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1

Nitride Deep Ultraviolet Light-Emitting Diodes with Microlens Array  

NASA Astrophysics Data System (ADS)

We report on the fabrication of 285 nm AlGaN-based deep ultraviolet light-emitting diodes (UV LEDs) on sapphire substrates with integrated microlens array. Microlenses with a diameter of 12 microns were fabricated on the sapphire substrate by resist thermal reflow and plasma dry etching. LED devices were flip-chip bonded on high thermal conductive AlN ceramic submounts to improve the thermal dissipation, and the emitted UV light was extracted through the sapphire substrates. With the integrated microlense array, a 55% enhancement in the output power at 20 mA DC driving was achieved compared with the same LED without microlens. The light extraction enhancement is the result of the reduced internal reflections of the light caused by the microlense surface profile. An output power of 0.22 mW at 20 mA was measured for a circular LED with a diameter of 275 microns.

Muhammad, Khizar

2005-03-01

2

Nitride deep-ultraviolet light-emitting diodes with microlens array  

NASA Astrophysics Data System (ADS)

We report on the fabrication of 280-nm AlGaN-based deep-ultraviolet light-emitting diodes (UV LEDs) on sapphire substrates with an integrated microlens array. Microlenses with a diameter of 12 ?m were fabricated on the sapphire substrate by resist thermal reflow and plasma dry etching. LED devices were flip-chip bonded on high thermal conductive AlN ceramic submounts to improve the thermal dissipation, and the emitted UV light was extracted through the sapphire substrates. With the integrated microlens array, a 55% enhancement in the output power at 20-mA dc driving was achieved compared with the same LED without microlens. The light extraction enhancement is the result of the reduced internal reflections of the light caused by the microlens surface profile.

Khizar, M.; Fan, Z. Y.; Kim, K. H.; Lin, J. Y.; Jiang, H. X.

2005-04-01

3

Ultraviolet electroluminescence from ordered ZnO nanorod array/p-GaN light emitting diodes  

NASA Astrophysics Data System (ADS)

The highly ordered and aligned ZnO nanorod arrays were grown on p-GaN substrates via a facile hydrothermal process assisted by the inverted self-assembled monolayer template, from which the ZnO nanorod/p-GaN heterojunction light emitting diodes (LEDs) were fabricated. The ZnO nanorod-based LEDs exhibit a stronger ultraviolet emission of 390 nm than the ZnO film-based counterpart, which is attributed to the low density of interfacial defects, the improved light extraction efficiency, and carrier injection efficiency through the nano-sized junctions. Furthermore, the LED with the 300 nm ZnO nanorods has a better electroluminescence performance compared with the device with the 500 nm nanorods.

Dong, J. J.; Zhang, X. W.; Yin, Z. G.; Wang, J. X.; Zhang, S. G.; Si, F. T.; Gao, H. L.; Liu, X.

2012-04-01

4

Enhancement of light extraction efficiency of ultraviolet light emitting diodes by patterning of SiO 2 nanosphere arrays  

Microsoft Academic Search

article i nfo Here we introduce a simple and robust method to improve the light extraction efficiency of ultraviolet light emitting diodes (UV LEDs). Although many previous efforts have focused on etching the GaN surfaces, we employed a simple solution process to texture the GaN surface. Arrays of SiO2 nanosphere monolayers were spun cast onto a polymer layer, consisting of

B. J. Kim; H. Jung; J. Shin; M. A. Mastro; C. R. Eddy Jr.; J. K. Hite; S. H. Kim; J. Bang; J. Kim

2009-01-01

5

Ultraviolet electroluminescence from horizontal ZnO microrods/GaN heterojunction light-emitting diode array  

NASA Astrophysics Data System (ADS)

ZnO microrods were assembled on p-GaN substrate to form a heterostructural light-emitting diode (LED) array. Ultraviolet (UV) emission was obtained under a low forward bias of 3.5 V. The investigation on the electroluminescence, photoluminescence demonstrated three distinct electron-hole recombination processes. The relative intensity of these three emission bands changed with increase of the forward bias, and resulted in blue shift and spectral narrowing of electroluminescence. The present work provides a facile technique for micro-/nano-devices fabrication besides obtaining UV LED arrays.

Zhu, G. Y.; Xu, C. X.; Lin, Y.; Shi, Z. L.; Li, J. T.; Ding, T.; Tian, Z. S.; Chen, G. F.

2012-07-01

6

Ultraviolet Array Detector Research.  

National Technical Information Service (NTIS)

Under this contract multiple tasks were performed in support of the development of Ultraviolet Array Detector Research. The Horizon Ultraviolet Program instrumentation was supported through a second Space shuttle launch. An Ebert-Fastie spectrometer was m...

M. Gangl M. Bullinger R. Cundiff J. McKay J. Middlestadt

1995-01-01

7

Diode Laser Arrays  

NASA Astrophysics Data System (ADS)

Contributors; 1. Monolithic phase-locked semiconductor laser arrays D. Botez; 2. High power coherent, semiconductor laser master oscillator power amplifiers and amplifier arrays D. F. Welch and D. G. Mehuys; 3. Microoptical components applied to incoherent and coherent laser arrays J. R. Leger; 4. Modeling of diode laser arrays G. R. Hadley; 5. Dynamics of coherent semiconductor laser arrays H. G. Winfuland and R. K. Defreez; 6. High average power semiconductor laser arrays and laser array packaging with an emphasis for pumping solid state lasers R. Solarz; 7. High power diode laser arrays and their reliability D. R. Scifres and H. H. Kung; 8. Strained layer quantum well heterostructure laser arrays J. J. Coleman; 9. Vertical cavity surface emitting laser arrays C. J. Chang-Hasnain; 10. Individually addressed arrays of diode lasers D. Carlin.

Botez, Dan; Scifres, Don R.

2005-11-01

8

Light Emitting Diode Array.  

National Technical Information Service (NTIS)

Four 15-element GaAsP light emitting diode arrays were fabricated and delivered to Night Vision Laboratory. Measured brightnesses of the emitting elements range higher than originally anticipated. The minimum brightness requirement at 10mA forward bias is...

G. A. Henderson

1973-01-01

9

Qualitative characterization of Desmodium adscendens constituents by high-performance liquid chromatography-diode array ultraviolet-electrospray ionization multistage mass spectrometry.  

PubMed

The many effects of the African medicinal herb Desmodium adscendens were studied in the 1980s and 1990s. In spite of this, a comprehensive analytical protocol for the quality control of its constituents (soyasaponins, alkaloids and flavonoids) has not yet been formulated and reported. This study deals with the optimization of extraction conditions from the plant and qualitative identification of the constituents by HPLC-diode array UV and multistage mass spectrometry. Plant constituents were extracted from leaves by liquid-liquid and solid matrix dispersion extraction. Separation was achieved via RP-C18 liquid chromatographywith UV and MS(n) detection and mass spectrometry analysis was conducted by electrospray ionization ion trap or orbitrap mass spectrometry. High resolution mass spectrometry (HRMS) was used for structural identification of active molecules relating to soyasaponins and alkaloids. The flavonoid fragmentations were preliminarily studied by HRMS in order to accurately characterize the more common neutral losses. However, the high number of isomeric species induced us to make recourse to a more extended chromatographic separation in order to enable useful tandem mass spectrometry and ultraviolet spectral interpretation to propose a reasonable chemical classification of these polyphenols. 35 compounds of this class were identified herein with respect to the five reported in literature in this way we made up a comprehensive protocol for the qualitative analysis of the high complexity content of this plant. This result paves the way for both reliable quality control of potential phytochemical medicaments and possible future systematic clinical studies. PMID:23841221

Baiocchi, Claudio; Medana, Claudio; Giancotti, Valeria; Aigotti, Riccardo; Dal Bello, Frederica; Massolino, Cristina; Gastaldi, Daniela; Grandi, Maurizio

2013-01-01

10

Fast liquid chromatography-diode array detection assisted by chemometrics for quantification of seven ultraviolet filters in effluent wastewater  

Microsoft Academic Search

A fast chromatographic method is presented for simultaneous quantification of seven organic ultraviolet (UV) filters (benzophenone-3,4-methylbenzilidene camphor, octocrylene, 1-(4-tert-butylphenyl)-3-(4-methyoxyphenyl)1,3-propanedione), ethylhexyl methoxy cinnamate, ethylhexyl salicylate and homosalate) in effluent wastewater samples. The UV filters were pre-concentrated by Bond Elut-ENV cartridges and separated on an ODS column (15cm×0.46cm, 5?m) in less than 2.5min using a non-aqueous mobile phase of methanol–acetonitrile (50:50, v\\/v)

Maryam Vosough; Nahal Rahimdoost Mojdehi

2011-01-01

11

Simultaneous determination of six triazolic pesticide residues in apple and pear pulps by liquid chromatography with ultraviolet diode array detection.  

PubMed

A method is described for the simultaneous determination of diclobutrazol, flusilazole, flutriafol, hexaconazole, paclobutrazol, and tetraconazole in apple and pear pulps used in baby food at a limit of 0.01 mg/kg. Apple and pear pulp samples are subjected to selective solid-phase microdispersion (SPMD) with SPE-ED Matrix-38 and acetone-cyclohexane, and the extracts are cleaned up on a Florisil cartridge with hexane-cyclohexane-acetone. The extracts are then analyzed by liquid chromatography with ultraviolet detection, using an octadecylsilane column with a gradient-programmed acetonitrile-water mobile phase. Recoveries were determined by spiking apple and pear pulps with the 6 pesticides under investigation at 0.1, 0.05, 0.03, and 0.01 mg/kg. Six determinations were performed at each level for each pesticide. Recoveries were > or = 70% at the 0.01 mg/kg level. PMID:11601474

Bicchi, C; Cordero, C; Rubiolo, P; Occelli, A

12

Conductively Cooled Laser Diode Array Pumped Laser.  

National Technical Information Service (NTIS)

A conductively cooled semiconductor laser comprises a laser rod surrounded by arrays of laser diodes. The laser diodes are mounted to ceramic plates that are excellent heat extractors and electrical insulators. The ceramic plates have steps which permit d...

L. K. Conaway

1986-01-01

13

Analysis of phased-array diode lasers  

SciTech Connect

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.

Hardy, A.; Streifer, W.

1985-07-01

14

Performance improvements in diode laser arrays  

SciTech Connect

The average power performance capability of semiconductor laser diode arrays has improved dramatically over the past several years. Additionally, optical conditioning technologies have been developed that increase the effective radiance of stacked two-dimensional arrays by nearly two orders of magnitude. These performance improvements have been accompanied by cost reductions that now make feasible the replacement of flashlamp pump sources by laser diode arrays in a large variety of military and commercial solid state laser systems.

Beach, R.J.; Emanuel, M.A.; Freitas, B.L.; Benett, W.J.; Skidmore, J.A.; Carlson, N.W.; Solarz, R.W.

1994-06-01

15

Diodes in photovoltaic modules and arrays  

NASA Astrophysics Data System (ADS)

The use of diodes to enhance the energy generation capability and improve the reliability of photovoltaic modules and arrays is discussed. Array-level considerations influencing the application of such diodes in a bypass mode are conserved. Several methods for the mechanical and electrical integration of these devices as an integral part of the module electrical termination means are described. Particular emphasis is placed on the description of innovative approaches for the external mounting of bypass diodes. These descriptions were used as the basis for a detailed cost analysis and comparison among the candidate concepts. It was concluded that the photovoltaic source circuit blocking or isolation function can be implemented using the same basic diode enclosure designs with provisions for the inclusion of a fuse for overcurrent protection.

1984-03-01

16

The Fuge Tube Diode Array Spectrophotometer  

ERIC Educational Resources Information Center

|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…

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

2008-01-01

17

Identification of flavonoids and their glycosides by high-performance liquid chromatography with electrospray ionization mass spectrometry and with diode array ultraviolet detection.  

PubMed

Identification of flavonoids and flavonoid glycosides was carried out on Psidium guajava Linn leaves by means of high-performance liquid chromatography ultraviolet (HPLC-UV) analysis and HPLC mass spectrometry. By using HPLC-UV, two known phenolics (gallic acid and quercetin) and five newly reported ones (procatechuic acid, chlorogenic acid, caffeic acid, kaempferol and ferulic acid) were identified in alcohol guava leaf extract. Structural information about the compounds was obtained from the retention times, the UV spectra and mass spectra without the need to isolate the individual compounds. Two flavonoids (quercetin and kaempferol) and four flavonoid glycosides (three known components, quercetin 3-O-alpha-L-arabinoside, quercetin 3-O-beta-D-glucoside and quercetin 3-O-beta-D-galactoside, along with one novel compound, kaempferol-glycoside) and three other unknown compounds have been identified in the fractions. PMID:15947448

Liang, Qingrong; Qian, He; Yao, Weirong

2005-01-01

18

Applications of microlens-conditioned laser diode arrays.  

National Technical Information Service (NTIS)

The ability to condition the radiance of laser diodes using shaped-fiber cylindrical-microlens technology has dramatically increased the number of applications that can be practically engaged by diode laser arrays. Lawrence Livermore National Laboratory (...

R. J. Beach M. A. Emanuel B. L. Freitas

1995-01-01

19

Tunnel Diode Arrays for Information Processing and Storage  

Microsoft Academic Search

The multimode oscillator properties of two-dimensional arrays of tunnel diode elements are analyzed in the quasi-harmonic approximation with the assumption of no resonant interaction between the normal modes in order to determine the capacity of an array for information storage. Experimental results for a 4 ?? 4 array of semiconductor tunnel diodes are discussed, and suggestions for possible future information

Alwyn C. Scott

1971-01-01

20

High average power diode array pumped frequency doubled YAG laser  

Microsoft Academic Search

In order to obtain high average power in the green, a diode pumped laser program is under development. High average power (tens of watts) and high repetition rate (tens of kilohertz) require: cw diode array pumping, high Q-switching and intra-cavity second harmonic array generation. We report the demonstration of a transversely diode array pumped frequency doubled Nd:YAG laser. The 35

B. J. Le Garrec; G. J. Raze; P. Y. Thro; M. Gilbert

1996-01-01

21

Large Chip High Power Deep Ultraviolet Light-Emitting Diodes  

Microsoft Academic Search

Single chip deep ultraviolet light-emitting diodes with junction area up to 1 mm2 were fabricated for high power applications. Lateral geometry devices were designed for low operating voltage, uniform current spreading and emission resulting in substantial improvement of high current performance. The maximum CW optical power of 30 and 6 mW was achieved for devices emitting at 273 and 247

Max Shatalov; Wenhong Sun; Yuri Bilenko; Ajay Sattu; Xuhong Hu; Jianyu Deng; Jinwei Yang; Michael Shur; Craig Moe; Michael Wraback; Remis Gaska

2010-01-01

22

Electronic scanning of linear slot arrays using diode irises  

Microsoft Academic Search

Semiconductor diodes were employed as electronic iris control elements to scan linear slot arrays atX-band. An iris cluster of four varactor diodes mounted inside the waveguide around each slot provided360degof phase control for slot coupling levels up to -15 dB and a reduced range of phase control for couplings up to -8 dB. Two linear arrays were fabricated with different

B. Forman

1968-01-01

23

Monolithic millimeter-wave diode grid frequency multiplier arrays  

NASA Astrophysics Data System (ADS)

Monolithic diode frequency multiplier arrays, including barrier-N-N(+) (BNN) doubler, multi-quantum-barrier-varactor (MQBV) tripler, Schottky-quantum-barrier-varactor (SQBV) tripler, and resonant-tunneling-diode (RTD) tripler arrays, have been successfully fabricated with yields between 85 and 99 percent. Frequency doubling and/or tripling have been observed for all the arrays. Output powers of 2.4-2.6 W (eta = 10-18 percent) at 66 GHz with the BNN doubler and 3.8-10 W (eta = 1.7-4 percent) at 99 GHz with the SQBV tripler have been achieved.

Liu, Hong-Xia L.; Qin, X.-H.; Sjogren, L. B.; Wu, W.; Chung, E.; Domier, C. W.; Luhmann, N. C., Jr.

24

Diodes in photovoltaic modules and arrays. Final report  

SciTech Connect

The use of diodes to enhance the energy generation capability and improve the reliability of photovoltaic modules and arrays is the subject of this final report. Beginning with a discussion of the array-level considerations influencing the application of such diodes in a bypass mode, the report continues further to describe several methods for the mechanical and electrical integration of these devices as an integral part of the module electrical termination means. Particular emphasis is placed on the description of innovative approaches for the external mounting of bypass diodes. These descriptions were used as the basis for a detailed cost analysis and comparison among the candidate concepts. The photovoltaic source circuit blocking or isolation function can be implemented using the same basic diode enclosure designs with provisions for the inclusion of a fuse for overcurrent protection.

Not Available

1984-03-15

25

High modulation rate potential for surface emitter laser diode arrays  

NASA Astrophysics Data System (ADS)

A vertical-cavity surface-emitting laser diode capable of narrow-line emission at injection currents below 1 mA during room temperature dc operation is described. It is estimated that surface-emitting laser diodes can potentially be modulated to speeds as high as 30 GHz. It is argued that phased array operation at high output powers should be possible, but that problems with thermal performance, wafer uniformity, and circuit layout need to be resolved.

Dziura, T. G.; Yang, Y. J.; Wang, S. C.

1990-06-01

26

High duty cycle hard soldered kilowatt laser diode arrays  

NASA Astrophysics Data System (ADS)

High-brightness laser diode arrays operating at a duty cycle of 10% - 20% are in ever-increasing demand for the optical pumping of solid state lasers and directed energy applications. Under high duty-cycle operation at 10% - 20%, passive (conductive) cooling is of limited use, while micro-coolers using de-ionized cooling water can considerably degrade device reliability. When designing and developing actively-cooled collimated laser diode arrays for high duty cycle operation, three main problems should be carefully addressed: an effective local and total heat removal, a minimization of packaging-induced and operational stresses, and high-precision fast axis collimation. In this paper, we present a novel laser diode array incorporating a built-in tap water cooling system, all-hard-solder bonded assembly, facet-passivated high-power 940 nm laser bars and tight fast axis collimation. By employing an appropriate layout of water cooling channels, careful choice of packaging materials, proper design of critical parts, and active optics alignment, we have demonstrated actively-cooled collimated laser diode arrays with extended lifetime and reliability, without compromising their efficiency, optical power density, brightness or compactness. Among the key performance benchmarks achieved are: 150 W/bar optical peak power at 10% duty cycle, >50% wallplug efficiency and <1° collimated fast axis divergence. A lifetime of >0.5 Ghots with <2% degradation has been experimentally proven. The laser diode arrays have also been successfully tested under harsh environmental conditions, including thermal cycling between -20°C and 40°C and mechanical shocks at 500g acceleration. The results of both performance and reliability testing bear out the effectiveness and robustness of the manufacturing technology for high duty-cycle laser arrays.

Klumel, Genady; Karni, Yoram; Oppenheim, Jacob; Berk, Yuri; Shamay, Moshe; Tessler, Renana; Cohen, Shalom

2010-02-01

27

Optical and thermal modeling of ultraviolet-LED array packaging for curing application  

NASA Astrophysics Data System (ADS)

High power Ultraviolet Light-Emitting Diode (UV-LED) is currently in high demand for a variety of applications including lighting, printing, and polymer curing, with its' advantages of durability, reliability, non-hazardous and safety. Recently, the technology of Semiconductor Light Matrix (SLM) by multiple individual LEDs mounted on panels was put forward to obtain higher power for curing application. However, the illumination uniformity of high power LED arrays still remains an issue. On the other hand, it has been also predicted previously that the lifetime of a device decays exponentially as the temperature increases. Therefore, the thermal management of high power LEDs is also a critical factor to the development of high-power UV-LED array light source. This paper presents our latest investigations of illumination uniformity and thermal management to satisfy the requirements of packaging UV-LED arrays for curing application.

Liu, Hai; Tang, Zirong; Shi, Tielin; Liao, Guanglan; Nie, Lei

2008-12-01

28

Fiber optic modification of a diode array spectrophotometer  

SciTech Connect

Fiber optics were adapted to a Hewlett-Packard diode array spectrophotometer to permit the analysis of radioactive samples without risking contamination of the instrument. Instrument performance was not compromised by the fiber optics. The instrument is in routine use at the Savannah River Plant control laboratories.

Van Hare, D.R.; Prather, W.S.

1986-01-01

29

Photodiode arrays having minimized cross-talk between diodes  

DOEpatents

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.

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

2000-10-17

30

Ultraviolet-Cured Polymer Microlens Arrays  

Microsoft Academic Search

A method for fabricating microlens arrays that uses the contraction effect of UV-curable photopolymers is presented. Lenses with diameters ranging from 0.2 to 2 mm that were made under different conditions are optically evaluated. The optimum conditions for producing low f -number lenses are discussed.

Takashi Okamoto; Miwa Mori; Tamae Karasawa; Seiichiro Hayakawa; Iwao Seo; Heihachi Sato

1999-01-01

31

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

SciTech Connect

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.

Arto V. Nurmikko; Jung Han

2005-09-30

32

Gamma radiation exposure of MCT diode arrays  

Microsoft Academic Search

Investigations of electrical properties of long-wavelength infrared (LWIR) mercury cadmium telluride arrays exposed to gamma-radiation have been performed. Resistance-area product characteristics of LWIR n+-p-photodiodes have been investigated using a microprobe technique at T ap 78 K before and after exposure to various doses of gamma-radiation (Co60 Gammas). The current transport mechanisms for those structures are described within the framework of

F. F. Sizov; I. O. Lysiuk; J. V. Gumenjuk-Sichevska; S. G. Bunchuk; V. V. Zabudsky

2006-01-01

33

Online analysis by a fiber-optic diode array spectrophotometer  

SciTech Connect

An online photometric analyzer has been developed which can make remote measurements over the 350 to 900 nm region at distances of up to 100 feet. The analyzer consists of a commercially available diode array spectrophotometer interfaced to a fiber-optic multiplexer to allow online monitoring of up to ten locations sequentially. The development of the fiber-optic interface is discussed and data from several online applications are presented to demonstrate the capabilities of the measurement system.

Van Hare, D.R.; Prather, W.S.; O'Rourke, P.E.

1987-01-01

34

Laser beam transformation technique for high-power laser diode linear arrays  

Microsoft Academic Search

This paper reports on a novel pair of microlens arrays (MLA's) for efficient coupling of the high aspect ratio optical beam emitted by high-power laser diode linear arrays (also referred to as laser diode bars) into the core of multimode optical fibers. These novel MLA's overcome the limitations observed when using high fill factors laser diode bars. The MLA designs

Paul Grenier; Yves Taillon; Min Wang; Patrice Topart; Daniel Asselin; André Parent

2006-01-01

35

Crosstalk of HgCdTe LWIR n-on-p diode arrays  

NASA Astrophysics Data System (ADS)

Crosstalk of HgCdTe long-wavelength infrared (LWIR) n-on-p diode arrays was measured using scanning laser microscopy. During the measurement, HgCdTe diode arrays with different diode pitches were frontside illuminated by a He-Ne laser at liquid nitrogen temperature and room temperature. The experimental results show that crosstalk between the nearest neighboring diodes decreases exponentially as the diode pitch increases, and the factors that affect the obtained crosstalk are presented and analyzed. Crosstalk out of the nominal diode area (optically sensitive area) is also measured and discussed.

Yinghui, Sun; Bo, Zhang; Meifang, Yu; Qingjun, Liao; Yan, Zhang; Xin, Wen; Peilu, Jiang; Xiaoning, Hu; Ning, Dai

2009-09-01

36

Application of ultraviolet light-emitting diode photocatalysis to remove volatile organic compounds from indoor air  

Microsoft Academic Search

Photocatalytic oxidation (PCO) is a promising technology for indoor air purification due to low operating cost, potentially long service life, and low maintenance. Ultraviolet light-emitting diode (UVLED) is a new concept in the field of PCO, which has several advantages over conventional UV light sources. Limited research has been conducted using UVLED PCO for air treatment. This study demonstrated the

Rifath Sharmin; Madhumita B. Ray

2012-01-01

37

Application of Ultraviolet Light Emitting Diode Photocatalysis to Remove VOCs from Indoor Air  

Microsoft Academic Search

Photocatalytic oxidation (PCO) is a promising technology for indoor air purification due to low operating cost, potentially long service life, and low maintenance. Ultraviolet light emitting diode (UVLED) is a new concept in the field of PCO, which has several advantages over conventional UV light sources. Limited research has been conducted using UVLED PCO for air treatment. This study demonstrated

Rifath Sharmin; Madhumita B. Ray

2012-01-01

38

Airborne intercomparison of vacuum ultraviolet fluorescence and tunable diode laser absorption measurements of tropospheric carbon monoxide  

Microsoft Academic Search

During the fall 1997 North Atlantic Regional Experiment (NARE 97), two separate intercomparisons of aircraft-based carbon monoxide measurement instrumentation were conducted. On September 2, CO measurements were simultaneously made aboard the National Oceanic and Atmospheric Administration (NOAA) WP-3 by vacuum ultraviolet (VUV) fluorescence and by tunable diode laser absorption spectroscopy (TDLAS). On September 18, an intercomparison flight was conducted between

John S. Holloway; Roger O. Jakoubek; David D. Parrish; Christoph Gerbig; Andreas Volz-Thomas; Sandra Schmitgen; Alan Fried; Brian Wert; Bruce Henry; James R. Drummond

2000-01-01

39

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

Microsoft Academic Search

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 duration of the contract period

Arto V. Nurmikko; Jung Han

2007-01-01

40

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

Microsoft Academic Search

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

Arto V. Nurmikko; Jung Han

2005-01-01

41

A 340-nm-band ultraviolet laser diode composed of GaN well layers.  

PubMed

We have demonstrated the laser operation of a short-wavelength ultraviolet laser diode with multiple-quantum-wells composed of GaN well layers. The laser action has been achieved in 340-nm-band far from the wavelength corresponding to GaN band gap under the pulsed current mode at room temperature. The device has been realized on the Al(0.2)Ga(0.8)N underlying layer. The AlN mole fraction of the underlying layer is 0.1 lower than that of the underlying layer which was used for the previously reported 342 nm laser diode. These results provide a chance to the next step for a shorter-wavelength ultraviolet laser diode. PMID:23481771

Yamashita, Yoji; Kuwabara, Masakazu; Torii, Kousuke; Yoshida, Harumasa

2013-02-11

42

Efficiency enhancement of AlGaInP based light emitting diodes via polystyrene microlens array  

NASA Astrophysics Data System (ADS)

A low cost and simple route was presented to fabricate large-scale ordered microlens arrays on gallium phosphide light emitting diodes with enhanced extraction efficiency. The different morphological microlens arrays were simply fabricated by controlling heat treatment temperature. Light extraction efficiency and light output power of gallium phosphide light emitting diodes were enhanced by different array structures of the polystyrene microlens. Compared to conventional gallium phosphide light emitting diodes, light intensity of the light emitting diodes covered by hemispherical polystyrene microlens shows 1.32 times enhancement under the forward current of 20 mA. The mechanism of enhanced light output with microlens arrays is discussed in detail.

Liu, Xiaoyan; Yin, Zhengmao; Wu, Yongzhong; Hao, Xiaopeng; Xu, Xiangang

2013-03-01

43

Protection circuitry for high-power diode laser arrays  

NASA Astrophysics Data System (ADS)

A comprehensive protection scheme is presented for use with high-power (~500 W dc input) diode laser arrays. The circuitry requires no separate power, using instead the voltage from the laser's power supply. Overcurrent and overvoltage silicon controlled rectifier crowbars are the primary protection circuits. In addition, tripping of either crowbar will turn off the main power to the laser's power supply. This feature makes use of a main power controller that incorporates two interlock loops, for protection against overtemperature, low coolant flow, undervoltage, and other undesirable conditions.

Saam, Brian T.; Conradi, Mark S.

1998-06-01

44

Low-cost diode arrays for the LIFE project  

NASA Astrophysics Data System (ADS)

One of the primary challenges of the Laser Inertial Fusion Engine (LIFE) project is the cost and availability of the laser diode arrays needed to pump the solid-state laser gain media in the system. Current projections indicate that the arrays need to be available for approximately one cent per Watt of output power, which is one to two orders of magnitude cheaper than currently available. This work focuses on potential manufacturing approaches to meet the projected specifications of the LIFE project. Special attention will be paid to requirements related to power density (25 kW/cm2), bar pitch (150 - 400 microns), output wavelength (87x), and fast-axis divergence (+/- 4 degrees). A summary of the supply limitations and cost ramifications of each requirement is presented. Also discussed are potential supply chain limitations that are anticipated as a result of the immense size of the LIFE project.

Feeler, Ryan; Junghans, Jeremy; Stephens, Ed

2011-02-01

45

Deep ultraviolet plasmon resonance in aluminum nanoparticle arrays.  

PubMed

Small aluminum nanoparticles have the potential to exhibit localized surface plasmon resonances in the deep ultraviolet region of the electromagnetic spectrum, however technical and scientific challenges make it difficult to attain this limit. We report the fabrication of arrays of Al/Al2O3 core/shell nanoparticles with a metallic-core diameter between 12 and 25 nm that display sharp plasmonic resonances at very high energies, up to 5.8 eV (down to ? = 215 nm). The arrays were fabricated by means of a straightforward self-organization approach. The experimental spectra were compared with theoretical calculations that allow the correlation of each feature to the corresponding plasmon modes. PMID:23725571

Maidecchi, Giulia; Gonella, Grazia; Proietti Zaccaria, Remo; Moroni, Riccardo; Anghinolfi, Luca; Giglia, Angelo; Nannarone, Stefano; Mattera, Lorenzo; Dai, Hai-Lung; Canepa, Maurizio; Bisio, Francesco

2013-06-11

46

High-density pulsed laser diode arrays for SSL pumping  

NASA Astrophysics Data System (ADS)

Northrop Grumman Cutting Edge Optronics has developed a new laser diode array package with minimal bar-to-bar spacing. These High Density Stack (HDS) packages allow for a power density increase on the order of ~ 2.5x when compared to industry-standard arrays. This work contains an overview of the manufacturing process, as well as representative data for 5-, 10-, and 20-bar arrays. Near-field and power vs. current data is presented in each case. Power densities approaching 15 kW/cm2 are presented. In addition, power and wavelength are presented as a function of pulse width in order to determine the acceptable operational parameters for this type of array. In the low repetition rate Nd:YAG pumping regime, all devices are shown to operate with relatively low junction temperatures. A discussion of future work is also presented, with a focus on extending the HDS architecture to reliable operation at 300W per bar. This will enable power densities of approximately 25 kW/cm2.

Feeler, Ryan; Stephens, Edward

2010-04-01

47

A smile insensitive method for spectral linewidth narrowing on high power laser diode arrays  

NASA Astrophysics Data System (ADS)

To eliminate the smile effect in spectral linewidth narrowing on high power laser diode arrays, we have introduced a plane reflective mirror into a common Littrow configuration external cavity to enhance the correlation among emitters. By this way, we obtained uniform spectral distribution among emitters of a 64-elements laser diode array with 35 GHz linewidth and 41 W output laser power.

Yang, Zining; Wang, Hongyan; Li, Yuandong; Lu, Qisheng; Hua, Weihong; Xu, Xiaojun; Chen, Jinbao

2011-10-01

48

Ultraviolet light-emitting diodes based on group three nitrides  

NASA Astrophysics Data System (ADS)

Light-emitting diodes with emission wavelengths less than 400 nm have been developed using the AlInGaN material system. For devices operating at shorter wavelengths, alloy compositions with a greater aluminium content are required. The material properties of these materials lie on the border between conventional semiconductors and insulators, which adds a degree of complexity to the development of efficient light-emitting devices. A number of technical developments have enabled the fabrication of LEDs based on group three nitrides (III-nitrides) that emit in the UV part of the spectrum, providing useful tools for a wealth of applications in optoelectronic systems.

Khan, Asif; Balakrishnan, Krishnan; Katona, Tom

2008-02-01

49

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip  

Microsoft Academic Search

We fabricated a phosphor-conversion white light emitting diode (LED) using an InGaN chip that emits 400 nm near-ultraviolet (n-UV) light and phosphors that emit in the blue and yellow region. When the white LED was operated at a forward-bias current of 20 mA at room temperature (RT), the color temperature (Tcp), average color rendering (Ra), operating voltage (Vf) and luminous

Yukio Narukawa; Isamu Niki; Kunihiro Izuno; Motokazu Yamada; Yoshinori Murazaki; Takashi Mukai

2002-01-01

50

Evaluation of ultraviolet light-emitting diodes for detection of atmospheric NO 2 by photolysis - chemiluminescence  

Microsoft Academic Search

Commercially available ultraviolet light-emitting diodes (UV-LEDs) are evaluated in the laboratory as a light source for photolysis\\u000a of atmospheric nitrogen dioxide (NO2) followed by chemiluminescence detection (P-CL) of the resulting nitric oxide (NO). Sensitivity, selectivity, and engineering\\u000a simplicity of three UV-LED sources are compared. The most powerful source uses two 9-W Nichia LED modules and provides an\\u000a NO2 photolysis frequency

Ilana B. Pollack; Brian M. Lerner; Thomas B. Ryerson

2010-01-01

51

Single Photon Avalanche Diodes: Towards the Large Bidimensional Arrays  

PubMed Central

Single photon detection is one of the most challenging goals of photonics. In recent years, the study of ultra-fast and/or low-intensity phenomena has received renewed attention from the academic and industrial communities. Intense research activity has been focused on bio-imaging applications, bio-luminescence, bio-scattering methods, and, more in general, on several applications requiring high speed operation and high timing resolution. In this paper we present design and characterization of bi-dimensional arrays of a next generation of single photon avalanche diodes (SPADs). Single photon sensitivity, dark noise, afterpulsing and timing resolution of the single SPAD have been examined in several experimental conditions. Moreover, the effects arising from their integration and the readout mode have also been deeply investigated.

Privitera, Simona; Tudisco, Salvatore; Lanzano, Luca; Musumeci, Francesco; Pluchino, Alessandro; Scordino, Agata; Campisi, Angelo; Cosentino, Luigi; Finocchiaro, Paolo; Condorelli, Giovanni; Mazzillo, Massimo; Lombardo, Salvo; Sciacca, Emilio

2008-01-01

52

Mid-ultraviolet light-emitting diode detects dipicolinic acid.  

SciTech Connect

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.

Bogart, Katherine Huderle Andersen; Lee, Stephen Roger; Temkin, Henryk (Texas Tech University, Lubbock, TX); Crawford, Mary Hagerott; Dasgupta, Purnendu K. (Texas Tech University, Lubbock, TX); Li, Qingyang (Texas Tech University, Lubbock, TX); Allerman, Andrew Alan; Fischer, Arthur Joseph

2005-06-01

53

MgZnO nanowires based deep ultraviolet heterojunction light emitting diodes.  

PubMed

Vertically aligned Mg alloyed ZnO nanowires were successfully grown by Chemical Vapor deposition method in a tube furnace. Structural analysis found that the MgZnO nanowires are with single crystalline without phase separations. The atomic ratio of Mg/O in the nanowire was determined to be approximately 15%. Photoluminescence spectra show that the band gap of ZnO nanowire was tuned to approximately 3.6 eV due to Mg incorporation. N-type MgZnO nanowires/p-type GaN was used for heterojunctional light emitting diode fabrication. Electroluminescence measurement yielded ultraviolet emission peaks, which includes a deep ultraviolet at approximately 340 nm. The results suggest that successful Mg alloying in ZnO nanowires was achieved and is promising for deep ultraviolet devices. PMID:22400219

Chu, Sheng; Zhao, Shijia; Xiong, Zhiqun; Chu, Guang

2011-10-01

54

Nanodiamond lateral comb array field emission diode for high current applications  

Microsoft Academic Search

Nanodiamond comb-shaped lateral field emitter arrays in diode configuration were fabricated and characterized for high current field emission. Nitrogen-incorporated nanocrystalline diamond with grain size of 5–10 nm was micropatterned using RIE to realize interconnected arrays of comb structures equipped with uniformly spaced high aspect ratio lateral emitter fingers. A 9000-fingered nanodiamond lateral comb array diode with an inter-electrode spacing of 8 ?m

K. Subramanian; W. P. Kang; J. L. Davidson; B. K. Choi; M. Howell

2006-01-01

55

Spectrally narrowed external-cavity high-power stack of laser diode arrays  

PubMed Central

We describe an effective external cavity for narrowing the spectral linewidth of a multiarray stack of laser diode arrays. For a commercially available 279-W free-running five-array laser diode array operating at 60 A, we narrow the spectral linewidth to 0.40 nm at FWHM with 115 W of cw power output. This technique leads to the possibility of higher-efficiency, lower-cost production of hyperpolarized noble gases for magnetic resonance imaging.

Zhu, H.; Ruset, I. C.; Hersman, F. W.

2005-01-01

56

The design and fabrication of a GaN-based monolithic light-emitting diode array  

NASA Astrophysics Data System (ADS)

We report a new monolithic structure of GaN-based light-emitting diode (LED) which can be operated under high voltage or alternative current. Differing from the conventional single LED chip, the monolithic light-emitting diode (MLED) array contains microchips which are interconnected in series or parallel. The key chip fabrication processing methods of the monolithic LED array include deep dry etching, sidewall insulated protection, and electrode interconnection. A 12 V GaN-based blue high voltage light emitting diode was designed and fabricated in our experiment. The forward current—voltage characteristics of MLEDs were consistent with those of conventional single junction light emitting diodes.

Teng, Zhan; Yang, Zhang; Jing, Li; Jun, Ma; Zhiqiang, Liu; Xiaoyan, Yi; Guohong, Wang; Jinmin, Li

2013-09-01

57

Expected progress based on aluminium galium nitride Focal Plan Array for near and deep Ultraviolet  

NASA Astrophysics Data System (ADS)

The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet detection. A camera based on such a material presents an extremely low dark current at room temperature. It can compete with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays for low flux measurements. First, we will present results on focal plane array of 320 × 256 pixels with a pitch of 30 ?m. The peak responsivity is tuned from 260 nm to 360 nm in different cameras. All these results are obtained in a standard SWIR supply chaine and with AlGaN Schottky diodes grown on sapphire. We will present here the first attempts to transfer the standard design Schottky photodiodes on from sapphire to silicon substrates. We will show the capability to remove the silicon substrate, to etch the window layer in order to extend the band width to lower wavelength and to maintain the AlGaN membrane integrity.

Reverchon, J.-L.; Robin, K.; Bansropun, S.; Gourdel, Y.; Robo, J.-A.; Truffer, J.-P.; Costard, E.; Brault, J.; Frayssinet, E.; Duboz, J.-Y.

58

Criteria for design of single-lobe phased-array diode lasers  

NASA Astrophysics Data System (ADS)

A design for a real-refractive-index waveguide semiconductor laser array which radiates in a single narrow far-field lobe is presented. An example of such an array is given. It is shown that phased-array diode lasers lase preferentially in the v = 1 supermode if the gain between the waveguides exceeds that of the guiding regions themselves.

Streifer, W.; Hardy, A.; Burnham, R. D.; Thornton, R. L.; Scifres, D. R.

1985-05-01

59

Pixel scaling for SOI-diode uncooled infrared focal plane arrays  

Microsoft Academic Search

Pixel scaling for SOI diode uncooled infrared focal plane arrays (IRFPAs) was investigated in order to achieve the realization of small size and low cost IRFPAs. Since the SOI diode pixel has two different layers -- one for the temperature sensor and the thermal isolation structure, and the other for the infrared absorption structure -- each layer can be independently

Yasuhiro Kosasayama; Takaki Sugino; Yoshiyuki Nakaki; Yoshio Fujii; Hiromoto Inoue; Hirofumi Yagi; Hisatoshi Hata; Masashi Ueno; Munehisa Takeda; Masafumi Kimata

2004-01-01

60

Polarization engineering in III-nitride based ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

In this study, the polarization effect in III-nitride based ultraviolet (UV) light-emitting diodes (LEDs) has been investigated theoretically. Some specific designs in active region are proposed to reduce the polarization effect and, hence, improve the device performance. Simulation results show that by utilizing properly designed quaternary AlInGaN material in active region, the hole injection efficiency can be enhanced due to the reduction of polarization mismatch between hetero-layers. On the other hand, the electron leakage is suppressed owing to that the effective potential height for electrons is increased. Therefore, the performance of UV LEDs is significantly improved by the polarization engineering in active region.

Lin, Yu-Rui; Liou, Bo-Ting; Chang, Jih-Yuan; Kuo, Yen-Kuang

2013-03-01

61

Influence of storage causing packaging stress changes on smile effect for diode laser arrays  

NASA Astrophysics Data System (ADS)

The smile effect is caused by the thermal stress in the packaging process. If packaging technology of a diode laser array is poor, smile effect will be very bad and the smile effect will vary with storage time. To accurately measure smile effect and to objectively compare the different measuring methods for smile effect, a set of optical system is designed for measuring the smile effect. By using an image amplification method, the smile effect of a diode laser array is accurately measured, and the measurement error is about +/-0.1?m. By researching, the heat sink surface flatness has little influence on smile effect. However the solder quality is a critical factor for smile effect. That is to say, there is more voids, the corresponding smile effect is more serious in this area. Reflow soldering curve has a major impact on smile effect in the packaging process of a diode laser array .During reflow soldering process, accelerated cooling before solidification and slow cooling after solidification not only can commendably reduce voids and smile effect ,but also can effectively solve the smile effect with storage time variation problem .By optimizing the reflow soldering curve of a diode laser array , the smile effect has been controlled within +/-0.5?m..As the smile effect values of a semiconductor laser array is diminished and the beam quality of a laser diode array is improved significantly. The recommended method provides favorable conditions for the beam collimation and shaping of a semiconductor laser array.

Xu, Hui-wu; Zhang, Yong; Fang, Yu-suo; Liu, Xiao-wen; Niu, Jiang-li; Yuan, Chun-sheng; Li, Cheng-yan; Wang, Yuan-yuan; Wang, Xiao-yan; Shen, Mu; An, Zhen-feng

2013-09-01

62

Two-Dimensional Surface-Emitting Arrays of GaAs/AlGaAs Diode Lasers.  

National Technical Information Service (NTIS)

Three approaches to fabricating two-dimensional surface-emitting GaAs/AlGaAs diode laser arrays are discussed: a hybrid approach in which linear arrays of edge-emitting lasers with cleaved end facets are mounted on microchanneled Si heatsinks with integra...

J. P. Donnelly K. Rauschenbach C. A. Wang W. D. Goodhue R. J. Bailey

1989-01-01

63

Evaluation of a diode array for QA measurements on a helical tomotherapy unit  

SciTech Connect

A helical tomotherapy system is used in our clinic to deliver intensity-modulated radiation therapy (IMRT) treatments. Since this machine is designed to deliver IMRT treatments, the traditional field flatness requirements are no longer applicable. This allows the unit to operate without a field flatness filter and consequently the 400 mm wide fan beam is highly inhomogeneous in intensity. The shape of this beam profile is mapped during machine commissioning and for quality assurance purposes the shape of the beam profile needs to be monitored. The use of a commercial diode array for quality assurance measurements is investigated. Central axis beam profiles were acquired at different depths using solid water built-up material. These profiles were compared with ion chamber scans taken in a water tank to test the accuracy of the diode array measurements. The sensitivity of the diode array to variations in the beam profile was checked. Over a seven week period, beam profiles were repeatedly measured. The observed variations are compared with those observed with an on-board beam profile monitor. The diode measurements were in agreement with the ion chamber scans. In the high dose, low gradient region the average ratio between the diode and ion chamber readings was 1.000{+-}0.005 ({+-}1 standard deviation). In the penumbra region the agreement was poorer but all diodes passed the distance to agreement (DTA) requirement of 2 mm. The trend in the beam profile variations that was measured with the diode array device was in agreement with the on-board monitor. While the calculated amount of variation differs between the devices, both were sensitive to subtle variations in the beam profile. The diode array is a valuable tool to quickly and accurately monitor the beam profile on a helical tomotherapy unit.

Langen, K.M.; Meeks, S.L.; Poole, D.O.; Wagner, T.H.; Willoughby, T.R.; Zeidan, O.A.; Kupelian, P.A.; Ruchala, K.J.; Olivera, G.H. [Department of Radiation Oncology, M.D. Anderson Cancer Center Orlando, Orlando, Florida (United States); TomoTherapy Inc., Madison, Wisconsin (United States)

2005-11-15

64

Diode-pumped micro-laser arrays. Final report, 30 September 1993-18 February 1994  

SciTech Connect

In this work, SDL investigated the operation of 2-D high power micro-laser arrays based on novel monolithic surface-emitting laser diode arrays coupled to Yb:YAG and Er:YSGG micro-laser crystals. The experimental demonstrations include: (1) 200 mW, q-cw single Yb:YAG microlaser; (2) 930 mW cw linear, 12-element Er:YSGG micro-laser; (3) 130 Watt q-cw 2-D surface-emitting laser diode array at 970 nm; and (4) 600 mW, q-cw from an 18-element 3-D Er:YSGG microlaser array. The experiments performed at SDL under this contract demonstrate the suitability of monolithic 2-D laser diode arrays for pumping solids state lasers. In addition, the experiments show the flexibility of the micro-laser concept. Using different pump wavelengths in combination with different micro-lasers a wide output wavelength range from 1 micron to 3 micron is demonstrated. Finally, the micro-laser array is shown to be scalable by exploiting one- and two-dimensional laser diode pump arrays.

Waarts, R.

1994-06-01

65

Performance of high-power laser diode arrays for space borne lasers  

SciTech Connect

The adequacy of commercial quasi-continuous high-power laser diode arrays (HPLDAs) as pump sources for space borne lasers has been assessed by endurance tests up to 3x109 shots under various stress conditions, vacuum operation up to 0.36x109 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.

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

2006-08-01

66

Diode Characterization of Rockwell LWIR HgCdTe Detector Arrays  

NASA Astrophysics Data System (ADS)

Future infrared space missions will undoubtedly employ passively cooled focal planes (T ~ 30K), as well as passively cooled telescopes. Most long-wave detector arrays (e.g. Si:As IBC) require cooling to temperatures of ~ 6-8K. We have been working with Rockwell to produce 10?m cutoff HgCdTe detector arrays that, at temperatures of ~ 30K, exhibit sufficiently low dark current and sufficiently high detective quantum efficiency to be interesting for astronomy. In pursuit of these goals, Rockwell Scientific Company has delivered twelve 256 x 256 arrays (several of them engineering arrays), with cutoff wavelengths at 30K between 7.4 and 11?m for characterization at Rochester. Seven of these arrays utilize advanced structure diodes with differing capacitances arranged in rows (banded arrays), and the materials properties of the HgCdTe also vary significantly from array to array. Of ultimate interest to astronomy is the fraction of pixels with dark current below the target value of ~ 100e-/s with 10-60mV of actual reverse bias across the diodes at T ~ 30K. These arrays were developed for the purpose of selecting diode architecture: we use this fraction as one criterion for selection. We have determined from these experiments the optimal diode architecture for future array development. Measurement of the dark current as a function of reverse bias and temperature allows us to ascertain the extent to which trap-to-band tunneling dominates the dark current at this temperature. We present the results for one representative array, UR008.

Bacon, Candice; Pipher, Judith L.; Forrest, William J.; McMurtry, Craig W.; Garnett, James D.

2003-03-01

67

Rapid fabrication of ultraviolet-cured polymer microlens arrays by soft roller stamping process  

Microsoft Academic Search

This paper reports an innovative technique for rapid fabrication of ultraviolet-cured polymer microlens arrays based on soft roller stamping process. In this method, a soft roller with microlens array cavity is made by casting a pre-polymer of polydimethylsiloxane (PDMS) in a plastic master of microlens array. The plastic master is prepared using gas-assisted hot embossing of polycarbonate (PC) film over

Chih-Yuan Chang; Sen-Yeu Yang; Ming-Hui Chu

2007-01-01

68

Millimeter wave monolithic high electron mobility (HEM) varactor diode-grid frequency tripler arrays  

NASA Astrophysics Data System (ADS)

High-electron-mobility (HEM) varactor structures are studied for mm-wave monolithic diode-grid frequency-tripler array applications. The improved HEM varactor-diode structures provide a highly nonlinear C-V characteristic (i.e., a steep slope of the C-V curve and a large capacitance ratio) which produces high harmonic-generation efficiency and reduce the power requirement for efficiently pumping each device. The effects of the light illumination on the C-V characteristics of the barrier-intrinsic-N(+) (BIN) varactor diode are also studied and the results are discussed in this paper. In the development of a monolithic diode-grid frequency-multiplier array, the low-loss quasi-optical configuration is used for the construction of the multiplier circuit. The study of the effects of the light illumination on the C-V characteristics of varactor diode is important in understanding the potential applications of the quasi-optical varactor diode-grid frequency-multiplier array circuit.

Hwu, R. J.; Sadwick, L. P.; Streit, D. C.

1991-12-01

69

Structural and interface properties of an AlN diamond ultraviolet light emitting diode  

SciTech Connect

Two practically fully relaxed AlN domains were identified by x-ray diffractometry for AlN grown on (100) diamond. The epitaxial orientation relationships (0001)[1010] AlN{sup I} parallel (100)[011] diamond for the predominant AlN domain (type I) and (0001)[1210] AlN{sup II} parallel (100)[011] diamond for the second domain (type II) are obtained. Surface morphology measurements corroborate the good structural quality of the AlN film. In addition, the intrinsic built-in voltage of a n-AlN/p-diamond diode was determined as 1.15 V. By spectrally resolved photocurrent measurements, the ultraviolet electroluminescence emission was confirmed to originate at the heterojunction interface, and is most probably due to a defect center.

Miskys, C.R.; Garrido, J.A.; Hermann, M.; Eickhoff, M.; Nebel, C.E.; Stutzmann, M.; Vogg, G. [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Fraunhofer-Institut fuer Zuverlaessigkeit und Mikrointegration, Hansastr. 27d, 80686 Munich (Germany)

2004-10-25

70

Real-time monitoring and diagnosis of scintillation dosimeters using an ultraviolet light emitting diode.  

PubMed

Plastic scintillator fibre optic dosimeters (FODs) have advantages for both brachytherapy and external beam radiotherapy applications. Convenient real-time monitoring and diagnosis of such dosimeters are desirable because of changes in the optical circuit that may arise in use. In this paper, we propose and demonstrate a real-time method using ultraviolet light emitting diodes (LED) to stimulate the scintillator and to diagnose failures of FODs. Key aspects of the LED FOD dosimetry design are investigated, enabling the design of a stable and accurate real-time monitoring dosimetry system. We demonstrate experimentally that the real-time monitoring FOD system is convenient to be used to monitor FOD dosimeters and to diagnose their failures resulted from different mechanisms. PMID:18401065

Yin, Y; Lambert, J; McKenzie, D R; Suchowerska, N

2008-04-09

71

Suitability of ultraviolet (A)-light emitting diode for air stream disinfection.  

PubMed

We previously developed a high powered light-emitting diode device capable of discharging germicidal ultraviolet irradiation (UVA-LED) at an approximate wavelength of 365 nm. This study examined the bactericidal activity of UVA-LED in moving air streams. Aerosols of Escherichia coli DH5alpha were exposed to UVA-LED irradiation using a stable current (0.5 A and 1.2 mW/cm(2)) or pulse current (1.0 A and 0.2 mW/cm(2)). Settle plate analysis was used for bioaerosol sampling, where results were expressed as Colony Forming Units. A -3 Log inactivation of the E. coli population occurred after 75 minutes of constant exposure to stable current. The pulse current produced inactivation within a similar timeframe. Our results might be significant as a basic study for further investigations about the effect of UVA-LED on airborne bacteria and its suitability for air disinfection applications. PMID:19763028

Gadelmoula, Mostafa; Lian, Xin; Maeda, Miku; Aihara, Mutsumi; Mawatari, Kazuaki; Hamamoto, Akiko; Harada, Yumi; Yamato, Masayuki; Akutagawa, Masatake; Nakaya, Yutaka; Kinouchi, Yohsuke; Takahashi, Akira

2009-08-01

72

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

PubMed

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

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

2010-10-01

73

Transparent conductive graphene electrode in GaN-based ultra-violet light emitting diodes.  

PubMed

We report a graphene-based transparent conductive electrode for use in ultraviolet (UV) GaN light emitting diodes (LEDs). A few-layer graphene (FLG) layer was mechanically deposited. UV light at a peak wavelength of 368 nm was successfully emitted by the FLG layer as transparent contact to p-GaN. The emission of UV light through the thin graphene layer was brighter than through the thick graphene layer. The thickness of the graphene layer was characterized by micro-Raman spectroscopy. Our results indicate that this novel graphene-based transparent conductive electrode holds great promise for use in UV optoelectronics for which conventional ITO is less transparent than graphene. PMID:21164643

Kim, Byung-Jae; Mastro, Michael A; Hite, Jennifer; Eddy, Charles R; Kim, Jihyun

2010-10-25

74

Crossbar memory array of organic bistable rectifying diodes for nonvolatile data storage  

NASA Astrophysics Data System (ADS)

Cross-talk in memories using resistive switches in a cross-bar geometry can be prevented by integration of a rectifying diode. We present a functional cross bar memory array using a phase separated blend of a ferroelectric and a semiconducting polymer as storage medium. Each intersection acts simultaneously as a bistable rectifying diode. A logic table of a 4-bit memory and integration into a 3×3 cross bar array are demonstrated. The most difficult state, a high resistance bit completely surrounded by low resistance bits could be unambiguously identified.

Asadi, Kamal; Li, Mengyuan; Stingelin, Natalie; Blom, Paul W. M.; de Leeuw, Dago M.

2010-11-01

75

Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods.  

SciTech Connect

The junction temperature of AlGaN ultraviolet light-emitting diodes emitting at 295 nm is measured by using the temperature coefficients of the diode forward voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-forward voltage is the most accurate ({+-}3 C). A theoretical model for the dependence of the diode forward voltage (V{sub f}) on junction temperature (T{sub j}) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6 K/W is obtained with the device mounted with thermal paste on a heat sink.

Fischer, Arthur Joseph; Kim, Jin K. (Rensselaer Polytechnic Institute, Troy, NY); Crawford, Mary Hagerott; Gessmann, Th. (Rensselaer Polytechnic Institute, Troy, NY); Shah, J. M. (Rensselaer Polytechnic Institute, Troy, NY); Xi, J.-Q. (Rensselaer Polytechnic Institute, Troy, NY); Xi, Y. (Rensselaer Polytechnic Institute, Troy, NY); Allerman, Andrew Alan; Schubert, E. Fred (Rensselaer Polytechnic Institute, Troy, NY); Bogart, Katherine Huderle Andersen

2004-11-01

76

Fast and sensitive ultraviolet spectrum detection based on 32-anode photomultiplier tube array  

NASA Astrophysics Data System (ADS)

In view of low sensitivity of CCD arrays in the ultraviolet range, a new measuring method for ultraviolet spectrum with a 32-anode linear photomultiplier tube (PMT) array is presented. A spectrum measurement system that includes a spectroscopic design and data acquisition circuits, together with the system-controlling software, has been developed for the PMT array. Compared with a spectrometer which employs a back-thinned CCD with the highest ultraviolet sensitivity, experiments indicate that the system has the same sensitivity as the spectrometer which works at the integration time of about 2 s, while requiring less than 7 ms for one single measurement. It is able to perform timeresolved measurements even in weak light applications where CCD spectrometers need to work at long integration times.

Lu, Li-Gen; Zhang, Bao-Zhou; Zhang, Jun-Yuan

2012-01-01

77

Diffuser array for a light-emitting diode backlight system  

Microsoft Academic Search

A novel light-emitting diode backlight module applied in liquid crystal displays is demonstrated. With microgrooves on the bottom surface and diffusive dots on the upper surface of the light guide plate (LGP), most of the incident backlight is utilized effectively and the dispersion of light is decreased obviously. The design procedure of optimization for the backlight module is accomplished by

Yeu-Jent Hu; Jiunn-Chyi Lee; Yi-Ping Wang; Ya-Fen Wu; Lih-Gen Sheu

2007-01-01

78

Progress of laser diode arrays operating under harsh conditions  

Microsoft Academic Search

High Power Laser Diodes (HPLD) are increasingly used in different fields of applications such as Industry, Medical and Defense. Significant improvements of performances (especially in 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 (range finders, designators and countermeasures) but

Andreas Kohl; Thierry Fillardet; Herve Moisan; Eric Brousse

2010-01-01

79

Optical and thermal modeling of ultraviolet-LED array packaging for curing application  

Microsoft Academic Search

High power Ultraviolet Light-Emitting Diode (UV-LED) is currently in high demand for a variety of applications including lighting, printing, and polymer curing, with its' advantages of durability, reliability, non-hazardous and safety. Recently, the technology of Semiconductor Light Matrix (SLM) by multiple individual LEDs mounted on panels was put forward to obtain higher power for curing application. However, the illumination uniformity

Hai Liu; Zirong Tang; Tielin Shi; Guanglan Liao; Lei Nie

2008-01-01

80

Microchannel heat sinks for two-dimensional high-power-density diode laser arrays  

Microsoft Academic Search

A two-dimensional GaInAsP\\/InP diode laser array was operated with CW power dissipation up to 500 W\\/cc into a Si microchannel heat sink. The approximately 1 x 4 sq mm laser array was used to characterize the heat sink and a value of 0.040 C sq cm\\/W for the thermal resistance per unit area was deduced. The extrapolated value for a

L. J. Missaggia; J. N. Walpole; Z. L. Liau; R. J. Phillips

1989-01-01

81

Impact of temperature-dependent hole injection on low-temperature electroluminescence collapse in ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

Optical and electronic properties of mid-ultraviolet light emitting diodes with a two-step p-AlGaN region are measured at temperatures from 8 to 300 K. While the electroluminescence intensity increases down to a temperature lower than that reported in InGaN light emitting diodes (LEDs), there is still a collapse at cryogenic temperatures. Capacitance-voltage measurements across the same range of temperatures reveal an increasing depletion region with decreasing temperature indicating that hole injection is a significant factor in the temperature dependent behavior, as well as the cause of electroluminescence collapse.

Moe, Craig G.; Garrett, Gregory A.; Rotella, Paul; Shen, Hongen; Wraback, Michael; Shatalov, Max; Sun, Wenhong; Deng, Jianyu; Hu, Xuhong; Bilenko, Yuri; Yang, Jinwei; Gaska, Remis

2012-12-01

82

Low-leakage p-type diamond Schottky diodes prepared using vacuum ultraviolet light/ozone treatment  

NASA Astrophysics Data System (ADS)

Room-temperature fabrication of Schottky diodes was demonstrated for p-type boron-doped diamond. This fabrication method's key technique is selective modification of surface termination from monohydride into oxygen groups using vacuum ultraviolet light irradiation in oxygen. The Au contacts, formed on the hydrogen-terminated surface, maintained Ohmic properties after this selective surface oxidation. The Au contacts then deposited on the oxidized surface, imparting Schottky properties. The lateral-type diodes comprising Au Schottky contacts and Au Ohmic contacts showed blocking voltage higher than 1 kV without electrode guarding. The leakage current at 1 kV was as low as 30 pA.

Teraji, T.; Garino, Y.; Koide, Y.; Ito, T.

2009-06-01

83

Anode modification of polymer light-emitting diode using graphene oxide interfacial layer: The role of ultraviolet-ozone treatment  

NASA Astrophysics Data System (ADS)

A simple and efficient method has been developed to modify the anode interface of polymer light-emitting diode by incorporating solution-processable graphene oxide as hole transport layer. Interface engineering of ultraviolet-ozone treatment on graphene oxide is demonstrated to dramatically enhance the electrical properties, leading to 15% increase in efficiency compared to that with a traditionally used poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) layer. As determined by photoelectron spectroscopy and impedance spectroscopy, an optimized ultraviolet-ozone treatment results in a more favorable energy level alignment and a decrease in series resistance, which can subsequently facilitate charge injection at the anodic interface.

Jiang, Xiao-Chen; Li, Yan-Qing; Deng, Yan-Hong; Zhuo, Qi-Qi; Lee, Shuit-Tong; Tang, Jian-Xin

2013-08-01

84

Laser diode array beam shaping system based on fly's eye lens  

NASA Astrophysics Data System (ADS)

The main drawback of diode laser array is the inhomogeneous intensity distribution in the far field. So the beam shaping technology is very important in the application of laser diode array. This work present a novel beam shaping optical system based on fly's eye lens. The system can homogenize the diode laser array based on the multi-aperture beam integrating theory. Such beam shaping system was designed by ray tracing method using ZEMAX™ Non-Sequential Components analysis tools. The ray-tracing simulation shows that a 5 × 5 mm2 Top-Hat intensity profile was got at a working distance of 40 mm and the homogeneity of the intensity distribution is better than 90%. And it is verified that such beam shaping system is adapted for the aberrations of bars very well by simulation. Based on the design, a relative experimental research on the beam shaping system for 5 bars LD stack is carried out. Through the beam shaping system the laser diode power intensity is improved 4 times, light field distribution nonuniformity is less than 10%, and the system coupling efficiency is more than 80%, which validated the engineering feasibility and applied value of this novel LD array beam shaping system.

Huang, Feng; Lei, Ming; Jia, Wenwu; Yin, Zhiyong; Zhou, Bin; Wang, Yuefeng

2012-10-01

85

Analysis of sonolytic degradation products of azo dye Orange G using liquid chromatography-diode array detection-mass spectrometry.  

PubMed

In this paper, seven new sonolytic degradation products of Orange G were found and identified using powerful analytical techniques such as liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS), tandem mass spectrometry (MS/MS), and liquid chromatography with diode-array detection (LC-DAD). Each technique provided complementary information for the degradation products identification. In order to resolve the MS and MS/MS spectra obtained, the separation conditions were optimized. Among them, Orange G was unambiguously identified based on its abundant [M-H](-) ion, [M+H](+) ion, ultra-violet and visible spectra, retention time, and tandem mass spectrometric analysis compared with an authentic standard. The seven new degradation products were tentatively identified based on ultra-violet and visible spectra, [M-H](-) ions, and tandem mass spectrometry. The neutral losses of SO(2), SO(3), N(2) and H(2)O for MS/MS spectra which appear to be characteristic of the negative ion mode were observed. Based on this by-product identification, a possible multi-step degradation scheme is proposed. The analysis results of degradation products reveal that the degradation mechanism proceeds via reductive cleavage of the azo linkage, as well as intermolecular dehydration and desulfonation due to the powerful oxidizing hydroxyl radicals as well as hydrogen radical. PMID:21459655

Cai, Meiqiang; Jin, Micong; Weavers, Linda K

2011-03-21

86

A High Power InGaN-Based Blue-Violet Laser Diode Array with a Broad-Area Stripe  

NASA Astrophysics Data System (ADS)

An array of high power InGaN/GaN multi-quantum-well laser diodes with a broad waveguide is fabricated. The laser diode structure is grown on a GaN substrate by metal-organic chemical vapor deposition. The laser diode array consists of five emitter stripes which share common electrodes on one laser chip. The electrical and optical characteristics of the laser diode array are investigated under the pulse current injection with 10kHz frequency and 100 ns pulse width. The laser diode array emits at the wavelength of 409 nm, which is located in the blue-violet region, and the threshold current is 2.9 A. The maximum output light peak power is measured to be 7.5 W at the wavelength of 411.8 nm under the current of 25 A.

Chen, Ping; Zhao, De-Gang; Feng, Mei-Xin; Jiang, De-Sheng; Liu, Zong-Shun; Zhang, Li-Qun; Li, De-Yao; Liu, Jian-Ping; Wang, Hui; Zhu, Jian-Jun; Zhang, Shu-Ming; Zhang, Bao-Shun; Yang, Hui

2013-10-01

87

High-performance liquid chromatography–diode array and electrospray-mass spectrometry analysis of non-allowed substances in cosmetic products for preventing hair loss and other hormone-dependent skin diseases  

Microsoft Academic Search

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 minoxidil, progesterone, estrone, spironolactone, canrenone, hydrocortisone and triamcinolone acetonide in cosmetic products. The presence of these substances in commercial cosmetic samples is prohibited. The compounds were separated by reversed phase chromatography with water (0.1%

Daniela De Orsi; Manuela Pellegrini; Simona Pichini; Donatella Mattioli; Emilia Marchei; Luigi Gagliardi

2008-01-01

88

Low-leakage p-type diamond Schottky diodes prepared using vacuum ultraviolet light\\/ozone treatment  

Microsoft Academic Search

Room-temperature fabrication of Schottky diodes was demonstrated for p-type boron-doped diamond. This fabrication method's key technique is selective modification of surface termination from monohydride into oxygen groups using vacuum ultraviolet light irradiation in oxygen. The Au contacts, formed on the hydrogen-terminated surface, maintained Ohmic properties after this selective surface oxidation. The Au contacts then deposited on the oxidized surface, imparting

T. Teraji; Y. Garino; Y. Koide; T. Ito

2009-01-01

89

Phase-delayed laser diode array allows ultrasonic guided wave mode selection and tuning  

NASA Astrophysics Data System (ADS)

Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT) since certain modes at various center frequencies are sensitive to specific types of defects. Ideally one should be able to select both the mode and the center frequency of the launched waves. We demonstrated that an affordable laser diode array can selectively launch either the S0 or A0 ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching the selected mode and frequency was employed between the output of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.

Karppinen, Pasi; Salmi, Ari; Moilanen, Petro; Karppinen, Timo; Zhao, Zuomin; Myllylä, Risto; Timonen, Jussi; Hæggström, Edward

2013-04-01

90

Thermal properties of InGaN laser diodes and arrays  

NASA Astrophysics Data System (ADS)

Junction temperature of a laser diode (LD) determines the value of threshold current, maximum achievable power and device lifetime. In this work we studied this parameter by a method of comparing current-voltage characteristics measured under pulse bias (at various temperatures) with DC characteristic obtained at room temperature. As exemplary devices we chose various laser diode arrays and single emitter laser with different substrate thickness. The results show, that the primary factor determining thermal resistance of the device is the chip's surface, which means, that a dominating mechanism is related with a heat transfer between the chip and the heat sink.

Sta?czyk, Szymon; Kafar, Anna; Targowski, Grzegorz; Wi?niewski, Przemek; Makarowa, Irina; Suski, Tadeusz; Perlin, Piotr

2013-03-01

91

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

SciTech Connect

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.

Arto V. Nurmikko; Jung Han

2004-10-01

92

Diffuser array for a light-emitting diode backlight system  

NASA Astrophysics Data System (ADS)

A novel light-emitting diode backlight module applied in liquid crystal displays is demonstrated. With microgrooves on the bottom surface and diffusive dots on the upper surface of the light guide plate (LGP), most of the incident backlight is utilized effectively and the dispersion of light is decreased obviously. The design procedure of optimization for the backlight module is accomplished by the TracePro optical simulation software. Relationship between the dimensions of microgrooves and diffusive dots are investigated and discussed in detail. By using the structure of microgrooves and diffusive dots on the LGP, the incident light satisfies the total internal reflection conditions and reflects from the bottom surface then spread by the diffusive dots. Compared to the conventional backlight devices, the light uniformity and light intensity for the LGP are improved by our design.

Hu, Yeu-Jent; Lee, Jiunn-Chyi; Wang, Yi-Ping; Wu, Ya-Fen; Sheu, Lih-Gen

2007-09-01

93

Reliable QCW diode laser arrays for operation with high duty cycles  

NASA Astrophysics Data System (ADS)

We present performance and reliability data of high-brightness QCW arrays with a custom, compact and robust design for an operation with high duty cycles. The presented designs are based on single diodes consisting of a 1cm laser bar that is AuSn soldered between two CuW submounts. Arrays of up to 15 diodes as well as one single diode are connected to ceramic base plates on different heat sinks. The available optical output power is shown to be strongly depending on the wavelength and fill factor of the laser bars as well as on the duty cycle, the base plate temperature and the thermal conductivity of the applied ceramic materials. Operation at increased heat sink temperatures up to 45°C is possible without active water cooling or conduction cooling with the help of Peltier elements. Using an array of 15 bars at 980 nm with 20% fill factor and 2 mm cavity on standard ceramics, we can reach an optical output power of 1150 W at 45°C base plate temperature operating the array with 15 Hz and 15% duty cycle. Novel materials allow for more efficient operation and higher optical output powers.

Kissel, Heiko; Faßbender, Wilhelm; Lotz, Jens; Alegria, Kim; Koenning, Tobias; Stapleton, Dean; Patterson, Steve; Biesenbach, Jens

2013-02-01

94

1.1-W cw Cr:LiSAF laser pumped by a 1-cm diode array  

Microsoft Academic Search

We demonstrate 1.1-W cw output power from a diode-laser array-pumped Cr:LiSAF laser based on a concept that allows for pumping low-gain solid-state lasers at reduced temperature rise. We discuss scaling to higher powers as a function of diode power and define a figure of merit for evaluating given diode lasers as pump sources for low-gain solid-state lasers. {copyright} {ital 1997}

D. Kopf; U. Keller; M. A. Emanuel; R. J. Beach; J. A. Skidmore

1997-01-01

95

1.1-W cw Cr:LiSAF laser pumped by a 1-cm diode array.  

PubMed

We demonstrate 1.1-W cw output power from a diode-laser array-pumped Cr:LiSAF laser based on a concept that allows for pumping low-gain solid-state lasers at reduced temperature rise. We discuss scaling to higher powers as a function of diode power and define a figure of merit for evaluating given diode lasers as pump sources for low-gain solid-state lasers. PMID:18183115

Kopf, D; Keller, U; Emanuel, M A; Beach, R J; Skidmore, J A

1997-01-15

96

Design of microlens illuminated aperture array fabricated by aligned ultraviolet imprinting process for optical read only memory card system  

Microsoft Academic Search

A microlens illuminated aperture array (MLIAA) was designed for the multiprobe optical read only memory card system. As a method to integrate the microlens array (MLA) with the aperture array containing 1000×1000 apertures, an aligned ultraviolet imprinting process was used to satisfy the system objectives of reduced focal length and reduced spot size. An analysis using diffraction theory was performed

Hongmin Kim; Jeeseung Lee; Jiseok Lim; Seok-Min Kim; Shinill Kang; Young-Joo Kim; Christopher Busch

2006-01-01

97

Progress of laser diode arrays operating under harsh conditions  

NASA Astrophysics Data System (ADS)

High Power Laser Diodes (HPLD) are increasingly used in different fields of applications such as Industry, Medical and Defense. Significant improvements of performances (especially in 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 (range finders, designators and countermeasures) but also as direct light source (illuminator, pointer,...). For these applications the devices not only have to show outstanding electro optical performances but the packaging must also be robust enough to sustain the harsh environmental requirements. Due to recent progress in both semiconductor technology and packaging, QLD was able to push the peak power up to 400W per bar at 808nm. At this wavelength QLD has achieved record high efficiencies close to 65% in production. Thanks to a very small bar to bar pitch down to 330?m our stacks deliver peak power densities as high as 12 kW/cm². Even at 400 ?m pitch the bars can be collimated in order to improve the beam quality.

Kohl, Andreas; Fillardet, Thierry; Moisan, Herve; Brousse, Eric

2010-10-01

98

Construction of a fast, inexpensive rapid-scanning diode-array detector and spectrometer.  

PubMed

A 512-element diode-array spectroscopic detection system capable of acquiring multiple spectra at a rate of 5 ms per spectrum with an effective scan rate of 102.9 kHz has been constructed. Spectra with fewer diode elements can also be acquired at scan rates up to 128 kHz. The detector utilizes a Hamamatsu silicon photodiode-array sensor that is interfaced to Hamamatsu driver/amplifier and clock generator boards and a DRA laboratories 12-bit 160-kHz analog-to-digital converter. These are standard, commercially available devices which cost approximately $3500. The system is interfaced to and controlled by an IBM XT microcomputer. Detailed descriptions of the home-built detector housing and control/interface circuitry are presented and its application to the study of the reaction of horseradish peroxidase with hydrogen peroxide is demonstrated. PMID:2285140

Carter, T P; Baek, H K; Bonninghausen, L; Morris, R J; van Wart, H E

1990-10-01

99

Screening of radical scavengers in Scutellaria baicalensis using HPLC with diode array and chemiluminescence detection.  

PubMed

Scutellaria baicalensis Georgi is a well-known medical plant widely used as a famous traditional Chinese medicine. It has been reported that S. baicalensis can protect against oxidative stress and possess anti-inflammatory effect. In the present paper, an HPLC-diode array-chemiluminescence detection method for on-line detection was successfully developed to screen antioxidants in complex S. baicalensis extracts. Using the proposed approach, eight compounds in the S. baicalensis extracts were found to possess a potential antioxidant activity. Furthermore, the effects of purified compounds on protecting RAW 264.7 cells from hydrogen peroxide injury were also investigated in vitro to confirm the established method, which were consistent with the results of HPLC-diode array-chemiluminescence detection method. These results demonstrated that this method was a useful technique for rapidly screening and identifying bioactive components from complex herbal medicines. PMID:22815263

Wang, Rui; Luo, Jianguang; Kong, Lingyi

2012-07-20

100

Coupling method for laser-diode-array end-pumped solid-state amplifiers.  

PubMed

A new coupling method is proposed for high-power laser-diode-array (LDA) end-pumped large-aperture amplifiers. In this method, stacks in the LDA are distributed on a spherical surface, and a hollow duct is placed after them. Both numerical simulations and experimental research have been done for this method. All results show that high coupling efficiency and uniform pumping field can be obtained simultaneously using this method. PMID:19122733

Qinghua, Deng; Hansheng, Peng; Zhan, Sui; Lei, Ding; Mingzhong, Li; Yiming, Luo; Jun, Tang; Shaobo, He; Jianjun, Wang; Honghuan, Lin; Rui, Zhang; Ying, Deng; Yuanbin, Cheng; Zhenhua, Lu; Jianguo, Liu; Yong, Liu

2008-11-01

101

Enhancement in light output of InGaN-based microhole array light-emitting diodes  

Microsoft Academic Search

InGaN-based microhole array light-emitting diodes (LEDs) with hole diameters (d) of 3-15 ?m were fabricated using self-aligned etching. The effects of size on the device characteristics, including current density-voltage and light output-current density, were measured and compared with those of conventional broad-area (BA) LEDs fabricated from the same wafer. The electrical characteristics of the devices are similar to those of

T. H. Hsueh; J. K. Sheu; H. W. Huang; J. Y. Chu; C. C. Kao; H. C. Kuo; S. C. Wang

2005-01-01

102

Illumination Based on High-Power White Light-Emitting Diode Array  

Microsoft Academic Search

In this study, a high-power white light emitting diode (LED) array for illumination is realized and investigated. Since the brightness and life-span of an LED depend markedly on its thermal design and the stability of its power, some issues that govern the structure of the heat dissipation components and the power supply circuit are initially discussed. TracePro optical analysis and

Chi-Yuan Lee; Jian-Lin Liu

2012-01-01

103

The ArcCHECK diode array for dosimetric verification of HybridArc  

Microsoft Academic Search

The aim of this work is to evaluate dosimetric accuracy of a new treatment modality, HybridArc, in iPlan RT Dose 4.5 (BrainLAB, Feldkirchen, Germany) using a four-dimensional diode array (ArcCHECK, Sun Nuclear Corporation, Melbourne, USA). HybridArc is able to enhance dynamic conformal arcs with inversely planned elements. HybridArc plans for various sites (intracranial and extracranial) were constructed and after that

A. L. Petoukhova; J. van Egmond; M. G. C. Eenink; R. G. J. Wiggenraad; J. P. C. van Santvoort

2011-01-01

104

Diode arrays, crystals, and thermal management for solid-state lasers  

Microsoft Academic Search

We summarize our efforts in the development of solid-state lasers, including the laser diode arrays, pump light delivery, approaches to thermal management, and novel gain media. Our interests are in developing unique solid-state lasers, including those operating at higher powers, offering less common wavelengths, and having other specialized features. In this paper, we discuss high-power Tm:YAG and Yb:YAG lasers. The

Stephen A. Payne; Raymond J. Beach; Camille Bibeau; Christopher A. Ebbers; Mark A. Emanuel; Eric C. Honea; Christopher D. Marshall; Ralph H. Page; Kathleen I. Schaffers; Jay A. Skidmore; Steven B. Sutton; William F. Krupke

1997-01-01

105

Microlens array diffuser for a light-emitting diode backlight system  

Microsoft Academic Search

Microlens array (MLA) diffusers for light-emitting diode (LED) backlight systems have been developed. A high fill-factor photoresist mold for the MLA was fabricated using three-dimensional diffuser lithography, and the patterns were transferred to a nickel master mold for UV-curable polymer replication. The fabricated microlens had various paraboloidal profiles, and its aspect ratio was controlled from 1.0 to 2.1. The MLA

Sung-Il Chang; Jun-Bo Yoon; Hongki Kim; Jin-Jong Kim; Baik-Kyu Lee; Dong Ho Shin

2006-01-01

106

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

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

107

Coherent operation of injection-locked monolithic surface-emitting diode laser arrays  

SciTech Connect

A row of six surface-emitting GaAlAs laser diode arrays was locked in a coupled resonator configuration by means of interconnecting waveguides. An external master oscillator was injected into the first array in order to achieve single longitudinal mode operation and wavelength tunability. Spectral data show all six devices were locked in a single longitudinal mode, with tunable operation of over 60 A. Far-field fringe visibilities greater than 60% were achieved at 100 mW output powers.

Jansen, M.; Yang, J. J.; Heflinger, L.; Ou, S. S.; Sergant, M.; Huang, J.; Wilcox, J.; Eaton, L.; Simmons, W.

1989-06-26

108

Architecture of CuS/PbS heterojunction semiconductor nanowire arrays for electrical switches and diodes.  

PubMed

CuS/PbS p-n heterojunction nanowires arrays have been successfully synthesized. Association of template and DC power sources by controllable electrochemistry processes offers a technique platform to efficiently grow a combined heterojunction nanowire arrays driven by a minimization of interfacial energy. The resulting p-n junction materials of CuS/PbS show highly uniform 1D wire architecture. The single CuS/PbS p-n heterojunction nanowire based devices were fabricated, and their electrical behaviors were investigated. The independent nanowires exhibited a very high ON/OFF ratio of 1195, due to the association effect of electrical switches and diodes. PMID:22671306

Qian, Xuemin; Liu, Huibiao; Chen, Nan; Zhou, Haiqing; Sun, Lianfeng; Li, Yongjun; Li, Yuliang

2012-06-06

109

1.47-1.49-?m InGaAsP/InP diode laser arrays  

NASA Astrophysics Data System (ADS)

Continuous-wave power of 25 W at 1.47-?m was obtained from a 20-element, 1-cm-wide, one-dimensional diode laser array mounted in a microchannel water-cooled heat sink. The coolant temperature was 16 °C. A two-dimensional array comprising four laser bars achieved a quasi-cw output of 110 W at a wavelength of 1.49 ?m, with an 8-9-nm full width at half-maximum spectrum width. The coolant temperature was 18 °C. We developed a theoretical model that describes array heating. Thermal resistances of 0.56, 0.4, and 0.34 K/W were experimentally and theoretically determined for arrays with fill factors of 10%, 20%, and 40%, respectively.

Gourevitch, A.; Belenky, G.; Donetsky, D.; Laikhtman, B.; Westerfeld, D.; Trussell, C. W.; An, H.; Shellenbarger, Z.; Martinelli, R.

2003-07-01

110

Sampling of Atmospheric Carbonyls with Small DNPH-Coated C18 Cartridges and Liquid Chromatography Analysis with Diode Array Detection  

Microsoft Academic Search

Carbonyls in air are sampled using small DNPH-coated C18 cartridges and analyzed by liquid chromatography with diode array detection. Carbonyl structure confirmation is obtained by comparing diode array spectral scans of samples to the uv-visible spectra (190–600 nm) of some 20 carbonyl hydrazones recorded in the CH3CN—H2O eluent used for LC analysis. Analytical detection limits are 0.09–3.4 nanograms carbonyl and

Cecily M. Druzik; Daniel Grosjean; Antoinette Van Neste; Sucha S. Parmar

1990-01-01

111

Wavelength stabilization and spectrum narrowing of high-power multimode laser diodes and arrays by use of volume Bragg gratings  

Microsoft Academic Search

Spectral line narrowing (by a factor of 8) and stabilization of the emission wavelength (by a factor of 30) of multimode high-power laser diodes and arrays is demonstrated by use of volume Bragg gratings fabricated in high-stability inorganic photorefractive glasses. Applications include stabilization of pump laser diodes and arrays for solid-state lasers and metal-vapor lasers, spin hyperpolarization of noble gases

B. L. Volodin; S. V. Dolgy; E. D. Melnik; E. Downs; J. Shaw; V. S. Ban

2004-01-01

112

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

113

Analysis of phenolic compounds in spruce needle extracts using an UV-VIS-diode array detector  

Microsoft Academic Search

High-performance liquid chromatography (HPLC) coupled with ultraviolet-visible spectroscopy, using a photodiode-array detector, was applied to the investigation of plant extracts for polyphenolic compounds. Simultaneous detection at different wavelengths and measurement of the UV spectrum of each separated compound during the elution allows an easy and rapid identification of the derivatives of benzoic acid, o-coumaric acid, p-hydroxyacetophenone, stilbenes and flavonoide compounds

H. G. Kicinski; A. Kettrup

1987-01-01

114

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

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

115

Anti-Reflective Fluoride Coatings for Widely Tunable Deep-Ultraviolet Diode-Pumped Solid-State Laser Applications  

NASA Astrophysics Data System (ADS)

An anti-reflective (AR) fluoride coating in the 170-230 nm spectral range is prepared by the thermal evaporation method for the applications of widely tunable deep-ultraviolet diode-pumped solid-state lasers. The transmittance of an AR coated calcium fluoride (CaF2) window in thickness 3 mm is measured to be in the range of 95.8% at 170 nm to 97.1% at 230 nm, with the maximum transmittance 99.2% and the minimum residual reflectance 0.04% appeared at 195 nm. The experimental results indicate that treating the AR coated window and the bare substrate with ultraviolet irradiation can significantly improve their optical performance.

Li, Bin-Cheng; Lin, Da-Wei; Han, Yan-Ling; Guo, Chun; Zhang, Yun-Dong; Liu, Hong-Xiang

2010-04-01

116

Message encoding and decoding using an asynchronous chaotic laser diode transmitter-receiver array.  

PubMed

We have numerically investigated a chaotic laser diode transmitter-receiver array scheme (CLDTRAS), which is a secure digital communication scheme using a difference between two types of transmitter-receiver array consisting of two self-pulsating laser diodes (LDs), i.e., a receiver LD and a transmitter LD. By analyzing the bit error rate, particularly its dependence on the parameter mismatches of the hardware and channel noise and on the correlation coefficient between a transmitter LD and receiver LD, we examined the problems of sensitivity to parameter mismatches and channel noise and a dependence on chaos synchronization between a transmitter LD and a receiver LD. The former makes communication difficult, and the latter makes it possible for an eavesdropper to estimate the receiver LD using chaos synchronization and to forge the hardware. Then we studied the effects of the bit error rate for various values of the threshold, which determines a binary message, and for various numbers of transmitters-receivers making up a LD transmitter-receiver array. It has been shown that a highly noise-tolerant and hardware-dependent communication scheme can be achieved with the LD transmitter-receiver array, whose transmitter and receiver LDs are asynchronous with respect to each other, by choosing the proper threshold and increasing the number of LD transmitters-receivers. Since it is possible to communicate without chaos synchronization, it becomes difficult to forge hardware and to eavesdrop with the forged hardware even if the key is stolen. PMID:17579693

Ebisawa, Satoshi; Komatsu, Shinichi

2007-07-10

117

Ultraviolet laser diodes grown on semipolar (2021) GaN substrates by plasma-assisted molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

We demonstrate ultra-violet laser diodes emitting at 388 nm grown by plasma-assisted molecular beam epitaxy on semipolar (2021)GaN substrates under metal-rich conditions. The threshold current density and voltage of 13.2 kA/cm2 and 10.8 V were measured at room temperature for devices with the laser ridge waveguide oriented along the [1210] direction. We show smooth, atomically flat surface morphology after growth. The excellent structural quality of the laser heterostructure was corroborated by transmission electron microscopy.

Sawicka, M.; Muziol, G.; Turski, H.; Grzanka, S.; Grzanka, E.; Smalc-Koziorowska, J.; Weyher, J. L.; Chèze, C.; Albrecht, M.; Kucharski, R.; Perlin, P.; Skierbiszewski, C.

2013-06-01

118

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

SciTech Connect

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.

Chen, H.L. [Lawrence Livermore National Lab., CA (United States); Francis, D.; Nguyen, T.; Yuen, W.; Li, G.; Chang-Hasnain, C. [Univ. of California, Berkeley, CA (United States)

1999-05-01

119

1.5 and 2.3 ?m diode laser arrays for optical pumping  

NASA Astrophysics Data System (ADS)

High wall-plug efficiency and a wide range of available wavelengths make laser diode arrays preferable for many high-power applications, including optical pumping of solid state lasers. Recently, we designed and fabricated InGaAsP/InP arrays operating at 1.5-?m and In(Al)GaAsSb/GaSb arrays operating at 2.3-?m. We have demonstrated a high continuous-wave (CW) output power of 25 W from a one dimensional laser array and a quasi-CW (q-CW) output power of 110 W from a two dimensional laser array both operating near 1.5-?m. We have obtained a CW output power of 10 W from the 2.3-?m laser array. The 1.5-?m arrays are suitable for resonant pumping of erbium doped solid-state lasers, which require high power optical sources emitting in the narrow erbium absorption bands. Long current-injection pulses produce a considerable temperature increase within the diode laser structure which induces a red-shift of the output wavelength. This thermal drift of the laser array emission spectrum can lead to misalignment with the erbium absorption bands, which decreases pumping efficiency. We have developed an experimental technique to measure the time dependence of the laser emission spectrum during a single current pulse. From the red-shift of the laser emission, we determine the temperature of the laser active region as a function of time. The spacing between the individual laser emitters has an effect on the array heating. In steady state operation, this spacing is a contributing factor in the non-uniformity of the thermal field within the bar, and thus to the overall thermal resistance of the laser bar. Under pulse operation, the transient heating process can be divided into three time periods; each with its own heat transport condition. It was shown that in the initial period of time the heat propagates within the laser bar structure and the laser bar design (fill factor) strongly affects the active region temperature rise. In the later periods the temperature kinetics is insensitive to the fill factor. This analysis has been verified in experimental studies using the 1.5-?m laser arrays.

Gourevitch, A.; Belenky, G.; Shterengas, L.; Donetsky, D.; Westerfeld, D.; Laikhtman, B.; Martinelli, R. U.; Kim, G.

2005-08-01

120

Theoretical and experimental studies of Schottky diodes that use aligned arrays of single-walled carbon nanotubes  

Microsoft Academic Search

We present theoretical and experimental studies of Schottky diodes that use aligned arrays of single-walled carbon nanotubes.\\u000a A simple physical model, taking into account the basic physics of current rectification, can adequately describe the single-tube\\u000a and array devices. We show that for as-grown array diodes, the rectification ratio, defined by the maximum-to-minimum-current-ratio,\\u000a is low due to the presence of metallic-single-walled

Xinning Ho; Lina Ye; Slava V. Rotkin; Xu Xie; Frank Du; Simon Dunham; Jana Zaumseil; John A. Rogers

2010-01-01

121

Simplified thermal analysis of impact of diamond heat spreader on InGaN laser diode arrays  

NASA Astrophysics Data System (ADS)

This paper shows results obtained by simplified thermal modeling of one-dimensional laser arrays designed based on a single InGaN edge-emitting laser diode. Laser arrays were designed using 2 - 7 emitters with a pitch ranging from 10 ?m to 70 ?m. Heat flux calculations using three-dimensional finite-element analysis have been undertaken for the evaluation of efficiency of diamond heat spreader applied to these devices. An impact of size (thickness, length, width) of diamond heat spreaders on maximal temperature increase in active region of designed epi-up and epi-down laser diode arrays has been determined.

Jawulski, Konrad; Kuc, Maciej; Sarzala, Robert P.

2013-01-01

122

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

NASA Astrophysics Data System (ADS)

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.

Kao, Chen-Kai

123

Online Photolytic Optical Gating of Caged Fluorophores in Capillary Zone Electrophoresis Utilizing an Ultraviolet-Light Emitting Diode  

PubMed Central

Photolytic optical gating (POG) facilitates rapid, on-line and highly sensitive analyses, though POG utilizes UV lasers for sample injection. We present a lower-cost, more portable alternative, employing an ultraviolet (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 Hadamard transformation, resulting in increased sensitivity. This work shows, for the first time, the use of a UV-LED for online POG with comparable sensitivity to conventional laser sources but for lower cost.

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

2013-01-01

124

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

PubMed

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

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

2012-09-01

125

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

SciTech Connect

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.

Xu Zhouxiang; Zhang Xian; Huang Kaikai; Lu Xuanhui [Physics Department, Zhejiang University, Hangzhou, 310027 (China)

2012-09-15

126

Design and analysis of a high fill-factor SOI diode uncooled infrared focal plane array  

NASA Astrophysics Data System (ADS)

A new concept for uncooled infrared (IR) imaging with a high fill-factor SOI diode structure has been proposed. This approach has the potential of reaching a noise equivalent temperature difference (NETD) in the milli-Kelvin range. This detector makes the IR absorbing structure cover almost the entire pixel area, in which the fill factor can reach 80%. Using the multilever structure, thermal isolation can be independently optimized without sacrificing the IR absorption area. The analysis shows that this high fill-factor SOI diode uncooled IR focal plane array can be made without failure of structure breakdown or buckling. The design shows that the sensitivity is of 7.75 × 10-3 V K-1, and the NETD is of 42 mK (f/1.0, 30Hz) which can be achieved in a 35 µm × 35 µm micromachined structure.

Jiang, Wenjing; Ou, Wen; Ming, Anjie; Liu, Zhanfeng; Zhang, Xinwei

2013-06-01

127

Microlens array coated as a high-efficiency reflective diffuser for the vacuum ultraviolet  

NASA Astrophysics Data System (ADS)

The stimulus for ultraviolet flat fields (STUFF) was developed to supply spatially flat, broadband, far ultraviolet irradiance in thermal vacuum testing of the Solar Blind Channel (SBC) of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) which will fly on Servicing Mission 3b in mid-2001. Because the SBC's 1K X 1K multi-anode microchannel array (MAMA) detector has a global count rate limit of about 300,000 events/s, it takes a minimum of roughly 10 hours of expensive test time in thermal vacuum to collect a deep flat field having 10,000 signal counts in each pixel (1% certainty in Poisson statistics). As such, a diffuser with far ultraviolet (FUV) throughput substantially higher than conventional state-of-the-art Lambertian diffuser material was sought to insure that the length of flat field exposures could be minimized. An FUV diffuser with concentrating properties was conceived as the overcoating of the convex lens side of commercially available microlens array material with Goddard Space Flight Center's (GSFC) standard aluminum-magnesium fluoride coating optimized for reflectance at 120 nm. The concept for this diffuser, a geometric optical model of its performance, visible light measurements to test that model, and the diffuser's FUV performance in STUFF relative to conventional diffuser material is presented.

Leviton, Douglas B.; Miner, Linda A.; Rice, Stephen H.; Struss, Sharon M.; Norton, Todd A.; McNeil, Brian

2000-12-01

128

The ArcCHECK diode array for dosimetric verification of HybridArc.  

PubMed

The aim of this work is to evaluate dosimetric accuracy of a new treatment modality, HybridArc, in iPlan RT Dose 4.5 (BrainLAB, Feldkirchen, Germany) using a four-dimensional diode array (ArcCHECK, Sun Nuclear Corporation, Melbourne, USA). HybridArc is able to enhance dynamic conformal arcs with inversely planned elements. HybridArc plans for various sites (intracranial and extracranial) were constructed and after that these plans were recalculated for the ArcCHECK diode array with Monte Carlo (MC) and Pencil Beam (PB) dose algorithms in iPlan RT Dose. All measurements of these HybridArc plans were performed with 6 MV photon beams of a Novalis accelerator (BrainLAB, Feldkirchen, Germany) using the ArcCHECK device without and with an insert containing an ionization chamber. Comparison of the absolute dose distributions measured and calculated in iPlan RT Dose with the MC algorithm at the cylinder of the ArcCHECK diode array for HybridArc plans gives good agreement, even for the 2% dose difference and 2 mm distance-to-agreement criteria. The PB calculations significantly differ from the ArcCHECK measurements so that the MC algorithm is found to be superior to the PB algorithm in the calculation of the HybridArc plans. One of the drawbacks of the PB calculations in iPlan RT Dose is the too large arc step size of 10°. Use of a finer angular resolution may improve the PB results significantly. PMID:21804180

Petoukhova, A L; van Egmond, J; Eenink, M G C; Wiggenraad, R G J; van Santvoort, J P C

2011-07-29

129

The ArcCHECK diode array for dosimetric verification of HybridArc  

NASA Astrophysics Data System (ADS)

The aim of this work is to evaluate dosimetric accuracy of a new treatment modality, HybridArc, in iPlan RT Dose 4.5 (BrainLAB, Feldkirchen, Germany) using a four-dimensional diode array (ArcCHECK, Sun Nuclear Corporation, Melbourne, USA). HybridArc is able to enhance dynamic conformal arcs with inversely planned elements. HybridArc plans for various sites (intracranial and extracranial) were constructed and after that these plans were recalculated for the ArcCHECK diode array with Monte Carlo (MC) and Pencil Beam (PB) dose algorithms in iPlan RT Dose. All measurements of these HybridArc plans were performed with 6 MV photon beams of a Novalis accelerator (BrainLAB, Feldkirchen, Germany) using the ArcCHECK device without and with an insert containing an ionization chamber. Comparison of the absolute dose distributions measured and calculated in iPlan RT Dose with the MC algorithm at the cylinder of the ArcCHECK diode array for HybridArc plans gives good agreement, even for the 2% dose difference and 2 mm distance-to-agreement criteria. The PB calculations significantly differ from the ArcCHECK measurements so that the MC algorithm is found to be superior to the PB algorithm in the calculation of the HybridArc plans. One of the drawbacks of the PB calculations in iPlan RT Dose is the too large arc step size of 10°. Use of a finer angular resolution may improve the PB results significantly.

Petoukhova, A. L.; van Egmond, J.; Eenink, M. G. C.; Wiggenraad, R. G. J.; van Santvoort, J. P. C.

2011-08-01

130

HPLC determination of carminic acid in foodstuffs and beverages using diode array and fluorescence detection  

Microsoft Academic Search

Summary  Carmine extracted from cochineal insects is one of the most used natural colorings for beverages and other foods. Its active\\u000a ingredient is carminic acid (7-?-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracenecarboxylic\\u000a acid). This work describes a rapid HPLC determination of carminic acid and compares diode array and fluorescence detections\\u000a for quantification. Samples with higher protein levels, such as milk and yogurt, are first treated with 1

P. R. N. Carvalho; C. H. Collins

1997-01-01

131

Field effect modulated nanofluidic diode membrane based on Al2O3/W heterogeneous nanopore arrays  

NASA Astrophysics Data System (ADS)

We developed Al2O3/W heterogeneous nanopore arrays for field effect modulated nanofluidic diodes. They are fabricated by transferring self-organized nanopores of anodic aluminium oxide into a W thin film. The nanopores are ~20 nm in diameter and 400 nm in length. After mild oxidation, approximately 10 nm WO3 grows on the surface of W, forming a conformal and dense dielectric layer. It allows the application of an electrical field through the surrounding W electrode to modulate the ionic transport across the entire membrane. Our experimental findings have potential applications in high throughput controlled delivery and electrostatic sorting of biomolecules.

Wu, Songmei; Wildhaber, Fabien; Bertsch, Arnaud; Brugger, Juergen; Renaud, Philippe

2013-05-01

132

FAST TRACK COMMUNICATION: (La,Sr)CoO3/ZnO nanofilm-nanorod diode arrays for photo-responsive moisture and humidity detection  

NASA Astrophysics Data System (ADS)

Large scale (La,Sr)CoO3 (LSCO)/ZnO nanofilm-nanorod diode arrays have been successfully fabricated using a combination of hydrothermal synthesis and colloidal deposition. With well-controlled dimensionality, crystallinity, crystal structures and device structures, LSCO/ZnO nanofilm-nanorod diode arrays display an excellent rectifying current-voltage (I-V) characteristic under ±1 V bias with negligible leakage current upon reverse bias. These nanostructured diode arrays have been found to be sensitive to UV illumination and different relative humidities at room temperature upon forward bias. A negative photoconductivity response is revealed upon UV illumination on the diode arrays as a result of the desorption process of nanofilm-nanorod surface moisture. The forward current of LSCO/ZnO nanofilm-nanorod diodes increases significantly with increasing relative humidity. These unique nanostructured diode arrays could be useful as photo-responsive moisture and humidity detectors.

Gao, Haiyong; Cai, Wenjie; Shimpi, Paresh; Lin, Hui-Jan; Gao, Pu-Xian

2010-07-01

133

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

SciTech Connect

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.

Li Jing [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Institute of Fluid Physics, CAEP, Mianyang 621900 (China); Huang Xianbin; Zhang Siqun; Yang Libing; Xie Weiping [Institute of Fluid Physics, CAEP, Mianyang 621900 (China); Pu Yikang [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2009-06-15

134

Highly efficient, spectrally pure 340 nm ultraviolet emission from AlxGa?-xN nanowire based light emitting diodes.  

PubMed

High crystal quality, vertically aligned AlxGa1-xN nanowire based double heterojunction light emitting diodes (LEDs) are grown on Si substrate by molecular beam epitaxy. Such AlxGa1-xN nanowires exhibit unique core-shell structures, which can significantly suppress surface nonradiative recombination. We successfully demonstrate highly efficient AlxGa1-xN nanowire array based LEDs operating at ?340 nm. Such nanowire devices exhibit superior electrical and optical performance, including an internal quantum efficiency of ?59% at room temperature, a relatively small series resistance, highly stable emission characteristics, and the absence of efficiency droop under pulsed biasing conditions. PMID:23899873

Wang, Q; Connie, A T; Nguyen, H P T; Kibria, M G; Zhao, S; Sharif, S; Shih, I; Mi, Z

2013-07-30

135

AlGaN-based ultraviolet light-emitting diodes using fluorine-doped indium tin oxide electrodes  

NASA Astrophysics Data System (ADS)

In this paper, improved electrical and optical properties of aluminum gallium nitride (AlGaN)-based ultraviolet light-emitting diodes using fluorine-doped indium tin oxide (F-ITO) electrodes are reported. F-doping was found to increase the work function as well as the energy bandgap of the ITO and, thereby, reduce the Shottky barrier height in contact with p-(Al)GaN. As a result, the optical transmittance increased from 79.7% to 86.9% at 380 nm, while the specific contact resistance decreased from 1.04 × 10-3 ?.cm2 to 9.12 × 10-4 ?.cm2 after F-doping, which led to an increase in the output power from 2.41 mW to 5.99 mW.

Ju Chae, Dong; Yoon Kim, Dong; Geun Kim, Tae; Mo Sung, Yun; Doeck Kim, Moon

2012-02-01

136

Deep-Ultraviolet Light-Emitting Diodes Fabricated on AlN Substrates Prepared by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were fabricated on AlN substrates. The AlN substrates were prepared by growing thick hydride vapor phase epitaxy (HVPE)-AlN layers on bulk AlN substrates prepared by physical vapor transport (PVT). After growing an LED structure, the PVT-AlN substrates were removed by mechanical polishing. This process allowed the fabrication of DUV-LEDs on HVPE-AlN substrates with high crystalline quality and DUV optical transparency. The DUV-LEDs exhibited a single emission peaking at 268 nm through the HVPE-AlN substrates. The output power as high as 28 mW was obtained at an injection current of 250 mA.

Kinoshita, Toru; Hironaka, Keiichiro; Obata, Toshiyuki; Nagashima, Toru; Dalmau, Rafael; Schlesser, Raoul; Moody, Baxter; Xie, Jinqiao; Inoue, Shin-ichiro; Kumagai, Yoshinao; Koukitu, Akinori; Sitar, Zlatko

2012-12-01

137

Electrochemical potentiostatic activation for improvement of internal quantum efficiency of 385-nm ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

The electrochemical potentiostatic activation (EPA) method is proven to effectively improve the internal quantum efficiency (IQE) of 385-nm ultraviolet light-emitting diodes (UV-LEDs). UV-LEDs wafers were immersed into 1.0 M HCl solution, and an electric voltage of 3.0 V was applied to the p-type GaN layer in order to increase the hole concentration by breaking the MgH complex. Secondary ion mass spectroscopy analysis clearly indicates the successful removal of hydrogen atoms by the EPA process, which is a ˜35% reduction of the hydrogen concentration compared to the conventional N2 annealing. The light-output power was enhanced by ˜20% at an input current of 50 mA, which originated from an improvement of the IQE by ˜20%. The reverse leakage current was also lowered by about one order after the EPA process.

Choi, Hee Seok; Kim, Hak Jun; Lee, Jung Ju; Seo, Hyo Won; Tawfik, Wael Z.; Ha, Jun-Seok; Ryu, Sang-Wan; Jun, Seong Ran; Jeong, Tak; Lee, June Key

2013-10-01

138

Individually-addressable flip-chip AlInGaN micropixelated light emitting diode arrays with high continuous and nanosecond output power.  

PubMed

Micropixelated blue (470 nm) and ultraviolet (370 nm) AlInGaN light emitting diode ('micro-LED') arrays have been fabricated in flip-chip format with different pixel diameters (72 microm and 30 microm at, respectively, 100 and 278 pixels/mm(2)). Each micro-LED pixel can be individually-addressed and the devices possess a specially designed n-common contact incorporated to ensure uniform current injection and consequently uniform light emission across the array. The flip-chip micro-LEDs show, per pixel, high continuous output intensity of up to 0.55 microW/microm(2) (55 W/cm(2)) at an injection current density of 10 kA/cm(2) and can sustain continuous injection current densities of up to 12 kA/cm(2) before breakdown. We also demonstrate that nanosecond pulsed output operation of these devices with per pixel onaxis average peak intensity up to 2.9 microW/microm(2) (corresponding to energy of 45pJ per 22ns optical pulse) can be achieved. We investigate the pertinent performance characteristics of these arrays for micro-projection applications, including the prospect of integrated optical pumping of organic semiconductor lasers. PMID:18575561

Zhang, H X; Massoubre, D; McKendry, J; Gong, Z; Guilhabert, B; Griffin, C; Gu, E; Jessop, P E; Girkin, J M; Dawson, M D

2008-06-23

139

Design of microlens illuminated aperture array fabricated by aligned ultraviolet imprinting process for optical read only memory card system  

NASA Astrophysics Data System (ADS)

A microlens illuminated aperture array (MLIAA) was designed for the multiprobe optical read only memory card system. As a method to integrate the microlens array (MLA) with the aperture array containing 1000×1000 apertures, an aligned ultraviolet imprinting process was used to satisfy the system objectives of reduced focal length and reduced spot size. An analysis using diffraction theory was performed to obtain the design tolerances for both MLIAA and the imprinting process. The maximum intensity of the optical probes at the Talbot [Philos. Mag. 9, 401 (1836)] position from the fabricated MLIAA was 12 times higher than that from the aperture array without a MLA.

Kim, Hongmin; Lee, Jeeseung; Lim, Jiseok; Kim, Seok-Min; Kang, Shinill; Kim, Young-Joo; Busch, Christopher

2006-06-01

140

Electrical Characteristics of Glucose-Sensitive Diode Arrays Based on WO3 and IrO2 for Microsensor Applications  

NASA Astrophysics Data System (ADS)

Arrays based on the contacts of sputtered WO3 and IrO2 that are covered by a glucose-oxidase-containing polymer exhibit reversible and reproducible glucose-dependent, diodelike current rectification. The glucose concentration as a function of current in the forward direction can be spatially resolved. These chemical-sensitive diode arrays are useful as a basis of construction of durable microsensors for tracing the concentration gradient of biological molecules, as in food freshness sensing.

Chao, Shuchi

2003-11-01

141

Silicon PIN diode array hybrids as building blocks for a vertex detector at an asymmetric B-factory.  

National Technical Information Service (NTIS)

Silicon PIN diode hybrid arrays are proposed as the ideal building blocks for a vertex detector at an asymmetric B-factory. The two-dimensional nature of the detector segmentation allows for the maximum in confusion elimination. Fine spatial resolution, o...

S. L. Shapiro

1990-01-01

142

Optical pumping of Rb vapor using high-power Ga1-xAlxAs diode laser arrays  

NASA Astrophysics Data System (ADS)

The use of high-power Ga1-xAlxAs diode laser arrays for optical pumping of Rb vapor has been examined both theoretically and experimentally. Our studies show that large atomic polarizations can be obtained using the broad spectral output of a diode laser array if the Rb resonance line is collisionally broadened by several atmospheres of a buffer gas. The objective was to study the effectiveness of diode laser arrays as light sources for optically pumped spin-exchange polarized 3He targets. The average Rb polarization was deduced at three different Rb vapor pressures using the polarization induced in the 3He buffer gas. The largest 3He polarization observed was 53% using a 20-W diode array with 1.9-nm full width at half maximum spectral width in 10.5 amagat of 3He. This result compares favorably with other light sources for this target. The measured average Rb polarizations are compared to theoretical calculations.

Cummings, W. J.; Häusser, O.; Lorenzon, W.; Swenson, D. R.; Larson, B.

1995-06-01

143

Breakthroughs in laser bar component packaging enable a new generation of applications for self-cooled laser diode arrays  

Microsoft Academic Search

Laser Diode Arrays continue to gain momentum as versatile, cost effective, reliable solution for a wide variety of existing and emerging illumination and pumping applications. In order to meet these growing demands, designers find themselves faced with three challenges: reducing system size, improving user serviceability, and managing cost. We developed a compact laser package platform that offers high output power,

M. Behringer; H. Koenig; A. Schmitt; S. Nagappan; R. Kojima

2005-01-01

144

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

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.

Clifford, D.J.; McKinney, D.E.; Hou, Lei; Hatcher, P.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1994-01-01

145

High-performance, high-reliability 880-nm diode laser bars and fiber-array packages  

NASA Astrophysics Data System (ADS)

The 880 nm diode laser is emerging as the source of choice for pumping Nd:YV04 laser crystals because it offers higher pumping efficiency than 808 nm diode lasers[1]. This paper reports on recent progress in the development of high power, high reliability, 880 nm laser bars. Specifically, high performance has been achieved based on Coherent's aluminum-free active (AAA) epitaxial structures while maintaining lifetimes greater than 10,000 hours. This includes 30% fill factor, 1 cm bars on conductively cooled packages (CCP) operating at 51 W with proven manufacturability. We observed power conversion efficiency (PCE) of up to 56%. These lasers have a far field fast axis divergence of 32° (FWHM), and slow axis divergence of <7° (FWHM). Typical value of the FWHM of output spectrum is 2.5 nm. These bars were used to build fiber array packages (FAPs) operating at 45 W. We have achieved FAP PCE of 50% and numerical aperture of <0.12. Reliability of both bars and FAP was shown to exceed 10000h MTBF.

Fouksman, M.; Lehconen, S.; Haapamaa, J.; Kennedy, K.; Li, J.

2006-03-01

146

A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics.  

PubMed

Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophysical instruments usable from the ground and space. MKIDs could eventually supplant semiconductor detectors for most astronomical instrumentation, and will be useful for other disciplines such as quantum optics and biological imaging. PMID:22274494

Mazin, Benjamin A; Bumble, Bruce; Meeker, Seth R; O'Brien, Kieran; McHugh, Sean; Langman, Eric

2012-01-16

147

Determination of phenolic compounds in Prunella L. by liquid chromatography-diode array detection.  

PubMed

Four species of Prunella L. (Prunella vulgaris L., Prunella laciniata L., Prunella grandiflora L. and Prunella orientalis Bornm.) belong to the family of Lamiaceae and representing popular Western and Chinese herbal medicine were examined for the content of phenolic compounds. Phenolic acids (rosmarinic acid, caffeic acid, ferulic acid, chlorogenic acid, protocatechuic acid), flavonoids (rutin, quercetin) in different quantitative proportions depending on extracts were determined by the rapid, selective and accurate method combining solvent/acid hydrolysis extraction and high performance liquid chromatography-diode array detection (HPLC-DAD). Water, methanol, butanol, acetonitrile, ethyl acetate, hexane and their acidic solutions were used to examine the efficiency of different solvent systems for the extraction of phenolic compounds. Acid hydrolysis extraction was established as the most suitable extraction method for phenolic compounds. PMID:21498022

Sahin, Saliha; Demir, Cevdet; Malyer, Hulusi

2011-03-16

148

A Single-Photon Avalanche Diode Array for Fluorescence Lifetime Imaging Microscopy  

PubMed Central

We describe the design, characterization, and demonstration of a fully integrated single-photon avalanche diode (SPAD) imager for use in time-resolved fluorescence imaging. The imager consists of a 64-by-64 array of active SPAD pixels and an on-chip time-to-digital converter (TDC) based on a delay-locked loop (DLL) and calibrated interpolators. The imager can perform both standard time-correlated single-photon counting (TCSPC) and an alternative gated-window detection useful for avoiding pulse pile-up when measuring bright signal levels. To illustrate the use of the imager, we present measurements of the decay lifetimes of fluorescent dyes of several types with a timing resolution of 350 ps.

Schwartz, David Eric; Charbon, Edoardo; Shepard, Kenneth L.

2013-01-01

149

Front-Light Source Using Inverted Organic Light-Emitting Diodes with Microcathode Arrays  

NASA Astrophysics Data System (ADS)

We have demonstrated an organic light-emitting diode (OLED) front-light source with a blinding microcathode array on a transparent electrode and a top-emission structure. Contrast ratio was improved by inserting MoO3 at the indium-tin-oxide (ITO)/Al interface. In a device of glass substrate/ITO/MoO3/meshed Al/lithium fluoride (LiF)/tris(8-hydroxyquinolinato) aluminum(III) (Alq3)/bis[N-(1-naphthyl)-N-phenyl] benzidine (?-NPD)/MoO3/semitransparent Au structure, the maximum luminance of top-side emission was 1,140 cd/m2, and the contrast ratio was 19:1. The transmittance was 44% at 555 nm.

Kohei Urata,; Shigeki Naka,; Hiroyuki Okada,

2010-04-01

150

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

SciTech Connect

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).

Liu, Bo [ORNL; Braiman, Yehuda [ORNL

2012-01-01

151

High-performance thin layer chromatography using fiber optics and diode-array detection  

NASA Astrophysics Data System (ADS)

HPTLC (High Performance Thin Layer Chromatography) is a well known and versatile separation method which shows a lot of advantages and options in comparison to other separation techniques. The method is fast and inexpensive and does not need time-consuming pretreatments. Using fiber-optic elements for controlled light-guiding, the TLC-method was significantly improved: the new HPTLC-system is able to measure simultaneously at different wavelengths without destroying the plate surface or the analytes on the surface. For registration of the sample distribution on a HPTLC-plate we developed a new and sturdy diode-array HPTLC- scanner which allows registration of spectra on the TLC- plates in the range of 198 nm to 610 nm with a spectral resolution better than 1.2 nm. The spatial resolution on plate is better than 160 micrometers . In the spectral mode, the new HPTLC-scanner delivers much more information than the commonly used TLC-scanner. The measurement of 450 spectra of one separation track does not need more than three minutes. However, in the fixed wavelength mode the contour plot can be measured within 15 seconds. In this case, the signal will be summarized and averaged over a spectral range having FWHM from 10 nm to 25 nm depending on the substance under test. The new diode-array HPTLC-scanner makes various chemometric applications possible. The new method can be used easily in clinical diagnostic systems easily, e.g. for blood and uring investigations. In addition, new applications are possible. For example, the rich structured PAHs were studied. Although the separation is incomplete the 16 compounds can be quantified using suitable wavelengths.

Spangenberg, Bernd; Klein, Karl-Friedrich; Mannhardt, J.

2002-06-01

152

GaN-based laser diodes emitting from ultraviolet to blue-green  

Microsoft Academic Search

GaN-based laser diodes (LDs), which emit from UV to blue-green, are reviewed. For fabricating the UV LDs, we used the AlInGaN active layer instead of InGaN one. We demonstrated the UV LDs with a lasing wavelength 368nm under continuous-wave (cw) operation. Moreover, we fabricated the blue-green LDs whose lasing wavelength was 480 nm. It was investigated that the relationship between

Shinichi Nagahama; Masahiko Sano; Tomoya Yanamoto; Daisuke Morita; Osamu Miki; Keiji Sakamoto; Masashi Yamamoto; Yuuji Matsuyama; Yasuhiro Kawata; Takashi Murayama; Takashi Mukai

2003-01-01

153

Indium--Tin Oxide/Al Reflective Electrodes for Ultraviolet Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

We investigated indium--tin oxide (ITO)/Al reflective electrodes for improving the light extraction efficiency of UV light-emitting diodes (LEDs). The ITO layer showed high transparency in the UV region upon optimization of the thickness and annealing temperature. As a result, the ITO/Al electrode exhibited both high reflectivity in the UV region and good contact characteristics simultaneously. Using this electrode, we succeeded in improving the light output power of a 350 nm UV-A LED.

Takehara, Kosuke; Takeda, Kenichiro; Ito, Shun; Aoshima, Hiroki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

2012-04-01

154

A novel sensor array for field based ocular ultraviolet radiation measurements.  

PubMed

The intensification of terrestrial solar ultraviolet radiation (UVR) due to the diminution of the ozone layer has promoted a variety of research into establishing the impact of this elevated potential dose of UVR on biological tissues. Certain anterior ocular tissues have been found to be susceptible to damage by incident UVR and potentially blinding diseases such as pterygium are thought to be a direct result of absorbed UVR at the nasal limbus. There is a need for more accurate quantification and localisation of incident UVR at the anterior ocular surface. A novel solar blind photodiode sensor array system has been designed, constructed and tested for this purpose. Initial measurements to quantify the irradiance across the anterior ocular surface within the latitudes known as the 'pterygium belt' provide us with a set of core data for different head orientations and tilt angles and indicate the accuracy and stability of the system. PMID:16192325

Fleming, D P; Walsh, J E; Moore, L A; Bergmanson, J P; McMahon, D

2005-09-28

155

Ultraviolet photodetector arrays assembled by dielectrophoresis of ZnO nanoparticles  

NASA Astrophysics Data System (ADS)

Sensitive and fast ultraviolet sensor arrays have been produced by dielectrophoretic assembling of ZnO nanoparticles. The sub-micron device dimensions induce low operating voltage and low power consumption. The devices are long-term stable and operate in air, oxygen and nitrogen. We have determined the absorption and desorption dynamics from the time-resolved photoresponse and conclude that oxygen or carbon dioxide are the photodesorbed species. We could derive the charge carrier concentration and mobility of the device from measurements of the low-bias and high-bias photocurrent. The presence of defects is discussed by comparing electroluminescence spectra from biased devices with photoluminescence spectral maps of ZnO dispersions.

Yan, Wenjing; Mechau, Norman; Hahn, Horst; Krupke, Ralph

2010-03-01

156

Ultraviolet photodetector arrays assembled by dielectrophoresis of ZnO nanoparticles.  

PubMed

Sensitive and fast ultraviolet sensor arrays have been produced by dielectrophoretic assembling of ZnO nanoparticles. The sub-micron device dimensions induce low operating voltage and low power consumption. The devices are long-term stable and operate in air, oxygen and nitrogen. We have determined the absorption and desorption dynamics from the time-resolved photoresponse and conclude that oxygen or carbon dioxide are the photodesorbed species. We could derive the charge carrier concentration and mobility of the device from measurements of the low-bias and high-bias photocurrent. The presence of defects is discussed by comparing electroluminescence spectra from biased devices with photoluminescence spectral maps of ZnO dispersions. PMID:20173238

Yan, Wenjing; Mechau, Norman; Hahn, Horst; Krupke, Ralph

2010-02-22

157

A theoretical model for Schottky diodes for excluding the sneak current in cross bar array resistive memory.  

PubMed

Kirchhoff's law was used to examine the electrical specifications of selection diodes, which are essential for suppressing the read interference problems in nano-scale resistive switching cross bar arrays with a high block density. The diode in the cross bar array with a 100 Mb block density should have a reverse/forward resistance ratio of > 10(8), and a forward current density of > 10(5) A cm(-2) for stable reading and writing operation. Whilst normal circuit simulators are heavily overloaded when the number of cells (m) connected to one bit and word line is larger (m > 100), which is the desired range for high density cross bar arrays, the present model can provide a simple simulation. The validity of this new method was confirmed by a comparison with the previously reported method based on a voltage estimation. PMID:20739739

Kim, Gun Hwan; Kim, Kyung Min; Seok, Jun Yeong; Lee, Hyun Ju; Cho, Deok-Yong; Han, Jeong Hwan; Hwang, Cheol Seong

2010-08-26

158

Fabrication of Organic Light-Emitting Diode Arrays on Flexible Plastic Substrates by Imprint Lithography  

NASA Astrophysics Data System (ADS)

Imprint lithography has been employed as a patterning technology for the fabrication of organic light-emitting diode (OLED) device arrays on flexible poly(ethylene terephthalate) (PET) substrates. Poly(methyl methacrylate) (PMMA) was used as the etching barrier coated on an indium tin oxide (ITO)/PET substrate. A silicon mold fabricated by photolithography was coated with a fluorinated diamond-like carbon film for easy mold-releasing. By hot pressing the silicon mold on the PMMA-coated ITO/PET substrate and etching in oxalic acid solution, patterned ITO strips were obtained. Imprint lithography was repeated to fabricate PMMA ribs vertical to the ITO strips. Finally, a matrix of 40× 40 OLED devices (300× 300 ?m2) was fabricated with an area of 25× 25 mm2 after depositing the organic and cathode layers consisting of TPD/Alq3/Bphen/LiF/Al. High quality OLED arrays on flexible PET substrate were obtained with a turn-on voltage of around 5 V, a luminous efficiency of 3 cd/A, a power efficiency of 1.2 lm/W, and a luminance of 800 cd/m2 operated at 7 V on the basis of the actual light emitting area.

Cheng, Chiao-Yang; Hong, Franklin Chau-Nan

2006-11-01

159

Reversible tuning of the wettability of carbon nanotube arrays: the effect of ultraviolet/ozone and vacuum pyrolysis treatments.  

PubMed

Among diverse types of synthetic materials, arrays of vertically aligned carbon nanotubes have attracted the most attention, mainly because of their exceptional mechanical, electrical, optical, and thermal properties. However, their wetting properties are yet to be understood. In this present study, oxygenated surface functional groups have been identified as a vital factor in controlling the wetting properties of carbon nanotube arrays. The results presented herein indeed show that a combination of ultraviolet/ozone and vacuum pyrolysis treatments can be used to vary the surface concentration of these functional groups such that the carbon nanotube array can be repeatedly switched between hydrophilic and hydrophobic. PMID:21671597

Aria, Adrianus I; Gharib, Morteza

2011-06-27

160

High speed GaN micro-light-emitting diode arrays for data communications  

NASA Astrophysics Data System (ADS)

Micro light-emitting diode (micro-LED) arrays based on an AlInGaN structure have attracted much interest recently as light sources for data communications. Visible light communication (VLC), over free space or plastic optical fibre (POF), has become a very important technique in the role of data transmission. The micro-LEDs which are reported here contain pixels ranging in diameter from 14 to 84?m and can be driven directly using a high speed probe or via complementary metal-oxide semiconductor (CMOS) technology. The CMOS arrays allow for easy, computer control of individual pixels within arrays containing up to 16×16 elements. The micro-LEDs best suited for data transmission have peak emissions of 450nm or 520nm, however various other wavelengths across the visible spectrum can also be used. Optical modulation bandwidths of over 400MHz have been achieved as well as error-free (defined as an error rate of <1x10-10) data transmission using on-off keying (OOK) non-return-to-zero (NRZ) modulation at data rates of over 500Mbit/s over free space. Also, as a step towards a more practical multi-emitter data transmitter, the frequency response of a micro-LED integrated with CMOS circuitry was measured and found to be up to 185MHz. Despite the reduction in bandwidth compared to the bare measurements using a high speed probe, a good compromise is achieved from the additional control available to select each pixel. It has been shown that modulating more than one pixel simultaneously can increase the data rate. As work continues in this area, the aim will be to further increase the data transmission rate by modulating more pixels on a single device to transmit multiple parallel data channels simultaneously.

Watson, Scott; McKendry, Jonathan J. D.; Zhang, Shuailong; Massoubre, David; Rae, Bruce R.; Green, Richard P.; Gu, Erdan; Henderson, Robert K.; Kelly, A. E.; Dawson, Martin D.

2012-10-01

161

Coherent Beam Combining of High-Power Broad-Area Laser Diode Array in CW and Pulsed Modes  

SciTech Connect

We present experimental results on coherent beam combining from large arrays of high power broad-area semiconductor lasers. Our laser array consists of 47 high-power anti-reflection coated broad-area semiconductor lasers and each laser emitter is capable of emitting 1.8 W when uncoated with a maximum array output power of 80W. The total available power from the AR coated array is approximately 40W. By using an external V-shape cavity design, we experimentally demonstrated a coherently combined beam at the output power of {approx}13 W with the 0.07 nm FWHM spectrum linewidth that is limited by the sensitivity of the optical spectrum analyzer. We also discuss coherent beam combining of high power broad area laser diode array in current driver pulse mode operation.

Liu, Bo [ORNL; Liu, Yun [ORNL; Braiman, Yehuda [ORNL

2010-01-01

162

Combinatorial fabrication and studies of intense efficient ultraviolet--violet organic light-emitting device arrays  

SciTech Connect

Arrays of ultraviolet--violet (indium tin oxide)/[copper phthalocyanine (CuPc)]/[4,4'-bis(9-carbazolyl)biphenyl (CBP)]/[2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4oxadiazole (Bu-PBD)]/CsF/Al organic light-emitting devices, fabricated combinatorially using a sliding shutter technique, are described. Comparison of the OLED electroluminescence and CBP photoluminescence spectra indicates that the emission originates from the bulk of that layer. In arrays of devices in which the thickness of the CuPc and Bu--PBD were varied, but that of CBP was fixed at 50 nm, the optimal radiance R was obtained at CuPc and Bu--PBD thicknesses of 15 and 18 nm, respectively. At 10 mA/cm{sup 2}, R was 0.38 mW/cm{sup 2}, i.e., the external quantum efficiency was 1.25%; R increased to {approx}1.2 mW/cm{sup 2} at 100 mA/cm{sup 2}.

Zou, L.; Savvate'ev, V.; Booher, J.; Kim, C.-H.; Shinar, J.

2001-10-01

163

Efficient compact watt-level deep-ultraviolet laser generated from a multi-kHz Q-switched diode-pumped solid-state laser system  

Microsoft Academic Search

Stable high-power operation in the deep ultraviolet is achieved from a multi-kHz diode-pumped multi-longitudinal-mode Q-switched Nd:YAG laser by fourth harmonic generation in an external resonant cavity and by fifth harmonic generation using sum-frequency mixing of the fourth harmonic and the residual fundamental in a ?-BBO crystal. Over 2.1 W of 266 nm radiation and 540 mW of 213 nm radiation

L. B. Chang; S. C. Wang; A. H. Kung

2002-01-01

164

Efficient compact watt-level deep-ultraviolet laser generated from a multi-kHz Q-switched diode-pumped solid-state laser system  

Microsoft Academic Search

Stable high-power operation in the deep ultraviolet is achieved from a multi-kHz diode-pumped multi-longitudinal-mode Q-switched Nd:YAG laser by fourth harmonic generation in an external resonant cavity and by fifth harmonic generation using sum-frequency mixing of the fourth harmonic and the residual fundamental in a beta-BBO crystal. Over 2.1 W of 266 nm radiation and 540 mW of 213 nm radiation

L. B. Chang; S. C. Wang; A. H. Kung

2002-01-01

165

Migration enhanced lateral epitaxial overgrowth of AlN and AlGaN for high reliability deep ultraviolet light emitting diodes  

Microsoft Academic Search

We report on the growth of low-defect thick films of AlN and AlGaN on trenched AlGaN\\/sapphire templates using migration enhanced lateral epitaxial overgrowth. Incoherent coalescence-related defects were alleviated by controlling the tilt angle of growth fronts and by allowing Al adatoms sufficient residence time to incorporate at the most energetically favorable lattice sites. Deep ultraviolet light emitting diode structures (310

R. Jain; W. Sun; J. Yang; M. Shatalov; X. Hu; A. Sattu; A. Lunev; J. Deng; I. Shturm; Y. Bilenko; R. Gaska; M. S. Shur

2008-01-01

166

Ultraviolet InGaN and GaN Single-Quantum-Well-Structure Light-Emitting Diodes Grown on Epitaxially Laterally Overgrown GaN Substrates  

Microsoft Academic Search

Ultraviolet (UV) InGaN and GaN single-quantum-well-structure light-emitting diodes (LEDs) were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. When the emission wavelength of UV InGaN LEDs was shorter than 380 nm, the external quantum efficiency (EQE) of the LED on ELOG was much higher than that on sapphire only under high-current operation. At low-current operation, both LEDs had

Takashi Mukai; Shuji Nakamura

1999-01-01

167

Large-area transparent conductive few-layer graphene electrode in GaN-based ultra-violet light-emitting diodes  

Microsoft Academic Search

We report on the development of a large-area few-layer graphene (FLG)--based transparent conductive electrode as a current spreading layer for GaN-based ultraviolet (UV) light-emitting diodes (LEDs). Large-area FLG was deposited on Cu using the chemical vapor deposition (CVD) method and subsequently transferred to the surface of the UV LED. UV light at a peak of 372 nm was emitted through

Byung-Jae Kim; Chongmin Lee; Younghun Jung; Kwang Hyeon Baik; Michael A. Mastro; Jennifer K. Hite; Charles R. Eddy; Jihyun Kim

2011-01-01

168

Nanosecond time-resolved vacuum ultraviolet spectrometer for ion diode spectroscopy  

SciTech Connect

A 1-m normal incidence spectrometer has been modified for use as a diagnostic of ion diode plasmas. To improve instrumental sensitivity, an elliptical mirror images an anode surface plasma onto the entrance slit of an [ital f]/10 normal incidence spectrometer. The detector is a time-resolving copper iodide coated microchannel plate stripline framing camera with 60-[mu]m resolution, limiting instrumental resolution to 1 A with a 600 l/mm grating in first order. Reflectivity of optics and photoelectron efficiency limit the spectral range from 400 to 2000 A. With a 600-l/mm grating the detector spans a 600-A range. Applications of the instrument may include ion source divergence measurements from Doppler broadening, electric field measurements from Stark splittings or shifts, electron temperature from mean ionization state, and magnetic field measurements on high-power [ital Z] pinches from Zeeman splitting.

Nash, T.; Noack, D.; Filuk, A.B. (Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States))

1993-09-01

169

Confinement factor and absorption loss of AlInGaN based laser diodes emitting from ultraviolet to green  

NASA Astrophysics Data System (ADS)

Confinement factor and absorption loss of AlInGaN based multiquantum well laser diodes (LDs) were investigated by numerical simulation based on a two-dimensional waveguide model. The simulation results indicate that an increased ridge height of the waveguide structure can enhance the lateral optical confinement and reduce the threshold current. For 405 nm violet LDs, the effects of p-AlGaN cladding layer composition and thickness on confinement factor and absorption loss were analyzed. The experimental results are in good agreement with the simulation analysis. Compared to violet LD, the confinement factors of 450 nm blue LD and 530 nm green LD were much lower. Using InGaN as waveguide layers that has higher refractive index than GaN will effectively enhance the optical confinement for blue and green LDs. The LDs based on nonpolar substrate allow for thick well layers and will increase the confinement factor several times. Furthermore, the confinement factor is less sensitive to alloys composition of waveguide and cladding layers, being an advantage especially important for ultraviolet and green LDs.

Zhang, L. Q.; Jiang, D. S.; Zhu, J. J.; Zhao, D. G.; Liu, Z. S.; Zhang, S. M.; Yang, H.

2009-01-01

170

Deep-ultraviolet tailored- and low-refractive index antireflection coatings for light-extraction enhancement of light emitting diodes  

NASA Astrophysics Data System (ADS)

An omnidirectional antireflection (AR) coating for a deep-ultraviolet (UV) AR band is designed and fabricated on the sapphire substrate of a deep-UV flip-chip light-emitting diode (LED) device. The two-layer AR coating uses the tailored- and low-refractive index nanoporous alumina fabricated by glancing-angle deposition methodology. The AR coating effectively matches the refractive indices between the air and sapphire substrate. At close-to-normal angles of incidence, this AR coating almost completely eliminates the Fresnel reflection at the sapphire/air interface of the deep-UV LED device. The resulting improvement of the light-extraction efficiency by 8% is in good agreement with the simulation results. For a total thickness of 172 nm for the two-layer AR coating, extinction was negligible (<2%). The results show that nanoporous alumina thin films are excellent tailored- and low-refractive index thin film materials for high-performance deep-UV AR coating applications.

Yan, Xing; Shatalov, Max; Saxena, Tanuj; Shur, Michael S.

2013-04-01

171

Study of optical anisotropy in nonpolar and semipolar AlGaN quantum well deep ultraviolet light emission diode  

NASA Astrophysics Data System (ADS)

This paper analyzes the optical polarization characteristics and internal quantum efficiency (IQE) of an AlGaN based polar, nonpolar, and semipolar deep ultra-violet (UV) light emitting diode (LED). A one dimensional model is used to solve drift-diffusion, Poisson equations, and 6 × 6 k.p Schrodinger equations to investigate band structure and emission characteristics. The light emission polarization ratios of c-plane, nonpolar, and semipolar AlGaN based deep UV LEDs with different Al compositions and injection current were studied. The study shows that the optical polarization of the c-plane AlGaN based deep UV LED is dominated by the out-plane polarization as the Al composition increases. For nonpolar and semipolar structures, the light polarization direction is mainly dominated by the in-plane polarized light which is good for the surface emitting. Finally, influences of the IQE by changing the p-type activation energy, growth orientation, and nonradiatve lifetime are studied in this paper.

Wang, Chang-Pei; Wu, Yuh-Renn

2012-08-01

172

Quantitative analysis of colistin and tiamulin in liquid and solid medicated premixes by HPLC with diode-array detection  

Microsoft Academic Search

Summary  Colistin (COL) and tiamulin (TML) are antibiotics used in veterinary practice. Diseases in animals are usually treated by\\u000a adding the drug (liquid and\\/or solid medicated premix) to animal feed. Two simple, inexpensive, and rapid methods have been\\u000a developed for quantification of COL and TML in liquid and solid medicated premixes by HPLC with diode-array detection, on\\u000a the basis of scanning

B. Cancho Grande; M. S. García Falcón; C. Pérez-Lamela; M. Rodríguez Comesaña; J. Simal Gándara

2001-01-01

173

Trace analysis of fumagillin in honey by liquid chromatography-diode array–electrospray ionization mass spectrometry  

Microsoft Academic Search

In this work a new liquid chromatography with diode array detection and electrospray ionization mass spectrometry (LC-DAD–ESI-MS) method has been developed for the determination of fumagillin residues in honey. This procedure involves a solid-phase extraction on polymeric cartridges for the isolation of fumagillin from diluted honey. Chromatographic separation of fumagillin was performed in isocratic mode, on a C18 column (150mm×4.60mm

M Nozal; J. L. Bernal; M Martín; A. Álvaro; R. Martín; M. Higes

2008-01-01

174

Trace analysis of tiamulin in honey by liquid chromatography–diode array–electrospray ionization mass spectrometry detection  

Microsoft Academic Search

A liquid chromatography with diode array or electrospray ionisation mass spectrometry detection (LC–DAD–ESI–MS) method for the determination of tiamulin residues in honey is presented. The procedure employs a solid-phase extraction (SPE) on polymeric cartridges for the isolation of tiamulin from honey samples diluted in aqueous solution of tartaric acid. Chromatographic separation of the tiamulin is performed, in isocratic mode, on

M. J. Nozal; J. L. Bernal; M. T. Martín; J. J. Jiménez; M. Higes

2006-01-01

175

Determination of curcuminoids in substances and dosage forms by cyclodextrin-mediated capillary electrophoresis with diode array detection  

Microsoft Academic Search

The present work illustrates the potential of the capillary zone electrophoresis (CZE) separation technique coupled with the\\u000a on-capillary diode array detector (DAD) for highly reliable determination of curcuminoids (curcumin, CUR, demethoxycurcumin,\\u000a DCUR, and bisdemethoxycurcumin, BCUR) in substances (commercially available plant extract) and pharmaceutical preparation\\u000a (commercial pharmaceutical capsules) with minimal sample preparation; (2-hydroxypropyl)-?-cyclodextrin (HP-?-CD) was chosen for an anionic separation of

Katarína Maráková; Peter Mikuš; Juraj Pieš?anský; Emil Havránek

2011-01-01

176

High-performance liquid chromatographic screening method for mycotoxins using new retention indexes and diode array detection  

Microsoft Academic Search

A reversed-phase high-performance liquid chromatographic (RP-HPLC) screening method for the determination of mycotoxins has been developed. The toxins were characterized by retention indexes and on-line UV spectra produced with a diode array detector (DAD). Retention indexes of mycotoxins exhibiting a wide range of polarities and chemical structures were determined during linear gradient elution with an acetonitrile\\/ water solvent system. The

Pirjo Kuronen

1989-01-01

177

Development of an HPLC\\/Diode-Array Detector Method for Simultaneous Determination of Trigonelline, Nicotinic Acid, and Caffeine in Coffee  

Microsoft Academic Search

This paper describes an adequate procedure of reversed-phase HPLC\\/diode-array detector to be used in quality control to simultaneously quantify three nitrogen compounds: trigonelline, nicotinic acid, and caffeine, in coffee samples either in the green or roasted states. The chromatographic separation was achieved using a reversed-phase column (Spherisorb ODS2) with gradient elution of 0.01M phosphate buffer pH 4.0 (A) and methanol

S. Casal; M. B. Oliveira; M. A. Ferreira

1998-01-01

178

HPLC\\/diode-array applied to the thermal degradation of trigonelline, nicotinic acid and caffeine in coffee  

Microsoft Academic Search

A simultaneous determination of trigonelline, nicotinic acid and caffeine was performed in samples of arabica and robusta coffees, before and after roasting at either different temperatures (160–240°C) or different periods of time exposures, in order to study their thermal degradation. A reverse-phase HPLC\\/Diode-array detector method was used. The results were compared with a model dry system roast of the compounds

S. Casal; M. Beatriz Oliveira; Margarida A. Ferreira

2000-01-01

179

Enhanced Light Out-Coupling Efficiency of Organic Light-Emitting Diodes with Self-Organized Microlens Arrays  

Microsoft Academic Search

A method for enhancing the light out-coupling efficiency of organic light-emitting diodes (OLEDs) by incorporating microlens arrays (MLAs) is demonstrated. MLAs made of prepolymer NOA65 were fabricated on a substrate prepatterned by the microcontact printing of hydrophobic self-assembled monolayers (SAMs). Owing to the hydrophobic effect, the lens material was self-organized on the hydrophilic regions. After assembling the MLA onto an

Wen-Kuei Huang; Wen-Sheng Wang; Hui-Chun Kan; Fang-Chung Chen

2006-01-01

180

Solution-Processed Organic Thin-Film Transistor Array for Active-Matrix Organic Light-Emitting Diode  

NASA Astrophysics Data System (ADS)

We developed a 3-in. organic thin-film transistor (OTFT) array with an ink-jetted organic semiconductor. All layers except electrodes were fabricated by solution processes. The OTFT performed well without hysteresis, and the field-effect mobility in the saturation region was 0.45 cm2 V-1 s-1, the threshold voltage was 3.3 V, and the on/off current ratio was more than 106. We demonstrated a 3-in. active-matrix organic light-emitting diode (AMOLED) display driven by the OTFT array. The display could provide clear moving images. The peak luminance of the display was 170 cd/m2.

Harada, Chihiro; Hata, Takuya; Chuman, Takashi; Ishizuka, Shinichi; Yoshizawa, Atsushi

2013-05-01

181

Conjugated polymer-silicon nanowire array hybrid Schottky diode for solar cell application  

NASA Astrophysics Data System (ADS)

The hybrid Schottky diode based on silicon nanowire arrays (SiNWs) and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) has been fabricated for high performance solar cells. The length of SiNWs on a silicon substrate, which is prepared by metal-assisted chemical etching, can be tuned by adjusting the length of the etching time. In addition, the average distances between the adjacent silicon nanowires can be controlled by changing the immersing time in a saturated PCl5 solution. The hybrid devices are made from the SiNWs with different wire lengths and various distances between adjacent wires by spin-casting PEDOT:PSS on the silicon substrates. It is found that the length and density play leading roles in the electric output characteristics. The device made from SiNWs with optimum morphology can achieve a power conversion efficiency of 7.3%, which is much improved in comparison with that of the planar one. The measurement of the transient photovoltage decay and the analysis of the current versus voltage curve indicate that the charge recombination process is a dominant factor on the device performance.

Zhang, Fute; Song, Tao; Sun, Baoquan

2012-05-01

182

Growth and fabrication of deep ultraviolet light emitting diodes on silicon carbide substrates  

NASA Astrophysics Data System (ADS)

Interest in deep ultraviolet (< 280 nm) emitters has developed rapidly in recent years, with its use in applications such as water purification, solid state lighting, and biochemical detection now being explored. The aluminum nitride and aluminum gallium nitride material systems are ideal for low cost, highly efficient emitters at these wavelengths, in the same manner that the InGaN LED revolutionized light emitters in the blue, green, and near-ultraviolet wavelengths. While the work to date on such devices have made use of sapphire as a substrate for epitaxial growth, silicon carbide has significant advantages including ease of growth and manufacture, reproducibility, and the potential for fewer dislocations in the material. This work follows the development of AlN and high-composition AlGaN films on SiC to a sufficient quality for emitter applications. A comprehensive examination of the AlN nucleation and buffer layers led to dislocation densities in the low 109cm-2. An extensive study of the n- and p-type doping of AlxGa 1-xN (x > 0.5) was undertaken to develop highly conductive material. The internal quantum efficiency of the quantum well region was significantly improved through modified growth conditions and precursor selection, and a device fabrication process was developed to obtain low turn-on voltages below 5 V and reliable device performance for over 100 hours of use. Careful thermal management of the devices through novel mask designs and improvement in packaging allowed for significant advances in light extraction, resulting in high-power LED emission at 280 nm. Packaged dies exhibited powers as high as 52 muW at 20 mA and 0.24 mW at 100 mA. The greatest obstacle to high external quantum efficiency in these devices is the absorbing nature SiC substrate. This has been successfully mitigated through two different techniques. First, distributed Bragg reflectors consisting of AlGaN/AlN stacks have been developed, with reflectivities greater than 80% at 275 nm, and incorporated into the LED. Showing even greater promise is a method to fully remove the substrate, allowing for a flip-chip LED design and increased light extraction. While such work remains in its infancy, the substrate removal has been accomplished through inductively-coupled plasma reactive-ion etching, demonstrating a three-fold improvement in light output.

Moe, Craig Gunar

183

Fluorescence-lifetime identification of biological agents using deep ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

Recently developed deep-UV light-emitting diodes (LEDs) are already used in prototype fluorescence sensors for detection of hazardous biological agents. However, increasing of the sensor ability of discrimination against common interferents requires further development of measurement technique. In particular, LED-based fluorescence lifetime measurements are to be considered as a technique supplementary to fluorescence spectral and excitation measurements. Here we report on application of UVTOP® series deep-UV LEDs developed by Sensor Electronic Technology, Inc. for real-time measurements of fluorescence lifetime in the frequency domain. LEDs with the wavelengths of 280 nm (targeted to protein excitation) and 340 nm (for excitation of coenzymes NADH and flavins) were used. The output of the LEDs was harmonically modulated at frequencies up to 100 MHz and fluorescence lifetime on the nanosecond and subnanosecond scale was estimated by measuring the phase angle of the fluorescence signal in respect of the LED output. Dual-wavelength LED-based phase-resolved measurement technique was tested for discrimination of B. globigii against a variety of interferents such as diesel fuel, paper, cotton, dust, etc. We conclude that fluorescence phase measurements have potential to improve the discrimination ability of the "detect-to-warn" optical bioparticle sensors.

Vitta, P.; Kurilcik, N.; Jursenas, S.; Zukauskas, A.; Bakien?, E.; Zhang, J.; Katona, T.; Bilenko, Y.; Lunev, A.; Hu, X.; Deng, J.; Gaska, R.

2005-10-01

184

Near-Ultraviolet Light-Emitting Devices Using Vertical ZnO Nanorod Arrays  

NASA Astrophysics Data System (ADS)

Reports on electroluminescence (EL) in solid-state, nanomaterial-based devices emitting in the lower wavelength range of the visible spectrum are limited, and the emission stability of these devices is rarely reported. We have fabricated light-emitting devices (LEDs) based on integration of n-ZnO nanorods and p-GaN films, which emit in the violet to near-ultraviolet (NUV) region. We also present data on the stability of EL in fabricated devices. Vertical arrays on ZnO nanorods, with estimated ZnO nanorod density ~108 cm-2, were grown on p-GaN films with typical length of ~4 ?m and width of ~120 nm. The NUV LEDs show low turn-on voltage (~3.0 V), small reverse saturation current (~10 ?A), and more than two orders of magnitude rectification ratio, all of which indicates a good-quality p- n junction at the p-GaN/ n-ZnO nanorod interface. The EL spectra of LEDs present an emission band centered at ~403 nm. Gaussian fitting of the EL peak revealed three emission peaks at 378 nm, 405 nm, and 431 nm with dominant emission in the NUV region. Significantly, the fabricated NUV LEDs present stable and repeatable EL characteristics, as revealed by bias-stress stability tests. The good electrical properties and stable EL performance make these nanostructure-based NUV LEDs potential candidates for mass production of next-generation lighting devices.

Jha, S.; Wang, C. D.; Luan, C. Y.; Liu, C. P.; Bin, H.; Kutsay, O.; Bello, I.; Zapien, J. A.; Zhang, W. J.; Lee, S. T.

2012-05-01

185

Arrays of wirelike microstructures of Ag with visible wavelength transparent plasmonic response at near-ultraviolet and midinfrared regions  

SciTech Connect

We present a simple masked thermal evaporation technique to fabricate arrays of wirelike Ag microstructures of width 8 {mu}m with an extremely high aspect ratio on either silicon or glass substrates. In accordance with the theory of periodic arrays of thin wires, the electromagnetic response of Ag microstructures has shown a characteristic low-frequency plasmonic behavior with a transparent visible region. Plasmon absorption is observed to be splitted largely into transverse and predominating longitudinal bands at near-ultraviolet (415 nm) and midinfrared wavelengths (2867 nm), corresponding to the oscillation of the free electrons perpendicular to and along the long axis of the wires.

Biswas, A.; Kunz, R.; Aktas, O.C.; Elbahri, M.; Adelung, R.; Takele, H.; Saeed, U.; Schuermann, U.; Zaporojtchenko, V.; Faupel, F. [Nano and Microstructure Fabrication Laboratory, Lehrstuhl fuer Materialverbunde, Technische Fakultaet der CAU, Kaiserstrasse 2, D-24143, Kiel (Germany)

2004-09-13

186

Low frequency noise of gallium nitride-based deep ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

This study covers the investigation of deep UV GaN-based light emitting diodes using low frequency noise characterization. Using this technique, device improvements were analyzed as feedback to developers and practical parameters were created for system use. AlGaN LEDs emit wavelengths into the deep UV spectral region (lambda < 290 nm). These devices are an integral component for applications including biological hazard detection systems, biological experimentation, food and water sterilization, non-line-of-sight short range communication, counterfeit identification, photolithography, and general white lighting. The current technological trend demonstrates a decrease in material quality and device performance with decreasing wavelength. However, progress has allowed for its commercialization in a relatively short period of time. Characterization of material and device improvements provides feedback for changes in development. Secondly, methods to determine the reliability and stability of these devices are essential to the applications for which they are used. One such method is through optical and current low frequency noise (LFN) measurements in which both system related parameters such as a signal-to-noise ratio for light sources and insight into the fundamental physics within the devices can be determined. The quality of the device can be compared before costly integration into systems that require low noise, high reliability, and optical stability. It not only quantifies performance limiting noise levels, but it is known to be a sensitive, nondestructive measure of material quality and reliability. The research highlighted in this thesis demonstrates a new measurement technique in analyzing the light intensity fluctuations through low frequency optical noise. From this work, a proposed figure-of-merit is presented. Low frequency current noise was performed as a well known indicator of material quality. Each technique compares LEDs grown by SET Inc. LEDs of varying wavelengths along the UV spectrum, with different growth methods and device structures. The cross-correlation between optical and current noise was analyzed to further understand the physical mechanism of low frequency noise in LEDs. Finally, low frequency current noise analysis for the packaging process and electrical degradation were determined.

Sawyer, Shayla Maya Louise

187

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

ERIC Educational Resources Information Center

|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…

Jones, Dianna G.

1985-01-01

188

Simultaneous Determination of Dihydromyricetin and Resveratrol in Ampelopsis sinica (Miq.) W.T. Wang by High-Performance Liquid Chromatography Coupled with a Diode Array Detection Method.  

PubMed

Yeputaoteng is the dried ground part of Ampelopsis sinica (Miq.) W.T. Wang, which is widely used in traditional Chinese medicine for preventing and treating tumors, chronic nephritis, hepatitis, rubella, traumatic bleeding, stomach heat and vomiting. A simple and reliable method using high-performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the simultaneous determination of dihydromyricetin and resveratrol in Yeputaoteng. The chromatographic analysis was performed on a Dikma C18 column (250 × 4.6 mm, 5 µm) at 30°C with a gradient elution of acetonitrile and 0.1% phosphoric acid at a flow rate of 1 mL/min, and used ultraviolet detection at 292 and 306 nm. The established method was validated in terms of linearity, precision, reproducibility, stability and recovery. The calibration curves showed good linear regression (R(2) > 0.9994). Limits of detection and quantification fell in the ranges of 1.47-2.48 and 2.93-4.97 µg/mL, respectively. The mean recovery of dihydromyricetin and resveratrol was 104.1% [relative standard deviation (RSD): 2.94%] and 100.8% (RSD: 2.80%), respectively. The quantitative results indicated that the HPLC-DAD method can be effectively applied to the quality control of Yeputaoteng and its preparations. PMID:23616429

Jin, Min-Yi; Ding, Yue; Zhang, Tong; Cai, Zhen-Zhen; Tao, Jian-Sheng

2013-04-24

189

Azimuthally isotropic irradiance of GaN-based light-emitting diodes with GaN microlens arrays.  

PubMed

In this paper, the irradiance-modifying concept is proposed by introducing a microlens array on the p-GaN layer of GaN-based light-emitting diode (LED). Every microlens can locally modulate photons emitting from a micro-scaled active region of multiple quantum wells (MQWs) just beneath the microlens. The azimuthally isotropic irradiance from the GaN-based LED with microlens arrays is demonstrated numerically and experimentally. To realize such a novel LED, one-dimensional GaN microlens array with a period of 1.6 microm and a filling factor of 0.64 are fabricated by using dry etching. According to experimental results, the azimuthally isotropic light emission of proposed LED is observed. By using the angular-resolved photoluminescence, its intensity variation corresponding to the azimuth angles is as low as 10% within the angle region of +/-50 degrees. PMID:19365437

Wu, Mount-Learn; Lee, Yun-Chih; Yang, Shih-Pu; Lee, Po-Shen; Chang, Jenq-Yang

2009-04-13

190

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

NASA Astrophysics Data System (ADS)

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.

Iwasaki, Jun-ya; Horiuchi, Toshiyuki

2012-05-01

191

Variable FOV optical illumination system with constant aspect ratio for 2-D array lasers diodes  

NASA Astrophysics Data System (ADS)

In this contribution we present a compact system to create an illumination distribution with a constant aspect ratio 3:4 and FOV from 0.4 to 1 degree. Besides, the system must delivery 40 W from 170 individual laser diodes placed in a regular 2-D array distribution of 10 x 20 mm. The main problem that must be solved is the high asymmetry of the individual sources; emission divergence's ratio 3:73 (0.3 vs. 7.4 degree) combined with the flux holes due to the laser's heat drain. In one axis (divergence of 0.3º) the best design strategy approach is a Galileo telescope but in the other axis a collimator configuration is the best solution. To manage both solutions at the same time is the aim of this contribution. Unfortunately for the Galileo strategy, source dimensions are too large so aspheric surfaces are needed, and the collimator configuration requires an EFL that must change from 573 to 1432 mm. The presented solution uses a set of three fixed anamorphic lenses, two of them pure cylinders, combined with a wheel of anamorphic lenses that have the function to change the FOV of the system. The most important contribution of the design is to obtain a constant final ratio 3:4 from an initial ratio of 3:73 with no losses of energy. The proposed solution produces an illumination pattern with peaks and valleys lower than 40%. This pattern distribution might be unacceptable for a standard illumination solution. However, the actual FOV is used to illuminate far away targets thus air turbulence is enough to homogenize the distribution on the target.

Arasa, J.; de la Fuente, M. C.; Ibañez, C.

2008-09-01

192

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

SciTech Connect

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.

Wong, J. H. D.; Fuduli, I.; Carolan, M.; Petasecca, M.; Lerch, M. L. F.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B. [Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia and Faculty of Medicine, University of Malaya, Kuala Lumpur 50603 (Malaysia); Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia); Illawarra Cancer Care Centre, Wollongong Hospital, NSW 2500, Australia and Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia); Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia); SPA BIT, Kiev, Ukraine, 04136 (Ukraine); Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia)

2012-05-15

193

White light emission from blue and near ultraviolet light-emitting diodes precoated with a Sr3SiO5:Ce3+,Li+ phosphor.  

PubMed

White-light-emitting diodes (WLEDs) were fabricated by combining a yellow Sr3SiO5:Ce3+, Li+ phosphor with a blue light-emitting diode (LED) (460 nm chip) or a near ultraviolet (n-UV) LED (405 nm chip), respectively. Color temperature (Tc) of Sr3SiO5:Ce3+, Li+-based WLEDs could be tuned from 6500 to 100,000 K (blue LED pumping) and from 4900 to 50,000 K (n-UV LED pumping) without mixing with other phosphors. The blue LED-pumped WLED showed excellent white light (luminous efficiency=31.7 lm/W, Tc=6857 K) at 20 mA. This WLED showed a stable color coordinates property against an increase of the forward current. An n-UV LED-pumped WLED also showed bright white light (25.0 lm/W, 5784 K) at 20 mA. PMID:18059961

Jang, Ho Seong; Jeon, Duk Young

2007-12-01

194

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

Microsoft Academic Search

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

Hideki Hirayama; Tohru Yatabe; Norimichi Noguchi; Norihiko Kamata

2008-01-01

195

High intensity light emitting diode array as an alternative exposure source for the fabrication of electrophoretic microfluidic devices.  

PubMed

A commercially available array of light emitting diodes (LEDs), namely a UV Shark series LED high flux array, was evaluated as a light source for photolithographic patterning of SU-8 photoresist for the fabrication of templates suitable to make poly(dimethylsiloxane) (PDMS) microchips for electrophoresis. At a distance of 15 cm from the substrate, a relatively even intensity of 0.76+/-0.05 mW/cm(2) was obtained over an area sufficient for patterning a 10 cm (4 in.) silicon wafer. The exposure source was evaluated using a spiral mask design covering a 10 cm wafer. PDMS replicates of this template made in a 25 microm thick layer of SU-8 3025 showed little variation in width over the surface of the substrate, with a variation of 3.2% RSD (n=36) and a maximum range in widths of 7.8% of the mean channel width. The use of the optional metal reflector available with the LED array provided partial collimation of the light allowing near vertical structures to be produced across the entire wafer, something which was not possible without the reflector. SU-8 masters prepared using the LED array were compared to masters made using an alternative cheap lithographic source, namely a gel crosslinker. The SU-8 features were much narrower with the LED array than the crosslinker due to the multiple light sources in the crosslinker. A PDMS microchip made using a SU-8 template created using the Shark UV LED array was used for the electrophoretic separation of three anionic fluorescent dyes, with efficiencies up to 32,000 plates. Given that the LED array can be purchased and assembled for less than US$ 500, the Shark UV LED array is a promising alternative to more expensive lithographic light sources and will have significant appeal to many researchers wishing to undertake research in microfluidics around the world. PMID:18930463

Breadmore, Michael C; Guijt, Rosanne M

2008-10-02

196

Toward compact millimeter-wave diode in thin stacked-hole array assisted by a dielectric grating  

NASA Astrophysics Data System (ADS)

Unidirectional transmission in thin stacked hole arrays (SHAs), whose spatial inversion symmetry is broken by adding a dielectric grating at one of the interfaces, is theoretically predicted and experimentally validated in the millimeter-wave regime. It appears at a fixed nonzero angle of incidence due to hybridization of SHA resonances with diffraction effects. In contrast to the earlier suggested structures with the diffraction relevant unidirectional transmission mechanism, the nonsymmetric diode-like structure founded on the intrinsically subwavelength SHA, which supports left-handed propagation, is less than one wavelength thick.

Beruete, M.; Serebryannikov, A. E.; Torres, V.; Navarro-Cía, M.; Sorolla, M.

2011-10-01

197

Amplified luminescence and output characteristics of high-power InGaAs/AlGaAs laser diode arrays  

SciTech Connect

The influence of the amplified luminescence (AL) and spreading of nonequilibrium charge carriers on the threshold, dynamic, and power characteristics of high-power InGaAs/AlGaAs laser diode arrays (LDAs) is studied. It is found that, depending on the near-field fill factor, the contribution of AL-induced recombination to the lasing threshold of LDAs may reach 11%. It is shown that the losses of the LDA pump energy, associated with the AL, increase with the injection current growth above its threshold value because of the increase in the intensity of radiation, propagating normally to the LDA cavity axis. (lasers)

Kabanov, V V; Lebiadok, E V; Ramanenka, A A; Ryabtsev, A G; Ryabtsev, G I; Shchemelev, M A; Mekhta, S K

2011-02-28

198

Enhanced Light Out-Coupling Efficiency of Organic Light-Emitting Diodes with Self-Organized Microlens Arrays  

NASA Astrophysics Data System (ADS)

A method for enhancing the light out-coupling efficiency of organic light-emitting diodes (OLEDs) by incorporating microlens arrays (MLAs) is demonstrated. MLAs made of prepolymer NOA65 were fabricated on a substrate prepatterned by the microcontact printing of hydrophobic self-assembled monolayers (SAMs). Owing to the hydrophobic effect, the lens material was self-organized on the hydrophilic regions. After assembling the MLA onto an OLED, the optical measurement showed that the light out-coupling efficiency of the OLED with MLAs is increased without any apparent color shift.

Huang, Wen-Kuei; Wang, Wen-Sheng; Kan, Hui-Chun; Chen, Fang-Chung

2006-10-01

199

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

NASA Astrophysics Data System (ADS)

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.

Hattori, Masashi; Noda, Kei; Matsushige, Kazumi

2011-09-01

200

Astigmatic Wavefront Correction of a Gain-Guided Laser Diode Array Using Anamorphic Diffractive Microlenses.  

National Technical Information Service (NTIS)

A diffractive microlens array was used to collimate a one dimensional array of gain guided AlGaAs lasers. The astigmatism of the lasers was removed by using anamorphic microlenses. The Strehl ratio of the resulting wavefront was 0.98. The microlens array ...

J. R. Leger M. L. Scott P. Bundman M. P. Griswold

1988-01-01

201

Design of a portable noninvasive photoacoustic glucose monitoring system integrated laser diode excitation with annular array detection  

NASA Astrophysics Data System (ADS)

A near-infrared photoacoustic glucose monitoring system, which is integrated dual-wavelength pulsed laser diode excitation with eight-element planar annular array detection technique, is designed and fabricated during this study. It has the characteristics of nonivasive, inexpensive, portable, accurate location, and high signal-to-noise ratio. In the system, the exciting source is based on two laser diodes with wavelengths of 905 nm and 1550 nm, respectively, with optical pulse energy of 20 ?J and 6 ?J. The laser beam is optically focused and jointly projected to a confocal point with a diameter of 0.7 mm approximately. A 7.5 MHz 8-element annular array transducer with a hollow structure is machined to capture photoacoustic signal in backward mode. The captured signals excitated from blood glucose are processed with a synthetic focusing algorithm to obtain high signal-to-noise ratio and accurate location over a range of axial detection depth. The custom-made transducer with equal area elements is coaxially collimated with the laser source to improve the photoacoustic excite/receive efficiency. In the paper, we introduce the photoacoustic theory, receive/process technique, and design method of the portable noninvasive photoacoustic glucose monitoring system, which can potentially be developed as a powerful diagnosis and treatment tool for diabetes mellitus.

Zeng, Lvming; Liu, Guodong; Yang, Diwu; Ren, Zhong; Huang, Zhen

2008-12-01

202

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

NASA Astrophysics Data System (ADS)

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 × 107 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).

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

2013-03-01

203

Linewidth narrowing and wavelength stabilization of high-power laser diode array by use of volume Bragg grating  

NASA Astrophysics Data System (ADS)

The characteristics of the LDA operating in the steady state are analyzed. The carrier density, oscillating frequency, photon density compared to those in free-running state operating in the in-phase mode are analyzed. In this paper, linewidth narrowing and wavelength stabilization of a high-power laser diode array are obtained by using an external cavity consisting of Volume Bragg Grating (VBG) with the reflectivity of 15 %. At the driven current up to 40 A, an output power of 28 W is obtained with the linewidth down to 0.3 nm, which corresponds to the efficiency of 93.3% compared to the output power in free-running LDA. The intensity of the external-cavity LDA is improved by a factor of approximately 3.3, and the wavelength is stabilized at 808nm determined by the VBG. This kind of laser diode array has potential applications in pumping solid-state lasers, medical treatment and gas sensing.

Wang, Hao; Yuan, Xiao

2011-11-01

204

Radial-symmetric N-way TEM-line IMPATT diode power combining arrays  

NASA Astrophysics Data System (ADS)

Two basic types of IMPATT diode power combiners, lossless radially symmetric N-way combiners and resistively stabilized symmetric N-way combiners, are discussed. The conditions for oscillation are reviewed and specified in terms of circuit eigenvectors and eigenvalues for the case of identical active devices. At X-band, the lossless combiner demonstrated a locked oscillator bandwidth several times larger than TM(0n0)-mode combiners in a simple r geometry. Predictions for a 30-W ten-diode lossless X-band combiner indicate a 1-dB locking bandwidth of 300 MHz and 10-dB gain; for a 100-W resistively stabilized 10-GHz ten-diode combiner, a 150 MHz locking bandwidth and a 10-dB locking gain are predicted.

Peterson, D. F.

1982-02-01

205

885-nm laser diode array pumped ceramic Nd:YAG master oscillator power amplifier system  

NASA Astrophysics Data System (ADS)

The objective of this effort is to develop more reliable, higher efficiency diode pumped Nd:YAG laser systems for space applications by leveraging technology investments from the DoD and other commercial industries. Our goal is to design, build, test and demonstrate the effectiveness of combining 885 nm laser pump diodes and the use of ceramic Nd:YAG for future flight missions. The significant reduction in thermal loading on the gain medium by the use of 885 nm pump lasers will improve system efficiency.

Yu, Anthony W.; Li, Steven X.; Stephen, Mark A.; Seas, Antonios; Troupaki, Elisavet; Vasilyev, Aleksey; Conley, Heather; Filemyr, Tim; Kirchner, Cynthia; Rosanova, Alberto

2010-04-01

206

Compact ultraviolet laser  

Microsoft Academic Search

This dissertation presents theoretical analysis and experimental investigation of a compact ultraviolet laser, comprising an unstable resonator semiconductor (URSL) laser-pumped potassium titanyl phosphate (KTP) periodically segmented waveguide (PSW) laser. A comprehensive survey of existing short wavelength visible and near ultraviolet laser technologies suitable for the development of compact ultraviolet lasers is presented. This survey establishes the suitability of a diode-pumped

Brian Walter Baird

1997-01-01

207

Submicrometre bridge electrode arrays for light emitting polymer diodes and photodiodes  

Microsoft Academic Search

We have used a method of soft lithography, soft imprinting, to fabricate submicrometre structures to be used as light emitting polymer diodes and photodiodes. Using a silicone rubber replica (stamp) of an optical diffraction grating we transferred the grating pattern to an organic resist layer by placing the stamp in conformal contact with the resist. The transferred pattern was subsequently

Tobias Nyberg; Fengling Zhang; Olle Inganäs

2002-01-01

208

Optimization and Fabrication of III-Nitride Light-Emitting Diodes with Self-assembled Colloidal-based Convex Microlens Arrays  

Microsoft Academic Search

Improvement of light extraction efficiency of InGaN light emitting diodes (LEDs) using colloidal-based SiO2 \\/ polystyrene microlens arrays was demonstrated. The size effect of the SiO2 microspheres and the thickness of the polystyrene layer on the light extraction efficiency were studied. Ray tracing simulations show that the use of microlens arrays leads to increase in light extraction efficiency by 2.6

Yik-Khoon Ee; P. Kumnorkaew; James F. Gilchrist; R. A. Arif; H. Tong; N. Tansu

2008-01-01

209

Diffraction-limited operation from monolithically integrated diode laser array and self-imaging (Talbot) cavity  

SciTech Connect

The monolithic integration of a linear array and a separately pumped self-imaging Talbot cavity has resulted in diffraction-limited single-lobe output beams to output powers in excess of 100 mW/facet. A study was made of the device operation as a function of the drive currents applied to the array region and the Talbot cavity.

Jansen, M.; Yang, J.J.; Ou, S.S.; Botez, D.; Wilcox, J.; Mawst, L. (TRW Space Technology Group, Group Research Staff, One Space Park, Redondo Beach, California 90278 (US))

1989-11-06

210

Temperature-controlled transfer and self-wiring for multi-color light-emitting diode arrays  

NASA Astrophysics Data System (ADS)

We propose an integration method for arranging light-emitting diode (LED) bare chips on a flexible substrate for multi-color inorganic LED displays. The LED bare chips (240 µm × 240 µm × 75 µm), which were diced on an adhesive sheet by the manufacturer, were transferred to a flexible polyimide substrate by our temperature-controlled transfer (TCT) and self-wiring (SW) processes. In these processes, low-melting point solder (LMPS) and poly-(ethylene glycol) (PEG) worked as adhesive layers for the LED chips during the TCT processes, and the adhesion force of the LMPS and PEG layers was controlled by changing the temperature to melt and solidify the layers. After the TCT processes, electrical connection between the transferred LED chips and the flexible substrate was automatically established via the SW process, by using the surface tension of the melted LMPS. This TCT/SW method enabled us to (i) handle arrays of commercially available bare chips, (ii) arrange multiple types of chips on the circuit substrate by simply repeating the TCT processes and (iii) establish electrical connection between the chips and the substrate automatically. Applying this transfer printing and wiring method, we experimentally demonstrated a 5-by-5 flexible LED array and a two-color (blue and green) LED array.

Onoe, Hiroaki; Nakai, Akihito; Iwase, Eiji; Matsumoto, Kiyoshi; Shimoyama, Isao

2009-07-01

211

Determination of steroid sex hormones in urine matrix by stir bar sorptive extraction based on monolithic material and liquid chromatography with diode array detection  

Microsoft Academic Search

A simple, rapid and sensitive method for simultaneous determination of six steroid sex hormones in urine matrix was developed by the combination of stir bar sorptive extraction (SBSE) with high performance liquid chromatography (HPLC) and diode array detection (DAD). A poly (methacrylic acid stearyl ester–ethylene dimethacrylate) was synthesized and selected as SBSE extraction medium. To achieve the optimum extraction performance,

Xiaojia Huang; Dongxing Yuan; Benli Huang

2008-01-01

212

Determination of steroid sex hormones and related synthetic compounds considered as endocrine disrupters in water by liquid chromatography–diode array detection–mass spectrometry  

Microsoft Academic Search

In this study, a procedure for the determination of various naturally occurring hormones and of some related synthetic chemicals, commonly used for birth control and treatment of certain hormonal disorders and cancers, in water is described. The procedure includes solid-phase extraction of 0.5 l of water and subsequent analysis of the extract by liquid chromatography with diode array detection and

Maria J López de Alda; Damià Barceló

2000-01-01

213

DETERMINATION OF CARBENDAZIM IN WATER BY HIGH-PERFORMANCE IMMUNOAFFINITY CHROMATOGRAPHY ON-LINE WITH HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH DIODE-ARRAY OR MASS SPECTROMETRIC DETECTION  

EPA Science Inventory

An automated method for the determination of carbendazim in water that combines high-performance immunoaffinity chromatography (HPIAC), high-performance liquid chromatography (HPLC) in the reversed-phase mode, and detection by either UV-Vis diode array detector (DAD) spectroscopy...

214

Improved light emission through an AlGaN coalescence layer of 365-nm ultraviolet lighting-emitting diodes on patterned sapphire substrates  

NASA Astrophysics Data System (ADS)

Ultraviolet (UV), 365-nm light-emitting diodes (LEDs) were grown on an AlGaN template on patterned sapphire substrates (PSS) and then compared with those grown on a conventional GaN template. Complete coalescence was achieved by using AlGaN up to 4.9% Al composition, although the AlGaN template displayed more dislocations than the GaN template. The 365-nm UV LEDs on the AlGaN template showed no emission absorption in the template, as seen in the GaN template, because AlGaN is sufficiently far from the absorption edge of GaN. As a result, a total emission enhancement about 4 times stronger than that obtained w hat using the GaN template was obtained at 80 mA.

Kwak, Young-Sun; Lee, Jun-Youb; Choi, Hye-Rin; Kim, Do-Hyung; Lee, Dong-Seon; Jeon, Seong-Ran; Kong, Bo-Hyun; Cho, Hyung-Koun

2013-03-01

215

Influence of pulse width on electroluminescence and junction temperature of AlInGaN deep ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

The behavior of electroluminescence (EL) and junction temperature of AlInGaN deep ultraviolet light-emitting diodes under pulse-width modulation is investigated. The redshift of both emissions from quantum-well (P1) and localized (P2) states in the EL spectra and the increase of intensity ratio of P1 to P2 are observed with the increase of duty cycle. The photoluminescence of p-GaN contact layer is adopted to measure the junction temperature, which shows a linear relation with the duty cycle. Meanwhile, the duty cycle coefficient of junction temperature increases with the increase of injection current. The EL behaviors are explained by the thermal effect induced by pulse current at high duty cycle.

Zhang, J. C.; Zhu, Y. H.; Egawa, T.; Sumiya, S.; Miyoshi, M.; Tanaka, M.

2008-05-01

216

Migration enhanced lateral epitaxial overgrowth of AlN and AlGaN for high reliability deep ultraviolet light emitting diodes  

SciTech Connect

We report on the growth of low-defect thick films of AlN and AlGaN on trenched AlGaN/sapphire templates using migration enhanced lateral epitaxial overgrowth. Incoherent coalescence-related defects were alleviated by controlling the tilt angle of growth fronts and by allowing Al adatoms sufficient residence time to incorporate at the most energetically favorable lattice sites. Deep ultraviolet light emitting diode structures (310 nm) deposited over fully coalesced thick AlN films exhibited cw output power of 1.6 mW at 50 mA current with extrapolated lifetime in excess of 5000 hours. The results demonstrate substantial improvement in the device lifetime, primarily due to the reduced density of growth defects.

Jain, R.; Sun, W.; Yang, J.; Shatalov, M.; Hu, X.; Sattu, A.; Lunev, A.; Deng, J.; Shturm, I.; Bilenko, Y.; Gaska, R. [Sensor Electronic Technology, Inc., 1195 Atlas Road, Columbia, South Carolina 29209 (United States); Shur, M. S. [Electrical Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy New York 12180 (United States)

2008-08-04

217

Nitrogen- and fluorine-doped ZrO2: a promising p-n junction for an ultraviolet light-emitting diode.  

PubMed

In this work we study the effect of nitrogen (N) and fluorine (F) doping on the electronic properties of ZrO(2) by using ab initio electronic structure calculations. Our calculations show the importance of on-site Coulomb correlation in estimating the correct band gap of ZrO(2). The N and F doping provide hole- and electron-type impurity states in the band gap closer to the top of the valence band and the bottom of the conduction band, respectively. The formation of such impurity states may be exploited in fabricating a p-n junction expected to be useful in making an ultraviolet light-emitting diode. PMID:22809869

Pandey, Sudhir K

2012-07-18

218

Ultraviolet electroluminescence from nitrogen-doped ZnO-based heterojuntion light-emitting diodes prepared by remote plasma in situ atomic layer-doping technique.  

PubMed

Remote plasma in situ atomic layer doping technique was applied to prepare an n-type nitrogen-doped ZnO (n-ZnO:N) layer upon p-type magnesium-doped GaN (p-GaN:Mg) to fabricate the n-ZnO:N/p-GaN:Mg heterojuntion light-emitting diodes. The room-temperature electroluminescence exhibits a dominant ultraviolet peak at ? ? 370 nm from ZnO band-edge emission and suppressed luminescence from GaN, as a result of the decrease in electron concentration in ZnO and reduced electron injection from n-ZnO:N to p-GaN:Mg because of the nitrogen incorporation. The result indicates that the in situ atomic layer doping technique is an effective approach to tailoring the electrical properties of materials in device applications. PMID:23259506

Chien, Jui-Fen; Liao, Hua-Yang; Yu, Sheng-Fu; Lin, Ray-Ming; Shiojiri, Makoto; Shyue, Jing-Jong; Chen, Miin-Jang

2012-12-31

219

Note: design and characterization of an optical light source based on mixture of white and near-ultraviolet light emitting diode spectra.  

PubMed

An optical light source based on a solid-state lighting technology is designed. Main components of the light source are a phosphor-converted white and a near-ultraviolet (near-UV) light emitting diodes (LEDs), the spectral power distributions (SPDs) of which are mixed using a fiber optic combiner. The near-UV LED is used for improving insufficient SPDs of the white LED at shorter wavelengths of the visible radiation. Stable direct current power supplies are also designed and used to operate each of the LED separately. Three steps of the driving current can be selected by means of serial resistors altered with a commutator at nominal current values of ?40%, ?50%, and ?69%. The light source can be used for many characteristic measurements within the scope of photometry and colorimetry. PMID:21529055

Sametoglu, Ferhat; Celikel, Oguz

2011-04-01

220

Breakthroughs in laser bar component packaging enable a new generation of applications for self-cooled laser diode arrays  

NASA Astrophysics Data System (ADS)

Laser Diode Arrays continue to gain momentum as versatile, cost effective, reliable solution for a wide variety of existing and emerging illumination and pumping applications. In order to meet these growing demands, designers find themselves faced with three challenges: reducing system size, improving user serviceability, and managing cost. We developed a compact laser package platform that offers high output power, good reliability, and different beam collimation options. Both active cooling and passive cooling is possible with this new packaging concept. It has the footprint of the TO263 package and is based on packaging concepts that were developed for high power semiconductor devices and high volume opto semiconductor products like Light Emitting Diodes. High efficiency and high power laser bars are critical to various pumping and material processing applications. Wavelength multiplexing is an option to increase output power from laser systems. Typical wavelengths used are 808nm, 940nm and 980nm. We discuss the results of wavelength multiplexing of 880nm high power lasers.

Behringer, M.; Koenig, H.; Schmitt, A.; Nagappan, S.; Kojima, R.

2005-09-01

221

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

NASA Astrophysics Data System (ADS)

We report phosphorescent organic light-emitting diodes with a substantially improved light outcoupling efficiency and a wider angular distribution through applying a layer of zinc oxide periodic nanopillar arrays by pattern replication in non-wetting templates technique. The devices exhibited the peak emission intensity at an emission angle of 40° compared to 0° for reference device using bare ITO-glass. The best device showed a peak luminance efficiency of 95.5 +/- 1.5 cd/A at 0° emission (external quantum efficiency--EQE of 38.5 +/- 0.1%, power efficiency of 127 +/- 1 lm/W), compared to that of the reference device, which has a peak luminance efficiency of 68.0 +/- 1.4 cd/A (EQE of 22.0 +/- 0.1%, power efficiency of 72 +/- 1 lm/W).

Liu, S. W.; Wang, J. X.; Divayana, Y.; Dev, K.; Tan, S. T.; Demir, H. V.; Sun, X. W.

2013-02-01

222

GaAs pillar array-based light emitting diodes fabricated by metal-assisted chemical etching  

NASA Astrophysics Data System (ADS)

We demonstrate GaAs pillar array-based light emitting diodes (LEDs) with axial p-i-n junctions fabricated using a room-temperature metal-assisted chemical etching (MacEtch) method. Variations in vertical etch rates for all three doping types of GaAs are investigated as a function of etching temperature, oxidant/acid concentration ratio, and dilution of the etching solution. Control over nanopillar morphologies is demonstrated, simply through modification of the etching conditions. Optical emission enhancement from the MacEtched p-i-n GaAs nanopillar LED is observed, relative to the non-etched planar counterpart, through room-temperature photoluminescence and electroluminescence characterization.

Mohseni, Parsian K.; Hyun Kim, Seung; Zhao, Xiang; Balasundaram, Karthik; Dong Kim, Jeong; Pan, Lei; Rogers, John A.; Coleman, James J.; Li, Xiuling

2013-08-01

223

Trace analysis of tiamulin in honey by liquid chromatography-diode array-electrospray ionization mass spectrometry detection.  

PubMed

A liquid chromatography with diode array or electrospray ionisation mass spectrometry detection (LC-DAD-ESI-MS) method for the determination of tiamulin residues in honey is presented. The procedure employs a solid-phase extraction (SPE) on polymeric cartridges for the isolation of tiamulin from honey samples diluted in aqueous solution of tartaric acid. Chromatographic separation of the tiamulin is performed, in isocratic mode, on a C18 column using methanol and ammonium carbonate 0.1% in water, in proportion (30:70, v/v). Average analyte recoveries were from 88 to 106% in replica sets of fortified honey samples. The LC-ESI-MS method detection limits differ from 0.5 microg kg(-1) for clear honeys to 1.2 microg kg(-1) for dark honeys. The developed method has been applied to the analysis of tiamulin residues in multifloral honey samples collected from veterinary treated beehives. PMID:16574136

Nozal, M J; Bernal, J L; Martín, M T; Jiménez, J J; Bernal, J; Higes, M

2006-03-30

224

Generation of laser-polarized xenon using fiber-coupled laser-diode arrays narrowed with integrated volume holographic gratings.  

PubMed

Volume holographic gratings (VHGs) can be exploited to narrow the spectral output of high-power laser-diode arrays (LDAs) by nearly an order of magnitude, permitting more efficient generation of laser-polarized noble gases for various applications. A approximately 3-fold improvement in (129)Xe nuclear spin polarization, P(Xe), (compared to a conventional LDA) was achieved with the VHG-LDA's center wavelength tuned to a wing of the Rb D(1) line. Additionally, an anomalous dependence of P(Xe) on the xenon density within the OP cell is reported-including high P(Xe) values (>10%) at high xenon partial pressures (approximately 1000 torr). PMID:19162517

Nikolaou, Panayiotis; Whiting, Nicholas; Eschmann, Neil A; Chaffee, Kathleen E; Goodson, Boyd M; Barlow, Michael J

2008-12-24

225

Recover soft x-ray spectrum using virtual flat response channels with filtered x-ray diode array  

NASA Astrophysics Data System (ADS)

A method for the recovery of soft x-ray spectra in indirect-drive inertial confinement fusion experiments is presented. Virtual detection channels with bandpass responses are obtained using linear combinations of the channel response functions of a filtered x-ray diode array and a weighted correction is introduced to improve the recovery. These virtual channels can be used to calculate radiation fluxes in some specific photon energy bands and hence to recover the spectrum of the whole photon energy range from 80 eV to 4.5 keV. Examples are listed which demonstrate the capability of this method to unfold various spectra such as Planck spectra with different radiation temperatures and to obtain x-ray flux of certain narrow energy interval.

Tianming, Song; Jiamin, Yang; Rongqing, Yi

2012-11-01

226

A high-sag microlens array film with a full fill factor and its application to organic light emitting diodes  

NASA Astrophysics Data System (ADS)

This paper reports a novel high-sag microlens array (MLA) film with a full fill factor and presents its application to organic light emitting diodes (OLEDs) for the purpose of improving their outcoupling efficiency. A gapless hexagonal MLA film having a high sag ratio is proposed and fabricated by a simple micromachining process including trench formation and the conformal vapor phase deposition of a polymer. By applying the MLA films to OLED panels, the outcoupling efficiency was increased by a maximum of 48% without any apparent color shift. A high-sag MLA film with a full fill factor is expected to impart remarkable optical efficiency to various display or lighting applications with flat panel light sources including OLEDs.

Kwon, Hyouk; Yee, Youngjoo; Jeong, Chi-Hwan; Nam, Hyo-Jin; Bu, Jong-Uk

2008-06-01

227

A Low-cost, Off-the-Shelf Ready Field Programmable Gate Array diode Laser Controller With adjustable parameters  

NASA Astrophysics Data System (ADS)

We have constructed a field programmable gate array (FPGA) based lock-in amplifier/PID servo controller for use in laser frequency locking and other applications. Our system is constructed from a commercial FPGA evaluation board with total cost less than 400 and no additional electronic component is required. FPGA technology allows us to implement parallel real-time signal processing with great flexibility. Internal parameters such as the modulation frequency, phase delay, gains and filter time constants, etc. can be changed on the fly within a very wide dynamic range through an iPod-like interface. This system was used to lock a tunable diode laser to an external Fabry Perot cavity with piezo and current feedback. A loop bandwidth of 200 kHz was achieved, limited only by the slow ADCs available on the FPGA board. Further improvements in both hardware and software seem possible, and will be discussed.

Yang, Ge; Barry, John. F.; Shuman, Edward; Demille, David

2010-03-01

228

Fabrication of polymer-based optical microsystem arrays suited for the active focusing of vertical laser diodes  

NASA Astrophysics Data System (ADS)

We present a low-cost fabrication technique of a polymer-based micro-optical-electrical-mechanical systems (MOEMS) suited for the dynamic focusing of VCSELs (vertical-cavity surface-emitting lasers). A simple method based on an SU(8) double exposure is proposed for the collective integration of small footprint transparent suspended membrane arrays on vertical laser diodes. We demonstrate that this kind of MOEMS can provide under thermal actuation a vertical displacement of around 0.2 µm W-1 over a maximal range of 8 µm. As a wide range of initial gaps between the membrane and the laser source can be chosen, this approach opens new insights into the dynamic control of the VCSEL beam waist position as well as for tunable VCSEL fabrication.

Reig, B.; Camps, T.; Bardinal, V.; Bourrier, D.; Daran, E.; Doucet, J. B.; Launay, J.; Fourniols, J. Y.

2012-06-01

229

Floral classification of honey using liquid chromatography-diode array detection-tandem mass spectrometry and chemometric analysis.  

PubMed

A high performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS) method for the floral origin traceability of chaste honey and rape honey samples was firstly presented in this study. Kaempferol, morin and ferulic acid were used as floral markers to distinguish chaste honey from rape honey. Chromatographic fingerprinting at 270nm and 360nm could be used to characterise chaste honey and rape honey according to the analytical profiles. Principal component analysis (PCA), partial least squares (PLS), partial least squares-discrimination analysis (PLS-DA) and soft independent modeling of class analogy (SIMCA) were applied to classify the honey samples according to their floral origins. The results showed that chaste honey and rape honey could be successfully classified by their floral sources with the analytical methods developed through this study and could be considered encouraging and promising for the honey traceability from unifloral or multifloral nectariferous sources. PMID:24128567

Zhou, Jinhui; Yao, Lihu; Li, Yi; Chen, Lanzhen; Wu, Liming; Zhao, Jing

2013-09-04

230

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

PubMed

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

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

2013-04-01

231

Enhanced Light Extraction Mechanism of GaN-Based Light-Emitting Diodes Using Top Surface and SideWall Nanorod Arrays  

Microsoft Academic Search

Using a self-catalyst vapor-liquid-solid mechanism, random indium-tin-oxide (ITO) nanorod arrays were deposited on the top surface and side-wall of GaN-based light-emitting diodes (LEDs) by electron-beam deposition. When the side-wall nanorod arrays and the top surface ITO nanorod arrays were deposited at an oblique-angle of 45°, roughened surface morphology and matched refractive index of 1.6 between air and the p-GaN layer

Chih-Chien Lin; Ching-Ting Lee

2010-01-01

232

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

233

Ground-state configurations and unresolved transition arrays in extreme ultraviolet spectra of lanthanide ions  

SciTech Connect

Theoretical ground-state configurations of lanthanide ions calculated with the Cowan suite of codes are presented. Theoretical 4d-4f and 4p-4d spectra of Pd-like to Rb-like lanthanide ions calculated using the relativistic flexible atomic code are also shown. The effects of configuration interaction are investigated, and the results compare favorably with experiments in which, for increasing nuclear charge, strong emission peaks are observed to move toward shorter wavelength. The application of these strong emitters as extreme ultraviolet radiation sources, a topic of emerging interest, is discussed.

Kilbane, D.; O'Sullivan, G. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)

2010-12-15

234

Fabrication of large area resin microlens arrays using gas-assisted ultraviolet embossing.  

PubMed

Large-area microlens arrays are becoming important components in many applications such as LCD-TV diffusers. This paper reports a uniform pressure, low temperature process for their fabrication. The process integrates gas-assisted embossing and UV-curing embossing. During the process, the 230mm x 203mm PMMA substrate is pressed against the stainless-steel stamper coated with UV-curable resin. Under the gas pressuring and UV irradiating, a large array of microlens can be formed. By using this process, high embossing temperature and high embossing pressure can be avoided. Little residual stress is observed in the embossed PMMA substrate. The uniformity of large-area fabrication and optical properties of fabricated resin microlens array have been verified. This study has successfully shown the potential of this gas-assisted UV embossing process for the replication of large-area microstructures. PMID:18542390

Huang, Po-Hsun; Huang, Tzu-Chien; Sun, Yi-Ting; Yang, Sen-Yeu

2008-03-01

235

Ultraviolet emission from Sb-doped p-type ZnO based heterojunction light-emitting diodes  

NASA Astrophysics Data System (ADS)

Heterojunction light emitting diodes (LEDs) were fabricated by making Au/Ni top Ohmic contacts on Sb-doped p-type ZnO film with low specific contact resistivity and Al/Ti back Ohmic contacts on n-type Si substrate. Near-band edge and deep-level emissions were observed from the LED devices at both low temperatures and room temperature, which is due to band-to-band and band-to-deep level radiative recombinations in ZnO, respectively. The electroluminescence emissions precisely match those of photoluminescence spectra from Sb-doped p-type ZnO, indicating that the ZnO layer acts as the active region for the radiative recombinations of electrons and holes in the diode operation.

Mandalapu, L. J.; Yang, Z.; Chu, S.; Liu, J. L.

2008-03-01

236

Ultraviolet emission from Sb-doped p-type ZnO based heterojunction light-emitting diodes  

SciTech Connect

Heterojunction light emitting diodes (LEDs) were fabricated by making Au/Ni top Ohmic contacts on Sb-doped p-type ZnO film with low specific contact resistivity and Al/Ti back Ohmic contacts on n-type Si substrate. Near-band edge and deep-level emissions were observed from the LED devices at both low temperatures and room temperature, which is due to band-to-band and band-to-deep level radiative recombinations in ZnO, respectively. The electroluminescence emissions precisely match those of photoluminescence spectra from Sb-doped p-type ZnO, indicating that the ZnO layer acts as the active region for the radiative recombinations of electrons and holes in the diode operation.

Mandalapu, L. J.; Yang, Z.; Chu, S.; Liu, J. L. [Quantum Structures Laboratory, Department of Electrical Engineering, University of California at Riverside, Riverside, California 92521 (United States)

2008-03-24

237

Photoelectric characteristics of diodes in prototype photosensitive pixels for a monolithic array infrared photodetector  

SciTech Connect

Test photodiodes in the form of mesa structures with different areas from 30 Multiplication-Sign 30 to 100 Multiplication-Sign 100 {mu}m in size are fabricated based on a Cd{sub x}Hg{sub 1-x}Te/Si structure at x = 0.235, grown by molecular-beam epitaxy (MBE). The current-voltage characteristics of the diodes are measured in the dark and under background light conditions. The experimental results are compared with theoretical calculations. It is found that the dependence of the photodiode photocurrent and dark current on the mesa structure size appears in the mesa size ranges from 30 Multiplication-Sign 30 to 80 Multiplication-Sign 80 {mu}m. The dark current decreases and the photocurrent increases with decreasing mesa size. The mechanisms affecting the behavior of current-voltage characteristics are discussed.

Sorochkin, A. V., E-mail: alexandersm@mail.ru; Varavin, V. S.; Predein, A. V.; Sabinina, I. V.; Yakushev, M. V. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2012-04-15

238

P-type Cu--Ti--O nanotube arrays and their use in self-biased heterojunction photoelectrochemical diodes for hydrogen generation.  

PubMed

Copper and titanium remain relatively plentiful in the earth's crust; hence, their use for large-scale solar energy conversion technologies is of significant interest. We describe fabrication of vertically oriented p-type Cu-Ti-O nanotube array films by anodization of copper rich (60% to 74%) Ti metal films cosputtered onto fluorine doped tin oxide (FTO) coated glass. Cu-Ti-O nanotube array films 1 mum thick exhibit external quantum efficiencies up to 11%, with a spectral photoresponse indicating that the complete visible spectrum, 380 to 885 nm, contributes significantly to the photocurrent generation. Water-splitting photoelectrochemical pn-junction diodes are fabricated using p-type Cu-Ti-O nanotube array films in combination with n-type TiO 2 nanotube array films. With the glass substrates oriented back-to-back, light is incident upon the UV absorbing n-TiO 2 side, with the visible light passing to the p-Cu-Ti-O side. In a manner analogous to photosynthesis, photocatalytic reactions are powered only by the incident light to generate fuel with oxygen evolved from the n-TiO 2 side of the diode and hydrogen from the p-Cu-Ti-O side. To date, we find under global AM 1.5 illumination that such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 mA/cm (2), at a photoconversion efficiency of 0.30%. PMID:18540655

Mor, Gopal K; Varghese, Oomman K; Wilke, Rudeger H T; Sharma, Sanjeev; Shankar, Karthik; Latempa, Thomas J; Choi, Kyoung-Shin; Grimes, Craig A

2008-06-10

239

Optical studies of degradation of AlGaN quantum well based deep ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

Aging under high current stress of AlGaN quantum well based light emitting diodes with high and low Al content in the wells emitting at 270 nm and 335 nm, respectively, has been studied by scanning near field optical spectroscopy and far field electroluminescence, photoluminescence and time-resolved photoluminescence. In the high Al content devices emission band related to optical transitions in the cladding involving nitrogen vacancies has been found. Evolution of this band during aging suggests that the role of N vacancies is crucial in the aging process by aiding defect generation and formation of high conductivity channels.

Pinos, A.; Marcinkevi?ius, S.; Yang, J.; Gaska, R.; Shatalov, M.; Shur, M. S.

2010-11-01

240

Coherent Beam Combining of High Power Broad-Area Laser Diode Array with a Closed-V-shape External Talbot Cavity  

SciTech Connect

We have coherently combined a high-power broad-area laser diode array by using a feedback loop closed off-axis external Talbot cavity. The off-axis feedback from two gratings provides transverse-mode control of broad-area lasers. The Talbot configuration of the external cavity implements diffractive coupling among laser diodes. Feedback from two gratings increases external cavity quality factor and spectrum selection capability. As a result, spatial coherence was improved and spectral linewidth was narrowed down. The high visibility of the far-field profile indicates that high spatial coherence was achieved. We also observed symmetric far-field profiles indicating that laser array was phase locked to in-phase and out-of-phase super-modes, respectively. Transition between these super-modes was observed by tuning one grating's tilted angle.

Liu, Bo [ORNL; Liu, Yun [ORNL; Braiman, Yehuda [ORNL

2010-01-01

241

High-resolution pulse-counting array detectors for imaging and spectroscopy at ultraviolet wavelengths  

NASA Astrophysics Data System (ADS)

The performance characteristics of multianode microchannel array (MAMA) detector systems which have formats as large as 256 x 1024 pixels and which have application to imaging and spectroscopy at UV wavelengths are evaluated. Sealed and open-structure MAMA detector tubes with opaque CsI photocathodes can determine the arrival time of the detected photon to an accuracy of 100 ns or better. Very large format MAMA detectors with CsI and Cs2Te photocathodes and active areas of 52 x 52 mm (2048 x 2048 pixels) will be used as the UV solar blind detectors for the NASA STIS.

Timothy, J. Gethyn; Bybee, Richard L.

1986-01-01

242

Simultaneous determination of water-soluble and fat-soluble synthetic colorants in foodstuff by high-performance liquid chromatography–diode array detection–electrospray mass spectrometry  

Microsoft Academic Search

An accurate method was developed for the simultaneous determination of water-Tartrazine, Amaranth, Ponceau 4R, Sunset Yellow FCF, and fat-Sudan (I–IV), synthetic soluble colorants in foodstuff. This method uses dimethylsulfoxide (DMSO) as the extraction solvent in the sample preparation process and high performance liquid chromatography (HPLC)–diode array detector (DAD)–electrospray mass spectrometry (ESI-MS), applying selected ion recording in positive\\/negative alternate mode to

Ming Ma; Xubiao Luo; Bo Chen; Shengpei Su; Shouzhuo Yao

2006-01-01

243

Reversed-phase high-performance liquid chromatographic screening method for serum steroids using retention index and diode-array detection  

Microsoft Academic Search

A multisteroid screening method has been developed based on the use of 1-[4-(2,3-dihydroxypropoxy)phenyl]-1-alkanones as retention index standards and UV absorbance spectra recorded on-line with a diode-array detector using reversed-phase high-performance liquid chromatographic gradient elution with acetonitrile and water. The effect of chromatographic conditions on retention indices of steroids were studied. The method was tentatively applied to profiling of steroids in

Pirjo Kuronen; Pirkko Volin; Tarja Laitalainen

1998-01-01

244

Spatial radiation intensity distribution of linear diode arrays and calculation of inversion in fibre-coupled end-pumped solid-state lasers  

SciTech Connect

The radiation intensity distribution of linear diode arrays used for longitudinal pumping fibre-coupled solid-state lasers is studied experimentally and theoretically. A simple model describing the propagation of radiation is proposed which allows the calculation of the inversion population distribution in an active element. The radiation intensity distributions are calculated in cross sections for different angular distributions at the fibre output. (lasers)

Gorbunkov, Mikhail V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Kostryukov, P V; Morozov, V B; Olenin, A N; Telegin, L S; Tunkin, V G; Yakovlev, D V [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

2005-12-31

245

Comparison of extraction solvents and conditions for herbicide residues in milled rice with liquid chromatography-diode array detection analysis (LC-DAD)  

Microsoft Academic Search

Different extraction procedures and clean-up methods were compared in order to develop a sample preparation procedure for the multi-residue analysis of six post-emergence herbicides (metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium and cyhalofop butyl) in rice grains followed by liquid chromatography-diode array detection (LC-DAD). Optimum results were obtained dispersing milled rice grain in water, followed by the addition

S. Niell; L. Pareja; L. Geis Asteggiante; M. V. Cesio; H. Heinzen

2010-01-01

246

Identification of amino-tadalafil and rimonabant in electronic cigarette products using high pressure liquid chromatography with diode array and tandem mass spectrometric detection  

Microsoft Academic Search

A high-pressure liquid chromatography-diode array detection and multi-mode ionization tandem mass spectrometry (HPLC-DAD–MMI-MS\\/MS) method was used to identify amino-tadalafil and rimonabant in electronic cigarette (e-cigarette) cartridges. Amino-tadalafil is a drug analogue of the commercially approved Cialis™ (i.e. tadalafil). Rimonabant is a drug that was, at one time, approved for weight loss in Europe (although approval has been retracted), but not

Michael E. Hadwiger; Michael L. Trehy; Wei Ye; Terry Moore; James Allgire; Benjamin Westenberger

247

Diode array pumped, non-linear mirror Q-switched and mode-locked Nd : YVO 4 laser — a good tool for powder SHG measurement  

Microsoft Academic Search

A non-linear mirror consisting of a lithium triborate crystal and a dichroic output coupler are used to mode-lock (passively)\\u000a an Nd : YVO4 laser, pumped by a diode laser array. The laser can operate both in cw mode-locked and simultaneously Q-switched and mode-locked\\u000a (QML) regime. The peak power of the laser while operating in QML regime is much higher but

P. K. Datta; Chandrajit Basu; S. Mukhopadhyay; S. K. Das; G. K. Samanta; Antonio Agensi

2004-01-01

248

Quantitative analysis of flavonols, flavones, and flavanones in fruits, vegetables and beverages by high-performance liquid chromatography with photo-diode array and mass spectrometric detection  

Microsoft Academic Search

A high-performance liquid chromatographic (HPLC) separation method with photo-diode array (PDA) and mass spectrometric (MS) detection was developed to determine and quantify flavonols, flavones, and flavanones in fruits, vegetables and beverages. The compounds were analysed as aglycones, obtained after acid hydrolysis of freeze-dried food material. Identification was based on retention time, UV and mass spectra by comparison with commercial standards,

Ulla Justesen; Pia Knuthsen; Torben Leth

1998-01-01

249

Identification of nonvolatile components in lemon peel by high-performance liquid chromatography with confirmation by mass spectrometry and diode-array detection  

Microsoft Academic Search

High-performance liquid chromatography (HPLC) with diode-array detection and thermospray mass spectrometry (LC-TSP-MS) were used to identify nonvolatile compounds in a lemon peel extract. In this way, the retention time characteristics, the UV-Vis spectra and the mass spectra provide structural information without the necessity of isolating the individual compounds. The lemon peel extract was separated into petroleum ether, chloroform, ethyl acetate

Alessandro Baldi; Robert T. Rosen; Elaine K. Fukuda; Chi-Tang Ho

1995-01-01

250

Three-Dimensional Mapping of Quantum Wells in a GaN/InGaN Core-Shell Nanowire Light-Emitting Diode Array.  

PubMed

Correlated atom probe tomography, cross-sectional scanning transmission electron microscopy, and cathodoluminescence spectroscopy are used to analyze InGaN/GaN multiquantum wells (QWs) in nanowire array light-emitting diodes (LEDs). Tomographic analysis of the In distribution, interface morphology, and dopant clustering reveals material quality comparable to that of planar LED QWs. The position-dependent CL emission wavelength of the nonpolar side-facet QWs and semipolar top QWs is correlated with In composition. PMID:23919559

Riley, James R; Padalkar, Sonal; Li, Qiming; Lu, Ping; Koleske, Daniel D; Wierer, Jonathan J; Wang, George T; Lauhon, Lincoln J

2013-08-12

251

Epitaxial growth of InGaN nanowire arrays for light emitting diodes.  

PubMed

Significant synthetic challenges remain for the epitaxial growth of high-quality InGaN across the entire compositional range. One strategy to address these challenges has been to use the nanowire geometry because of its strain relieving properties. Here, we demonstrate the heteroepitaxial growth of In(x)Ga(1-x)N nanowire arrays (0.06 ? x ? 0.43) on c-plane sapphire (Al(2)O(3)(001)) using a halide chemical vapor deposition (HCVD) technique. Scanning electron microscopy and X-ray diffraction characterization confirmed the long-range order and epitaxy of vertically oriented nanowires. Structural characterization by transmission electron microscopy showed that single crystalline nanowires were grown in the ?002? direction. Optical properties of InGaN nanowire arrays were investigated by absorption and photoluminescence measurements. These measurements show the tunable direct band gap properties of InGaN nanowires into the yellow-orange region of the visible spectrum. To demonstrate the utility of our HCVD method for implementation into devices, LEDs were fabricated from In(x)Ga(1-x)N nanowires epitaxially grown on p-GaN(001). Devices showed blue (x = 0.06), green (x = 0.28), and orange (x = 0.43) electroluminescence, demonstrating electrically driven color tunable emission from this p-n junction. PMID:21495684

Hahn, Christopher; Zhang, Zhaoyu; Fu, Anthony; Wu, Cheng Hao; Hwang, Yun Jeong; Gargas, Daniel J; Yang, Peidong

2011-04-25

252

High-power operation of InGaAsP-InP laser diode array at 1.73{micro}m  

SciTech Connect

InGaAsP-InP laser bars with an emission wavelength of 1.73 {micro}m have been fabricated using compressively strained multiple-quantum-well (MQW) separate-confinement heterostructures (SCH). One-cm-wide, 0.7-fill-factor, diode bars are bonded onto Si microchannel heatsinks and stacked into a two-dimensional (2-D) laser array. 16 W of continuous-wave (CW) power was produced from a 1-cm bar and 200 W of peak power was generated from a 10-bar array with an emitting aperture of 1 cm{sup 2}.

Skidmore, J.A.; Freitas, B.L.; Reinhardt, C.E.; Utterback, E.J.; Page, R.H.; Emanuel, M.A. [Lawrence Livermore National Lab., CA (United States)

1997-10-01

253

Out-of-plane high-density piezoresistive silicon microwire/p-n diode array for force- and temperature-sensitive artificial whisker sensors  

NASA Astrophysics Data System (ADS)

We propose an out-of-plane high-aspect-ratio 'whisker-like' microwire array sensor for use in multisite contact force and temperature detection with high spatial resolution. Although the wire element has two terminal electrodes, the device consists of force-sensitive wire arrays where one end of the wire is attached to the substrate and the other end is free to be touched. We fabricated a force-sensitive wire array based on p-type (p-) silicon with 3 µm diameter and 30 µm length (1 ? cm) assembled over an n-type (n-) silicon substrate (3-6 ? cm), which resulted in a p-silicon wire/p-n diode system array. Due to the piezoresistance effect of the p-silicon wire, the electrical conductance changes upon contact of an individual wire with an object. The shift in the rectifying current-voltage (I-V) curves of the embedded p-n diode depends on the temperature through the silicon wire. Thus, the same alignment can be used as a force sensor and a temperature sensor. Both force- and temperature-sensitive microwire sensor arrays with a small detection area (~20 µm2) and high spatial resolution (~100 µm in pitch) have potential in numerous applications, including artificial electronic fingertips in a robot hand/prosthetics, multisite sensing of contact force, shear force, surface roughness and slip, and local temperature sensing capabilities.

Ikedo, Akihito; Ishida, Makoto; Kawano, Takeshi

2011-03-01

254

Application of RP-HPLC-diode array detector after SPE to the determination of pesticides in pepper samples.  

PubMed

The application of HPLC-diode array detector (DAD) after SPE for identification and quantitative analysis of pesticides in red and green pepper samples is demonstrated. An HPLC procedure on an RP column (C18) was developed for analysis of selected pesticides from different chemical groups: metamitron, metalaxyl, linuron, and prometryn. Average recoveries for C18 Polar Plus cartridges and solvents by the proposed RP-HPLC-DAD method after SPE are presented. Average recoveries from the spiked samples and the SDs were 22.5 +/- 2.2, 138.0 +/- 4.1, 78.6 +/- 2.8, and 109.2 +/- 2.3% for metamitron, metalaxyl, linuron, and prometryn, respectively, at concentrations of 7 microg/g in the plant material. The efficiency of the SPE procedure was evaluated using real food samples. The quantities of prometryn, linuron, metalaxyl, and metamitron determined were in the ranges of 0.02-2.24 microg/g (n = 24), 0.08-1.01 microg/g (n = 9), 1.61-2.28 microg/g (n=4), and 0.05-1.07 microg/g (n = 3), respectively, in plant material sampled in 2011. The method was validated for precision, repeatability, and accuracy. PMID:23175966

Tuzimski, Tomasz

255

Determination of free and total phenolic acids in plant-derived foods by HPLC with diode-array detection.  

PubMed

A high-performance liquid chromatographic (HPLC) method with diode-array detection (DAD) was used to identify and quantify free and total phenolic acids (m-hydroxybenzoic acid, p-hydroxybenzoic acid, protocatechuic acid, gallic acid, vanillic acid, syringic acid, o-coumaric acid, m-coumaric acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid, chlorogenic acid, and ellagic acid) in plant foods. Free phenolic acids were extracted with a mixture of methanol and 10% acetic acid. Bound phenolic acids were liberated using first alkaline and then acid hydrolysis followed by extraction with diethyl ether/ethyl acetate (1:1). All fractions were quantified separately by HPLC. After HPLC quantification, results of alkali and acid hydrolysates were calculated to represent total phenolic acids. Ellagic acid was quantified separately after long (20 h) acid hydrolysis. The methods developed were effective for the determination of phenolic acids in plant foods. DAD response was linear for all phenolic acids within the ranges evaluated, with correlation coefficients exceeding 0.999. Coefficients of variation for 4-8 sample replicates were consistently below 10%. Recovery tests of phenolic acids were performed for every hydrolysis condition using several samples. Recoveries were generally good (mean >90%) with the exceptions of gallic acid and, in some cases, caffeic acid samples. PMID:12059140

Mattila, Pirjo; Kumpulainen, Jorma

2002-06-19

256

Fingerprint analysis and simultaneous determination of phenolic compounds in extracts of Curculiginis Rhizoma by HPLC-diode array detector.  

PubMed

Curculiginis Rhizoma (Curculigo orchioides GAERTN.) is a well-known Chinese herbal medicine, as well as an important Rasayana drug in India. Current criteria of quality control on this herb are to quantitatively analyze single compound curculigoside, which fail to comprehensively evaluate quality of this herb. In this paper, a simple and reliable HPLC coupled with diode array detector (DAD) method was developed to evaluate the quality of Curculiginis Rhizoma through establishing chromatographic fingerprint and simultaneously quantitating four phenolic compounds, orcinol glucoside, orcinol, 2,6-dimethoxybenzoic acid and curculigoside. The fingerprint displayed eleven common peaks, and the similarity index of different samples was in a range of 0.890-0.977. Validation of the method was acceptable, with 96.03-102.82% accuracy in recovery test and inter and intra-day precisions were less than 2%. This developed method by having a combination of chromatographic fingerprint and quantitation analysis could be applied to the quality control of Curculiginis Rhizoma. PMID:23902862

Bian, Qingya; Yang, Hui; Chan, Chi-On; Jin, Dengping; Mok, Daniel Kam-Wah; Chen, Sibao

2013-01-01

257

On-line high-performance liquid chromatographic diode array spectrophotometric analysis of steroidal hormones in illegal preparations.  

PubMed

An on-line high-performance liquid chromatographic diode array spectroscopic analytical method for the identification of more than 60 different steroidal compounds is described. For the chromatographic separation, a gradient elution that could distinguish the esterified and non-esterified steroids in the same run on a reversed-phase C18 column, using methanol as modifier, was developed. For both types of compound an internal standard was chosen to establish reproducible relative retention times that could be used as one element of the identification; the second element is the UV spectrum, which is recorded on-line during the separation. The combination of chromatographic and UV spectroscopic recordings selects only a few probable steroids, which could be the unknown. This approach has been applied to forensic analysis of illicit preparations used in cattle-breeding, some examples of which are shown. For those steroids that are very difficult to distinguish using this procedure, because of their chromatographic and spectroscopic similarity on this system, other solvent mixtures are used in place of methanol as modifier, namely acetonitrile or tetrahydrofuran, or both, with the same solvent strength, as proposed by Snyder. In this way totally different elution patterns and separations are obtained, providing complementary information for identification, as shown by the systematic analysis on two other isoeluotropic solvent systems. PMID:2745645

De Beer, J O

1989-04-01

258

Progress toward a monolithically integrated coherent diode laser array. Interim report  

SciTech Connect

Progress toward the design and fabrication of a GaAlAs semiconductor laser array capable of high average power levels (0.1 to 1.0 watt) and low (approx 1 millirad) beam divergence is reported. A large optical cavity (LOC) configuration is grown by liquid phase epitaxy. The LOC structure is characterized by photoluminescence scans, ion microprobe mass analysis (IMMA), and optical waveguiding measurements. Fabry-Perot, active-passive, and DBR lasers are fabricated using chemical and ion beam etching. Gratings formed using holographic and ion beam etching techniques provide third order feedback for the DBR lasers, and are also used as distributed beam deflectors (DBDs) and output couplers. Comparisons of the results of experiments performed on DBR lasers, DBDs, and coupled lasers are made with theoretical models. Details of the material growth, material characterization, device fabrication, experiments, and theoretical models are presented in this report.

Evans, G.A.; Garmire, E.M.; Stoll, H.M.; Osmer, J.A.; Soady, W.E.

1981-02-20

259

InGaN/GaN microcolumn light-emitting diode arrays with sidewall metal contact.  

PubMed

In this study, we produce InGaN/GaN microcolumn LED (MC-LED) arrays having nonpolar metal sidewall contacts using a top-down method, where the metal contacts only with the sidewall of the columnar LEDs with an open top for transparency. The trapezoidal profile of the as-etched columns was altered to a rectangular profile through KOH treatment, exposing the nonpolar sidewalls. While the MC-LED with no treatment emitted no light because of the etch-damaged region, the MC-LEDs with KOH treatment exhibited much improved the electrical properties with the much higher shunt resistance due to the removal of the etch-damaged region. The optical output power was strongest for the MC-LED with a 5-min treatment indicating an almost complete removal of the damaged region. PMID:24104122

Kong, Duk-Jo; Bae, Si-Young; Kang, Chang-Mo; Lee, Dong-Seon

2013-09-23

260

Quantum-well and localized state emissions in AlInGaN deep ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

Injection current and temperature dependence of electroluminescence (EL) is investigated in AlInGaN deep untraviolet light-emitting diodes. Two EL bands with different behaviors are observed. The high-energy band (P1) shows a monotonous redshift and an amazing increase of intensity with increasing current, however, a ``U''-shaped shift and a saturation of intensity at high current are measured for the low-energy band (P2). Accordingly, P1 and P2 are attributed to emissions from quantum-well and localized states, respectively, with P1 dominant at high current and high temperature and P2 the main emission mechanism under low temperature and low current. Modeled data based on the theory of random population for localized states in quantum wells taking into account self-heating effect agree well with the experimental results.

Zhang, J. C.; Zhu, Y. H.; Egawa, T.; Sumiya, S.; Miyoshi, M.; Tanaka, M.

2007-11-01

261

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

NASA Astrophysics Data System (ADS)

Self-assembled AlxGa1-xN 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.

Kent, Thomas F.; Carnevale, Santino D.; Myers, Roberto C.

2013-05-01

262

Improvement of AlGaN-based deep-ultraviolet light emitting diodes performance with a nano-textured/roughened sapphire substrate  

NASA Astrophysics Data System (ADS)

Performance improvement of the fabricated AlGaN-based deep-ultraviolet light emitting diode (DUV LEDs) on sapphire with nano-textured/roughned substrate is reported. The output optical powers as well as the current-voltage characteristics of the processed devices with and without textured/roughened substrate are compared. Lapping/polishing and dry-etching techniques were employed for nano-texturing/roughening of the substrate. Magnetron dry etching was performed using a mixed CF2Cl2/Ar feed gases followed by an inductively coupled plasma (ICP) etching in BCl3/Cl2 plasma chemistry. An etching rate of ˜145 nm/min for the sapphire was easily obtained. The result show that the optical emission power of the fabricated devices with textured/roughened sapphire substrate is higher as compared to similar un-textured/roughened devices. Based on the analysis, it is concluded that a textured/roughened substrate surface with an RMS ˜ 15 -- 25 nm shows improved light extraction efficiency, which is the result of the reduced internal reflection of the light caused by the nano-textured/roughened surface profile thereby causing deviation for critical angle.

Khizar, Muhammad; Raja, Yasin

2006-03-01

263

Design and characterization of indium gallium arsenic phosphide/indium phosphide and indium(aluminum) gallium arsenic antimonide/gallium antimonide laser diode arrays  

NASA Astrophysics Data System (ADS)

Semiconductor laser diodes and laser diode arrays are efficient electrical to optical power converters providing their output energy in relatively narrow emission spectra. The different wavelength ranges are well covered by different semiconductor materials. InP-based laser diodes cover the wavelength range from 1-mum to 2-mum. The region between 2 and 3-mum is well handled by type-I devices based on the GaSb material system. We designed, fabricated and characterized InP-based and GaSb-based laser arrays with record high continuous wave output power emitting at 1.5-mum and 2.3-mum, correspondingly. A laser array based on the InGaAsP/InP material system was developed for optical pumping of erbium doped solid state lasers emitting eye-safe light around 1.6-mum. The 2.3-mum laser arrays can be used for optical pumping of recently developed type-II semiconductor lasers operating in the mid-infrared atmospheric transparency window between 3.5-mum and 5-mum. Optical pumping requires pump sources that reliably provide output energy in a relatively narrow spectral range matching with absorption bands of illuminated materials. Also the compact size of laser diodes and laser arrays is preferable and convenient in different implementations, but it leads to significant overheating in high power operations. The inherent properties of semiconductor materials result in a red-shift of the laser emission spectrum with increased temperature. This thermal drift of the laser emission spectrum can lead to misalignment with the narrow absorption bands of illuminated material. We have developed an experimental technique to measure the time-resolved evolution of the laser emission spectrum. The data obtained from the emission spectrum measurements have been used to optimize the laser device design. In this dissertation the progress in the development of high-power infrared laser arrays have been discussed. The different aspects of laser array design, thermal analysis and laser bar optimization have been studied analytically and experimentally.

Gourevitch, Alexandre

264

SiMPl—An avalanche diode array with bulk integrated quench resistors for single photon detection  

NASA Astrophysics Data System (ADS)

The so-called silicon photomultipliers (SiPMs, MPPCs, etc.) are already replacing photomultiplier tubes in many applications. Still the reproducibility and the cost requirements are not at the level required for the coverage of many square meters of detector area. Therefore a simple technology is desired which allows a high yield and keeps the detector costs in a reasonable range. In the existing devices the need of high ohmic polysilicon for the quench resistors is one of the most yield and cost driving technological issues. We are proposing a front-side illuminated detector structure with quench resistors integrated into the silicon bulk. In this concept other obstacles for light like metal lines or contacts can be omitted and therefore the fill factor is only limited by the gaps necessary for optical cross-talk suppression. Within the array the entire surface area remains non-structured and can be easily coated with an anti-reflective layer. Compared to existing devices the proposed detector has the potential of higher photon detection efficiency especially in the blue and the UV range, an improved hardness against ionizing radiation and a much simpler processing resulting in a higher production yield and lower costs. The quenching mechanism has been demonstrated in a proof-of-principle production performed in house. The second prototype fabrication on silicon on isolator substrates has been done and allows testing of the device performance. The results from the first measurements are presented.

Ninkovi?, Jelena; Andri?ek, Ladislav; Liemann, Gerhard; Lutz, Gerhard; Moser, Hans-Günther; Richter, Rainer; Schopper, Florian

2010-05-01

265

High-performance liquid chromatography-diode array and electrospray-mass spectrometry analysis of non-allowed substances in cosmetic products for preventing hair loss and other hormone-dependent skin diseases.  

PubMed

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 minoxidil, progesterone, estrone, spironolactone, canrenone, hydrocortisone and triamcinolone acetonide in cosmetic products. The presence of these substances in commercial cosmetic samples is prohibited. The compounds were separated by reversed phase chromatography with water (0.1% trifluoroacetic acid) and acetonitrile gradient elution and detected by UV-DAD at 230, 254 and 280 nm and by ESI-MS positive ionisation mode. Benzoic acid was used as internal standard. Linearity was studied with UV-DAD detection from 1.50 to 1,000 microg/ml or mug/g range, depending on the different compounds and type of cosmetic preparation and with ESI-MS in the 50-1,000 ng/ml or ng/g range. Good determination coefficients (r(2)>or=0.99) were found in both UV and ESI-MS. 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. This method was successfully applied to the analysis of substances under investigations illegally added in cosmetic cream and lotions, sold on internet web sites to prevent hair loss and other hormone-dependent skin diseases, like acne and hirsutism. PMID:18656319

De Orsi, Daniela; Pellegrini, Manuela; Pichini, Simona; Mattioli, Donatella; Marchei, Emilia; Gagliardi, Luigi

2008-06-25

266

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

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

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

2013-09-13

267

Video-rate fluorescence lifetime imaging camera with CMOS single-photon avalanche diode arrays and high-speed imaging algorithm.  

PubMed

A high-speed and hardware-only algorithm using a center of mass method has been proposed for single-detector fluorescence lifetime sensing applications. This algorithm is now implemented on a field programmable gate array to provide fast lifetime estimates from a 32 × 32 low dark count 0.13 ?m complementary metal-oxide-semiconductor single-photon avalanche diode (SPAD) plus time-to-digital converter array. A simple look-up table is included to enhance the lifetime resolvability range and photon economics, making it comparable to the commonly used least-square method and maximum-likelihood estimation based software. To demonstrate its performance, a widefield microscope was adapted to accommodate the SPAD array and image different test samples. Fluorescence lifetime imaging microscopy on fluorescent beads in Rhodamine 6G at a frame rate of 50 fps is also shown. PMID:21950926

Li, David D-U; Arlt, Jochen; Tyndall, David; Walker, Richard; Richardson, Justin; Stoppa, David; Charbon, Edoardo; Henderson, Robert K

2011-09-01

268

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

PubMed

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

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

2008-02-01

269

Differentiation of Herba Cistanches by fingerprint with high-performance liquid chromatography-diode array detection-mass spectrometry.  

PubMed

Herba Cistanche (Rou Cong Rong in Chinese), dried succulent stems of Cistanche deserticola or C. tubulosa, is a famous Chinese herbal medicine and has been recorded in the Chinese Pharmacopoeia. In recent years, another two non-official species, C. salsa and C. sinensis have also been used as Herba Cistanche in some regions of China. To investigate the possibility of using these two non-official species as alternatives to the official species, a high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS) fingerprint method was developed to comparatively analyze the crude herbs of these four species. The fingerprint of C. deserticola, a historically certified species of Herba Cistanche, serves as 'standard pattern' for comparing the similarities with the other species by means of similarity and Principle Component Analysis. Additionally, 18 characteristic peaks in the fingerprints were identified by comparing their retention times, UV spectra and ESI-MS data with those of the reference substances and/or the data in the literatures. The comparative results demonstrate that the fingerprints of C. tubulosa and C. salsa possess high similarity to the standard pattern, suggesting that these two species may be used as alternative species; while that of C. sinensis has low similarity (0.053 correlation coefficient) to the standard pattern, indicating that it cannot be used as the substitute of the official herb. However, the varying fingerprint patterns among the samples of C. deserticola collected from various habitats illustrate that the quality consistency of crude herbs is still a problem worthy of serious concern. PMID:18502433

Jiang, Y; Li, S P; Wang, Y T; Chen, X J; Tu, P F

2008-04-23

270

p-n hetero-junction diode arrays of p-type single walled carbon nanotubes and aligned n-type SnO? nanowires.  

PubMed

p-n hetero-junction diode arrays were fabricated using specific direct techniques for the transfer of p-type single walled carbon nanotubes (SWCNTs) and aligned n-type SnO? nanowires (NWs) onto a patterned substrate surface. Their electronic and optoelectronic properties were characterized. Perpendicular crossings of the p- and the n-channels with each other were confirmed by transfer characteristics with respect to the bottom gate. The resulting diode showed a good rectifying behavior with a rectification ratio of over 10² at ±5 V, where the equivalent circuit model of a serially connected diode and resistor was used for analysis of the electrical properties. Both the forward and the reverse currents were observed to increase with the application of a positive gate bias, indicating an n-type gate dependence. Under a forward bias, the dominant contribution of the SnO? NW channel to the total resistance of the equivalent model is attributed to the n-type gate dependence since the resistance of the n-channel increased with a negative gate bias, resulting in the decrease of the forward current. Under a reverse bias, positive gate increased the concentration of valence electrons in the SWCNTs, enhancing direct tunneling to the conduction band of the SnO? NWs. High sensitivity to UV irradiation under the reverse bias was also demonstrated with a photosensitivity over 10², suggesting potential applicability of the hetero-junction diodes in optoelectronic devices. PMID:22699118

Yoon, Jangyeol; Min, Kyung Whon; Kim, Joonsung; Kim, Gyu Tae; Ha, Jeong Sook

2012-06-15

271

Quaternary ultraviolet AlInGaN MQW laser diode performance using quaternary AlInGaN electron blocking layer.  

PubMed

The effect of polarization-matched Al(0.25)In(0.08)Ga(0.67)N electron-blocking layer (EBL) on the optical performance of ultraviolet Al(0.08)In(0.08)Ga(0.84)N/Al(0.1)In(0.01)Ga(0.84)N multi-quantum well (MQW) laser diodes (LDs) was investigated. The polarization-matched Al(0.25)In(0.08)Ga(0.67)N electron blocking layer (EBL) was employed in an attempt to reduce the polarization effect inside the active region of the diodes. The device performance which is affected by piezoelectric was studied via drift-diffusion model for carrier transport, optical gain and losses using the simulation program of Integrated System Engineering Technical Computer Aided design (ISE TCAD). The optical performance of the LD using quaternary Al(0.25)In(0.08)Ga(0.67)N EBL was compared with the LD using ternary Al(0.3)Ga(0.7)N EBL where both materials have the same energy band gap of Eg = 3.53 eV. The self-consistent ISE-TCAD simulation program results showed that the polarization-matched quaternary Al(0.25)In(0.08)Ga(0.67)N EBL is beneficial as it confines the electrons inside the quantum well region better than ternary Al(0.3)Ga(0.7)N EBL. The results indicated that the use of Al(0.25)In(0.08)Ga(0.67)N EBL has lower threshold current and higher optical intensity than those for Al(0.3)Ga(0.7)N EBL. The effect of Al(0.25)In(0.08)Ga(0.67)N EBL thickness on the performance of LDs has also been studied. Results at room temperature indicated that lower threshold current, high slope efficiency, high output power, and high differential quantum efficiency DQE occurred when the thickness of Al(0.25)In(0.08)Ga(0.67)N EBL was 0.25 µm. PMID:21643179

Ghazai, A J; Thahab, S M; Abu Hassan, H; Hassan, Z

2011-05-01

272

Room-temperature, continuous-wave, 946-nm Nd:YAG laser pumped by laser-diode arrays and intracavity frequency doubling to 473 nm.  

PubMed

We report the use of GaAlAs laser-diode arrays to pump a cw Nd:YAG laser operating on the 946-nm (4)F(3/2) ? (4)I(9/2) transition. At room temperature, the lasing threshold was reached with 58 mW of absorbed pump power, and, with 175 mW of absorbed pump power, 42 mW of output power at 946 nm was obtained in a TEM(00) mode by using 0.7% output coupling. In addition, pumping with an infrared dye laser operating in a pure TEM(00) mode was used to investigate the effects of reabsorption loss that are characteristic of the 946-nm laser transition. LiIO(3) was used as an intracavity doubling crystal, and 100 microW of blue light was generated by using diode-laser pumping in a nonoptimized cavity. PMID:19741939

Risk, W P; Lenth, W

1987-12-01

273

Room-temperature, continuous-wave, 946-nm Nd:YAG laser pumped by laser-diode arrays and intracavity frequency doubling to 473 nm  

SciTech Connect

We report the use of GaAlAs laser-diode arrays to pump a cw Nd:YAG laser operating on the 946-nm /sup 4/F/sub 3/2/..-->../sup 4/I/sub 9/2/ transition. At room temperature, the lasing threshold was reached with 58 mW of absorbed pump power, and, with 175 mW of absorbed pump power, 42 mW of output power at 946 nm was obtained in a TEM/sub 00/ mode by using 0.7% output coupling. In addition, pumping with an infrared dye laser operating in a pure TEM/sub 00/ mode was used to investigate the effects of reabsorption loss that are characteristic of the 946-nm laser transition. LiIO/sub 3/ was used as an intracavity doubling crystal, and 100 ..mu..W of blue light was generated by using diode-laser pumping in a nonoptimized cavity.

Risk, W.P.; Lenth, W.

1987-12-01

274

Influence of free-standing GaN substrate on ultraviolet light-emitting-diodes by atmospheric-pressure metal-organic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

We reported the influence of free-standing (FS) GaN substrate on ultraviolet light-emitting-diodes (UV LEDs) by atmospheric-pressure metal-organic chemical vapor deposition (APMOCVD). The Raman spectrum shows the in-plane compressive stress of the GaN epitaxial structures grown on FS GaN substrate. Besides, the Raman spectrum reveals the relation between the crystal quality and the carrier localization degree in multi-quantum wells (MQWs). High resolution X-ray diffraction (HRXRD) analysis results show that the In0.025Ga0.975N/Al0.08Ga0.92N MQWs grown on FS GaN substrate has higher indium mole fraction than sapphire at the same growth conditions. The higher indium incorporation is corresponding with the red-shift 6 nm (387 nm) of the room temperature photoluminescence (PL) peak. The full widths at half maximum (FWHM) of omega-scan rocking curve in (002) and (102) reflectance on FS GaN substrate (83 arcsec and 77 arcsec) are narrower than UV LEDs grown on sapphire (288 arcsec and 446 arcsec). This superior quality may attribute to homoepitaxial growth structure and better strain relaxation in the FS GaN substrate. An anomalous temperature behavior of PL in UV LEDs designated as an S-shaped peak position dependence and W-shaped linewidth dependence indicate that exciton/carrier motion occurs via photon-assisted tunneling through localized states, what results in incomplete thermalization of localized excitons at low temperature. The Gaussian broadening parameters of carrier localization is about 16.98 meV from the temperature dependent photoluminescence (TDPL) measurement. The saturation temperature from the TDPL linewidth of UV LEDs on FS GaN substrate at about 175 K represents a crossover from a nonthermalized to thermalized energy distribution of excitons.

Shieh, C. Y.; Li, Z. Y.; Chiu, C. H.; Tu, P. M.; Kuo, H. C.; Chi, G. C.

2013-03-01

275

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

SciTech Connect

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.

Kozelka, Jakub; Robinson, Joshua; Nelms, Benjamin; Zhang, Geoffrey; Savitskij, Dennis; Feygelman, Vladimir [Sun Nuclear Corp., Melbourne, Florida 32940 (United States); Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Canis Lupus LLC, Sauk County, Wisconsin 53561 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Sun Nuclear Corp., Melbourne, Florida 32940 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States)

2011-09-15

276

Color tunable light-emitting diodes based on p+Si\\/p-CuAlO2\\/n-ZnO nanorod array heterojunctions  

Microsoft Academic Search

Wide-range color tuning from red to blue was achieved in phosphor-free p+-Si\\/p-CuAlO2\\/n-ZnO nanorod light-emitting diodes at room temperature. CuAlO2 films were deposited on p+-Si substrates by sputtering followed by annealing. ZnO nanorods were further grown on the annealed p+-Si\\/p-CuAlO2 substrates by vapor phase transport. The color of the p-CuAlO2\\/n-ZnO nanorod array heterojunction electroluminescence depended on the annealing temperature of the

Bo Ling; Jun Liang Zhao; Xiao Wei Sun; Swee Tiam Tan; Aung Ko Ko Kyaw; Yoga Divayana; Zhi Li Dong

2010-01-01

277

High-power CW Nd:GdVO4 solid-state laser end-pumped by a diode-laser-array  

NASA Astrophysics Data System (ADS)

A high-power CW Nd:GdVO4 laser end-pumped by a diode-laser-array has been demonstrated. TEM00 mode output power of 5.05 W was obtained at the incident pump power of 12 W, leading to an optical conversion efficiency of 42.1%, while the slope efficiency was determined to be 47.6%. These results were shown to be slightly better than those achieved with Nd:YVO4 crystal having the same Nd3+ concentration.

Liu, Junhai; Shao, Zongshu; Meng, Xianlin; Zhang, Huaijin; Zhu, Li; Jiang, Minhua

1999-06-01

278

Rapid analysis of benzoylecgonine, cocaine, and cocaethylene in urine, serum, and saliva by isocratic high-performance liquid chromatography with diode-array detection  

Microsoft Academic Search

Summary  An isocratic high-performance liquid-chromatographic (HPLC) procedure with diode-array detection has been developed for the\\u000a determination of benzoylecgonine, cocaine, and cocaethylene in urine, serum, and saliva. After solid-phase extraction with\\u000a mixed-mode extraction cartridges the three solutes are separated, in less than 20 min, by HPLC on a Supelcosil ABZ+column\\u000a with 17?83 (v\\/v) acetonitrile-0.04 M phosphate buffer, pH 2.3, as mobile phase.

C. Foulon; M.-C. Menet; N. Manuel; C. Pham-Huy; H. Galons; J.-R. Claude; F. Guyon

1999-01-01

279

The effect of trimethylgallium flows in the AlInGaN barrier on optoelectronic characteristics of near ultraviolet light-emitting diodes grown by atmospheric pressure metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The letter reports a theoretical and experimental study on the device performance of near ultraviolet light-emitting diodes (LEDs) with quaternary AlInGaN quantum barrier (QB). The indium mole fraction of AlInGaN QB could be enhanced as we increased the trimethylgallium flow rate. It was found the AlInGaN/InGaN LEDs can reduce forward voltage and improve light output power, compared with conventional GaN QB. By using advanced device simulation, it should be attributed to a reduction in lattice mismatch induced polarization mismatch in the active layer, which results in the suppression of electron overflow.

Fu, Yi-Keng; Jiang, Ren-Hao; Lu, Yu-Hsuan; Chen, Bo-Chun; Xuan, Rong; Fang, Yen-Hsiang; Lin, Chia-Feng; Su, Yan-Kuin; Chen, Jenn-Fang

2011-03-01

280

Combustion synthesis and luminescent properties of a new material Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ for ultraviolet light emitting diodes  

Microsoft Academic Search

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li2(Ba0.99,Eu0.01)SiO4:B3+ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li2(Ba0.99,Eu0.01)SiO4:B3+ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and

Shanshan Yao; Donghua Chen

2008-01-01

281

Influence of the alignment of ZnO nanorod arrays on light extraction enhancement of GaN-based light-emitting diodes  

NASA Astrophysics Data System (ADS)

ZnO nanorod arrays (ZNAs) were hydrothermally synthesized on the surface of patterned indium-doped tin oxide p-type contact (PIPC) of GaN-based light-emitting diodes (GaN-LEDs) for enhancing the light extraction efficiency (LEE). It was found that the alignment of the ZnO nanorod arrays in the grooves of the PIPC was poorer than these grown on the ridges of the PIPC. By comparing the light output of the GaN-LEDs with and without ZNAs grown in the grooves of PIPC, the influence of the alignment of ZNAs on the LEE of GaN-LEDs was revealed and investigated. Numerical analysis based on the finite difference of time domain (FDTD) method suggested that the poorer alignment of ZNAs grown on GaN-LEDs resulted in more energy reflected back into GaN-LEDs and lower light extraction efficiency.

Dai, Kehui; Soh, Chew Beng; Chua, Soo Jin; Wang, Lianshan; Huang, Dexiu

2011-04-01

282

High performance InGaN/GaN nanorod light emitting diode arrays fabricated by nanosphere lithography and chemical mechanical polishing processes.  

PubMed

We fabricated InGaN/GaN nanorod light emitting diode (LED) arrays using nanosphere lithography for nanorod formation, PECVD (plasma enhanced chemical vapor deposition) grown SiO(2) layer for sidewall passivation, and chemical mechanical polishing for uniform nanorod contact. The nano-device demonstrates a reverse current 4.77nA at -5V, an ideality factor 7.35, and an optical output intensity 6807mW/cm(2) at the injection current density 32A/cm(2) (20mA). Moreover, the investigation of the droop effect for such a nanorod LED array reveals that junction heating is responsible for the sharp decrease at the low current. PMID:20588606

Chen, Liang-Yi; Huang, Ying-Yuan; Chang, Chun-Hsiang; Sun, Yu-Hsuan; Cheng, Yun-Wei; Ke, Min-Yung; Chen, Cheng-Pin; Huang, Jianjang

2010-04-12

283

Determination of phenolic compounds in rose hip (Rosa canina) using liquid chromatography coupled to electrospray ionisation tandem mass spectrometry and diode-array detection.  

PubMed

Liquid chromatography coupled with negative and positive electrospray ionisation (ESI) tandem mass spectrometry (MS/MS) and diode-array detection (DAD) was used for determination of phenols in rose hip (Rosa canina) extract. ESI mass spectra of the chromatographically separated phenols gave the molecular weight of the compounds through prominent [M - H](-) ions for most of the compounds and M(+) ions for the anthocyanins. Collision induced dissociation (CID) of the [M - H](-) (or M(+)) precursor ions yielded product ions which determined the molecular weight of the aglycones. In-source fragmentation followed by CID of the resulting deprotonated aglycone ([A - H](-)) provided product ions for the identification of the unconjugated phenols. The identification was based on comparison with product ion spectra of commercial standards. UV-diode-array spectra were used for identity confirmation. This combined approach allowed the identification in rose hip extract of an anthocyanin, i.e. cyanidin-3-O-glucoside, several glycosides of quercetin and glycosides of taxifolin and eriodictyol. Phloridzin was identified, and several conjugates of methyl gallate were also found, one of which was tentatively identified as methyl gallate-rutinoside. Catechin and quercetin were found as the aglycones in the extract. PMID:11921243

Hvattum, Erlend

2002-01-01

284

A Pt/TiO2/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays  

NASA Astrophysics Data System (ADS)

This study examined the properties of Schottky-type diodes composed of Pt/TiO2/Ti, where the Pt/TiO2 and TiO2/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection device for a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of ~ 109 was achieved at 1 V when the TiO2 film thickness was 19 nm. TiO2 film was grown by atomic layer deposition at a substrate temperature of 250 °C. Conductive atomic force microscopy revealed that the forward current flew locally, which limits the maximum forward current density to < 10 A cm - 2 for a large electrode (an area of ~ 60 000 µm2). However, the local current measurement showed a local forward current density as high as ~ 105 A cm - 2. Therefore, it is expected that this type of Schottky diode effectively suppresses the sneak current without adverse interference effects in a nano-scale resistive switching cross-bar array with high block density.

Park, Woo Young; Kim, Gun Hwan; Seok, Jun Yeong; Kim, Kyung Min; Song, Seul Ji; Lee, Min Hwan; Hwang, Cheol Seong

2010-05-01

285

Simultaneous Determination of Iron, Copper and Cobalt in Food Samples by CCD-diode Array Detection-Flow Injection Analysis with Partial Least Squares Calibration Model  

NASA Astrophysics Data System (ADS)

A flow injection-CCD diode array detection spectrophotometry with partial least squares (PLS) program for simultaneous determination of iron, copper and cobalt in food samples has been established. The method was based on the chromogenic reaction of the three metal ions and 2- (5-Bromo-2-pyridylazo)-5-diethylaminophenol, 5-Br-PADAP in acetic acid - sodium acetate buffer solution (pH5) with Triton X-100 and ascorbic acid. The overlapped spectra of the colored complexes were collected by charge-coupled device (CCD) - diode array detector and the multi-wavelength absorbance data was processed using partial least squares (PLS) algorithm. Optimum reaction conditions and parameters of flow injection analysis were investigated. The samples of tea, sesame, laver, millet, cornmeal, mung bean and soybean powder were determined by the proposed method. The average recoveries of spiked samples were 91.80%~100.9% for Iron, 92.50%~108.0% for Copper, 93.00%~110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%~12.1%. The sampling rate is 45 samples h-1. The determination results of the food samples were in good agreement between the proposed method and ICP-AES.

Mi, Jiaping; Li, Yuanqian; Zhou, Xiaoli; Zheng, Bo; Zhou, Ying

2006-01-01

286

Bicolor Light-Emitting Diode Based on Zinc Oxide Nanorod Arrays and Poly(2-methoxy,5-octoxy)-1,4-phenylenevinylene  

NASA Astrophysics Data System (ADS)

The current study reports a novel inorganic/organic light-emitting diode (LED), consisting of zinc oxide (ZnO) nanorod arrays and poly(2-methoxy, 5-octoxy)-1,4-phenylenevinylene (MOPPV). ZnO nanorod arrays passivated using polyacrylamide (PAM) with 70 nm diameter were successfully prepared by a simple polymer-assisted chemical method. Enhancement of the ZnO defect emission is caused by PAM passivation, as observed in photoluminescence spectra. Infrared absorption spectra reveal that PAM is chemically or physically adsorbed on the surfaces of ZnO nanorod arrays. The electroluminescence (EL) spectrum shows bluish light at 406 nm from ZnO transition emission, and light emission with center at 600 nm from exciton emission in MOPPV. The potential EL mechanism is electron transition to zinc vacancy in PAM/ZnO nanorod arrays, and exciton radiation luminescence in MOPPV film. This novel PAM/ZnO-MOPPV device may be helpful to promote development of multicolor LEDs.

Song, Jizhong; He, Ying; Chen, Jie; Zhu, Di; Pan, Zhaodong; Zhang, Yaofei; Wang, Jun-An

2012-03-01

287

5.8GHz circularly polarized dual-diode rectenna and rectenna array for microwave power transmission  

Microsoft Academic Search

This paper reports a new circularly polarized rectenna whose rectifying circuit includes two diodes. The rectenna consists of a coplanar stripline (CPS) truncated patch antenna and CPS bandpass filter, which can block harmonic signals up to the third order reradiating from the rectifying circuit. The rectenna is printed on Rogers Duroid 5880 substrate with ?r=2.2 and a thickness of 20

Yu-Jiun Ren; Kai Chang

2006-01-01

288

PtSi Schottky-Barrier Focal Plane Arrays for Multispectral Imaging in Ultraviolet, Visible, and Infrared Spectral Bands.  

National Technical Information Service (NTIS)

PtSi Schottky-barrier detectors, which are conventionally used in t he back-illumination mode for thermal imaging in the 3-5 micron infrared (IR) spectral band, are shown to exhibit excellent photoresponse in the near-ultraviolet and visible regions when ...

B. Y. Tsaur C. K. Chen J. P. Mattia

1990-01-01

289

Effects of Aluminium Doping and Electrode Distance on the Performance of Aligned Zinc Oxide Nanorod Array-Based Ultraviolet Photoconductive Sensors  

NASA Astrophysics Data System (ADS)

Metal--semiconductor--metal (MSM) ultraviolet (UV) photoconductive sensors were fabricated using undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays prepared via the sonicated sol--gel immersion method. Notably, the nanorod diameter decreased with Al-doping, varying in the size range of 30 to 70 nm, compared with undoped ZnO, which had a size range of 80--120 nm. The Al-doped nanorod arrays exhibited optical properties superior to those of the undoped ZnO, with an average transmittance of 85% in the visible region; the Al-doped arrays also showed good UV absorption properties. Photoluminescence measurements indicate that the suppression of defects was observed for the Al-doped ZnO nanorod, as shown by a bigger IUV/Ivis of 1.24 compared to that of undoped ZnO (0.97). According to the experimental results, the UV responsivity was significantly improved by the Al-doping, with the highest value of 373 A/W obtained at an inter-electrode distance of 0.07 mm under UV light (365 nm, 750 ?W/cm2) with a 10 V bias. In addition, the responsivity of the UV sensor also significantly improved when the inter-electrode distances were reduced from 2.00 to 0.07 mm.

Mamat, Mohamad Hafiz; Khusaimi, Zuraida; Zahidi, Musa Mohamed; Bakar, Suriani Abu; Yusop, Mohd Zamri; Tanemura, Masaki; Mahmood, Mohamad Rusop

2012-06-01

290

Simultaneous determination of nucleosides, myriocin, and carbohydrates in Cordyceps by HPLC coupled with diode array detection and evaporative light scattering detection.  

PubMed

A HPLC coupled with diode array detection (DAD) and evaporative light scattering detection (ELSD) method for qualitative and quantitative analysis of eight nucleosides and nucleobases, three carbohydrates and myriocin in Cordyceps was developed. A Prevail Carbohydrate ES column was employed for the separation within 50 min. Nucleosides and their bases were tested at UV 254 nm. ELSD was connected with DAD to determine myriocin and carbohydrates. The optimum drift tube temperature of ELSD was at 94 degrees C with the nitrogen flow rate of 2.0 L/min. All calibration curves showed good linearity (R(2)>0.9933) during the test ranges. The precision, repeatability, accuracy, LOD and LOQ were also fully investigated. This developed method was successfully applied to quantify 12 components, eight nucleosides and nucleobases, three carbohydrates and myriocin, in natural and cultured Cordyceps, which provides another view for quality control of Cordyceps sinensis. PMID:20066678

Wang, Shuang; Yang, Feng-Qing; Feng, Kun; Li, De-Qiang; Zhao, Jing; Li, Shao-Ping

2009-12-01

291

Simultaneous extraction and analysis by high performance liquid chromatography coupled to diode array and mass spectrometric detectors of bixin and phenolic compounds from annatto seeds.  

PubMed

This study was designed to identify and quantify the carotenoids and phenolic compounds from annatto seeds using high performance liquid chromatography coupled to diode array and mass spectrometer detectors (HPLC-DAD-MS/MS). Furthermore, using response surface methodology, an optimized procedure for simultaneous extraction of these compounds was established. In addition to bixin, known to be the main carotenoid in annatto seeds, hypolaetin and a caffeoyl acid derivative were identified as the main phenolic compounds. The optimized procedure involved 15 extractions using acetone:methanol:water (50:40:10, v/v/v) as solvent, a solid-liquid ratio of 1:9 (m/v) and an extraction time of 5 min. Validation data indicated that the HPLC method proposed provided good linearity, sensitivity, procedure accuracy, system precision and suggested its suitability for the simultaneous analysis of phenolic compounds and carotenoids in annatto seeds. PMID:21111424

Chisté, Renan Campos; Yamashita, Fábio; Gozzo, Fábio Cesar; Mercadante, Adriana Zerlotti

2010-10-30

292

Analysis by high-performance liquid chromatography diode array detection mass spectrometry of phenolic compounds in fruit of Eucalyptus globulus cultivated in Algeria.  

PubMed

A method based on high-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS) following fractionation by chromatography on a Sephadex LH-20 column has been developed to determine the phenolic composition of fruit of Eucalyptus globulus growing in Algeria. The presence of 18 gallotannins, 26 ellagitannins, and 2 flavonols was established. Tentative identification is provided for these compounds on the basis of UV-visible spectra and mass spectrometry data. Most compounds described in this study have not previously detected in fruit of E. globulus. Moreover, this is the first report of methyl digalloyl diglucose, 3,3'-O-dimethylellagic acid 4-O-?-glucopyranoside, ellagic acid hexose, methyl ellagic acid pentose, methyltetragalloylglucose, and valoneic acid isomers (sanguisorbic, flavogallic acid dilactone) in the genus Eucalyptus. Quantitatively, ellagic acid and its derivatives, including ellagitannins, are largely predominant. PMID:21121679

Boulekbache-Makhlouf, Lila; Meudec, Emmanuelle; Chibane, Mohamed; Mazauric, Jean-Paul; Slimani, Sakina; Henry, Max; Cheynier, Veronique; Madani, Khodir

2010-12-01

293

Strong Light-Extraction Enhancement of GaN-Based Light-Emitting Diodes with Top and Sidewall GaOOH Nanorod Arrays  

NASA Astrophysics Data System (ADS)

We reported the gallium nitride-based blue light-emitting diodes (LEDs) with top and sidewall gallium oxide hydroxide (GaOOH) nanorod arrays (NRAs). Highly-oriented GaOOH NRAs were formed on the surfaces of LEDs by the electrochemical deposition method using a sputtered tin oxide seed layer. The as-synthesized GaOOH NRAs exhibited a high light-scattering property while maintaining high transparency of >90% in the visible wavelength range. For LEDs with top and sidewall GaOOH NRAs, the light output power was significantly enhanced by ˜36% and the far-field radiation pattern also became wider compared to the conventional LED. This improvement in light extraction is attributed to the relatively graded refractive index profile and the formation of roughened top and sidewall surfaces by the GaOOH NRAs.

Lee, Hee Kwan; Yu, Jae Su

2012-10-01

294

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

DOEpatents

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.

Beach, R.J.

1997-11-18

295

Direct characterization of aqueous extract of Hibiscus sabdariffa using HPLC with diode array detection coupled to ESI and ion trap MS.  

PubMed

The phenolic fraction and other polar compounds of the Hibiscus sabdariffa were separated and identified by HPLC with diode array detection coupled to electrospray TOF and IT tandem MS (DAD-HPLC-ESI-TOF-MS and IT-MS). The H. sabdariffa aqueous extract was filtered and directly injected into the LC system. The analysis of the compounds was carried out by RP HPLC coupled to DAD and TOF-MS in order to obtain molecular formula and exact mass. Posterior analyses with IT-MS were performed and the fragmentation pattern and confirmation of the structures were achieved. The H. sabdariffa samples were successfully analyzed in positive and negative ionization modes with two optimized linear gradients. In positive mode, the two most representative anthocyanins and other compounds were identified whereas the phenolic fraction, hydroxycitric acid and its lactone were identified using the negative ionization mode. PMID:19750503

Rodríguez-Medina, Inmaculada C; Beltrán-Debón, Raúl; Molina, Vicente Micol; Alonso-Villaverde, Carlos; Joven, Jorge; Menéndez, Javier A; Segura-Carretero, Antonio; Fernández-Gutiérrez, Alberto

2009-10-01

296

On the depolarisation of radiation of a transversely diode-laser-array-pumped Yb, Er-doped phosphate glass active element  

SciTech Connect

Repetitively pulsed lasing in a Yb, Er-doped phosphate glass transversely pumped by a diode laser array is studied. Lasing on the lowest TEM{sub 00} resonator mode is obtained both in the quasi-continuous regime with an output power of 4.1 W and in the passive Q-switching regime (23-ns, 1.2-mJ pulses). The depolarisation of linearly polarised radiation of a He-Ne laser transmitted through the phosphate glass active element (AE) along the resonator axis is investigated. The dependences of depolarisation on the AE heating and experimental conditions are determined. It is shown that radiation losses caused by its depolarisation can present problems in the development of lasers emitting at 1.5 {mu}m, in which polarisers should be used (for example, regenerative amplifiers). (lasers)

Shachkin, L V [State Research Center of Russian Federation 'Troitsk Institute for Innovation and Fusion Research', Troitsk, Moscow Region (Russian Federation)

2007-02-28

297

Quantitative analysis of flavonols, flavones, and flavanones in fruits, vegetables and beverages by high-performance liquid chromatography with photo-diode array and mass spectrometric detection.  

PubMed

A high-performance liquid chromatographic (HPLC) separation method with photo-diode array (PDA) and mass spectrometric (MS) detection was developed to determine and quantify flavonols, flavones, and flavanones in fruits, vegetables and beverages. The compounds were analysed as aglycones, obtained after acid hydrolysis of freeze-dried food material. Identification was based on retention time, UV and mass spectra by comparison with commercial standards, and the UV peak areas were used for quantitation of the flavonoid contents. Examples of HPLC-MS, analyses of orange pulp, tomato, and apple are presented. The method has been used to screen foods on the Danish market, and the contents of flavones, flavonols, and flavanones were measured. PMID:9550103

Justesen, U; Knuthsen, P; Leth, T

1998-03-13

298

N-polar GaN etching and approaches to quasi-perfect micro-scale pyramid vertical light-emitting diodes array  

NASA Astrophysics Data System (ADS)

N-polar GaN etching process and mechanism has been investigated in detail by varying the etching parameter (etchant temperature, etchant concentration, and etching duration) in KOH and H3PO4. Quasi-perfect micro-scale hexagonal pyramids vertical light emitting diodes (?-HP VLEDs) array with least active area loss (<12%) has been fabricated by N-polar etching. The ?-HP VLEDs shows massively improved crystal quality with X-ray diffraction full width at half maxima decreased from 442 s to 273 s, and the room temperature minority carriers decay time increased from 252 ps to 747 ps. Temperature dependence of photoluminescence result reveals a ~30% improved internal quantum efficiency, and transmission electron microscope further reveals its quasi-perfect crystalline quality clearly.

Wang, Liancheng; Ma, Jun; Liu, Zhiqiang; Yi, Xiaoyan; Yuan, Guodong; Wang, Guohong

2013-10-01

299

Hard modeling methods for the curve resolution of data from liquid chromatography with a diode array detector and on-flow liquid chromatography with nuclear magnetic resonance spectroscopy.  

PubMed

Hard modeling methods have been performed on data from high-performance liquid chromatography with a diode array detector (LC-DAD) and on-flow liquid chromatography with 1H nuclear magnetic spectroscopy (LC-NMR). Four methods have been used to optimize parameters to model concentration profiles, three of which belong to classical optimization methods (the simplex method of Nelder-Mead, sequential quadratic programming approach, and Levenberg-Marquardt method), and the fourth is the application of genetic algorithms using real-value encoding. Only classical methods worked well for LC-DAD data, while all of the methods produced good results when LC-NMR data were divided into small spectral windows of peak clusters and parameters were optimized over each window. PMID:16711734

Wasim, Mohammad; Brereton, Richard G

300

Yellow-green and amber InGaN micro-pixellated light-emitting diode arrays  

Microsoft Academic Search

Micro-pixel InGaN LED arrays operating at 560nm and 600nm, respectively, are demonstrated, based on new epitaxial structures. Such devices have applications in areas including bioinstrumentation, visible light communications and micro-displays.

Z. Gong; D. Massoubre; E. Y. Xie; J. McKendry; E. Gu; M. D. Dawson; N. Y. Liu; Y. B. Tao; Z. Z. Chen; G. Y. Zhang; Y. B. Pan; M. S. Hao

2010-01-01

301

The enhancement of light-emitting efficiency using GaN-based multiple quantum well light-emitting diodes with nanopillar arrays  

NASA Astrophysics Data System (ADS)

The quest for higher modulation speed and lower energy consumption has inevitably promoted the rapid development of semiconductor-based solid lighting devices in recent years. GaN-based light-emitting diodes (LEDs) have emerged as promising candidates for achieving high efficiency and high intensity, and have received increasing attention among many researchers in this field. In this paper, we use a self-assembled array-patterned mask to fabricate InGaN/GaN multi-quantum well (MQW) LEDs with the intention of enhancing the light-emitting efficiency. By utilizing inductively coupled plasma etching with a self-assembled Ni cluster as the mask, nanopillar arrays are formed on the surface of the InGaN/GaN MQWs. We then observe the structure of the nanopillars and find that the V-defects on the surface of the conventional structure and the negative effects of threading dislocation are effectively reduced. Simultaneously, we make a comparison of the photoluminescence (PL) spectrum between the conventional structure and the nanopillar arrays, achieved under an experimental set-up with an excitation wavelength of 325 mm. The analysis demonstrates that MQW-LEDs with nanopillar arrays achieve a PL intensity 2.7 times that of conventional LEDs. In response to the PL spectrum, some reasons are proposed for the enhancement in the light-emitting efficiency as follows: 1) the improvement in crystal quality, namely the reduction in V-defects; 2) the roughened surface effect on the expansion of the critical angle and the attenuated total reflection; and 3) the enhancement of the light-extraction efficiency due to forward scattering by surface plasmon polariton modes in Ni particles deposited above the p-type GaN layer at the top of the nanopillars.

Wan, Tu-Tu; Ye, Zhan-Qi; Tao, Tao; Xie, Zi-Li; Zhang, Rong; Liu, Bin; Xiu, Xiang-Qian; Li, Yi; Han, Ping; Shi, Yi; Zheng, You-Dou

2013-08-01

302

ZnO homojunction photodiodes based on Sb-doped p-type nanowire array and n-type film for ultraviolet detection  

SciTech Connect

ZnO p-n homojunctions based on Sb-doped p-type nanowire array and n-type film were grown by combining chemical vapor deposition (for nanowires) with molecular-beam epitaxy (for film). Indium tin oxide and Ti/Au were used as contacts to the ZnO nanowires and film, respectively. Characteristics of field-effect transistors using ZnO nanowires as channels indicate p-type conductivity of the nanowires. Electron beam induced current profiling confirmed the existence of ZnO p-n homojunction. Rectifying I-V characteristic showed a turn-on voltage of around 3 V. Very good response to ultraviolet light illumination was observed from photocurrent measurements.

Wang Guoping; Chu Sheng; Zhan Ning; Liu Jianlin [Department of Electrical Engineering, Quantum Structures Laboratory, University of California at Riverside, Riverside, California 92521 (United States); Lin Yuqing; Chernyak, Leonid [Department of Physics, University of Central Florida, Orlando, Florida 32816-2385 (United States)

2011-01-24

303

Effects of double layer AlN buffer layers on properties of Si-doped AlxGa1-xN for improved performance of deep ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

Si-doped Al0.77Ga0.23N epilayers were grown on AlN/sapphire templates by metal organic chemical vapor deposition using double AlN buffer layers. It was found that the use of double AlN buffer layers improved the overall material quality of the Si-doped Al0.77Ga0.23N epilayers, as evidenced in the decreased density of screw dislocations and surface pits and increased emission intensity ratio of the band-edge to the deep level impurity transition. Hall effect measurements also indicated improved n-type conductivity. The performance of the deep ultraviolet light-emitting diodes fabricated using double buffer layers was significantly improved, as manifested by enhanced output power and reduced turn-on voltage.

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

2013-03-01

304

Transient thermal analysis of InGaAsP-InP high-power diode laser arrays with different fill factors  

NASA Astrophysics Data System (ADS)

The temperature kinetics of InGaAsP/InP high-power laser diode arrays with different fill factors was studied experimentally and theoretically. It was shown that except during a short initial period, the laser array heating is determined by the heat flux propagation through the heat spreader. To characterize this heating, we developed a two-dimensional analytical model. Experimentally, the temperature change in the active region was obtained by measuring the laser spectrum's temporal evolution during a single current pulse. Three distinctive periods in the transient heating process were clearly identified-an initial temperature rise, a square-root-of-time dependence of the active-region temperature increase, and an exponential approach of the active-region temperature to its steady-state value. We demonstrated that in the initial period of time, the heat propagates within the laser bar structure, and the laser bar design (fill factor) strongly affects the active-region temperature rise. In the later periods the temperature kinetics is insensitive to the fill factor.

Gourevitch, A.; Laikhtman, B.; Westerfeld, D.; Donetsky, D.; Belenky, G.; Trussell, C. W.; Shellenbarger, Z.; An, H.; Martinelli, R. U.

2005-04-01

305

Enhanced light out-coupling of organic light-emitting diode using metallic nanomesh electrodes and microlens array.  

PubMed

A precisely controlled metallic nanomesh was fabricated by using nanosphere lithography to pattern the silver thin film to form hexagonal nanohole arrays with excellent uniformity, high conductivity and good transparency. An Alq(3) based OLED, with the silver nanomesh electrode of high ðll factor of 70.2% demonstrated a considerable luminous efðciency of 4.8 cd/A, which is 60.9% higher than the referenced device with ITO anode. The periodical nanohole array not only increased the transparency but also helped extracting surface plasmonic wave in organic layers. By attaching the microlens array to further extract the trapped light in substrate, the extraction efficiency enhancement of device with nanomesh anode was 73.8% higher than 50.2% of the referenced device with ITO anode. And the overall current efficiency of device with nanomesh anode was 87.7% higher than traditional ITO based device. PMID:23571942

Ho, Yu-Hsuan; Chen, Kuan-Yu; Peng, Kai-Yu; Tsai, Ming-Chih; Tian, Wei-Cheng; Wei, Pei-Kuen

2013-04-01

306

Fabrication of cylindrical lens arrays utilizing the pinning effect of the partition walls on ultraviolet curable polymers  

NASA Astrophysics Data System (ADS)

A technique of controlling the pitch and radius of curvature of a cylindrical lens array is presented. The lens pitch is controlled by producing the linear partition walls that sandwich a UV-curable polymer. The partition walls are created by scratching a polymeric substrate with a sharp edge. The radius of curvature can be controlled by designating the volume of the UV-curable polymer dispensed between the partition walls that prevent the spreading of the polymer due to the pinning effect. This technique can contribute to realizing a practical fabrication method for cylindrical lens arrays owing to its simplicity and flexibility.

Yasuda, Shin; Shimizu, Keishi

2012-09-01

307

High-brightness line generators and fiber-coupled sources based on low-smile laser diode arrays  

NASA Astrophysics Data System (ADS)

We describe the performance of diode laser bars mounted on conductive and water cooled platforms using low smile processes. Total smile of <1?m is readily achieved on both In and AuSn based platforms. Combined with environmentally robust lensing, these mounts form the basis of multiple, high-brightness products. Free-space-coupled devices utilizing conductively-cooled bars delivering 100W from a 200?m, 0.22NA fiber at 976nm have been developed for pumping fiber lasers, as well as for materials processing. Additionally, line generators for graphics and materials processing applications have been produced. Starting from single bars mounted on water-cooled packages that do not require de-ionized or pH-controlled water, these line generators deliver over 80W of power into a line with an aspect ratio of 600:1, and have a BPP of <2mm-mrad in the direction orthogonal to the line.

Watson, J.; Schleuning, D.; Lavikko, P.; Alander, T.; Lee, D.; Lovato, P.; Winhold, H.; Griffin, M.; Tolman, S.; Liang, P.; Hasenberg, T.; Reed, M.

2008-03-01

308

Photovoltaic module bypass diode encapsulation  

NASA Astrophysics Data System (ADS)

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.

Shepard, N. J., Jr.

1983-06-01

309

Determination of triazines in water samples by high-performance liquid chromatography with diode-array detection.  

PubMed

Triazines are widely used herbicides that can be detected in the environment at trace level. A preconcentration step is necessary to determinate them before analysis. In this study, carbonaceous and polymeric adsorbents are compared with C18 for the solid-phase extraction of simazine, atrazine, and propazine in water samples in order to quantitate their levels by high-performance liquid chromatography using photodiode-array detection. PMID:12433116

Dopico, M S; González, M V; Castro, J M; González, E; Pérez, J; Rodríguez, M; Calleja, A

2002-10-01

310

Fully Integrated Linear Single Photon Avalanche Diode (SPAD) Array with Parallel Readout Circuit in a Standard 180 nm CMOS Process  

NASA Astrophysics Data System (ADS)

This paper reports on the development of a SPAD device and its subsequent use in an actively quenched single photon counting imaging system, and was fabricated in a UMC 0.18 ?m CMOS process. A low-doped p- guard ring (t-well layer) encircling the active area to prevent the premature reverse breakdown. The array is a 16×1 parallel output SPAD array, which comprises of an active quenched SPAD circuit in each pixel with the current value being set by an external resistor RRef = 300 k?. The SPAD I-V response, ID was found to slowly increase until VBD was reached at excess bias voltage, Ve = 11.03 V, and then rapidly increase due to avalanche multiplication. Digital circuitry to control the SPAD array and perform the necessary data processing was designed in VHDL and implemented on a FPGA chip. At room temperature, the dark count was found to be approximately 13 KHz for most of the 16 SPAD pixels and the dead time was estimated to be 40 ns.

Isaak, S.; Bull, S.; Pitter, M. C.; Harrison, Ian.

2011-05-01

311

Evaluation of the sensitivity of two 3D diode array dosimetry systems to setup error for quality assurance (QA) of volumetric-modulated arc therapy (VMAT).  

PubMed

The purpose of this study is to evaluate the sensitivities of 3D diode arrays to setup error for patient-specific quality assurance (QA) of volumetric-modulated arc therapy (VMAT). Translational setup errors of ± 1, ± 2, and ± 3 mm in the RL, SI, and AP directions and rotational setup errors of ± 1° and ± 2° in the pitch, roll, and yaw directions were set up in two phantom systems, ArcCHECK and Delta4, with VMAT plans for 11 patients. Cone-beam computed tomography (CBCT) followed by automatic correction using a HexaPOD 6D treatment couch ensured the position accuracy. Dose distributions of the two phantoms were compared in order to evaluate the agreement between calculated and measured values by using ? analysis with 3%/3 mm, 3%/2 mm, and 2%/2 mm criteria. To determine the impact on setup error for VMAT QA, we evaluated the sensitivity of results acquired by both 3D diode array systems to setup errors in translation and rotation. For the VMAT QA of all patients, the pass rate with the 3%/3 mm criteria exceeded 95% using either phantom. For setup errors of 3 mm and 2°, respectively, the pass rates with the 3%/3mm criteria decreased by a maximum of 14.0% and 23.5% using ArcCHECK, and 14.4% and 5.0% using Delta4. Both systems are sensitive to setup error, and do not have mechanisms to account for setup errors in the software. The sensitivity of both VMAT QA systems was strongly dependent on the patient-specific plan. The sensitivity of ArcCHECK to the rotational error was higher than that of Delta4. In order to achieve less than 3% mean pass rate reduction of VMAT plan QA with the 3%/3 mm criteria, a setup accuracy of 2 mm/1° and 2 mm/2° is required for ArcCheck and Delta4 devices, respectively. The cumulative effect of the combined 2 mm translational and 1° rotational errors caused 3.8% and 2.4% mean pass rates reduction with 3%/3 mm criteria, respectively, for ArcCHECK and Delta4 systems. For QA of VMAT plans for nasopharyngeal cancer (NPC) using the ArcCHECK system, the setup should be more accurate. PMID:24036856

Li, Guangjun; Bai, Sen; Chen, Nianyong; Henderson, Lansdale; Wu, Kui; Xiao, Jianghong; Zhang, Yingjie; Jiang, Qingfeng; Jiang, Xiaoqin

2013-09-06

312

PIN Diode Detectors  

SciTech Connect

A review of the application of PIN diodes as radiation detectors in particle counting, X- and {gamma}-ray spectroscopy, medical applications and charged particle spectroscopy is presented. As a practical example of its usefulness, a PIN diode and a low noise preamplifier are included in a nuclear spectroscopy chain for X-ray measurements. This is a laboratory session designed to review the main concepts needed to set up the detector-preamplifier array and to make measurements of X-ray energy spectra with a room temperature PIN diode. The results obtained are compared with those obtained with a high resolution cooled Si-Li detector.

Ramirez-Jimenez, F. J. [Instituto Nacional de Investigaciones Nucleares Carretera Mexico-Toluca S/N, La Marquesa, Ocoyoacac, 57150 (Mexico)

2008-07-02

313

A rapid method for simultaneous determination of 14 phenolic compounds in Radix Puerariae using microwave-assisted extraction and ultra high performance liquid chromatography coupled with diode array detection and time-of-flight mass spectrometry  

Microsoft Academic Search

A microwave-assisted extraction (MAE) and ultra high performance liquid chromatography coupled with diode array detection and time-of-flight mass spectrometry (UHPLC-DAD-TOF-MS) method was developed for simultaneous determination of 14 phenolic compounds in the root of Pueraria lobata (Wild.) Ohwi and Pueraria thomsonii Benth. Operational conditions of MAE were optimized by central composite design (CCD). The optimized result was 65% ethanol as

G. Du; H. Y. Zhao; Q. W. Zhang; G. H. Li; F. Q. Yang; Y. Wang; Y. C. Li

2010-01-01

314

Determination of pharmaceuticals in river water by column switching of large sample volumes and liquid chromatography–diode array detection, assisted by chemometrics: An integrated approach to green analytical methodologies  

Microsoft Academic Search

An analytical method for the simultaneous determination of nine ?-blockers (sotalol atenolol, nadolol, pindolol, metoprolol, timolol, bisoprolol, propanolol and betaxolol) and two analgesics (paracetamol and phenazone) in river water by liquid chromatography and diode array detection is reported. The method involves a modified precolumn switching methodology replacing the small precolumn with a short C18 liquid chromatography column (50mm×4.6mm, 5?m particle

M. Martínez Galera; M. D. Gil García; M. J. Culzoni; H. C. Goicoechea

2010-01-01

315

Application of high-speed counter-current chromatography coupled with high-performance liquid chromatography–diode array detection for the preparative isolation and purification of hyperoside from Hypericum perforatum with online purity monitoring  

Microsoft Academic Search

Following preparative isolation and purification by high-speed counter-current chromatography (HSCCC), the collected fractions were generally analyzed by high-performance liquid chromatography (HPLC) to determine the relative purities of each fraction. Our paper reports for the first time a preparative isolation-purity detection hyphenated system: online coupling of HSCCC with high-performance liquid chromatography–diode array detection (HSCCC–HPLC–DAD). The introduction of online purity analysis in

Tingting Zhou; Bin Chen; Guorong Fan; Yifeng Chai; Yutian Wu

2006-01-01

316

On-line determination of carboxylic acids, aldehydes and ketones by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionisation mass spectrometry after derivatization with 2-nitrophenylhydrazine  

Microsoft Academic Search

2-Nitrophenylhydrazine (2-NPH) is widely used for the derivatization of carboxylic acids, aldehydes and ketones, in industrial and biological samples. These compounds react with 2-NPH to form derivatives, which are separated by high-performance liquid chromatography (HPLC) and detected with diode array detection (DAD). The UV spectra give information about the functionality of the compounds: carboxylic acid or ketone\\/aldehyde. Most of the

R. Peters; J. Hellenbrand; Y. Mengerink; Sj. Van der Wal

2004-01-01

317

Identification of antioxidants from Taraxacum mongolicum by high-performance liquid chromatography–diode array detection–radical-scavenging detection–electrospray ionization mass spectrometry and nuclear magnetic resonance experiments  

Microsoft Academic Search

Taraxacum mongolicum was a traditional Chinese medicine for the treatment of inflammatory disorders and viral infectious diseases. Furthermore, fresh leaves of T. mongolicum have been used by local people as vegetable food in Northern China. An on-line rapid screening method, high-performance liquid chromatography–diode array detection–radical-scavenging detection–electrospray ionization mass spectrometry (HPLC–DAD–RSD–ESI-MS) system, has been developed for the separation and identification of

Shuyun Shi; Yu Zhao; Honghao Zhou; Yuping Zhang; Xinyu Jiang; Kelong Huang

2008-01-01

318

The offline combination of thin-layer chromatography and high-performance liquid chromatography with diode array detection and micrOTOF-Q mass spectrometry for the separation and identification of spinochromes from sea urchin ( Strongylocentrotus droebachiensis) shells  

Microsoft Academic Search

Thin-layer chromatography (TLC) with off-line high-performance liquid chromatography coupled to diode array detection and micrOTOF-Q mass spectrometry (HPLC–DAD–MS) resulted in the successful fractionation, separation and identification of spinochrome pigments from sea urchin (Strongylocentrotus droebachiensis) shells. Two fractions of pigments were separated by TLC and eluted with methanol using a TLC–MS interface. HPLC–DAD–MS analysis of the fractions indicated the presence of

Alexander N. Shikov; Vladimir I. Ossipov; Olli Martiskainen; Olga N. Pozharitskaya; Svetlana A. Ivanova; Valery G. Makarov

319

A comparison of the environmental impact of pesticide multiresidues and their occurrence in river waters surveyed by liquid chromatography coupled in tandem with UV diode array detection and mass spectrometry  

Microsoft Academic Search

Twenty-two pesticides and metabolites selected on the basis of a regional priority list, were surveyed in surface river waters by high performance liquid chromatography coupled in tandem with UV diode array detection and mass spectrometry, after an off-line pre-concentration step. Pesticide concentrations ranged between 0.07 and 4.8 ?g\\/l according to the compound and sampling period. Analytical results were linked to

S Irace-Guigand; J. J Aaron; P Scribe; D Barcelo

2004-01-01

320

290 and 340 nm UV LED arrays for fluorescence detection from single airborne particles.  

PubMed

We demonstrate a compact system, incorporating a 32-element linear array of ultraviolet (290 nm and 340 nm) light-emitting diodes (LEDs) and a multi-anode photomultiplier tube, to the in-flight fluorescence detection of aerosolized particles, here containing the biological molecules tryptophan and NADH. This system illustrates substantial advances in the growth and fabrication of new semiconductor UV light emitting devices and an evolution in packaging details for LEDs tailored to the bio-aerosol warning problem. Optical engineering strategies are employed which take advantage of the size and versatility of light-emitting diodes to develop a truly compact fluorescence detector. PMID:19503158

Davitt, Kristina; Song, Yoon-Kyu; Patterson Iii, William; Nurmikko, Arto; Gherasimova, Maria; Han, Jung; Pan, Yong-Le; Chang, Richard

2005-11-14

321

Analysis of alkaloids in Macleaya cordata (Willd.) R. Br. using high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry.  

PubMed

A method for the analysis of alkaloids in Macleaya cordata (Willd.) R. Br. using high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI/MS) was developed. Using protopine (PRO), allocryptopine (ALL), sanguinarine (SA), and chelerythrine (CHE) as the model components, different columns for the separation and different mobile phases for the signal intensities of alkaloids in ESI/MS were investigated, respectively. The results showed that good separation and high signal intensities can be obtained on a high carbon loading (17%) reversed-phase C(18) column with 30 mM formic acid in mobile phase for the analysis of alkaloids. Under the optimal separation condition and UV detection (284 nm), linearity of the six alkaloids was obtained over concentration range from 0.05 to 100.00 microg/ml. The limit of detection (LOD) was 1.62, 1.87, 1.79, 1.76, 1.10, and 0.94 ng/ml for SA, CHE, PRO, ALL, dihydrosanguinarine (DHSA), and dihydrochelerythrine (DHCHE), respectively. The LODs with ESI/MS detection were lower three orders of magnitude than those obtained with UV detection. The proposed method could be used to control quality of the raw materials of the herb more comprehensively. PMID:18774138

Chen, Ying-Zhuang; Liu, Guo-Zhu; Shen, Yao; Chen, Bo; Zeng, Jian-Guo

2008-08-22

322

Simultaneous determination of water-soluble and fat-soluble synthetic colorants in foodstuff by high-performance liquid chromatography-diode array detection-electrospray mass spectrometry.  

PubMed

An accurate method was developed for the simultaneous determination of water-Tartrazine, Amaranth, Ponceau 4R, Sunset Yellow FCF, and fat-Sudan (I-IV), synthetic soluble colorants in foodstuff. This method uses dimethylsulfoxide (DMSO) as the extraction solvent in the sample preparation process and high performance liquid chromatography (HPLC)-diode array detector (DAD)-electrospray mass spectrometry (ESI-MS), applying selected ion recording in positive/negative alternate mode to acquire mass spectral data, as the analytical technique. Linearity of around three orders in the magnitude of concentration was generally obtained. Detection and quantification limits of the investigated dyes, which were evaluated at signal to noise ratio of 3 for detection limit and 10 for quantification limit, were in the ranges of 0.01-4 and 0.03-11.2 ng, respectively. The recoveries of the eight synthetic colorants in four matrices ranged from 93.2 to 108.3%. Relative standard deviations of less than 8.2% were also achieved. This method has been applied successfully in the determination of water-soluble colorants in the soft drink and the delicious ginger, and fat-soluble dyes in chilli powders and chilli spices. PMID:16337640

Ma, Ming; Luo, Xubiao; Chen, Bo; Su, Shengpei; Yao, Shouzhuo

2005-12-07

323

Comparison of extraction solvents and conditions for herbicide residues in milled rice with liquid chromatography-diode array detection analysis (LC-DAD).  

PubMed

Different extraction procedures and clean-up methods were compared in order to develop a sample preparation procedure for the multi-residue analysis of six post-emergence herbicides (metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium and cyhalofop butyl) in rice grains followed by liquid chromatography-diode array detection (LC-DAD). Optimum results were obtained dispersing milled rice grain in water, followed by the addition of 1% acetic acid in acetonitrile, MgSO(4) and sodium acetate as a modification of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method but no primary and secondary amine (PSA) sorbent was added due to the acidic nature of the herbicides. The method was further expanded to other post-emergence herbicides (quinclorac, clomazone and propanil). Except for quinclorac, which cannot be analysed with this method, the recoveries of the other eight herbicides were in the range 73-111%, with relative standard deviations lower than 12%. Limits of detection (LODs) ranged from 0.03 to 0.08 mg kg(-1). A single analyst can extract twelve samples in 4 h. The method presented here allows the simultaneous residue determination of the most common post-emergence herbicides employed in cultivating rice. It is simple, rapid, sensitive, and can be applied routinely to polished rice grain herbicide residue analysis. PMID:20013445

Niell, S; Pareja, L; Geis Asteggiante, L; Cesio, M V; Heinzen, H

2010-02-01

324

An application of wavelet moments to the similarity analysis of three-dimensional fingerprint spectra obtained by high-performance liquid chromatography coupled with diode array detector.  

PubMed

More and more the three-dimensional (3D) fingerprint spectra, which can be obtained by high performance liquid chromatography coupled with diode array detector (HPLC-DAD), are applied to the analysis of drugs and foods. A novel approach to the similarity analysis of traditional Chinese medicines (TCMs) was proposed based on the digital image processing using 3D HPLC-DAD fingerprint spectra. As the one of shape features of digital grayscale image, wavelet moments were employed to extract the shape features from the grayscale images of 3D fingerprint spectra of different Coptis chinensis samples, and used to the similarity analysis of these samples. Compared with the results obtained by traditional features including principal components and spectrum data under single-wavelength, our results represented the more reliable assessment. This work indicates that the better features of fingerprint spectra are more important than similarity evaluation methods. Wavelet moments, which possess multi-resolution specialty and the invariance property in image processing, are more effective than traditional spectral features for the description of the systemic characterisation of mixture sample. PMID:24128524

Zhai, Hong Lin; Li, Bao Qiong; Tian, Yue Li; Li, Pei Zhen; Zhang, Xiao Yun

2013-09-05

325

Compositional changes induced by UV-B radiation treatment of common bean and soybean seedlings monitored by capillary electrophoresis with diode array detection.  

PubMed

In this work, a new CE method with diode array detection (DAD) was developed for the monitoring and quantitation of flavonoids in different beans treated and untreated with UV-B radiation. Flavonoid concentration was monitored in UV-B-treated and untreated sprouts of three common beans (Zolfino ecotype, cv. Verdone, cv. Lingua di Fuoco) and one soybean (cv. Pacific). After acid hydrolysis of extracts, the CE-DAD method provides reproducible quantitative determinations of daidzein, glycitein, genistein, and kaempferol at ppm level in these natural matrices within a relatively short time (less than 16 min). Total flavonoid content determined by CE-DAD was 159 +/- 8, 26 +/- 2, 13 +/- 1, and 1.3 +/- 0.3 microg/g fresh weight for untreated sprouts of Pacific soybean, Verdone bean, Zolfino bean, and Lingua di Fuoco bean, respectively. UV-B treatment caused no significant quantitative effect on Pacific soybean sprouts, whereas it enhanced the total isoflavone content by 1.5, 1.8, and 3.2-fold in Verdone, Zolfino, and Lingua di Fuoco beans, respectively. The proposed method shows (i) the potentialities of bean sprouts as a natural source of bioactive compounds (antioxidants); (ii) the technological role of UV-B treatment for sprout isoflavone enrichment; and (iii) the good capabilities of CE-DAD to monitor this process. PMID:17444230

Dinelli, Giovanni; Aloisio, Irene; Bonetti, Alessandra; Marotti, Ilaria; Cifuentes, Alejandro

2007-03-01

326

Evaluation of polyphenol contents in differently processed apricots using accelerated solvent extraction followed by high-performance liquid chromatography-diode array detector.  

PubMed

Concentrations of 17 polyphenols in ripe-fresh, sun-dried and sulfited-dried apricots either harvested from organic or pesticide-treated trees before harvest were determined using reverse-phase high-performance liquid chromatography with UV-Vis diode array detector, and the change of polyphenol profile with origin of the apricot product was established. Extraction of polyphenols was achieved using the accelerated solvent extraction technique (ASE). A mixture of methanol, water (70:30 v/v) including 0.1 g of tert-butylhydroquinone as solvent, 60 min extraction time, 60°C temperature and 1,500 psi pressure were found the most productive operating conditions for ASE. Concentrations of polyphenols in organic apricots were higher than pesticide-treated samples, and roughly the same in ripe-fresh and sun-dried apricots. Polyphenol concentrations of either organic or pesticide-treated sulfited-dried apricots were lower than the ripe-fresh apricots. Considering the organic ripe-fresh apricots, there was a decrease in some polyphenol concentration in the sulfited-dried apricots compared with the ripe-fresh apricot, and the range of decrease is between 1.4 and 53%. PMID:21599463

Erdo?an, Sel?m; Erdemo?lu, Sema

2011-05-20

327

Identification of amino-tadalafil and rimonabant in electronic cigarette products using high pressure liquid chromatography with diode array and tandem mass spectrometric detection.  

PubMed

A high-pressure liquid chromatography-diode array detection and multi-mode ionization tandem mass spectrometry (HPLC-DAD-MMI-MS/MS) method was used to identify amino-tadalafil and rimonabant in electronic cigarette (e-cigarette) cartridges. Amino-tadalafil is a drug analogue of the commercially approved Cialis™ (i.e. tadalafil). Rimonabant is a drug that was, at one time, approved for weight loss in Europe (although approval has been retracted), but not in the United States. In addition, poor quality control over the e-cigarette products analyzed here is shown by the presence of nicotine in products labeled as containing no nicotine or by the presence of significant amounts of rimonabant oxidative degradant in e-cigarette products containing rimonabant. Identification was accomplished by comparing the retention time of relevant peaks in the sample with those of standard compounds, in addition to comparison of the UV spectra, mass spectra and/or product ion mass spectra. PMID:20980012

Hadwiger, Michael E; Trehy, Michael L; Ye, Wei; Moore, Terry; Allgire, James; Westenberger, Benjamin

2010-10-11

328

Determination of antitubercular drugs in urine and pharmaceuticals by LC using a gradient flow combined with programmed diode array photometric detection.  

PubMed

The simultaneous determination of the antitubercular drugs rifampicin, pyrazinamide, isoniazid and the acetylisoniazid metabolite has been accomplished by LC, using a C-18 analytical column. The assayed drugs are usually administered together in the treatment of tuberculosis. Creatinine was also included in the chromatographic determination, in order to establish the curve of excretion of the drugs in urine. The chromatographic method uses a gradient flow in three steps, in conjunction with a programmed diode array photometric detection. In a 0.02 M potassium dihydrogen phosphate pH 7.0 buffer, a 5% (v/v) content of methanol for 1 min, a 8% (v/v) content of methanol for 3.4 min, and a 75% (v/v) content of methanol for 4 min were used. At 4.5 min, the wavelength value of detection was changed from 254 to 475 nm. Creatinine, acetylisoniazid, isoniazid and pyrazinamide were eluted in the first 4.5 min and rifampicin before 8 min. The method has been satisfactorily applied to the determination of the drugs in urine samples and in pharmaceuticals. The proposed LC method is simple, and a short time, less than 8 min is necessary for compounds elution. PMID:18968751

Espinosa-Mansilla, A; Acedo-Valenzuela, M I; Muñoz de la Peña, A; Cañada Cañada, F; Salinas López, F

2002-08-23

329

Rapid separation and determination of process-related substances of paracetamol using reversed-phase HPLC with photo diode array as a detector.  

PubMed

A simple and rapid gradient reversed-phase high-performance liquid chromatographic method for simultaneous separation and determination of paracetamol and its related compounds in bulk drugs and pharmaceutical formulations has been developed. As many as nine process impurities and one degradation product of paracetamol have been separated on a Symmetry C18 column (4.6 x 250 mm i.d., particle size 5 microm) with gradient elution using 0.01 M potassium dihydrogen phosphate buffer (pH 3.0) and acetonitrile as mobile phase and photo diode array detection at 215 nm. The chromatographic behavior of all the compounds was examined under variable compositions of different solvents, temperatures, buffer concentrations and pH values. The correlation coefficients for calibration curves for paracetamol as well as impurities were in the range of 0.9951 - 0.9994. The proposed RP-LC method was successfully applied to the analysis of commercial formulations; the recoveries of paracetamol were in the range of 99-101%. The method could be of use not only for rapid and routine evaluation of the quality of paracetamol in bulk drug manufacturing units but also for detection of its impurities in pharmaceutical formulations. PMID:16512424

Rao, R Nageswara; Narasaraju, A

2006-02-01

330

Characterization of grape seed procyanidins by comprehensive two-dimensional hydrophilic interaction × reversed phase liquid chromatography coupled to diode array detection and tandem mass spectrometry.  

PubMed

In this work, the development and optimization of a new methodology to analyze grape seed procyanidins based on the application of two-dimensional comprehensive LC is presented. This two-dimensional method involves the use of a microbore column containing a diol stationary phase in the first dimension coupled to either a C18 partially porous short column or a C18 monolithic column in the second dimension. The orthogonal hydrophilic interaction × reversed phase liquid chromatography (HILIC×RP-LC) system is interfaced through a ten-port two-position switching valve. The optimized HILIC×RP-LC separation followed by diode array and tandem mass spectrometry detection (HILIC×RP-LC-DAD-MS/MS) made possible the direct analysis of a complex grape seed extract and allowed the tentative identification of 43 flavan-3-ols, including monomers and procyanidin oligomers till a polymerization degree of 7 units with different galloylation degrees. To the best of our knowledge, this is the first time that this powerful analytical technique is employed to characterize complex procyanidin samples. This work successfully demonstrates the great capabilities of the HILIC×RP-LC-DAD-MS/MS coupling for the direct analysis of very complex natural samples like grape seeds. PMID:23224621

Montero, Lidia; Herrero, Miguel; Prodanov, Marin; Ibáñez, Elena; Cifuentes, Alejandro

2012-12-08

331

Simultaneous quantitative and qualitative analysis of bioactive phenols in Dendrobium aurantiacum var. denneanum by high-performance liquid chromatography coupled with mass spectrometry and diode array detection.  

PubMed

A novel high-performance liquid chromatographic method with mass spectrometry and diode array detection method for the simultaneous qualitative and quantitative analysis of bioactive phenols was developed. In total, nine chemically diverse phenols including five bibenzyls, three phenanthrenes and a coumarin were unambiguously identified in Dendrobium aurantiacum var. denneanum by comparison with the available references or reported data according to their retention behaviors, UV spectra and fragmentations of ESI-MS. The contents of the four main phenolic compounds, moscatilin, gigantol, moscatin and coumarin, in D. aurantiacum var. denneanum from the wild and various cultivated populations were determined by HPLC-UV. The sample preparation involved a rapid and simple procedure based on solid-phase extraction using a C(18) reversed-phase cartridge. The quantitative analysis was performed on a Beckman Coulter ODS column (5 microm, 250 x 4.6 mm) using a linear gradient elution system of acetonitrile-0.5% formic acid. The method was validated for linearity, limits of detection (LOD) and quantification (LOQ), precision and accuracy. Good results were obtained with respect to the overall intra- and inter-day variations (RSD less than 3.22%) and the percentage recoveries (ranging from 90.50 to 99.22%). Notable differences in the contents of phenols were observed among different cultivated populations. The samples colleted in April and May (spring), or October and November (autumn) accumulated much higher contents of phenols than those collected in other seasons. PMID:17428009

Yang, Li; Wang, Yun; Zhang, Guangnong; Zhang, Fang; Zhang, Zijia; Wang, Zhengtao; Xu, Luoshan

2007-07-01

332

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

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.

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

2012-01-01

333

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

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

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

2013-03-08

334

Determination of crystal violet in seawater and seafood samples through off-line molecularly imprinted SPE followed by HPLC with diode-array detection.  

PubMed

A highly selective sample cleanup procedure combined with molecularly imprinted SPE was developed for the isolation of crystal violet from seawater and seafood samples. The molecularly imprinted polymer was prepared using crystal violet as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The crystal violet-imprinted polymer was used as the selective sorbent for the SPE of crystal violet. An off-line molecularly imprinted SPE method followed by HPLC with diode-array detection for the analysis of crystal violet was also established. Good linearity on the molecularly imprinted SPE columns was obtained from 0 to 200 ?g/L (R(2) > 0.99). The result demonstrated that the proposed method can be used for the direct determination of crystal violet in seawater and seafood samples. Finally, five samples were analyzed and the following crystal violet concentrations were obtained: 0.92 and 0.52 ?g/L in two seawater samples, as well as 0.36 and 0.27 ?g/kg in two seafood samples. There is no crystal violet detected in the third seawater sample. PMID:23390113

Lian, Ziru; Wang, Jiangtao

2013-02-06

335

Identification and analysis of the constituents in an aqueous extract of tricholoma matsutake by HPLC coupled with diode array detection/electrospray ionization mass spectrometry.  

PubMed

The main constituents in an aqueous extract of Tricholoma matsutake (Tm) were identified by high-performance liquid chromatography coupled with diode array detection and electrospray ionization time-of-flight mass spectrometry (HPLC-DAD/TOF-MS) and ion trap mass spectrometry (HPLC-DAD/Trap-MSn). The main factors in the extraction process which affect the yields of nutrients were optimized by single-factor experiments and orthogonal experiment design. In total, 12 constituents were identified from the aqueous extract of Tm, including tyrosine, cytidine, uridine, eritadenine, phenylalanine, nicotinamide, inosine, guanosine, tryptophan, adenosine, 5'-deoxy-5'-methylthioadenosine and riboflavin. The optimized extraction conditions were: the ratio of water to sample was 10 : 1 (v/w), Tm was extracted by ultrasonic-assisted extraction for 10 min, followed by water bath heating at 60 °C for 1 h. Among these extraction factors, the heating temperature is significant based on analysis of variance (ANOVA). The yields of nutrients were affected dramatically at high temperature leading to the loss of nutrients, especially for nucleosides and some amino acids. PMID:23957403

Ying, Xuhui; Ma, Jinfang; Liang, Qionglin; Wang, Yiming; Bai, Gang; Luo, Guoan

2013-08-01

336

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

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.

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

2000-01-01

337

Light Output Enhancement of GaN-Based Light-Emitting Diodes by Optimizing SiO2 Nanorod-Array Depth Patterned Sapphire Substrate  

NASA Astrophysics Data System (ADS)

In this study, we investigated high-efficiency InGaN/GaN light-emitting diodes (LEDs) grown on sapphire substrates with SiO2 nanorod arrays (NRAs) of different heights. The GaN film showed an improved crystal quality through X-ray diffraction (XRD) full-width at half-maximum (FWHM), photoluminescence (PL), and cathodoluminescence (CL) measurements. The light output power and internal quantum efficiency (IQE) of the fabricated LEDs were increased when compared with those of conventional LEDs. Transmission electron microscopy (TEM) images suggested that the voids between SiO2 nanorods and the stacking faults introduced during the nanoscale epitaxial lateral overgrowth (NELOG) of GaN can effectively reduce the threading dislocation density (TDD). We believe that the improvements could be attributed to both the enhanced light extraction by utilizing SiO2 NRAs and the improved crystal quality through the NELOG method. We found that the sample with SiO2 NRA structures of 200 nm height can increase the LED output power by more than 70% in our study.

Chiu, Ching-Hsueh; Tu, Po-Min; Chang, Shih-Pang; Lin, Chien-Chung; Jang, Chung-Ying; Li, Zhen-Yu; Yang, Hung-Chih; Zan, Hsiao-Wen; Kuo, Hao-Chung; Lu, Tien-Chang; Wang, Shing-Chung; Chang, Chun-Yen

2012-04-01

338

Quality evaluation of cortex moutan by high performance liquid chromatography coupled with diode array detector and electrospary ionization tandem mass spectrometry.  

PubMed

An high performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and electrospray ionization tandem mass spectrometry (ESI/MS(n)) method was developed for quality evaluation of Cortex Moutan through identification of common constituents based on chromatographic fingerprints and determination of key pharmacological compounds. The representative chromatographic fingerprints of Cortex Moutan were obtained by analyzing 10 batches of samples under the optimized HPLC conditions and the results showed that the chromatographic profiles of the analyzed samples were very similar. Total of nineteen common peaks were detected and seventeen of them were identified rapidly by their characteristic UV profile and the information of molecular structure provided by ESI/MS(n) experiments. Simultaneously, five key pharmacological compounds, namely gallic acid, oxypaeoniflorin, paeoniflorin, benzoylpaeoniflorin and paeonol, were determined by the validated HPLC-DAD method. The linear calibration curves were acquired with correlation coefficients higher than 0.999. The precisions of intra-day and inter-day were not exceeding 3.1%, and the recoveries of five analytes were from 92.86 to 99.35%. This developed method that combined the chromatographic fingerprints and quantification assay ensured the phytoequivalence and pharmacological effects of Cortex Moutan and was successfully applied to the quality control of Cortex Moutan. PMID:16946533

He, Qing; Ge, Zhi-Wei; Song, Yue; Cheng, Yi-Yu

2006-09-01

339

Comparative analysis of three Callicarpa herbs using high performance liquid chromatography with diode array detector and electrospray ionization-trap mass spectrometry method.  

PubMed

Three Callicarpa species, namely Callicarpa nudiflora Hook. et Arn., Callicarpa macrophylla Vahl. and Callicarpa kwangtungensis Chun. are astringency and hemostasis herbs in the traditional Chinese medical systems. Despite their wide use in Chinese medicine, no report on system comparison on their chemical constituents is available so far. High-performance liquid chromatography coupled with diode array detector and electrospray ionization trap mass spectrometry (HPLC-DAD-ESI-Trap MS) technique was used for qualitative and quantitative analyses of the three Callicarpa herbs. Phenylpropanoid glycosides, flavonoids and organic acids were identified by comparing with reference standards or according to their MS/MS fragmentation behaviors. A total of 33 compounds were identified identified or tentatively identified, and 23 of them were reported from these herbs for the first time. Phenylpropanoid glycosides were featured in the three species with their types and contents presenting significant differences. Furthermore, quantitative analysis was conducted by determining four marker phenylpropanoid glycosides (forsythoside B (14), acteoside (15), poliumoside (19), isoacteoside (21)) and two flavonoids (luteolin (30), apigenin (32)). Three flavonoid glucuronides (luteolin-diglucuronide-glucuronide (5), luteolin-diglucuronide (12), apigenin-7-O-?-glucuronide (24)) were semi-quantified according to their corresponding aglycones. The total contents of the nine major compounds in the three species varied significantly from 8.92 to 40.89 mg/g. PMID:23277156

Shi, Yatao; Wu, Chunyong; Chen, Yanhua; Liu, Wenyuan; Feng, Feng; Xie, Ning

2012-12-07

340

ZnO nanowires array p-n homojunction and its application as a visible-blind ultraviolet photodetector  

NASA Astrophysics Data System (ADS)

We demonstrated a simple and low-cost fabrication of ZnO p-n homojunction. The junction consists of n-type ZnO nanowires array by a hydrothermal method covered with p-type Al, N co-doped ZnO film by a sol-gel method. The junction exhibits good rectification characteristics, with reverse leakage current and rectification ratio of ~5 ?A and ~150 at bias of 3 V, respectively. The junction is operated as a photodetector when light radiation is shined on the glass-side of the device. The photodetector shows a peak responsivity at 384 nm with UV-visible responsivity ratio (R384 nm/R550 nm) of ~70 at an operating bias of -3 V.

Leung, Y. H.; He, Z. B.; Luo, L. B.; Tsang, C. H. A.; Wong, N. B.; Zhang, W. J.; Lee, S. T.

2010-02-01

341

Patterning and integration of polyfluorene polymers on micro-pixellated UV AlInGaN light-emitting diodes  

NASA Astrophysics Data System (ADS)

We report the integration of micro-patterned polyfluorene conjugated polymers onto GaN-based ultraviolet (UV) micro-pixellated light-emitting diode arrays (micro-LEDs). The 64 × 64 element matrix-addressable AlInGaN devices have a pixel size of 20 µm diameter on a 50 µm pitch, emitting at 368 nm. Each array is covered with a 2.5 µm thick photo-curable deep-UV-transparent polymer and a 30 nm thick polyfluorene film. This polymer bi-layer is subsequently patterned into an array of 28 µm diameter discs aligned with the pixels of the micro-LED array. Polymer down-converted visible emission from these pattern-programmable organic/inorganic electroluminescent micro-arrays is achieved.

Guilhabert, B.; Gong, Z.; Zhang, H.; Belton, C.; Mack Intosh, A.; Gu, E.; Campoy-Quiles, M.; Stavrinou, P. N.; Bradley, D. D. C.; Pethrick, R. A.; Dawson, M. D.

2008-05-01

342

Combination of Indium--Tin Oxide and SiO2/AlN Dielectric Multilayer Reflective Electrodes for Ultraviolet-Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

We have investigated novel reflective electrodes by combining an indium--tin oxide (ITO) layer and a SiO2/AlN dielectric multilayer (DM) for UV-light-emitting diodes (LEDs). The reflectance of 10 pairs of SiO2/AlN DM reached 98.5% at 350 nm. As a result, the ITO/DM electrodes simultaneously satisfied the requirements of high reflectivity in the UV region, good contact characteristics, and current spreading. The light output power of the UV LED with an ITO/DM electrode is 1.2 and 1.6 times higher than those of LEDs with ITO/Al and Ni/Au electrodes, respectively.

Nakashima, Tsubasa; Takeda, Kenichiro; Shinzato, Hiroshi; Iwaya, Motoaki; Kamiyama, Satoshi; Takeuchi, Tetsuya; Akasaki, Isamu; Amano, Hiroshi

2013-08-01

343

Intense violet-blue-emitting Ba(2)AlB(4)O(9)Cl:Eu(2+) phosphors for applications in fluorescent lamps and ultraviolet-light-emitting diodes.  

PubMed

We synthesized a violet-blue phosphor Ba(2)AlB(4)O(9)Cl:Eu(2+) with a solid-state reaction. The excitation and emission spectra of this phosphor showed that all were broadband due to 4f(7)-4f(6)d(1) transitions of Eu(2+). The phosphors with different Eu(2+) concentrations presented violet-blue luminescence for ultraviolet [(UV) 250-390nm] excitation. The optimum concentration of Eu(2+) in Ba(2)AlB(4)O(9)Cl:Eu(2+) is determined to be 6mol.%. The luminous efficiency was found to be 8.1lm/W for the violet-blue fluorescent lamp and 3.2lm/W for the violet-blue phosphor-converted light-emitting diode, respectively. Ba(2)AlB(4)O(9)Cl:Eu(2+) would be a promising phosphor for converting the UV radiation to violet-blue emission for a novel high light-conversion efficiency phototherapy illuminator. PMID:20676174

Kuo, Te-Wen; Huang, Chien-Hao; Chen, Teng-Ming

2010-08-01

344

Study of 375 nm ultraviolet InGaN/AlGaN light-emitting diodes with heavily Si-doped GaN transition layer in growth mode, internal quantum efficiency, and device performance  

NASA Astrophysics Data System (ADS)

High performance 375 nm ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) were demonstrated with inserting a heavy Si-doped GaN transition layer by metal-organic chemical vapor deposition. From transmission electron microcopy (TEM) image, the dislocation densities were significantly reduced due to the existence of the heavily Si-doping growth mode transition layer (GMTL), which results in residual stress relaxation and 3D growth. The internal quantum efficiency (IQE) of the LEDs with GMTL was measured by power-dependent photoluminescence (PL) to be 40.6% higher than ones without GMTL. The GMTL leads to the superior IQE performance of LEDs not only in decreasing carrier consumption at nonradiative recombination centers but also in partially mitigating the efficiency droop tendency. When the vertical-type LED chips (size: 1 mm × 1 mm) was driven with a 350 mA injection current, the output powers of the LEDs with and without GMTL were measured to be 286.7 and 204.2 mW, respectively. A 40.4% enhancement of light output power was achieved. Therefore, using the GMTL to reduce dislocations would be a promising prospective for InGaN/AlGaN UV-LEDs to achieve high IQE.

Huang, Shih-Cheng; Shen, Kun-Ching; Wuu, Dong-Sing; Tu, Po-Min; Kuo, Hao-Chung; Tu, Chia-Cheng; Horng, Ray-Hua

2011-12-01

345

Quantification of pralidoxime (2-PAM) in urine by ion pair chromatography-diode array detection: application to in vivo samples from minipig.  

PubMed

Pralidoxime (2-PAM) is a monopyridinium oxime used as an antidote for the treatment of poisoning with organophosphorus (OP) compounds, for example, pesticides and nerve agents, reactivating OP-inhibited acetylcholinesterase. However, appropriate dosing and efficacy remains a matter of discussion requiring experimental data. Therefore, we developed and validated an ion pair chromatography-diode array detection (IPC-DAD) method suitable for quantitative analysis of 2-PAM in human and porcine urine. Before injection of 20?µl, urine was acidified with trichloroacetic acid, mixed with internal standard (pyridine-4-aldoxime, 4-PAO), and diluted with IPC solvent yielding a total dilution of 1:49.5 and a 100% recovery. Isocratic separation was carried out at 25?°C on a LiChrospher 60 RP-select B column (125?x?4.0?mm I.D.) using phosphate buffer (7.5?mM Na(2) HPO(4) , 7.5?mM KH(2) PO(4) , pH?2.6) mixed with octanesulfonate (2.5?mM) as ion pair reagent and acetonitrile (6% v/v) as organic modifier (1?ml/min). 2-PAM was detected at 293?nm and 4-PAO at 275?nm. The method is rugged, selective, and characterized by good intra-day and inter-day precision (RSD, 1.3-6.0%) and accuracy (88-100%) with a limit of detection at 4.9?µg/ml, a limit of quantification at 9.8?µg/ml, and a broad calibration range from 4.9-2500?µg/ml. The procedure was applied to urine samples obtained from dimethoate poisoned minipigs receiving 2-PAM therapy (intravenous bolus injection and infusion). Results indicate that 60-80% of infused 2-PAM is rapidly (within 1-2?h) excreted in the urine. PMID:22102522

John, Harald; Eddleston, Michael; Eddie Clutton, R; Worek, Franz; Thiermann, Horst

2011-11-18

346

Determination of low levels of polycyclic aromatic hydrocarbons in soil by high performance liquid chromatography with tandem fluorescence and diode-array detectors.  

PubMed

Risk assessment of polycyclic aromatic hydrocarbons (PAHs) contaminated soil and source apportionment require accurate analysis of the concentration of each PAH congener in the soil. However, determination of low level PAH congeners in soil is difficult because of similarity in the chemical properties of 16 PAHs and severe matrix interferences due to complex composition of soils. It is therefore imperative to develop a sensitive and accurate method for determination of low level PAHs in soil. In this work, high performance liquid chromatography equipped with fluorescence and diode-array detectors (HPLC-FLD-DAD) was used to determine the concentration of 16 PAHs in soil. The separation of the 16 PAHs was achieved by optimization of the mobile phase gradient elution program and FLD wavelength switching program. Qualitative analysis of the 16 PAHs was based on the retention time (RT) and each PAH specific spectrum obtained from DAD. In contrast, the quantitative analysis of individual PAH congeners was based on the peak areas at the specific wavelength with DAD and FLD. Under optimal conditions the detection limit was in the range 1.0-9.5 ?g L(-1) for 16 PAHs with DAD and 0.01-0.1 ?g L(-1) for 15 PAHs with FLD, and the RSD of PAHs was less than 5% with DAD and 3% with FLD. The spiked recoveries were in the range 61-96%, with the exception of NaP (<40%). The results show that HPLC-FLD-DAD can provide more accurate and reliable analysis of low level PAH congeners in soil samples. PMID:23659963

Huang, Yujuan; Wei, Jing; Song, Jing; Chen, Mengfang; Luo, Yongming

2013-05-06

347

Determination of caffeine as a tracer of sewage effluent in natural waters by on-line solid-phase extraction and liquid chromatography with diode-array detection.  

PubMed

A new liquid chromatographic (LC) method with automated on-line solid phase extraction was developed to determine caffeine at sub-microgram per litre concentrations in waters. The filtered sample was pre-concentrated in a pre-column, which was backwashed with acidic water at pH of 2.70. The concentrated caffeine was separated using a C18 column with a gradient of water-acetonitrile and detected by diode array detection (DAD) at 210 nm. Four different pre-columns: C18, PRP-1, PLRP-s and Env were evaluated for the on-line solid phase extraction of caffeine. The PLRP-s pre-column allowed the enrichment of up to 100 mL of environmental water sample with highest recovery. The procedure was validated by recovery experiments in water spiked at 0.5 1.0 and 4.0 microg/L. Average recoveries were between 92.1 +/- 5.2% and 97.8 +/- 2.6%. Detection limits as low as 0.1 microg/L from 50 ml of sample were achieved. The proposed method has the advantages of higher reliability and sensitivity, simpler sample preparation and shorter analysis time in comparison with off-line solid-phase extraction. The utility of the method was demonstrated at two field sites: Bolivar and Halls Head (Australia). At Bolivar, the treatment process included 6-week lagoon storage which is believed to have attenuated caffeine, and thus limited its use as an environmental tracer of reclaimed water. At the Halls Head site, where the storage period is shorter, caffeine was detected in both the treated sewage effluent and in groundwater near ponds where the reclaimed water is at similar concentrations. These results suggest that the environmental conditions under which caffeine is conservative require better definition. PMID:12448526

Chen, Zuliang; Pavelic, Paul; Dillon, Peter; Naidu, Ravenda

2002-11-01

348

Determination of cocaine and benzoylecgonine by direct injection of human urine into a column-switching liquid chromatography system with diode-array detection.  

PubMed

A method for the determination of cocaine (COC) and benzoylecgonine (BZE) in human urine using a column-switching liquid chromatography system is reported. A homemade precolumn (20 mm x 4.6 mm i.d.) dry-packed with Alltech ODS-C18 (35-750 microm) was employed as an extraction precolumn in order to extract and concentrate the COC and BZE from the human urine sample. The analytes were continuously transferred to the analytical column (Spherisorb-C8, 250 mm x 4.6 mm i.d.; dp = 5 microm) by means of the switching arrangement in the backflush mode. Detection was carried out at 235 nm in a UV-diode array detector. The validation of the method revealed analytes quantitative recoveries (96-102%) at three concentrations in the range from 0.25 to 4.00 and from 0.5 to 12.0 microg/mL for COC and BZE, respectively. These values demonstrate the excellent extraction efficiency of the precolumn. The detection limits for COC and BZE at a signal-to-noise ratio of 3 were 0.08 and 0.15 microg/mL when a sample volume of 50 microL was injected. The overlap of sample preparation, analysis and recondition of the precolumn increases the sample throughput to four samples per hour. The proposed method has been applied to the determination of COC and BZE in human urine samples from 73 suspecting drug addicts. Urine concentrations of 1.0-118.10 microg of BZE/mL and 0.1-41.0 microg of COC/mL were found. PMID:15664750

Brunetto, M R; Delgado Cayama, Y; Gutiérrez García, L; Gallignani, M; Obando, M A

2005-02-01

349

Determination of chlorophylls in Taraxacum formosanum by high-performance liquid chromatography-diode array detection-mass spectrometry and preparation by column chromatography.  

PubMed

Taraxacum formosanum, a well-known Chinese herb shown to be protective against hepatic cancer as well as liver and lung damage, may be attributed to the presence of abundant carotenoids and chlorophylls. However, the variety and content of chlorophylls remain uncertain. The objectives of this study were to develop an high-performance liquid chromatography-diode array detection-mass spectrometry method for determination of chlorophylls in T. formosanum and preparation by column chromatography. An HyPURITY C18 column and a gradient mobile phase of water (A), methanol (B), acetonitrile (C), and acetone (D) could resolve 10 chlorophylls and an internal standard Fast Green FCF within 30 min with a flow rate at 1 mL/min and detection at 660 nm. Both chlorophylls a and a' were present in the largest amount (1389.6 ?g/g), followed by chlorophylls b and b' (561.2 ?g/g), pheophytins a and a' (31.7 ?g/g), hydroxychlorophyll b (26.5 ?g/g), hydroxychlorophylls a and a' (9.8 ?g/g), and chlorophyllides a and a' (0.35 ?g/g). A glass column containing 52 g of magnesium oxide-diatomaceous earth (1:3, w/w) could elute chlorophylls with 800 mL of acetone containing 50% ethanol at a flow rate of 10 mL/min. Some new chlorophyll derivatives including chlorophyllide b, pyropheophorbide b, hydroxypheophytin a, and hydroxypheophytin a' were generated during column chromatography but accompanied by a 63% loss in total chlorophylls. Thus, the possibility of chlorophyll fraction prepared from T. formosanum as a raw material for future production of functional food needs further investigation. PMID:22656126

Loh, Chin Hoe; Inbaraj, Baskaran Stephen; Liu, Man Hai; Chen, Bing Huei

2012-06-12

350

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

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.

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

2012-01-01

351

High-Performance and Low-Power Rewritable SiOx 1 kbit One Diode-One Resistor Crossbar Memory Array.  

PubMed

An entire 1-kilobit crossbar device based upon SiOx resistive memories with integrated diodes has been made. The SiOx -based one diode-one resistor device system has promise to satisfy the prerequisite conditions for next generation non-volatile memory applications. PMID:23836363

Wang, Gunuk; Lauchner, Adam C; Lin, Jian; Natelson, Douglas; Palem, Krishna V; Tour, James M

2013-07-08

352

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)

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.

Yata, Tatsuya; Miyamoto, Yoshinobu; Ohmi, Koutoku

2012-02-01

353

Improvement of III-nitride visible and ultraviolet light-emitting diode performance, including extraction efficiency, electrical efficiency, thermal management and efficiency maintenance at high current densities  

NASA Astrophysics Data System (ADS)

In this work, highly efficient broad-area LEDs on bulk GaN substrates were developed and the fabrication process and device layout were optimized. This optimization relied in part on electrical, optical, thermal and recombination models. The peak external quantum efficiency of the 450 nm LEDs was over 68% when biased at 20 mA. The efficiency characteristic showed a typical droop curve, decreasing at high current densities. The cause of this droop is unknown. An exploratory experiment was conducted to characterize electron overflow and its role in efficiency droop. Novel device structures were developed, allowing direct measurement of overflow electrons in LED-like structures under electrical injection. In these test structures, electrons were observed in the p-type region of the LED only at current densities where efficiency droop was active. The onset of efficiency droop was preceded by the onset of electron overflow. However, the magnitude of the overflow current could not be measured and it is undetermined whether the dominant cause of efficiency droop is electron overflow or some other process such as Auger recombination. Calibration structures allowing measurement of the magnitude of the overflow are proposed. Work on deep-ultraviolet, 275 nm, LEDs is also presented. Demonstration of direct-wafer bonded LEDs to beta-Ga2O3 is presented. A SiC substrate removal process is discussed. LEDs fabricated by this flip-chip process exhibited up to 1.8 times greater power compared to LEDs fabricated by a standard process but suffered from increased forward voltage and premature failure. Further process development leading to electrically efficient operation is proposed.

Vampola, Kenneth

354

Quality evaluation of Radix Astragali through a simultaneous determination of six major active isoflavonoids and four main saponins by high-performance liquid chromatography coupled with diode array and evaporative light scattering detectors  

Microsoft Academic Search

A method, high-performance liquid chromatography coupled with diode array and evaporative light scattering detectors (HPLC-DAD-ELSD), was developed to evaluate the quality of Radix Astragali through a simultaneous determination of six major active isoflavonoids and four main saponins. The wavelength at 280nm was chosen to determine six isoflavonoids: calycosin-7-O-?-d-glucoside (1), ononin (2), (6?R, 11?R)-9,10-dimethoxypterocarpan-3-O-?-d-glucoside (3), (3R)-2?-hydroxy-3?,4?-dimethoxyisoflavan-7-O-?-d-glucoside (4), calycosin (5), and formononetin

Lian-Wen Qi; Qing-Tao Yu; Ping Li; Song-Lin Li; Yu-Xia Wang; Liang-Hong Sheng; Ling Yi

2006-01-01

355

Temperature dependent ultraviolet-visible absorption cross sections of NO2 and N2O4: Low-temperature measurements of the equilibrium constant for 2NO2 reversible reaction N2O4  

Microsoft Academic Search

A study of the temperature dependence of the ultraviolet-visible absorption cross sections for NO2 has been made in the temperature range 213-298 K and between 310 and 570 nm using a diode array spectrometer. Analysis of the experimental data allowed the simultaneous measurement of the NO2 and N2O4 cross sections and the equilibrium constant for the dimerization of NO2. The

M. H. Harwood; R. L. Jones

1994-01-01

356

Development and validation of a rapid ultra-high performance liquid chromatography diode array detector method for Vitex agnus-castus.  

PubMed

A rapid ultra-high performance liquid chromatography diode array detector (UHPLC-DAD) method was developed and validated for the simultaneous determination of all classes of non-volatile phytochemicals (iridoids, flavonoids and diterpenes) in Vitex agnus-castus (Lamiaceae) fruits, a traditional medicinal plant used against premenstrual symptoms (PMS) and other disorders. Seven marker compounds, 3,4-dihydroxybenzoic acid, p-hydroxybenzoic acid, agnuside, 5-hydroxykaempferol-3,6,7,4'-tetramethylether, 1,2-dibenzoic acid glucose, methoxy-vitexilactone, and vitetrifolin D were isolated from the methanol extract of V. agnus-castus to be used as reference substances. Chromatographic separation was performed on a Zorbax Eclipse XDB-C18 (50mm×2.1mm) UHPLC column with 1.8?m particle size, within 20min. A solvent gradient from 0.5% acetic acid to acetonitrile at a flow rate of 0.6mL/min was used as mobile phase. Analyte detection and quantification was realized at 210nm and 260nm. The UHPLC-DAD assay was validated for the quantitative analysis of agnuside, isovitexin, casticin, 5-hydroxykaempferol-3,6,7,4'-tetramethylether and vitetrifolin D. It was found to be specific, accurate, precise, and reproducible for the quantification of these compound within a concentration range of 0.7-500.0?g/mL for casticin and 5-hydroxykaempferol-3,6,7,4'-tetramethylether, 1.4-1000.0?g/mL for isovitexin and agnuside, and 12.4-1000.0?g/mL for vitetrifolin D. Intra- and inter-day variations showed relative standard deviations (RSD) of less than 3.9% and 6.4%, respectively. Tentatively assignment of 62 chromatographic features found in the UHPLC-DAD assay was carried out by coupling the UHPLC instrument to a quadrupole time-of-flight mass spectrometer via an electrospray ionization interface (ESI-QTOF-MS) operated in positive and negative ion mode. By using the established quantitative UHPLC-DAD assay to asses agnuside, isovitexin, casticin, 5-hydroxykaempferol-3,6,7,4'-tetramethylether and vitetrifolin D in V. agnus-castus derived preparations as extracts, tinctures and tablets, the applicability of the developed assay to phytopharmaceuticals was successfully proven. PMID:23522912

Högner, C; Sturm, S; Seger, C; Stuppner, H

2013-03-04

357

Simple and rapid simultaneous profiling of minor components of honey by size exclusion chromatography (SEC) coupled to ultraviolet diode array detection (UV-DAD), combined with chemometric methods.  

PubMed

This paper discusses the importance of profiling UV-responsive components, properly integrated with chemometric techniques, in detecting indicative parameters for quality control of honey. The minor components in honeys of different botanical and geographical origins were investigated by size SEC-UV-DAD. We diluted honey with mobile phase before injection into the chromatographic apparatus and a single chromatographic run gave a fast profile of high- (proteins and enzymes), intermediate- (e.g. terpenoid glycosides in lime tree honey) and low-molecular-weight components (secondary metabolites, e.g. kynurenic acid in chestnut honey). The analysis of a total number of 32 honey samples from different regions (Italy, Western Balkan countries, Brazil, Cameroon, Kenya) and of different botanical origins (herbal flower and arboreal flower nectars/honeydews) showed peculiar and characteristic distribution of these markers, which were basically related to their floral origin. Chemometric examination carried out using principal component analysis (PCA) and hierarchical cluster analysis (HCA) of the chromatograms (RT vs. absorption) detected four main clusters in which the groups of (i) chestnut honeys, (ii) honeys from rain forests and (iii) counterfeit/adulterated honeys were clearly separated from the main group of flower nectar honeys. The method is fast, requiring minimal sample handling, and the chromatographic data can be analyzed by multivariate statistical techniques to obtain descriptive information about the honey's quality and composition. PMID:21962760

Beretta, Giangiacomo; Fermo, Paola; Maffei Facino, Roberto

2011-09-16

358

Determination of linezolid in human serum by reversed-phase high-performance liquid chromatography with ultraviolet and diode array detection.  

PubMed

A high-performance liquid chromatographic (HPLC) method with UV and DAD detection for the quantitative determination of linezolid in human serum was developed in present work. Chromatography was carried out by reversed-phase technique on a RP-18 column with a mobile phase composed of 50 mM phosphate buffer and acetonitrile (76 : 26, v/v), adjusted to pH 3.5 with orthophosphoric acid. Serum samples were deproteinized with methanol centrifuged and then, the supernatant was analyzed using HPLC procedure. No interference was observed at the retention times of linezolid from blank serum or ten commonly used antibiotics. A concentration range from 0.50 to 30.0 g/mL was utilized to construct calibration curves. The lower limit of detection was determined to be 0.1 microg/mL of serum for both detectors. The lower limit of quantification of 0.25 microg/mL (CV = 2.6%) was established for determination using HPLC-UV and 0.5 microg/mL (CV = 5.42%) for HPLC-DAD. The recovery of linezolid was approximately 100%. Intra-day accuracy ranged from 0.97 to 12.63% and 0.74 to 10.85% for HPLC-UV and HPLC-DAD method, respectively. Intra-day precision was less than 4.69% for HPLC-UV and less than 5.42% for HPLC-DAD method. Tests confirmed the stability of linezolid in serum during three freeze-thaw cycles and during long-term storage of frozen serum for up to 6 weeks; in extracts it was stable in the HPLC autosampler over 24 h. Statistical analysis by Student's t-test showed no significant difference between the results obtained by these two methods. In summary, these methods will be used and adapted for infected patients in intensive care unit, to determine linezolid serum concentrations in order to know the pharmacokinetic profiles of linezolid. PMID:23923387

Cios, Agnieszka; Ku?, Kamil; Szymura-Oleksiak, Joanna

359

High performance 375 nm ultraviolet InGaN/AlGaN light-emitting diodes by using a heavily Si-doped GaN growth mode transition layer  

NASA Astrophysics Data System (ADS)

High performance 375 nm ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) with a heavy Si-doped GaN growth mode transition layer (GMTL) were fabricated by metal-organic chemical vapor deposition (MOCVD). From transmission electron microcopy (TEM) image, the dislocation densities are reduced significantly by using the GMTL technique. The threading dislocation (TD) value of AlGaN grown on GMTL was significantly decreased from the control sample value of 8×108 to 8×107 cm-2. Furthermore, the internal quantum efficiency (IQE) of the LEDs with GMTL was measured by power-dependent photoluminescence (PL) to be 40.6% higher than ones without GMTL. After vertical-type (size:1mm×1mm) LED chips were fabricated, the output power were measured by integrating sphere detector under 350 mA injection current driving. The output powers of the LEDs with and without GMTL were measured to be 286.7 and 204.2 mW, respectively. As much as 40.4% increased light output power was achieved. The GMTL leads to the superior IQE performance of the LEDs not only in decreasing the carrier consumption at nonradiative recombination centers but also in partially mitigating the efficiency droop tendency. Therefore, forming the GMTL between un-doped GaN and n-AlGaN to reduce dislocations would be a promising prospective for InGaN/AlGaN UV-LEDs to achieve high IQE.n the abstract two lines below author names and addresses.

Huang, Shih-Cheng; Tu, Po-Min; Yang, Shun-Kuei; Lin, Ya-Wen; Hsu, Chih-Peng

2012-02-01

360

Cryogenic thermal diodes  

NASA Astrophysics Data System (ADS)

Space based cryogenic thermal management systems for advanced infrared sensor platforms are a critical failure mode to the spacecraft missions they are supporting. Recent advances in cryocooler technologies have increased the achievable cooling capacities and decreased the operating temperatures of these systems, but there is still a fundamental need for redundancy in these systems. Cryogenic thermal diodes act as thermal switches, allowing heat to flow through them when in a conduction mode and restricting the flow of heat when in an isolation mode. These diodes will allow multiple cryocoolers to cool a single infrared focal plane array. The Space Dynamics Laboratory has undertaken an internal research and development effort to develop this innovative technology. This paper briefly describes the design parameters of several prototype thermal diodes that were developed and tested. .

Paulsen, Brandon R.; Batty, J. C.; Agren, John

2000-01-01

361

Electroluminescence from ZnO-nanorod-based double heterostructured light-emitting diodes  

NASA Astrophysics Data System (ADS)

Light-emitting diodes (LEDs) with MgZnO/ZnO/MgZnO double heterojunction structure have been fabricated and the room temperature electroluminescence (EL) spectra have been studied. With the help of double heterostructure, LEDs show better visible EL performance than that of LED with ordinary p-i-n structure. By replacing ZnO film with ZnO nanorod arrays in this double heterostructure, strong ultraviolet EL emission around 380 nm was achieved. The ZnO-nanorod-based double heterostructured light-emitting diode exhibits superior stability with an intensity degradation of less than 3% over 8 h. The EL mechanisms were discussed in terms of carrier confinement and carrier transport based on semiconductor heterojunction theory.

Long, Hao; Li, Songzhan; Mo, Xiaoming; Wang, Haoning; Huang, Huihui; Chen, Zhao; Liu, Yuping; Fang, Guojia

2013-09-01

362

Tunnel Diode.  

National Technical Information Service (NTIS)

The mesa structure of the proposed germanium-base tunnel diode is mounted on a multilayer metal-germanium-glass structure. To decrease the capacitance and inductance and to improve the mechanical stability of the mesa structure, the diode contains an annu...

L. A. Logunov

1967-01-01

363

Integrated injection-locked semiconductor diode laser  

DOEpatents

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.

Hadley, G.R.; Hohimer, J.P.; Owyoung, A.

1991-02-19

364

ZnO1-x nanorod arrays/ZnO thin film bilayer structure: from homojunction diode and high-performance memristor to complementary 1D1R application.  

PubMed

We present a ZnO(1-x) nanorod array (NR)/ZnO thin film (TF) bilayer structure synthesized at a low temperature, exhibiting a uniquely rectifying characteristic as a homojunction diode and a resistive switching behavior as memory at different biases. The homojunction diode is due to asymmetric Schottky barriers at interfaces of the Pt/ZnO NRs and the ZnO TF/Pt, respectively. The ZnO(1-x) NRs/ZnO TF bilayer structure also shows an excellent resistive switching behavior, including a reduced operation power and enhanced performances resulting from supplements of confined oxygen vacancies by the ZnO(1-x) NRs for rupture and recovery of conducting filaments inside the ZnO TF layer. A hydrophobic behavior with a contact angle of ~125° can be found on the ZnO(1-x) NRs/ZnO TF bilayer structure, demonstrating a self-cleaning effect. Finally, a successful demonstration of complementary 1D1R configurations can be achieved by simply connecting two identical devices back to back in series, realizing the possibility of a low-temperature all-ZnO-based memory system. PMID:22900519

Huang, Chi-Hsin; Huang, Jian-Shiou; Lin, Shih-Ming; Chang, Wen-Yuan; He, Jr-Hau; Chueh, Yu-Lun

2012-09-06

365

{sup 129}Xe-Cs (D{sub 1},D{sub 2}) versus {sup 129}Xe-Rb (D{sub 1}) spin-exchange optical pumping at high xenon densities using high-power laser diode arrays  

SciTech Connect

We investigate {sup 129}Xe-Cs (D{sub 1},D{sub 2}) spin exchange optical pumping (SEOP) at high Xe densities ({approx}0.12-2.44 amagat) using newly available high-power (>40 W) laser diode arrays and compare with {sup 129}Xe-Rb D{sub 1} SEOP under similar conditions. At elevated Xe densities, the spin-exchange rate (per alkali-metal atom, {gamma}{sup '}) for Cs-{sup 129}Xe is {approx}1.5-fold greater than that for Rb-{sup 129}Xe. Higher spin-exchange rates and lower {sup 129}Xe spin-destruction rates for Cs-{sup 129}Xe versus Rb-{sup 129}Xe contribute to {approx}twofold improvement in {sup 129}Xe nuclear spin polarization measured at 9.4 T - with the largest gains observed at the highest Xe densities.

Whiting, Nicholas; Eschmann, Neil A.; Goodson, Boyd M.; Barlow, Michael J. [Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois 62901 (United States); Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)

2011-05-15

366

Validation and global uncertainty of a liquid chromatographic with diode array detection method for the screening of azoxystrobin, kresoxim-methyl, trifloxystrobin, famoxadone, pyraclostrobin and fenamidone in grapes and wine.  

PubMed

Azoxystrobin, kresoxim-methyl, trifloxystrobin, pyraclostrobin, famoxadone and fenamidone are permitted Q(o) Inhibitor (Q(o)I) fungicides applied to vine in some European countries for the treatment of downy and powdery mildews. In this work, a method is validated for the analysis of these fungicides in grapes and wine. This screening method consists in a simple one step liquid-liquid extraction followed by liquid chromatography (LC) fitted with a diode array detector (DAD). Limits of detection for grapes and wine were below 0.2 mg kg(-1) or mg l(-1), precision was not above 13%, and recoveries were, on average, 95+/-5% for grapes and 104+/-6% for wine. Global uncertainties evaluated in the concentration range from 0.25 to 2.50 mg l(-1) were below 20%. A confirmatory method by gas chromatography (GC) with mass spectrometry (MS) detection was used. PMID:17723536

de Melo Abreu, Susana; Caboni, Pierluigi; Cabras, Paolo; Garau, Vincenzo Luigi; Alves, Arminda

2006-03-09

367

Compact ultraviolet laser  

NASA Astrophysics Data System (ADS)

This dissertation presents theoretical analysis and experimental investigation of a compact ultraviolet laser, comprising an unstable resonator semiconductor (URSL) laser-pumped potassium titanyl phosphate (KTP) periodically segmented waveguide (PSW) laser. A comprehensive survey of existing short wavelength visible and near ultraviolet laser technologies suitable for the development of compact ultraviolet lasers is presented. This survey establishes the suitability of a diode-pumped KTP PSW laser as an attractive approach for developing a compact ultraviolet laser. Requirements for an efficient diode-pumped KTP PSW laser are given, leading to the selection of a frequency-stabilized URSL and hydrothermal KTP PSWs as the component technologies to be developed and integrated. Since the design requirements for the URSL and KTP PSW are critically dependent on a thorough understanding of the spatial mode properties of KTP PSWs, analyses and modeling of the spatial mode properties of these devices is presented using effective index method (EIM) and beam propagation method (BPM) models. In addition, a new expression for the normalized conversion efficiency is presented which explicitly incorporates the dependence of this important parameter on the lateral variation of the refractive index and d coefficient. To assess the theoretical performance of an URSL-pumped KTP PSW, the BPM model was extended to incorporate second harmonic generation. This represents an important contribution to the development of numerical methods for modeling nonlinear waveguides, in general, and provides important information on the cooperative effects of diffraction and spatial mode beating on the SHG output from KTP PSWs. Extensive optical characterization of NUV SHG in hydrothermal KTP PSWs using an argon-ion laser-pumped Ti:Sapphire laser as the infrared laser pump source is presented. Spectral characterization, spatial mode characterization, and the temperature dependence of the QPM wavelength are presented. This work includes results for the highest cw output powers reported for NUV SHG output from a laser-pumped KTP PSW. In an important step towards demonstration of an URSL- pumped KTP PSW laser, fabrication methods and test results ate reported for half-symmetric, low magnification SQW AlGaAs URSLs emitting at 770 nm and designed for use as diode pump sources for hydrothermal KTP PSWs. These devices utilize a 200 /mu m × 500 /mu m active region profile and were focused-ion- beam micromachined to achieve a total resonator magnification of 2.9. The first demonstration of high brightness, single-longitudinal mode operation from a core grating URSL is reported. This dissertation concludes with results for the first demonstration of an URSL-pumped KTP waveguide laser. This compact ultraviolet laser represents a pioneering effort to take advantage of the high cw output powers available from high brightness URSLs to increase the SH output powers obtainable from diode-pumped nonlinear waveguide lasers and to extend the useful spectral range from these sources into the near ultraviolet.

Baird, Brian Walter

1997-09-01

368

GaN-based light-emitting diodes by laser lift-off with electroplated copper  

NASA Astrophysics Data System (ADS)

This study presents a GaN thin film light-emitting diode (TF-LED) on an electroplated flexible copper substrate to improve thermal conduction effect of the LED. The optoelectronic characteristics and stress effect of the GaN TF-LEDs on the electroplated flexible copper prepared by laser lift-off technique was examined. The surface of the peeled GaN TF-LED after laser lift-off process demonstrated a pore array. The GaN pore array surface was etched by photo-electrochemical method to form hexagonal pyramid hillocks on the surface using KOH solution. Then, freestanding peeled GaN TF-LEDs with the front surface protected by wax were immersed into 3M KOH solution at 10, 20, 30min under ultraviolet illuminations to perform the photo-electrochemical etching. Surface morphologies with and without photo-electrochemical etching were observed by field emission scanning electron microscope (FESEM) (LEO 1530).

Lin, Wun-Wei; Chen, Lung-Chien; Chiou, Chung-An

2013-09-01

369

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

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

Gentili, Alessandra; Caretti, Fulvia

2010-12-09

370

High-power laser diodes at various wavelengths  

SciTech Connect

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.

Emanuel, M.A.

1997-02-19

371

Multimode-diode-pumped gas (alkali-vapor) laser  

NASA Astrophysics Data System (ADS)

We report what we believe to be the first demonstration of a multimode-diode-pumped gas laser: Rb vapor operating on the 795 nm D1 resonance transition. Peak output of ˜1W was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.

Page, Ralph H.; Beach, Raymond J.; Kanz, V. Keith; Krupke, William F.

2006-02-01

372

Multimode-diode-pumped gas (alkali-vapor) laser  

Microsoft Academic Search

We report the first demonstration of a multimode-diode-pumped gas laser--Rb vapor operating on the 795 nm resonance transition. Peak output of â1 Watt was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.

R H Page; R J Beach; V K Kanz

2005-01-01

373

Multimode-diode-pumped gas (alkali-vapor) laser  

SciTech Connect

We report the first demonstration of a multimode-diode-pumped gas laser--Rb vapor operating on the 795 nm resonance transition. Peak output of {approx}1 Watt was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.

Page, R H; Beach, R J; Kanz, V K

2005-08-22

374

Multimode-diode-pumped gas (alkali-vapor) laser  

Microsoft Academic Search

We report what we believe to be the first demonstration of a multimode-diode-pumped gas laser: Rb vapor operating on the 795 nm D1 resonance transition. Peak output of ˜1W was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays)

Ralph H. Page; Raymond J. Beach; V. Keith Kanz; William F. Krupke

2006-01-01

375

Electrodeposition of Cu-doped ZnO nanowire arrays and heterojunction formation with p-GaN for color tunable light emitting diode applications  

Microsoft Academic Search

Copper-doped zinc oxide (ZnO:Cu) nanowires (NWs) were electrochemically deposited at low temperature on fluor-doped tin oxide (FTO) substrates. The electrochemical behavior of the Cu–Zn system for Cu-doped ZnO electrodeposition was studied and the electrochemical reaction mechanism is discussed. The synthesized ZnO arrayed layers were investigated by using SEM, XRD, EDX, photoluminescence and Raman techniques. X-ray diffraction analysis demonstrates a decrease

O. Lupan; T. Pauporté; B. Viana; P. Aschehoug

376

Perforated diode neutron sensors  

NASA Astrophysics Data System (ADS)

A novel design of neutron sensor was investigated and developed. The perforated, or micro-structured, diode neutron sensor is a concept that has the potential to enhance neutron sensitivity of a common solid-state sensor configuration. The common thin-film coated diode neutron sensor is the only semiconductor-based neutron sensor that has proven feasible for commercial use. However, the thin-film coating restricts neutron counting efficiency and severely limits the usefulness of the sensor. This research has shown that the perforated design, when properly implemented, can increase the neutron counting efficiency by greater than a factor of 4. Methods developed in this work enable detectors to be fabricated to meet needs such as miniaturization, portability, ruggedness, and adaptability. The new detectors may be used for unique applications such as neutron imaging or the search for special nuclear materials. The research and developments described in the work include the successful fabrication of variant perforated diode neutron detector designs, general explanations of fundamental radiation detector design (with added focus on neutron detection and compactness), as well as descriptive theory and sensor design modeling useful in predicting performance of these unique solid-state radiation sensors. Several aspects in design, fabrication, and operational performance have been considered and tested including neutron counting efficiency, gamma-ray response, perforation shapes and depths, and silicon processing variations. Finally, the successfully proven technology was applied to a 1-dimensional neutron sensor array system.

McNeil, Walter J.

377

Advances in high power semiconductor diode lasers  

NASA Astrophysics Data System (ADS)

High power semiconductor lasers have broad applications in the fields of military and industry. Recent advances in high power semiconductor lasers are reviewed mainly in two aspects: improvements of diode lasers performance and optimization of packaging architectures of diode laser bars. Factors which determine the performance of diode lasers, such as power conversion efficiency, temperature of operation, reliability, wavelength stabilization etc., result from a combination of new semiconductor materials, new diode structures, careful material processing of bars. The latest progress of today's high-power diode lasers at home and abroad is briefly discussed and typical data are presented. The packaging process is of decisive importance for the applicability of high-power diode laser bars, not only technically but also economically. The packaging techniques include the material choosing and the structure optimizing of heat-sinks, the bonding between the array and the heat-sink, the cooling and the fiber coupling, etc. The status of packaging techniques is stressed. There are basically three different diode package architectural options according to the integration grade. Since the package design is dominated by the cooling aspect, different effective cooling techniques are promoted by different package architectures and specific demands. The benefit and utility of each package are strongly dependent upon the fundamental optoelectronic properties of the individual diode laser bars. Factors which influence these properties are outlined and comparisons of packaging approaches for these materials are made. Modularity of package for special application requirements is an important developing tendency for high power diode lasers.

Ma, Xiaoyu; Zhong, Li

2008-03-01

378

Matrix solid-phase dispersion extraction followed by HPLC-diode array detection method for the determination of major constituents in a traditional Chinese medicine Folium isatidis (Da-qing-ye).  

PubMed

A simple and low-cost method based on matrix solid-phase dispersion (MSPD) extraction, HPLC separation, and diode array detection has been developed for the determination of indigo and indirubin in Folium isatidis. 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 C18 was used as dispersing sorbent, the ratio of C18 to sample mass was selected to be 4:1, and 10 mL of N,N-dimethyl formamide 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 > 0.9995) and precision (RSD < 3.0%) for indigo and indirubin, with the limits of detection of 18 and 22.5 ng/mL, respectively. The recoveries were in the range of 90.33-100.74% with RSD values ranging from 1.7 to 3.6%. 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 analyzed three real samples that were collected from different localities. PMID:22997033

Zhang, Qi; Hong, Bo; Zheng, Lihong; Wang, Xiuhua; Cai, Defu

2012-09-01

379

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

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 22min. 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

Ramirez-Ambrosi, M; Abad-Garcia, B; Viloria-Bernal, M; Garmon-Lobato, S; Berrueta, L A; Gallo, B

2013-09-29

380

Method validation and simultaneous determination of retinol, retinyl palmitate, ?-carotene, ?-tocopherol and vitamin C in rat serum treated with 7,12 dimethylbenz[a]anthracene and Plantago major L. by high- performance liquid chromatography using diode-array detection.  

PubMed

A new and simple high-performance liquid chromatography method was developed and validated for the simultaneous determination of retinol, retinyl palmitate, ?-carotene, ?-tocopherol and vitamin C in rat serum treated with Plantago Major L. and 7,12 dimethylbenz[a]anthracene. High-performance liquid chromatography analysis was performed utilizing an Inertsil ODS3 reversed phase column with methanol-tetrahydrofuran-water as mobile phase under gradient conditions, at 1.5 mL min(-1) flow rate and 25 °C. Diode-array detection was at 325, 450, 290 and 270 nm (retinol and retinyl palmitate), ?-carotene, ?-tocopherol and vitamin C, respectively and runnig time 18 min. The high-performance liquid chromatography assay and extraction procedure proposed are simple, rapid, sensitive and accurate. The method was then applied for the determination of retinol, retinyl palmitate, ?-carotene, ?-tocopherol and vitamin C in rat serum. Results of this study demonstrated that; at 60th day DMBA-treated group, there was a significant decrease in vitamin levels compared to the levels of control group. A significant increase was observed in vitamin levels of 7,12 dimethylbenz[?]anthracene+Plantago Major L.-treated group compared to the DMBA-treated group. Additionally, the results obtained in the study are found to be in agreement with data reported in the literature. PMID:23176060

Levent, Abdulkadi; Oto, Gokhan; Ekin, Suat; Berber, Ismet

2013-02-01

381

Identification and characterization of anthocyanins in yard-long beans (Vigna unguiculata ssp. sesquipedalis L.) by High-performance liquid chromatography with diode array detection and electrospray ionization/mass spectrometry (HPLC-DAD-ESI/MS) analysis.  

PubMed

Anthocyanins play an important role in physiological functions related to human health. The objective of this study was to investigate the profiles of anthocyanins in the immature purple pods and black seeds of yard-long beans ( Vigna unguiculata ssp. sesquipedalis L.) using high-performance liquid chromatography (HPLC) with diode array detection and electrospray ionization/mass spectrometry (DAD-ESI/MS) analysis. The individual anthocyanins were identified by comparing their mass spectrometric data and retention times. In the purple pods, five individual anthocyanins were identified: delphinidin-3-O-glucoside (2), cyanidin-3-O-sambubioside (4), cyanidin-3-O-glucoside (5), pelargonidin-3-O-glucoside (7), and peonidin-3-O-glucoside (8). From the black seed coat of the yard-long beans, seven anthocyanins were identified, including delphinidin-3-O-galactoside (1), cyanidin-3-O-galactoside (3), petunidin-3-O-glucoside (6), and malvidin-3-O-glucoside (9), together with compounds 2, 5, and 8. In this study, we report for the first time anthocyanin profiles for the pod and seed coat of yard-long beans. PMID:20121192

Ha, Tae Joung; Lee, Myoung-Hee; Park, Chang-Hwan; Pae, Suk-Bok; Shim, Kang-Bo; Ko, Jong-Min; Shin, Sang-Ouk; Baek, In-Youl; Park, Keum-Yong

2010-02-24

382

Determination of steroid sex hormones and related synthetic compounds considered as endocrine disrupters in water by fully automated on-line solid-phase extraction-liquid chromatography-diode array detection.  

PubMed

In this study, a procedure for the simultaneous determination in water of six estrogens (estradiol, estriol, estrone, ethynyl estradiol, mestranol, and diethylstilbestrol) and three progestogens (progesterone, norethindrone, and levonorgestrel), selected based on their abundance in the human body, their estrogenic potency, and the extent of their use in contraceptive pills, was developed. The procedure, based on the on-line solid-phase extraction (SPE) of the water sample and subsequent analysis by liquid chromatography/diode array detection (LC/DAD), allows for the monitoring of up to 16 samples in a completely automated, unattended way. The SPE experimental conditions were optimized and the polymeric cartridge PLRP-S selected out of four different cartridges evaluated. The chromatographic separation was carried out on a LiChrospher 100 RP-18 and detection was performed at 200, 225, and 240 nm. The applicability of the method to the analysis of various environmental water samples, including drinking water, groundwater, surface water and sewage treatment plant effluents, was evaluated. Method detection limits were in the range 10-20 ng/l. The method precision and accuracy were satisfactory with recovery percentages ranging from 96 to 111% and relative standard deviations lower than 3%. The technique is also considerably cheap, fast, and easy, and, therefore, very adequate for routing monitoring. To the authors' knowledge it constitutes the first work describing a fully automated, on-line methodology for the continuous monitoring of these compounds in water. PMID:11293581

López de Alda, M J; Barceló, D

2001-03-16

383

Detection and quantification of provitamin D2 and vitamin D2 in hop (Humulus lupulus L.) by liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry.  

PubMed

In this work, ergosterol and ergocalciferol were identified for the first time in hop. In addition, in this article, a simple and reliable analytical methodology for analysis of these compounds in different commercial forms of hop is presented. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (higher than 70%), repeatability (lower than 3 %), linearity ( r(2) > 0.9988) and limits of detection (ranging from 0.034 for ergocalciferol to 0.058 mg/L for ergosterol) and quantification (ranging from 0.113 for ergocalciferol to 0.195 mg/L for ergosterol). On the basis of standard additions applied with the optimized procedure and high-performance liquid chromatography with diode array detection, it appears that the Nugget hop plant (crop 2006) contains 1.84 +/- 0.09 microg/g of ergosterol and 1.95 +/- 0.05 microg/g of ergocalciferol. The identity of the compounds was confirmed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry in the positive ion mode. The presence of ergosterol here reported should have great potential for the assessment of hop as related to the fungal contamination proportion and hence the quality of this raw material. PMID:17760411

Magalhães, Paulo J; Carvalho, Daniel O; Guido, Luís F; Barros, Aquiles A

2007-08-31

384

Screening and analysis of the multiple absorbed bioactive components and metabolites of Baihe Zhimu Tang by the metabolic fingerprinting technique and liquid chromatography/diode array detection-electrospray ionization-mass spectrometry  

PubMed Central

Background: Baihe Zhimu Tang (BZT) is a widely used traditional Chinese medicinal formula in treating various diseases; however, its active components have remained unknown. Materials and Methods: Based on the metabolic fingerprinting technique and liquid chromatography/diode array detection-electrospray ionization-mass spectrometry (LC/DAD-ESI-MS), a method for rapid screening and analysis of the multiple absorbed bioactive components and metabolites of an oral solution of Baihe Zhimu Tang (BZT) in rabbit plasma, urine and feces after oral administration of BZT was developed. Results: The results obtained from a comprehensive comparative analysis of the fingerprints of the BZT and its metabolic fingerprints in rabbit biological samples indicated that 19 components in the BZT were absorbed into the rabbit's body. Both of them were tentatively identified from their MS and UV spectra and retention behaviors by comparing the results with the reported literature. In addition, only six components were found in the metabolic fingerprints, which suggested that they might be metabolites of some components in the BZT. Conclusion: The findings demonstrated that the proposed method could be used to rapidly and simultaneously analyze and screen the multiple absorbed bioactive constituents and metabolites in a formula of traditional Chinese medicines (TCMs) by comparing and contrasting the chromatographic fingerprints with its metabolic fingerprints. This is very important not only for the pharmaceutical discovery process and the quality control of crude drugs, but also for explaining the curative mechanism of TCMs.

Qin, Kunming; Cai, Hao; Liu, Xiao; Lu, Tulin; Fang, Qianbo; Yao, Zhongqing; Xu, Zisheng; Cai, Baochang

2011-01-01

385

Characterization of weld (Reseda luteola L.) and spurge flax (Daphne gnidium L.) by high-performance liquid chromatography-diode array detection-mass spectrometry in Arraiolos historical textiles.  

PubMed

The natural dyes, and dye sources, in two seventeenth century Arraiolos carpets from the National Museum of Machado de Castro were analysed by high-performance liquid chromatography with UV-vis diode array detection (HPLC-DAD) and HPLC-mass spectrometry (LC-MS). Weld (Reseda luteola L.), indigo and spurge flax (Daphne gnidium L.) were found to be the dye sources, in agreement with original dyeing recipes collected during the nineteenth century. In order to fully characterize the plant sources, LC-MS conditions were optimized with plant extracts and the chromatographic separation and mass detection were enhanced. Extraction of the dyes, in the Arraiolos carpet samples, was performed using mild conditions that avoid glycoside decomposition. For the blues a dimethylformamide solution proved to be efficient for indigotin recovery. For all the other colours, an improved mild extraction method (with oxalic acid, methanol, acetone and water) was used, enabling to obtain the full dye source fingerprint, namely the flavonoid glycosides in the yellow dyes. PMID:19168183

Marques, Rita; Sousa, Micaela M; Oliveira, Maria C; Melo, Maria J

2009-01-06

386

A simple and rapid 3D view method for selective and sensitive determination of paclitaxel in micro volume rat plasma by LC-diode array UV and its application to a pharmacokinetic study.  

PubMed

A simple, highly repeatable and reproducible method for the estimation of Paclitaxel (TAX) in micro volume amounts of rat plasma is successfully developed and validated. The extraction procedure using 800 µL of ice-cold acetonitrile is very simple and economical with high sensitivity. The rectangular ratiograms and purity curve demonstrate the selectivity of the method. The validation and stability results show that propylparaben (PP) is a suitable internal standard (resolution 7.70 ± 0.15 min) for the estimation of TAX in micro volume rat plasma. TAX and PP are separated by isocratic reversed-phase high-performance liquid chromatography with diode array UV method with a retention time of 8.0 ± 0.25 and 5.3 ± 0.15 min, respectively, with a total run time of 10 min. The system suitability results show that the method has good reproducibility. The stability of TAX is well studied in rat plasma, and the % RSD of all stability studies of TAX are well within the acceptable range of ± 20 % at the lower limit of quantitation (LLOQ) and ± 15% at all quality control levels. The limit of detection (LOD) and LLOQ of the method are 5 and 10 ng/mL, respectively. This rapid method is successfully used to study the i.v pharmacokinetic of TAX at 10 mg/kg in wistar rats, and drug concentration is detected up to 24 h. PMID:22337803

Kumar, Sekar Vasantha; Srinath, Selladurai; Saha, Ranendra N

2012-03-01

387

Quantitative analysis of triazine herbicides in environmental samples by using high performance liquid chromatography and diode array detection combined with second-order calibration based on an alternating penalty trilinear decomposition algorithm.  

PubMed

A novel application of second-order calibration method based on an alternating penalty trilinear decomposition (APTLD) algorithm is presented to treat the data from high performance liquid chromatography-diode array detection (HPLC-DAD). The method makes it possible to accurately and reliably analyze atrazine (ATR), ametryn (AME) and prometryne (PRO) contents in soil, river sediment and wastewater samples. Satisfactory results are obtained although the elution and spectral profiles of the analytes are heavily overlapped with the background in environmental samples. The obtained average recoveries for ATR, AME and PRO are 99.7±1.5, 98.4±4.7 and 97.0±4.4% in soil samples, 100.1±3.2, 100.7±3.4 and 96.4±3.8% in river sediment samples, and 100.1±3.5, 101.8±4.2 and 101.4±3.6% in wastewater samples, respectively. Furthermore, the accuracy and precision of the proposed method are evaluated with the elliptical joint confidence region (EJCR) test. It lights a new avenue to determine quantitatively herbicides in environmental samples with a simple pretreatment procedure and provides the scientific basis for an improved environment management through a better understanding of the wastewater-soil-river sediment system as a whole. PMID:20869500

Li, Yuan-Na; Wu, Hai-Long; Qing, Xiang-Dong; Li, Quan; Li, Shu-Fang; Fu, Hai-Yan; Yu, Yong-Jie; Yu, Ru-Qin

2010-08-14

388

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

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

Ebrahimzadeh, H; Molaei, K; Asgharinezhad, A A; Shekari, N; Dehghani, Z

2013-01-18

389

Matrix solid-phase dispersion extraction coupled with HPLC-diode array detection method for the analysis of sesquiterpene lactones in root of Saussurea lappa C.B.Clarke.  

PubMed

We developed a reliable and effective method to determine costunolide and dehydrocostuslactone in the root of Saussurea lappa C. B.Clarke using matrix solid-phase dispersion (MSPD) extraction, HPLC separation and diode array detection (DAD). Several extraction parameters for the MSPD were optimized. Florisil was chosen as dispersing adsorbent with methanol as elution solvent. The ratio of Florisil to sample was selected to be 4:1 and no additional clean-up steps were needed. Linearities (r>0.9995) were determined to be in the range of 22.5-360.0 ?g/mL for costunolide and 25.0-400.0 ?g/mL for dehydrocostuslactone. Intra- and inter-day precisions were also determined with a relative standard deviation (RSD) less than 3.2%. The limits of detection were found to be 0.122 ?g/mL for costunolide and 0.135 ?g/mL for dehydrocostuslactone. The recoveries were in the range of 92.5-99.8% with relative standard deviations ranged from 1.2% to 3.5%. The proposed MSPD method required shorter time and lower solvent volume than maceration-ultrasonic and Soxhlet extraction methods. PMID:21873122

Zhang, Qi; Cai, Defu; Liu, Jianhua

2011-08-17

390

Characterization of physalins and fingerprint analysis for the quality evaluation of Physalis alkekengi L. var. franchetii by ultra-performance liquid chromatography combined with diode array detection and electrospray ionization tandem mass spectrometry.  

PubMed

Physalins are important bioactive compounds from genus Physalis. They often occur as isomers, which makes the structural elucidation difficult. In the present study, the fragmentation behavior and UV characteristics of seven physalins from genus Physalis were firstly investigated using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and diode array detection (DAD). Combined with ultra-performance liquid chromatography (UPLC) and DAD, the established approach to the structural identification of physalins by ESI-MS/MS was then applied to the analysis of Physalis alkekengi L. According to the UPLC retention behavior, the diagnostic UV spectra and the molecular structural information provided by MS/MS spectra, about 19 fingerprint peaks were identified, including 14 physalins and 5 other compounds. Finally, the established fingerprint method was applied to the analysis of 31 P. alkekengi L. samples collected from different locations, which reflected their similar chemical constituent properties. The proposed method provides a scientific and technical platform to the herbal industry for quality control and safety assurance of herbal preparations that contain this class of physalins. PMID:22964457

Zheng, Yunliang; Luan, Lianjun; Chen, Yong; Ren, Yiping; Wu, Yongjiang

2012-08-24

391

Therapeutic drug monitoring of levetiracetam by high-performance liquid chromatography with photodiode array ultraviolet detection: preliminary observations on correlation between plasma concentration and clinical response in patients with refractory epilepsy.  

PubMed

Levetiracetam is a new antiepileptic drug prescribed for the treatment of patients with refractory partial seizures with or without secondary generalization as well as for the treatment of juvenile myoclonic epilepsy. A rapid and specific method by high-performance liquid chromatography diode array detection was developed to measure the concentration of levetiracetam in human plasma. The trough plasma concentrations measured in 69 epileptic patients treated with 500 to 3000 mg/d of levetiracetam ranged from 1.1 to 33.5 microg/mL. The mean (range) levetiracetam plasma concentrations in responders and nonresponders were 12.9 microg/mL (4.6-21 microg/mL) and 9.5 microg/mL (1.1-20.9 microg/mL), respectively. A wide variability in concentration-response relationships was observed in patients. Using a receiver operating characteristic curve, the threshold levetiracetam concentration for a therapeutic response was 11 microg/mL. The sensitivity and specificity for this threshold levetiracetam concentration were 73% and 71%, respectively. According to chi analysis, this finding was not significant probably because of the small number of patients and because of their refractory seizure type. Nevertheless, the levetiracetam plasma concentration could be used to help clinicians detect severe intoxication or to verify compliance by repeating the measurement in patients. PMID:17898647

Lancelin, Frédérique; Franchon, Emilie; Kraoul, Linda; Garciau, Isabelle; Brovedani, Sophie; Tabaouti, Khalid; Landré, Elisabeth; Chassoux, Francine; Paubel, Pascal; Piketty, Marie-Liesse

2007-10-01

392

X-Ray Spectroscopy with PIN diodes  

SciTech Connect

A PIN diode and a low noise preamplifier are included in a nuclear spectroscopy chain for X-ray measurements. This is a laboratory session designed to review the main concepts needed to set up the detector-preamplifier array and to make measurements of X-ray energy spectra with a room temperature PIN diode. The results obtained are compared with those obtained from radioactive sources with a high resolution cooled Si-Li detector.

Ramirez-Jimenez, F. J. [Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca S/N, La Marquesa, Ocoyoacac, 57150 (Mexico)

2006-09-25

393

[Studies on identification of drugs of abuse by diode array detection. I. Screening-test and identification of benzodiazepines by HPLC-DAD with ICOS software system].  

PubMed

For the establishment of screening-test and identification of 20 benzodiazepines (Alprazolam, Bromazepam, Chlordiazepoxide, Clonazepam, Clotiazepam, Cloxazolam, Diazepam, Estazolam, Fludiazepam, Flunitrazepam, Flurazepam, Lorazepam, Lormetazepam, Medazolam, Midazepam, Nimetazepam, Nitrazepam, Oxazepam, Prazepam, Triazolam), the optimum separation condition on HPLC was investigated by using Interactive Computer Optimization for HPLC Separation (ICOS) software. The two eluent systems of 0.02M KH2PO4 (pH 3.1)-methanol-acetonitrile (66.4:5.7:27.9) and 0.1% TFA-methanol-acetonitrile (61.6:16.1:22.3) were selected by HPLC analyses using ICOS. These optimum separation conditions enabled the screening test and identification of the 20 benzodiazepines on HPLC with photodiode array detection. PMID:7920567

Shimamine, M; Masunari, T; Nakahara, Y

1993-01-01

394

Semiconductor surface emitting laser diodes  

NASA Astrophysics Data System (ADS)

The conventional edge emitting laser diode uses either a single-stripe or multiple structure consisting of an active layer in a plane parallel to the semiconductor surface; two cleaved facets, functioning as laser cavity mirrors are perpendicular to this active layer. It is relatively difficult to fabricate and diagnose in situ, and only one-dimensional laser arrays have been monolithically fabricated. The surface emitting laser (SEL), on the other hand, utilizes both surfaces of the wafer as laser mirrors and the light output is perpendicular to the wafer plane. This makes planar fabrication and diagnosis easier, and more importantly, allows for two-dimensional (2-D) monolithic integration and array formation. This 2-D SEL array can be in scale in number and size while maintaining a high filling factor. The SEL array diodes can also be individually addressed and controlled, as well as the output beam. The output beam can also be easily accessed from both the front and back surfaces of the wafer. These features are very important and desirable when a large array of coherent emission semiconductor lasers is needed.

Wang, S. C.; Dziura, T. G.

1989-03-01

395

Analysis of total caffeine and other xanthines in specialty coffees using mixed mode solid-phase extraction and liquid chromatography-diode-array detection after microwave digestion.  

PubMed

In this study, solid-phase extraction (SPE) in mixed mode operation was employed to isolate xanthines including caffeine and theobromine from milled caffeinated and decaffeinated coffee samples after microwave digestion. 8-Chlorotheophylline was used as an internal standard. SPE was performed in hydrophobic mode using ethyl acetate/methanol (90:10, 2 mL) as the first elution solvent and in ionic exchange mode using ethyl acetate/ acetonitrile/ammonium hydroxide (78:20:2, 3 mL) as the second elution solvent. The eluates were combined, evaporated to dryness and dissolved in aqueous formic acid for analysis. Liquid chromatography with photodiode-array detection was used in isocratic mode employing a C18 column and a mobile phase consisting of acetonitrile/formic acid (0.1% aqueous). The limits of quantitation and detection for this method were 1 and 0.1 mg/L, respectively. The method was linear from 1 to 200 mg/L (r2 > 0.999) with recoveries of the individual xanthines greater than 95%. The decaffeinated coffees contained caffeine at levels less than 0.5 mg/g (range 0.23 to 0.49 mg/g) and caffeinated samples had wide range of levels of caffeine (5.18 to 12.21 mg/g). PMID:19007523

Hackett, Jeffery; Telepchak, Michael J; Coyer, Michael J

2008-10-01

396

Novel polymer systems for deep UV microlens arrays  

NASA Astrophysics Data System (ADS)

We report for the first time a UV curable polymer with effective optical transmission below 300 nm. Through careful control of kinetics, various viscosities can be generated to optimize the film forming properties via spin coating. The transmission of the monomers and films is investigated over a spectral range which spans the 240-370 nm output of ultraviolet AlInGaN light-emitting diodes. The refractive index of the polymer has been measured by ellipsometry to give a value of 1.57 at 280 nm. Using standard lithography techniques with reactive ion etching, arrays of microlenses have been fabricated in this polymer with diameters of 30 µm and below and are characterized by atomic force microscopy and confocal microscopy.

Mackintosh, A. R.; Kuehne, A. J. C.; Pethrick, R. A.; Guilhabert, B.; Gu, E.; Lee, C. L.; Dawson, M. D.; Heliotis, G.; Bradley, D. D. C.

2008-05-01

397

Highly efficient coupling between LD array and optical fiber array using Si microlens array  

Microsoft Academic Search

By using a Si microlens array, highly efficient coupling is realized between laser diode (LD) and optical-fiber arrays. The Si microlens is fabricated by transferring the lens shape of photoresist onto the Si surface using an etching process. For an optimal coupling scheme, a high-NA microlens with a diameter of 240 ?m and focal length of 190 ?m is designed

Gohji Nakagawa; Kazunori Miura; Masao Makiuchi; Mitsuhiro Yano

1993-01-01

398

Integrated Quantum Dot Schottky Diodes for RECTENNA (Rectifying Antenna)  

Microsoft Academic Search

In this paper we will present our latest research results of integrated quantum dot Schottky diodes and integrated silicon antenna for RF applications. Both, the quantum dot Schottky diodes and the antenna are integrated on Si substrates forming a simple mm-wave detection system, the rectifying antenna (RECTENNA). Within this work a specific antenna design, 1-dimensional array (single line antenna), will

H. Xu; A. Karmous; M. Morschbach; O. Kirfel; S. Spiessberger; E. Kasper

2009-01-01

399

GaAs(P) Light Emitting Diode Display.  

National Technical Information Service (NTIS)

The purpose of this program was to fabricate and supply the following visible display arrays: A two element light emitting diode display, A one hundred element light emitting diode display, in order to complete the work successfully, detailed design and a...

E. H. Lim

1969-01-01

400

A multi-residue method for pesticide residue analysis in rice grains using matrix solid-phase dispersion extraction and high-performance liquid chromatography-diode array detection.  

PubMed

Pesticides are widely used in rice cultivation, often resulting in detection of their residues in rice grains. So far, no analytical method has been available for the simultaneous determination of most rice pesticides in rice grains. This paper reports the development and validation of such a method for the determination of eight rice pesticides (penoxsulam tricyclazole, propanil, azoxystrobin, molinate, profoxydim, cyhalofop-butyl, deltamethrin) and 3,4-dichloroaniline, the main metabolite of propanil. Pesticide extraction and clean-up was performed by an optimized matrix solid-phase dispersion (MSPD) protocol on neutral alumina (5 g) using acetonitrile as the elution solvent. Samples were analyzed in a high-performance liquid chromatography-diode array detection (HPLC-DAD) system. Pesticide separation was achieved with a mobile phase of acetonitrile/water in a linear elution gradient from 30:70% (v/v) to 100:0% (v/v) in 14 min at a flow rate of 0.8 mL min(-1). Method validation was performed by means of linearity, intra-day accuracy, inter-day precision and sensitivity. Linear regression coefficients (R(2)) were always above 0.9948. Limits of detection (LOD) and quantification (LOQ) varied from 0.002 to 0.200 mg kg(-1) and 0.006 to 0.600 mg kg(-1), respectively. Recoveries were investigated at three fortification levels and were found to be acceptable (74-127%) with relative standard deviations (RSD) below 12%. Application of the method for the analysis of five commercial rice grain samples showed that the pesticide levels were below the LOD. Overall, the method developed is suitable for the determination of residues of most rice pesticides in rice grains at levels below the established MRLs. PMID:20379813

Tsochatzis, Emmanouil D; Menkissoglu-Spiroudi, Urania; Karpouzas, Dimitrios G; Tzimou-Tsitouridou, Roxani

2010-04-09

401

Validated reversed phase-high performance liquid chromatography-diode array detector method for the quantitation of Rutin, a natural immunostimulant for improving survival in aquaculture practice, in toonea sinensis folium  

PubMed Central

Background: Rutin is a bioflavonoid of strong immunostimulating activity from the Toonea Sinensis Folium, which has shown a significant ability to increase the survival rate of white shrimp with bacterial infection. However, no method for the quantitation of this active ingredient in the herb has been reported to date. Materials and Methods: A reversed phase-high performance liquid chromatography-diode array detector (RP-HPLC-DAD) method was developed to quantify Rutin in the Toonea Sinensis Folium, with the HPLC conditions optimized, followed by validation for linearity, accuracy, precision, limit of detection (LOD), repeatability, and stability. Then, the established method was used to determine the content of Rutin in two samples. Results: The separation was performed on a Waters XBridge Shield RP18 column (150 mm × 4.6 mm, 5 ?m) kept at 25°C, and acetonitrile and water containing 0.1% acetate acid (18:82, v / v)-composed mobile phase was constantly driven at 1.0 mL / minute during the analysis. Twenty microliters of sample solution or standard solution were injected into the HPLC system and 254 nm was selected to monitor the separation. A strong linear relationship between the peak area and concentration of Rutin was observed within the range of 0.01044 – 0.2610 mg / mL (r2 = 1.0000). The LOD was 0.03915 ?g / mL, and recovery of Rutin was from 97.6 to 99.6%. In addition, the method was also validated to be repeatable, stable, precise, and accurate. Conclusions: An efficient and reliable RP-HPLC-DAD method was established, which could be used for routine analysis of Rutin in Toonea Sinensis Folium and to assist in the quality control of this herb.

Shen, Yuping; Yin, Huawu; Chen, Bin; Xia, Guohua; Yang, Huan; Jia, Xiaobin

2012-01-01

402

Identification of complex, naturally occurring flavonoid glycosides in kale (Brassica oleracea var. sabellica) by high-performance liquid chromatography diode-array detection/electrospray ionization multi-stage mass spectrometry.  

PubMed

Kale is a member of the Brassicaceae family and has a complex profile of flavonoid glycosides. Therefore, kale is a suitable matrix to discuss in a comprehensive study the different fragmentation patterns of flavonoid glycosides. The wide variety of glycosylation and acylation patterns determines the health-promoting effects of these glycosides. The aim of this study is to investigate the naturally occurring flavonoids in kale. A total of 71 flavonoid glycosides of quercetin, kaempferol and isorhamnetin were identified using a high-performance liquid chromatography diode-array detection/electrospray ionization multi-stage mass spectrometry (HPLC-DAD/ESI-MS(n)) method. Of these 71 flavonol glycosides, 27 were non-acylated, 30 were monoacylated and 14 were diacylated. Non-acylated flavonol glycosides were present as mono-, di-, tri- and tetraglycosides. This is the first time that the occurrence of four different fragmentation patterns of non-acylated flavonol triglycosides has been reported in one matrix simultaneously. In addition, 44 flavonol glycosides were acylated with p-coumaric, caffeic, ferulic, hydroxyferulic or sinapic acid. While monoacylated glycosides existed as di-, tri- and tetraglycosides, diacylated glycosides occurred as tetra- and pentaglycosides. To the best of our knowledge, 28 compounds in kale are reported here for the first time. These include three acylated isorhamnetin glycosides (isorhamnetin-3-O-sinapoyl-sophoroside-7-O-D-glucoside, isorhamnetin-3-O-feruloyl-sophoroside-7-O-diglucoside and isorhamnetin-3-O-disinapoyl-triglucoside-7-O-diglucoside) and seven non-acylated isorhamnetin glycosides. PMID:20552580

Schmidt, Susanne; Zietz, Michaela; Schreiner, Monika; Rohn, Sascha; Kroh, Lothar W; Krumbein, Angelika

2010-07-30

403

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

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

Babula, Petr; Mikelova, Radka; Adam, Vojtech; Kizek, Rene; Havel, Ladislav; Sladky, Zdenek

2006-06-09

404

The Ultraviolet Spectrum of the Crab Pulsar  

Microsoft Academic Search

The time-averaged ultraviolet spectrum of the Crab pulsar will be measured with the FOS using the G160L grating in the ACCUM mode. The grating covers from 1150 A to 2510 A at a dispersion of 6.87 A\\/diode. The 0.3 arcsec diameter aperture will be used in order to exclude as much as possible of the surrounding nebula. The observed spectrum

Robert Bless

1995-01-01

405

Development of new SOI diode structure for beyond 17 ?m pixel pitch SOI diode uncooled IRFPAs  

NASA Astrophysics Data System (ADS)

Scalable new SOI diode structure has been proposed and developed for beyond 17?m pixel pitch mega-pixel-class SOI diode uncooled infrared focal plane arrays (IRFPAs). Conventionally, each p+n vertical diode is formed between a p+diffusion and an n-body in each SOI active area, and 8-10 diodes are serially connected with interconnections. In the proposed new structure, we employ two kinds of diodes, namely, p+n and n+p vertical diodes. First, two regions of an nbody and a p-body are prepared in an SOI active area. In the n-body, a p+ diffusion is formed apart from the n-body /pbody boundary. In the p-body, an n+ diffusion is formed apart from the boundary. In this way, a p+n vertical diode and an n+p vertical diode are formed together in an SOI active area. Moreover, a contact hole, which is formed in touch with both n- and p-bodies, electrically connects these two kinds of diodes. With this new structure which is named "new 2-in- 1 SOI diode structure", we have realized remarkable reduction of the diode area. It leads to significant increase of the diode series number in a pixel, which increases infrared responsivity of the pixel. As a result, designing a 15?m pixel pitch IRFPA with the new structure, 12 series diodes can be arranged in a pixel, although 10 series diodes have been used even in the case of our 25?m pitch generation pixel. To confirm the ability of the new diodes, test elements of 12-17?m pitch pixels were fabricated and evaluated. Furthermore, the fabrication of 17?m pixel pitch 320 x 240 IRFPAs with the new diodes was carried out and their favorable FPA operations were successfully verified. In conclusion, the proposed and developed new SOI diode technology is very promising for beyond 17?m pixel pitch mega-pixel-class uncooled IRFPAs.

Takamuro, Daisuke; Maegawa, Tomohiro; Sugino, Takaki; Kosasayama, Yasuhiro; Ohnakado, Takahiro; Hata, Hisatoshi; Ueno, Masashi; Fukumoto, Hiroshi; Ishida, Kozo; Katayama, Haruyoshi; Imai, Tadashi; Ueno, Munetaka

2011-05-01

406

Sr{sub 3}Al{sub 2}O{sub 5}Cl{sub 2}:Ce{sup 3+},Eu{sup 2+}: A potential tunable yellow-to-white-emitting phosphor for ultraviolet light emitting diodes  

SciTech Connect

The Sr{sub 3}Al{sub 2}O{sub 5}Cl{sub 2}:Ce{sup 3+},Eu{sup 2+} phosphors were prepared by solid state reaction. The obtained phosphors exhibit a strong absorption in the UV-visible region and have two intense emission bands at 444 and 609 nm. The energy transfer from the Ce{sup 3+} to Eu{sup 2+} ions was observed, and the critical distance has been estimated to be about 24.5 A by spectral overlap method. Furthermore, the developed phosphors can generate lights from yellow-to-white region under the excitation of UV radiation by appropriately tuning the activator content, indicating that they have potential applications as an UV-convertible phosphor for white light emitting diodes.

Song Yanhua; Jia Guang; Yang Mei; Huang Yeju; You Hongpeng; Zhang Hongjie [State Key laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China) and Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China)

2009-03-02

407

Diode-laser deceleration and collimation of a rubidium beam  

SciTech Connect

We report the use of frequency-chirped diode lasers to decelerate a thermal atomic beam of Rb and, in a separate experiment, the use of frequency-stabilized diode lasers to collimate the beam with optical molasses. For this we used a 100-mW cw laser-diode array injection locked to light from a low-power, frequency-narrowed, single-stripe diode laser. Also, a novel scheme for imaging the neutral-atom beam profile has been developed for monitoring the collimation experiments in two dimensions. We have increased both beam brightness and intensity by a factor of more than 20.

Sheehy, B.; Shang, S.; Watts, R.; Hatamian, S.; Metcalf, H. (Department of Physics, State University of New York, Stony Brook, New York 11794 (US))

1989-11-01

408

Individually addressable optoelectronic arrays for optogenetic neural stimulation  

Microsoft Academic Search

Here we demonstrate the use of a micro-Light Emitting Diode Arrays as a powerful tool for complex spatiotemporal control of photosensitized neurons. The array can generate arbitrary, 2D, excitation patterns with millisecond and micrometer resolution. In particular, we describe an active matrix control address system to allow simultaneous control of 256 individual micro light emitting diodes. We present the system

P. Degenaar; B. McGovern; R. Berlinguer-Palmini; N. Vysokov; N. Grossman; V. Pohrer; E. Drakakis; M. Neil

2010-01-01

409

Mass transfer ways of ultraviolet printing ink ingredients into foodstuffs.  

PubMed

The case of isopropylthioxanthone (ITX) showed conclusively that the ingredients of ultraviolet printing inks may migrate into packaged foodstuffs. For multilayered materials like beverage cartons, the only way that mass transfer can occur is by the so-called set-off effect. In contrast, in the case of rigid plastics like yoghurt cups, two other methods of mass transfer, permeation and gas phase, have to be considered. In cooperation with producers of ink, plastic cups and yoghurt, a project was conducted in order to elucidate the mass transfer of ink ingredients. In addition, the influence of storage time and the age of ultraviolet lamps on the migration level was examined. The suitability of 50% ethanol as a simulant for yoghurt was also tested. ITX was chosen as a model migrant, as it is easily detectable. Furthermore, the migration of two other substances, the photo-initiator 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) and the amine synergist ethyl-4-(dimethylamino)benzoate (EDAB), which may be used in combination with ITX, was studied. Before being filled with yoghurt or 50% ethanol, the printed cups were stored under different contact conditions, with and without contact between the inner layer and the printed surfaces, in order to distinguish between the possible mass transfer ways. All analyses were performed by means of high performance liquid chromatography with diode array and fluorescence detection (HPLC-DAD/FLD). It was shown that contamination with ITX and EDAB occurs via set-off and that the degree of migration increases with lamp age and storage time of the unfilled cups. Migration of MTMP was not detectable. The results show that besides the careful selection of the appropriate raw materials for printing ink, a close monitoring of the process also plays a major role in migration control. In addition, the results proved that 50% ethanol is a suitable simulant for yoghurt. PMID:20432097

Jung, T; Simat, T J; Altkofer, W

2010-07-01

410

Light-Emitting Diodes: Research, Manufacturing, and Applications III.  

National Technical Information Service (NTIS)

High-efficient light emitting diodes (LEDs) emitting red, amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layers instead of GaN active layers. Red LEDs with an emission wavelength of 680 nm which emission en...

E. F. Schubert H. W. Yao I. T. Ferguson

1999-01-01

411

Development of a fully automated on-line solid phase extraction and high-performance liquid chromatography with diode array detection method for the pharmacokinetic evaluation of bavachinin: a study on absolute bioavailability and dose proportionality.  

PubMed

A fully automated on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with diode array detection (DAD) method was developed for determination of bavachinin in mouse plasma. Analytical process was performed on two reversed-phase columns (SPE cartridge and analytical column) connected via a Valco 6-port switching valve. Plasma samples (10 ?L) were injected directly onto a C18 SPE cartridge (MF Ph-1 C18, 10 mm × 4 mm, 5 ?m) and the biological matrix was washed out for 2 min with the loading solvent (5 mM NaH(2)PO(4) buffer, pH 3.5) at a flow rate of 1 mL/min. By rotation of the switching valve, bavachinin was eluted from the SPE cartridge in the back-flush mode and transferred to the analytical column (Venusil MP C18, 4.6 mm × 150 mm, 5 ?m) by the chromatographic mobile phase consisted of acetonitrile-5mM NaH(2)PO(4) buffer 65/35 (v/v, pH 3.5) at a flow rate of 1 mL/min. The complete cycle of the on-line SPE purification and chromatographic separation of the analyte was 13 min with UV detection performed at 236 nm. Calibration curve with good linearity (r=0.9997) was obtained in the range of 20-4000 ng/mL in mouse plasma. The intra-day and inter-day precisions (RSD) of bavachinin were in the range of 0.20-2.32% and the accuracies were between 98.47% and 102.95%. The lower limit of quantification (LLOQ) of the assay was 20 ng/mL. In conclusion, the established automated on-line SPE-HPLC-DAD method demonstrated good performance in terms of linearity, specificity, detection and quantification limits, precision and accuracy, and was successfully utilized to quantify bavachinin in mouse plasma to support the pharmacokinetic (PK) studies. The PK properties of bavachinin were characterized as rapid oral absorption, high clearance, and poor absolute bioavailability. PMID:22444438

Liu, Lei; Liu, Kang-Ning; Wen, Ya-Bin; Zhang, Han-Wen; Lu, Ya-Xin; Yin, Zheng

2012-02-21

412

Enhancement of outcoupling efficiency of organic light-emitting diodes using a planarized moth-eye structure on glass substrate.  

PubMed

To improve optical properties of organic light-emitting diodes (OLEDs), we developed a planarized moth-eye structure by ultraviolet nanoimprint lithography (UV-NIL). The moth-eye pattern was fabricated on a glass substrate by UV-NIL using AMONIL polymer resin. It contains nanoscaled, cone-shaped, periodic pattern arrays with a 250 nm diameter and a 550 nm pitch. The glass substrate with the moth-eye structure exhibited a 1%-2% improvement in transmittance of visible wavelengths, but it requires a planarized layer with high-refractive-index materials. Photosensitive titanium precursor resin annealed by UV was used to improve the current efficiency by up to 26% versus conventional OLEDs. PMID:24081049

Kim, Jeong Ho; Do, Lee-Mi; Choi, Je-Hong; Park, Jaehoon; Lee, Heon

2013-10-01

413

ZnO-nanowires/PANI inorganic/organic heterostructure light-emitting diode.  

PubMed

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

He, Ying; Wang, Jun-an; Zhang, Wenfei; Song, Jizhong; Pei, Changlong; Chen, Xiaoban

2010-11-01

414

Method for extreme ultraviolet lithography  

DOEpatents

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.

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

415

Method for extreme ultraviolet lithography  

DOEpatents

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.

Felter, T. E. (Livermore, CA); Kubiak, Glenn D. (Livermore, CA)

1999-01-01

416

Photovoltaic-module bypass-diode encapsulation. Annual report  

SciTech Connect

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.

Not Available

1983-06-20

417

Diode and Diode Circuits, a Programmed Text.  

ERIC Educational Resources Information Center

|This programed text on diode and diode circuits was developed under contract with the United States Office of Education as Number 4 in a series of materials for use in an electrical engineering sequence. It is intended as a supplement to a regular text and other instructional material. (DH)|

Balabanian, Norman; Kirwin, Gerald J.

418

Diode Random Noise Generator.  

National Technical Information Service (NTIS)

The noise generator utilizes the reverse breakdown characteristic of avalanche diodes. In the circuit the noise output of one diode randomly varies the bias voltage of a second diode. The circuit includes a power supply, a bias resistor, a coupling capaci...

E. Hirschmann G. N. Kambouris

1965-01-01

419

Hybrid flexible vertical nanoscale diodes prepared at low temperature in large area  

NASA Astrophysics Data System (ADS)

Fabrication and operation of hybrid flexible vertical nanoscale diodes are reported. The diodes, formed by n-type ZnO and p-type CuSCN, were embedded in a 6 µm polymer foil, provided with vertical cylindrical openings of about 100 nm, by using a low temperature solution based electrochemical deposition technique. Electrical measurements show diode function with sound device characteristics at operation temperatures up to 67 °C. This heterojunction shows the potential for ZnO based ultraviolet light-emitting diodes.

Aé, L.; Chen, Jie; Lux-Steiner, M. Ch

2008-11-01

420

Lighting with laser diodes  

NASA Astrophysics Data System (ADS)

Contemporary white light-emitting diodes (LEDs) are much more efficient than compact fluorescent lamps and hence are rapidly capturing the market for general illumination. LEDs are also replacing halogen lamps or even newer xenon based lamps in automotive headlamps. Because laser diodes are inherently much brighter and often more efficient than corresponding LEDs, there is great research interest in developing laser diode based illumination systems. Operating at higher current densities and with smaller form factors, laser diodes may outperform LEDs in the future. This article reviews the possibilities and challenges in the integration of visible laser diodes in future illumination systems.

Basu, Chandrajit; Meinhardt-Wollweber, Merve; Roth, Bernhard

2013-08-01

421

Qualification of diode foil materials for excimer lasers  

NASA Astrophysics Data System (ADS)

The Aurora facility at Los Alamos National Laboratory uses KrF excimer lasers to produce 248 nm light for inertial confinement fusion applications. Diodes in each amplifier produce relativistic electron beams to pump a Kr-F-Ar gas mixture. A foil is necessary to separate the vacuum diode from the laser gas. High tensile strength, high electron transmission, low ultraviolet reflectivity, and chemical compatibility with fluorine have been identified as requisite foil properties. Several different materials were acquired and tested for use as diode foils. Transmission and fluorine compatibility tests were performed using the Electron Gun Test Facility (EGTF) at Los Alamos. Off-line tests of tensile strength and reflectivity were performed. Titanium foil, which is commonly used as a diode foil, was found to generate solid and gaseous fluoride compounds, some of which are highly reactive in contact with water vapor.

Anderson, R. G.; Shurter, R. P.; Rose, E. A.

422

Confirmation of malachite green, gentian violet and their leuco analogs in catfish and trout tissue by high-performance liquid chromatography utilizing electrochemistry with ultraviolet-visible diode array detection and fluorescence detection  

Microsoft Academic Search

A sensitive analytical procedure for the confirmation of residues of malachite green (MG), gentian violet (GV) and their leuco analogs (LMG and LGV) in catfish and trout tissue at 10 ng\\/g is described. Frozen (?20°C) fish fillets were cut into small pieces and homogenized in Waring blendors. The compounds of interest were extracted from 20-g amounts of homogenized fish tissue

Larry G. Rushing; Eugene B. Hansen

1997-01-01

423

Design of high voltage photovoltaic arrays  

Microsoft Academic Search

Safety and the need to protect modules from high reverse voltages dictate the criteria for the electrical design of high voltage photovoltaic arrays. Photovoltaic modules are inherently 'live', and therefore present special safety problems during installation and maintenance. However, by proper use of connectors, blocking and bypass diodes, and disconnect switches, an array may be made safe and reliable at

P. A. Lawson; R. R. Addiss Jr.

1980-01-01

424

n-ZnO nanorods/p+-Si (111) heterojunction light emitting diodes  

PubMed Central

In this study, we report the effects of thermal annealing in nitrogen ambient on the optical and electrical properties of zinc oxide (ZnO) nanorod (NR) arrays for the application in light emission diodes (LED). The single-crystalline ZnO NR array was synthesized on p+-Si (111) substrate without seed layer using simple, low-cost, and low-temperature hydrothermal method. The substrate surface was functionalized by hydrofluoric acid and self-assembled monolayer of octadecyltrimethoxysilane ((CH3 (CH2)17Si(OCH3)3). ZnO NRs were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and micro-photoluminescence (micro-PL). The results of FESEM and XRD indicate that single crystalline ZnO NRs with (002) preferred orientation along the substrate surface is successfully grown on functionalized p+-Si (111) substrate. The current–voltage and electroluminescence (EL) characteristics of the LED show that the most suitable annealing temperature ranges from 400°C to 600°C. Both PL and EL spectra show broadband emissions, ultraviolet and visible (green-yellow) light. The white-like light emission is able to be observed by naked eyes.

2012-01-01

425

Graded nanowire ultraviolet LEDs by polarization engineering  

NASA Astrophysics Data System (ADS)

Given the large thermal activation energy of acceptors in high %Al AlGaN, a new approach is needed to control p-type conductivity in this material. One promising alternative to using impurity doping with thermal activation is using the intrinsic characteristics of the III-nitrides to activate dopants with polarization-induced charge in graded heterostructures. In this work polarization-induced activation of dopants is used in graded AlGaN nanowires grown by plasma-assisted molecular beam epitaxy to form ultraviolet light-emitting diodes. Electrical and optical characterization is provided, showing clear diode behavior and electroluminescent emission at 336nm. Variable temperature electrical measurements show little change in device performance at cryogenic temperatures, proving that dopant ionization is polarizationinduced rather than thermally activated.

Carnevale, Santino D.; Kent, Thomas F.; Phillips, Patrick J.; Sarwar, A. T. M. Golam; Klie, Robert F.; Rajan, Siddharth; Myers, Roberto C.

2012-10-01

426

Solar Maximum: Solar Array Degradation.  

National Technical Information Service (NTIS)

The 5-year in-orbit power degradation of the silicon solar array aboard the Solar Maximum Satellite was evaluated. This was the first spacecraft to use Teflon R FEP as a coverglass adhesive, thus avoiding the necessity of an ultraviolet filter. The peak p...

T. Miller

1985-01-01

427

Photoresist composition for extreme ultraviolet lithography  

DOEpatents

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.

Felter, T. E. (Alameda County, CA); Kubiak, G. D. (Alameda County, CA)

1999-01-01

428

Diodes and Rectifiers  

NSDL National Science Digital Library

Written by Tony R. Kuphaldt, this chapter of All About Circuit's third volume on Semiconductors describes the physics behind diodes and rectifiers. The chapter is divided into fourteen sections on topics including diode ratings, voltage multipliers, and zener diodes. Each section has clear illustrations and examples, and most have a concise, bulleted review of what was covered at the end of the page. This is an excellent resource for educators in physics and electronic engineering classrooms to introduce lessons or units on semiconductors, diodes, and rectifiers. [ASC

Kuphaldt, Tony R.

2008-07-02

429

A transparent ultraviolet triggered amorphous selenium p-n junction  

SciTech Connect

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.

Saito, Ichitaro; Soga, Kenichi; Overend, Mauro; Amaratunga, Gehan A. J. [Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Miyazaki, Wataru; Onishi, Masanori; Masuzawa, Tomoaki; Okano, Ken [Department of Physics, International Christian University, 3-10-2 Osawa Mitaka, Tokyo 181-8585 (Japan); Kudo, Yuki [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Yamada, Takatoshi [Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Koh, Angel; Chua, Daniel [Department of Materials Science and Engineering, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077 (Singapore); Aono, Masami [Department of Materials Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu Yokosuka, Kanagawa 239-8686 (Japan)

2011-04-11

430

Infrared phased-array sensor  

NASA Astrophysics Data System (ADS)

Metal-oxide-metal (MOM) tunnel diode detectors when integrated with phased-array antennas provide determination of the angle of arrival and degree of coherence of received infrared radiation. Angle-of-arrival measurements are made with a pair of dipole antennas coupled to a MOM diode through a coplanar strip transmission line. The direction of maximum angular response is altered by varying the position of the MOM diode along the transmission line connecting the antenna elements. Phased-array antennas can also be used to measure the degree of coherence of a partially coherent infrared field. With a two-element array, the degree of coherence is a measure of the correlation of electric fields received by the antennas as a function of the element separation. Antenna-coupled MOM diode devices are fabricated using electron beam lithography and thin-film deposition through a resist shadow mask. Measurements at 10.6 ?m are substantiated by electromagnetic simulations and compared to analytic results.

Slovick, Brian A.; Bean, Jeffrey A.; Florence, Lou A.; Boreman, Glenn D.

2011-05-01

431

Room-Temperature Ultraviolet Nanowire Nanolasers  

Microsoft Academic Search

Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated. The self-organized, oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process. These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers. Under optical excitation, surface-emitting lasing action was

Michael H. Huang; Samuel Mao; Henning Feick; Haoquan Yan; Yiying Wu; Hannes Kind; Eicke Weber; Richard Russo; Peidong Yang

2001-01-01

432

Integrated ultraviolet sensor system with on-chip 1 G? transimpedance amplifier  

Microsoft Academic Search

The output current delivered by photo-diodes with enhanced ultraviolet (UV) responsivity is in most cases small, thus requiring an interface circuit with high current gain. Generally, this is achieved using discrete components. This integrated system includes a 1G? transimpedance stage and an IC-compatible UV photo-diode on a single chip. The industrial application motivating this work is flame detection for combustion

Daniel Bolliger; Piero Malcovati; Andreas Haberli; Henry Baltes; Pasqualina Sarro; F. Maloberti

1996-01-01

433

GaAs Schottky varactor diode optimization for high-performance nonlinear transmission lines  

Microsoft Academic Search

Nonlinear transmission lines (NLTLs) using Schottky diodes as varactor loads provide significant performance and efficiency advantages for both frequency multiplication and phase shifting applications that will benefit comb generator and phased array applications, respectively. Prior NLTL optimization has been limited only to analytical studies of specific diode profiles. This paper describes, for the first time, the optimization of NLTL performance

D. Sawdai; D. Ko; M. Kintis; S. Maas; X. Zhang; S. Valdes; E. Garber; G. Barber; E. Quach; J. Newman; F. Fong

2002-01-01

434

High Power High Reliable Single Emitter Laser Diodes At 808 nm  

Microsoft Academic Search

High power laser diodes and diode arrays emitting at the wavelength of 808nm are widely used for pumping neodymium (Nd+) doped solid state lasers and fiber lasers, medical surgery, dental treatment and material processing. In general, the power is limited by catastrophic optical mirror damage (COMD) and heat dissipation. In this paper we demonstrate 29W CW output power at 808

Wei Gao; Zuntu Xu; Lisen Cheng; Kejian Luo; Andre Mastrovito; Kun Shen

435

High-power highly reliable single emitter laser diodes at 808 nm  

Microsoft Academic Search

High power laser diodes and diode arrays emitting at the wavelength of 808nm are widely used for pumping neodymium (Nd+) doped solid state lasers and fiber lasers, medical surgery, dental treatment and material processing. In general, the power is limited by catastrophic optical mirror damage (COMD) and heat dissipation. In this paper we demonstrate 29W CW output power at 808

Wei Gao; Zuntu Xu; Lisen Cheng; Kejian Luo; Andre Mastrovito; Kun Shen

2007-01-01

436

Long pulse diode experiments.  

National Technical Information Service (NTIS)

A diode employing a thermionic cathode has produced 80 A beams at 200 kV for at least 6 (mu)s. Moreover, the diode operates at rates as high as 1 Hz. EGUN simulations of the experimental geometry agree with the experiments. Finally, simulation of a propos...

C. R. McClenahan G. J. Weber M. W. O'Malley J. Stewart L. F. Rinehart

1990-01-01

437

Vortex diode jet  

DOEpatents

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

Houck, Edward D. (Idaho Falls, ID)

1994-01-01

438

Vortex diode jet.  

National Technical Information Service (NTIS)

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high re...

E. D. Houck

1993-01-01

439

Wavelength Elongation of GaN-based Laser Diodes  

NASA Astrophysics Data System (ADS)

Starting with next generation high density optical disc, commercial use of GaN based violet laser diodes (LD) has been adopted in many new fields, such as bio-medical, reprographic, exposure and etc. Recently, the lasing wavelength has broadened to cover from ultraviolet (UV) to blue-green region, which enabled other new applications. In this paper, current status of GaN based LDs in UV to Blue-green region are reported and next target is discussed.

Nagahama, Shinichi; Kozaki, Tokuya; Yanamoto, Tomoya; Mukai, Takashi