measurements reveal the implication of these wavelength-depen...

Hydrogenated amorphous silicon oxide (a-SiOx:H) single junction solar cell with 8.8% initial efficiency by reducing parasitic absorptions

Hydrogenated amorphous silicon oxide (a-SiOx:H) solar cells have been successfully implemented to multi-junction thin film silicon solar cells. The efficiency of these solar cells, however, has still been below that of state-of-the-art solar cells mainly due to the low Jsc of the a-SiOx:H solar cells and the unbalanced current matching between sub-cells. In this study, we carry out optical simulations to find the main optical losses for the a-SiOx:H solar cell, which so far was mainly optimized for Voc and fill-factor (FF). It is observed that a large portion of the incident light is absorbed parasitically by the p-a-SiOx:H and n-a-SiOx:H layers, although the use of these layers leads to the highest Voc × FF product. When a more transparent and conductive p-nc-SiOx:H layer is substituted for the p-a-SiOx:H layer, the parasitic absorption loss at short wavelengths is notably reduced, leading to higher Jsc. However, this gain in Jsc by the use of the p-nc-SiOx:H compromises the Voc. When replacing the n-a-SiOx:H layer for an n-nc-SiOx:H layer that has low n and k values, the plasmonic absorption loss at the n-nc-SiOx:H/Ag interfaces and the parasitic absorption in the n-nc-SiOx:H are substantially reduced. Implementation of this n-nc-SiOx:H leads to an increase of the Jsc without a drop of the Voc and FF. When implementing a thinner p-a-SiOx:H layer, a thicker i-a-SiOx:H layer, and an n-nc-SiOx:H layer, a-SiOx:H solar cells with not only high Jsc but also high Voc and FF can be fabricated. As a result, an 8.8% a-SiOx:H single junction solar cell is successfully fabricated with a Voc of 1.02 V, a FF of 0.70, and a Jsc of 12.3 mA/cm2, which is the highest efficiency ever reported for this type of solar cell.

Ilmenite type nano-crystalline Co–Ti–O ternary oxides: sol–gel thin film on borosilicate glass, characterization and photocatalytic activity in mineralization of reactive red 198

The sol–gel preparation of cobalt titanium oxide nano-crystals using the reaction between cobalt chloride (CoCl2·6H2O) and tetraisopropyl orthotitanate (Ti[OCH(CH3)2]4) with 1:1 molar ratio was studied. The nano-crystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDAX), fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG-DTG) analysis and UV–Vis diffuse reflectance spectra (UV–Vis DRS) spectroscopy. TG-DTG results revealed that the weight loss with peak temperatures of 189, 267 and 692 °C. The XRD results showed that the sample calcinated at 550 and 750 °C were mixtures of CoTiO3, Co3O4, and TiO2 phases while at 650 °C a single crystalline phase of CoTiO3 was formed. FESEM results of the cobalt titanium oxide nanocrystalles demonstrate that CoTiO3 is nano-particles with an average size of 70 nm. FTIR results showed the formation of cobalt–oxygen, titanium–oxygen, and titanium–oxygen–cobalt bonds. DRS spectroscopy results of the sample calcinated at 650 °C showed band gap of 1.734 eV (715 nm) and 2.389 eV (519 nm) well in the visible portion of sun light. The cobalt titanium oxide nano crystales thin films on borosilicate glass showed an excellent photocatalytic activity on mineralization of Reactive Red 198 textille dye as environmental pollutant of industrial wastewater. An excellent photocatalytic activity in mineralization of Reactive Red 198 is related to the efficient separation of cobalt titanium oxide nano-crystals and visible-light absorption.

Enhanced water use efficiency in global terrestrial ecosystems under increasing aerosol loadings

Aerosols play a crucial role in the climate system, affecting incoming radiation and cloud formation. Based on a modelling framework that couples ecosystem processes with the atmospheric transfer of radiation, we analyze the effect of aerosols on surface incoming radiation, gross primary productivity (GPP), water losses from ecosystems through evapotranspiration (ET) and ecosystem water use efficiency (WUE, defined as GPP/ET) for 2003–2010 and validate them at global FLUXNET sites. The total diffuse radiation increases under relatively low or intermediate aerosol loadings, but decreases under more polluted conditions. We find that aerosol-induced changes in GPP depend on leaf area index, aerosol loading and cloudiness. Specifically, low and moderate aerosol loadings cause increases in GPP for all plant types, while heavy aerosol loadings result in enhancement (decrease) in GPP for dense (sparse) vegetation. On the other hand, ET is mainly negatively affected by aerosol loadings due to the reduction in total incoming radiation. Finally, WUE shows a consistent rise in all plant types under increasing aerosol loadings. Overall, the simulated daily WUE compares well with observations at 43 eddy-covariance tower sites (R2=0.84 and RMSE=0.01gC (kg H2O)−1) with better performance at forest sites. In addition to the increasing portions of diffuse light, the rise in WUE is also favored by the reduction in radiation- and heat-stress caused by the aerosols, especially for wet and hot climates.

Hazards Caused by UV Rays of Xenon Light Based High Performance Solar Simulators.

BackgroundSolar furnaces are used worldwide to conduct experiments to demonstrate the feasibility of solar–chemical processes with the aid of concentrated sunlight, or to qualify high temperature-resistant components. In recent years, high-flux solar simulators (HFSSs) based on short-arc xenon lamps are more frequently used. The emitted spectrum is very similar to natural sunlight but with dangerous portions of ultraviolet light as well. Due to special benefits of solar simulators the increase of construction activity for HFSS can be observed worldwide. Hence, it is quite important to protect employees against serious injuries caused by ultraviolet radiation (UVR) in a range of 100 nm to 400 nm.MethodsThe UV measurements were made at the German Aerospace Center (DLR), Cologne and Paul-Scherrer-Institute (PSI), Switzerland, during normal operations of the HFSS, with a high-precision UV-A/B radiometer using different experiment setups at different power levels. Thus, the measurement results represent UV emissions which are typical when operating a HFSS. Therefore, the biological effects on people exposed to UVR was investigated systematically to identify the existing hazard potential.ResultsIt should be noted that the permissible workplace exposure limits for UV emissions significantly exceeded after a few seconds. One critical value was strongly exceeded by a factor of 770.ConclusionThe prevention of emissions must first and foremost be carried out by structural measures. Furthermore, unambiguous protocols have to be defined and compliance must be monitored. For short-term activities in the hazard area, measures for the protection of eyes and skin must be taken.

Solar water splitting on porous-alumina-assisted TiO2-doped WOx nanorod photoanodes: Paradoxes and challenges

Arrays of self-organized WO3-based semiconductor nanorods are prepared from a thin W layer, W/Ti bilayer (tungsten-on-titanium), and W-10at.%Ti alloy layer via the porous-anodic-alumina (PAA)-assisted anodization at various conditions to address the radius/length ratio of~13/130 and ~70/700nm (respectively ‘small’ and ‘big’ nanorods). Doping the WO3 nanorods with TiO2 was achieved, for the first time, simply by anodizing the W/Ti and W-10at.%Ti layers through the alumina nanopores. The post-anodizing treatments combined PAA dissolution with annealing in air and vacuum at 500–550°C to alter the film composition, crystal structure, and electrical properties. The air-annealed big nanorods comprising monoclinic and triclinic WO3 crystal phases reveal their superior performance in photoelectrochemical (PEC) water splitting, showing a low onset potential (0.5 VRHE) and a competitive value of photocurrent (15.5mAcm−2) in 0.1moldm−3 Na2SO4 solution (pH 5.0) under chopped illumination at a single wavelength of 405nm, 1Wcm−2, with no sign of photocorrosion. Paradoxically, the presence of monoclinic WO2.9 phase in the vacuum-annealed nanorods worsens the PEC behavior and stimulates the peroxo-assisted dissolution. Unexpectedly, electrochemically doping both the WO3 and WO2.9 big nanorods with TiO2 causes the photocurrent to decrease dramatically. An advanced approach developed for modeling charge transport processes in the PAA-assisted WOx nanorods predicts a 7-fold further rise in the solar current should the big nanorods grow longer (1.5µm) and wider (300nm) to absorb a bigger portion of light and support a thicker depletion layer, without, however, getting fully depleted, which is the case of the small nanorods.

Absorption-Modulated Crossed-Optical Fiber-Sensor Platform for Measurements in Liquid Environments and Flow Streams

A new evanescent-wave fiber sensor is described that utilizes absorption-modulated luminescence (AML) in combination with a crossed-fiber sensor platform. The luminescence signals of two crossed-fiber reference regions, placed on opposite sides of the stretch of fiber supporting the absorbance sensor, monitor the optical intensity in the fiber core. Evanescent absorption of the sensor reduces a portion of the excitation light and modulates the luminescence of the second reference region. The attenuation is determined from the luminescence intensity of both reference regions similar to the Beer-Lambert Law. The AML-Crossed-Fiber technique was demonstrated using the absorbance of the Zn(II)-PAN2 complex at 555 nm. A linear response was obtained over a zinc(II) concentration range of 0 to 20 μM (approximately 0 to 1.3 ppm). A nonlinear response was observed at higher zinc(II) concentrations and was attributed to depletion of higher-order modes in the fiber. This was corroborated by the measured induced repopulation of these modes.

Characterization of coherence-or-power selectable operation of an external-cavity semiconductor diode laser.

The properties of the coherence-or-power selectable operation of an external-cavity semiconductor diode laser through the control of intracavity polarization states have been characterized in detail. In our technique, a diffraction grating and a reflector functioned as a polarization-dependent output coupler, such that the portion of light fed back to the gain medium was readily controlled by rotating the intracavity polarization axis, which resulted in the selectable operation of either a high degree of coherence or a high power for the laser output. We could continuously sweep the correlation widths over a range of approximately one order of magnitude, as well as four-fold output powers by simply rotating the intracavity half-wave plate. We also demonstrated experiments on optical phase locking, using two independent coherence-or-power selectable lasers.