Short Wavelength Range Research Articles

Dispersion relations of refractive indices suitable for KBe2BO3F2 crystal deep-ultraviolet applications.

KBe2BO3F2 (KBBF) is the only nonlinear optical crystal available to generate deep-ultraviolet (DUV) laser output by direct harmonic generation. High-precision refractive indices, including in the DUV region, were measured, and starting from a double resonance model of polarizability, new dispersion relations of the refractive indices were deduced from the measured data. The predicted phase matching angles for second-harmonic generation down to 165 nm from the new relations agree well with the previous reported values. Moreover, the new dispersion relations show superior results in an even shorter wavelength range, giving perfectly calculated phase matching angles for fifth-harmonic generation down to as short as 149.8 nm.

Improving the performance of solar cells with novel buffer structure by the chemical bath deposition technique

This paper explores and compares the characteristics of eight different kinds of Cu(In, Ga)Se2 (CIGS) solar cells. Through the technique of chemical bath deposition (CBD), single- (i-ZnO) and double-layer (ZnS/CdS) CIGS cells were prepared and evaluated. The results of this research signify the potential of high-performance CIGS cells for photovoltaic (PV) industrial applications. This study focused on the growth-dependency and optical properties of ZnS/CdS-buffer stacked thin films, which were prepared through the CBD process. The best sample developed from this process consisted of a double-layer buffer and no i-ZnO layer. This sample yielded a conversion efficiency (η) of 9.23% and a short-circuit current density (JSC) of 26.72mA/cm2. The performance of this sample was about 25% (absolute gain) better than that of the standard CdS cells.Furthermore, the average quantum efficiency in the short wavelength range (350–500nm) for two of the ZnS/CdS buffer structures was 6.8% better than that of a single-layer CdS cell. This improvement can be attributed to the anti-reflective effect of the ZnS/CdS buffer structure, which increases the light-intensity incident on the main absorption layer. In addition, the ZnS/CdS-buffer layer not only eliminates the need for an i-ZnO layer but also reduces the usage of toxic Cd. The procedures to develop these flexible CIGS cells containing a ZnS/CdS buffer structure are simple, efficient, and reliable. These eco-friendly cells could be effectively applied to mass production for commercial PV applications.

Analysis of the double-layer α-Si:H emitter with different doping concentrations for α-Si:H/c-Si heterojunction solar cells

Double-layer emitters with different doping concentrations (DLE) have been designed and prepared for amorphous silicon/crystalline silicon (α-Si:H/c-Si) heterojunction solar cells. Compared with the traditional single layer emitter, both the experiment and the simulation (AFORS-HET, http://www.paper.edu.cn/html/releasepaper/2014/04/282/) prove that the double-layer emitter increases the short circuit current of the cells significantly. Based on the quantum efficiency (QE) results and the current-voltage-temperature analysis, the mechanism for the experimental results above has been investigated. The possible reasons for the increased current include the enhancement of the QE in the short wavelength range, the increase of the tunneling probability of the current transport and the decrease of the activation energy of the emitter layers.

Effect of Se flux on CuGaSe2 absorbers deposited on ITO-coated SLG substrates by using a three-stage co-evaporation process

As the key factor for top-cell application in a tandem structure, wide-bandgap chalcopyrite CuGaSe2 (CGS) absorbers were deposited at a thickness of 2 μm on soda-lime glass (SLG) which was coated with radio-frequency sputtered indium-tin-oxide (ITO) films. The semi-transparent CGS absorbers with a bandgap energy of 1.65 eV were grown by using a three-stage co-evaporation process with Cu, Ga, and Se elemental sources. During CGS absorber growth, the composition ratio [Cu]/[Ga] was fixed at about 0.85 and the Se-to-Ga flux ratio P[Se]/[Ga] was varied from 22 to 61 by increasing the temperature of the Se source. In this study, the compositional, structural, optical and electrical properties of top-cell CGS absorbers, which absorbed the short wavelength range of the solar spectrums for tandem solar cell application, were investigated as a function of the Se flux. On the basis of our experimental results, the highest CGS solar cell efficiency of 4.7 % in the cell structure described as Al/ZnO:Al/i-ZnO/CdS/CGS/ITO/SLG was demonstrated using a P[Se]/[Ga] value of 22.

Condition assessment of concrete pavements using both ground penetrating radar and stress-wave based techniques

Two stress-wave based techniques, ultrasonic surface wave (USW) and impact echo (IE), as well as ground penetrating radar (GPR) were used to assess the condition of a segment of concrete pavement that includes a layer of concrete, a granular base and their interface. Core specimens retrieved at multiple locations were used to confirm the accuracy and reliability of each non-destructive testing (NDT) result. Results from this study demonstrate that the GPR method is accurate for estimating the pavement thickness and locating separations (air voids) between the concrete and granular base layers. The USW method is a rapid way to estimate the in-situ elastic modulus (dynamic elastic modulus) of the concrete, however, the existence of air voids at the interface could potentially affect the accuracy and reliability of the USW test results. The estimation of the dynamic modulus and the P-wave velocity of concrete was improved when a shorter wavelength range (3in. to 8.5in.) corresponding to the concrete layer thickness was applied instead of the full wavelength rage (3in. to 11in.) based on the standard spacing of the receiver transducers. The IE method is proved to be fairly accurate in estimating the thickness of concrete pavements. However, the flexural mode vibration could affect the accuracy and reliability of the test results. Furthermore, the existence of air voids between the concrete and granular base layers could affect the estimation of the compression wave velocity of concrete when the full wavelength range was applied (3in. to 11in.). Future work is needed in order to improve the accuracy and reliability of both USW and IE test results.

Optical Absorption of Fullerene C60 Within the Concept of a Strongly Correlated State

Energy spectrum of fullerene C60 is calculated in the approximation of static fluctuations within the Hubbard model. Allowed optical transitions are chosen in the approximation of molecular orbitals, and the optical absorption spectrum is simulated. A good qualitative agreement with the available experimental data is obtained not only in the short-wavelength range, but also in the visible range. This demonstrates the correctness of the approach to the study of fullerenes as systems with strong correlations.

Relationship between Human Pupillary Light Reflex and Circadian System Status

Intrinsically photosensitive retinal ganglion cells (ipRGCs), whose photopigment melanopsin has a peak of sensitivity in the short wavelength range of the spectrum, constitute a common light input pathway to the olivary pretectal nucleus (OPN), the pupillary light reflex (PLR) regulatory centre, and to the suprachiasmatic nuclei (SCN), the major pacemaker of the circadian system. Thus, evaluating PLR under short wavelength light (λmax ≤ 500 nm) and creating an integrated PLR parameter, as a possible tool to indirectly assess the status of the circadian system, becomes of interest. Nine monochromatic, photon-matched light stimuli (300 s), in 10 nm increments from λmax 420 to 500 nm were administered to 15 healthy young participants (8 females), analyzing: i) the PLR; ii) wrist temperature (WT) and motor activity rhythms (WA), iii) light exposure (L) pattern and iv) diurnal preference (Horne-Östberg), sleep quality (Pittsburgh) and daytime sleepiness (Epworth). Linear correlations between the different PLR parameters and circadian status index obtained from WT, WA and L recordings and scores from questionnaires were calculated. In summary, we found markers of robust circadian rhythms, namely high stability, reduced fragmentation, high amplitude, phase advance and low internal desynchronization, were correlated with a reduced PLR to 460–490 nm wavelengths. Integrated circadian (CSI) and PLR (cp-PLR) parameters are proposed, that also showed an inverse correlation. These results demonstrate, for the first time, the existence of a close relationship between the circadian system robustness and the pupillary reflex response, two non-visual functions primarily under melanopsin-ipRGC input.

Transition from conventional to light‐emitting diode street lighting changes activity of urban bats

Summary Light pollution is rapidly increasing and can have deleterious effects on biodiversity, yet light types differ in their effect on wildlife. Among the light types used for street lamps, light‐emitting diodes (LEDs) are expected to become globally predominant within the next few years. In a large‐scale field experiment, we recorded bat activity at 46 street lights for 12 nights each and investigated how the widespread replacement of conventional illuminants by LEDs affects urban bats: we compared bat activity at municipal mercury vapour (MV) street lamps that were replaced by LEDs with control sites that were not changed. Pipistrellus pipistrellus was the most frequently recorded species; it was 45% less active at LEDs than at MV street lamps, but the activity did not depend on illuminance level. Light type did not affect the activity of Pipistrellus nathusii, Pipistrellus pygmaeus or bats in the Nyctalus/Eptesicus/Vespertilio (NEV) group, yet the activity of P. nathusii increased with illuminance level. Bats of the genus Myotis increased activity 4·5‐fold at LEDs compared with MV lights, but illuminance level had no effect. Decreased activity of P. pipistrellus, which are considered light tolerant, probably paralleled insect densities around lights. Further, our results suggest that LEDs may be less repelling for light‐averse Myotis spp. than MV lights. Accordingly, the transition from conventional lighting techniques to LEDs may greatly alter the anthropogenic impact of artificial light on urban bats and might eventually affect the resilience of urban bat populations. Synthesis and applications. At light‐emitting diodes (LEDs), the competitive advantage – the exclusive ability to forage on insect aggregations at lights – is reduced for light‐tolerant bats. Thus, the global spread of LED street lamps might lead to a more natural level of competition between light‐tolerant and light‐averse bats. This effect could be reinforced if the potential advantages of LEDs over conventional illuminants are applied in practice: choice of spectra with relatively little energy in the short wavelength range; reduced spillover by precisely directing light; dimming during low human activity times; and control by motion sensors. Yet, the potential benefits of LEDs could be negated if low costs foster an overall increase in artificial lighting.

Ecotoxicity of ∼1 nm silver and palladium nanoclusters protected by l -glutathione on the microbial growth under light and dark conditions

Abstract Herein, we synthesized some ultra small silver nanoclusters (AgNCs) and palladium nanoclusters (PdNCs) protected by L -glutathione (L-GSH) reduced ligand to study their antimicrobial properties in the visible and dark conditions. These clusters can be dissolved, dried, and redissolved in water without suffering from any agglomeration or degradation. The particles sizes of the synthesized nanoclusters were around 1 nm, which investigated by high-resolution transmission electron microscopy (HRTEM). The optical properties of the synthesized nanoclusters were studied by UV–vis spectroscopy. Ag n (SG) m clusters exhibited two plasmon peaks in the visible region at 478 and 641 nm. However, Pd n (SG) m clusters showed a steep rise absorption in the short wavelength range of the spectrum and featureless in the visible region. Fourier transform infrared spectroscopy (FTIR) was measured for the free ligand and protected clusters Ag n (SG) m and Pd n (SG) m . Compared with palladium nanoclusters (in vitro), silver nanoclusters exhibited higher biocidal activity (MIC). The influence of silver and palladium nanoclusters (0.0, 2.5, 3.5, 5.0, 8.0 mg/l) on soil fungal community density was investigated under dark and light condition. Interestingly, silver NPs were more effective than palladium nanoclusters. Moreover, silver NPs were more effective in light than in the dark. However, palladium nanoclusters showed more or less similar effect under both contrasting conditions. This might be attributed to the disappearance of the plasmonic effect of palladium clusters in the UV–vis region. The novelty of our method is due to using ligand (L-GSH) as a capping agent with palladium. Besides, l -glutathione is considered as a part of the microbial system to detoxify metals. This guarantees the safety of the synthesized nanoparticles to be applied commercially than the naked isotopes. These nanoclusters could be considered a basic unit for medicine industry such as drug delivery tools or applied in paints industry (antimicrobial agents).

Performance of ZnSe(Te) as fiberoptic dosimetry detector

Fiberoptic dosimetry (FOD) is an experimental technique suitable for in-vivo, real time dosimetry in radiotherapy treatments. FOD relies on using a small scintillator coupled to one end of a long optical fiber. The scintillator is placed at the point where the dose rate is to be determined whereas a light detector at the other end of the fiber measures the intensity of the radioluminescence emitted by the scintillator. One of the problems hampering the straightforward application of this technique in clinics is the presence of Cherenkov radiation generated in the fiber by the ionizing radiation, which adds to the scintillating light and introduces a bias in the dose measurement. Since Cherenkov radiation is more important in short wavelength range of the visible spectrum, using red-emitting scintillators as FOD detectors permits to reduce the Cherenkov contribution by using optical filters. In this work, the performance of red-emitting tellurium-doped zinc selenide crystal as FOD detector is evaluated and compared to the response of an ion-chamber.

Polarization memory effect in the photoluminescence of nc-Si-SiOx light-emitting structures.

The polarization memory (PM) effect in the photoluminescence (PL) of the porous nc-Si−SiOx light-emitting structures, containing nanoparticles of silicon (nc-Si) in the oxide matrix and passivated in a solution of hydrofluoric acid (HF), has been investigated. The studied nc-Si−SiOx structures were produced by evaporation of Si monoxide (SiO) powder in vacuum and oblique deposition on Si wafer, and then the deposited silicon oxide (SiOx) films were annealed in the vacuum at 975 °C to grow nc-Si. It was found that the PM effect in the PL is observed only after passivation of nanostructures: during etching in HF solution, the initial symmetric nc-Si becomes asymmetric elongated. It was also found that in investigated nanostructures, there is a defined orientational dependence of the PL polarization degree (ρ) in the sample plane which correlates with the orientation of SiOx nanocolumns, forming the structure of the porous layer. The increase of the ρ values in the long-wavelength spectral range with time of HF treatment can be associated with increasing of the anisotropy of large Si nanoparticles. The PM effect for this spectral interval can be described by the dielectric model. In the short-wavelength spectral range, the dependence of the ρ values agrees qualitatively with the quantum confinement effect.

PTU-001 Chromoendoscopy for Angiectasias in Capsule Endoscopy; Blue or Just White?

Introduction Blue mode (BM) is one of the features of proprietary software (RAPID®; Medtronic Ltd) for capsule endoscopy (CE) review. BM is a colour coefficient shift of light in the short wavelength range (490–430 nm) superimposed onto a white light (WL) image.1 Recently, studies have shown that BM improves visualisation of vascular and erythematous non-vascular CE lesions.1,2 We aimed to objectively evaluate the validity of BM in CE in assessing the surface annotations of angiectasias as compared to WL. Methods A set of 100 anonymised images of angiectasias was used, with the lesions captured both in WL and BM in the same pose. The entire dataset is available in our online database, KID (http://is-innovation.eu/kid). Three reviewers (2 experts and one novice in CE review) graphically annotated the lesions using Ratsnake annotation tool (http://is-innovation.eu/ratsnake). The images were reviewed in WL and BM twice to estimate the inter- and intra-observer variability (at least 7 days apart). The Jaccard index (JI) was used to assess the similarity (agreement) of the annotations performed by the reviewers. Results Under WL, the average inter-observer agreement ranged between 65±15% (novice vs. expert reviewer) and 67±13% (between experts), while the intra-observer agreement, ranged between 69±17% and 71±13%. Under BM, the average inter-observer agreement ranged between 56±19% (novice vs. expert reviewer) and 78±18% (between experts). The average intra-observer agreement in BM ranged between 69±20% and 73±8. Conclusion BM CE image review does not improve significantly the surface annotations of angiectasias -as compared to WL- for expert or novice reviewers.3,4 References 1 Abdelaal UM, et al. Blue mode imaging may improve the detection and visualisation of small-bowel lesions: A capsule endoscopy study. Saudi J Gastroentero 2015;21:418–22. 2 Krystallis C, et al. Chromoendoscopy in small bowel capsule endoscopy: Blue mode or Fuji Intelligent Colour Enhancement? Dig Liver Dis 2011;43:953–7. 3 Koulaouzidis A, et al. Blue mode does not offer any benefit over white light when calculating Lewis score in small-bowel capsule endoscopy. World J Gastrointest Endosc 2012;4:33–7. 4 Koulaouzidis A, et al. QuickView in small-bowelcapsule endoscopy is useful in certain clinical settings, but QuickView with BlueMode is of no additional benefit. Eur J Gastroenterol Hepatol 2012;24:1099–104. Disclosure of Interest None Declared

Spectral dependence of the efficiency of direct optical excitation of molecular oxygen in tetrachloromethane

The spectral dependence of the efficiency of direct optical excitation of an oxygen molecule in tetrachloromethane using cw LED sources with different wavelengths and an optical parametric oscillator with single-shot output radiation (tuning range of 415–670 nm) has been studied by recording the phosphorescence of singlet oxygen at the O2(1Δg)–O2(3Σg) transition (λ = 1270 nm). The results show that single-shot irradiation of tetrachloromethane in the short-wavelength spectral range leads to efficient quenching of singlet- oxygen phosphorescence by the products of photolytic decomposition of solvent.

Photoabsorption by the electronic subsystem of semiconductor quantum dots

The cross section for photoabsorption by a semiconductor quantum dot has been calculated with the previously obtained densities of electrons in the surface traps, conduction electrons, and electrons in unionized impurities. It has been found that the total photoabsorption cross section has two characteristic maxima corresponding to absorption by conduction electrons and by electrons in traps in the bulk of the quantum dot. The contribution of electrons in traps on the surface of the quantum dot is small and manifests itself only in a relatively short-wavelength range of the spectrum.

Spectral and photoelectric characteristics of the gamma irradiated intrinsic oxide–ІnSe heterostructures obtained under different conditions

The investigations of photoelectric characteristics and photoresponce spectral dependences were carried out for intrinsic oxide–InSe heterostructures (HSs) and their changes induced by bremsstrahlung γ-quanta with an energy of 1–34MeV at fluences of 1012–1015cm−2. The thermal oxidation of the p-InSe:Cd substrates was carried out at a temperature of 420°С. For three selected groups of samples the duration of the process was 15min, 60min, and 96h. At a short-term oxidation (15 and 60min) a layer of In2O3 appears. The only difference between the samples of these two groups is a higher photosensitivity in the range of energy 1.25–2.8eV of the HSs obtained after the 60min oxidation. At the long-term oxidation the photoresponce spectra η(hν) of the obtained HSs are characterized with a sharp short-wavelength decrease at hν≅2.0eV. It is established that the intrinsic oxide films act as transparent barrier electrodes in the corresponding HSs and are low-sensitive to γ-irradiation in the all range of fluences. The shape of the photoresponce spectra for all the gamma irradiated HSs remains practically the same. However, it was found: (i) some decrease of photosensitivity at the long-wavelength edge, (ii) decreasing the width of η(hν) at half-height, (iii) the appearance of the exciton peak, (iv) the improvement of a slope of the low-energy edge of the photoresponce spectra with increasing irradiation dose whereas at the maximum fluence this parameter decreases, and (v) the slight extension of the spectral sensitivity to the short-wavelength range for the structures obtained after oxidation for 96h. The photoelectric parameters of the intrinsic oxide–p-InSe HSs, open circuit voltage Voc, short-circuit current Jsc, current SIλmax and voltage SVλmax sensitivities become only improved after irradiation with the fluences 1012–1013cm−2. At the maximum fluence a small decreasing of the values of Voc and Jsc was detected except for the structures obtained after oxidation for 15min. An increase of the SIλmax and SVλmax sensitivities in comparison with the initial value were found for all the HSs even at the maximum fluence except for the structures obtained by a long-term oxidation.

Boron Oxygen Pair Effect in p+ Emitter and Nanosized Boron Rich Layer by Fold Coordination Analysis for Crystalline Silicon Solar Cell Applications.

N-type substrates possess better material characteristics than p-type substrates for high efficiency mass producible Si solar cells with HIT, IBC structures. The major drawbacks of these structures are a complicated fabrication process and an expensive unit cost. In this paper, the boron emitter doping profile of a nanosized boron rich layer (BRL), for which the boron and oxygen concentrations are correlated, is optimized to fabricate high efficiency solar cells on an n-type substrate. Boron doping was carried out using a BBr3 furnace with varying oxygen gas ratios and the surface was treated with acid etching. The effect of the oxygen on the nanosized BRL was analyzed using both FTIR spectroscopy and XPS, where by conductivity and the Si-B bond were observed for the three-fold and four-fold coordinated borons, respectively. The results showed that the oxygen quantities in the boron doped emitter and the nanosized BRL affected the characteristics of the solar cell. Regarding the solar cells that were fabricated using the boron emitter and shallow emitter (90 ohm/sq) processes, the open-circuit voltage increased by 54 mV and the short circuit current (J(sc)) increased by 3.7 mA/cm2. The J(sc) increase was due to an increased quantum efficiency in the short wavelength range. The shallow emitter etch back process minimized the boron-oxygen defects in the doping profile.

Compact Z-pinch radiation source dedicated to broadband absorption measurements

In order to acquire a broadband absorption spectrum in a single shot, a compact radiation source was developed by using a Z-pinch type electric discharge. This paper presents the mechanical and electrical construction of the source, as well as its electrical and optical characteristics, including the intense continuum of radiation emitted by the source in the UV and visible spectral range. It also shows that the compactness of the source allows direct coupling with the probed medium, enabling broadband absorption measurement in the spectral range of 200–300 nm without use of an optical fiber which strongly attenuates the light in the short wavelength range. Concretely, thanks to this source, broadband spectral absorption of NO molecules around 210 nm and that of OH molecules around 310 nm were recorded in this direct coupling arrangement. Copper atom spectral absorption around 325 nm of the peripheral cold zones of an intense transient arc was also recorded.

Third harmonic generation in the short-wavelength UV range by a single plasmonic nanostructure

The nonlinear optical interaction of laser radiation with nanostructures formed in gold and aluminium nanofilms has been experimentally studied. It is shown that, despite the high susceptibility of aluminium in comparison with gold, the third-harmonic generation efficiency at a wavelength of is much higher for the nanostructures formed in a gold nanofilm because of the efficient excitation of a localised plasmon resonance at the fundamental frequency.

Variation of Jupiter's aurora observed by Hisaki/EXCEED: 1. Observed characteristics of the auroral electron energies compared with observations performed using HST/STIS

AbstractTemporal variation of Jupiter's northern aurora is detected using the Extreme Ultraviolet Spectroscope for Exospheric Dynamics (EXCEED) on board JAXA's Earth‐orbiting planetary space telescope Hisaki. The wavelength coverage of EXCEED includes the H2 Lyman and Werner bands at 80–148 nm from the entire northern polar region. The prominent periodic modulation of the observed emission corresponds to the rotation of Jupiter's main auroral oval through the aperture, with additional superposed −50%–100% temporal variations. The hydrocarbon color ratio (CR) adopted for the wavelength range of EXCEED is defined as the ratio of the emission intensity in the long wavelength range of 138.5–144.8 nm to that in the short wavelength range of 126.3–130 nm. This CR varies with the planetary rotation phase. Short‐ (within one planetary rotation) and long‐term (> one planetary rotation) enhancements of the auroral power are observed in both wavelength ranges and result in a small CR variation. The occurrence timing of the auroral power enhancement does not clearly depend on the central meridian longitude. Despite the limitations of the wavelength coverage and the large field of view of the observation, the auroral spectra and CR‐brightness distribution measured using EXCEED are consistent with other observations.

Light absorption enhancement for ultra-thin Cu(In1−xGax)Se2 solar cells using closely packed 2-D SiO2 nanosphere arrays

2-D closely packed SiO2 nanosphere arrays serving as the photonic structure for light absorption enhancement on top of ultra-thin Cu(In1−xGax)Se2 solar cells are investigated both theoretically and experimentally. It is theoretically demonstrated that whispering gallery modes and high order Mie resonances contribute to the light absorption enhancement for the large spheres and an anti-reflection effect is prominent for small ones. The ultra-thin CIGSe solar cells achieve the optimum absorption enhancement for the small sphere array with a diameter of 110nm, contrary to the larger spheres used in Si solar cells. The reason is attributed to the strong parasitic absorption in the AZO/ZnO/CdS front layers. They absorb mainly in the short wavelength range where the Mie resonances occur. Additionally, it is shown that the 110-nm-diameter sphere array exhibits a better angular tolerance than a conventional planar anti-reflection layer, which shows the potential as a promising anti-reflection structure.