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1

Enhanced ultraviolet emission and improved spatial distribution uniformity of ZnO nanorod array light-emitting diodes via Ag nanoparticles decoration  

NASA Astrophysics Data System (ADS)

Localized surface plasmon (LSP) enhanced ultraviolet (UV) light-emitting diodes (LEDs) were fabricated by embedding a ZnO nanorod array/p-GaN film heterostructure into a Ag-nanoparticles/PMMA composite. By optimizing the concentration of Ag nanoparticles in PMMA, two distinct changes in electroluminescence (EL) spectra were observed: (1) the UV EL component from ZnO excitons was selectively enhanced more than 13-fold and the entire spectral lineshape was changed and (2) the spatial uniformity of the output photon intensity was improved and the linewidth of an angular distribution curve was increased by ~2 times. These observations can be attributed to near-field optical coupling between Ag LSPs and ZnO excitons. Time-resolved luminescence measurements and a model calculation reveal that the optical coupling results in the increase of the spontaneous emission rate and internal quantum efficiency of Ag-nanoparticles-decorated ZnO nanorod arrays. Moreover, the LSP-exciton interaction allows the device's EL to be coupled out of the nanorod waveguide and to be isotropically scattered into every direction, thus broadening the angular distribution of the EL intensity.

Liu, Wei Zhen; Xu, Hai Yang; Wang, Chun Liang; Zhang, Li Xia; Zhang, Cen; Sun, Shi Yu; Ma, Jian Gang; Zhang, Xin Tong; Wang, Jian Nong; Liu, Yi Chun

2013-08-01

2

Enhanced ultraviolet emission and improved spatial distribution uniformity of ZnO nanorod array light-emitting diodes via Ag nanoparticles decoration.  

PubMed

Localized surface plasmon (LSP) enhanced ultraviolet (UV) light-emitting diodes (LEDs) were fabricated by embedding a ZnO nanorod array/p-GaN film heterostructure into a Ag-nanoparticles/PMMA composite. By optimizing the concentration of Ag nanoparticles in PMMA, two distinct changes in electroluminescence (EL) spectra were observed: (1) the UV EL component from ZnO excitons was selectively enhanced more than 13-fold and the entire spectral lineshape was changed and (2) the spatial uniformity of the output photon intensity was improved and the linewidth of an angular distribution curve was increased by ?2 times. These observations can be attributed to near-field optical coupling between Ag LSPs and ZnO excitons. Time-resolved luminescence measurements and a model calculation reveal that the optical coupling results in the increase of the spontaneous emission rate and internal quantum efficiency of Ag-nanoparticles-decorated ZnO nanorod arrays. Moreover, the LSP-exciton interaction allows the device's EL to be coupled out of the nanorod waveguide and to be isotropically scattered into every direction, thus broadening the angular distribution of the EL intensity. PMID:23897294

Liu, Wei Zhen; Xu, Hai Yang; Wang, Chun Liang; Zhang, Li Xia; Zhang, Cen; Sun, Shi Yu; Ma, Jian Gang; Zhang, Xin Tong; Wang, Jian Nong; Liu, Yi Chun

2013-09-21

3

Diode laser array  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

4

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

5

Application of high-performance liquid chromatography with ultraviolet diode array detection and refractive index detection to the determination of class composition and to the analysis of gasoline.  

PubMed

A method of effective application of normal-phase high-performance liquid chromatography (NP-HPLC) with ultraviolet diode array detection (DAD) and refractive index detection (RID) for the determination of class composition of gasoline and its components, i.e. for the determination of content of alkenes, aromatic and saturated hydrocarbons in gasoline meeting modern quality standards, has been developed. An aminopropyl-bonded silica stationary phase was used along with n-hexane or n-heptane as the mobile phase. A DAD signal integrated over the 207-240 nm range was used to determine alkenes. This eliminates the necessity of separating alkenes from saturates, because the latter do not absorb UV radiation above 200 nm. The content of aromatic hydrocarbons is determined by means of a refractive index detector. Calibration was based on hydrocarbon type composition determined by the fluorescent indicator adsorption method, ASTM D1319. The results obtained by the developed method were found to be consistent with those obtained by fluorescent indicator adsorption or by a multidimensional GC method (PIONA) (ASTM D5443). The method can be applied to gasoline meeting recent quality standards, irrespective of refining technology used in the production of gasoline components, including gasoline with various contents of oxygenates. The developed method cannot be used to determine the hydrocarbon type composition of gasoline that contains as a component the so-called pyrocondensate, i.e. the fraction with a boiling point up to 220 degrees C, obtained through thermal pyrolysis of distillation residues of crude oil or coal and, consequently, does not meet the quality standards. The paper includes the procedure for identification of this type of gasoline. PMID:15032352

Kami?ski, Marian; Kartanowicz, Rafa?; Przyjazny, Andrzej

2004-03-12

6

Performance measurements of hybrid PIN diode arrays  

SciTech Connect

We report the successful development of hybrid PIN diode arrays and a series of room-temperature measurements in a high-energy pion beam at FNAL. A PMOS VLSI 256 {times} 256 readout array having 30 {mu}m square pixels was indium-bump bonded to a mating PIN diode detector array. Preliminary measurements on the resulting hybrid show excellent signal-to-noise at room temperature. 3 refs., 5 figs.

Shapiro, S.L. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)); Arens, J.F.; Jernigan, J.G. (California Univ., Berkeley, CA (USA). Space Sciences Lab.); Kramer, G. (Hughes Aircraft Co., El Segundo, CA (USA)); Collins, T.; Worley, S. (Hughes Aircraft Co., Carlsbad, CA (USA)); Wilburn, C.D. (Micron Semiconductor, Inc., Longwood, FL (USA)); Skubic, P. (Oklahoma Univ., Norman, OK (USA))

1990-10-01

7

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

8

Integrated power conditioning for laser diode arrays  

SciTech Connect

This compact modulator has demonstated its ability to efficiently and accurately drive a laser diode array. The addition of the crowbar protection circuit is an invaluable addition to the integrated system and is capable of protecting the laser diode array against severe damage. We showed that the correlation between measured data and simulation indicates that our modulator model is valid and can be used as a tool in the design of future systems. The spectrometer measurements that we conducted underline the imprtance of current regulation to stable laser operation.

Hanks, R.L.; Kirbie, H.C.; Newton, M.A.; Farhoud, M.S.

1995-06-30

9

International ultraviolet explorer solar array power degradation  

NASA Technical Reports Server (NTRS)

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

Day, J. H., Jr.

1983-01-01

10

Rapid analysis of oxidized cholesterol derivatives by high-performance liquid chromatography combined with diode-array ultraviolet and evaporative laser light-scattering detection  

Microsoft Academic Search

Extensive evidence of the deleterious biological effects of oxidized 5-cholesten-3?-ol (cholesterol) derivatives has led to\\u000a great interest in their detection. We observed that known oxidized cholesterol derivatives can be rapidly quantitated by combining\\u000a reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) absorption and evaporative laser light-scattering\\u000a (ELSD) detection. Using a 20 × 0.46 cm C18 HPLC column and methanol\\/acetonitrile (60:40,

Kyoichi Osada; Amir Ravandi; Arnis Kuksis

1999-01-01

11

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

12

Low-cost laser diode array  

DOEpatents

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

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

1999-06-01

13

Ultraviolet light-emitting diodes in water disinfection  

Microsoft Academic Search

Background, aim, and scope  The novel system of ultraviolet light-emitting diodes (UV LEDs) was studied in water disinfection. Conventional UV lamps,\\u000a like mercury vapor lamp, consume much energy and are considered to be problem waste after use. UV LEDs are energy efficient\\u000a and free of toxicants. This study showed the suitability of LEDs in disinfection and provided information of the effect

Sari Vilhunen; Heikki Särkkä; Mika Sillanpää

2009-01-01

14

Microlens frames for laser diode arrays  

DOEpatents

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

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

1999-07-13

15

Space Qualification of Laser Diode Arrays  

NASA Technical Reports Server (NTRS)

Laser instruments have great potential in enabling a new generation of remote-sensing scientific instruments. NASA s desire to employ laser instruments aboard satellites, imposes stringent reliability requirements under severe conditions. As a result of these requirements, NASA has a research program to understand, quantify and reduce the risk of failure to these instruments when deployed on satellites. Most of NASA s proposed laser missions have base-lined diode-pumped Nd:YAG lasers that generally use quasi-constant wave (QCW), 808 nm Laser Diode Arrays (LDAs). Our group has an on-going test program to measure the performance of these LDAs when operated in conditions replicating launch and orbit. In this paper, we report on the results of tests designed to measure the effect of vibration loads simulating launch into space and the radiation environment encountered on orbit. Our primary objective is to quantify the performance of the LDAs in conditions replicating those of a satellite instrument, determine their limitations and strengths which will enable better and more robust designs. To this end we have developed a systematic testing strategy to quantify the effect of environmental stresses on the optical and electrical properties of the LDA.

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

2005-01-01

16

Combustion exhaust measurements of nitric oxide with an ultraviolet diode-laser-based absorption sensor  

Microsoft Academic Search

A diode-laser-based sensor has been developed for ultraviolet absorption measurements of the nitric oxide (NO) molecule. The sensor is based on the sum-frequency mixing (SFM) of the output of a tunable, 395-nm external-cavity diode laser and a 532-nm diode-pumped, frequency-doubled Nd:YAG laser in a beta-barium borate crystal. The SFM process generates 325 ± 75 nW of ultraviolet radiation at 226.8

Thomas N. Anderson; Robert P. Lucht; Rodolfo Barron-Jimenez; Sherif F. Hanna; Jerald A. Caton; Thomas Walther; Sukesh Roy; Michael S. Brown; James R. Gord; Ian Critchley; Luis Flamand

2005-01-01

17

Modular package for cooling a laser diode array  

DOEpatents

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

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

1992-01-01

18

Tuning electrical parameters of graphene/p-type polycrystalline silicon Schottky diodes by ultraviolet irradiation  

NASA Astrophysics Data System (ADS)

The present work reports the fabrication and detailed electrical properties of graphene/p-type polycrystalline silicon (poly-Si) Schottky diodes with and without ultraviolet irradiation. Ultraviolet treatment may lead to the reduced work function of graphene, thus increasing the Schottky barrier height at the graphene/poly-Si interface. Compared to the graphene/poly-Si Schottky diodes without ultraviolet treatment, the ultraviolet-treated graphene/poly-Si Schottky diodes exhibit lower ideality factor and higher responsivity. The sensitivity of the work function of graphene to the ultraviolet irradiation time provides an opportunity to tune the electrical parameters of graphene/poly-Si Schottky diodes. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices.

Lin, Jian-Huang; Lin, Yow-Jon; Chang, Hsing-Cheng

2015-01-01

19

Infrared vidicons employing metal-silicon Schottky diode arrays  

Microsoft Academic Search

Metal-silicon Schottky barrier diode arrays have been suggested for use as retinas in infrared ridicons (1). Such arrays permit the fabrication of camera tubes having highly uniform retina response out to the mid infrared, thus permitting sensitive storage mode imagery even in the presence of substantial background radiation (2). To achieve the required long wavelength cutoff, high work function metals

J. P. Spratt; R. F. Schwarz; G. W. Racette

1975-01-01

20

Pushing technologies: single-photon avalanche diode arrays  

Microsoft Academic Search

We present the development of silicon monolithic arrays of 60 photon-counters (SPADA, Single-Photon Avalanche Diode Array) for the visible. The SPADA system is suitable for state-of-the-art Adaptive Optics operations and Fast Transient image acquisitions, at quite a fraction of the current cost of imaging arrays. The fabricated solid-state photon counters are rugged, easy to be integrated in the optical system.

Franco Zappa; Simone Tisa; Sergio Cova; Piera Maccagnani; Domenico Bonaccini Calia; Giovanni Bonanno; Massimiliano Belluso; Roberto Saletti; Roberto Roncella

2004-01-01

21

III-nitride blue and ultraviolet photonic crystal light emitting diodes T. N. Oder,a)  

E-print Network

III-nitride blue and ultraviolet photonic crystal light emitting diodes T. N. Oder,a) K. H. Kim, J. Figures 1 a and 1 b shows the schematic diagrams a Present address: Department of Physics and Astronomy

Jiang, Hongxing

22

Applications of microlens-conditioned laser diode arrays  

SciTech Connect

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 (LLNL) has actively pursued optical efficiency and engineering improvements in this technology in an effort to supply large radiance-conditioned laser diode array sources for its own internal programs. This effort has centered on the development of a modular integrated laser diode packaging technology with the goal of enabling the simple and flexible construction of high average power, high density, two-dimensional arrays with integrated cylindrical microlenses. Within LLNL, the principal applications of microlens-conditioned laser diode arrays are as high intensity pump sources for diode pumped solid state lasers (DPSSLs). A simple end-pumping architecture has been developed and demonstrated that allows the radiation from microlens-conditioned, two-dimensional diode array apertures to be efficiently delivered to the end of rod lasers. To date, pump powers as high as 2.5 kW have been delivered to 3 mm diameter laser rods. Such high power levels are critical for pumping solid state lasers in which the terminal laser level is a Stark level lying in the ground state manifold. Previously, such systems have often required operation of the solid state gain medium at low temperature to freeze out the terminal laser Stark level population. The authors recently developed high intensity pump sources overcome this difficulty by effectively pumping to much higher inversion levels, allowing efficient operation at or near room temperature. Because the end-pumping technology is scalable in absolute power, the number of rare-earth ions and transitions that can be effectively accessed for use in practical DPSSL systems has grown tremendously.

Beach, R.J.; Emanuel, M.A.; Freitas, B.L. [and others

1995-01-01

23

Method and system for homogenizing diode laser pump arrays  

DOEpatents

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

Bayramian, Andy J

2013-10-01

24

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

25

Ultraviolet electroluminescence from two-dimensional ZnO nanomesh/GaN heterojunction light emitting diodes  

NASA Astrophysics Data System (ADS)

The authors report the fabrication of heterojunction light emitting diodes (LEDs) based on two-dimensional (2D) hexagonal ordered n-type ZnO nanomesh and p-type GaN. The 2D ZnO nanomesh array was prepared by employing polystyrene spheres as a template. When a forward bias was applied to the LED, a strong ultraviolet (UV) electroluminescence peaked at 385 nm can be observed. The peak deconvolution revealed three emission peaks at 370, 388, and 420 nm. The origin of these emission peaks will be discussed. In addition, the LED was capable of exciting a red phosphor to convert UV light into red light.

Ye, Jing; Zhao, Yu; Tang, Libin; Chen, Li-Miao; Luk, C. M.; Yu, S. F.; Lee, S. T.; Lau, S. P.

2011-06-01

26

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

27

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

28

Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90%). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize products yields and to identify side products. The use of UV-LED arrays offers many advantages over conventional Hg lamp setups, including greater light output over a narrower wavelength range, lower power consumption, and minimal generation of heat.

Rider, N. D.; Taha, Y. M.; Odame-Ankrah, C. A.; Huo, J. A.; Tokarek, T. W.; Cairns, E.; Moussa, S. G.; Liggio, J.; Osthoff, H. D.

2015-01-01

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

Coherently Combined Diode Laser Arrays and Stacks  

E-print Network

We have coherently combined up to 7.2 W CW using an individually addressable 10-element-array of 960-nm slab-coupled optical waveguide lasers (SCOWLs). We are currently scaling the phase-locked output power to 100 W using ...

Hostetler, John L.

31

Ultraviolet light emitting diodes and bio-aerosol sensing  

NASA Astrophysics Data System (ADS)

Recent interest in compact ultraviolet (UV) light emitters has produced advances in material quality and device performance from aluminum-rich alloys of the nitride semiconductor system. The epitaxial growth of device structures from this material poses remarkable challenges, and state-of-the-art in semiconductor UV light sources at wavelengths shorter than 350 nm is currently limited to LEDs. A portion of the work presented in this thesis involves the design and characterization of UV LED structures, with particular focus on sub-300 nm LEDs which have only been demonstrated within the last four years. Emphasis has been placed on the integration of early devices with modest efficiencies and output powers into a practical, fluorescence-based bio-sensing instrument. The quality of AlGaInN and AlGaN-based materials is characterized by way of the performance of 340 nm and 290 nm LEDs respectively. A competitive level of device operation is achieved, although much room remains for improvement in the efficiency of light emission from this material system. A preliminary investigation of 300 nm LEDs grown on bulk AIN shows promising electrical and optical characteristics, and illustrates the numerous advantages that this native substrate offers to the epitaxy of wide bandgap nitride semiconductors. The application of UV LEDs to the field of bio-aerosol sensing is pursued by constructing an on-the-fly fluorescence detection system. A linear array of UV LEDs is designed and implemented, and the capability of test devices to excite native fluorescence from bacterial spores is established. In order to fully capitalize on the reduction in size afforded by LEDs, effort is invested in re-engineering the remaining sensor components. Operation of a prototype system for physically sorting bio-aerosols based on fluorescence spectra acquired in real-time from single airborne particles excited by a UV-LED array is demonstrated using the bio-fluorophores NADH and tryptophan. Sensor performance is shown to be ultimately linked to the material quality of high aluminum fraction nitrides, and is expected to show progress as this field matures.

Davitt, Kristina M.

32

Qualification of Laser Diode Arrays for Mercury Laser Altimeter Mission  

NASA Technical Reports Server (NTRS)

NASA's requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. The MESSENGER mission is flying the Mercury Laser Altimeter (MLA) which is a diode-pumped Nd:YAG laser instrument designed to map the topography of Mercury. The environment imposed on the instrument by the orbital dynamics places special requirements on the laser diode arrays. In order to limit the radiative heating of the satellite from the surface of Mercury, the satellite is designed to have a highly elliptical orbit. The satellite will heat near perigee and cool near apogee. The laser power is cycled during these orbits so that the laser is on for only 30 minutes (perigee) in a 12 hour orbit. The laser heats 10 C while powered up and cools while powered down. In order to simulate these operational conditions, we designed a test to measure the LDA performance while being temperature and power cycled. Though the mission requirements are specific to NASA and performance requirements are derived from unique operating conditions, the results are general and widely applicable. We present results on the performance of twelve LDAs operating for several hundred million pulses. The arrays are 100 watt, quasi-CW, conductively-cooled, 808 nm devices. Prior to testing, we fully characterize each device to establish a baseline for individual array performance and status. Details of this characterization can be found in reference. Arrays are divided into four groups and subjected to the temperature and power cycling matrix are shown.

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

2004-01-01

33

Linear laser diode arrays for improvement in optical disk recording  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

34

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

35

Diode-array-pumped repetitively pulsed neodymium phosphate glass laser  

SciTech Connect

Repetitively pulsed generation (200 {mu}s, 40 Hz) was obtained in a neodymium phosphate glass laser pumped by a 870-nm diode array. The maximum slope lasing efficiency with respect to the optical pump energy equal to 13% is restricted by the factor ({approx}0.23) of active-medium filling by the mode field. By adjusting the laser cavity, the single-transverse mode regime, in particular, the generation of the TEM{sub 00} mode is obtained in the entire range of pump energies. (active media. lasers)

Bogatov, A P; Drakin, A E; Miftakhutdinov, D R; Starodub, A N [P. N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Mikaelyan, G T [Inject Research and Manufacturing Enterprise, Saratov (Russian Federation)

2008-09-30

36

Ultraviolet light-emitting diodes based on group three nitrides  

Microsoft Academic Search

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.

Asif Khan; Krishnan Balakrishnan; Tom Katona

2008-01-01

37

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

2011-03-01

38

Ultraviolet photodetectors and imaging arrays based on III-V nitride heterostructures  

NASA Astrophysics Data System (ADS)

The III-V nitride class of compound semiconductors has received much attention in the last decade. These materials have a wide, direct bandgap, making them a prime candidate for optoelectronic devices in the blue, green, and ultraviolet spectral regions. These materials exhibit impressive optical, electrical, and thermal properties, even though there are fundamental materials issues that are thus far unresolved. This work explores the application of III-V nitride semiconductors to optical detectors in the ultraviolet region of the electromagnetic spectrum. Metalorganic vapor phase epitaxy was used to synthesize thin film p-i-n photodiode structures on double side polished sapphire substrates; these films were characterized for optical, electrical and structural properties. The grown structures were designed to respond to a predetermined region of the UV spectrum when illuminated from the substrate side. These structures were fabricated into devices using generally accepted techniques for dry etching and p and n-contact metallizations. Test devices were characterized using tools developed by the author. These devices demonstrated as high as 80% quantum efficiency and extremely low dark currents; resulting in spectral detectivities as large as 6 * 1013 cmHz1/2W-1. Devices were designed and demonstrated for a series of detection regions ranging from 365 nm to 250 nm. Photolithography masks were designed to allow the fabrication of photodiode arrays that would hybridize to commercially available CMOS based readout integrated circuits (ROICs), used routinely for infrared photodiode imaging. Photodiode arrays were fabricated and indium bumps were deposited onto the diode contacts and the ROICs to provide electrical connection. The hybrid detector arrays were placed in leadless chip carriers, wirebonded, and connected to commercially available drive and readout circuitry. Images of UV scenes were focused onto the arrays using fused quartz lenses. These images and movies were successfully collected at frame rates up to 240 Hz using both 32 x 32 and 128 x 128 III-V nitride based UV photodiode imagers.

Brown, Jeffrey David

2000-10-01

39

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

DOEpatents

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

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

2012-12-25

40

Modular microchannel cooled heatsinks for high average power laser diode arrays  

Microsoft Academic Search

Detailed performance results for an efficient and low thermal impedance laser diode array heatsink are presented. High duty factor or CW operation of fully filled laser diode arrays is made possible at high average power. Low thermal impedance is achieved using a liquid coolant and laminar flow through microchannels. The microchannels are fabricated in silicon using an anisotropic chemical etching

Ray Beach; William J. Benett; Barry L. Freitas; D. Mundinger; Brian J. Comaskey; R. W. Solarz; Mark A. Emanuel

1992-01-01

41

Characterization of High-power Quasi-cw Laser Diode Arrays  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

42

Design Proposal of Light Emitting Diode in Vacuum Ultraviolet Based on Perovskite-Like Fluoride Crystals  

Microsoft Academic Search

The variation of band gap energy, band structure and lattice constant of mixed LiBaF3, LiCaF3 and LiSrF3 perovskites is studied. The band structure and transition type of these fluorides is predicted by ab initio band calculation based on the local density approximation. The design principle of vacuum ultraviolet light emitting diode is proposed. The lattice-matched double-hetero structure of different perovskite-like

Riadh El Ouenzerfi; Shingo Ono; Alex Quema; Masahiro Goto; Nobuhiko Sarukura; Takeshi Nishimatsu; Noriaki Terakubo; Hiroshi Mizuseki; Yoshiyuki Kawazoe; Akira Yoshikawa; Tsuguo Fukuda

2004-01-01

43

3D Simulation and Analysis of AlGaN\\/GaN Ultraviolet Light Emitting Diodes  

Microsoft Academic Search

Compact ultraviolet light sources are currently of high interest for applications in solid-state lighting, short-range communication, and bio-chemical detection. Our nitride-based light-emitting diode (LED) includes AlGaN quantum wells with an emission wavelength of approximately 340 nm. In this paper, we analyze internal device physics by three-dimensional (3D) numerical simulation. The simulation incorporated a 3D drift-diffusion model for the carrier transport,

Joachim Piprek; Tom Katona; Steven P. DenBaars; Simon Li

44

3,4,9,10-Perylenetetracarboxylicdiimide as an interlayer for ultraviolet organic light emitting diodes  

Microsoft Academic Search

Ultraviolet organic light emitting diodes with 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI) interlayer have been achieved. The emission spectrum and intensity were strongly dependent on the thickness of PTCDI interlayer, in spite of the fact that PTCDI has neither much lower HOMO nor much higher LUMO level, which is considered necessary for efficient charge blocking layers. The influence of PTCDI layer was investigated in

Alan Man-Ching Ng; Aleksandra B. Djuriši?; Kai-Hang Tam; Kai Wing Cheng; Wai-Kin Chan; Hoi Lam Tam; Kok-Wai Cheah; Albert W. Lu; Jesse Chan; Aleksandar D. Raki?

2008-01-01

45

Watt-Class High-Output-Power 365 nm Ultraviolet Light-Emitting Diodes  

Microsoft Academic Search

Ultraviolet (UV) light-emitting diode (LED) epilayers were grown on low dislocation density (1× 108\\/cm2) GaN templates with sapphire substrates. Then, the GaN templates and sapphire substrates were removed using laser-induced lift-off and polishing techniques. Additionally, to enhance the extraction efficiency, this LED chip used a higher reflectance Ag p-type electrode, patterned surface, and silicone resin molding package. When this UV

Daisuke Morita; Masashi Yamamoto; Kazuyuki Akaishi; Kousuke Matoba; Katsuhiro Yasutomo; Yoshio Kasai; Masahiko Sano; Shin-ichi Nagahama; Takashi Mukai

2004-01-01

46

365 nm Ultraviolet Laser Diodes Composed of Quaternary AlInGaN Alloy  

Microsoft Academic Search

Ultraviolet (UV) laser diodes (LDs), whose active layer were quaternary AlxInyGa1-x-yN single-quantum well structure, were grown on epitaxial lateral overgrown GaN substrates by a metalorganic chemical vapor deposition method. We investigated the lasing wavelength dependence of UV LDs on the threshold current density. As a result, we succeeded in fabricating 365 nm UV LDs which are useful for various industrial

Shingo Masui; Yuji Matsuyama; Tomoya Yanamoto; Tokuya Kozaki; Shin-Ichi Nagahama; Takashi Mukai

2003-01-01

47

High Output Power 365 nm Ultraviolet Light Emitting Diode of GaN-Free Structure  

Microsoft Academic Search

We have fabricated high-power ultraviolet (UV) light emitting diodes (LEDs). Epi-layers of UV LEDs were grown on high-quality GaN templates with sapphire substrates, and then the GaN templates and the sapphire substrates were removed by using laser-induced liftoff and polishing techniques in order to reduce the absorption of UV light by the GaN layer. As a result, we obtained the

Daisuke Morita; Masahiko Sano; Masashi Yamamoto; Takashi Murayama; Shin-ichi Nagahama; Takashi Mukai

2002-01-01

48

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

49

Diode-pumped doubly resonant all-intracavity continuous-wave ultraviolet laser at 336 nm  

NASA Astrophysics Data System (ADS)

We report for the first time a coherent ultraviolet radiation at 336 nm by intracavity sum-frequency generation of a 912 nm Nd:GdVO4 laser and a 532 nm frequency doubling Nd:YVO4 laser. The ultraviolet laser is obtained by using a doubly resonator, type-I critical phase matching CsLiB6O10 (CLBO) crystal sum-frequency mixing. With a total diode pump power of 31.8 W (13.1 W pump power for 912 nm Nd:GdVO4 laser and 18.7 W pump power for 532 nm Nd:YVO4 frequency doubling laser), TEM00 mode ultraviolet laser at 336 nm of 93 mW is obtained. The power stability is better than 3.4% and laser beam quality M2 factors are 1.52 and 1.27 in both horizontal and vertical dimensions respectively.

Lü, Y. F.; Sun, G. C.; Fu, X. H.; Liu, Z. T.; Chen, J. F.

2010-08-01

50

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; Lanzanò, Luca; Musumeci, Francesco; Pluchino, Alessandro; Scordino, Agata; Campisi, Angelo; Cosentino, Luigi; Finocchiaro, Paolo; Condorelli, Giovanni; Mazzillo, Massimo; Lombardo, Salvo; Sciacca, Emilio

2008-01-01

51

Vacuum nano-hole array embedded organic light emitting diodes.  

PubMed

We demonstrated a nano-hole array (NHA) embedded structure that was fabricated for organic light emitting diodes (OLEDs) using a robust reverse transfer process. The NHA structure is proposed in this study as a strategy for maximizing the diffraction strength of two dimensional photonic crystals (PCs) by engineering vacuum nano-holes inside a dielectric slab. The electroluminescence (EL) intensity of the OLED was improved by more than twice. Such an optical enhancement was evaluated by using the angular dependence of photoluminescence (PL). The FDTD simulation was carried out to optimize the NHA structure for extraction of the emission induced from both vertical and horizontal dipoles. We explored the effect of the NHA structure on the extraction improvement converted from waveguide mode by measuring EL intensities of the devices with a hemisphere lens. In addition, the transfer process employed in this study yielded extremely low surface roughness, and thus outstanding electrical characteristics. PMID:24336917

Jeon, Sohee; Jeong, Jun-ho; Song, Young Seok; Jeong, Won-Ik; Kim, Jang-Joo; Youn, Jae Ryoun

2014-03-01

52

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. PMID:15981527

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

2005-01-01

53

Influence of Interference on Extraction Efficiency of Ultraviolet Vertical Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

We report on enhanced efficiency of ultraviolet vertical light-emitting diodes (VLEDs) with interference between the reflective mirror and the multiple quantum well. The dimensions of the cavity are fixed at 30 nm for the p-AlGaN layer, while various thicknesses of p-GaN from 60 nm to 140 nm were used. The light output power of the VLED in constructive compared with destructive interference condition increased by 23.9% at 350 mA. These improvements could be attributed to the predominant constructive interference of vertical radiation due to an optical cavity with optimal p-GaN thickness.

Kim, Seung Hwan; Song, Young Ho; Jeon, Seong Ran; Yang, Gye Mo; Ha, Jun Seok; Lee, Sang Hern; Baek, Jong Hyeob; Park, Hyung Jo

2013-08-01

54

3,4,9,10-Perylenetetracarboxylicdiimide as an interlayer for ultraviolet organic light emitting diodes  

NASA Astrophysics Data System (ADS)

Ultraviolet organic light emitting diodes with 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI) interlayer have been achieved. The emission spectrum and intensity were strongly dependent on the thickness of PTCDI interlayer, in spite of the fact that PTCDI has neither much lower HOMO nor much higher LUMO level, which is considered necessary for efficient charge blocking layers. The influence of PTCDI layer was investigated in three different device configurations and obtained results are discussed. For optimal device configuration, OLED with emission centered at 370 nm and turn-on voltage of 4.5 V is obtained.

Ng, Alan Man-Ching; Djuriši?, Aleksandra B.; Tam, Kai-Hang; Cheng, Kai Wing; Chan, Wai-Kin; Tam, Hoi Lam; Cheah, Kok-Wai; Lu, Albert W.; Chan, Jesse; Raki?, Aleksandar D.

2008-05-01

55

Ultraviolet electroluminescence from ZnO/polymer heterojunction light-emitting diodes.  

PubMed

We report ultraviolet electroluminescence at 390 nm from diode structures consisting of electrodeposited ZnO nanorods sandwiched between a transparent SnO(2) film and a p-type conducting polymer. The nanorods are embedded in an insulating polystyrene layer. ZnO deposition occurs at 90 degrees C and produces vertically oriented nanorods with very high uniformity over areas of approximately 20 cm(2). Electron diffraction shows the nanorods to be single crystalline wurtzite ZnO. As-grown films show a broad electroluminescence band over the visible spectrum. Annealing at moderate temperatures (T = 300 degrees C) increases the emission and strongly raises the excitonic contribution. Optimally processed films show a narrow ultraviolet electroluminescence line at approximately 390 nm. PMID:16218727

Könenkamp, R; Word, R C; Godinez, M

2005-10-01

56

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

SciTech Connect

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

Endo, Kuniaki [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Yokohama Research Laboratories, Mitsubishi Rayon Co., Ltd., 10-1 Daikoku, Tsurumi, Yokohama 230-0053 (Japan); Adachi, Chihaya [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)

2014-03-24

57

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

NASA Astrophysics Data System (ADS)

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

Endo, Kuniaki; Adachi, Chihaya

2014-03-01

58

Vacuum nano-hole array embedded organic light emitting diodes  

NASA Astrophysics Data System (ADS)

We demonstrated a nano-hole array (NHA) embedded structure that was fabricated for organic light emitting diodes (OLEDs) using a robust reverse transfer process. The NHA structure is proposed in this study as a strategy for maximizing the diffraction strength of two dimensional photonic crystals (PCs) by engineering vacuum nano-holes inside a dielectric slab. The electroluminescence (EL) intensity of the OLED was improved by more than twice. Such an optical enhancement was evaluated by using the angular dependence of photoluminescence (PL). The FDTD simulation was carried out to optimize the NHA structure for extraction of the emission induced from both vertical and horizontal dipoles. We explored the effect of the NHA structure on the extraction improvement converted from waveguide mode by measuring EL intensities of the devices with a hemisphere lens. In addition, the transfer process employed in this study yielded extremely low surface roughness, and thus outstanding electrical characteristics.We demonstrated a nano-hole array (NHA) embedded structure that was fabricated for organic light emitting diodes (OLEDs) using a robust reverse transfer process. The NHA structure is proposed in this study as a strategy for maximizing the diffraction strength of two dimensional photonic crystals (PCs) by engineering vacuum nano-holes inside a dielectric slab. The electroluminescence (EL) intensity of the OLED was improved by more than twice. Such an optical enhancement was evaluated by using the angular dependence of photoluminescence (PL). The FDTD simulation was carried out to optimize the NHA structure for extraction of the emission induced from both vertical and horizontal dipoles. We explored the effect of the NHA structure on the extraction improvement converted from waveguide mode by measuring EL intensities of the devices with a hemisphere lens. In addition, the transfer process employed in this study yielded extremely low surface roughness, and thus outstanding electrical characteristics. Electronic supplementary information (ESI) available: The contents include details about the FDTD modeling, PL specimen fabrication, OLED device fabrication, and PL/EL measurement set-up. Further information is provided relating to the NHA substrate as well. See DOI: 10.1039/c3nr05331h

Jeon, Sohee; Jeong, Jun-Ho; Song, Young Seok; Jeong, Won-Ik; Kim, Jang-Joo; Youn, Jae Ryoun

2014-02-01

59

Rockwell H1RG silicon PIN diode array gamma and proton radiation characterization at cryo temperatures  

Microsoft Academic Search

The Rockwell Scientific Company, HAWAII-1RG PIN silicon diode array, designed for high performance, low noise applications in ground-based astronomy, has been tested for suitability in space application ranging over a wide selection of orbits. Gamma testing for total ionizing dose (TID) effects in the read out integrated circuit (ROIC) and proton transient and damage testing to characterize the PIN diode

R. Lowell; C. Conger; S. Rainwater; M. Lazo; Y. Bai

2005-01-01

60

The use of diode array spectroradiometers for dosimetry in phototherapy  

NASA Astrophysics Data System (ADS)

An evaluation of two diode array radiometers, an UV spectroradiometer, Type SC-MP-A, from 4D Controls (Redruth, UK) and an USB2000-UV-VIS spectrometer from Ocean Optics (Duiven, NL), was carried out at the Photobiology Unit, University of Dundee. Three parameters of the instruments' performance were investigated, having been identified as the most likely sources of error in phototherapy dosimetry: (1) calibration, (2) stray light rejection, (3) angular response. An assessment was then made of the reliability of this type of instrument for dosimetry in clinical practice by measurement of a selection of phototherapy sources, in direct comparison with calibrated radiometers. Both instruments were found to have significant stray light levels (SC: 13% and USB: 39%). The use of stray light compensation and a high output calibration source improves accuracy to within acceptable limits. Angular responses were satisfactory: f2 values (+/-60°) of 5.9% and 7.8% for SC and USB, respectively. The SC spectroradiometer is supplied as a calibrated instrument. Using the supplied calibration resulted in errors in measuring phototherapy sources of up to 44% in UVA. Alternative calibration reduced the error in measuring UVA and UVB sources to within 12%. The USB spectrometer was found to have insufficient responsivity in both UVB and UVA to provide reproducible measurements of most phototherapy sources.

Oliver, Hannah; Moseley, Harry

2002-12-01

61

Volume Bragg Grating temperature gradient effect on laser diode array and stack spectra narrowing  

NASA Astrophysics Data System (ADS)

A strip Volume Bragg Grating (VBG) locked 64 emitter diode laser array's center wavelength shift of each emitter according to VBG's local temperature is experimentally studied, which is consistent well with thermal imaging temperature distribution, Finite element analysis (FEA) is then used to study strip and large area VBG's temperature gradients, we find even with minute heat deposition, due to PTR glass's low heat conductivity, tens degrees temperature gradient could easily be built, we suggest it may be partially respond for stack's poor spectra narrowing performance compared to single laser diode and diode array. Finally, some measures are further suggested to alleviate the effect.

Wang, Hongyan; Yang, Zining; Hua, Weihong; Liu, Wenguang; Xu, Xiaojun

2012-01-01

62

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

63

Deep Ultraviolet AlGaInN-Based Light-Emitting Diodes on Si(111) and Sapphire  

E-print Network

Ultraviolet light-emitting diodes (LEDs) with emission wavelength as short as 280 nm, grown by gas source molecular beam epitaxy with ammonia, are described. The typical multi-quantum well (MQW) structure LED. Hall measurements of the p-type SL consisting of 1 nm thick layers of GaN separated by 5 nm thick

Holtz, Mark

64

Dominant ultraviolet light emissions in packed ZnO columnar homojunction diodes  

NASA Astrophysics Data System (ADS)

The growth of Sb-doped p-type ZnO /Ga-doped n-type ZnO homojunction on Si (100) substrate by molecular beam epitaxy led to closely packed vertical ZnO columns with lateral diameters ranging from 100to400nm. Mesa structures were defined and Ohmic contact of both n-type ZnO and p-type ZnO was realized with Au /Ti and Au /NiO, respectively. I-V and C-V curves present typical electrical properties of a diode, indicating that reliable p-type ZnO was formed. Electroluminescence shows dominant ultraviolet emissions with insignificant deep-level related yellow/green band emissions at different drive currents from 60to100mA at room temperature.

Kong, Jieying; Chu, Sheng; Olmedo, Mario; Li, Lin; Yang, Zheng; Liu, Jianlin

2008-09-01

65

High-power pseudomorphic mid-ultraviolet light-emitting diodes with improved efficiency and lifetime  

NASA Astrophysics Data System (ADS)

Recent advances in mid-ultraviolet light-emitting diodes grown pseudomorphically on bulk AlN substrates have led to improved efficiencies and lifetimes. For a 266 nm device an output power of 66 mW at 300 mA has been achieved with an external quantum efficiency of 4.5%. More importantly, the lifetimes of these devices have been increased substantially. Testing of LEDs in both surface mount design (SMD) and TO-39 packages show L50 lifetimes well in excess of 1,000 hours under a variety of case temperatures and currents. Package-related catastrophic failures are eliminated through encapsulation and hermetic sealing, further reducing failure rates and extending the lifetime.

Moe, Craig G.; Grandusky, James R.; Chen, Jianfeng; Kitamura, Ken; Mendrick, Mark C.; Jamil, Muhammad; Toita, Masato; Gibb, Shawn R.; Schowalter, Leo J.

2014-03-01

66

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

DOEpatents

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

Freitas, Barry L. (Livermore, CA)

1998-01-01

67

Uniformity of pump intensity distribution in diode-array side-pumped laser rod  

NASA Astrophysics Data System (ADS)

Diode-pumped solid-state lasers are high efficiency, long lifetime, compact and reliable, so they have been covering a wide range of applications. Thermal effect is a major limiting factor in scaling the average power of high-power solid-state lasers, so it is a critical issue in designing diode-pumped solid-state lasers. The uniform pump intensity distribution in laser rod can weaken the influence of thermal effects in laser, and the research of improving the pump distribution uniformity has attracted a great deal of attention. People usually establish a model of single diode-bar pumped laser rod to calculate the distribution. However, for diode-array pumped high-power lasers, the model is limited and has deviation with the actual pump distribution, which cannot reflect the real working conditions in the laser. In this paper, the theoretical model of diode-array pumped laser rod is built. Based on the actual working environment of diode-array side-pumped Tm:YAG laser rod, the expression of pump intensity distribution in the laser medium is deduced. Additionally, the influence of total pump power, pump structure, Tm:YAG rod characteristic parameters and pump beam radius on pump intensity distribution are simulated and analyzed. Moreover, the parameters are optimized in order to obtain the optimistic results which are efficient to improve the uniformity of pump distribution. The results show that when the pumping distance from diode-array to the rod's surface is 3mm, the distance between two rows of diode-bars is 1mm, the absorption coefficient is 330m-1,the pump beam width is 2.5mm,the pump intensity distribution of five-way pumped laser rod is improved, and then the thermal effects could be weakened. The presented results can provide theoretical guidance to design and optimization of high-power lasers.

Liu, Wenwen; Niu, Yanxiong; Liu, Haixia; Wang, Caili; Niu, Haisha; Man, Da

2014-11-01

68

Improved performance of high average power semiconductor arrays for applications in diode pumped solid state lasers  

Microsoft Academic Search

ABSTRACT The average power performance,capability of semiconductordiode laser arrays has improved,dramatically over the past several years. These performance,improvements, combined with cost reductions pursued by LLNL and others in the fabrication and packaging of diode lasers, have continued to reduce the price per average watt of laser diode radiation. Presently, we are at the point where the manufacturers of commercial high

Raymond J. Beach; Mark A. Emanuel; William J. Benett; Barry L. Freitas; Dma Ciarlo; Nils W. Carison; Steven B. Sutton; Jay A. Skidmore; Richard W. Solarz

69

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

DOEpatents

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

Freitas, B.L.

1998-10-27

70

Fabrication and electrical properties of axial and radial GaAs nanowire pn junction diode arrays  

NASA Astrophysics Data System (ADS)

We report on the fabrications and characterizations of axial and radial GaAs nanowire pn junction diode arrays. The nanowires are grown on n-doped GaAs (111)B substrates using the Au-catalyzed vapor—liquid—solid mechanism by metal—organic chemical vapor deposition (MOCVD). Diethyl—zinc and silane are used as p- and n-type dopant precursors, respectively. Both the axial and radial diodes exhibit diode-like J—V characteristics and have similar performances under forward bias. Under backward bias, the axial diode has a large leakage current, which is attributed to the bending of the pn junction interface induced by two doping mechanisms in Au-catalyzed nanowires. The low leakage current and high rectification ratio make the radial diode more promising in electrical and optoelectronic devices.

Li, Jun-Shuai; Zhang, Xia; Yan, Xin; Chen, Xiong; Li, Liang; Cui, Jian-Gong; Huang, Yong-Qing; Ren, Xiao-Min

2014-12-01

71

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

DOEpatents

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

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

1997-01-01

72

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

DOEpatents

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

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

1997-04-01

73

III-Nitride Ultraviolet Light Emitting Diodes with Delta-Doping  

NASA Astrophysics Data System (ADS)

Currently, there is a great need of solid-state ultraviolet (UV) emitters for many applications, ranging from the fluorescence detection of chemical and biological agents to the next generation solid-state lighting. Other applications include the use of compact UV sources (? <350 nm) in medical and health research. We present the results on the fabrication and characterization of 310 nm ultraviolet (UV) light-emitting diodes (LEDs) based on InAlGaN quaternary alloys grown by metal organic chemical vapor deposition. By employing ? -doping in the n- and p-type layers together with the use of AlN epilayer template, we have demonstrated enhanced structural quality. The output power of a 300 x 300 ? m^2 LED chip measured from the sapphire side reached a maximum value of about 1.0 mW under a DC operating condition at 120 mA, 0.25 mW under a standard DC operating condition at 20 mA and about 10 mW under a pulsed current driving at 1A with 1% duty cycle. The improved performance was attributed to the reduction in dislocation density in the device structure by ? -doping and the use of AlN epilayer template. Preliminary results on deep UV emitters (? 300 nm) will also be discussed.

Kim, K. H.; Fan, Z. Y.; Nakarmi, M. L.; Li, J.; Jin, S. X.; Lin, J. Y.; Jiang, H. X.

2004-03-01

74

Improved performance of high average power semiconductor arrays for applications in diode pumped solid state lasers  

SciTech Connect

The average power performance capability of semiconductor diode laser arrays has improved dramatically over the past several years. These performance improvements, combined with cost reductions pursued by LLNL and others in the fabrication and packaging of diode lasers, have continued to reduce the price per average watt of laser diode radiation. Presently, we are at the point where the manufacturers of commercial high average power solid state laser systems used in material processing applications can now seriously consider the replacement of their flashlamp pumps with laser diode pump sources. Additionally, a low cost technique developed and demonstrated at LLNL for optically conditioning the output radiation of diode laser arrays has enabled a new and scalable average power diode-end-pumping architecture that can be simply implemented in diode pumped solid state laser systems (DPSSL`s). This development allows the high average power DPSSL designer to look beyond the Nd ion for the first time. Along with high average power DPSSL`s which are appropriate for material processing applications, low and intermediate average power DPSSL`s are now realizable at low enough costs to be attractive for use in many medical, electronic, and lithographic applications.

Beach, R.; Emanuel, M.; Benett, W.; Freitas, B.; Ciarlo, D.; Carlson, N.; Sutton, S.; Skidmore, J.; Solarz, R.

1994-01-01

75

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

76

Preliminary demonstration of power beaming with non-coherent laser diode arrays  

SciTech Connect

A preliminary demonstration of free-space electric power transmission has been conducted using non-coherent laser diode arrays as the transmitter and standard silicon photovoltaic cell arrays as the receiver. The transmitter assembly used a high-power-density array of infrared laser diode bars, water cooled via integrated microchannel heat sinks and focused by cylindrical microlenses. The diode array composite beam was refocused by a parabolic mirror over a 10 meter path, and received on a {approximately}15 x 25 cm panel of thinned single crystal high efficiency silicon solar cells. The maximum cell output obtained was several watts, and the cell output was used to drive a small motor. Due to operating constraints and unexpected effects, particularly the high nonuniformity of the output beam, both the distance and total received power in this demonstration were modest. However, the existing transmitter is capable of supplying several hundred watts of light output, with a projected received electric power in excess of 200 watts. The source radiance is approximately 5 x 10{sup 9} W/m{sup 2}-steradian. With the existing 20 cm aperture, useful power transmission over ranges to {approximately}100 meters should be achievable with a DC to DC efficiency of greater than 10%. Non-coherent sources of this type are readily scalable to powers of tens of kilowatts, and with larger apertures can be used directly for power transmission up to several kilometers. Future non-coherent diode laser sources may be suitable for power transmission over hundreds of kilometers. Also, the experience gained with non-coherent arrays will be directly applicable to power beaming systems using coherent diode arrays or other array-type laser sources.

Kare, J T; Militsky, F; Weisberg, A

1999-02-26

77

Preliminary demonstration of power beaming with non-coherent laser diode arrays  

SciTech Connect

A preliminary demonstration of free-space electric power transmission has been conducted using non-coherent laser diode arrays as the transmitter and standard silicon photovoltaic cell arrays as the receiver. The transmitter assembly used a high-power-density array of infrared laser diode bars, water cooled via integrated microchannel heat sinks and focused by cylindrical microlenses. The diode array composite beam was refocused by a parabolic mirror over a 10 meter path, and received on a {approximately}15{times}25&hthinsp;cm panel of thin film high efficiency silicon solar cells. The maximum cell output obtained was several watts, and the cell output was used to drive a small motor. Due to operating constraints and unexpected effects, particularly the high nonuniformity of the output beam, both the distance and total received power in this demonstration were modest. However, the existing transmitter is capable of supplying several hundred watts of light output, with a projected received electric power in excess of 200 watts. The source radiance is approximately 5{times}10{sup 9}&hthinsp;W/m{sup 2}-steradian. With the existing 20 cm aperture, useful power transmission over ranges to {approximately}100 meters should be achievable with a DC to DC efficiency of greater than 10{percent}. Non-coherent sources of this type are readily scalable to powers of tens of kilowatts, and with larger apertures can be used directly for power transmission up to several kilometers. Future non-coherent diode laser sources may be suitable for power transmission over hundreds of kilometers. Also, the experience gained with non-coherent arrays will be directly applicable to power beaming systems using coherent diode arrays or other array-type laser sources. {copyright} {ital 1999 American Institute of Physics.}

Kare, J.T. [Kare Technical Consulting, 222 Canyon Lakes Pl., San Ramon, California 94583 (United States); Mitlitsky, F.; Weisberg, A. [Lawrence Livermore National Laboratory, L-174, P.O. Box 808, Livermore, California 94551 (United States)

1999-01-01

78

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

SciTech Connect

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. [Sensor Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Ito, T. [Department of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2009-06-15

79

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

80

Single-photon avalanche diode arrays for fast transients and adaptive optics  

Microsoft Academic Search

An instrumentation based on a silicon monolithic array of 60 photon counters [single-photon avalanche diode array (SPADA)] for state-of-the-art measurements of fast transient phenomena and adaptive optics (AO) is presented. The fabricated solid-state photon counters are rugged, easy to be integrated in the optical system, free from read-out noise, and provide very fast frame rates (> 10 kHz) and nanosecond

Franco Zappa; Simone Tisa; Sergio Cova; Piera Maccagnani; Domenico Bonaccini Calia; Roberto Saletti; Roberto Roncella; Giovanni Bonanno; Massimiliano Belluso

2006-01-01

81

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

82

Line Narrowing of Fiber Coupled Laser Diode Array He Lung MRI  

E-print Network

at a single mode. This low power beam is injected into the broadband high power "slave laser" (SL), thusLine Narrowing of Fiber Coupled Laser Diode Array and 3 He Lung MRI by Jermane E. Massey B. . . . . . . . . . . . . . . . . . . . . . . . Thomas J. Greytak Associate Professor, Department Head for Education #12;2 Line Narrowing of Fiber

Walsworth, Ronald L.

83

Photonics Europe 2010 Modal conversion of a phase-locked extended-cavity diode laser array  

E-print Network

setup provides an actual measurement of the power in the selected array supermode. 1. INTRODUCTION The constant and growing demand for efficient and powerful laser sources leads to explore new architectures aiming at increasing the output power of lasers diodes. The most promising approach is to use multiple

Paris-Sud XI, Université de

84

3D simulation and analysis of AlGaN\\/GaN ultraviolet light-emittings diodes  

Microsoft Academic Search

Compact ultraviolet light sources are currently of high interest for applications in solid-state lighting, short-range communication, and bio-chemical detection. Our nitride-based light-emitting diode (LED) includes AlGaN quantum wells with an emission wavelength of approximately 340 nm. In this paper, we analyze internal device physics by three-dimensional (3D) numerical simulation. The simulation incorporated a 3D drift-diffusion model for the carrier transport,

Joachim Piprek; Thomas M. Katona; Steven P. DenBaars; Simon Li

2004-01-01

85

A low-cost low-maintenance ultraviolet lithography light source based on light-emitting diodes.  

PubMed

A source of collimated ultraviolet (UV) light is a central piece of equipment needed for lithographic fabrication of microfluidic devices. Conventional UV light sources based on high-pressure mercury lamps require considerable maintenance and provide broad-band illumination with intensity that often changes with time. Here we present a source of narrow-band UV light based on an array of nine 365 nm light-emitting diodes (LEDs). Each LED has two dedicated converging lenses, reducing the divergence of light emanating from it to 5.4°. Partial overlap of the areas illuminated by individual LEDs provides UV illumination with a mean intensity of ~1.7 mW cm(-2) and coefficient of variation <3% over a 90 × 90 mm target area. The light source was used to lithographically fabricate micro-reliefs with thicknesses from ~25 to 311 ?m with SU8 photoresists. A cumulative irradiation of 370 mJ cm(-2) (4 min exposure) produced reliefs of good quality for all SU8 thicknesses. Polydimethylsiloxane (PDMS) replicas of the SU8 reliefs had microchannels with nearly rectangular cross-sections that were highly consistent over the entire target area, and partitions between the channels had depth to width ratios up to 5. The UV light source has also been successfully used for photolithography with positive photoresists, AZ40XT and SPR-220. The proposed light source is built with a total cost of <$1000, consumes a minimal amount of power, is expected to last for ~50,000 exposures, is maintenance-free, and is particularly appealing for small research-and-development microfluidic fabrication. PMID:25322205

Erickstad, M; Gutierrez, E; Groisman, A

2015-01-01

86

Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

87

Ultraviolet Light Emitting Diode with High Quality Epilayer Grown by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

In this paper, the selective area growth (SAG) of SAG-UV light-emitting diode (LED) was performed by mixed-source hydride vapor phase epitaxy (HVPE) with a multi-sliding boat system. The SAG-UV LED consists of a Si-doped GaN layer, an Si-doped AlGaN cladding layer, an AlGaN active layer, an Zn-doped AlGaN cladding layer, and a Zn-doped GaN capping layer. All of the epitaxial layers of LED structure were grown consecutively with a multi-sliding boat system. Room-temperature electroluminescence (EL) characteristics show an emission peak wavelength of 330 nm at room temperature. The aging test result of SAG-UV LED shows that the current was changed from 27.7 to 31.2 mA during 170 h at room temperature. At the current-voltage (I-V) measurement, the turn-on voltage of the SAG-UV LED is 3.5 V at room temperature. The value of the series resistance is about 200 ?. We find that the mixed-source HVPE method with multi-sliding boat system is possible to be one of the growth methods of ultra-violet LEDs with high quality epi-layer.

Jeon, Hunsoo; Lee, Gang Seok; Jung, Se-Gyo; Bae, Seon Min; Shin, Min Jeong; Kim, Kyoung Hwa; Yang, Min; Yi, Sam Nyung; Ahn, Hyung Soo; Yu, Young-Moon; Huh, Yoon; Kim, Suck-Whan; Ha, Hong-Ju; Sawaki, Nobuhiko

2012-01-01

88

Photoemission ambient pressure ionization (PAPI) with an ultraviolet light emitting diode and detection of organic compounds.  

PubMed

The development of compact, rugged and low-power ion sources is critical for the further advancement of handheld mass analyzers. Further, there is a need to replace the common (63)Ni source used at atmospheric pressure with a non-radioactive substitute. We present here a description of a light emitting diode (LED) photoemission ionization source for use in mass spectrometry for the detection of volatile organic compounds. This technique relies upon the generation of photoelectrons from a low-work function metal via low-energy ultraviolet (UV) light (280 or 240 nm) generated by a single LED in air at atmospheric pressure. These low-energy photoelectrons result in either direct electron capture by the analyte or chemical ionization. Currently, only negative ions are demonstrated due to operation at atmospheric pressure. Ion generation occurs without use of high electric fields such as those found in corona discharge or electrospray ionization. This source is effective for measuring organic vapors from gases, liquids and surface residues via atmospheric pressure chemical ionization, initiated by photoemission off a conductive surface. Several classes of organic vapors are analyzed and found to be effectively detected, including compounds that ionize via electron attachment, dissociative electron capture, proton abstraction, adduct formation and replacement ionization. PMID:21913267

Short, Luke C; Ewing, Robert G; Barinaga, Charles J

2011-10-15

89

Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes  

SciTech Connect

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

Verma, Jai; Kandaswamy, Prem Kumar; Protasenko, Vladimir; Verma, Amit; Grace Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)] [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

2013-01-28

90

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

SciTech Connect

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

Kurose, N., E-mail: kurose@fc.ritsumei.ac.jp; Aoyagi, Y. [The Research Organization of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)] [The Research Organization of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan); Shibano, K.; Araki, T. [Department of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)] [Department of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)

2014-02-15

91

GaN-based ultraviolet light-emitting diodes with AuCl?-doped graphene electrodes.  

PubMed

We demonstrate AuCl3-doped graphene transparent conductive electrodes integrated in GaN-based ultraviolet (UV) light-emitting diodes (LEDs) with an emission peak of 363 nm. AuCl3 doping was accomplished by dipping the graphene electrodes in 5, 10 and 20 mM concentrations of AuCl3 solutions. The effects of AuCl3 doping on graphene electrodes were investigated by current-voltage characteristics, sheet resistance, scanning electron microscope, optical transmittance, micro-Raman scattering and electroluminescence images. The optical transmittance was decreased with increasing the AuCl3 concentrations. However, the forward currents of UV LEDs with p-doped (5, 10 and 20 mM of AuCl3 solutions) graphene transparent conductive electrodes at a forward bias of 8 V were increased by ~48, 63 and 73%, respectively, which can be attributed to the reduction of sheet resistance and the increase of work function of the graphene. The performance of UV LEDs was drastically improved by AuCl3 doping of graphene transparent conductive electrodes. PMID:24514418

Kim, Byung-Jae; Yang, Gwangseok; Kim, Hong-Yeol; Baik, Kwang Hyeon; Mastro, Michael A; Hite, Jennifer K; Eddy, Charles R; Ren, Fan; Pearton, Stephen J; Kim, Jihyun

2013-11-18

92

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

93

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

PubMed

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

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

2015-01-01

94

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

95

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

96

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

97

Clinical ultraviolet dosimetry with a CCD monochromator array spectroradiometer  

NASA Astrophysics Data System (ADS)

Single monochromator charge-coupled device (CCD) array spectroradiometers have the advantage of ease of use and speed compared with double grating instruments. Their inherently inferior stray-light rejection, however, can critically affect their accuracy in phototherapy and research-related dosimetry applications. This paper shows that without adequate correction the HR4000 (Ocean Optics Inc., Dunedin, USA) array device can overestimate the CIE erythema-weighted irradiance of common phototherapy sources and solar simulator beams by over 100%. A software stray-light correction (Ylianttila et al 2005 Photochem. Photobiol. 81 333-41), using the measured slit function of the HR4000, has been applied to spectra acquired from sources used in phototherapy and photobiology (PUVA, UV21, TL01 and solar simulator). The resulting corrected erythema-weighted irradiance measurements from the HR4000 are within 10% of those from a DM150 double grating spectroradiometer (Bentham Instruments Ltd, Reading, UK). A simple model is considered for combining estimates of measurement uncertainties. The importance of exposure bracketing to improve the dynamic range of the HR4000 is illustrated, along with the difficulty in making direct comparison of spectral values between two instruments due to wavelength scale uncertainties. Comparison with a double grating instrument in a solar simulator beam is examined here as a basis for validating CCD array device measurements. The study demonstrates that the HR4000 array spectroradiometer can provide an adequate level of accuracy for common phototherapy and photobiology applications only where a suitable stray-light correction is carefully applied and where the instrument's effective dynamic range is improved.

Coleman, Andrew; Sarkany, Robert; Walker, Susan

2008-09-01

98

Clinical ultraviolet dosimetry with a CCD monochromator array spectroradiometer.  

PubMed

Single monochromator charge-coupled device (CCD) array spectroradiometers have the advantage of ease of use and speed compared with double grating instruments. Their inherently inferior stray-light rejection, however, can critically affect their accuracy in phototherapy and research-related dosimetry applications. This paper shows that without adequate correction the HR4000 (Ocean Optics Inc., Dunedin, USA) array device can overestimate the CIE erythema-weighted irradiance of common phototherapy sources and solar simulator beams by over 100%. A software stray-light correction (Ylianttila et al 2005 Photochem. Photobiol. 81 333-41), using the measured slit function of the HR4000, has been applied to spectra acquired from sources used in phototherapy and photobiology (PUVA, UV21, TL01 and solar simulator). The resulting corrected erythema-weighted irradiance measurements from the HR4000 are within 10% of those from a DM150 double grating spectroradiometer (Bentham Instruments Ltd, Reading, UK). A simple model is considered for combining estimates of measurement uncertainties. The importance of exposure bracketing to improve the dynamic range of the HR4000 is illustrated, along with the difficulty in making direct comparison of spectral values between two instruments due to wavelength scale uncertainties. Comparison with a double grating instrument in a solar simulator beam is examined here as a basis for validating CCD array device measurements. The study demonstrates that the HR4000 array spectroradiometer can provide an adequate level of accuracy for common phototherapy and photobiology applications only where a suitable stray-light correction is carefully applied and where the instrument's effective dynamic range is improved. PMID:18728310

Coleman, Andrew; Sarkany, Robert; Walker, Susan

2008-09-21

99

High energy erbium laser end-pumped by a laser diode bar array coupled to a Nonimaging Optic Concentrator  

E-print Network

, 3q w xYb phosphate glass 2 end pumped by a laser diode bar array leads to a low-cost, compact micro-laser Concentrator NOC to increase the efficiency of a w xNd:YVO laser 5 . In this paper, we present an Er:Yb:glass4High energy erbium laser end-pumped by a laser diode bar array coupled to a Nonimaging Optic

Boyer, Edmond

100

Identification of organic colourants in cosmetics by HPLC-diode array detection  

Microsoft Academic Search

Summary  A method for the analysis of organic cosmetic colourants was developed. The colourants extracted from the cosmetic products\\u000a were analysed by HPLC followed by diode-array detection across the wavelength range 275 nm–760 nm. The chromatographic separation\\u000a was performed on a column with a polymeric packing using gradient elution with a mobile phase composed of citrate buffer,\\u000a the ion-pairing reagent tetrabutylammonium

S. C. Rastogi; V. J. Barwick; S. V. Carter

1997-01-01

101

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

102

Dynamic characteristics of far-field radiation of current modulated phase-locked diode laser arrays  

NASA Technical Reports Server (NTRS)

A versatile and powerful streak camera/frame grabber system for studying the evolution of the near and far field radiation patterns of diode lasers was assembled and tested. Software needed to analyze and display the data acquired with the steak camera/frame grabber system was written and the total package used to record and perform preliminary analyses on the behavior of two types of laser, a ten emitter gain guided array and a flared waveguide Y-coupled array. Examples of the information which can be gathered with this system are presented.

Elliott, R. A.; Hartnett, K.

1987-01-01

103

LOUISA - A lunar optical-ultraviolet-infrared synthesis array  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

104

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

SciTech Connect

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

Kang, Jang-Won; Choi, Yong-Seok; Goo Kang, Chang; Hun Lee, Byoung [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kim, Byeong-Hyeok [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Tu, C. W. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093-0407 (United States); Park, Seong-Ju, E-mail: sjpark@gist.ac.kr [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

2014-02-03

105

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

106

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

Microsoft Academic Search

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being

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

1982-01-01

107

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

108

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

109

Quantitative Detection of Combustion Species using Ultra-Violet Diode Lasers  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

110

Beam shaping of high power diode lasers benefits from asymmetrical refractive micro-lens arrays  

NASA Astrophysics Data System (ADS)

Micro-lens arrays are widely used for beam shaping, especially beam homogenization of various laser sources. Monolithic arrays of cylindrical lenslets made of glass, semiconductors or crystals provide great advantages in laser applications, e.g. high efficiency, intensity stability and very low absorption. However, up to now, mainly symmetrical micro-lens surfaces are utilized in most applications due to design and manufacturing restrictions. The manufacture and application benefits of asymmetrical cylindrical-like micro-lens surfaces are enabled by LIMO's unique production technology. The asymmetrical shape is defined by uneven-polynomial terms and/or an asymmetrical cut-off from an even polynomial surface. Advantages of asymmetrical micro-lenses are off-axis light propagation, the correction of aberration effects or intensity profile deformations when the illuminated surfaces are not orthogonal to the optical axis. Additionally, the opportunities in simultaneous illumination from numerous light sources to one target are extended by just geometrical arrangement without the need for collinear beam alignment. First application results of such micro-lens arrays are presented for beam shaping of high power diode lasers. The generation of a homogeneous light field by a 100 W laser with tilted illumination at an angle of 35° is shown. A multi-kW line generator based on the superposition of over 50 diode laser bars under different illumination angles is demonstrated as well. Thus, laser material processing like plastics welding, soldering or annealing becomes much more convenient and less demanding regarding beam steering.

Homburg, O.; Bayer, A.; Mitra, T.; Meinschien, J.; Aschke, L.

2008-02-01

111

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

112

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

2011-08-21

113

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

114

New silicon technologies enable high-performance arrays of Single Photon Avalanche Diodes.  

PubMed

In order to fulfill the requirements of many applications, we recently developed a new technology aimed at combining the advantages of traditional thin and thick silicon Single Photon Avalanche Diodes (SPAD). In particular we demonstrated single-pixel detectors with a remarkable improvement in the Photon Detection Efficiency at the longer wavelengths (e.g. 40% at 800nm) while maintaining a timing jitter better than 100ps. In this paper we will analyze the factors the currently prevent the fabrication of arrays of SPADs by adopting such a Red-Enhanced (RE) technology and we will propose further modifications to the device structure that will enable the fabrication of high performance RE-SPAD arrays for photon timing applications. PMID:24353395

Gulinatti, Angelo; Rech, Ivan; Maccagnani, Piera; Cova, Sergio; Ghioni, Massimo

2013-05-29

115

New silicon technologies enable high-performance arrays of Single Photon Avalanche Diodes  

PubMed Central

In order to fulfill the requirements of many applications, we recently developed a new technology aimed at combining the advantages of traditional thin and thick silicon Single Photon Avalanche Diodes (SPAD). In particular we demonstrated single-pixel detectors with a remarkable improvement in the Photon Detection Efficiency at the longer wavelengths (e.g. 40% at 800nm) while maintaining a timing jitter better than 100ps. In this paper we will analyze the factors the currently prevent the fabrication of arrays of SPADs by adopting such a Red-Enhanced (RE) technology and we will propose further modifications to the device structure that will enable the fabrication of high performance RE-SPAD arrays for photon timing applications. PMID:24353395

Gulinatti, Angelo; Rech, Ivan; Maccagnani, Piera; Cova, Sergio; Ghioni, Massimo

2013-01-01

116

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

PubMed

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

Liu, Yifan; Yobas, Levent

2014-12-10

117

Measurement of central nickel density in Doublet III plasmas with a soft x-ray diode array  

NASA Astrophysics Data System (ADS)

An array of soft x-ray diodes has been used to obtain central nickel densities for discharges in the Doublet III tokamak, during operation with an inconel primary limiter, in which nickel L-line radiation dominated the diode signals. The nature of the diode signals is determined primarily by comparison with soft x-ray spectra. The contribution of the continuum portion of the spectra to the central diode signal can be calculated and compared to the observed signal. When the diode signal is dominated by nickel L-line emission, the observed signal is considerably larger than the calculated continuum contribution. Chordal data from the array of diodes are inverted to provide the spatial profile of soft x-ray emission. Because the diodes are absolute detectors of radiation, the soft x-ray emission profile is used to obtain the absolute nickel concentration and density profile in the center of the plasma. A computer code, including over 100 nickel L-line transitions, has been developed to obtain the nickel density. The nickel L-line cooling rate, calculated with the code, is presented. The nickel density obtained by this technique agrees well with that obtained from the K? line intensity measured with a soft x-ray spectrometer and that obtained from a bolometric measurement of central radiated power coupled with a coronal equilibrium model of the radiation.

Groebner, R. J.; Jahns, G. L.; Ejima, S.; Hsieh, C. L.

1985-02-01

118

Optical and Thermal Analyses of High-Power Laser Diode Arrays  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

119

High-output-power 255/280/310 nm deep ultraviolet light-emitting diodes and their lifetime characteristics  

NASA Astrophysics Data System (ADS)

255/280/310 nm deep ultraviolet light-emitting diodes (DUV LEDs) suitable for high-current operation are reported. Newly developed 1 mm sized chips are installed in a commercial package with a two-series configuration. At a forward current of 350 mA, we measured powers of 45.2, 93.3, and 65.8 mW for the 255, 280, and 310 nm LEDs, respectively. The corresponding external quantum efficiencies per serial circuit were 1.3, 3.0, and 2.4%, and successful chip scalability was demonstrated. The 50% lifetime of the 280 nm LED die was estimated to be 3000 h at a junction temperature of 30 °C.

Fujioka, A.; Asada, K.; Yamada, H.; Ohtsuka, T.; Ogawa, T.; Kosugi, T.; Kishikawa, D.; Mukai, T.

2014-06-01

120

Investigation of Light Extraction Efficiency in AlGaN Deep-Ultraviolet Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

Light extraction efficiency (LEE) in AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) is investigated using finite-difference time-domain simulations. For flip-chip and vertical LED structures, LEE is obtained to be <10% due to strong DUV light absorption in the p-GaN layer. In flip-chip LEDs, LEE of transverse-magnetic (TM) modes is found to be more than ten times smaller than that of transverse-electric (TE) modes, which explains the decreasing behavior of external quantum efficiency of DUV LEDs with decreasing wavelength. It is also found that vertical LED structures can have advantages over flip-chip structures for increasing LEE in the TM mode.

Ryu, Han-Youl; Choi, Il-Gyun; Choi, Hyo-Sik; Shim, Jong-In

2013-06-01

121

Enhanced Output Power of Near-Ultraviolet Light-Emitting Diodes by p-GaN Micro-Rods  

NASA Astrophysics Data System (ADS)

Near-ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) are grown by low-pressure metal-organic chemical vapor deposition. The scanning electronic microscope image shows that the p-GaN micro-rods are formed above the interface of p-AlGaN/p-GaN due to the rapid growth rate of p-GaN in the vertical direction. The p-GaN micro-rods greatly increase the escape probability of photons inside the LED structure. Electroluminescence intensities of the 372 nm UV LED lamps with p-GaN micro rods are 88% higher than those of the flat surface LED samples.

Wang, Dong-Sheng; Zhang, Ke-Xiong; Liang, Hong-Wei; Song, Shi-Wei; Yang, De-Chao; Shen, Ren-Sheng; Liu, Yang; Xia, Xiao-Chuan; Luo, Ying-Min; Du, Guo-Tong

2014-02-01

122

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

PubMed Central

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

2014-01-01

123

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

SciTech Connect

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

Lu, Yu-Hsuan; Pilkuhn, Manfred H. [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Fu, Yi-Keng; Chu, Mu-Tao [Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China); Huang, Shyh-Jer, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States); Su, Yan-Kuin, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electronic Engineering, Kun-Shan University, Tainan 71003, Taiwan (China); Wang, Kang L. [Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States)

2014-03-21

124

AlGaN-based laser diodes for the short-wavelength ultraviolet region  

NASA Astrophysics Data System (ADS)

We have demonstrated the room-temperature operation of GaN/AlGaN and indium-free AlGaN multiple-quantum-well (MQW) laser diodes under the pulsed-current mode. We have successfully grown low-dislocation-density AlGaN films with AlN mole fractions of 20 and 30% on sapphire substrates using the hetero-facet-controlled epitaxial lateral overgrowth (hetero-FACELO) method. GaN/AlGaN and AlGaN MQW laser diodes have been fabricated on the low-dislocation-density Al0.2Ga0.8N and Al0.3Ga0.7N films, respectively. The GaN/AlGaN MQW laser diodes lased at a peak wavelength ranging between 359.6 and 354.4 nm. A threshold current density of 8 kA cm-2, an output power as high as 80 mW and a differential external quantum efficiency (DEQE) of 17.4% have been achieved. The AlGaN MQW laser diodes lased at a peak wavelength down to 336.0 nm far beyond the GaN band gap. For the GaN/AlGaN MQW laser diodes, the modal gain coefficient and the optical internal loss are estimated to be 4.7±0.6 cm kA-1 and 10.6±2.7 cm-1, respectively. We have observed that the characteristic temperature T0 ranges from 132 to 89 K and DEQE shows an almost stable tendency with increase of temperature. A temperature coefficient of 0.049 nm K-1 is also found for the GaN/AlGaN MQW laser diode. The results for the AlGaN-based laser diodes grown on high-quality AlGaN films presented here will be essential for the future development of laser diodes emitting much shorter wavelengths.

Yoshida, Harumasa; Kuwabara, Masakazu; Yamashita, Yoji; Takagi, Yasufumi; Uchiyama, Kazuya; Kan, Hirofumi

2009-12-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

126

Comparison of continuous versus pulsed ultraviolet light emitting diode use for the inactivation of Bacillus globigii spores.  

PubMed

Light emitting diodes (LEDs) in the ultraviolet (UV) range offer a promising alternative for the disinfection of water. LEDs have many advantages over conventional UV lamps but there are concerns related to the operating life of the LED lamps. In this project Bacillus globigii was inactivated using UV LED technology. The experimental strategy included using pulsed ultraviolet (PUV) output rather than continuous UV (CUV) current in order to reduce the power requirements and extend the life of the lamps. The kinetic profiles for CUV experiments reached 6-log inactivation faster than PUV at 9.1% duty cycle (approx. 840 vs. 5,000 s) but the PUV required lower fluence (365 vs. 665 J/m²). In addition, the inactivation rate constants associated with PUV were generally higher than those of CUV (4.6-5.1 vs. 3.6-4.4 m²/J), which supports the notion that high energy bursts are more effective at causing cellular damage. Multi-target kinetics applied to most of the kinetic observations and tailing effects were generally observed. PUV LED appears to have potential to extend the lifetime of the LEDs for inactivation of spore-forming pathogens. PMID:25401310

Tran, Tho; Racz, LeeAnn; Grimaila, Michael R; Miller, Michael; Harper, Willie F

2014-01-01

127

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

SciTech Connect

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

Robinson, Joshua; Opp, Daniel; Zhang, Geoffrey; Cashon, Ken; Kozelka, Jakub; Hunt, Dylan; Walker, Luke; Hoffe, Sarah; Shridhar, Ravi; Feygelman, Vladimir [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); decimal Inc., Sanford, Florida 32771 (United States); Sun Nuclear Corp., Melbourne, Florida 32940 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States)

2012-01-15

128

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

PubMed

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

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

2015-04-01

129

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

PubMed

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

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

2013-01-01

130

Separation and Identification of Phenolic Acids from Some Species of the Asteraceae Family Using HPLC with a Diode Array Detector  

Microsoft Academic Search

The qualitative and quantitative analysis of phenolic acids was carried out using methods of HPLC with the diode array detector (DAD). The quantitative analysis of chosen phenolic acids was carried out using the Multicomponent Analysis method (MCA). Solid-phase extraction was applied for the purification of crude extract from aerial part of three species of fam. Asteraceae (Chrysanthemum maximum Ram.(DC), Chrysanthemum

W. Markowski; L. K. Czapi?ska; A. J. Józefczyk; K. Glowniak

1998-01-01

131

Disinfection of Pseudomonas aeruginosa biofilm contaminated tube lumens with ultraviolet C light emitting diodes  

Microsoft Academic Search

Bacterial biofilms on long-term catheters are a major source of infection. Exposure to ultraviolet C (UVC – 265 nm) light was shown in an earlier study to reduce the number of bacteria substantially on ex vivo treated urinary patient catheters. Very large doses (long treatment times) should, however, be applied to obtain 99.9% disinfection rates. The major reason was that besides cells the

Jimmy Bak; Søren D. Ladefoged; Michael Tvede; Tanja Begovic; Annette Gregersen

2010-01-01

132

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

133

Determination of dissociation constants of pharmacologically active xanthones by capillary zone electrophoresis with diode array detection.  

PubMed

In this article, the dissociation constants (pKa) of 10 pharmacologically active xanthones isolated from herbal medicine Securidaca inappendiculata were determined by capillary zone electrophoresis with diode array detection. The pKa values determined by the method based on the electrophoretic mobilities (calculated from migration times) have been proved by the method based on UV absorbance calculated from the online spectra corresponding peaks. No conspicuous difference was observed between the two methods with acceptable reproducibility. Two pKa values (pKa1 and pKa2) were found for four xanthones while generally the 10 compounds possess the pKa values ranging from 6.4 to 9.2. PMID:15641365

Wu, Xiaomu; Gong, Suxuan; Bo, Tao; Liao, Yiping; Liu, Huwei

2004-12-24

134

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

2011-07-15

135

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

136

Beam shaping and fiber coupling of high-power laser diode arrays  

NASA Astrophysics Data System (ADS)

The extreme divergence and the astigmatism of the high power laser diode array (LDA) require optics with complex lens structure and high performance. A monolithic micro- optic system is designed to shape the beam of LDA and couple the output of LDA with low NA fiber. The structure and principle of the micro-optic system is described in detail. The actual performance of the micro-optic system is studied by measuring P-I properties for both fiber coupled output and the LDA output, and their dependences on deviations in x, y, z directions. The light output of 980nm, 19-emitter LDA is shaped by this micro-optic system and coupled into a fiber with 400?m diameter, Numerical Aperture (NA) 0.22. The overall efficiency is more than 60%. The main factors effecting coupling efficiency are analyzed.

Ma, Xiao-hui; Li, Xu; Liu, Guo-Jun; Shi, Quanlin; Xin, Desheng; Zhang, Jian-jia

2005-01-01

137

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

NASA Technical Reports Server (NTRS)

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

Hemmati, Hamid (inventor)

1990-01-01

138

Quality assurance of asymmetric jaw alignment using 2D diode array  

SciTech Connect

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

Kim, Sun Mo [Department of Medical Physics, Stronach Regional Cancer Centre, Southlake Regional Health Centre, Newmarket, Ontario L3Y 2P9, Canada and Radiation Medicine Program, Princess Margaret Hospital/University Health Network, Toronto, Ontario M5G 2M9 (Canada)] [Department of Medical Physics, Stronach Regional Cancer Centre, Southlake Regional Health Centre, Newmarket, Ontario L3Y 2P9, Canada and Radiation Medicine Program, Princess Margaret Hospital/University Health Network, Toronto, Ontario M5G 2M9 (Canada); Chmielewski, Renata; Abbas, Ahmar [Department of Medical Physics, Stronach Regional Cancer Centre, Southlake Regional Health Centre, Newmarket, Ontario L3Y 2P9 (Canada)] [Department of Medical Physics, Stronach Regional Cancer Centre, Southlake Regional Health Centre, Newmarket, Ontario L3Y 2P9 (Canada); Yeung, Ivan W. T.; Moseley, Douglas J. [Department of Medical Physics, Stronach Regional Cancer Centre, Southlake Regional Health Centre, Newmarket, Ontario L3Y 2P9 (Canada) [Department of Medical Physics, Stronach Regional Cancer Centre, Southlake Regional Health Centre, Newmarket, Ontario L3Y 2P9 (Canada); Radiation Medicine Program, Princess Margaret Hospital/University Health Network, Toronto, Ontario M5G 2M9 (Canada); Department of Radiation Oncology, University of Toronto, Ontario M5G 2M9 (Canada)

2013-12-15

139

Slanted n-ZnO/p-GaN nanorod arrays light-emitting diodes grown by oblique-angle deposition  

NASA Astrophysics Data System (ADS)

High-efficient ZnO-based nanorod array light-emitting diodes (LEDs) were grown by an oblique-angle deposition scheme. Due to the shadowing effect, the inclined ZnO vapor-flow was selectively deposited on the tip surfaces of pre-fabricated p-GaN nanorod arrays, resulting in the formation of nanosized heterojunctions. The LED architecture composed of the slanted n-ZnO film on p-GaN nanorod arrays exhibits a well-behaving current rectification of junction diode with low turn-on voltage of 4.7 V, and stably emits bluish-white luminescence with dominant peak of 390 nm under the operation of forward injection currents. In general, as the device fabrication does not involve passivation of using a polymer or sophisticated material growth techniques, the revealed scheme might be readily applied on other kinds of nanoscale optoelectronic devices.

Lee, Ya-Ju; Yang, Zu-Po; Lo, Fang-Yuh; Siao, Jhih-Jhong; Xie, Zhong-Han; Chuang, Yi-Lun; Lin, Tai-Yuan; Sheu, Jinn-Kong

2014-05-01

140

InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner.  

PubMed

We present a terahertz (THz) broadband antenna-integrated 1 × 20 InGaAs Schottky barrier diode (SBD) array detector with an average responsivity of 98.5 V/W at a frequency of 250 GHz, which is measured without attaching external amplifiers and Si lenses, and an average noise equivalent power (NEP) of 106.6 pW/?Hz. The 3-dB bandwidth of the SBD detector is also investigated at approximately 180 GHz. For implementing an array-type SBD detector by a simple fabrication process to achieve a high yield, a structure comprising an SiN(x) layer instead of an air bridge between the anode and the cathode is designed. THz line beam imaging using a Gunn diode emitter with a center frequency of 250 GHz and a 1 × 20 SBD array detector is successfully demonstrated. PMID:24216813

Han, Sang-Pil; Ko, Hyunsung; Park, Jeong-Woo; Kim, Namje; Yoon, Young-Jong; Shin, Jun-Hwan; Kim, Dae Yong; Lee, Dong Hun; Park, Kyung Hyun

2013-11-01

141

High-Performance 348 nm AlGaN\\/GaN-Based Ultraviolet-Light-Emitting Diode with a SiN Buffer Layer  

Microsoft Academic Search

A 348 nm ultraviolet-light-emitting diode (UV-LED) based on an AlGaN\\/GaN single quantum well (SQW) with a high optical power is reported. In this structure, a thin SiN buffer is introduced before the growth of a conventional low-temperature GaN buffer layer. Such a buffer layer can dramatically reduce the density of threading dislocation as we have previously reported. Since the optical

Young-Bae Lee; Tao Wang; Yu-Huai Liu; Jin-Ping Ao; Yuji Izumi; Yves Lacroix; Hong-Dong Li; Jie Bai; Yoshiki Naoi; Shiro Sakai

2002-01-01

142

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

143

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

144

Large enhancement of light extraction efficiency in AlGaN-based nanorod ultraviolet light-emitting diode structures  

NASA Astrophysics Data System (ADS)

Light extraction efficiency (LEE) of AlGaN-based nanorod deep ultraviolet (UV) light-emitting diodes (LEDs) is numerically investigated using three-dimensional finite-difference time-domain simulations. LEE of deep UV LEDs is limited by strong light absorption in the p-GaN contact layer and total internal reflection. The nanorod structure is found to be quite effective in increasing LEE of deep UV LEDs especially for the transverse magnetic (TM) mode. In the nanorod LED, strong dependence of LEE on structural parameters such as the diameter of a nanorod and the p-GaN thickness is observed, which can be attributed to the formation of resonant modes inside the nanorod structure. Simulation results show that, when the structural parameters of the nanorod LED are optimized, LEE can be higher than 50% and 60% for the transverse electric (TE) and TM modes, respectively. The nanorod structure is expected to be a good candidate for the application to future high-efficiency deep UV LEDs.

Ryu, Han-Youl

2014-02-01

145

Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters.  

PubMed

For many decades, populations in rural and remote developing regions will be unable to access centralised piped potable water supplies, and indeed, decentralised options may be more sustainable. Accordingly, improved household point-of-use (POU) disinfection technologies are urgently needed. Compared to alternatives, ultraviolet (UV) light disinfection is very attractive because of its efficacy against all pathogen groups and minimal operational consumables. Though mercury arc lamp technology is very efficient, it requires frequent lamp replacement, involves a toxic heavy metal, and their quartz envelopes and sleeves are expensive, fragile and require regular cleaning. An emerging alternative is semiconductor-based units where UV light emitting diodes (UV-LEDs) are powered by photovoltaics (PV). Our review charts the development of these two technologies, their current status, and challenges to their integration and POU application. It explores the themes of UV-C-LEDs, non-UV-C LED technology (e.g. UV-A, visible light, Advanced Oxidation), PV power supplies, PV/LED integration and POU suitability. While UV-C LED technology should mature in the next 10 years, research is also needed to address other unresolved barriers to in situ application as well as emerging research opportunities especially UV-A, photocatalyst/photosensitiser use and pulsed emission options. PMID:24946032

Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas; Jagals, Paul; Stuetz, Richard

2014-09-15

146

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

147

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

148

200Mb\\/s\\/ch 100-m optical subsystem interconnections using 8-channel 1.3-?m laser diode arrays and single-mode fiber arrays  

Microsoft Academic Search

Synchronous parallel optical-fiber transmission is an attractive method for providing increased interconnection throughput and higher density in advanced information systems. Skew suppression (reducing transmission delay time variation), error-free fully DC-coupled data transmission capability, compactness, and low power consumption of modules are important requirements. In order to meet these requirements, we developed optical subsystem interconnections using long-wavelength laser diode arrays and

A. Takai; T. Kato; S. Yamashita; S. Hanatani; Y. Motegi; K. Ito; H. Abe; H. Kodera

1994-01-01

149

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

150

Monolithic two-dimensional surface-emitting arrays of GaAs/AlGaAs diode lasers  

NASA Technical Reports Server (NTRS)

Monolithic two-dimensional arrays of GaAs/AlGaAs diode lasers with light emission normal to the surface have been obtained by fabricating edge-emitting quantum-well lasers coupled with external mirrors that deflect the radiation from the laser facets by 90 degrees. Linear arrays of GaAs/AlGaAs devices in which one of the laser facets was cleaved while the other facet and an adjacent 45 degree deflector were formed by ion-beam-assisted etching (IBAE) have been reported. For the arrays reported in this section, IBAE was used to form all of the laser facets and the deflecting mirrors. A mass transport process of the type employed to fabricate two-dimensional arrays of GaInAsP/InP lasers coupled with deflecting mirrors is not known for AlGaAs.

1988-01-01

151

Silicon PIN diode hybrid arrays for charged particle detection: Building blocks for vertex detectors at the SSC  

SciTech Connect

Two-dimensional arrays of solid state detectors have long been used in visible and infrared systems. Hybrid arrays with separately optimized detector and readout substrates have been extensively developed for infrared sensors. The characteristics and use of these infrared readout chips with silicon PIN diode arrays produced by MICRON SEMICONDUCTOR for detecting high-energy particles are reported. Some of these arrays have been produced in formats as large as 512 /times/ 512 pixels; others have been radiation hardened to total dose levels beyond 1 Mrad. Data generation rates of 380 megasamples/second have been achieved. Analog and digital signal transmission and processing techniques have also been developed to accept and reduce these high data rates. 9 refs., 15 figs., 2 tabs.

Kramer, G.; Gaalema, S.; Shapiro, S.L.; Dunwoodie, W.M.; Arens, J.F.; Jernigan, J.G.

1989-05-01

152

Identification of natural dyes in archeological Coptic textiles by liquid chromatography with diode array detection.  

PubMed

Reversed-phase HPLC with diode-array UV-Vis spectrophotometric detection has been used for identification of natural dyes in extracts from wool and silk fibres from archeological textiles. The examined objects originate from 4th to 12th Century Egypt and belong to the collection of Early Christian Art of the National Museum in Warsaw. Extraction from fibres was carried out with HCl solution containing ethanol or with warm pyridine. As the main individual chemical components of natural dyes, anthraquinone, indigoid and flavonoid dyes including alizarin, purpurin, luteolin, apigenin, carminic acid, ellagic acid, gallic acid, laccaic acids A and B and indigotin were found. For pyridine extracts another mobile phase with an optimized gradient of organic modifier concentration was used. With such an eluent the appearance of double peaks for indigotin and indirubin was eliminated. For acidic extraction of dyes from fibres, ethanol was used. Due to its higher boiling point than methanol it evaporates slower from the extraction solution enabling a more efficient extraction of dyes. PMID:12650256

Orska-Gawry?, Jowita; Surowiec, Izabella; Kehl, Jerzy; Rejniak, Hanna; Urbaniak-Walczak, Katarzyna; Trojanowicz, Marek

2003-03-14

153

Analysis of methylglyoxal in water and biological matrices by capillary zone electrophoresis with diode array detection.  

PubMed

We describe a new method for the determination of methylglyoxal in water and biological matrices, using o-phenylenediamine as derivatizing agent and solid-phase extraction followed by capillary zone electrophoresis with diode array detection. 25 mM sodium phosphate running buffers at pH 2.2, 30 kV, and 25 degrees C allowed the best instrumental conditions for the optimum separation of methylglyoxal in a suitable analytical time (< 10 min), using an uncoated fused-silica capillary of 75 microm inner diameter and an effective length of 45.1 cm with an extended light path and the wavelength set to 200 nm. Under optimized instrumental conditions, good reproducibility of the migration time (< 1.1%), precision (< 5%), an excellent linear dynamic range from 0.1 to 3.6 mg/L (r(2) = 0.9997), and low limits of detection (7.2 microg/L) were obtained for methylglyoxal measurements, using the internal standard methodology. Assays on laboratory-spiked tap and ground water samples allowed a remarkable accuracy, presenting yields of 95.0 +/- 4.3 and 94.0 +/- 1.1%, respectively, and good performance to determine methylglyoxal in beer and yeast cells suspensions matrices was also obtained at trace level. The present methodology is a cost-effective alternative for routine quality control analysis, showing to be reliable, sensitive, and with a low sample volume requirement to monitor methylglyoxal in water and biological matrices. PMID:15761920

do Rosário, Pedro Miguel Alvaro; Cordeiro, Carlos A Alves; Freire, Ana Ponces; Nogueira, José M Florêncio

2005-05-01

154

The Effect of Light Therapy on Superficial Radial Nerve Conduction Using a Clustered Array of Infrared Super luminous Diodes and Red Light Emitting Diodes  

PubMed Central

Introduction: Lasers, light emitting diodes (LEDs) and super luminous diodes (SLDs) are widely used to treat selected musculoskeletal, integumentary and neurological conditions.The mechanisms underlying the reported treatment effects of light therapy are unclear and the physiologic effect of light on a variety of tissues, particularly neurological, is mostly unknown. A few researchers have reported on the effects of lasers and to a lesser extent infrared LEDs on nerve conduction in superficial nerves, but there is little evidence of the effects of SLDs and red LEDs on conduction parameters of peripheral nerves. The purpose of this study was to examine the effects of a light therapy generated by cluste rprobe containing an array of infrared super luminous and red light emitting diodes on superficial radial nerve conduction. Methods: This was a single blind, randomized controlled trial conducted in an academic clinical laboratory. Thirty-two healthy participants (mean age = 25 years) were randomized to a treatment group or a placebo group. The treatment group received light irradiation through the application of a cluster probe containing 32 infrared (880nm) SLDs and 4 red (660nm) LEDs for 30 seconds at a dose of 6 J/cm2 to each of the two 5 cm2 segments of skin overlying the superficial radial nerve. The placebo group received identical set-up without the application of light irradiation. Negative peak latency (NPL) and conduction velocity (NCV) for the superficial radial nerve were measured before treatment and for 10-minutes following treatment at 2-minute intervals. Skin temperature was monitored throughout. Results: No significant differences between groups and over time for NPL, NCV, or temperature difference scores were identified. However, a significant increase in skin temperature was measured over time at each time point compared to baseline. Conclusion: Light irradiation using a cluster probe containing infrared super luminous and red light emitting diodes does not impact the neurophysiological properties of the superficial radial nerve.

Telemeco, Todd Allen; Schrank, Edward Carl

2013-01-01

155

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

156

Enhancement of light output power in ultraviolet light emitting diodes using graphene film on self-assembled Au nanocluster by agglomeration process  

NASA Astrophysics Data System (ADS)

We applied graphene network on Au nanoclusters as a transparent and current spreading electrode in GaN-based ultraviolet (UV) light emitting diode (LED). The electroluminescence (EL) of UV-LEDs with graphene film on Au nanoclusters was enhanced by 10% at injection current of 20 mA, while keeping reasonably good injected current-voltage (I-V) characteristics. This result is attributed to the reduction of absorption at UV wavelength region, effective current spreading and injection by reduced sheet and contact resistance, and texturing effect through Au nanocluster.

Seo, Tae Hoon; Shin, GangU; Kyoung Kim, Bo; Choi, Chel-Jong; Lee, Changhyup; Jong Kim, Myung; Suh, Eun-Kyung

2013-12-01

157

Influence of undoped GaN layer thickness to the performance of AlGaN\\/GaN-based ultraviolet light-emitting diodes  

Microsoft Academic Search

Structural and optical properties of AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) with a thin undoped GaN layer and thick n-type AlGaN\\/GaN superlattices have been investigated. Some V-defects were observed in the n-type superlattice layers. The V-defect density decreases enormously with increasing the undoped GaN thickness. Simultaneously, the output power of the UV-LEDs increases remarkably as the undoped GaN thickness increases.

Y. H Liu; H. D Li; J. P Ao; Y. B Lee; T Wang; S Sakai

2004-01-01

158

[Saliva cotinine determination using high-performance liquid chromatography with diode - array detection].  

PubMed

The use of tobacco is a very serious threat to public health. Reducing the proportion of smokers easily leads to improved health of the general population. Smoking is a proven risk factor for respiratory disease, cardiovascular disease and cancer and complications during pregnancy. To verify the level of exposure to tobacco smoke in most patients used a simple test markers of exposure. The most commonly used marker in the evaluation of exposure to tobacco products is cotinine, which is a major metabolite of nicotine contained in tobacco smoke. Biological material most commonly used in this type of study is blood, urine and saliva. In the present study Sarstedt Salivette tubes were used to samples collection. In order to determine the concentration of cotinine in saliva samples analyzed with high performance liquid chromatography with diode array detection after extraction of cotinine from saliva by solid phase extraction. The method was linear of 10 to 400 ng/ml. The limit of detection was the value of the signal-to-noise ratio S/N=3, it amounted to 6 ng/ml, the limit of quantification was 10 ng/ml. The intraday repeatability was 8% for lowconcentrations, for high concentrations - 3.7%. Reproducibility interdays for low concentrations was 2.4%, for high concentrations - 4.1%. We analyzed 18 samples of saliva derived from patients smoking volunteers from the Department of Conservative Dentistry and Periodontology, University of Medical Sciences. University of Medical Sciences and the Chair and Department of Endocrinology, Metabolism and Internal Medicine, University of Medical Sciences. University of Medical Sciences. Mean concentrations of cotinine in patients was 240.9 ng/ml of saliva. In this study we demonstrated the usefulness of the saliva cotinine determination method in the assessment of patient exposure to tobacco smoke. PMID:23421043

Kulza, Maksymilian; Wo?niak, Anna; Se?czuk-Przyby?owska, Monika; Czarnywojtek, Agata; Kurha?ska-Flisykowska, Anna; Florek, Ewa

2012-01-01

159

Z .Sensors and Actuators 75 1999 6569 Fabrication of arrays of Schottky diodes using microtransfer molding  

E-print Network

molding Junmin Hu a , Tao Deng a , R.G. Beck b , R.M. Westervelt b , George M. Whitesides a,) a Department the application of microtransfer molding--a representative soft lithographic technique--to the fabrication of simple Schottky diodes on silicon. The fabrication of a diode involved two microtransfer molding steps

Prentiss, Mara

160

Analysis of surface and bulk effects in HgCdTe photodetector arrays by variable-area diode test structures  

NASA Astrophysics Data System (ADS)

This study describes variable-area diode data analysis of surface and bulk effects of HgCdTe infrared photodiodes passivated with dual-layer CdTe/ZnS films. We attempt to present a general analytical relation between the zero-bias resistance-area product and the perimeter-to-area ratio of the diodes by variable-area diode array test structures. We have taken contributions into consideration from surface leakage between HgCdTe and passivant due to band bending, surface generation currents in the depletion region close to the HgCdTe-passivant interface, and the bulk currents. The model we use is based on the one put forward by Vishnu Gopal. The variable-area diode data analysis can be of great practical help in identifying the various possible mechanism contributing to the surface leakage currents. Through data analysis and curve fitting, we can also get some other useful parameters (like junction depth), which can be the reference to other experiment results. The experimental samples we used range from 20?m to 200?m in size and include both square and circular diode geometries. The conventional boron implantation was used to form the p-n junction and Au was used for the metal pads. The insulating layers of CdTe and ZnS were both electron-beam evaporated at a rate of 1.3 Å/sec. The fabricated diode test patterns were wire-bonded and packaged into a dewar system. I-V measurements were performed using a Keithley 4200 parameter analyzer. The data analysis and curve fitting are all dealt with by MATLAB. Through the results we can find that the surface leakage is nearly the same to the bulk current in diameter between 50~150?m, which indicate that surface leakage is still a dominating dark current in small dimension diode. The results also showed that diodes from 50 to 150?m in size have better performance than the larger or smaller ones and this can be explained by the limit of material imperfection and the limit of processing techniques.

Deng, Yi; Lin, Chun; Hu, Xiaoning

2009-07-01

161

Patterning the Cone Mosaic Array in Zebrafish Retina Requires Specification of Ultraviolet-Sensitive Cones  

PubMed Central

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

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

2014-01-01

162

Airborne laser-diode-array illuminator assessment for the night vision's airborne mine-detection arid test  

NASA Astrophysics Data System (ADS)

The Airborne Littoral Reconnaissance Technologies (ALRT) project has developed and tested a nighttime operational minefield detection capability using commercial off-the-shelf high-power Laser Diode Arrays (LDAs). The Coastal System Station"s ALRT project, under funding from the Office of Naval Research (ONR), has been designing, developing, integrating, and testing commercial arrays using a Cessna airborne platform over the last several years. This has led to the development of the Airborne Laser Diode Array Illuminator wide field-of-view (ALDAI-W) imaging test bed system. The ALRT project tested ALDAI-W at the Army"s Night Vision Lab"s Airborne Mine Detection Arid Test. By participating in Night Vision"s test, ALRT was able to collect initial prototype nighttime operational data using ALDAI-W, showing impressive results and pioneering the way for final test bed demonstration conducted in September 2003. This paper describes the ALDAI-W Arid Test and results, along with processing steps used to generate imagery.

Stetson, Suzanne; Weber, Hadley; Crosby, Frank J.; Tinsley, Kenneth; Kloess, Edmund; Nevis, Andrew J.; Holloway, John H., Jr.; Witherspoon, Ned H.

2004-09-01

163

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

SciTech Connect

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

Verma, Jai, E-mail: jverma@nd.edu; Islam, S. M.; Protasenko, Vladimir; Kumar Kandaswamy, Prem; Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2014-01-13

164

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

SciTech Connect

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

Mamat, M. H.; Malek, M. F.; Musa, M. Z. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Khusaimi, Z. [NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Rusop, M. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia) and NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia)

2011-05-25

165

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

166

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

167

Toward single-molecule detection with very compact DNA sequencer based on single-photon avalanche diode array  

NASA Astrophysics Data System (ADS)

The development of a very-compact DNA sequencer instrument based on Single Photon Avalanche Diode (SPAD) for microchip electrophoresis is here reported. The planar epitaxial SPAD combines the typical advantages of microelectronic devices with high sensitivity. We present a miniaturized system based on a custom array of SPAD, purposely designed to be compatible with Amersham Biosciences commercial markers. This system is the first example of very compact, ultra-sensitive, portable and low cost DNA sequencer. It may represent a breakthrough in DNA sequencing system and open the way to the development of a new category of portable low-cost apparatus.

Rech, Ivan; Marangoni, Stefano; Gulinatti, Angelo; Ghioni, Massimo; Cova, Sergio

2008-02-01

168

A Comparative Analysis for Verification of IMRT and VMAT Treatment Plans using a 2-D and 3-D Diode Array  

NASA Astrophysics Data System (ADS)

With the added complexity of current radiation treatment dose delivery modalities such as IMRT (Intensity Modulated Radiation Therapy) and VMAT (Volumetric Modulated Arc Therapy), quality assurance (QA) of these plans become multifaceted and labor intensive. To simplify the patient specific quality assurance process, 2D or 3D diode arrays are used to measure the radiation fluence for IMRT and VMAT treatments which can then be quickly and easily compared against the planned dose distribution. Because the arrays that can be used for IMRT and VMAT patient-specific quality assurance are of different geometry (planar vs. cylindrical), the same IMRT or VMAT treatment plan measured by two different arrays could lead to different measured radiation fluences, regardless of the output and performance of linear accelerator. Thus, the purpose of this study is to compare patient specific QA results as measured by the MapCHECK 2 and ArcCHECK diode arrays for the same IMRT and VMAT treatment plans to see if one diode array consistently provides a closer comparison to reference data. Six prostate and three thoracic spine IMRT treatment plans as well as three prostate and three thoracic spine VMAT treatment plans were produced. Radiotherapy plans for this study were generated using the Pinnacle TPS v9.6 (Philips Radiation Oncology Systems, Fitchburg, WI) using 6 MV, 6 MV FFF, and 10 MV x-ray beams from a Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA) with a 120-millenium multi-leaf collimator (MLC). Each IMRT and VMAT therapy plan was measured on Sun Nuclear's MapCHECK 2 and ArcCHECK diode arrays. IMRT measured data was compared with planned dose distribution using Sun Nuclear's 3DVH quality assurance software program using gamma analysis and dose-volume histograms for target volumes and critical structures comparison. VMAT arc plans measured on the MapCHECK 2 and ArcCHECK were compared using beam-by-beam analysis with the gamma evaluation method with Sun Nuclear's SNC Patient (TM) analysis software. MapCHECK 2 showed a slightly better agreement with planned data for IMRT verifications with a mean pass rate of 99.4% for clinically used acceptance criteria of 3%/3mm. MapCHECK 2's 99.4% mean pass rate for IMRT verifications was 1.4% higher than ArcCHECK's mean pass rate. For VMAT verifications, the MapCHECK 2 had a mean pass rate of 99.6% and 100% for each arc respectively, resulting in a 1.25% to 1.92% higher mean passing rates than those measured by the ArcCHECK using an acceptance criteria of 3%/3mm. MapCHECK 2 showed consistently higher ROI-specific mean gamma passing rates, ranging from +0.2% to +5.6%. While neither diode array showed any advantage in regards to D95 measurements within the PTV, MapCHECK 2 again showed closer comparison data in the CTV/GTV with an absolute deviation of -1.14 Gy compared to -3.39 Gy as measured by the ArcCHECK. Lastly, while the MapCHECK 2 and ArcCHECK both closely matched with the reference doses within the PTV and CTV/GTV, the ArcCHECK consistently overestimated the maximum absolute dose to all ROI, from 0.026 Gy to 2.243 Gy. In conclusion, the MapCHECK 2 diode array measured data more closely matched with planned data compared to the ArcCHECK diode array for IMRT verifications. While MapCHECK 2 showed a marginally better gamma passing rates over the ArcCHECK diode array, the ArcCHECK's ability to simultaneously measure flatness, symmetry, output, and MLC positional accuracy as a function of gantry angle make it a more realistic and efficient measurement device for VMAT verifications.

Dance, Michael J.

169

Color-tunable, phosphor-free InGaN nanowire light-emitting diode arrays monolithically integrated on silicon.  

PubMed

We demonstrate controllable and tunable full color light generation through the monolithic integration of blue, green/yellow, and orange/red InGaN nanowire light-emitting diodes (LEDs). Such multi-color nanowire LED arrays are fabricated directly on Si substrate using a three-step selective area molecular beam epitaxy growth process. The lateral-arranged multi-color subpixels enable controlled light mixing at the chip-level and yield color-tunable light emission with CCT values in the range from 1900 K to 6800 K, while maintaining excellent color rendering capability. This work provides a viable approach for achieving micron and nanoscale tunable full-color LED arrays without the compromise between the device efficiency and light quality associated with conventional phosphor-based LEDs. PMID:25607491

Wang, Renjie; Nguyen, Hieu P T; Connie, Ashfiqua T; Lee, J; Shih, Ishiang; Mi, Zetian

2014-12-15

170

Photovoltaic ultraviolet detectors based on Zr(0.04)Ti(0.96)O2 solid solution nanowire arrays.  

PubMed

A Zr(0.04)Ti(0.96)O(2) solid solution nanowire (NW) array was prepared and characterized in detail. Zr doping effectively changed Zr(x)Ti(1-x)O(2)'s bandgap and led to better photoelectric properties, which indicated the possibility for deep UV detector fabrication. Based on the NW array, high-performance Schottky diode UV detector with Ag electrode was fabricated. At -3 V bias, the dark current of the detector is only 5 nA, and a high photoresponse of 5.6 A/W was achieved because of the internal gain. The ratio of photocurrent to dark current is more than three orders of magnitude. The device is promising for large-area UV detector applications. PMID:23385916

Zhang, Haifeng; Li, Hailong; Zhang, Min; Feng, Caihui; Gu, Xuehui; Xu, Yang; Zhou, Jingran; Ruan, Shengping

2013-02-01

171

Amzajerdian-SSDLTR 2004 Solid State and Diode Laser Technology Review, Directed Energy Professional Society, Albuquerque, New Mexico, June 2004. Risk Reduction and Advancement of High Power Quasi-CW Laser Diode Pump Arrays  

E-print Network

The reliability of moderate to high power solid-state lasers that can operate autonomously over a sufficiently long period, are constrained by their laser diode pump arrays (LDAs). For laser remote sensing instruments operating in space, the reliability and lifetime of LDAs are particularly critical because of high development and launch cost of instruments and their

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

172

Technique for Radiometer and Antenna Array Calibration with a Radiated Noise Diode  

NASA Technical Reports Server (NTRS)

This paper presents a new technique to calibrate a microwave radiometer and antenna array system. This calibration technique uses a radiated noise source in addition to two calibration sources internal to the radiometer. The method accurately calibrates antenna arrays with embedded active devices (such as amplifiers) which are used extensively in active phased array antennas.

Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul

2009-01-01

173

Measurement of lipid hydroperoxides in normal human blood plasma using HPLC-chemiluminescence linked to a diode array detector for measuring conjugated dienes.  

PubMed

A modification of a method using high-performance liquid chromatography (HPLC) with chemiluminescence (CL) detection for the measurement of lipid hydroperoxides (LOOH) in human blood plasma has been developed. The system involves separation of different classes of LOOH using reverse-phase HPLC, and post-column detection of CL produced by isoluminol oxidation during the reaction of LOOH with microperoxidase. Complete ultra-violet absorption spectra are collected with an in-line diode-array detector and used to confirm a positive CL response due to LOOH, or other compounds, by the presence or absence, respectively, of the LOOH conjugated diene chromophore. We have used the method to investigate the stability of exogenous 15(S)-HPETE (a hydroperoxide of eicosatetraenoic acid) and conjugated dienes (of both 15(S)-HPETE and its reduced metabolite, 15(S)-HETE) in human plasma stored at various temperatures. A large and rapid loss of the hydroperoxide occurred in plasma incubated at 0 degrees C or 27 degrees C, whereas only a small reduction in the level of conjugated dienes was found. 15(S)-HPETE in PBS was stable under the same conditions, and zero time recovery of the hydroperoxide from denatured plasma and from buffer containing albumin was identical to that of fresh plasma. Our data suggest that the observed temperature-dependent loss of exogenous hydroperoxide from fresh plasma results from a combination of enzymatic degradation to the hydroxy derivative and binding to plasma albumin. 15(S)-HPETE was found to be stable in plasma stored at -70 degrees C for up to 2 weeks and in liquid nitrogen for 3 months in the presence of the antioxidants butylated hydroxytoluene (BHT) and desferal, with no significant loss of conjugated dienes. PMID:1769613

Holley, A E; Slater, T F

1991-01-01

174

Deep ultraviolet emitting polarization induced nanowire light emitting diodes with AlxGa1?xN active regions  

NASA Astrophysics Data System (ADS)

In this report, we demonstrate band gap tuning of the active region emission wavelength from 365 nm to 250 nm in light emitting diodes fashioned from catalyst-free III-nitride nanowires. Optical characteristics of the nanowire heterostructures and fabricated devices are studied via electroluminescence (EL) and photoluminescence spectroscopy over a wide range of active region compositions. It is observed that for typical nanowire plasma assisted molecular beam epitaxy growth conditions, tuning of emission to wavelengths shorter than 300 nm is hampered by the presence of an optically active defect level. We show that by increasing the AlGaN nanowire growth temperatures this defect emission can be suppressed. These findings are applied to growth of the active region of a nanowire light emitting diode, resulting in a polarization-induced nanowire light emitting diode with peak EL at 250 nm.

Kent, Thomas F.; Carnevale, Santino D.; Sarwar, A. T. M.; Phillips, Patrick J.; Klie, Robert F.; Myers, Roberto C.

2014-11-01

175

Compound Ag nanocluster-graphene electrodes as transparent and current spreading electrodes for improved light output power in near-ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

We introduced a two-dimensional graphene network on a Ag nanocluster as a transparent and current spreading electrode (TCSE) for a near-ultraviolet light emitting diode (NUV-LED), and compared the performance with those with graphene electrodes or conventional indium tin oxide (ITO) electrodes. The current-voltage characteristics and electroluminescence (EL) data showed that compound Ag nanocluster-graphene (CA-G) electrodes operated well as TCSEs in NUV-LED devices. The forward voltage at an input current of 20 mA was 4.06 V for the NUV-LED of current spreading electrodes with CA-G electrodes, which is only slightly higher than the value 3.96 V with ITO electrodes as TCSEs. The EL intensity of NUV-LEDs with CA-G electrodes also showed a slight increase, compared to that of NUV-LEDs with planar ITO transparent conducting electrodes.

Seo, Tae Hoon; Kim, Seongjun; Jong Kim, Myung; Kim, Hyunsoo; Suh, Eun-Kyung

2014-05-01

176

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

NASA Astrophysics Data System (ADS)

The reliability and output power of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) fabricated on AlN substrates prepared by hydride vapor phase epitaxy are reported. TEM analysis revealed that dislocation density in LED layers, except the p-GaN layer, was below 106 cm-2. DUV-LEDs emitting at 261 nm exhibited an output power of 10.8 mW at 150 mA. The lifetime of these LEDs was estimated to be over 10,000 h for cw operation at 50 mA. No significant acceleration of output power decay at higher operation currents was observed. The estimated lifetime at the operation current of 150 mA was over 5,000 h.

Kinoshita, Toru; Obata, Toshiyuki; Nagashima, Toru; Yanagi, Hiroyuki; Moody, Baxter; Mita, Seiji; Inoue, Shin-ichiro; Kumagai, Yoshinao; Koukitu, Akinori; Sitar, Zlatko

2013-09-01

177

Efficient and high-power AlGaN-based ultraviolet light-emitting diode grown on bulk GaN  

SciTech Connect

By introducing thick bulk GaN as a substrate, we improved the performance of an AlGaN-based ultraviolet (UV) light-emitting diode (LED). The output power exceeds 3 mW at the injection current of 100 mA under a bare-chip geometry. Internal quantum efficiency is estimated as more than 80%, and the peak wavelength is 352 nm. The maximum power exceeds 10 mW at a large current injection of 400 mA, with an operation voltage of less than 6 V. These results indicate that an efficient UV LED is intrinsically possible by the combination of appropriate device design and the nitride substrate. By introducing packaging technology to enhance extraction efficiency, we will have a compact and efficient UV light source in the wide wavelength range of 200--360 nm, similar to conventional longer-wavelength LEDs. {copyright} 2001 American Institute of Physics.

Nishida, Toshio; Saito, Hisao; Kobayashi, Naoki

2001-08-06

178

Enhancement of the light output of GaN-based ultraviolet light-emitting diodes by a one-dimensional nanopatterning process  

NASA Astrophysics Data System (ADS)

We have demonstrated the enhancement of the output power of ultraviolet GaN-based light-emitting diodes (LEDs) by using one-dimensionally nanopatterned Cu-doped indium oxide(CIO)/indium tin oxide (ITO) p-type contact layers. The one-dimensional (1D) nanopatterns (250nm in width and 100nm in depth) are defined using a TiO2 1D nanomask fabricated by means of a surface relief grating technique. When fabricated with the nanopatterned p-contact layers, the output power of LEDs is improved by 40 and 63% at 20mA as compared to those fabricated with the unpatterned CIO/ITO and conventional Ni /Au contacts, respectively.

Hong, Hyun-Gi; Kim, Seok-Soon; Kim, Dong-Yu; Lee, Takhee; Song, June-O.; Cho, J. H.; Sone, C.; Park, Y.; Seong, Tae-Yeon

2006-03-01

179

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

NASA Astrophysics Data System (ADS)

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.

Sametoglu, Ferhat; Celikel, Oguz

2011-04-01

180

Investigation of AlGaN-based deep-ultraviolet light-emitting diodes with composition-varying AlGaN multilayer barriers  

NASA Astrophysics Data System (ADS)

In this study, the characteristics of deep-ultraviolet light-emitting diodes (DUV-LEDs) with composition-varying AlGaN multilayer barriers are investigated numerically. The simulation results demonstrate that the proposed DUV-LEDs have better device performances, i.e., higher light output power and internal quantum efficiency, over their counterparts with typical single-layer AlGaN barriers. These improvements are attributed to the reduced markedly polarization-induced electrostatic field within the quantum wells (QWs), which is beneficial to enhance the electron-hole spatial overlap in QWs, suppress the electron leakage and increase the hole injection efficiency. Furthermore, the efficiency droop is also reduced significantly when the composition-varying AlGaN multilayer barriers are adopted.

Yin, Yi An; Wang, Naiyin; Fan, Guanghan; Zhang, Yong

2014-12-01

181

AlGaN-based deep ultraviolet light-emitting diodes grown on nano-patterned sapphire substrates with significant improvement in internal quantum efficiency  

NASA Astrophysics Data System (ADS)

We report high-performance AlGaN-based deep ultraviolet light-emitting diodes grown on nano-patterned sapphire substrates (NPSS) using metal-organic chemical vapor deposition. By nanoscale epitaxial lateral overgrowth on NPSS, 4-?m AlN buffer layer has shown strain relaxation and a coalescence thickness of only 2.5 ?m. The full widths at half-maximum of X-ray diffraction (002) and (102) ?-scan rocking curves of AlN on NPSS are only 69.4 and 319.1 arcsec. The threading dislocation density in AlGaN-based multi-quantum wells, which are grown on this AlN/NPSS template with a light-emitting wavelength at 283 nm at room temperature, is reduced by 33% compared with that on flat sapphire substrate indicated by atomic force microscopy measurements, and the internal quantum efficiency increases from 30% to 43% revealed by temperature-dependent photoluminescent measurement.

Dong, Peng; Yan, Jianchang; Zhang, Yun; Wang, Junxi; Zeng, Jianping; Geng, Chong; Cong, Peipei; Sun, Lili; Wei, Tongbo; Zhao, Lixia; Yan, Qingfeng; He, Chenguang; Qin, Zhixin; Li, Jinmin

2014-06-01

182

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

183

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

184

On-line identification of phytochemical constituents in botanical extracts by combined high-performance liquid chromatographic–diode array detection–mass spectrometric techniques  

Microsoft Academic Search

It is necessary to determine all of the phytochemical constituents of botanical extracts in order to ensure the reliability and repeatability of pharmacological and clinical research, to understand their bioactivities and possible side effects of active compounds and to enhance product quality control. HPLC chromatographic fingerprints can be applied for this kind of documentation. Combined HPLC-diode array detection–MS techniques can

Xian-Guo He

2000-01-01

185

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

SciTech Connect

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

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

2014-06-03

186

3D thermal analysis of AlGaN\\/GaN high power ultraviolet light-emitting diodes  

Microsoft Academic Search

We report 3D simulation of AlGaN\\/GaN high power (? ? 350 nm) light emitting diodes (LEDs) for their advance thermal management. Theoretical transit thermal analysis study has been carried out for an efficient heat distribution and dissipation from the junction layer. The designed package was mainly consists of three layers namely, thermal interfacial materials (TIM), specialty designed submount and high

Nicolas Kudsieh; M. Khizar; M. Yasin Akhtar Raja

2011-01-01

187

Triggering GaAs lock-on switches with laser diode arrays  

SciTech Connect

Many of the applications that require the unique capabilities of Photoconductive Semiconductor Switches (PCSS) demand a compact package. We have been able to demonstrate that GaAs switches operated in the high gain mode called lock-on'' meet the required electrical switching parameters of several such applications using small switch sizes. The only light source that has enough power to trigger a PCSS and is compatible with a small package is a laser diode. This paper will describe the progress that leads to the triggering of high power PCSS switches with laser diodes. Our goal is to switch up to 5 kA in a single shot mode and up to 100 MW repetitively at up to 10 kHz. These goals are feasible since the switches can be used in parallel or in series. Low light level triggering became possible after the discovery of a high electric field, high gain switching mode in GaAs (and later in InP). At electric fields below 3 kV/cm GaAs switches are activated by creation of, at most, only one conduction electron- valence hole pair per photon absorbed in the sample. This linear mode demands high laser power and, after the light is extinguished, the carriers live for only a few nanoseconds. At higher electric fields GaAs behaves as a light activated Zener diode. The laser light generates carriers as in the linear mode and the field induces gain such that the amount of light required to trigger the switch is reduced by a factor of up to 500. The gain continues until the field across the sample drops to a material dependent lock-on field. At this point the switch will carry as much current as, and for as long as, the circuit can maintain the lock-on field. The gain in the switch allows for the use of laser diodes. 8 refs., 11 figs.

Loubriel, G.M.; Helgeson, W.D.; McLaughlin, D.L.; O'Malley, M.W.; Zutavern, F.J. (Sandia National Labs., Albuquerque, NM (USA)); Rosen, A.; Stabile, P.J. (David Sarnoff Research Center, Princeton, NJ (USA))

1990-01-01

188

High-power CW diode-laser-array-pumped solid-state lasers and efficient nonlinear optical frequency  

NASA Astrophysics Data System (ADS)

During the interim period of this bridging contract, we have continued to work on the development of high-power cw diode-laser-array-pumped solid-state lasers. Towards that end, we have built lower power lasers in order to test individual components needed for the high-power laser, specifically we have built a 1 watt ring laser and a 5 watt slab laser. The 1 watt laser was used to study the injection locking process while assembling all the necessary electronics. We have demonstrated that it is possible to injection lock a diode-pumped laser using a single piezo-mounted mirror due to the lower intrinsic laser noise compared to an arc-lamp-pumped system. This allows us to optimize the injection locking servo loop and build a more stable locking system. The 5 watt laser was used as a test bed to find a practical way to mount the slab laser while minimizing the losses that occur at the total internal reflection (TIR) points in the slab. After trying many different means of protecting the TIR surfaces, we found that a new product from DuPont, Teflon AF 1600, has all the properties needed to provide a low loss protective coating. Using this material, the laser had a cavity loss of below 2%, which allowed for efficient operation of the laser in a side-pumped design. This laser produced 5 watts of output power with a slope efficiency near 20%.

Shine, Robert J.; Byer, Robert L.

1994-01-01

189

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

190

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

SciTech Connect

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, on the order of 10 {mu}m per layer, is more than adequate to resolve the displaced vertices of beauty and charm decays. A high signal-to-noise ratio allows for the thinning of the detectors, reducing multiple scattering. Time tagging within the detector permits higher background levels than could otherwise be tolerated, and on-board electronics which includes zero suppression and ghost elimination, eases downstream data handling and analysis. 8 refs., 3 figs.

Shapiro, S.L.

1990-09-01

191

Determination of pyrethrin and pyrethroid pesticides in urine and water matrixes by liquid chromatography with diode array detection.  

PubMed

The following pyrethrin and pyrethroid pesticides were determined in urine and water matrixes by liquid chromatography with diode array detection (LC-DAD): pyrethrin I, pyrethrin II, tetramethrin, baythroid, bifenthrin, fenvalerate, phenothrin, allethrin, resmethrin, cis-permethrin, and trans-permethrin. In addition, 3-phenoxybenzyl alcohol, a metabolite of various pyrethroids, was also successfully determined by the analytical method. The matrix extraction was simple, inexpensive, and fast, using only sodium chloride and acetonitrile. The acetonitrile extract was filtered and analyzed by LC-DAD. The method detection limits for the pyrethrin pesticides in 5 mL urine were determined to range from 0.002 to 0.04 microg/mL, depending on the individual pyrethrin. Recoveries from spiked tap water ranged from 77 to 96%; recoveries from urine ranged from 80 to 117%. This method is especially well-suited to clinical investigations, in which rapid analysis of forensic samples is often required. PMID:14979708

Loper, Bobby L; Anderson, Kim A

2003-01-01

192

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 270 nm and 360 nm 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

2014-02-15

193

Technique for Radiometer and Antenna Array Calibration with Two Antenna Noise Diodes  

NASA Technical Reports Server (NTRS)

This paper presents a new technique to calibrate a microwave radiometer and phased array antenna system. This calibration technique uses a radiated noise source in addition to an injected noise sources for calibration. The plane of reference for this calibration technique is the face of the antenna and therefore can effectively calibration the gain fluctuations in the active phased array antennas. This paper gives the mathematical formulation for the technique and discusses the improvements brought by the method over the existing calibration techniques.

Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul

2011-01-01

194

Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer  

NASA Astrophysics Data System (ADS)

Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on.

Dong, Jing-Jing; Hao, Hui-Ying; Xing, Jie; Fan, Zhen-Jun; Zhang, Zi-Li

2014-11-01

195

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

196

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

197

Defect controlled ultra high ultraviolet photocurrent gain in Cu-doped ZnO nanorod arrays: De-trapping yield  

NASA Astrophysics Data System (ADS)

Understanding the mechanism behind high photocurrent gain is very important to realize a highly functional material for photodetector devices. Herein, we report a very high ultraviolet photocurrent gain of 2.8 × 105 in hydrothermally grown Cu-doped ZnO nanorod arrays which is two orders of magnitude higher as compared to the undoped sample. Trapping of carriers under dark and de-trapping them under illumination by Cu-related defects is responsible for high gain. The trap state at ˜1.65 eV is attributed to the [{CuZn+(3d10)}- - Zni+(4s1)]0 type of defects. A model is shown to explain the dark and photocurrent states in the doped samples.

Sarkar, Sanjit; Basak, Durga

2013-07-01

198

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

SciTech Connect

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

Jung, Mi, E-mail: jmnano00@gmail.com, E-mail: Dockha@kist.re.kr [Sensor System Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); School of Mechanical Systems Engineering, Kookmin University, Seoul 136-702 (Korea, Republic of); Mo Yoon, Dang; Kim, Miyoung [Korea Printed Electronics Center, Korea Electronics Technology Institute, Jeollabuk-do, 561-844 (Korea, Republic of); Kim, Chulki; Lee, Taikjin; Hun Kim, Jae; Lee, Seok; Woo, Deokha, E-mail: jmnano00@gmail.com, E-mail: Dockha@kist.re.kr [Sensor System Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Lim, Si-Hyung [School of Mechanical Systems Engineering, Kookmin University, Seoul 136-702 (Korea, Republic of)

2014-07-07

199

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

NASA Astrophysics Data System (ADS)

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

Jung, Mi; Mo Yoon, Dang; Kim, Miyoung; Kim, Chulki; Lee, Taikjin; Hun Kim, Jae; Lee, Seok; Lim, Si-Hyung; Woo, Deokha

2014-07-01

200

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

SciTech Connect

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

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

2011-01-13

201

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

SciTech Connect

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

Sawicka, M.; Grzanka, S.; Skierbiszewski, C. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland) [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); TopGaN Sp. z o.o., Sokolowska 29/37, 01-142 Warsaw (Poland); Cheze, C. [TopGaN Sp. z o.o., Sokolowska 29/37, 01-142 Warsaw (Poland) [TopGaN Sp. z o.o., Sokolowska 29/37, 01-142 Warsaw (Poland); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Turski, H.; Muziol, G.; Krysko, M.; Grzanka, E.; Sochacki, T. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland)] [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); Hauswald, C.; Brandt, O. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)] [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Siekacz, M. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland) [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Kucharski, R. [Ammono S.A., Czerwonego Krzyza 2/31, 00-377 Warsaw (Poland)] [Ammono S.A., Czerwonego Krzyza 2/31, 00-377 Warsaw (Poland); Remmele, T.; Albrecht, M. [Leibniz Institute for Crystal Growth, Max-Born Strasse 2, Berlin 12489 (Germany)] [Leibniz Institute for Crystal Growth, Max-Born Strasse 2, Berlin 12489 (Germany)

2013-03-18

202

High power ultraviolet light emitting diodes based on GaN/AlGaN quantum wells produced by molecular beam epitaxy  

SciTech Connect

In this paper, we report on the growth by molecular beam epitaxy and fabrication of high power nitride-based ultraviolet light emitting diodes emitting in the spectral range between 340 and 350 nm. The devices were grown on (0001) sapphire substrates via plasma-assisted molecular beam epitaxy. The growth of the light emitting diode (LED) structures was preceded by detailed materials studies of the bottom n-AlGaN contact layer, as well as the GaN/AlGaN multiple quantum well (MQW) active region. Specifically, kinetic conditions were identified for the growth of the thick n-AlGaN films to be both smooth and to have fewer defects at the surface. Transmission-electron microscopy studies on identical GaN/AlGaN MQWs showed good quality and well-defined interfaces between wells and barriers. Large area mesa devices (800x800 {mu}m{sup 2}) were fabricated and were designed for backside light extraction. The LEDs were flip-chip bonded onto a Si submount for better heat sinking. For devices emitting at 340 nm, the measured differential on-series resistance is 3 {omega} with electroluminescence spectrum full width at half maximum of 18 nm. The output power under dc bias saturates at 0.5 mW, while under pulsed operation it saturates at approximately 700 mA to a value of 3 mW, suggesting that thermal heating limits the efficiency of these devices. The output power of the investigated devices was found to be equivalent with those produced by the metal-organic chemical vapor deposition and hydride vapor-phase epitaxy methods. The devices emitting at 350 nm were investigated under dc operation and the output power saturates at 4.5 mW under 200 mA drive current.

Cabalu, J. S.; Bhattacharyya, A.; Thomidis, C.; Friel, I.; Moustakas, T. D.; Collins, C. J.; Komninou, Ph. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 and Center of Photonics Research, Boston University, Boston, Massachusetts 02215 (United States); U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States); Physics Department, Aristotle University, 54124 Thessaloniki (Greece)

2006-11-15

203

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

NASA Technical Reports Server (NTRS)

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

Raines, J. K.

1975-01-01

204

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

PubMed

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

Tuzimski, Tomasz

2011-01-01

205

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

206

Determination of taxol in Taxus species grown in Hungary by high-performance liquid chromatography-diode array detection effect of vegetative period  

Microsoft Academic Search

The influence of a vegetative period on the taxol content in the needles of Taxus brevifolia grown in Hungary was determined using porous graphitized carbon column and a HPLC-diode array detection system. The relative standard deviation of the retention time of taxol peak was 1.24%, the peak symmetry 1.06–1.07 indicating the reliability of the HPLC systems. It was found that

Veronika Németh-Kiss; Esther Forgács; Tibor Cserháti; Gábor Schmidt

1996-01-01

207

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

208

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

Microsoft Academic Search

A simple and sensitive high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) method was investigated for simultaneous determination of 11 components (chlorogenic acid, coptisine, epiberberine, jatrorrhizine, berberine, palmatine, baicalin, wogonoside, baicalein, wogonin and chrysin) in Qinhuanghouzheng (QHHZ) capsule and Xiaoerqingre (XEQR) tablet, for quality control of these two well-known traditional Chinese medicines (TCMs). The method was established using an

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

2009-01-01

209

A deuterium-labelling mass spectrometry–tandem diode-array detector screening method for rapid discovery of naturally occurring electrophiles  

Microsoft Academic Search

Because electrophiles regulate many signalling pathways in cells, by modifying cysteine residues in proteins, they have a\\u000a wide range of biological activity. In this study, a deuterium-labelling mass spectrometry–tandem diode-array detector (MS–DAD)\\u000a screening method was established for rapid discovery of naturally occurring electrophiles. Glutathione (GSH) was used as a\\u000a probe and incubated with natural product extracts. To distinguish different types

Xiaoyu Zhang; Liping Luo; Zhongjun Ma

210

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

2013-09-11

211

Analysis of multicomponent formulations containing pseudoephedrine HCl and chlorpheniramine maleate using first-derivative spectroscopy on a diode-array spectrophotometer.  

PubMed

Pseudoephedrine HCl and chlorpheniramine maleate are compounds which have overlapping UV spectra in solutions of phosphate buffer (pH 7.2), water, and 0.1 M HCl. The quantitation of both compounds was achieved by using first-derivative spectroscopy on a diode-array spectrophotometer. The application of this method for the analysis of content uniformity testing and measuring dissolution profiles was demonstrated. PMID:3585742

Hoover, J M; Soltero, R A; Bansal, P C

1987-03-01

212

Ultra-violet GaN/Al0.5Ga0.5N quantum dot based light emitting diodes  

NASA Astrophysics Data System (ADS)

Taking advantage of the strain-induced 2-dimensional (2D)-3D "Stransky-Krastanov type" growth mode of GaN on AlxGa1-xN, we report on the fabrication of ultraviolet (UV) light emitting diodes (LEDs) using GaN quantum dots (QDs) as emitters. The structures have been grown by molecular beam epitaxy on sapphire (0001) substrates. GaN QDs, with density ˜8×1010 cm-2, are formed on Al0.5Ga0.5N layers. The electroluminescence (EL) spectrum is dominated by a blue-violet emission (400-430 nm) at very low injection currents (?2 A/cm2). At currents above 10 A/cm2, a UV emission (<390 nm) is observed. An additional peak, at wavelength ˜314 nm, originates from the EL emission from the GaN wetting layer. For increasing current, we observe a large shift (˜300 meV) towards higher energies and a reduction by one third of the full width at half maximum of the EL peak. Furthermore, the appearance of an additional peak on the EL high energy side is observed. These properties are governed by the quantum confined Stark effect and band-filling in the QDs. AlxGa1-xN-based QD-LED performances (optical power, external quantum efficiency) are presented and discussed in correlation to the specific 3D localization of excitons in the QDs.

Brault, J.; Damilano, B.; Kahouli, A.; Chenot, S.; Leroux, M.; Vinter, B.; Massies, J.

2013-01-01

213

Light Improvement of Near Ultraviolet Light-Emitting Diodes by Utilizing Lattice-Matched InAlGaN as Barrier Layers in Active Region  

NASA Astrophysics Data System (ADS)

The effects of lattice-matched InAlGaN used as barriers in the active region were investigated in near ultraviolet light-emitting diodes (LEDs). By changing the thickness of InAlGaN barriers, it is observed that there exists an optimal thickness. Besides the better carrier confinement in the case of using thick barriers, the simulation results showed that hole distribution in the case of using wide barriers should also play a role in the improvement of optical performance. Hence, an excessive increment in the width of barriers will degrade the optical performance contrarily, owing to the accumulated stress and the difficulty in hole transport in the active region from thick barriers. In addition, the calculated energy bandgap of InAlGaN is higher than that of GaN, which is beneficial for increasing the capability of carrier confinement and simultaneously enhancing the radiative recombination. Under 100 mA, the light output power of the LED with 7.3-nm-thick In0.018Al0.09Ga0.892N barriers can be increased by 36% as compared with the LED with GaN barrier.

Lu, Yu-Hsuan; Fu, Yi-Keng; Huang, Shyh-Jer; Su, Yan-Kuin; Xuan, Rong; Pilkuhn, Manfred H.; Chen, Ying-Chih

2013-08-01

214

Growth and characterization of quaternary AlGaInN layers and performance of AlGaInN-based ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

We report the growth and the characterization of both quaternary AlGaInN bulk layers and AlGaInN/InGaN multiple-quantum-well (MQW) layers grown by using metal-organic chemical vapor deposition for high-efficiency ultraviolet light-emitting diodes (UV LEDs). Inclusion of a small fraction of indium in the AlGaInN layer was found to reduce the number of structural defects and the strain in the layer. From the intensities of temperature-dependent photoluminescence and time-resolved photoluminescence, the internal quantum efficiency at 300 K was obtained as 60% for the sample grown with a quaternary AlGaInN barrier in the MQWs and 25% for the sample with a ternary AlGaN barrier. The dominant optical transition in the AlGaInN/InGaN MQWs was considered to be caused by localized exciton recombination and reduction of the strain in the MQW stack, with indium incorporation in the barriers, resulting in the longest decay lifetime from quaternary AlGaInN alloys. We measured the optical output power from the UV LED device grown with quaternary AlGaInN barriers. The LEDs reached a maximum output power of 50.6 mW and a wall-plug efficiency of 2.99% under an input current level of 400 mA.

Jeon, Seong-Ran; Son, Sung-Jin; Park, Si-Hyun

2013-12-01

215

Thermally stable white-emitting single composition Na(Sr,Ba)PO4:Eu2+, Mn2+ phosphor for near-ultraviolet-pumped light-emitting diodes.  

PubMed

Eu(2+) and Mn(2+) codoped, white-emitting Na(Sr,Ba)PO(4) phosphors are prepared, and their emission properties, especially for thermal stability, are thoroughly investigated. The thermal quenching and Eu(2+)/Mn(2+) energy transfer efficiency are totally different in the ratio of alkaline earth metals in host composition, NaBaPO(4), Na(Sr(0.5)Ba(0.5))PO(4), and NaSrPO(4), respectively. Furthermore, by using near-ultraviolet light-emitting diodes (LEDs) and the corresponding Na(Sr(0.5)Ba(0.5))PO(4):Eu(2+), Mn(2+) phosphor as light converters, we demonstrate a bright and thermally stable white-emitting LED. The resultant LED exhibits a warm white light [~4900 K, CIE coordinates of (0.33, 0.31)] with excellent thermal and hydrolytic stabilities comparable to those of commercially available ones, Y(3)Al(5)O(12):Ce(3+) and BaMg(2)Al(16)O(27):Eu(2+). The proposed composition, with its efficient energy transfer, could enable Eu(2+) and Mn(2+) codoped Na(Sr,Ba)PO(4) to be a promising single component phosphor for cost-effective white-emitting LEDs. PMID:23595480

Choi, Sungho; Yun, Young Jun; Kim, Sue Jin; Jung, Ha-Kyun

2013-04-15

216

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

NASA Astrophysics Data System (ADS)

Electrical current transport through leakage paths in AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) and their effect on LED performance are investigated. Open-core threading dislocations, or nanopipes, are found to conduct current through nominally insulating Al0.7Ga0.3N layers and limit the performance of DUV-LEDs. A defect-sensitive phosphoric acid etch reveals these open-core threading dislocations in the form of large, micron-scale hexagonal etch pits visible with optical microscopy, while closed-core screw-, edge-, and mixed-type threading dislocations are represented by smaller and more numerous nanometer-scale pits visible by atomic-force microscopy. The electrical and optical performances of DUV-LEDs fabricated on similar Si-doped Al0.7Ga0.3N templates are found to have a strong correlation to the density of these nanopipes, despite their small fraction (<0.1% in this study) of the total density of threading dislocations.

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

2014-08-01

217

High efficiency and output power of near-ultraviolet light-emitting diodes grown on GaN substrate with back-side etching  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the differences between optical and electrical properties of near-ultraviolet (NUV) InGaN/GaN multi-quantum well light-emitting diodes (LEDs) grown on GaN substrate with a roughened back-side on the N-face surface of GaN substrate through a chemical wet-etching process, and on pattern sapphire substrate (PSS). Back-side etching-treated NUV-LEDs have larger output power than conventional NUV-LEDs, NUV-LEDs with wider wells and NUV-LEDs grown on PSS. When the NUV-LEDs were operated at a forward current of 20?mA, the output power of back-side etching-treated NUV-LEDs was improved by approximately 100, 106 and 8% compared with that of conventional NUV-LEDs, NUV-LEDs with wider wells and NUV-LEDs grown on PSS, respectively. This larger enhancement results from the improved light extraction that was attributed to the different transmittance because a hexagonal pyramid on the N-face GaN that was etched formed at the stable crystallographic etching planes of the GaN {1011} planes.

Fang, Yen-Hsiang; Fu, Yi-Keng; Xuan, Rong

2012-04-01

218

Disinfection of B. SUBTILIS Cells in Suspension Using Ultraviolet Light Emitting Diodes (leds) in the Presence of TiO2  

NASA Astrophysics Data System (ADS)

The concentration of vegetative Bacillus subtilis (B. subtilis) in phosphate buffered saline decreased when subjected to ultraviolet (UV) light from light emitting diodes (LEDs) in the presence of 0.01% Degussa P25 titanium dioxide (TiO2) as compared to a sample that contained bacteria only, a sample of bacteria that contained 0.01% TiO2, and bacteria that was subjected to the same UV light but no TiO2. The starting concentration of each sample was on the order of 104 colony forming units per milliliter (CFU/mL) and the time required for complete kill was less than 100min when the peak wavelength was 370 nm for the four LED light source at a total LED power of 0.8 milliWatts (mW), decreasing to less than 75 min for a total LED power of 3 mW. Changing the peak wavelength by 7 nm to 377 nm decreased the kill of vegetative B. subtilis to less than 1 log at 100 min for 5 mW total LED power. This work was performed under Federal Contract W9113M-09-C-0136 in support of the Radiance Technologies, Inc., prime contract from US Army SMDC, Huntsville, AL.

Province, Dennis W.; O'Neil, Shannon; Higgins, Keri; Smith, Paul J.; Dooley, Kristin; Curtis, Joey; Grippo, Adam M.; Rino, John W.; Allen, Susan D.

2011-06-01

219

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

PubMed Central

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

2013-01-01

220

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

PubMed Central

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

2014-01-01

221

Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

In this paper, recent advances in AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) are demonstrated. 220–350-nm-band DUV LEDs have been realized by developing crystal growth techniques for wide-bandgap AlN and AlGaN semiconductors. Significant increases in internal quantum efficiency (IQE) have been achieved for AlGaN DUV emissions by developing low-threading-dislocation-density (TDD) AlN buffer layers grown on sapphire substrates. The electron injection efficiency (EIE) of the LEDs was also significantly increased by introducing a multiquantum barrier (MQB). We also discuss light extraction efficiency (LEE), which is the most important parameter for achieving high-efficiency DUV LEDs. We succeeded in improving LEE by developing a transparent p-AlGaN contact layer. The maximum external quantum efficiency (EQE) obtained was 7% for a 279 nm DUV LED. EQE could be increased by up to several tens of percent through the improvement of LEE by utilizing transparent contact layers and photonic nanostructures in the near future.

Hirayama, Hideki; Maeda, Noritoshi; Fujikawa, Sachie; Toyoda, Shiro; Kamata, Norihiko

2014-10-01

222

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

223

Superior Illuminant Characteristics of Color Rendering and Luminous Efficacy in Multilayered Phosphor Conversion White Light Sources Excited by Near-Ultraviolet Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

We have demonstrated that a phosphor conversion (PC) white light-emitting diode (LED) light source composed of multi-layered (ML) red, green, and blue (RGB) phosphors with a near-ultraviolet (n-UV) LED as an excitation source shows excellent color rendering, luminous efficacy, and luminous flux. The ML-phosphor structure consists of vertically stacked layers and could significantly reduce cascade excitation loss compared with a mixed RGB PC white LED. A high luminous efficacy of 82 lm/W with a high color-rendering index (CRI) of over 90 was achieved using a ML-RGB PC white LED. The ML-RGB structure also enables a white LED with an ultrahigh CRI of 99 and a high luminous efficacy comparable to that of a high CRI fluorescent lamp. We have also fabricated a high-power ML-PC white LED excited by an n-UV LED. In one package, a high luminous flux of 61 lm at a high CRI of 94 was obtained.

Fukui, Takeshi; Kamon, Kunihito; Takeshita, Junichi; Hayashi, Hideki; Miyachi, Tsutomu; Uchida, Yuji; Kurai, Satoshi; Taguchi, Tsunemasa

2009-11-01

224

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

SciTech Connect

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

Scarcella, Carmelo; Tosi, Alberto, E-mail: alberto.tosi@polimi.it; Villa, Federica; Tisa, Simone; Zappa, Franco [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)] [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)

2013-12-15

225

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

NASA Astrophysics Data System (ADS)

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

Huang, Jinying; Ma, Dongge

2014-09-01

226

Commissioning and comprehensive evaluation of the ArcCHECK cylindrical diode array for VMAT pretreatment delivery QA.  

PubMed

We present commissioning and comprehensive evaluation for ArcCHECK as a QA equipment for volumetric-modulated arc therapy (VMAT), using the 6 MV photon beam with and without the flattening filter, and the SNC patient software (version 6.2). In addition to commissioning involving absolute dose calibration, array calibration, and PMMA density verification, ArcCHECK was evaluated for its response dependency on linac dose rate, instantaneous dose rate, radiation field size, beam angle, and couch insertion. Scatter dose characterization, consistency and symmetry of response, and dosimetry accuracy evaluation for fixed aperture arcs and clinical VMAT patient plans were also investigated. All the evaluation tests were performed with the central plug inserted and the homogeneous PMMA density value. Results of gamma analysis demonstrated an overall agreement between ArcCHECK-measured and TPS-calculated reference doses. The diode based field size dependency was found to be within 0.5% of the reference. The dose rate-based dependency was well within 1% of the TPS reference, and the angular dependency was found to be ± 3% of the reference, as tested for BEV angles, for both beams. Dosimetry of fixed arcs, using both narrow and wide field widths, resulted in clinically acceptable global gamma passing rates on the 3%/3mm level and 10% threshold. Dosimetry of narrow arcs showed an improvement over published literature. The clinical VMAT cases demonstrated high level of dosimetry accuracy in gamma passing rates. PMID:25207411

Chaswal, Vibha; Weldon, Michael; Gupta, Nilendu; Chakravarti, Arnab; Rong, Yi

2014-01-01

227

Sampling and identification of natural dyes in historical maps and drawings by liquid chromatography with diode-array detection.  

PubMed

A simple and rapid liquid chromatographic with diode-array UV-vis spectrophotometric detection (HPLC-DAD) method for identification of natural dyes has been developed. Chromatographic retention of carminic acid, indigotin, crocetin, gambogic acid, alizarin and purpurin has been studied. The mobile phase consisted of 40 mM SDS-10 mM phosphate buffer solution (pH 2.3)-0.1% TFA (eluent A) and acetonitrile (eluent B) using a programmed gradient (5% B to 95% B). Analyses were carried out on a Phenomenex, Luna 5u NH2 100(a) column (250 mm x 4.60 mm i.d., 5 microm particle) and the operating conditions were: 0.6 ml min(-1) flow rate, 20 microl volume injection and 35 degrees C column temperature. Extracts of samples of natural dyes taken from historical maps belonging to The Royal Chancellery Archives in Granada were successfully analyzed using the proposed method including a new technique for sampling. PMID:16759664

Blanc, Rosario; Espejo, Teresa; López-Montes, Ana; Torres, David; Crovetto, Guillermo; Navalón, Alberto; Vílchez, José Luis

2006-07-28

228

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

PubMed

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

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

2015-02-01

229

Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array.  

PubMed

The growth and process of a regularly patterned nanorod (NR)- light-emitting diode (LED) array with its emission from sidewall non-polar quantum wells (QWs) are demonstrated. A pyramidal un-doped GaN structure is intentionally formed at the NR top for minimizing the current flow through this portion of the NR such that the injection current can be effectively guided to the sidewall m-plane InGaN/GaN QWs for emission excitation by a conformal transparent conductor (GaZnO). The injected current density at a given applied voltage of the NR LED device is similar to that of a planar c-plane or m-plane LED. The blue-shift trend of NR LED output spectrum with increasing injection current is caused by the non-uniform distributions of QW width and indium content along the height on a sidewall. The photoluminescence spectral shift under reversed bias confirms that the emission of the fabricated NR LED comes from non-polar QWs. PMID:25607494

Tu, Charng-Gan; Liao, Che-Hao; Yao, Yu-Feng; Chen, Horng-Shyang; Lin, Chun-Han; Su, Chia-Ying; Shih, Pei-Ying; Chen, Wei-Han; Zhu, Erwin; Kiang, Yean-Woei; Yang, C C

2014-12-15

230

Simultaneous determination of 11 bioactive compounds in Jaeumganghwa-tang by high performance liquid chromatography-diode array detection  

PubMed Central

Background: Jaeumganghwa-tang (JEGH) is a traditional Korean herbal medicine for the treatment of chronic bronchitis, nephritis and diabetes mellitus. Objective: A high performance liquid chromatography-diode array detector (HPLC-DAD) method was developed for simultaneous determination of 11 major compounds such as 5- hydroxymethylfurfural, mangiferin, paeoniflorin, nodakenin, naringin, hesperidin, decursinol, berberine, glycyrrhizin, atractylenolide III and decursin, in JEGH. Materials and Methods: The separation was conducted on Shishedo C18 column with gradient elution of 0.1% trifluoroacetic acid–acetonitrile. Detection of wavelength was set at 205, 250, 280 and 330 nm. Results: The developed analysis showed a good linearity (R2 >0.9997). The range of limit of detection and limit of quantification were observed from 0.04 to 0.43 and from 0.11 to 1.30, respectively. The intra- and inter-day test relative standard deviations (RSD) were less than 3% and the accuracy was 95.98-108.44%. The recoveries were between 92.75% and 109.19% and RSD range of recoveries was measured from 0.52% to 2.78%. Conclusion: This HPLC-DAD method can be successfully applied for simultaneous determination of 11 major compounds in JEGH samples. PMID:24991100

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

2014-01-01

231

Determination of polyacetylenes in carrot roots (Daucus carota L.) by high-performance liquid chromatography coupled with diode array detection.  

PubMed

A new high-performance liquid chromatographic method with diode array detection was developed for the separation and simultaneous determination of the carrot polyacetylenes falcarindiol (FaDOH), falcarindiol 3-acetate (FaDOAc) and falcarinol (FaOH) in carrot root extracts. The optimal chromatographic conditions were achieved on a C18 column with a linear gradient elution of water and acetonitrile as mobile phases, at the flow rate of 1.0 mL/min. All calibration curves of the three carrot polyacetylenes showed good linear regression (R2 > 0.998) within the test ranges. The developed method showed good precision for quantification of all polyacetylenes with overall intraday and interday variation of less than 3.3% and with average recovery rates of 99.2, 96.8 and 99.7% for FaDOH, FaDOAc and FaOH, respectively. The LOD (S/N = 3) and LOQ (S/N = 10) were less than 0.19 and 0.42 microg/mL, respectively, for all analytes. The established method was successfully used to determine the spatial distribution of FaDOH, FaDOAc and FaOH in six carrot genotypes (Bolero, Independent, Line 1, Mello Yello, Purple Haze and Tornado) by analysing peeled carrots and the corresponding peels for these polyacetylenes. PMID:17444217

Christensen, Lars P; Kreutzmann, Stine

2007-03-01

232

Liquid chromatography-diode array detection-mass spectrometry for compositional analysis of low molecular weight heparins.  

PubMed

Low molecular weight heparins (LMWHs) are important artificial preparations from heparin polysaccharide and are widely used as anticoagulant drugs. To analyze the structure and composition of LMWHs, identification and quantitation of their natural and modified building blocks are indispensable. We have established a novel reversed-phase high-performance liquid chromatography-diode array detection-electrospray ionization-mass spectrometry approach for compositional analysis of LMWHs. After being exhaustively digested and labeled with 2-aminoacridone, the structural motifs constructing LMWHs, including 17 components from dalteparin and 15 components from enoxaparin, were well separated, identified, and quantified. Besides the eight natural heparin disaccharides, many characteristic structures from dalteparin and enoxaparin, such as modified structures from the reducing end and nonreducing end, 3-O-sulfated tetrasaccharides, and trisaccharides, have been unambiguously identified based on their retention time and mass spectra. Compared with the traditional heparin compositional analysis methods, the approach described here is not only robust but also comprehensive because it is capable of identifying and quantifying nearly all components from lyase digests of LMWHs. PMID:24530286

Wang, Zhangjie; Li, Daoyuan; Sun, Xiaojun; Bai, Xue; Jin, Lan; Chi, Lianli

2014-04-15

233

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

234

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

SciTech Connect

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

Shindo, Francois [Measurement Standards Laboratory of New Zealand, Industrial Research, Lower Hutt (New Zealand); Woolliams, Emma; Scott, Barry; Harris, Subrena [National Physical Laboratory, Teddington (United Kingdom)

2013-05-10

235

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

236

AlGaN-Based Light Emitting Diodes Using Self-Assembled GaN Quantum Dots for Ultraviolet Emission  

NASA Astrophysics Data System (ADS)

Self-assembled GaN quantum dots (QDs) grown on Al0.5Ga0.5N have been used as the active region of light emitting diodes (LEDs). The LED emission wavelength exhibits a strong shift towards higher energies with increasing current density, which allows obtaining an emission in the UV range (down to 375 nm) above 100 A/cm2. Together with this shift, a reduction of the electroluminescence (EL) peak full width at half maximum (FWHM) is observed. These features are a consequence of the quantum confined Stark effect caused by the built-in electric field in the heterostructure. At larger current densities, an opposite behavior (i.e., an increase of the FWHM) is observed concomitant with the appearance of an additional peak on the EL high energy side. This characteristic has been confronted with calculations and attributed to a transition between the lowest electron state and the first excited hole state in the QDs.

Brault, Julien; Damilano, Benjamin; Vinter, Borge; Vennéguès, Philippe; Leroux, Mathieu; Kahouli, Abdelkarim; Massies, Jean

2013-08-01

237

Absorption spectroscopy diagnostics of a dual-frequency capacitive dielectric etch tool using Ultraviolet Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

Dual-frequency capacitively-coupled etch reactors using Ar/fluorocarbon/O2 mixtures are widely employed for etching of dielectric films for integrated circuit manufacture. CF2 radicals play an important role in the gas-phase and surface chemistry controlling etching and polymer deposition, and their density can be measured by UV absorption via the A-X band (230-270 nm). Previously Xe arc lamps have been used as the light source, but they are rather unstable, limiting the sensitivity of the technique, as well as being cumbersome and relatively expensive. We have successfully replaced the Xe arc with UV light-emitting diodes. The CF2 density was determined as a function of gas composition and power in a modified 2 + 27MHz commercial etch reactor operating in Ar/C4F8/O2. The CF2 density decreases rapidly as the O2/C4F8 ratio is increased, and increases with RF power at both frequencies, but is most affected by 27 MHz power. There is speculation that CF2 may play an important role in the creation and destruction of F- negative ions. However, we did not find any simple correlation between CF2 density and electro-negativity.

Booth, Jean-Paul; Bredin, Jerome

2009-10-01

238

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Determination of the spatial characteristics of the radiation emitted by pulsed ultraviolet lasers using a photodiode array  

NASA Astrophysics Data System (ADS)

An MF-14 photodiode array was used to determine the radiation field of pulsed ultraviolet lasers. The responsivity of this array at the wavelength of 0.337 ?m was S = 4 × 108 V/J. The distributions of the radiation from an N2 laser were determined in the near-field zone. The distributions were also obtained for XeF, XeCl, and KrF excimer lasers in the far-field zone. The angular dimensions of the distributions were determined.

Gorbachev, V. M.; Gorokhov, V. V.; Kalutski?, A. V.; Karelin, V. I.; Korolev, V. N.; Smerdov, V. I.

1992-09-01

239

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

240

Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer  

PubMed Central

Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on. PACS 78.60.Fi; 85.60.Jb; 78.67.Lt; 81.10.Dn PMID:25489284

2014-01-01

241

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

242

Real-time continuous-wave terahertz line scanner based on a compact 1 × 240 InGaAs Schottky barrier diode array detector.  

PubMed

We demonstrate real-time continuous-wave terahertz (THz) line-scanned imaging based on a 1 × 240 InGaAs Schottky barrier diode (SBD) array detector with a scan velocity of 25 cm/s, a scan line length of 12 cm, and a pixel size of 0.5 × 0.5 mm². Foreign substances, such as a paper clip with a spatial resolution of approximately 1 mm that is hidden under a cracker, are clearly detected by this THz line-scanning system. The system consists of the SBD array detector, a 200-GHz gyrotron source, a conveyor system, and several optical components such as a high-density polyethylene cylindrical lens, metal cylindrical mirror, and THz wire-grid polarizer. Using the THz polarizer, the signal-to-noise ratio of the SBD array detector improves because the quality of the source beam is enhanced. PMID:25402136

Han, Sang-Pil; Ko, Hyunsung; Kim, Namje; Lee, Won-Hui; Moon, Kiwon; Lee, Il-Min; Lee, Eui Su; Lee, Dong Hun; Lee, Wangjoo; Han, Seong-Tae; Choi, Sung-Wook; Park, Kyung Hyun

2014-11-17

243

Simultaneous determination of eight flavonoids in propolis using chemometrics-assisted high performance liquid chromatography-diode array detection.  

PubMed

A fast analytical strategy of second-order calibration method based on the alternating trilinear decomposition algorithm (ATLD)-assisted high performance liquid chromatography coupled with a diode array detector (HPLC-DAD) was established for the simultaneous determination of eight flavonoids (rutin, quercetin, luteolin, kaempferol, isorhamnetin, apigenin, galangin and chrysin) in propolis capsules samples. The chromatographic separation was implemented on a Wondasil™ C18 column (250mm×4.6mm, 5?m) within 13min with a binary mobile phase composed of water with 1% formic acid and methanol at a flow rate of 1.0mLmin(-1) after flavonoids were only extracted with methanol by ultrasound extraction for 15min. The baseline problem was overcome by considering background drift as additional compositions or factors as well as the target analytes, and ATLD was employed to handle the overlapping peaks from analytes of interest or from analytes and co-eluting matrix compounds. The linearity was good with the correlation coefficients no less than 0.9947; the limit of detections (LODs) within the range of 3.39-33.05ngmL(-1) were low enough; the accuracy was confirmed by the recoveries ranged from 91.9% to 110.2% and the root-mean-square-error of predictions (RMSEPs) less than 1.1?g/mL. The results indicated that the chromatographic method with the aid of ATLD is efficient, sensitive and cost-effective and can realize the resolution and accurate quantification of flavonoids even in the presence of interferences, thus providing an alternative method for accurate quantification of analytes especially when the complete separation is not easily accomplished. The method was successfully applied to propolis capsules samples and the satisfactory results were obtained. PMID:24907544

Sun, Yan-Mei; Wu, Hai-Long; Wang, Jian-Yao; Liu, Zhi; Zhai, Min; Yu, Ru-Qin

2014-07-01

244

High-reflectance of hybrid reflector with distributed Bragg reflector and metal mirror for flip-chip ultra-violet light-emitting diodes  

NASA Astrophysics Data System (ADS)

Three types of reflectors, including the distributed Bragg reflectors (DBRs), the first hybrid reflectors composed of DBR and Al mirror (DBR-Al), and the second hybrid reflectors composed of DBR, an additional low-refractive-index layer, and Al mirror (DBR-L-Al), were investigated by use of thin-film theory at the central wavelength of 300 nm for flip-chip ultra-violet light-emitting diodes (UV-LEDs). The number of DBR pairs and various high-refractive-index materials were studied. It is shown that the lossless materials with high refractive-index contrast should be selected for DBRs, and the DBR-Al hybrid reflectors provides higher reflectance comparing to DBRs. However, the Al mirror causes a sharp drop near the central wavelength and a blue shift of the peak position. These drawbacks can be suppressed by additional low-refractive-index layer attached on the Al mirror. In addition, the DBR-L-Al reflector leads to higher reflectivity and larger FWHM as compared to DBR-Al reflectors. By use of Monte Carlo ray tracing method, the light-extraction efficiency (LEE) for flip-chip UV-LEDs with (SiO2/ZrO2) 3 -SiO2-Al hybrid reflector or perfect mirror were simulated. The calculated LEE for the (SiO2/ZrO2) 3 -SiO2-Al hybrid reflector is 97 % of that for the perfect mirror. Moreover, the sharp drop in the angular reflectance spectrum of the (SiO2/ZrO2)3 -SiO2-Al hybrid reflector induces a slightly reduction of light intensity as compared to the perfect mirror.

Yang, Guang; Huang, Huamao; Wang, Hong

2014-12-01

245

Laser Diode Ignition (LDI)  

NASA Technical Reports Server (NTRS)

This paper reviews the status of the Laser Diode Ignition (LDI) program at Sandia National Labs. One watt laser diodes have been characterized for use with a single explosive actuator. Extensive measurements of the effect of electrostatic discharge (ESD) pulses on the laser diode optical output have been made. Characterization of optical fiber and connectors over temperature has been done. Multiple laser diodes have been packaged to ignite multiple explosive devices and an eight element laser diode array has been recently tested by igniting eight explosive devices at predetermined 100 ms intervals.

Kass, William J.; Andrews, Larry A.; Boney, Craig M.; Chow, Weng W.; Clements, James W.; Merson, John A.; Salas, F. Jim; Williams, Randy J.; Hinkle, Lane R.

1994-01-01

246

Luminescent properties of Li 2 (Ca 0.99 , Eu 0.01 ) SiO 4 : B 3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes  

Microsoft Academic Search

In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs)\\u000a used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated.\\u000a The crystallization and particle sizes of

Shanshan Yao; Donghua Chen

2007-01-01

247

Determination of diflubenzuron and its main metabolites in forestry matrices by liquid chromatography with on-line diode-array and electrochemical detection  

Microsoft Academic Search

A liquid chromatography (LC) method with on-line diode-array (DAD) and electrochemical detection (ED) has been developed for the determination of the pesticide diflubenzuron (DFB) and its main metabolites: 2,6-diflurobenzamide (2,6-DFBA), 4-chlorophenylurea (4-CPU), 4-chloroacetanilide (4-CAA), 4-chloroaniline (4-CA) and N-methyl-4-chloroaniline (NM-4-CA) in forestry matrices. Liquid chromatography was performed on a Spherisorb C18 column 5?m (4.1×150mm), using acetonitrile\\/methanol\\/citrate-disodium hydrogenphosphate buffer (50:2:48) at pH

E. Rodr??guez; R. J. Barrio; A. Goicolea; Z. Gómez de Balugera

1999-01-01

248

Enantiospecific resolution of rabeprazole by liquid chromatography on amylose-derived chiral stationary phase using photo diode array and polarimetric detectors in series  

Microsoft Academic Search

A simple and rapid liquid chromatographic method for enantioselective separation and determination of R-(+) and S-(?) enantiomers of rabeprazole in drugs and pharmaceuticals using photo diode array (PDA) and polarimetric detectors connected in series was developed. Chiralpak AD-H (250mm×4.6mm) 5?m column packed with amylose tris(3,5-dimethylphenyl carbamate) as a stationary phase and the mobile phase containing n-hexane:ethanol:2-propanol(75:15:10, v\\/v\\/v) in an isocratic

R. Nageswara Rao; A. Narasa raju; D. Nagaraju

2006-01-01

249

Simultaneous determination of seven azole antifungal drugs in serum by ultra-high pressure liquid chromatography and diode array detection.  

PubMed

Azole antifungals are a group of fungistatic agents that can be administered orally or parenterally. The determination of the concentrations of these antifungals (miconazole, fluconazole, ketoconazole, posaconazole, voriconazole, itraconazole, and its major active metabolite, hydroxy-itraconazole) in serum can be useful to adapt the doses to pharmacological ranges because of large variability in the absorption and metabolism of the drugs, multiple drug interactions, but also potential resistance or toxicity. A method was developed and validated for the simultaneous determination of these drugs in serum utilizing ultra-high pressure liquid chromatography and diode array detection (UHPLC-DAD). After a simple and rapid liquid-liquid extraction, the pre-treated sample was analysed on an UHPLC-DAD system (Waters Corporation(®)). The chromatographic separation was carried out on an Acquity BEH C18 column (Waters Corporation) with a gradient mode of mobile phase composed of acetonitrile and aqueous ammonium bicarbonate 10·0 M pH10. The flow rate was 0·4 ml/min and the injection volume was 5 ?l. The identification wavelength varied according to the drug from 210 to 260 nm. The method was validated by the total error method approach by using an analytical validation software (e•noval V3·0 Arlenda(®)). The seven azole antifungals were identified by retention time and specific UV spectra, over a 13-minute run time. All calibration curves showed good linearity (r(2)>0·99) in ranges considered clinically adequate. The assay was linear from 0·05 to 10 mg/l for voriconazole, posaconazole, itraconazole, hydroxy-itraconazole, and ketoconazole, from 0·3 to 10 mg/l for fluconazole, and from 0·1 to 10 mg/l for miconazole. The bias and imprecision values for intra- and inter-assays were lower than 10% and than 15%, respectively. In conclusion, a simple, sensitive, and selective UHPLC-DAD method was developed and validated to determine seven azole antifungal drugs in human serum. This method is applicable to patient samples, and can be applied successfully to clinical applications and therapeutic drug monitoring. PMID:24635400

Mistretta, V; Dubois, N; Denooz, R; Charlier, C

2014-01-01

250

Development of gallium nitride-based ultraviolet and visible light-emitting diodes using hydride vapor-phase epitaxy and molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Much of the work done on ultraviolet (UV) and visible III-Nitrides-based light emitting diodes (LEDs) involves growth by metal-organic chemical vapor deposition (MOCVD). In this dissertation, the growth, development, and fabrication of III-Nitrides-based UV and visible LEDs with very high photon conversion and extraction efficiencies using hydride vapor-phase epitaxy (HVPE) and radio frequency (rf) plasma-assisted molecular beam epitaxy (PAMBE) is presented. High-power electrically-pumped UV-LEDs based on GaN/AlGaN multiple quantum wells (MQWs) emitting at 340 nm and 350 nm have been fabricated in a flip-chip configuration and evaluated. Under pulsed operation, UV-LEDs emitting at 340 nm have output powers that saturate, due to device heating, at approximately 3 mW. Devices emitting at 350 nm show DC operation output powers as high as 4.5 mW under 200 mA drive current. These results were found to be equivalent with those of UV-LEDs produced by the MOCVD and HVPE methods. The concept of using textured MQWs on UV-LED structures was tested by optical pumping of GaN/AlGaN MQWs grown on textured GaN templates. Results show highly enhanced (>700 times) blue-shifted photoluminescence (PL) at 360 nm compared to similarly produced MQWs on smooth GaN templates whose PL emission is red-shifted. These results are attributed partly to enhancement in light extraction efficiency (LEE) and partly to enhancement in internal quantum efficiency (IQE). The origin of the increase in IQE is partly due to reduction of the quantum-confined Stark effect (QCSE) on QW-planes not perpendicular to the polarization direction and partly due to charge redistribution in the QWs caused by the polarization component parallel to the planes of the QWs. Similar studies have been done for visible LEDs using InGaN/GaN MQWs. Growth of LED structures on textured GaN templates employing textured MQW-active regions resulted in the production of dichromatic (430 nm and 530 nm) phosphorless white LEDs with good electrical characteristics. We attribute this behavior to different incorporation of In in different QW-planes. These studies show that textured MQW-based LEDs not only offers the benefit of enhanced IQE and LEE, but also the benefit of producing efficient white LEDs without the use of phosphor.

Cabalu, Jasper Sicat

251

Ultraviolet Extensions  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

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

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

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

2008-01-01

252

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

253

Simultaneous determination of tin, germanium and molybdenum by diode array detection-flow injection analysis with partial least squares calibration model.  

PubMed

Simultaneous determination of tin, germanium and molybdenum in food samples has been established by flow injection-charge coupled detector (CCD) diode array detection spectrophotometry with partial least squares (PLS) algorithm. The method was based on the chromogenic reaction of metal ions and salicylflurone in the presence of cetyltrimethyl ammonium bromide. The overlapping spectra of these complexes are collected by CCD diode array detector and the multi-wavelength absorbance data are processed using partial least squares algorithm. The reaction conditions and analytical parameters of flow injection analysis have been investigated. The method was applied to directly determine Ge, Mo and Sn in several food samples after digestion with satisfactory results. The recoveries of spiked samples were 80.0-102.0% for tin, 86.3-92.0% for germanium and 83.2-95.2% for molybdenum, and the relative standard deviations for samples were 4.4-7.8%. Molybdenum in certified reference material of cattle liver was determined by the proposed method (n=8). The differential values between determined and guarantee values were within the given uncertain value ranges (t=1.687, P>0.05 for t-test). The samples of mung bean, kelp and pork liver were analyzed by the proposed method and inductively couple plasma-atomic emission spectroscopy (ICP-AES) method. The determination results of the two methods are in good agreement. The sampling rate is 30 samplesh(-1). PMID:18969354

Zou, Xiaoli; Li, Yuanqian; Li, Menglong; Zheng, Bo; Yang, Jingguo

2004-03-10

254

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

SciTech Connect

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

Espinoza, A.; Beeksma, B.; Petasecca, M.; Fuduli, I.; Porumb, C.; Cutajar, D.; Lerch, M. L. F.; Rosenfeld, A. B. [Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia)] [Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia); Corde, S.; Jackson, M. [Department of Radiation Oncology, Prince of Wales Hospital, New South Wales 2031 (Australia)] [Department of Radiation Oncology, Prince of Wales Hospital, New South Wales 2031 (Australia)

2013-11-15

255

Determination of brilliant green from fish pond water using carbon nanotube assisted pseudo-stir bar solid/liquid microextraction combined with UV-vis spectroscopy-diode array detection  

NASA Astrophysics Data System (ADS)

This paper describes the development of a new design of hollow fiber solid/liquid phase microextraction (HF-SLPME) for determination of brilliant green (BG) residues in water fish ponds. This method consists of an aqueous donor phase and carbon nanotube reinforced organic solvent (acceptor phase) operated in direct immersion sampling mode. The multi-walled carbon nanotube dispersed in the organic solvent is held in the pores and lumen of a porous polypropylene hollow fiber. It is in contact directly with the aqueous donor phase. In this method the solid/liquid extractor phase is supported using a polypropylene hollow fiber membrane. Both ends of the hollow fiber segment are sealed with magnetic stoppers. This device is placed inside the donor solution and plays the rule of a pseudo-stir bar. It is disposable, so single use of the fiber reduces the risk of carry-over problems. Brilliant green (BG) after extraction from the aqueous samples with mentioned HF-SLPME device was determined by ultraviolet-visible spectroscopy with diode array detection (UV-vis/DAD). The absorption wavelength was set to 625 nm ( ?max). The effect of different variables on the extraction was evaluated and optimized to enhance the sensitivity and extraction efficiency of the proposed method. The calibration curve was linear in the range of 1.00-10,000 ?g L -1 of BG in the initial solution with R2 = 0.979. Detection limit, based on three times the standard deviation of the blank, was 0.55 ?g L -1. All experiments were carried out at room temperature (25 ± 0.5 °C).

Es'haghi, Zarrin; Khooni, Maliheh Ahmadi-Kalateh; Heidari, Tahereh

2011-08-01

256

Far ultraviolet sensitivity of silicon CMOS sensors  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

257

Dosimetric verification for intensity-modulated arc therapy plans by use of 2D diode array, radiochromic film and radiosensitive polymer gel  

PubMed Central

Several tools are used for the dosimetric verification of intensity-modulated arc therapy (IMAT) treatment delivery. However, limited information is available for composite on-line evaluation of these tools. The purpose of this study was to evaluate the dosimetric verification of IMAT treatment plans using a 2D diode array detector (2D array), radiochromic film (RCF) and radiosensitive polymer gel dosimeter (RPGD). The specific verification plans were created for IMAT for two prostate cancer patients by use of the clinical treatment plans. Accordingly, the IMAT deliveries were performed with the 2D array on a gantry-mounting device, RCF in a cylindrical acrylic phantom, and the RPGD in two cylindrical phantoms. After the irradiation, the planar dose distributions from the 2D array and the RCFs, and the 3D dose distributions from the RPGD measurements were compared with the calculated dose distributions using the gamma analysis method (3% dose difference and 3-mm distance-to-agreement criterion), dose-dependent dose difference diagrams, dose difference histograms, and isodose distributions. The gamma passing rates of 2D array, RCFs and RPGD for one patient were 99.5%, 96.5% and 93.7%, respectively; the corresponding values for the second patient were 97.5%, 92.6% and 92.9%. Mean percentage differences between the RPGD measured and calculated doses in 3D volumes containing PTVs were –0.29 ± 7.1% and 0.97 ± 7.6% for the two patients, respectively. In conclusion, IMAT prostate plans can be delivered with high accuracy, although the 3D measurements indicated less satisfactory agreement with the treatment plans, mainly due to the dosimetric inaccuracy in low-dose regions of the RPGD measurements. PMID:24449714

Hayashi, Naoki; Malmin, Ryan L.; Watanabe, Yoichi

2014-01-01

258

Liquid chromatography with diode array detection and multivariate curve resolution for the selective and sensitive quantification of estrogens in natural waters.  

PubMed

Following the green analytical chemistry principles, an efficient strategy involving second-order data provided by liquid chromatography (LC) with diode array detection (DAD) was applied for the simultaneous determination of estriol, 17?-estradiol, 17?-ethinylestradiol and estrone in natural water samples. After a simple pre-concentration step, LC-DAD matrix data were rapidly obtained (in less than 5 min) with a chromatographic system operating isocratically. Applying a second-order calibration algorithm based on multivariate curve resolution with alternating least-squares (MCR-ALS), successful resolution was achieved in the presence of sample constituents that strongly coelute with the analytes. The flexibility of this multivariate model allowed the quantification of the four estrogens in tap, mineral, underground and river water samples. Limits of detection in the range between 3 and 13 ng L(-1), and relative prediction errors from 2 to 11% were achieved. PMID:24952625

Pérez, Rocío L; Escandar, Graciela M

2014-07-01

259

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

260

Binary HPLC-diode array detector and HPLC-evaporative light-scattering detector fingerprints of methanol extracts from the selected sage (Salvia) species.  

PubMed

This study is focused on an important family of the sage (Salvia) species, with Salvia officinalis L. having a long-established position in European traditional medicine. Binary fingerprints (chromatographic profiles) of six different sage species were compared using HPLC coupled with two different detectors: the diode-array detector and the evaporative light-scattering detector. Advantages of using binary fingerprinting over single-detector fingerprinting are demonstrated and discussed, with selected examples. Experimental data are provided for a comparison of the chemical composition of sage samples originating from two harvesting seasons (2007 and 2008). A number of phytochemical standards (i.e., certain phenolic acids, flavonoids, and coumarin) were used that allowed identification and semiquantitative estimation of these particular compounds in the analyzed methanol extracts. PMID:21391482

Sajewicz, Mieczys?aw; Staszek, Dorota; Wojtal, ?ukasz; Kowalska, Teresa; Hajnos, Micha? ?; Waksmundzka-Hajnos, Monika

2011-01-01

261

A deuterium-labelling mass spectrometry-tandem diode-array detector screening method for rapid discovery of naturally occurring electrophiles.  

PubMed

Because electrophiles regulate many signalling pathways in cells, by modifying cysteine residues in proteins, they have a wide range of biological activity. In this study, a deuterium-labelling mass spectrometry-tandem diode-array detector (MS-DAD) screening method was established for rapid discovery of naturally occurring electrophiles. Glutathione (GSH) was used as a probe and incubated with natural product extracts. To distinguish different types of electrophile, incubation was performed in two reaction solvents, H(2)O and D(2)O. Ten types of naturally occurring electrophile were chosen, on the basis of their properties, to undergo the screening assay. By using this screening method, we successfully discovered the bioactive electrophile 4-hydroxyderricin in an ethanol extract of Angelica keiskei. This electrophile had potent NAD(P)H:quinone oxidoreductase 1 (NQO1)-inducing activity at a concentration of 20 ?mol L(-1). PMID:21544543

Zhang, Xiaoyu; Luo, Liping; Ma, Zhongjun

2011-07-01

262

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

263

Arrays  

NSDL National Science Digital Library

This interactive Flash applet helps students develop the concept of equal groups as a foundation for multiplication and division. The applet displays an array of dots, some of which are covered by a card. Student use the visible number of rows and columns to determine the total number of dots. Clicking on the card reveals the full array, and a voice announces the total.

2011-01-01

264

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

SciTech Connect

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

Al tahtamouni, T. M., E-mail: talal@yu.edu.jo [Department of Physics, Yarmouk University, Irbid 21163 (Jordan); Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)] [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

2014-04-15

265

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

266

Self-Injection Locking Of Diode Lasers  

NASA Technical Reports Server (NTRS)

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

Hemmati, H.

1991-01-01

267

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

268

ZnO-nanorod-array/p-GaN high-performance ultra-violet light emitting devices prepared by simple solution synthesis  

NASA Astrophysics Data System (ADS)

Pure ultra-violet (UV) (378 nm) electroluminescence (EL) from zinc oxide (ZnO)-nanorod-array/p-gallium nitride (GaN) light emitting devices (LEDs) is demonstrated at low bias-voltages (˜4.3 V). Devices were prepared merely by solution-synthesis, without any involvement of sophisticated material growth techniques or preparation methods. Three different luminescence characterization techniques, i.e., photo-luminescence, cathodo-luminescence, and EL, provided insight into the nature of the UV emission mechanism in solution-synthesized LEDs. Bias dependent EL behaviour revealed blue-shift of EL peaks and increased peak sharpness, with increasing the operating voltage. Accelerated bias stress tests showed very stable and repeatable electrical and EL performance of the solution-synthesized nanorod LEDs.

Jha, Shrawan Kumar; Luan, Chunyan; To, Chap Hang; Kutsay, Oleksandr; Ková?, Jaroslav; Zapien, Juan Antonio; Bello, Igor; Lee, Shuit-Tong

2012-11-01

269

Room-temperature violet luminescence and ultraviolet photodetection of Sb-doped ZnO/Al-doped ZnO homojunction array  

PubMed Central

A Sb-doped ZnO microrod array was fabricated on an Al-doped ZnO thin film by electrodeposition. Strong violet luminescence, originated from free electron-to-acceptor level transitions, was identified by temperature-dependent photoluminescence measurements. This acceptor-related transition was attributed to substitution of Sb dopants for Zn sites, instead of O sites, to form a complex with two Zn vacancies (VZn), the SbZn-2VZn complex. This SbZn-2VZn complex has a lower formation energy and acts as a shallow acceptor which can induce the observed strong violet luminescence. The photoresponsivity of our ZnO p-n homojunction device under a negative bias demonstrated a nearly 40-fold current gain, illustrating that our device is potentially an excellent candidate for photodetector applications in the ultraviolet wavelength region. PMID:23826909

2013-01-01

270

Photovoltaic module bypass diode encapsulation  

NASA Technical Reports Server (NTRS)

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.

1983-01-01

271

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

272

Light-Output Enhancement of GaN-Based Light-Emitting Diodes with Three-Dimensional Backside Reflectors Patterned by Microscale Cone Array  

PubMed Central

Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2 cone array followed by a 16-pair Ti3O5/SiO2 distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2 cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE. PMID:25133262

Hu, Jinyong; Wang, Hong

2014-01-01

273

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

SciTech Connect

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

Wei, Tongbo, E-mail: tbwei@semi.ac.cn; Wu, Kui; Sun, Bo; Zhang, Yonghui; Chen, Yu; Huo, Ziqiang; Hu, Qiang; Wang, Junxi; Zeng, Yiping; Li, Jinmin [State Key Laboratory of Solid-State Lighting, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083 (China); Lan, Ding [National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100080 (China)

2014-06-15

274

1.471.49-m InGaAsPInP diode laser arrays A. Gourevitch,a)  

E-print Network

for high-duty- cycle HDC operation. 1D arrays output 25 W cw at a cool- ant temperature of 16 °C. In quasi and analytically investigated. The InGaAsP/InP heterostructures were grown by orga- nometallic chemical vapor deposition. The active region con- sisted of three 6-nm-thick compressively strained quantum wells

275

Monolithic multichannel ultraviolet detector arrays and continuous phase evolution in MgxZn1xO composition spreads  

E-print Network

the spread is used as a basis for compact broadband photodetector arrays with a range of detection whose potential device applications include UV lasers,1,2 transparent con- ducting films for solar cells In the present experiment, the entire spread acts as a single compact device for simul- taneous detection

Rubloff, Gary W.

276

High beam quality in two directions and high efficiency output of a diode laser array by spectral-beam-combining.  

PubMed

Improvement is made in the traditional spectral beam combining structure by adding beam shaping element, namely Beam Transformation System (BTS). Spectral beam combination is performed in a horizontal direction by the external cavity after beam shaping. The effect of smile and the divergence of the slow axis are reduced. A standard semiconductor laser array is used in this experiment. A CW output power of 58.8 W and an electro-optic conversion efficiency of 51% are achieved. The spectral line-width is 12.7 nm. M(2) of 1.3 × 11.6 in horizontal and vertical directions are obtained. The beam quality of the output is close to that of a single emitter of the array in two directions. PMID:25089401

Zhu, Zhanda; Gou, Long; Jiang, Menghua; Hui, Yongling; Lei, Hong; Li, Qiang

2014-07-28

277

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

278

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

2013-01-01

279

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  

Microsoft Academic Search

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

Rita Marques; Micaela M. Sousa; Maria C. Oliveira; Maria J. Melo

2009-01-01

280

Simultaneous determination of in total 17 opium alkaloids and opioids in blood and urine by fast liquid chromatography–diode-array detection–fluorescence detection, after solid-phase extraction  

Microsoft Academic Search

A fast liquid chromatographic method with tandem diode array–fluorescence detection for the simultaneous determination of in total 17 opium alkaloids and opioids is presented. Blank blood and urine samples (1 ml) were spiked with different concentrations of a standard mixture, as well as with the internal standard, butorphanol (2000 ng\\/ml). After solid-phase extraction, based on weak cation exchange (Bond Elut®

R Dams; T Benijts; W. E Lambert; A. P De Leenheer

2002-01-01

281

Identification and quantification of eight flavones in root and shoot tissues of the medicinal plant Huang-qin ( Scutellaria baicalensis Georgi) using high-performance liquid chromatography with diode array and mass spectrometric detection  

Microsoft Academic Search

A method of analysis of eight flavones using high-performance liquid chromatography (HPLC)-diode array detection (DAD)-mass spectrometry (MS) in root and aerial tissues of the medicinal plant Scutellaria baicalensis was developed. The identity of the analytes was confirmed using retention time, UV–vis and mass spectral comparisons to commercial standards. Both UV–vis and mass spectral patterns were characterized for glycosylated flavones. Two

Christopher R. Horvath; Perry A. Martos; Praveen K. Saxena

2005-01-01

282

Simultaneous determination of synthetic phosphodiesterase-5 inhibitors found in a dietary supplement and pre-mixed bulk powders for dietary supplements using high-performance liquid chromatography with diode array detection and liquid chromatography–electrospray ionization tandem mass spectrometry  

Microsoft Academic Search

A high-performance liquid chromatography–diode array detection (HPLC–DAD) method and a liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI–MS\\/MS) method were developed to screen for the presence of synthetic phosphodiesterase-5 (PDE-5) inhibitors and their analogues, namely sildenafil, vardenafil, tadalafil, homosildenafil, acetildenafil and hydroxyhomosildenafil. The methods were applied to pre-market samples submitted to the Health Sciences Authority of Singapore (HSA) for testing. One

Peng Zou; Sharon Sze-Yin Oh; Peiling Hou; Min-Yong Low; Hwee-Ling Koh

2006-01-01

283

Wavelength error analysis in a multiple-beam Fizeau laser wavemeter having a linear diode array readout  

NASA Technical Reports Server (NTRS)

An estimate of the wavelength accuracy of a laser wavemeter is performed for a system consisting of a multiple-beam Fizeau interferometer and a linear photosensor array readout. The analysis consists of determining the fringe position errors which result when various noise sources are included in the fringe forming and detection process. Two methods of estimating the fringe centers are considered: (1) maximum pixel current location, and (2) average pixel location for two detectors with nearly equal output currents. Wavelength error results for these two methods are compared for some typical wavemeter parameters.

Robinson, D. M.; Fales, C. L., Jr.; Skolaut, M. W., Jr.

1985-01-01

284

Structural elucidation of catechin and epicatechin in sorrel leaf extracts using liquid-chromatography coupled to diode array-, fluorescence-, and mass spectrometric detection.  

PubMed

Flavonoids are natural compounds in medicinal herbs and posses several biological activities important in plant drug design. Especially strong antioxidant effects play an important role against radical oxidative stress causing pathological processes, such as arteriosclerosis or cancer. The aim of this work was to investigate unknown analytes found in sorrel leaf (Rumex acetosa) extracts in order to discover new leading compounds to enable quality control in phytopharmaceuticals made thereof. Therefore compounds of interest were separated after methanolic extraction by reversed-phase liquid chromatography (RP-LC) employing silica-C18 as stationary phase using gradient elution with water (10 mM H3PO4) and acetonitrile as mobile phase. Structural elucidation was carried out by diode array, fluorescence, and mass spectroscopic detection. Photodiode-array detection allowed the extraction of UV-absorbance spectra from the peaks of interest. Absorbance maxima were found at 203 and 279 nm with a shoulder at 230 nm. Additionally fluorescence emission and excitation spectra were recorded from the analytes using a fluorescence detector (FLD) after stop flow (lambdaex = 279 nm, lambdaem = 307 nm). The chromatographic reversed-phase system was coupled to an ion-trap mass spectrometer (LC-MS) by using an electrospray ionization interface (ESI). After optimization processes the separation was carried out using an ammonium acetate buffer at pH 5.5. Mass spectrometric detection turned out to be more sensitive in negative mode. Collisionally induced dissociation (CID) was used to obtain fragment ions of structural relevance (LC-MS/MS). Finally, compounds of interest coming from sorrel leaf (Rumex acetosa) eluting at low acetonitrile concentrations were confirmed to be catechin and epicatechin. PMID:15335034

Stöggl, W M; Huck, C W; Bonn, Günther K

2004-05-01

285

Simultaneous multielemental determination using a low-resolution inductively coupled plasma spectrometer/diode array detection system  

NASA Astrophysics Data System (ADS)

This work presents a versatile method for simultaneous multielemental analysis using detection with photodiode arrays and multivariate calibration techniques. A multidetection system based on an array of 1024 photodiodes was built and adapted to a commercial plasma emission scanning spectrometer. Spectral data were acquired at low resolution, allowing simultaneous monitoring of a broad spectral range and resulting in very informative but considerably overlapped spectra. Partial least squares and principal component regressions were employed to minimize overlapping problems. A numerical procedure for window selection was also developed. The new method was applied to the simultaneous determination of manganese, molybdenum, nickel, chromium and iron in steel samples, resulting in average relative prediction errors of 2.1% for Mn, 3.4% for Mo, 0.6% for Cr, 1.5% for Ni and 0.8% for Fe. These errors are comparable to those observed with conventional scanning detection systems and separate univariate calibrations, but the new method allows simultaneous determination of the five elements, with data acquisition significantly faster than in scanning instruments.

Pimentel, Maria Fernanda; de Barros Neto, Benício; Ugulino de Araújo, Mário César; Pasquini, Célio

1997-12-01

286

Analysis of alkylamides in Echinacea plant materials and dietary supplements by ultrafast liquid chromatography with diode array and mass spectrometric detection.  

PubMed

Alkylamides are a class of compounds present in plants of the genus Echinacea (Asteraceae), which have been shown to have high bioavailability and immunomodulatory effects. Fast analysis to identify these components in a variety of products is essential to profile products used in clinical trials and for quality control of these products. A method based on ultrafast liquid chromatography (UFLC) coupled with diode array detection and electrospray ionization mass spectrometry was developed for the analysis of alkylamides from the roots of Echinacea angustifolia (DC.) Hell., Echinacea purpurea (L.) Moench, and commercial dietary supplements. A total of 24 alkylamides were identified by LC-MS. The analysis time for these components is 15 min. Compared to the alkylamide profiles determined in the Echinacea root materials, the commercial products showed a more complex profile due to the blending of root and aerial parts of E. purpurea. This versatile method allows for the identification of alkylamides in a variety of Echinacea products and presents the most extensive characterization of alkylamides in E. angustifolia roots so far. PMID:21702479

Mudge, Elizabeth; Lopes-Lutz, Daise; Brown, Paula; Schieber, Andreas

2011-08-10

287

Dispersive liquid-liquid microextraction for the determination of flavonoid aglycone compounds in honey using liquid chromatography with diode array detection and time-of-flight mass spectrometry.  

PubMed

A rapid approach for the determination of eight flavonoid aglycone compounds, baicalein, hesperitin, fisetin, naringenin, chrysin, myricetin, quercetin and kaempferol, in honey samples and related products has been optimized and validated. The enriched extracts obtained by dispersive liquid-liquid microextraction (DLLME) were analyzed by liquid chromatography with diode array detection coupled to electrospray ionization and time-of-flight mass spectrometry (LC-DAD-ESI-ToFMS). For DLLME, using acetonitrile and chloroform as disperser and extractant solvents, respectively, a Taguchi experimental method was applied to find the optimal combination of following six factors: disperser and extractant solvent volumes, sodium chloride concentration, pH of the aqueous phase, honey mass and centrifugation time. The sedimented organic phase obtained after centrifugation was evaporated, reconstituted in acetonitrile and submitted to LC. The matrix effect was evaluated, and it was concluded that sample quantification can be carried out against aqueous external standards when using DAD and by matrix-matched calibration in the case of ToFMS. Detection limits in the ranges of 0.4-4 and 0.01-0.5 ng g(-1) were obtained for DAD and ToFMS, respectively. Satisfactory recovery values between 80 and 111% were obtained for three spiked samples. Honeys and related products were analyzed and flavonoids were found within a wide range. PMID:25281091

Campillo, Natalia; Viñas, Pilar; Férez-Melgarejo, Gema; Hernández-Córdoba, Manuel

2015-01-01

288

Determination of benzimidazole anthelmintics in milk and honey by monolithic fiber-based solid-phase microextraction combined with high-performance liquid chromatography-diode array detection.  

PubMed

A porous poly(methacrylic acid-co-ethylene dimethacrylate) monolithic fiber (MEMF) for solid-phase microextraction (SPME) of five benzimidazole anthelmintics was prepared by in-situ polymerization. The effect of polymerization conditions on SPME of the target analytes was studied thoroughly. The physicochemical properties of the monolith were characterized by infrared spectroscopy, elemental analysis, scanning electron microscopy, and mercury intrusion porosimetry. Several conditions affecting the extraction efficiency were investigated and, under the optimized conditions, a simple and sensitive method for the determination of trace benzimidazoles residues in milk and honey was established by coupling MEMF-SPME with high-performance liquid chromatography-diode array detection (MEMF-SPME-HPLC-DAD). Under the optimum experimental conditions, the limits of detection (S/N = 3) of the method were 0.11-0.30 ?g L(-1) for milk and 0.086-0.28 ?g L(-1) for honey. Evaluation of intra-day and inter-day precision showed reproducibility was satisfactory-relative standard deviations (RSD) for both were <10 %. Finally, the method was successfully used for determination of benzimidazole residues in milk and honey. Recoveries obtained for determination of benzimidazole anthelmintics in spiked samples ranged from 72.3 to 121 %, with RSD always <11 %. PMID:25407428

Zhang, Yong; Huang, Xiaojia; Yuan, Dongxing

2015-01-01

289

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

2014-02-15

290

Fingerprinting and simultaneous determination of alkaloids and limonins in phellodendri amurensis cortex from different locations by high-performance liquid chromatography with diode array detection.  

PubMed

A sensitive high-performance liquid chromatography method coupled with diode array detection (HPLC-DAD) was developed for the quality control of Phellodendri amurensis cortex (PAC), the quality control included the simultaneous determination of seven major constituents, namely phellodendrine, magnoflorine, jatrorrhizine, palmatine, berberine, obaculactone and obacunone. The chromatographic separation was accomplished on a Diamonsil-C18 column (4.6 mm × 200 mm, 5 ?m) with acetonitrile and 0.1% phosphoric acid (0.02 mol sodium dihydrogen phosphate per liter) by linear gradient elution. The established method was successfully validated by acceptable linearity, limits of detection and quantitation, precision, repeatability, stability and accuracy. The HPLC-DAD fingerprint chromatograph under 220 nm consisting of 21 peaks was constructed for the evaluation of the 11 batches of PAC. The HPLC fingerprints were analyzed by similarity analysis, hierarchical clustering analysis and principal component analysis. The results indicated that the combination of multicomponent determination method and chromatographic fingerprint analysis could be employed for the quantitative analysis and identification of PAC, as well as pharmaceutical products containing this herbal material. PMID:24872523

Wang, Lihong; Yan, Guangli; Zhang, Aihua; Shi, Hui; Sun, Hui; Wang, Xijun

2015-01-01

291

Ionic liquids for improving the extraction of NSAIDs in water samples using dispersive liquid-liquid microextraction by high performance liquid chromatography-diode array-fluorescence detection.  

PubMed

A rapid, sensitive and efficient analytical method based on the use of ionic liquids for determination of non-steroidal anti-inflammatory drugs (NSAIDs) in water samples was developed. High-performance liquid chromatography equipped with a diode array and fluorescence detector was used for quantification of ketoprofen, ibuprofen and diclofenac in tap and river water samples. This new method relies on the use of two ionic liquids with multiple functionalities: one functions as an extraction solvent (1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the other changes the polarity in the aqueous medium (1-butyl-3-methylimidazolium tetrafluoroborate, ([BMIM][BF4]). Factors such as the type and volume of the ILs and dispersive solvent, sample volume, and centrifugation time were investigated and optimized. The optimized method exhibited good precision, with relative standard deviation values between 2% and 3%, for the three NSAIDs. Limits of detection achieved for all of the analytes were between 17 and 95ngmL(-1), and the recoveries ranged from 89% to 103%. Furthermore, the enrichment factors ranged from 49 to 57. The proposed method was successfully applied to the analysis of NSAIDs in tap and river water samples. PMID:25618715

Toledo-Neira, Carla; Álvarez-Lueje, Alejandro

2015-03-01

292

Development and validation of a confirmatory method for the determination of sulphonamides in milk by liquid chromatography with diode array detection.  

PubMed

A simple and rapid multiresidue method for the determination of seven sulphonamides residues (sulfadiazine, sulfapyridine, sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfadimethoxine and sulfaquinoxaline) in milk samples was developed and validated. The drugs were extracted with a mixture chloroform/acetone and simply cleaned up on a cation exchange solid phase extraction column. The analytes determination was carried out using liquid chromatography with diode array detection (DAD). The procedure has validated as a quantitative confirmatory method according to the European Union (EU) Decision 2002/657/EC. The developed method shows good linearity, specificity, precision (repeatability and intra-laboratory reproducibility), ruggedness and is able to confirm each sulphonamide residue above 30mugkg(-1). Decision limits (CCalpha) around 110mugkg(-1) and recovery above 56% were obtained for all the analytes. The results of the validation process demonstrate that the method is suitable for application, as confirmatory method, in European Union statutory veterinary drug residue surveillance programmes. In addition, a hypothetical situation of sample judgement (compliance or not) in the case in which, at the same time, two different sulphonamides are found, is discussed. PMID:19286007

Gamba, Valentina; Terzano, Chiara; Fioroni, Laura; Moretti, Simone; Dusi, Guglielmo; Galarini, Roberta

2009-04-01

293

Characterisation of phenolic compounds in South African plum fruits (Prunus salicina Lindl.) using HPLC coupled with diode-array, fluorescence, mass spectrometry and on-line antioxidant detection.  

PubMed

Phenolic compounds are abundant secondary metabolites in plums, with potential health benefits believed to be due to their antioxidant activity, amongst others. Phenolic characterisation of South African Prunus salicina Lindl. plums is necessary to fully evaluate their potential health benefits. An HPLC method using diode-array detection (DAD) for quantification of phenolic compounds was improved and fluorescence detection (FLD) was added for quantification of flavan-3-ols. Validation of the HPLC-DAD-FLD method showed its suitability for quantification of 18 phenolic compounds, including flavan-3-ols using FLD, and phenolic acids, anthocyanins and flavonols using DAD. The method was suitable for characterisation of the phenolic composition of 11 South African plum cultivars and selections, including various types with yellow and red skin and flesh. The method was used in conjunction with mass spectrometry (MS) to identify 24 phenolic compounds. Neochlorogenic acid and cyanidin-3-O-glucoside were the major compounds in most of the plums, while cyanidin-3-O-glucoside was absent in Sun Breeze plums with yellow skin and flesh. Post-column on-line coupling of the ABTS•+ scavenging assay with HPLC-DAD enabled qualitative evaluation of the relative contribution of individual phenolic compounds to the antioxidant activity. The flavan-3-ols, neochlorogenic acid and cyanidin-3-O-glucoside displayed the largest antioxidant response peaks. PMID:23644975

Venter, Alet; Joubert, Elizabeth; de Beer, Dalene

2013-01-01

294

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

PubMed

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

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

2013-09-15

295

Multiresidue method for fourteen fungicides in white grapes by liquid-liquid and solid-phase extraction followed by liquid chromatography-diode array detection.  

PubMed

A quantitative, selective and sensitive HPLC method for the analysis of 14 fungicides in white grapes for vinification is described. The proposed method is based on liquid-liquid extraction (LLE) and solid-phase extraction (SPE) followed by liquid chromatography and diode array detection (HPLC-DAD). Dichloromethane-acetone (75:25, v/v) was the most appropriate solvent mix for extracting fungicides in white grapes. Silica cartridges resulted the most appropriate for extract purification purposes. Quality parameters of the proposed multiresidue method presented good recovery (ca. 85% for almost all target compounds) and precision (between 1.5 and 16%), and detection limits lower than maxima residual limits set by the 76/895/ECC and 90/642/ECC Directive. Five different white grapes for vinification produced in Rias Baixas area in Galicia (NW Spain) were analyzed in order to assess the performance of the method with real samples and to determine whether the concentration of the pesticides used exceed their maxima residue levels (MRLs). Results showed that grape concentrations for those identified fungicides were lower than those established by European legislation. PMID:12735468

Rial Otero, R; Cancho Grande, B; Simal Gándara, J

2003-04-11

296

Systematic chemical profiling of Citrus grandis 'Tomentosa' by ultra-fast liquid chromatography/diode-array detector/quadrupole time-of-flight tandem mass spectrometry.  

PubMed

Citrus grandis 'Tomentosa', as the original plant of the traditional Chinese medicine "Huajuhong", has been used as antitussive and expectorant in clinic for thousands of years. The fruit epicarp and whole fruit of this plant were both literarily recorded and commonly used. In the present study, an ultra-fast liquid chromatography coupled with diode-array detection and quadrupole/time-of-flight mass spectrometry (UFLC-DAD-Q-TOF-MS/MS) based chemical profiling method was developed for rapid holistic quality evaluation of C. grandis 'Tomentosa', which laid basis for chemical comparison of two medicinal parts. As a result, forty-eight constituents, mainly belonging to flavonoids and coumarins, were unambiguously identified by comparison with reference standards and/or tentatively characterized by elucidating UV spectra, quasi-molecular ions and fragment ions referring to information available in literature. Both of the epicarp and whole fruit samples were rich in flavonoids and coumarins, but major flavonoids contents in whole fruit were significantly higher than in epicarp (P<0.5). The proposed method could be useful in quality control and standardization of C. grandis 'Tomentosa' raw materials and its products. Results obtained in this study will provide a basis for quality assessment and further study in vivo. PMID:24370611

Li, Pan-lin; Liu, Meng-hua; Hu, Jie-hui; Su, Wei-wei

2014-03-01

297

Evaluation of Drying Process on the Composition of Black Pepper Ethanolic Extract by High Performance Liquid Chromatography With Diode Array Detector  

PubMed Central

Background Black pepper (Piper nigrum) is one of the well-known spices extensively used worldwide especially in India, and Southeast Asia. The presence of alkaloids in the pepper, namely, piperine and its three stereoisomers, isopiperine, chavicine and isochavicine are well noticed. Objectives The current study evaluated the effect of lyophilization and oven drying on the stability and decomposition of constituents of black pepper ethanolic extract. Materials and Methods In the current study ethanolic extract of black pepper obtained by maceration method was dried using two methods. The effect of freeze and oven drying on the chemical composition of the extract especially piperine and its three isomers were evaluated by HPLC analysis of the ethanolic extract before and after drying processes using diode array detector. The UV Vis spectra of the peaks at piperine retention time before and after each drying methods indicated maximum absorbance at 341.2 nm corresponding to standard piperine. Results The results indicated a decrease in intensity of the chromatogram peaks at approximately all retention times after freeze drying, indicating a few percent loss of piperine and its isomers upon lyophilization. Two impurity peaks were completely removed from the extract. Conclusions In oven dried samples two of the piperine stereoisomers were completely removed from the extract and the intensity of piperine peak was increased. PMID:24624176

Namjoyan, Foroogh; Hejazi, Hoda; Ramezani, Zahra

2012-01-01

298

Simultaneous determination of ginsenosides and lignans in Sheng-mai injection by ultra-performance liquid chromatography with diode array detection.  

PubMed

An ultra-performance liquid chromatography (UPLC) method with diode array detection was developed for simultaneous analysis of eight ginsenosides (ginsenosides Rg1, Re, Rf, Rb1, Rc, Rb2, Rb3, Rd) and one lignan (schizandrin) in Sheng-mai injection, a traditional Chinese medicine prescription widely used for the treatment of cardiovascular diseases. The chromatographic separation was performed on a Waters ACQUITY UPLC HSS T3 column (1.8 microm, 100 mm x 2.1 mm i.d.) using a linear gradient elution over 28 min with a mixture of water and acetonitrile as the mobile phase. All calibration curves showed good linearity (r2 > 0.9998) within the test ranges. Validation proved the repeatability of the method was good and recovery was satisfactory. The validated method was successfully applied to 12 batches of Sheng-mai injection. The results showed that there was a great variation among different samples. Principal component analysis (PCA) further proved considerable variations among the samples from different factories and suggested that schizandrin, ginsenosides Rb1 and Rg1 might have the greatest influence on the variation of 12 samples. In conclusion, these results demonstrated that the UPLC method proposed was very useful for the analysis and quality evaluation of Sheng-mai injection. PMID:22393825

Liu, Rui; Nie, Li-Xing; Li, Xiao-Feng; Cheng, Xian-Long; Zhang, Yuan-Yuan; Wang, Gang-Li; Lin, Rui-Chao

2012-01-01

299

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

PubMed Central

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

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

2014-01-01

300

Application of isoabsorption plots generated by high-performance liquid chromatography with diode array detection to the development of multicomponent quantitative analysis of traditional herbal medicines.  

PubMed

Multicomponent quantitative analysis is one of the mainstream quality control methods of traditional herbal medicines. Since the constituents of traditional herbal medicines samples are complex, the development of high-performance liquid chromatography methods is laborious. In this study, an isoabsorption plot, a chromatographic/spectrometric data image plotted by diode array detection was utilized to facilitate the establishment of a high-performance liquid chromatography method by optimizing and validating the detection conditions off-line. Consequently a simple, reliable and accurate method for simultaneous determination of seven active polyphenolic components (protocatechuic acid, chlorogenic acid, caffeic acid, p-coumaric acid, rosmarinic acid, scutellarin, and apigenin) in Qingfei mixture, a long-used Chinese prescription, was developed. The chromatographic separation was performed on a C18 column with gradient elution of phosphoric acid aqueous solution (0.05%, v/v) and acetonitrile, and a wavelength switch program optimized with isoplot was adopted for detection. The method was validated in terms of linearity, sensitivity, precision, repeatability, and accuracy and was successfully applied to the simultaneous determination of the seven polyphenolic components in different production batches of Qingfei Mixture. These results indicated that isoplot is an effective tool to improve the establishment of multicomponent quantitative analysis methods. PMID:25146493

Fang, Luo; Yang, Guonong; Song, Yu; Li, Fanzhu; Lin, Nengming

2014-11-01

301

Simultaneous determination of five marker compounds in Xuanfu Daizhe Tang by high-performance liquid chromatography coupled with diode array detection for quality control  

PubMed Central

Background: Xuanfu Daizhe Tang (XDT) is a classical traditional Chinese medicinal prescription that has been widely used for treating digestive system illnesses for hundreds of years. Materials and Methods: In this study, a simple and sensitive high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) method was established for the simultaneous determination of five marker compounds in XDT including chlorogenic acid, glycyrrhizic acid, ginsenoside Rg1, ginsenoside Rb1 and ginsenoside Re, for quality control of this well-known traditional Chinese medicine (TCM). Results: These compounds were separated in less than 130 min using a YMC C18 column with a gradient elution system of acetonitrile and 0.1% phosphoric acid water solution at a flow rate of 1 ml/min. All calibration curves of standard components showed good linearity with R2 >0.9991. Limit of detection and limit of quantification varied from 0.11 to 4.3 ?g/ml and 0.20 to 11.6 ?g/ml, respectively. The relative standard deviations (RSDs) of the intra-day and inter-day experiments were less than 4.72 and 5.48%, respectively. The accuracy of recovery test ranged from 95.0 to 105.0% with RSD values 1.28- 4.32%. Conclusion: The validated method is simple, reliable, and successfully applied to determine the contents of the selected compounds in XDT for quality control. PMID:24082626

Qin, Kunming; Wang, Bin; Cai, Hao; Li, Weidong; Yao, Zhongqing; Zhang, Xingde; Lu, Tulin; Cai, Baochang

2012-01-01

302

New reagent for trace determination of protein-bound metabolites of nitrofurans in shrimp using liquid chromatography with diode array detector.  

PubMed

The synthesis of derivatives of metabolites from furazolidone, furaltadone, nitrofurazone, and nitrofurantoin using a new derivatizing reagent, 2-naphthaldehyde (NTA), is described. The reaction product was used in liquid chromatography with diode array detector (LC-DAD) for determination of protein-bound metabolites of nitrofurans in shrimp followed by two steps of liquid-liquid extraction. Derivatives of nitrofuran metabolites are well separated from NTA remaining in the extract upon separation on a ChromSpher 5 Pesticide (250 x 4.6 mm, 5 microm) column at 40 degrees C with acetonitrile/5 mM ammonium acetate adjusted to pH 7.5 gradient as the mobile phase and DAD detection at 308 nm except for naphthyl derivative of 1-aminohydantoin at 310 nm. The high absorptivity of these derivatives makes simultaneous screening of these metabolites in shrimp at 1 microg/kg possible for the first time using LC-DAD. The method was validated using blank shrimp fortified with all four metabolites at 1, 1.5, and 2 microg/kg. Recoveries were >86% with relative standard deviations of <14% for all four metabolites. Comparison between LC-DAD and APCI-MS/MS shows very good agreement for shrimp samples. PMID:19199604

Chumanee, Saowapa; Sutthivaiyakit, Somyote; Sutthivaiyakit, Pakawadee

2009-03-11

303

Determination of sulfadiazine in Jiaozhou Bay using molecularly imprinted solid-phase extraction followed by high-performance liquid chromatography with a diode-array detector.  

PubMed

A highly selective sample cleanup procedure featuring molecularly imprinted solid-phase extraction (MISPE) was developed for the isolation and determination of sulfadiazine (SDZ) in seawater samples from Jiaozhou Bay, China. The molecularly imprinted polymer (MIP) was prepared using SDZ as the template molecule and methacrylic acid as the functional monomer. The MIP was used as a selective sorbent for the solid-phase extraction of SDZ. An off-line MISPE method followed by high-performance liquid chromatography (HPLC) with diode-array detection was established for the analysis of SDZ. Good linearity of the MISPE column for SDZ standard solutions was obtained within 0-200?gL(-1) (R(2)>0.99). The recoveries of spiked seawater samples were satisfactory as high as 88%. Finally, seven samples in Jiaozhou Bay were determined and there was no sulfadiazine found except #2 and #5 sample. The concentrations were respectively 0.33?gL(-1) and 0.28?gL(-1), and the relative standard deviations were 1.35% and 4.13% (n=3). PMID:24657411

Lian, Ziru; He, Xingliang; Wang, Jiangtao

2014-04-15

304

New method for the quantification of dequalinium cations in pharmaceutical samples by absorption and fluorescence diode array thin-layer chromatography.  

PubMed

A diode array HPTLC method for dequalinium chloride in pharmaceutical preparations is presented. For separation a Nano TLC silica gel plate (Merck) is used with the mobile phase methanol-7.8% aqueous NH(4)(+)CH(3)COO(-) (17:3, v/v) over a distance of 6 cm. Dequalinium chloride shows an R(F) value of 0.58. Pure dequalinium chloride is measured in the wavelength range from 200 to 500 nm and shows several by-products, contour plot visualized in absorption, fluorescence and using the Kubelka-Munk transformation. Scanning of a single track in absorption and fluorescence measuring 600 spectra in the range from 200 to 1100 nm takes 30s. As a sample pre-treatment of an ointment it is simply dissolved in methanol and can be quantified in absorption from 315 to 340 nm. The same separation can also be quantified using fluorescence spectrometry in the range from 355 to 370 nm. A new staining method for dequalinium chloride, using sodium tetraphenyl borate/HCl in water allows a fluorescence quantification in the range from 445 to 485 nm. The linearity range of absorption and fluorescence measurements is from 10 to 2000 ng. Sugar-containing preparations like liquids or lozenges with a reduced sample pre-treatment can be reliably quantified only in fluorescence. The total for the quantification of an ointment sample (measuring four standards and five samples), including all sample pre-treatment steps takes less than 45 min! PMID:19446824

Hiegel, Katharina; Spangenberg, Bernd

2009-06-19

305

Enantiospecific resolution of rabeprazole by liquid chromatography on amylose-derived chiral stationary phase using photo diode array and polarimetric detectors in series.  

PubMed

A simple and rapid liquid chromatographic method for enantioselective separation and determination of R-(+) and S-(-) enantiomers of rabeprazole in drugs and pharmaceuticals using photo diode array (PDA) and polarimetric detectors connected in series was developed. Chiralpak AD-H (250mmx4.6mm) 5mum column packed with amylose tris(3,5-dimethylphenyl carbamate) as a stationary phase and the mobile phase containing n-hexane:ethanol:2-propanol(75:15:10, v/v/v) in an isocratic mode has yielded baseline separation with resolution greater than 3.0 at 40 degrees C. Effects of ethanol, 2-propanol and temperature on separation were studied for optimum resolution. Lansoprazole sulphone was used as an internal standard (IS) for quantitative determination of individual enantiomers in bulk drugs as well as pharmaceutical formulations. The method was validated in terms of accuracy, precision and linearity according to ICH guidelines. The linearity of the method was studied in the range of 0.5-50mug/ml and the r(2) was >0.9997. The inter- and intra-day precision of assay were determined (R.S.D.<1%) and the recoveries were in the range of 99.63-100.22% with <1% R.S.D. The limits of detection (LOD) and quantification (LOQ) were 0.02mug/ml and 0.07mug/ml for both the enantiomers, respectively. PMID:18970843

Nageswara Rao, R; Narasa Raju, A; Nagaraju, D

2006-11-15

306

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

307

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

308

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

309

Ultraviolet Light Stable and Transparent Sol-Gel Methyl Siloxane Hybrid Material for UV Light-Emitting Diode (UV LED) Encapsulant.  

PubMed

An ultraviolet (UV) transparent and stable methyl-siloxane hybrid material was prepared by a facile sol-gel method. The transparency and stability of a UV-LED encapsulant is an important issue because it affects UV light extraction efficiency and long-term reliability. We introduced a novel concept for UV-LED encapsulation using a thermally curable oligosiloxane resin. The encapsulant was fabricated by a hydrosilylation of hydrogen-methyl oligosiloxane resin and vinyl-methyl siloxane resin, and showed a comparable transmittance to polydimethylsiloxane (PDMS) in the UVB (?300 nm) region. Most remarkably, the methyl-siloxane hybrid materials exhibited long-term UV stability under light soaking in UVB (?300 nm) for 1000 h. PMID:25564875

Bae, Jun-Young; Kim, YongHo; Kim, HweaYoon; Kim, YuBae; Jin, Jungho; Bae, Byeong-Soo

2015-01-21

310

Qualitative and quantitative analysis of anthraquinones in rhubarbs by high performance liquid chromatography with diode array detector and mass spectrometry.  

PubMed

Rhubarb is well known in traditional Chinese medicines (TCMs) mainly due to its effective purgative activity. Anthraquinones, including anthraquinone derivatives and their glycosides, are thought to be the major active components in rhubarb. To improve the quality control method of rhubarb, we studied on the extraction method, and did qualitative and quantitative analysis of widely used rhubarbs, Rheum tanguticum Maxim. ex Balf. and Rheum palmatum L., by HPLC-photodiode array detection (HPLC-DAD) and HPLC-mass spectrum (HPLC-MS) on a Waters SymmetryShield RP18 column (250 mm × 4.6 mm i.d., 5 ?m). Amount of five anthraquinones was viewed as the evaluating standard. A standardized characteristic fingerprint of rhubarb was provided. From the quantitative analysis, the rationality was demonstrated for ancestors to use these two species of rhubarb equally. Under modern extraction methods, the amount of five anthraquinones in Rheum tanguticum Maxim. ex Balf. is higher than that in Rheum palmatum L. Among various extraction methods, ultrasonication with 70% methanol for 30 min is a promising one. For HPLC analysis, mobile phase consisted of methanol and 0.1% phosphoric acid in water with a gradient program, the detection wavelength at 280nm for fingerprinting analysis and 254 nm for quantitative analysis are good choices. PMID:23870882

Wei, Shao-yin; Yao, Wen-xin; Ji, Wen-yuan; Wei, Jia-qi; Peng, Shi-qi

2013-12-01

311

Quantitative Analysis of the Head Scatter and Jaw Transmission Correction Factor for Commissioning of Enhanced Dynamic Wedge Fields Using a MapCHECK 2 Diode Array  

NASA Astrophysics Data System (ADS)

Quality assurance in radiation oncology treatment planning requires independent verification of dose to be delivered to a patient through "second check" calculations for simple plans as well as planar dose fluence measurements for more complex treatments, such as intensity modulated radiation treatments (IMRT). Discrepancies between treatment planning system (TPS) and second check calculations created a need for treatment plan verification using a two dimensional diode array for Enhanced Dynamic Wedge (EDW) fields. While these measurements met clinical standards for treatment, they revealed room for improvement in the EDW model. The purpose of this study is to analyze the head scatter and jaw transmission effects of the moving jaw in EDW fields by measuring dose profiles with a two dimensional diode array in order to minimize differences between the manufacturer provided fluence table (Golden Segmented Treatment Table) and actual machine output. The jaw transmission effect reduces the dose gradient in the wedge direction due to transmission photons adding dose to the heel region of the field. The head scatter effect also reduces the gradient in the dose profile due to decreased accelerator output at increasingly smaller field sizes caused by the moving jaw. The field size continuously decreases with jaw motion, and thus the toe region of the wedge receives less dose than anticipated due to less head scatter contribution for small field sizes. The Golden Segmented Treatment Table (GSTT) does not take these factors into account since they are specific to each individual machine. Thus, these factors need to be accounted for in the TPS to accurately model the gradient of the wedge. The TPS used in this clinic uses one correction factor (transmission factor) to account for both effects since both factors reduce the dose gradient of the wedge. Dose profile measurements were made for 5x5 cm2, 10x10 cm2, and 20x20 cm2 field sizes with open fields and 10°, 15°, 20°, 25°, 30°, 45°, and 60° wedges for 6 MV and 18 MV beams and compared with TPS generated profiles. The transmission factor was adjusted for the 18 MV beam to obtain a better correlation between planned and measured dose gradient by reducing the gradient of the wedge in the TPS. This correction resulted in an average and maximum pass rate improvement for patient plans at a distance to agreement of 3% 3mm of 1.07% and 3.9% respectively. The off axis ratio data in the second check calculation software was also adjusted to bring the dose agreement between the initial TPS calculation and second check calculation within clinical standards. This study demonstrated the ability to adjust the EDW gradient in a treatment planning system to improve the differences in machine output specific to each machine and the manufacturer provided GSTT.

Dickerson, Edward C.

312

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. PMID:23060695

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

2012-01-01

313

Characterization of aquatic dissolved organic matter by asymmetrical flow field-flow fractionation coupled to UV-Visible diode array and excitation emission matrix fluorescence.  

PubMed

Flow field-flow fractionation (FlFFF) with on-line UV/Visible diode array detector (DAD) and excitation emission matrix (EEM) fluorescence detector has been developed for the characterization of optical properties of aquatic dissolved organic matter (DOM) collected in the Otonabee River (Ontario, Canada) and Athabasca River (Alberta, Canada). The molecular weight (MW) distribution of DOM was estimated using a series of organic macromolecules ranging from 479 to 66,000 Da. Both the number-average (M(n)) and weight-average (M(w)) molecular weights of Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA) determined using these macromolecular standards were comparable to those obtained using polystyrenesulfonate (PSS) standards, suggesting that organic macromolecules can be used to estimate MW of natural organic colloids. The MW of eight river DOM samples determined by this method was found to have an M(n) range of 0.8-1.1 kDa, which agrees with available literature estimates. The FlFFF-DAD-EEM system provided insight into the MW components of river DOM including the optical properties by on-line absorbance and fluorescence measurement. A red-shift in emission and excitation wavelength maxima associated with lower spectral slope ratios (S(R)=S???????:S???????) was related to higher MW DOM. However, DOM of different origins at similar MW also showed significant difference in optical properties. A difference of 47 and 40 nm in excitation and emission peak C maxima was found. This supports the hypothesis that river DOM is not uniform in size and optical composition. PMID:21227433

Guéguen, Céline; Cuss, Chad W

2011-07-01

314

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

2012-06-20

315

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

PubMed

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

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

2015-01-15

316

Near ultraviolet InGaN/AlGaN-based light-emitting diodes with highly reflective tin-doped indium oxide/Al-based reflectors.  

PubMed

The enhanced light output power of a InGaN/AlGaN-based light-emitting diodes (LEDs) using three different types of highly reflective Sn-doped indium oxide (ITO)/Al-based p-type reflectors, namely, ITO/Al, Cu-doped indium oxide (CIO)/s-ITO(sputtered)/Al, and Ag nano-dots(n-Ag)/CIO/s-ITO/Al, is presented. The ITO/Al-based reflectors exhibit lower reflectance (76 - 84% at 365 nm) than Al only reflector (91.1%). However, unlike Al only n-type contact, the ITO/Al-based contacts to p-GaN show good ohmic characteristics. Near-UV (365 nm) InGaN/AlGaN-based LEDs with ITO/Al, CIO/s-ITO/Al, and n-Ag/CIO/s-ITO/Al reflectors exhibit forward-bias voltages of 3.55, 3.48, and 3.34 V at 20 mA, respectively. The LEDs with the ITO/Al and CIO/s-ITO/Al reflectors exhibit 9.5% and 13.5% higher light output power (at 20 mA), respectively, than the LEDs with the n-Ag/CIO/s-ITO/Al reflector. The improved performance of near UV LEDs is attributed to the high reflectance and low contact resistivity of the ITO/Al-based reflectors, which are better than those of conventional Al-based reflectors. PMID:24216898

Choi, Chang-Hoon; Han, Jaecheon; Park, Jae-Seong; Seong, Tae-Yeon

2013-11-01

317

Preparation of Phi29 DNA Polymerase Free of Amplifiable DNA Using Ethidium Monoazide, an Ultraviolet-Free Light-Emitting Diode Lamp and Trehalose  

PubMed Central

We previously reported that multiply-primed rolling circle amplification (MRPCA) using modified random RNA primers can amplify tiny amounts of circular DNA without producing any byproducts. However, contaminating DNA in recombinant Phi29 DNA polymerase adversely affects the outcome of MPRCA, especially for negative controls such as non-template controls. The amplified DNA in negative control casts doubt on the result of DNA amplification. Since Phi29 DNA polymerase has high affinity for both single-strand and double-stranded DNA, some amount of host DNA will always remain in the recombinant polymerase. Here we describe a procedure for preparing Phi29 DNA polymerase which is essentially free of amplifiable DNA. This procedure is realized by a combination of host DNA removal using appropriate salt concentrations, inactivation of amplifiable DNA using ethidium monoazide, and irradiation with visible light from a light-emitting diode lamp. Any remaining DNA, which likely exists as oligonucleotides captured by the Phi29 DNA polymerase, is degraded by the 3?-5? exonuclease activity of the polymerase itself in the presence of trehalose, used as an anti-aggregation reagent. Phi29 DNA polymerase purified by this procedure has little amplifiable DNA, resulting in reproducible amplification of at least ten copies of plasmid DNA without any byproducts and reducing reaction volume. This procedure could aid the amplification of tiny amounts DNA, thereby providing clear evidence of contamination from laboratory environments, tools and reagents. PMID:24505243

Takahashi, Hirokazu; Yamazaki, Hiroyuki; Akanuma, Satoshi; Kanahara, Hiroko; Saito, Toshiyuki; Chimuro, Tomoyuki; Kobayashi, Takayoshi; Ohtani, Toshio; Yamamoto, Kimiko; Sugiyama, Shigeru; Kobori, Toshiro

2014-01-01

318

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

319

Ultraviolet C upconversion fluorescence of trivalent erbium in BaGd2ZnO5 phosphor excited by a visible commercial light-emitting diode.  

PubMed

Multiple ultraviolet (UV) emission bands have been obtained in Er3+ doped BaGd2ZnO5 phosphor under the excitation of a 532 nm solid-state laser, and the emission peaks at 217, 254, 278, 296, 314, 348, 374 and 394 nm were determined to stem from the high-energy states 4D(1/2), 4D(7/2), 2H(9/2), 2P(1/2), 2P(3/2), 4G(7/2), 4G(11/2), 4H(9/2) of trivalent erbium, respectively. Some UV emission bands in the UVC region can be observed when the sample was excited by commercial green (529 nm) and blue (460 nm) LED. In view of the small size, low-drive voltage and price of LED, UVC upconversion phosphor BaGd2ZnO5:Er3+ excited by visible LED has potential application in environmental sciences. PMID:24686659

Yang, Yanmin; Mi, Chao; Su, Xianyuan; Jiao, Fuyun; Liu, Linlin; Zhang, Jiao; Yu, Fang; Li, Xiaodong; Liu, Yanzhou; Mai, Yaohua

2014-04-01

320

Design of a silicon avalanche photodiode pixel with integrated laser diode using back-illuminated crystallographically etched silicon-on-sapphire with monolithically integrated microlens for dual-mode passive and active imaging arrays  

NASA Astrophysics Data System (ADS)

There is a growing need in scientific research applications for dual-mode, passive and active 2D and 3D LADAR imaging methods. To fill this need, an advanced back-illuminated silicon avalanche photodiode (APD) design is presented using a novel silicon-on-sapphire substrate incorporating a crystalline aluminum nitride (AlN) antireflective layer between the silicon and R-plane sapphire. This allows integration of a high quantum efficiency silicon APD with a gallium nitride (GaN) laser diode in each pixel. The pixel design enables single photon sensitive, solid-state focal plane arrays (FPAs) with wide dynamic range, supporting passive and active imaging capability in a single FPA. When (100) silicon is properly etched with TMAH solution, square based pyramidal frustum or mesa arrays result with the four mesa sidewalls of the APD formed by (111) silicon planes that intersect the (100) planes at a crystallographic angle, ? c = 54.7°. The APD device is fabricated in the mesa using conventional silicon processing technology. The GaN laser diode is fabricated by epitaxial growth inside of an inverted, etched cavity in the silicon mesa. Microlenses are fabricated in the thinned, and AR-coated sapphire substrate. The APDs share a common, front-side anode contact, and laser diodes share a common cathode. A low resistance (Al) or (Cu) metal anode grid fills the space between pixels and also inhibits optical crosstalk. SOS-APD arrays are flip-chip bump-bonded to CMOS readout ICs to produce hybrid FPAs. The square 27 ?m emitter-detector pixel achieves SNR > 1 in active detection mode for Lambert surfaces at 1,000 meters.

Stern, Alvin G.

2010-08-01

321

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

2012-03-01

322

Multi-residue determination of eleven anticoagulant rodenticides by high-performance liquid chromatography with diode array/fluorimetric detection: investigation of suspected animal poisoning in the period 2012-2013 in north-eastern Italy.  

PubMed

Misuse or deliberate abuse of anticoagulant rodenticides (AR) may often result in incidental or malicious non-target animal poisoning. This study presents preliminary results of the analysis of 561 real suspected samples, ranging from baits to livers and stomach contents, collected at the Istituto Zooprofilattico Sperimentale delle Venezie (official referral laboratory for the regions of north-eastern Italy), in the period 2012-2013. Samples were analyzed by a method based on a combination of liquid chromatography with diode array/fluorescence detection (HPLC-DAD/F) able to identify 11 different AR (brodifacoum, bromadiolone, chloropahacinone, coumachlor, coumafuryl, coumatetralyl, difenacoum, diphacinone, flocoumafen, pindone, warfarin). PMID:25195128

Gallocchio, Federica; Basilicata, Lara; Benetti, Cristiana; Angeletti, Roberto; Binato, Giovanni

2014-11-01

323

[Analysis of ginsenosides in Sheng-Mai-Yin decoction by high performance liquid chromatography-diode array detection-electrospray mass spectrometry].  

PubMed

A method of high performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD/MS) in negative ion mode was developed for the analysis of ginsenosides in Sheng-Mai-Yin decoction (Panax gingeng C. A. Mey, Ophiopogon japonicus (Thunb.) Ker-Gawl, Shisandra chinensis (Turcz.) Baill.). The analyses were preformed on a reversed-phase C18 column (4.6 mm i.d. x 150 mm, 5 microm) using a binary eluent (10 mmol/L ammonium acetate (A) and acetonitrile (B), 1 mL/min) under gradient conditions (60% A - 40% A at 0 - 30 min, 40% A - 30% A at 30 - 40 min). Seventeen ginsenosides (20 (R) -Rh1, Rh2, Rg3, Rg2; 20 (S) -Rh1, Rh2, Rg3, Rg2; Rf, Rg6, Rg5, F4, Rk1, Rk3, Rh4; 20 (S)- and 20 (R) -protopanaxatriol) were well separated and detected at 203 nm by a DAD detector. The effluent from the DAD detector was introduced into the electrospray ionization (ESI) source in a post-column splitting flow rate at 0.3 mL/min. In the mass spectrum two major ions [M - H]- and [M + AcO]- were observed for ginsenoside standards (20 (R) -Rh1, Rg3, Rh2; 20 (S) -Rh1, Rg3, Rh2; 20 (S)- and 20 (R) -protopanaxatriol) and ginsenosides in Sheng-Mai-Yin decoction. Some other ions [M - Glc - H]-, [M - 2Glc - H]-, [M - Rha - H- and [M - Rha - Glc - H]- were also found in the mass spectrum of ginsenosides of Sheng-Mai-Yin decoction. In the decoction process ginsenosides changed into constituents of moderate and low polarity by hydrolysis, isomerization and dehydration at the site of C-20 and hydrolysis reaction also occurred at the site of C-3 or C-6. The work above presents a quick and accurate assay method which can could be used for the qualitative analysis of ginsenosides in Sheng-Mai-Yin decoction and the quality control of Sheng-Mai-Yin preparation. PMID:17017152

Wang, Zhanliang; Wang, Hong; Chen, Shizhong

2006-07-01

324

The detection of iron protoporphyrin (heme b) in phytoplankton and marine particulate material by electrospray ionisation mass spectrometry - comparison with diode array detection.  

PubMed

A mass spectrometric (MS) method for the identification of iron protoporphyrin (IX) (FePTP, heme b) in marine particulate material and phytoplankton is described. Electrospray ionisation of FePTP produced the molecular Fe(III)PTP(+) ion (m/z=616) or the pseudomolecular [Fe(II)PTP + H](+) ion (m/z=617), depending on the oxidation state of the central iron ion. Collision induced dissociation (CID) in the ion trap mass spectrometer resulted in a single detected product ion (m/z=557) indicative of loss of ethanoic acid from a carboxylic acid side chain. Widening the isolation width to 616±3 resulted in production of a mass spectrum demonstrating the distinctive isotopic ratio of the iron containing fragment, further increasing the specificity of the analysis. Selective reactant monitoring (SRM) of the fragment ion (m/z=557) was applied to the detection of FePTP after chromatography of ammoniacal OGP extracts of marine samples. The detection limit for FePTP analysed by SRM after chromatography was 1.2±0.5fmol. For phytoplankton samples, reasonably good agreement was achieved between results obtained with SRM and those obtained by monitoring absorbance at ?=400nm using a diode array detector (DAD). Use of SRM for analysis of particulate material obtained from the high latitude North Atlantic allowed for the analysis of FePTP in the presence of a co-eluting compound that interfered with detection by DAD. Simultaneous collection of mass spectra from m/z=300 to 1500 resulted in identification of the pseudomolecular ion for the interfering compound. The CID fragmentation pattern and UV-visible mass spectra indicated that the interfering compound was a previously unidentified chlorin type compound. Comparison of FePTP determined by SRM and DAD on samples where this compound could not be detected showed that results collected using the two methods correlated. The use of both MS and DAD results in a powerful tool for quantifying this important biogenic component of the particulate iron pool. PMID:25109859

Gledhill, Martha

2014-09-01

325

Extending the Astronomical Application of Photon Counting HgCdTe Linear Avalanche Photo-Diode Arrays to Low Background Space Observations.  

NASA Astrophysics Data System (ADS)

The high quantum efficiency and very low dark current, together with the ability to set the wavelength cutoff from one to far beyond 5.5 microns, of large format HAWAII HgCdTe arrays have already made them the workhorse for NASA space astronomy (and related) observations in the 1 to 5.5 micron infrared. They have performed outstandingly on Hubble Wide Field Camera 3 and WISE (and also Deep Impact/EPOXI and OCO-2) and are crucial to the two major NASA Astrophysics missions, JWST and WFIRST, and to Euclid. The proposed investigation seeks to extend these benefits to the most demanding observations those that seek to wring information from only a few photons (starved due to either the intrinsic faintness of the source or the need for high spectral or time resolution) or to discriminate a weak signature against a bright source. We will characterize, and optimize for space astronomy observations, the unique linear avalanche properties of HgCdTe photo-diodes (HgCdTe L-APDs) that allow noiseless (i.e. faithfully preserves the Poisson statistics of the incoming photons) avalanche multiplication of individual photo-electrons. 2.5 micron HgCdTe L-APD technology, developed for infrared eye-safe LIDAR and range gated imaging, is already benefiting infrared wavefront sensing for ground based adaptive optics. In HgCdTe the L-APD gain and the onset voltage for tunneling current are exponential functions of bandgap while also varying with cryogenic operating temperature. The unique HgCdTe bandgap engineering that allows tuning of the cutoff wavelength can be used to critically improve avalanche performance for specific applications. We will thoroughly evaluate avalanche performance at several representative bandgaps so as to allow model prediction of performance over the critical 1 to 5 micron spectral interval. The proposed investigation will hybridize modest 32x32 arrays of HgCdTe L-APDs to photon counting readouts already developed under another award and characterize their infrared photon counting performance at the low and ultra-low backgrounds required for NASA space astronomy missions. Specifically this will involve 1) Measuring the gain normalized dark count rate and avalanche gain of 2.5, 3.3 and 4 micron cutoff HgCdTe at cryogenic temperatures from 30 to 80 K and bias voltages up to 20 V, 2) Using these results to validate and refine models of avalanche gain along with generation- recombination and surface trap induced tunneling current in L-APD HgCdTe and, 3) Modeling the gain normalized dark count rate, surface tunneling current and avalanche gain of 2 to 5 micron cutoff HgCdTe L-APD arrays for astrophysics and other NASA missions. The overall objective of the investigation is to develop the tools to identify the sweet spot in bandgap and cryogenic operating temperature for each specific NASA astrophysics mission and to accurately predict ultimate performance. HgCdTe L-APD technology offers to NASA the ultimate performance for space astronomy in photon starved applications such as: 1) ultra-low background, extra- Zodiacal imaging and faint object spectroscopy from elliptical orbits beyond the asteroid belt with missions such as Extra-Zodiacal Explorer, 2) spectroscopy of the faintest O/IR sources from near earth and L-2 orbit at moderate to high resolution and, 3) time domain astronomy observations (photometric or spectral variations at frequencies above 1 Hz) of sources as diverse as close binaries, accretion disks, compact objects etc. HgCdTe L- APD arrays have the potential to enable new classes of missions and to bring critical observations within reach of the capabilities of the NASA SMD Astrophysics Explorer program. As they utilize the same mature TRL base as the large format JWST HgCdTe arrays, requiring only qualification of n-on-p material operated at higher bias voltages, the path to flight qualification is unusually direct.

Hall, Donald

326

Determination of aldicarb, carbofuran and some of their main metabolites in groundwater by application of micellar electrokinetic capillary chromatography with diode-array detection and solid-phase extraction.  

PubMed

This paper describes a UV detection method for the pesticides aldicarb and carbofuran, and some of their main metabolites, aldicarb-sulfoxide, aldicarb-sulfone and 3-hydroxy-carbofuran, in ground waters. Micellar electrokinetic chromatography (MEKC) with diode-array detection was developed for their determination at 210 nm. The experimental study was performed using sodium dodecyl sulfate (SDS) at a concentration level of 140 mM, and a buffer of borax/HCl 20 mM at pH 8 which gives the best resolution with an analysis time of less than 20 min. Different instrumental parameters such as voltage (23 kV), injection time (12 s) and temperature (25 degrees C) were optimized. The detection limits were in the range 2-7.4 microg glitre(-1) by solid-phase extraction (SPE) with a subsequent evaporation step. Groundwater spiked samples were pre-concentrated off-line with graphite carbon and subsequently analyzed by MEKC with diode-array detection yielding average recoveries between 77 and 97% (n = 4) with RSD between 2-7%. PMID:15260298

Arráez-Román, David; Segura-Carretero, Antonio; Cruces-Blanco, Carmen; Fernández-Gutiérrez, Alberto

2004-07-01

327

Satellite laser ranging using pseudonoise code modulated laser diodes  

Microsoft Academic Search

Techniques for satellite laser ranging have historically employed high-energy pulsed lasers as the optical transmitter. The output power currently available from laser diodes and laser diode arrays makes them a viable alternative to the pulsed laser for ranging applications. The modulation of a laser diode is examined by a pseudonoise code which produces a CW ranging signal with equivalent average

David M. Norman; Chester S. Gardner

1988-01-01

328

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.

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

1991-01-01

329

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

330

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

2012-09-25

331

{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

332

Semicondictor Diode  

NSDL National Science Digital Library

Presented by the University of Cambridge's Engineering Department, this page contains an interactive semicondictor diode animation. Additionally, a quiz and short exam are attached to help users better understand the concept of this digital model.

2008-10-23

333

Qualitative and quantitative analysis of the major constituents in Jin-Mu-Gan-Mao tablet by high-performance liquid chromatography with diode-array detection and quadrupole time-of-flight tandem mass spectrometry.  

PubMed

Jin-Mu-Gan-Mao tablet is a well-known traditional Chinese medicinal preparation, which has been used to treat the common cold in China. In this study, a systematic method was established for the qualitative and quantitative analysis of the major constituents in Jin-Mu-Gan-Mao tablet. First, a method of high-performance liquid chromatography with diode-array detection and quadrupole time-of-flight mass spectrometry was developed for identification of the multi-constituents. Thirty-one compounds including ten phenolic acids, 18 flavonoids, and three iridoid glycosides were clearly identified by comparison with the reference standards, and 11 compounds were deduced by comparison with the literature data. Second, a new quantitative analysis method of Jin-Mu-Gan-Mao tablet was established by high-performance liquid chromatography with diode-array detection. Twelve compounds, either with high contents or strong bioactivities, were chosen as marker components. This analytical method was validated through intra- and interday precision, repeatability, and stability, with respective relative standard deviations less than 1.74, 2.54, 2.44, and 2.48%. The limits of detection and quantification were less than 0.327 and 0.881 ?g/mL, respectively. The overall recoveries ranged from 97.04-102.76% (relative standard deviation ? 2.91%). Then this validated method was applied to determine ten batches of Jin-Mu-Gan-Mao tablet. The results indicated that these new approaches can be applicable for the qualitative and quantitative analysis of Jin-Mu-Gan-Mao tablet. PMID:25229383

Huang, Mingqing; Xu, Shuyu; Xu, Wen; Chen, Daxing; Chu, Kedan; Xu, Wei; Peng, Jun; Lu, Jinjian

2014-12-01

334

Ultraviolet Astronomy  

Microsoft Academic Search

Ultraviolet (UV) astronomy is the study of the electromagnetic radiation emitted by celestial bodies in the UV wavelength range, a portion of the spectrum simultaneously shielded by our own atmosphere and beyond the sensory limits of our sight....

L. Buson

2003-01-01

335

Preparing nano-hole arrays by using porous anodic aluminum oxide nano-structural masks for the enhanced emission from InGaN/GaN blue light-emitting diodes  

NASA Astrophysics Data System (ADS)

We report on the achievement of the enhanced cathodoluminescence (CL) from InGaN/GaN light-emitting diodes (LEDs) by using roughening surface. Nanoporous anodic aluminum oxide (AAO) mask was utilized to form nano-hole arrays on the surface of InGaN/GaN LEDs. AAO membranes with ordered hexagonal structures were fabricated from aluminum foils by a two-step anodization method. The average pore densities of ?1.0 × 1010 cm?2 and 3.0 × 1010 cm?2 were fabricated with the constant anodization voltages of 25 and 40 V, respectively. Anodic porous alumina film with a thickness of ?600 nm has been used as a mask for the induced couple plasma etching process to fabricate nano-hole arrays on the LED surface. Diameter and depth of nano-holes can be controlled by varying the etching duration and/or the diameter of AAO membranes. Due to the reduction of total internal reflection obtained in the patterned samples, we have observed that the cathodoluminescence intensity of LEDs with nanoporous structures is increased up to eight times compared to that of samples without using nanoporous structure.

Nguyen, Hoang-Duy; Nguyen, Hieu Pham Trung; Lee, Jae-jin; Mho, Sun-Il

2012-12-01

336

Isolation and identification of phenolic compounds from rum aged in oak barrels by high-speed countercurrent chromatography/high-performance liquid chromatography-diode array detection-electrospray ionization mass spectrometry and screening for antioxidant activity.  

PubMed

Beverages, especially wines are well-known to contain a variety of health-beneficial bioactive substances, mainly of phenolic nature which frequently exhibit antioxidant activity. Significant information is available about the separation and identification of polyphenols from some beverages by chromatographic and spectroscopic techniques, but considerably poor is chemical data related to the polyphenolic content in rums. In this paper, a method involving the all-liquid chromatographic technique of high-speed countercurrent chromatography (HSCCC) combined with high-performance liquid chromatography coupled with diode-array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS(n)) has been successfully applied for separation and identification of phenolic compounds in an aged rum. Besides, the phenolic fraction (PF) was assayed for its antioxidant effects using three different free radical in vitro assays (DPPH·, RO(2)· and spontaneous lipid peroxidation (LPO) on brain homogenates) and on ferric reducing antioxidant power (FRAP). Results showed that PF potently scavenged DPPH and strongly scavenged peroxyl radicals compared to ascorbic acid and butylated hydroxytoluene (BHT); and almost equally inhibited LPO on brain homogenates subjected to spontaneous LPO when compared to quercetin. Moreover, PF also exhibited strong reducing power. This chemical analysis illustrates the rich array of phenols in the aged rum and represents a rapid and suitable method for the isolation and identification of phenolic compounds from mixtures of considerable complexity, achieving high purity and reproducibility with the use of two separation steps. PMID:21907994

Regalado, Erik L; Tolle, Sebastian; Pino, Jorge A; Winterhalter, Peter; Menendez, Roberto; Morales, Ana R; Rodríguez, José L

2011-10-14

337

Efficient flip-chip InGaN micro-pixellated light-emitting diode arrays: promising candidates for micro-displays and colour conversion  

Microsoft Academic Search

Flip-chip InGaN micro-pixellated LED arrays with high pixel density and improved device performance are presented. The devices, with 64 × 64 elements, each of which have a 20 µm emission aperture on a 50 µm pitch, are fabricated with a matrix-addressable scheme at blue (470 nm) and UV (370 nm) wavelengths, respectively. These devices are then flip-chip bonded onto silicon

Z. Gong; E. Gu; S. R. Jin; D. Massoubre; B. Guilhabert; H. X. Zhang; M. D. Dawson; V. Poher; G. T. Kennedy; P. M. W. French; M. A. A. Neil

2008-01-01

338

A 64 single photon avalanche diode array in 0.18 µm CMOS standard technology with versatile quenching circuit for quick prototyping  

NASA Astrophysics Data System (ADS)

Several works have demonstrated the successfully integration of Single-photon avalanche photodiodes (SPADs) operating in Geiger mode in a standard CMOS circuit for the last 10 years. These devices offer an exceptional temporal resolution as well as a very good optical sensitivity. Nevertheless, it is difficult to predict the expected performances of such a device. Indeed, for a similar structure of SPAD, some parameter values can differ by two orders of magnitude from a technology to another. We proposed here a procedure to identify in just one or two runs the optimal structure of SPAD available for a given technology. A circuit with an array of 64 SPAD has been realized in the Tower-Jazz 0.18 ?m CMOS image sensor process. It encompasses an array of 8 different structures of SPAD reproduced in 8 diameters in the range from 5 ?m up to 40 ?m. According to the SPAD structures, efficient shallow trench insulator and/or P-Well guard ring are used for preventing edge breakdown. Low dark count rate of about 100 Hz are expected thanks to the use of buried n-well layer and a high resistivity substrate. Each photodiode is embedded in a pixel which includes a versatile quenching circuitry and an analog output of its cathode voltage. The quenching system is configurable in four operation modes; the SPAD is disabled, the quenching is completely passive, the reset of the photodiode is active and the quenching is fully active. The architecture of the array makes possible the characterization of every single photodiode individually. The parameters to be measured for a SPAD are the breakdown avalanche voltage, the dark count rate, the dead time, the timing jitter, the photon detection probability and the after-pulsing rate.

Uhring, Wilfried; Le Normand, Jean-Pierre; Zint, Virginie; Dumas, Norbert; Dadouche, Foudil; Malasse, Imane; Scholz, Jeremy

2012-04-01

339

Note: Multi-confocal fluorescence correlation spectroscopy in living cells using a complementary metal oxide semiconductor-single photon avalanche diode array  

NASA Astrophysics Data System (ADS)

Living cells are heterogeneous and rapidly changing biological samples. It is thus desirable to measure molecular concentration and dynamics in many locations at the same time. In this note, we present a multi-confocal setup capable of performing simultaneous fluorescence correlation spectroscopy measurements, by focusing the spots with a spatial light modulator and acquiring data with a monolithic 32 × 32 single-photon avalanche photodiode array. A post-processing method is proposed to correct cross-talk effects between neighboring spots. We demonstrate the applicability of our system by simultaneously measuring the diffusion of free enhanced Green Fluorescent Protein (eGFP) molecules at nine different points in living cells.

Kloster-Landsberg, M.; Tyndall, D.; Wang, I.; Walker, R.; Richardson, J.; Henderson, R.; Delon, A.

2013-07-01

340

Simultaneous determination of the content of isoquinoline alkaloids in Dicranostigma leptopodum (Maxim) Fedde and the effective fractionation of the alkaloids by high-performance liquid chromatography with diode array detection.  

PubMed

A simple and efficient method was developed for the simultaneous determination of eight isoquinoline alkaloids in methanol extracts of Dicranostigma leptopodum (Maxim) Fedde and the effective fractionation of the alkaloids of D. leptopodum by high-performance liquid chromatography with diode array detection. The chromatographic conditions were optimized on a SinoChrom ODS-BP column to obtain a good separation of the four types of alkaloid analytes, including two aporphines (isocorydine, corydine), two protopines (protopine and allocryptopine), a morphine (sinoacutine), and three quaternary protoberberine alkaloids (berberrubine, 5-hydroxycoptisine, and berberine). The separation of these alkaloids was significantly affected by the composition of the mobile phase, and particularly by its pH value. Acetonitrile (A) and 0.2% phosphoric acid solution adjusted to pH 6.32 with triethylamine (B) were selected as the mobile phase with a gradient elution. With this method, a new quaternary protoberberine alkaloid was isolated and the two structural isomers (isocorydine and corydine) were baseline separated. The appropriate harvest period for D. leptopodum was also recommended based on our analysis. The method for the effective fraction of the alkaloids of D. leptopodum was optimized under this method with regard to the varying significant pharmacological activities of the alkaloids. PMID:25330407

Chen, Yali; Li, Min; Liu, Jianjun; Yan, Qian; Zhong, Mei; Liu, Junxi; Di, Duolong; Liu, Jinxia

2015-01-01

341

Computer-aided method for identification of major flavone/flavonol glycosides by high-performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS).  

PubMed

A new computational tool is proposed here for tentatively identifying major (UV quantifiable) flavone/flavonol glycoside peaks of high performance liquid chromatogram (HPLC)-diode array detection (DAD)-tandem mass spectrometry (MS/MS) profiles based on a MATLAB-based script implementing an in-house algorithm. The HPLC-DAD-MS/MS profiles of red onion, Chinese lettuce, carrot leaf, and celery seed extracts were analyzed by the proposed computer-aided screening method for identifying possible flavone/flavonol glycoside peaks from the HPLC-UV and MS total ion current (TIC) chromatograms. The number of identified flavone/flavonol glycoside peaks of the HPLC-UV chromatograms is four, four, six, and nine for red onion, Chinese lettuce, carrot leaf, and celery seed, respectively. These results have been validated by human(s) experts. For the batch processing of nine HPLC-DAD-MS/MS profiles of celery seed extract, the entire script execution time was within 15 s while manual calculation of only one HPLC-DAD-MS/MS profile by a flavonoid expert could take hours. Therefore, this MATLAB-based screening method is able to facilitate the HPLC-DAD-MS/MS analysis of flavone/flavonol glycosides in plants to a large extent. PMID:25270867

Wang, Zhengfang; Lin, Longze; Harnly, James M; Harrington, Peter de B; Chen, Pei

2014-11-01

342

Identification and quantification of flavonoids and phenolic acids in burr parsley (Caucalis platycarpos L.), using high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry.  

PubMed

A sensitive method coupling high-performance liquid chromatography (HPLC) with diode-array detector (DAD) and electrospray ionization mass spectrometry (MS) was optimized for the separation and identification of phenolic acids, flavonoid glycosides and flavonoid aglycones in the extract of burr parsley (Caucalis platycarpos L.). Fragmentation behavior of flavonoid glycosides and phenolic acids were investigated using ion trap mass spectrometry in negative electrospray ionization. The MS, MS(n) and UV data together with HPLC retention time (T(R)) of phenolic acids and flavonoids allowed structural characterization of these compounds. Caffeoylquinic acid (CQA) isomers, p-coumaroyl-quinic acids (p-CoQA), feruloylquinic acids (FQA), dicaffeoylquinic acids (diCQA), luteolin-7-O-rutinoside, apigenin-7-O-rutinoside as well as isolated chrysoeriol-7-O-rutinoside have been identified as constituents of C. platycarpos for the first time. An accurate, precise and sensitive LC-DAD method for quantification of four phenolic acids (3-O-caffeoylquinic, caffeic, p-coumaric, o-coumaric acid), four flavonoid glycosides (luteolin-7-O-glucoside, apigenin-7-O-glucoside, quercetin-3-O-galactoside, quercetin-3-O-rhamnoside), and three flavonoid aglycones (luteolin, apigenin, chrysoeriol) in C. platycarpos extract was validated in terms of linearity, limit of detection, limit of quantification, precision and accuracy. 3-O-caffeoylquinic acid was the predominant phenolic acid and luteolin-7-O-glucoside was the predominant flavonoid glycoside. PMID:19633617

Plazoni?, Ana; Bucar, Franz; Males, Zeljan; Mornar, Ana; Nigovi?, Biljana; Kujundzi?, Nikola

2009-01-01

343

Determination of flibanserin and tadalafil in supplements for women sexual desire enhancement using high-performance liquid chromatography with tandem mass spectrometer, diode array detector and charged aerosol detector.  

PubMed

The new compound - flibanserin - begun to appear as a synthetic adulterant in counterfeit herbal supplements used to stimulate women sexual drive. It was detected in two samples submitted to the Polish National Medicines Institute for analysis. The second sample contained also tadalafil. This study presents the LC method development which enables the determination of flibanserin and tadalafil. It employs three different detectors charged aerosol detector (CAD), diode array detector (DAD) and mass spectrometer (MS). The conditions of the elaborated method were optimized to obtain the highest sensitivity and the best resolution, especially the separation of icariin - the natural compound observed often in supplements for sexual disorders. The validation of the method proved good linearity, good accuracy and precision of the measurements recorded by all three detectors. Additionally, for CAD data, an alternative calculation method using a unified calibration function was presented and evaluated. It seems that this is the way to overcome the problem of non-availability of the reference standard of a target compound. Flibanserin content was quantified using the data of other reference standard (tadalafil). The inaccuracy of proposed indirect determination was found to be ±3%. A statistical evaluation proved that the results obtained with all detection modes and the results calculated using a unified calibration were not significantly different (p>0.05). PMID:24531007

Poplawska, Magdalena; Blazewicz, Agata; Zolek, Paulina; Fijalek, Zbigniew

2014-06-01

344

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

2013-03-12

345

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. PMID:21969787

Qin, Kunming; Cai, Hao; Liu, Xiao; Lu, Tulin; Fang, Qianbo; Yao, Zhongqing; Xu, Zisheng; Cai, Baochang

2011-01-01

346

Determination of rice herbicides, their transformation products and clofibric acid using on-line solid-phase extraction followed by liquid chromatography with diode array and atmospheric pressure chemical ionization mass spectrometric detection.  

PubMed

A simultaneous method for the trace determination of acidic, neutral herbicides and their transformation products in estuarine waters has been developed through an on-line solid-phase extraction method followed by liquid chromatography with diode array and mass spectrometric detection. An atmospheric pressure chemical ionization (APCI) interface was used in the negative ionization mode after optimization of the main APCI parameters. Limits of detection ranged from 0.1 to 0.02 ng/ml for 50 ml of acidified estuarine waters preconcentrated into polymeric precolumns and using time-scheduled selected ion monitoring mode. Two degradation products of the acidic herbicides (4-chloro-2-methylphenol and 2,4-dichlorophenol) did not show good signal response using APCI-MS at the concentration studied due to the higher fragmentor voltage needed for their determination. For molinate and the major degradation product of propanil, 3,4-dichloroaniline, positive ion mode was needed for APCI-MS detection. The proposed method was applied to the determination of herbicides in drainage waters from rice fields of the Delta del Ebro (Spain). During the 3-month monitoring of the herbicides, 8-hydroxybentazone and 4-chloro-2-methylphenoxyacetic acid were successively found in those samples. PMID:10870691

Santos, T C; Rocha, J C; Barceló, D

2000-05-19

347

Rapid Identification and Simultaneous Quantification of Multiple Constituents in Nao-Shuan-Tong Capsule by Ultra-Fast Liquid Chromatography/Diode-Array Detector/Quadrupole Time-of-Flight Tandem Mass Spectrometry.  

PubMed

A rapid and high-sensitive ultra-fast liquid chromatography coupled with a diode-array detector and a quadrupole/time-of-flight mass spectrometry (MS) method was established and validated for the chemical profiling of Nao-shuan-tong capsule (NSTC) and simultaneous quantification of five major constituents. A total of 59 components including monoterpene glycosides, flavonoids, sesquiterpenoids, ketosteroids, thiophenes, organic acids and alkaloids were identified or tentatively characterized in NSTC based on the accurate mass and tandem MS behavior. Five major bioactive constituents were chosen as the chemical indexes of holistic quality evaluation and quantified simultaneously. All calibration curves showed good linear regression (r(2) > 0.9991) in the range 25.2-510, 145-2,900, 1.84-36.8, 2.61-52.2 and 3.25-26.2 ?g/mL for gastrodin, paeoniflorin, typhaneoside, ?-ecdysterone and isorhamnetin-3-O-neohesperidoside, respectively. It also showed good precision, stability and accuracy for quantification of these five compounds. The limit of detections and limit of quantitations for the analytes ranged from 0.14 to 1.09 ?g/mL and from 0.47 to 3.63 ?g/mL, respectively. The validated quantification method was applied to analyze 10 batches of commercial NSTC. These results will provide a basis for quality control of the production process and the further pharmacological study in vivo of NSTC. PMID:25355899

Li, Panlin; Su, Weiwei; Xie, Chengshi; Zeng, Xuan; Peng, Wei; Liu, Menghua

2014-10-29

348

Identification of metabolites of Si-Ni-San, a traditional Chinese medicine formula, in rat plasma and urine using liquid chromatography/diode array detection/triple-quadrupole spectrometry.  

PubMed

Si-Ni-San (SNS) is a widely used traditional Chinese medicine formula (TCMF) in treating various diseases. However, the in vivo integrated metabolism of its multiple components remains unknown. In this paper, a liquid chromatography coupled with diode array detection and triple-quadrupole spectrometry (LC-DAD-MS/MS) method was developed for detection and identification of SNS metabolites in rat plasma and urine at a normal clinical dosage. Accurate structural elucidation was performed using MS/MS, UV data and n-octanol/water partition coefficient. Based on the proposed strategy, 36 absorbed compounds and 29 metabolites in plasma and 33 metabolites in urine were detected by a highly sensitive MRM method. Our results indicated that phase II reactions (e.g., methylation, glucuronidation and sulfation) were the main metabolic pathways of gallic acid and flavanones, while phase I reactions (e.g., hydroxylation) were the major metabolic reaction for triterpenoid saponins. The metabolite profile analysis of SNS provided a comprehensive understanding of the in vivo metabolic fates of constituents in SNS. Moreover, the results in this work demonstrated the present strategy based on the combination of chromatographic, spectrophotometric, mass-spectrometric, and software prediction to detect and identify metabolites was effective and reliable. And such a strategy may also be extended to investigate the metabolism of other TCMF. PMID:22226767

Yan, Zhixiang; Chen, Ying; Li, Tianxue; Zhang, Jie; Yang, Xinghao

2012-02-15

349

An approach to develop binary chromatographic fingerprints of the total alkaloids from Caulophyllum robustum by high performance liquid chromatography/diode array detector and gas chromatography/mass spectrometry.  

PubMed

An approach was proposed to develop binary chromatographic fingerprints by means of high performance liquid chromatography/diode array detector (HPLC/DAD) and gas chromatography/mass spectrometry (GC/MS). HPLC fingerprint and GC/MS fingerprint that, respectively, represent chemical characteristics of aporphinoid and quinolizidine alkaloids of the total alkaloids from Caulophyllum robustum were developed, which were used to construct binary chromatographic fingerprints of the total alkaloids. Moreover, the authentication and validation of the binary fingerprints were performed. Then, a data-level information fusion method was employed to capture the chemical information encoded in two chromatographic fingerprints. Finally, based on the fusion results, the quality of 10 batches of the total alkaloids samples was further evaluated by similarity measure and cluster analysis method. In comparison with conventional fingerprint, the binary chromatographic fingerprints which represent the characteristics of more constitutions can comprehensively and properly reveal the quality characteristics of the total alkaloids. The binary chromatographic fingerprints can reach more objective conclusions in the practice of quality control of the total alkaloids. In conclusion, the binary chromatographic fingerprints are suitable for quality control of the total alkaloids. The presented approach is a powerful and meaningful tool to comprehensively conduct the quality control of traditional Chinese medicine (TCM). PMID:17291705

Li, Yiping; Hu, Zhen; He, Langchong

2007-04-11

350

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

351

Orthogonal array designs for the optimization of liquid-liquid-liquid microextraction of nonsteroidal anti-inflammatory drugs combined with high-performance liquid chromatography-ultraviolet detection.  

PubMed

Orthogonal array designs (OADs) were applied for the first time to optimize liquid-liquid-liquid microextraction (LLLME) conditions for the analysis of three nonsteroidal anti-inflammatory drug residues (2-(4-chlorophenoxy)-2-methylpropionic acid, ketoprofen, and naproxen) in wastewater samples. Six relevant factors were investigated: type of organic solvent, composition of donor phase and acceptor phase, stirring speed, extraction time and salt concentration. In the first stage, mixed-level orthogonal array design, an OA16 (4(1) x 2(12)) matrix was employed to study the effect of six factors, by which the effect of each factor was estimated using individual contributions as response functions. Based on the results of the first stage, 1-octanol was chosen as organic solvent for extraction. The other five factors were selected for further optimization using an OA16 (4(5)) matrix and a 4 x 4 table to locate more exact levels for each variable. The relative standard deviations for the reproducibility of optimized LLLME varied from 6.2 to 7.1%. The coefficients of determination for calibration curves were higher than 0.9950. The method detection limits for drugs spiked in ultrapure water were in the range of 0.03-0.3 ng/mL. The final optimized conditions were applied to the analysis of drug residues in three wastewater samples in Singapore. PMID:16199224

Wu, Jingming; Lee, Hian Kee

2005-10-28

352

Flat-Topped Emission with Spectral Width above 500 nm from InAs/InP Quantum Dot Waveguide Array Light-Emitting Diode  

NASA Astrophysics Data System (ADS)

Flat-topped emission with a spectral width greater than 500 nm was obtained from self-assembled Stranski-Krastanov (SK) InAs/InP quantum dots (QDs) grown by selective area low-pressure metal organic vapor phase epitaxy using a double-capping procedure. Selective area growth using an SiO2 mask with narrow stripes was carried out to tailor a wide emission range for the QDs in sixteen arrayed waveguides. Each waveguide core contained three stacked QD layers with different QD heights and Ga content in the GaInAs buffer layer. An investigation was carried out into the optimum Ga content and QD height for increasing the emission intensity and obtaining equal intensity from each QD layer.

Yoshikawa, Shohei; Saegusa, Tomomitsu; Iwane, Yuto; Yamauchi, Masayuki; Shimomura, Kazuhiko

2012-09-01

353

Ultraviolet dosimetry  

SciTech Connect

An ultraviolet radiation dosimeter is described comprising: a sensor exposed to ultraviolet radiation impinging upon the sensor and responsive thereto for developing a signal corresponding to the level of the radiation. The sensor includes a filter medium that exhibits a transmissivity of the radiation that rises at about three-hundred-seventy nanometers and extends to below three-hundred nanometers, and a filtering layer that exhibits a peak transmissivity at substantially three-hundred-twenty-two nanometers. It also consists of a processor responsive to the signal and accumulating a representation of the magnitude of the signal as effectively integrated with elapsed time of exposure of the sensor to the radiation; and means responsive to the representation for yielding an indication of the degree of such accumulation.

Leber, L.C.; Tenhulzen, N.L.

1987-11-03

354

Determination of 1-(4'-aminophenyl)-4-methyl-7,8-methylene-dioxy-2,3-benzodiazepine by high-performance liquid chromatography-diode array detection in plasma and brain in healthy and hypoxic-ischaemic rats.  

PubMed

Previously we showed that 1-(4'-aminophenyl)-4-methyl-7,8-methylene-dioxy-2,3-benzodiazepine (GYKI-52466), an ionotropic AMPA receptor antagonist, can trigger strong, presumably metabotropic, protection against seizures and stroke at very low doses. To date, no study has determined brain and plasma concentrations of GYKI-52466 following subcutaneous administration in animals with or without brain damage. Here we developed and validated a rapid method of high-performance liquid chromatography with diode array detection. Chromatographic separation was achieved by a Luna C18 column using a mixture of 25 mM phosphate buffer (pH 7.0)-methanol-acetonitrile (40:37.5:22.5, v/v/v) as the mobile phase at a flow rate of 1.2 mL/min. The method showed acceptable precision and accuracy and allowed a precise quantification of 25 ng/mL GYKI-52466 in the plasma and brain. Recovery of GYKI-52466 from the plasma and brain was >87%, and GYKI was stable at room temperature and during prolonged storage at -20 °C. The method was successfully applied in measuring levels of GYKI-52466 following administration of 3 and 20 mg/kg of GYKI-52466 in control and brain damaged rats. A low brain concentration of 0.56 ?M GYKI-52466 was observed with 3mg/kg compared to 10.7 ?M with 20 mg/kg at 90 min post drug administration. Severe ataxia was observed with the 20mg/kg dose for up to 90 min. Furthermore, in ischaemic animals, there was no evidence of a 'surge' in brain GYKI concentrations at the injury site, confirming the integrity of the blood-brain barrier in the region of infarct. Taken together, our findings support a metabotropic mode of action underlying the low-dose neuroprotective efficacy of GYKI-52466. PMID:23232259

Nayak, P K; Zhang, H; Kerr, D S

2013-03-01

355

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

2006-09-14

356

Chemometrics-enhanced high performance liquid chromatography-diode array detection strategy for simultaneous determination of eight co-eluted compounds in ten kinds of Chinese teas using second-order calibration method based on alternating trilinear decomposition algorithm.  

PubMed

In this work, an attractive chemometrics-enhanced high performance liquid chromatography-diode array detection (HPLC-DAD) strategy was proposed for simultaneous and fast determination of eight co-eluted compounds including gallic acid, caffeine and six catechins in ten kinds of Chinese teas by using second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm. This new strategy proved to be a useful tool for handling the co-eluted peaks, uncalibrated interferences and baseline drifts existing in the process of chromatographic separation, which benefited from the "second-order advantages", making the determination of gallic acid, caffeine and six catechins in tea infusions within 8 min under a simple mobile phase condition. The average recoveries of the analytes on two selected tea samples ranged from 91.7 to 103.1% with standard deviations (SD) ranged from 1.9 to 11.9%. Figures of merit including sensitivity (SEN), selectivity (SEL), root-mean-square error of prediction (RMSEP) and limit of detection (LOD) have been calculated to validate the accuracy of the proposed method. To further confirm the reliability of the method, a multiple reaction monitoring (MRM) method based on LC-MS/MS was employed for comparison and the obtained results of both methods were consistent with each other. Furthermore, as a universal strategy, this new proposed analytical method was applied for the determination of gallic acid, caffeine and catechins in several other kinds of Chinese teas, including different levels and varieties. Finally, based on the quantitative results, principal component analysis (PCA) was used to conduct a cluster analysis for these Chinese teas. The green tea, Oolong tea and Pu-erh raw tea samples were classified successfully. All results demonstrated that the proposed method is accurate, sensitive, fast, universal and ideal for the rapid, routine analysis and discrimination of gallic acid, caffeine and catechins in Chinese tea samples. PMID:25223614

Yin, Xiao-Li; Wu, Hai-Long; Gu, Hui-Wen; Zhang, Xiao-Hua; Sun, Yan-Mei; Hu, Yong; Liu, Lu; Rong, Qi-Ming; Yu, Ru-Qin

2014-10-17

357

Simultaneous determination of phenolic compounds and saponins in quinoa (Chenopodium quinoa Willd) by a liquid chromatography-diode array detection-electrospray ionization-time-of-flight mass spectrometry methodology.  

PubMed

A new liquid chromatography methodology coupled to a diode array detector and a time-of-flight mass spectrometer has been developed for the simultaneous determination of phenolic compounds and saponins in quinoa (Chenopodium quinoa Willd). This method has allowed the simultaneous determination of these two families of compounds with the same analytical method for the first time. A fused-core column C18 has been used, and the analysis has been performed in less than 27 min. Both chromatographic and electrospray ionization time-of-flight mass spectrometry parameters have been optimized to improve the sensitivity and to maximize the number of compounds detected. A validation of the method has also been carried out, and free and bound polar fractions of quinoa have been studied. Twenty-five compounds have been tentatively identified and quantified in the free polar fraction, while five compounds have been tentatively identified and quantified in the bound polar fraction. It is important to highlight that 1-O-galloyl-?-D-glucoside, acacetin, protocatechuic acid 4-O-glucoside, penstebioside, ethyl-m-digallate, (epi)-gallocatechin, and canthoside have been tentatively identified for the first time in quinoa. Free phenolic compounds have been found to be in the range of 2.746-3.803 g/kg of quinoa, while bound phenolic compounds were present in a concentration that varies from 0.139 and 0.164 g/kg. Indeed, saponins have been found to be in a concentration that ranged from 5.6 to 7.5% of the total composition of whole quinoa flour. PMID:21905641

Gómez-Caravaca, Ana María; Segura-Carretero, Antonio; Fernández-Gutiérrez, Alberto; Caboni, Maria Fiorenza

2011-10-26

358

Blue to bluish-green tunable phosphor Sr2LiSiO4F:Ce3+,Tb3+ and efficient energy transfer for near-ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

Ce3+ and Tb3+ activated Sr2LiSiO4F phosphors were prepared by a solid state reaction technique at high temperature, and their ultraviolet (UV)-visible spectroscopic properties were investigated. Under ultraviolet light excitation, Ce3+-doped Sr2LiSiO4F phosphors emit blue light (420 nm), while Tb3+-doped phosphors show yellowish green emission. Efficient energy transfer from Ce3+ to Tb3+ ions in co-doped samples was confirmed in terms of corresponding excitation and emission spectra. The energy transfer mechanism between Ce3+ and Tb3+ was discussed and demonstrated to be dipole-dipole interaction in Sr2LiSiO4F:Ce3+,Tb3+ phosphors. Due to energy transfer from Ce3+ to Tb3+, Ce3+ and Tb3+ co-doped Sr2LiSiO4F phosphors show intense absorption in near-UV region, and present tunable emission from blue to bluish green under 360 nm light excitation. The results indicate that these phosphors can be considered as candidates for white LEDs pumped by n-UV chips.

Xie, Mubiao; Zeng, Lihua; Ye, TingLi; Yang, Xi; Zhu, Xianmei; Peng, Siyun; Lei, Lei

2014-09-01

359

Enhanced ultraviolet electroluminescence and spectral narrowing from ZnO quantum dots/GaN heterojunction diodes by using high-k HfO2 electron blocking layer  

NASA Astrophysics Data System (ADS)

We demonstrated the capability of realizing enhanced ZnO-related UV emissions by using the low-cost and solution-processable ZnO quantum dots (QDs) with the help of a high-k HfO2 electron blocking layer (EBL) for the ZnO QDs/p-GaN light-emitting diodes (LEDs). Full-width at half maximum of the LED devices was greatly decreased from ˜110 to ˜54 nm, and recombinations related to nonradiative centers were significantly suppressed with inserting HfO2 EBL. The electroluminescence of the ZnO QDs/HfO2/p-GaN LEDs demonstrated an interesting spectral narrowing effect with increasing HfO2 thickness. The Gaussian fitting revealed that the great enhancement of the Zni-related emission at ˜414 nm whereas the deep suppression of the interfacial recombination at ˜477 nm should be the main reason for the spectral narrowing effect.

Mo, Xiaoming; Long, Hao; Wang, Haoning; Li, Songzhan; Chen, Zhao; Wan, Jiawei; Feng, Yamin; Liu, Yuping; Ouyang, Yifang; Fang, Guojia

2014-08-01

360

Advancement of High Power Laser Diodes for Pumping 2-micron Solid State Lasers  

E-print Network

Abstract- The reliability and lifetime demanded by spacebased applications of 2-micron solid state lasers are beyond the capability of currently available laser diode arrays. This paper provides the status of an ongoing technology advancement effort toward long-lifetime high power laser diode arrays suitable for pumping Thulium and Holmium based solid state lasers. I.

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

361

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

362

Deep ultraviolet semiconductor light sources for sensing and security  

Microsoft Academic Search

III-Nitride based deep ultraviolet (DUV) light emitting diodes (LEDs) rapidly penetrate into sensing market owing to several advantages over traditional UV sources (i.e. mercury, xenon and deuterium lamps). Small size, a wide choice of peak emission wavelengths, lower power consumption and reduced cost offer flexibility to system integrators. Short emission wavelength offer advantages for gas detection and optical sensing systems

Max Shatalov; Yuri Bilenko; Jinwei Yang; Remis Gaska

2009-01-01

363

Qualification and Selection of Flight Diode Lasers for Space Applications  

NASA Technical Reports Server (NTRS)

The reliability and lifetime of laser diodes is critical to space missions. The Nuclear Spectroscopic Telescope Array (NuSTAR) mission includes a metrology system that is based upon laser diodes. An operational test facility has been developed to qualify and select, by mission standards, laser diodes that will survive the intended space environment and mission lifetime. The facility is situated in an electrostatic discharge (ESD) certified clean-room and consist of an enclosed temperature-controlled stage that can accommodate up to 20 laser diodes. The facility is designed to characterize a single laser diode, in addition to conducting laser lifetime testing on up to 20 laser diodes simultaneously. A standard laser current driver is used to drive a single laser diode. Laser diode current, voltage, power, and wavelength are measured for each laser diode, and a method of selecting the most adequate laser diodes for space deployment is implemented. The method consists of creating histograms of laser threshold currents, powers at a designated current, and wavelengths at designated power. From these histograms, the laser diodes that illustrate a performance that is outside the normal are rejected and the remaining lasers are considered spaceborne candidates. To perform laser lifetime testing, the facility is equipped with 20 custom laser drivers that were designed and built by California Institute of Technology specifically to drive NuSTAR metrology lasers. The laser drivers can be operated in constant-current mode or alternating-current mode. Situated inside the enclosure, in front of the laser diodes, are 20 power-meter heads to record laser power throughout the duration of lifetime testing. Prior to connecting a laser diode to the current source for characterization and lifetime testing, a background program is initiated to collect current, voltage, and resistance. This backstage data collection enables the operational test facility to have full laser diode traceablity.

Liebe, Carl C.; Dillon, Robert P.; Gontijo, Ivair; Forouhar, Siamak; Shapiro, Andrew A.; Cooper, Mark S.; Meras, Patrick L.

2010-01-01

364

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

365

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

366

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

2012-04-15

367

New features on the fragmentation patterns of homoisoflavonoids in Ophiopogon japonicus by high-performance liquid chromatography/diode-array detection/electrospray ionization with multi-stage tandem mass spectrometry.  

PubMed

Homoisoflavonoids, a special class of flavonoids, are mainly distributed in the Liliaceae family and have various biological activities. Previously, very little research has been reported on the gas-phase fragmentation patterns of homoisoflavonoids by electrospray ionization mass spectrometry. In this paper, we report the use of high-performance liquid chromatography with a diode-array detector (HPLC-DAD) and electrospray ionization multi-stage tandem mass spectrometry (ESI-MS(n)) to study the fragmentation behavior of 11 homoisoflavonoid standards and to analyze homoisoflavonoids in Ophiopogon japonicus. In total, 28 homoisoflavonoids (including seven novel constituents) were characterized. The deprotonated [M--H](-) molecules of the homoisoflavonoids containing a saturated C2--C3 bond afforded the A or B product ion (base peak) according to whether the B-ring was substituted with a hydroxyl group. For the homoisoflavonoids containing a C-2-C-3 double bond, the product ions (A or C ion) were created from the precursor [M-H](-) ion as the base peak when the B-ring was substituted with a hydroxyl group. The homoisoflavonoids carrying a formyl group in the A-ring readily eliminated one molecule of CO to form the product ion [M + H-CO](-) (base peak) irrespective whether the C-2-C-3 bond was saturated or not. This product ion afforded the [M-H-CO-B-ring--CH(2) + H](-) ion by cleavage of the C3-C9 bond. This latter product ion always appeared in tandem mass (MS/MS) spectra of type I homoisoflavonoids. The common features of flavonoids observed during the gas-phase fragmentation mechanisms were the loss of the following groups: 15 Da (CH(3)), 18 Da (H(2)O), 28 Da (CO), 44 Da (CO(2)) and 46 Da (CH(2)O(2)). A retro-Diels-Alder (RDA)-like cleavage was also observed for the homoisoflavonoids. The different gas-phase fragmentation routes were characterized for the deprotonated molecules obtained from the various homoisoflavonoids and collision-induced dissociation (CID) fragmentation differences were noted for the different locations of the various substituents. In conclusion, we can say that this study allowed us to structurally elucidate and identify homoisoflavonoids distributed in related plants and their complex prescriptions. PMID:20583326

Qi, Jin; Xu, Deran; Zhou, Yi-Feng; Qin, Min-Jian; Yu, Bo-Yang

2010-08-15

368

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

369

The Extreme Ultraviolet Problem of Cataclysmic Variables  

Microsoft Academic Search

Observations of EUV radiation of astrophysical sources provide direct information of the accretion energy balance and the nature of the accretion region on the white dwarf surface of cataclysmic variable stars (CV's). Unattainable until recently, these EUV observation have been made possible with new satellites such as the Extreme Ultraviolet Explorer (EUVE) and the Array of Low Energy X-ray Imaging

John Kennedy Warren

1998-01-01

370

Energy transfer from Sm3+ to Eu3+ in red-emitting phosphor LaMgAl11O19:Sm3+, Eu3+ for solar cells and near-ultraviolet white light-emitting diodes.  

PubMed

The red-emitting phosphor LaMgAl11O19:Sm(3+), Eu(3+) was prepared by solid-state reaction at 1600 °C for 4 h. The phase formation, luminescence properties, and energy transfer from Sm(3+) to Eu(3+) were studied. With the addition of 5 mol % Sm(3+) as the sensitizer, the excitation wavelength of LaMgAl11O19:Eu(3+) phosphor was extended from 464 to 403 nm, and the emission intensity under the excitation at 403 nm was also enhanced. The host material LaMgAl11O19 could contain the high doping content of Eu(3+) (20 mol %) without concentration quenching. This energy transfer from Sm(3+) to Eu(3+) was confirmed by the decay times of energy donor Sm(3+). The mechanism of energy transfer (Sm(3+) ? Eu(3+)) was proved to be quadrupole-quadrupole interaction. Under the 403 nm excitation at 150 °C, the emission intensities of the characteristic peaks of Sm(3+) and Eu(3+) in LaMgAl11O19:0.05Sm(3+), 0.2Eu(3+) phosphor were decreased to 65% and 56% of the initial intensities at room temperature, and the relatively high activation energy proved that this phosphor had a good thermal stability. The CIE coordinate was calculated to be (x = 0.601, y = 0.390). The LaMgAl11O19:0.05Sm(3+), 0.2Eu(3+) phosphor is a candidate for copper phthalocyanine-based solar cells and white light-emitting diodes. PMID:24884208

Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan-Gai; Tang, Chao; Wu, Xiaowen

2014-06-16

371

Ba(1.3)Ca(0.7)SiO4:Eu(2+),Mn(2+): a promising single-phase, color-tunable phosphor for near-ultraviolet white-light-emitting diodes.  

PubMed

In this paper, Eu(2+)-doped and Eu(2+)/Mn(2+)-codoped Ba1.3Ca0.7SiO4 phosphors were synthesized by means of a conventional solid-state reaction process. The single-phase purity was checked by means of X-ray diffraction and the Rietveld method. Under excitation at 390 nm, the emission spectra of the Eu(2+)-doped phosphors exhibit a broad-band emission centered at 500 nm caused by the electric dipole allowed transition of the Eu(2+) ions. The emission spectra of codoped phosphors show one more broad emission centered at 600 nm attributable to the transitions from the (4)T1((4)G) ? (6)A1((6)S) of Mn(2+) ions. The luminescent color of the codoped phosphors can be easily adjusted from blue to red with variation of the Mn(2+) content. The energy transfer mechanism from the Eu(2+) to Mn(2+) ions in Ba1.3Ca0.7SiO4 phosphors has been confirmed to be the resonant type via dipole-quadrupole interaction, and the critical distance has been calculated quantitatively. All these results demonstrate that the Eu(2+)/Mn(2+)-codoped Ba1.3Ca0.7SiO4 phosphors can be a promising single-phase, color-tunable phosphor for near-UV white-light-emitting diodes after a further optimization process. Additionally, a great red shift from 593 to 620 nm has been observed following the increase of Mn(2+) content, and the phenomenon has been discussed in relation to the changes in the crystal field surrounding the Mn(2+) ions and the exchange interactions caused by the formation of Mn(2+) pairs. PMID:25260073

Lv, Wenzhen; Jiao, Mengmeng; Zhao, Qi; Shao, Baiqi; Lü, Wei; You, Hongpeng

2014-10-20

372

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

373

Diode pumped solid-state laser oscillators for spectroscopic applications  

NASA Technical Reports Server (NTRS)

The rapid improvement in diode laser pump sources has led to the recent progress in diode laser pumped solid state lasers. To date, electrical efficiencies of greater than 10 percent were demonstrated. As diode laser costs decrease with increased production volume, diode laser and diode laser array pumped solid state lasers will replace the traditional flashlamp pumped Nd:YAG laser sources. The use of laser diode array pumping of slab geometry lasers will allow efficient, high peak and average power solid state laser sources to be developed. Perhaps the greatest impact of diode laser pumped solid state lasers will be in spectroscopic applications of miniature, monolithic devices. Single-stripe diode-pumped operation of a continuous-wave 946 nm Nd:YAG laser with less than 10 m/w threshold was demonstrated. A slope efficiency of 16 percent near threshold was shown with a projected slope efficiency well above a threshold of 34 percent based on results under Rhodamine 6G dye-laser pumping. Nonlinear crystals for second-harmonic generation of this source were evaluated. The KNbO3 and periodically poled LiNbO3 appear to be the most promising.

Byer, R. L.; Basu, S.; Fan, T. Y.; Kozlovsky, W. J.; Nabors, C. D.; Nilsson, A.; Huber, G.

1987-01-01

374

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

375

Extreme ultraviolet spectroscopy diagnostics of low-temperature plasmas based on a sliced multilayer grating and glass capillary optics  

Microsoft Academic Search

New extreme ultraviolet (EUV) spectroscopic diagnostics of relatively low-temperature plasmas based on the application of an EUV spectrometer and fast EUV diodes combined with glass capillary optics is described. An advanced high resolution dispersive element sliced multilayer grating was used in the compact EUV spectrometer. For monitoring of the time history of radiation, filtered fast EUV diodes were used in

V. L. Kantsyrev; A. S. Safronova; K. M. Williamson; P. Wilcox; N. D. Ouart; M. F. Yilmaz; K. W. Struve; D. L. Voronov; R. M. Feshchenko; I. A. Artyukov; A. V. Vinogradov

2008-01-01

376

Improved heat-sink design for coherent laser arrays  

NASA Astrophysics Data System (ADS)

An analysis using the PATRAN and NASTRAN computer programs is applied to the problem of minimizing the lateral temperature variation between diodes so that an array may be phase-locked. It is shown that the use of a cap region on a heat sink whose lateral dimensions are the same as the laser diode array substantially reduces the temperature variation across the array, facilitating phase-locked operation.

Tavis, M. T.; Garmire, E. M.

1984-08-01

377

Galileo Ultraviolet Spectrometer experiment  

Microsoft Academic Search

The Galileo ultraviolet spectrometer experiment uses data obtained by the Ultraviolet Spectrometer (UVS) mounted on the pointed orbiter scan platform and from the Extreme Ultraviolet Spectrometer (EUVS) mounted on the spinning part of the orbiter with the field of view perpendicular to the spin axis. The UVS is a Ebert-Fastie design that covers the range 113–432 nm with a wavelength

C. W. Hord; A. I. F. Stewart; C. A. Barth; L. W. Esposito; G. E. Thomas; B. R. Sandel; D. M. Hunten; A. L. Broadfoot; D. E. Shemansky; J. M. Ajello; R. A. West

1992-01-01

378

Millimeter-wave imaging using preamplified diode detector  

NASA Astrophysics Data System (ADS)

A 2-pixel imaging array was developed to demonstrate millimeter-wave imaging. Each pixel consists of a Q-band Vivaldi antenna and a preamplified diode detector, using InGaAs pseudomorphic HEMT MMIC low noise amplifiers and beam-lead Schottky-diode detector. The approach does not require local oscillator power, is compatible with MMIC technology, and can reduce the complexity and manufacturing cost of millimeter-wave imaging arrays. The preamplified diode detector exhibited 17 V/uW responsivity at 44 GHz and -75 dBm tangential sensitivity at 1-MHz video bandwidth. The array demonstrated millimeter-wave imaging of three vehicles in a parking lot.

Lam, Wayne; Lee, Paul; Yujiri, Larry; Berenz, John; Pearlman, Jay

1992-07-01

379

Bypass diode integration  

NASA Technical Reports Server (NTRS)

Protective bypass diodes and mounting configurations which are applicable for use with photovoltaic modules having power dissipation requirements in the 5 to 50 watt range were investigated. Using PN silicon and Schottky diode characterization data on packaged diodes and diode chips, typical diodes were selected as representative for each range of current carrying capacity, an appropriate heat dissipating mounting concept along with its environmental enclosure was defined, and a thermal analysis relating junction temperature as a function of power dissipation was performed. In addition, the heat dissipating mounting device dimensions were varied to determine the effect on junction temperature. The results of the analysis are presented as a set of curves indicating junction temperature as a function of power dissipation for each diode package.

Shepard, N. F., Jr.

1981-01-01

380

"Diode Pumped Solid State Lasers At 2 And 3 µm"  

NASA Astrophysics Data System (ADS)

The most attractive alternative to flashlamp pumping of solid state lasers is the diode laser. In the past two decades numerous laboratory devices have been assembled which incorporated single diode lasers, small laser diode arrays or LED's for pumping of Nd:YAG, Nd:glass and a host of other Nd lasers. The low power output, low packaging density, and extremely high cost of diode lasers prevented any serious applications for laser pumping in the past. The reason for the continued interest in this area stems from the potential dramatic increase in system efficiency and component lifetime, and reduction of thermal load of the solid-state laser material. The latter not only will reduce thereto-optic effects and therefore lead to better beam quality but also will enable an increase in pulse repetition frequency. The attractive operating parameters combined with low voltage operation and the compactness of an all solid-state laser system have a potential high payoff. The high pumping efficiency compared to flashlamps stems from the good spectral match between the laser diode emission and the rare earth activator absorption bands. A significant advantage of laser diode pumping compared to arc lamps is system lifetime and reliability. Laser diode arrays have exhibited lifetimes on the order of 10,000 hours in cw operation and 109 shots in the pulsed mode. Flashlamp life is on the order of 107 shots, and about 200 hours for cw operation. In addition, the high pump flux combined with a substantial UV content in lamp pumped systems causes material degradation in the pump cavity and in the coolant. Such problems are virtually eliminated with laser diode pump sources. The absence of high voltage pulses, high temperatures and UV radiation encountered with arc lamps leads to much more benign operating features for solid state laser systems employing laser diode pumps. Laser diode technology dates back to 1962 when laser action in GaAs diodes was first demonstrated. However, it took a decade to transform a fragile device requiring cryogenic temperatures into one capable of emitting a continuous beam at room temperature. In the last few years the rapid progress in fabricating diode lasers has increased interest in developing diode pumped solid state lasers. Device fabrication improvements such as double hetero-structures, multiple quantum well structures, monolithic phased arrays and multiple stripe lasers which were made possible by improved manufacturing technologies have produced a dramatic reduction of threshold current and increases of slope efficiency, lifetime and output power.

Esterowitz, Leon

1988-06-01

381

LED array unit with silicon microreflector  

Microsoft Academic Search

A light emitting diode (LED) array unit for a light source of isolated power transmission or a display panel was fabricated using LED chips which were mounted on a silicon microreflector. The reflector was formed on a (100) silicon wafer by means of anisotropic chemical etching. An isolated power supply which consisted of an infrared LED array unit and single

Kohrou Takahashi; Nobuyuki Tadokoro; S. Takeuti

1994-01-01

382

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.

383

Coaxial foilless diode  

SciTech Connect

A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves.

Kong, Long; Liu, QingXiang; Li, XiangQiang; Wang, ShaoMeng [College of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031 (China)] [College of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031 (China)

2014-05-15

384

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

385

Fast, High-Precision Readout Circuit for Detector Arrays  

NASA Technical Reports Server (NTRS)

The GEO-CAPE mission described in NASA's Earth Science and Applications Decadal Survey requires high spatial, temporal, and spectral resolution measurements to monitor and characterize the rapidly changing chemistry of the troposphere over North and South Americas. High-frame-rate focal plane arrays (FPAs) with many pixels are needed to enable such measurements. A high-throughput digital detector readout integrated circuit (ROIC) that meets the GEO-CAPE FPA needs has been developed, fabricated, and tested. The ROIC is based on an innovative charge integrating, fast, high-precision analog-to-digital circuit that is built into each pixel. The 128×128-pixel ROIC digitizes all 16,384 pixels simultaneously at frame rates up to 16 kHz to provide a completely digital output on a single integrated circuit at an unprecedented rate of 262 million pixels per second. The approach eliminates the need for off focal plane electronics, greatly reducing volume, mass, and power compared to conventional FPA implementations. A focal plane based on this ROIC will require less than 2 W of power on a 1×1-cm integrated circuit. The ROIC is fabricated of silicon using CMOS technology. It is designed to be indium bump bonded to a variety of detector materials including silicon PIN diodes, indium antimonide (InSb), indium gallium arsenide (In- GaAs), and mercury cadmium telluride (HgCdTe) detector arrays to provide coverage over a broad spectral range in the infrared, visible, and ultraviolet spectral ranges.

Rider, David M.; Hancock, Bruce R.; Key, Richard W.; Cunningham, Thomas J.; Wrigley, Chris J.; Seshadri, Suresh; Sander, Stanley P.; Blavier, Jean-Francois L.

2013-01-01

386

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

387

Blue laser diode (LD) and light emitting diode (LED) applications  

NASA Astrophysics Data System (ADS)

In the LED Highlight session at the 5th International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004), held in Gyeongju, Korea, 15-19 March 2004, Arpad A. Bergh [1] gave an overview on current and future LD and LED applications including prospects for industry and market developments. Papers from this session can be found in a special coloured section of this issue on pages 2730-2754.The cover picture shows a GaN vertical cavity surface emitting laser (VCSEL) array for white light illumination, designed to raise the light extraction efficieny of the device above 60% (courtesy of S. Nakamura, UCSB). Further papers from ISBLLED-2004 are published in phys. stat. sol. (b) 241, No. 12 (2004) and phys. stat. sol. (c) 1, No. 10 (2004).

Bergh, Arpad A.

2004-09-01

388

Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes  

E-print Network

Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes, IEEE DOI: 10.1109/JPHOT.2011.2150745 1943-0655/$26.00 ©2011 IEEE #12;Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes With Colloidal Microlens Arrays With Various Aspect

Gilchrist, James F.

389

Diodes stabilize LED output  

NASA Technical Reports Server (NTRS)

Small-signal diodes are placed in series with light-emitting diodes (LED's) to stabilize LED output against temperature fluctuations. Simple inexpensive method compensates for thermal fluctuations over a broad temperature range. Requiring few components, technique is particularly useful where circuit-board space is limited.

Deters, R. A.

1977-01-01

390

Spada: An Array of Spad Detectors For Astrophysical Applications  

Microsoft Academic Search

Astrophysical studies require accurate, sensitive and fast detectors to detect faint sources with high variability. Recently an array of Single Photon Avalanche Diodes (SPAD), SPADA, has been developed. This array is suitable for competitive adaptive optics operations and fast transient image acquisition at a fraction of the current cost of imaging arrays. The fabricated solid-state photon counters are rugged, easily

Giovanni Bonanno; Massimiliano Belluso; Franco Zappa; Simone Tisa; Sergio Cova; Piera Maccagnani; Domenico Bonaccini Calia; Roberto Saletti; Roberto Roncella; Sergio Billotta

2005-01-01

391

Study on the digitized and quantified evaluating method for the super information cluster of traditional Chinese medicine ultraviolet spectral fingerprints  

PubMed Central

The theories of ultraviolet spectral fingerprint (UVFP) index, information index, fluctuation index, information fluctuation index combined with the quantified UV fingerprint method (QUFM) had been established and put into practice in the Ginkgo Tablets (GT) quality evaluation. The flowing injection analysis (FIA) coupled with a diode array detector was applied as a novel method to obtain the UVFP in the region of 190-400 nm at which the absorption can reflect all the information of the chemical constituents contained ???*, n??* and n??* transition. The result showed that all batches were qualified (Grade ?3) except S8 for its too high contents. It was proved that this method made the expression of superposed information in UVFP of traditional Chinese medicine (TCM) digitized and simple. What’s more, an approach which can test the total chemical content with the chromophoric characteristics in the complex system of TCM rapidly, simply and accurately was achieved by the application of QUFM. In one word, it made the exploration of the general characteristic information of the molecular absorption complex TCM in the ultraviolet regions feasible and possible. PMID:25332974

Li, Lifeng; Liu, Zhongbo; Li, Yanfei

2013-01-01

392

Fully inorganic oxide-in-oxide ultraviolet nanocrystal light emitting devices  

Microsoft Academic Search

The development of integrated photonics and lab-on-a-chip platforms for environmental and biomedical diagnostics demands ultraviolet electroluminescent materials with high mechanical, chemical and environmental stability and almost complete compatibility with existing silicon technology. Here we report the realization of fully inorganic ultraviolet light-emitting diodes emitting at 390 nm with a maximum external quantum efficiency of ~0.3%, based on SnO2 nanoparticles embedded

Norberto Chiodini; Roberto Lorenzi; Alessandro Lauria; Marco Romagnoli; Sergio Brovelli; Alberto Paleari

2012-01-01

393

Heatsink requirements for coherent operation of high-power semiconductor laser arrays  

NASA Astrophysics Data System (ADS)

The heatsink requirements for coherent operation of laser-diode arrays are examined through thermal analysis of semi-infinite heatsinks and the phase locking of laser diodes. The thermal analysis is extended to shaped heatsinks by the use of PATRAN and NASTRAN computer programs. It is shown that mounting laser-diode arrays at the edge of semi-infinite copper heatsinks results in temperature variations between individual laser-diode elements that are too large to permit coherent operation except at relatively low power levels. It is also shown that the use of diamond and shaped heatsinks makes it possible to operate large arrays coherently to high optical output levels.

Garmire, E.; Tavis, M. T.

1984-08-01

394

Eve: Extreme Ultraviolet Variability Experiment  

NSDL National Science Digital Library

In this NASA video, scientists describe how the Extreme Ultraviolet Variability Experiment will sample and track the Sun's ultraviolet irradiance, providing a detailed time sequence of extreme ultraviolet output -- data that can provide advance warning for potentially disruptive energy bursts.

2011-10-28

395

Diode-Pumped Solid State Lasers  

E-print Network

III The use ofdiode lasers instead ofHashlamps as optical pump sources for solid state lasers offers significant advantages such as higher efficiency and longer lifetime. We have demonstrated three novel lasers based on this technology. The first is a zig-zag slab laser pumped by hybrid planar microchannel-cooled diode arrays that allow high-repetition-rate operation in a pulsed mode. The second is an end-pumped laser that uses multiple diode lasers for power scalabilitywhile maintaining high efficiency and good beam quality. The third is a Yb:YAG laser, pumped by strained-layer InGaAs diode lasers, that offers advantages over AlGaAs-pumped Nd:YAG lasers. These advances should lead to lower-cost higher-power solid state lasers. I NTEREST HAS INCREASED in the past few years in using semiconductor diode lasers to excite solid state lasers based on rare-earth ion-doped transparent solids such as neodymium-doped yttrium aluminum

T. Y Fan

396

Defect Tolerance of an Optically Reconfigurable Gate Array with a One-time Writable Volume Holographic Memory  

Microsoft Academic Search

Optically reconfigurable gate arrays (ORGAs) have been developed as a type of multi-context field programmable gate array to realize fast reconfiguration and numerous reconfiguration contexts. Along with such advantages, ORGAs have high defect tolerance. They consist simply of a holographic memory, a laser diode array, and a gate array VLSI. Even if a gate array VLSI includes defective areas, the

Takayuki Mabuchi; Kenji Miyashiro; M. Watanabe; A. Ogiwara

2009-01-01

397

Ultraviolet absorption experiment MA-059  

NASA Technical Reports Server (NTRS)

The ultraviolet absorption experiment performed during the Apollo Soyuz mission involved sending a beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation, all filling the same 3 deg-wide field of view from the Apollo to the Soyuz. The radiation struck a retroreflector array on the Soyuz and was returned to a spectrometer onboard the Apollo. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Information concerning oxygen densities was also obtained by observation of resonantly fluorescent light. The absorption experiments for atomic oxygen and atomic nitrogen were successfully performed at a range of 500 meters, and abundant resonance fluorescence data were obtained.

Donahue, T. M.; Hudson, R. D.; Anderson, J.; Kaufman, F.; Mcelroy, M. B.

1976-01-01

398

Silicon Diode Basics  

NSDL National Science Digital Library

Created by Patrick Hoppe of the Wisconsin Online Resource Center, this primer introduces the student to the key terms and concepts associated with the silicon diode. This is a nice introductory flash presentation for those interested in this topic.

Hoppe, Patrick

2010-09-27

399

Chemically Modulated Graphene Diodes  

PubMed Central

We report the manufacture of novel graphene diode sensors (GDS), which are composed of monolayer graphene on silicon substrates, allowing exposure to liquids and gases. Parameter changes in the diode can be correlated with charge transfer from various adsorbates. The GDS allows for investigation and tuning of extrinsic doping of graphene with great reliability. The demonstrated recovery and long-term stability qualifies the GDS as a new platform for gas, environmental, and biocompatible sensors. PMID:23547771

2013-01-01

400

Application of AXUV diode detectors at ASDEX Upgrade  

NASA Astrophysics Data System (ADS)

In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5?s was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales.

Bernert, M.; Eich, T.; Burckhart, A.; Fuchs, J. C.; Giannone, L.; Kallenbach, A.; McDermott, R. M.; Sieglin, B.

2014-03-01

401

Application of AXUV diode detectors at ASDEX Upgrade  

SciTech Connect

In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5?s was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales.

Bernert, M., E-mail: matthias.bernert@ipp.mpg.de; Eich, T.; Burckhart, A.; Fuchs, J. C.; Giannone, L.; Kallenbach, A.; McDermott, R. M.; Sieglin, B. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)] [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)

2014-03-15

402

Ultraviolet detectors Photon detectors  

E-print Network

of aluminum gallium nitride (AlxGa1-xN)-based thin films varies as a function of x, with x ranging from 0 to 1Ultraviolet detectors Photon detectors Photoelectric Semiconductor Photoconductive Schottky barrier

403

Extreme Ultraviolet Astronomy  

Microsoft Academic Search

The Extreme Ultraviolet Explorer pours back billions of bits of data that deepen understanding of galaxies, pulsars, quasars, black holes, and other astrophysical objects. The extreme UV data also illuminate cosmological mysteries.

Stuart Bowyer

1994-01-01

404

Diode laser power module for beamed power transmission  

NASA Technical Reports Server (NTRS)

Recent progress with powerful, efficient, and coherent monolithic diode master-oscillator/power-amplifier (M-MOPA) systems is promising for the development of a space-based diode laser power station. A conceptual design of a 50-kW diode laser power module was made for space-based power stations capable of beaming coherent power to the moon, Martian rovers, or other satellites. The laser diode power module consists of a solar photovoltaic array or nuclear power source, diode laser arrays (LDAs), a phase controller, beam-steering optics, a thermal management unit, and a radiator. Thermal load management and other relevant aspects of the system (such as power requirements and system mass) are considered. The 50-kW power module described includes the highest available efficiency of LD M-MOPA system to date. However, the overall efficiency of three amplifier stages, including the coupling efficiency, turns out to be 55.5 percent. Though a chain of PA stages generates a high-power coherent beam, there is a penalty due to the coupling loss between stages. The specific power of the 50-kW module using solar power is 6.58 W/kg.

Choi, S. H.; Williams, M. D.; Lee, J. H.; Conway, E. J.

1991-01-01

405

High brightness light emitting diode based on single ZnO microwire  

NASA Astrophysics Data System (ADS)

The ZnO microwires were synthesized repetitively via chemical vapor deposition method. The high power light emitting diode based on the single ZnO microwire/p-GaN heterojunction was realized. A strong ultraviolet emission accompanied by a relatively weak defects-related emission was observed at room temperature photoluminescence spectra of single ZnO microwire. The I-V curve of the heterojunction diode showed obvious rectifying characteristics with a turn-on voltage of about 7 V. Under the forward injection current of 1.1 mA, the ultraviolet electroluminescence centered at 389 nm wavelength could be obtained based on the single ZnO microwire/p-GaN heterojunction diode.

Ding, Meng; Zhao, Dongxu; Yao, Bin; Zhao, Bin; Xu, Xijin

2013-07-01

406

Far-Ultraviolet Stopped-Flow Circular Dichroism  

Microsoft Academic Search

A stopped-flow circular dichroism instrument, with a total accessible wavelength range of 200 to 750 nanometers, has been constructed and provides a spectroscopic method for kinetic investigations of a wide array of fast reactions in which optical activity changes in absorbing regions are involved. An important biochemical application depends on the far-ultraviolet capability, which allows observation of the rapid alterations

J. Luchins; S. Beychok

1978-01-01

407

Advances in AlGaInN laser diode technology  

NASA Astrophysics Data System (ADS)

The latest developments in AlGaInN laser diode technology are reviewed. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., i.e, 380nm, to the visible, i.e., 530nm, by tuning the indium content of the laser GaInN quantum well. Advantages of using Plasma assisted MBE (PAMBE) compared to more conventional MOCVD epitaxy to grow AlGaInN laser structures are highlighted. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of >100mW in the 400-420nm wavelength range that are suitable for telecom applications. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Galliumnitride (GaN) blue laser diode is reported. High power operation of AlGaInN laser diodes is demonstrated with a single chip, AlGaInN laser diode `mini-array' with a common p-contact configuration at powers up to 2.5W cw at 410nm. Low defectivity and highly uniform GaN substrates allow arrays and bars of nitride lasers to be fabricated. GaN laser bars of up to 5mm with 20 emitters, mounted in a CS mount package, give optical powers up to 4W cw at ~410nm with a common contact configuration. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be individually addressable allowing complex free-space and/or fibre optic system integration within a very small form-factor.

Najda, S. P.; Perlin, P.; Suski, T.; Marona, L.; Bockowski, Mike; Leszczy?ski, M.; Wisniewski, P.; Czernecki, R.; Kucharski, R.; Targowski, G.; Watson, S.; Kelly, A. E.

2014-03-01

408

JANTX1N5622 diode  

NASA Technical Reports Server (NTRS)

Report describes effects of power and temperature overstress on Semtech and Micro Semiconductor diodes. Semtech devices failed with excessive reverse bias leakage due to external paint. Micro Semiconductor diodes had reverse bias leakage failure due to damaged silicon.

1980-01-01

409

Dual function conducting polymer diodes  

DOEpatents

Dual function diodes based on conjugated organic polymer active layers are disclosed. When positively biased the diodes function as light emitters. When negatively biased they are highly efficient photodiodes. Methods of preparation and use of these diodes in displays and input/output devices are also disclosed.

Heeger, Alan J. (Santa Barbara, CA); Yu, Gang (Goleta, CA)

1996-01-01

410

Magnetic arrays  

DOEpatents

Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

Trumper, D.L.; Kim, W.; Williams, M.E.

1997-05-20

411

Magnetic arrays  

SciTech Connect

Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

Trumper, David L. (Plaistow, NH); Kim, Won-jong (Cambridge, MA); Williams, Mark E. (Pelham, NH)

1997-05-20

412

Diode laser--pumped solid-state lasers.  

PubMed

Diode laser-pumped solid-state lasers are efficient, compact, all solid-state sources of coherent optical radiation. Major advances in solid-state laser technology have historically been preceded by advances in pumping technology. The helical flash lamps used to pump early ruby lasers were superseded by the linear flash lamp and arc lamp now used to pump neodymium-doped yttrium-aluminum-garnet lasers. The latest advance in pumping technology is the diode laser. Diode laser-pumped neodymium lasers have operated at greater than 10 percent electrical to optical efficiency in a single spatial mode and with linewidths of less than 10 kilohertz. The high spectral power brightness of these lasers has allowed frequency extension by harmonic generation in nonlinear crystals, which has led to green and blue sources of coherent radiation. Diode laser pumping has also been used with ions other than neodymium to produce wavelengths from 946 to 2010 nanometers. In addition, Q-switched operation with kilowatt peak powers and mode-locked operation with 10-picosecond pulse widths have been demonstrated. Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode lasers for average power levels in excess of tens of watts and at a price that is competitive with flash lamp-pumped laser systems. Power levels exceeding 1 kilowatt appear possible within the next 5 years. Potential applications of diode laser-pumped solid-state lasers include coherent radar, global sensing from satellites, medical uses, micromachining, and miniature visible sources for digital optical storage. PMID:17832940

Byer, R L

1988-02-12

413

Fast cleanup method for the analysis of Sudan I-IV and para red in various foods and paprika color (oleoresin) by high-performance liquid chromatography/diode array detection: focus on removal of fat and oil as fatty acid methyl esters prepared by transesterification of acylglycerols.  

PubMed

A fast and effective cleanup method was developed for the analysis of Sudan I, II, III, IV, and Para Red (Sudan dyes) in various foods and paprika color (oleoresin) by high-performance liquid chromatography (LC) with a diode array detector (DAD). Removal of fat or oil in fatty sample was a critical point for reducing the volume of the final sample solution in order to obtain a sufficient level of the analytes. Separation of fat or oil from the dyes with a silica gel solid-phase extraction (SPE) column seemed unfeasible, because elution profiles of oil, fat, and the dyes were similar. Finally, fat and oil were separated from the dyes by elution from the SPE column with n-hexane, not as intact compounds but as fatty acid methyl esters prepared by direct transesterification of acylglycerols in fat and oil, leaving the dyes on the column. The dyes were eluted with n-hexane-diethyl ether (9 + 1). Gradient elution with water and tetrahydrofuran was used for separation on a C18 column by LC. Measurement of spectral of 0.5 microg/g of Sudan dyes in foods and 1 microg/g in paprika color (oleoresin) with the DAD was achieved. PMID:17474514

Uematsu, Yoko; Ogimoto, Mami; Kabashima, Junichirou; Suzuki, Kumi; Ito, Kouichi

2007-01-01

414

A photon thermal diode.  

PubMed

A thermal diode is a two-terminal nonlinear device that rectifies energy carriers (for example, photons, phonons and electrons) in the thermal domain, the heat transfer analogue to the familiar electrical diode. Effective thermal rectifiers could have an impact on diverse applications ranging from heat engines to refrigeration, thermal regulation of buildings and thermal logic. However, experimental demonstrations have lagged far behind theoretical proposals. Here we present the first experimental results for a photon thermal diode. The device is based on asymmetric scattering of ballistic energy carriers by pyramidal reflectors. Recent theoretical work has predicted that this ballistic mechanism also requires a nonlinearity in order to yield asymmetric thermal transport, a requirement of all thermal diodes arising from the second Law of Thermodynamics, and realized here using an 'inelastic thermal collimator' element. Experiments confirm both effects: with pyramids and collimator the thermal rectification is 10.9 ± 0.8%, while without the collimator no rectification is detectable (<0.3%). PMID:25399761

Chen, Zhen; Wong, Carlaton; Lubner, Sean; Yee, Shannon; Miller, John; Jang, Wanyoung; Hardin, Corey; Fong, Anthony; Garay, Javier E; Dames, Chris

2014-01-01

415

Diode pumped alkali lasers  

NASA Astrophysics Data System (ADS)

Diode pumped alkali lasers attract growing attention during the past several years because they have demonstrated potential to compete and, possibly, replace the best existing high power laser systems. In spite of the fact that an optically pumped alkali (potassium) vapor laser was first proposed by A.L. Schawlow and C.H. Townes in 1958, the intensive research and development of alkali vapor started only in 2003, when really efficient lasing in Rb and Cs vapors was demonstrated. The interest to this research was stimulated by the possibility of using efficient diode lasers for optical pumping of the alkali gain medium that promises high overall efficiency of the device. A variety of experiments on alkali lasers, including the demonstration of efficient Rb, Cs and K vapor lasers, power scaling experiments with multiple diode laser pumping sources and experiments on diode pumped alkali vapor amplifiers were performed during the past several years. In this paper we present a review of the most important achievements in high power alkali lasers research and development, discuss some problems existing in this field and future perspectives in DPAL development.

Zhdanov, B. V.; Knize, R. J.

2011-11-01

416

Reverse bias protected solar array with integrated bypass battery  

NASA Technical Reports Server (NTRS)

A method for protecting the photovoltaic cells in a photovoltaic (PV) array from reverse bias damage by utilizing a rechargeable battery for bypassing current from a shaded photovoltaic cell or group of cells, avoiding the need for a bypass diode. Further, the method mitigates the voltage degradation of a PV array caused by shaded cells.

Landis, Geoffrey A (Inventor)

2012-01-01

417

Junction temperature measurements in deep-UV light-emitting diodes.  

SciTech Connect

The junction temperature of AlGaN/GaN ultraviolet (UV) Light-Emitting Diodes (LEDs) emitting at 295 nm is measured by using the temperature coefficients of the diode forward volt-age 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 method (,,b 3 ,,aC). A theoretical model for the dependence of the diode junction voltage (Vj) on junction temperature (T) 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 AlGaN/GaN LED sample mounted with thermal paste on a heat sink.

Fischer, Arthur Joseph; 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; Bogart, Katherine Huderle Andersen

2004-12-01

418

Research in extreme ultraviolet and far ultraviolet astronomy  

Microsoft Academic Search

Instruments designed to explore different aspects of far and extreme ultraviolet cosmic radiation were studied. The far ultraviolet imager (FUVI) was flown on the Aries sounding rocket. Its unique large format 75mm detector mapped out the far ultraviolet background radiation with a resolution of only a few arc minutes. Analysis of this data indicates to what extent the FUVI background

S. E. Labov

1985-01-01

419

High-power semiconductor laser array packaged on microchannel cooler using gold-tin soldering technology  

NASA Astrophysics Data System (ADS)

High power semiconductor laser arrays have found increased applications in many fields. In this work, a hard soldering microchannel cooler (HSMCC) technology was developed for packaging high power diode laser array. Numerical simulations of the thermal behavior characteristics of hard solder and indium solder MCC-packaged diode lasers were conducted and analyzed. Based on the simulated results, a series of high power HSMCC packaged diode laser arrays were fabricated and characterized. The test and statistical results indicated that under the same output power the HSMCC packaged laser bar has lower smile and high reliability in comparison with the conventional copper MCC packaged laser bar using indium soldering technology.

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

2012-03-01

420

Upgrade of absolute extreme ultraviolet diagnostic on J-TEXT.  

PubMed

The absolute extreme ultraviolet (AXUV) diagnostic system is used for radiation observation on J-TEXT tokamak [J. Zhang, G. Zhuang, Z. J. Wang, Y. H. Ding, X. Q. Zhang, and Y. J. Tang, Rev. Sci. Instrum. 81, 073509 (2010)]. The upgrade of the AXUV system is aimed to improve the spatial resolution and provide a three-dimensional image on J-TEXT. The new system consists of 12 AXUV arrays (4 AXUV16ELG arrays, 8 AXUV20ELG arrays). The spatial resolution in the cross-section is 21 mm for the AXUV16ELG arrays and 17 mm for the AXUV20ELG arrays. The pre-amplifier is also upgraded for a higher signal to noise ratio. By upgrading the AXUV imaging system, a more accurate observation on the radiation information is obtained. PMID:25430327

Zhang, X L; Cheng, Z F; Hou, S Y; Zhuang, G; Luo, J

2014-11-01