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Sample records for ultraviolet diode array

  1. Effect of oxygen-related surface adsorption on the efficiency and stability of ZnO nanorod array ultraviolet light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liu, W. Z.; Xu, H. Y.; Ma, J. G.; Liu, C. Y.; Liu, Y. X.; Liu, Y. C.

    2012-05-01

    Ultraviolet light-emitting diodes using MgZnO-coated and bare ZnO nanorod arrays as active layers were manufactured. Both types were exposed to ambient air over a 1-yr period to assess their stability. By monitoring the electroluminescence evolution with air-exposure time and comparing the changes of electroluminescence and x-ray photoelectron spectra before and after vacuum desorption, it is concluded that surface-adsorbed O2 and OH- species, as acceptor and donor surface states, quench ultraviolet electroluminescence, and favor undesirable surface-mediated nonradiative and deep-level recombination. The MgZnO coating prevents surface adsorption, and so the coated nanorod device shows higher efficiency and stability than the uncoated one.

  2. Diode laser array

    NASA Technical Reports Server (NTRS)

    Carlson, Nils W. (Inventor); Evans, Gary A. (Inventor); Kaiser, Charlie J. (Inventor)

    1990-01-01

    A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections. Also, the grating period provides an operating wavelength which is on the short wavelength side of the gain period of the gain sections required for laser oscillation. An RF pulse is applied so as to maximize the magnitude of the loss modulation and the differential gain in the gain sections. The array is operated by applying a DC bias to all the gain sections at a level just below the threshold of the gain sections to only one of the gain sections which raises the bias in all of the gain sections to a level that causes all of the gain sections to oscillate. Thus, a small bias can turn the array on and off.

  3. Simultaneous determination three phytosterol compounds, campesterol, stigmasterol and daucosterol in Artemisia apiacea by high performance liquid chromatography-diode array ultraviolet/visible detector

    PubMed Central

    Lee, Jiwoo; Weon, Jin Bae; Yun, Bo-Ra; Eom, Min Rye; Ma, Choong Je

    2015-01-01

    Background: Artemisia apiacea is a traditional herbal medicine using treatment of eczema and jaundice in Eastern Asia, including China, Korea, and Japan. Objective: An accurate and sensitive analysis method using high performance liquid chromatography-diode array ultraviolet/visible detector and liquid chromatography–mass spectrometry for the simultaneous determination of three phytosterol compounds, campesterol, stigmasterol and daucosterol in A. apiacea was established. Materials and Methods: The analytes were separated on a Shiseido C18 column (5 ?m, 4.6 mm I.D. ×250 mm) with gradient elution of 0.1% trifluoroacetic acid and acetonitrile. The flow rate was 1 mL/min and detection wavelengths were set at 205 and 254 nm. Results: Validation of the method was performed to demonstrate its linearity, precision and accuracy. The calibration curves showed good linearity (R2 > 0.9994). The limits of detection and limits of quantification were within the ranges 0.55–7.07 ?g/mL and 1.67–21.44 ?g/mL, respectively. And, the relative standard deviations of intra- and inter-day precision were <2.93%. The recoveries were found to be in the range of 90.03–104.91%. Conclusion: The developed method has been successfully applied to the analysis for quality control of campesterol, stigmasterol and daucosterol in A. apiacea. PMID:25829768

  4. Determination of hydroxyalkyl derivatives of cobalamin (vitamin B12) using reversed phase high performance liquid chromatography with electrospray tandem mass spectrometry and ultraviolet diode array detection.

    PubMed

    Alsberg, T; Minten, J; Haglund, J; Törnqvist, M

    2001-01-01

    Electrospray ionization tandem mass spectrometry (ESI-MS/MS) and ultraviolet diode array detection (UV-DAD), coupled on-line to reversed phase high performance liquid chromatography (HPLC), was used for the characterization of hydroxyalkyl derivatives of cob(I)alamin. The reduced form of vitamin B12, cob(I)alamin, denoted a supernucleophile due to its high nucleophilic strength, has shown promise as an analytical tool in studies of electrophilically reactive compounds in vitro and in vivo. A method for analysis of DNA-phosphate adducts was developed earlier utilizing the supernucleophilicity of cob(I)alamin to transfer alkyl groups from the phosphotriester configuration in DNA, with the formation of a Co-substituted alkyl-cobalamin (alkyl-Cbl) complex. For the purpose of identification and quantification of alkyl-Cbls at high sensitivity, an MS/MS method has been developed with application to a number of 2-hydroxyalkyl-cobalamins (OHalkyl-Cbls). The precursor oxiranes were reacted with cob(I)alamin, followed by clean-up and mass spectrometric analysis of the resulting OHalkyl-Cbls. It was found that ionization was highly dependent on solvent composition. By using acetonitrile/water/trifluoroacetic acid (TFA) (eluent I), the base peak was the doubly protonated molecule [M + 2H](2+), whereas acetonitrile/water/1-methylpiperidine (eluent II) yielded the singly protonated molecule [M + H](+) as the base peak. Excellent separation was obtained with eluent II, with good separation between stereoisomers, thus enabling the characterization of these by means of UV spectra. Limits of quantitation for 2-hydroxypropyl-cobalamin (OHPr-Cbl) were 0.2 and 2 pg/microL (or 0.1 and 1 fmol/microL) using selected ion recording (SIR) with eluent I and II, respectively. The obtained detection level should be sufficient for analysis of alkyl-Cbls from a wide range of toxicological applications. PMID:11746915

  5. Analysis of phased-array diode lasers

    SciTech Connect

    Hardy, A.; Streifer, W.

    1985-07-01

    An improved, more accurate analysis of phased-array diode lasers is presented, which yields results that differ both qualitatively and quantitatively from those previously employed. A numerical example indicating decreased splitting in array mode gains is included.

  6. Enhanced waveguide-type ultraviolet electroluminescence from ZnO/MgZnO core/shell nanorod array light-emitting diodes via coupling with Ag nanoparticles localized surface plasmons

    NASA Astrophysics Data System (ADS)

    Zhang, Cen; Marvinney, Claire Elizabeth; Xu, Hai Yang; Liu, Wei Zhen; Wang, Chun Liang; Zhang, Li Xia; Wang, Jian Nong; Ma, Jian Gang; Liu, Yi Chun

    2014-12-01

    Localized surface plasmon (LSP) enhanced waveguide-type ultraviolet light-emitting diodes (LEDs) were fabricated by sputtering Ag nanoparticles (Ag-NPs) onto ZnO/MgZnO core/shell nanorod array (CS-NRA)/p-GaN heterostructures. A ~9-fold enhancement of ZnO ultraviolet electroluminescence (EL) was demonstrated by the Ag-NPs decorated LED compared with the device without Ag-NPs. Angle-dependent EL measurements, as well as finite-difference time-domain simulations of the EL intensity spatial distribution, confirmed the waveguide-type EL transmission mode along the NR's axial direction. The increased spontaneous emission rate observed in time-resolved spectroscopy suggested that the ZnO EL enhancement was attributed to LSP-exciton/polariton coupling. However, a direct coupling is very difficult to achieve between Ag-LSPs and electron-hole pairs in the active region due to their ``remote'' separation. Thereby, two possible models involving the dynamic process of interactions among excitons, photons, and LSPs, were established to understand the selective enhancement of ZnO EL.Localized surface plasmon (LSP) enhanced waveguide-type ultraviolet light-emitting diodes (LEDs) were fabricated by sputtering Ag nanoparticles (Ag-NPs) onto ZnO/MgZnO core/shell nanorod array (CS-NRA)/p-GaN heterostructures. A ~9-fold enhancement of ZnO ultraviolet electroluminescence (EL) was demonstrated by the Ag-NPs decorated LED compared with the device without Ag-NPs. Angle-dependent EL measurements, as well as finite-difference time-domain simulations of the EL intensity spatial distribution, confirmed the waveguide-type EL transmission mode along the NR's axial direction. The increased spontaneous emission rate observed in time-resolved spectroscopy suggested that the ZnO EL enhancement was attributed to LSP-exciton/polariton coupling. However, a direct coupling is very difficult to achieve between Ag-LSPs and electron-hole pairs in the active region due to their ``remote'' separation. Thereby, two possible models involving the dynamic process of interactions among excitons, photons, and LSPs, were established to understand the selective enhancement of ZnO EL. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04966g

  7. Beam multiplexing of diode laser arrays

    NASA Astrophysics Data System (ADS)

    Ruicong, Liu; Yuanyuan, Liu; Xue, Chen; Fuhua, Yang

    2015-04-01

    Design and experimental studies on the wavelength multiplexing and polarization multiplexing of diode laser arrays were carried out. First, the structure of a AlGaInAs/GaAs/AlGaAs quantum well under compressive strain was used because the characteristic of wavelength was easier to adjust. We obtained diode laser arrays lasing in five different wavelengths, about 760 nm, 800 nm, 860 nm, 930 nm, and 976 nm. At the same time, four edge filters were designed, and an experimental study on the beam multiplexing of diode laser arrays was carried out. Second, two beams with different polarization states were composited using a half wave plate and a polarizing beam-splitter prism. After that, the beam focusing system was designed. Ultimately, ten beams of diode laser arrays in five wavelengths and two polarization states were composited, the total output power was 196 W and the overall efficiency was 76%. The size of the output focus spot was 144 × 1330 ?m2, and the power density of the focused light was as high as 1.02 × 105 W/cm2. Compared with a single diode laser array, the power density of the composite beam was improved by 4.3 times. Project supported by the National Science Foundation of China (No. 61275145).

  8. The Fuge Tube Diode Array Spectrophotometer

    ERIC Educational Resources Information Center

    Arneson, B. T.; Long, S. R.; Stewart, K. K.; Lagowski, J. J.

    2008-01-01

    We present the details for adapting a diode array UV-vis spectrophotometer to incorporate the use of polypropylene microcentrifuge tubes--fuge tubes--as cuvettes. Optical data are presented validating that the polyethylene fuge tubes are equivalent to the standard square cross section polystyrene or glass cuvettes generally used in…

  9. Graphene/GaN diodes for ultraviolet and visible photodetectors

    SciTech Connect

    Lin, Fang; Chen, Shao-Wen; Meng, Jie; Tse, Geoffrey; Fu, Xue-Wen; Xu, Fu-Jun; Shen, Bo; Liao, Zhi-Min E-mail: yudp@pku.edu.cn; Yu, Da-Peng E-mail: yudp@pku.edu.cn

    2014-08-18

    The Schottky diodes based on graphene/GaN interface are fabricated and demonstrated for the dual-wavelength photodetection of ultraviolet (UV) and green lights. The physical mechanisms of the photoelectric response of the diodes with different light wavelengths are different. For UV illumination, the photo-generated carriers lower the Schottky barrier and increase the photocurrent. For green light illumination, as the photon energy is smaller than the bandgap of GaN, the hot electrons excited in graphene via internal photoemission are responsible for the photoelectric response. Using graphene as a transparent electrode, the diodes show a ?mS photoresponse, providing an alternative route toward multi-wavelength photodetectors.

  10. International ultraviolet explorer solar array power degradation

    NASA Technical Reports Server (NTRS)

    Day, J. H., Jr.

    1983-01-01

    The characteristic electrical performance of each International Ultraviolet Explorer (IUE) solar array panel is evaluated as a function of several prevailing variables (namely, solar illumination, array temperature and solar cell radiation damage). Based on degradation in the current-voltage characteristics of the array due to solar cell damage accumulated over time by space charged particle radiations, the available IUE solar array power is determined for life goals up to 10 years. Best and worst case calculations are normalized to actual IUE flight data (available solar array power versus observatory position) to accurately predict the future IUE solar array output. It is shown that the IUE solar array can continue to produce more power than is required at most observatory positions for at least 5 more years.

  11. Low-cost laser diode array

    DOEpatents

    Freitas, Barry L. (Livermore, CA); Skidmore, Jay A. (Livermore, CA)

    1999-01-01

    A substrate is used to fabricate a low-cost laser diode array. A substrate is machined from an electrically insulative material that is thermally conductive, or two substrates can be bonded together in which the top substrate is electrically as well as thermally conductive. The substrate thickness is slightly longer than the cavity length, and the width of the groove is wide enough to contain a bar and spring (which secures the laser bar firmly along one face of the groove). The spring also provides electrical continuity from the backside of the bar to the adjacent metalization layer on the laser bar substrate. Arrays containing one or more bars can be formed by creating many grooves at various spacings. Along the groove, many bars can be adjoined at the edges to provide parallel electrical conduction. This architecture allows precise and predictable registration of an array of laser bars to a self-aligned microlens array at low cost.

  12. Low-cost laser diode array

    DOEpatents

    Freitas, B.L.; Skidmore, J.A.

    1999-06-01

    A substrate is used to fabricate a low-cost laser diode array. A substrate is machined from an electrically insulative material that is thermally conductive, or two substrates can be bonded together in which the top substrate is electrically as well as thermally conductive. The substrate thickness is slightly longer than the cavity length, and the width of the groove is wide enough to contain a bar and spring (which secures the laser bar firmly along one face of the groove). The spring also provides electrical continuity from the backside of the bar to the adjacent metalization layer on the laser bar substrate. Arrays containing one or more bars can be formed by creating many grooves at various spacings. Along the groove, many bars can be adjoined at the edges to provide parallel electrical conduction. This architecture allows precise and predictable registration of an array of laser bars to a self-aligned microlens array at low cost. 19 figs.

  13. High extraction efficiency ultraviolet light-emitting diode

    DOEpatents

    Wierer, Jonathan; Montano, Ines; Allerman, Andrew A.

    2015-11-24

    Ultraviolet light-emitting diodes with tailored AlGaN quantum wells can achieve high extraction efficiency. For efficient bottom light extraction, parallel polarized light is preferred, because it propagates predominately perpendicular to the QW plane and into the typical and more efficient light escape cones. This is favored over perpendicular polarized light that propagates along the QW plane which requires multiple, lossy bounces before extraction. The thickness and carrier density of AlGaN QW layers have a strong influence on the valence subband structure, and the resulting optical polarization and light extraction of ultraviolet light-emitting diodes. At Al>0.3, thinner QW layers (<2.5 nm are preferred) result in light preferentially polarized parallel to the QW plane. Also, active regions consisting of six or more QWs, to reduce carrier density, and with thin barriers, to efficiently inject carriers in all the QWs, are preferred.

  14. Microcontroller interface for diode array spectrometry

    NASA Astrophysics Data System (ADS)

    Aguo, L.; Williams, R. R.

    An alternative to bus-based computer interfacing is presented using diode array spectrometry as a typical application. The new interface consists of an embedded single-chip microcomputer, known as a microcontroller, which provides all necessary digital I/O and analog-to-digital conversion (ADC) along with an unprecedented amount of intelligence. Communication with a host computer system is accomplished by a standard serial interface so this type of interfacing is applicable to a wide range of personal and minicomputers and can be easily networked. Data are acquired asynchronousty and sent to the host on command. New operating modes which have no traditional counterparts are presented.

  15. Microlens frames for laser diode arrays

    DOEpatents

    Skidmore, Jay A. (Livermore, CA); Freitas, Barry L. (Livermore, CA)

    1999-01-01

    Monolithic microlens frames enable the fabrication of monolithic laser diode arrays and are manufactured inexpensively with high registration, and with inherent focal length compensation for any lens diameter variation. A monolithic substrate is used to fabricate a low-cost microlens array. The substrate is wet-etched or sawed with a series of v-grooves. The v-grooves can be created by wet-etching, by exploiting the large etch-rate selectivity of different crystal planes. The v-grooves provide a support frame for either cylindrical or custom-shaped microlenses. Because the microlens frames are formed by photolithographic semiconductor batch-processing techniques, they can be formed inexpensively over large areas with precise lateral and vertical registration. The v-groove has an important advantage for preserving the correct focus for lenses of varying diameter.

  16. Microlens frames for laser diode arrays

    DOEpatents

    Skidmore, J.A.; Freitas, B.L.

    1999-07-13

    Monolithic microlens frames enable the fabrication of monolithic laser diode arrays and are manufactured inexpensively with high registration, and with inherent focal length compensation for any lens diameter variation. A monolithic substrate is used to fabricate a low-cost microlens array. The substrate is wet-etched or sawed with a series of v-grooves. The v-grooves can be created by wet-etching, by exploiting the large etch-rate selectivity of different crystal planes. The v-grooves provide a support frame for either cylindrical or custom-shaped microlenses. Because the microlens frames are formed by photolithographic semiconductor batch-processing techniques, they can be formed inexpensively over large areas with precise lateral and vertical registration. The v-groove has an important advantage for preserving the correct focus for lenses of varying diameter. 12 figs.

  17. Calibration of a novel four-dimensional diode array

    SciTech Connect

    Yan Guanghua; Lu Bo; Kozelka, Jakub; Liu, Chihray; Li, Jonathan G.

    2010-01-15

    Purpose: The aim of this work is to develop effective calibration methods for a novel four-dimensional (4D) diode array for pretreatment verification of intensity-modulated radiation therapy (IMRT) and rotational therapy. Methods: A novel 4D diode array (ArcCHECK, Sun Nuclear, Melbourne, FL) was developed to meet the needs of appropriate and efficient quality assurance for IMRT and especially rotational radiotherapy. The diode array presents a consistent detector image in beam's eye view at arbitrary gantry angles due to isotropic arrangement of diodes in a three-dimensional (3D) cylindrical phantom. The 50 ms simultaneous update of all diodes on the detector array (fourth dimension) makes it capable of time-resolved beam delivery analysis with any rotational delivery techniques. The calibration procedure consisted of delivering and measuring a series of calibration beams with 5.8 deg. angular spacing surrounding the cylindrical diode array. Correction factors for diode intrinsic sensitivity and directional response dependence were derived from these measurements. A real-time algorithm to derive gantry angles based on the detector signal was developed to interpolate and apply the corresponding angular correction factors. Results: The calibration was validated with ion chamber scanned beam profiles in a 3D water tank. Excellent agreement was observed between diode array measurement and treatment planning system calculation. The accuracy of the gantry angle derivation algorithm was within 1 deg. which caused a less than 0.2% dosimetric uncertainty. Conclusions: With the proposed calibration method and the automatic gantry angle derivation algorithm, the 4D diode array achieved isotropic detector response and is suitable for both IMRT and rotational therapy pretreatment verification.

  18. Modular package for cooling a laser diode array

    DOEpatents

    Mundinger, David C. (Stockton, CA); Benett, William J. (Livermore, CA); Beach, Raymond J. (Livermore, CA)

    1992-01-01

    A laser diode array is disclosed that includes a plurality of planar packages and active cooling. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar package having the laser diode bar located proximate to one edge. In an array, a number of such thin planar packages are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink that is attached proximate to the laser bar so that it absorbs heat generated by laser operation. To provide the coolant to the microchannels, each thin planar package comprises a thin inlet manifold and a thin outlet manifold connected to an inlet corridor and an outlet corridor. The inlet corridor comprises a hole extending through each of the packages in the array, and the outlet corridor comprises a hole extending through each of the packages in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has application as an optical pump for high power solid state lasers. Further, it can be incorporated in equipment such as communications devices and active sensors, and in military and space applications, and it can be useful in applications having space constraints and energy limitations.

  19. Tunnel junction enhanced nanowire ultraviolet light emitting diodes

    NASA Astrophysics Data System (ADS)

    Sarwar, A. T. M. Golam; May, Brelon J.; Deitz, Julia I.; Grassman, Tyler J.; McComb, David W.; Myers, Roberto C.

    2015-09-01

    Polarization engineered interband tunnel junctions (TJs) are integrated in nanowire ultraviolet (UV) light emitting diodes (LEDs). A ˜6 V reduction in turn-on voltage is achieved by the integration of tunnel junction at the base of polarization doped nanowire UV LEDs. Moreover, efficient hole injection into the nanowire LEDs leads to suppressed efficiency droop in TJ integrated nanowire LEDs. The combination of both reduced bias voltage and increased hole injection increases the wall plug efficiency in these devices. More than 100 ?W of UV emission at ˜310 nm is measured with external quantum efficiency in the range of 4-6 m%. The realization of tunnel junction within the nanowire LEDs opens a pathway towards the monolithic integration of cascaded multi-junction nanowire LEDs on silicon.

  20. Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback

    E-print Network

    Samutpraphoot, Polnop

    We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve ...

  1. Heteroepitaxy of AlGaN on bulk AlN substrates for deep ultraviolet light emitting diodes

    E-print Network

    Davitt, Kristina

    Heteroepitaxy of AlGaN on bulk AlN substrates for deep ultraviolet light emitting diodes Z. Ren, Q report the growth of AlGaN epilayers and deep ultraviolet UV light emitting diodes LEDs on bulk Al optoelectronics. © 2007 American Institute of Physics. DOI: 10.1063/1.2766841 Most of AlGaN deep ultraviolet 300

  2. Reliability of High Power Laser Diode Arrays Operating in Long Pulse Mode

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

    2006-01-01

    Reliability and lifetime of quasi-CW laser diode arrays are greatly influenced by their thermal characteristics. This paper examines the thermal properties of laser diode arrays operating in long pulse duration regime.

  3. Online photolytic optical gating of caged fluorophores in capillary zone electrophoresis utilizing an ultraviolet light-emitting diode.

    PubMed

    Gallagher, Elyssia S; Comi, Troy J; Braun, Kevin L; Aspinwall, Craig A

    2012-09-01

    Photolytic optical gating (POG) facilitates rapid, on-line and highly sensitive analyses, though POG utilizes UV lasers for sample injection. We present a low-cost, more portable alternative, employing an ultraviolet light-emitting diode (UV-LED) array to inject caged fluorescent dyes via photolysis. Utilizing the UV-LED array, labeled amino acids were injected with nanomolar limits of detection (270 ± 30 nM and 250 ± 30 nM for arginine and citrulline, respectively). When normalized for the difference in light intensity, the UV-LED array provides comparable sensitivity to POG utilizing UV lasers. Additionally, the UV-LED array yielded sufficient beam quality and stability to facilitate coupling with a Hadamard transform, resulting in increased sensitivity. This work shows, for the first time, the use of an UV-LED for online POG with comparable sensitivity to conventional laser sources but at a lower cost. PMID:22911376

  4. High-power laser diode array phase locking

    NASA Astrophysics Data System (ADS)

    Apollonov, Victor V.; Derzhavin, Sergei I.; Filonenko, Vladimir A.; Kuzminov, Vitaly V.; Mashkovsky, Dmitry A.; Prokhorov, Alexander M.

    2000-04-01

    The overview of the phase-locking problem for the powerful laser diode arrays is presented. Comparison of the external Talbot cavity configuration with the other ones is held. Attention is paid to both investigation and employment of the laser diode arrays consisting of wide aperture lasers. Such arrays, placed in the external cavity, allow easier solution of the scaling up problem that results in the output lobes with both significantly increased power and low divergence. Our experiments confirm feasibility of both QCW and CW phase- locking of the LDA in the external quarter-Talbot (Lc equals ZT/4) cavity at the output power of more than 10 W with the lobes divergence of (delta) (Psi) approximately equals 0.5 mrad. Employment of the efficient porous heatexchanger along with the system that cancels both induced phase distortions arising due to heat release and existing optical imperfections has allowed a breakthrough in powerful arrays phase-locking.

  5. Method and system for homogenizing diode laser pump arrays

    DOEpatents

    Bayramian, Andy J

    2013-10-01

    An optical amplifier system includes a diode pump array including a plurality of semiconductor diode laser bars disposed in an array configuration and characterized by a periodic distance between adjacent semiconductor diode laser bars. The periodic distance is measured in a first direction perpendicular to each of the plurality of semiconductor diode laser bars. The diode pump array provides a pump output propagating along an optical path and characterized by a first intensity profile measured as a function of the first direction and having a variation greater than 10%. The optical amplifier system also includes a diffractive optic disposed along the optical path. The diffractive optic includes a photo-thermo-refractive glass member. The optical amplifier system further includes an amplifier slab having an input face and position along the optical path and separated from the diffractive optic by a predetermined distance. A second intensity profile measured at the input face of the amplifier slab as a function of the first direction has a variation less than 10%.

  6. The integration of laser diode arrays into bondable solder-grid-arrays C. Gimkiewicz, D. Hagedorn

    E-print Network

    Jahns, Jürgen

    The integration of laser diode arrays into bondable solder-grid-arrays C. Gimkiewicz, D. Hagedorn, [1]. We have proposed to integrate the optical emitters into the solder joints to simplify the IC chip mounting, see fig. 1, [2]. ;;;; ;;;; solder VCSEL solder and ring micro lens local wiring

  7. Photodiode arrays having minimized cross-talk between diodes

    DOEpatents

    Guckel, Henry (Madison, WI); McNamara, Shamus P. (Madison, WI)

    2000-10-17

    Photodiode arrays are formed with close diode-to-diode spacing and minimized cross-talk between diodes in the array by isolating the diodes from one another with trenches that are formed between the photodiodes in the array. The photodiodes are formed of spaced regions in a base layer, each spaced region having an impurity type opposite to that of the base layer to define a p-n junction between the spaced regions and the base layer. The base layer meets a substrate at a boundary, with the substrate being much more heavily doped than the base layer with the same impurity type. The trenches extend through the base layer and preferably into the substrate. Minority carriers generated by absorption of light photons in the base layer can only migrate to an adjacent photodiode through the substrate. The lifetime and the corresponding diffusion length of the minority carriers in the substrate is very short so that all minority carriers recombine in the substrate before reaching an adjacent photodiode.

  8. Nanostructured High Performance Ultraviolet and Blue Light Emitting Diodes for Solid State Lighting

    SciTech Connect

    Arto V. Nurmikko; Jung Han

    2005-09-30

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the second 12 month contract period include (i) new means of synthesizing AlGaN and InN quantum dots by droplet heteroepitaxy, (ii) synthesis of AlGaInN nanowires as building blocks for GaN-based microcavity devices, (iii) progress towards direct epitaxial alignment of the dense arrays of nanowires, (iv) observation and measurements of stimulated emission in dense InGaN nanopost arrays, (v) design and fabrication of InGaN photonic crystal emitters, and (vi) observation and measurements of enhanced fluorescence from coupled quantum dot and plasmonic nanostructures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  9. Highly efficient heat exchangers for laser diode arrays

    NASA Astrophysics Data System (ADS)

    Apollonov, Victor V.; Derzhavin, Sergei I.; Filonenko, Vladimir A.; Kuzminov, Vitaly V.; Mashkovsky, Dmitry A.; Prokhorov, Alexander M.; Timoshkin, Valery N.

    2000-04-01

    Highly efficient heat exchangers with uniform temperature distribution based on microchannel and porous structure are developed. The heat exchange efficiency dependence on construction peculiarities of the devices and cooling liquids properties are shown. Basing on the comparison of both experimental results and the numerical simulation, the ways to obtain the device thermal resistance about 0,2 C/W are discussed. Practical neededs for fabrication both linear diode arrays with power more than 1 kW will be observed.

  10. Multiple-wavelength diode laser SuperArray

    SciTech Connect

    Epler, J.E. ); Treat, D.W.; Nelson, S.E.; Paoli, T.L. )

    1990-04-01

    A monolithic array of four diode laser arrays operating at four widely separated wavelengths over a 30 nm bandwidth is demonstrated. The multiple-wavelength SuperArray is fabricated from GaAs/AlGaAs separate confinement laser material in which the thickness of the single quantum well active layer is laterally graded to control its effective bandgap. Lateral thickness control is achieved by using laser-induced desorption to selectively thin the epitaxial layer during the MOCVD growth cycle. Transmission electron microscopy is used to demonstrate the variation of the quantum well thickness from approximately 8 to 13 nm across the 1 mm long chip as a result of the desorption. Individually addressable subarrays containing ten gain-guided emitters are defined after growth by conventional proton bombardment and localized metallization. Optical performance characteristics of the SuperArray are presented and discussed.

  11. Air cooling of a VCSEL diode array on quartz Christiane Gimkiewicz, Jurgen Jahns

    E-print Network

    Jahns, Jürgen

    Air cooling of a VCSEL diode array on quartz Christiane Gimkiewicz, J¨urgen Jahns Planar optics in combination with VCSEL arrays has been suggested as a viable approach to overcome the bottleneck of electronic [2]. An 8 × 8 vertical cavity surface emitting laser diode (VCSEL) array was flipchip bonded onto

  12. Deep diode arrays for X-ray detection

    NASA Technical Reports Server (NTRS)

    Zemel, J. N.

    1984-01-01

    Temperature gradient zone melting process was used to form p-n junctions in bulk of high purity silicon wafers. These diodes were patterned to form arrays for X-ray spectrometers. The whole fabrication processes for these X-ray detectors are reviewed in detail. The p-n junctions were evaluated by (1) the dark diode I-V measurements, (2) the diode C sub I - V measurements, and (3) the MOS C-V measurements. The results showed that these junctions were linearly graded in charge distribution with low reverse bias leakage current flowing through them (few nA at -10 volts). The X-ray detection experiments showed that an FWHM of 500 eV was obtained from these diodes with a small bias of just -5 volts (for X-ray source Fe55). A theoretical model was proposed to explain the extra peaks found in the energy spectra and a very interesting point - cross talk effect was pointed out. This might be a solution to the problem of making really high resolution X-ray spectrometers.

  13. Linear laser diode arrays for improvement in optical disk recording

    NASA Technical Reports Server (NTRS)

    Alphonse, G. A.; Carlin, D. B.; Connolly, J. C.

    1990-01-01

    The development of individually addressable laser diode arrays for multitrack magneto-optic recorders for space stations is discussed. Three multi-element channeled substrate planar (CSP) arrays with output power greater than 30 mW with linear light vs current characteristics and stable single mode spectra were delivered to NASA. These devices have been used to demonstrate for the first time the simultaneous recording of eight data tracks on a 14-inch magneto-optic erasable disk. The yield of these devices is low, mainly due to non-uniformities inherent to the LPE growth that was used to fabricate them. The authors have recently developed the inverted CSP, based on the much more uniform MOCVD growth techniques, and have made low threshold quantum well arrays requiring about three times less current than the CSP to deliver 30 mW CW in a single spatial mode. The inverted CSP is very promising for use in space flight recorder applications.

  14. Vacuum Nanohole Array Embedded Phosphorescent Organic Light Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Jeon, Sohee; Lee, Jeong-Hwan; Jeong, Jun-Ho; Song, Young Seok; Moon, Chang-Ki; Kim, Jang-Joo; Youn, Jae Ryoun

    2015-03-01

    Light extraction from organic light-emitting diodes that utilize phosphorescent materials has an internal efficiency of 100% but is limited by an external quantum efficiency (EQE) of 30%. In this study, extremely high-efficiency organic light emitting diodes (OLEDs) with an EQE of greater than 50% and low roll-off were produced by inserting a vacuum nanohole array (VNHA) into phosphorescent OLEDs (PhOLEDs). The resultant extraction enhancement was quantified in terms of EQE by comparing experimentally measured results with those produced from optical modeling analysis, which assumes the near-perfect electric characteristics of the device. A comparison of the experimental data and optical modeling results indicated that the VNHA extracts the entire waveguide loss into the air. The EQE obtained in this study is the highest value obtained to date for bottom-emitting OLEDs.

  15. Vacuum nanohole array embedded phosphorescent organic light emitting diodes.

    PubMed

    Jeon, Sohee; Lee, Jeong-Hwan; Jeong, Jun-Ho; Song, Young Seok; Moon, Chang-Ki; Kim, Jang-Joo; Youn, Jae Ryoun

    2015-01-01

    Light extraction from organic light-emitting diodes that utilize phosphorescent materials has an internal efficiency of 100% but is limited by an external quantum efficiency (EQE) of 30%. In this study, extremely high-efficiency organic light emitting diodes (OLEDs) with an EQE of greater than 50% and low roll-off were produced by inserting a vacuum nanohole array (VNHA) into phosphorescent OLEDs (PhOLEDs). The resultant extraction enhancement was quantified in terms of EQE by comparing experimentally measured results with those produced from optical modeling analysis, which assumes the near-perfect electric characteristics of the device. A comparison of the experimental data and optical modeling results indicated that the VNHA extracts the entire waveguide loss into the air. The EQE obtained in this study is the highest value obtained to date for bottom-emitting OLEDs. PMID:25732061

  16. Vacuum Nanohole Array Embedded Phosphorescent Organic Light Emitting Diodes

    PubMed Central

    Jeon, Sohee; Lee, Jeong-Hwan; Jeong, Jun-Ho; Song, Young Seok; Moon, Chang-Ki; Kim, Jang-Joo; Youn, Jae Ryoun

    2015-01-01

    Light extraction from organic light-emitting diodes that utilize phosphorescent materials has an internal efficiency of 100% but is limited by an external quantum efficiency (EQE) of 30%. In this study, extremely high-efficiency organic light emitting diodes (OLEDs) with an EQE of greater than 50% and low roll-off were produced by inserting a vacuum nanohole array (VNHA) into phosphorescent OLEDs (PhOLEDs). The resultant extraction enhancement was quantified in terms of EQE by comparing experimentally measured results with those produced from optical modeling analysis, which assumes the near-perfect electric characteristics of the device. A comparison of the experimental data and optical modeling results indicated that the VNHA extracts the entire waveguide loss into the air. The EQE obtained in this study is the highest value obtained to date for bottom-emitting OLEDs. PMID:25732061

  17. Photoluminescence performance enhancement of ZnO/MgO heterostructured nanowires and their applications in ultraviolet laser diodes.

    PubMed

    Shi, Zhi-Feng; Zhang, Yuan-Tao; Cui, Xi-Jun; Zhuang, Shi-Wei; Wu, Bin; Chu, Xian-Wei; Dong, Xin; Zhang, Bao-Lin; Du, Guo-Tong

    2015-06-01

    Vertically aligned ZnO/MgO coaxial nanowire (NW) arrays were prepared on sapphire substrates by metal-organic chemical vapor deposition combined with a sputtering system. We present a comparative investigation of the morphological and optical properties of the produced heterostructures with different MgO layer thicknesses. Photoluminescence measurements showed that the optical performances of ZnO/MgO coaxial NWs were strongly dependent on the MgO layer thickness. The intensity of deep-level emission (DLE) decreased monotonously with the increase of MgO thickness, while the enhancement of ultraviolet (UV) emission showed a critical thickness of 15 nm, achieving a maximum intensity ratio (?226) of IUV/IDLE at the same time. The significantly improved exciton emission efficiency of the coaxial NW structures allows us to study the surface passivation effect, photogenerated carrier confinement and transfer in terms of energy band theory. More importantly, we achieved an ultralow threshold (4.5 mA, 0.58 A cm(-2)) electrically driven UV lasing action based on the ZnO/MgO NW structures by constructing an Au/MgO/ZnO metal/insulator/semiconductor diode, and the continuous-current-driven diode shows a good temperature tolerance. The results obtained on the unique optical properties of ZnO/MgO coaxial NWs shed light on the design and development of ZnO-based UV laser diodes assembled with nanoscale building blocks. PMID:25803480

  18. Photon counting photodiode array detector for far ultraviolet (FUV) astronomy

    NASA Technical Reports Server (NTRS)

    Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

    1982-01-01

    A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location. Previously announced in STAR as N82-19118

  19. Characterization of Solar Cell Substrates Using Diode Array Technique

    SciTech Connect

    Appel, J. S.; Sopori, B.; Rupnowski, P.; Duda, A.; Roybal, L.; Mehta, V.; Ravindra, N. M.

    2007-01-01

    In current manufacturing regimes, silicon solar cells are made from low-cost silicon wafers, which are produced in one of three ways: low-grade, Czochralski-type single-crystal wafers; multicrystalline silicon wafers grown by casting; or shaped ribbons produced by directional solidification. These materials contain high concentrations of impurities and defects, which lead to spatial variations in the material properties. A detailed characterization of the substrates is needed to understand the nature of defects and impurities and their influence on solar cell performance. Although many techniques can be applied to map material properties, the influence of the various materials on cell performance is difficult to determine. We have developed a technique to fabricate arrays of edge-passivated diodes (small-area solar cells), which can be probed using an automatic prober to generate dark and illuminated I-V characteristics of each device. These devices can be readily used for other measurements, such as measurement of minority-carrier diffusion length, light or electron beam induced current, C-V analyses, and DLTS. The data from diode arrays are used to study influence of defects and impurities on cell performance and to predict the highest large-area cell performance.

  20. V-shaped resonators for addition of broad-area laser diode arrays

    DOEpatents

    Liu, Bo; Liu, Yun; Braiman, Yehuda Y.

    2012-12-25

    A system and method for addition of broad-area semiconductor laser diode arrays are described. The system can include an array of laser diodes, a V-shaped external cavity, and grating systems to provide feedback for phase-locking of the laser diode array. A V-shaped mirror used to couple the laser diode emissions along two optical paths can be a V-shaped prism mirror, a V-shaped stepped mirror or include multiple V-shaped micro-mirrors. The V-shaped external cavity can be a ring cavity. The system can include an external injection laser to further improve coherence and phase-locking.

  1. Line Narrowing of Fiber Coupled Laser Diode Array He Lung MRI

    E-print Network

    Walsworth, Ronald L.

    Line Narrowing of Fiber Coupled Laser Diode Array and 3 He Lung MRI by Jermane E. Massey B Coupled Laser Diode Array and 3 He Lung MRI by Jermane E. Massey Submitted to the Department of PhysicsW of injected power. A novel MRI coil and polarization system were developed for hyper-polarized 3 He lung

  2. Characterization of High-power Quasi-cw Laser Diode Arrays

    NASA Technical Reports Server (NTRS)

    Stephen, Mark A.; Vasilyev, Aleksey; Troupaki, Elisavet; Allan, Graham R.; Kashem, Nasir B.

    2005-01-01

    NASA s requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. Performance and comprehensive characterization data of Quasi-CW, High-power, laser diode arrays is presented.

  3. Ruggedized microchannel-cooled laser diode array with self-aligned microlens

    DOEpatents

    Freitas, Barry L.; Skidmore, Jay A.

    2003-11-11

    A microchannel-cooled, optically corrected, laser diode array is fabricated by mounting laser diode bars onto Si surfaces. This approach allows for the highest thermal impedance, in a ruggedized, low-cost assembly that includes passive microlens attachment without the need for lens frames. The microlensed laser diode array is usable in all solid-state laser systems that require efficient, directional, narrow bandwidth, high optical power density pump sources.

  4. Diode pumped Pr3+:LiYF4-BBO ultraviolet laser at 320 nm

    NASA Astrophysics Data System (ADS)

    Li, J. H.; Liu, X. H.; Wu, J. B.; Zhang, X.; Li, Y. L.

    2012-03-01

    A diode pumped Pr3+:LiYF4 laser at 639.5 nm has been demonstrated. With an incident pump power of 920 mW, the maximum red output power was 272 mW. Moreover, intracavity second-harmonic generation (SHG) has also been achieved with a maximum ultraviolet power of 23 mW by using a ?-BaB2O4 (BBO) nonlinear crystal. To the best of our knowledge, this is the first report on continuous-wave ultraviolet generation by intracavity frequency doubling Pr3+:LiYF4 laser.

  5. Improving Reliability of High Power Quasi-CW Laser Diode Arrays for Pumping Solid State Lasers

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Baggott, Renee S.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.

    2005-01-01

    Most Lidar applications rely on moderate to high power solid state lasers to generate the required transmitted pulses. However, the reliability of solid state lasers, which can operate autonomously over long periods, is constrained by their laser diode pump arrays. Thermal cycling of the active regions is considered the primary reason for rapid degradation of the quasi-CW high power laser diode arrays, and the excessive temperature rise is the leading suspect in premature failure. The thermal issues of laser diode arrays are even more drastic for 2-micron solid state lasers which require considerably longer pump pulses compared to the more commonly used pump arrays for 1-micron lasers. This paper describes several advanced packaging techniques being employed for more efficient heat removal from the active regions of the laser diode bars. Experimental results for several high power laser diode array devices will be reported and their performance when operated at long pulsewidths of about 1msec will be described.

  6. Thin planar package for cooling an array of edge-emitting laser diodes

    DOEpatents

    Mundinger, David C. (Stockton, CA); Benett, William J. (Livermore, CA)

    1992-01-01

    A laser diode array is disclosed that includes a plurality of planar assemblies and active cooling of each assembly. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar assembly having the laser diode bar located proximate to one edge. In an array, a number of such thin planar assemblies are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink proximate to the laser diode bar to absorb heat generated by laser operation. To provide the coolant to the microchannels, each thin planar assembly comprises passageways that connect the microchannels to inlet and outlet corridors. Each inlet passageway may comprise a narrow slot that directs coolant into the microchannels and increases the velocity of flow therethrough. The corridors comprises holes extending through each of the assemblies in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has applications as an optical pump for high power solid state lasers, or by mating the diodes with fiber optic lenses. Further, the arrays can be useful in applications having space constraints and energy limitations, and in military and space applications. The arrays can be incorporated in equipment such as communications devices and active sensors.

  7. Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms.

    PubMed

    Hosoya, Toshiyuki; Miranda, Martin; Inoue, Ryotaro; Kozuma, Mikio

    2015-07-01

    We developed a high-power laser system at a wavelength of 399?nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40?mW and another laser diode for amplifying the laser power up to 220?mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system does not depend on complex nonlinear frequency-doubling and can be made compact, which will be useful for providing light sources for laser cooling experiments including transportable optical lattice clocks. PMID:26233359

  8. Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms

    NASA Astrophysics Data System (ADS)

    Hosoya, Toshiyuki; Miranda, Martin; Inoue, Ryotaro; Kozuma, Mikio

    2015-07-01

    We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system does not depend on complex nonlinear frequency-doubling and can be made compact, which will be useful for providing light sources for laser cooling experiments including transportable optical lattice clocks.

  9. Mid-ultraviolet light-emitting diode detects dipicolinic acid.

    SciTech Connect

    Bogart, Katherine Huderle Andersen; Lee, Stephen Roger; Temkin, Henryk; Crawford, Mary Hagerott; Dasgupta, Purnendu K.; Li, Qingyang; Allerman, Andrew Alan; Fischer, Arthur Joseph

    2005-06-01

    Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA ({lambda}{sub max} doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.

  10. Linewidth-tunable laser diode array for rubidium laser pumping

    SciTech Connect

    Li Zhiyong; Tan Rongqing; Xu Cheng; Li Lin

    2013-02-28

    To optimise the pump source for a high-power diodepumped rubidium vapour laser, we have designed a laser diode array (LDA) with a narrowed and tunable linewidth and an external cavity formed by two volume Bragg gratings (VBGs). Through controlling the temperature differences between the two VBGs, the LDA linewidth, which was 1.8 nm before mounting the two VBGs, was tunable from 100 pm to 0.2 nm, while the output power changed by no more than 4 %. By changing simultaneously the temperature in both VBGs, the centre wavelength in air of the linewidth-tunable LDA was tunable from 779.40 nm to 780.05 nm. (control of laser radiation parameters)

  11. Environmental testing of a diode-laser-pumped Nd:YAG laser and a set of diode-laser-arrays

    NASA Technical Reports Server (NTRS)

    Hemmati, H.; Lesh, J. R.

    1989-01-01

    Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a set of 20 semiconductor diode laser arrays were environmentally tested by being subjected to vibrational and thermal conditions similar to those experienced during launch of the Space Shuttle, and both performed well. Nevertheless, some damage to the laser front facet in diode lasers was observed. Significant degradation was observed only on lasers which performed poorly in the life test. Improvements in the reliability of the Nd:YAG laser are suggested.

  12. Facile fabrication of a ultraviolet tunable MoS{sub 2}/p-Si junction diode

    SciTech Connect

    Serrano, William; Pinto, Nicholas J.; Naylor, Carl H.; Kybert, Nicholas J.; Johnson, A. T. Charlie

    2015-05-11

    Chemical vapor deposition grown MoS{sub 2} single crystals were transferred onto the edge of a p-Si/SiO{sub 2} wafer, forming an abrupt heterogeneous junction diode at the MoS{sub 2}/p-Si interface. When electrically characterized as a field effect transistor, MoS{sub 2} exhibits an n-type response and can be doped in the presence of ultraviolet (UV) light. As a diode, it operates satisfactorily in air, but has higher currents in vacuum with a turn on voltage of ?1.3?V and an on/off ratio of 20 at ±2?V. UV irradiation increases the diode on state current, decreases the turn-on voltage, and reduces the ideality parameter below 2. These changes are reversible after annealing in air as desorption of electron trapping species like O{sub 2}{sup ?} and H{sub 2}O{sup ?} are believed responsible for this effect. A circuit integrating this diode was used to rectify a 1?kHz signal with an efficiency of 12%. Its simple design, coupled with the ability to clip AC signals, sense UV light, and reversibly tune these diodes, makes them inexpensive, multifunctional, and usable as active or passive circuit components in complex electronics.

  13. Facile fabrication of a ultraviolet tunable MoS2/p-Si junction diode

    NASA Astrophysics Data System (ADS)

    Serrano, William; Pinto, Nicholas J.; Naylor, Carl H.; Kybert, Nicholas J.; Johnson, A. T. Charlie

    2015-05-01

    Chemical vapor deposition grown MoS2 single crystals were transferred onto the edge of a p-Si/SiO2 wafer, forming an abrupt heterogeneous junction diode at the MoS2/p-Si interface. When electrically characterized as a field effect transistor, MoS2 exhibits an n-type response and can be doped in the presence of ultraviolet (UV) light. As a diode, it operates satisfactorily in air, but has higher currents in vacuum with a turn on voltage of ˜1.3 V and an on/off ratio of 20 at ±2 V. UV irradiation increases the diode on state current, decreases the turn-on voltage, and reduces the ideality parameter below 2. These changes are reversible after annealing in air as desorption of electron trapping species like O2- and H2O- are believed responsible for this effect. A circuit integrating this diode was used to rectify a 1 kHz signal with an efficiency of 12%. Its simple design, coupled with the ability to clip AC signals, sense UV light, and reversibly tune these diodes, makes them inexpensive, multifunctional, and usable as active or passive circuit components in complex electronics.

  14. Effect of interface layer on the performance of high power diode laser arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Pu; Wang, Jingwei; Xiong, Lingling; Li, Xiaoning; Hou, Dong; Liu, Xingsheng

    2015-02-01

    Packaging is an important part of high power diode laser (HPLD) development and has become one of the key factors affecting the performance of high power diode lasers. In the package structure of HPLD, the interface layer of die bonding has significant effects on the thermal behavior of high power diode laser packages and most degradations and failures in high power diode laser packages are directly related to the interface layer. In this work, the effects of interface layer on the performance of high power diode laser array were studied numerically by modeling and experimentally. Firstly, numerical simulations using finite element method (FEM) were conducted to analyze the effects of voids in the interface layer on the temperature rise in active region of diode laser array. The correlation between junction temperature rise and voids was analyzed. According to the numerical simulation results, it was found that the local temperature rise of active region originated from the voids in the solder layer will lead to wavelength shift of some emitters. Secondly, the effects of solder interface layer on the spectrum properties of high power diode laser array were studied. It showed that the spectrum shape of diode laser array appeared "right shoulder" or "multi-peaks", which were related to the voids in the solder interface layer. Finally, "void-free" techniques were developed to minimize the voids in the solder interface layer and achieve high power diode lasers with better optical-electrical performances.

  15. Means for phase locking the outputs of a surface emitting laser diode array

    SciTech Connect

    Lesh, J.R.

    1987-06-30

    An array of injection phase-locked diode lasers is described utilizing as a master a separate laser source, and means for coupling light from the master laser source into each diode laser of the array of diode lasers. The array is fabricated in a body of semi-conductor material. Each diode laser has a back facet on one side of the body of semiconductor material and a front facet on an opposite side of the body of semiconductor material. The light coupling means comprises a hologram prepared for producing from the output of the master laser source a set of distinct, spatially separated beams, each one directed into the back facet of each diode laser . To assure emission of phase coherent light from the array of diode lasers, the hologram is positioned between the master laser source and the one side of the body of semiconductor material. The hologram is prepared by illuminating a holographic emulsion plate with an image of the array of diode lasers using coherent light of substantially the same wavelength as the master laser source, and a coherent reference beam of substantially the same wavelength as the master laser source.

  16. Enhanced out-coupling efficiency of organic light-emitting diodes using an nanostructure imprinted by an alumina nanohole array

    SciTech Connect

    Endo, Kuniaki; Adachi, Chihaya

    2014-03-24

    We demonstrate organic light-emitting diodes (OLEDs) with enhanced out-coupling efficiency containing nanostructures imprinted by an alumina nanohole array template that can be applied to large-emitting-area and flexible devices using a roll-to-roll process. The nanostructures are imprinted on a glass substrate by an ultraviolet nanoimprint process using an alumina nanohole array mold and then an OLED is fabricated on the nanostructures. The enhancement of out-coupling efficiency is proportional to the root-mean-square roughness of the nanostructures, and a maximum improvement of external electroluminescence quantum efficiency of 17% is achieved. The electroluminescence spectra of the OLEDs indicate that this improvement is caused by enhancement of the out-coupling of surface plasmon polaritons.

  17. Current status of the laser diode array projector technology

    NASA Astrophysics Data System (ADS)

    Beasley, D. Brett; Saylor, Daniel A.

    1998-07-01

    This paper describes recent developments and the current status of the Laser Diode Array Projector (LDAP) Technology. The LDAP is a state-of-the-art dynamic infrared scene projector system capable of generating high resolution in-band infrared imagery at high frame rates. Three LDAPs are now operational at the U.S. Army Aviation and Missile Command's (AMCOM) Missile Research, Development, and Engineering Center (MRDEC). These projectors have been used to support multiple Hardware-in-the-Loop test entries of various seeker configurations. Seeker configurations tested include an InSb 256 X $256 focal-plane array (FPA), an InSb 512 X 512 FPA, a PtSi 640 X 480 FPA, a PtSi 256 X 256 FPA, an uncooled 320 X 240 microbolometer FPA, and two dual field- of-view (FOV) seekers. Several improvements in the projector technology have been made since we last reported in 1997. The format size has been increased to 544 X 544, and 672 X 512, and it has been proven that the LDAP can be synchronized without a signal from the unit-under test (UUT). The control software has been enhanced to provide 'point and click' control for setup, calibration, image display, image capture, and data analysis. In addition, the first long-wave infrared (LWIR) LDAP is now operational, as well as a dual field of view LDAP which can change its FOV within 0.25 seconds. The projector is interfaced to a Silicon Graphics scene generation computer which is capable of real-time 3-D scene generation. Sample images generated with the projector and captured by an InSb FPA sensor are included in the text.

  18. Largely Enhanced Efficiency in ZnO Nanowire/p-Polymer Hybridized Inorganic/Organic Ultraviolet Light-Emitting Diode by Piezo-

    E-print Network

    Wang, Zhong L.

    generation optoelectronic devices operating in ultraviolet (UV) region, such as light-emitting diodes (LEDsLargely Enhanced Efficiency in ZnO Nanowire/p-Polymer Hybridized Inorganic/Organic Ultraviolet Light-Emitting Diode by Piezo- Phototronic Effect Qing Yang,,, Ying Liu,, Caofeng Pan, Jun Chen, Xiaonan

  19. Advancement of High Power Quasi-CW Laser Diode Arrays For Space-based Laser Instruments

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Baker, nathaniel R.; Baggott, Renee S.; Singh, Upendra N.; Kavaya, Michael J.

    2004-01-01

    Space-based laser and lidar instruments play an important role in NASA s plans for meeting its objectives in both Earth Science and Space Exploration areas. Almost all the lidar instrument concepts being considered by NASA scientist utilize moderate to high power diode-pumped solid state lasers as their transmitter source. Perhaps the most critical component of any solid state laser system is its pump laser diode array which essentially dictates instrument efficiency, reliability and lifetime. For this reason, premature failures and rapid degradation of high power laser diode arrays that have been experienced by laser system designers are of major concern to NASA. This work addresses these reliability and lifetime issues by attempting to eliminate the causes of failures and developing methods for screening laser diode arrays and qualifying them for operation in space.

  20. Triggering GaAs lock-on switches with laser diode arrays

    SciTech Connect

    Loubriel, G.M.; Buttram, M.T.; Helgeson, W.D.; McLaughlin, D.L.; O'Malley, M.W.; Zutavern, F.J. ); Rosen, A.; Stabile, P.J. )

    1990-01-01

    Laser diode arrays have been used to trigger GaAs Photoconducting Semiconductor Switches (PCSS) charged to voltages of up to 60 kV and conducting currents of 580 A. The driving forces behind the use of laser diode arrays are compactness, elimination of complicated optics, and the ability to run at high repetition rates. Laser diode arrays are compactness, elimination of complicated optics, and the ability to run at high repetition rates. Laser diode arrays can trigger GaAs at high fields as the result of a new switching mode (lock-on) with very high carrier number gain. We have achieved switching of up to 10 MW in a 60 {Omega} system, with a pulse rise time of 500 ps. At 1.2 MW we have achieved repetition rates of 1 kHz with switch rise time of 500 ps for 10{sup 5} shots. The laser diode array used for these experiments delivers a 166 W pulse. In a single shot mode we have switched 4 kA with a flash lamp pumped laser and 600 A with the 166 W array. 7 refs., 5 figs.

  1. Newly Packaged 50-?m-Spaced 8-Element Laser Diode Array with a Thermoelectric Cooler

    NASA Astrophysics Data System (ADS)

    Murata, Setsuko; Nakada, Hiroshi; Abe, Tetsuo; Tanaka, Hidenao; Watabe, Akinori

    1993-11-01

    We report that the junction temperature of individually addressable high-power laser diode elements in an array can be reduced by adjusting cavity length and by mounting the array in a copper package that has a thermoelectric cooler and cooling fins. We fabricated a 50-?m-spaced 8-element array and verified its low thermal interaction. We also experimentally evaluated the cooling characteristics of the new package: when all array elements operate simultaneously and continuously at 50 mW, the measured temperature reduction achieved with this package corresponds to an 8-fold increase in array lifetime.

  2. Performance of high-power laser diode arrays for spaceborne lasers.

    PubMed

    Durand, Yannig; Culoma, Alain; Meynart, Roland; Pinsard, Jean-Luc; Volluet, Gerard

    2006-08-01

    The adequacy of commercial quasi-continuous high-power laser diode arrays (HPLDAs) as pump sources for spaceborne lasers has been assessed by endurance tests up to 3 x 10(9) shots under various stress conditions, vacuum operation up to 0.36 x 10(9) shots, and proton radiation tests. Observations of the evolution of the electro-optic parameters and of the near-field patterns of the HPLDAs during endurance tests have revealed that some diode bars could reach the required lifetime of a multibillion shots, suggesting how to build long lifetime HPLDAs by proper selection of the diode bars. The robustness of the HPLDAs against the proton environment experienced in a typical low Earth orbit has been checked. Finally, high-power laser diode arrays have been operated under vacuum, showing a behavior similar to that of HPLDAs operating in atmospheric conditions. PMID:16855676

  3. High density, optically corrected, micro-channel cooled, v-groove monolithic laser diode array

    DOEpatents

    Freitas, B.L.

    1998-10-27

    An optically corrected, micro-channel cooled, high density laser diode array achieves stacking pitches to 33 bars/cm by mounting laser diodes into V-shaped grooves. This design will deliver > 4kW/cm{sup 2} of directional pulsed laser power. This optically corrected, micro-channel cooled, high density laser is usable in all solid state laser systems which require efficient, directional, narrow bandwidth, high optical power density pump sources. 13 figs.

  4. Wide-aperture laser diode array in the external V-shaped cavity

    SciTech Connect

    Svetikov, V V; Nurligareev, D Kh

    2014-09-30

    The operation of a wide-aperture laser diode array with the radiation wavelength 980 nm in external V-shaped symmetric and asymmetric cavities is experimentally studied. The regimes of stable oscillation are studied as functions of the feedback beam direction. The spectra and the intensity distribution of radiation in the far zone are presented for the laser diode in symmetric and asymmetric cavities. Tuning of the radiation wavelength is demonstrated using the Littman geometry in the asymmetric cavity. (lasers)

  5. High density, optically corrected, micro-channel cooled, v-groove monolithic laser diode array

    DOEpatents

    Freitas, Barry L. (Livermore, CA)

    1998-01-01

    An optically corrected, micro-channel cooled, high density laser diode array achieves stacking pitches to 33 bars/cm by mounting laser diodes into V-shaped grooves. This design will deliver>4kW/cm2 of directional pulsed laser power. This optically corrected, micro-channel cooled, high density laser is usable in all solid state laser systems which require efficient, directional, narrow bandwidth, high optical power density pump sources.

  6. Fiber optic coupling of a microlens conditioned, stacked semiconductor laser diode array

    DOEpatents

    Beach, R.J.; Benett, W.J.; Mills, S.T.

    1997-04-01

    The output radiation from the two-dimensional aperture of a semiconductor laser diode array is efficiently coupled into an optical fiber. The two-dimensional aperture is formed by stacking individual laser diode bars on top of another in a ``rack and stack`` configuration. Coupling into the fiber is then accomplished using individual microlenses to condition the output radiation of the laser diode bars. A lens that matches the divergence properties and wavefront characteristics of the laser light to the fiber optic is used to focus this conditioned radiation into the fiber. 3 figs.

  7. Fiber optic coupling of a microlens conditioned, stacked semiconductor laser diode array

    DOEpatents

    Beach, Raymond J. (Livermore, CA); Benett, William J. (Livermore, CA); Mills, Steven T. (Antioch, CA)

    1997-01-01

    The output radiation from the two-dimensional aperture of a semiconductor laser diode array is efficiently coupled into an optical fiber. The two-dimensional aperture is formed by stacking individual laser diode bars on top of another in a "rack and stack" configuration. Coupling into the fiber is then accomplished using individual microlenses to condition the output radiation of the laser diode bars. A lens that matches the divergence properties and wavefront characteristics of the laser light to the fiber optic is used to focus this conditioned radiation into the fiber.

  8. AlGaN/GaN quantum well ultraviolet light emitting diodes

    SciTech Connect

    Han, J.; Crawford, M.H.; Shul, R.J.; Figiel, J.J.; Banas, M.; Zhang, L.; Song, Y.K.; Zhou, H.; Nurmikko, A.V.

    1998-09-01

    We report on the growth and characterization of ultraviolet GaN quantum well light emitting diodes. The room-temperature electroluminescence emission was peaked at 353.6 nm with a narrow linewidth of 5.8 nm. In the simple planar devices, without any efforts to improve light extraction efficiency, an output power of 13 {mu}W at 20 mA was measured, limited in the present design by absorption in the GaN cap layer and buffer layer. Pulsed electroluminescence data demonstrate that the output power does not saturate up to current densities approaching 9 kA/cm{sup 2}. {copyright} {ital 1998 American Institute of Physics.}

  9. Improved calibration technique of the infrared imaging bolometer using ultraviolet light-emitting diodes.

    PubMed

    Drapiko, E; Peterson, B; Alekseev, A; Seo, D C

    2010-10-01

    The technique used until recently utilizing the Ne-He laser for imaging bolometer foils calibration [B. J. Peterson et al., J. Plasma Fusion Res. 2, S1018 (2007)] has showed several issues. The method was based on irradiation of 1 cm spaced set of points on a foil by the laser beam moved by set of mirrors. Issues were the nonuniformity of laser power due to the vacuum window transmission nonuniformity and high reflection coefficient for the laser. Also, due to the limited infrared (IR) window size, it was very time consuming. The new methodology uses a compact ultraviolet (uv) light-emitting diodes installed inside the vacuum chamber in a fixed position and the foil itself will be moved in the XY directions by two vacuum feedthroughs. These will help to avoid the above mentioned issues due to lack of a vacuum window, fixed emitters, higher uv power absorption, and a fixed IR camera position. PMID:21033981

  10. Improved calibration technique of the infrared imaging bolometer using ultraviolet light-emitting diodes

    SciTech Connect

    Drapiko, E.; Peterson, B.; Alekseev, A.; Seo, D. C.

    2010-10-15

    The technique used until recently utilizing the Ne-He laser for imaging bolometer foils calibration [B. J. Peterson et al., J. Plasma Fusion Res. 2, S1018 (2007)] has showed several issues. The method was based on irradiation of 1 cm spaced set of points on a foil by the laser beam moved by set of mirrors. Issues were the nonuniformity of laser power due to the vacuum window transmission nonuniformity and high reflection coefficient for the laser. Also, due to the limited infrared (IR) window size, it was very time consuming. The new methodology uses a compact ultraviolet (uv) light-emitting diodes installed inside the vacuum chamber in a fixed position and the foil itself will be moved in the XY directions by two vacuum feedthroughs. These will help to avoid the above mentioned issues due to lack of a vacuum window, fixed emitters, higher uv power absorption, and a fixed IR camera position.

  11. Improving Lifetime of Quasi-CW Laser Diode Arrays for Pumping 2-Micron Solid State Lasers

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    Operating high power laser diode arrays in long pulse regime of about 1 msec, which is required for pumping 2-micron thulium and holmium-based lasers, greatly limits their useful lifetime. This paper describes performance of laser diode arrays operating in long pulse mode and presents experimental data on the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.

  12. Linear laser diode arrays for improvement in optical disk recording for space stations

    NASA Technical Reports Server (NTRS)

    Alphonse, G. A.; Carlin, D. B.; Connolly, J. C.

    1990-01-01

    The design and fabrication of individually addressable laser diode arrays for high performance magneto-optic recording systems are presented. Ten diode arrays with 30 mW cW light output, linear light vs. current characteristics and single longitudinal mode spectrum were fabricated using channel substrate planar (CSP) structures. Preliminary results on the inverse CSP structure, whose fabrication is less critically dependent on device parameters than the CSP, are also presented. The impact of systems parameters and requirements, in particular, the effect of feedback on laser design is assessed, and techniques to reduce feedback or minimize its effect on systems performance, including mode-stabilized structures, are evaluated.

  13. Improving Reliability of High Power Quasi-CW Laser Diode Arrays Operating in Long Pulse Mode

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

    2006-01-01

    Operating high power laser diode arrays in long pulse regime of about 1 msec, which is required for pumping 2-micron thulium and holmium-based lasers, greatly limits their useful lifetime. This paper describes performance of laser diode arrays operating in long pulse mode and presents experimental data of the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.

  14. Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region

    NASA Astrophysics Data System (ADS)

    Wu, YanQing; Dong, Bin

    2014-12-01

    Aluminium nanohole arrays with fixed diameter were fabricated by focused ion beam and the periodicities were turned. Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region were studied experimentally and theoretically, which revealed that the SERRS enhancement factor was as high as 6 orders.

  15. Performance of a TiN-coated monolithic silicon pin-diode array under mechanical stress

    E-print Network

    B. A. VanDevender; L. I. Bodine; A. W. Myers; J. F. Amsbaugh; M. A. Howe; M. L. Leber; R. G. H. Robertson; K. Tolich; T. D. Van Wechel; B. L. Wall

    2012-02-01

    The Karlsruhe Tritium Neutrino Experiment (KATRIN) will detect tritium beta- decay electrons that pass through its electromagnetic spectrometer with a highly- segmented monolithic silicon pin-diode focal-plane detector (FPD). This pin-diode array will be on a single piece of 500-{\\mu}m-thick silicon, with contact between titanium nitride (TiN) coated detector pixels and front-end electronics made by spring-loaded pogo pins. The pogo pins will exert a total force of up to 50N on the detector, deforming it and resulting in mechanical stress up to 50 MPa in the silicon bulk. We have evaluated a prototype pin-diode array with a pogo-pin connection scheme similar to the KATRIN FPD. We find that pogo pins make good electrical contact to TiN and observe no effects on detector resolution or reverse-bias leakage current which can be attributed to mechanical stress.

  16. High power, high efficiency, 2D laser diode arrays for pumping solid state lasers

    SciTech Connect

    Rosenberg, A.; McShea, J.C.; Bogdan, A.R.; Petheram, J.C.; Rosen, A.

    1987-11-01

    This document reports the current performance of 2D laser diode arrays operating at 770 nm and 808 nm for pumping promethium and neodymium solid state lasers, respectively. Typical power densities are in excess of 2kw/cm/sup 2/ with overall efficiencies greater than 30%.

  17. Multilayer mirror and foil filter AXUV diode arrays on CDX-U spherical torus

    NASA Astrophysics Data System (ADS)

    Soukhanovskii, V. A.; Stutman, D.; Iovea, M.; Finkenthal, M.; Moos, H. W.; Munsat, T.; Jones, B.; Hoffman, D.; Kaita, R.; Majeski, R.

    2001-01-01

    Recent upgrades to CDX-U spherical torus diagnostics include two 10-channel AXUV diode arrays. The multilayer mirror (MLM) array measures the ?150 O VI brightness profile in the poloidal plane using the Mo/B4C synthetic multilayer structures as dispersive elements. The foil filter array has a tangential view and is equipped with interchangeable clear aperture, beryllium and titanium filters. This allows measurements of radiated power, O VI or C V radial distributions, respectively. The O VI and C V emissivity and the radiated power profiles are highly peaked. A Neoclassical impurity accumulation mechanism is considered as an explanation. For radiated power measurements in the Te?100 eV plasmas, photon energy dependent corrections must be used in order to account for nonlinear AXUV sensitivity in the range Ephot?20 eV. The arrays are also used for characterization of resistive MHD phenomena, such as the low m modes, saw-tooth oscillations and internal reconnection events. Based on the successful operation of the diagnostics, a new ultra soft x-ray multilayer mirror diode AXUV diode array monitoring the 34 Å emissivity distribution of C VI will be built and installed on the National Spherical Torus Experiment.

  18. Qualification Testing of Laser Diode Pump Arrays for a Space-Based 2-micron Coherent Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    The 2-micron thulium and holmium-based lasers being considered as the transmitter source for space-based coherent Doppler lidar require high power laser diode pump arrays operating in a long pulse regime of about 1 msec. Operating laser diode arrays over such long pulses drastically impact their useful lifetime due to the excessive localized heating and substantial pulse-to-pulse thermal cycling of their active regions. This paper describes the long pulse performance of laser diode arrays and their critical thermal characteristics. A viable approach is then offered that allows for determining the optimum operational parameters leading to the maximum attainable lifetime.

  19. Semiconductor-laser-diode arrays by MOCVD (metalorganic chemical vapor deposition). Final report, 1 September 1984-31 August 1987

    SciTech Connect

    Coleman, J.J.

    1987-09-01

    The purpose of this program is to develop the metalorganic chemical vapor deposition (MOCVD) epitaxial growth process for semiconductor heterostructure laser-diode arrays. These laser diode arrays are intended to be used as an optical pump for solid-state yttrium aluminum garnet (YAG) lasers. In particular, linear uniform arrays having high output power, high efficiency, low laser threshold current density and precisely controlled emission wavelength are required. There are three technical problems associated with this task. The first problem is development of individual laser-diode device structures that satisfy the requirements for efficiency, threshold, and wavelength control and are suitable for incorporation into laser arrays. There are a number of possible structures varying in complexity from conventional five-layer double heterostructures having alloy AlGaAs active regions to very-sophisticated quantum-well heterostructures (QWH). The second problem is an analytical study of the waveguide properties of multi-element laser arrays. Simple arrays of conventional double heterostructure laser diodes were studied, but extension of this work to other laser-diode geometries is non-trivial. Preliminary and optimum geometries for the individual structures and the photomasks used for device processing require some modeling of the optical properties of these arrays. The third problem, and the major point of this entire program, is experimental development of suitably designed individual laser-diode structures in a well-modeled multi-element array.

  20. Development of substrate-removal-free vertical ultraviolet light-emitting diode (RefV-LED)

    SciTech Connect

    Kurose, N. Aoyagi, Y.; Shibano, K.; Araki, T.

    2014-02-15

    A vertical ultraviolet (UV) light-emitting diode (LED) that does not require substrate removal is developed. Spontaneous via holes are formed in n-AlN layer epitaxially grown on a high conductive n+Si substrate and the injected current flows directly from the p-electrode to high doped n{sup +} Si substrate through p-AlGaN, multi-quantum wells, n-AlGaN and spontaneous via holes in n-AlN. The spontaneous via holes were formed by controlling feeding-sequence of metal-organic gas sources and NH{sub 3} and growth temperature in MOCVD. The via holes make insulating n-AlN to be conductive. We measured the current-voltage, current-light intensity and emission characteristics of this device. It exhibited a built-in voltage of 3.8 V and emission was stated at 350 nm from quantum wells with successive emission centered at 400?nm. This UV LED can be produced, including formation of n and p electrodes, without any resist process.

  1. Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes

    SciTech Connect

    Verma, Jai; Kandaswamy, Prem Kumar; Protasenko, Vladimir; Verma, Amit; Grace Xing, Huili; Jena, Debdeep

    2013-01-28

    We demonstrate a GaN quantum dot ultraviolet light-emitting diode that uses tunnel injection of carriers through AlN barriers into the active region. The quantum dot heterostructure is grown by molecular beam epitaxy on AlN templates. The large lattice mismatch between GaN and AlN favors the formation of GaN quantum dots in the Stranski-Krastanov growth mode. Carrier injection by tunneling can mitigate losses incurred in hot-carrier injection in light emitting heterostructures. To achieve tunnel injection, relatively low composition AlGaN is used for n- and p-type layers to simultaneously take advantage of effective band alignment and efficient doping. The small height of the quantum dots results in short-wavelength emission and are simultaneously an effective tool to fight the reduction of oscillator strength from quantum-confined Stark effect due to polarization fields. The strong quantum confinement results in room-temperature electroluminescence peaks at 261 and 340 nm, well above the 365 nm bandgap of bulk GaN. The demonstration opens the doorway to exploit many varied features of quantum dot physics to realize high-efficiency short-wavelength light sources.

  2. Optical fluence modelling for ultraviolet light emitting diode-based water treatment systems.

    PubMed

    Simons, R; Gabbai, U E; Moram, M A

    2014-12-01

    This work presents a validated optical fluence rate model optimised for ultraviolet light-emitting diodes (UV-LEDs), which allow a very wide range of emission wavelengths and source geometries to be used in water treatment units. The model is based on a Monte Carlo approach, in which an incremental ray-tracing algorithm is used to calculate the local volumetric rate of energy absorption and subsequently convert it to the local fluence rate distribution for an UV-LED water treatment chamber of arbitrary design. The model includes contributions from optical reflections and scattering by treatment chamber walls and from scattering due to particulates and/or microorganisms. The model successfully predicts optical fluence rates in point-of-use water treatment units, as verified using biodosimetry with MS-2 bacteriophage at a UV-LED emission wavelength of 254 nm. The effects of chamber geometry are also modelled effectively and are consistent with the inactivation data for E. coli at 254 nm. The data indicate that this model is suitable for application in the design and optimisation of UV-LED-based water treatment systems. PMID:25222335

  3. Exciplex formation and electroluminescent absorption in ultraviolet organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Zhang, Hao; Zhang, Xiao-Wen; Xu, Tao; Wei, Bin

    2015-02-01

    We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes (UV OLEDs) using different heterojunction structures. It is found that an energy barrier of over 0.3 eV between the emissive layer (EML) and adjacent transport layer facilitates exciplex formation. The electron blocking layer effectively confines electrons in the EML, which contributes to pure UV emission and enhances efficiency. The change in EML thickness generates tunable UV emission from 376 nm to 406 nm. In addition, the UV emission excites low-energy organic function layers and produces photoluminescent emission. In UV OLED, avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency. A maximum external quantum efficiency of 1.2% with a UV emission peak of 376 nm is realized. Project supported by the National Natural Science Foundation of China (Grant Nos. 61136003 and 61275041) and the Guangxi Provincial Natural Science Foundation, China (Grant No. 2012GXNSFBA053168).

  4. High-Power Genuine Ultraviolet Light-Emitting Diodes Based On Colloidal Nanocrystal Quantum Dots.

    PubMed

    Kwak, Jeonghun; Lim, Jaehoon; Park, Myeongjin; Lee, Seonghoon; Char, Kookheon; Lee, Changhee

    2015-06-10

    Thin-film ultraviolet (UV) light-emitting diodes (LEDs) with emission wavelengths below 400 nm are emerging as promising light sources for various purposes, from our daily lives to industrial applications. However, current thin-film UV-emitting devices radiate not only UV light but also visible light. Here, we introduce genuine UV-emitting colloidal nanocrystal quantum dot (NQD) LEDs (QLEDs) using precisely controlled NQDs consisting of a 2.5-nm-sized CdZnS ternary core and a ZnS shell. The effective core size is further reduced during the shell growth via the atomic diffusion of interior Cd atoms to the exterior ZnS shell, compensating for the photoluminescence red shift. This design enables us to develop CdZnS@ZnS UV QLEDs with pure UV emission and minimal parasitic peaks. The irradiance is as high as 2.0-13.9 mW cm(-2) at the peak wavelengths of 377-390 nm, several orders of magnitude higher than that of other thin-film UV LEDs. PMID:25961530

  5. Development of substrate-removal-free vertical ultraviolet light-emitting diode (RefV-LED)

    NASA Astrophysics Data System (ADS)

    Kurose, N.; Shibano, K.; Araki, T.; Aoyagi, Y.

    2014-02-01

    A vertical ultraviolet (UV) light-emitting diode (LED) that does not require substrate removal is developed. Spontaneous via holes are formed in n-AlN layer epitaxially grown on a high conductive n+Si substrate and the injected current flows directly from the p-electrode to high doped n+ Si substrate through p-AlGaN, multi-quantum wells, n-AlGaN and spontaneous via holes in n-AlN. The spontaneous via holes were formed by controlling feeding-sequence of metal-organic gas sources and NH3 and growth temperature in MOCVD. The via holes make insulating n-AlN to be conductive. We measured the current-voltage, current-light intensity and emission characteristics of this device. It exhibited a built-in voltage of 3.8 V and emission was stated at 350 nm from quantum wells with successive emission centered at 400 nm. This UV LED can be produced, including formation of n and p electrodes, without any resist process.

  6. Aluminum nitride nanowire light emitting diodes: Breaking the fundamental bottleneck of deep ultraviolet light sources

    PubMed Central

    Zhao, S.; Connie, A. T.; Dastjerdi, M. H. T.; Kong, X. H.; Wang, Q.; Djavid, M.; Sadaf, S.; Liu, X. D.; Shih, I.; Guo, H.; Mi, Z.

    2015-01-01

    Despite broad interest in aluminum gallium nitride (AlGaN) optoelectronic devices for deep ultraviolet (DUV) applications, the performance of conventional Al(Ga)N planar devices drastically decays when approaching the AlN end, including low internal quantum efficiencies (IQEs) and high device operation voltages. Here we show that these challenges can be addressed by utilizing nitrogen (N) polar Al(Ga)N nanowires grown directly on Si substrate. By carefully tuning the synthesis conditions, a record IQE of 80% can be realized with N-polar AlN nanowires, which is nearly ten times higher compared to high quality planar AlN. The first 210?nm emitting AlN nanowire light emitting diodes (LEDs) were achieved, with a turn on voltage of about 6?V, which is significantly lower than the commonly observed 20 – 40?V. This can be ascribed to both efficient Mg doping by controlling the nanowire growth rate and N-polarity induced internal electrical field that favors hole injection. In the end, high performance N-polar AlGaN nanowire LEDs with emission wavelengths covering the UV-B/C bands were also demonstrated. PMID:25684335

  7. NANOSTRUCTURED HIGH PERFORMANCE ULTRAVIOLET AND BLUE LIGHT EMITTING DIODES FOR SOLID STATE LIGHTING

    SciTech Connect

    Arto V. Nurmikko; Jung Han

    2004-10-01

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the first 12 month contract period include (1) new means of synthesizing zero- and one-dimensional GaN nanostructures, (2) establishment of the building blocks for making GaN-based microcavity devices, and (3) demonstration of top-down approach to nano-scale photonic devices for enhanced spontaneous emission and light extraction. These include a demonstration of eight-fold enhancement of the external emission efficiency in new InGaN QW photonic crystal structures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  8. High performance near-ultraviolet flip-chip light-emitting diodes with distributed Bragg reflector

    NASA Astrophysics Data System (ADS)

    Choi, Il-Gyun; Jin, Geun-Mo; Park, Jun-Cheon; Jeon, Soo-Kun; Park, Eun-Hyun

    2015-09-01

    We have fabricated the near-ultraviolet (NUV) flip-chip (FC) light-emitting diodes (LEDs) with the high external quantum efficiency (EQE) using distributed Bragg reflectors (DBRs) and compared with conventional FC-LED using silver (Ag) reflector. Reflectance of Ag is very high (90 ~ 95 %) at visible spectrum region, but sharply decrease at NUV region. Therefore we used DBR composed of two different materials which have high-index contrast, such as TiO2 and SiO2. However, to achieve high-performance NUV flip-chip LEDs, we used Ta2O5 instead of TiO2 that absorbs lights of NUV region. Thus, we have designed a DBR composed of twenty pairs of Ta2O5 and SiO2 using optical coating design software. The DBR designed by our group achieves a reflectance of ~99 % in the NUV region (350 ~ 500 nm), which is much better than Ag reflector. Optical power is higher than the Ag-LED up to 22 % @ 390 nm.

  9. Room-temperature ultraviolet emission from an organic light-emitting diode C. F. Qiu, L. D. Wang, H. Y. Chen, M. Wong, and H. S. Kwok

    E-print Network

    emission from the silicon chain of a polymer.3 External efficiency of 0.1% was obtained. For the caseRoom-temperature ultraviolet emission from an organic light-emitting diode C. F. Qiu, L. D. Wang, H Ultraviolet emission was obtained from N,N -diphenyl-N,N -bis 3-methylphenyl - 1,1 -bi phenyl -4,4 -diamine

  10. Hard solder 20-kW QCW stack array diode laser

    NASA Astrophysics Data System (ADS)

    Li, Xiaoning; Kang, Lijun; Wang, Jingwei; Zhang, Pu; Xiong, Lingling; Liu, Xingsheng

    2012-03-01

    With the increasing applications of high power semiconductor lasers in industry, advanced manufacturing, aerospace, medical systems, display, entertainment, etc., semiconductor lasers with high power and high performances are required. The performance of semiconductor lasers is greatly affected by packaging structure, packaging process and beam shaping. A novel macro channel cooler (MaCC) for stack array laser with good heat dissipation capacity and high reliability is presented in this work. Based on the MaCC package, a high power stack array diode laser is successfully fabricated. A series of techniques such as spectrum control and beam control are used to achieve narrow spectrum and high beam quality. The performances of the semiconductor laser stack array are characterized. A high power 20kW QCW hard solder packaged stack array laser is fabricated; a narrow spectrum of 3.94 nm and an excellent rectangular beam shape are obtained. The lifetime of the stack array laser is tested as well.

  11. A Lunar Optical-Ultraviolet-Infrared Synthesis Array (LOUISA)

    NASA Technical Reports Server (NTRS)

    Burns, Jack O. (editor); Johnson, Stewart W. (editor); Duric, Nebojsa (editor)

    1992-01-01

    This document contains papers presented at a workshop held to consider 'optical ultraviolet infrared' interferometric observations from the moon. Part 1 is an introduction. Part 2 is a description of current and planned ground-based interferometers. Part 3 is a description of potential space-based interferometers. Part 4 addresses the potential for interferometry on the moon. Part 5 is the report of the workshop's working groups. Concluding remarks, summary, and conclusions are presented in Part 6.

  12. Modelling of field emitter array characteristics in diode system

    NASA Astrophysics Data System (ADS)

    Nikiforov, K. A.; Sayfullin, M. F.

    2015-11-01

    In terms of a mathematical model, this paper studies features of the current characteristics of a thin-film matrix field emission array cathode with vertical blade-shaped emitters. Microscopical distribution of electric field strength was calculated and its dependence on geometric parameters of the structures was defined.

  13. Dosimetric Characteristics of a Two-Dimensional Diode Array Detector Irradiated with Passively Scattered Proton Beams

    PubMed Central

    Liengsawangwong, Praimakorn; Sahoo, Nanayan; Ding, Xiaoning; Lii, MingFwu; Gillin, Michale T.; Zhu, Xiaorong Ronald

    2015-01-01

    Purpose: To evaluate the dosimetric characteristics of a two-dimensional (2D) diode array detector irradiated with passively scattered proton beams. Materials and Methods: A diode array detector, MapCHECK (Model 1175, Sun Nuclear, Melbourne, FL, USA) was characterized in passive-scattered proton beams. The relative sensitivity of the diodes and absolute dose calibration were determined using a 250 MeV beam. The pristine Bragg curves (PBCs) measured by MapCHECK diodes were compared with those of an ion chamber using a range shift method. The water-equivalent thickness (WET) of the diode array detector’s intrinsic buildup also was determined. The inverse square dependence, linearity, and other proton dosimetric quantities measured by MapCHECK were also compared with those of the ion chambers. The change in the absolute dose response of the MapCHECK as a function of accumulated radiation dose was used as an indicator of radiation damage to the diodes. 2D dose distribution with and without the compensator were measured and compared with the treatment planning system (TPS) calculations. Results: The WET of the MapCHECK diode’s buildup was determined to be 1.7 cm. The MapCHECK-measured PBC were virtually identical to those measured by a parallel-plate ion chamber for 160, 180, and 250 MeV proton beams. The inverse square results of the MapCHECK were within ±0.4% of the ion chamber results. The linearity of MapCHECK results was within 1% of those from the ion chamber as measured in the range between 10 and 300 MU. All other dosimetric quantities were within 1.3% of the ion chamber results. The 2D dose distributions for non-clinical fields without compensator and the patient treatment fields with the compensator were consistent with the TPS results. The absolute dose response of the MapCHECK was changed by 7.4% after an accumulated dose increased by 170 Gy. Conclusions: The MapCHECK is a convenient and useful tool for 2D dose distribution measurements using passively scattered proton beams. Variations in MapCHECK’s dose response with increasing levels of total accumulated radiation dose should be carefully monitored. PMID:26264024

  14. An efficient non-Lambertian organic light-emitting diode using imprinted submicron-size zinc oxide pillar arrays

    E-print Network

    Demir, Hilmi Volkan

    An efficient non-Lambertian organic light-emitting diode using imprinted submicron-size zinc oxide. Related Articles Conical air prism arrays as an embedded reflector for high efficient InGaN/GaN light://apl.aip.org/about/rights_and_permissions #12;An efficient non-Lambertian organic light-emitting diode using imprinted submicron-size zinc oxide

  15. Optimization of rod diameter in solid state lasers side pumped with multiple laser diode arrays

    NASA Technical Reports Server (NTRS)

    Sims, Newton, Jr.; Chamblee, Christyl M.; Barnes, Norman P.; Lockard, George E.; Cross, Patricia L.

    1992-01-01

    Results of a study to determine the optimum laser rod diameter for maximum output energy in a solid state neodymium laser transversely pumped with multiple laser diode arrays are reported here. Experiments were performed with 1.0 mm, 1.5 mm and 2.0 mm rod radii of both neodymium doped Y3Al5O12 (Nd:YAG) and La2Be2O5 (Nd:BeL) pumped with laser diode arrays having a maximum combined energy of 10.5 mJ. Equations were derived which predict the optimum rod radius and corresponding output mirror reflectivity for a given laser material and total pump energy. Predictions of the equations agreed well with the experiments for each of the laser materials which possessed significantly different laser properties from one another.

  16. Single-photon avalanche diode arrays and CMOS microelectronics for counting, timing, and imaging quantum events

    NASA Astrophysics Data System (ADS)

    Zappa, F.; Tosi, A.; Dalla Mora, A.; Guerrieri, F.; Tisa, S.

    2010-01-01

    Aim of the paper is to discuss design, fabrication and performances of Single-Photon Avalanche Diode (SPAD) arrays developed at the SPADLab of Politecnico di Milano, in both custom and fully-CMOS technologies. Applications span from 2D imagers for high sensitivity fast frame-rate (close to Mframe/s) video acquisitions, to molecular imaging, to functional time-resolved Near-Infrared Spectroscopy (fNIRS) of organs and tissues, to Fluorescence Correlation Spectroscopy (FCS), Fluorescence Lifetime Imaging (FLIM) with 30psFWHM photon timing resolution. Various microelectronic single-chip detection modules and monolithic SPAD arrays will be presented and discussed.

  17. Development of 260 nm band deep-ultraviolet light emitting diodes on Si substrates

    NASA Astrophysics Data System (ADS)

    Mino, Takuya; Hirayama, Hideki; Takano, Takayoshi; Tsubaki, Kenji; Sugiyama, Masakazu

    2013-03-01

    Deep-ultraviolet (DUV) light-emitting diodes (LEDs) have a wide range of potential applications, such as sterilization, water purification, and medicine. In recent years, the external quantum efficiency (EQE) and the performance of AlGaNbased DUV LEDs on sapphire substrates have increased markedly due to improvements in the crystalline-quality of high Al-content AlGaN layers, and the optimization of LED structures. On the other hand, DUV LEDs fabricated on Si substrates are very promising as a low-cost DUV light-source in the near future. However, AlN layers on Si have suffered from cracking induced by the large mismatch in lattice constants and thermal expansion coefficients between AlN and Si. In this paper, DUV LEDs on Si were realized by a combination of a reduction in the number of cracks and of the threading dislocation density (TDD) of AlN templates by using the epitaxial lateral overgrowth (ELO) method. The ELO-AlN templates were successfully coalesced on trench-patterned substrates, with the stripes running along the <1-100> direction of AlN. The density of cracks was greatly reduced in 4- ?m-thick ELO-AlN templates, because voids formed by the ELO process relaxed the tensile stress in the AlN layer. Furthermore, the AlN templates showed low-TDD. The full-width-at-half-maximum values of the (0002) and (10-12) X-ray rocking curves were 780 and 980 arcsec, respectively. DUV LEDs fabricated on these high-quality ELO-AlN/Si substrates showed single peak emission at 256- 278 nm in electroluminescence measurements. It is expected that we will be able to realize low-cost DUV LEDs on Si substrates by using ELO-AlN templates.

  18. Robotic radiosurgery system patient-specific QA for extracranial treatments using the planar ion chamber array and the cylindrical diode array.

    PubMed

    Lin, Mu-Han; Veltchev, Iavor; Koren, Sion; Ma, Charlie; Li, Jinsgeng

    2015-01-01

    Robotic radiosurgery system has been increasingly employed for extracranial treatments. This work is aimed to study the feasibility of a cylindrical diode array and a planar ion chamber array for patient-specific QA with this robotic radiosurgery system and compare their performance. Fiducial markers were implanted in both systems to enable image-based setup. An in-house program was developed to postprocess the movie file of the measurements and apply the beam-by-beam angular corrections for both systems. The impact of noncoplanar delivery was then assessed by evaluating the angles created by the incident beams with respect to the two detector arrangements and cross-comparing the planned dose distribution to the measured ones with/without the angular corrections. The sensitivity of detecting the translational (1-3 mm) and the rotational (1°-3°) delivery errors were also evaluated for both systems. Six extracranial patient plans (PTV 7-137 cm³) were measured with these two systems and compared with the calculated doses. The plan dose distributions were calculated with ray-tracing and the Monte Carlo (MC) method, respectively. With 0.8 by 0.8 mm² diodes, the output factors measured with the cylindrical diode array agree better with the commissioning data. The maximum angular correction for a given beam is 8.2% for the planar ion chamber array and 2.4% for the cylindrical diode array. The two systems demonstrate a comparable sensitivity of detecting the translational targeting errors, while the cylindrical diode array is more sensitive to the rotational targeting error. The MC method is necessary for dose calculations in the cylindrical diode array phantom because the ray-tracing algorithm fails to handle the high-Z diodes and the acrylic phantom. For all the patient plans, the cylindrical diode array/ planar ion chamber array demonstrate 100% / > 92% (3%/3 mm) and > 96% / ~ 80% (2%/2 mm) passing rates. The feasibility of using both systems for robotic radiosurgery system patient-specific QA has been demonstrated. For gamma evaluation, 2%/2 mm criteria for cylindrical diode array and 3%/3 mm criteria for planar ion chamber array are suggested. The customized angular correction is necessary as proven by the improved passing rate, especially with the planar ion chamber array system. PMID:26219013

  19. High Power Laser Diode Arrays for 2-Micron Solid State Coherent Lidars Applications

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron; Kavaya, Michael J.; Singh, Upendra; Sudesh, Vikas; Baker, Nathaniel

    2003-01-01

    Laser diode arrays are critical components of any diode-pumped solid state laser systems, constraining their performance and reliability. Laser diode arrays (LDAs) are used as the pump source for energizing the solid state lasing media to generate an intense coherent laser beam with a high spatial and spectral quality. The solid state laser design and the characteristics of its lasing materials define the operating wavelength, pulse duration, and power of the laser diodes. The pump requirements for high pulse energy 2-micron solid state lasers are substantially different from those of more widely used 1-micron lasers and in many aspects more challenging [1]. Furthermore, the reliability and lifetime demanded by many coherent lidar applications, such as global wind profiling from space and long-range clear air turbulence detection from aircraft, are beyond the capability of currently available LDAs. In addition to the need for more reliable LDAs with longer lifetime, further improvement in the operational parameters of high power quasi-cw LDAs, such as electrical efficiency, brightness, and duty cycle, are also necessary for developing cost-effective 2-micron coherent lidar systems for applications that impose stringent size, heat dissipation, and power constraints. Global wind sounding from space is one of such applications, which is the main driver for this work as part of NASA s Laser Risk Reduction Program. This paper discusses the current state of the 792 nm LDA technology and the technology areas being pursued toward improving their performance. The design and development of a unique characterization facility for addressing the specific issues associated with the LDAs for pumping 2-micron coherent lidar transmitters and identifying areas of technological improvement will be described. Finally, the results of measurements to date on various standard laser diode packages, as well as custom-designed packages with potentially longer lifetime, will be reported.

  20. Characteristics of deep ultraviolet AlGaN-based light emitting diodes with p-hBN layer

    NASA Astrophysics Data System (ADS)

    Dong, K. X.; Chen, D. J.; Shi, J. P.; Liu, B.; Lu, H.; Zhang, R.; Zheng, Y. D.

    2016-01-01

    The AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) with p-hBN layer are investigated numerically. In comparison with the conventional AlGaN DUV LEDs, the proposed LED can significantly improve the carrier injection, radiative efficiency, as well as the electroluminescence (EL) intensity under the same applied forward bias. Simultaneously, the light extraction efficiency in the LED using p-hBN instead of p-AlGaN exhibits a more than 250% increase at the applied voltage of 7.5 V due to the smaller loss of reflection and absorption of the emitted light.

  1. Indium Tin Oxide-Free Transparent Conductive Electrode for GaN-Based Ultraviolet Light-Emitting Diodes.

    PubMed

    Kim, Ja-Yeon; Jeon, Jong-Hyun; Kwon, Min-Ki

    2015-04-22

    Transparent conducting electrodes are important components of highly efficient ultraviolet light-emitting diodes (UV LEDs). Indium tin oxide (ITO) is commonly used to form a current spreading layer, but its UV-range optical transparency is limited with a low sheet resistance. We demonstrate a simple solution-based coating technique to obtain large-area, highly uniform, and conductive silver-nanowire-based electrodes that exhibit UV-range optical transparency better than that of ITO for the same sheet resistance. The UV LEDs fabricated using this current spreading layer showed improved optical power emission as well as improvement in electrical properties. PMID:25830932

  2. Ultraviolet emission from a multi-layer graphene/MgZnO/ZnO light-emitting diode

    SciTech Connect

    Kang, Jang-Won; Choi, Yong-Seok; Goo Kang, Chang; Hun Lee, Byoung; Kim, Byeong-Hyeok; Tu, C. W.; Park, Seong-Ju

    2014-02-03

    We report on ultraviolet emission from a multi-layer graphene (MLG)/MgZnO/ZnO light-emitting diodes (LED). The p-type MLG and MgZnO in the MLG/MgZnO/ZnO LED are used as transparent hole injection and electron blocking layers, respectively. The current-voltage characteristics of the MLG/MgZnO/ZnO LED show that current transport is dominated by tunneling processes in the MgZnO barrier layer under forward bias conditions. The holes injected from p-type MLG recombine efficiently with the electrons accumulated in ZnO, and the MLG/MgZnO/ZnO LED shows strong ultraviolet emission from the band edge of ZnO and weak red-orange emission from the deep levels of ZnO.

  3. LOUISA - A lunar optical-ultraviolet-infrared synthesis array

    NASA Technical Reports Server (NTRS)

    Burns, Jack O.; Duric, Nebojsa; Taylor, Jeffrey; Johnson, Stewart

    1990-01-01

    The emplacement of an optical wavelength interferometric array on the lunar surface is proposed. It will consist of 42 1.5-m mirrors distributed in two concentric circles with an outer diameter of 10-km. The resolution of LOUISA will be 10 microarcsec at a wavelength of 0.5 microns - a factor of 4100 times better than the HST. With such a resolution, astronomers will be able to image earthlike extrasolar planets, active regions on other stars, and collimated outflows from young stellar objects and the nuclei of active galaxies.

  4. Omnidirectional multiview three-dimensional display based on direction-selective light-emitting diode array

    NASA Astrophysics Data System (ADS)

    Yan, Caijie; Liu, Xu; Liu, Di; Xie, Jing; Xia, Xin Xing; Li, Haifeng

    2011-03-01

    A volumetric display system based on a rotating light-emitting diode (LED) array panel can realize a three-dimensional (3-D) display truthfully in the space, but the drawback is missing the occlusion of a 3-D image. We propose an omnidirectional 3-D display with correct occlusion based on a direction-selective LED array panel, which is realized by setting a direction-convergent diaphragm array in front of the LED array. Every diaphragm restricts a light-emitting characteristic of every LED. By using direction-convergent diaphragm array, the observer around the display system can only see one image displayed by the LED array at the corresponding position. With the high-speed rotation of the LED panel, a series of views of a 3-D scene are displayed every angle patch in one circle. We set up an acquisition system to record 180 views of the 3-D scene with a rotating camera along a circle, and then the 180 images are displayed sequentially on the rotating direction-selective LED array to get a 360 deg 3-D display. This 3-D display technology has two main advantages: easy to get viewer-position-dependent correct occlusion and simplify the 3-D data preprocessing process which is helpful to real-time 3-D display.

  5. 10?m pitch design of HgCdTe diode array in Sofradir

    NASA Astrophysics Data System (ADS)

    Péré-Laperne, Nicolas; Rubaldo, Laurent; Kerlain, Alexandre; Carrère, Emmanuel; Dargent, Loïc.; Taalat, Rachid; Berthoz, Jocelyn

    2015-01-01

    Sofradir recently presented Daphnis, its latest 10?m pitch XGA and HD720 products. Daphnis XGA is a 10?m pitch 1024x768 mid-wave infrared focal plane array. The development of small pixel pitch is opening the way to very compact products with high spatial resolution. This new product is key contribution to the HOT technology competition allowing reductions in size, weight and power of the overall package. This paper presents the recent developments achieved at Sofradir to make this 10?m pitch HgCdTe focal plane array. Electrical and electro-optical characterizations are presented to define the appropriate design of 10?m pitch diode array. The technological tradeoffs are explained to lower the dark current, to keep high quantum efficiency with a high operability above 110K, F/4.

  6. Feasibility of Ultraviolet Light Emitting Diodes as an Alternative Light Source for Photocatalysis

    NASA Technical Reports Server (NTRS)

    Levine, Langanf H.; Richards, Jeffrey T.; Soler, Robert; Maxik, Fred; Coutts, Janelle; Wheeler, Raymond M.

    2011-01-01

    The objective of this study was to determine whether ultraviolet light emitting diodes (UV-LEDs) could serve as an alternative photon source efficiently for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp in a Silica-Titania Composite (STC) packed bed annular reactor. Lighting and thermal properties were characterized to assess the uniformity and total irradiant output. A forward current of (I(sub F)) 100 mA delivered an average irradiance of 4.0 m W cm(exp -2), which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED- and BLB-reactors were tested for the oxidization of 50 ppmv ethanol in a continuous flow-through mode with 0.94 sec space time. At the same irradiance, the UV-A LED reactor resulted in a lower PCO rate constant than the UV-A BLB reactor (19.8 vs. 28.6 nM CO2 sec-I), and consequently lower ethanol removal (80% vs. 91%) and mineralization efficiency (28% vs. 44%). Ethanol mineralization increased in direct proportion to the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED- reactor could be traced to uneven irradiance over the photocatalyst, leaving a portion of the catalyst was under-irradiated. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off' feature for periodic irradiation. Nevertheless, the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB. These results demonstrated that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency.

  7. Development of ultraviolet electroabsorption modulators and light emitting diodes based on AlGaN alloys

    NASA Astrophysics Data System (ADS)

    Kao, Chen-Kai

    The research in this dissertation addressed the development of ultraviolet (UV) electroabsorption modulators and ultraviolet light emitting diodes (UV-LEDs), covering the spectral range from 360 to 265 nm. The materials system for both types of devices is the AlGaN alloys, either in bulk or quantum well (QW) form, grown by plasma-assisted molecular beam epitaxy (MBE). Potential applications of these devices either individually or in combination include UV non-line-of-sight free-space-optical communications, UV sensing and spectroscopic systems, Q-switched pulsed lasers, water/air purification and various medical applications. Optical modulators based on cubic III-V semiconductors have been the subject of extensive research over the past several years. Such devices are typically based on the quantum-confined Stark effect to modify the absorption spectrum of multiple-quantum-well active regions. On the other hand, in wurtzite III-Nitride semiconductors, strong electric fields are already present in the quantum wells due to intrinsic and piezoelectric polarizations; as a result, an even greater change in absorption is achievable, especially if the internal fields are compensated by the external bias so that the net field in the quantum wells is reduced. A number of UV electroabsorption modulators based on Schottky barriers on bulk GaN and GaN /AlGaN multiple quantum wells (MQWs) were designed, fabricated and characterized. Record modulation ratio of 30 % was obtained from bulk GaN Schottky barrier modulators at the excitonic resonant energy of 3.45 eV (360 nm) upon the application of 12 V reverse bias. Similarly, record modulation ratio of 43% was obtained from GaN / AlGaN MQWs Schottky barrier modulators at the excitonic resonant energy of 3.48 eV (356 nm) upon the application of 17 V reverse bias. The external quantum efficiency (EQE) of AlGaN based deep UV LEDS is relatively low (˜1% at 270 nm). This is generally attributed to the poor internal quantum efficiency (IQE) of this material system due to the high concentration of line and point defects. In the current work the deep UV-LED structures were grown on inexpensive and widely available sapphire substrates, which resulted in materials with dislocation density of 1010 cm-2. To prevent the non-radiative recombination of the injected electron-hole pairs, the active region of the devices were grown under conditions which lead to band structure potential fluctuations, which lead to exciton localization and thus efficient radiative recombination. Using such a growth method AlGaN MQWs emitting at 265 nm with an IQE as high as 58.8% were demonstrated. Using such QWs a number UV LEDs emitting in the spectral region from 340 to 265 nm were fabricated and evaluated at the die level. A number of milliwatt output power LEDs emitting at 280 nm were demonstrated.

  8. Collimating diode laser beams from a large-area VCSEL-array using microlens array

    SciTech Connect

    Chen, H.L.; Francis, D.; Nguyen, T.; Yuen, W.; Li, G.; Chang-Hasnain, C.

    1999-05-01

    In this letter, the authors demonstrate the fabrication and bonding of a 1 cm {times} 1 cm monolithic two-dimensional (2-D) vertical-cavity surface-emitting laser (VCSEL) array. They coupled the array to a matched microlens array to individually collimate light from each laser. They found the beam divergence of the collimated array to be 1.6{degree} (1/e{sup 2}) for the entire array. Using a 1-cm diameter F2 lens, they were able to focus the collimated beams to a spot of 400 {micro}m in diameter and to couple more than 75% of the array power into a 1-mm core fiber. The results show that it is possible to uniformly bond large area VCSEL arrays to heat sinks, and to collimate light from each element into parallel beams using a single 2-D microlens array. The results also show that the brightness of the focused beam can be further increased with a lens to near 10{sup 5}-W/cm{sup 2} Steradian, a level that is useful for many high-power applications.

  9. Inorganic-organic p-n heterojunction nanotree arrays for a high-sensitivity diode humidity sensor.

    PubMed

    Wang, Ke; Qian, Xuemin; Zhang, Liang; Li, Yongjun; Liu, Huibiao

    2013-06-26

    Large-area and ordered arrays (16 cm(2)) of an inorganic-organic p-n heterojunction nanotree (NT) were successfully fabricated. The nanotree arrays consist of ZnO nanorods (NRs) as backbones and CuTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) NRs as branches. The sizes of CuTCNQ NRs can be tuned by the thickness of the Cu layer deposited on the surface of ZnO NR. The CuTCNQ/ZnO NT arrays displayed excellent diode nature and obvious size-dependent rectification ratios were observed. Moreover, the CuTCNQ/ZnO NT arrays were first applied for the fabrication of a diode-type humidity sensor, which displayed ultrahigh sensitivity and quick response/recovery properties at room temperature. The detection limitation of this new diode-type humidity sensor lowers to 5% relative humidity (RH). PMID:23721049

  10. A digital optical phase-locked loop for diode lasers based on field programmable gate array.

    PubMed

    Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

    2012-09-01

    We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382?MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad(2) and transition time of 100 ?s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers. PMID:23020359

  11. Numerical analysis of the beam quality and spectrum of wavelength-beam-combined laser diode arrays

    NASA Astrophysics Data System (ADS)

    Tang, Xuan; Wang, Xiao-Jun; Ke, Wei-Wei

    2015-02-01

    In this paper, a numerical model is presented to simulation the performance of the wavelength-beam-combined laser diode arrays (LDA) system. The eigen mode expansion method is used to describe the two-dimensional optical amplification and the strength of field feedback of external cavity. To describe the mode competition in laser diodes, the gain saturation effect is considered. The two-dimension distributions of the carrier concentration, recombination rates, and optical gain are calculated for solving the laser dynamic equation. The Fresnel integration, grating equation and mode overlap integration are used to obtain the feedback coefficient of extent cavity diffraction. Quantum noise is considered to evaluate the spectral linewidth of semiconductor laser. Based on the numerical model, the impact of the mutual optical feedback on the beam quality and spectrum of the LDA is present and analysis.

  12. A digital optical phase-locked loop for diode lasers based on field programmable gate array

    SciTech Connect

    Xu Zhouxiang; Zhang Xian; Huang Kaikai; Lu Xuanhui

    2012-09-15

    We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

  13. Quantitative Detection of Combustion Species using Ultra-Violet Diode Lasers

    NASA Technical Reports Server (NTRS)

    Pilgrim, J. S.; Peterson, K. A.

    2001-01-01

    Southwest Sciences is developing a new microgravity combustion diagnostic based on UV diode lasers. The instrument will allow absolute concentration measurements of combustion species on a variety of microgravity combustion platforms including the Space Station. Our approach uses newly available room temperature UV diode lasers, thereby keeping the instrument compact, rugged and energy efficient. The feasibility of the technique was demonstrated by measurement of CH radicals in laboratory flames. Further progress in fabrication technology of UV diode lasers at shorter wavelengths and higher power will result in detection of transient species in the deeper UV. High sensitivity detection of combustion radicals is provided with wavelength modulation absorption spectroscopy.

  14. Near-infrared compressive line sensing imaging system using individually addressable laser diode array

    NASA Astrophysics Data System (ADS)

    Ouyang, Bing; Hou, Weilin; Caimi, Frank M.; Dalgleish, Fraser R.; Vuorenkoski, Anni K.; Gong, Sue; Britton, Walter

    2015-05-01

    The compressive line sensing (CLS) active imaging system was proposed and validated through a series of test-tank experiments. As an energy-efficient alternative to the traditional line-scan serial image, the CLS system will be highly beneficial for long-duration surveillance missions using unmanned, power-constrained platforms such as unmanned aerial or underwater vehicles. In this paper, the application of an active spatial light modulator (SLM), the individually addressable laser diode array, in a CLS imaging system is investigated. In the CLS context, active SLM technology can be advantageous over passive SLMs such as the digital micro-mirror device. Initial experimental results are discussed.

  15. Investigation of spectra unfolded for a filtered x-ray diode array with improved smoothness.

    PubMed

    Li, Jing; Huang, Xian-Bin; Zhang, Si-Qun; Yang, Li-Bing; Xie, Wei-Ping; Pu, Yi-Kang

    2009-06-01

    An unfolding algorithm using parabolic B-splines to smoothly reconstruct the soft x-ray spectra from the measurements of a filtered x-ray diode array is proposed. This array has been fabricated for the study of the soft x ray emitted by Z-pinch plasma. Unfolding results show that for the simulated noise-free blackbody spectra with temperature ranging from 20 to 250 eV, both the spectra and the total power are accurately recovered. Typical experimental waveforms along with the unfolded spectra and total power of x rays are presented. Possible defects due to the adoption of parabolic B-splines instead of conventionally used histograms are discussed. PMID:19566195

  16. A photon-counting photodiode array detector for far ultraviolet (FUV) astronomy

    NASA Technical Reports Server (NTRS)

    Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

    1982-01-01

    A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location.

  17. Printed array of thin-dielectric metal-oxide-metal (MOM) tunneling diodes

    NASA Astrophysics Data System (ADS)

    Bareiß, Mario; Hochmeister, Andreas; Jegert, Gunther; Zschieschang, Ute; Klauk, Hagen; Huber, Rupert; Grundler, Dirk; Porod, Wolfgang; Fabel, Bernhard; Scarpa, Giuseppe; Lugli, Paolo

    2011-08-01

    A large area array of metal-oxide-metal (MOM) tunneling diodes with an ultrathin dielectric (˜3.6 nm aluminum oxide) have been fabricated via a transfer-printing process. The MOM diodes exhibit an excellent tunneling behavior that is suitable for rectifying high-frequency ac current into direct current (dc). Direct tunneling and Fowler-Nordheim tunneling have been observed over eight orders of magnitude in current density. The ratio between forward and reverse current is as large as two orders of magnitude. Simulations have been carried out to extract the static device parameters and have confirmed the existence of a dipole layer at the aluminum/aluminum oxide interface of the printed tunneling diodes. Capacitance measurements have shown that the permittivity of the ultrathin aluminum oxide film is smaller than that of bulk aluminum oxide. The mechanical yield of the transfer-printing process is better than 80%, confirming that transfer printing is a promising candidate for the efficient fabrication of quantum devices over large areas.

  18. Arrays of high quality SAM-based junctions and their application in molecular diode based logic.

    PubMed

    Wan, Albert; Suchand Sangeeth, C S; Wang, Lejia; Yuan, Li; Jiang, Li; Nijhuis, Christian A

    2015-11-19

    This paper describes a method to fabricate a microfluidic top-electrode that can be utilized to generate arrays of self-assembled monolayer (SAM)-based junctions. The top-electrodes consist of a liquid-metal of GaOx/EGaIn mechanically stabilized in microchannels and through-holes in polydimethylsiloxane (PDMS); these top-electrodes form molecular junctions by directly placing them onto the SAM supported by template-stripped (TS) Ag or Au bottom-electrodes. Unlike conventional techniques to form multiple junctions, our method does not require lithography to pattern the bottom-electrode and is compatible with TS bottom-electrodes, which are ultra-flat with large grains, free from potential contamination of photoresist residues, and do not have electrode-edges where the molecules are unable to pack well. We formed tunneling junctions with n-alkanethiolate SAMs in yields of ?80%, with good reproducibility and electrical stability. Temperature dependent J(V) measurements indicated that the mechanism of charge transport across the junction is coherent tunneling. To demonstrate the usefulness of these junctions, we formed molecular diodes based on SAMs with Fc head groups. These junctions rectify currents with a rectification ratio R of 45. These molecular diodes were incorporated in simple electronic circuitry to demonstrate molecular diode-based Boolean logic. PMID:26537895

  19. Label-free specific detection of femtomolar cardiac troponin using an integrated nanoslit array fluidic diode.

    PubMed

    Liu, Yifan; Yobas, Levent

    2014-12-10

    We demonstrate here for the first time the utility of an integrated nanofluidic diode for detecting and quantifying physiologically relevant macromolecules. Troponin T, a key human cardiac protein biomarker, was selectively and rapidly detected free of labels for concentrations down to 10 fg/mL (? 0.3 fM) in buffer as well as 10 pg/mL (? 300 fM) in untreated human serum. This ultrasensitive detection arises from monolithic integration of a unique nanofluidic diode structure that is highly robust and amenable to site-specific surface modification. The structure features a planar nanoslit array where each nanoslit is defined at a nominal width of 70 nm over a micrometer-scale silicon trench without the use of high-resolution patterning techniques. Through vapor deposition, a glass layer is placed at a nonuniform thickness, tapering the trench profile upward and contributing to the triangular nanoslit structure. This asymmetric profile is essential for ionic current rectification noted here at various pH values, ionic strengths, and captured target species, which modulate the surface-charge density within the sensitive region of the nanoslit. The nanoslit, unlike nanopores, offers only 1D confinement, which appears to be adequate for reasonable rectification. The measurements are found in quantitative agreement with the diode simulations for the first time based on a pH- and salt-dependent surface-charge model. PMID:25366228

  20. Optical and Thermal Analyses of High-Power Laser Diode Arrays

    NASA Technical Reports Server (NTRS)

    Vasilyev, Aleksey; Allan, Graham R.; Schafer, John; Stephen, Mark A.; Young, Stefano

    2004-01-01

    An important need, especially for space-borne applications, is the early identification and rejection of laser diode arrays which may fail prematurely. The search for reliable failure predictors is ongoing and has led to the development of two techniques, infrared imagery and monitoring the Temporally-resolved and Spectrally-Resolved (TSR) optical output from which temperature of the device can be measured. This is in addition to power monitoring on long term burn stations. A direct measurement of the temperature of the active region is an important parameter as the lifetime of Laser Diode Arrays (LDA) decreases exponentially with increasing temperature. We measure the temperature from time-resolving the spectral emission in an analogous method to Voss et al. In this paper we briefly discuss the measurement setup and present temperature data derived from thermal images and TSR data for two differently designed high-power 808 nanometer LDA packages of similar specification operated in an electrical and thermal environment that mimic the expected operational conditions.

  1. Development and characterisation of a silicon PIN diode array based highly sensitive portable continuous radon monitor.

    PubMed

    Ashokkumar, P; Sahoo, B K; Raman, Anand; Mayya, Y S

    2014-03-01

    This paper discusses the development and characterisation of a portable and highly sensitive continuous radon monitor (CRM) based on an array of in-house developed silicon PIN diode detectors. The development of this system was initiated in view of the limitations of the available similar radon measurement systems with regards to low sensitivity. The system utilises a hemispherical metal chamber (1 L capacity) for active air sampling. A quantitative estimation of radon concentration is carried out through alpha spectroscopy of electro-deposited (222)Rn decay products on the detector surface. The system was successfully tested and characterised in laboratory conditions. The characterisation experiments included optimisation of sensitivity, calibration with respect to linearity and a study of the influence of humidity on its performance. The novel PIN diode array design yields a high sensitivity of 1.76 ± 0.003 counts h(-1)/(Bq m(-3)) at a relative humidity level of 10% in the sampled air, which is more than two times as high as that reported for similar commercial systems. This instrument displayed a minimum detectable activity level of 0.80 Bq m(-3). PMID:24334292

  2. Calibration and linearity verification of capacitance type cryo level indicators using cryogenically multiplexed diode array

    NASA Astrophysics Data System (ADS)

    Karunanithi, R.; Jacob, Subhash; Singh Gour, Abhay Singh; Das, M.; Nadig, D. S.; Prasad, M. V. N.

    2012-06-01

    In space application the precision level measurement of cryogenic liquids in the storage tanks is done using triple redundant capacitance level sensor, for control and safety point of view. The linearity of each sensor element depends upon the cylindricity and concentricity of the internal and external electrodes. The complexity of calibrating all sensors together has been addressed by two step calibration methodology which has been developed and used for the calibration of six capacitance sensors. All calibrations are done using Liquid Nitrogen (LN2) as a cryogenic fluid. In the first step of calibration, one of the elements of Liquid Hydrogen (LH2) level sensor is calibrated using 700mm eleven point discrete diode array. Four wire method has been used for the diode array. Thus a linearity curve for a single element of LH2 is obtained. In second step of calibration, using the equation thus obtained for the above sensor, it is considered as a reference for calibrating remaining elements of the same LH2 sensor and other level sensor (either Liquid Oxygen (LOX) or LH2). The elimination of stray capacitance for the capacitance level probes has been attempted. The automatic data logging of capacitance values through GPIB is done using LabVIEW 8.5.

  3. Feasibility study of using a Zener diode as the selection device for bipolar RRAM and WORM memory arrays

    NASA Astrophysics Data System (ADS)

    Li, Yingtao; Fu, Liping; Tao, Chunlan; Jiang, Xinyu; Sun, Pengxiao

    2014-01-01

    Cross-bar arrays are usually used for the high density application of resistive random access memory (RRAM) devices. However, cross-talk interference limits an increase in the integration density. In this paper, the Zener diode is proposed as a selection device to suppress the sneak current in bipolar RRAM arrays. Measurement results show that the Zener diode can act as a good selection device, and the sneak current can be effectively suppressed. The readout margin is sufficiently improved compared to that obtained without the selection device. Due to the improvement for the reading disturbance, the size of the cross-bar array can be enhanced to more than 103 × 103. Furthermore, the possibility of using a write-once-read-many-times (WORM) cross-bar array is also demonstrated by connecting the Zener diode and the bipolar RRAM in series. These results strongly suggest that using a Zener diode as a selection device opens up great opportunities to realize high density bipolar RRAM arrays.

  4. Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

    SciTech Connect

    Lu, Yu-Hsuan; Pilkuhn, Manfred H.; Fu, Yi-Keng; Chu, Mu-Tao; Huang, Shyh-Jer E-mail: totaljer48@gmail.com; Su, Yan-Kuin E-mail: totaljer48@gmail.com; Wang, Kang L.

    2014-03-21

    The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

  5. High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

    SciTech Connect

    Wu, Y.; Li, X.; Xu, P.; Wang, Y.; Shen, X.; Liu, X.; Yang, Q.; Hasan, T.

    2015-02-02

    We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5?nm. The dominant emission, detectable at ultralow (<1??A) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25??A current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter?

  6. Characterization of biological materials by frequency-domain fluorescence lifetime measurements using ultraviolet light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Žukauskas, A.; Vitta, P.; Kuril?ik, N.; Jurš?nas, S.; Bakien?, E.

    2008-01-01

    Recently developed deep-ultraviolet light-emitting diodes (UV LEDs) emit at wavelengths short enough to excitate fluorescence in most biological autofluorophores. We demonstrate the possibility of harmonical modulation of the output of group-III-nitride based UV LEDs ranging from 255 to 375 nm at frequencies up to 200 MHz. This enables the application of UV LEDs for frequency-domain fluorescence lifetime sensing with subnanosecond resolution. We report on measurements of fluorescence decay time in common biofluorophores (tyrosine, tryptophan, NADPH, NADH, collagen, DPA, elastin and riboflavin) using commercially available UV LEDs. We demonstrate the capacity of a multichannel LED-based frequency-resolved measurement technique to discriminate between Bacillus globigii and a variety of ambient interferants such as diesel fuel, paper, cotton, dust, etc.

  7. Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes

    NASA Astrophysics Data System (ADS)

    Reich, Christoph; Guttmann, Martin; Feneberg, Martin; Wernicke, Tim; Mehnke, Frank; Kuhn, Christian; Rass, Jens; Lapeyrade, Mickael; Einfeldt, Sven; Knauer, Arne; Kueller, Viola; Weyers, Markus; Goldhahn, Rüdiger; Kneissl, Michael

    2015-10-01

    The optical polarization of emission from ultraviolet (UV) light emitting diodes (LEDs) based on (0001)-oriented AlxGa1-xN multiple quantum wells (MQWs) has been studied by simulations and electroluminescence measurements. With increasing aluminum mole fraction in the quantum well x, the in-plane intensity of transverse-electric (TE) polarized light decreases relative to that of the transverse-magnetic polarized light, attributed to a reordering of the valence bands in AlxGa1-xN. Using k ? p theoretical model calculations, the AlGaN MQW active region design has been optimized, yielding increased TE polarization and thus higher extraction efficiency for bottom-emitting LEDs in the deep UV spectral range. Using (i) narrow quantum wells, (ii) barriers with high aluminum mole fractions, and (iii) compressive growth on patterned aluminum nitride sapphire templates, strongly TE-polarized emission was observed at wavelengths as short as 239 nm.

  8. Ultraviolet/blue light-emitting diodes based on single horizontal ZnO microrod/GaN heterojunction

    PubMed Central

    2014-01-01

    We report electroluminescence (EL) from single horizontal ZnO microrod (MR) and p-GaN heterojunction light-emitting diodes under forward and reverse bias. EL spectra were composed of two blue emissions centered at 431 and 490 nm under forward biases, but were dominated by a ultraviolet (UV) emission located at 380 nm from n-ZnO MR under high reverse biases. Light-output-current characteristic of the UV emission reveals that the rate of radiative recombination is faster than that of the nonradiative recombination. Highly efficient ZnO excitonic recombination at reverse bias is caused by electrons tunneling from deep-level states near the n-ZnO/p-GaN interface to the conduction band in n-ZnO. PMID:25232299

  9. AlGaN based deep ultraviolet light emitting diodes with high internal quantum efficiency grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Liao, Yitao; Thomidis, Christos; Kao, Chen-kai; Moustakas, Theodore D.

    2011-02-01

    We report the development of AlGaN based deep ultraviolet light emitting diodes (UV-LEDs) by molecular beam epitaxy. By growing the AlGaN well layer under Ga-rich conditions to produce strong potential fluctuations, internal quantum efficiency of a quantum well structure emitting at 300 nm was found to be 32%. By combining such Ga-rich growth condition in the active region with polarization field enhanced carrier injection layers, deep UV-LEDs emitting at 273 nm were obtained with output power of 0.35 mW and 1.3 mW at 20 mA continuous wave and 100 mA pulsed drive current, respectively. The maximum external quantum efficiency was 0.4%.

  10. High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Hasan, T.; Li, X.; Xu, P.; Wang, Y.; Shen, X.; Liu, X.; Yang, Q.

    2015-02-01

    We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5 nm. The dominant emission, detectable at ultralow (<1 ?A) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25 ?A current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter < 250 nm), this trend breaks down due to heat accumulation in the NWs. Our simple device architecture offers a potentially cost-effective scheme to fabricate high efficiency Schottky junction-based UV-LEDs.

  11. Ultraviolet laser quantum well intermixing based prototyping of bandgap tuned heterostructures for the fabrication of superluminescent diodes

    NASA Astrophysics Data System (ADS)

    Beal, Romain; Moumanis, Khalid; Aimez, Vincent; Dubowski, Jan J.

    2016-04-01

    The ultraviolet laser induced quantum well intermixing process has been investigated for prototyping of multiple bandgap quantum well (QW) wafers designed for the fabrication of superluminescent diodes (SLDs). The process takes advantage of a krypton fluoride excimer laser (?=248 nm) that by irradiating an InP layer capping GaInAs/GaInAsP QW heterostructure leads to the modification of its surface chemical composition and formation of point defects. A subsequent rapid thermal annealing step results in the selective area intermixing of the investigated heterostructures achieving a high quality bandgap tuned material for the fabrication of broad spectrum SLDs. The devices made from a 3-bandgap material are characterized by ~100 nm wide emission spectra with relatively flat profiles and emission exceeding 1 mW.

  12. Advantages of AlGaN-based deep ultraviolet light-emitting diodes with a superlattice electron blocking layer

    NASA Astrophysics Data System (ADS)

    Sun, Pai; Bao, Xianglong; Liu, Songqing; Ye, Chunya; Yuan, Zhaorong; Wu, Yukun; Li, Shuping; Kang, Junyong

    2015-09-01

    The properties of 298 nm AlGaN based deep ultraviolet light-emitting diodes (UV LEDs) with different Al mole compositions in the conventional electron blocking layer (EBL) are discussed in this paper, the optimal Al mole composition of the conventional EBL is identified at 0.8. The improved structure with an AlGaN/AlGaN superlattice (SL) electron blocking layer (EBL) was then investigated numerically. The electrical and optical properties, band diagrams, carrier concentrations, radiative recombination rates and internal quantum efficiency (IQE) were investigated by APSYS software, and results show that the deep UV LED with superlattice EBL performed much better than the conventional EBL deep UV LED, attributed to reduced electrons leakage and increased holes injection.

  13. Evaluating dosimetric accuracy of flattening filter free compensator-based IMRT: Measurements with diode arrays

    SciTech Connect

    Robinson, Joshua; Opp, Daniel; Zhang, Geoffrey; Cashon, Ken; Kozelka, Jakub; Hunt, Dylan; Walker, Luke; Hoffe, Sarah; Shridhar, Ravi; Feygelman, Vladimir

    2012-01-15

    Purpose: Compensator-based IMRT coupled with the high dose rate flattening filter free (FFF) beams offers an intriguing possibility of delivering an intensity modulated radiation field in just a few seconds. As a first step, the authors evaluate the dosimetric accuracy of the treatment planning system (TPS) FFF beam model with compensators. Methods: A 6 MV FFF beam from a TrueBeam accelerator (Varian Medical Systems, Palo Alto CA) was modeled in PINNACLE TPS (v. 9.0, Philips Radiation Oncology, Fitchburg WI). Flat brass slabs from 0.3 to 7 cm thick and an 18 deg. brass wedge were used to adjust the beam model. A 2D (MAPCHECK) and 3D (ARCCHECK) diode arrays (Sun Nuclear Corp, Melbourne FL), were investigated for use with the compensator FFF beams. Corrections for diode sensitivity caused by the spectral changes in the beam were introduced. Four compensator plans based on the AAPM TG-119 report were developed. A composite ion chamber measurement, beam by beam MAPCHECK measurements, and a composite ARCCHECK measurement were performed. The array results were analyzed with the same thresholds as in TG-119 report--3%/3 mm with global dose normalization--as well as with the more stringent combinations of the gamma analysis criteria. Results: The FFF beam shows a greater variation of the effective attenuation coefficient with brass thickness due to the prevalence of the low energy photons compared to the conventional 6X beam. As a result, a compromise had to be made while trying to achieve dose agreement for a combination of field sizes, brass thicknesses, and measurement depths ({>=}5 cm in water). An agreement of measured and calculated dose to within 1% was observed for brass thicknesses up to 2 cm. For the 3 cm slab, an error of up to 2.8% was noted for the field sizes above 10 x 10 cm{sup 2}, and up to 3.8% for the 5 x 5 cm{sup 2} field. Both diode arrays exhibit a substantial sensitivity drop as the compensator thickness increases, reaching 10% for a 7 cm brass slab. A simple correction based on the brass thickness along the ray was introduced to counteract this effect. Pooled for five profiles, the average ratio of uncorrected and corrected MAPCHECK to ion chamber readings are 0.966 and 1.008, respectively. With the proper correction, all MAPCHECK measurement to calculation comparisons exhibit 100%{gamma}(3%/3 mm) passing rates with global dose-error normalization. For the TG-119-type plans, the average {gamma}(2%/2 mm) passing rate with local normalization is 94% (range 87.8%-98.3%). The lower ARCCHECK{gamma}-analysis passing rates (corrected for diode sensitivity) are predictable based on the observed PDD discrepancies. However, with the 3%/3 mm thresholds and global normalization, the average {gamma}-analysis passing rate is 96.4% (range 89.9%-100%). Conclusions: MAPCHECK analysis demonstrates high passing rates with the stringent {gamma}(2%/2 mm) and local normalization criteria combination. The geometry of the ARCCHECK array creates a stress test for the FFF TPS model because of the shallow depth of the entrance diodes and large air cavity. Hence, the ARCCHECK{gamma}-analysis passing rates are lower than with the MAPCHECK, while still on par with TG-119.

  14. Multiple detector focal plane array ultraviolet spectrometer for the AMPS laboratory

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.

    1975-01-01

    The possibility of meeting the requirements of the amps spectroscopic instrumentation by using a multi-element focal plane detector array in a conventional spectrograph mount was examined. The requirements of the detector array were determined from the optical design of the spectrometer which in turn depends on the desired level of resolution and sensitivity required. The choice of available detectors and their associated electronics and controls was surveyed, bearing in mind that the data collection rate from this system is so great that on-board processing and reduction of data are absolutely essential. Finally, parallel developments in instrumentation for imaging in astronomy were examined, both in the ultraviolet (for the Large Space Telescope as well as other rocket and satellite programs) and in the visible, to determine what progress in that area can have direct bearing on atmospheric spectroscopy.

  15. Flexible and twistable non-volatile memory cell array with all-organic one diode-one resistor architecture.

    PubMed

    Ji, Yongsung; Zeigler, David F; Lee, Dong Su; Choi, Hyejung; Jen, Alex K-Y; Ko, Heung Cho; Kim, Tae-Wook

    2013-01-01

    Flexible organic memory devices are one of the integral components for future flexible organic electronics. However, high-density all-organic memory cell arrays on malleable substrates without cross-talk have not been demonstrated because of difficulties in their fabrication and relatively poor performances to date. Here we demonstrate the first flexible all-organic 64-bit memory cell array possessing one diode-one resistor architectures. Our all-organic one diode-one resistor cell exhibits excellent rewritable switching characteristics, even during and after harsh physical stresses. The write-read-erase-read output sequence of the cells perfectly correspond to the external pulse signal regardless of substrate deformation. The one diode-one resistor cell array is clearly addressed at the specified cells and encoded letters based on the standard ASCII character code. Our study on integrated organic memory cell arrays suggests that the all-organic one diode-one resistor cell architecture is suitable for high-density flexible organic memory applications in the future. PMID:24176930

  16. High Power Laser Diode Array Qualification and Guidelines for Space Flight Environments

    NASA Technical Reports Server (NTRS)

    Ott, Melanie N.; Eegholm, Niels; Stephen, Mark; Leidecker, Henning; Plante, Jeannette; Meadows, Byron; Amzajerdian, Farzin; Jamison, Tracee; LaRocca, Frank

    2006-01-01

    High-power laser diode arrays (LDAs) are used for a variety of space-based remote sensor laser programs as an energy source for diode-pumped solid-state lasers. LDAs have been flown on NASA missions including MOLA, GLAS and MLA and have continued to be viewed as an important part of the laser-based instrument component suite. There are currently no military or NASA-grade, -specified, or - qualified LDAs available for "off-the-shelf" use by NASA programs. There has also been no prior attempt to define a standard screening and qualification test flow for LDAs for space applications. Initial reliability studies have also produced good results from an optical performance and stability standpoint. Usage experience has shown, howeve that the current designs being offered may be susceptible to catastrophic failures due to their physical construction (packaging) combined with the electro-optical operational modes and the environmental factors of space application. design combined with operational mode was at the root of the failures which have greatly reduced the functionality of the GLAS instrument. The continued need for LDAs for laser-based science instruments and past catastrophic failures of this part type demand examination of LDAs in a manner which enables NASA to select, buy, validate and apply them in a manner which poses as little risk to the success of the mission as possible.

  17. Tm,Ho:YLF laser end-pumped by a semiconductor diode laser array

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid (inventor)

    1990-01-01

    An Ho:YLF crystal including Tm as sensitizers for the activator Ho, is optically pumped with a semiconductor diode laser array to generate 2.1 micron radiation with a pump power to output power of efficiency as high as 68 percent. The prior-art dual sensitizer system of Er and Tm requires cooling, such as by LN2, but by using Tm alone and decreasing the concentrations of Tm and Ho, and decreasing the length of the laser rod to about 1 cm, it has been demonstrated that laser operation can be obtained from a temperature of 77 K with an efficiency as high as 68 percent up to ambient room temperature with an efficiency at that temperature as high as 9 percent.

  18. Spectral Linewidth Narrowing and Tunable Two-Color Laser Operation of Two Diode Laser Arrays

    SciTech Connect

    Liu, Bo; Braiman, Yehuda

    2012-01-01

    We propose and implement a common external cavity to narrow spectral linewidth of two broad-area laser diode arrays (LDAs) and align their center wavelengths. The locked center wavelength of two LDAs can be tuned in the range of {approx}10 nm by tuning the tilted angle of the diffraction grating. The output beams of two LDAs are spatially overlapped through the polarization beam splitter of the common external cavity, and the total output power equals the power of two LDAs. The center wavelength of each LDA can be independently tuned by shifting the corresponding fast-axis collimation lens. As a result, the high-power two-color LDA operation is demonstrated with the tunable wavelength difference of up to 2 nm ({approx}1 THz).

  19. Fabrication of an optical lens array using ultraviolet light and ultrasonication.

    PubMed

    Taniguchi, Satoki; Koyama, Daisuke; Nakamura, Kentaro; Matsukawa, Mami

    2015-04-01

    A technique to form an optical lens array using an ultraviolet (UV)-curable resin and ultrasound was investigated. A UV-curable gel film was formed on a glass plate having four lead zirconate titanate (PZT) transducers. Excitation of the transducers generated a lattice flexural vibration mode on the glass plate. The acoustic radiation force acted to deform the surface of the gel film, so that a lens array could be fabricated on the gel film. The lens array was exposed to UV light under ultrasonication to cure the UV-curable film. The quality factor of the transducer resonance was decreased upon curing of the resin film because the cured resin dampened the vibration of the plate. The acoustic characteristics of the UV-curable gel film were measured by using an ultrasound pulse technique at the MHz range. The sound speed of the gel increased from 987 to 1006 m/s (increase of 1.9%) as the UV exposure time increased. The attenuation coefficient also increased and the larger attenuation of the resin caused the lens array to have a lower quality factor. PMID:25497498

  20. Coal liquefaction process streams characterization and evaluation: High performance liquid chromatography (HPLC) of coal liquefaction process streams using normal-phase separation with uv diode array detection

    SciTech Connect

    Clifford, D.J.; McKinney, D.E.; Hou, Lei; Hatcher, P.G.

    1994-01-01

    This study demonstrated the considerable potential of using two-dimensional, high performance liquid chromatography (HPLC) with normal-phase separation and ultraviolet (UV) diode array detection for the examination of filtered process liquids and the 850{degrees}F{sup {minus}} distillate materials derived from direct coal liquefaction process streams. A commercially available HPLC column (Hypersil Green PAH-2) provided excellent separation of the complex mixture of polynuclear aromatic hydrocarbons (PAHs) found in coal-derived process streams process. Some characteristics of the samples delineated by separation could be attributed to processing parameters. Mass recovery of the process derived samples was low (5--50 wt %). Penn State believes, however, that, improved recovery can be achieved. High resolution mass spectrometry and gas chromatography/mass spectrometry (GC/MS) also were used in this study to characterize the samples and the HPLC fractions. The GC/MS technique was used to preliminarily examine the GC-elutable portion of the samples. The GC/MS data were compared with the data from the HPLC technique. The use of an ultraviolet detector in the HPLC work precludes detecting the aliphatic portion of the sample. The GC/MS allowed for identification and quantification of that portion of the samples. Further development of the 2-D HPLC analytical method as a process development tool appears justified based on the results of this project.

  1. Quality assurance of asymmetric jaw alignment using 2D diode array

    SciTech Connect

    Kim, Sun Mo; Yeung, Ivan W. T.; Moseley, Douglas J.; Radiation Medicine Program, Princess Margaret Hospital Department of Radiation Oncology, University of Toronto, Ontario M5G 2M9

    2013-12-15

    Purpose: A method using a 2D diode array is proposed to measure the junction gap (or overlap) and dose with high precision for routine quality assurance of the asymmetric jaw alignment.Methods: The central axis (CAX) of the radiation field was determined with a 15 × 15 cm{sup 2} photon field at four cardinal collimator angles so that the junction gap (or overlap) can be measured with respect to the CAX. Two abutting fields having a field size of 15 cm (length along the axis parallel to the junction) × 7.5 cm (width along the axis perpendicular to the junction) were used to irradiate the 2D diode array (MapCHECK2) with 100 MU delivered at the photon energy of 6 MV. The collimator was slightly rotated at 15° with respect to the beam central axis to increase the number of diodes effective on the measurement of junction gap. The junction gap and dose measured in high spatial resolution were compared to the conventional methods using an electronic portal imaging device (EPID) and radiochromic film, respectively. In addition, the reproducibility and sensitivity of the proposed method to the measurements of junction gap and dose were investigated.Results: The junction gap (or overlap) and dose measured by MapCHECK2 agreed well to those measured by the conventional methods of EPID and film (the differences ranged from ?0.01 to 0 cm and from ?1.34% to 0.6% for the gap and dose, respectively). No variation in the repeat measurements of the junction gap was found whereas the measurements of junction dose were found to vary in quite a small range over the days of measurement (0.21%–0.35%). While the sensitivity of the measured junction gap to the actual junction gap applied was the ideal value of 1 cm/cm as expected, the sensitivity of the junction dose to the actual junction gap increased as the junction gap (or overlap) decreased (maximum sensitivity: 201.7%/cm).Conclusions: The initial results suggest that the method is applicable for a comprehensive quality assurance of the asymmetric jaw alignment.

  2. Optical injection and spectral filtering of high-power ultraviolet laser diodes.

    PubMed

    Schäfer, V M; Ballance, C J; Tock, C J; Lucas, D M

    2015-09-15

    We demonstrate injection locking of high-power laser diodes operating at 397 nm. We achieve stable operation with an injection power of ?100???W and a slave laser output power of up to 110 mW. We investigate the spectral purity of the slave laser light via photon scattering experiments on a single trapped (40)Ca(+) ion. We show that it is possible to achieve a scattering rate indistinguishable from that of monochromatic light by filtering the laser light with a diffraction grating to remove amplified spontaneous emission. PMID:26371912

  3. Proposed Use of Zero Bias Diode Arrays as Thermal Electric Noise Rectifiers and Non-Thermal Energy Harvesters

    NASA Astrophysics Data System (ADS)

    Valone, Thomas F.

    2009-03-01

    The well known built-in voltage potential for some select semiconductor p-n junctions and various rectifying devices is proposed to be favorable for generating DC electricity at "zero bias" (with no DC bias voltage applied) in the presence of Johnson noise or 1/f noise which originates from the quantum vacuum (Koch et al., 1982). The 1982 Koch discovery that certain solid state devices exhibit measurable quantum noise has also recently been labeled a finding of dark energy in the lab (Beck and Mackey, 2004). Tunnel diodes are a class of rectifiers that are qualified and some have been credited with conducting only because of quantum fluctuations. Microwave diodes are also good choices since many are designed for zero bias operation. A completely passive, unamplified zero bias diode converter/detector for millimeter (GHz) waves was developed by HRL Labs in 2006 under a DARPA contract, utilizing a Sb-based "backward tunnel diode" (BTD). It is reported to be a "true zero-bias diode." It was developed for a "field radiometer" to "collect thermally radiated power" (in other words, 'night vision'). The diode array mounting allows a feed from horn antenna, which functions as a passive concentrating amplifier. An important clue is the "noise equivalent power" of 1.1 pW per root hertz and the "noise equivalent temperature difference" of 10° K, which indicate sensitivity to Johnson noise (Lynch, et al., 2006). There also have been other inventions such as "single electron transistors" that also have "the highest signal to noise ratio" near zero bias. Furthermore, "ultrasensitive" devices that convert radio frequencies have been invented that operate at outer space temperatures (3 degrees above zero point: 3° K). These devices are tiny nanotech devices which are suitable for assembly in parallel circuits (such as a 2-D array) to possibly produce zero point energy direct current electricity with significant power density (Brenning et al., 2006). Photovoltaic p-n junction cells are also considered for possible higher frequency ZPE transduction. Diode arrays of self-assembled molecular rectifiers or preferably, nano-sized cylindrical diodes are shown to reasonably provide for rectification of electron fluctuations from thermal and non-thermal ZPE sources to create an alternative energy DC electrical generator in the picowatt per diode range.

  4. Dendritic Nanowire Ultraviolet Laser Array Haoquan Yan, Rongrui He, Justin Johnson, Matthew Law, Richard J. Saykally, and Peidong Yang*

    E-print Network

    Cohen, Ronald C.

    Dendritic Nanowire Ultraviolet Laser Array Haoquan Yan, Rongrui He, Justin Johnson, Matthew Law (nanocrystals, nanowires, and nanotubes) is a crucial step toward realization of functional nanosystems growth4 to assemble uniform semiconductor nanowires into highly ordered one-dimensional (1D) microscale

  5. Ultraviolet-enhanced light emitting diode employing individual ZnO microwire with SiO{sub 2} barrier layers

    SciTech Connect

    Xu, Yingtian; Xu, Li; Dai, Jun; Ma, Yan; Chu, Xianwei; Zhang, Yuantao; Du, Guotong; Zhang, Baolin; Yin, Jingzhi

    2015-05-25

    This paper details the fabrication of n-ZnO single microwire (SMW)-based high-purity ultraviolet light-emitting diodes (UV-LEDs) with an added SiO{sub 2} barrier layer on the p-Si substrate. However, the current-voltage (I-V) curve exhibited non-ideal rectifying characteristics. Under forward bias, both UV and visible emissions could be detected by electroluminescence (EL) measurement. When bias voltage reached 60?V at room temperature, a UV emission spike occurred at 390?nm originating from the n-ZnO SMW. Compared with the EL spectrum of the n-ZnO SMW/p-Si heterojunction device without the SiO{sub 2} barrier layer, we saw improved UV light extraction efficiency from the current-blocking effect of the SiO{sub 2} layer. The intense UV emission in the n-ZnO SMW/SiO{sub 2}/p-Si heterojunction indicated that the SiO{sub 2} barrier layer can restrict the movement of electrons as expected and result in effective electron-hole recombination in ZnO SMW.

  6. Improved output power of GaN-based ultraviolet light-emitting diodes with sputtered AlN nucleation layer

    NASA Astrophysics Data System (ADS)

    Chiu, C. H.; Lin, Y. W.; Tsai, M. T.; Lin, B. C.; Li, Z. Y.; Tu, P. M.; Huang, S. C.; Hsu, Earl; Uen, W. Y.; Lee, W. I.; Kuo, H. C.

    2015-03-01

    In this work, the ultraviolet light-emitting diodes (UV-LEDs) at 380 nm were grown on patterned sapphire substrate (PSS) by atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD). A sputtered AlN nucleation layer was utilized on the PSS to enhance the quality of the epitaxial layer. By using high-resolution X-ray diffraction, the full-width at half-maximum of the rocking curve shows that the UV-LEDs with sputtered AlN nucleation layer had better crystalline quality when compared to conventional GaN nucleation samples. From the scanning electron microscope (SEM) and transmission electron microscopy (TEM) images, it can be observed that the tip and sidewall portion of the pattern was smooth using the sputtered AlN nucleation layer. The threading dislocation densities (TDDs) are reduced from 6×107 cm-2 to 2.5×107 cm-2 at the interface between the u-GaN layers for conventional and AlN PSS devices, respectively. As a result, a much higher light output power was achieved. The light output power at an injection current of 20 mA was enhanced by 30%. Further photoluminescence (PL) measurement and numerical simulation confirm that this increase of output power can be attributed to the improvement of material quality and light extraction.

  7. Calibration of optimal use parameters for an ultraviolet light-emitting diode in eliminating bacterial contamination on needleless connectors

    PubMed Central

    Hutchens, M.P.; Drennan, S.L.; Cambronne, E.D.

    2015-01-01

    Aims Needleless connectors may develop bacterial contamination and cause central-line-associated bloodstream infections (CLABSI) despite rigorous application of best-practice. Ultraviolet (UV) light-emitting diodes (LED) are an emerging, increasingly affordable disinfection technology. We tested the hypothesis that a low-power UV LED could reliably eliminate bacteria on needleless central-line ports in a laboratory model of central-line contamination. Methods and Results Needleless central-line connectors were inoculated with Staphylococcus aureus. A 285 nm UV LED was used in calibrated fashion to expose contaminated connectors. Ports were directly applied to agar plates and flushed with sterile saline, allowing assessment of bacterial survival on the port surface and in simulated usage flow-through fluid. UV applied to needleless central-line connectors was highly lethal at 0·5 cm distance at all tested exposure times. At distances >1·5 cm both simulated flow-through and port surface cultures demonstrated significant bacterial growth following UV exposure. Logarithmic-phase S. aureus subcultures were highly susceptible to UV induction/maintenance dosing. Conclusions Low-power UV LED doses at fixed time and distance from needleless central-line connector ports reduced cultivable S. aureus from >106 CFU to below detectable levels in this laboratory simulation of central-line port contamination. Significance and Impact of the study Low-power UV LEDs may represent a feasible alternative to current best-practice in connector decontamination. PMID:25801979

  8. ZnO-based ultra-violet light emitting diodes and nanostructures fabricated by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Chen, Miin-Jang; Yang, Jer-Ren; Shiojiri, Makoto

    2012-07-01

    We have investigated ZnO-based light-emitting diodes (LEDs) fabricated by atomic layer deposition (ALD), demonstrating that ALD is one of the noteworthy techniques to prepare high-quality ZnO required for ultraviolet (UV) photonic devices. Here, we review our recent investigations on different ZnO-based heterojunction LEDs such as n-ZnO/p-GaN LEDS, n-ZnO:Al/ZnO nanodots-SiO2 composite/p-GaN LEDS, n-ZnO/ZnO nanodots-SiO2 composite/p-AlGaN LEDs, n-ZnO:Al/i-ZnO/p-SiC(4H) LEDs, and also on ZnO-based nanostructures including ZnO quantum dots embedded in SiO2 nanoparticle layer, ZnO nanopillars on sapphire substrates, Al-doped ZnO films on sapphire substrate and highly (0?0?0?1)-oriented ZnO films on amorphous glass substrate. The latest investigation also demonstrated p-type ZnO:P films prepared on amorphous silica substrates, which allow us to fabricate ZnO-based homojunction LEDs. These devices and structures were studied by x-ray diffraction and various analytical electron microscopy observations as well as electric and electro-optical measurements.

  9. Wearable red–green–blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing

    PubMed Central

    Choi, Moon Kee; Yang, Jiwoong; Kang, Kwanghun; Kim, Dong Chan; Choi, Changsoon; Park, Chaneui; Kim, Seok Joo; Chae, Sue In; Kim, Tae-Ho; Kim, Ji Hoon; Hyeon, Taeghwan; Kim, Dae-Hyeong

    2015-01-01

    Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red–green–blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot light-emitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000?cd?m?2 at 7?V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics. PMID:25971194

  10. Wearable red-green-blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing.

    PubMed

    Choi, Moon Kee; Yang, Jiwoong; Kang, Kwanghun; Kim, Dong Chan; Choi, Changsoon; Park, Chaneui; Kim, Seok Joo; Chae, Sue In; Kim, Tae-Ho; Kim, Ji Hoon; Hyeon, Taeghwan; Kim, Dae-Hyeong

    2015-01-01

    Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red-green-blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot light-emitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000 cd m(-2) at 7 V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics. PMID:25971194

  11. LETTERS TO THE EDITOR: Phase-locking of a linear array of high-power laser diodes

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Derzhavin, S. I.; Kuz'minov, V. V.; Mashkovskii, D. A.; Prokhorov, A. M.; Timoshkin, V. N.; Filonenko, V. A.

    1999-10-01

    Continuous emission was obtained from a phase-locked (in an external cavity) linear array of laser diodes with a power in excess of 10 W. This was done by using an efficient heat sink based on a porous structure with a thermal resistance better than 0.3 °C W-1. For a power of 1.5 W, a divergence of the lobes was ~0.1 mrad in the plane of the p—n junction, corresponding to the diffraction limit at the radiation wavelength ?=0.94 ?m for an aperture of 1 cm. The promising trends in the development of technologies based on laser-diode arrays are considered.

  12. Large-area anodized alumina nanopore arrays assisted by soft ultraviolet nanoimprint prepatterning.

    PubMed

    Ng, S M; Wong, H F; Lau, H K; Leung, C W

    2012-08-01

    Aluminium anodization under optimized conditions can naturally generate close-packed and aligned nanopore arrays, but the spatial extent of such regular pore arrangement is generally limited. Here we demonstrated the use of soft ultraviolet nanoimprint lithography to guide the formation of nanopores at specific locations, using an elastomer negative mold for the process. By anodizing at voltages which naturally led to the formation of pores with matching averaged interpore separation, pre-patterned triangular holes (diameter 100 nm, periodicity 350 nm) on aluminium thin films induced conformal growth of nanopores at pre-defined positions. In addition, pores in geometries other than close-packed patterns were prepared, with square pore arrangement being demonstrated in this work. The influence of the anodization voltage on the final pore formation was also studied. Our results illustrated the possibility to fabricate well-organized nanopore arrays with conditions far less stringent than those reported in literature, which has the potential to be adopted for applications where regular pore alignment are critical. PMID:22962742

  13. High-performance timing electronics for single photon avalanche diode arrays

    NASA Astrophysics Data System (ADS)

    Acconcia, G.; Crotti, M.; Rech, I.; Ghioni, M.

    2015-05-01

    Time correlated photon counting techniques have been proved to be very effective, especially when very fast and faint optical signals have to be recorded with extremely high precision. Nowadays, a steadily increasing number of applications require not only high performance in terms of photon detection efficiency, time resolution and linearity but also a high number of pixels operating in parallel. In order to combine the features of the most performing detectors and state of art timing electronics, an innovative architecture has been conceived and the main circuits have been designed. The system will employ dense arrays of custom technology Single Photon Avalanche Diode (SPAD) detectors, in order to perform a truly concurrent analysis of the sample, while it will have only a small number of acquisition chains with the ultimate purpose of obtaining very high performance while limiting area occupation and power dissipation. To this aim, three main circuits have been designed: first of all, a pick-up circuit capable of directly reading the signal coming from the sensor; secondly, a timing circuit to measure the arrival time of the each photon with picoseconds resolution and very high linearity and finally, a circuit to perform a dynamic binding between the many sensors and the few conversion chains.

  14. Validated HPLC-Diode Array Detector Method for Simultaneous Evaluation of Six Quality Markers in Coffee.

    PubMed

    Gant, Anastasia; Leyva, Vanessa E; Gonzalez, Ana E; Maruenda, Helena

    2015-01-01

    Nicotinic acid, N-methylpyridinium ion, and trigonelline are well studied nutritional biomarkers present in coffee, and they are indicators of thermal decomposition during roasting. However, no method is yet available for their simultaneous determination. This paper describes a rapid and validated HPLC-diode array detector method for the simultaneous quantitation of caffeine, trigonelline, nicotinic acid, N-methylpyridinium ion, 5-caffeoylquinic acid, and 5-hydroxymethyl furfural that is applicable to three coffee matrixes: green, roasted, and instant. Baseline separation among all compounds was achieved in 30 min using a phenyl-hexyl RP column (250×4.6 mm, 5 ?m particle size), 0.3% aqueous formic buffer (pH 2.4)-methanol mobile phase at a flow rate of 1 mL/min, and a column temperature at 30°C. The method showed good linear correlation (r2>0.9985), precision (less than 3.9%), sensitivity (LOD=0.023-0.237 ?g/mL; LOQ=0.069-0.711 ?g/mL), and recovery (84-102%) for all compounds. This simplified method is amenable for a more complete routine evaluation of coffee in industry. PMID:25857885

  15. A blue-emitting Sc silicate phosphor for ultraviolet excited light-emitting diodes.

    PubMed

    Wang, Qian; Zhu, Ge; Xin, Shuangyu; Ding, Xin; Xu, Ju; Wang, Yuansheng; Wang, Yuhua

    2015-10-14

    A blue-emitting phosphor BaSc2Si3O10:Eu(2+) was synthesized using the conventional solid-state reaction. The crystallographic occupancy of Eu(2+) in the BaSc2Si3O10 matrix was studied based on the Rietveld refinement results and the photoluminescence properties. BaSc2Si3O10 exhibits blue emission ascribed to (3)T2-(1)A1 and (3)T1-(1)A1 charge transfer of SiO4(4-) excited by 360 nm. All the phosphors of BaSc2Si3O10:Eu(2+) exhibit strong broad absorption bands in the near ultraviolet range, and give abnormal blue emission upon 330 nm excitation. The abnormal phenomenon was explored in detail through many pieces of experimental evidence. The concentration of Eu(2+) is optimized to be 3 mol% according to emission intensity and the quenching mechanism is verified to be a quadrupole-quadrupole interaction. The CIE coordinates of BaSc2Si3O10:0.03Eu(2+) are calculated to be (0.15, 0.05) and BaSc2Si3O10:0.03Eu(2+) shows similar thermal stability to commercial BaMgAl10O17:Eu(2+). PMID:26242881

  16. Polarization-induced pn diodes in wide-band-gap nanowires with ultraviolet electroluminescence.

    PubMed

    Carnevale, Santino D; Kent, Thomas F; Phillips, Patrick J; Mills, Michael J; Rajan, Siddharth; Myers, Roberto C

    2012-02-01

    Almost all electronic devices utilize a pn junction formed by random doping of donor and acceptor impurity atoms. We developed a fundamentally new type of pn junction not formed by impurity-doping, but rather by grading the composition of a semiconductor nanowire resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlGaN nanowires from 0% to 100% and back to 0% Al, we show the formation of a polarization-induced pn junction even in the absence of any impurity doping. Since electrons and holes are injected from AlN barriers into quantum disk active regions, graded nanowires allow deep ultraviolet LEDs across the AlGaN band-gap range with electroluminescence observed from 3.4 to 5 eV. Polarization-induced p-type conductivity in nanowires is shown to be possible even without supplemental acceptor doping, demonstrating the advantage of polarization engineering in nanowires compared with planar films and providing a strategy for improving conductivity in wide-band-gap semiconductors. As polarization charge is uniform within each unit cell, polarization-induced conductivity without impurity doping provides a solution to the problem of conductivity uniformity in nanowires and nanoelectronics and opens a new field of polarization engineering in nanostructures that may be applied to other polar semiconductors. PMID:22268600

  17. Application of GaN-based ultraviolet-C light emitting diodes--UV LEDs--for water disinfection.

    PubMed

    Würtele, M A; Kolbe, T; Lipsz, M; Külberg, A; Weyers, M; Kneissl, M; Jekel, M

    2011-01-01

    GaN-based ultraviolet-C (UV-C) light emitting diodes (LEDs) are of great interest for water disinfection. They offer significant advantages compared to conventional mercury lamps due to their compact form factor, low power requirements, high efficiency, non-toxicity, and overall robustness. However, despite the significant progress in the performance of semiconductor based UV LEDs that has been achieved in recent years, these devices still suffer from low emission power and relatively short lifetimes. Even the best UV LEDs exhibit external quantum efficiencies of only 1-2%. The objective of this study was to investigate the suitability of GaN-based UV LEDs for water disinfection. The investigation included the evaluation of the performance characteristics of UV LEDs at different operating conditions as well as the design of a UV LED module in view of the requirements for water treatment applications. Bioanalytical testing was conducted using Bacillus subtilis spores as test organism and UV LED modules with emission wavelengths of 269 nm and 282 nm. The results demonstrate the functionality of the developed UV LED disinfection modules. GaN-based UV LEDs effectively inactivated B. subtilis spores during static and flow-through tests applying varying water qualities. The 269 nm LEDs reached a higher level of inactivation than the 282 nm LEDs for the same applied fluence. The lower inactivation achieved by the 282 nm LEDs was compensated by their higher photon flux. First flow-through tests indicate a linear correlation between inactivation and fluence, demonstrating a well designed flow-through reactor. With improved light output and reduced costs, GaN-based UV LEDs can provide a promising alternative for decentralised and mobile water disinfection systems. PMID:21115187

  18. Instrumentation: Photodiode Array Detectors in UV-VIS Spectroscopy. Part II.

    ERIC Educational Resources Information Center

    Jones, Dianna G.

    1985-01-01

    A previous part (Analytical Chemistry; v57 n9 p1057A) discussed the theoretical aspects of diode ultraviolet-visual (UV-VIS) spectroscopy. This part describes the applications of diode arrays in analytical chemistry, also considering spectroelectrochemistry, high performance liquid chromatography (HPLC), HPLC data processing, stopped flow, and…

  19. Characterization of a novel two dimensional diode array the ''magic plate'' as a radiation detector for radiation therapy treatment

    SciTech Connect

    Wong, J. H. D.; Fuduli, I.; Carolan, M.; Petasecca, M.; Lerch, M. L. F.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B.

    2012-05-15

    Purpose: Intensity modulated radiation therapy (IMRT) utilizes the technology of multileaf collimators to deliver highly modulated and complex radiation treatment. Dosimetric verification of the IMRT treatment requires the verification of the delivered dose distribution. Two dimensional ion chamber or diode arrays are gaining popularity as a dosimeter of choice due to their real time feedback compared to film dosimetry. This paper describes the characterization of a novel 2D diode array, which has been named the ''magic plate'' (MP). It was designed to function as a 2D transmission detector as well as a planar detector for dose distribution measurements in a solid water phantom for the dosimetric verification of IMRT treatment delivery. Methods: The prototype MP is an 11 x 11 detector array based on thin (50 {mu}m) epitaxial diode technology mounted on a 0.6 mm thick Kapton substrate using a proprietary ''drop-in'' technology developed by the Centre for Medical Radiation Physics, University of Wollongong. A full characterization of the detector was performed, including radiation damage study, dose per pulse effect, percent depth dose comparison with CC13 ion chamber and build up characteristics with a parallel plane ion chamber measurements, dose linearity, energy response and angular response. Results: Postirradiated magic plate diodes showed a reproducibility of 2.1%. The MP dose per pulse response decreased at higher dose rates while at lower dose rates the MP appears to be dose rate independent. The depth dose measurement of the MP agrees with ion chamber depth dose measurements to within 0.7% while dose linearity was excellent. MP showed angular response dependency due to the anisotropy of the silicon diode with the maximum variation in angular response of 10.8% at gantry angle 180 deg. Angular dependence was within 3.5% for the gantry angles {+-} 75 deg. The field size dependence of the MP at isocenter agrees with ion chamber measurement to within 1.1%. In the beam perturbation study, the surface dose increased by 12.1% for a 30 x 30 cm{sup 2} field size at the source to detector distance (SDD) of 80 cm whilst the transmission for the MP was 99%. Conclusions: The radiation response of the magic plate was successfully characterized. The array of epitaxial silicon based detectors with ''drop-in'' packaging showed properties suitable to be used as a simplified multipurpose and nonperturbing 2D radiation detector for radiation therapy dosimetric verification.

  20. Novel exposure system using light-emitting diodes and an optical fiber array for printing code marks

    NASA Astrophysics Data System (ADS)

    Iwasaki, Jun-ya; Horiuchi, Toshiyuki

    2012-05-01

    The feasibility of a novel economical and environmentally friendly exposure system using a light-emitting diode (LED) array as a light source was demonstrated. Such an exposure system is especially useful for printing two-dimensional code marks for the production management of semiconductor devices and liquid crystal display panels. The new system also uses an optical fiber matrix array connected to the LED array. The tips of the plastic optical fibers of 1mm diameter are heated and deformed into a square shape, and the square fiber ends are projected by a 1/10 reduction lens. Using LEDs with a central wavelength of 405 nm and an output power of 40mW/cm2, quasi-square code mark patterns are printed with good size repeatability in a practically feasible short time of less than 2 s.

  1. Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application

    NASA Astrophysics Data System (ADS)

    Yuan, Zhaolin

    2015-04-01

    A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 × 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.

  2. 1352 OPTICS LETTERS / Vol. 25, No. 18 / September 15, 2000 Frequency-narrowed external-cavity diode-laser-array bar

    E-print Network

    Walker, Thad G.

    collimating lens minimize broadening owing to curvature in the alignment of the diode-array elements. © 2000 parallel to the array, with substantial astigmatism.6 The princi- pal difficulty in using an external emitter needs to be appropriately collimated, ref lected off a diffraction grating at a uniform angle

  3. Enhanced optical output of InGaN/GaN near-ultraviolet light-emitting diodes by localized surface plasmon of colloidal silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Hong, Sang-Hyun; Kim, Jae-Joon; Kang, Jang-Won; Jung, Yen-Sook; Kim, Dong-Yu; Yim, Sang-Youp; Park, Seong-Ju

    2015-09-01

    We report on the characteristics of localized surface plasmon (LSP)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) fabricated by using colloidal silver (Ag) nanoparticles (NPs). Colloidal Ag NPs were deposited on the 20 nm thick p-GaN spacer layer using a spray process. The optical output power of NUV-LEDs with colloidal Ag NPs was increased by 48.7% at 20 mA compared with NUV-LEDs without colloidal Ag NPs. The enhancement was attributed to increased internal quantum efficiency caused by the resonance coupling between excitons in the multiple quantum wells and the LSPs in the Ag NPs.

  4. Enhanced optical output of InGaN/GaN near-ultraviolet light-emitting diodes by localized surface plasmon of colloidal silver nanoparticles.

    PubMed

    Hong, Sang-Hyun; Kim, Jae-Joon; Kang, Jang-Won; Jung, Yen-Sook; Kim, Dong-Yu; Yim, Sang-Youp; Park, Seong-Ju

    2015-09-25

    We report on the characteristics of localized surface plasmon (LSP)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) fabricated by using colloidal silver (Ag) nanoparticles (NPs). Colloidal Ag NPs were deposited on the 20 nm thick p-GaN spacer layer using a spray process. The optical output power of NUV-LEDs with colloidal Ag NPs was increased by 48.7% at 20 mA compared with NUV-LEDs without colloidal Ag NPs. The enhancement was attributed to increased internal quantum efficiency caused by the resonance coupling between excitons in the multiple quantum wells and the LSPs in the Ag NPs. PMID:26335045

  5. Excellent nonlinearity of a selection device based on anti-series connected Zener diodes for ultrahigh-density bipolar RRAM arrays

    NASA Astrophysics Data System (ADS)

    Li, Yingtao; Li, Rongrong; Fu, Liping; Gao, Xiaoping; Wang, Yang; Tao, Chunlan

    2015-10-01

    A crossbar array is usually used for the high-density application of a resistive random access memory (RRAM) device. However, the cross-talk interference limits the increase in the integration density. In this paper, anti-series connected Zener diodes as a selection device are proposed for bipolar RRAM arrays. Simulation results show that, by using the anti-series connected Zener diodes as a selection device, the readout margin is sufficiently improved compared to that obtained without a selection device or with anti-parallel connected diodes as the selection device. The maximum size of the crossbar arrays with anti-series connected Zener diodes as a selection device over 1 TB is estimated by theoretical simulation. In addition, the feasibility of using the anti-series connected Zener diodes as a selection device for bipolar RRAM is demonstrated experimentally. These results indicate that anti-series connected Zener diodes as a selection device opens up great opportunities to realize ultrahigh-density bipolar RRAM arrays.

  6. Space-grade reliability of 808nm QCW laser diode arrays (LDAs) delivering over 20 billion shots

    NASA Astrophysics Data System (ADS)

    Berk, Yuri; Karni, Yoram; Klumel, Genadi; Levy, Moshe; Openhaim, Yaki; Risemberg, Shlomo; Rech, Markus; Becht, Hubert; Frei, Bruno; Monti di Sopra, Fabrice

    2009-02-01

    Space missions are probably the most demanding environment for laser diodes. A comprehensive study on the reliability of commercially available laser diodes arrays (LDA), with the objective of bar stacks for ESA's BepiColombo Laser Altimeter mission to the planet Mercury was performed. We report the best results of lifetime tests performed on SCD 808 nm QCW stacks at different levels of current load in a unique combination with operational temperature cycles in the range of -10°C to 60 °C. Based on a field-proven design that includes Al-free wafer material and a robust packaging solution, these arrays exhibit long operational lifetime of up to 20 billion pulses monitored in the course of several years. Zero failures and stable performance of these QCW arrays were demonstrated in severe environmental conditions reflecting both, military and space applications. In order to achieve maximum device efficiency at different operational conditions of the base temperature and current, an optimum combination of the wafer structure and bar design is required. We demonstrate different types of QCW stacks delivering peak power of up to 1 kW with a usable range of 50-55% wall plug efficiency at base temperatures up to 60 °C.

  7. Miniaturized high throughput detection system for capillary array electrophoresis on chip with integrated light emitting diode array as addressed ring-shaped light source.

    PubMed

    Ren, Kangning; Liang, Qionglin; Mu, Xuan; Luo, Guoan; Wang, Yiming

    2009-03-01

    A novel miniaturized, portable fluorescence detection system for capillary array electrophoresis (CAE) on a microfluidic chip was developed, consisting of a scanning light-emitting diode (LED) light source and a single point photoelectric sensor. Without charge coupled detector (CCD), lens, fibers and moving parts, the system was extremely simplified. Pulsed driving of the LED significantly increased the sensitivity, and greatly reduced the power consumption and photobleaching effect. The highly integrated system was robust and easy to use. All the advantages realized the concept of a portable micro-total analysis system (micro-TAS), which could work on a single universal serial bus (USB) port. Compared with traditional CAE detecting systems, the current system could scan the radial capillary array with high scanning rate. An 8-channel CAE of fluorescein isothiocyanate (FITC) labeled arginine (Arg) on chip was demonstrated with this system, resulting in a limit of detection (LOD) of 640 amol. PMID:19224025

  8. Optical performance of top-down fabricated InGaN/GaN nanorod light emitting diode arrays

    SciTech Connect

    Li, Qiming; Westlake, Karl R.; Crawford, Mary H.; Lee, Stephen R.; Koleske, Daniel D.; Figiel, Jeffery J.; Cross, Karen C.; Fathololoumi, Saeed; Mi, Zetian; Wang, George T.

    2011-12-05

    Vertically aligned InGaN/GaN nanorod light emitting diode (LED) arrays were created from planar LED structures using a new top-down fabrication technique consisting of a plasma etch followed by an anisotropic wet etch. The wet etch results in straight, smooth, well-faceted nanorods with controllable diameters and removes the plasma etch damage. 94% of the nanorod LEDs are dislocation-free and a reduced quantum confined Stark effect is observed due to reduced piezoelectric fields. Despite these advantages, the IQE of the nanorod LEDs measured by photoluminescence is comparable to the planar LED, perhaps due to inefficient thermal transport and enhanced nonradiative surface recombination.

  9. Continuous-wave broadly tunable diode laser array-pumped mid-infrared Cr2+:CdSe laser

    NASA Astrophysics Data System (ADS)

    Lazarev, V. A.; Tarabrin, M. K.; Kovtun, A. A.; Karasik, V. E.; Kireev, A. N.; Kozlovsky, V. I.; Korostelin, Yu V.; Podmar’kov, Yu P.; Frolov, M. P.; Gubin, M. A.

    2015-12-01

    We demonstrate the operation of a room-temperature, solid-state, broadly tunable Cr-doped CdSe single-crystal continuous-wave laser. Longitudinal pumping with a continuous-wave diode laser array at 1.94 ?m produced a broadband output of 280 mW at 2.6 ?m with an incident power slope efficiency of 12%. With an intracavity Brewster-cut CaF2 prism, we tuned the Cr2+:CdSe laser from 2.45 to 3.06 ?m with a resolution of 10?nm and an output power up to 55 mW.

  10. Single-element optical injection locking of diode-laser arrays

    DOEpatents

    Hadley, G. Ronald (Albuquerque, NM); Hohimer, John P. (Albuquerque, NM); Owyoung, Adelbert (Albuquerque, NM)

    1988-01-01

    By optically injecting a single end-element of a semiconductor laser array, both the spatial and spectral emission characteristics of the entire laser array is controlled. With the output of the array locked, the far-field emission angle of the array is continuously scanned over several degrees by varying the injection frequency.

  11. Patterning the cone mosaic array in zebrafish retina requires specification of ultraviolet-sensitive cones.

    PubMed

    Raymond, Pamela A; Colvin, Steven M; Jabeen, Zahera; Nagashima, Mikiko; Barthel, Linda K; Hadidjojo, Jeremy; Popova, Lilia; Pejaver, Vivek R; Lubensky, David K

    2014-01-01

    Cone photoreceptors in teleost fish are organized in precise, crystalline arrays in the epithelial plane of the retina. In zebrafish, four distinct morphological/spectral cone types occupy specific, invariant positions within a regular lattice. The cone lattice is aligned orthogonal and parallel to circumference of the retinal hemisphere: it emerges as cones generated in a germinal zone at the retinal periphery are incorporated as single-cell columns into the cone lattice. Genetic disruption of the transcription factor Tbx2b eliminates most of the cone subtype maximally sensitive to ultraviolet (UV) wavelengths and also perturbs the long-range organization of the cone lattice. In the tbx2b mutant, the other three cone types (red, green, and blue cones) are specified in the correct proportion, differentiate normally, and acquire normal, planar polarized adhesive interactions mediated by Crumbs 2a and Crumbs 2b. Quantitative image analysis of cell adjacency revealed that the cones in the tbx2b mutant primarily have two nearest neighbors and align in single-cell-wide column fragments that are separated by rod photoreceptors. Some UV cones differentiate at the dorsal retinal margin in the tbx2b mutant, although they are severely dysmorphic and are eventually eliminated. Incorporating loss of UV cones during formation of cone columns at the margin into our previously published mathematical model of zebrafish cone mosaic formation (which uses bidirectional interactions between planar cell polarity proteins and anisotropic mechanical stresses in the plane of the retinal epithelium to generate regular columns of cones parallel to the margin) reproduces many features of the pattern disruptions seen in the tbx2b mutant. PMID:24465536

  12. Tunnel-injection quantum dot deep-ultraviolet light-emitting diodes with polarization-induced doping in III-nitride heterostructures

    SciTech Connect

    Verma, Jai Islam, S. M.; Protasenko, Vladimir; Kumar Kandaswamy, Prem; Xing, Huili; Jena, Debdeep

    2014-01-13

    Efficient semiconductor optical emitters in the deep-ultraviolet spectral window are encountering some of the most deep rooted problems of semiconductor physics. In III-Nitride heterostructures, obtaining short-wavelength photon emission requires the use of wide bandgap high Al composition AlGaN active regions. High conductivity electron (n-) and hole (p-) injection layers of even higher bandgaps are necessary for electrical carrier injection. This approach requires the activation of very deep dopants in very wide bandgap semiconductors, which is a difficult task. In this work, an approach is proposed and experimentally demonstrated to counter the challenges. The active region of the heterostructure light emitting diode uses ultrasmall epitaxially grown GaN quantum dots. Remarkably, the optical emission energy from GaN is pushed from 365?nm (3.4?eV, the bulk bandgap) to below 240?nm (>5.2?eV) because of extreme quantum confinement in the dots. This is possible because of the peculiar bandstructure and band alignments in the GaN/AlN system. This active region design crucially enables two further innovations for efficient carrier injection: Tunnel injection of carriers and polarization-induced p-type doping. The combination of these three advances results in major boosts in electroluminescence in deep-ultraviolet light emitting diodes and lays the groundwork for electrically pumped short-wavelength lasers.

  13. Ultra-violet Sensing Characteristic and Field Emission Properties of Vertically Aligned Aluminum Doped Zinc Oxide Nanorod Arrays

    SciTech Connect

    Mamat, M. H.; Malek, M. F.; Musa, M. Z.; Khusaimi, Z.; Rusop, M.

    2011-05-25

    Ultra-violet (UV) sensing behavior and field emission characteristic have been investigated on vertically aligned aluminum (Al) doped zinc oxide (ZnO) nanorod arrays prepared using sol-gel immersion method. Uniform and high coverage density of ZnO nanorod arrays have been successfully deposited on seeded-catalyst coated substrates. The synthesized nanorods have diameter sizes between 50 nm to 150 nm. The XRD spectra show Al doped ZnO nanorod array has high crystallinity properties with the dominancy of crystal growth along (002) plane or c-axis. UV photoresponse measurement indicates that Al doped ZnO nanorod array sensitively detects UV light as shown by conductance increment after UV illumination exposure. The nanorod array shows good field emission properties with low turn on field and threshold field at 2.1 V/{mu}m and 5.6 V/{mu}m, respectively. The result suggested that Al doped ZnO nanorod arrays prepared by low-cost sol-gel immersion method show promising result towards fabrication of multi applications especially in UV photoconductive sensor and field emission displays.

  14. ATTRACTION OF FRANKLINIELLA OCCIDENTALIS, LYGUS HESPERUS, LEAF HOPPERS, CULEX QUINQUEFASCIATUS, AND MUSCA DOMESTICA TO ULTRAVIOLET FLUORESCENT LIGHT AND ULTRAVIOLET EMITTING DIODE TRAPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The attraction of selected insects to ultraviolet (UV) and blue light traps was studied under laboratory darkroom, greenhouse, and field conditions. Results showed that western lygus bugs, Lygus Hesperus (Knight), were attracted to UV light traps in laboratory studies. Leaf hoppers, mosquitoes, Cu...

  15. High-purity hydrogen generation by ultraviolet illumination with the membrane composed of titanium dioxide nanotube array and Pd layer

    NASA Astrophysics Data System (ADS)

    Hattori, Masashi; Noda, Kei; Matsushige, Kazumi

    2011-09-01

    High-purity hydrogen generation was observed by using a membrane composed of a bilayer of an anodized titanium dioxide nanotube array (TNA) and a hydrogen permeable metal. This membrane was fabricated by transferring a TNA embedded in a titanium foil onto a sputtered 10-?m-thick palladium film. Alcohols are reformed photocatalytically and concurrently generated hydrogen is purified through the Pd layer. H2 with a purity of more than 99% was obtained from liquid alcohols under ultraviolet illumination onto the membrane. Thus, we demonstrated the integration of photocatalytic hydrogen production and purification within a single membrane.

  16. Monolithic arrays of grating-surface-emitting diode lasers and quantum well modulators for optical communications

    NASA Technical Reports Server (NTRS)

    Carlson, N. W.; Evans, G. A.; Liew, S. K.; Kaiser, C. J.

    1990-01-01

    The electro-optic switching properties of injection-coupled coherent 2-D grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high power grading-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator.

  17. Use of a priori spectral information in the measurement of x-ray flux with filtered diode arrays

    NASA Astrophysics Data System (ADS)

    Marrs, R. E.; Widmann, K.; Brown, G. V.; Heeter, R. F.; MacLaren, S. A.; May, M. J.; Moore, A. S.; Schneider, M. B.

    2015-10-01

    Filtered x-ray diode (XRD) arrays are often used to measure x-ray spectra vs. time from spectrally continuous x-ray sources such as hohlraums. A priori models of the incident x-ray spectrum enable a more accurate unfolding of the x-ray flux as compared to the standard technique of modifying a thermal Planckian with spectral peaks or dips at the response energy of each filtered XRD channel. A model x-ray spectrum consisting of a thermal Planckian, a Gaussian at higher energy, and (in some cases) a high energy background provides an excellent fit to XRD-array measurements of x-ray emission from laser heated hohlraums. If high-resolution measurements of part of the x-ray emission spectrum are available, that information can be included in the a priori model. In cases where the x-ray emission spectrum is not Planckian, candidate x-ray spectra can be allowed or excluded by fitting them to measured XRD voltages. Examples are presented from the filtered XRD arrays, named Dante, at the National Ignition Facility and the Laboratory for Laser Energetics.

  18. Use of a priori spectral information in the measurement of x-ray flux with filtered diode arrays.

    PubMed

    Marrs, R E; Widmann, K; Brown, G V; Heeter, R F; MacLaren, S A; May, M J; Moore, A S; Schneider, M B

    2015-10-01

    Filtered x-ray diode (XRD) arrays are often used to measure x-ray spectra vs. time from spectrally continuous x-ray sources such as hohlraums. A priori models of the incident x-ray spectrum enable a more accurate unfolding of the x-ray flux as compared to the standard technique of modifying a thermal Planckian with spectral peaks or dips at the response energy of each filtered XRD channel. A model x-ray spectrum consisting of a thermal Planckian, a Gaussian at higher energy, and (in some cases) a high energy background provides an excellent fit to XRD-array measurements of x-ray emission from laser heated hohlraums. If high-resolution measurements of part of the x-ray emission spectrum are available, that information can be included in the a priori model. In cases where the x-ray emission spectrum is not Planckian, candidate x-ray spectra can be allowed or excluded by fitting them to measured XRD voltages. Examples are presented from the filtered XRD arrays, named Dante, at the National Ignition Facility and the Laboratory for Laser Energetics. PMID:26520959

  19. Design of electron blocking layers for improving internal quantum efficiency of InGaN/AlGaN-based ultraviolet light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Park, Tae Hoon; Kim, Tae Geun

    2015-09-01

    In this paper, we designed and simulated InGaN/AlGaN-based near-ultraviolet light-emitting diode (NUV LED) epi-structures to obtain high internal quantum efficiency and low efficiency droop. When the conventional epi-structure of an last quantum barrier and an electron blocking layer (EBL) was replaced with a graded last quantum barrier and multi-step EBLs, the NUV LED showed 35 % higher internal quantum efficiency and 25 % more suppression of efficiency droop than the conventional NUV LED. Furthermore, a detailed study of the grading effect of the EBL revealed that 10-step EBLs increase performance when compared to other structures. These results are attributed to the polarization-induced effect, which reduces the electron leakage and increases the hole injection efficiency.

  20. Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes

    SciTech Connect

    Wierer, J. J. Allerman, A. A.; Montaño, I.; Moseley, M. W.

    2014-08-11

    The improvement in light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes (UVLEDs) emitting at ?270?nm is shown to be influenced by optical polarization. Three UVLEDs with different reflective scattering structures are investigated and compared to standard UVLEDs without scattering structures. The optical polarization and therefore the direction of light propagation within the various UVLEDs are altered by changes in the quantum well (QW) thickness. The improvement in light extraction efficiency of the UVLEDs with reflective scattering structures increases, compared to the UVLEDs without scattering structures, as the fraction of emitted light propagating parallel to the QW plane increases. Additionally, the light extraction efficiency increases as the average distance to the reflective scattering structures decreases.

  1. Light extraction enhancement of 265?nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure

    SciTech Connect

    Inoue, Shin-ichiro; Naoki, Tamari; Kinoshita, Toru; Obata, Toshiyuki; Yanagi, Hiroyuki

    2015-03-30

    Deep-ultraviolet (DUV) aluminum gallium nitride-based light-emitting diodes (LEDs) on transparent aluminum nitride (AlN) substrates with high light extraction efficiency and high power are proposed and demonstrated. The AlN bottom side surface configuration, which is composed of a hybrid structure of photonic crystals and subwavelength nanostructures, has been designed using finite-difference time-domain calculations to enhance light extraction. We have experimentally demonstrated an output power improvement of up to 196% as a result of the use of the embedded high-light-extraction hybrid nanophotonic structure. The DUV-LEDs produced have demonstrated output power as high as 90 mW in DC operation at a peak emission wavelength of 265?nm.

  2. Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes.

    PubMed

    Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

    2015-01-01

    This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378

  3. Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes

    PubMed Central

    Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

    2015-01-01

    This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378

  4. Soft lithography microlens fabrication and array for enhanced light extraction from organic light emitting diodes (OLEDs)

    SciTech Connect

    Leung, Wai Y.; Park, Joong-Mok; Gan, Zhengqing; Constant, Kristen P.; Shinar, Joseph; Shinar, Ruth; ho, Kai-Ming

    2014-06-03

    Provided are microlens arrays for use on the substrate of OLEDs to extract more light that is trapped in waveguided modes inside the devices and methods of manufacturing same. Light extraction with microlens arrays is not limited to the light emitting area, but is also efficient in extracting light from the whole microlens patterned area where waveguiding occurs. Large microlens array, compared to the size of the light emitting area, extract more light and result in over 100% enhancement. Such a microlens array is not limited to (O)LEDs of specific emission, configuration, pixel size, or pixel shape. It is suitable for all colors, including white, for microcavity OLEDs, and OLEDs fabricated directly on the (modified) microlens array.

  5. Rapid method for the determination of 14 isoflavones in food using UHPLC coupled to photo diode array detection.

    PubMed

    Shim, You-Shin; Yoon, Won-Jin; Hwang, Jin-Bong; Park, Hyun-Jin; Seo, Dongwon; Ha, Jaeho

    2015-11-15

    A rapid method for the determination of 14 types of isoflavones in food using ultra-high performance liquid chromatography (UHPLC) was validated in terms of precision, accuracy, sensitivity and linearity. The UHPLC separation was performed on a reverse-phase C18 column (particle size 2 ?m, i.d. 2 mm, length 100 mm) using a photo diode array detector that was fixed to 260 nm. The limits of detection and quantification of the UHPLC analyses ranged from 0.03 to 0.33 mg kg(-1). The intra-day and inter-day precision of the individual isoflavones were less than 11.77% and calibration curves exhibited good linearity (r(2) = 0.99) within the tested ranges. These results suggest that the rapid method used in this study could be available to determine of 14 types of isoflavones in a variety of food such as soy bean, black bean, red bean and soybean paste. PMID:25977042

  6. Simultaneous determination of aromatic and terpenic constituents of cloves by means of HPLC with diode array detection.

    PubMed

    Musenga, Alessandro; Ferranti, Anna; Saracino, Maria Addolorata; Fanali, Salvatore; Raggi, Maria Augusta

    2006-06-01

    An HPLC method has been developed for the simultaneous determination of aromatic and terpenic constituents of cloves on a C8 RP column, with the mobile phase consisting of a pH 3.5 phosphate buffer-triethylamine (30%) and acetonitrile (70%); a flow rate of 1.2 mL/min and a diode-array detector were used. Complete separation of all analytes (eugenol (EUG), eugenol acetate (AEUG), beta-caryophyllene, a-humulene and caryophyllene oxide) was achieved within 7 min. Good linearity was found in the range 0.125-40.0 microg/mL for EUG and AEUG and in the range 0.250-20.0 microg/mL for the terpenic compounds. After validation, the method was successfully applied to the analysis of clove oil and clove extract samples. The results obtained indicate good accuracy (recovery percentage mean value corresponding to 99.9%) and satisfactory precision. PMID:16833083

  7. Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.

    PubMed

    Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

    2013-04-01

    We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute). PMID:23455517

  8. SU-F-BRE-06: Evaluation of Patient CT Dose Reconstruction From 3D Diode Array Measurements Using Anthropomorphic Phantoms

    SciTech Connect

    Huang, M; Benhabib, S; Cardan, R; Brezovich, I; Popple, R; Faught, A; Followill, D

    2014-06-15

    Purpose: To compare 3D reconstructed dose of IMRT plans from 3D diode array measurements with measurements in anthropomorphic phantoms. Methods: Six IMRT plans were created for the IROC Houston (RPC) head and neck (H and N) and lung phantoms following IROC Houston planning protocols. The plans included flattened and unflattened beam energies ranging from 6 MV to 15 MV and both static and dynamic MLC tecH and Niques. Each plan was delivered three times to the respective anthropomorphic phantom, each of which contained thermoluminescent dosimeters (TLDs) and radiochromic films (RCFs). The plans were also delivered to a Delta4 diode array (Scandidos, Uppsala, Sweden). Irradiations were done using a TrueBeam STx (Varian Medical Systems, Palo Alto, CA). The dose in the patient was calculated by the Delta4 software, which used the diode measurements to estimate incident energy fluence and a kernel-based pencil beam algorithm to calculate dose. The 3D dose results were compared with the TLD and RCF measurements. Results: In the lung, the average difference between TLDs and Delta4 calculations was 5% (range 2%–7%). For the H and N, the average differences were 2.4% (range 0%–4.5%) and 1.1% (range 0%–2%) for the high- and low-dose targets, respectively, and 12% (range 10%-13%) for the organ-at-risk simulating the spinal cord. For the RCF and criteria of 7%/4mm, 5%/3mm, and 3%/3mm, the average gamma-index pass rates were 95.4%, 85.7%, and 76.1%, respectively for the H and N and 76.2%, 57.8%, and 49.5% for the lung. The pass-rate in the lung decreased with increasing beam energy, as expected for a pencil beam algorithm. Conclusion: The H and N phantom dose reconstruction met the IROC Houston acceptance criteria for clinical trials; however, the lung phantom dose did not, most likely due to the inaccuracy of the pencil beam algorithm in the presence of low-density inhomogeneities. Work supported by PHS grant CA10953 and CA81647 (NCI, DHHS)

  9. Effect of chip spacing on light extraction for light-emitting diode array.

    PubMed

    Chung, Shuang-Chao; Ho, Pei-Chen; Li, Dun-Ru; Lee, Tsung-Xian; Yang, Tsung-Hsun; Sun, Ching-Cherng

    2015-06-01

    GaN LED array in packaging is important for the demand of high optical flux. In order to tighten the whole packaging size, the spacing among LED chips becomes an important factor in the packaging design. This study is to investigate the change of the light extraction when a GaN LED chip array packaging is applied. The shielding effect with various spacing for the GaN LED array with or without silicon encapsulation is obtained. We apply the Monte Carlo ray-tracing method in the simulations to analyze the optical behavior of the two major types of the GaN LED array. The shielding effect is more dominant for bare chip packaging. When a silicone thin dispensing layer is applied, the shielding effect is not obvious because of more light extraction, the neighbor dies play an important role in photon recycling. PMID:26072888

  10. Ultra high brightness laser diode arrays for pumping of compact solid state lasers and direct applications

    NASA Astrophysics Data System (ADS)

    Kohl, Andreas; Fillardet, Thierry; Laugustin, Arnaud; Rabot, Olivier

    2012-10-01

    High Power Laser Diodes (HPLD) are increasingly used in different fields of applications such as Industry, Medicine and Defense. Our significant improvements of performances (especially in power and efficiency) and a reproducible manufacturing process have led to reliable, highly robust components. For defense and security applications these devices are used predominantly for pumping of solid state lasers (ranging, designation, countermeasures, and sensors). Due to the drastically falling price per watt they are more and more replacing flash lamps as pump sources. By collimating the laser beam even with a bar to bar pitch of only 400?m. cutting edge brightness of our stacks.is achieved Due the extremely high brightness and high power density these stacks are an enabling technology for the development of compact highly efficient portable solid state lasers for applications as telemeters and designators on small platforms such as small UAVs and handheld devices. In combination with beam homogenizing optics their compact size and high efficiency makes these devices perfectly suited as illuminators for portable active imaging systems. For gated active imaging systems a very short pulse at high PRF operation is required. For this application we have developed a diode driver board with an efficiency several times higher than that of a standard driver. As a consequence this laser source has very low power consumption and low waste heat dissipation. In combination with its compact size and the integrated beam homogenizing optics it is therefore ideally suited for use in portable gated active imaging systems. The kWatt peak power enables a range of several hundred meters. The devices described in this paper mostly operate at wavelength between 800 nm and 980nm. Results from diodes operating between 1300 nm and 1550 nm are presented as well.

  11. Gun muzzle flash detection using a single photon avalanche diode array in 0.18µm CMOS technology

    NASA Astrophysics Data System (ADS)

    Savuskan, Vitali; Jakobson, Claudio; Merhav, Tomer; Shoham, Avi; Brouk, Igor; Nemirovsky, Yael

    2015-05-01

    In this study, a CMOS Single Photon Avalanche Diode (SPAD) 2D array is used to record and sample muzzle flash events in the visible spectrum, from representative weapons. SPADs detect the emission peaks of alkali salts, potassium or sodium, with spectral emission lines around 769nm and 589nm, respectively. The alkali salts are included in the gunpowder to suppress secondary flashes ignited during the muzzle flash event. The SPADs possess two crucial properties for muzzle flash imaging: (i) very high photon detection sensitivity, (ii) a unique ability to convert the optical signal to a digital signal at the source pixel, thus practically eliminating readout noise. The sole noise sources are the ones prior to the readout circuitry (optical signal distribution, avalanche initiation distribution and nonphotonic generation). This enables high sampling frequencies in the kilohertz range without significant SNR degradation, in contrast to regular CMOS image sensors. This research will demonstrate the SPAD's ability to accurately sample and reconstruct the temporal behavior of the muzzle flash in the visible wavelength, in the presence of sunlight. The reconstructed signal is clearly distinguishable from background clutter, through exploitation of flash temporal characteristics and signal processing, which will be reported. The frame rate of ~16 KHz was chosen as an optimum between SNR degradation and temporal profile recognition accuracy. In contrast to a single SPAD, the 2D array allows for multiple events to be processed simultaneously. Moreover, a significant field of view is covered, enabling comprehensive surveillance and imaging.

  12. Planarization of High Aspect Ratio P-I-N Diode Pillar Arrays for Blanket Electrical Contacts

    SciTech Connect

    Voss, L F; Shao, Q; Reinhardt, C E; Graff, R T; Conway, A M; Nikolic, R J; Deo, N; Cheung, C L

    2009-03-05

    Two planarization techniques for high aspect ratio three dimensional pillar structured P-I-N diodes have been developed in order to enable a continuous coating of metal on the top of the structures. The first technique allows for coating of structures with topography through the use of a planarizing photoresist followed by RIE etch back to expose the tops of the pillar structure. The second technique also utilizes photoresist, but instead allows for planarization of a structure in which the pillars are filled and coated with a conformal coating by matching the etch rate of the photoresist to the underlying layers. These techniques enable deposition using either sputtering or electron beam evaporation of metal films to allow for electrical contact to the tops of the underlying pillar structure. These processes have potential applications for many devices comprised of 3-D high aspect ratio structures. Two separate processes have been developed in order to ensure a uniform surface for deposition of an electrode on the {sup 10}Boron filled P-I-N pillar structured diodes. Each uses S1518 photoresist in order to achieve a relatively uniform surface despite the non-uniformity of the underlying detector. Both processes allow for metallization of the final structure and provide good electrical continuity over a 3D pillar structure.

  13. Enhancement of hole injection and electroluminescence by ordered Ag nanodot array on indium tin oxide anode in organic light emitting diode

    SciTech Connect

    Jung, Mi E-mail: Dockha@kist.re.kr; Mo Yoon, Dang; Kim, Miyoung; Kim, Chulki; Lee, Taikjin; Hun Kim, Jae; Lee, Seok; Woo, Deokha E-mail: Dockha@kist.re.kr; Lim, Si-Hyung

    2014-07-07

    We report the enhancement of hole injection and electroluminescence (EL) in an organic light emitting diode (OLED) with an ordered Ag nanodot array on indium-tin-oxide (ITO) anode. Until now, most researches have focused on the improved performance of OLEDs by plasmonic effects of metal nanoparticles due to the difficulty in fabricating metal nanodot arrays. A well-ordered Ag nanodot array is fabricated on the ITO anode of OLED using the nanoporous alumina as an evaporation mask. The OLED device with Ag nanodot arrays on the ITO anode shows higher current density and EL enhancement than the one without any nano-structure. These results suggest that the Ag nanodot array with the plasmonic effect has potential as one of attractive approaches to enhance the hole injection and EL in the application of the OLEDs.

  14. Feasibility of High-Power Diode Laser Array Surrogate to Support Development of Predictive Laser Lethality Model

    SciTech Connect

    Lowdermilk, W H; Rubenchik, A M; Springer, H K

    2011-01-13

    Predictive modeling and simulation of high power laser-target interactions is sufficiently undeveloped that full-scale, field testing is required to assess lethality of military directed-energy (DE) systems. The cost and complexity of such testing programs severely limit the ability to vary and optimize parameters of the interaction. Thus development of advanced simulation tools, validated by experiments under well-controlled and diagnosed laboratory conditions that are able to provide detailed physics insight into the laser-target interaction and reduce requirements for full-scale testing will accelerate development of DE weapon systems. The ultimate goal is a comprehensive end-to-end simulation capability, from targeting and firing the laser system through laser-target interaction and dispersal of target debris; a 'Stockpile Science' - like capability for DE weapon systems. To support development of advanced modeling and simulation tools requires laboratory experiments to generate laser-target interaction data. Until now, to make relevant measurements required construction and operation of very high power and complex lasers, which are themselves costly and often unique devices, operating in dedicated facilities that don't permit experiments on targets containing energetic materials. High power diode laser arrays, pioneered by LLNL, provide a way to circumvent this limitation, as such arrays capable of delivering irradiances characteristic of De weapon requires are self-contained, compact, light weight and thus easily transportable to facilities, such as the High Explosives Applications Facility (HEAF) at Lawrence Livermore National Laboratory (LLNL) where testing with energetic materials can be performed. The purpose of this study was to establish the feasibility of using such arrays to support future development of advanced laser lethality and vulnerability simulation codes through providing data for materials characterization and laser-material interaction models and to validate the accuracy of code predictions. This project was a Feasibility Study under the LLNL Laboratory Directed Research and Development (LDRD) Program.

  15. Monolithic millimeter-wave diode array beam controllers: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Sjogren, L. B.; Liu, H.-X. L.; Wang, F.; Liu, T.; Wu, W.; Qin, X.-H.; Chung, E.; Domier, C. W.; Luhmann, N. C., Jr.; Maserjian, J.

    1992-01-01

    In the current work, multi-function beam control arrays have been fabricated and have successfully demonstrated amplitude control of transmitted beams in the W and D bands (75-170 GHz). While these arrays are designed to provide beam control under DC bias operation, new designs for high-speed electronic and optical control are under development. These arrays will fill a need for high-speed watt-level beam switches in pulsed reflectometer systems under development for magnetic fusion plasma diagnostics. A second experimental accomplishment of the current work is the demonstration in the 100-170 GHz (D band) frequency range of a new technique for the measurement of the transmission phase as well as amplitude. Transmission data can serve as a means to extract ('de-embed') the grid parameters; phase information provides more complete data to assist in this process. Additional functions of the array beam controller yet to be tested include electronically controlled steering and focusing of a reflected beam. These have application in the areas of millimeter-wave electronic scanning radar and reflectometry, respectively.

  16. Broadband localized surface-plasmon-enhanced green light-emitting diodes by silver nanocone array

    NASA Astrophysics Data System (ADS)

    Liu, Hao; Li, Yufeng; Huang, Yaping; Wang, Shuai; Feng, Lungang; Gong, Zhina; Wang, Jiangteng; Ding, Wen; Zhang, Ye; Yun, Feng

    2015-12-01

    Green light-emitting diodes (LEDs) with silver nanocone-shaped structures embedded in p-GaN have been demonstrated with the surface plasmon (SP) enhancement effect. The resonance frequency has been broadened and the strength of coupling has been considerably enhanced. Compared with the LED without Ag nanocones, the integrated photoluminescence (PL) intensity of the SP-enhanced LED was improved by ?275%, and the electroluminescence (EL) enhancement ratio at a different wavelength was evaluated at an injection current of 50 mA/mm2. At the same time, a reduction in the recombination lifetime indicated an increased internal quantum efficiency of LEDs. The results of simulation using nanocones as well as nanorods indicate good correlation with the experimental observation of the broadening effect. This structure is promising for converting incident photons into the localized surface plasmon (LSP) mode, to enhance the emission of LEDs within a broad wavelength range.

  17. Ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy on semipolar GaN (2021) substrates

    SciTech Connect

    Sawicka, M.; Grzanka, S.; Skierbiszewski, C.; Turski, H.; Muziol, G.; Krysko, M.; Grzanka, E.; Sochacki, T.; Siekacz, M.; Kucharski, R.

    2013-03-18

    Multi-quantum well (MQW) structures and light emitting diodes (LEDs) were grown on semipolar (2021) and polar (0001) GaN substrates by plasma-assisted molecular beam epitaxy. The In incorporation efficiency was found to be significantly lower for the semipolar plane as compared to the polar one. The semipolar MQWs exhibit a smooth surface morphology, abrupt interfaces, and a high photoluminescence intensity. The electroluminescence of semipolar (2021) and polar (0001) LEDs fabricated in the same growth run peaks at 387 and 462 nm, respectively. Semipolar LEDs with additional (Al,Ga)N cladding layers exhibit a higher optical output power but simultaneously a higher turn-on voltage.

  18. Fabrication and characterization of p-ZnO:(P,N)/n-ZnO:Al homojunction ultra-violet (UV) light emitting diodes (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Rafiudeen, Amiruddin; Reddy, T. Srinivasa; Cheemadan, Shaheer; Kumar, M. C. Santhosh

    2015-10-01

    ZnO possess distinctive characteristics such as low cost, wide band gap (3.36 eV) and large exciton binding energy (60meV). As the band gap lies in ultra violet (UV) region, ZnO is considered as a novel material for the fabrication of ultra violet light emitting diodes (UV-LEDs). However, ZnO being intrinsic n-type semiconductor the key challenge lies in realization of stable and reproducible p-type ZnO. In the present research dual acceptor group-V elements such as P and N are simultaneously doped in ZnO films to obtain the p-type characteristics. The deposition is made by programmable spray pyrolysis technique upon glass substrates at 697K. The optimum doping concentration of P and N were found to be 0.75 at% which exhibits hole concentration of 4.48 x 10^18 cm-3 and resistivity value of 9.6 ?.cm. The deposited p-ZnO were found to be stable for a period over six months. Highly conducting n-type ZnO films is made by doping aluminum (3 at%) which exhibits higher electron concentration of 1.52 x 10^19 cm-3 with lower electrical resistivity of 3.51 x 10-2 ?.cm. The structural, morphological, optical and electrical properties of the deposited n-ZnO and p-ZnO thin films are investigated. An efficient p-n homojunction has been fabricated using the optimum p-ZnO:(P,N) and n-ZnO:Al layers. The current-voltage (I-V) characteristics show typical rectifying characteristics of p-n junction with a low turn on voltage. Electroluminescence (EL) studies reveals the fabricated p-n homojunction diodes exhibits strong emission features in ultra-violet (UV) region around 378 nm.

  19. Determination of analytes in medical herbs extracts by SPE coupled with two-dimensional planar chromatography in combination with diode array scanning densitometry and HPLC-diode array detector.

    PubMed

    Tuzimski, Tomasz

    2011-01-01

    The purpose of this study is to demonstrate an application of 2-D high-performance planar chromatography-diode array detector (DAD) and HPLC-DAD after solid-phase extraction (SPE) for identification and quantitative analysis of pesticides (isoproturon, aziprotryne, hexazinone, flufenoxuron, methabenzthiazuron, procymidone, and ?-cypermethrin) in Melissa officinalis L. (Labiatae) samples. The procedure described for the determination of compounds is inexpensive and can be applied to routine analysis of analytes in medical herbs' samples after preliminary cleanup and concentration by SPE. Average recoveries on C18 SPE cartridges of pesticides eluted with 5 mL tetrahydrofuran by the proposed HPLC-DAD method, before and after 2-D-high-performance planar chromatography separation of analytes from M. officinalis L. samples spiked with pesticide at a concentration level of 10 ?g/g in plant material are presented. Method validation parameters for the quantification of pesticides by the proposed HPLC-DAD after SPE method are also presented. PMID:21171173

  20. Quasi-isotropic VHF antenna array design study for the International Ultraviolet Explorer satellite

    NASA Technical Reports Server (NTRS)

    Raines, J. K.

    1975-01-01

    Results of a study to design a quasi-isotropic VHF antenna array for the IUE satellite are presented. A free space configuration was obtained that has no nulls deeper than -6.4 dbi in each of two orthogonal polarizations. A computer program named SOAP that analyzes the electromagnetic interaction between antennas and complicated conducting bodies, such as satellites was developed.

  1. Fabrication of a High-Brightness Blue-Light-Emitting Diode Using a ZnO-Nanowire Array Grown on p-GaN

    E-print Network

    Wang, Zhong L.

    Fabrication of a High-Brightness Blue-Light-Emitting Diode Using a ZnO-Nanowire Array Grown on p-GaN GaN nanowires (NWs) have also been fabricated, and nanoLEDs are an active field of research.[5-brightness n- ZnO NWs/p-GaN film hybrid heterojunction LED devices by directly growing n-type ZnO nanowires

  2. Photonic Power Delivery Through Optical Fiber Using Very High Power Laser Diode Arrays

    SciTech Connect

    Heino, Matthew; Saethre, Robert

    1999-05-01

    Described is a system that will provide isolated electric power for a circuit that drives the core reset of a pulsed power modulator. This can be accomplished by coupling light from a number of diode laser bars to bundles of 200 um multimode optical fibers. This is then coupled to photo-voltaic power converters that will deliver 16 V 29mA of electricity from 1 watt of optical power. Spot size at the bundle face is a Gausian ellipse with a major axis of 1.4 mm radius and a minor axis of four bundles of 12 fibers generating a total of 24 W of electrical power. Various schemes are used to maximize coupling into the optical filber while limiting the number of optical components, and comparing components such as fresnel and aspheric lenses and lens ducts for effectiveness and cost. This will provide a completely isolated low power source for high voltage, high current environments where tradional isolation techniques yield inadequate isolation or prove too cumbersome.

  3. Low-noise low-jitter 32-pixels CMOS single-photon avalanche diodes array for single-photon counting from 300 nm to 900 nm

    SciTech Connect

    Scarcella, Carmelo; Tosi, Alberto Villa, Federica; Tisa, Simone; Zappa, Franco

    2013-12-15

    We developed a single-photon counting multichannel detection system, based on a monolithic linear array of 32 CMOS SPADs (Complementary Metal-Oxide-Semiconductor Single-Photon Avalanche Diodes). All channels achieve a timing resolution of 100 ps (full-width at half maximum) and a photon detection efficiency of 50% at 400 nm. Dark count rate is very low even at room temperature, being about 125 counts/s for 50 ?m active area diameter SPADs. Detection performance and microelectronic compactness of this CMOS SPAD array make it the best candidate for ultra-compact time-resolved spectrometers with single-photon sensitivity from 300 nm to 900 nm.

  4. Absorbance detector for capillary electrophoresis based on light-emitting diodes and photodiodes for the deep-ultraviolet range.

    PubMed

    Bui, Duy Anh; Hauser, Peter C

    2015-11-20

    A new absorbance detector for capillary electrophoresis featuring relatively high intensity light-emitting diodes as radiation sources and photodiodes for the deep-UV range was developed. The direct relationship of absorbance values and concentrations was obtained by emulating Lambert-Beer's law with the application of a beam splitter to obtain a reference signal and a log-ratio amplifier circuitry. The performance of the cell was investigated at 255nm with the detection of sulfanilic, 4-nitrobenzoic, 4-hydroxybenzoic and 4-aminobenzoic acid and the indirect detection of acetate, propionate, butyrate and caproate using benzoate as the displacement dye molecule. Vanillic acid, L-tyrosine and DL-tryptophan as well as the sulfonamides sulfamerazine, sulfathiazole and sulfamethazine were determined at 280nm. Good linearities over 3 orders of magnitude were obtained. The noise level recorded was as low as 50?AU and the drift typically <200?AU/5min. PMID:26091783

  5. Atomically sharp 318 nm Gd:AlGaN ultraviolet light emitting diodes on Si with low threshold voltage

    SciTech Connect

    Kent, Thomas F.; Carnevale, Santino D.; Myers, Roberto C.; Deparment of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210

    2013-05-20

    Self-assembled Al{sub x}Ga{sub 1-x}N polarization-induced nanowire light emitting diodes (PINLEDs) with Gd-doped AlN active regions are prepared by plasma-assisted molecular beam epitaxy on Si substrates. Atomically sharp electroluminescence (EL) from Gd intra-f-shell electronic transitions at 313 nm and 318 nm is observed under forward biases above 5 V. The intensity of the Gd 4f EL scales linearly with current density and increases at lower temperature. The low field excitation of Gd 4f EL in PINLEDs is contrasted with high field excitation in metal/Gd:AlN/polarization-induced n-AlGaN devices; PINLED devices offer over a three fold enhancement in 4f EL intensity at a given device bias.

  6. Enhancement of radiative efficiencies of near-ultraviolet organic light-emitting diodes by localized surfacee Plasmon resonance enhancement effect

    NASA Astrophysics Data System (ADS)

    Matsuoka, A.; Emoto, A.; Ohtani, N.

    2015-10-01

    Near-UV emission organic light emitting diodes (OLEDs) containing silver (Ag) nanoparticles (NPs) were fabricated to improve their radiative efficiencies by the localized surface plasmon resonance (LSPR) enhancement effect. The samples studied were simple bilayer structures consisting of an active layer and a hole-transporting layer (HTL). Poly[(9,9- dihexylfluoren-2,7-diyl)-co-(1,4-dimethyl-benzene-2,5-diyl)] (PF-DMB) was used as a UV emission material, whose emission peaking-wavelength is about 395 nm. Ag NPs were inserted between ITO and HTL, whose absorption peaking wavelength is corresponding to about 395 nm. Thus, the electroluminescence (EL) intensity of UV OLEDs containing Ag NPs was enhanced to about 2.5 times as large as that without Ag NP by the LSPR enhancement effect.

  7. Simultaneous determination of four neuroprotective compounds of Tilia amurensis by high performance liquid chromatography coupled with diode array detector

    PubMed Central

    Lee, Bohyung; Weon, Jin Bae; Yun, Bo-Ra; Lee, Jiwoo; Eom, Min Rye; Ma, Choong Je

    2014-01-01

    Background: Tilia amurensis consists of various compounds, such as flavonoids and terpenoids. Objective: A simple and reliable high performance liquid chromatography (HPLC) coupled with the diode array detector (DAD) method has been established for simultaneous determination of epicatechin, nudiposide, lyoniside, and scopoletin isolated from Tilia amurensis. Materials and Methods: Optimum separations were obtained with a SHISEIDO C18 column by gradient eluton, with 0.1% Trifluoroacetic acid (TFA) water-methanol as the mobile phase. The gradient elution system was completed within 40 minutes. The flow rate and detection wavelength were 1 mL/minute, 205 nm, 250 nm, and 280 nm, respectively. Results: Validation of the analytical method was evaluated by linearity, precision, and the accuracy test. The calibration curve was linear over the established range with R2 > 0.997. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.01-15.20 ?g/mL and 0.03-46.06 ?g/mL. The method exhibited an intraday and interday precision range of 96.25-105.66% and 93.52-109.92%, respectively (RSD <2.80%). The recoveries and relative standard deviation (RSD) of the four compounds in Tilia amurensis were in the range of 90.42-104.84% and 0.2-2.58%. Conclusion: This developed method was accurate and reliable for the quality evaluation of the four compounds isolated from Tilia amurensis. PMID:25210303

  8. A simultaneous determination of principal compounds in tokishakuyakusan by high-performance liquid chromatography with diode array detector.

    PubMed

    Sumino, Megumi; Saito, Yuko; Ikegami, Fumio; Namiki, Takao

    2015-02-01

    We developed a simultaneous analysis method using high-performance liquid chromatography coupled with diode-array detector (HPLC-DAD) for six principal compounds (atractylenolide III, alisol A, alisol B, paeoniflorin, ferulic acid and (Z)-ligustilide) in a traditional Japanese (Kampo) medicine, tokishakuyakusan (TSS). The HPLC separation was conducted on a reversed-phase TSK-gel ODS-80TS column (4.6 i.d. × 250 mm, 5 µm) at 40°C with a 0.1% phosphoric acid-acetonitrile gradient system. The DAD detection wavelength was set at 205, 232 and 330 nm. Calibration curves for the compounds showed linear regressions with correlation coefficients of >0.999. The intra- and inter-day precision (i.e., the relative standard deviation) were in the range of 0.50-1.55 and 0.70-1.80%, respectively. The average recovery yields of the compounds ranged from 98.3 to 103%. The present results will contribute to shorter analysis times with less organic solvent compared with the individual analysis of each compound for the evaluation of TSS. The application of the established method to TSS will also provide helpful information for the further pharmacological and clinical studies. PMID:24981981

  9. Multi-Spectral Solar Telescope Array. IV - The soft X-ray and extreme ultraviolet filters

    NASA Technical Reports Server (NTRS)

    Lindblom, Joakim F.; O'Neal, Ray H.; Walker, Arthur B. C., Jr.; Powell, Forbes R.; Barbee, Troy W., Jr.; Hoover, Richard B.

    1991-01-01

    NASA's Multi-Spectral Solar Telescope Array uses various combinations of thin foil filters composed of Al, C, Te, Be, Mo, Rh, and phthalocyanine to achieve the requisite radiation-rejection characteristics. Such rejection is demanded by the presence of strong EUV radiation at longer wavelengths where the specular reflectivity of multilayer mirrors can cause 'contamination' of the image in the narrow band defined by the Bragg condition.

  10. Vacuum-ultraviolet beam array generation by flat micro-optical structures.

    PubMed

    Grunwald, R; Neumann, U; Kebbel, V; Kühn, H J; Mann, K; Leinhos, U; Mischke, H; Wulff-Molder, D

    2004-05-01

    Micro-optical structures for VUV laser beam shaping and wave-front sensing were manufactured by thin-film deposition onto CaF2 and transfer by etching. Arrays of Bessel-like F2 laser beams at a wavelength of 157 nm with extremely small conical angles were generated by microaxicon lenses. Beam propagation was studied in simulations and experiments. Apodization by absorbing layers is proposed for beam cleaning. PMID:15143646

  11. Electrical current leakage and open-core threading dislocations in AlGaN-based deep ultraviolet light-emitting diodes

    SciTech Connect

    Moseley, Michael Allerman, Andrew; Crawford, Mary; Wierer, Jonathan J.; Smith, Michael; Biedermann, Laura

    2014-08-07

    Electrical current transport through leakage paths in AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) and their effect on LED performance are investigated. Open-core threading dislocations, or nanopipes, are found to conduct current through nominally insulating Al{sub 0.7}Ga{sub 0.3}N layers and limit the performance of DUV-LEDs. A defect-sensitive phosphoric acid etch reveals these open-core threading dislocations in the form of large, micron-scale hexagonal etch pits visible with optical microscopy, while closed-core screw-, edge-, and mixed-type threading dislocations are represented by smaller and more numerous nanometer-scale pits visible by atomic-force microscopy. The electrical and optical performances of DUV-LEDs fabricated on similar Si-doped Al{sub 0.7}Ga{sub 0.3}N templates are found to have a strong correlation to the density of these nanopipes, despite their small fraction (<0.1% in this study) of the total density of threading dislocations.

  12. Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate

    NASA Astrophysics Data System (ADS)

    Lee, Chia-Yu; Tzou, An-Jye; Lin, Bing-Cheng; Lan, Yu-Pin; Chiu, Ching-Hsueh; Chi, Gou-Chung; Chen, Chi-Hsiang; Kuo, Hao-Chung; Lin, Ray-Ming; Chang, Chun-Yen

    2014-09-01

    The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 × 107 cm-2 to 2.6 × 107 cm-2. Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.

  13. Near milliwatt power AlGaN-based ultraviolet light emitting diodes based on lateral epitaxial overgrowth of AlN on Si(111)

    NASA Astrophysics Data System (ADS)

    Zhang, Yinjun; Gautier, Simon; Cho, Chu-Young; Cicek, Erdem; Vashaei, Zahra; McClintock, Ryan; Bayram, Can; Bai, Yanbo; Razeghi, M.

    2013-01-01

    We report on the growth, fabrication, and device characterization of AlGaN-based thin-film ultraviolet (UV) (? ˜ 359 nm) light emitting diodes (LEDs). First, AlN/Si(111) template is patterned. Then, a fully coalesced 7-?m-thick lateral epitaxial overgrowth (LEO) of AlN layer is realized on patterned AlN/Si(111) template followed by UV LED epi-regrowth. Metalorganic chemical vapor deposition is employed to optimize LEO AlN and UV LED epitaxy. Back-emission UV LEDs are fabricated and flip-chip bonded to AlN heat sinks followed by Si(111) substrate removal. A peak pulsed power and slope efficiency of ˜0.6 mW and ˜1.3 ?W/mA are demonstrated from these thin-film UV LEDs, respectively. For comparison, top-emission UV LEDs are fabricated and back-emission LEDs are shown to extract 50% more light than top-emission ones.

  14. 227-261 nm AlGaN-based Deep Ultraviolet Light-emitting Diodes Fabricated on High-quality AlN Buffer on Sapphire

    NASA Astrophysics Data System (ADS)

    Hirayama, Hideki; Yatabe, Tohru; Noguchi, Norimichi; Kamata, Norihiko

    We demonstrated AlGaN multi-quantum well (MQW) deep ultraviolet (UV) light-emitting diodes (LEDs) with wavelength in the range of 227-261 nm fabricated on high-quality AlN buffers on sapphire substrates. We achieved crack-free, thick AlN buffer on sapphire with low threading dislocation density (TDD) and atomically flat surface by introducing an ammonia (NH3) pulse-flow multi-layer (ML) growth method through metal-organic chemical vapor deposition (MOCVD). The edge- and screw-type dislocation densities of AlGaN layer on AlN buffer were reduced to 7.5×108 and 3.8×107 cm-2, respectively, by using a ML-AlN buffer. We achieved single-peaked high-brightness operations of AlGaN deep-UV LEDs by fabricating them on the ML-AlN buffers on sapphire substrates. The maximum output power and external quantum efficiency (EQE) of the 261 nm and 227.5 nm LEDs were 1.65 mW and 0.23% under room-temperature (RT) CW operation, and 0.15 mW and 0.2%, under RT pulsed operation, respectively.

  15. Improved performance of AlGaN-based deep ultraviolet light-emitting diodes with n-AlGaN underlayers

    NASA Astrophysics Data System (ADS)

    Li, Lei; Tsutsumi, Tatsuya; Miyachi, Yuta; Miyoshi, Makoto; Egawa, Takashi

    2015-12-01

    We demonstrate notable performance improvement of 270 nm deep ultraviolet light-emitting diodes (DUV-LEDs) by inserting an n-AlGaN underlayer (UL), which was directly beneath an AlGaN multiple quantum well (MQW) active region. This DUV-LED exhibited significantly improved forward and reverse bias current-voltage characteristics, and spectral properties. As a result, the turn-on voltage was decreased from 7 to 4.6 V by introducing the n-AlGaN UL, and the maximum light output power and external quantum efficiency of DUV-LEDs with the n-AlGaN UL, obtained via on-wafer measurement, were increased by factors of 3.6 and 2.2, respectively. Further enhancements can be realized by using high-quality AlN/sapphire templates together with the n-AlGaN UL. These improvements were considered to be attributed to the introduction of the n-AlGaN UL which improved electron injection and reduced the quantum confined stark effect in the AlGaN MQWs.

  16. A facile route to realize ultraviolet emission in a nano-engineered SnO2-based light-emitting diode

    NASA Astrophysics Data System (ADS)

    Huang, Yanan; Li, Yongfeng; Yao, Bin; Ding, Zhanhui; Deng, Rui; Zhang, Ligong; Zhao, Haifeng

    2015-11-01

    We reported a facile route to fabricate a tin dioxide (SnO2)-based light-emitting diode (LED) and obtain an electrically pumped band-edge ultraviolet (UV) emission. We first investigated the photoluminescence (PL) properties of the SnO2 thin films deposited on quartz substrates annealed at various temperatures. It was found that SnO2 nanocrystals were embedded in the SnO2 amorphous matrix after annealing at 400 °C to form a SnO2 nanoparticle/amorphous hybrid film; the band-edge UV emission was observed from the hybrid film due to the hybrid structure breaking the dipole-forbidden rule of bulk SnO2. This hybrid SnO2 film was then deposited on a p-type GaN substrate to form a SnO2 hybrid film-based LED and a band-edge UV electroluminescence (EL) was observed. Our results suggest that this easy and effective approach may find extensive application in the field of optoelectronics, displays and solid-state lighting.

  17. Transparent conductive oxide films mixed with gallium oxide nanoparticle/single-walled carbon nanotube layer for deep ultraviolet light-emitting diodes

    PubMed Central

    2013-01-01

    We propose a transparent conductive oxide electrode scheme of gallium oxide nanoparticle mixed with a single-walled carbon nanotube (Ga2O3 NP/SWNT) layer for deep ultraviolet light-emitting diodes using spin and dipping methods. We investigated the electrical, optical and morphological properties of the Ga2O3 NP/SWNT layers by increasing the thickness of SWNTs via multiple dipping processes. Compared with the undoped Ga2O3 films (current level 9.9?×?10-9 A @ 1 V, transmittance 68% @ 280 nm), the current level flowing in the Ga2O3 NP/SWNT increased by approximately 4?×?105 times and the transmittance improved by 9% after 15 times dip-coating (current level 4?×?10-4 A at 1 V; transmittance 77.0% at 280 nm). These improvements result from both native high transparency of Ga2O3 NPs and high conductivity and effective current spreading of SWNTs. PMID:24295342

  18. Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate

    PubMed Central

    2014-01-01

    The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8?×?107 cm?2 to 2.6?×?107 cm?2. Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer. PMID:25258616

  19. Luminescent properties of Eu2+-doped BaGdF5 glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

    NASA Astrophysics Data System (ADS)

    Zhang, Weihuan; Zhang, Yuepin; Ouyang, Shaoye; Zhang, Zhixiong; Wang, Qian; Xia, Haiping

    2015-01-01

    Eu2+ doped transparent oxyfluoride glass ceramics containing BaGdF5 nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd3+ ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu2+ doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd3+ to Eu2+ ions, the energy transfer efficiency from Gd3+ to Eu2+ ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu2+ doped BaGdF5 glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.

  20. Luminescent properties of Eu{sup 2+}-doped BaGdF{sub 5} glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

    SciTech Connect

    Zhang, Weihuan; Zhang, Yuepin Ouyang, Shaoye; Zhang, Zhixiong; Wang, Qian; Xia, Haiping

    2015-01-14

    Eu{sup 2+} doped transparent oxyfluoride glass ceramics containing BaGdF{sub 5} nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd{sup 3+} ions at 312?nm excited with 275?nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu{sup 2+} doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions, the energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu{sup 2+} doped BaGdF{sub 5} glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.

  1. Electrical switching and memory behaviors in organic diodes based on polymer blend films treated by ultraviolet ozone

    NASA Astrophysics Data System (ADS)

    Huang, Jinying; Ma, Dongge

    2014-09-01

    Resistive memory devices with resistive switching characteristics were fabricated based on poly (3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) doping with polyvinyl alcohol. It has been demonstrated that the resistive switching characteristics in the memory device was strongly dependent on the treatment of the polymer blend film by ultraviolet ozone (UV-ozone). The UV-ozone treated device exhibited improved performance with the ON/OFF current ratio of more than 102, and its ON and OFF states can be maintained over 96 h without deterioration. The resistive switching behavior in the UV-ozone treated device was attributed to the formation and rupture of the PEDOT:PSS filaments as well as the narrow conducting paths through the native oxide of aluminum.

  2. Micro-lens array design on a flexible light-emitting diode package for indoor lighting.

    PubMed

    Lee, Hsiao-Wen; Lin, Bor-Shyh

    2015-10-01

    An advanced, ultra-thin, flexible LED (FLED) package technique is first proposed in this study, where a polyimide substrate was used as the lead frame package material due to its physical stability in thermal processing. The experimental results showed that the thickness of the mockup sample measured by a vernier caliper was 260 ?m and 35% thinner than the Panasonic organic LED lighting panel announced on 4 March 2014 in Tokyo. Moreover, the flexible angle of the ultra-thin LED package was 200.54° when it surrounded a disk with a 1 cm radius. A design of a micro-lens array manufactured by silicone molding on the FLED is also proposed in this study. Finally, different types of micro-lenses were applied to different lighting regions to investigate their lighting effects. PMID:26479655

  3. Characterization and calibration of compact array spectrometers in the ultraviolet spectral region

    SciTech Connect

    Shindo, Francois; Woolliams, Emma; Scott, Barry; Harris, Subrena

    2013-05-10

    Array-based spectrometers, with their compact size, low weight, low cost, and fast measurement time, are now frequently used in place of both conventional single-channel scanning monochromators, and broadband meters. Their rapid measurement capability makes them an attractive option for routine solar UV spectral measurements, where shortterm variability in signal is a challenge. However, compactness, portability, low cost and high speed are achieved at the expense of the spectrometer's optical and electronic performance. Thus such spectrometers are more prone to measurement error from environmental changes, and more prone to other intrinsic sources of error such as stray light and detector non-linearity, which significantly affect solar UV measurements, than a scanning monochromator. The effects of stray light and non-linearity can be reduced either by improved optical and detector design or by a detailed spectrometer characterization. We present in this paper our investigation of the performance of three different commercial array spectrometers: two mini-spectrometers, and a more elaborate array spectrometer with an on-board image amplifier device. These were tested for a subset of performance parameters: their wavelength accuracy and stability, electronic linearity, responsivity linearity, stray light sensitivity, and mechanical stability and repeatability. With all three spectrometers we found that these parameters, particularly but not limited to stray light, had a significant impact on the measurement of the incoming optical radiation. This meant that, without characterization, the instruments would be unable to accurately measure the UV component of any source with significant visible radiation. We discuss various simple and low-cost solutions for improving the performance of these instruments, and providing a rigorous calibration using a straightforward set-up including optical filters and the quasi-monochromatic light from a double monochromator.

  4. In2-XO3-Y 1D perpendicular nanostructure arrays as ultraviolet detector

    NASA Astrophysics Data System (ADS)

    Goswami, Tamal; Mondal, Aniruddha; Singh, Pankaj; Choudhuri, Bijit

    2015-10-01

    The 1D perpendicular In2-xO3-y nanostructure arrays have been synthesized by using glancing angle deposition (GLAD) technique. A low deposition rate of 0.5 A°/S produced highly porous structure. The characteristics of junction defects and photocurrent were measured to verify the detector performance. The junction capacitance and charge retention due to presence of trap states in the device decreased with an increase in frequency. The high value of Dit? 5.5 × 1017 cm-2 eV-1 was calculated for the device. The detector processes low ideality factor of ?2.04 at 300 K. The maximum photo responsivity of ?15 A/W and internal gain of ?47 were measured for the 1D In2-xO3-y based detector at ?380 nm in UV region. The device shows very high current density ?20 A/cm2 (-2 V, 300 K) under dark, which deflects to 32 A/cm2 due to illumination. Under white light on/off switching irradiation, the device operates with rise time of 1.9 s and decay time of 2.3 s. Therefore In2-xO3-y nanostructure arrays can be used as sensitive UV light detector.

  5. Vacuum ultraviolet radiation and thermal cycling effects on atomic oxygen protective photovoltaic array blanket materials

    NASA Technical Reports Server (NTRS)

    Brady, J.; Banks, B.

    1990-01-01

    The importance of synergistic environmental exposure is demonstrated through the evaluation of DuPont 93-1 in simulated LEO environment. Changes in optical properties, surface condition, and mass loss data are described. The qualitative results indicate the necessity for exposure of materials to a series of simulated LEO environments in order to properly determine synergistic effects and demonstrate the overall LEO durability of candidate materials. It is shown that synergistic effects may occur with vacuum thermal cycling combined with VUV radiation followed by atomic oxygen exposure. Testing the durability of candidate solar array blanket materials in a test sequence with necessary synergistic effects makes it possible to determine the appropriate material for providing structural support and maintaining the proper operating temperature for solar cells in the SSF Photovaltaic Power System.

  6. Enhanced light emission in vertical-structured GaN-based light-emitting diodes with trench etching and arrayed p-electrodes

    NASA Astrophysics Data System (ADS)

    Lin, Tseng-Hsing; Wang, Shui-Jinn; Tu, Yung-Chun; Hung, Chien-Hsiung; Lin, Che-An; Lin, Yung-Cheng; You, Zong-Sian

    2015-05-01

    We investigate the effect of trench etching and arrayed p-electrodes in improving current spreading and the efficiency of light extraction of GaN-based vertical-structured light-emitting diodes (VLEDs). Both simulated and experimental results on the uniformities of current distribution and light emission are presented and discussed. For a 2 × 2 array VLED with a die size of 1020 × 1020 ?m2, enhancements in light output power by 0.38% (6.03%) and wall-plug efficiency by 2.79% (2.32%) at 364.4 mA/mm2 (728.9 mA/mm2) as compared with that of regular VLED are achieved experimentally, which are attributed to improved current spreading from the arrayed p-electrode and trench designs as well as enhanced light emission from the trench region.

  7. Integration of magnetic solid phase fishing and off-line two-dimensional high-performance liquid chromatography-diode array detector-mass spectrometry for screening and identification of human serum albumin binders from Radix Astragali.

    PubMed

    Zhang, Yuping; Nie, Mingkun; Shi, Shuyun; You, Qingping; Guo, Junfang; Liu, Liangliang

    2014-03-01

    Radix Astragali is one of the most popular traditional medicinal herb and healthy dietary supplement. Isoflavonoids and astragalosides are the main bioactive ingredients. However, the systematic bioactive component analysis is inadequate so far. Then a facile method based on Fe3O4@SiO2-human serum albumin (Fe3O4@SiO2-HSA) magnetic solid phase fishing integrated with two-dimensional high-performance liquid chromatography-diode array detector-mass spectrometry (2D HPLC-DAD-MS(n)) was developed to fish out and identify HSA binders from Radix Astragali. The immobilized HSA displayed a high stability with 96.2% retained after ten consecutive cycles. 2D HPLC system (size exclusion chromatography×reversed phase chromatography, SEC×RP) were developed and optimised. Forty-seven bioactive compounds including thirty-four isoflavonoids and thirteen astragalosides were screened and identified or tentatively deduced based on their retention time, ultraviolet (UV), accurate molecular weight and diagnostic fragment ions. The results indicated that the integrated method could be widely applied for systematical fishing and identification of bioactive compounds, especially for low-abundance and overlapped compounds, from complex mixtures. PMID:24176313

  8. Simultaneous determination of catechins, rutin, and gallic acid in Cistus species extracts by HPLC with diode array detection.

    PubMed

    Santagati, Natale Alfredo; Salerno, Loredana; Attaguile, Giuseppina; Savoca, Francesca; Ronsisvalle, Giuseppe

    2008-02-01

    A simple high-performance liquid chromatography method using a diode array detector (DAD) is developed for the simultaneous analysis of five major catechins: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GCT), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), and the phenolic plant metabolites gallic acid (GA) and rutin (RT) in lyophilized extracts of Cistus species. The optimal analytical conditions are investigated to obtain the best resolution and the highest UV sensitivity for the quantitative detection of catechins. The optimized conditions (acetonitrile-phosphate buffer 50 mM, pH 2.5, gradient elution system on a C18 reversed-phase column with a flow rate of 1 mL/min and UV absorbance at 210 nm) allowed a specific and repeatable separation of the studied analytes to be achieved. All compounds are successfully separated within 32 min. Calibration curves are linear in the 2-50 microg/mL range for GCT, C, and EGCG and in the 5-50 microg/mL range for GA, EGC, EC, and RT. The limit of detection values ranged from 0.24 to 0.74 microg/mL. The limit of quantitation limit values ranged from 0.77 to 1.94 microg/mL. The validated method is applied to the determination of the specific phytochemical markers GA, GCT, C, and RT in Cistus incanus and Cistus monspeliensis lyophilised extracts. The recovery values ranged between 78.7% and 98.2%. The described HPLC method appears suitable for the differentiation and determination of the most common catechins together with the glycoside rutin and the phenolic compound gallic acid and can be considered an effective and alternative procedure for the analyses of this important class of natural compounds. PMID:18366875

  9. Quantification of maltol in Korean ginseng (Panax ginseng) products by high-performance liquid chromatography-diode array detector

    PubMed Central

    Jeong, Hyun Cheol; Hong, Hee-Do; Kim, Young-Chan; Rhee, Young Kyoung; Choi, Sang Yoon; Kim, Kyung-Tack; Kim, Sung Soo; Lee, Young-Chul; Cho, Chang-Won

    2015-01-01

    Background: Maltol, as a type of phenolic compounds, is produced by the browning reaction during the high-temperature treatment of ginseng. Thus, maltol can be used as a marker for the quality control of various ginseng products manufactured by high-temperature treatment including red ginseng. For the quantification of maltol in Korean ginseng products, an effective high-performance liquid chromatography-diode array detector (HPLC-DAD) method was developed. Materials and Methods: The HPLC-DAD method for maltol quantification coupled with a liquid-liquid extraction (LLE) method was developed and validated in terms of linearity, precision, and accuracy. An HPLC separation was performed on a C18 column. Results: The LLE methods and HPLC running conditions for maltol quantification were optimized. The calibration curve of the maltol exhibited good linearity (R2 = 1.00). The limit of detection value of maltol was 0.26 ?g/mL, and the limit of quantification value was 0.79 ?g/mL. The relative standard deviations (RSDs) of the data of the intra- and inter-day experiments were <1.27% and 0.61%, respectively. The results of the recovery test were 101.35–101.75% with an RSD value of 0.21–1.65%. The developed method was applied successfully to quantify the maltol in three ginseng products manufactured by different methods. Conclusion: The results of validation demonstrated that the proposed HPLC-DAD method was useful for the quantification of maltol in various ginseng products. PMID:26246746

  10. Self-powered ultraviolet photodetectors based on selectively grown ZnO nanowire arrays with thermal tuning performance.

    PubMed

    Bai, Zhiming; Chen, Xiang; Yan, Xiaoqin; Zheng, Xin; Kang, Zhuo; Zhang, Yue

    2014-05-28

    A self-powered Schottky-type ultraviolet photodetector with Al-Pt interdigitated electrodes has been fabricated based on selectively grown ZnO nanowire arrays. At zero bias, the fabricated photodetector exhibited high sensitivity and excellent selectivity to UV light illumination with a fast response time of 81 ms. By tuning the Schottky barrier height through the thermally induced variation of the interface chemisorbed oxygen, an ultrahigh sensitivity of 3.1 × 10(4) was achieved at 340 K without an external power source, which was 82% higher than that obtained at room temperature. According to the thermionic emission-diffusion theory and the solar cell theory, the changes in the photocurrent of the photodetector at zero bias with various system temperatures were calculated, which agreed well with the experimental data. This work demonstrates a promising approach to modulating the performance of a self-powered photodetector by heating and provides theoretical support for studying the thermal effect on the future photoelectric device. PMID:24728006

  11. Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes.

    PubMed

    Lee, Keon Hwa; Park, Hyun Jung; Kim, Seung Hwan; Asadirad, Mojtaba; Moon, Yong-Tae; Kwak, Joon Seop; Ryou, Jae-Hyun

    2015-08-10

    We study light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) using flip-chip (FC) devices with varied thickness in remaining sapphire substrate by experimental output power measurement and computational methods using 3-dimensional finite-difference time-domain (3D-FDTD) and Monte Carlo ray-tracing simulations. Light-output power of DUV-FCLEDs compared at a current of 20 mA increases with thicker sapphire, showing higher LEE for an LED with 250-?m-thick sapphire by ~39% than that with 100-?m-thick sapphire. In contrast, LEEs of visible FCLEDs show only marginal improvement with increasing sapphire thickness, that is, ~6% improvement for an LED with 250-?m-thick sapphire. 3D-FDTD simulation reveals a mechanism of enhanced light extraction with various sidewall roughness and thickness in sapphire substrates. Ray tracing simulation examines the light propagation behavior of DUV-FCLED structures. The enhanced output power and higher LEE strongly depends on the sidewall roughness of the sapphire substrate rather than thickness itself. The thickness starts playing a role only when the sapphire sidewalls become rough. The roughened surface of sapphire sidewall during chip-separation process is critical for TM-polarized photons from AlGaN quantum wells to escape in lateral directions before they are absorbed by p-GaN and Au-metal. Furthermore, the ray tracing results show a reasonably good agreement with the experimental result of the LEE. PMID:26367889

  12. The effect of free-standing GaN substrate on carrier localization in ultraviolet InGaN light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Tsai, Ming-Ta; Chu, Chung-Ming; Huang, Che-Hsuan; Wu, Yin-Hao; Chiu, Ching-Hsueh; Li, Zhen-Yu; Tu, Po-Min; Lee, Wei-I.; Kuo, Hao-Chung

    2014-12-01

    In this study, we have grown 380-nm ultraviolet light-emitting diodes (UV-LEDs) based on InGaN/AlInGaN multiple quantum well (MQW) structures on free-standing GaN (FS-GaN) substrate by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD), and investigated the relationship between carrier localization degree and FS-GaN. The micro-Raman shift peak mapping image shows low standard deviation (STD), indicating that the UV-LED epi-wafer of low curvature and MQWs of weak quantum-confined Stark effect (QCSE) were grown. High-resolution X-ray diffraction (HRXRD) analyses demonstrated high-order satellite peaks and clear fringes between them for the UV-LEDs grown on the FS-GaN substrate, from which the interface roughness (IRN) was estimated. The temperature-dependent photoluminescence (PL) measurement confirmed that the UV-LEDs grown on the FS-GaN substrate exhibited better carrier confinement. Besides, the high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) mapping images verified that the UV-LEDs on FS-GaN have fairly uniform distribution of indium and more ordered InGaN/AlInGaN MQW structure. Clearly, the FS-GaN can not only improve the light output power but also reduce the efficiency droop phenomenon at high injection current. Based on the results mentioned above, the FS-GaN can offer UV-LEDs based on InGaN/AlInGaN MQW structures with benefits, such as high crystal quality and small carrier localization degree, compared with the UV-LEDs on sapphire.

  13. High performance 380-nm ultraviolet light-emitting-diodes with 3% efficiency droop by using free-standing GaN substrate manufacturing from GaAs substrate

    NASA Astrophysics Data System (ADS)

    Shieh, Chen-Yu; Tsai, Ming-Ta; Li, Zhen-Yu; Kuo, Hao-Chung; Chang, Jenq-Yang; Chi, Gou-Chung; Lee, Wei-I.

    2014-01-01

    We investigated the influence of free-standing GaN (FS-GaN) substrates on the performance of ultraviolet light-emitting-diodes (UV-LEDs) grown on top by atmospheric pressure metal-organic chemical vapor deposition. High-resolution double-crystal x-ray diffraction (HRDCXD) analysis demonstrated high-order satellite peaks and clear fringes between them for UV-LEDs grown on the FS-GaN substrate, from which the interface roughness was estimated. In addition, the full width at half maximum of the HRDCXD rocking curve in the (0002) and the (10 1¯ 2) reflections were reduced to below 90 arc sec. The Raman results indicated that the GaN-based epilayer of strain free was grown. Additionally, the effect of the FS-GaN substrate on the crystal quality of the UV-LEDs was examined in detail by transmission electron microscopy (TEM). The TEM characterizations revealed no defects and V-pits were found in the scanned area. Based on the results mentioned above, the light output power of UV-LEDs on the FS-GaN substrate can be enhanced drastically by 80% and 90% at 20 and 100 mA, respectively. Furthermore, an ultralow efficiency degradation of about 3% can be obtained for the UV-LEDs on the FS-GaN substrate at a high injection current. The use of an FS-GaN substrate is suggested to be effective for improving the emission efficiency and droop of UV-LEDs grown thereon.

  14. Optimizing the accuracy of a helical diode array dosimeter: A comprehensive calibration methodology coupled with a novel virtual inclinometer

    SciTech Connect

    Kozelka, Jakub; Robinson, Joshua; Nelms, Benjamin; Zhang, Geoffrey; Savitskij, Dennis; Feygelman, Vladimir

    2011-09-15

    Purpose: The goal of any dosimeter is to be as accurate as possible when measuring absolute dose to compare with calculated dose. This limits the uncertainties associated with the dosimeter itself and allows the task of dose QA to focus on detecting errors in the treatment planning (TPS) and/or delivery systems. This work introduces enhancements to the measurement accuracy of a 3D dosimeter comprised of a helical plane of diodes in a volumetric phantom. Methods: We describe the methods and derivations of new corrections that account for repetition rate dependence, intrinsic relative sensitivity per diode, field size dependence based on the dynamic field size determination, and positional correction. Required and described is an accurate ''virtual inclinometer'' algorithm. The system allows for calibrating the array directly against an ion chamber signal collected with high angular resolution. These enhancements are quantitatively validated using several strategies including ion chamber measurements taken using a ''blank'' plastic shell mimicking the actual phantom, and comparison to high resolution dose calculations for a variety of fields: static, simple arcs, and VMAT. A number of sophisticated treatment planning algorithms were benchmarked against ion chamber measurements for their ability to handle a large air cavity in the phantom. Results: Each calibration correction is quantified and presented vs its independent variable(s). The virtual inclinometer is validated by direct comparison to the gantry angle vs time data from machine log files. The effects of the calibration are quantified and improvements are seen in the dose agreement with the ion chamber reference measurements and with the TPS calculations. These improved agreements are a result of removing prior limitations and assumptions in the calibration methodology. Average gamma analysis passing rates for VMAT plans based on the AAPM TG-119 report are 98.4 and 93.3% for the 3%/3 mm and 2%/2 mm dose-error/distance to agreement threshold criteria, respectively, with the global dose-error normalization. With the local dose-error normalization, the average passing rates are reduced to 94.6 and 85.7% for the 3%/3 mm and 2%/2 mm criteria, respectively. Some algorithms in the convolution/superposition family are not sufficiently accurate in predicting the exit dose in the presence of a 15 cm diameter air cavity. Conclusions: Introduction of the improved calibration methodology, enabled by a robust virtual inclinometer algorithm, improves the accuracy of the dosimeter's absolute dose measurements. With our treatment planning and delivery chain, gamma analysis passing rates for the VMAT plans based on the AAPM TG-119 report are expected to be above 91% and average at about 95% level for {gamma}(3%/3 mm) with the local dose-error normalization. This stringent comparison methodology is more indicative of the true VMAT system commissioning accuracy compared to the often quoted dose-error normalization to a single high value.

  15. Macroscopic Violation of Three Cauchy-Schwarz Inequalities Using Correlated Light Beams From an Infra-Red Emitting Semiconductor Diode Array

    NASA Technical Reports Server (NTRS)

    Edwards, P. J.; Huang, X.; Li, Y. Q. (Editor); Wang, Y. Z. (Editor)

    1996-01-01

    We briefly review quantum mechanical and semi-classical descriptions of experiments which demonstrate the macroscopic violation of the three Cauchy-Schwarz inequalities: g(sup 2)(sub 11)(0) greater than or equal to 1; g(sup 2)(sub 11)(0) greater than or equal to g(sup 2)(sub 11)(t), (t approaches infinity); (the absolute value of g(sup 2)(sub 11)(0))(exp 2) less than or equal to g(sup 2)(sub 11)(0) g(sup 2)(sub 11)(0). Our measurements demonstrate the violation, at macroscopic intensities, of each of these inequalities. We show that their violation, although weak, can be demonstrated through photodetector current covariance measurements on correlated sub-Poissonian Poissonian, and super Poissonian light beams. Such beams are readily generated by a tandem array of infrared-emitting semiconductor junction diodes. Our measurements utilize an electrically coupled array of one or more infrared-emitting diodes, optically coupled to a detector array. The emitting array is operated in such a way as to generate highly correlated beams of variable photon Fano Factor. Because the measurements are made on time scales long compared with the first order coherence time and with detector areas large compared with the corresponding coherence areas, first order interference effects are negligible. The first and second inequalities are violated, as expected, when a sub-Poissonian light beam is split and the intensity fluctuations of the two split beams are measured by two photodetectors and subsequently cross-correlated. The third inequality is violated by bunched (as well as anti-bunched) beams of equal intensity provided the measured cross correlation coefficient exceeds (F - 1)/F, where F is the measured Fano Factor of each beam. We also investigate the violation for the case of unequal beams.

  16. Integrating qualitative and quantitative characterization of traditional Chinese medicine injection by high-performance liquid chromatography with diode array detection and tandem mass spectrometry.

    PubMed

    Xie, Yuan-yuan; Xiao, Xue; Luo, Juan-min; Fu, Chan; Wang, Qiao-wei; Wang, Yi-ming; Liang, Qiong-lin; Luo, Guo-an

    2014-06-01

    The present study aims to describe and exemplify an integrated strategy of the combination of qualitative and quantitative characterization of a multicomponent mixture for the quality control of traditional Chinese medicine injections with the example of Danhong injection (DHI). The standardized chemical profile of DHI has been established based on liquid chromatography with diode array detection. High-performance liquid chromatography coupled with time-of-flight mass spectrometry and high-performance liquid chromatography with electrospray multistage tandem ion-trap mass spectrometry have been developed to identify the major constituents in DHI. The structures of 26 compounds including nucleotides, phenolic acids, and flavonoid glycosides were identified or tentatively characterized. Meanwhile, the simultaneous determination of seven marker constituents, including uridine, adenosine, danshensu, protocatechuic aldehyde, p-coumaric acid, rosmarinic acid, and salvianolic acid B, in DHI was performed by multiwavelength detection based on high-performance liquid chromatography with diode array detection. The integrated qualitative and quantitative characterization strategy provided an effective and reliable pattern for the comprehensive and systematic characterization of the complex traditional Chinese medicine system. PMID:24723550

  17. Quality assessment of crude and processed ginger by high-performance liquid chromatography with diode array detection and mass spectrometry combined with chemometrics.

    PubMed

    Deng, Xianmei; Yu, Jiangyong; Zhao, Ming; Zhao, Bin; Xue, Xingyang; Che, ChunTao; Meng, Jiang; Wang, Shumei

    2015-09-01

    A sensitive, simple, and validated high-performance liquid chromatography with diode array detection and mass spectrometry detection method was developed for three ginger-based traditional Chinese herbal drugs, Zingiberis Rhizoma, Zingiberis Rhizome Preparatum, and Zingiberis Rhizome Carbonisata. Chemometrics methods, such as principal component analysis, hierarchical cluster analysis, and analysis of variance, were also employed in the data analysis. The results clearly revealed significant differences among Zingiberis Rhizoma, Zingiberis Rhizome Preparatum, and Zingiberis Rhizome Carbonisata, indicating variations in their chemical compositions during the processing, which may elucidate the relationship of the thermal treatment with the change of the constituents and interpret their different clinical uses. Furthermore, the sample consistency of Zingiberis Rhizoma, Zingiberis Rhizome Preparatum, and Zingiberis Rhizome Carbonisata can also be visualized by high-performance liquid chromatography with diode array detection and mass spectrometry analysis followed by principal component analysis/hierarchical cluster analysis. The comprehensive strategy of liquid chromatography with mass spectrometry analysis coupled with chemometrics should be useful in quality assurance for ginger-based herbal drugs and other herbal medicines. PMID:26174663

  18. High-performance GaSb laser diodes and diode arrays in the 2.1-3.3 micron wavelength range for sensing and defense applications

    NASA Astrophysics Data System (ADS)

    Dvinelis, Edgaras; TrinkÅ«nas, Augustinas; Greibus, Mindaugas; Kaušylas, Mindaugas; Žukauskas, Tomas; Å imonytÄ--, Ieva; Songaila, RamÅ«nas; Vizbaras, Augustinas; Vizbaras, Kristijonas

    2015-01-01

    Mid-infrared spectral region (2-4 ?m) is gaining significant attention recently due to the presence of numerous enabling applications in the field of gas sensing, medical, and defense applications. Gas sensing in this spectral region is attractive due to the presence of numerous absorption lines for such gases as methane, ethane, ozone, carbon dioxide, carbon monoxide, etc. Sensing of the mentioned gas species is of particular importance for applications such as atmospheric LIDAR, petrochemical industry, greenhouse gas monitoring, etc. Defense applications benefit from the presence of covert atmospheric transmission window in the 2.1-2.3 micron band which is more eye-safe and offers less Rayleigh scattering than the conventional atmospheric windows in the near-infrared. Major requirement to enable these application is the availability of high-performance, continuous-wave laser sources in this window. Type-I GaSb-based laser diodes are ideal candidates for these applications as they offer direct emission possibility, high-gain and continuous wave operation. Moreover, due to the nature of type-I transition, these devices have a characteristic low operation voltage, which results in very low input powers and high wall-plug efficiency. In this work, we present recent results of 2 ?m - 3.0 ?m wavelength room-temperature CW light sources based on type-I GaSb developed at Brolis Semiconductors. We discuss performance of defense oriented high-power multimode laser diodes with < 1 W CW power output with over 30 % WPE as well as ~ 100 mW single TE00 Fabry-Perot chips. In addition, recent development efforts on sensing oriented broad gain superluminescent gain chips will be presented.

  19. The feasibility study and characterization of a two-dimensional diode array in “magic phantom” for high dose rate brachytherapy quality assurance

    SciTech Connect

    Espinoza, A.; Beeksma, B.; Petasecca, M.; Fuduli, I.; Porumb, C.; Cutajar, D.; Lerch, M. L. F.; Rosenfeld, A. B.; Corde, S.; Jackson, M.

    2013-11-15

    Purpose: High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly {sup 192}Ir with an air KERMA strength range between 20 000 and 40 000 U, where 1 U = 1 ?Gy m{sup 2}/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named “magic phantom.”Methods: The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array “magic plate” (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the {sup 192}Ir source, sampled at 100 ms intervals by a fast data acquisition (DAQ) system. Using a {sup 192}Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ.Results: The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm the relative response of the epitaxial diodes used in the MP is in good agreement (within 8%) with radial dose function measurements found within the TG-43 protocol, with SDD of up to 70 mm showing a 40% over response. A method for four-dimensional localization of the HDR source was developed, allowing the source dwell position to be derived within 0.50 mm of the expected position. An estimation of the average transit speed for varying step sizes was determined and was found to increase from (12.8 ± 0.3) up to (38.6 ± 0.4) cm/s for a step size of 2.5 and 50 mm, respectively.Conclusions: Our characterization of the designed QA “magic phantom” with MP in realistic HDR photon fields demonstrates the promising performance for real-time source position tracking in four dimensions and measurements of transit times. Further development of this system will allow a full suite for QA in HDR brachytherapy and analysis, and for future in vivo tracking.

  20. Ultraviolet Extensions

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Side-by-Side Comparison Click on image for larger view

    This ultraviolet image from NASA's Galaxy Evolution Explorer shows the Southern Pinwheel galaxy, also know as Messier 83 or M83. It is located 15 million light-years away in the southern constellation Hydra.

    Ultraviolet light traces young populations of stars; in this image, young stars can be seen way beyond the main spiral disk of M83 up to 140,000 light-years from its center. Could life exist around one of these far-flung stars? Scientists say it's unlikely because the outlying regions of a galaxy are lacking in the metals required for planets to form.

    The image was taken at scheduled intervals between March 15 and May 20, 2007. It is one of the longest-exposure, or deepest, images ever taken of a nearby galaxy in ultraviolet light. Near-ultraviolet light (or longer-wavelength ultraviolet light) is colored yellow, and far-ultraviolet light is blue.

    What Lies Beyond the Edge of a Galaxy The side-by-side comparison shows the Southern Pinwheel galaxy, or M83, as seen in ultraviolet light (right) and at both ultraviolet and radio wavelengths (left). While the radio data highlight the galaxy's long, octopus-like arms stretching far beyond its main spiral disk (red), the ultraviolet data reveal clusters of baby stars (blue) within the extended arms.

    The ultraviolet image was taken by NASA's Galaxy Evolution Explorer between March 15 and May 20, 2007, at scheduled intervals. Back in 2005, the telescope first photographed M83 over a shorter period of time. That picture was the first to reveal far-flung baby stars forming up to 63,000 light-years from the edge of the main spiral disk. This came as a surprise to astronomers because a galaxy's outer territory typically lacks high densities of star-forming materials.

    The newest picture of M83 from the Galaxy Evolution Explorer is shown at the right, and was taken over a longer period of time. In fact, it is one of the 'deepest,' or longest-exposure, images of a nearby galaxy in ultraviolet light. This deeper view shows more clusters of stars, as well as stars in the very remote reaches of the galaxy, up to 140,000 light-years away from its core.

    The view at the left is a combination of the ultraviolet picture at the right and data taken by the telescopes of the National Science Foundation's Very Large Array in New Mexico. The radio data, colored here in red, reveal extended galactic arms of gaseous hydrogen atoms, which are raw ingredients for stars. Astronomers are excited that the remote clusters of baby stars match up with the extended arms, because this helps them better understand how stars can be created out in the boondocks of a galaxy.

    M83 is located 15 million light-years away in the southern constellation Hydra.

    In the Galaxy Evolution Explorer image on the right, near-ultraviolet light (or longer-wavelength ultraviolet light) is colored yellow and far-ultraviolet light is blue. In the combined image at the left, far-ultraviolet light is blue, near-ultraviolet light is green, and the radio emission at a wavelength of 21 centimeters is red.

  1. Determination of the anthraquinones aloe-emodin and aloin-A by liquid chromatography with mass spectrometric and diode array detection.

    PubMed

    Elsohly, Mahmoud A; Gul, Waseem; Avula, Bharathi; Khan, Ikhlas A

    2007-01-01

    Methods using liquid chromatography/mass spectrometry (LC/MS) and LC with diode array detection (DAD) in the UV range (LC/UV) were developed for the determination of low levels of the anthraquinones aloe-emodin and aloin-A (barbaloin) in aloe-based products. The methods were used to analyze several commercial products (liquids, semisolids, and solids) for the 2 anthraquinones. The wavelengths used for quantification of aloin-A, aloe-emodin, and emodin (internal standard) by DAD were 357, 257, and 289 nm, respectively. The on-column sensitivities were 0.25 and 0.05 ng by LC/UV and 0.01 and 0.025 ng by LC/MS for aloin-A and aloe-emodin, respectively. The methods are simple and sensitive and provide reproducible results; therefore, they are suitable for the determination of these anthraquinones in various aloe-based products. PMID:17373434

  2. Simultaneous Detection of Sulfamethoxazole, Diclofenac, Carbamazepine, and Bezafibrate by Solid Phase Extraction and High Performance Liquid Chromatography with Diode Array Detection

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Jiang, J.-Q.

    2014-05-01

    A method of solid phase extraction (SPE) coupled with high performance liquid chromatography and diode array detection (HPLC-DAD) was studied for the simultaneous determination of sulfamethoxazole (SMX), diclofenac (DCF), carbamazepine (CBZ), and bezafi brate (BZF) in test solutions. The target compounds were extracted by SPE from samples, and the resulting elutes were analyzed using a HPLC-DAD system at wavelengths of 270, 280, 290, and 230 nm for SMX, DCF, CBZ, and BZF, respectively. This method shows good recoveries for SMX, DCF, CBZ, and BZF with mean recoveries of 89.7 ± 9.3%, 86.1 ± 7.6%, 95.0 ± 6.5%, and 94.0 ± 5.4%, respectively.

  3. Characterization of Compounds in Psoralea corylifolia Using High-Performance Liquid Chromatography Diode Array Detection, Time-of-Flight Mass Spectrometry and Quadrupole Ion Trap Mass Spectrometry.

    PubMed

    Tan, Guangguo; Yang, Tiehong; Miao, Huayan; Chen, Hao; Chai, Yifeng; Wu, Hong

    2015-10-01

    High-performance liquid chromatography with diode array detection (HPLC-DAD), time-of-flight mass spectrometry (HPLC-TOFMS) and quadrupole ion trap mass spectrometry (HPLC-QITMS) were used for separation and identification of multi-components in Psoralea corylifolia. Benefiting from combining the accurate mass measurement of HPLC-TOFMS to generate elemental compositions, the complementary multilevel structural information provided by HPLC-QITMS and the characteristic UV spectra obtained from HPLC-DAD, 24 components in P. corylifolia were identified. The five groups of isomers were differentiated based on the fragmentation behaviors in QITMS and UV spectra. It can be concluded that an effective method based on the combination of HPLC-DAD, HPLC-TOFMS and HPLC-QITMS for identification of chemical components in P. corylifolia was established. The results provide essential data for further pharmacological and clinical studies of P. corylifolia and facilitate the rapid quality control of the crude drug. PMID:25903696

  4. High efficiency 2 micrometer laser utilizing wing-pumped Tm.sup.3+ and a laser diode array end-pumping architecture

    DOEpatents

    Beach, Raymond J. (Livermore, CA)

    1997-01-01

    Wing pumping a Tm.sup.3+ doped, end pumped solid state laser generates 2 .mu.m laser radiation at high average powers with high efficiency. Using laser diode arrays to end-pump the laser rod or slab in the wing of the Tm.sup.3+ absorption band near 785 nm results in 2-for-1 quantum efficiency in Tm.sup.3+ because high Tm.sup.3+ concentrations can be used. Wing pumping allows the thermal power generated in the rod or slab to be distributed over a large enough volume to make thermal management practical in the laser gain medium even at high average power operation. The approach is applicable to CW, Q-switched, and rep-pulsed free-laser operation.

  5. High efficiency 2 micrometer laser utilizing wing-pumped Tm{sup 3+} and a laser diode array end-pumping architecture

    DOEpatents

    Beach, R.J.

    1997-11-18

    Wing pumping a Tm{sup 3+} doped, end pumped solid state laser generates 2 {micro}m laser radiation at high average powers with high efficiency. Using laser diode arrays to end-pump the laser rod or slab in the wing of the Tm{sup 3+} absorption band near 785 nm results in 2-for-1 quantum efficiency in Tm{sup 3+} because high Tm{sup 3+} concentrations can be used. Wing pumping allows the thermal power generated in the rod or slab to be distributed over a large enough volume to make thermal management practical in the laser gain medium even at high average power operation. The approach is applicable to CW, Q-switched, and rep-pulsed free-laser operation. 7 figs.

  6. Far ultraviolet sensitivity of silicon CMOS sensors

    NASA Astrophysics Data System (ADS)

    Davis, Michael W.; Greathouse, Thomas K.; Retherford, Kurt D.; Winters, Gregory S.; Bai, Yibin; Beletic, James W.

    2012-07-01

    We describe vacuum ultraviolet sensitivity measurements of a new high performance silicon-based CMOS sensor from Teledyne Imaging Sensors. These sensors do not require the high voltages of MCP detectors, making them a lower mass and power alternative to the more mature MCP technology. These devices demonstrate up to 40 percent quantum efficiency at vacuum ultraviolet wavelengths, either meeting or greatly exceeding 10 percent quantum efficiency across the entire 100-200 nm wavelength region. As with similar visible sensitive devices, backside illumination results in a higher quantum efficiency than frontside illumination. Measurements of the vacuum ultraviolet sensitivity of the Teledyne silicon PIN detectors were made by directing a known intensity of ultraviolet light at discrete wavelengths onto the test detectors and reading out the resulting photocurrent. The sensitivity of the detector at a given wavelength was then calculated from the intensity and wavelength of the incoming light and the relative photodiode to NIST-traceable calibration diode active areas. A custom electromechanical interface was developed to make these measurements within the SwRI Vacuum Radiometric Calibration Chamber. While still in the single pixel stage, full 1K × 1K focal plane arrays are possible using existing CMOS readout electronics and hold great promise for inclusion in future spaceflight instrument concepts.

  7. Self-Injection Locking Of Diode Lasers

    NASA Technical Reports Server (NTRS)

    Hemmati, H.

    1991-01-01

    Simple optical coupling scheme locks array of gain-guided diode lasers into oscillation in single mode and with single-lobed output beam. Selective feedback from thin etalon self-injection-locks array into desired mode. One application of new scheme for pumping of neodymium: yttrium aluminum garnet lasers with diode-laser arrays.

  8. Photovoltaic module bypass diode encapsulation

    NASA Technical Reports Server (NTRS)

    Shepard, N. J., Jr.

    1983-01-01

    The design and processing techniques necessary to incorporate bypass diodes within the module encapsulant are presented. The Semicon PN junction diode cells were selected. Diode junction to heat spreader thermal resistance measurements, performed on a variety of mounted diode chip types and sizes, have yielded values which are consistently below 1 deg C per watt, but show some instability when thermally cycled over the temperature range from -40 to 150 deg C. Three representative experimental modules, each incorporating integral bypass diode/heat spreader assemblies of various sizes, were designed. Thermal testing of these modules enabled the formulation of a recommended heat spreader plate sizing relationship. The production cost of three encapsulated bypass diode/heat spreader assemblies were compared with similarly rated externally mounted packaged diodes. It is concluded that, when proper designed and installed, these bypass diode devices will improve the overall reliability of a terrestrial array over a 20 year design lifetime.

  9. High-speed GaN/GaInN nanowire array light-emitting diode on silicon(111).

    PubMed

    Koester, Robert; Sager, Daniel; Quitsch, Wolf-Alexander; Pfingsten, Oliver; Poloczek, Artur; Blumenthal, Sarah; Keller, Gregor; Prost, Werner; Bacher, Gerd; Tegude, Franz-Josef

    2015-04-01

    The high speed on-off performance of GaN-based light-emitting diodes (LEDs) grown in c-plane direction is limited by long carrier lifetimes caused by spontaneous and piezoelectric polarization. This work demonstrates that this limitation can be overcome by m-planar core-shell InGaN/GaN nanowire LEDs grown on Si(111). Time-resolved electroluminescence studies exhibit 90-10% rise- and fall-times of about 220 ps under GHz electrical excitation. The data underline the potential of these devices for optical data communication in polymer fibers and free space. PMID:25758029

  10. Effects of Mg-doped AlN/AlGaN superlattices on properties of p-GaN contact layer and performance of deep ultraviolet light emitting diodes

    SciTech Connect

    Al tahtamouni, T. M.; Lin, J. Y.; Jiang, H. X.

    2014-04-15

    Mg-doped AlN/AlGaN superlattice (Mg-SL) and Mg-doped AlGaN epilayers have been investigated in the 284 nm deep ultraviolet (DUV) light emitting diodes (LEDs) as electron blocking layers. It was found that the use of Mg-SL improved the material quality of the p-GaN contact layer, as evidenced in the decreased density of surface pits and improved surface morphology and crystalline quality. The performance of the DUV LEDs fabricated using Mg-SL was significantly improved, as manifested by enhanced light intensity and output power, and reduced turn-on voltage. The improved performance is attributed to the enhanced blocking of electron overflow, and enhanced hole injection.

  11. KOH based selective wet chemical etching of AlN, Al{sub x}Ga{sub 1?x}N, and GaN crystals: A way towards substrate removal in deep ultraviolet-light emitting diode

    SciTech Connect

    Guo, W. Kirste, R.; Bryan, I.; Bryan, Z.; Hussey, L.; Reddy, P.; Collazo, R.; Sitar, Z.; Tweedie, J.

    2015-02-23

    A controllable and smooth potassium hydroxide-based wet etching technique was developed for the AlGaN system. High selectivity between AlN and Al{sub x}Ga{sub 1?x}N (up to 12×) was found to be critical in achieving effective substrate thinning or removal for AlGaN-based deep ultraviolet light emitting diodes, thus increasing light extraction efficiency. The mechanism of high selectivity of AlGaN as a function of Al composition can be explained as related to the formation and dissolution of oxide/hydroxide on top of N-polar surface. Cross-sectional transmission electron microscopic analysis served as ultimate proof that these hillocks were not related to underlying threading dislocations.

  12. Nanospherical-lens lithographical Ag nanodisk arrays embedded in p-GaN for localized surface plasmon-enhanced blue light emitting diodes

    SciTech Connect

    Wei, Tongbo Wu, Kui; Sun, Bo; Zhang, Yonghui; Chen, Yu; Huo, Ziqiang; Hu, Qiang; Wang, Junxi; Zeng, Yiping; Li, Jinmin; Lan, Ding

    2014-06-15

    Large-scale Ag nanodisks (NDs) arrays fabricated using nanospherical-lens lithography (NLL) are embedded in p-GaN layer of an InGaN/GaN light-emitting diode (LED) for generating localized surface plasmon (LSP) coupling with the radiating dipoles in the quantum-well (QWs). Based on the Ag NDs with the controlled surface coverage, LSP leads to the improved crystalline quality of regrowth p-GaN, increased photoluminescence (PL) intensity, reduced PL decay time, and enhanced output power of LED. Compared with the LED without Ag NDs, the optical output power at a current of 350 mA of the LSP-enhanced LEDs with Ag NDs having a distance of 20 and 35 nm to QWs is increased by 26.7% and 31.1%, respectively. The electrical characteristics and optical properties of LEDs with embedded Ag NPs are dependent on the distance of between Ag NPs and QWs region. The LED with Ag NDs array structure is also found to exhibit reduced emission divergence, compared to that without Ag NDs.

  13. Luminescent properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Yao, Shanshan; Chen, Donghua

    2007-12-01

    In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs) used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated. The crystallization and particle sizes of Li2 (Ca0.99, Eu0.01) SiO4: B3+ has been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by UV to the visible region, and exhibited bluish green light with a peak of 480 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li2 (Ca0.99, Eu0.01) SiO4: B3+ and the optimum molar ratio of boric acid to calcium nitrate was about 0.06. The optimized phosphors Li2 (Ca0.99, Eu0.01) SiO4: B{0.06/3+} showed 180% improved emission intensity compared with that of the Li2 (Ca0.99, Eu0.01) SiO4 phosphors under ultraviolet (?ex =287 nm) excitation.

  14. Measurement and Simulation of the Variation in Proton-Induced Energy Deposition in Large Silicon Diode Arrays

    NASA Technical Reports Server (NTRS)

    Howe, Christina L.; Weller, Robert A.; Reed, Robert A.; Sierawski, Brian D.; Marshall, Paul W.; Marshall, Cheryl J.; Mendenhall, Marcus H.; Schrimpf, Ronald D.

    2007-01-01

    The proton induced charge deposition in a well characterized silicon P-i-N focal plane array is analyzed with Monte Carlo based simulations. These simulations include all physical processes, together with pile up, to accurately describe the experimental data. Simulation results reveal important high energy events not easily detected through experiment due to low statistics. The effects of each physical mechanism on the device response is shown for a single proton energy as well as a full proton space flux.

  15. Degradation of the Adhesive Properties of MD-944 Diode Tape by Simulated Low Earth Orbit Environmental Factors

    NASA Technical Reports Server (NTRS)

    Albyn, K.; Finckenor, M.

    2006-01-01

    The International Space Station (ISS) solar arrays utilize MD-944 diode tape with silicone pressure-sensitive adhesive to protect the underlying diodes and also provide a high-emittance surface. On-orbit, the silicone adhesive will be exposed and ultimately convert to a glass-like silicate due to atomic oxygen (AO). The current operational plan is to retract ISS solar array P6 and leave it stored under load for a long duration (6 mo or more). The exposed silicone adhesive must not cause the solar array to stick to itself or cause the solar array to fail during redeployment. The Environmental Effects Branch at Marshall Space Flight Center, under direction from the ISS Program Office Environments Team, performed simulated space environment exposures with 5-eV AO, near ultraviolet radiation and ionizing radiation. The exposed diode tape samples were put under preload and then the resulting blocking force was measured using a tensile test machine. Test results indicate that high-energy AO, ultraviolet radiation, and electron ionizing radiation exposure all reduce the blocking force for a silicone-to-silicone bond. AO exposure produces the most significant reduction in blocking force

  16. INVITED PAPER: III-nitride micro-emitter arrays: development and applications

    NASA Astrophysics Data System (ADS)

    Fan, Z. Y.; Lin, J. Y.; Jiang, H. X.

    2008-05-01

    III-nitride micro-emitter array technology was developed in the authors' laboratory around 1999. Since its inception, much progress has been made by several groups and the technology has led to the invention of several novel devices. This paper provides an overview on recent progress in single-chip ac-micro-size light emitting diodes (?LEDs) that can be plugged directly into standard high ac voltage power outlets, self-emissive microdisplays and interconnected ?LEDs for boosting light emitting diodes's wall-plug efficiency, all of which were evolved from III-nitride micro-emitter array technology. Finally, potential applications of III-nitride visible micro-emitter arrays as a light source for DNA microarrays and future prospects of III-nitride deep ultraviolet micro-emitter arrays for label-free protein analysis in microarray format by taking advantage of the direct excitation of intrinsic protein fluorescence are discussed.

  17. High performance liquid chromatography-diode array and electrospray-mass spectrometry analysis of vardenafil, sildenafil, tadalafil, testosterone and local anesthetics in cosmetic creams sold on the Internet web sites.

    PubMed

    De Orsi, Daniela; Pellegrini, Manuela; Marchei, Emilia; Nebuloni, Paolo; Gallinella, Bruno; Scaravelli, Giulia; Martufi, Alessio; Gagliardi, Luigi; Pichini, Simona

    2009-10-15

    A simple high-performance liquid chromatography (HPLC) method with ultraviolet diode array (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of vardenafil, sildenafil, tadalafil, testosterone, procaine, lidocaine, prilocaine, and benzocaine in cosmetic creams sold as promising remedies for male erectile dysfunction and female genitals stimulation. The presence of these substances in commercial cosmetic samples is prohibited. Aliquots (1 g) of the cosmetic creams under investigation were diluted 1:100 in methanol, subjected to ultrasonic treatment, added with benzoic acid as internal standard, and analyzed by HPLC-DAD and HPLC-ESI-MS after a further 1:1000 dilution. The compounds were separated by reversed phase chromatography with water (0.02% trifluoroacetic acid) and acetonitrile gradient elution and detected by UV-DAD at 228, 255 and 290 nm and by ESI-MS positive ionisation mode. Benzoic acid was used as internal standard. Linearity was studied with UV-DAD detection from 2.5-7.8 to 250 microg/g range, depending on the different compounds and with ESI-MS in the 3.3-8.9 to 250 ng/g range. Good determination coefficients (r(2) > or = 0.99) were found in both UV-DAD and ESI-MS. Limits of quantifications ranged between 2.5 and 7.8 microg/g for HPLC-UV-DAD assay and between 3.3 and 8.9 ng/g for HPLC-ESI-MS assay depending on different analyzed substances. At three concentrations spanning the linear dynamic ranges of both UV-DAD and ESI-MS assay, mean recoveries were always higher than 90% for the different analytes and intra-assay and inter-assay precision always better than 15% and 12%. This method was successfully applied to the analysis of substances under investigations present in cosmetic creams, freely sold on the Internet web-sites. PMID:19540086

  18. Fibre coupled micro-light emitting diode array light source with integrated band-pass filter for fluorescence detection in miniaturised analytical systems.

    PubMed

    Vaculovi?ová, Markéta; Akther, Mahbub; Maaskant, Pleun; Brabazon, Dermot; Macka, Mirek

    2015-04-29

    In this work, a new type of miniaturized fibre-coupled solid-state light source is demonstrated as an excitation source for fluorescence detection in capillary electrophoresis. It is based on a parabolically shaped micro-light emitting diode (?-LED) array with a custom band-pass optical interference filter (IF) deposited at the back of the LED substrate. The GaN ?-LED array consisted of 270 individual ?-LED elements with a peak emission at 470 nm, each about 14 ?m in diameter and operated as a single unit. Light was extracted through the transparent substrate material, and coupled to an optical fibre (OF, 400 ?m in diameter, numerical aperture NA=0.37), to form an integrated ?-LED-IF-OF light source component. This packaged ?-LED-IF-OF light source emitted approximately 225 ?W of optical power at a bias current of 20 mA. The bandpass IF filter was designed to reduce undesirable LED light emissions in the wavelength range above 490 nm. Devices with and without IF were compared in terms of the optical power output, spectral characteristics as well as LOD values. While the IF consisted of only 7.5 pairs (15 layers) of SiO2/HfO2 layers, it resulted in an improvement of the baseline noise as well as the detection limit measured using fluorescein as test analyte, both by approximately one order of magnitude, with a LOD of 1×10(-8) mol L(-1) obtained under optimised conditions. The ?-LED-IF-OF light source was then demonstrated for use in capillary electrophoresis with fluorimetric detection. The limits of detection obtained by this device were compared to those obtained with a commercial fibre coupled LED device. PMID:25847165

  19. Simultaneous determination of 10 active components in Baizhu Shaoyao San and its single herbs by high-performance liquid chromatography coupled with diode array detection.

    PubMed

    Zheng, Lijuan; Zhang, Miao; Qin, Kunming; Cai, Hao; Cao, Gang; Cai, Baochang

    2015-04-01

    Baizhu Shaoyao San (BSS) is a famous traditional Chinese medicinal prescription, which is composed of Rhizome atractylodis macrocephalae, Radix Paeoniae Alba, Pericarpium Citri Reticulatae and Radix Saposhnikovia. In this study, a simple and sensitive high-performance liquid chromatography coupled with diode array detection method was established for the simultaneous determination of 10 marker compounds including atractylenolide I, gallic acid, albiflorin, paeoniflorin, narirutin, hesperidin, nobiletin, cimifugin, prim-O-glucosylcimifugin, 4'-O-?-d-glucosyl-5-O-methylvismminol in BSS and its single herbs. The chromatographic separation was performed using a YMC C18 column with a gradient elution system of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 1 mL/min. The results demonstrated that the validated method was simple, reliable and successfully applied to evaluate the selected compounds in BSS and its single herbs for quality control. Moreover, the experimental data showed that the contents of two major active components detected in BSS decoction were significantly higher than those in the single herbs, which indicated that the combination of single herbs could result in the difference in the amount of active constituents. PMID:25217704

  20. Determination of chloroacetanilide herbicide metabolites in water using high-performance liquid chromatography-diode array detection and high-performance liquid chromatography/mass spectrometry

    USGS Publications Warehouse

    Hostetler, K.A.; Thurman, E.M.

    2000-01-01

    Analytical methods using high-performance liquid chromatography-diode array detection (HPLC-DAD) and high-performance liquid chromatography/mass spectrometry (HPLC/MS) were developed for the analysis of the following chloroacetanilide herbicide metabolites in water: alachlor ethanesulfonic acid (ESA); alachlor oxanilic acid; acetochlor ESA; acetochlor oxanilic acid; metolachlor ESA; and metolachlor oxanilic acid. Good precision and accuracy were demonstrated for both the HPLC-DAD and HPLC/MS methods in reagent water, surface water, and ground water. The average HPLC-DAD recoveries of the chloroacetanilide herbicide metabolites from water samples spiked at 0.25, 0.5 and 2.0 ??g/l ranged from 84 to 112%, with relative standard deviations of 18% or less. The average HPLC/MS recoveries of the metabolites from water samples spiked at 0.05, 0.2 and 2.0 ??g/l ranged from 81 to 118%, with relative standard deviations of 20% or less. The limit of quantitation (LOQ) for all metabolites using the HPLC-DAD method was 0.20 ??g/l, whereas the LOQ using the HPLC/MS method was at 0.05 ??g/l. These metabolite-determination methods are valuable for acquiring information about water quality and the fate and transport of the parent chloroacetanilide herbicides in water. Copyright (C) 2000 Elsevier Science B.V.

  1. Laser-induced breakdown spectra in the infrared region from 750 to 2000 nm using a cooled InGaAs diode array detector.

    PubMed

    Radziemski, Leon J; Cremers, David A; Bostian, Melissa; Chinni, Rosemarie C; Navarro-Northrup, Claudia

    2007-11-01

    Emissions from a laser-induced breakdown spectroscopy (LIBS) plasma were examined in the region from 750 nm to 2000 nm. A Nd:YAG laser at 532 nm and 75 mJ per pulse were used to initiate the plasma. The detector was an InGaAs 1024 element diode array cooled to -100 degrees C. An f/4 spectrometer with gratings blazed for this region was used as the dispersive element. Survey spectra of soils, uranium, and other selected samples were taken in air and in a flow cell purged with argon at a local pressure of 0.84 x 10(5) Pa. Strong infrared lines of neutral aluminum, carbon, potassium, silicon, sulfur, and uranium, as well as once ionized lines of calcium, were observed out to 1670 nm. For potassium, the detection limits of the infrared (IR) system were compared with those obtained from a standard intensified charge-coupled device (ICCD) spectrometer arrangement, using the 766-770 nm doublet. Detection limits with the IR system were twice as high as those obtained from the ICCD detector. PMID:18028691

  2. Online screening of nitric oxide scavengers in natural products using high performance liquid chromatography coupled with tandem diode array and fluorescence detection.

    PubMed

    Li, Dapeng; Wang, Ting; Guo, Yujie; Hu, Yuanjia; Yu, Boyang; Qi, Jin

    2015-12-18

    Nitric oxide (NO) is an important cellular signaling molecule with extensive physiological and pathophysiological effects. NO scavengers have the potential to treat inflammation, septic shock and other related diseases, and numerous examples have been chemically synthesized or isolated from natural products. The chemical diversity of natural products, however, means that a huge effort is necessary to efficiently screen and identify bioactive compounds, especially NO scavengers. In this article, we propose an effective analytical method to screen for NO scavengers in three natural products using an online system that couples high performance liquid chromatography with tandem diode array and fluorescence detection (HPLC-DAD-FLD). Eighteen compounds from radix of Scutellaria baicalensis Georgi and green tea displayed significant NO scavenging activity whereas components of Pueraria lobata (Willd.) Ohwi had no discernable activity. The structures of the active compounds were elucidated using Agilent Accurate-Mass Q-TOF LC/MS system. Preliminary analysis of structure-activity relationships indicated that, in flavonoids, a 2,3-double bond and a 3-H atom or a 3-OH group are essential for activity. In tannins, poly-hydroxyl groups are important for NO scavenging activity. Method validation indicated that the newly developed method is both reliable and repeatable. The online method that we present provides a simple, rapid and effective way to identify and characterize NO scavengers present in natural products. PMID:26607316

  3. A simple and robust high-performance liquid chromatography coupled to a diode-array detector method for the analysis of genistein in mouse tissues.

    PubMed

    Tamames-Tabar, C; Imbuluzqueta, E; Campanero, M A; Horcajada, P; Blanco-Prieto, M J

    2013-09-15

    A simple liquid-liquid extraction procedure and quantification by high-performance liquid chromatography (HPLC) method coupled to a diode-array detector (DAD) of genistein (GEN) was developed in various mouse biological matrices. 7-ethoxycoumarin was used as internal standard (IS) and peaks were optimally separated using a Kinetex C18 column (2.6?m, 150mm×2.10mm I.D.) at 40°C with an isocratic elution of mobile phase with sodium dihydrogen phosphate 0.01M in water at pH 2.5 and methanol (55:45, v/v), at a flow rate of 0.25mL/min. The injection volume was 10?L. In all cases, the range of GEN recovery was higher than 61%. The low limit of quantification (LLOQ) was 25ng/mL. The linearity of the calibration curves was satisfactory in all cases as shown by correlation coefficients >0.996. The within-day and between-day precisions were <15% and the accuracy ranged in all cases between 90.14% and 106.05%. This method was successfully applied to quantify GEN in liver, spleen, kidney and plasma after intravenous administration of a single dose (30mg/kg) in female BALB/C mice. PMID:23939202

  4. Simultaneous quantitative determination of six active components in traditional Chinese medicinal preparation Cerebralcare Granule® by RP-HPLC coupled with diode array detection for quality control.

    PubMed

    Wang, Xiang-yang; Ma, Xiao-hui; Li, Wei; Chu, Yang; Guo, Jia-hua; Zhou, Shui-ping; Zhu, Yong-hong

    2014-09-01

    A simple, accurate and reliable method for the simultaneous separation and determination of six active components (protocatechuic acid, chlorogenic acid, caffeic acid, paeoniflorin, ferulic acid and rosmarinic acid) in traditional Chinese medicinal preparation Cerebralcare Granule(®) (CG) was developed using reverse-phase high-performance liquid chromatography coupled with diode array detector detection. The chromatographic separation was performed on a Hypersil GOLD C18 column with aqueous formic acid (0.1%, v/v) and acetonitrile as mobile phase at a flow rate of 0.2 ml/min at 30 °C. Because of the different UV characteristics of these components, change detection wavelength method was used for quantitative analysis. All of the analytes showed good linearity (r > 0.9992). The established method showed good precision and relative standard deviations (%) for intra-day and inter-day variations of 0.15-1.81 and 0.11-1.98%, respectively. The validated method was successfully applied to the simultaneously determination of six active components in CG from different batches. PMID:23934038

  5. Chemical analysis of raw and processed Fructus arctii by high-performance liquid chromatography/diode array detection-electrospray ionization-mass spectrometry

    PubMed Central

    Qin, Kunming; Liu, Qidi; Cai, Hao; Cao, Gang; Lu, Tulin; Shen, Baojia; Shu, Yachun; Cai, Baochang

    2014-01-01

    Background: In traditional Chinese medicine (TCM), raw and processed herbs are used to treat the different diseases. Fructus Arctii, the dried fruits of Arctium lappa l. (Compositae), is widely used in the TCM. Stir-frying is the most common processing method, which might modify the chemical compositions in Fructus Arctii. Materials and Methods: To test this hypothesis, we focused on analysis and identification of the main chemical constituents in raw and processed Fructus Arctii (PFA) by high-performance liquid chromatography/diode array detection-electrospray ionization-mass spectrometry. Results: The results indicated that there was less arctiin in stir-fried materials than in raw materials. however, there were higher levels of arctigenin in stir-fried materials than in raw materials. Conclusion: We suggest that arctiin reduced significantly following the thermal conversion of arctiin to arctigenin. In conclusion, this finding may shed some light on understanding the differences in the therapeutic values of raw versus PFA in TCM. PMID:25422559

  6. Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.

    PubMed

    Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song

    2013-09-24

    We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy. PMID:23952783

  7. Microwave-assisted extraction and rapid isolation of ursolic acid from the leaves of Eucalyptus × hybrida Maiden and its quantification using HPLC-diode array technique.

    PubMed

    Verma, Subash C; Jain, Chhoten L; Kumari, Amita; Padhi, Madan M; Devalla, Ramesh B

    2013-04-01

    Ursolic acid (UA) is the most important bioactive phytoconstituent of Eucalyptus × hybrida Maiden leaves and exhibits anticancer, antimutagenic, anti-inflammatory, antioxidative, and antiprotozoal activities. In this study, microwave-assisted extraction technique was employed for rapid isolation of UA from the leaves of Eucalyptus × hybrida and simultaneously HPLC-diode array method was developed for the quantification of UA. Effects of several experimental parameters on the extraction efficiencies of UA, such as type and volume of extraction solvents, microwave power and extraction time, were evaluated. The optimal extraction conditions were found to be 20 mL of a mixture of chloroform/methanol, 60:40; liquid-to-material ratio, 4:1; preleaching time, 10 min; microwave power, 600 W; temperature, 50°C; and microwave irradiation time, 5 min. Under the optimum conditions, the yield of UA was found to be 1.95 ± 0.08% in the dry leaves of Eucalyptus × hybrida. The results showed that microwave-assisted extraction is a more rapid extraction method with higher yield and lower solvent consumptions than the conventional method. It is a faster, convenient, and appropriate method and it may be used for rapid isolation and quantification of UA and other important phytoconstituents present in the leaves of Eucalyptus × hybrida. PMID:23471897

  8. Detection of hazardous weight-loss substances in adulterated slimming formulations using ultra-high-pressure liquid chromatography with diode-array detection.

    PubMed

    Rebiere, H; Guinot, P; Civade, C; Bonnet, P-A; Nicolas, A

    2012-01-01

    The presence on the market of illegal products for slimming purposes or the treatment of overweight is a public health issue. These products may contain illicit chemicals in order to improve their effectiveness. Some of these weight-loss compounds are responsible for adverse events, including fatal outcomes. A general strategy for the analysis of any suspect formulation begins with a large screening for the general search of a wide range of compounds. A methodology for the qualitative and quantitative determination of 34 compounds in slimming preparations (such as dietary supplements or medicinal products) was used for the control of slimming formulations from the market, including over the Internet. The fast liquid chromatography system (ultra-high-pressure liquid chromatography) used a gradient of solvent (phosphate buffer and acetonitrile), a C18 endcapped column and a diode array detector. This system allows dual identification based on retention time and UV spectra. The analytical method is simple, fast and selective since 34 weight-loss compounds can be detected in a 15-min run time. Thus, 32 commercial slimming formulations were analysed using this method, allowing the detection and quantification of hazardous active substances: caffeine, clenbuterol, nicotinamide, phenolphthalein, rimonabant, sibutramine, didesmethylsibutramine, synephrine and yohimbine. PMID:22150438

  9. Development of a rapid resolution liquid chromatography-diode array detector method for the determination of three compounds in Ziziphora clinopodioides Lam from different origins of Xinjiang

    PubMed Central

    Tian, Shuge; Yu, Qian; Wang, Dongdong; Upur, Halmuart

    2012-01-01

    Context: As a traditional Uygur medicinal plant, Z. clinopodioides Lam has various uses in Xinjiang. Aims: A reversed-phase rapid resolution liquid chromatography (RP-RRLC) method with diode array detector (DAD) was developed for simultaneous determination of diosmin, linarin, and pulegone from Ziziphora clinopodioides Lam, a widely used in traditional Uygur medicine for treating heart disease, high blood pressure, and other diseases. Settings and Design: Compounds were separated on a XDB-C18 reversed-phase analytical column (50 mm × 4.6 mm, 1.8 ?m) with gradient elution using methanol and 1% aqueous acetic acid (v/v) at 0.9 mL/min. he detection wavelength was set at 270 nm. Materials and Methods: Ziziphora clinopodioides Lam. were collected from ten different origins in Xinjiang, including the Ban fang ditch, Tuoli, the Altay mountains, Terks, Xiata Road, Zhaosu Highway, Guozigou, Fukang, Jimsar, Wulabo. Statistical Analysis Used: The intra-day and inter-day precisions of all three compounds were less than 0.89% and the average recoveries ranged from 97.4 to 104.1%. There were highly significant linear correlations between component concentrations and specific chromatographic peak areas (R2 > 0.999). Results: The proposed method was successfully applied to determine the levels of three active components in Z. clinopodioides Lam. samples from different locations in Xinjiang. Conclusions: The proposed method is simple, consistent, accurate, and could be utilized as a quality control method for Z. clinopodioides Lam. PMID:24082631

  10. Development of a method for the analysis of drugs of abuse in vitreous humor by capillary electrophoresis with diode array detection (CE-DAD).

    PubMed

    Costa, Jose Luiz; Morrone, Andre Ribeiro; Resende, Rodrigo Ribeiro; Chasin, Alice Aparecida da Matta; Tavares, Marina Franco Maggi

    2014-01-15

    This work presents the development of an analytical method based on capillary electrophoresis with diode array detection for the analysis of drugs of abuse and biotransformation products in vitreous humor. Composition of the background electrolyte, implementation of an online pre-concentration strategy and sample preparation procedures were objects of study. The complete electrophoretic separation of 12 analytes (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyethylamphetamine (MDEA), ketamine, cocaine, cocaethylene, lidocaine, morphine, 6-monoacetylmorphine and heroin) and the internal standard N-methyl-1-(3,4-methylenedioxyphenyl)-2-butamine (MBDB) was obtained within 13min of run. The method was validated presenting good linearity (r(2)>0.99), recovery ?90%, precision better than 12% RSD and acceptable accuracy in the range of 86-118% at three concentration levels (50, 100 and 500ng/mL). LODs and LOQs in the order of 1-5ng/mL and 5-10ng/mL, respectively, were obtained. After validation, the method was applied to eighty-seven vitreous humor samples and the results were compared to those obtained by a liquid chromatography tandem mass spectrometry (LC-MS/MS) screening method, routinely used by the forensic toxicology laboratory of the Sao Paulo State Police, Brazil. Cocaine was detected in 7.1%, cocaethylene in 3.6%, lidocaine in 2.4% and ketamine in 1.2% of the total number of analyzed samples. PMID:24325829

  11. Determination of neonicotinoid insecticides residues in bovine milk samples by solid-phase extraction clean-up and liquid chromatography with diode-array detection.

    PubMed

    Seccia, Serenella; Fidente, Paola; Montesano, Domenico; Morrica, Patrizia

    2008-12-19

    In this paper we have developed an analytical method for the simultaneous determination of four nicotinoid insecticides [acetamiprid (ACT), imidacloprid (ICL), thiacloprid (TCL) and thiamethoxam (TMX)] in bovine whole milk. These analytes were extracted, in a single step with dichloromethane, from fortified milk samples, using Chem Elut cartridges, containing diatomaceous earth material. Insecticide's determination and quantification were performed by HPLC with diode-array detection (DAD). Average recoveries of the four insecticides from bovine milk samples were between 85.1 and 99.7% at spiking levels 0.01, 0.05 and 0.1 mg kg(-1). Relative standard deviations (RSDs) were no larger than 10% for all of the recovery tests. The calculated limits of quantitation (LOQ) ranged from 0.01 to 0.04 mg kg(-1) for the four insecticides, being equal to or lower than the maximum residue limits (MRLs) established by European legislation (0.01-0.05 mg kg(-1)). The developed method is linear at concentrations within the tested interval, with coefficients of determination higher than 0.9990. According to Commission Decision 2002/657/EC, decision limit (CCalpha) and detection capability (CCbeta) have been calculated. The proposed method is rapid, simple and could be utilized for the routine analysis of pesticides residues. PMID:19004450

  12. Ultrasound-assisted dispersive extraction for the high pressure liquid chromatographic determination of tetracyclines residues in milk with diode array detection.

    PubMed

    Karageorgou, Eftichia; Armeni, Marina; Moschou, Ioulia; Samanidou, Victoria

    2014-05-01

    Ultrasound assisted matrix solid phase dispersive extraction was applied for the selective isolation and clean-up of tetracyclines (oxytetracycline, tetracycline, epi-chlorotetracycline, chlorotetracycline and doxycycline) from milk. Target analytes were determined by an accurate and sensitive chromatographic analytical method, which was validated to meet the European Legislation criteria. The separation was performed on a LiChroCART-LiChrospher® 100 RP-18 (5?m, 250×4mm) analytical column, operated at ambient temperature, followed by diode array detection. Validation included investigation of linearity, selectivity, stability, limits of detection and quantitation, decision limit, detection capability, trueness, precision and ruggedness according to the Youden's approach. Limits of quantitation of examined tetracyclines were from 14.5 to 56.6?g/kg significantly lower than respective Maximum Residue Limits, whereas recoveries ranged from 82.0% to 108%. The applicability of the method was evaluated using milk samples purchased from local market. Accuracy of the method was additionally proved by analysis of bovine milk certified reference material (BCR®-492). PMID:24360458

  13. Selective microextraction of mononucleotides from milk using alumina and stannia hollow fibers prior to their determination by hydrophilic interaction liquid chromatography-diode array detection.

    PubMed

    Sfakianaki, A G; Stalikas, C D

    2015-10-01

    Alumina- and stannia-based hollow fibers were synthesized via simple sol-gel procedures and characterized with respect to morphology, crystalline phase and specific surface area. Then, an optimization study was undertaken for the preconcentration of five 5'-mononucleotides using the hollow fibers. The separation and quantification of the analytes were carried out by HILIC with diode array detection, after proper optimization of the chromatographic conditions. The method demonstrated satisfactory linearities over a concentration range of 0.09-50 ?g mL(-1) with regression coefficients to range from 0.9993 to 0.9997. A range of commercially available 5'-mononucleotide supplemented infant formulas and three human breast milk samples were used to apply alumina hollow fibers, as a proof of concept. Recoveries ranged from 84% to 104%, while the calculated RSDs were from 3.6% to 4.3%. The proposed preconcentration-clean-up method is environmentally friendly and convenient, indicating that alumina and stannia are suitable for the applications by immersing them into milk samples, after removal of proteins. PMID:25872443

  14. Using frequency-narrowed, tunable laser diode arrays with integrated volume holographic gratings for spin-exchange optical pumping at high resonant fluxes and xenon densities

    NASA Astrophysics Data System (ADS)

    Whiting, N.; Nikolaou, P.; Eschmann, N. A.; Barlow, M. J.; Lammert, R.; Ungar, J.; Hu, W.; Vaissie, L.; Goodson, B. M.

    2012-03-01

    Next-generation laser diode arrays with integrated `on-chip' volume holographic gratings can provide high power with spectrally narrowed output that can be tuned about the rubidium D1 line—without causing significant changes to the laser's flux or spectral profile. These properties were exploited to independently evaluate the effects of varying the laser centroid wavelength and power on batch-mode Rb/129Xe spin-exchange optical pumping (SEOP) as functions of xenon partial pressure and cell temperature. Locally optimized SEOP was often achieved with the laser tuned to either the red or blue side of the Rb D1 line; global optimization of SEOP was observed at lower cell temperatures and followed the D1 absorption profile, which was asymmetrically broadened and red-shifted from the nominal wavelength. The complex dependence of the optimal wavelength for laser excitation on the cell temperature and Xe density appears to result from an interplay between cell illumination and the Rb/129Xe spin-exchange rate, as well as [Xe]cell-dependent changes to the Rb absorption lineshape that are in qualitative agreement with expectations based on previous work [Romalis et al., Phys. Rev. A, 56:4569-4578, (1997)], but significantly greater in magnitude. These next-generation lasers provide a ˜2-3-fold improvement in 129Xe polarization compared to conventional broadband lasers.

  15. The determination of 3-nitrophenol and some other aromatic impurities in 4-nitrophenol by reversed phase HPLC with peak suppression diode array detection.

    PubMed

    Wróbel, K; Wróbel, K; Madai Colunga Urbina, E; Muñoz Romero, J

    2000-03-01

    In this work the peak suppression technique is used for the determination of 3-nitrophenol and some other aromatic impurities in 4-nitrophenol by reversed phase HPLC with diode array detection. Taking into account the differences between the absorption spectra of the two compounds, two wavelengths were selected in order to obtain the maximum difference between the spectral contribution for 3-nitrophenol and to maintain a small, similar spectral contribution for 4-nitrophenol (the main compound). Then we used the wavelength corresponding to a small spectral contribution of 3-nitrophenol as the reference wavelength. It was shown that taking lambda(an) = 266 nm and lambda(ref) = 364 nm, a broad elution peak of 4-nitrophenol was suppressed deconvoluting the peak of 3-nitrophenol. Moreover, quantitation of 3-nitrophenol was achieved without chemometric tools. Under the proposed conditions the detection limits for 3-nitrophenol and other common impurities of 4-nitrophenol used in the pharmaceutical industry (4-chlorophenol, 4-nitrophenol, 1-chloro-2-nitrobenzene, 1-chloro-4-nitrobenzene, 4,4'-bisfenilether, and 4,4'-dichloroazobenzene) were not significantly affected as compared with respective detection limits evaluated in the absence of 4-nitrophenol and using standard detection conditions (lambda(an) = 280 nm and lambda(ref) = 420 nm). PMID:10719912

  16. Characterization of an Optical Device with an Array of Blue Light Emitting Diodes LEDS for Treatment of Neonatal Jaundice.

    NASA Astrophysics Data System (ADS)

    Sebbe, Priscilla Fróes; Villaverde, Antonio G. J. Balbin; Nicolau, Renata Amadei; Barbosa, Ana Maria; Veissid, Nelson

    2008-04-01

    Phototherapy is a treatment that consists in irradiating a patient with light of high intensity, which promotes beneficial photochemical transformations in the irradiated area. The phototherapy for neonates is applied to break down the bilirubin, an organic pigment that is a sub product of the erythrocytes degradation, and to increase its excretion by the organism. Neonates should be irradiated with light of wavelength that the bilirubin can absorb, and with spectral irradiances between 4 and 16 ?W/cm2/nm. The efficiency of the treatment depends on the irradiance and the area of the body that is irradiated. A convenient source of light for treatment of neonatal jaundice is the blue Light Emitter Diode (LED), emitting in the range of 400 to 500 nm, with power of the order of 10-150 mW. Some of the advantages for using LEDS are: low cost, operating long lifetime (over 100,000 hours), narrow emission linewith, low voltage power supply requirement and low heating. The aim of this work was to build and characterize a device for phototherapy treatment of neonatal jaundice. This consists of a blanket with 88 blue LEDs (emission peak at 472 nm), arranged in an 8×11 matrix, all connected in parallel and powered by a 5V-2A power supply. The device was characterized by using a spectroradiometer USB2000 (Ocean Optics Inc, USA), with a sensitivity range of 339-1019 nm. For determination of light spatial uniformity was used a calibrated photovoltaic sensor for measuring light intensity and mapping of the light intensity spatial distribution. Results indicate that our device shows a uniform spatial distribution for distances from the blanket larger than 10 cm, with a maximum of irradiance at such a distance. This device presenting a large and uniform area of irradiation, efficient wavelength emission and high irradiance seems to be promising for neonates' phototherapy treatment.

  17. Study of ablation and implosion stages in wire arrays using coupled ultraviolet and X-ray probing diagnostics

    NASA Astrophysics Data System (ADS)

    Anderson, A. A.; Ivanov, V. V.; Astanovitskiy, A. L.; Papp, D.; Wiewior, P. P.; Chalyy, O.

    2015-11-01

    Star and cylindrical wire arrays were studied using laser probing and X-ray radiography at the 1-MA Zebra pulse power generator at the University of Nevada, Reno. The Leopard laser provided backlighting, producing a laser plasma from a Si target which emitted an X-ray probing pulse at the wavelength of 6.65 Å. A spherically bent quartz crystal imaged the backlit wires onto X-ray film. Laser probing diagnostics at the wavelength of 266 nm included a 3-channel polarimeter for Faraday rotation diagnostic and two-frame laser interferometry with two shearing interferometers to study the evolution of the plasma electron density at the ablation and implosion stages. Dynamics of the plasma density profile in Al wire arrays at the ablation stage were directly studied with interferometry, and expansion of wire cores was measured with X-ray radiography. The magnetic field in the imploding plasma was measured with the Faraday rotation diagnostic, and current was reconstructed.

  18. Controlling the properties of electrodeposited ZnO nanowire arrays for light emitting diode, photodetector and gas sensor applications

    NASA Astrophysics Data System (ADS)

    Pauporté, T.; Lupan, Oleg; Viana, Bruno; Chow, Lee; Tchernycheva, Maria

    2014-03-01

    Electrochemical deposition (ECD) is a versatile technique for the preparation of ZnO nanowires (NWs) and nanorods (NRs) with high structural and optical quality. The bandgap of the ZnO NWs can be engineered by doping. Depending on the doping cation and concentration, the bandgap is increased or decreased in a controlled manner. The NW arrays have been grown on various substrates. The epitaxial growth on single-crystal conducting substrates has been demonstrated. By using p-type GaN layers, heterostructures have been fabricated with a high rectifying electrical behavior. They have been integrated in low-voltage LEDs emitting in the UV or in the visible region depending on the NW composition. For visible-blind UV-photodetector application, ZnO NW ensembles, electrochemically grown on F:SnO2, have been contacted on their top with a transparent graphene sheet. The photodetector had a responsivity larger than 104 A/W at 1V in the near-UV range. ECD ZnO NWs have also been isolated and electrically connected on their both ends by Al contacts. The obtained nanodevice, made of an individual NW, was shown to be a H2 gas sensor with a high selectivity and sensitivity. Moreover, it was shown that Cd-doping of ZnO NWs significantly improved the performance of the sensor.

  19. An on-line high-performance liquid chromatography-diode-array detector-electrospray ionization-ion-trap-time-of-flight-mass spectrometry-total antioxidant capacity detection system applying two antioxidant methods for activity evaluation of the edible flowers from Prunus mume.

    PubMed

    Zhang, Xiaoxia; Lin, Zongtao; Fang, Jinggui; Liu, Meixian; Niu, Yanyan; Chen, Shizhong; Wang, Hong

    2015-10-01

    An on-line high-performance liquid chromatography-diode-array detector-electrospray ionization-ion-trap-time-of-flight-mass spectrometry-total antioxidant capacity detection (HPLC-DAD-ESI-IT-TOF-MS-TACD) system was created for identification and evaluation of antioxidants in Prunus (P.) mume flowers. Applying this system, the HPLC fingerprint, ultraviolet (UV) spectra, mass fragmentations, active profiles against 1,1-diphenylpicryl-2-hydrazyl radical (DPPH•) scavenging activity and ferric reducing antioxidant power (FRAP) of each complex sample were obtained simultaneously after one injection. Synchronous structure identification and activities screening of complex samples were thus accomplished. In this study, 78 compounds were identified from P. mume flowers by their chromatographic behaviors, UV spectra and MS data with the assistance of standard compounds and literature reports. The DPPH and FRAP activity of 24 samples (23 different P. mume varieties and 1 related herbal medicine) were then quantified by their detailed activity profiles from the on-line system, and by the total activity of each sample extract from off-line 96-well plate method. As a result, 21 and 32 compounds in the on-line system showed anti-oxidative effects against DPPH and FRAP, respectively. The established on-line system is efficient, sensitive and reliable to tell the DPPH and FRAP antioxidant activities of individual compound in complex samples, and therefore would be a useful and promising technique for antioxidant screening from different food and medicinal matrices. PMID:26321507

  20. The simultaneous determination of coumarins in Angelica gigas root by high performance liquid chromatography-diode array detector coupled with electrospray ionization/mass spectrometry.

    PubMed

    Ahn, Mi-Jeong; Lee, Mi Kyeong; Kim, Young Choong; Sung, Sang Hyun

    2008-01-22

    An high performance liquid chromatography-diode array detector coupled with electrospray ionization/mass spectrometry (HPLC-DAD/MS) based method has been developed for the simultaneous determination of nine coumarin compounds, nodakenin (1), peucedanone (2), marmesin (3), decursinol (4), 7-hydroxy-6-(2R-hydroxy-3-methylbut-3-enyl)coumarin (5), demethylsuberosin (6), decursin (7), decursinol angelate (8) and isoimperatorin (9) in the Korean medicinal herb, Cham-Dang-Gui, the dried root of Angelica gigas (Umbelliferae). The methanol extracts were analyzed by HPLC using a reversed-phase C18 column (5 microm, 4.5 mm x 250 mm) using a gradient acetonitrile-water solvent system at a flow rate of 1.0 ml/min. The analysis of six coumarins (1, 3, 4 and 6-8) with DAD was done at 330 nm and showed excellent linearity (r(2)=0.998-0.999) in a range of 0.2-250 microg/ml for all the compounds. The average recoveries (n=3) were between 96.5% and 110.8%. Identification of each peak was also discussed with the electrospray ionization multi-stage tandem mass spectroscopy (ESI-MS(n)). The amount of these coumarin compounds was evaluated in A. gigas samples. Meanwhile, three coumarins (2, 5 and 9) could not been quantified by DAD because these peaks were overlapped with others. Determination of these compounds could be successfully accomplished with the HPLC-ESI/MS in selected ion monitoring/selected reaction monitoring mode. PMID:17997069

  1. Fast extraction of amphenicols residues from raw milk using novel fabric phase sorptive extraction followed by high-performance liquid chromatography-diode array detection.

    PubMed

    Samanidou, Victoria; Galanopoulos, Lavrentis-Demetrios; Kabir, Abuzar; Furton, Kenneth G

    2015-01-15

    A simple, sensitive, reliable, and fast analytical method was developed for the simultaneous determination of amphenicols residues in raw milk by combining fabric phase sorptive extraction (FPSE) and high-performance liquid chromatography-diode array detection. FPSE, a new generation green sample preparation technique, efficiently incorporates the advanced and tunable material properties of sol-gel derived microextraction sorbents with the rich surface chemistry of a cellulose fabric substrate, resulting in a flexible, highly sensitive, and fast microextraction device capable of extracting target analytes directly from complicated sample matrices. Due to the strong chemical bonding between the sol-gel sorbent and substrate, the microextraction device demonstrates a very high chemical and solvent stability. Therefore, any organic solvent/solvent mixture can be used as the eluent/back-extraction solvent. Herein, a highly polar polymer coated FPSE media was created using short-chain poly(ethylene glycol) (PEG) and the applicability of this novel microextraction device to extract highly polar amphenicol antibiotics from raw milk was investigated. Due to the intense affinity of amphenicols towards the strongly polar sol-gel PEG-coated FPSE device, absolute recovery of the selected antibiotics residues were found to be 44% for thiamphenicol, 66.4% for florfenicol, and 81.4% for chloramphenicol. The developed method was validated in terms of sensitivity, linearity, accuracy, precision, and selectivity according to European Decision 657/2002/EC. Decision limit (CC?) values were 52.49 ?g kg(-1) for thiamphenicol, 55.23 ?g kg(-1) for florfenicol, and 53.8 ?g kg(-1) for chloramphenicol, while the corresponding results for detection capability (CC?) were 56.8 ?g kg(-1), 58.99 ?g kg(-1), and 55.9 ?g kg(-1), respectively. PMID:25542088

  2. Determination of 13 synthetic food colorants in water-soluble foods by reversed-phase high-performance liquid chromatography coupled with diode-array detector.

    PubMed

    Minioti, Katerina S; Sakellariou, Christina F; Thomaidis, Nikolaos S

    2007-01-30

    A reversed-phase high performance liquid chromatographic method for the successful separation and determination of 13 synthetic food colorants (Tartrazine E 102, Quinoline Yellow E 104, Sunset Yellow E 110, Carmoisine E 122, Amaranth E 123, Ponceau 4R E 124, Erythrosine E 127, Red 2G E 128, Allura Red AC E 129, Patent Blue V E 131, Indigo Carmine E 132, Brilliant Blue FCF E 133 and Green S E 142) was developed. A C18 stationary phase was used and the mobile phase contained an acetonitrile-methanol (20:80 v/v) mixture and a 1% (m/v) ammonium acetate buffer solution at pH 7.5. Successful separation was obtained for all the compounds using an optimized gradient elution within 29 min. The diode-array detector was used to monitor the colorants between 350 and 800 nm. The method was thoroughly validated. Detection limits for all substances varied between 1.59 (E 142) and 22.1 (E 124) microg L(-1). The intra-day precision (as R.S.D.(r)) ranged from 0.37% (E 122 in fruit flavored drink at a concentration of 100 mg L(-1)) to 4.8% (E 142 in icing sugar at a level of 0.9 mg kg(-1)). The inter-day precision (as R.S.D.(R)) was between 0.86% for E 122 in fruit flavored drink at 100 mg L(-1) and 10% for E142 in jam at a concentration of 9 mg kg(-1). Satisfactory recoveries, ranging from 94% (E 142 in jam) to 102% (E 131 in sweets), were obtained. The method was applied to the determination of colorants in various water-soluble foods, such as fruit flavoured drinks, alcoholic drinks, jams, sugar confectionery and sweets, with simple pre-treatment (dilution or water extraction). PMID:17386533

  3. Semi-automated alignment and quantification of peaks using parallel factor analysis for comprehensive two-dimensional liquid chromatography-diode array detector data sets

    PubMed Central

    Allen, Robert C.

    2012-01-01

    Parallel factor analysis was used to quantify the relative concentrations of peaks within four-way comprehensive two dimensional liquid chromatography-diode array detector data sets. Since parallel factor analysis requires that the retention times of peaks between each injection are reproducible, a semi-automated alignment method was developed that utilizes the spectra of the compounds to independently align the peaks without the need for a reference injection. Peak alignment is achieved by shifting the optimized chromatographic component profiles from a three-way parallel factor analysis model applied to each injection. To ensure accurate shifting, components are matched up based on their spectral signature and the position of the peak in both chromatographic dimensions. The degree of shift, for each peak, is determined by calculating the distance between the median data point of the respective dimension (in either the second or first chromatographic dimension) and the maximum data point of the peak furthest from the median. All peaks that were matched to this peak are then aligned to this common retention data point. Target analyte recoveries for four simulated data sets were within 2 % of 100 % recovery in all cases. Two different experimental data sets were also evaluated. Precision of quantification of two spectrally similar and partially coeluting peaks present in urine was as good as or better than 4 %. Good results were also obtained for a challenging analysis of phenytoin in waste water effluent, where the results of the semi-automated alignment method agreed with the reference LC-LCMS/MS method within the precision of the methods. PMID:22444567

  4. Gradient HPLC-diode array detector stability-indicating determination of lidocaine hydrochloride and cetylpyridinium chloride in two combined oral gel dosage forms.

    PubMed

    Belal, Tarek S; Shaalan, Rasha A; Haggag, Rim S

    2011-01-01

    A simple, rapid, and selective HPLC-diode array detector method was developed for the simultaneous determination of lidocaine hydrochloride (LD) and cetylpyridinium chloride (CPC) in two combined pharmaceutical formulations. Effective chromatographic separation was achieved on a Zorbax SB-C8 (4.6 x 250 mm, 5 microm particle size) column with gradient elution using a mobile phase composed of 0.05 M phosphoric acid and acetonitrile. The gradient elution started with 25% (v/v) acetonitrile, ramped up linearly to 85% in 5 min, and then was constant until the end of the run. The mobile phase was pumped at a flow rate of 1.2 mL/min. The multiple wavelength detector was set at 214 and 258 nm, and quantification of the analytes was based on measuring their peak areas. The retention times for LD and CPC were about 3.4 and 7.3 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to linearity, range, precision, accuracy, selectivity, robustness, LOD, and LOQ. Calibration curves were linear in the range of 5-200 and 10-400 microg/mL for LD and CPC, respectively, with correlation coefficients > 0.999. The proposed method was proven to be stability-indicating by the resolution of the two analytes from the related substance and potential impurity (2,6-dimethylaniline) as well as from forced-degradation products. The validated HPLC method was extended to the analysis of LD and CPC in two combined oral gel preparations for which the two analytes were successfully resolved from the pharmaceutical adjuvants and quantified with recoveries not less than 97.9%. PMID:21563684

  5. Diagnosing x-ray power and energy of tungsten wire array z-pinch with a flat spectral response x-ray diode

    NASA Astrophysics Data System (ADS)

    Wang, Kun-lun; Ren, Xiao-dong; Huang, Xian-bin; Zhang, Si-qun; Zhou, Shao-tong; Dan, Jia-kun; Li, Jing; Xu, Qiang; Ouyang, Kai; Cai, Hong-chun; Wei, Bing; Ji, Ce; Feng, Shu-ping; Wang, Meng; Xie, Wei-ping; Deng, Jian-jun

    2015-11-01

    Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter to yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%.

  6. Fast Gradient Elution Reversed-Phase Liquid Chromatography with Diode-Array Detection as a High-throughput Screening Method for Drugs of Abuse II. Data Analysis

    PubMed Central

    Porter, Sarah E. G.; Stoll, Dwight R.; Paek, Changyub; Rutan, Sarah C.; Carr, Peter W.

    2009-01-01

    In Part I of this work, we developed a method for the detection of drugs of abuse in biological samples based on fast gradient elution liquid-chromatography coupled with diode array spectroscopic detection (LC-DAD). In this part of the work, we apply the chemometric method of target factor analysis (TFA) to the chromatograms. This algorithm identifies the target compounds present in chromatograms based on a spectral library, resolves nearly co-eluting components, and differentiates between drugs with similar spectra. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguishes the present method from conventional library searching methods. Our library has a mean list length of 1.255 and a discriminating power of 0.997 when both retention index and spectral factors are considered. The algorithm compares a library of 47 different compounds of toxicological relevance to unknown samples and identifies which compounds are present based on spectral and retention index matching. The application of a corrected retention index for identification rather than raw retention times compensates for long-term and column-to-column retention time shifts and allows for the use of a single library of spectral and retention data. Training data sets were used to establish the search and identification parameters of the method. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were found to be 92 % and 94% respectively. PMID:17070534

  7. Simultaneous determination of 11 active components in two well-known traditional Chinese medicines by HPLC coupled with diode array detection for quality control.

    PubMed

    Yin, Lianhong; Lu, Binan; Qi, Yan; Xu, Lina; Han, Xu; Xu, Youwei; Peng, Jinyong; Sun, Changkai

    2009-05-01

    A simple and sensitive high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) method was investigated for simultaneous determination of 11 components (chlorogenic acid, coptisine, epiberberine, jatrorrhizine, berberine, palmatine, baicalin, wogonoside, baicalein, wogonin and chrysin) in Qinhuanghouzheng (QHHZ) capsule and Xiaoerqingre (XEQR) tablet, for quality control of these two well-known traditional Chinese medicines (TCMs). The method was established using an Eclipse Plus C(18) (150 mm x 4.6 mm i.d., 5 microm) column. The mobile phase comprising methanol (A) 3% phosphoric acid (B) (pH 2.0, adjusted by triethylamine) was used to elute the targets in gradient elution mode. Flow rate and detection wavelength were set at 0.8 mL/min and 270 nm, respectively. All calibration curves showed good linearity with R(2) > 0.9995. Inter- and intra-day precisions for all investigated components expressed as relative standard deviation (R.S.D.) ranged from 0.26% to 1.77%. Recoveries measured at three concentrations were in the range of 95.0-103.0% with R.S.D. < or = 3%. The validated method is simple, reliable, and successfully applied to determine the contents of the selected compounds in QHHZ capsule and XEQR tablet for quality evaluation and control. The 11 main active marker compounds measured occur only in 2 or 3 plant species out of 7-10 species comprising the two TCMs. Additional procedures need to be developed for the quality control of plant materials other than Coptis chinensis Franch, Scutellaria baicalensis Georgi and Phellodendron amurense Rupr. PMID:19264437

  8. Development and validation of an high-performance liquid chromatography-diode array detector method for the simultaneous determination of six phenolic compounds in abnormal savda munziq decoction

    PubMed Central

    Tian, Shuge; Liu, Wenxian; Liu, Feng; Zhang, Xuejia; Upur, Halmuart

    2015-01-01

    Aims: Given the high-effectiveness and low-toxicity of abnormal savda munziq (ASMQ), its herbal formulation has long been used in traditional Uyghur medicine to treat complex diseases, such as cancer, diabetes, and cardiovascular diseases. Settings and Design: ASMQ decoction by reversed-phase high-performance liquid chromatography coupled with a diode array detector was successfully developed for the simultaneous quality assessment of gallic acid, protocatechuic acid, caffeic acid, rutin, rosmarinic acid, and luteolin. The six phenolic compounds were separated on an Agilent TC-C18 reversed-phase analytical column (4.6 × 250 mm, 5 ?m) by gradient elution using 0.3% aqueous formic acid (v/v) and 0.3% methanol formic acid (v/v) at 1.0 mL/min. Materials and Methods: The plant material was separately ground and mixed at the following ratios (10): Cordia dichotoma (10.6), Anchusa italic (10.6), Euphorbia humifusa (4.9), Adiantum capillus-veneris (4.9), Ziziphus jujube (4.9), Glycyrrhiza uralensis (7.1), Foeniculum vulgare (4.9), Lavandula angustifolia (4.9), Dracocephalum moldavica L. (4.9), and Alhagi pseudoalhagi (42.3). Statistical Analysis Used: The precisions of all six compounds were <0.60%, and the average recoveries ranged from 99.39% to 104.85%. Highly significant linear correlations were found between component concentrations and specific chromatographic peak areas (R2 > 0.999). Results: The proposed method was successfully applied to determine the levels of six active components in ASMQ. Conclusions: Given the simplicity, precision, specificity, and sensitivity of the method, it can be utilized as a quality control approach to simultaneously determining the six phenolic compounds in AMSQ. PMID:25709227

  9. Antimicrobial activity of Marcetia DC species (Melastomataceae) and analysis of its flavonoids by reverse phase-high performance liquid chromatography coupled-diode array detector

    PubMed Central

    Leite, Tonny Cley Campos; de Sena, Amanda Reges; dos Santos Silva, Tânia Regina; dos Santos, Andrea Karla Almeida; Uetanabaro, Ana Paula Trovatti; Branco, Alexsandro

    2012-01-01

    Background: Marcetia genera currently comprises 29 species, with approximately 90% inhabiting Bahia (Brazil), and most are endemic to the highlands of the Chapada Diamantina (Bahia). Among the species, only M. taxifolia (A.St.-Hil.) DC. populates Brazil (state of Roraima to Paraná) and also Venezuela, Colombia, and Guyana. Objective: This work evaluated the antimicrobial activity of hexane, ethyl acetate, and methanol extracts of three species of Marcetia (Marcetia canescens Naud., M. macrophylla Wurdack, and M. taxifolia A.StHil) against several microorganism. In addition, the flavonoids were analyzed in extracts by HPLC-DAD. Materials and methods: The tests were made using Gram-positive (three strains of Staphylococcus aureus) and Gram-negative (two strains of Escherichia coli, a strain of Pseudomonas aeruginosa and another of Salmonella choleraesius) bacteria resistant and nonresistant to antibiotics and yeasts (two strains of Candida albicans and one of C. parapsilosis) by the disk diffusion method. Solid-phase extraction (SPE) was performed on the above extracts to isolate flavonoids, which were subsequently analyzed by high performance liquid chromatography coupled diode array detector (HPLC-DAD). Results: Results showed that extracts inhibited the Gram-positive bacteria and yeast. The hexane extracts possessed the lowest activity, while the ethyl acetate and methanolic extracts were more active. Conclusion: Marcetia taxifolia was more effective (active against 10 microorganisms studied), and only its methanol extract inhibited Gram-negative bacteria (P. aeruginosa and S. choleraesius). SPE and HPLC-DAD analysis showed that M. canescens and M. macrophylla contain glycosylated flavonoids, while the majority of extracts from M. taxifolia were aglycone flavonoids. PMID:23060695

  10. Diagnosing x-ray power and energy of tungsten wire array z-pinch with a flat spectral response x-ray diode.

    PubMed

    Wang, Kun-Lun; Ren, Xiao-Dong; Huang, Xian-Bin; Zhang, Si-Qun; Zhou, Shao-Tong; Dan, Jia-Kun; Li, Jing; Xu, Qiang; Ouyang, Kai; Cai, Hong-Chun; Wei, Bing; Ji, Ce; Feng, Shu-Ping; Wang, Meng; Xie, Wei-Ping; Deng, Jian-Jun

    2015-11-01

    Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter to yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%. PMID:26628136

  11. Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays

    E-print Network

    Gilchrist, James F.

    Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using SiO2 Institute of Physics. DOI: 10.1063/1.2816891 The external quantum efficiency EQE of InGaN quan- tum wells QWs light-emitting diodes LEDs ,1 depends on the injection efficiency inj , radiative efficiency rad

  12. Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using Si O 2 /polystyrene microlens arrays

    E-print Network

    Gilchrist, James F.

    Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using Si O://scitation.aip.org/termsconditions. Downloaded to IP: 128.180.2.168 On: Sat, 09 Nov 2013 07:17:24 #12;Enhancement of light extraction efficiency November 2007 Improvement of light extraction efficiency of InGaN quantum wells light emitting diodes LEDs

  13. Emissive Liquid-Crystal Display Panels Consisting of Red-Green-Blue Patterned Phosphor Layers and Near-Ultraviolet Light-Emitting-Diode Backlight

    NASA Astrophysics Data System (ADS)

    Yata, Tatsuya; Miyamoto, Yoshinobu; Ohmi, Koutoku

    2012-02-01

    Emissive liquid crystal display (e-LCD) panels consisting of 405 nm near-UV light-emitting-diode (LED) backlight and patterned red-green-blue phosphor layers have been proposed. Improvements in luminous efficiency and lifetime have been systematically attempted. From the results of the accelerated aging test under near-UV irradiation under high temperature and humidity conditions, it has been confirmed that the e-LCD panel has a sufficiently long lifetime for practical use. The light conversion efficiency of the phosphor layer has been significantly improved by using optical filters. Commission Internationale de l'Eclairage (CIE) color coordinates are (0.69, 0.31) for red, (0.27, 0.68) for green and (0.15, 0.04) for blue sub-pixels. The corresponding color gamut is over 100% compared with that of the National Television System Committee. The e-LCD panel also has a considerable wide-viewing-angle property, and its overall luminous efficiency is more than twice higher than those of conventional LCD panels consisting of white-LED and color filters.

  14. SU-E-T-223: Investigation of the Accuracy of Two-Dimensional Dose Distributions Measurement From High-Dose-Rate Brachytherapy Ir-192 Source Using Multiple-Diode-Array Detector (MapCheck2)

    SciTech Connect

    Taguenang, J; De La Fuente, T Herman; Ahmad, S; Ali, I

    2014-06-01

    Purpose: To investigate the dosimetric accuracy of multiple-diode-array detector (Mapcheck2) for high-dose-rate brachytherapy Ir-192 source. The two-dimensional (2D) dose distributions measured with MapCheck2 were validated with EBT2 Gafchromic film measurement and AAPM task-group- 43 (TG-43) modeling. Methods: 2D-dose distributions from Ir-192 source were measured with MapCheck2 and EBT2-films. MapCheck2 response was corrected for effects: directional dependence, diode and phantom heterogeneity. Optical density growth of the film was controlled by synchronized scanning of the film exposed to Ir-192 and calibration films exposed to 6 MV linac beams. Similarly, MapCheck2 response was calibrated to dose using 6 MV beams. An empirical model was developed for the dose distributions measured with Mapcheck2 that considered directional, diode and phantom heterogeneity corrections. The dose deposited in solid-state-detectors was modeled using a cavity theory model for the diode. This model was then validated with measurements using EBT2-films and calculations with TG-43. Results: The response of MapCheck2 has been corrected for different effects including: (a) directional dependence of 0–20% over angular range 0o–90o, (b) phantom heterogeneity (3%) and (c) diode heterogeneity (9%). The corrected dose distributions measured with MapCheck2 agreed well with the measured dose distributions from EBT2-film and with calculations using TG-43 within 5% over a wide range of dose levels and rates. The advantages of MapCheck2 include less noisy, linear and stable response compared with film. The response of MapCheck2 exposed to 192Ir-source showed no energy dependence similar to its response to MV energy beam. Detection spatial-resolution of individual diodes was 0.8×0.8 mm2, however, 2DMapCheck2 resolution is limited by distance between diodes (7.07 mm). Conclusion: The dose distribution measured with MapCheck2 agreed well within 5% with that measured using EBT2-films; and calculations with TG- 43. Considering correction of artifacts, MapCheck2 provides a compact, practical and accurate dosimetric tool for measurement of 2D-dose distributions for brachytherapy Ir-192.

  15. The effects of ultraviolet-ozone-treated ultra-thin MnO-doped ZnO film as anode buffer layer on the electrical characteristics of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Lu, Hsin-Wei; Kao, Po-Ching; Juang, Yung-Der; Chu, Sheng-Yuan

    2015-11-01

    In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing an MnO-doped ZnO film as a buffer layer between the indium tin oxide (ITO) electrode and the ?-naphthylphenylbiphenyldiamine hole transport layer. The enhancement mechanism was systematically investigated, and the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone-treated MnO-doped ZnO film. With this film, the work function increased from 4.8 eV (standard ITO electrode (˜ 10 ±5 ?/? )) to 5.27 eV (UV-ozone-treated MnO-doped ZnO deposited on the ITO electrode with 1 wt. % for 1 nm), while the surface roughness of the UV-ozone-treated MnO-doped ZnO film was smoother than that of the ITO electrode. The deposited UV-ozone-treated MnO-doped ZnO film increased the surface energy and polarity of the ITO surface, as determined from contact angle measurements. Further, results from admittance spectroscopy showed that the inserted UV-ozone-treated MnO-doped ZnO film increased the capacitance and conductance of the OLEDs. It was also found that the carrier injection increased in the space-charge region when the UV-ozone-treated MnO-doped ZnO buffer layer was inserted. Moreover, the turn-on voltage of the devices decreased from 3.8 V to 3.2 V, the luminance increased from 7588 cd/m2 to 20 350 cd/m2, and the current efficiency increased from 3.2 cd/A to 5.8 cd/A when a 1 nm-thick UV-ozone-treated MnO-doped ZnO film with 1 wt. % was inserted as a buffer layer in the OLEDs.

  16. Ultraviolet Waves

    ERIC Educational Resources Information Center

    Molde, Trevor

    1973-01-01

    Outlines the discovery and nature of ultraviolet light, discusses some applications for these wavelengths, and describes a number of experiments with ultraviolet radiation suitable for secondary school science classes. (JR)

  17. Diode-pumped laser research

    NASA Technical Reports Server (NTRS)

    Ramos-Izquierdo, L.; Bufton, J. L.; Chan, K.

    1988-01-01

    The Laboratory for Oceans is currently working on the development of compact laser diode array (LD) pumped Nd:YAG lasers for use in space-based altimetry and ranging. Laser diode-array pumping technology promises to increase the electrical to optical efficiency of solid state lasers by an order of magnitude with a lifetime increase of nearly three orders of magnitude relative to today's conventional flashlamp-pumped laser systems. The small size, efficiency, and ruggedness make LD-pumped solid state lasers ideal for space based applications. In an in-house RTOP effort, a novel multiple-pass LD-pumped Nd:YAG laser amplifier was designed and tested to increase the 100 microjoule output pulse energy of the Lightwave laser oscillator. Preliminary results have yielded a round trip amplifier gain of about 15 percent using 7 microjoule LD-pump energy. As a parallel activity, funding was recently obtained to investigate the possible use of custom made fiber optic arrays to obtain an efficient optical coupling mechanism between the emitting laser diode-arrays and the target solid state laser material. Fiber optic coupling arrays would allow for the easy manipulation of the spatial emitting pattern of the diode pump sources to match either an end or side pumping laser configuration.

  18. Diode-pumped laser research

    NASA Astrophysics Data System (ADS)

    Ramos-Izquierdo, L.; Bufton, J. L.; Chan, K.

    The Laboratory for Oceans is currently working on the development of compact laser diode array (LD) pumped Nd:YAG lasers for use in space-based altimetry and ranging. Laser diode-array pumping technology promises to increase the electrical to optical efficiency of solid state lasers by an order of magnitude with a lifetime increase of nearly three orders of magnitude relative to today's conventional flashlamp-pumped laser systems. The small size, efficiency, and ruggedness make LD-pumped solid state lasers ideal for space based applications. In an in-house RTOP effort, a novel multiple-pass LD-pumped Nd:YAG laser amplifier was designed and tested to increase the 100 microjoule output pulse energy of the Lightwave laser oscillator. Preliminary results have yielded a round trip amplifier gain of about 15 percent using 7 microjoule LD-pump energy. As a parallel activity, funding was recently obtained to investigate the possible use of custom made fiber optic arrays to obtain an efficient optical coupling mechanism between the emitting laser diode-arrays and the target solid state laser material. Fiber optic coupling arrays would allow for the easy manipulation of the spatial emitting pattern of the diode pump sources to match either an end or side pumping laser configuration.

  19. The evaluation of a 2D diode array in “magic phantom” for use in high dose rate brachytherapy pretreatment quality assurance

    SciTech Connect

    Espinoza, A.; Petasecca, M.; Fuduli, I.; Lerch, M. L. F.; Rosenfeld, A. B.; Howie, A.; Bucci, J.; Corde, S.; Jackson, M.

    2015-02-15

    Purpose: High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The development of a sound quality assurance program for the verification of treatment deliveries can be challenging due to the high source activity utilized and the need for precise measurements of dwell positions and times. This paper describes the application of a novel phantom, based on a 2D 11 × 11 diode array detection system, named “magic phantom” (MPh), to accurately measure plan dwell positions and times, compare them directly to the treatment plan, determine errors in treatment delivery, and calculate absorbed dose. Methods: The magic phantom system was CT scanned and a 20 catheter plan was generated to simulate a nonspecific treatment scenario. This plan was delivered to the MPh and, using a custom developed software suite, the dwell positions and times were measured and compared to the plan. The original plan was also modified, with changes not disclosed to the primary authors, and measured again using the device and software to determine the modifications. A new metric, the “position–time gamma index,” was developed to quantify the quality of a treatment delivery when compared to the treatment plan. The MPh was evaluated to determine the minimum measurable dwell time and step size. The incorporation of the TG-43U1 formalism directly into the software allows for dose calculations to be made based on the measured plan. The estimated dose distributions calculated by the software were compared to the treatment plan and to calibrated EBT3 film, using the 2D gamma analysis method. Results: For the original plan, the magic phantom system was capable of measuring all dwell points and dwell times and the majority were found to be within 0.93 mm and 0.25 s, respectively, from the plan. By measuring the altered plan and comparing it to the unmodified treatment plan, the use of the position–time gamma index showed that all modifications made could be readily detected. The MPh was able to measure dwell times down to 0.067 ± 0.001 s and planned dwell positions separated by 1 mm. The dose calculation carried out by the MPh software was found to be in agreement with values calculated by the treatment planning system within 0.75%. Using the 2D gamma index, the dose map of the MPh plane and measured EBT3 were found to have a pass rate of over 95% when compared to the original plan. Conclusions: The application of this magic phantom quality assurance system to HDR brachytherapy has demonstrated promising ability to perform the verification of treatment plans, based upon the measured dwell positions and times. The introduction of the quantitative position–time gamma index allows for direct comparison of measured parameters against the plan and could be used prior to patient treatment to ensure accurate delivery.

  20. Integrated injection-locked semiconductor diode laser

    DOEpatents

    Hadley, G. Ronald (Albuquerque, NM); Hohimer, John P. (Albuquerque, NM); Owyoung, Adelbert (Albuquerque, NM)

    1991-01-01

    A continuous wave integrated injection-locked high-power diode laser array is provided with an on-chip independently-controlled master laser. The integrated injection locked high-power diode laser array is capable of continuous wave lasing in a single near-diffraction limited output beam at single-facet power levels up to 125 mW (250 mW total). Electronic steering of the array emission over an angle of 0.5 degrees is obtained by varying current to the master laser. The master laser injects a laser beam into the slave array by reflection of a rear facet.

  1. Integrated injection-locked semiconductor diode laser

    DOEpatents

    Hadley, G.R.; Hohimer, J.P.; Owyoung, A.

    1991-02-19

    A continuous wave integrated injection-locked high-power diode laser array is provided with an on-chip independently-controlled master laser. The integrated injection locked high-power diode laser array is capable of continuous wave lasing in a single near-diffraction limited output beam at single-facet power levels up to 125 mW (250 mW total). Electronic steering of the array emission over an angle of 0.5 degrees is obtained by varying current to the master laser. The master laser injects a laser beam into the slave array by reflection of a rear facet. 18 figures.

  2. SiC-Based Schottky Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai

    1997-01-01

    Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one can affect the diode stability as well as the diode sensitivity to various gases. It is concluded that the ability of SiC to operate as a high temperature semiconductor significantly enhances the versatility of the Schottky diode gas sensing structure and will potentially allow the fabrication of a SiC-based gas sensor arrays for versatile high temperature gas sensing applications.

  3. High-power laser diodes at various wavelengths

    SciTech Connect

    Emanuel, M.A.

    1997-02-19

    High power laser diodes at various wavelengths are described. First, performance and reliability of an optimized large transverse mode diode structure at 808 and 941 nm are presented. Next, data are presented on a 9.5 kW peak power array at 900 nm having a narrow emission bandwidth suitable for pumping Yb:S-FAP laser materials. Finally, results on a fiber-coupled laser diode array at {approx}730 nm are presented.

  4. Characterization and quantitative analysis of phenylpropanoid amides in eggplant (Solanum melongena L.) by high performance liquid chromatography coupled with diode array detection and hybrid ion trap time-of-flight mass spectrometry.

    PubMed

    Sun, Jing; Song, Yue-Lin; Zhang, Jing; Huang, Zheng; Huo, Hui-Xia; Zheng, Jiao; Zhang, Qian; Zhao, Yun-Fang; Li, Jun; Tu, Peng-Fei

    2015-04-01

    Eggplant (Solanum melongena L.) is a famous edible and medicinal plant. Despite being widely cultivated and used, data on certain parts other than the fruit are limited. The present study focused on the qualitative and quantitative analysis of the chemical constituents, particularly phenylpropanoid amides (PAs), in eggplant. The mass fragmentation patterns of PAs were proposed using seven authentic compounds with the assistance of a hybrid ion trap time-of-flight mass spectrometer. Thirty-seven compounds (27 PAs and 10 others) were detected and plausibly assigned in the different parts of eggplant. Afterward, a reliable method based on liquid chromatography coupled with diode array detection was developed, validated, and applied for the simultaneous determination of seven PAs and three caffeoylquinic acids in 17 batches of eggplant roots with satisfactory accuracy, precision, and reproducibility, which could not only provide global chemical insight of eggplant but also offer a reliable tool for quality control. PMID:25796999

  5. Qualitative and quantitative analysis of the major constituents in Jin-Mu-Gan-Mao tablet by high-performance liquid chromatography with diode-array detection and quadrupole time-of-flight tandem mass spectrometry.

    PubMed

    Huang, Mingqing; Xu, Shuyu; Xu, Wen; Chen, Daxing; Chu, Kedan; Xu, Wei; Peng, Jun; Lu, Jinjian

    2014-12-01

    Jin-Mu-Gan-Mao tablet is a well-known traditional Chinese medicinal preparation, which has been used to treat the common cold in China. In this study, a systematic method was established for the qualitative and quantitative analysis of the major constituents in Jin-Mu-Gan-Mao tablet. First, a method of high-performance liquid chromatography with diode-array detection and quadrupole time-of-flight mass spectrometry was developed for identification of the multi-constituents. Thirty-one compounds including ten phenolic acids, 18 flavonoids, and three iridoid glycosides were clearly identified by comparison with the reference standards, and 11 compounds were deduced by comparison with the literature data. Second, a new quantitative analysis method of Jin-Mu-Gan-Mao tablet was established by high-performance liquid chromatography with diode-array detection. Twelve compounds, either with high contents or strong bioactivities, were chosen as marker components. This analytical method was validated through intra- and interday precision, repeatability, and stability, with respective relative standard deviations less than 1.74, 2.54, 2.44, and 2.48%. The limits of detection and quantification were less than 0.327 and 0.881 ?g/mL, respectively. The overall recoveries ranged from 97.04-102.76% (relative standard deviation ? 2.91%). Then this validated method was applied to determine ten batches of Jin-Mu-Gan-Mao tablet. The results indicated that these new approaches can be applicable for the qualitative and quantitative analysis of Jin-Mu-Gan-Mao tablet. PMID:25229383

  6. Qualitative and quantitative analysis of the major constituents in Chinese medicinal preparation Dan-Lou tablet by ultra high performance liquid chromatography/diode-array detector/quadrupole time-of-flight tandem mass spectrometry.

    PubMed

    Dong, Juan; Zhu, Yan; Gao, Xiumei; Chang, Yanxu; Wang, Meng; Zhang, Peng

    2013-06-01

    A rapid ultra high performance liquid chromatography/diode-array detector/quadrupole time-of-flight tandem mass spectrometry (UPLC-DAD-QTOF) method and a ultra high performance liquid chromatography coupled with diode-array detector (UPLC-DAD) method were developed for qualitative and quantitative analyses of the major chemical constituents in Dan-Lou tablet. Sixty-eight compounds including flavonoids, phenolic acids, tanshinones, protostane triterpenoids, lactones, and paeoniflorins were unambiguously or tentatively identified by comparing their retention times and accurate mass measurement in 40min with references or literature data. Among them, 19 compounds: gallic acid, danshensu, 5-hydroxymethyl-2-furaldehyde, 3'-hydroxy puerarin, puerarin, 3'-methoxy puerarin, mirificin, daidzin, paeoniflorin, calycosin-7-O-?-D-glucoside, naringin, genistin, rosmarinic acid, salvianolic acid B, salvianolic acid A, formononetin, calycosin, cryptotanshinone and tanshinone IIA were further quantified in 30min as marker substances. It was found that the calibration curves for all analytes showed good linearity (R(2)>0.9997) within the test ranges. The overall limits of detection (LODs) and limits of quantification (LOQs) were 0.0073-0.34?g/mL and 0.022-1.04?g/mL, respectively. The relative standard deviations (RSDs) for intra- and inter-day precisions were below 1.90% and 2.85%, respectively. The results of repeatability were less than 2.74%. The sample was stable for at least 48h. The mean recovery rates ranged from 95.5% to 105% with the relative standard deviations (RSDs) less than 2.96%. The results showed that the developed quantitative method was linear, sensitive, and precise for quality control of Dan-Lou tablet. PMID:23518306

  7. Evaluation of a method based on liquid chromatography-diode array detector-tandem mass spectrometry for a rapid and comprehensive characterization of the fat-soluble vitamin and carotenoid profile of selected plant foods.

    PubMed

    Gentili, Alessandra; Caretti, Fulvia

    2011-02-01

    The feasibility of using reversed-phase liquid chromatography/diode array/tandem mass spectrometry (LC-DAD-MS/MS) for a rapid and comprehensive profiling of fat soluble vitamins and pigments in some foods of plant origin (maize flour, green and golden kiwi) was evaluated. The instrumental approach was planned for obtaining two main outcomes within the same chromatographic run: (i) the quantitative analysis of ten target analytes, whose standards are commercially available; (ii) the screening of pigments occurring in the selected matrices. The quantitative analysis was performed simultaneously for four carotenoids (lutein, zeaxanthin, ?-cryptoxanthin, and ?-carotene) and six compounds with fat-soluble activity (?-tocopherol, ?-tocopherol, ?-tocopherol, ergocalciferol, phylloquinone and menaquinone-4), separated on a C30 reversed-phase column and detected by atmospheric pressure chemical ionization (APCI) tandem mass spectrometry, operating in Selected Reaction Monitoring (SRM) mode. Extraction procedure was based on matrix solid-phase dispersion with recoveries of all compounds under study exceeding 78 and 60% from maize flour and kiwi, respectively. The method intra-day precision ranged between 3 and 7%, while the inter-day one was below 12%. The mild isolation conditions precluded artefacts creation, such as cis-isomerization phenomena for carotenoids. During the quantitative LC-SRM determination of the ten target analytes, the identification power of the diode array detector joined to that of the triple quadrupole (QqQ) allowed the tentatively identification of several pigments (chlorophylls and carotenoids), without the aid of standards, on the basis of: (i) the UV-vis spectra recorded in the range of 200-700nm; (ii) the expected retention time; (iii) the two SRM transitions, chosen for the target carotenoids but also common to many of isomeric carotenoids occurring in the selected foods. PMID:21190690

  8. Ultraviolet emission intensity, visible luminance, and electrical characteristics of small arrays of Al/Al2O3 microcavity plasma devices operating in Ar/N2 or Ne at high-power loadings

    NASA Astrophysics Data System (ADS)

    Park, S.-J.; Kim, K.-S.; Eden, J. G.

    2006-01-01

    Small arrays (3×3-->10×10) of microcavity plasma devices, having a two-stage structure comprising multilayer stacks of nanostructured Al2O3 grown on Al foil with cylindrical microcavities 100-300 ?m in diameter, produce intense ultraviolet (UV) and visible emission when operated in Ar/3% N2 gas mixtures or Ne and excited by a sinusoidal ac voltage wave form. Near-UV (300-400 nm) intensities emitted into a solid angle of ~10-2 sr above 30 mW per cm2 of radiating area are measured for Ar/N2 gas mixture pressures of 400-800 Torr, an excitation frequency of 15 kHz, and an average current >=20 mA (rms). Two or more conjoined cylindrical microcavities of differing diameters allow for the confinement of the plasma to progressively smaller volumes as the power deposited is increased (thereby decreasing the Debye length and the spatial extent of the cathode fall region) and provides a convenient tool with which the luminosity of an array can be modulated. The transition of a microplasma from confinement in a 200-?m-diam cavity into an adjacent 100-?m-diam microcavity is accompanied by an order-of-magnitude increase in the luminance of Ne plasmas in a 3×3 array as the rms current is increased by ~1 mA.

  9. Isolation and identification of phenolic compounds from rum aged in oak barrels by high-speed countercurrent chromatography/high-performance liquid chromatography-diode array detection-electrospray ionization mass spectrometry and screening for antioxidant activity.

    PubMed

    Regalado, Erik L; Tolle, Sebastian; Pino, Jorge A; Winterhalter, Peter; Menendez, Roberto; Morales, Ana R; Rodríguez, José L

    2011-10-14

    Beverages, especially wines are well-known to contain a variety of health-beneficial bioactive substances, mainly of phenolic nature which frequently exhibit antioxidant activity. Significant information is available about the separation and identification of polyphenols from some beverages by chromatographic and spectroscopic techniques, but considerably poor is chemical data related to the polyphenolic content in rums. In this paper, a method involving the all-liquid chromatographic technique of high-speed countercurrent chromatography (HSCCC) combined with high-performance liquid chromatography coupled with diode-array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS(n)) has been successfully applied for separation and identification of phenolic compounds in an aged rum. Besides, the phenolic fraction (PF) was assayed for its antioxidant effects using three different free radical in vitro assays (DPPH·, RO(2)· and spontaneous lipid peroxidation (LPO) on brain homogenates) and on ferric reducing antioxidant power (FRAP). Results showed that PF potently scavenged DPPH and strongly scavenged peroxyl radicals compared to ascorbic acid and butylated hydroxytoluene (BHT); and almost equally inhibited LPO on brain homogenates subjected to spontaneous LPO when compared to quercetin. Moreover, PF also exhibited strong reducing power. This chemical analysis illustrates the rich array of phenols in the aged rum and represents a rapid and suitable method for the isolation and identification of phenolic compounds from mixtures of considerable complexity, achieving high purity and reproducibility with the use of two separation steps. PMID:21907994

  10. New diode wavelengths for pumping solid-state lasers

    SciTech Connect

    Skidmore, J.A.; Emanuel, M.A.; Beach, R.J.

    1995-01-01

    High-power laser-diode arrays have been demonstrated to be viable pump sources for solid-state lasers. The diode bars (fill factor of 0.7) were bonded to silicon microchannel heatsinks for high-average-power operation. Over 12 W of CW output power was achieved from a one cm AlGaInP tensile-strained single-quantum-well laser diode bar. At 690 nm, a compressively-strained single-quantum-well laser-diode array produced 360 W/cm{sup 2} per emitting aperture under CW operation, and 2.85 kW of pulsed power from a 3.8 cm{sup 2} emitting-aperture array. InGaAs strained single-quantum-well laser diodes emitting at 900 nm produced 2.8 kW pulsed power from a 4.4 cm{sup 2} emitting-aperture array.

  11. Applications of Circular Array Sensors

    E-print Network

    Trawick, Charles D.

    The application of the Reticon RO-64 annular photo-diode array to the task of optical tracking of special targets, direct optical focusing, and automatic printed circuit board inspection were studied. In order to facilitate ...

  12. Schottky barrier diode and method thereof

    NASA Technical Reports Server (NTRS)

    Aslam, Shahid (Inventor); Franz, David (Inventor)

    2008-01-01

    Pt/n.sup.-GaN Schottky barrier diodes are disclosed that are particularly suited to serve as ultra-violet sensors operating at wavelengths below 200 nm. The Pt/n.sup.-GaN Schottky barrier diodes have very large active areas, up to 1 cm.sup.2, which exhibit extremely low leakage current at low reverse biases. Very large area Pt/n.sup.-GaN Schottky diodes of sizes 0.25 cm.sup.2 and 1 cm.sup.2 have been fabricated from n.sup.-/n.sup.+ GaN epitaxial layers grown by vapor phase epitaxy on single crystal c-plane sapphire, which showed leakage currents of 14 pA and 2.7 nA, respectively for the 0.25 cm.sup.2 and 1 cm.sup.2 diodes both configured at a 0.5V reverse bias.

  13. Electrical and optical study of semiconductor laser diodes and materials

    NASA Technical Reports Server (NTRS)

    Albin, Sacharia

    1987-01-01

    The characterization of a 2-D diode laser array from McDonald Douglas has been completed. The array consisted of 8 linear arrays of approximately 11 mm x 0.18 mm. Each array has between 7 and 8 diodes per mm. The threshold current is approximately 15 amps. The power output vs drive current (above threshold) of the array was measured. A peak power of 50 W was obtained at a drive current of 26 amps. Its far field pattern has a double lobe.

  14. Determination of flibanserin and tadalafil in supplements for women sexual desire enhancement using high-performance liquid chromatography with tandem mass spectrometer, diode array detector and charged aerosol detector.

    PubMed

    Poplawska, Magdalena; Blazewicz, Agata; Zolek, Paulina; Fijalek, Zbigniew

    2014-06-01

    The new compound - flibanserin - begun to appear as a synthetic adulterant in counterfeit herbal supplements used to stimulate women sexual drive. It was detected in two samples submitted to the Polish National Medicines Institute for analysis. The second sample contained also tadalafil. This study presents the LC method development which enables the determination of flibanserin and tadalafil. It employs three different detectors charged aerosol detector (CAD), diode array detector (DAD) and mass spectrometer (MS). The conditions of the elaborated method were optimized to obtain the highest sensitivity and the best resolution, especially the separation of icariin - the natural compound observed often in supplements for sexual disorders. The validation of the method proved good linearity, good accuracy and precision of the measurements recorded by all three detectors. Additionally, for CAD data, an alternative calculation method using a unified calibration function was presented and evaluated. It seems that this is the way to overcome the problem of non-availability of the reference standard of a target compound. Flibanserin content was quantified using the data of other reference standard (tadalafil). The inaccuracy of proposed indirect determination was found to be ±3%. A statistical evaluation proved that the results obtained with all detection modes and the results calculated using a unified calibration were not significantly different (p>0.05). PMID:24531007

  15. Improvement of signal-to-noise ratio of optoacoustic signals from double-walled carbon nanotubes by using an array of dual-wavelength high-power diode lasers

    NASA Astrophysics Data System (ADS)

    Leggio, Luca; de Varona, Omar E.; Escudero, Pedro; Carpintero del Barrio, Guillermo; Osi?ski, Marek; Lamela Rivera, Horacio

    2015-07-01

    Optoacoustic (OA) imaging is a rising biomedical technique that has attracted much interest over the last 15 years. This technique permits to visualize the internal soft tissues in depth by using short laser pulses, able to generate ultrasonic signals in a large frequency range. It combines the high contrast of optical imaging with the high resolution of ultrasound systems. The OA signals detected from the whole surface of the body serve to reconstruct in detail the image of the internal tissues, where the absorbed optical energy distribution outlines the regions of interest. In fact, the use of contrast agents could improve the detection of growing anomalies in soft tissues, such as carcinomas. This work proposes the use of double-walled carbon nanotubes (DWCNTs) as a potential nontoxic biodegradable contrast agent applicable in OA to reveal the presence of malignant in-depth tissues in near infrared (NIR) wavelength range (0.75-1.4 ?m), where the biological tissues are fairly transparent to optical radiation. A dual-wavelength (870 and 905 nm) OA system is presented, based on arrays of high power diode lasers (HPDLs) that generate ultrasound signals from a DWCNT solution embedded within a biological phantom. The OA signals generated by DWCNTs are compared with those obtained using black ink, considered to be a very good absorber at these wavelengths. The experiments prove that DWCNTs are a potential contrast agent for optoacoustic spectroscopy (OAS).

  16. Computer-aided method for identification of major flavone/flavonol glycosides by high-performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS).

    PubMed

    Wang, Zhengfang; Lin, Longze; Harnly, James M; Harrington, Peter de B; Chen, Pei

    2014-11-01

    A new computational tool is proposed here for tentatively identifying major (UV quantifiable) flavone/flavonol glycoside peaks of high performance liquid chromatogram (HPLC)-diode array detection (DAD)-tandem mass spectrometry (MS/MS) profiles based on a MATLAB-based script implementing an in-house algorithm. The HPLC-DAD-MS/MS profiles of red onion, Chinese lettuce, carrot leaf, and celery seed extracts were analyzed by the proposed computer-aided screening method for identifying possible flavone/flavonol glycoside peaks from the HPLC-UV and MS total ion current (TIC) chromatograms. The number of identified flavone/flavonol glycoside peaks of the HPLC-UV chromatograms is four, four, six, and nine for red onion, Chinese lettuce, carrot leaf, and celery seed, respectively. These results have been validated by human(s) experts. For the batch processing of nine HPLC-DAD-MS/MS profiles of celery seed extract, the entire script execution time was within 15 s while manual calculation of only one HPLC-DAD-MS/MS profile by a flavonoid expert could take hours. Therefore, this MATLAB-based screening method is able to facilitate the HPLC-DAD-MS/MS analysis of flavone/flavonol glycosides in plants to a large extent. PMID:25270867

  17. Molecularly imprinted nano particles combined with miniaturized homogenous liquid-liquid extraction for the selective extraction of loratadine in plasma and urine samples followed by high performance liquid chromatography-photo diode array detection.

    PubMed

    Ebrahimzadeh, H; Molaei, K; Asgharinezhad, A A; Shekari, N; Dehghani, Z

    2013-03-12

    In this work a molecularly imprinted polymer was developed as a selective sorbent for extraction of loratadine (as a model) in complex matrices followed by miniaturized homogeneous liquid-liquid extraction (MHLLE) for the first time. The molecularly imprinted polymer (MIP) which is based on loratadine as the template was synthesized successfully by precipitation polymerization and was used as a selective sorbent. This technique was applied for preconcentration, sample preparation, and determination of loratadine using high performance liquid chromatography-photo diode array detection (HPLC-PDA). Optimization of various parameters affecting molecular imprinted solid phase extraction (MISPE), such as pH of adsorption, composition and volume of eluent, adsorption and desorption times were investigated. Besides, in the subsequent stage (MHLLE) the type and volume of extraction solvent, sodium hydroxide amount, surfactant concentration, and extraction time were investigated and optimized. Under the optimal condition, maximum enrichment capacity and Langmuir constant were 91mgg(-1) and 0.014Lmg(-1), respectively. Furthermore, enrichment factor and extraction recovery of MIP-MHLLE method were 30 and 90%, respectively. The LOD of the proposed method was 0.2?gL(-1) and a linear dynamic range of 1-1000?gL(-1) was obtained with correlation coefficient of greater than 0.998. The present method was applied for extraction and determination of loratadine in plasma and urine samples in ?gL(-1) levels and satisfactory results were achieved (RSD <8% based on three replicate measurements). PMID:23452800

  18. Dispersive liquid-liquid microextraction for the determination of macrocyclic lactones in milk by liquid chromatography with diode array detection and atmospheric pressure chemical ionization ion-trap tandem mass spectrometry.

    PubMed

    Campillo, Natalia; Viñas, Pilar; Férez-Melgarejo, Gema; Hernández-Córdoba, Manuel

    2013-03-22

    Eprinomectin (EPRI), abamectin (ABA), doramectin (DOR), moxidectin (MOX) and ivermectin (IVM) were determined in milk samples using dispersive liquid-liquid microextraction (DLLME) and liquid chromatography with diode array detection (LC-DAD) coupled to atmospheric pressure chemical ionization in negative ion mode ion-trap tandem mass spectrometry (APCI-IT-MS/MS). Milk proteins were removed by precipitation with trichloroacetic acid and the analytes were preconcentrated using 2mL of acetonitrile containing 200?L of chloroform as extraction mixture. The effect of several parameters for the liquid-liquid microextraction efficiency was evaluated. Standard additions method was used for quantification purposes, the correlation coefficients were better than 0.9970 in all cases and the quantification limits ranged from 1.0 to 4.7ngg(-1) and from 0.1 to 2.4ngg(-1) when using DAD and MS, respectively. The DLLME-LC-APCI-IT-MS/MS optimized method was successfully applied to different milk samples and none of the studied analytes was detected in the samples studied. The recoveries for milk samples spiked at concentration levels ranging between 0.5 and 50ngg(-1), depending on the compound, were between 89.5 and 105%, with relative standard deviations lower than 9% (n=135). Simplicity, rapidity and reliability are important advantages of the proposed method, while the sample preparation step can be regarded as environmentally friendly. PMID:23415139

  19. A new ultrahigh performance liquid chromatography with diode array detection coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry analytical strategy for fast analysis and improved characterization of phenolic compounds in apple products.

    PubMed

    Ramirez-Ambrosi, M; Abad-Garcia, B; Viloria-Bernal, M; Garmon-Lobato, S; Berrueta, L A; Gallo, B

    2013-11-01

    A new, rapid, selective and sensitive ultrahigh performance liquid chromatography with diode array detection coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (UHPLC-DAD-ESI-Q-ToF-MS) strategy using automatic and simultaneous acquisition of exact mass at high and low collision energy, MS(E), has been developed to obtain polyphenolic profile of apples, apple pomace and apple juice from Asturian cider apples in a single run injection of 22 min. MS(E) spectral data acquisition overcomes chromatographic co-elution problems, performing simultaneous collection of precursor ions as well as other ions produced as a result of their fragmentation, which allows resolving complex spectra from mixtures of precursor ions in an unsupervised way and eases their interpretation. Using this technique, 52 phenolic compounds of five different classes were readily characterized in these apple extracts in both positive and negative ionization modes. The spectral data for phenolic compounds obtained using this acquisition mode are comparable to those obtained by conventional LC-MS/MS as exemplified in this work. Among the 52 phenolic compounds identified in this work, 2 dihydrochalcones and 3 flavonols have been tentatively identified for the first time in apple products. Moreover, 2 flavanols, 4 dihydrochalcones, 9 hydroxycinnamic acids and 4 flavonols had not been previously reported in apple by ToF analysis to our knowledge. PMID:24120027

  20. Silane modified magnetic nanoparticles as a novel adsorbent for determination of morphine at trace levels in human hair samples by high-performance liquid chromatography with diode array detection.

    PubMed

    Boojaria, Ali; Masrournia, Mahboubeh; Ghorbani, Hamideh; Ebrahimitalab, Abdolhossein; Miandarhoie, Mina

    2015-12-01

    In this paper we report a novel, sensitive, and rapid method of magnetic solid phase extraction based on surface modified magnetic nanoparticles as a novel nano sorbent for HPLC determination of morphine with diode array detection in human hair samples. Factors affecting the extraction efficiency of the proposed method, including the sample pH, quantity of magnetic nanoparticles, sample volume, desorption solvent type and its volume, and extraction time were investigated and optimized. Under the optimized experimental conditions, a good linearity was observed in the range of 1-800 µgL(-1) for the morphine, with a correlation coefficient (R (2)) of 0.990. The pre-concentration factor of 208.69 was achieved in this method. The detection limit of the method was 0.1 ?gL(-1) based on S/N = 3 and good reproducibility with a relative standard deviations lower than (n = 5) 2.59 %. The proposed method has been successfully applied to the analysis of trace amounts of morphine in human hair samples with satisfactory results. This method can be applied in medical toxicology research and forensic medical centers. PMID:26318597

  1. Methods of analysis by the U.S. Geological Survey Organic Geochemistry Research Group; determination of chloroacetanilide herbicide metabolites in water using high-performance liquid chromatography-diode array detection and high-performance liquid chromatography/mass spectrometry

    USGS Publications Warehouse

    Zimmerman, L.R.; Hostetler, K.A.; Thurman, E.M.

    2000-01-01

    Analytical methods using high-performance liquid chromatography-diode array detection (HPLC-DAD) and high-performance liquid chromatography/mass spectrometry (HPLC/MS) were developed for the analysis of the following chloroacetanilide herbicide metabolites in water: acetochlor ethanesulfonic acid (ESA), acetochlor oxanilic acid (OXA), alachlor ESA, alachlor OXA, metolachlor ESA, and metolachlor OXA. Good precision and accuracy were demonstrated for both the HPLC-DAD and HPLC/MS methods in reagent water, surface water, and ground water. The mean HPLC-DAD recoveries of the chloroacetanilide herbicide metabolites from water samples spiked at 0.25, 0.50, and 2.0 mg/L (micrograms per liter) ranged from 84 to 112 percent, with relative standard deviations of 18 percent or less. The mean HPLC/MS recoveries of the metabolites from water samples spiked at 0.05, 0.20, and 2.0 mg/L ranged from 81 to 125 percent, with relative standard deviations of 20 percent or less. The limit of quantitation (LOQ) for all metabolites using the HPLC-DAD method was 0.20 mg/L, whereas the LOQ using the HPLC/MS method was 0.05 mg/L. These metabolite-determination methods are valuable for acquiring information about water quality and the fate and transport of the parent chloroacetanilide herbicides in water.

  2. Metabolism of calcium antagonist Ro 40-5967: a case history of the use of diode-array u.v. spectroscopy and thermospray-mass spectrometry in the elucidation of a complex metabolic pathway.

    PubMed

    Wiltshire, H R; Harris, S R; Prior, K J; Kozlowski, U M; Worth, E

    1992-07-01

    1. The calcium antagonist, Ro 40-5967, is metabolized to a multitude of products by the rat and drug-related material is excreted predominantly via the bile. 2. Diode-array u.v. spectroscopy, following reverse phase h.p.l.c. separation of the partially purified metabolites, has been used to classify these compounds into six spectral classes which have been correlated with different metabolic reactions. 3. Connection of a mass spectrometer directly to the h.p.l.c. equipment by a thermospray interface, produced useful mass spectra. These, together with the u.v. spectra, enabled the structures of many metabolites to be elucidated. 4. Confirmation of structural assignments was provided by n.m.r. spectra of the major metabolites. 5. Major metabolic pathways included N-demethylation (16% of the biliary metabolites), hydrolysis of the ester side-chain (32%), hydroxylation at 4- (19%) and 5- (29%) positions of the benzimidazole ring, aromatization of the tetrahydronaphthyl system (26%), loss of the benzimidazole (15%) and glucuronidation of hydroxyl groups (81%). PMID:1455903

  3. Fragmentation study of iridoid glycosides and phenylpropanoid glycosides in Radix Scrophulariae by rapid resolution liquid chromatography with diode-array detection and electrospray ionization time-of-flight mass spectrometry.

    PubMed

    Wu, Qian; Yuan, Quan; Liu, E-Hu; Qi, Lian-Wen; Bi, Zhi-Ming; Li, Ping

    2010-08-01

    Rapid resolution liquid chromatography (RRLC) coupled with diode array detection (DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS) method was applied to the mass spectral study of a series of naturally occurring iridoid glycosides and phenylpropanoid glycosides in Radix Scrophulariae, which provides higher speed and increased sensitivity without loss of resolution. With dynamic adjustment as the key role of the fragmentor voltage and confirmed with authentic standards, valuable structural information regarding the nature of both the glycoside skeletons was thus obtained. Most compositions were found to possess organic acid moiety such as cinnamoyl, caffeoyl and ferulyol. Besides extensive fragmentation of the carbohydrate moiety, losses of the hydroxyl and glucose residue units showed in the spectra, permitting the exploration of the skeleton and the identity of substituents in the molecule. Ten major iridoid glycosides and 10 phenylpropanoid glycosides were identified or tentatively characterized based on their retention times, UV and TOF MS data. The major fragmentation pathways of PGs in Radix Scrophulariae obtained through the MS data was schemed systematically for the first time, which provides a reference for other PGs derivatives. PMID:20017212

  4. Strong photonic crystal behavior in regular arrays of core-shell and quantum disc InGaN/GaN nanorod light-emitting diodes

    SciTech Connect

    Lewins, C. J. Le Boulbar, E. D.; Lis, S. M.; Shields, P. A.; Allsopp, D. W. E.; Edwards, P. R.; Martin, R. W.

    2014-07-28

    We show that arrays of emissive nanorod structures can exhibit strong photonic crystal behavior, via observations of the far-field luminescence from core-shell and quantum disc InGaN/GaN nanorods. The conditions needed for the formation of directional Bloch modes characteristic of strong photonic behavior are found to depend critically upon the vertical shape of the nanorod sidewalls. Index guiding by a region of lower volume-averaged refractive index near the base of the nanorods creates a quasi-suspended photonic crystal slab at the top of the nanorods which supports Bloch modes. Only diffractive behavior could be observed without this region. Slab waveguide modelling of the vertical structure shows that the behavioral regime of the emissive nanorod arrays depends strongly upon the optical coupling between the nanorod region and the planar layers below. The controlled crossover between the two regimes of photonic crystal operation enables the design of photonic nanorod structures formed on planar substrates that exploit either behavior depending on device requirements.

  5. Matrix-free analysis of selected benzodiazepines in human serum samples using alternating trilinear decomposition modeling of fast liquid chromatography diode array detection data.

    PubMed

    Vosough, Maryam; Iravani, Negar J

    2016-02-01

    This paper describes the development and validation of a simple and efficient bioanalytical procedure for simultaneous determination of alprazolam, clonazepam, diazepam in human serum samples using high performance liquid chromatography with photodiode-array detection, regarding a fast elution methodology in 4min. Briefly, this method consists of a simple liquid extraction step of serum samples followed by HPLC analysis on a C18 column. After confirming the absence of matrix effect, an external standard methodology has been applied for quantification purposes. Due to the presence of serum endogenous components as uncalibrated components in the sample, the second-order calibration based on alternating trilinear decomposition has been applied on a set of absorbance matrices collected as a function of retention time and wavelengths. Acceptable resolution and quantification results were achieved in the presence of matrix interferences and the second-order advantage was fully exploited. The average recoveries for alprazolam, clonazepam and diazepam were 89.1%, 96.3% and 94.7% and relative standard deviation values for intra- and inter-day precision were equal or lower than 8.1% and 9.4%, respectively. The developed method enabled us to determine the analytes in the various serum samples in the presence of overlapped profiles, while keeping experimental time and extraction step at the minimum. PMID:26653472

  6. Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

    PubMed

    Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

    2015-06-10

    Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material. PMID:25990263

  7. Using of liquid chromatography coupled with diode array detector for determination of naphthoquinones in plants and for investigation of influence of pH of cultivation medium on content of plumbagin in Dionaea muscipula.

    PubMed

    Babula, Petr; Mikelova, Radka; Adam, Vojtech; Kizek, Rene; Havel, Ladislav; Sladky, Zdenek

    2006-09-14

    The interest of many investigators in naphthoquinones is due to their broad-range of biological actions from phytotoxic to fungicidal. The main aim of this work was to investigate the influence of different pH values of cultivation medium on naphthoquinone content in Dionaea muscipula. For this purpose, we optimized the simultaneous analysis of the most commonly occurring naphthoquinones (1,4-naphthoquinone, lawsone, juglone and plumbagin) by high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The most suitable chromatographic conditions were as follows: mobile phase: 0.1 mol l-1 acetic acid:methanol in ratio of 33:67 (%, v/v), flow rate: 0.75 ml min-1 and temperature: 42 degrees C. Moreover, we looked for the most suitable technique for preparation of plant samples (D. muscipula, Juglans regia, Paulownia tomentosa, Impatience glandulifera, Impatience parviflora, Drosera rotundifolia, Drosera spathulata and Drosera capensis) due to their consequent analysis by HPLC-DAD. It clearly follows from the results obtained that sonication were the most suitable technique for preparation of J. regia plants. We also checked the recoveries of the determined naphthoquinones, which were from 96 to 104%. Finally, we investigated the changes in content of plumbagin in D. muscipula plants according to different pH of cultivation medium. The content increased with increasing pH up to 5 and, then, changed gradually. The lower content of plumbagin at lower pH values was of interest to us. Therefore, we determined the content of this naphthoquinone in the cultivation medium, what has not been studied before. We discovered that the lower tissue content of plumbagin was due to secretion of this naphthoquinone into the cultivation medium. PMID:16765109

  8. Chemometrics-enhanced high performance liquid chromatography-diode array detection strategy for simultaneous determination of eight co-eluted compounds in ten kinds of Chinese teas using second-order calibration method based on alternating trilinear decomposition algorithm.

    PubMed

    Yin, Xiao-Li; Wu, Hai-Long; Gu, Hui-Wen; Zhang, Xiao-Hua; Sun, Yan-Mei; Hu, Yong; Liu, Lu; Rong, Qi-Ming; Yu, Ru-Qin

    2014-10-17

    In this work, an attractive chemometrics-enhanced high performance liquid chromatography-diode array detection (HPLC-DAD) strategy was proposed for simultaneous and fast determination of eight co-eluted compounds including gallic acid, caffeine and six catechins in ten kinds of Chinese teas by using second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm. This new strategy proved to be a useful tool for handling the co-eluted peaks, uncalibrated interferences and baseline drifts existing in the process of chromatographic separation, which benefited from the "second-order advantages", making the determination of gallic acid, caffeine and six catechins in tea infusions within 8 min under a simple mobile phase condition. The average recoveries of the analytes on two selected tea samples ranged from 91.7 to 103.1% with standard deviations (SD) ranged from 1.9 to 11.9%. Figures of merit including sensitivity (SEN), selectivity (SEL), root-mean-square error of prediction (RMSEP) and limit of detection (LOD) have been calculated to validate the accuracy of the proposed method. To further confirm the reliability of the method, a multiple reaction monitoring (MRM) method based on LC-MS/MS was employed for comparison and the obtained results of both methods were consistent with each other. Furthermore, as a universal strategy, this new proposed analytical method was applied for the determination of gallic acid, caffeine and catechins in several other kinds of Chinese teas, including different levels and varieties. Finally, based on the quantitative results, principal component analysis (PCA) was used to conduct a cluster analysis for these Chinese teas. The green tea, Oolong tea and Pu-erh raw tea samples were classified successfully. All results demonstrated that the proposed method is accurate, sensitive, fast, universal and ideal for the rapid, routine analysis and discrimination of gallic acid, caffeine and catechins in Chinese tea samples. PMID:25223614

  9. Qualitative and Quantitative Analysis of Major Triterpenoids in Alismatis Rhizoma by High Performance Liquid Chromatography/Diode-Array Detector/Quadrupole-Time-of-Flight Mass Spectrometry and Ultra-Performance Liquid Chromatography/Triple Quadrupole Mass Spectrometry.

    PubMed

    Zhao, Wanli; Huang, Xiaoqiang; Li, Xiaoyan; Zhang, Fangfang; Chen, Sainan; Ye, Miao; Huang, Mingqing; Xu, Wen; Wu, Shuisheng

    2015-01-01

    Alismatis Rhizoma (AMR) is a well-known natural medicine with a long history in Chinese medicine and has been commonly used for treating a wide range of ailments related to dysuria, edema, nephropathy, hyperlipidaemia, diabetes, inflammation as well as tumors in clinical applications. Most beneficial effects of AMR are attributed to the presence of protostane terpenoids, the major active ingredients of Alismatis Rhizoma (AMR). In this study, a systematic high performance liquid chromatography/diode-array detector/quadrupole-time-of-flight mass spectrometry (HPLC-DAD-Q-TOF MS) and ultra-performance liquid chromatography/triple quadrupole mass spectrometry (UPLC-QqQ MS) method was developed for qualitative and quantitative analyses of the major AMR triterpenoids. First, a total of 25 triterpenoid components, including 24 known compounds and one new compound were identified by comparison with UV spectra, molecular ions and fragmentation behaviors of reference standards or the literature. Second, an efficient method was established for the rapid simultaneous determination of 14 representative triterpenoids by UPLC-QqQ MS. Forty-three batches of AMR were analyzed with linearity (r, 0.9980-0.9999), intra-day precision (RSD, 1.18%-3.79%), inter-day precision (RSD, 1.53%-3.96%), stability (RSD, 1.32%-3.97%), repeatability (RSD, 2.21%-4.25%), and recovery (98.11%-103.8%). These results indicated that new approaches combining HPLC-DAD-Q-TOF MS and UPLC-QqQ MS are applicable in the qualitative and quantitative analysis of AMR. PMID:26263967

  10. Status of AlGaN based focal plane arrays for UV solar blind detection

    NASA Astrophysics Data System (ADS)

    Reverchon, Jean-Luc; Mazzeo, Giovanni; Dussaigne, Amélie; Duboz, Jean-Yves

    2005-10-01

    The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet solar blind detection in competition with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays. All of the them must be associated to UV blocking filters. These new detectors present both an intrinsic spectral selectivity and an extremely low dark current at room temperature. First we will present the ultimate properties of the AlGaN based devices. These spectral properties are analysed in regards to the sharp cut off required for solar blind detection around 280nm, and we will quantify how the stringent difficulties to achieve solar blind filters can be reduced. We also investigated the electrical capabilities of Schottky diodes or Metal-Semiconductor-Metal (MSM) technologies to detect extremely low UV signal. We will especially present results from a linear array based on a CCD readout multiplexor.

  11. Large-Area Vacuum Ultraviolet Sensors

    NASA Technical Reports Server (NTRS)

    Aslam, Shahid; Franz, David

    2012-01-01

    Pt/(n-doped GaN) Schottky-barrier diodes having active areas as large as 1 cm square have been designed and fabricated as prototypes of photodetectors for the vacuum ultraviolet portion (wavelengths approximately equal 200 nm) of the solar spectrum. In addition to having adequate sensitivity to photons in this wavelength range, these photodetectors are required to be insensitive to visible and infrared components of sunlight and to have relatively low levels of dark current.

  12. Optical Spectroscopy Results for the Self-Magnetic Pinch Electron Beam Diode on the ITS-6 Accelerator.

    SciTech Connect

    Johnston, Mark D.; Oliver, Bryan V.; Hahn, Kelly; Droemer, Darryl W.; Crain, Marlon D.; Welch, Dale R.; Yitzhak, Maron

    2012-06-01

    Experiments have been conducted at Sandia National Laboratories' RITS-6 accelerator facility [1] (operating at 7.5 MV and 180 kA) investigating plasma formation and propagation in relativistic electron beam diodes used for flash x-ray radiography. High resolution, visible and ultraviolet spectra were collected in the anode-cathode (A-K) vacuum gap of the Self-Magnetic Pinch (SMP) diode [2-4]. Time and space resolved spectra are compared with time-dependent, collisional-radiative (CR) calculations [5-7] and Lsp, hybrid particle-in-cell code simulations [8,9]. Results indicate the presence of a dense (>1x1017cm-3), low temperature (few eV), on-axis plasma, composed of hydrocarbon and metal ion species, which expands at a rate of several cm/s from the anode to the cathode. In addition, cathode plasmas are observed which extend several millimeters into the A-K gap [10]. It is believed that the interaction of these electrode plasmas cause premature impedance collapse of the diode and subsequent reduction in the total radiation output. Diagnostics include high speed imaging and spectroscopy using nanosecond gated ICCD cameras, streak cameras, and photodiode arrays.

  13. Qualification and Selection of Flight Diode Lasers for Space Applications

    NASA Technical Reports Server (NTRS)

    Liebe, Carl C.; Dillon, Robert P.; Gontijo, Ivair; Forouhar, Siamak; Shapiro, Andrew A.; Cooper, Mark S.; Meras, Patrick L.

    2010-01-01

    The reliability and lifetime of laser diodes is critical to space missions. The Nuclear Spectroscopic Telescope Array (NuSTAR) mission includes a metrology system that is based upon laser diodes. An operational test facility has been developed to qualify and select, by mission standards, laser diodes that will survive the intended space environment and mission lifetime. The facility is situated in an electrostatic discharge (ESD) certified clean-room and consist of an enclosed temperature-controlled stage that can accommodate up to 20 laser diodes. The facility is designed to characterize a single laser diode, in addition to conducting laser lifetime testing on up to 20 laser diodes simultaneously. A standard laser current driver is used to drive a single laser diode. Laser diode current, voltage, power, and wavelength are measured for each laser diode, and a method of selecting the most adequate laser diodes for space deployment is implemented. The method consists of creating histograms of laser threshold currents, powers at a designated current, and wavelengths at designated power. From these histograms, the laser diodes that illustrate a performance that is outside the normal are rejected and the remaining lasers are considered spaceborne candidates. To perform laser lifetime testing, the facility is equipped with 20 custom laser drivers that were designed and built by California Institute of Technology specifically to drive NuSTAR metrology lasers. The laser drivers can be operated in constant-current mode or alternating-current mode. Situated inside the enclosure, in front of the laser diodes, are 20 power-meter heads to record laser power throughout the duration of lifetime testing. Prior to connecting a laser diode to the current source for characterization and lifetime testing, a background program is initiated to collect current, voltage, and resistance. This backstage data collection enables the operational test facility to have full laser diode traceablity.

  14. Photovoltaic-module bypass-diode encapsulation. Annual report

    SciTech Connect

    Not Available

    1983-06-20

    The design and processing techniques necessary to incorporate bypass diodes within the module encapsulant are presented in this annual report. A comprehensive survey of available pad-mounted PN junction and Schottky diodes led to the selection of Semicon PN junction diode cells for this application. Diode junction-to-heat spreader thermal resistance measurements, performed on a variety of mounted diode chip types and sizes, have yielded values which are consistently below 1/sup 0/C per watt, but show some instability when thermally cycled over the temperature range from -40 to 150/sup 0/C. Based on the results of a detailed thermal analysis, which covered the range of bypass currents from 2 to 20 amperes, three representative experimental modules, each incorporating integral bypass diode/heat spreader assemblies of various sizes, were designed and fabricated. Thermal testing of these modules has enabled the formation of a recommended heat spreader plate sizing relationship. The production cost of three encapsulated bypass diode/heat spreader assemblies were compared with similarly rated externally-mounted packaged diodes. An assessment of bypass diode reliability, which relies heavily on rectifying diode failure rate data, leads to the general conclusion that, when proper designed and installed, these devices will improve the overall reliability of a terrestrial array over a 20 year design lifetime.

  15. Enhanced ultraviolet electroluminescence and spectral narrowing from ZnO quantum dots/GaN heterojunction diodes by using high-k HfO{sub 2} electron blocking layer

    SciTech Connect

    Mo, Xiaoming; Long, Hao; Wang, Haoning; Chen, Zhao; Wan, Jiawei; Liu, Yuping; Fang, Guojia; Li, Songzhan; Feng, Yamin; Ouyang, Yifang

    2014-08-11

    We demonstrated the capability of realizing enhanced ZnO-related UV emissions by using the low-cost and solution-processable ZnO quantum dots (QDs) with the help of a high-k HfO{sub 2} electron blocking layer (EBL) for the ZnO QDs/p-GaN light-emitting diodes (LEDs). Full-width at half maximum of the LED devices was greatly decreased from ?110 to ?54?nm, and recombinations related to nonradiative centers were significantly suppressed with inserting HfO{sub 2} EBL. The electroluminescence of the ZnO QDs/HfO{sub 2}/p-GaN LEDs demonstrated an interesting spectral narrowing effect with increasing HfO{sub 2} thickness. The Gaussian fitting revealed that the great enhancement of the Zn{sub i}-related emission at ?414?nm whereas the deep suppression of the interfacial recombination at ?477?nm should be the main reason for the spectral narrowing effect.

  16. Diode pumped Nd:YAG laser development

    NASA Technical Reports Server (NTRS)

    Reno, C. W.; Herzog, D. G.

    1976-01-01

    A low power Nd:YAG laser was constructed which employs GaAs injection lasers as a pump source. Power outputs of 125 mW TEM CW with the rod at 250 K and the pump at 180 K were achieved for 45 W input power to the pump source. Operation of the laser, with array and laser at a common heat sink temperature of 250 K, was inhibited by difficulties in constructing long-life GaAs LOC laser arrays. Tests verified pumping with output power of 20 to 30 mW with rod and pump at 250 K. Although life tests with single LOC GaAs diodes were somewhat encouraging (with single diodes operating as long as 9000 hours without degradation), failures of single diodes in arrays continue to occur, and 50 percent power is lost in a few hundred hours at 1 percent duty factor. Because of the large recent advances in the state of the art of CW room temperature AlGaAs diodes, their demonstrated lifetimes of greater than 5,000 hours, and their inherent advantages for this task, it is recommended that these sources be used for further CW YAG injection laser pumping work.

  17. Simultaneous determination of 10 components in Bu-Zhong-Yi-Qi Wan by solid phase extraction-high performance liquid chromatography with diode array detection and evaporative light scattering detection.

    PubMed

    Hu, Fang; Zhu, Ruijuan; Liu, Xiaohua; Yang, Yinglai; Li, Can; Feng, Shilan; Li, Yingdong

    2015-01-01

    An effective, accurate and reliable method for the simultaneous separation and determination of 10 major components in Chinese medicine Bu-Zhong-Yi-Qi Wan (BZYQW) was developed and validated using solid phase extraction column-high performance liquid chromatography-diode array detection-evaporative light scattering detection (SPE-HPLC-DAD-ELSD). The chromatographic separation was performed on a Spursil™ C18 column (250 mm × 4.6 mm, 5 µm) at 30°C with an acetonitrile-water gradient as mobile phase. The DAD detection wavelength 254 nm was utilized for the quantitative analysis. The drift tube temperature and the carrier gas flow rate of the ELSD detection was set at 110.5°C and 3.1 mL/min. The total run time is 103 min, these determined components peak out within 81 min. Excellent linear behaviors over the investigated concentration ranges were observed with the values of r(2) higher than 0.9990 for all the analytes. The Linear range over hesperidin, senkyunolide I, senkyunolide H, ononin, calycosin, formononetin, ligustilide, butylene phthalide, astragaloside IV, astragaloside I is 4.50-94.50 µg/mL, 22.75-364.00 µg/mL, 2.30-45.00 µg/mL, 11.76-125.14 µg/mL, 4.62-50.35 µg/mL, 1.90-28.93 µg/mL, 1.29-159.00 µg/mL, 2.90-36.00 µg/mL, 35.40-192.40 µg/mL, 41.40-96.60 µg/mL, respectively. The method was validated by its repeatability [relative standard deviation (RSD) < 3.54%] and intra-day (RSD < 2.11%) and inter-day precision (RSD < 3.45%). The limits of detection and quantification of each component were in the ranges of 0.04-10.24 and 0.12-39.22 µg/mL, respectively. The average recovery yields of the 10 compounds ranged from 95.79 to 101.25%. The validated method was successfully applied to the simultaneous determination of these principal components in 10 commercial samples of BZYQW from different manufacturers. PMID:25214498

  18. Header For Laser Diode

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.; Spadin, Paul L.

    1990-01-01

    Header designed to contain laser diode. Output combined incoherently with outputs of other laser diodes in grating laser-beam combiner in optical communication system. Provides electrical connections to laser diode, cooling to thermally stabilize laser operation, and optomechanical adjustments that steer and focus laser beam. Range of adjustments provides for correction of worst-case decentering and defocusing of laser beam encountered with laser diodes. Mechanical configuration made simple to promote stability and keep cost low.

  19. ZnO-nanowires/PANI inorganic/organic heterostructure light-emitting diode.

    PubMed

    He, Ying; Wang, Jun-an; Zhang, Wenfei; Song, Jizhong; Pei, Changlong; Chen, Xiaoban

    2010-11-01

    In this paper, we report a flexible inorganic/organic heterostructure light-emitting diode, in which inorganic ZnO nanowires are the optically active components and organic polyaniline (PANI) is the hole-transporting layer. The fabrication of the hybrid LED is as follows, the ordered single-crystalline ZnO nanowires were uniformly distributed on flexible polyethylene terephthalate (PET)-based indium-tin-oxide-coated substrates by our polymer-assisted growth method, and proper materials were chosen as electrode and carrier. In this construction, an array of ZnO nanowires grown on PET substrate is successfully embedded in a polyaniline thin film. The performance of the hybrid device of organic-inorganic hetero-junction of ITO/(ZnO nanowires-PANI) for LED application in the blue and UV ranges are investigated, and tunable electroluminescence has been demonstrated by contacting the upper tips of ZnO nanowires and the PET substrate. The effect of surface capping with polyvinyl alcohol (PANI) on the photocarrier relaxation of the aqueous chemically grown ZnO nanowires has been investigated. The photoluminescence spectrum shows an enhanced ultraviolet emission and reduced defect-related emission in the capped ZnO NWs compared to bare ZnO. The results of our study may offer a fundamental understanding in the field of inorganic/organic heterostructure light-emitting diode, which may be useful for potential applications of hybrid ZnO nanowires with conductive polymers. PMID:21137909

  20. Optical communication with laser diode arrays

    NASA Technical Reports Server (NTRS)

    Davidson, F.

    1984-01-01

    The performance of a direct-detection optical communication system in which the laser transmitter sends short optical pulses of selected nonoverlapping center frequencies is analysed. This modulation format, in which a single light pulse is sent in one of M time slots at one of N optical center frequencies, is referred to as color coded optical pulse position modulation (CCPPM). The optimum energy-efficiency of this system, as measured by the channel capacity in nats per photon, exceeds that of ordinary optical pulse position modulation which uses a pulsed laser of fixed optical frequency. Reliable communication at optimal energy efficiency is easily achieved through the use of modest block length Reed-Solomon codes with the code words represented as CCPPM symbols.

  1. Photoluminescence properties and energy transfer in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8) phosphors for potential application in ultraviolet white light-emitting diodes.

    PubMed

    Yu, Hong; Zi, Wenwen; Lan, Shi; Gan, Shucai; Zou, Haifeng; Xu, Xuechun; Hong, Guangyan

    2013-01-01

    Sr(3) MgSi(2) O(8) :Ce(3+) , Dy(3+) phosphors were prepared by a solid-state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce(3+) ions (403?nm) but also as a band due to Dy(3+) ions (480, 575?nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8)phosphors, and the co-doping of Ce(3+) could enhance the emission intensity of Dy(3+) to a certain extent by transferring its energy to Dy(3+) . The Ce(3+) /Dy(3+) energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr2.94 MgSi2 O8 :0.01Ce(3+) , 0.05Dy(3+) phosphors, the fluorescence lifetime of Dy(3+) (from 3.35 to 27.59?ns) is increased whereas that of Ce(3+) is greatly decreased (from 43.59 to 13.55?ns), and this provides indirect evidence of the Ce(3+) to Dy(3+) energy transfer. The varied emitted color of Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) phosphors from blue to white were achieved by altering the concentration ratio of Ce(3+) and Dy(3+) . These results indicate Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) may be as a candidate phosphor for white light-emitting diodes. PMID:22987772

  2. Energy transfer from Sm3+ to Eu3+ in red-emitting phosphor LaMgAl11O19:Sm3+, Eu3+ for solar cells and near-ultraviolet white light-emitting diodes.

    PubMed

    Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan-Gai; Tang, Chao; Wu, Xiaowen

    2014-06-16

    The red-emitting phosphor LaMgAl11O19:Sm(3+), Eu(3+) was prepared by solid-state reaction at 1600 °C for 4 h. The phase formation, luminescence properties, and energy transfer from Sm(3+) to Eu(3+) were studied. With the addition of 5 mol % Sm(3+) as the sensitizer, the excitation wavelength of LaMgAl11O19:Eu(3+) phosphor was extended from 464 to 403 nm, and the emission intensity under the excitation at 403 nm was also enhanced. The host material LaMgAl11O19 could contain the high doping content of Eu(3+) (20 mol %) without concentration quenching. This energy transfer from Sm(3+) to Eu(3+) was confirmed by the decay times of energy donor Sm(3+). The mechanism of energy transfer (Sm(3+) ? Eu(3+)) was proved to be quadrupole-quadrupole interaction. Under the 403 nm excitation at 150 °C, the emission intensities of the characteristic peaks of Sm(3+) and Eu(3+) in LaMgAl11O19:0.05Sm(3+), 0.2Eu(3+) phosphor were decreased to 65% and 56% of the initial intensities at room temperature, and the relatively high activation energy proved that this phosphor had a good thermal stability. The CIE coordinate was calculated to be (x = 0.601, y = 0.390). The LaMgAl11O19:0.05Sm(3+), 0.2Eu(3+) phosphor is a candidate for copper phthalocyanine-based solar cells and white light-emitting diodes. PMID:24884208

  3. Ba(1.3)Ca(0.7)SiO4:Eu(2+),Mn(2+): a promising single-phase, color-tunable phosphor for near-ultraviolet white-light-emitting diodes.

    PubMed

    Lv, Wenzhen; Jiao, Mengmeng; Zhao, Qi; Shao, Baiqi; Lü, Wei; You, Hongpeng

    2014-10-20

    In this paper, Eu(2+)-doped and Eu(2+)/Mn(2+)-codoped Ba1.3Ca0.7SiO4 phosphors were synthesized by means of a conventional solid-state reaction process. The single-phase purity was checked by means of X-ray diffraction and the Rietveld method. Under excitation at 390 nm, the emission spectra of the Eu(2+)-doped phosphors exhibit a broad-band emission centered at 500 nm caused by the electric dipole allowed transition of the Eu(2+) ions. The emission spectra of codoped phosphors show one more broad emission centered at 600 nm attributable to the transitions from the (4)T1((4)G) ? (6)A1((6)S) of Mn(2+) ions. The luminescent color of the codoped phosphors can be easily adjusted from blue to red with variation of the Mn(2+) content. The energy transfer mechanism from the Eu(2+) to Mn(2+) ions in Ba1.3Ca0.7SiO4 phosphors has been confirmed to be the resonant type via dipole-quadrupole interaction, and the critical distance has been calculated quantitatively. All these results demonstrate that the Eu(2+)/Mn(2+)-codoped Ba1.3Ca0.7SiO4 phosphors can be a promising single-phase, color-tunable phosphor for near-UV white-light-emitting diodes after a further optimization process. Additionally, a great red shift from 593 to 620 nm has been observed following the increase of Mn(2+) content, and the phenomenon has been discussed in relation to the changes in the crystal field surrounding the Mn(2+) ions and the exchange interactions caused by the formation of Mn(2+) pairs. PMID:25260073

  4. Far-infrared imaging antenna arrays

    SciTech Connect

    Neikirk, D.P.; Rutledge, D.B.; Muha, M.S.; Park, H.; Yu, C.

    1982-02-01

    A far-infrared imaging antenna array has been demonstrated for the first time. The array is a line of evaporated silver bow-tie antennas on a fused-quartz substrate with bismuth-microbolometer detectors. The measured optical transfer function shows that the system is diffraction limited. This imaging array should find direct application in fusion plasma diagnostics. If the microbolometers can be replaced by more sensitive diode detectors, the array should also find application in radiometry and radar.

  5. Metal silicide/Si thin-film Schottky-diode bolometers

    NASA Astrophysics Data System (ADS)

    Yuryev, Vladimir A.; Chizh, Kirill V.; Chapnin, Valery V.; Kalinushkin, Victor P.

    2015-06-01

    Recently, we have demonstrated Ni silicide/poly-Si diodes as a budget alternative to SOI-diode temperature sensors in uncooled microbolometer FPAs. This paper introduces a solution still more suitable for industry: We have developed PtSi/poly-Si Schottky diodes for microbolometers. Ease of integration of the PtSi/poly-Si diode formation process into the CMOS technology, in analogy with the internal photoemission PtSi/Si IR FPAs, is the merit of the PtSi/poly-Si sensors. Now we demonstrate PtSi/poly-Si diode microbolometers and propose them as a promising solution for focal plane arrays.

  6. Method for extreme ultraviolet lithography

    DOEpatents

    Felter, T. E. (727 Clara St., Livermore, Alameda County, CA 94550); Kubiak, G. D. (475 Maple St., Livermore, Alameda County, CA 94550)

    2000-01-01

    A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods.

  7. Method for extreme ultraviolet lithography

    DOEpatents

    Felter, T. E. (Livermore, CA); Kubiak, Glenn D. (Livermore, CA)

    1999-01-01

    A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods.

  8. Bypass diode integration

    NASA Technical Reports Server (NTRS)

    Shepard, N. F., Jr.

    1981-01-01

    Protective bypass diodes and mounting configurations which are applicable for use with photovoltaic modules having power dissipation requirements in the 5 to 50 watt range were investigated. Using PN silicon and Schottky diode characterization data on packaged diodes and diode chips, typical diodes were selected as representative for each range of current carrying capacity, an appropriate heat dissipating mounting concept along with its environmental enclosure was defined, and a thermal analysis relating junction temperature as a function of power dissipation was performed. In addition, the heat dissipating mounting device dimensions were varied to determine the effect on junction temperature. The results of the analysis are presented as a set of curves indicating junction temperature as a function of power dissipation for each diode package.

  9. Coaxial foilless diode

    NASA Astrophysics Data System (ADS)

    Kong, Long; Liu, QingXiang; Li, XiangQiang; Wang, ShaoMeng

    2014-05-01

    A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves.

  10. GaAs laser diode pumped Nd:YAG laser

    NASA Technical Reports Server (NTRS)

    Conant, L. C.; Reno, C. W.

    1974-01-01

    A 1.5-mm by 3-cm neodymium-ion doped YAG laser rod has been side pumped using a GaAs laser diode array tuned to the 8680-A absorption line, achieving a multimode average output power of 120 mW for a total input power of 20 W to the final-stage laser diode drivers. The pumped arrangement was designed to take advantage of the high brightness of a conventional GaAs array as a linear source by introducing the pump light through a slit into a close-wrapped gold coated pump cavity. This cavity forms an integrating chamber for the pump light.

  11. Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes

    E-print Network

    Gilchrist, James F.

    Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes, IEEE DOI: 10.1109/JPHOT.2011.2150745 1943-0655/$26.00 ©2011 IEEE #12;Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes With Colloidal Microlens Arrays With Various Aspect

  12. A Monolithic HEMT Diode Balanced Mixer for 100-140 GHz Matthew Morgan1

    E-print Network

    Rutledge, David B.

    A Monolithic HEMT Diode Balanced Mixer for 100-140 GHz Matthew Morgan1 and Sander Weinreb2 1 IF bandwidth extending beyond 50 GHz. This is the first demonstration of a monolithic HEMT diode balanced mixer. A monolithic approach enables compact receivers to be assembled into a focal plane array for millimeter

  13. Two-Pass, Diode-Pumped Nd:YAG Slab Laser Head

    NASA Technical Reports Server (NTRS)

    Coyle, D. Barry

    1992-01-01

    Neodymium/yttrium aluminum garnet (Nd:YAG) ring-laser head designed for compactness, simplicity, and increased efficiency for side pumping by diode lasers. Laser head includes two linear arrays of diode lasers, two fused-silica collimating rods, and Nd:YAG slab. Slab mounted on finned copper block, providing good thermal dissipation.

  14. Ultraviolet O2 transmittance - AURIC implementation

    NASA Technical Reports Server (NTRS)

    Anderson, G. P.; Hall, L. A.; Minschwaner, K.; Yoshino, K.; Betchley, C.; Conant, J. A.

    1993-01-01

    A new spectrally precise approach to Schumann-Runge synthesis has been devised, employing nine (9) different spectral arrays containing polynomial coefficients. The coefficients were fit to calculated cross sections obtained from a detailed Schumann-Runge model that incorporates the most recent high resolution spectroscopic data for a temperature range between 130 and 500K. This large data base is being used to reexamine the existing parameterizations of UV transmission and photolysis. In addition, it is now possible to extend atmospheric radiance codes further into the ultraviolet. Initial implementation has been accomplished for the MODTRAN code as part of the eventual development of AURIC, the Atmospheric Ultraviolet Radiance Integrated Code.

  15. Blue laser diode (LD) and light emitting diode (LED) applications

    NASA Astrophysics Data System (ADS)

    Bergh, Arpad A.

    2004-09-01

    In the LED Highlight session at the 5th International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004), held in Gyeongju, Korea, 15-19 March 2004, Arpad A. Bergh [1] gave an overview on current and future LD and LED applications including prospects for industry and market developments. Papers from this session can be found in a special coloured section of this issue on pages 2730-2754.The cover picture shows a GaN vertical cavity surface emitting laser (VCSEL) array for white light illumination, designed to raise the light extraction efficieny of the device above 60% (courtesy of S. Nakamura, UCSB). Further papers from ISBLLED-2004 are published in phys. stat. sol. (b) 241, No. 12 (2004) and phys. stat. sol. (c) 1, No. 10 (2004).

  16. Diodes stabilize LED output

    NASA Technical Reports Server (NTRS)

    Deters, R. A.

    1977-01-01

    Small-signal diodes are placed in series with light-emitting diodes (LED's) to stabilize LED output against temperature fluctuations. Simple inexpensive method compensates for thermal fluctuations over a broad temperature range. Requiring few components, technique is particularly useful where circuit-board space is limited.

  17. A strategy for the use of light emitting diodes by autonomous underwater vehicles

    E-print Network

    Curran, Joseph R. (Joseph Robinson)

    2004-01-01

    Light Emitting Diode (LED) technology has advanced dramatically in a few short years. An expensive and difficult to manufacture LED array containing nearly 100 individual LEDs and measuring at least 5 cm² can now be replaced ...

  18. Compound semiconductor SPAD arrays

    NASA Astrophysics Data System (ADS)

    Harmon, Eric S.; Naydenkov, Mikhail; Hyland, James T.

    2013-06-01

    Single photon avalanche diodes (SPADs) are revolutionizing ultra-sensitive photodetection applications, providing single photon sensitivity, high quantum efficiency and low dark noise at or near room temperature. When aggregated into arrays, these devices have demonstrated the ability to operate as photon number resolving detectors with wide dynamic range, or as single-photon imaging detectors. SPAD array performance has reached a point where replacing vacuum tube based MCP and PMT photodetectors for most applications is inevitable. Compound semiconductor SPAD arrays offer the unique proposition to tailor performance to match application specific wavelength, speed and radiation hardness requirements. We present a theoretical framework describing performance limits to compound semiconductor SPAD arrays and our latest experimental results detailing the performance of GaAs SPAD arrays. These devices achieve nanosecond rise and fall times, excellent photon number resolving capability, and low dark count rates. Single photon number resolving is demonstrated with 4% single photon detection efficiency at room temperature with dark count rates below 7 Mcps/mm2. Compound semiconductor SPAD arrays have the opportunity to provide orders of magnitude improvement in dark count rate and radiation hardness over silicon SPAD arrays, as well as the ability to detect wavelengths where silicon is blind.

  19. Fast, High-Precision Readout Circuit for Detector Arrays

    NASA Technical Reports Server (NTRS)

    Rider, David M.; Hancock, Bruce R.; Key, Richard W.; Cunningham, Thomas J.; Wrigley, Chris J.; Seshadri, Suresh; Sander, Stanley P.; Blavier, Jean-Francois L.

    2013-01-01

    The GEO-CAPE mission described in NASA's Earth Science and Applications Decadal Survey requires high spatial, temporal, and spectral resolution measurements to monitor and characterize the rapidly changing chemistry of the troposphere over North and South Americas. High-frame-rate focal plane arrays (FPAs) with many pixels are needed to enable such measurements. A high-throughput digital detector readout integrated circuit (ROIC) that meets the GEO-CAPE FPA needs has been developed, fabricated, and tested. The ROIC is based on an innovative charge integrating, fast, high-precision analog-to-digital circuit that is built into each pixel. The 128×128-pixel ROIC digitizes all 16,384 pixels simultaneously at frame rates up to 16 kHz to provide a completely digital output on a single integrated circuit at an unprecedented rate of 262 million pixels per second. The approach eliminates the need for off focal plane electronics, greatly reducing volume, mass, and power compared to conventional FPA implementations. A focal plane based on this ROIC will require less than 2 W of power on a 1×1-cm integrated circuit. The ROIC is fabricated of silicon using CMOS technology. It is designed to be indium bump bonded to a variety of detector materials including silicon PIN diodes, indium antimonide (InSb), indium gallium arsenide (In- GaAs), and mercury cadmium telluride (HgCdTe) detector arrays to provide coverage over a broad spectral range in the infrared, visible, and ultraviolet spectral ranges.

  20. Space Environment Testing of Photovoltaic Array Systems at NASA's Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Schneider, Todd A.; Vaughn, Jason A.; Wright, Kenneth H., Jr.; Phillips, Brandon S.

    2015-01-01

    CubeSats, Communication Satellites, and Outer Planet Science Satellites all share one thing in common: Mission success depends on maintaining power in the harsh space environment. For a vast majority of satellites, spacecraft power is sourced by a photovoltaic (PV) array system. Built around PV cells, the array systems also include wiring, substrates, connectors, and protection diodes. Each of these components must function properly throughout the mission in order for power production to remain at nominal levels. Failure of even one component can lead to a crippling loss of power. To help ensure PV array systems do not suffer failures on-orbit due to the space environment, NASA's Marshall Space Flight Center (MSFC) has developed a wide ranging test and evaluation capability. Key elements of this capability include: Testing: a. Ultraviolet (UV) Exposure b. Charged Particle Radiation (Electron and Proton) c. Thermal Cycling d. Plasma and Beam Environments Evaluation: a. Electrostatic Discharge (ESD) Screening b. Optical Inspection and easurement c. PV Power Output including Large Area Pulsed Solar Simulator (LAPSS) measurements This paper will describe the elements of the space environment which particularly impact PV array systems. MSFC test capabilities will be described to show how the relevant space environments can be applied to PV array systems in the laboratory. A discussion of MSFC evaluation capabilities will also be provided. The sample evaluation capabilities offer test engineers a means to quantify the effects of the space environment on their PV array system or component. Finally, examples will be shown of the effects of the space environment on actual PV array materials tested at MSFC.

  1. A transparent ultraviolet triggered amorphous selenium p-n junction

    SciTech Connect

    Saito, Ichitaro; Soga, Kenichi; Overend, Mauro; Amaratunga, Gehan A. J.; Miyazaki, Wataru; Onishi, Masanori; Masuzawa, Tomoaki; Okano, Ken; Kudo, Yuki; Yamada, Takatoshi; Koh, Angel; Chua, Daniel; Aono, Masami

    2011-04-11

    This paper will introduce a semitransparent amorphous selenium (a-Se) film exhibiting photovoltaic effects under ultraviolet light created through a simple and inexpensive method. We found that chlorine can be doped into a-Se through electrolysis of saturated salt water, and converts the weak p-type material into an n-type material. Furthermore, we found that a p-n diode fabricated through this process has shown an open circuit voltage of 0.35 V toward ultraviolet illumination. Our results suggest the possibility of doping control depending on the electric current during electrolysis and the possibility of developing a simple doping method for amorphous photoconductors.

  2. Versatile multispectral microscope based on light emitting diodes

    NASA Astrophysics Data System (ADS)

    Brydegaard, Mikkel; Merdasa, Aboma; Jayaweera, Hiran; Ålebring, Jens; Svanberg, Sune

    2011-12-01

    We describe the development of a novel multispectral microscope, based on light-emitting diodes, capable of acquiring megapixel images in thirteen spectral bands from the ultraviolet to the near infrared. The system captures images and spectra in transmittance, reflectance, and scattering modes. We present as examples of applications ground truth measurements for remote sensing and parasitology diagnostics. The system is a general purpose scientific instrument that could be used to develop dedicated simplified instruments with optimal bands and mode selection.

  3. Photoresist composition for extreme ultraviolet lithography

    DOEpatents

    Felter, T. E. (Alameda County, CA); Kubiak, G. D. (Alameda County, CA)

    1999-01-01

    A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods. A photoresist composition for extreme ultraviolet radiation of boron carbide polymers, hydrochlorocarbons and mixtures thereof.

  4. Study on the digitized and quantified evaluating method for the super information cluster of traditional Chinese medicine ultraviolet spectral fingerprints

    PubMed Central

    Li, Lifeng; Liu, Zhongbo; Li, Yanfei

    2013-01-01

    The theories of ultraviolet spectral fingerprint (UVFP) index, information index, fluctuation index, information fluctuation index combined with the quantified UV fingerprint method (QUFM) had been established and put into practice in the Ginkgo Tablets (GT) quality evaluation. The flowing injection analysis (FIA) coupled with a diode array detector was applied as a novel method to obtain the UVFP in the region of 190-400 nm at which the absorption can reflect all the information of the chemical constituents contained ???*, n??* and n??* transition. The result showed that all batches were qualified (Grade ?3) except S8 for its too high contents. It was proved that this method made the expression of superposed information in UVFP of traditional Chinese medicine (TCM) digitized and simple. What’s more, an approach which can test the total chemical content with the chromophoric characteristics in the complex system of TCM rapidly, simply and accurately was achieved by the application of QUFM. In one word, it made the exploration of the general characteristic information of the molecular absorption complex TCM in the ultraviolet regions feasible and possible. PMID:25332974

  5. A compact efficient deep ultraviolet laser at 266 nm

    NASA Astrophysics Data System (ADS)

    Zhai, S. Y.; Wang, X. L.; Wei, Y.; Chen, W. D.; Zhuang, F. J.; Xu, S.; Li, B. X.; Fu, J. J.; Chen, Z. Q.; Wang, H. W.; Huang, C. H.; Zhang, G.

    2013-04-01

    We present a highly efficient and cost-effective watt-level deep-ultraviolet laser operating at 266 nm. Type-I phase-matching LBO crystals and type-I phase-matching BBO crystals were used for frequency doubling and fourth-harmonic generation, respectively. The highest 1.82 W average power of the 266 nm laser was obtained from nonlinear frequency conversion at a repetition rate of 30 kHz and a pump power of 18.8 W. The conversion efficiency from the diode to the deep-ultraviolet laser scales up to 10.7%. This is, to our knowledge, the highest efficiency ever reported generated from a laser diode single-end-pumped acousto-optic Q-switched system.

  6. Ultraviolet absorption spectrum of HOCl

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.

    1993-01-01

    The room temperature UV absorption spectrum of HOCl was measured over the wavelength range 200 to 380 nm with a diode array spectrometer. The absorption spectrum was identified from UV absorption spectra recorded following UV photolysis of equilibrium mixtures of Cl2O/H2O/HOCl. The HOCl spectrum is continuous with a maximum at 242 nm and a secondary peak at 304 nm. The measured absorption cross section at 242 nm was (2.1 +/- 0.3) x 10 exp -19/sq cm (2 sigma error limits). These results are in excellent agreement with the work of Knauth et al. (1979) but in poor agreement with the more recent measurements of Mishalanie et al. (1986) and Permien et al. (1988). An HOCl nu2 infrared band intensity of 230 +/- 35/sq cm atm was determined based on this UV absorption cross section. The present results are compared with these previous measurements and the discrepancies are discussed.

  7. Diamond Schottky barrier diodes

    E-print Network

    Brezeanu, Mihai

    2008-03-11

    Research on wide band gap semiconductors suitable for power electronic devices has spread rapidly in the last decade. The remarkable results exhibited by silicon carbide (SiC) Schottky batTier diodes (SBDs), commercially available since 2001...

  8. Ultraviolet absorption spectrum of chlorine peroxide, ClOOCl.

    PubMed

    Pope, Francis D; Hansen, Jaron C; Bayes, Kyle D; Friedl, Randall R; Sander, Stanley P

    2007-05-24

    The photolysis of chlorine peroxide (ClOOCl) is understood to be a key step in the destruction of polar stratospheric ozone. This study generated and purified ClOOCl in a novel fashion, which resulted in spectra with low impurity levels and high peak absorbances. The ClOOCl was generated by laser photolysis of Cl2 in the presence of ozone, or by photolysis of ozone in the presence of CF2Cl2. The product ClOOCl was collected, along with small amounts of impurities, in a trap at about -125 degrees C. Gas-phase ultraviolet spectra were recorded using a long path cell and spectrograph/diode array detector as the trap was slowly warmed. The spectrum of ClOOCl could be fit with two Gaussian-like expressions, corresponding to two different electronic transitions, having similar energies but different widths. The energies and band strengths of these two transitions compare favorably with previous ab initio calculations. The cross sections of ClOOCl at wavelengths longer than 300 nm are significantly lower than all previous measurements or estimates. These low cross sections in the photolytically active region of the solar spectrum result in a rate of photolysis of ClOOCl in the stratosphere that is much lower than currently recommended. For conditions representative of the polar vortex (solar zenith angle of 86 degrees, 20 km altitude, and O3 and temperature profiles measured in March 2000) calculated photolysis rates are a factor of 6 lower than the current JPL/NASA recommendation. This large discrepancy calls into question the completeness of present atmospheric models of polar ozone depletion. PMID:17474723

  9. Ultraviolet emissions from Gd3 + ions excited by energy transfer

    E-print Network

    Cao, Wenwu

    investigated in Y1.838ÀxGdxYb0.16Ho0.002O3 (x¼0, 0.16, 0.4, 1, 1.4) bulk ceramics under 976 nm laser diode (LD rights reserved. 1. Introduction Ultraviolet (UV) compact all-solid-state lasers have attracted much, photodynamic therapy, environmental monitoring, and so on [1­3]. To produce UV lasers, continuous population

  10. Light-emitting Diodes

    PubMed Central

    Opel, Daniel R.; Hagstrom, Erika; Pace, Aaron K.; Sisto, Krisanne; Hirano-Ali, Stefanie A.; Desai, Shraddha

    2015-01-01

    Background: In the early 1990s, the biological significance of light-emitting diodes was realized. Since this discovery, various light sources have been investigated for their cutaneous effects. Study design: A Medline search was performed on light-emitting diode lights and their therapeutic effects between 1996 and 2010. Additionally, an open-label, investigator-blinded study was performed using a yellow light-emitting diode device to treat acne, rosacea, photoaging, alopecia areata, and androgenetic alopecia. Results: The authors identified several case-based reports, small case series, and a few randomized controlled trials evaluating the use of four different wavelengths of light-emitting diodes. These devices were classified as red, blue, yellow, or infrared, and covered a wide range of clinical applications. The 21 patients the authors treated had mixed results regarding patient satisfaction and pre- and post-treatment evaluation of improvement in clinical appearance. Conclusion: Review of the literature revealed that differing wavelengths of light-emitting diode devices have many beneficial effects, including wound healing, acne treatment, sunburn prevention, phototherapy for facial rhytides, and skin rejuvenation. The authors’ clinical experience with a specific yellow light-emitting diode device was mixed, depending on the condition being treated, and was likely influenced by the device parameters. PMID:26155326

  11. Diode-pumped optical parametric oscillator

    SciTech Connect

    Geiger, A.R.; Hemmati, H.; Farr, W.H.

    1996-02-01

    Diode-pumped optical parametric oscillation has been demonstrated for the first time to our knowledge in a single Nd:MgO:LiNbO{sub 3} nonlinear crystal. The crystal is pumped by a semiconductor diode laser array at 812 nm. The Nd{sup 3+} ions absorb the 812-nm radiation to generate 1084-nm laser oscillation. On internal {ital Q} switching the 1084-nm radiation pumps the LiNbO{sub 3} host crystal that is angle cut at 46.5{degree} and generates optical parametric oscillation. The oscillation threshold that is due to the 1084-nm laser pump with a pulse length of 80 ns in a 1-mm-diameter beam was measured to be {approx_equal}1 mJ and produced 0.5-mJ output at 3400-nm signal wavelength. {copyright} {ital 1996 Optical Society of America.}

  12. Space Environment Testing of Photovoltaic Array Systems at NASA's Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Phillips, Brandon S.; Schneider, Todd A.; Vaughn, Jason A.; Wright, Kenneth H., Jr.

    2015-01-01

    To successfully operate a photovoltaic (PV) array system in space requires planning and testing to account for the effects of the space environment. It is critical to understand space environment interactions not only on the PV components, but also the array substrate materials, wiring harnesses, connectors, and protection circuitry (e.g. blocking diodes). Key elements of the space environment which must be accounted for in a PV system design include: Solar Photon Radiation, Charged Particle Radiation, Plasma, and Thermal Cycling. While solar photon radiation is central to generating power in PV systems, the complete spectrum includes short wavelength ultraviolet components, which photo-ionize materials, as well as long wavelength infrared which heat materials. High energy electron radiation has been demonstrated to significantly reduce the output power of III-V type PV cells; and proton radiation damages material surfaces - often impacting coverglasses and antireflective coatings. Plasma environments influence electrostatic charging of PV array materials, and must be understood to ensure that long duration arcs do not form and potentially destroy PV cells. Thermal cycling impacts all components on a PV array by inducing stresses due to thermal expansion and contraction. Given such demanding environments, and the complexity of structures and materials that form a PV array system, mission success can only be ensured through realistic testing in the laboratory. NASA's Marshall Space Flight Center has developed a broad space environment test capability to allow PV array designers and manufacturers to verify their system's integrity and avoid costly on-orbit failures. The Marshall Space Flight Center test capabilities are available to government, commercial, and university customers. Test solutions are tailored to meet the customer's needs, and can include performance assessments, such as flash testing in the case of PV cells.

  13. Nonvolatile Array Of Synapses For Neural Network

    NASA Technical Reports Server (NTRS)

    Tawel, Raoul

    1993-01-01

    Elements of array programmed with help of ultraviolet light. A 32 x 32 very-large-scale integrated-circuit array of electronic synapses serves as building-block chip for analog neural-network computer. Synaptic weights stored in nonvolatile manner. Makes information content of array invulnerable to loss of power, and, by eliminating need for circuitry to refresh volatile synaptic memory, makes architecture simpler and more compact.

  14. Application of AXUV diode detectors at ASDEX Upgrade

    SciTech Connect

    Bernert, M. Eich, T.; Burckhart, A.; Fuchs, J. C.; Giannone, L.; Kallenbach, A.; McDermott, R. M.; Sieglin, B.

    2014-03-15

    In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5?s was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales.

  15. Dual-band ultraviolet-short-wavelength infrared imaging via luminescent downshifting with colloidal quantum dots

    E-print Network

    Geyer, Scott Mitchell

    The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging ...

  16. Analysis of Photovoltaic (PV) Module during Partial Shading based on Simplified Two-Diode Model

    NASA Astrophysics Data System (ADS)

    Chitti Babu, B.; Gurjar, Suresh; Meher, Ashish

    2015-02-01

    Generally, the characteristics of photovoltaic (PV) array are largely affected by solar temperature, solar irradiance, shading patterns, array configuration and location of shading modules. Partial shading is due to moving clouds and shadows of nearby obstacles and can cause a significant degradation in the output of PV system. Hence, the characteristics of PV array get more multifaceted with multiple peaks. The ultimate aim of the paper is to analyze the performance of PV module during such adverse condition based on simplified two-diode model. To reduce the computational time, the simplified two-diode model has a photocurrent source in parallel with two ideal diodes. Only four parameters are required to be calculated from datasheet in order to simulate the model. Moreover, the performance of PV array is evaluated at different shaded patterns and it is found that the model has less computational time and gives accurate results.

  17. Far Ultraviolet Astronomy and Origins: The Far Ultraviolet Spectroscopic Explorer

    E-print Network

    Bianchi, Luciana

    Far Ultraviolet Astronomy and Origins: The Far Ultraviolet Spectroscopic Explorer (FUSE) Mission through high­resolution spectroscopy (R = 24,000­30,000) at far ultraviolet wavelengths (905­­1195 Å mission within the NASA Origins program. Keywords: abundances, atoms, dust, ISM, ultraviolet spectroscopy

  18. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, M.E.; Bien, F.; Bernstein, L.S.

    1986-12-09

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

  19. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, Michael E. (Bedford, MA); Bien, Fritz (Concord, MA); Bernstein, Lawrence S. (Bedford, MA)

    1986-01-01

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.

  20. Diode laser--pumped solid-state lasers.

    PubMed

    Byer, R L

    1988-02-12

    Diode laser-pumped solid-state lasers are efficient, compact, all solid-state sources of coherent optical radiation. Major advances in solid-state laser technology have historically been preceded by advances in pumping technology. The helical flash lamps used to pump early ruby lasers were superseded by the linear flash lamp and arc lamp now used to pump neodymium-doped yttrium-aluminum-garnet lasers. The latest advance in pumping technology is the diode laser. Diode laser-pumped neodymium lasers have operated at greater than 10 percent electrical to optical efficiency in a single spatial mode and with linewidths of less than 10 kilohertz. The high spectral power brightness of these lasers has allowed frequency extension by harmonic generation in nonlinear crystals, which has led to green and blue sources of coherent radiation. Diode laser pumping has also been used with ions other than neodymium to produce wavelengths from 946 to 2010 nanometers. In addition, Q-switched operation with kilowatt peak powers and mode-locked operation with 10-picosecond pulse widths have been demonstrated. Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode lasers for average power levels in excess of tens of watts and at a price that is competitive with flash lamp-pumped laser systems. Power levels exceeding 1 kilowatt appear possible within the next 5 years. Potential applications of diode laser-pumped solid-state lasers include coherent radar, global sensing from satellites, medical uses, micromachining, and miniature visible sources for digital optical storage. PMID:17832940

  1. Extreme Ultraviolet Light Chris Cosio

    E-print Network

    Hart, Gus

    Prospectus Extreme Ultraviolet Light Chris Cosio #12;The field of extreme ultraviolet light (XUV to the way XUV interacts with object, XUV properties are difficult to observe. Extreme ultraviolet light is absorbed by all objects it comes in contact with. Furthermore, extreme ultraviolet light also has low

  2. Magnetic arrays

    DOEpatents

    Trumper, D.L.; Kim, W.; Williams, M.E.

    1997-05-20

    Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

  3. Magnetic arrays

    DOEpatents

    Trumper, David L. (Plaistow, NH); Kim, Won-jong (Cambridge, MA); Williams, Mark E. (Pelham, NH)

    1997-05-20

    Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

  4. Image monitoring of pharmaceutical blending processes and the determination of an end point by using a portable near-infrared imaging device based on a polychromator-type near-infrared spectrometer with a high-speed and high-resolution photo diode array detector.

    PubMed

    Murayama, Kodai; Ishikawa, Daitaro; Genkawa, Takuma; Sugino, Hiroyuki; Komiyama, Makoto; Ozaki, Yukihiro

    2015-01-01

    In the present study we have developed a new version (ND-NIRs) of a polychromator-type near-infrared (NIR) spectrometer with a high-resolution photo diode array detector, which we built before (D-NIRs). The new version has four 5 W halogen lamps compared with the three lamps for the older version. The new version also has a condenser lens with a shorter focal point length. The increase in the number of the lamps and the shortening of the focal point of the condenser lens realize high signal-to-noise ratio and high-speed NIR imaging measurement. By using the ND-NIRs we carried out the in-line monitoring of pharmaceutical blending and determined an end point of the blending process. Moreover, to determinate a more accurate end point, a NIR image of the blending sample was acquired by means of a portable NIR imaging device based on ND-NIRs. The imaging result has demonstrated that the mixing time of 8 min is enough for homogeneous mixing. In this way the present study has demonstrated that ND-NIRs and the imaging system based on a ND-NIRs hold considerable promise for process analysis. PMID:25741896

  5. Reverse bias protected solar array with integrated bypass battery

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A (Inventor)

    2012-01-01

    A method for protecting the photovoltaic cells in a photovoltaic (PV) array from reverse bias damage by utilizing a rechargeable battery for bypassing current from a shaded photovoltaic cell or group of cells, avoiding the need for a bypass diode. Further, the method mitigates the voltage degradation of a PV array caused by shaded cells.

  6. SU-E-T-87: Comparison Study of Dose Reconstruction From Cylindrical Diode Array Measurements, with TLD Measurements and Treatment Planning System Calculations in Anthropomorphic Head and Neck and Lung Phantoms

    SciTech Connect

    Benhabib, S; Cardan, R; Huang, M; Brezovich, I; Popple, R; Faught, A; Followill, D

    2014-06-01

    Purpose: To assess dose calculated by the 3DVH software (Sun Nuclear Systems, Melbourne, FL) against TLD measurements and treatment planning system calculations in anthropomorphic phantoms. Methods: The IROC Houston (RPC) head and neck (HN) and lung phantoms were scanned and plans were generated using Eclipse (Varian Medical Systems, Milpitas, CA) following IROC Houston procedures. For the H and N phantom, 6 MV VMAT and 9-field dynamic MLC (DMLC) plans were created. For the lung phantom 6 MV VMAT and 15 MV 9-field dynamic MLC (DMLC) plans were created. The plans were delivered to the phantoms and to an ArcCHECK (Sun Nuclear Systems, Melbourne, FL). The head and neck phantom contained 8 TLDs located at PTV1 (4), PTV2 (2), and OAR Cord (2). The lung phantom contained 4 TLDs, 2 in the PTV, 1 in the cord, and 1 in the heart. Daily outputs were recorded before each measurement for correction. 3DVH dose reconstruction software was used to project the calculated dose to patient anatomy. Results: For the HN phantom, the maximum difference between 3DVH and TLDs was -3.4% and between 3DVH and Eclipse was 1.2%. For the lung plan the maximum difference between 3DVH and TLDs was 4.3%, except for the spinal cord for which 3DVH overestimated the TLD dose by 12%. The maximum difference between 3DVH and Eclipse was 0.3%. 3DVH agreed well with Eclipse because the dose reconstruction algorithm uses the diode measurements to perturb the dose calculated by the treatment planning system; therefore, if there is a problem in the modeling or heterogeneity correction, it will be carried through to 3DVH. Conclusion: 3DVH agreed well with Eclipse and TLD measurements. Comparison of 3DVH with film measurements is ongoing. Work supported by PHS grant CA10953 and CA81647 (NCI, DHHS)

  7. GaAs optoelectronic neuron arrays

    NASA Technical Reports Server (NTRS)

    Lin, Steven; Grot, Annette; Luo, Jiafu; Psaltis, Demetri

    1993-01-01

    A simple optoelectronic circuit integrated monolithically in GaAs to implement sigmoidal neuron responses is presented. The circuit integrates a light-emitting diode with one or two transistors and one or two photodetectors. The design considerations for building arrays with densities of up to 10,000/sq cm are discussed.

  8. Whiskerless Schottky diode

    NASA Technical Reports Server (NTRS)

    Bishop, William L. (inventor); Mcleod, Kathleen A. (inventor); Mattauch, Robert J. (inventor)

    1991-01-01

    A Schottky diode for millimeter and submillimeter wave applications is comprised of a multi-layered structure including active layers of gallium arsenide on a semi-insulating gallium arsenide substrate with first and second insulating layers of silicon dioxide on the active layers of gallium arsenide. An ohmic contact pad lays on the silicon dioxide layers. An anode is formed in a window which is in and through the silicon dioxide layers. An elongated contact finger extends from the pad to the anode and a trench, preferably a transverse channel or trench of predetermined width, is formed in the active layers of the diode structure under the contact finger. The channel extends through the active layers to or substantially to the interface of the semi-insulating gallium arsenide substrate and the adjacent gallium arsenide layer which constitutes a buffer layer. Such a structure minimizes the effect of the major source of shunt capacitance by interrupting the current path between the conductive layers beneath the anode contact pad and the ohmic contact. Other embodiments of the diode may substitute various insulating or semi-insulating materials for the silicon dioxide, various semi-conductors for the active layers of gallium arsenide, and other materials for the substrate, which may be insulating or semi-insulating.

  9. Silicon nanowire Esaki diodes.

    PubMed

    Schmid, Heinz; Bessire, Cedric; Björk, Mikael T; Schenk, Andreas; Riel, Heike

    2012-02-01

    We report on the fabrication and characterization of silicon nanowire tunnel diodes. The silicon nanowires were grown on p-type Si substrates using Au-catalyzed vapor-liquid-solid growth and in situ n-type doping. Electrical measurements reveal Esaki diode characteristics with peak current densities of 3.6 kA/cm(2), peak-to-valley current ratios of up to 4.3, and reverse current densities of up to 300 kA/cm(2) at 0.5 V reverse bias. Strain-dependent current-voltage (I-V) measurements exhibit a decrease of the peak tunnel current with uniaxial tensile stress and an increase of 48% for 1.3 GPa compressive stress along the <111> growth direction, revealing the strain dependence of the Si band structure and thus the tunnel barrier. The contributions of phonons to the indirect tunneling process were probed by conductance measurements at 4.2 K. These measurements show phonon peaks at energies corresponding to the transverse acoustical and transverse optical phonons. In addition, the low-temperature conductance measurements were extended to higher biases to identify potential impurity states in the band gap. The results demonstrate that the most likely impurity, namely, Au from the catalyst particle, is not detectable, a finding that is also supported by the excellent device properties of the Esaki diodes reported here. PMID:22214422

  10. Whiskerless Schottky diode

    NASA Astrophysics Data System (ADS)

    Bishop, William L.; McLeod, Kathleen A.; Mattauch, Robert J.

    1991-08-01

    A Schottky diode for millimeter and submillimeter wave applications is comprised of a multi-layered structure including active layers of gallium arsenide on a semi-insulating gallium arsenide substrate with first and second insulating layers of silicon dioxide on the active layers of gallium arsenide. An ohmic contact pad lays on the silicon dioxide layers. An anode is formed in a window which is in and through the silicon dioxide layers. An elongated contact finger extends from the pad to the anode and a trench, preferably a transverse channel or trench of predetermined width, is formed in the active layers of the diode structure under the contact finger. The channel extends through the active layers to or substantially to the interface of the semi-insulating gallium arsenide substrate and the adjacent gallium arsenide layer which constitutes a buffer layer. Such a structure minimizes the effect of the major source of shunt capacitance by interrupting the current path between the conductive layers beneath the anode contact pad and the ohmic contact. Other embodiments of the diode may substitute various insulating or semi-insulating materials for the silicon dioxide, various semi-conductors for the active layers of gallium arsenide, and other materials for the substrate, which may be insulating or semi-insulating.

  11. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark (Shutesbury, MA); Schotter, Joerg (Bielefeld, DE); Thurn-Albrecht, Thomas (Freiburg, DE); Russell, Thomas P. (Amherst, MA)

    2009-08-11

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  12. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark; Schotter, Joerg; Thurn-Albrecht, Thomas; Russell, Thomas P.

    2007-03-13

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  13. Cryogenic thermal diode heat pipes

    NASA Technical Reports Server (NTRS)

    Alario, J.

    1979-01-01

    The development of spiral artery cryogenic thermal diode heat pipes was continued. Ethane was the working fluid and stainless steel the heat pipe material in all cases. The major tasks included: (1) building a liquid blockage (blocking orifice) thermal diode suitable for the HEPP space flight experiment; (2) building a liquid trap thermal diode engineering model; (3) retesting the original liquid blockage engineering model, and (4) investigating the startup dynamics of artery cryogenic thermal diodes. An experimental investigation was also conducted into the wetting characteristics of ethane/stainless steel systems using a specially constructed chamber that permitted in situ observations.

  14. High power diode lasers for solid-state laser pumps

    NASA Technical Reports Server (NTRS)

    Linden, Kurt J.; Mcdonnell, Patrick N.

    1994-01-01

    The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

  15. Investigation of irradiance efficiency for LED phototherapy with different arrays

    NASA Astrophysics Data System (ADS)

    Chen, Hsi-Chao; Wu, Guo-Yang

    2010-12-01

    Red and yellow light emitting diodes (LEDs) are currently utilized as lighting sources during LED phototherapy. These LEDs were arranged on a disk with an external diameter of 70 mm with different arrays — radial, rhombus, square radial, and square rhombus arrays. The radial and square radial arrays had better irradiance efficiency than rhombus and square rhombus arrays by optical simulation. Additionally, the radial array had 76 sets of LEDs, but the square radial array had 100 sets. Thus, a mockup sample of radial array phototherapy was constructed for performance tests. The mixture efficiency of the radial array was observed at distances of 1-100 mm and lighting was well mixed when distance exceeded 50 mm by optical simulation. Irradiance variation with angle was approximated by experiment and theory at a treatment distance of 50 mm and 100 mm using the phototherapy mockup. The radial array was one good choice for LED phototherapy.

  16. Upgrade of absolute extreme ultraviolet diagnostic on J-TEXT

    SciTech Connect

    Zhang, X. L.; Cheng, Z. F. Hou, S. Y.; Zhuang, G.; Luo, J.

    2014-11-15

    The absolute extreme ultraviolet (AXUV) diagnostic system is used for radiation observation on J-TEXT tokamak [J. Zhang, G. Zhuang, Z. J. Wang, Y. H. Ding, X. Q. Zhang, and Y. J. Tang, Rev. Sci. Instrum. 81, 073509 (2010)]. The upgrade of the AXUV system is aimed to improve the spatial resolution and provide a three-dimensional image on J-TEXT. The new system consists of 12 AXUV arrays (4 AXUV16ELG arrays, 8 AXUV20ELG arrays). The spatial resolution in the cross-section is 21 mm for the AXUV16ELG arrays and 17 mm for the AXUV20ELG arrays. The pre-amplifier is also upgraded for a higher signal to noise ratio. By upgrading the AXUV imaging system, a more accurate observation on the radiation information is obtained.

  17. Upgrade of absolute extreme ultraviolet diagnostic on J-TEXTa)

    NASA Astrophysics Data System (ADS)

    Zhang, X. L.; Cheng, Z. F.; Hou, S. Y.; Zhuang, G.; Luo, J.

    2014-11-01

    The absolute extreme ultraviolet (AXUV) diagnostic system is used for radiation observation on J-TEXT tokamak [J. Zhang, G. Zhuang, Z. J. Wang, Y. H. Ding, X. Q. Zhang, and Y. J. Tang, Rev. Sci. Instrum. 81, 073509 (2010)]. The upgrade of the AXUV system is aimed to improve the spatial resolution and provide a three-dimensional image on J-TEXT. The new system consists of 12 AXUV arrays (4 AXUV16ELG arrays, 8 AXUV20ELG arrays). The spatial resolution in the cross-section is 21 mm for the AXUV16ELG arrays and 17 mm for the AXUV20ELG arrays. The pre-amplifier is also upgraded for a higher signal to noise ratio. By upgrading the AXUV imaging system, a more accurate observation on the radiation information is obtained.

  18. Dense Array Effects in SWIR HgCdTe Photodetecting Arrays

    NASA Astrophysics Data System (ADS)

    Wichman, A. R.; Pinkie, B.; Bellotti, E.

    2015-09-01

    This paper presents results from three-dimensional quantitative modeling on dense, moderately doped [ N D ( N A) = 5 × 1015 cm-3] short-wave infrared (SWIR) p + n and n + p Hg1- x Cd x Te double planar heterostructure photodetecting arrays with absorber x = 0.451 and cap x = 0.55. At uniform reverse bias, the competition for minority carriers between closely spaced diodes preserves densities below equilibrium levels throughout the absorber. This carrier suppression has several consequences in addition to suppressing dark current by constraining the minority-carrier gradients at each diode junction. First, the dense arrays maintain volume-average negative net radiative recombination rates (negative luminescence) roughly an order of magnitude larger than comparably biased isolated diodes. Second, the negative excess minority-carrier densities suppress the volume-average net Auger recombination rate by roughly an order of magnitude in dense n-type HgCdTe arrays compared with a single diode. Third, the long minority electron diffusion lengths in the p-type HgCdTe absorber not only suppress lateral diffusion currents, but do so in a manner that provides negative differential resistance. By suppressing intrinsic recombination rates, or lateral diffusion currents, each effect can contribute to increasing R 0 A products in SWIR HgCdTe dense arrays. These effects should be considered when optimizing device structures for pitch, thickness, feature size, doping, and bias points.

  19. An on-line high-performance liquid chromatography-diode-array detector-multi-stage mass spectrometry-deoxyribonucleic acid-4',6-diamidino-2-phenylindole-fluorescence detector system for screening the DNA-binding active compounds in Fufang Banbianlian Injection.

    PubMed

    Li, Sensen; Jiang, Haixiu; Lin, Zongtao; Deng, Shanshan; Guan, Yanqing; Wang, Hong; Chen, Shizhong

    2015-12-11

    Fufang Banbianlian Injection (FBI), a well-known traditional Chinese medicine formula, has been recently approved and extensively used as a newly anti-inflammatory and anti-tumor drug. This prescription comprises an equal ratio of three traditional Chinese herbs, Lobelia chinensis Lour, Scutellaria barbata D. Don and Hedyotis diffusa Willd. The relationships between its chemical compositions and activities have not been understood well yet. To investigate the ingredients and their DNA-binding activities in FBI, an on-line high-performance liquid chromatography-diode-array detector-multi-stage mass spectrometry-deoxyribonucleic acid-4',6-diamidino-2-phenylindole-fluorescence detector (HPLC-DAD-MS(n)-DNA-DAPI-FLD) system was developed using a combination of chromatographic, mass spectrometric and fluorescent detection techniques. 4',6-Diamidino-2-phenylindole (DAPI) specifically binds to three ATT base pairs on the DNA minor groove, and thus can be used as a fluorescent probe for screening active compounds that compete ATT sequences with DAPI. Using this system, 21 of 58 identified or tentatively characterized compounds in FBI showed DNA-binding activities, with most of the active compounds being flavone glycosides. In addition, the structure-activity relationships of these active compounds suggested that conjugated planar structures are favorable for DNA-binding activities, and adjacent hydroxyl groups in flavonoids can significantly improve their activities. This is, to the best of our knowledge, the first application of DAPI as a fluorescent probe for the screening of DNA-binding active compounds in complex samples. PMID:26592560

  20. Matrix solid-phase dispersion extraction followed by high performance liquid chromatography-diode array detection and ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometer method for the determination of the main compounds from Carthamus tinctorius L. (Hong-hua).

    PubMed

    Hong, Bo; Wang, Zhe; Xu, Tianjiao; Li, Chengchong; Li, Wenjing

    2015-03-25

    A simple and low-cost method based on matrix solid-phase dispersion (MSPD) extraction, HPLC separation, diode array detection and UPLC-Q-TOF-MS have been developed for the determination of Hydroxysafflor yellow A (HSYA), Kaempferol and other main compounds in Carthamus tinctorius. The experimental parameters that may affect the MSPD method, including dispersing sorbent, ratio of dispersing sorbent to sample, elution solvent, and volume of the elution solvent were examined and optimized. The optimized conditions were determined to be that silica gel was used as dispersing sorbent, the ratio of silica gel to sample mass was selected to be 3:1, and 10 mL of methanol: water (1:3, v:v) was used as elution solvent. The highest extraction yields of the two compounds were obtained under the optimized conditions. The method showed good linearity (r(2)?0.999 2) and precision (RSD?3.4%) for HSYA and Kaempferol, with the limits of detection of 35.2 and 14.5 ng mL(-1), respectively. The recoveries were in the range of 92.62-101.7% with RSD values ranging from 1.5 to 3.5%. At the meanwhile, there were 21 compounds in the extraction by MSPD method were identified by TOF-MS method to improve the quality control for safflower. Comparing to ultrasonic and soxhlet methods, the proposed MSPD procedure was more convenient and less time-consuming with reduced requirements on sample and solvent amounts. The proposed procedure was applied to analyze four real samples that were collected from different localities. PMID:25676855

  1. Psoriasis and ultraviolet radiation

    SciTech Connect

    Farber, E.M.; Nall, L. )

    1993-09-01

    Prevention and detection screening programs as a public health service in curtailing the ever-increasing incidence of all forms of skin cancer are reviewed. The effect of solar and artificial ultraviolet radiation on the general population and persons with psoriasis is examined. 54 refs.

  2. Development of ultraviolet lasers

    NASA Technical Reports Server (NTRS)

    Walters, G. K.

    1974-01-01

    The pulsed electron accelerator selected for use in the development of ultraviolet laser capability suitable for use in photoexcitation and photoionization studies of the upper atmosphere is reported. Performance figures, installation specifications, and total cost of the equipment are briefly shown, and plans for further studies are outlined.

  3. ULTRAVIOLET MONITORING PROGRAM

    EPA Science Inventory

    The U.S. EPA operates a network of 21 Brewer spectrophotometers located at strategic points around the United States to monitor and study ultraviolet (UV) solar radiation and ozone levels. Many different types of instruments have been designed specifically for UV and ozone data ...

  4. Line Tunable Ultraviolet Laser

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Barnes, Norman P.

    2004-01-01

    An ultraviolet laser is demonstrated using a dual wavelength Nd:YAG oscillator, sum frequency and second harmonic process. Synchronous pulses at 1.052 and 1.319 micrometers are amplified, mixed and subsequently doubled, producing pulses at 0.293 micrometers.

  5. Ultraviolet radiation changes

    NASA Technical Reports Server (NTRS)

    Mckenzie, Richard L.; Frederick, John E.; Ilyas, Mohammad; Filyushkin, V.; Wahner, Andreas; Stamnes, K.; Muthusubramanian, P.; Blumthaler, M.; Roy, Colin E.; Madronich, Sasha

    1991-01-01

    A major consequence of ozone depletion is an increase in solar ultraviolet (UV) radiation received at the Earth's surface. This chapter discusses advances that were made since the previous assessment (World Meteorological Organization (WMO)) to our understanding of UV radiation. The impacts of these changes in UV on the biosphere are not included, because they are discussed in the effects assessment.

  6. Array biosensor: recent developments

    NASA Astrophysics Data System (ADS)

    Golden, Joel P.; Rowe-Taitt, Chris A.; Feldstein, Mark J.; Ligler, Frances S.

    1999-05-01

    A fluorescence-based immunosensor has been developed for simultaneous analyses of multiple samples for 1 to 6 different antigens. A patterned array of recognition antibodies immobilized on the surface of a planar waveguide is used to 'capture' analyte present in samples. Bound analyte is then quantified by means of fluorescent detector molecules. Upon excitation of the fluorescent label by a small diode laser, a CCD camera detects the pattern of fluorescent antigen:antibody complexes on the sensor surface. Image analysis software correlates the position of fluorescent signals with the identity of the analyte. A new design for a fluidics distribution system is shown, as well as results from assays for physiologically relevant concentrations of staphylococcal enterotoxin B (SEB), F1 antigen from Yersinia pestis, and D- dimer, a marker of sepsis and thrombotic disorders.

  7. JANTX1N3893 diode

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Diodes manufactured by Siemens and Motorola were tested. Testing of Motorola diodes was stopped in all 3 groups because 50% failure-rate limit was reached. Siemens lot endured more testing in groups 1 and 2 and completed testing on group 3. Failure analysis was performed for group 2 testing.

  8. Astro-1 Image Taken by Ultraviolet Imaging Telescope

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This image shows a part of the Cygnus loop supernova remnant, taken by the Ultraviolet Imaging Telescope (UIT) on the Astro Observatory during the Astro-1 mission (STS-35) on December 5, 1990. Pictured is a portion of the huge Cygnus loop, an array of interstellar gas clouds that have been blasted by a 900,000 mile per hour shock wave from a prehistoric stellar explosion, which occurred about 20,000 years ago, known as supernova. With ultraviolet and x-rays, astronomers can see emissions from extremely hot gases, intense magnetic fields, and other high-energy phenomena that more faintly appear in visible and infrared light or in radio waves that are crucial to deepening the understanding of the universe. The Astro Observatory was designed to explore the universe by observing and measuring the ultraviolet radiation from celestial objects. Three instruments make up the Astro Observatory: The Hopkins Ultraviolet Telescope (HUT), the Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE). The Marshall Space Flight Center had managment responsibilities for the Astro-1 mission. The Astro-1 Observatory was launched aboard the Space Shuttle Orbiter Columbia (STS-35) on December 2, 1990.

  9. Silicon photodiode with selective Zr/Si coating for extreme ultraviolet spectral range

    SciTech Connect

    Aruev, P N; Barysheva, Mariya M; Ber, B Ya; Zabrodskaya, N V; Zabrodskii, V V; Lopatin, A Ya; Pestov, Alexey E; Petrenko, M V; Polkovnikov, V N; Salashchenko, Nikolai N; Sukhanov, V L; Chkhalo, Nikolai I

    2012-10-31

    The procedure of manufacturing silicon photodiodes with an integrated Zr/Si filter for extreme ultraviolet (EUV) spectral range is developed. A setup for measuring the sensitivity profile of detectors with spatial resolution better than 100 {mu}m is fabricated. The optical properties of silicon photodiodes in the EUV and visible spectral ranges are investigated. Some characteristics of SPD-100UV diodes with Zr/Si coating and without it, as well as of AXUV-100 diodes, are compared. In all types of detectors a narrow region beyond the operating aperture is found to be sensitive to the visible light. (photodetectors)

  10. Transceiver array development for submillimeter-wave imaging radars

    NASA Astrophysics Data System (ADS)

    Cooper, Ken B.; Reck, Theodore A.; Jung-Kubiak, Cecile; Lee, Choonsup; Siles, Jose V.; Lin, Robert H.; Peralta, Alejandro; Decrossas, Emmanuel; Schlecht, Erich T.; Chattopadhyay, Goutam; Mehdi, Imran

    2013-05-01

    The Jet Propulsion Laboratory (JPL) is developing compact transceiver arrays housing discrete GaAs Schottky diodes with integrated waveguides in order to increase the frame rate and lower the cost of active submillimeter-wave imaging radar systems. As part of this effort, high performance diode frequency multiplier and mixer devices optimized for a 30 GHz bandwidth centered near 340 GHz have been fabricated using JPL's MoMeD process. A two-element array unit cell was designed using a layered architecture with three-dimensional waveguide routing for maximum scalability to multiple array elements. Prototype two-element arrays have been built using both conventionally machined metal blocks as well as gold-plated micromachined silicon substrates. Preliminary performance characterization has been accomplished in terms of transmit power, and conversion loss, and promising 3D radar images of concealed weapons have been acquired using the array.

  11. Impurity transport study in the low aspect ratio tokamak CDX-U based on vacuum ultraviolet spectroscopy

    NASA Astrophysics Data System (ADS)

    Soukhanovskii, Vsevolod A.

    2001-04-01

    Vacuum ultraviolet spectroscopy has been used to study intrinsic impurity transport in the low aspect ratio tokamak CDX-U. In this context, several novel spectroscopic diagnostics have been developed and successfully operated. A class of compact stacked grid collimator-based grating instruments has been designed for impurity characterization in the boundary fusion plasmas. The C IV ? = 1550 Å monochromator prototype of the instrument has been built, radiometrically calibrated and operated on CDX-U. Other upgrades to CDX-U spectroscopic diagnostics include visible and extreme ultraviolet spectrometers and two ten channel AXUV diode arrays. The poloidal multilayer mirror array measures the 0 VI ? = 150 Å brightness profile, whereas the tangential foil filter array measures radiated power, 0 VI or C V brightness profiles. In combination with CDX-U temperature, density and magnetic measurements the spectroscopic diagnostics have been used for plasma regime characterization, investigation of the impact of the magnetohydrodynamic (MHD) activity on impurity profiles and the steady-state low Z impurity transport studies. MHD- dominated and quiescent ohmic hydrogen as well as ohmic and high harmonic fast wave heated deuterium plasmas with Te >= 80 eV, n¯e ~= (0.6-3) × 1013 cm-3 and Zeff ~= 1.5-3 have been studied. The MHD instabilities observed in CDX-U are the low n/m modes, the sawtooth oscillations and the internal reconnection events. The range of possible impurity diffusion coefficients D and convection velocities v has been inferred from time-dependent numerical simulations of impurity emissivity profiles. The estimated values are 0.2 m2/s <= D <= 0.6 m2/s and v <= 10 m/s. One dimensional transport code MIST and the collisional- radiative package CRMLIN have been used. Analytical predictions of the neoclassical impurity transport theory give D <= 20 m2/s and v <= 500 m/s. The neoclassical v/ D ratio is close to the measured ratio. The calculated impurity profiles are more peaked than the measured. The peaked impurity distributions in CDX-U are the result of large ion density and temperature gradients. The applicability of the neoclassical theory of impurity transport developed for large aspect ratio high field circular cross-section tokamaks to the small aspect ratio low field CDX-U tokamak is discussed.

  12. Angle sensitive single photon avalanche diode

    NASA Astrophysics Data System (ADS)

    Lee, Changhyuk; Johnson, Ben; Molnar, Alyosha

    2015-06-01

    An ideal light sensor would provide exact information on intensity, timing, location, and angle of incoming photons. Single photon avalanche diodes (SPADs) provide such desired high (single photon) sensitivity with precise time information and can be implemented at a pixel-scale to form an array to extract spatial information. Furthermore, recent work has demonstrated photodiode-based structures (combined with micro-lenses or diffraction gratings) that are capable of encoding both spatial and angular information of incident light. In this letter, we describe the implementation of such a grating structure on SPADs to realize a pixel-scale angle-sensitive single photon avalanche diode (A-SPAD) built in a standard CMOS process. While the underlying SPAD structure provides high sensitivity, the time information of the two layers of diffraction gratings above offers angle-sensitivity. Such a unique combination of SPAD and diffraction gratings expands the sensing dimensions to pave a path towards lens-less 3-D imaging and light-field time-of-flight imaging.

  13. Light Emitting Diode (LED)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique called photodynamic therapy, requires the surgeon to use tiny pinhead-size Light Emitting Diodes (LEDs) (a source releasing long wavelengths of light) to activate light-sensitive, tumor-treating drugs. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can also be used for hours at a time while still remaining cool to the touch. The LED probe consists of 144 tiny pinhead-size diodes, is 9-inches long, and about one-half-inch in diameter. The small balloon aids in even distribution of the light source. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The probe was developed for photodynamic cancer therapy by the Marshall Space Flight Center under a NASA Small Business Innovative Research program grant.

  14. Coordinated ultraviolet and radio observations of selected nearby stars

    NASA Technical Reports Server (NTRS)

    Lang, Kenneth R.

    1987-01-01

    All of the US2 shifts assigned were successfully completed with simultaneous International Ultraviolet Explorer (IUE) and the Very Large Array (VLA) observations of the proposed target stars. The target stars included dwarf M flare stars and RS CVn stars. The combined ultraviolet (IUE) and microwave (VLA) observations have provided important new insights to the radiation mechanisms at these two widely-separated regions of the electromagnetic spectrum. The VLA results included the discovery of narrow-band microwave radiation and rapid time variations in the microwave radiation of dwarf M flare stars. The results indicate that conventional radiation mechanisms cannot explain the microwave emission from these stars. In general, ultraviolet variations and bursts occur when no similar variations are detected at microwave wavelengths and vice versa. Although these is some overlap, the variations in these two spectral regions are usually uncorrelated, suggesting that there is little interaction between the activity centers at the two associated atmospheric levels.

  15. International Ultraviolet Explorer (IUE) Post Launch Report 2

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The International Ultraviolet Explorer (IUE), an Explorer class ultraviolet astronomy mission, is an international cooperative program between the United States, the United Kingdom (UK), and the European Space Agency (ESA) which provides for a single launch into geosynchronous orbit to conduct spectral distribution studies of celestial and solar system ultraviolet sources. The spacecraft and scientific instruments were designed and fabricated at the Goddard Space Flight Center. The spectrograph camera was provided by the UK; ESA provided the solar array as well as the European ground station. The IUE observatory system was designed to functionally resemble a ground-based optical observatory at which guest observers could execute observing programs in real time. Observatory performance substantially exceeded design and mission objectives. The secondary mission objectives were also met.

  16. Research in extreme ultraviolet and far ultraviolet astronomy

    NASA Technical Reports Server (NTRS)

    Labov, S. E.

    1985-01-01

    Instruments designed to explore different aspects of far and extreme ultraviolet cosmic radiation were studied. The far ultraviolet imager (FUVI) was flown on the Aries sounding rocket. Its unique large format 75mm detector mapped out the far ultraviolet background radiation with a resolution of only a few arc minutes. Analysis of this data indicates to what extent the FUVI background is extra galactic in origin. A power spectrum of the spatial fluctuations will have direct consequences for galactic evolution.

  17. Emitron: microwave diode

    DOEpatents

    Craig, G.D.; Pettibone, J.S.; Drobot, A.T.

    1982-05-06

    The invention comprises a new class of device, driven by electron or other charged particle flow, for producing coherent microwaves by utilizing the interaction of electromagnetic waves with electron flow in diodes not requiring an external magnetic field. Anode and cathode surfaces are electrically charged with respect to one another by electron flow, for example caused by a Marx bank voltage source or by other charged particle flow, for example by a high energy charged particle beam. This produces an electric field which stimulates an emitted electron beam to flow in the anode-cathode region. The emitted electrons are accelerated by the electric field and coherent microwaves are produced by the three dimensional spatial and temporal interaction of the accelerated electrons with geometrically allowed microwave modes which results in the bunching of the electrons and the pumping of at least one dominant microwave mode.

  18. White light emitting diodes

    NASA Astrophysics Data System (ADS)

    Baur, J.; Schlotter, P.; Schneider, J.

    Using blue-emitting GaN LEDs on SiC substrate chips as primary light sources, we have fabricated green, yellow, red and white light emitting diodes (LUCOLEDs). The generation of mixed colors, as turquoise and magenta, is also demonstrated. The underlying physical principle is that of luminescence downconversion (Stokes shift), as typical for organic dye molecules and many inorganic phosphors. For white light generation via the LUCOLED principle, the phosphor Y3Al5O12:Ce3+(4f1) is ideally suited. The optical characteristics of Ce3+(4f1) in Y3Al5O12(YAG) are discussed in detail. Possibilities to "tune" the white color by various substitutions in the garnet lattice are shortly outlined.

  19. Nanofluidic osmotic diodes

    NASA Astrophysics Data System (ADS)

    Bocquet, Lyderic; Picallo, Clara; Gravelle, Simon; Joly, Laurent; Charlaix, Elisabeth

    2013-11-01

    Osmosis describes the flow of water across semipermeable membranes powered by the chemical free energy extracted from salinity gradients. While osmosis can be expressed in simple terms via the van't Hoff ideal gas formula for the osmotic pressure, it is a complex phenomenon taking its roots in the subtle interactions occurring at the scale of the membrane nanopores. Here we use new opportunities offered by nanofluidic systems to create an osmotic diode exhibiting asymmetric water flow under reversal of osmotic driving. We show that a surface charge asymmetry built on a nanochannel surface leads to non-linear couplings between water flow and the ion dynamics, which are capable of water flow rectification. This phenomenon opens new opportunities for water purification and complex flow control in nanochannels.

  20. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

    PubMed

    Binh, P H; Trong, V D; Renucci, P; Marie, X

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power. PMID:24007048

  1. Laterally injected light-emitting diode and laser diode

    DOEpatents

    Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

    2015-06-16

    A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

  2. Broad Spectrum Photoelectrochemical Diodes for Solar Hydrogen Generation

    SciTech Connect

    Grimes, Craig A.

    2014-11-26

    Under program auspices we have investigated material chemistries suitable for the solar generation of hydrogen by water photoelectrolysis. We have built upon, and extended, our knowledge base on the synthesis and application of TiO2 nanotube arrays, a material architecture that appears ideal for water photoelectrolysis. To date we have optimized, refined, and greatly extended synthesis techniques suitable for achieving highly ordered TiO2 nanotube arrays of given length, wall thickness, pore diameter, and tube-to-tube spacing for use in water photoelectrolysis. We have built upon this knowledge based to achieve visible light responsive, photocorrosion stable n-type and p-type ternary oxide nanotube arrays for use in photoelectrochemical diodes.

  3. An aluminium nitride light-emitting diode with a wavelength of 210nanometres

    NASA Astrophysics Data System (ADS)

    Taniyasu, Yoshitaka; Kasu, Makoto; Makimoto, Toshiki

    2006-05-01

    Compact high-efficiency ultraviolet solid-state light sources-such as light-emitting diodes (LEDs) and laser diodes-are of considerable technological interest as alternatives to large, toxic, low-efficiency gas lasers and mercury lamps. Microelectronic fabrication technologies and the environmental sciences both require light sources with shorter emission wavelengths: the former for improved resolution in photolithography and the latter for sensors that can detect minute hazardous particles. In addition, ultraviolet solid-state light sources are also attracting attention for potential applications in high-density optical data storage, biomedical research, water and air purification, and sterilization. Wide-bandgap materials, such as diamond and III-V nitride semiconductors (GaN, AlGaN and AlN; refs 3-10), are potential materials for ultraviolet LEDs and laser diodes, but suffer from difficulties in controlling electrical conduction. Here we report the successful control of both n-type and p-type doping in aluminium nitride (AlN), which has a very wide direct bandgap of 6eV. This doping strategy allows us to develop an AlN PIN (p-type/intrinsic/n-type) homojunction LED with an emission wavelength of 210nm, which is the shortest reported to date for any kind of LED. The emission is attributed to an exciton transition, and represents an important step towards achieving exciton-related light-emitting devices as well as replacing gas light sources with solid-state light sources.

  4. Compact high brightness diode laser emitting 500W from a 100?m fiber

    NASA Astrophysics Data System (ADS)

    Heinemann, Stefan; Fritsche, Haro; Kruschke, Bastian; Schmidt, Torsten; Gries, Wolfgang

    2013-02-01

    High power, high brightness diode lasers are beginning to compete with solid state lasers, i.e. disk and fiber lasers. The core technologies for brightness scaling of diode lasers are optical stacking and dense spectral combining (DSC), as well as improvements of the diode material. Diode lasers have the lowest cost of ownership, highest efficiency and most compact design among all lasers. Multiple Single Emitter (MSE) modules allow highest power and highest brightness diode lasers based on standard broad area diodes. Multiple single emitters, each rated at 12 W, are stacked in the fast axis with a monolithic slow axis collimator (SAC) array. Volume Bragg Gratings (VBG) stabilizes the wavelength and narrow the linewidth to less than 1 nm. Dichroic mirrors are used for dense wavelength multiplexing of 4 channels within 12 nm. Subsequently polarization multiplexing generates 450 W with a beam quality of 4.5 mm*mrad. Fast control electronics and miniaturized switched power supplies enable pulse rise times of less than 10 ?s, with pulse widths continuously adjustable from 20 ?s to cw. Further power scaling up to multi-kilowatts can be achieved by multiplexing up to 16 channels. The power and brightness of these systems enables the use of direct diode lasers for cutting and welding. The technologies can be transferred to other wavelengths to include 793 nm and 1530 nm. Optimized spectral combining enables further improvements in spectral brightness and power.

  5. Exploring Faraday's Law of Electrolysis Using Zinc-Air Batteries with Current Regulative Diodes

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Paku, Miei

    2007-01-01

    Current regulative diodes (CRDs) are applied to develop new educational experiments on Faraday's law by using a zinc-air battery (PR2330) and a resistor to discharge it. The results concluded that the combination of zinc-air batteries and the CRD array is simpler, less expensive, and quantitative and gives accurate data.

  6. Cosmic Ray Measurements by Scintillators with Metal Resistor Semiconductor Avalanche Photo Diodes

    ERIC Educational Resources Information Center

    Blanco, Francesco; La Rocca, Paola; Riggi, Francesco; Akindinov, Alexandre; Mal'kevich, Dmitry

    2008-01-01

    An educational set-up for cosmic ray physics experiments is described. The detector is based on scintillator tiles with a readout through metal resistor semiconductor (MRS) avalanche photo diode (APD) arrays. Typical measurements of the cosmic angular distribution at sea level and a study of the East-West asymmetry obtained by such a device are…

  7. Enhanced vbasis laser diode package

    DOEpatents

    Deri, Robert J.; Chen, Diana; Bayramian, Andy; Freitas, Barry; Kotovsky, Jack

    2014-08-19

    A substrate having an upper surface and a lower surface is provided. The substrate includes a plurality of v-grooves formed in the upper surface. Each v-groove includes a first side and a second side perpendicular to the first side. A laser diode bar assembly is disposed within each of the v-grooves and attached to the first side. The laser diode bar assembly includes a first adhesion layer disposed on the first side of the v-groove, a metal plate attached to the first adhesion layer, a second adhesion layer disposed over the metal plate, and a laser diode bar attached to the second adhesion layer. The laser diode bar has a coefficient of thermal expansion (CTE) substantially similar to that of the metal plate.

  8. Thermometric Property of a Diode.

    ERIC Educational Resources Information Center

    Inman, Fred W.; Woodruff, Dan

    1995-01-01

    Presents a simple way to implement the thermometric property of a semiconductor diode to produce a thermometer with a nearly linear dependence upon temperature over a wide range of temperatures. (JRH)

  9. Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

    E-print Network

    Chizh, K V; Kalinushkin, V P; Resnik, V Ya; Storozhevykh, M S; Yuryev, V A

    2013-01-01

    Nickel silicide Schottky diodes formed on polycrystalline Si films are proposed as temperature sensors of monolithic uncooled microbolometer IR focal plane arrays. Structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by transmission electron microscopy. The Ni silicide has been identified as two-phase compound with the volume fraction of Ni_2Si:NiSi>~4:1. Two potential barriers (~0.74 and ~0.51 meV) are registered by photo-emf spectroscopy at 80K and attributed to Ni/Si and Ni-silicide/Si interfaces. I-V characteristics of the diodes studied at different temperatures demonstrate temperature coefficients of voltage and current to vary in absolute value from 0.3 to 0.6%/K for forward biased structures and around 2.5%/K for reverse biased ones.

  10. Extreme ultraviolet multilayer reflectors

    SciTech Connect

    Scott, M.L.; Arendt, P.N.; Cameron, B.J.; Newman, B.E.; Windt, D.; Cash, W.

    1986-01-01

    We have investigated the design, fabrication, and reflectance measurements of a multilayer silver/silicon reflector for use at 58.4 nm. Our results indicate that reflectors in the extreme ultraviolet do not perform as well as predicted due to the presence of surface oxides and other surface contamination layers. In addition, we have found that the correct optical constants for silver have now been published. We find also that these multilayer coatings can be utilized as reflective polarizers in the EUV with an extinction ratio of 75:1 and a throughput of 28% for the s-polarized component of the beam.

  11. Ultraviolet atomic emission detector

    NASA Technical Reports Server (NTRS)

    Braun, W.; Peterson, N. C.; Bass, A. M.; Kurylo, M. J., III (inventors)

    1972-01-01

    A device and method are provided for performing qualitative and quantitative elemental analysis through the utilization of a vacuum UV chromatographic detector. The method involves the use of a carrier gas at low pressure. The gas carries a sample to a gas chromatograph column; the column output is directed to a microwave cavity. In this cavity, a low pressure microwave discharge produces fragmentation of the compounds present and generates intense atomic emissions in the vacuum ultraviolet. These emissions are isolated by a monochromator and measured by photometer to establish absolute concentration for the elements.

  12. Characterization and stabilization of fiber-coupled laser diode arrays

    E-print Network

    Walsworth, Ronald L.

    , D. Bear, R. E. Stoner, and R. L. Walsworth Harvard-Smithsonian Center for Astrophysics, Cambridge spin- exchange can polarize 3 He and 129 Xe nuclei.1 These polar- ized noble gases have recently found is polarized by spin-exchange collisions with Rb vapor atoms that have been spin polarized by depopulation

  13. Monolithic laser diode array with one metalized sidewall

    DOEpatents

    Freitas, Barry L. (Livermore, CA); Skidmore, Jay A. (Livermore, CA); Wooldridge, John P. (Livermore, CA); Emanuel, Mark A. (Livermore, CA); Payne, Stephen A. (Castro Valley, CA)

    2001-01-01

    A monolithic, electrically-insulating substrate that contains a series of notched grooves is fabricated. The substrate is then metalized so that only the top surface and one wall adjacent to the notch are metalized. Within the grooves is located a laser bar, an electrically-conductive ribbon or contact bar and an elastomer which secures/registers the laser bar and ribbon (or contact bar) firmly along the wall of the groove that is adjacent to the notch. The invention includes several embodiments for providing electrical contact to the corresponding top surface of the adjacent wall. In one embodiment, after the bar is located in the proper position, the electrically conductive ribbon is bent so that it makes electrical contact with the adjoining metalized top side of the heatsink.

  14. Parallel reconfigurable single photon avalanche diode array for optical communications 

    E-print Network

    Fisher, Edward Michael Dennis

    2015-11-26

    There is a pressing need to develop alternative communications links due to a number of physical phenomena, limiting the bandwidth and energy efficiency of wire-based systems or economic factors such as cost, material-supply ...

  15. Broadband cavity enhanced spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    NASA Astrophysics Data System (ADS)

    Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Rudich, Y.; Brown, S. S.

    2015-09-01

    Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity enhanced spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99933 ± 0.00003 (670 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.49 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device (CCD) array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity enhanced spectroscopy and cavity ringdown spectroscopy agree within 2 % (slope for linear fit = 0.98 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity enhanced spectroscopy and calculated based on flow dilution are also well-correlated, with r2 = 0.9998. During constant, mixed additions of NO2 and CH2O, the 30 s measurement precisions (1?) of the current configuration were 140 and 210 pptv, respectively. The current 1-min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically-based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to trace gases, this approach will be appropriate for measurements of aerosol extinction in ambient air, and this spectral region is important for characterizing the strong ultraviolet absorption by brown carbon aerosol.

  16. Light-emitting diodes and their potential in callus growth, plantlet development and saponin accumulation during somatic embryogenesis of Panax vietnamensis Ha et Grushv.

    PubMed Central

    Nhut, Duong Tan; Huy, Nguyen Phuc; Tai, Ngo Thanh; Nam, Nguyen Ba; Luan, Vu Quoc; Hien, Vu Thi; Tung, Hoang Thanh; Vinh, Bui The; Luan, Tran Cong

    2015-01-01

    In recent years, LED (light-emitting diode) has been the subject of research within the field of plant growth and development. However, there has been little discussion about using LED in vitro cultures of Panax vietnamensis, one of the important medicinal plants belonging to the Panax genus. This study examines the influence of various LED lamps on callus growth and plant formation of P. vietnamensis. Results show significant differences in growth and development, as various light conditions were suitable for different stages. Callus of 70 mg in fresh weight cultured under yellow LEDs resulted in growth of 1197 mg in fresh weight and 91.7 mg of dry weight, within a period of three months. The most effective plant formation was obtained when embryogenic calli were cultured under the combination of 60% red LED and 40% blue LED with an average of 11.21 plantlets per explant; the shoot clump fresh weight and dry weight were of 1147 and 127 mg, respectively, and the average plant height was 3.1 cm. It was also shown that this light condition was the most efficient for P. vietnamensis in vitro plant growth and development. This study provided additional evidence regarding the influence of different LEDs on ginsenoside production applying high-performance liquid chromatography (HPLC) analysis with photo-diode array (PDA) detection at ultraviolet (UV) wavelength 203 nm. The highest MR2 content was recorded when plants maintained under 20% red LED combined with 80% blue LED. However, the highest Rg1 and Rb1 content was found under fluorescent light. The results presented might provide new strategies using LEDs for adequate micropropagation protocols of P. vietnamensis. PMID:26019644

  17. IDENTIFICATION AND QUANTITATION OF ALKYLATED NUCLEOBASIS BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH UV PHOTODIODE ARRAY DETECTION

    EPA Science Inventory

    The application of UV diode array detection in high-performance liquid chromatographic (HPLC) identification and quantitation of several classes of synthetic and commercially available alkylated nucleobases is investigated. uantitative spectral overlays of these compounds to meth...

  18. 21 CFR 872.6350 - Ultraviolet detector.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...DENTAL DEVICES Miscellaneous Devices § 872.6350 Ultraviolet detector. (a) Identification. An ultraviolet detector is a device intended to provide a source of ultraviolet light which is used to identify otherwise invisible...

  19. 21 CFR 872.6350 - Ultraviolet detector.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...DENTAL DEVICES Miscellaneous Devices § 872.6350 Ultraviolet detector. (a) Identification. An ultraviolet detector is a device intended to provide a source of ultraviolet light which is used to identify otherwise invisible...

  20. Borescope Inspects With Visible Or Ultraviolet Light

    NASA Technical Reports Server (NTRS)

    Molina, Orlando G.

    1989-01-01

    Quartz optical fibers improve performance at ultraviolet wavelengths. Borescope used to inspect interior of small-diameter tubing by visible light and ultraviolet light. Employs quartz fibers to conduct ultraviolet light and visible light with high efficiency.

  1. 21 CFR 872.6350 - Ultraviolet detector.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...DENTAL DEVICES Miscellaneous Devices § 872.6350 Ultraviolet detector. (a) Identification. An ultraviolet detector is a device intended to provide a source of ultraviolet light which is used to identify otherwise invisible...

  2. 21 CFR 872.6350 - Ultraviolet detector.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...DENTAL DEVICES Miscellaneous Devices § 872.6350 Ultraviolet detector. (a) Identification. An ultraviolet detector is a device intended to provide a source of ultraviolet light which is used to identify otherwise invisible...

  3. 21 CFR 872.6350 - Ultraviolet detector.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...DENTAL DEVICES Miscellaneous Devices § 872.6350 Ultraviolet detector. (a) Identification. An ultraviolet detector is a device intended to provide a source of ultraviolet light which is used to identify otherwise invisible...

  4. Gas Sensing Diode Comprising SiC

    NASA Technical Reports Server (NTRS)

    Hunter, Gary William (Inventor)

    2001-01-01

    A diode for sensing hydrogen and hydrocarbons and the process for manufacturing the diode are disclosed. The diode is a Schottky diode which has a palladium chrome contact on the C-face of an n-type 6H Silicon carbide epilayer. The epilayer is grown on the C-face of a 6H silicon carbide substrate. The diode is capable of measuring low concentrations of hydrogen and hydrocarbons at high temperatures, for example, 800 degrees C. The diode is both sensitive and stable at elevated temperatures.

  5. Light Emitting Diodes (LEDs)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique, called Photodynamic Therapy, requires the surgeon to use tiny, pinhead-size Light Emitting Diodes (LEDs) (a source that releases long wavelengths of light ) to activate light-sensitive, tumor-treating drugs. 'A young woman operated on in May 1999 has fully recovered with no complications and no evidence of the tumor coming back,' said Dr. Harry Whelan, a pediatric neurologist at the Medical Hospital of Wisconsin in Milwaukee. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can be used for hours at a time while still remaining cool to the touch. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The LEDs, developed and managed by NASA's Marshall Space Flight Center, have been used on seven Space Shuttle flights inside the Microgravity Astroculture Facility. This technology has also been successfully used to further commercial research in crop growth.

  6. Carbon-Nanotube Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Wong, Eric; Schlecht, Erich; Hunt, Brian; Siegel, Peter

    2006-01-01

    Schottky diodes based on semiconducting single-walled carbon nanotubes are being developed as essential components of the next generation of submillimeter-wave sensors and sources. Initial performance predictions have shown that the performance characteristics of these devices can exceed those of the state-of-the-art solid-state Schottky diodes that have been the components of choice for room-temperature submillimeter-wave sensors for more than 50 years. For state-of-the-art Schottky diodes used as detectors at frequencies above a few hundred gigahertz, the inherent parasitic capacitances associated with their semiconductor junction areas and the resistances associated with low electron mobilities limit achievable sensitivity. The performance of such a detector falls off approximately exponentially with frequency above 500 GHz. Moreover, when used as frequency multipliers for generating signals, state-of-the-art solid-state Schottky diodes exhibit extremely low efficiencies, generally putting out only micro-watts of power at frequencies up to 1.5 THz. The shortcomings of the state-of-the-art solid-state Schottky diodes can be overcome by exploiting the unique electronic properties of semiconducting carbon nanotubes. A single-walled carbon nanotube can be metallic or semiconducting, depending on its chirality, and exhibits high electron mobility (recently reported to be approx.= 2x10(exp 5)sq cm/V-s) and low parasitic capacitance. Because of the narrowness of nanotubes, Schottky diodes based on carbon nanotubes have ultra-small junction areas (of the order of a few square nanometers) and consequent junction capacitances of the order of 10(exp -18) F, which translates to cutoff frequency >5 THz. Because the turn-on power levels of these devices are very low (of the order of nano-watts), the input power levels needed for pumping local oscillators containing these devices should be lower than those needed for local oscillators containing state-of-the-art solid-state Schottky diodes.

  7. Imaging air pollutants in the near ultraviolet

    NASA Technical Reports Server (NTRS)

    Norris, D.; Conley, J.; Seng, S.

    1976-01-01

    This paper discusses a program for remote sensing of air pollutants called Multispectral Observation of Pollutants System (MOPS). The broad objective of the program is to photograph 'invisible' gaseous pollutants by combining ultraviolet imaging in several spectral bands with portable data processing equipment. Electronic cameras using solid state imaging arrays of large dynamic range will permit very low contrast images to be electronically ratioed and contrast enhanced, thus bringing out pollutant images which are below the contrast threshold of film. Such photographs will allow synoptic coverage of geographic areas providing source, sink, and flow data on pollutants, and will provide reconnaissance and pointing information for other remote sensors. The principle gases to be mapped by MOPS will be ozone, sulfur dioxide, and nitrogen dioxide.

  8. Babinet's principle and the band structure of surface waves on patterned metal arrays

    E-print Network

    Exeter, University of

    2010 The microwave response of an array of square metal patches and its complementary structure in the ultraviolet region, yielding a predominantly Drude-type dielectric function dominated by a negative real part typically occurs in the ultraviolet. Since ksw k0 Eq. 1 , these modes are nonradiative but can be coupled

  9. Investigation of ultraviolet interstellar extinction

    NASA Technical Reports Server (NTRS)

    Payne, C.; Haramundanis, K. L.

    1973-01-01

    Results concerning interstellar extinction in the ultraviolet are reported. These results were initially obtained by using data from main-sequence stars and were extended to include supergiants and emission stars. The principal finding of the analysis of ultraviolet extinction is not only that it is wavelength dependent, but that if changes with galactic longitude in the U3 passband (lambda sub eff = 1621 A); it does not change significantly in the U2 passband (lambda sub eff = 2308 A). Where data are available in the U4 passband (lambda sub eff = 1537 A), they confirm the rapid rise of extinction in the ultraviolet found by other investigators. However, in all cases, emission stars must be used with great caution. It is important to realize that while extinction continues to rise toward shorter wavelengths in the ultraviolet, including the shortest ultraviolet wavelengths measured (1100 A), it no longer plays an important role in the X-ray region (50 A).

  10. Close-packed array of light emitting devices

    DOEpatents

    Ivanov, Ilia N.; Simpson, John T.

    2013-04-09

    A close-packed array of light emitting diodes includes a nonconductive substrate having a plurality of elongate channels extending therethrough from a first side to a second side, where each of the elongate channels in at least a portion of the substrate includes a conductive rod therein. The conductive rods have a density over the substrate of at least about 1,000 rods per square centimeter and include first conductive rods and second conductive rods. The close-packed array further includes a plurality of light emitting diodes on the first side of the substrate, where each light emitting diode is in physical contact with at least one first conductive rod and in electrical contact with at least one second conductive rod.

  11. Pixel array detectors for time resolved radiography ,,invited... M. J. Renzi,a)

    E-print Network

    Gruner, Sol M.

    Pixel array detectors for time resolved radiography ,,invited... M. J. Renzi,a) M. W. Tate, A. The silicon pixel array detector PAD is an extremely flexible technology which is currently being developed with submicrosecond frame times. This 100 92 pixel prototype PAD consists of a pixelated silicon diode layer

  12. Reverse Polarized Inductive Coupling to Transmit and Receive Radiofrequency Coil Arrays

    E-print Network

    Atalar, Ergin

    that an ICRF decoupled from the transmit field using back-to-back diodes is called a receptively coupled RF polarization through RF transmit-array systems. ``Wireless'' active catheter tracking (4) and fiducial markerReverse Polarized Inductive Coupling to Transmit and Receive Radiofrequency Coil Arrays Haydar

  13. Multifunctional Deployment Hinges Rigidified by Ultraviolet

    NASA Technical Reports Server (NTRS)

    Kerslake, Thomas W.; Simburger, Edward J.; Matusmoto, James; Giants, Thomas W.; Garcia, Alexander; Perry, Alan; Rawal, Suraj; Marshall, Craig; Lin, John Kun Hung; Day, Jonathan Robert; Scarborough, Stephen Emerson

    2005-01-01

    Multifunctional hinges have been developed for deploying and electrically connecting panels comprising planar arrays of thin-film solar photovoltaic cells. In the original intended application of these hinges, the panels would be facets of a 32-sided (and approximately spherical) polyhedral microsatellite (see figure), denoted a PowerSphere, that would be delivered to orbit in a compact folded configuration, then deployed by expansion of gas in inflation bladders. Once deployment was complete, the hinges would be rigidified to provide structural connections that would hold the panels in their assigned relative positions without backlash. Such hinges could also be used on Earth for electrically connecting and structurally supporting solar panels that are similarly shipped in compact form and deployed at their destinations. As shown in section A-A in the figure, a hinge of this type is partly integrated with an inflation bladder and partly integrated with the frame of a solar panel. During assembly of the hinge, strip extensions from a flexible circuit harness on the bladder are connected to corresponding thin-film conductors on the solar panel by use of laser welding and wrap-around contacts. The main structural component of the hinge is a layer of glass fiber impregnated with an ultraviolet-curable resin. After deployment, exposure to ultraviolet light from the Sun cures the resin, thereby rigidifying the hinge.

  14. Measuring the Photocatalytic Breakdown of Crystal Violet Dye using a Light Emitting Diode Approach

    NASA Technical Reports Server (NTRS)

    Ryan, Robert E.; Underwood, Lauren W.; O'Neal, Duane; Pagnutti, Mary; Davis, Bruce A.

    2009-01-01

    A simple method to estimate the photocatalytic reactivity performance of spray-on titanium dioxide coatings for transmissive glass surfaces was developed. This novel technique provides a standardized method to evaluate the efficiency of photocatalytic material systems over a variety of illumination levels. To date, photocatalysis assessments have generally been conducted using mercury black light lamps. Illumination levels for these types of lamps are difficult to vary, consequently limiting their use for assessing material performance under a diverse range of simulated environmental conditions. This new technique uses an ultraviolet (UV) gallium nitride (GaN) light emitting diode (LED) array instead of a traditional black light to initiate and sustain photocatalytic breakdown. This method was tested with a UV-resistant dye (crystal violet) applied to a titanium dioxide coated glass slide. Experimental control is accomplished by applying crystal violet to both titanium dioxide coated slides and uncoated control slides. A slide is illuminated by the UV LED array, at various light levels representative of outdoor and indoor conditions, from the dye side of the slide. To monitor degradation of the dye over time, a temperature-stabilized white light LED, whose emission spectrum overlaps with the dye absorption spectrum, is used to illuminate the opposite side of the slide. Using a spectrometer, the amount of light from the white light LED transmitted through the slide as the dye degrades is monitored as a function of wavelength and time and is subsequently analyzed. In this way, the rate of degradation for photocatalytically coated versus uncoated slide surfaces can be compared. Results demonstrate that the dye absorption decreased much more rapidly on the photocatalytically coated slides than on the control uncoated slides, and that dye degradation is dependent on illumination level. For photocatalytic activity assessment purposes, this experimental configuration and methodology minimizes many external variable effects and enables small changes in absorption to be measured. This research also compares the advantages of this innovative LED light source design over traditional mercury black light systems and non- LED lamp approaches. This novel technology begins to address the growing need for a standard method that can assess the performance of photocatalytic materials before deployment for large scale, real world use.

  15. Semiconductor Laser Diode Pumps for Inertial Fusion Energy Lasers

    SciTech Connect

    Deri, R J

    2011-01-03

    Solid-state lasers have been demonstrated as attractive drivers for inertial confinement fusion on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) and at the Omega Facility at the Laboratory for Laser Energetics (LLE) in Rochester, NY. For power plant applications, these lasers must be pumped by semiconductor diode lasers to achieve the required laser system efficiency, repetition rate, and lifetime. Inertial fusion energy (IFE) power plants will require approximately 40-to-80 GW of peak pump power, and must operate efficiently and with high system availability for decades. These considerations lead to requirements on the efficiency, price, and production capacity of the semiconductor pump sources. This document provides a brief summary of these requirements, and how they can be met by a natural evolution of the current semiconductor laser industry. The detailed technical requirements described in this document flow down from a laser ampl9ifier design described elsewhere. In brief, laser amplifiers comprising multiple Nd:glass gain slabs are face-pumped by two planar diode arrays, each delivering 30 to 40 MW of peak power at 872 nm during a {approx} 200 {micro}s quasi-CW (QCW) pulse with a repetition rate in the range of 10 to 20 Hz. The baseline design of the diode array employs a 2D mosaic of submodules to facilitate manufacturing. As a baseline, they envision that each submodule is an array of vertically stacked, 1 cm wide, edge-emitting diode bars, an industry standard form factor. These stacks are mounted on a common backplane providing cooling and current drive. Stacks are conductively cooled to the backplane, to minimize both diode package cost and the number of fluid interconnects for improved reliability. While the baseline assessment in this document is based on edge-emitting devices, the amplifier design does not preclude future use of surface emitting diodes, which may offer appreciable future cost reductions and increased reliability. The high-level requirements on the semiconductor lasers involve reliability, price points on a price-per-Watt basis, and a set of technical requirements. The technical requirements for the amplifier design in reference 1 are discussed in detail and are summarized in Table 1. These values are still subject to changes as the overall laser system continues to be optimized. Since pump costs can be a significant fraction of the overall laser system cost, it is important to achieve sufficiently low price points for these components. At this time, the price target for tenth-of-akind IFE plant is $0.007/Watt for packaged devices. At this target level, the pumps account for approximately one third of the laser cost. The pump lasers should last for the life of the power plant, leading to a target component lifetime requirement of roughly 14 Ghosts, corresponding to a 30 year plant life and 15 Hz repetition rate. An attractive path forward involes pump operation at high output power levels, on a Watts-per-bar (Watts/chip) basis. This reduces the cost of pump power (price-per-Watt), since to first order the unit price does not increase with power/bar. The industry has seen a continual improvement in power output, with current 1 cm-wide bars emitting up to 500 W QCW (quasi-continuous wave). Increased power/bar also facilitates achieving high irradiance in the array plane. On the other hand, increased power implies greater heat loads and (possibly) higher current drive, which will require increased attention to thermal management and parasitic series resistance. Diode chips containing multiple p-n junctions and quantum wells (also called nanostack structures) may provide an additional approach to reduce the peak current.

  16. Ultraviolet radiation effects

    NASA Technical Reports Server (NTRS)

    Slemp, Wayne S.

    1989-01-01

    Solar ultraviolet testing was not developed which will provide highly accelerated (20 to 50X) exposures that correlate to flight test data. Additional studies are required to develop an exposure methodology which will assure that accelerated testing can be used for qualification of materials and coatings for long duration space flight. Some conclusions are listed: Solar UV radiation is present in all orbital environments; Solar UV does not change in flux with orbital altitude; UV radiation can degrade most coatings and polymeric films; Laboratory UV simulation methodology is needed for accelerated testing to 20 UV solar constants; Simulation of extreme UV (below 200 nm) is needed to evaluate requirements for EUV in solar simulation.

  17. Microlens arrays

    NASA Astrophysics Data System (ADS)

    Hutley, Michael C.; Stevens, Richard F.; Daly, Daniel J.

    1992-04-01

    Microlenses have been with us for a long time as indeed the very word lens reminds us. Many early lenses,including those made by Hooke and Leeuwenhoek in the 17th century were small and resembled lentils. Many languages use the same word for both (French tilentillelt and German "Linse") and the connection is only obscure in English because we use the French word for the vegetable and the German for the optic. Many of the applications for arrays of inicrolenses are also well established. Lippmann's work on integral photography at the turn of the century required lens arrays and stimulated an interest that is very much alive today. At one stage, lens arrays played an important part in high speed photography and various schemes have been put forward to take advantage of the compact imaging properties of combinations of lens arrays. The fact that many of these ingenious schemes have not been developed to their full potential has to a large degree been due to the absence of lens arrays of a suitable quality and cost.

  18. AlGaInN laser diode technology for defence, security and sensing applications

    NASA Astrophysics Data System (ADS)

    Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lucja; Bo?kowski, Mike; Leszczy?ski, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Watson, Scott; Kelly, Antony E.

    2014-10-01

    The latest developments in AlGaInN laser diode technology are reviewed for defence, security and sensing applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., i.e, 380nm, to the visible, i.e., 530nm, by tuning the indium content of the laser GaInN quantum well. Advantages of using Plasma assisted MBE (PAMBE) compared to more conventional MOCVD epitaxy to grow AlGaInN laser structures are highlighted. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of <100mW in the 400-420nm wavelength range that are suitable for telecom applications. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Gallium-nitride (GaN) blue laser diode is reported. High power operation of AlGaInN laser diodes is demonstrated with a single chip, AlGaInN laser diode `mini-array' with a common p-contact configuration at powers up to 2.5W cw at 410nm. Low defectivity and highly uniform GaN substrates allow arrays and bars of nitride lasers to be fabricated. GaN laser bars of up to 5mm with 20 emitters, mounted in a CS mount package, give optical powers up to 4W cw at ~410nm with a common contact configuration. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be individually addressable allowing complex free-space and/or fibre optic system integration within a very small form-factor.or.

  19. Noise Diode Stability Measurements Using a 4.3 GHz Laboratory Radiometer

    NASA Technical Reports Server (NTRS)

    Scherner, M. J.; Lawrence, R. W.

    1997-01-01

    The need for passive microwave radiometry using aperture synthesis and phased arrays for large apertures requiring more stability has generated several studies. The in-flight calibration and, therefore, the stability of such systems is an important design consideration. A 4.3 GHz laboratory radiometry operating in a balanced Dicke mode has been developed for making precise brightness (noise) temperature measurements. The stability of the noise diode source used in the noise-injection loop is of interest. A statistical Allan variance method to characterize the stability of the radiometer and the noise diode is presented in this paper. Noise measurements which demonstrate this approach are also included.

  20. Analytical solution for the lateral current distribution in multiple stripe laser diodes

    SciTech Connect

    Amann, M.; Kappeler, F.

    1986-06-23

    The lateral profile of the injection current along the active layer in multiple stripe laser diodes is analyzed for the practical case of homogeneous current density within each individual stripe contact. By means of conformal mapping an exact analytical solution is found for arbitrary contact configurations (number, width, and location) driven with different currents. The simple form of the solution eases the analysis of modal gain and supermode discrimination in gain-guided and index-guided arrays of stripe-geometry laser diodes.

  1. Low Temperature Thermometry Using Inexpensive Silicon Diodes.

    ERIC Educational Resources Information Center

    Waltham, N. R.; And Others

    1981-01-01

    Describes the use of silicon diodes for low temperature thermometry in the teaching laboratory. A simple and inexpensive circuit for display of the diode forward voltage under constant current conditions is described, and its application in the evaluation of low cost silicon diodes as low temperature thermometers is presented. (SK)

  2. Diode laser atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Zybin, A.; Koch, J.; Wizemann, H. D.; Franzke, J.; Niemax, K.

    2005-01-01

    The paper reviews the past 11 years of literature on the application of diode lasers in atomic absorption spectrometry with graphite furnaces (GF), plasmas and flames as atomizers. Experimental arrangements and techniques for powerful absorption measurements as well as the theoretical background are covered. The analytical possibilities of high-resolution spectroscopy, including Doppler-free techniques for isotope selective measurements and isotope dilution analysis are discussed and various applications of element-selective detection by diode laser atomic absorption in combination with separation techniques, such as liquid (LC) and gas chromatography (GC), and with laser ablation of solid samples, are presented.

  3. Method of making diode structures

    DOEpatents

    Compaan, Alvin D.; Gupta, Akhlesh

    2006-11-28

    A method of making a diode structure includes the step of depositing a transparent electrode layer of any one or more of the group ZnO, ZnS and CdO onto a substrate layer, and depositing an active semiconductor junction having an n-type layer and a p-type layer onto the transparent electrode layer under process conditions that avoid substantial degradation of the electrode layer. A back electrode coating layer is applied to form a diode structure.

  4. ULTRAVIOLET PROTECTIVE COMPOUNDS AS A RESPONSE TO ULTRAVIOLET RADIATION EXPOSURE

    EPA Science Inventory

    Life on Earth has evolved adaptations to many environmental stresses over the epochs. One consistent stress has been exposure to ultraviolet radiation. In response to UVR organisms have adapted myriad responses; behavioral, morphological and physiological. Behaviorally, some orga...

  5. Sonar Arrays and Array Processing

    NASA Astrophysics Data System (ADS)

    Baggeroer, A. B.

    2005-04-01

    Arrays of hydrophones have been part of Navy sonar systems for over fifty years now. They are used both passively and actively and now are quite sophisticated. These arrays were used in fixed configuration such as the SOSUS system and towed arrays deployed from surface ships and submarines. One can assert that these arrays were a key factor in winning the cold war. Similarly, medical ultrasonics have used many of the techniques initially developed for sonar systems save four orders of magnitude in frequency. The major area where modern sonars differ involves the use of adaptive array processing whereby one usually needs to localize a weak signal in the presence of strong interference in a nonstationary environment. Most of the recent literature concerns advancing these techniques especially making them more robust to environmental uncertainties including calibration and properties of the ocean. This presentation will give an overview of the state of the art in sonar and hopefully establish a few points of relevance with nondestructive testing.

  6. Research in extreme ultraviolet and far ultraviolet astronomy

    NASA Technical Reports Server (NTRS)

    Bowyer, C. S.

    1985-01-01

    The Far Ultraviolet imager (FUVI) was flown on the Aries class sounding rocket 24.015, producing outstanding results. The diffuse extreme ultraviolet (EUV) background spectrometer which is under construction is described. It will be launched on the Black Brant sounding rocket flight number 27.086. Ongoing design studies of a high resolution spectrometer are discussed. This instrument incorporates a one meter normal incidence mirror and will be suitable for an advanced Spartan mission.

  7. Inductively coupled wireless RF coil arrays.

    PubMed

    Bulumulla, S B; Fiveland, E; Park, K J; Foo, T K; Hardy, C J

    2015-04-01

    As the number of coils increases in multi-channel MRI receiver-coil arrays, RF cables and connectors become increasingly bulky and heavy, degrading patient comfort and slowing workflow. Inductive coupling of signals provides an attractive "wireless" approach, with the potential to reduce coil weight and cost while simplifying patient setup. In this work, multi-channel inductively coupled anterior arrays were developed and characterized for 1.5T imaging. These comprised MR receiver coils inductively (or "wirelessly") linked to secondary or "sniffer" coils whose outputs were transmitted via preamps to the MR system cabinet. The induced currents in the imaging coils were blocked by passive diode circuits during RF transmit. The imaging arrays were totally passive, obviating the need to deliver power to the coils, and providing lightweight, untethered signal reception with easily positioned coils. Single-shot fast spin echo images were acquired from 5 volunteers using a 7-element inductively coupled coil array and a conventionally cabled 7-element coil array of identical geometry, with the inductively-coupled array showing a relative signal-to-noise ratio of 0.86 +/- 0.07. The concept was extended to a larger 9-element coil array to demonstrate the effect of coil element size on signal transfer and RF-transmit blocking. PMID:25523607

  8. Transmitting and reflecting diffuser. [for ultraviolet light

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.; Burcher, E. E.; Kopia, L. P. (inventors)

    1973-01-01

    A near-Lambertian diffuser is described which transmits and reflects ultraviolet light. An ultraviolet grade fused silica substrate is coated with vaporized fuse silica. The coating thickness is controlled, one thickness causing ultraviolet light to diffuse and another thickness causing ultraviolet light to reflect a near Lambertian pattern.

  9. Plasmonic cladding InGaN MQW laser diodes

    NASA Astrophysics Data System (ADS)

    Perlin, P.; Holc, K.; Sarzynski, M.; Leszczynski, M.; Czernecki, R.; Marona, L.; Wisniewski, P.; Cywinski, G.; Skierbiszewski, C.; Bockowski, M.; Grzegory, I.; Suski, T.

    2011-02-01

    In the present work we demonstrate a concept of a "weak plasmonic cladding" for the improved transversal optical confinement in the structures of nitride lasers diodes emitting in the violet and blue spectral region. We show that by using highly doped GaN:O or GaN:Si layers we can induced the reduction of the refractive index by around 1-2% comparing to a lightly doped material. Such a material can be effectively used as optical cladding replacing thick, highly strained AlGaN layers. Plasmonic claddings can be grown by two methods: first of them is High Nitrogen Pressure Solution growth (an introduced donor is an oxygen) and Molecular Beam Epitaxy with silicon as a donor. In the both cases we can reach a free carrier concentration of up to around 1020cm-3. MOVPE method so far did not show capabilities for achieving so high doping level. We demonstrate the use of such layers for the construction of the violet and blue laser diodes and laser diodes mini-arrays showing a total suppression of the substrate mode leakage.

  10. Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

    PubMed Central

    2013-01-01

    Nickel silicide Schottky diodes formed on polycrystalline Si ?P? films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22℃ to 70℃; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%℃ to 0.6%/℃ for forward bias and around 2.5%/℃ for reverse bias of the diodes. PMID:23594606

  11. Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

    NASA Astrophysics Data System (ADS)

    Chizh, Kirill V.; Chapnin, Valery A.; Kalinushkin, Victor P.; Resnik, Vladimir Y.; Storozhevykh, Mikhail S.; Yuryev, Vladimir A.

    2013-04-01

    Nickel silicide Schottky diodes formed on polycrystalline Si < P> films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22° to 70 °; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%° to 0.6%/° for forward bias and around 2.5%/° for reverse bias of the diodes.

  12. Metal silicide/poly-Si Schottky diodes for uncooled microbolometers.

    PubMed

    Chizh, Kirill V; Chapnin, Valery A; Kalinushkin, Victor P; Resnik, Vladimir Y; Storozhevykh, Mikhail S; Yuryev, Vladimir A

    2013-01-01

    : Nickel silicide Schottky diodes formed on polycrystalline Si ?P? films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22â"ƒ to 70â"ƒ; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%â"ƒ to 0.6%/â"ƒ for forward bias and around 2.5%/â"ƒ for reverse bias of the diodes. PMID:23594606

  13. Pacific Array

    NASA Astrophysics Data System (ADS)

    Kawakatsu, H.; Takeo, A.; Isse, T.; Nishida, K.; Shiobara, H.; Suetsugu, D.

    2014-12-01

    Based on our recent results on broadband ocean bottom seismometry, we propose a next generation large-scale array experiment in the ocean. Recent advances in ocean bottom broadband seismometry (e.g., Suetsugu & Shiobara, 2014, Annual Review EPS), together with advances in the seismic analysis methodology, have now enabled us to resolve the regional 1-D structure of the entire lithosphere/asthenosphere system, including seismic anisotropy (both radial and azimuthal), with deployments of ~10-15 broadband ocean bottom seismometers (BBOBSs) (namely "ocean-bottom broadband dispersion survey"; Takeo et al., 2013, JGR; Kawakatsu et al., 2013, AGU; Takeo, 2014, Ph.D. Thesis; Takeo et al., 2014, JpGU). Having ~15 BBOBSs as an array unit for 2-year deployment, and repeating such deployments in a leap-frog way (an array of arrays) for a decade or so would enable us to cover a large portion of the Pacific basin. Such efforts, not only by giving regional constraints on the 1-D structure, but also by sharing waveform data for global scale waveform tomography, would drastically increase our knowledge of how plate tectonics works on this planet, as well as how it worked for the past 150 million years. International collaborations might be sought.

  14. Global Arrays

    Energy Science and Technology Software Center (ESTSC)

    2006-02-23

    The Global Arrays (GA) toolkit provides an efficient and portable ?shared-memory? programming interface for distributed-memory computers. Each process in a MIMD parallel program can asynchronously access logical blocks of physically distributed dense multi-dimensional arrays, without need for explicit cooperation by other processes. Unlike other shared-memory environments, the GA model exposes to the programmer the non-uniform memory access (NUMA) characteristics of the high performance computers and acknowledges that access to a remote portion of the sharedmore »data is slower than to the local portion. The locality information for the shared data is available, and a direct access to the local portions of shared data is provided. Global Arrays have been designed to complement rather than substitute for the message-passing programming model. The programmer is free to use both the shared-memory and message-passing paradigms in the same program, and to take advantage of existing message-passing software libraries. Global Arrays are compatible with the Message Passing Interface (MPI).« less

  15. Plasmonic enhancement of ultraviolet fluorescence

    NASA Astrophysics Data System (ADS)

    Jiao, Xiaojin

    Plasmonics relates to the interaction between electromagnetic radiation and conduction electrons at metallic interfaces or in metallic nanostructures. Surface plasmons are collective electron oscillations at a metal surface, which can be manipulated by shape, texture and material composition. Plasmonic applications cover a broad spectrum from visible to near infrared, including biosensing, nanolithography, spectroscopy, optoelectronics, photovoltaics and so on. However, there remains a gap in this activity in the ultraviolet (UV, < 400 nm), where significant opportunity exists for both fundamental and application research. Motivating factors in the study of UV Plasmonics are the direct access to biomolecular resonances and native fluorescence, resonant Raman scattering interactions, and the potential for exerting control over photochemical reactions. This dissertation aims to fill in the gap of Plasmonics in the UV with efforts of design, fabrication and characterization of aluminium (Al) and magnesium (Mg) nanostructures for the application of label-free bimolecular detection via native UV fluorescence. The first contribution of this dissertation addresses the design of Al nanostructures in the context of UV fluorescence enhancement. A design method that combines analytical analysis with numerical simulation has been developed. Performance of three canonical plasmonic structures---the dipole antenna, bullseye nanoaperture and nanoaperture array---has been compared. The optimal geometrical parameters have been determined. A novel design of a compound bullseye structure has been proposed and numerically analyzed for the purpose of compensating for the large Stokes shift typical of UV fluorescence. Second, UV lifetime modification of diffusing molecules by Al nanoapertures has been experimentally demonstrated for the first time. Lifetime reductions of ~3.5x have been observed for the high quantum yield (QY) laser dye p-terphenyl in a 60 nm diameter aperture with 50 nm undercut. Furthermore, quantum-yield-dependence of lifetime reduction has been experimentally demonstrated for the first time. Lifetime reduction as a function of aperture size and native quantum yield has been accurately predicted by simulation. Simulation further predicts greater net fluorescence enhancement for tryptophan compared to p-terphenyl. In order to increase fluorescence enhancement, the "poor" molecules and structures with proper undercuts are required. Third, UV lifetime modification by Mg nanoapertures has been experimentally demonstrated for the fisrt time. Lifetime reductions of ~13x have been observed for the laser dye p-terphenyl with high QY in a 50 nm diameter aperture with 125 nm undercut. In addition, extraordinary optical transmission of Mg nanohole arrays in the UV has been measured for the first time. By using Al as a reference, the feasibility of applying Mg in the UV plasmonic applications has been evaluated both numerically and experimentally. Finally, this work has established a methodology for the study of plasmonic enhancement of UV fluorescence, including design method, thin-film characterization, nanofabrication with focus ion beam milling, and fluorescence measurement. It has paved the way for more extensive research on UV fluorescence enhancement.

  16. N-polar III-nitride quantum well light-emitting diodes with polarization-induced doping

    SciTech Connect

    Verma, Jai; Simon, John; Protasenko, Vladimir; Kosel, Thomas; Xing, Huili Grace; Jena, Debdeep

    2011-10-24

    Nitrogen-polar III-nitride heterostructures present unexplored advantages over Ga(metal)-polar crystals for optoelectronic devices. This work reports N-polar III-nitride quantum-well ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy that integrate polarization-induced p-type doping by compositional grading from GaN to AlGaN along N-face. The graded AlGaN layer simultaneously acts as an electron blocking layer while facilitating smooth injection of holes into the active region, while the built-in electric field in the barriers improves carrier injection into quantum wells. The enhanced doping, carrier injection, and light extraction indicate that N-polar structures have the potential to exceed the performance of metal-polar ultraviolet light-emitting diodes.

  17. Extreme ultraviolet lithography machine

    DOEpatents

    Tichenor, Daniel A. (Castro Valley, CA); Kubiak, Glenn D. (Livermore, CA); Haney, Steven J. (Tracy, CA); Sweeney, Donald W. (San Ramon, CA)

    2000-01-01

    An extreme ultraviolet lithography (EUVL) machine or system for producing integrated circuit (IC) components, such as transistors, formed on a substrate. The EUVL machine utilizes a laser plasma point source directed via an optical arrangement onto a mask or reticle which is reflected by a multiple mirror system onto the substrate or target. The EUVL machine operates in the 10-14 nm wavelength soft x-ray photon. Basically the EUV machine includes an evacuated source chamber, an evacuated main or project chamber interconnected by a transport tube arrangement, wherein a laser beam is directed into a plasma generator which produces an illumination beam which is directed by optics from the source chamber through the connecting tube, into the projection chamber, and onto the reticle or mask, from which a patterned beam is reflected by optics in a projection optics (PO) box mounted in the main or projection chamber onto the substrate. In one embodiment of a EUVL machine, nine optical components are utilized, with four of the optical components located in the PO box. The main or projection chamber includes vibration isolators for the PO box and a vibration isolator mounting for the substrate, with the main or projection chamber being mounted on a support structure and being isolated.

  18. Ultraviolet fluorescence monitor

    SciTech Connect

    Hargis, P.J. Jr.; Preppernau, B.L.; Aragon, B.P.

    1997-05-01

    A multispectral ultraviolet (UV) fluorescence imaging fluorometer and a pulsed molecular beam laser fluorometer were developed to detect volatile organic compounds of interest in environmental monitoring and drug interdiction applications. The UV fluorescence imaging fluorometer is a relatively simple instrument which uses multiple excitation wavelengths to measure the excitation/emission matrix for irradiated samples. Detection limits in the high part-per-million to low part-per-million range were measured for a number of volatile organic vapors in the atmosphere. Detection limits in the low part-per-million range were obtained using cryogenic cooling to pre-concentrate unknown samples before introducing them into the imaging fluorometer. A multivariate analysis algorithm was developed to analyze the excitation/emission matrix and used to determine the relative concentrations of species in computer synthesized mixtures containing up to five organic compounds. Analysis results demonstrated the utility of multispectral UV fluorescence in analytical measurements. A transportable UV fluorescence imaging fluorometer was used in two field tests. Field test results demonstrated that detection limits in the part-per-billion range were needed to reliably identify volatile organic compounds in realistic field test measurements. The molecular beam laser fluorometer, a more complex instrument with detection limits in the part-per-billion to part-per-trillion range, was therefore developed to satisfy detection sensitivity requirements for field test measurements. High-resolution spectroscopic measurements made with the molecular beam laser fluorometer demonstrated its utility in identifying volatile organic compounds in the atmosphere.

  19. Ultraviolet radiation and cyanobacteria.

    PubMed

    Rastogi, Rajesh Prasad; Sinha, Rajeshwar P; Moh, Sang Hyun; Lee, Taek Kyun; Kottuparambil, Sreejith; Kim, Youn-Jung; Rhee, Jae-Sung; Choi, Eun-Mi; Brown, Murray T; Häder, Donat-Peter; Han, Taejun

    2014-12-01

    Cyanobacteria are the dominant photosynthetic prokaryotes from an ecological, economical, or evolutionary perspective, and depend on solar energy to conduct their normal life processes. However, the marked increase in solar ultraviolet radiation (UVR) caused by the continuous depletion of the stratospheric ozone shield has fueled serious concerns about the ecological consequences for all living organisms, including cyanobacteria. UV-B radiation can damage cellular DNA and several physiological and biochemical processes in cyanobacterial cells, either directly, through its interaction with certain biomolecules that absorb in the UV range, or indirectly, with the oxidative stress exerted by reactive oxygen species. However, cyanobacteria have a long history of survival on Earth, and they predate the existence of the present ozone shield. To withstand the detrimental effects of solar UVR, these prokaryotes have evolved several lines of defense and various tolerance mechanisms, including avoidance, antioxidant production, DNA repair, protein resynthesis, programmed cell death, and the synthesis of UV-absorbing/screening compounds, such as mycosporine-like amino acids (MAAs) and scytonemin. This study critically reviews the current information on the effects of UVR on several physiological and biochemical processes of cyanobacteria and the various tolerance mechanisms they have developed. Genomic insights into the biosynthesis of MAAs and scytonemin and recent advances in our understanding of the roles of exopolysaccharides and heat shock proteins in photoprotection are also discussed. PMID:25463663

  20. Ultraviolet investigations for lunar missions

    USGS Publications Warehouse

    Hemphill, William R.; Fischer, William A.; Dornbach, J.E.

    1966-01-01

    Preliminary field tests of an active ultraviolet imaging system have shown that it is possible to produce linages of the terrain from distances as great as 75 feet by means of reflected ultraviolet light at wavelengths longer than 3300 A. Minerals that luminesce when exposed to ultraviolet energy have been detected from distances as great as 200 feet. With appropriate design modifications, it may be possible to utilize a similar system in detecting luminescing minerals from greater distances. Also, with a similar system and appropriate auxiliary equipment such as image intensifiers, it may be possible to discriminate between naturally occurring materials on the basis of reflected ultraviolet energy at wavelengths shorter than 3000 A. In this part of the spectrum image contrast for some rock types may exceed that from visible light. Information from these and related ultraviolet spectralanalysis studies may be useful in evaluating data obtained from passive ultraviolet systems in lunar orbit as well as from active systems on the lunar surface.

  1. Electrical conduction through linear porphyrin arrays.

    PubMed

    Yoon, Dae Hwan; Lee, Sun Bae; Yoo, K-H; Kim, Jinhee; Lim, Jong Kuk; Aratani, Naoki; Tsuda, Akihiko; Osuka, Atsuhiro; Kim, Dongho

    2003-09-10

    Electrical conduction measurements were made on two extreme types of directly linked porphyrin arrays by using nanoelectrodes. One type is the directly linked Zn(II)porphyrin arrays, consisting of 48 Zn(II)porphyrin moieties (Z48), and the other type is the completely flat, tape-shaped Zn(II)porphyrin arrays, consisting of eight Zn(II)porphyrin units (T8). The I-V curve for Z48 exhibits the diode-like behavior and the hysteresis depending on the voltage sweep direction presumably due to the conformational heterogeneity arising from the dihedral angle distribution in Z48. On the other hand, the I-V curve for T8 is nearly symmetric without any hysteresis, leading to the higher conductivity and the smaller band gap. These results illustrate that the stronger pi-electron conjugation in T8, as compared with that of Z48, results in better electrical conduction. PMID:12952488

  2. Visible fiber lasers excited by GaN laser diodes

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yasushi; Nakanishi, Jun; Yamada, Tsuyoshi; Ishii, Osamu; Yamazaki, Masaaki

    2013-07-01

    This paper describes and discusses visible fiber lasers that are excited by GaN laser diodes. One of the attractive points of visible light is that the human eye is sensitive to it between 400 and 700 nm, and therefore we can see applications in display technology. Of course, many other applications exist. First, we briefly review previously developed visible lasers in the gas, liquid, and solid-state phases and describe the history of primary solid-state visible laser research by focusing on rare-earth doped fluoride media, including glasses and crystals, to clarify the differences and the merits of primary solid-state visible lasers. We also demonstrate over 1 W operation of a Pr:WPFG fiber laser due to high-power GaN laser diodes and low-loss optical fibers (0.1 dB/m) made by waterproof fluoride glasses. This new optical fiber glass is based on an AlF3 system fluoride glass, and its waterproof property is much better than the well known fluoride glass of ZBLAN. The configuration of primary visible fiber lasers promises highly efficient, cost-effective, and simple laser systems and will realize visible lasers with photon beam quality and quantity, such as high-power CW or tunable laser systems, compact ultraviolet lasers, and low-cost ultra-short pulse laser systems. We believe that primary visible fiber lasers, especially those excited by GaN laser diodes, will be effective tools for creating the next generation of research and light sources.

  3. Superhydrophobic anti-ultraviolet films by doctor blade coating

    SciTech Connect

    Cai, Chang-Yun; Yang, Hongta; Lin, Kun-Yi Andrew

    2014-11-17

    This article reports a scalable technology for fabricating polymer films with excellent water-repelling and anti-ultraviolet properties. A roll-to-roll compatible doctor blade coating technology is utilized to prepare silica colloidal crystal-polymer composites. The silica microspheres can then be selectively removed to create flexible self-standing macroporous polymer films with crystalline arrays of pores. The void sizes are controlled by tuning the duration of a reactive ion etching process prior to the removal of the templating silica microspheres. After surface modification, superhydrophobic surface can be achieved. This study further demonstrates that the as-prepared transparent porous films with 200?nm of pores exhibit diffraction of ultraviolet lights originated from the Bragg's diffractive of light from the three-dimensional highly ordered air cavities.

  4. Mathematical optimization of photovoltaic converters for diode lasers. [for spacecraft power supplies

    NASA Technical Reports Server (NTRS)

    Walker, Gilbert H.; Heinbockel, John H.

    1989-01-01

    The mathematical optimization of vertical-junction photovoltaic converters for use with diode laser arrays supplying powers up to 1 MW is discussed. Photovoltaic parameters were optimized using a mathematical model. The optimized converters have 500 single junctions connected in series. The efficiency varies from 41 percent for a 0.73-micron diode laser to 46 percent for a 0.83-micron diode laser. The optimum width of the single-junction converter is small, 3.0 microns, in order for the p-n junction to be within a diffusion length of the light-generated carriers. Another critical parameter is the series resistance; the optimum value of 0.001 ohms should be achievable. Another critical parameter is the donor carrier concentration, for which an optimum value of 5 x 10 to the 15th carriers/cu cm has been chosen.

  5. Genotyping Arrays

    NASA Astrophysics Data System (ADS)

    Lodes, Michael J.; Suciu, Dominic; Danley, David; McShea, Andrew

    Although the most common use of DNA microarrays is gene expression profiling, microarrays are also used for many other applications, including genotyping, resequencing, SNP analysis, and DNA methylation assays. Here we describe genotyping arrays for Influenza A subtype identification and for upper respiratory pathogen diagnostics using standard hybridization techniques and we also describe resequencing, SNP, and methylation assays using an enzyme-based strategy [25, 26].

  6. Far Ultraviolet Astronomy

    NASA Technical Reports Server (NTRS)

    Sonneborn, George; Rabin, Douglas M. (Technical Monitor)

    2002-01-01

    The Far Ultraviolet Spectroscopic Explorer (FUSE) is studying a wide range of astronomical problems in the 905-1187 Angstrom wavelength region through the use of high resolution spectroscopy. The FUSE bandpass forms a nearly optimal complement to the spectral coverage provided by the Hubble Space Telescope (HST), which extends down to approximately 1170 Angstroms. The photoionization threshold of atomic hydrogen (911 Angstroms) sets a natural short-wavelength limit for the FUV. FUSE was launched in June 1999 from Cape Canaveral, Florida, on a Delta II rocket into a 768 km circular orbit. Scientific observations started later that year. This spectral region is extremely rich in spectral diagnostics of astrophysical gases over a wide range of temperatures (100 K to over 10 million K). Important strong spectral lines in this wavelength range include those of neutral hydrogen, deuterium, nitrogen, oxygen, and argon (H I, D I, N I, O I, and Ar I), molecular hydrogen (H2), five-times ionized oxygen (O VI), and several ionization states of sulfur (S III - S VI). These elements are essential for understanding the origin and evolution of the chemical elements, the formation of stars and our Solar System, and the structure of galaxies, including our Milky Way. FUSE is one of NASA's Explorer missions and a cooperative project of NASA and the space agencies of Canada and France. These missions are smaller, more scientifically focused missions than the larger observatories, like Hubble and Chandra. FUSE was designed, built and operated for NASA by the Department of Physics and Astronomy at Johns Hopkins University. Hundreds of astronomers world-wide are using FUSE for a wide range of scientific research. Some of the important scientific discoveries from the first two years of the mission are described.

  7. Facile assembly of n-SnO(2) nanobelts-p-NiO heterojunctions with enhanced ultraviolet photoresponse.

    PubMed

    Huang, Siya; Wu, Hui; Matsubara, Kohei; Cheng, Jing; Pan, Wei

    2014-03-18

    We present a highly transparent heterojunction photodiode by precisely aligning n-type SnO2 nanobelts on top of a p-type NiO thin film. This p-n junction diode demonstrates stable rectifying characteristics as well as greatly enhanced ultraviolet photoresponse, which exhibits an ultrahigh photosensitivity of up to 10(5) with accelerated response speed under reverse bias. PMID:24345893

  8. Properties and Frequency Conversion of High-Brightness Diode-Laser Systems

    NASA Astrophysics Data System (ADS)

    Boller, Klaus-Jochen; Beier, Bernard; Wallenstein, Richard

    An overview of recent developments in the field of high-power, high-brightness diode-lasers, and the optically nonlinear conversion of their output into other wavelength ranges, is given. We describe the generation of continuous-wave (CW) laser beams at power levels of several hundreds of milliwatts to several watts with near-perfect spatial and spectral properties using Master-Oscillator Power-Amplifier (MOPA) systems. With single- or double-stage systems, using amplifiers of tapered or rectangular geometry, up to 2.85 W high-brightness radiation is generated at wavelengths around 810nm with AlGaAs diodes. Even higher powers, up to 5.2W of single-frequency and high spatial quality beams at 925nm, are obtained with InGaAs diodes. We describe the basic properties of the oscillators and amplifiers used. A strict proof-of-quality for the diode radiation is provided by direct and efficient nonlinear optical conversion of the diode MOPA output into other wavelength ranges. We review recent experiments with the highest power levels obtained so far by direct frequency doubling of diode radiation. In these experiments, 100mW single-frequency ultraviolet light at 403nm was generated, as well as 1W of single-frequency blue radiation at 465nm. Nonlinear conversion of diode radiation into widely tunable infrared radiation has recently yielded record values. We review the efficient generation of widely tunable single-frequency radiation in the infrared with diode-pumped Optical Parametric Oscillators (OPOs). With this system, single-frequency output radiation with powers of more than 0.5W was generated, widely tunable around wavelengths of 2.1,m and 1.65,m and with excellent spectral and spatial quality. These developments are clear indicators of recent advances in the field of high-brightness diode-MOPA systems, and may emphasize their future central importance for applications within a vast range of optical wavelengths.

  9. Harmful effects of ultraviolet radiation

    SciTech Connect

    Not Available

    1989-07-21

    Tanning for cosmetic purposes by sunbathing or by using artificial tanning devices is widespread. The hazards associated with exposure to ultraviolet radiation are of concern to the medical profession. Depending on the amount and form of the radiation, as well as on the skin type of the individual exposed, ultraviolet radiation causes erythema, sunburn, photodamage (photoaging), photocarcinogenesis, damage to the eyes, alteration of the immune system of the skin, and chemical hypersensitivity. Skin cancers most commonly produced by ultraviolet radiation are basal and squamous cell carcinomas. There also is much circumstantial evidence that the increase in the incidence of cutaneous malignant melanoma during the past half century is related to increased sun exposure, but this has not been proved. Effective and cosmetically acceptable sunscreen preparations have been developed that can do much to prevent or reduce most harmful effects to ultraviolet radiation if they are applied properly and consistently. Other safety measures include (1) minimizing exposure to ultraviolet radiation, (2) being aware of reflective surfaces while in the sun, (3) wearing protective clothing, (4) avoiding use of artificial tanning devices, and (5) protecting infants and children.

  10. Megahertz organic/polymer diodes

    DOEpatents

    Katz, Howard Edan; Sun, Jia; Pal, Nath Bhola

    2012-12-11

    Featured is an organic/polymer diode having a first layer composed essentially of one of an organic semiconductor material or a polymeric semiconductor material and a second layer formed on the first layer and being electrically coupled to the first layer such that current flows through the layers in one direction when a voltage is applied in one direction. The second layer is essentially composed of a material whose characteristics and properties are such that when formed on the first layer, the diode is capable of high frequency rectifications on the order of megahertz rectifications such as for example rectifications at one of above 100KHz, 500KhZ, IMHz, or 10 MHz. In further embodiments, the layers are arranged so as to be exposed to atmosphere.

  11. Quantum Noise in Laser Diodes

    NASA Technical Reports Server (NTRS)

    Giacobino, E.; Marin, F.; Bramati, A.; Jost, V.; Poizat, J. Ph.; Roch, J.-F.; Grangier, P.; Zhang, T.-C.

    1996-01-01

    We have investigated the intensity noise of single mode laser diodes, either free-running or using different types of line narrowing techniques at room temperature. We have measured an intensity squeezing of 1.2 dB with grating-extended cavity lasers and 1.4 dB with injection locked lasers (respectively 1.6 dB and 2.3 dB inferred at the laser output). We have observed that the intensity noise of a free-running nominally single mode laser diode results from a cancellation effect between large anti-correlated fluctuations of the main mode and of weak longitudinal side modes. Reducing the side modes by line narrowing techniques results in intensity squeezing.

  12. Double-cutting beam shaping technique for high-power diode laser area light source

    NASA Astrophysics Data System (ADS)

    Huang, Zhihua; Xiong, Lingling; Liu, Hui; Wang, Zhenfu; Zhang, Pu; Nie, Zhiqiang; Wu, Dihai; Liu, Xingsheng

    2013-10-01

    A new beam-shaping technique is proposed to improve the beam quality of a high-power diode laser area light source. It consists of two staggered prism arrays and a reflector array, which can cut the slow axis beam twice and rearrange the divided beams in fast axis to make the beam quality of both axes approximately equal. Furthermore, the beam transformation and compression can be carried out simultaneously, and the assembly error of this technique induced by the machining accuracy of prism's dimensions also can be greatly decreased. By this technique, a fiber-coupled system for one three-bar laser diode stack is designed and characterized. The experimental results demonstrate that the laser beams could be transformed into the required distribution with ˜93.4% reshaped efficiency and coupled into a 400 ?m/0.22 NA fiber, which are consistent with the theory.

  13. Extreme ultraviolet emission spectra of Gd and Tb ions

    SciTech Connect

    Kilbane, D.; O'Sullivan, G.

    2010-11-15

    Theoretical extreme ultraviolet emission spectra of gadolinium and terbium ions calculated with the Cowan suite of codes and the flexible atomic code (FAC) relativistic code are presented. 4d-4f and 4p-4d transitions give rise to unresolved transition arrays in a range of ions. The effects of configuration interaction are investigated for transitions between singly excited configurations. Optimization of emission at 6.775 nm and 6.515 nm is achieved for Gd and Tb ions, respectively, by consideration of plasma effects. The resulting synthetic spectra are compared with experimental spectra recorded using the laser produced plasma technique.

  14. Electromagnetically controlled multiferroic thermal diode

    NASA Astrophysics Data System (ADS)

    Chotorlishvili, L.; Etesami, S. R.; Berakdar, J.; Khomeriki, R.; Ren, Jie

    2015-10-01

    We propose an electromagnetically tunable thermal diode based on a two-phase multiferroic composite. Analytical and full numerical calculations for a prototypical heterojunction composed of iron on barium titanate in the tetragonal phase demonstrate a strong heat rectification effect that can be controlled externally by a moderate electric field. This finding is important for thermally based information processing and sensing and can also be integrated in (spin) electronic circuits for heat management and recycling.

  15. Modeling of tunnel diode oscillators

    NASA Astrophysics Data System (ADS)

    Van Degrift, Craig T.; Love, David P.

    1981-05-01

    The detailed behavior of tunnel diode LC oscillators is calculated by three different methods and compared with experiment. We present both analytic formulas and numerical methods which give corrections to the oscillator frequency calculated using the expression 1/(LC)1/2 and show that these corrections are often not negligible. The calculations also yield rf amplitude, bias current dependence, and other details necessary for the full realization of the performance of LC oscillators as transducers of pressure, temperature, and other physical quantities.

  16. Actinometric measurement of solar ultraviolet

    SciTech Connect

    Laue, E.G.; Gupta, A.

    1980-01-01

    O-nitrobenzaldhyde (NBA) and aminotriphenylamine actinometers provide a simple, reliable method of integrating solar ultraviolet irradiance. To achieve 30 days of continuous exposure it is necessary to attenuate the incident solar ultraviolet by a factor of 10/sup -4/ for the NBA actinometers. The Wratten No. 8 film filter (Kodak) is found to provide the necessary attenuation. This filter is sufficiently stable to withstand this exposure period without significant degradation. The spectral sensitivity of aminotriphenylamine actinometers increases by a factor of 10/sup 3/ from 400 to 280 nm, and an attenuation factor of only 10/sup -3/ would be required for a 30 day exposure to the solar ultraviolet. The spectral sensitivity of these actinometers, their response linearity ranges, and the design and operation of devices suitable for field installation are reported.

  17. Ultraviolet-radiation-curable paints

    SciTech Connect

    Grosset, A M; Su, W F.A.; Vanderglas, E

    1981-09-30

    In product finishing lines, ultraviolet radiation curing of paints on prefabricated structures could be more energy efficient than curing by natural gas fired ovens, and could eliminate solvent emission. Diffuse ultraviolet light can cure paints on three dimensional metal parts. In the uv curing process, the spectral output of radiation sources must complement the absorption spectra of pigments and photoactive agents. Photosensitive compounds, such as thioxanthones, can photoinitiate unsaturated resins, such as acrylated polyurethanes, by a free radical mechanism. Newly developed cationic photoinitiators, such as sulfonium or iodonium salts (the so-called onium salts) of complex metal halide anions, can be used in polymerization of epoxy paints by ultraviolet light radiation. One-coat enamels, topcoats, and primers have been developed which can be photoinitiated to produce hard, adherent films. This process has been tested in a laboratory scale unit by spray coating these materials on three-dimensional objects and passing them through a tunnel containing uv lamps.

  18. Amber light-emitting diode comprising a group III-nitride nanowire active region

    DOEpatents

    Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

    2014-07-22

    A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

  19. Thermal (Silicon Diode) Data Acquisition Systems

    NASA Technical Reports Server (NTRS)

    Wright, Ernest; Kegley, Jeff

    2008-01-01

    Marshall Space Flight Center s X-ray Cryogenic Facility (XRCF) has been performing cryogenic testing to 20 Kelvin since 1999. Two configurations for acquiring data from silicon diode temperature sensors have been implemented at the facility. The facility's environment is recorded via a data acquisition system capable of reading up to 60 silicon diodes. Test article temperature is recorded by a second data acquisition system capable of reading 150+ silicon diodes. The specifications and architecture of both systems will be presented.

  20. Laser diode technology for coherent communications

    NASA Technical Reports Server (NTRS)

    Channin, D. J.; Palfrey, S. L.; Toda, M.

    1989-01-01

    The effect of diode laser characteristics on the overall performance capabilities of coherent communication systems is discussed. In particular, attention is given to optical performance issues for diode lasers in coherent systems, measurements of key performance parameters, and optical requirements for coherent single-channel and multichannel communication systems. The discussion also covers limitations imposed by diode laser optical performance on multichannel system capabilities and implications for future developments.