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1

Validation of the analytical procedure for the determination of polyaromatic hydrocarbons in smoke flavourings using high performance liquid chromatography coupled to an ultraviolet, diode array or fluorescence detector  

Microsoft Academic Search

High performance liquid chromatography (HPLC) coupled to an ultraviolet (UV), diode array or fluorescence detector (UV\\/DAD\\/FLD)\\u000a has been used to set up an analytical procedure for the quantification of 16 EU priority polyaromatic hydrocarbons (PAHs)\\u000a in smoke flavourings. The following parameters have been determined for the 16 EU priority PAHs: limit of detection, limit\\u000a of quantification, precision (repeatability and intermediate

Catherine Brasseur; François Brose; Alain Pirlot; Caroline Douny; Gauthier Eppe; Guy Maghuin-Rogister; Marie-Louise Scippo

2007-01-01

2

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

3

Nitride laser diode arrays  

NASA Astrophysics Data System (ADS)

One of the most desired features of the semiconductor blue/near UV laser diodes (LDs) is the possibility to obtain high output powers from the devices. This can be realized by means of multi emitter structures. We demonstrate the construction of violet blue multi-quantum-well (MQW) InGaN/GaN laser mini - bars, yet quite novel system in nitride-based devices. It consists of three laser stripes (3 ?m wide), closely spaced with 40 ?m pitch. The structures were fabricated on high pressure grown, low dislocation density substrates. Under cw operation the measured spectra demonstrate sharp, almost single line emission (FWHM around 1.43 Å at ? = 406 nm). Measurements of the optical far field pattern revealed that when operated below threshold the device was emitting light from all three stripes, whereas during lasing we observed the optical mode only in the area of the middle laser stripe. The behavior of optical mode suggests the formation of the so called supermode (coherent emission from all three devices) which was observed also in case of structures fabricated with wider ridges (of 7 ?m with 20 ?m pitch).

Holc, K.; Leszczynski, M.; Suski, T.; Czernecki, R.; Braun, H.; Schwartz, U.; Perlin, P.

2009-02-01

4

Compact fiber-optic fluorosensor employing light-emitting ultraviolet diodes as excitation sources  

Microsoft Academic Search

A compact fluorosensor using three different ultraviolet light-emission diodes as excitation sources for fiber-optic recording of fluorescence spectra from samples is described. A compact integrated spectrometer with linear array wavelength recording is used, yielding a spectral resolution of about 8 nm. In two system implementations ultraviolet light-emitting diodes at 300, 340 and 395 nm, or at 360, 385 and 410 nm were used

Sara Ek; Benjamin Anderson; Sune Svanberg

2008-01-01

5

Compact diode array laser systems  

NASA Astrophysics Data System (ADS)

High pulse energy diode array laser systems have been constructed for therapeutic and diagnostic medical applications. Two systems are described. One system, constructed for therapeutic application in dermatology, uses 45 bars to generate > 10 joules of energy at approximately 800 nm in a 5-millisecond pulse. This system uses simple microlenses and non- imaging condensers to uniformly illuminate areas of 0.1 to 0.4 cm2 at fluences up to 40 joules per cm2. Cooling, power, and control electronics are housed within the control console, and the laser and condensing optics are housed in the handpiece connected to the control console by means of a two-meter umbilical. The complete system, including closed- cycle cooling, weighs under 14 kg and uses < 2 amps at 110 V. A second system, which is being developed as a burn diagnostic, utilizes a 15-bar diode laser array. The array generates over 3 joules of optical energy. The output light is homogenized and projected using microlenses, a non-imaging condenser, and projection optics. With this system an area of approximately 1000 cm2 can be uniformly illuminated at an intensity of one millijoule per square centimeter. The system, including receiving optics, can be battery-powered and packaged into a hand-held unit.

Holtz, James Z.; Grove, Robert E.

1995-04-01

6

Diode-Laser Array Suppresses Extraneous Modes  

NASA Technical Reports Server (NTRS)

Diode parameters varied to shape output beam. Array of phase-locked GaAs/GaAIAs diode lasers produces light beam with one main radiation lobe. Physical parameters of laser diodes differ from each other in way that favors oscillation in fundamental supermode, suppressing oscillation in higher-order modes.

Kapon, Elyahou; Lindsey, Chris P.; Katz, Joseph; Margalit, Shlomo; Yariv, Amnon

1988-01-01

7

Neutral, alkaline and difference ultraviolet spectra of secondary metabolites from Penicillium and other fungi, and comparisons to published maxima from gradient high-performance liquid chromatography with diode-array detection.  

PubMed

The ultraviolet spectra of 6 predominantly secondary metabolites from filamentous fungi which, inter alia, are useful in the identification of the compounds after chromatography, were obtained in neutral (methanol) and alkaline solvents. Difference spectra were obtained by subtracting the neutral from the alkaline spectrum for each metabolite, using the spectrophotometer software. The data and method are of use in differentiating metabolites with similar chromophores. A database of the maxima was stored on a microcomputer for flexible storage, retrieval and updating of information. These data are compared to those published previously, obtained by diode-array detection using gradient high-performance liquid chromatography, which indicated that changes in solvent concentrations of the gradient affect the spectra of some metabolites. This could cause misidentification of chemosyndromes and metabolites which have been claimed to be of use in fungal chemotaxonomy. PMID:2211911

Paterson, R R; Kemmelmeier, C

1990-07-01

8

Characterization and stabilization of fiber-coupled laser diode arrays  

E-print Network

Characterization and stabilization of fiber-coupled laser diode arrays D. F. Phillips,a) G. P. Wong the spectra and performance of an ensemble of 11 fiber-coupled laser diode arrays LDAs manufactured by Opto pumping light, many groups, including ours, now use fiber-coupled multistripe laser diode arrays LDAs

Walsworth, Ronald L.

9

Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source  

NASA Astrophysics Data System (ADS)

A compact, tunable and narrow-bandwidth laser source for ultraviolet radiation is presented. A grating stabilized diode laser at 1064 nm is frequency-stabilized to below 10 kHz by using a ultra low expansion (ULE) cavity. Injecting light of the diode laser into a tapered amplifier yields a power of 290 mW. In a first frequency-doubling stage, about 47 mW of green light at 532 nm is generated by using a periodically poled KTP crystal. Subsequent second-harmonic generation employing a BBO crystal leads to about 30 ?W of ultraviolet light at 266 nm.

Peng, Yu; Fang, Zhan-Jun; Zang, Er-Jun

2011-10-01

10

Graphene/GaN diodes for ultraviolet and visible photodetectors  

NASA Astrophysics Data System (ADS)

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

Lin, Fang; Chen, Shao-Wen; Meng, Jie; Tse, Geoffrey; Fu, Xue-Wen; Xu, Fu-Jun; Shen, Bo; Liao, Zhi-Min; Yu, Da-Peng

2014-08-01

11

High brightness multimode array laser diode  

Microsoft Academic Search

We have successfully demonstared 1x4 MMI array laser diode which is locked in phase achieving power in excess of 400 mW from a single mode output waveguide with slope efficiency of 20 % per facet. Far field measured at FWHM being 16.1deg at 418 mW and remained single lobed. This is an improvement over using single ridge waveguide by a

M. Murad; A. C. Bryce; V. Loyo-Maldonado

2009-01-01

12

Microcontroller interface for diode array spectrometry  

NASA Astrophysics Data System (ADS)

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

Aguo, L.; Williams, R. R.

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

Simulation of deep ultraviolet light-emitting diodes  

Microsoft Academic Search

Optical characteristics of deep ultraviolet light-emitting diodes with the consideration of spontaneous and piezoelectric polarizations are studied in this article with the APSYS (Advanced Physical Model of Semiconductor Devices) simulation program. The amounts of surface charges caused by different polarizations are calculated and compared. Moreover, the band diagram, carrier distribution, radiative recombination current, and light-current performance curves of the InAlGaN

Yen-Kuang Kuo; Sheng-Horng Yen; Yu-Wen Wang

2007-01-01

15

Silicon monolithic microchannel-cooled laser diode array  

SciTech Connect

A monolithic microchannel-cooled laser diode array is demonstrated that allows multiple diode-bar mounting with negligible thermal cross talk. The heat sink comprises two main components: a wet-etched Si layer that is anodically bonded to a machined glass block. The continuous wave (cw) thermal resistance of the 10 bar diode array is 0.032 degree sign C/W, which matches the performance of discrete microchannel-cooled arrays. Up to 1.5 kW/cm{sup 2} is achieved cw at an emission wavelength of {approx}808 nm. Collimation of a diode array using a monolithic lens frame produced a 7.5 mrad divergence angle by a single active alignment. This diode array offers high average power/brightness in a simple, rugged, scalable architecture that is suitable for large two-dimensional areas. (c) 2000 American Institute of Physics.

Skidmore, J. A. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); Freitas, B. L. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); Crawford, J. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); Satariano, J. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); Utterback, E. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); DiMercurio, L. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); Cutter, K. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States); Sutton, S. [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, L-482, Livermore, California 94551 (United States)

2000-07-03

16

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

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

2014-08-01

19

Simulation of deep ultraviolet light-emitting diodes  

NASA Astrophysics Data System (ADS)

Optical characteristics of deep ultraviolet light-emitting diodes with the consideration of spontaneous and piezoelectric polarizations are studied in this article with the APSYS (Advanced Physical Model of Semiconductor Devices) simulation program. The amounts of surface charges caused by different polarizations are calculated and compared. Moreover, the band diagram, carrier distribution, radiative recombination current, and light-current performance curves of the InAlGaN UV LED structures with different polarizations are also discussed and investigated. According to the simulated results, we find that the influence of the spontaneous polarization is more apparent than the piezoelectric polarization on band properties, carrier distribution, radiative recombination and output power in deep UV spectral region. In other words, for nitride materials in deep UV region, the polarization resulted from lattice-mismatch is smaller than that caused by asymmetry of the structure along the c-axis. This conclusion is quite different from the situation of blue InGaN light-emitting diodes. For blue LEDs, the piezoelectric polarization is the dominant polarization mechanism because the lattice mismatch between compound layers is a severe problem for these long-wavelength LED devices.

Kuo, Yen-Kuang; Yen, Sheng-Horng; Wang, Yu-Wen

2007-09-01

20

Monolithic millimeter-wave diode grid frequency multiplier arrays  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

21

Microchannel heatsinks for high average power laser diode arrays  

SciTech Connect

Detailed performance results and fabrication techniques for an efficient and low thermal impedance laser diode array heatsink are presented. High duty factor or even CW operation of fully filled laser diode arrays is enabled 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 a photolithographic pattern definition procedure followed by anisotropic chemical etching. A modular rack-and-stack architecture is adopted for the heatsink design allowing arbitrarily large two-dimensional arrays to be fabricated and easily maintained. The excellent thermal control of the microchannel cooled heatsinks is ideally suited to pump array requirements for high average power crystalline lasers because of the stringent temperature demands that result from coupling the diode light to several nanometers wide absorption features characteristic of leasing ions in crystals.

Beach, R.; Benett, B.; Freitas, B.; Ciarlo, D.; Sperry, V.; Comaskey, B.; Emanuel, M.; Solarz, R.; Mundinger, D.

1992-01-01

22

Development and validation of a solid-phase extraction method coupled to high-performance liquid chromatography with ultraviolet-diode array detection for the determination of sulfonylurea herbicide residues in bovine milk samples.  

PubMed

This study proposes a fast, simple and sensitive liquid chromatography diode array detector (LC/UV-DAD)-based method for the simultaneous determination of eight sulfonylurea herbicides (bensulfuron methyl, chlorsulfuron, metsulfuron methyl, primisulfuron methyl, rimsulfuron, thifensulfuron methyl, triasulfuron and tribenuron methyl) in bovine whole milk at concentrations lower than the default limit of 0.01 mg kg(-1) allowed by current legislation (Regulation EC/396/2005 and following Annexes). An effective one-step solid phase extraction (SPE) and clean up procedure was defined with use of Chem Elut cartridges, providing good recoveries for all the analytes tested and with no matrix effects affecting method accuracy. Separation of herbicides was obtained on a C(18) column by acetonitrile- water gradient elution. Method validation has been performed according to European Commission Decision 2002/657/EC criteria, in terms of linearity, recovery, precision, specificity, decision limit (CC(?)) and detection capability (CC(?)). Typical recoveries ranged between 78.4% and 99.7%, at the maximum residue limits (MRLs) levels established by Regulation EC/396/2005, with relative standard deviations (RSD) no larger than 10%. PMID:21277578

Seccia, Serenella; Albrizio, Stefania; Fidente, Paola; Montesano, Domenico

2011-03-01

23

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

24

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

25

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

26

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

27

Applications of microlens-conditioned laser diode arrays  

NASA Astrophysics Data System (ADS)

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. This architecture enables the generation of pump bemas that are scalable in absolute power with intensities approaching 100 kW/cm2. 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, so as to minimize losses resulting from reabsorption of the laser radiation. The necessity of low temperature operation has rendered such systems impractical for many applications. Our 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. Unique laser systems for applications in fields such as medicine and remote sensing can now be simply realized. We have also been involved in programs to evaluate the use of direct diodes for material processing applications. Here, diode radiation from an extended two-dimensional microlens-conditioned array is focused and delivered directly onto a work piece. Systems based on this concept can be utilized in the heat treating and hardening of metals. Another application of microlens-conditioned laser diode arrays is in the direct coupling of their radiation to optical fibers. Direct diode-to-fiber coupling has recently been demonstrated for a medical application in which 22 W of cw 690 nm radiation was delivered from a microlens-conditioned stack of AlGaInP laser diode bars through a 1 mm core fused silica fiber. This approach used a simple and inexpensive 1 cm focal length lens to direct the microlens-conditioned radiation from the diode stack into the optical fiber.

Beach, Raymond J.; Emanuel, Mark A.; Freitas, Barry L.; Skidmore, Jay A.; Carlson, Nils W.; Benett, William J.; Solarz, Richard W.

1995-05-01

28

Line Narrowing of Fiber Coupled Laser Diode Array He Lung MRI  

E-print Network

Line Narrowing of Fiber Coupled Laser Diode Array and 3 He Lung MRI by Jermane E. Massey B. For fiber coupled laser diode arrays, gains (~ 2) were limited by light polarization, coupling efficiency Coupled Laser Diode Array and 3 He Lung MRI by Jermane E. Massey Submitted to the Department of Physics

Walsworth, Ronald L.

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

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 duration of the 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

2007-03-31

32

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

Microsoft Academic Search

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

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

2006-01-01

33

Near-ultraviolet light-emitting diodes based on ?-conjugated linear silicon-backbone polymers  

Microsoft Academic Search

We report the basic device characteristics of light-emitting diodes (LEDs) based on linear silicon-backbone polymers, polysilanes, with a view to the possibility of employing them as an emissive material in a solid-state light source in the near-ultraviolet (NUV) or ultraviolet (UV) region. The LEDs we fabricated have a single-layer structure consisting of a thin film of polysilane polymer, together with

Hiroyuki Suzuki; Satoshi Hoshino; Chien-Hua Yuan; Michiya Fujiki; Seiji Toyoda; Nobuo Matsumoto

1998-01-01

34

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

35

Extreme ultraviolet imaging of wire array z-pinch experiments  

NASA Astrophysics Data System (ADS)

A multi-frame extreme ultraviolet imaging system based on four pinhole cameras, each backed by a gated microchannel plate (MCP) detector, was used to analyze plasma formation and dynamics in wire array z-pinch experiments on the MAGPIE generator (1 MA, 240 ns) at Imperial College (London). The use of pinhole size, object, and image distances, and MCP sensitivity to determine the spatial and spectral response of the diagnostic is discussed. A high magnification, high resolution version of the diagnostic has produced important information on wire initiation and plasma ablation in various materials. A low magnification version has allowed direct study of the snowplough sheath during array implosion, and of plasma instabilities during stagnation.

Bland, S. N.; Ampleford, D. J.; Bott, S. C.; Lebedev, S. V.; Palmer, J. B. A.; Pikuz, S. A.; Shelkovenko, T. A.

2004-10-01

36

Animation of Diode Array Detection in High Performance Liquid Chromatography  

NSDL National Science Digital Library

This animation site deals specifically with diode array detection for liquid chromatography. The animations are short (one to two minutes) and can easily be shown in class as part of a lecture. They are extremely helpful in illustrating key components and concepts of chromatographic systems. Users are encouraged to explore the site and the other brief animations as well. Separate links to other simulations by the same company (TRSL) are also listed on ASDL. This site requires FLASH version 7 or higher in order to work properly.

2011-05-03

37

Widely tunable ultraviolet C generation using wavelength selective external high-Q-cavity and a blue laser diode system  

NASA Astrophysics Data System (ADS)

This paper presents a second harmonic generation scheme using a nonlinear optic crystal and a multimode Fabry-Perot blue laser diode that has potential to generate widely tunable coherent deep ultraviolet at approximately 225 nm. Using the Fabry-Perot multimode laser diode with the sum-frequency technique, a high second harmonic power is hardly observed due to low conversion efficiency. In this paper, an approximately 1 ?W second harmonic ultraviolet power at around 225 nm ultraviolet wavelength and approximately 6 nm ultraviolet wavelength tunability can be obtained using a multi mode blue LD chip, a nonlinear optic crystal, and an external high-Q-cavity setup.

Tangtrongbenchasil, C.; Nonaka, K.

2008-04-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

39

The process and efficiency of ultraviolet generation from gallium nitride blue light emitting diodes  

NASA Astrophysics Data System (ADS)

To obtain small size, high speed ultraviolet sources, we studied the ultraviolet (UV) generation process and efficiency of gallium nitride (GaN) blue light emitting diodes (LEDs). The blue and UV emissions follow a four-level recombination model. Depending on the pump pulse amplitude, the UV-to-blue generation ratio increases and then saturates with increasing pump pulse duration. High efficiency, up to 450 ?W UV power at 380 nm, can be obtained from a 1.2 mW blue LED.

Basrur, J. P.; Choa, F. S.; Liu, P.-L.; Sipior, J.; Rao, G.; Carter, G. M.; Chen, Y. J.

1997-09-01

40

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

SciTech Connect

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

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

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

43

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

44

Phase-Modulation Fluorometer Using an Ultraviolet Light-Emitting Diode  

Microsoft Academic Search

We have constructed a phase-modulation fluorometer using a commercially-available ultraviolet light-emitting diode (UV LED) as an excitation light source. The center wavelength of the UV LED is 370 nm and its spectral bandwidth is 10 nm. A 10 mApp modulation-current was superimposed on a bias current of 5 mA with a fixed frequency in the range of 1-20 MHz. The

Tetsuo Iwata; Takeshi Kamada; Tsutomu Araki

2000-01-01

45

Ultraviolet light emitting diodes and hydrogen peroxide in the photodegradation of aqueous phenol  

Microsoft Academic Search

The novel system of ultraviolet (UV) light emitting diodes (LED) and hydrogen peroxide (H2O2) was studied for the degradation of phenol as a model organic pollutant in water. The effect of different viewing angles (15 and 120°), wavelengths (255, 265 and 280nm) and phenol and H2O2 concentrations were investigated in four photolytic batch reactors. Phenol degradation was observed to be

Sari H. Vilhunen; Mika E. T. Sillanpää

2009-01-01

46

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

47

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

Microsoft Academic Search

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

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

2002-01-01

48

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

DOEpatents

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

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

1992-01-01

49

Mid-ultraviolet light-emitting diode detects dipicolinic acid.  

SciTech Connect

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

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

2005-06-01

50

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

51

The integration of bypass diodes with terrestrial photovoltaic modules and arrays  

NASA Technical Reports Server (NTRS)

Bypass diodes are often required to limit the potential for reverse voltage 'hot-spot' heating in high voltage arrays or in arrays that undergo periodic operation near the short-circuit point. In addition, when properly applied, bypass diodes can minimize the effect of shadowing and various internal module failures on the array energy output. This paper discusses the mechanical and electrical integration of bypass diodes beginning with the array-level considerations which influence the selection of an implementation approach. Concepts for the mounting of these diodes, both internally within the module encapsulant and externally to the exposed rear surface of the module, are described. Factors affecting the reliability of bypass diodes, including the control of junction temperature through adequate heat sinking and the derating of reverse voltage, are discussed.

Shepard, N. F., Jr.; Sugimura, R. S.

1984-01-01

52

Effect of temperature and strain on the optical polarization of (In)(Al)GaN ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

The temperature and strain dependence of the polarization of the in-plane electroluminescence of (0001) orientated (In)(Al)GaN multiple quantum well light emitting diodes in the ultraviolet spectral range has been investigated. For light emitting diodes with emission wavelength shorter than 300 nm the transversal-electric polarized emission intensity increases relative to the transversal-magnetic emission with increasing temperature, whereas it decreases for ultraviolet light emitting diodes with longer emission wavelength. This effect can be attributed to occupation of deeper valence bands with increasing temperature. In addition, strain also strongly influence the in-plane light polarization of near ultraviolet light emitting diodes. The transversal-magnetic polarized emission becomes more dominant with decreasing in-plane tensile strain of the InGaN/(In)(Al)GaN multiple quantum well active region.

Kolbe, Tim; Knauer, Arne; Chua, Chris; Yang, Zhihong; Kueller, Viola; Einfeldt, Sven; Vogt, Patrick; Johnson, Noble M.; Weyers, Markus; Kneissl, Michael

2011-12-01

53

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

Microsoft Academic Search

Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a

H. Hemmati; J. R. Lesh

1989-01-01

54

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

55

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

56

High-power continuous wave 690 nm AlGaInP laser-diode arrays  

Microsoft Academic Search

High-power diode laser arrays emitting at 690 nm have been developed for solid-state laser pumping. The laser diode bars (fill factor ≊0.7) have been fabricated from single quantum well AlGaInP-based heterostructures. Using silicon microchannel heatsinks, a record high 360 W\\/cm2 per emitting aperture is achieved under continuous wave operation.

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

1995-01-01

57

Structure and Ultraviolet Electroluminescence of Nanocomposite\\/ GaN Heterostructure Light-Emitting Diodes  

Microsoft Academic Search

We fabricated and characterized ultraviolet (UV) light-emitting diodes (LEDs) composed of n-ZnO\\/SiO2-ZnO nanocomposite\\/p-GaN heterostructures. Significant UV electroluminescence at 387 nm from the n-ZnO layer in this heterostructure LED was observed at a forward-bias current of as low as 1.8 mA. This is ascribed to the high quality of the n-ZnO layer and the effective function of the SiO2-ZnO nanocomposite layer.

Miin-Jang Chen; Ying-Tsang Shih; Mong-Kai Wu; Hsing-Chao Chen; Hung-Ling Tsai; Wei-Chih Li; Jer-Ren Yang; Hon Kuan; Makoto Shiojiri

2010-01-01

58

Silicon carbide photomultipliers and avalanche photodiode arrays for ultraviolet and solar-blind light detection  

Microsoft Academic Search

Silicon carbide is known for its large bandgap and suitability to make highly sensitive ultraviolet photo-detectors. These devices show appreciable quantum efficiencies in the 240 nm - 350 nm wavelength range in combination with low dark currents. We present recent results on 4H-SiC avalanche photodiode arrays and SiC-based solid-state photomultiplier arrays suitable for ultraviolet and solar-blind light detection. A novel

Alexey Vert; Stanislav Soloviev; Alexander Bolotnikov; Peter Sandvik

2009-01-01

59

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

60

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

61

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

PubMed

A helical tomotherapy system is used in our clinic to deliver intensity-modulated radiation therapy (IMRT) treatments. Since this machine is designed to deliver IMRT treatments, the traditional field flatness requirements are no longer applicable. This allows the unit to operate without a field flatness filter and consequently the 400 mm wide fan beam is highly inhomogeneous in intensity. The shape of this beam profile is mapped during machine commissioning and for quality assurance purposes the shape of the beam profile needs to be monitored. The use of a commercial diode array for quality assurance measurements is investigated. Central axis beam profiles were acquired at different depths using solid water built-up material. These profiles were compared with ion chamber scans taken in a water tank to test the accuracy of the diode array measurements. The sensitivity of the diode array to variations in the beam profile was checked. Over a seven week period, beam profiles were repeatedly measured. The observed variations are compared with those observed with an on-board beam profile monitor. The diode measurements were in agreement with the ion chamber scans. In the high dose, low gradient region the average ratio between the diode and ion chamber readings was 1.000 +/- 0.005 (+/- 1 standard deviation). In the penumbra region the agreement was poorer but all diodes passed the distance to agreement (DTA) requirement of 2 mm. The trend in the beam profile variations that was measured with the diode array device was in agreement with the on-board monitor. While the calculated amount of variation differs between the devices, both were sensitive to subtle variations in the beam profile. The diode array is a valuable tool to quickly and accurately monitor the beam profile on a helical tomotherapy unit. PMID:16370429

Langen, K M; Meeks, S L; Poole, D O; Wagner, T H; Willoughby, T R; Zeidan, O A; Kupelian, P A; Ruchala, K J; Olivera, G H

2005-11-01

62

Low-frequency noise of GaN-based ultraviolet light-emitting diodes S. L. Rumyantsev,a  

E-print Network

for different types of ultraviolet UV light-emitting diodes LEDs with wavelengths from 280 to 375 nm. These UV LEDs are suitable for studying steady-state and time-varying UV fluorescences of biological materials the active region and from the LED series resistance. The noise level could be reduced by operating the UV

Pala, Nezih

63

A 2-D diode array and analysis software for verification of intensity modulated radiation therapy delivery.  

PubMed

An analysis is made of a two-dimensional array of diodes that can be used for measuring dose generated in a plane by a radiation beam. This measuring device is the MapCHECK Model 1175 (Sun Nuclear, Melbourne, FL). This device has 445 N-type diodes in a 22 x 22 cm2 2-D array with variable spacing. The entire array of diodes is easily calibrated to allow for measurements in absolute dose. For IMRT quality assurance, each beam is measured individually with the beam central axis oriented perpendicular to the plane of diodes. Software is available to do the analytical comparison of measurements versus dose distributions calculated by a treatment planning system. Comparison criteria of percent difference and distance-to-agreement are defined by the operator. Data are presented that show the diode array has linear response when beam fluence changes by over 300-fold, which is typical of the level of modulation in intensity modulated radiation therapy, IMRT, beams. A linear dependence is also shown for a 100-fold change in monitors units delivered. Methods for how this device can be used in the clinic for quality assurance of IMRT fields are described. Measurements of typical IMRT beams that are modulated by compensators and MLCs are presented with comparisons to treatment planning system dose calculations. A time analysis is done for typical IMRT quality assurance measurements. The setup, calibration, and analysis time for the 2-D diode array are on the order of 20 min, depending on numbers of fields. This is significantly less time than required to do similar analysis with radiographic film. The 2-D diode array is ideal for per-plan quality assurance after an IMRT system is fully commissioned. PMID:12772995

Jursinic, Paul A; Nelms, Ben E

2003-05-01

64

Optical Performance of N-Face AlGaN Ultraviolet Light Emitting Diodes  

NASA Astrophysics Data System (ADS)

The optical property and injection efficiency of N-face AlGaN based ultraviolet light emitting diodes (UV-LEDs) are studied and compared with Ga-face AlGaN based UV-LEDs. A staircase electron injector is introduced in the N-face AlGaN based UV-LED. The electroluminescence spectra, power-current performance curves, energy band diagrams, carrier concentration and radiative recombination rate are numerically calculated. The results indicate that the N-face UV-LED has a better optical performance than the Ga-face UV-LED, and the injection efficiency is enhanced owing to the fact that the staircase electron injector is available for UV-LEDs.

Yu, Hong-Ping; Li, Shi-Bin; Zhang, Peng; Wu, Shuang-Hong; Wei, Xiong-Bang; Wu, Zhi-Ming; Chen, Zhi

2014-10-01

65

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

SciTech Connect

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

Drapiko, E.; Peterson, B. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Alekseev, A. [TRINITI OFTR, Troitsk, Moscow Region 142190 (Russian Federation); Seo, D. C. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of)

2010-10-15

66

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

67

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

PubMed

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

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

2008-05-01

68

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

69

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

NASA Astrophysics Data System (ADS)

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

Svetikov, V. V.; Nurligareev, D. Kh

2014-09-01

70

High-power continuous wave 690 nm AlGaInP laser-diode arrays  

Microsoft Academic Search

High-power diode laser arrays emitting at 690 nm have been developed for solid-state laser pumping. The laser diode bars (fill factor [approx]0.7) have been fabricated from single quantum well AlGaInP-based heterostructures. Using silicon microchannel heatsinks, a record high 360 W\\/cm[sup 2] per emitting aperture is achieved under continuous wave operation.

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

1995-01-01

71

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

Microsoft Academic Search

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

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

2008-01-01

72

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

73

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

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 of the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.

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

2006-01-01

74

Phase Locking of Laser Diode Array by Using an Off-Axis External Talbot Cavity  

NASA Astrophysics Data System (ADS)

Phase locking of a laser diode array is demonstrated experimentally by using an off-axis external Talbot cavity with a feedback plane mirror. Due to good spatial mode discrimination, the cavity does not need a spatial filter. By employing the cavity, a clear and stable far-field interference pattern can be observed when the driver current is less than 14 A. In addition, the spectral line width can be reduced to 0.8 nm. The slope efficiency of the phase-locked laser diode array is about 0.62 W/A.

Su, Zhou-Ping; Ji, Zhi-Cheng; Zhu, Zhuo-Wei; Que, Li-Zhi; Zhu, Yun

2012-05-01

75

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

76

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

77

Demonstration of high-performance silicon microchannel heat exchangers for laser diode array cooling  

Microsoft Academic Search

A heat exchanger package has been demonstrated for semiconductor laser arrays using silicon microstructures with water as the coolant. A thermal impedance of 0.04 C sq cm\\/W has been achieved for a single linear bar. This design makes use of efficient edge-emitting laser diode arrays in a rack and stack architecture combined with a high-performance silicon microchannel structure to allow

D. Mundinger; R. Beach; W. Benett; R. Solarz; W. Krupke; R. Staver; D. Tuckerman

1988-01-01

78

Improved heat sinking for laser-diode arrays using microchannels in CVD diamond  

Microsoft Academic Search

This work proposes a novel cooling system for high-power laser-diode arrays, for which the maximum optical output power density per unit surface area is limited by the temperature rise due to self-heating. The proposed system uses a microchannel heat sink made of chemical-vapor-deposited (CVD) diamond, whose high thermal conductivity increases the efficiency of the channel-wall fins and reduces the array-to-coolant

Kenneth E. Goodson; Katsuo Kurabayashi; R. F. W. Pease

1997-01-01

79

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

E-print Network

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

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

2012-02-01

80

Discrete spectrum terahertz imaging using bow-tie diodes: optimized antenna designs and arrays  

NASA Astrophysics Data System (ADS)

Optimization routes to optimize the operation of InGaAs bow-tie diodes were demonstrated using simulations based on 3D finite-difference time-domain method. Calculations of the electromagnetic field amplitude distribution in a detector plane were performed. Three types of designs - bow-tie diode itself, log-periodic antenna and log-periodic antenna coupled with the bow-tie diode were analyzed; it was determined that frequency properties of such antennacoupled device can be tuned via variation of antenna shape and size. Multi-pixel InGaAs bow-tie diodes arrays of different designs - narrow band and broadband operation - were designed and fabricated. They were demonstrated to be well suited for continuous wave room temperature spectroscopic terahertz imaging at 0.58 THz and at 1.63 THz.

Minkevi?ius, Linas; Madeikis, Karolis; Kašalynas, Irmantas; Venckevi?ius, Rimvydas; Seliuta, Dalius; TamošiÅ«nas, Vincas; Valušis, Gintaras

2013-09-01

81

Remote online process measurements by a fiber optic diode array spectrometer  

Microsoft Academic Search

The development of remote online monitors for radioactive process streams is an active research area at the Savannah River Laboratory (SRL). A remote offline spectrophotometric measurement system has been developed and used at the Savannah River Plant (SRP) for the past year to determine the plutonium concentration of process solution samples. The system consists of a commercial diode array spectrophotometer

D. R. Van Hare; W. S. Prather; P. E. ORourke

1986-01-01

82

A Single Photon Avalanche Diode Array Fabricated in Deep-Submicron CMOS Technology  

Microsoft Academic Search

We report the first fully integrated single photon avalanche diode array fabricated in 0.35 mum CMOS technology. At 25 mum, the pixel pitch achieved by this design is the smallest ever reported. Thanks to the level of miniaturization enabled by this design, we were able to build the largest single photon streak camera ever built in any technology, thus proving

Cristiano Niclass; Maximilian Sergio; Edoardo Charbon

2006-01-01

83

A single photon avalanche diode array fabricated in deep-submicron CMOS technology  

Microsoft Academic Search

We report the first fully integrated single photon avalanche diode array fabricated in 0.35µm CMOS technology. At 25µm, the pixel pitch achieved by this design is the smallest ever reported. Thanks to the level of miniaturization enabled by this design, we were able to build the largest single photon streak camera ever built in any technology, thus proving the scalability

Cristiano Niclass; Maximilian Sergio; Edoardo Charbon

2006-01-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

85

Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp  

NASA Astrophysics Data System (ADS)

Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs.

Muramoto, Yoshihiko; Kimura, Masahiro; Nouda, Suguru

2014-06-01

86

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

87

Demonstration of high-performance silicon microchannel heat exchangers for laser diode array cooling  

SciTech Connect

A heat exchanger package has been demonstrated for semiconductor laser arrays using silicon microstructures with water as the coolant. A thermal impedance of 0.04 /sup 0/C cm/sup 2//W has been achieved for a single linear bar. This design makes use of efficient, edge-emitting laser diode arrays in a rack and stack architecture combined with a high-performance silicon microchannel structure to allow cw operation. The architecture can be scaled to large areas and we project a thermal impedance of 0.09 /sup 0/C cm/sup 2//W for close-packed two-dimensional arrays on this device.

Mundinger, D.; Beach, R.; Benett, W.; Solarz, R.; Krupke, W.; Staver, R.; Tuckerman, D.

1988-09-19

88

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

SciTech Connect

Recent upgrades to CDX-U spherical torus diagnostics include two 10-channel AXUV diode arrays. The multilayer mirror (MLM) array measures the {lambda}150 O VI brightness profile in the poloidal plane using the Mo/B{sub 4}C synthetic multilayer structures as dispersive elements. The foil filter array has a tangential view and is equipped with interchangeable clear aperture, beryllium and titanium filters. This allows measurements of radiated power, O VI or C V radial distributions, respectively. The O VI and C V emissivity and the radiated power profiles are highly peaked. A Neoclassical impurity accumulation mechanism is considered as an explanation. For radiated power measurements in the T{sub e}{<=}100 eV plasmas, photon energy dependent corrections must be used in order to account for nonlinear AXUV sensitivity in the range E{sub phot}{<=}20 eV. The arrays are also used for characterization of resistive MHD phenomena, such as the low m modes, saw-tooth oscillations and internal reconnection events. Based on the successful operation of the diagnostics, a new ultra soft x-ray multilayer mirror diode AXUV diode array monitoring the 34 Aa emissivity distribution of C VI will be built and installed on the National Spherical Torus Experiment.

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

2001-01-01

89

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

Microsoft Academic Search

A simple high-performance liquid chromatography (HPLC) method with ultraviolet diode array (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of vardenafil, sildenafil, tadalafil, testosterone, procaine, lidocaine, prilocaine, and benzocaine in cosmetic creams sold as promising remedies for male erectile dysfunction and female genitals stimulation. The presence of these substances in commercial cosmetic samples is

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

2009-01-01

90

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

E-print Network

O nanowire inorganic/organic hybrid ultra- violet (UV) light-emitting diodes (LEDs) have attracted film structures. However, up to date, the external quantum efficiency of UV LED based on Zn generation optoelectronic devices operating in ultraviolet (UV) region, such as light-emitting diodes (LEDs

Wang, Zhong L.

91

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

92

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

93

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

94

AlGaN-based ultraviolet light-emitting diodes grown on AlN epilayers  

SciTech Connect

AlGaN-based deep-ultraviolet light-emitting diode (LED) structures, which radiate light at 305 and 290 nm, have been grown on sapphire substrates using an AlN epilayer template. The fabricated devices have a circular geometry to enhance current spreading and light extraction. Circular UV LEDs of different sizes have been characterized. It was found that smaller disk LEDs had higher saturation optical power densities but lower optical powers than the larger devices. This trade-off between power and power density is a result of a compromise between electrical and thermal resistance, as well as the current crowding effect (which is due to the low electrical conductivity of high aluminum composition n- and p-AlGaN layers). Disk UV LEDs should thus have a moderate size to best utilize both total optical power and power density. For 0.85 mmx0.85 mm interdigitated LEDs, a saturation optical power of 2.9 mW (1.8 mW) at 305 nm (290 nm) was also obtained under dc operation.

Kim, K.H.; Fan, Z.Y.; Khizar, M.; Nakarmi, M.L.; Lin, J.Y.; Jiang, H.X. [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States)

2004-11-15

95

High power external cavity laser diode arrays for the generation of hyperpolarized noble gases  

NASA Astrophysics Data System (ADS)

Hyperpolarized noble gas magnetic resonance imaging promises to be a useful medical diagnostic tool due to its ability to image airways and brain function. A current limitation to widespread use is the time needed to generate gas quantities large enough for clinical patient imaging. Here I investigate line-narrowing of laser diode arrays in order to optimize the generation of hyperpolarized noble gases. Hyperpolarized noble gases are nuclear spin-½ isotopes that are polarized externally to have a large excess population of metastable spin up nuclei. When inhaled and imaged, they provide a novel tool for scientific studies and medical diagnosis in the human body. The gases are generated through a spin-exchange process via the spin-conserving hyperfine interaction of noble gas nuclei and optically pumped alkali metals. The net amount of polarized gas is limited by the optical power which is absorbed by the alkali metals as this is the first stage in the spin-exchange process. Laser diode arrays are typically used because they have a high available power for relatively low cost. Unfortunately, they are optically inefficient due to the factor of twenty larger inherent linewidth relative to the pressure broadened absorption linewidth of the alkali metal. In order to increase the efficiency of the system, I have designed and built an external cavity around the laser diode array consisting of a diffraction grating which acts as a wavelength dependent mirror tuned to the alkali metal rubidium absorption frequency. This causes the laser to operate solely at the desired wavelength, reducing the linewidth. External cavities have long been used for single element laser diodes. I extend this technique to laser diode arrays by imaging the diodes onto the grating using a set of imaging lenses forming individual cavities. I discuss the limitations on the power and linewidth achievable due to the optics of the cavity, as well as limitations caused by non-uniform heating effects. Finally, I present measurements of the nuclear polarization and absorption for Helium using our line-narrowed laser system and will compare and contrast the benefits of the line-narrowed system over the fiber-coupled laser diode arrays currently being used.

Blasche, Gregory Paul

96

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

97

Light emitting diode arrays for HWIL sensor testing  

NASA Astrophysics Data System (ADS)

We report here the light emission from IR interband-cascade (IC) Type-II-super lattice LED structures. We employed two different IC epitaxial structures for the LED experiments consisting of 9 or 18 periods of active super lattice gain regions separated by multilayer injection regions. The light output (and the voltage drop) of the LEDs is observed to increase with increase of number of IC active regions in the device. The voltage drop decreases with increase of mesa size and light emission increases with mesa sizes. We have made 8x7 2-D LED array flip-chip bonded to fan out array. The black body emissive temperature is 650 and 1050 K for LED operation at room and liquid nitrogen temperature respectively. A comparison of different IR sources for scene generation is presented.

Das, Naresh C.; Shen, P.; Simonis, George; Gomes, John; Olver, Kim

2005-05-01

98

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

99

Volume Bragg grating external cavities for the passive phase locking of high-brightness diode laser arrays  

E-print Network

, this approach benefits from superior simplicity due to the self-organization process, and it does not require of a phase-locked array of diode lasers in two configurations, the self-imaging cavity based on the Talbot Their outstanding electrical­optical efficiency and their un- beatable compactness and simplicity have made diode

Paris-Sud XI, Université de

100

A very high heat flux microchannel heat exchanger for cooling of semiconductor laser diode arrays  

Microsoft Academic Search

A low-cost, high heat flux heat exchanger for cooling of high power (of the order of 1000 W\\/cm2) semiconductor laser diode arrays has been designed and tested. The device uses a simple copper microchannel design to obtain very high fluid-to-wall heat transfer coefficients. Experimental results show that its overall thermal resistivity is less than 0.03°C\\/W, which is 2-3 times better

Sanjay K. Roy; Branko L. Avanic

1996-01-01

101

Use of high-performance liquid chromatography-diode array detection in forensic toxicology  

Microsoft Academic Search

A comprehensive approach to the analysis for many drugs in postmortem blood and biological fluids using high-performance liquid chromatography and diode array detection has been developed. To reduce the likelihood of co-eluting interference components of postmortem blood or other drugs, selective back-extraction was also used to screen and quantitate drugs in blood and biofluids. An isocratic mobile phase (acetonitrile, phosphoric

Eva M. Koves

1995-01-01

102

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

103

Evaluation of a 2D diode array for IMRT quality assurance  

Microsoft Academic Search

Background and purpose: The QA of intensity modulated radiotherapy (IMRT) dosimetry is a laborious task. The goal of this work is to evaluate the dosimetric characteristics of a new 2D diode array (MapCheck from Sun Nuclear Corporation, Melbourne, Florida) and assess the role it can play in routine IMRT QA.Material and methods: Fundamental properties of the MapCheck such as reproducibility,

Daniel Létourneau; Misbah Gulam; Di Yan; Mark Oldham; John W. Wong

2004-01-01

104

Microlens array diffuser for a light-emitting diode backlight system  

Microsoft Academic Search

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

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

2006-01-01

105

Multilevel Diode-Clamped Converter for Photovoltaic Generators With Independent Voltage Control of Each Solar Array  

Microsoft Academic Search

In photovoltaic (PV) power systems where a set of series-connected PV arrays (PVAs) is connected to a conventional two-level inverter, the occurrence of partial shades and\\/or the mismatching of PVAs leads to a reduction of the power generated from its potential maximum. To overcome these problems, the connection of the PVAs to a multilevel diode-clamped converter is considered in this

Sergio Busquets-Monge; Joan Rocabert; Pedro Rodriguez; Salvador Alepuz; Josep Bordonau

2008-01-01

106

A silicon diode array scan converter for high-speed transient recording  

Microsoft Academic Search

A double-ended scan converter tube has recently been developed which uses a silicon diode array for the storage target. The purpose of the device is to capture high-speed single transients or low-repetition-rate signals and to retain the information until it can be read out at speeds slow enough for handling by conventional processing and display circuits. Improvements in wide-bandwidth deflection

R. Hayes

1975-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

108

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

109

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

Microsoft Academic Search

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

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

2004-01-01

110

Demonstration of side coupling between high power laser diode array and double-clad fiber using sub-wavelength grating  

Microsoft Academic Search

A sub-wavelength gold-embedded silica binary grating for side coupling light emission from a 976-nm high-power laser diode array into the 400-?m-diameter inner cladding of a double-clad fiber was demonstrated with near 50% overall coupling efficiency. ©2010 Optical Society of America OCIS codes: (050.2770) Gratings; (140.2010) Diode laser arrays; (060.0060) Fiber optics and optical communications. For the realization of high-power fiber

Chieh-Wei Huang; Ding-Wei Huang; Chun-Lin Chang; Dong-Yo Jheng; Kuang-Yu Hsu; Chieh-Hsiung Kuan; Sheng-Lung Huang

2011-01-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2004-08-01

112

Effect of injection current on the optical polarization of AlGaN-based ultraviolet light-emitting diodes.  

PubMed

The injection current dependence of optical polarization of ultraviolet (UV) light-emitting diodes (LEDs) emitting at wavelength of 310 nm and 277 nm was investigated by electroluminescence (EL) measurements. For both diodes, it was found that the degree of polarization (DOP) decreased obviously as the injection current increased. We attribute the decrease in DOP to the different changing trend of the intensity of the light emission from transverse electric (TE) polarization (E?c) and transverse magnetic (TM) polarization (E?c) as the injected carriers occupy higher states above k = 0 with increasing the injection current. For the 277 nm LED, even the polarization switching from TE to TM mode was observed. PMID:25321042

Hou, Mengjun; Qin, Zhixin; He, Chenguang; Cai, Jun'an; Wang, Xinqiang; Shen, Bo

2014-08-11

113

In vitro bactericidal effects of near-ultraviolet light from light-emitting diodes on Helicobacter pylori.  

PubMed

We investigated whether near-ultraviolet light emitted from light-emitting diodes (LEDs) effects Helicobacter pylori viability and whether this new method can potentially apply to eradication therapy. Three H. pylori strains were used for near-ultraviolet (UV) LED irradiation experiments. Viability of isolates exposed to near-UV light was compared with controls by counting colony forming units. A time-dependent bactericidal effect of near-UV light was definitely observed. LED irradiation with near-UV light showed effective bactericidal activity against H. pylori strains. Eradication therapy with LED might provide a new avenue of treatment in patients refractory to eradication due to antibiotic resistance and/or adverse effects of antibiotics. PMID:24063529

Okamoto, Takeshi; Nishikawa, Jun; Yanai, Hideo; Nakamura, Hiroki; Takeuchi, Hiroaki; Kurai, Satoshi; Akada, Junko K; Sakaida, Isao

2013-12-01

114

270 nm Pseudomorphic Ultraviolet Light-Emitting Diodes with Over 60 mW Continuous Wave Output Power  

NASA Astrophysics Data System (ADS)

In this letter, the achievement of over 60 mW output power from pseudomorphic ultraviolet light-emitting diodes in continuous wave operation is reported. Die thinning and encapsulation improved the photon extraction efficiency to over 15%. Improved thermal management and a high characteristic temperature resulted in a low thermal rolloff up to 300 mA injection current with an output power of 67 mW, an external quantum efficiency (EQE) of 4.9%, and a wall plug efficiency (WPE) of 2.5% for a single-chip device emitting at 271 nm in continuous wave operation.

Grandusky, James R.; Chen, Jianfeng; Gibb, Shawn R.; Mendrick, Mark C.; Moe, Craig G.; Rodak, Lee; Garrett, Gregory A.; Wraback, Michael; Schowalter, Leo J.

2013-03-01

115

Suppression of Nonradiation Recombination by Selected Si Doping in AlGaN Barriers for Ultraviolet Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

The effect of selective Si doping on the emission efficiency in ultraviolet (UV) light-emitting diodes (LEDs) is investigated both experimentally and theoretically. The results show that the light output power increases with the number of Si-doped barriers (QBs). Experimental results indicate that compared with an all-undoped-QB LED, a factor of 3.17 can be achieved for the output power of an all-doped-QB LED at 350 mA. Detailed analysis on this phenomenon shows that the Si-doped QB is beneficial to suppress the nonradiative recombination rate by excess electrons in doped barriers.

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

2013-08-01

116

Graphene-silver nanowire hybrid structure as a transparent and current spreading electrode in ultraviolet light emitting diodes  

NASA Astrophysics Data System (ADS)

We report a device that combines graphene film and Ag nanowires (AgNWs) as transparent and current spreading electrodes for ultra-violet (UV) light emitting diode (LED) with interesting characteristics for the potential use in the deep UV region. The current-voltage characteristics and electroluminescence (EL) performance show that graphene network on AgNWs well-operates as a transparent and current spreading electrode in UV LED devices. In addition, scanning electron microscopy and EL images exhibit that graphene film act as the protection layer of AgNWs layer as well as a transparent conducting network, by bridging AgNWs.

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

2013-07-01

117

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

118

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

119

Feasibility of ultraviolet-light-emitting diodes as an alternative light source for photocatalysis.  

PubMed

The objective of this study was to determine whether ultraviolet-light-emitting diodes (UV-LEDs) could serve as an efficient photon source for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A (lambda max = 365 nm) LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp for a bench scale annular reactor packed with silica-titania composite (STC) pellets. Lighting and thermal properties of the module were characterized to assess its uniformity and total irradiance. A forward current (I(F)) of 100 mA delivered an average irradiance of 4.0 mW cm(-2) at a distance of 8 mm, which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED and BLB reactors were tested for the oxidization of ethanol (50 ppm(v)) in a continuous-flow-through mode with 0.94 sec residence time. At the same average irradiance, the UV-A LED reactor resulted in a lower CO2 production rate (19.8 vs. 28.6 nmol L(-1) s(-1)), lower ethanol removal (80% vs. 91%), and lower mineralization efficiency (28% vs. 44%) than the UV-A BLB reactor. Ethanol mineralization was enhanced with the increase of the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED reactor relative to the BLB reactor at the same average irradiance could be attributed to the nonuniform irradiance over the photocatalyst, that is, a portion of the catalyst was exposed to less than the average irradiance. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off" feature for periodic irradiation. Nevertheless, our results also showed that the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB, demonstrating that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency. PMID:22010378

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

2011-09-01

120

Diode array side-pumped neodymium-doped gadolinium scandium gallium garnet rod and slab lasers  

NASA Astrophysics Data System (ADS)

Gadolinium scandium gallium garnet (GSGG) was studied as a high average power laser host material utilizing diode array side pumping. Maximum optical slope efficiencies of 41.5% for Nd:GSGG in the rod geometry and 32.5% for a Nd:Cr:GSGG zig-zag slab were obtained at 1.06 ?m. Nd:GSGG and Nd:YAG have similar fluorescence lifetimes while Nd:GSGG has better energy storage capabilities due to its smaller stimulated-emission cross section.

Caffey, David P.; Utano, Richard A.; Allik, Toomas H.

1990-02-01

121

Scaling trends of single-photon avalanche diode arrays in nanometer CMOS technology  

NASA Astrophysics Data System (ADS)

A family of scaleable single photon avalanche diode (SPAD) structures in 130nm and 90nm CMOS is presented. Performance trends such as dark count rate (DCR), jitter and breakdown voltage are studied versus active diameter for devices ranging from 32?m down to 2?m. To address pixel pitch we introduce a shared buried n-well approach allowing compact arrays containing both NMOS-transistor readout circuitry and SPAD devices. A pixel pitch of 5?m has been achieved in 90nm CMOS technology, offering the potential for future megapixel single photon image sensors.

Richardson, Justin A.; Webster, Eric A. G.; Grant, Lindsay A.; Henderson, Robert K.

2011-05-01

122

Microlens array diffuser for a light-emitting diode backlight system.  

PubMed

Microlens array (MLA) diffusers for light-emitting diode (LED) backlight systems have been developed. A high fill-factor photoresist mold for the MLA was fabricated using three-dimensional diffuser lithography, and the patterns were transferred to a nickel master mold for UV-curable polymer replication. The fabricated microlens had various paraboloidal profiles, and its aspect ratio was controlled from 1.0 to 2.1. The MLA diffuser showed a batwing radiation pattern with a radiation angle of 150 degrees. The fabricated MLA diffuser may greatly enhance the color-mixing characteristics of LED backlight systems and help reduce the number of LEDs required. PMID:17001385

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

2006-10-15

123

Microlens array diffuser for a light-emitting diode backlight system  

NASA Astrophysics Data System (ADS)

Microlens array (MLA) diffusers for light-emitting diode (LED) backlight systems have been developed. A high fill-factor photoresist mold for the MLA was fabricated using three-dimensional diffuser lithography, and the patterns were transferred to a nickel master mold for UV-curable polymer replication. The fabricated microlens had various paraboloidal profiles, and its aspect ratio was controlled from 1.0 to 2.1. The MLA diffuser showed a batwing radiation pattern with a radiation angle of 150°. The fabricated MLA diffuser may greatly enhance the color-mixing characteristics of LED backlight systems and help reduce the number of LEDs required.

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

2006-10-01

124

12W CW operation of 640nm-band laser diode array  

NASA Astrophysics Data System (ADS)

A high-power and short-wavelength GaInP/AlGaInP quantum-well laser diode array was designed and fabricated. Because a conduction band offset of this material system is small, a carrier leakage from an active layer is an important limiting factor of the maximum light output. In this work, long cavity length of 1.5 mm, high front facet reflectivity of 18% and AlInP cladding layers were adopted to reduce the leakage. An evaluation test of the fabricated array was performed under CW operation. At 15°C, high light output of 12W was obtained with injection current of 16A. The lasing wavelength was 643.3 nm. Moreover, high wall-plug efficiency of 34% was achieved. These excellent characteristics are considered to be due to the effective suppression of the carrier leakage.

Shimada, Naoyuki; Shibata, Kimitaka; Hanamaki, Yoshihiko; Hamaguchi, Tsuneo; Yagi, Tetsuya

2008-02-01

125

Tunable absorption resonances in the ultraviolet for InP nanowire arrays.  

PubMed

The ability to tune the photon absorptance spectrum is an attracting way of tailoring the response of devices like photodetectors and solar cells. Here, we measure the reflectance spectra of InP substrates patterned with arrays of vertically standing InP nanowires. Using the reflectance spectra, we calculate and analyze the corresponding absorptance spectra of the nanowires. We show that we can tune absorption resonances for the nanowire arrays into the ultraviolet by decreasing the diameter of the nanowires. When we compare our measurements with electromagnetic modeling, we generally find good agreement. Interestingly, the remaining differences between modeled and measured spectra are attributed to a crystal-phase dependence in the refractive index of InP. Specifically, we find indication of significant differences in the refractive index between the modeled zinc-blende InP nanowires and the measured wurtzite InP nanowires in the ultraviolet. We believe that such crystal-phase dependent differences in the refractive index affect the possibility to excite optical resonances in the large wavelength range of 345 < ? < 390 nm. To support this claim, we investigated how resonances in nanostructures can be shifted in wavelength by geometrical tuning. We find that dispersion in the refractive index can dominate over geometrical tuning and stop the possibility for such shifting. Our results open the door for using crystal-phase engineering to optimize the absorption in InP nanowire-based solar cells and photodetectors. PMID:25402159

Aghaeipour, Mahtab; Anttu, Nicklas; Nylund, Gustav; Samuelson, Lars; Lehmann, Sebastian; Pistol, Mats-Erik

2014-11-17

126

Proton Irradiation of Ultraviolet 4H-SiC Single Photon Avalanche Diodes  

Microsoft Academic Search

The effects of proton irradiation on ultraviolet 4H-SiC single photon avalanche photodiodes (SPADs) are investigated for the first time. The SPADs, grown by chemical vapor deposition, were designed for operation in the ultraviolet having dark count rates (DCR) of about 30 kHz and single photon detection efficiency (SPDE) of 4.89%. The SPADs were irradiated with 2 MeV protons to a

Jun Hu; Xiaobin Xin; Jian H. Zhao; Brenda L. VanMil; Rachael Myers-Ward; Charles R. Eddy; David Kurt Gaskill

2011-01-01

127

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

E-print Network

. DOI: 10.1063/1.1407300 The organic light-emitting diode OLED offers many advantages in display OLED and converting the blue light to either red or green light with phosphors or ``color converters.'' If the OLED can emit in the ultraviolet UV , light conversion ef- ficiencies to the visible, in principle, can

128

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

129

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

PubMed

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

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

2013-08-30

130

Performance improvement of AlGaN-based deep ultraviolet light-emitting diodes by using staggered quantum wells  

NASA Astrophysics Data System (ADS)

The optical and physical properties of AlGaN-based deep ultraviolet light-emitting diodes (UV LEDs) with various specific designs of staggered quantum wells (QWs) are numerically investigated. Detailed analysis has been carried out on the light output power, energy band, overlap of electron and hole wavefunctions, carrier concentration, radiative recombination rate, spontaneous radiative spectrum and internal quantum efficiency. The simulated results reveal that the deep UV LEDs with the staggered quantum wells exhibit better performance than their conventional counterpart due to the diminished piezoelectric polarization fields in QWs which can increase the density of electron and hole and the overlap of the electron and hole wavefunctions, and thus enhance the radiative recombination rate.

Zhang, Min; Li, Yang; Chen, Shengchang; Tian, Wu; Xu, Jintong; Li, Xiangyang; Wu, Zhihao; Fang, Yanyan; Dai, Jiangnan; Chen, Changqing

2014-11-01

131

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

132

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

133

Surface plasmon enhanced light emission from AlGaN-based ultraviolet light-emitting diodes grown on Si (111)  

NASA Astrophysics Data System (ADS)

We report on the development of surface plasmon (SP) enhanced AlGaN-based multiple quantum wells (MQWs) ultraviolet (UV) light-emitting diodes (LEDs) grown on silicon (111) substrates. In order to generate SP-coupling with the radiating dipoles in MQWs, an aluminum layer is selectively deposited in holes etched in the top p-AlGaN to p-GaN layers. After flip-chip bonding and substrate removal, an optical output power of ˜1.2 mW is achieved at an emission wavelength of 346 nm; the output power of these UV LEDs with Al layer is increased by 45% compared to that of conventional UV LEDs without Al layer. This enhancement can be attributed to an increase in the spontaneous emission rate and improved internal quantum efficiency via resonance coupling between excitons in MQWs and SPs in the aluminum layer.

Cho, Chu-Young; Zhang, Yinjun; Cicek, Erdem; Rahnema, Benjamin; Bai, Yanbo; McClintock, Ryan; Razeghi, Manijeh

2013-05-01

134

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

135

Injection locking of a fiber-coupled laser diode array M.A. Humphrey, J.E. Massey, D.F. Phillips, and R.L. Walsworth  

E-print Network

1 Injection locking of a fiber-coupled laser diode array M.A. Humphrey, J.E. Massey, D.F. Phillips, fiber-coupled laser diode array was significantly narrowed by injection locking. Up to 72% of the 1 THz intrinsic to the fiber- coupling of the slave laser reduced the injection-locked gain to less than unity

Walsworth, Ronald L.

136

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

E-print Network

1352 OPTICS LETTERS / Vol. 25, No. 18 / September 15, 2000 Frequency-narrowed external-cavity diode-laser available from diode-laser arrays. In this Letter we describe the use of an external- cavity design-array bar B. Chann, I. Nelson, and T. G. Walker Department of Physics, University of Wisconsin

Walker, Thad G.

137

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

E-print Network

and 340 nm UV optical power output in III-nitride light emitting diodes LEDs using photonic crystals PCs mA of 300 300 m2 unpackaged LED chips revealed an increase by 63% and 95% for the blue and UV LEDs of extraction efficiency in LEDs is exceptionally great, especially for deep UV LEDs ( 340 nm) based on III

Jiang, Hongxing

138

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/m(2)). 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 m(2)/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

139

Quasi-instantaneous (less than 20 ps) phase locking in single-lobe Y-coupled laser diode arrays  

NASA Technical Reports Server (NTRS)

The time evolution of the far-field radiation pattern of an in-phase locked Y-coupled diode laser array has been observed with a streak camera. A strong central lobe 2.3 deg wide with faint secondary sidelobes separated by 15 deg forms in a time less than 20 ps. This indicates that the elements of the array are instantaneously locked in-phase.

Defreez, R. K.; Elliott, R. A.; Hartnett, K.; Welch, D. F.

1987-01-01

140

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

141

Thermal profile of high power laser diode arrays and implications in line-narrowing using external cavities  

E-print Network

nuclei and are generated via a hyperfine interaction with the polarized valence electrons of optically cavities G. Blasche and B. B. Goldberg, Department of Physics, Boston University, 590 Commonwealth Ave the profile imposes on the linewidth of the diode array in an external cavity configuration and discuss

142

Extraction, Detection, and Quantification of Heterocyclic Aromatic Amines in Portuguese Meat Dishes by HPLC\\/Diode Array  

Microsoft Academic Search

The present paper describes the results obtained in the analyses of heterocyclic aromatic amines (HAs) in bovine meat dishes prepared by three different coking methods; usually ingredients such as, salt, garlic, wine, olive oil, onion, and tomato were added. Control meat samples (cooked without ingredients) were also prepared. Analyses were performed by HPLC\\/diode array and detection of the eluted HAs

A. Melo; O. Viegas; R. Eça; C. Petisca; O. Pinho; I. M. P. L. V. O. Ferreira

2008-01-01

143

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

144

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

PubMed Central

We describe the design, characterization, and demonstration of a fully integrated single-photon avalanche diode (SPAD) imager for use in time-resolved fluorescence imaging. The imager consists of a 64-by-64 array of active SPAD pixels and an on-chip time-to-digital converter (TDC) based on a delay-locked loop (DLL) and calibrated interpolators. The imager can perform both standard time-correlated single-photon counting (TCSPC) and an alternative gated-window detection useful for avoiding pulse pile-up when measuring bright signal levels. To illustrate the use of the imager, we present measurements of the decay lifetimes of fluorescent dyes of several types with a timing resolution of 350 ps. PMID:23976789

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

2013-01-01

145

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

146

Handheld probe integrating laser diode and ultrasound transducer array for ultrasound/photoacoustic dual modality imaging.  

PubMed

Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expensive systems, which limits their clinical application and makes the combination costly and impracticable. In this work we present and evaluate a compact and ergonomically designed handheld probe, connected to a portable ultrasound system for inexpensive, real-time dual-modality ultrasound/photoacoustic imaging. The probe integrates an ultrasound transducer array and a highly efficient diode stack laser emitting 130 ns pulses at 805 nm wavelength and a pulse energy of 0.56 mJ, with a high pulse repetition frequency of up to 10 kHz. The diodes are driven by a customized laser driver, which can be triggered externally with a high temporal stability necessary to synchronize the ultrasound detection and laser pulsing. The emitted beam is collimated with cylindrical micro-lenses and shaped using a diffractive optical element, delivering a homogenized rectangular light intensity distribution. The system performance was tested in vitro and in vivo by imaging a human finger joint. PMID:25401669

Daoudi, K; van den Berg, P J; Rabot, O; Kohl, A; Tisserand, S; Brands, P; Steenbergen, W

2014-10-20

147

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

NASA Astrophysics Data System (ADS)

The 880 nm diode laser is emerging as the source of choice for pumping Nd:YV0 4 laser crystals because it offers higher pumping efficiency than 808 nm diode lasers[1]. This paper reports on recent progress in the development of high power, high reliability, 880 nm laser bars. Specifically, high performance has been achieved based on Coherent's aluminum-free active (AAA) epitaxial structures while maintaining lifetimes greater than 10,000 hours. This includes 30% fill factor, 1 cm bars on conductively cooled packages (CCP) operating at 51 W with proven manufacturability. We observed power conversion efficiency (PCE) of up to 56%. These lasers have a far field fast axis divergence of 32° (FWHM), and slow axis divergence of <7° (FWHM). Typical value of the FWHM of output spectrum is 2.5 nm. These bars were used to build fiber array packages (FAPs) operating at 45 W. We have achieved FAP PCE of 50% and numerical aperture of <0.12. Reliability of both bars and FAP was shown to exceed 10000h MTBF.

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

2006-02-01

148

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

149

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

150

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

Microsoft Academic Search

This study covers the investigation of deep UV GaN-based light emitting diodes using low frequency noise characterization. Using this technique, device improvements were analyzed as feedback to developers and practical parameters were created for system use. AlGaN LEDs emit wavelengths into the deep UV spectral region (lambda < 290 nm). These devices are an integral component for applications including biological

Shayla Maya Louise Sawyer

2006-01-01

151

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

152

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

153

MOCVD growth and characterization of ZnO nanowire arrays for advanced ultraviolet detectors  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) provides a unique wide bandgap biocompatible material system exhibiting both semiconducting and piezoelectric properties, and is a versatile functional material that has a diverse group of growth morphologies. Bulk ZnO has a bandgap of 3.37 eV that corresponds to emissions in the solar blind ultraviolet (UV) spectral band (240-280 nm). We have grown highly ordered vertical arrays of ZnO nanowires (NWs) and nanorods using a metal organic chemical vapor deposition (MOCVD) growth process on Si(111), SiO2, and sapphire substrates. The structural and optical properties of the grown vertically aligned ZnO nanostructure arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. The unique diffraction pattern for ZnO(002) concurred with the SEM inspection indicating vertical orientation of the NWs and nanorods. UV detectors based on ZnO NWs offer high UV sensitivity and low visible sensitivity for applications such as missile plume detection and threat warning. An analytical model that can predict sensor performance with and without gain for a desired UV band of interest has also been developed that has the potential for substantial improvements in sensor performance and reduction in size for a variety of threat warning applications. In addition, testing and characterization of photomultiplier tubes (PMTs) exposed to eight individual UV LEDs having peak wavelengths ranging from 248 nm to 370 nm has been performed to provide a relative UV detection performance benchmark. Compared to PMTs, the NW arrays are expected to exhibit low noise, extended lifetimes, high quantum efficiency, and very low power requirements.

Rivera, Abdiel; Zeller, John; Manzur, Tariq; Sood, Ashok; Anwar, Mehdi

2012-10-01

154

Fast single-photon avalanche diode arrays for laser Raman spectroscopy.  

PubMed

We incorporate newly developed solid-state detector technology into time-resolved laser Raman spectroscopy, demonstrating the ability to distinguish spectra from Raman and fluorescence processes. As a proof of concept, we show fluorescence rejection on highly fluorescent mineral samples willemite and spodumene using a 128×128 single-photon avalanche diode (SPAD) array with a measured photon detection efficiency of 5%. The sensitivity achieved in this new instrument architecture is comparable to the sensitivity of a technically more complicated system using a traditional photocathode-based imager. By increasing the SPAD active area and improving coupling efficiency, we expect further improvements in sensitivity by over an order of magnitude. We discuss the relevance of these results to in situ planetary instruments, where size, weight, power, and radiation hardness are of prime concern. The potential large-scale manufacturability of silicon SPAD arrays makes them prime candidates for future portable and in situ Raman instruments spanning numerous applications where fluorescence interference is problematic. PMID:21931428

Blacksberg, Jordana; Maruyama, Yuki; Charbon, Edoardo; Rossman, George R

2011-09-15

155

The development and application of a diode-laser-based ultraviolet absorption sensor for nitric oxide  

E-print Network

is required. The gas sample must also be dried to reduce interferences with water vapor. Interference with carbon dioxide (CO2) still presents a problem for FTIR analyzers. Similar to the FTIR analyzer, ultraviolet (UV) analyzers are available to measure... spectroscopic study of the NO molecule and water vapor, the P11(6) and P21(6) doublet lines were probed in order to minimize water vapor interference. Initial measurements were made in a room temperature absorption cell while higher temperature measurements...

Anderson, Thomas Nathan

2004-09-30

156

Quaternary InAlGaN-based high-efficiency ultraviolet light-emitting diodes  

Microsoft Academic Search

In order to realize 250-350-nm-band high-efficiency deep ultraviolet (UV) emitting devices using group-III-nitride materials, it is necessary to obtain high-efficiency UV emission from wide-band-gap (In)AlGaN. The use of the In-segregation effect, which has already been used for InGaN blue emitting devices, is quite effective for achieving high-efficiency deep UV emission. We have demonstrated high-efficiency UV emission from quaternary InAlGaN-based quantum

Hideki Hirayama

2005-01-01

157

Aluminum indium gallium nitride-based ultra-violet light emitting diodes: Microscopic physics of device operation  

NASA Astrophysics Data System (ADS)

Much progress has been made recently in the-advancement of III-Nitride based UV emitters, in particular light emitting diodes (LED). While high performance LEDs and diode lasers are available to wavelengths of about 360nm, a rather pronounced fall-off in the quantum efficiency occurs in today's devices towards shorter wavelengths. It is generally accepted that the necessity of introducing Al at higher concentrations into the quaternary AlInGaN system presents a significant level of difficulty in the control of defects that affect both the electronic transport and the radiative processes in the constituent layers within the LED structures. The microscopic details of the defect structure and their physical machinery remain still largely opaque, even though the first applications of the new generation of UV LEDs are beginning to emerge. In this present work, we investigate the performance of AlInGaN-based ultraviolet LEDs (UV LEDs) and compare their properties with the more extensively studied InGaN and low Al-concentration AlGaN systems. Additionally, we employ photoluminescence and time-correlated single photon counting (TCSPC) techniques in an effort to elucidate the defect mechanisms hindering the operation of the devices. Based upon our results, a model is suggested identifying some of the defects and their intricate interplay, responsible for the problematic electrical transport of carriers within the UV LED structures. This model, though qualitative in nature, may explain why the performance of the UV light emitters has not yet reached the metrics comparable to the LEDs in the blue and violet.

Makarona, Eleni

158

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

NASA Astrophysics Data System (ADS)

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

Valone, Thomas F.

2009-03-01

159

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

160

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

Microsoft Academic Search

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

Takashi Mukai; Shuji Nakamura

1999-01-01

161

High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy  

Microsoft Academic Search

Ultraviolet (UV) light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on a patterned sapphire substrate (PSS) using a single growth process of metalorganic vapor phase epitaxy. In this study, the PSS with parallel grooves along the sapphire direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). The GaN layer grown by lateral epitaxy on

Kazuyuki Tadatomo; Hiroaki Okagawa; Youichiro Ohuchi; Takashi Tsunekawa; Yoshiyuki Imada; Munehiro Kato; Tsunemasa Taguchi; H. Kudo

2001-01-01

162

Structure optimization of InGaN–GaN ultraviolet light-emitting diode with a low-energy electron injection mechanism  

Microsoft Academic Search

We propose a way of increasing overall efficiency of InGaN–GaN ultraviolet light-emitting diodes (UV LEDs) by placing a thin Si-doped AlGaN layer beneath the multiple quantum well (MQW). The AlGaN thin layer plays a role of tunneling barrier for the electrons, making a low-energy electron injection possible. The effect of the AlGaN thin film is verified by the simulation regarding

Tae Geun Kim; Kyoung Chan Kim; Dong-Ho Kim; Suk Ho Yoon; Jeoung Wook Lee; Cheol Soo Sone; Yong Jo Park

2004-01-01

163

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

164

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

165

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

166

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

167

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

NASA Astrophysics Data System (ADS)

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

Wang, Chang-Pei; Wu, Yuh-Renn

2012-08-01

168

Blue and near-ultraviolet light-emitting diodes on free-standing GaN substrates  

NASA Astrophysics Data System (ADS)

Blue and near-ultraviolet (UV) InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission at 465 nm and 405 nm, respectively, were grown on GaN and sapphire substrates. The densities of surface and bulk defects in the homoepitaxially grown LEDs were substantially reduced, leading to a decrease in reverse currents by more than six orders of magnitude. At a typical operating current of 20 mA, the internal quantum efficiency of the UV LED on GaN was twice as high compared to the UV LED on sapphire, whereas the performance of the blue LEDs was found to be comparable. This suggests that the high-density dislocations are of greater influence on the light emission of the UV LEDs due to less In-related localization effects. At high injection currents, both the blue and UV LEDs on GaN exhibited much higher output power than the LEDs on sapphire as a result of improved heat dissipation and current spreading.

Cao, X. A.; LeBoeuf, S. F.; D'Evelyn, M. P.; Arthur, S. D.; Kretchmer, J.; Yan, C. H.; Yang, Z. H.

2004-05-01

169

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

PubMed Central

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. PACS 41.20.Jb; 42.72.Bj; 85.60.Jb PMID:24495598

2014-01-01

170

Monolithic watt-level millimeter-wave diode-grid frequency tripler array  

NASA Technical Reports Server (NTRS)

In order to provide watt-level CW output power throughout the millimeter and submillimeter wave region, thousands of solid-state diodes have been monolithically integrated using a metal grid to produce a highly efficient frequency multiplier. Devices considered include GaAs Schottky diodes, thin MOS diodes, and GaAs Barrier-Intrinsic-N(+)diodes. The performance of the present compact low-cost device has been theoretically and experimentally validated.

Hwu, R. J.; Luhmann, N. C., Jr.; Rutledge, D. B.; Hancock, B.; Lieneweg, U.

1988-01-01

171

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

172

Liquid chromatography–UV diode-array detection method for multi-residue determination of macrolide antibiotics in sheep's milk  

Microsoft Academic Search

A rapid, simple and sensitive liquid chromatography–UV diode-array detection method was developed for the simultaneous determination of seven macrolides (erythromycin, oleandomycin, roxithromycin, josamycin, spiramycin, tylosin and ivermectin) in sheep's milk. The column, mobile phase, temperature and flow rate were optimised to provide the best resolution of these analytes. The extraction of the antibiotic residues involves the treatment of protein-free samples

M. A. García-Mayor; R. M. Garcinuño; P. Fernández-Hernando; J. S. Durand-Alegría

2006-01-01

173

Efficiency of transverse pumping of a solid-state pulsed Nd:YAG laser by laser diode arrays  

Microsoft Academic Search

A Nd3+:YAG laser with a cylindrical active element transversely pumped by quasi-continuous laser-diode arrays located around its side surface is studied experimentally. The developed pumping modules with symmetric and asymmetric geometries provide the differential efficiency of 48% and 55% for multimode free-running lasing upon pumping of elements of diameter 3 and 5 mm, respectively. Under the conditions corresponding to this

Aleksandr Yu Abazadze; Georgii M. Zverev; Yurii M. Kolbatskov

2002-01-01

174

Efficiency of transverse pumping of a solid-state pulsed Nd:YAG laser by laser diode arrays  

Microsoft Academic Search

A Nd{sup 3+}:YAG laser with a cylindrical active element transversely pumped by quasi-continuous laser-diode arrays located around its side surface is studied experimentally. The developed pumping modules with symmetric and asymmetric geometries provide the differential efficiency of 48% and 55% for multimode free-running lasing upon pumping of elements of diameter 3 and 5 mm, respectively. Under the conditions corresponding to

Aleksandr Yu Abazadze; Georgii M Zverev; Yurii M Kolbatskov

2002-01-01

175

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

176

Comprehensive Material Study of MOCVD grown Aluminum Indium Nitride and Development of Relaxed Template for Ultraviolet Diode Lasers  

NASA Astrophysics Data System (ADS)

AlGaN based conventional deep ultraviolet (UV) light emitting diodes (LEDs) grown on a sapphire or SiC substrate suffer from high threading dislocation density (TDD) (> 1 x 109 cm-2). The high quality bulk AlN substrate (TDD ˜ 1 x 104 cm-2) has shown promising results for high power deep UV LEDs but the substrates are not readily available yet. The performance of UV laser diodes (LDs) has been rapidly improved over the past few years. However, intrinsic valence band property of c-plane AlN could result in poor optical gain for c-plane LDs, especially in UV-C range. In this work, different approaches have been explored for further development of UV LEDs and LDs. The success of c-plane InGaN LEDs has been attributed to the indium induced local potential minima in a length scale shorter than the dislocation spacing. As a result, high internal quantum efficiency (IQE) can be achieved even with high TDD. UV LEDs could potentially benefit from this phenomenon by using AlInN as an active layer. However, due to the lack of understanding of this alloy, we start from the growth study of AlInN by metal organic chemical vapor deposition (MOCVD). High structural quality Al0.82In0.18N has been achieved on GaN, but large Stokes' shift of ˜0.6 eV and broad photoluminescence (PL) spectrum (˜0.3 eV) were also observed. The time resolved PL study revealed extremely long decay lifetime, suggesting the presence of deep traps. Electrical analysis of AlInN by capacitance -- voltage measurement showed n-type conductivity for UID Al0.82In0.18N, possibly due to oxygen. High quality semipolar (112¯2) Al0.76In 0.24N showed emission energy below the bandgap of GaN, allowing us to obtain the electroluminescence characteristics of AlInN. Appearance of a narrow peak under high injection current could shed a light on the emission property of AlInN. Semipolar substrates offer a number of advantages for UV emitting AlGaInN based laser diodes, including higher gain, an ability to operate with nearly transverse electric (TE) optical modes, and an ability to provide pseudo-substrates with tailorable lattice constants, something unavailable from bulk c-plane AlN substrates. AlInN and AlGaN lavers with various thicknesses and compositions have been grown on (202¯1) and (112¯2) bulk GaN substrates by MOCVD. With increasing thickness and Al composition, various defects -- c-plane misfit dislocations, cracks, and secondary defects -- were observed. The critical thickness of each process has been empirically estimated. We have also grown AlGaN on (202¯1) GaN, step grading to higher aluminum composition to minimize the generation of undesired defects. Multiple quantum wells (MQW) and LEDs were grown on a relaxed AlGaN on (202¯1) GaN. IQE measurements and the diode operation of near UV LEDs (lambda˜385 nm) on the relaxed buffer showed a promising result for device application of relaxed AlGaN template.

Chung, Roy B.

177

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

NASA Astrophysics Data System (ADS)

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

Zhang, Fute; Song, Tao; Sun, Baoquan

2012-05-01

178

A comparative study of the work involved in measuring profiles using an ion chamber, a linear diode array and film.  

PubMed

In this work a method of using Kodak X-Omat V film to measure beam profiles for dynamically wedged fields is presented. Also, the profiles determined by film measurement are compared with those measured with an ion chamber (0.12 cm3 Scanditronix RFA 300 RK) and an array of silicon diodes (11 channel Scanditronix linear diode array). The beam investigated is a 6 MV photon beam from a Varian 2100 C linear accelerator. The geometric method of positioning film and determining the central axis (CAX) position of the beam yielded results which agreed to within 1 mm with the software determined position of the CAX. The profiles measured by film agreed well with the ion chamber measured profiles in terms of overall field size, position, penumbral width, height and position of maximum and profile shape between the 20% dose levels. Film profiles deviated most from ion chamber profiles in the post-penumbra regions. Linear diode array (LDA) measured profiles matched ion chamber profiles in the post-penumbra regions, field size and general profile shape. In the region of maximum dose differences in dose of up to 4% were seen along with horizontal shifts of around 2 mm between LDA and ion chamber profiles. PMID:9745793

Rykers, K L; Geso, M; Brown, G M; Oliver, L D

1998-06-01

179

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

NASA Astrophysics Data System (ADS)

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

Sawyer, Shayla Maya Louise

180

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

ERIC Educational Resources Information Center

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

Jones, Dianna G.

1985-01-01

181

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

PubMed

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

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

2009-04-13

182

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

NASA Astrophysics Data System (ADS)

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 succesfully 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/?m and 5.6 V/?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.; Khusaimi, Z.; Malek, M. F.; Musa, M. Z.; Rusop, M.

2011-05-01

183

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

184

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

SciTech Connect

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

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

2012-05-15

185

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

E-print Network

2 /polystyrene microlens arrays Yik-Khoon Ee, Ronald A. Arif, Nelson Tansu, Pisist Kumnorkaew of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays Yik-Khoon Ee using SiO2/polystyrene microspheres was demonstrated experimentally. The utilization of SiO2/polystyrene

Gilchrist, James F.

186

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

E-print Network

/polystyrene microlens arrays Yik-Khoon Ee,a Ronald A. Arif, and Nelson Tansub Center for Optical TechnologiesGaN quantum wells light emitting diodes LEDs using SiO2/polystyrene microspheres was demonstrated experimentally. The utilization of SiO2/polystyrene microlens arrays on InGaN quantum wells LEDs, deposited via

Gilchrist, James F.

187

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

188

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

PubMed

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

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

2009-03-01

189

Efficiency Enhancement and Beam Shaping of GaN–InGaN Vertical-Injection Light-Emitting Diodes via High-Aspect-Ratio Nanorod Arrays  

Microsoft Academic Search

The enhanced light extraction and collimated output beam profile from GaN-InGaN vertical-injection light-emitting diodes (VI-LEDs) are demonstrated utilizing high-aspect-ratio nanorod arrays. The nanorod arrays are patterned by self-assembled silica spheres, followed by inductively coupled-plasma reactive ion etching. The fabricated nanorod arrays not only provide an omnidirectional escaping zone for photons, but also serve as waveguiding channels for the emitted light,

Min-An Tsai; Peichen Yu; C. L. Chao; C. H. Chiu; H. C. Kuo; S. H. Lin; J. J. Huang; T. C. Lu; S. C. Wang

2009-01-01

190

Diode-array pumping of Er[sup 3+]/Yb[sup 3+] co-doped fiber lasers and amplifiers  

SciTech Connect

The sensitization of erbium-doped fibers with ytterbium is well established as a technique for increasing the choice of pump wavelengths for the erbium system. Single-mode double-clad Er[sup 3+]/Yb[sup 3+] co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96 mW output power at 1.53 [mu]M and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported.

Minelly, J.D.; Barnes, W.L.; Laming, R.I.; Morkel, P.R.; Townsend, J.E.; Payne, D.N. (Southampton Univ. (United Kingdom)); Grubb, S.G. (Amoco Technology Co., Naperville, IL (United States))

1993-03-01

191

External-cavity designs for phase-coupled laser diode arrays  

E-print Network

We describe passive phase-locking architectures based on external-cavity setups to improve the brightness of diode laser bars. Volume Bragg gratings are used to stabilize the lase line. Numerical modelling and experimental results will be presented.

Lucas-Leclin, Gaelle; Georges, Patrick; Michel, Nicolas; Calligaro, Michel; Krakowski, Michel; Lim, Jun; Sujecki, Slawomir; Larkins, Eric

2010-01-01

192

Surface plasmon enhanced green light emitting diodes with silver nanorod arrays embedded in p-GaN  

NASA Astrophysics Data System (ADS)

We demonstrated surface-plasmon (SP) enhanced green light-emitting diodes (LEDs). Three types of Ag nanorod arrays with a minimum distance between the quantum well (QW) and Ag of 20, 40, and 55 nm respectively were fabricated on p-GaN layer. Photoluminescence measurements showed ?175% emission enhancement for the 20 nm spacing while almost no enhancement for the 55 nm spacing. Simulation result showed that a localized surface plasmon resonance (LSPR) at a wavelength of ?500 nm generated by Ag nanorod arrays induced InGaN/GaN QW and SP coupling. However, the electrical field of the LSPR generated by Ag nanorods only spread ?40 nm in the vertical direction in GaN. This simulation result well explains the observation of SP-QW coupling emission enhancement for 20 nm spacing between Ag and QW, and the lack of enhancement for the 55 nm spacing samples.

Huang, Yaping; Yun, Feng; Wang, Yue; Ding, Wen; Li, Yufeng; Wang, Hong; Zhang, Ye; Guo, Maofeng; Su, Xilin; Liu, Shuo; Hou, Xun

2014-08-01

193

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

194

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

195

Aluminum indium gallium nitride-based ultra-violet light emitting diodes: Microscopic physics of device operation  

Microsoft Academic Search

Much progress has been made recently in the-advancement of III-Nitride based UV emitters, in particular light emitting diodes (LED). While high performance LEDs and diode lasers are available to wavelengths of about 360nm, a rather pronounced fall-off in the quantum efficiency occurs in today's devices towards shorter wavelengths. It is generally accepted that the necessity of introducing Al at higher

Eleni Makarona

2004-01-01

196

Ultrahigh aggregate bandwidth two-dimensional multiple-wavelength diode laser arrays  

Microsoft Academic Search

Two-dimensional (2D) multi-wavelength vertical cavity surface emitting laser (VCSEL) arrays is promising for ultrahigh aggregate capacity optical networks. A 2D VCSEL array emitting 140 distinct wavelengths was reported by implementing a spatially graded layer in the VCSEL structure, which in turn creates a wavelength spread. Concentrtion was on epitaxial growth techniques to make reproducible and repeatable multi-wavelength VCSEL arrays. Our

Connie Chang-Hasnain

1993-01-01

197

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

198

Performance of an Ultraviolet Photoconductive Sensor Using Well-Aligned Aluminium-Doped Zinc-Oxide Nanorod Arrays Annealed in an Air and Oxygen Environment  

Microsoft Academic Search

Ultraviolet (UV) photoconductive sensors were fabricated using an aluminium (Al)-doped zinc-oxide (ZnO) nanorod array with a diameter between 40 and 150 nm and thickness of approximately 1.1 mum. The nanorod arrays were prepared using a sonicated sol--gel immersion and annealed at 500 °C under different ambient conditions of air and oxygen. The annealing process induced the formation of nanoholes on

Mohamad Hafiz Mamat; Zuraida Khusaimi; Musa Mohamed Zahidi; Mohamad Rusop Mahmood

2011-01-01

199

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

200

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

PubMed

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. PMID:25327762

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

2014-11-14

201

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

NASA Astrophysics Data System (ADS)

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.

Kim, Kyoeng Heon; An, Ho-Myoung; Kim, Hee-Dong; Kim, Tae Geun

2013-12-01

202

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

203

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

204

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

205

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

206

Variable-color light-emitting diodes using GaN microdonut arrays.  

PubMed

Microdonut-shaped GaN/Inx Ga1-x N light-emitting diode (LED) microarrays are fabricated for variable-color emitters. The figure shows clearly donut-shaped light emission from all the individual microdonut LEDs. Furthermore, microdonut LEDs exhibit spatially-resolved blue and green EL colors, which can be tuned by either controlling the external bias voltage or changing the size of the microdonut LED. PMID:24677202

Tchoe, Youngbin; Jo, Janghyun; Kim, Miyoung; Heo, Jaehyuk; Yoo, Geonwook; Sone, Cheolsoo; Yi, Gyu-Chul

2014-05-21

207

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

208

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

209

Determination of melamine in dairy products, fish feed, and fish by capillary zone electrophoresis with diode array detection.  

PubMed

This paper describes an approach to determine melamine (MEL) in liquid milk, yogurt, whole milk powder, fish feed, and fish at residue levels using capillary zone electrophoresis with diode array detection (CZE-DAD) for the first time. Suspicious samples were extracted with 1% trichloroacetic acid while 1 mL of chloroform was used to precipitate fat in the real samples. After centrifuging and filtering, the extract was analyzed by CZE-DAD directly. By investigating the variables of extraction, separation, and detection in detail, the entire analytical procedure including sample preparation could be completed within 30 min. The limits of detection and quantitation for MEL were found to be 0.01 and 0.05 microg mL(-1), respectively. The proposed method was successfully applied for the analysis of MEL in dairy products, fish feed, and fish with total recoveries ranging from 93 to 104%. PMID:19191668

Yan, Na; Zhou, Lei; Zhu, Zaifang; Chen, Xingguo

2009-02-11

210

Phase-front measurements of an injection-locked AlGaAs laser-diode array  

NASA Technical Reports Server (NTRS)

The phase-front quality of the primary spatial lobe emitted from an injection-locked gain-guided AlGaAs laser-diode array is measured by using an equal-path, phase-shifting Mach-Zehnder interferometer. Root-mean-square phase errors of 0.037 + or - 0.003 wave are measured for the single spatial lobe, which contained 240-mW cw output power in a single longitudinal mode. This phase-front quality corresponds to a Strehl ratio of S = 0.947, which results in a 0.23-dB power loss from the single lobe's ideal diffraction-limited power. These values are comparable with those measured for single-stripe index-guided AlGaAs lasers.

Cornwell, Donald M., Jr.; Rall, Jonathan A. R.; Abshire, James B.

1989-01-01

211

Phase-front measurements of an injection-locked AlGaAs laser-diode array  

SciTech Connect

The phase-front quality of the primary spatial lobe emitted from an injection-locked gain-guided AlGaAs laser-diode array is measured by using an equal-path, phase-shifting Mach--Zehnder interferometer. Root-mean-square phase errors of 0.037{congruent}0.003 wave ({Sigma}/27) are measured for the single spatial lobe, which contained 240-mW cw output power in a single longitudinal mode. This phase-front quality corresponds to a Strehl ratio of {ital S}=0.947, which results in a 0.23-dB power loss from the single lobe's ideal diffraction-limited power. These values are comparable with those measured for single-stripe index-guided AlGaAs lasers.

Cornwell, D.M. Jr.; Rall, J.A.R.; Abshire, J.B. (NASA-Goddard Space Flight Center, Instrument Electro-Optics Branch, Code 723, Greenbelt, Maryland 20771 (US))

1989-09-01

212

Optimal output mirror reflection coefficient for powerful InGaAs/AlGaAs laser diode arrays  

NASA Astrophysics Data System (ADS)

The optimal value of the output mirror reflection coefficient providing the maximum output power under a constant level of electrical power consumption and the maximum external (slope) lasing efficiency for powerful InGaAs/AlGaAs laser diode arrays (LDA) has been estimated experimentally and theoretically. The LDA active layer overheating and amplified spontaneous emission have been taken into account. For advanced LDAs with the thermal resistance of 0.2 K/W and the internal optical loss of 0.5 cm-1 the optimal output mirror reflection coefficient is equal to 20%. This value is shifted to the high output mirror reflection coefficient side with a decrease of the LDA excitation level, the LDA thermal resistivity and the internal optical loss. It has been shown that the right selection of the output mirror reflection coefficient optimal value provides the LDA operation with 20% excess of the lasing output power and 10% excess of the external lasing efficiency.

Bogdanovich, M. V.; Kabanov, V. V.; Lebiadok, Y. V.; Ryabtsev, A. G.; Ryabtsev, G. I.; Shchemelev, M. A.; Kurlenkov, S. S.; Sapozhnikov, S. M.; Mehta, S. K.

2013-02-01

213

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

PubMed

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

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

2013-04-01

214

a Comparison of Different Coherent Deep Ultraviolet Generations Using Second Harmonic Generation with Blue Laser Diode Excitation  

Microsoft Academic Search

Nano-focus beam applications of short wavelength approximately 220 nm now play important roles in engineering and industrial sections. At present, light sources at approximately 220 nm are commercially available but large size, difficult to maintain, and expensive. Compact wavelength tunable and cost effective light sources at approximately 220 nm are required. Laser diode with sum-frequency generation methods are employed to

C. Tangtrongbenchasil; K. Nonaka

2008-01-01

215

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

216

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

217

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

218

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

SciTech Connect

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

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

2009-03-05

219

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

PubMed

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

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

2004-05-01

220

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

221

1-?m Micro-Lens Array on Flip-Chip Light-Emitting Diode  

NASA Astrophysics Data System (ADS)

The fabrication of hexagonally close-packed micro-lens array on sapphire face of flip-chip bonded LED by nanosphere lithography is demonstrated. Self-assembled silica spheres serve as an etch mask to transfer hemispherical geometry onto the sapphire. The optical and electrical properties are evaluated. Without degrading the current--voltage (I--V) properties, the lensed LED shows an enhancement of 27.8% on light output power, compared with unpatterned LED. The emission characteristic is also investigated by performing finite-difference time-domain simulation, which is found to be consistent with the experimental results.

Li, Kwai Hei; Zhang, Qian; Choi, Hoi Wai

2013-08-01

222

1-µm Micro-Lens Array on Flip-Chip Light-Emitting Diode  

NASA Astrophysics Data System (ADS)

The fabrication of hexagonally close-packed micro-lens array on sapphire face of flip-chip bonded LED by nanosphere lithography is demonstrated. Self-assembled silica spheres serve as an etch mask to transfer hemispherical geometry onto the sapphire. The optical and electrical properties are evaluated. Without degrading the current-voltage (I-V) properties, the lensed LED shows an enhancement of 27.8% on light output power, compared with unpatterned LED. The emission characteristic is also investigated by performing finite-difference time-domain simulation, which is found to be consistent with the experimental results.

Hei Li, Kwai; Zhang, Qian; Choi, Hoi Wai

2013-08-01

223

Individually addressable monolithic 1 x 12 light-emitting diode array  

NASA Astrophysics Data System (ADS)

An optically and electrically interfaced array of twelve individually-addressable surface-emitting InP LED's aligned with a twelve-fiber-ribbon pigtail has been fabricated. The average coupled power per device into a 50-micron diameter core, graded index fiber at 150-mA drive current is 20 microW, with a FWHM spectral width at lambda = 1.3 microns of less than 1450 A. The p-contact diameter is 25 microns. Pulse rise and fall times in mesa-isolated devices are 4.5 and 5.5 ns, respectively.

Deimel, P. P.; Cheng, J.; Forrest, S. R.; Hu, P. H.-S.; Huntington, R. B.

1985-10-01

224

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

PubMed

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

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

2014-05-28

225

Determination of the human salivary peptides histatins 1, 3, 5 and statherin by high-performance liquid chromatography and by diode-array detection.  

PubMed

A reversed-phase high-performance liquid chromatography (HPLC) method with diode-array detection for the quantification of several human salivary peptides is described. Sample pretreatment consisted of the acidification of whole saliva by phosphate buffer. This treatment produced precipitation of mucins, alpha-amylases and other high-molecular-mass salivary proteins, simultaneous inhibition of intrinsic protease activities and reduction of sample viscosity. Direct HPLC analysis by diode-array detection of the resulting acidic sample allowed one to quantify histatin 1, histatin 3, histatin 5, statherin, as well as uric acid, in normal subjects. Moreover, the groups of peaks pertaining to proline-rich proteins and cystatins were tentatively identified. The method can be useful in assessing the concentration of salivary peptides from normal subjects and from patients suffering oral and/or periodontal diseases. PMID:11232845

Castagnola, M; Congiu, D; Denotti, G; Di Nunzio, A; Fadda, M B; Melis, S; Messana, I; Misiti, F; Murtas, R; Olianas, A; Piras, V; Pittau, A; Puddu, G

2001-02-10

226

Analysis of tetrabromobisphenol A and other phenolic compounds in water samples by non-aqueous capillary electrophoresis coupled to photodiode array ultraviolet detection  

Microsoft Academic Search

Non-aqueous capillary electrophoresis (NACE) with large-volume sample stacking injection using the electroosmotic flow pump (LVSEP) has been developed for the determination of tetrabromobisphenol A (TBBPA) and other phenolic compounds in environmental matrices. Methanol has been used as run buffer solvent to reduce the electroosmotic flow (EOF). Identification and quantification of the analytes was performed by photodiode array ultraviolet detection. LVSEP–NACE

E. Blanco; M. C. Casais; M. C. Mejuto; R. Cela

2005-01-01

227

Determination of phenolic compounds at low ?g 1 ?1 levels by various solid-phase extractions followed by liquid chromatography and diode-array detection  

Microsoft Academic Search

An off-line solid-phase extraction was carried out to determine thirteen phenolic compounds, which included eleven EPA priority phenols, using reversed-phase liquid chromatography and diode-array detection. Two different sorbents, carbon and a highly cross-linked styrene-divinylbenzene copolymer, were compared for the preconcentration process. To increase the retention of the most polar compounds, mainly phenol, tetrabutylammonium bromide was used as an ion-pair reagent

E. Pocurull; M. Calull; R. M. Marcé; F. Borrull

1996-01-01

228

Simultaneous determination of phenols (bibenzyl, phenanthrene, and fluorenone) in Dendrobium species by high-performance liquid chromatography with diode array detection  

Microsoft Academic Search

A new method of analysis of 11 phenols, including five bibenzyls, three phenanthrenes, and three fluorenones, using high-performance liquid chromatography (HPLC)–diode array detection (DAD) was described. The separation of 11 phenols was effected by RP-HPLC (Beckman Coulter™ ODS column, 5?m, 250mm×4.6mm) using linear gradient elution systems of acetonitrile–1‰ trifluoroacetic acid (TFA). Satisfactory separation of these compounds was obtained in less

Li Yang; Zhengtao Wang; Luoshan Xu

2006-01-01

229

Fingerprint analysis of the fruits of Cnidium monnieri extract by high-performance liquid chromatography–diode array detection–electrospray ionization tandem mass spectrometry  

Microsoft Academic Search

A method incorporating high-performance liquid chromatography (HPLC) with electrospray ionization (ESI) and tandem mass spectrometry (MS), with parallel analysis by HPLC with UV detection using a diode-array detector (DAD) was developed for the qualitative characterization of coumarin and chromone constituents in the fruits of Cnidium monnieri. The chromatographic separations were performed on a Diamonsil™ C18 column (4.6mm×200mm, 5?m) with water

Yi Chen; Guorong Fan; Qiaoyan Zhang; Huiling Wu; Yutian Wu

2007-01-01

230

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

231

Application of high-performance liquid chromatography diode array detection and mass spectrometry to the analysis of characteristic compounds in various essential oils  

Microsoft Academic Search

A high-performance liquid chromatography (HPLC) method was established using an analytical reversed-phase column and gradient\\u000a elution to achieve chromatographic separation of typical compounds in essential oils. For detection, a diode array detector\\u000a monitoring different wavelengths simultaneously as well as a mass spectrometer (MS) were used. Atmospheric pressure chemical\\u000a ionization operating in the positive mode turned out to be a suitable

Claudia Turek; Florian C. Stintzing

2011-01-01

232

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

Microsoft Academic Search

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

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

2006-01-01

233

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

234

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

235

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

SciTech Connect

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

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

1997-10-01

236

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

SciTech Connect

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

Kent, Thomas F.; Carnevale, Santino D. [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)] [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Myers, Roberto C. [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States) [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Deparment of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

2013-05-20

237

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

238

Liquid chromatographic-diode-array detection multiresidue determination of rice herbicides in drinking and paddy-field water.  

PubMed

A sensitive, rapid, and simple multiresidue method for the simultaneous determination of six postemergence herbicides currently used in rice cultivation--metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium, and cyhalofop butyl--in drinking and paddy-field water is presented. Water samples were extracted with solid-phase extraction cartridges. Final determination was made by LC with diode-array detection. The extraction efficiencies of C18 and HLB cartridges were compared. The average recovery obtained for these compounds for the lowest spiked level (0.1 microg/L) varied from 70 to 122% for C18 and 75-119% for HLB, with RSDs of 11 and 8.3%, respectively. The method had good linearity, and the lower detection limit for the pesticides studied varied from 0.03 to 0.04 microg/L. The proposed method was also tested in paddy-field water, with recovery studies giving good results with low RSDs at 1.0 microg/L. PMID:19714989

Roehrs, Rafael; Zanella, Renato; Pizzuti, Ionara; Adaime, Martha B; Pareja, Lucía; Niell, Silvina; Cesio, María V; Heinzen, Horacio

2009-01-01

239

Determination of imidocarb in animal biosamples using simple high-performance liquid chromatography with diode-array detection  

PubMed Central

The aim of this study was to develop an analytical method for detection of imidocarb [1,3-bis[3-(4,5-dihydro-1h-imidazol-2-yl)phenyl]urea] in beef and milk using high-performance liquid chromatography (HPLC) with diode-array detection (DAD). Imidocarb was separated on a reversed-phase column (4.6×250 mm, 5 ?m) with a mobile phase consisting of 85:15 (v/v) 0.1% trifluoroacetic acid/acetonitrile. The flow rate was 1 ml/min, and the column temperature was maintained at 20°C. Detection was carried out at 260 nm using a DAD detector. The analytical samples were extracted using a solid-phase extraction (SPE) method. The calibration curves showed good linearity (r?0.998). Limits of quantifications (LOQs) were 0.15 mg/kg in beef and 0.025 mg/kg in milk. Intra- and inter-day precisions were 3.2–6.1 and 1.4–6.9%, respectively, and the accuracy (recovery) was 80.4–82.2% and 80.1–89.5% in beef and milk, respectively. Thus, an analytical protocol using SPE extraction followed by HPLC with DAD was successfully developed, which demonstrated acceptable precision and recovery. PMID:24649075

PARK, JIN-A; CHO, HEE-JUNG; CHO, SOO-MIN; KIM, NA-HYUN; KIM, DONG-SOON; ZHANG, DAN; KIM, SEONG-KWAN; YI, HEE; SHIN, HO-CHUL

2014-01-01

240

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

241

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

PubMed

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

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

2013-09-23

242

Stray light correction for diode-array-based spectrometers using a monochromator.  

PubMed

Photodiode-array-based spectrometers are increasingly being used in a wide variety of applications. However, the signal measured by this type of instrument often is not what is anticipated by the user and is often subject to contamination from stray light. This paper describes an efficient and low-cost stray light correction approach based on a relatively simple system using a monochromator-based source. The paper further discusses the limitations of using a monochromator instead of a laser, as used by previous researchers, and its impact on the quality of the stray light correction. The reliability and robustness of the stray light correction matrix generated have been studied and are also reported. PMID:21946995

Salim, Saber G R; Fox, Nigel P; Hartree, William S; Woolliams, Emma R; Sun, Tong; Grattan, Kenneth T V

2011-09-10

243

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.

2014-01-01

244

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

NASA Astrophysics Data System (ADS)

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

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

245

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

246

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

247

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

248

Chandra, Extreme Ultraviolet Explorer, and Very Large Array Observations of the Active Binary System ?2 Coronae Borealis  

NASA Astrophysics Data System (ADS)

We present the results of a coordinated observing campaign on the short-period RS CVn binary ?2 Coronae Borealis (F6V+G0V Porb=1.14 days) with the Very Large Array, the Extreme Ultraviolet Explorer, and the Chandra X-Ray Observatory High-Energy Transmission Grating Spectrometer. The radio emission is consistent with previously determined quiescent gyrosynchrotron properties. Multiple flares were seen with Extreme Ultraviolet Explorer, five occurring within two consecutive orbital periods. The first of these flares was observed with Chandra. The Chandra observations of ?2 CrB showed no systematic variations of line fluxes, widths, or Doppler shifts with orbital phase, nor any response in line width or offset due to the flare. This is consistent with both stars being equally active coronal emitters. We have developed a self-consistent method of spectral analysis to derive information from the line and continuum emissions concerning the distribution of plasma with temperature and elemental abundances. A bimodal temperature distribution is appropriate for both quiescent and flare intervals, with a stable peak at 6-8 MK and another variable enhancement at higher temperatures, with evidence for significant contribution from temperatures up to 50 MK during the flare, compared to 30 MK during quiescence. The iron abundance is subsolar during quiescence but is enriched by about a factor of 2 during a large flare seen with Chandra. The noble gas elements neon and argon show elevated abundances with respect to iron, but there is no clear evidence for any first ionization potential-based abundance pattern during quiescence or the flare. We have determined coronal electron densities from the helium-like ions O VII, Ne IX, Mg XI, and Si XIII, which imply densities >=1010 cm-3. There is a small enhancement in the electron densities derived for the flare, but it is not statistically significant. We call attention to electron temperature constraints provided by the ratios of 1s2 1S0-1snp 1P1 transitions of the helium-like ions O VII, Ne IX, Mg XI, and Si XIII. The derived coronal electron pressures change by 1-2 orders of magnitude over a 25% change in temperature, implying nonisobaric coronal conditions. We find no evidence for significant departures from the effectively thin coronal assumption. The electron densities inferred from the soft X-ray spectra are inconsistent with cospatial gyrosynchrotron emission; further observations are necessary to discriminate the relative locations of the radio and soft X-ray-emitting plasma.

Osten, Rachel A.; Ayres, Thomas R.; Brown, Alexander; Linsky, Jeffrey L.; Krishnamurthi, Anita

2003-01-01

249

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

250

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

251

Potentialities of ITP-CZE method with diode array detection for enantiomeric purity control of dexbrompheniramine in pharmaceuticals.  

PubMed

The present work illustrates potentialities of on-line combined isotachophoresis-capillary zone electrophoresis (ITP-CZE) separation techniques coupled with on-capillary diode array detector (DAD) for enantiomeric purity testing of drugs in pharmaceuticals. The general advantages of the proposed method are its (i) high selectivity, (ii) low concentration limit of detection (LOD) obtainable, (iii) enhanced sample loadability, and (iv) enhanced reliability. For separation of brompheniramine (BP) enantiomers, serving as model analytes, carboxyethyl-beta-cyclodextrin (CE-beta-CD) was appropriate chiral selector providing complete enantioresolution. Given by a high sample load capacity (30 microl sample injection volume) and preconcentration of the analytes in ITP stage, concentration LOD of levobrompheniramine (LBP), serving as model impurity, was 2.5 ng/ml (8 x 10(-9)mol/l). Such separation and detection conditions enabled to easily determine LBP in samples containing a 10(3) excess of dexbrompheniramine (DBP). DAD detection in comparison with single wavelength detection can enhance value of analytical information when analytes and interferents have different spectra (distinguishing impurities in analyte zone, confirmation of migration positions of migrants). In this context purity of BP zones was confirmed with higher reliability in pharmaceutical sample. Moreover, distinguishing the trace analyte signal superposed on the baseline noise was provided with sufficient reliability (for this purpose the background correction and smoothing procedure had to be applied to the raw DAD spectra). Successful validation and application of the proposed ITP-CZE-DAD method suggest its routine use for the enantiomeric purity testing of pharmaceuticals. PMID:17618074

Marák, Jozef; Mikus, Peter; Maráková, Katarína; Kaniansky, Dusan; Valásková, Iva; Havránek, Emil

2008-04-14

252

Determination of pesticides in sunflower seeds by high-performance liquid chromatography coupled with a diode array detector.  

PubMed

The application of RP-HPLC with a diode array detector for identification and quantitative analysis of pesticides in sunflower seed samples is demonstrated. An HPLC procedure on C18 RP column has been developed for analysis of selected pesticides from different chemical groups: simazine, isoproturon, terbuthylazine, linuron, captan, terbutryn, procymidone, fenitrothion, clofentezine, and bromopropylate. We investigated the possibility of expanding the scope of the four analyte extraction procedures for isolation of pesticides from plant matrixes with high levels of lipids. The following procedures were tested: A, ultrasound-assisted solvent extraction (UAE) and SPE; B, dispersive-SPE (d-SPE); C, UAE and d-SPE; and D, UAE/SPE/d-SPE. Average recoveries from spiked samples at different concentrations in the range from 0.1 to 1.40 microg/g in the plant materials and the SDs for C18 cartridges and solvents by the proposed RP-HPLC-DAD method after the extraction procedures are also presented. The efficiency of procedures A-D was evaluated using real food samples from Hungary, Bulgaria, and Poland. The quantity of terbuthylazine determined was in the range of 7.1-12.7 ng/g (n = 6), whereas the quantity of procymidone determined was in the range of 3.7-5.7 ng/g (n = 3) in plant materials. The quantities of pesticides determined in sunflower seeds were below the maximum residue levels (excluding captan) established in the European Union legislation. The method was validated for precision and accuracy. PMID:25145131

Tuzimski, Tomasz; Rejczak, Tomasz

2014-01-01

253

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

SciTech Connect

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

Risk, W.P.; Lenth, W.

1987-12-01

254

Determination of two antifouling booster biocides and their degradation products in marine sediments by high performance liquid chromatography–diode array detection  

Microsoft Academic Search

A method for the simultaneous determination of two antifouling booster biocides, diuron [1-(3,4-dichlorophenyl)-3,3-dimethylurea] and irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) and their degradation products, DCPMU [1-(3,4-dichlorophenyl)-3-methylurea], DCPU [1-(3,4-dichlorophenyl) urea], DCA [3,4-dichloroaniline] and M1 (2-methylthio-4-tert-butylamino-s-triazine), in marine sediments by high performance liquid chromatography–diode array detection (HPLC–DAD) was developed. The extraction of these compounds from sediment was achieved by means of methanolic ultrasonic extraction. The

Georgia Gatidou; Anna Kotrikla; Nikolaos S Thomaidis; Themistokles D Lekkas

2004-01-01

255

Determination of the antifouling booster biocides irgarol 1051 and diuron and their metabolites in seawater by high performance liquid chromatography–diode array detector  

Microsoft Academic Search

A method for the simultaneous determination of two antifouling booster biocides, diuron (1-(3,4 dichlorophenyl) 3,3 dimethyl urea) and irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), and their metabolites, DCPMU (1-(3,4 dichlorophenyl)-3 methyl urea), DCPU (1-(3,4 dichlorophenyl) urea), DCA (3,4 dichloroaniline) and M1 (2-methylthio-4-tert-butylamino-s-triazine) in seawater by high performance liquid chromatography–diode array detector (HPLC–DAD) was developed. The optimization of the extraction procedure included the type

Georgia Gatidou; Anna Kotrikla; Nikolaos S. Thomaidis; Themistokles D. Lekkas

2005-01-01

256

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

Microsoft Academic Search

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

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

1999-01-01

257

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

258

Near UV LEDs Made with in Situ Doped p-n Homojunction ZnO Nanowire Arrays  

E-print Network

Near UV LEDs Made with in Situ Doped p-n Homojunction ZnO Nanowire Arrays Min-Teng Chen,,| Ming-wavelength lighting device and photoelectronics. KEYWORDS ZnO nanowires, p-n homojunction, Near UV LED, in situ doped T he short-wavelength photoelectronics devices, such as ultraviolet light-emitting diodes (UV LEDs

Wang, Zhong L.

259

Material and device studies for the development of ultra-violet light emitting diodes (UV-LEDS) along polar, non-polar and semi-polar directions  

NASA Astrophysics Data System (ADS)

Over the past few years, significant effort was dedicated to the development of ultraviolet light emitting diodes (UV-LEDs) for a variety of applications. Such applications include chemical and biological detection, water purification and solid-state lighting. III-Nitride LEDs based on multiple quantum wells (MQWs) grown along the conventional [0001] (polar) direction suffer from the quantum confined Stark effect (QCSE), due to the existence of strong electric fields that arise from spontaneous and piezoelectric polarization. Thus, there is strong motivation to develop MQW-based III-nitride LED structures grown along non-polar and semi-polar directions. The goal of this dissertation is to develop UV-LEDs along the [0001] polar and [11 2¯ 0] non-polar directions by the method of Molecular Beam Epitaxy (MBE). The polar and non-polar LEDs were grown on the C-plane and R-plane sapphire substrates respectively. This work is a combination of materials science studies related to the nucleation, growth and n- and p-type doping of III-nitride films on these two substrates, as well as device studies related to fabrication and characterization of UV-LEDs. It was observed that the crystallographic orientation of the III-nitride films grown on R-plane sapphire depends strongly on the kinetic conditions of growth of the Aluminum Nitride (AIN) buffer. Specifically, growth of the AIN buffer under group III-rich conditions leads to nitride films having the (11 2¯ 0) non polar planes parallel to the sapphire surface, while growth of the buffer under nitrogen rich conditions leads to nitride films with the (11 2¯ 6) semi-polar planes parallel to the sapphire surface. The electron concentration and mobility for the films grown along the polar, non-polar and semi-polar directions were investigated. P-type doping of Gallium Nitride (GaN) films grown on the nonpolar (11 2¯ 0) plane do not suffer from polarity inversion and thus the material was doped p-type with a hole concentration 1 x 1018 cm-3. MQWs were grown on polar, non-polar and semi-polar planes in order to study the QCSE. It was found that the QCSE is eliminated and minimized for the MQWs grown along the non-polar and semi-polar directions respectively. UV-LEDs emitting in the wavelength regime of 330-360 nm were grown and fabricated along the polar and non-polar directions.

Chandrasekaran, Ramya

260

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

PubMed

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

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

2014-06-01

261

Fingerprint analysis and multi-ingredient quantitative analysis for quality evaluation of Xiaoyanlidan tablets by ultra high performance liquid chromatography with diode array detection.  

PubMed

A rapid and sensitive ultra high performance liquid chromatography method with diode array detection was developed for the fingerprint analysis and simultaneous determination of seven active compounds in Xiaoyanlidan (XYLD) tablets. The chromatographic separations were obtained on an Agilent Eclipse plus C18 column (50 × 2.1 mm id, 1.8 ?m) using gradient elution with water/formic acid (1%) and acetonitrile at a flow rate of 0.4 mL/min. Within 63 min, 36 peaks could be selected as the common peaks for fingerprint analysis to evaluate the similarities among several samples of XYLD tablets collected from different manufacturers. In quantitative analysis, seven compounds showed good regression (R > 0.9990) within test ranges and the recovery of the method was within the range of 95.9-104.3%. The method was successfully applied to the simultaneous determination of seven compounds in six batches of XYLD tablets. These results demonstrate that the combination of chromatographic fingerprint analysis and simultaneous multi-ingredient quantification using the ultra high performance liquid chromatography method with diode array detection offers a rapid, efficient, and reliable approach for quality evaluation of XYLD tablets. PMID:24890779

Tang, Dao-quan; Li, Zheng; Jiang, Xiang-lan; Li, Yin-jie; Du, Qian; Yang, Dong-zhi

2014-08-01

262

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

263

Time evolution of pulsed far-field patterns of GaAlAs phase-locked laser-diode arrays  

NASA Technical Reports Server (NTRS)

The time evolution of pulsed far fields from commercially available gain-guided phase-locked arrays has been studied and compared to experimental results previously obtained by streak camera measurements, and to predictions of coupled-mode theories developed for index- and gain-guided arrays. Although phase locking is evident by 100 ps into the drive pulse, stable operation in a fixed superposition of array modes is not achieved until 1-2 ns after the drive pulse has stabilized.

Forrest, Kathrine A.; Abshire, James B.

1987-01-01

264

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

265

Light transmission enhancement from hybrid ZnO micro-mesh and nanorod arrays with application to GaN-based light-emitting diodes.  

PubMed

A hybrid ZnO micro-mesh and nanorod arrays (MMNR) was fabricated as a light output window for GaN-based light-emitting diodes (LEDs) to enhance the light extraction efficiency. The light output power of GaN-based LEDs with the ZnO MMNR is improved by 95% compared to the original planar LEDs. The ZnO MMNR is manufactured by photolithography techniques and a two-step wet chemical growth process. The incident angle-resolved light transmission of the ZnO MMNR beyond the critical angle of total internal reflection is greatly enhanced. The light diffraction pattern of the ZnO MMNR shows that it possesses both the two-dimensional diffraction grating effect of a ZnO micro-mesh and the light scattering effect of a ZnO nanorod array. LEDs with the ZnO MMNR have greater light extraction efficiency than those with only a ZnO micro-mesh or a ZnO nanorod array. The local optical field patterns of the ZnO micro-mesh and the ZnO MMNR are investigated using confocal scanning electroluminescence microscopy. The microscopic light extraction mechanism of the ZnO MMNR is analyzed in-depth. PMID:24514365

Yin, Zhengmao; Liu, Xiaoyan; Wang, Huining; Wu, Yongzhong; Hao, Xiaopeng; Ji, Ziwu; Xu, Xiangang

2013-11-18

266

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

NASA Astrophysics Data System (ADS)

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; Lin, Yuqing; Chernyak, Leonid; Liu, Jianlin

2011-01-01

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

Comparison of several curve resolution methods for drug impurity profiling using high-performance liquid chromatography with diode array detection  

Microsoft Academic Search

The performance of five curve resolution methods was compared systematically for the identification and quantification of impurities in drug impurity profiling. These methods are alternating least-squares (ALS) with either random or iterative key-set factor analysis (IKSFA) initialisation, iterative target transformation factor analysis (ITTFA), evolving factor analysis (EFA), and heuristic evolving latent projections (HELP). Real and simulated high-performance liquid chromatography diode

P. V van Zomeren; H Darwinkel; P. M. J Coenegracht; G. J de Jong

2003-01-01

269

High-power CW operation of AlGaInP laser-diode array at 640 nm  

Microsoft Academic Search

Visible-emitting high-power laser bars are investigated at an emission wavelength of 640 nm. AlGaInP\\/GaInP, single tensile-strained quantum well, separate confinement heterostructures are fabricated into one cm long laser bars using a 0.7 fill factor. The low threshold current of the diode, combined with the aggressive heatsinking of a silicon microchannel cooler has resulted in more than 12 W of continuous

J. A. Skidmore; M. A. Emanuel; R. J. Beach; W. J. Benett; B. L. W. J. Freitas; N. W. Carlson; R. W. Solarz; D. P. Bour; D. W. Treat

1995-01-01

270

Determination of huperzine A in formulated products by reversed-phase-liquid chromatography using diode array and electrospray ionization mass spectrometric detection.  

PubMed

A precise and selective high-performance liquid chromatographic (HPLC) method with diode-array detection for quantifying huperzine A in formulated products was developed and validated. A liquid chromatographic-mass spectrometric (LC/MS) procedure was devised to confirm the HPLC method. Huperzine A was dissolved in 1,2-dichloroethane, chromatographed on a YMCBasic C18 column, and detected at 308 nm. A gradient mobile phase of 10 mM ammonium acetate (pH = 3.5)--methanol was used. Identification was based on retention time, UV spectra and mass spectra by comparison with a commercial standard. The UV peak areas were used for quantitation of huperzine A content. The correlation coefficient (R2) of the calibration curve was 1 over the range 0.8-11.6 microg/ml. Overall recovery of huperzine A was 103.9% +/- 1.8 (mean +/- SD). Relative standard deviations for intra- and interday precision were < 2%. PMID:12725577

Yang, Q P; Kou, X L; Fugal, K B; McLaughlin, J L

2003-03-01

271

Fingerprint analysis of the fruits of Cnidium monnieri extract by high-performance liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry.  

PubMed

A method incorporating high-performance liquid chromatography (HPLC) with electrospray ionization (ESI) and tandem mass spectrometry (MS), with parallel analysis by HPLC with UV detection using a diode-array detector (DAD) was developed for the qualitative characterization of coumarin and chromone constituents in the fruits of Cnidium monnieri. The chromatographic separations were performed on a Diamonsil C18 column (4.6 mm x 200 mm, 5 microm) with water with 50 mM ammonium acetate and 2% acetic acid (A) and acetonitrile (B) as the mobile phase. According to the characteristic UV spectra, the information of molecular weight and structure provided by ESI-MS/MS, 13 coumarin and 7 chromone components were detected and identified. This method is rapid and reliable for identification of the constituents in the complex herbal system, and the fragmentation patterns proposed could be extended to the similar compounds. PMID:17046189

Chen, Yi; Fan, Guorong; Zhang, Qiaoyan; Wu, Huiling; Wu, Yutian

2007-02-19

272

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

Beach, Raymond J. (Livermore, CA)

1997-01-01

273

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.

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

2014-01-01

274

Spectral correlation of high-performance liquid chromatography-diode array detection data from two independent chromatographic runs peak tracking in pharmaceutical impurity profiling.  

PubMed

A novel qualitative analytical method for peak tracking in impurity profiling control by the correlation of spectra was established. Two-dimensional (2D) standard spectrochromatographic data produced by high-performance liquid chromatography with diode array detection (HPLC-DAD) were compared with sample data to develop two-dimensional chromatographic spectral correlative maps. Taking full advantage of separation efficiency of HPLC and spectral specificity of the analytes, the method was successfully used to recognize impurities in quinolone antibacterials, when in combination with relative retention times (RRTs). For the comparison of spectra was expanded to three-dimensional space, simultaneous identification of the chromatographic peaks can be obtained rapidly without preparation and injection of a reference solution, even when the mobile phase changed or the peaks of multi-component samples overlapped. PMID:18374928

Li, Wei; Hu, Chang-qin

2008-05-01

275

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

276

Determination of ten sulfonyl urea herbicides in unpolished rice by solid-phase extraction cleanup and LC-diode array detection.  

PubMed

A liquid chromatographic (LC) method with diode array detection (DAD) was developed for screening of 10 sulfonyl urea herbicide residues in unpolished rice. The investigated herbicides were azimsulfuron, bensulfuron-methyl, chlorimuron-ethyl, chlorsulfuron, ethoxysulfuron, flazasulfuron, imazosulfuron, metsulfuron-methyl, pyrazosulfuron-ethyl and tribenuron-methyl. Acetonitrile-water (2:1) extracts of rice samples were cleaned up with solid-phase extraction cartridges (octadecylsilane-bonded silica (ODS) and graphitized carbon black (GCB)). Three fractions of the GCB eluate were taken for analysis using 3 separate injections in order to avoid interference in LC-DAD analysis and to reduce analyte coelution problems. Recoveries from rice samples fortified with the 10 herbicides at 0.05 and 0.2 microgram/g ranged from 46.6 to 119.6%, and coefficients of variation were 3.1-12.6%. The quantitation limits were 0.01-0.02 microgram/g. PMID:12092420

Akiyama, Yumi; Yoshioka, Naoki; Tsuji, Masahiko

2002-04-01

277

Application of an intensified diode array system to diagnosis of matrix effects and the rapid sequential determination of thiamine and riboflavin with fluorescence detection.  

PubMed

The unique capabilities of a multiple wavelength spectrofluorometer based on an intensified diode array detector are used for diagnosis of matrix effects and for rapid sequential determination of two analytes. This system is used to investigate problems due to background fluorescence, blank reactions, and scattering for the determination of thiamine in cereal and urine samples by a fluorometric kinetic procedure. A novel determination of thiamine and riboflavin in vitamin pills is based on monitoring the native fluorescence of riboflavin over one wavelength region, and the rate of formation of fluorescent thiochrome from thiamine over another wavelength region, after a computer-controlled change in the pH of the reaction mixture. PMID:18962904

Ryan, M A; Ingle, J D

1981-04-01

278

Stable, single-(array)-mode operation from phase-locked, interferometric arrays of index-guided AlGaAs/GaAs diode lasers  

SciTech Connect

Single-array-mode (L = 8) oscillation is achieved with virtually diffraction-limited beams to three times above lasing threshold, and with beamwidths 1.5 times the diffraction limit at 4.7 times above lasing threshold and 130 mW output power per uncoated emitting facet. The arrays are 10/11-element wide-waveguide-interferometric (WWI) AlGaAs/GaAs lasers grown by liquid-phase epitaxy over channeled substrates. Selection of the L = 8 mode is a consequence of two mode-dependent loss mechanisms: transverse antiguiding between elements and radiation losses in the interferometer. Near-field pattern analysis indicates that the (high-order) array mode is self-stabilizing with increasing drive above threshold. Simple means of achieving single-lobe operation are discussed.

Botez, D.; Mawst, L.; Hayashida, P.; Roth, T.J.; Anderson, E.

1988-01-25

279

Stable, single-(array)-mode operation from phase-locked, interferometric arrays of index-guided AlGaAs/GaAs diode lasers  

NASA Astrophysics Data System (ADS)

Single-array-mode (L = 8) oscillation is achieved with virtually diffraction-limited beams to three times above lasing threshold, and with beamwidths 1.5 times the diffraction limit at 4.7 times above lasing threshold and 130 mW output power per uncoated emitting facet. The arrays are 10/11-element wide-waveguide-interferometric (WWI) AlGaAs/GaAs lasers grown by liquid-phase epitaxy over channeled substrates. Selection of the L = 8 mode is a consequence of two mode-dependent loss mechanisms: transverse antiguiding between elements and radiation losses in the interferometer. Near-field pattern analysis indicates that the (high-order) array mode is self-stabilizing with increasing drive above threshold. Simple means of achieving single-lobe operation are discussed.

Botez, D.; Mawst, L.; Hayashida, P.; Roth, T. J.; Anderson, E.

1988-01-01

280

Thickness-Dependent Characteristics of Aluminium-Doped Zinc Oxide Nanorod-Array-Based, Ultraviolet Photoconductive Sensors  

NASA Astrophysics Data System (ADS)

Aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays were prepared on a seed-layer-coated glass substrate by a sonicated sol-gel immersion method. We have shown, for the first time, that the thickness of the nanorod arrays can be increased incrementally without greatly affecting the diameter of the nanorods, by increasing the number of immersions. The field-emission scanning electron micrographs and thickness measurements revealed that the nanorods had diameters within the range from 40 to 150 nm and thicknesses from 629 to 834 nm with immersion times ranging from 1 to 5 h. The photoluminescence (PL) spectra revealed that the ZnO nanorod quality was enhanced with long immersion times as shown by an improvement in the ratio of the UV peak intensity to the visible emission peak intensity, or IUV/Ivis. The thickness-dependent characteristic of Al-doped ZnO nanorod-array-based, UV photoconductive sensors was studied; minimising the thickness of the nanorod arrays was found to provide high responsivity and good performance. Our experiments showed that a decrease in the thickness of the nanorod arrays improved the responsivity and response time of the UV sensors, with a maximum responsivity of 2.13 A/W observed for a 629-nm-thick nanorod film.

Hafiz Mamat, Mohamad; Izzah Ishak, Nurul; Khusaimi, Zuraida; Zahidi, Musa Mohamed; Hanapiah Abdullah, Mohd; Muhamad, Salina; Sin, Nor Diyana Md; Rusop Mahmood, Mohamad

2012-06-01

281

Thickness-Dependent Characteristics of Aluminium-Doped Zinc Oxide Nanorod-Array-Based, Ultraviolet Photoconductive Sensors  

NASA Astrophysics Data System (ADS)

Aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays were prepared on a seed-layer-coated glass substrate by a sonicated sol--gel immersion method. We have shown, for the first time, that the thickness of the nanorod arrays can be increased incrementally without greatly affecting the diameter of the nanorods, by increasing the number of immersions. The field-emission scanning electron micrographs and thickness measurements revealed that the nanorods had diameters within the range from 40 to 150 nm and thicknesses from 629 to 834 nm with immersion times ranging from 1 to 5 h. The photoluminescence (PL) spectra revealed that the ZnO nanorod quality was enhanced with long immersion times as shown by an improvement in the ratio of the UV peak intensity to the visible emission peak intensity, or IUV/Ivis. The thickness-dependent characteristic of Al-doped ZnO nanorod-array-based, UV photoconductive sensors was studied; minimising the thickness of the nanorod arrays was found to provide high responsivity and good performance. Our experiments showed that a decrease in the thickness of the nanorod arrays improved the responsivity and response time of the UV sensors, with a maximum responsivity of 2.13 A/W observed for a 629-nm-thick nanorod film.

Mamat, Mohamad Hafiz; Ishak, Nurul Izzah; Khusaimi, Zuraida; Zahidi, Musa Mohamed; Abdullah, Mohd Hanapiah; Muhamad, Salina; Sin, Nor Diyana Md; Mahmood, Mohamad Rusop

2012-06-01

282

The wavelength beam-combining fiber-coupled diode laser is the first  

E-print Network

The wavelength beam-combining fiber-coupled diode laser is the first direct-diode laser of fiber-coupled diode lasers is the diode-laser bar. A diode- laser bar typically consists of an array (e-combining fiber-coupled diode laser head developed by Tera- Diode is shown cutting through 0.26 inch steel. Tera

283

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

E-print Network

3 and phosphors.4 In addition to their excellent optical properties, high quality ZnO thin films with high spectral resolution, present technology relies on arrays of waveguide gratings or thin-film interesting ques- tions in thin film samples where nonequilibrium deposition processes and structural

Rubloff, Gary W.

284

Beam divergence measurements of InGaN /GaN micro-array light-emitting diodes using confocal microscopy  

NASA Astrophysics Data System (ADS)

The recent development of high-density, two-dimensional arrays of micrometer-sized InGaN /GaN light-emitting diodes (micro-LEDs) with potential applications from scientific instrumentation to microdisplays has created an urgent need for controlled manipulation of the light output from these devices. With directed light output these devices can be used in situations where collimated beams or light focused onto several thousand matrix points is desired. In order to do this effectively, the emission characteristics of the devices must be fully understood and characterized. Here we utilize confocal microscopy to directly determine the emission characteristics and angular beam divergences from the individual micro-LED elements. The technique is applied to both top (into air) and bottom (through substrate) emission in arrays of green (540nm), blue (470nm), and UV (370nm) micro-LED devices, at distances of up to 50?m from the emission plane. The results are consistent with simple optical modeling of the expected beam profiles.

Griffin, C.; Gu, E.; Choi, H. W.; Jeon, C. W.; Girkin, J. M.; Dawson, M. D.; McConnell, G.

2005-01-01

285

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

286

Ten-fold enhancement of ZnO thin film ultraviolet-luminescence by dielectric microsphere arrays.  

PubMed

Here we report strong enhancement in ultraviolet-photoluminescence (UV-PL) of ZnO thin films (grown on a SiC substrate) covered by monolayer dielectric fused silica or polystyrene microspheres with diameters ranging from 0.5 to 7.5 ?m. The excited light scatted in the film is collected by the microspheres to stimulate whispering gallery modes, by which the internal quantum efficiency of spontaneous emission is enhanced. Meanwhile, the microsphere monolayer efficiently couples emitted light energy from the luminescent film to the far-field for PL detection. A UV-PL enhancement up to 10-fold via a 5-µm-diameter microsphere monolayer is experimentally demonstrated in this work. The unique optical property of microsphere in photoluminescence (PL) enhancement makes them promising for high-sensitivity PL measurements as well as design of photoelectric devices with low loss and high efficiency. PMID:25321823

Yan, Yinzhou; Zeng, Yong; Wu, Yan; Zhao, Yan; Ji, Lingfei; Jiang, Yijian; Li, Lin

2014-09-22

287

Electrically pumped ultraviolet ZnO diode lasers on Si Sheng Chu, Mario Olmedo, Zheng Yang, Jieying Kong, and Jianlin Liua  

E-print Network

a continuous "thin film." Figure 1 e schematically shows detailed structure of the ZnO diode laser. After Au lasers ,3,4 hexagonal nanonails whispering gallery mode lasers ,5 and thin films.6­8 Recently by the growth of a thin ZnO buffer layer of about 15 nm at the same substrate temperature. On top of this thin

Yang, Zheng

288

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

NASA Astrophysics Data System (ADS)

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li 2(Ba 0.99,Eu 0.01)SiO 4 and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li 2(Ba 0.99,Eu 0.01)SiO 4:B 0.063+ showed 160% improved emission intensity compared with that of the Li 2(Ba 0.99,Eu 0.01)SiO 4 phosphors under UV ( ?ex=350 nm) excitation.

Yao, Shanshan; Chen, Donghua

2008-04-01

289

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

290

A study of the feasibility and performance of an active/passive imager using silicon focal plane arrays and incoherent continuous wave laser diodes  

NASA Astrophysics Data System (ADS)

This dissertation describes an active/passive imager (API) that provides reliable, nighttime, target acquisition in a man-portable package with effective visual range of about 4 kilometers. The reflective imagery is easier to interpret than currently used thermal imagery. Also, in the active mode, the API provides performance equivalent to the big-aperture, thermal systems used on weapons platforms like tanks and attack helicopters. This dissertation describes the research needed to demonstrate both the feasibility and utility of the API. Part of the research describes implementation of a silicon focal plane array (SFPA) capable of both active and passive imaging. The passive imaging mode exceeds the nighttime performance of currently fielded, man-portable sensors. Further, when scene illumination is insufficient for passive imaging, the low dark current of SFPA makes it possible to use continuous wave laser diodes (CWLD) to add an active imaging mode. CWLD have advantages of size, efficiency, and improved eye safety when compared to high peak-power diodes. Because of the improved eye safety, the API provides user-demanded features like video output and extended range gates in the active as well as passive imaging modes. Like any other night vision device, the API depends on natural illumination of the scene for passive operation. Although it has been known for decades that "starlight" illumination is actually from diffuse airglow emissions, the research described in this dissertation provides the first estimates of the global and temporal variation of ground illumination due to airglow. A third related element of the current research establishes the impact of atmospheric aerosols on API performance. We know from day experience that atmospheric scattering of sunlight into the imager line-of-sight can blind the imager and drastically degrade performance. Atmospheric scattering of sunlight is extensively covered in the literature. However, previous literature did not cover the impact of atmospheric scattering when the target is diffusely illuminated by airglow.

Vollmerhausen, Richard H.

291

Mechanics of cadmium telluride-zinc telluride nucleation on (112) Si for mercury cadmium telluride infrared photo-diode arrays  

Microsoft Academic Search

Epitaxy of CdTe\\/ZnTe on the extremely large lattice mismatched Si leads to high density of dislocations, multi-domain facets, rough surface morphology, and often Cd-terminated surface polarity. These problems, related to the mode of nucleation and growth, limit its application to manufacture improved HgCdTe based large area infrared focal plane arrays. Thermo-kinetics of ZnTe nucleation on \\

Nibir Kumar Dhar

1997-01-01

292

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

293

InGaN-Based Near-Ultraviolet and Blue-Light-Emitting Diodes with High External Quantum Efficiency Using a Patterned Sapphire Substrate and a Mesh Electrode  

Microsoft Academic Search

We markedly improved the extraction efficiency of emission light from the InGaN-based light-emitting diode (LED) chips grown on sapphire substrates. Two new techniques were adopted in the fabrication of these LEDs. One is to grow nitride films on the patterned sapphire substrate (PSS) in order to scatter emission light. Another is to use the Rh mesh electrode for p-GaN contact

Motokazu Yamada; Tomotsugu Mitani; Yukio Narukawa; Shuji Shioji; Isamu Niki; Shinya Sonobe; Kouichiro Deguchi; Masahiko Sano; Takashi Mukai

2002-01-01

294

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

295

White light emission from heterojunction diodes based on surface-oxidized porous Si nanowire arrays and amorphous In-Ga-Zn-O capping  

NASA Astrophysics Data System (ADS)

A novel heterojunction white light emitting diode (LED) structure based on an array of vertically aligned surface-passivated p-type porous Si nanowires (PSiNWs) with n-type amorphous In-Ga-Zn-O (a-IGZO) capping is introduced. PSiNWs were initially synthesized by electroless etching of p-type Si (100) wafers assisted by Ag nanoparticle catalysts and then surface-passivated by thermal oxidation. The nanowires synthesized by metal-assisted electroless etching were found to have longitudinally varying nanoporous morphologies due to differences in the duration of exposure to etching environment. These PSiNWs were optically active with orange red photoluminescence consisting of dark red to yellow emissions attributable to quantum confinement effects and to modified band structures. The LED structures emitted visible white light while exhibiting rectifying current-voltage characteristics. The white light emission was found to be the result of the combination of dark red to yellow emissions originating from the quantum confinement effect within the PSiNWs and green to blue emissions due to the oxygen-deficiency-related recombination centers introduced during the surface oxidation.A novel heterojunction white light emitting diode (LED) structure based on an array of vertically aligned surface-passivated p-type porous Si nanowires (PSiNWs) with n-type amorphous In-Ga-Zn-O (a-IGZO) capping is introduced. PSiNWs were initially synthesized by electroless etching of p-type Si (100) wafers assisted by Ag nanoparticle catalysts and then surface-passivated by thermal oxidation. The nanowires synthesized by metal-assisted electroless etching were found to have longitudinally varying nanoporous morphologies due to differences in the duration of exposure to etching environment. These PSiNWs were optically active with orange red photoluminescence consisting of dark red to yellow emissions attributable to quantum confinement effects and to modified band structures. The LED structures emitted visible white light while exhibiting rectifying current-voltage characteristics. The white light emission was found to be the result of the combination of dark red to yellow emissions originating from the quantum confinement effect within the PSiNWs and green to blue emissions due to the oxygen-deficiency-related recombination centers introduced during the surface oxidation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05328h

Moon, Kyeong-Ju; Lee, Tae Il; Lee, Woong; Myoung, Jae-Min

2014-03-01

296

A novel automated hydrophilic interaction liquid chromatography method using diode-array detector/electrospray ionization tandem mass spectrometry for analysis of sodium risedronate and related degradation products in pharmaceuticals.  

PubMed

A simple, sensitive and fast hydrophilic interaction liquid chromatography (HILIC) method using ultraviolet diode-array detector (UV-DAD)/electrospray ionization tandem mass spectrometry was developed for the automated high performance liquid chromatography (HPLC) determination of sodium risedronate (SR) and its degradation products in new pharmaceuticals. The chromatographic separations were performed on Ascentis Express HILIC 2.7?m (150mm×2.1mm, i.d.) stainless steel column (fused core). The mobile phase consisted of formate buffer solution (pH 3.4; 0.03M)/acetonitrile 42:58 and 45:55 (v/v) for granules for oral solution and effervescent tablet analysis, respectively, at a flow-rate of 0.2mL/min, setting the wavelength at 262nm. Stability characteristics of SR were evaluated by performing stress test studies. The main degradation product formed under oxidation conditions corresponding to sodium hydrogen (1-hydroxy-2-(1-oxidopyridin-3-yl)-1-phosphonoethyl)phosphonate was characterized by high performance liquid chromatography-electrospray ionization-mass tandem mass spectrometry (HPLC-ESI-MS/MS). The validation parameters such as linearity, sensitivity, accuracy, precision and selectivity were found to be highly satisfactory. Linear responses were observed in standard and in fortified placebo solutions. Intra-day precision (relative standard deviation, RSD) was ?1.1% for peak area and ?0.2% for retention times (tR) without significant differences between intra- and inter-day data. Recovery studies showed good results for all the examined compounds (from 98.7 to 101.0%) with RSD ranging from 0.6 to 0.7%. The limits of detection (LOD) and quantitation (LOQ) were 1 and 3ng/mL, respectively. The high stability of standard and sample solutions at room temperature means an undoubted advantage of the method allowing the simultaneous preparation of many samples and consecutive chromatographic analyses by using an autosampler. The developed stability indicating method is suitable for the quality control of SR in new and commercial pharmaceutical formulations. PMID:25242223

Bertolini, Tiziana; Vicentini, Lorenza; Boschetti, Silvia; Andreatta, Paolo; Gatti, Rita

2014-10-24

297

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

Microsoft Academic Search

We demonstrate a compact system, incorporating a 32-element linear array of ultraviolet (290 nm and 340 nm) light-emitting diodes (LEDs) and a multi-anode photomultiplier tube, to the in-flight fluorescence detection of aerosolized particles, here containing the biological molecules tryptophan and NADH. This system illustrates substantial advances in the growth and fabrication of new semiconductor UV light emitting devices and an

Kristina Davitt; Yoon-Kyu Song; William R. Patterson III; Arto V. Nurmikko; Maria Gherasimova; Jung Han; Yong-Le Pan; Richard K. Chang

2005-01-01

298

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

299

On-line and off-line solid-phase extraction with styrene-divinylbenzene-membrane extraction disks for determining pesticides in water by reversed-phase liquid chromatography-diode-array detection  

Microsoft Academic Search

The determination of a group of pesticides, two phenylureas, six triazines and four organophosphorous compounds was carried out using off-line and on-line solid-phase extraction-RPLC-diode-array detection using styrene-divinylbenzene-membrane extraction disks. Both systems are intercompared and their advantages and disadvantages are discussed. Lower limits of detection can be reached by the on-line method, which enables levels of 0.1 ?g 1?1 of most

C. Aguilar; F. Borrull; R. M. Marcé

1996-01-01

300

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

Microsoft Academic Search

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

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

2006-01-01

301

Evaluation of a method based on liquid chromatography–diode array detector–tandem mass spectrometry for a rapid and comprehensive characterization of the fat-soluble vitamin and carotenoid profile of selected plant foods  

Microsoft Academic Search

The feasibility of using reversed-phase liquid chromatography\\/diode array\\/tandem mass spectrometry (LC–DAD–MS\\/MS) for a rapid and comprehensive profiling of fat soluble vitamins and pigments in some foods of plant origin (maize flour, green and golden kiwi) was evaluated. The instrumental approach was planned for obtaining two main outcomes within the same chromatographic run: (i) the quantitative analysis of ten target analytes,

Alessandra Gentili; Fulvia Caretti

2011-01-01

302

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

303

Identification and analysis of the constituents in an aqueous extract of Tricholoma matsutake by HPLC coupled with diode array detection/electrospray ionization mass spectrometry.  

PubMed

The main constituents in an aqueous extract of Tricholoma matsutake (Tm) were identified by high-performance liquid chromatography coupled with diode array detection and electrospray ionization time-of-flight mass spectrometry (HPLC-DAD/TOF-MS) and ion trap mass spectrometry (HPLC-DAD/Trap-MSn). The main factors in the extraction process which affect the yields of nutrients were optimized by single-factor experiments and orthogonal experiment design. In total, 12 constituents were identified from the aqueous extract of Tm, including tyrosine, cytidine, uridine, eritadenine, phenylalanine, nicotinamide, inosine, guanosine, tryptophan, adenosine, 5'-deoxy-5'-methylthioadenosine and riboflavin. The optimized extraction conditions were: the ratio of water to sample was 10 : 1 (v/w), Tm was extracted by ultrasonic-assisted extraction for 10 min, followed by water bath heating at 60 °C for 1 h. Among these extraction factors, the heating temperature is significant based on analysis of variance (ANOVA). The yields of nutrients were affected dramatically at high temperature leading to the loss of nutrients, especially for nucleosides and some amino acids. PMID:23957403

Ying, Xuhui; Ma, Jinfang; Liang, Qionglin; Wang, Yiming; Bai, Gang; Luo, Guoan

2013-08-01

304

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

305

[Simultaneous determination of five groups of components in qingkailing injection by high performance liquid chromatography with photo diode array detector and evaporative light scattering detector].  

PubMed

A method was established for the simultaneous quantification of nine components of five different structural types in Qingkailing injection. High performance liquid chromatography coupled with a photo diode array detector and an evaporative light scattering detector (HPLC-DAD-ELSD) was employed in the determination. Four monitoring wavelengths of 240, 254, 280 and 330 nm were set to determine nucleosides (uridine and adenosine), iridoid glucoside (geniposide), flavone glycoside (baicalin) and organic acids (chlorogenic acid and caffeic acid) respectively, and a combined evaporative light scattering detector was used to detect three steroid compounds (cholic acid, ursodesoxycholic acid and hyodeoxycholic acid). The proposed method permitted the simultaneous separation and determination of five groups of compounds in Qingkailing injection, and acceptable validation results of the precision, repeatability, stability and accuracy tests were achieved. The method was applied to the analysis of 19 Qingkailing injection samples from three different plants, and the results indicated that the method could be used as a convenient and reliable method in the multi-component determination and quality control of traditional Chinese medicines. PMID:16350790

Yan, Shikai; Xin, Wenfeng; Luo, Guoan; Wang, Yiming; Cheng, Yiyu

2005-09-01

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

Quality evaluation of mycelial Antrodia camphorata using high-performance liquid chromatography (HPLC) coupled with diode array detector and mass spectrometry (DAD-MS)  

PubMed Central

Background Antrodia camphorata (AC) is an important fungus native to Taiwanese forested regions. Scientific studies have demonstrated that extracts of AC possess a variety of pharmacological functions. This study aims to identify the full profile fingerprint of nucleosides and nucleobases in mycelial AC and to assess the quality of two commercial mycelial AC products. Methods High-performance liquid chromatography coupled with diode array detector and mass spectrometry was employed to identify the major components in mycelial AC. The chemical separation was carried out using a gradient program on a reverse phase Alltima C18 AQ analytical column (250 × 4.6 mm, 5 ?m) with the mobile phase consisting of deionized water and methanol. Results Ten nucleosides and nucleobases, two maleimide derivatives, and a sterol were identified as the major constituents in mycelial AC. These groups of chemical compounds constitute the first chromatographic fingerprint as an index for quality assessment of this medicinal fungus. Conclusions This study provides the first chromatographic fingerprint to assess the quality of mycelial AC. PMID:20205903

2010-01-01

308

Chemical profiling of Radix Paeoniae evaluated by ultra-performance liquid chromatography/photo-diode-array/quadrupole time-of-flight mass spectrometry.  

PubMed

In this study, an ultra-performance liquid chromatography/photo-diode-array/quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOFMS) based chemical profiling method was established for rapid global quality evaluation of Radix Paeoniae. By virtue of the high resolution, high speed of UPLC and the accurate mass measurement of TOFMS, a total of 40 components including 29 monoterpene glycosides, 8 galloyl glucoses and 3 phenolic compounds were simultaneously separated within 12min, and identified through the matching of empirical molecular formulae with those of published components in the in-house library, and were further elucidated by adjusted lower energy collision-induced dissociation (CID) mass spectra. Among forty components, five monoterpene glycoside sulfonates were identified as novel components. The established method was successfully applied to rapidly and globally compare the quality of Radix Paeoniae Alba and Radix Paeoniae Rubra, two post-harvesting handled products of Radix Paeoniae. Together with paeoniflorin sulfonate, five newly assigned monoterpene glycoside sulfonates were characteristic markers to detect non-official sulfur dioxide gas fumigated Radix Paeoniae Alba samples. It could be concluded that UPLC-PDA-QTOFMS based chemical profiling is a powerful approach for the global quality evaluation of Radix Paeoniae as well as other herbal medicines. PMID:19097720

Li, Song-Lin; Song, Jing-Zheng; Choi, Franky F K; Qiao, Chun-Feng; Zhou, Yan; Han, Quan-Bin; Xu, Hong-Xi

2009-02-20

309

Simultaneous determination of ten bioactive compaounds from the roots of Cynanchum paniculatum by using high performance liquid chromatography coupled-diode array detector  

PubMed Central

Background: Cynanchum paniculatum Kitagawa belongs to Asclepiadaceae and was used in traditional medicine to invigorate blood, alleviate edema, relieve pain, and relieve toxicity for a long time. Objective: A novel and reliable high performance liquid chromatography coupled with diode array detector method has been established for simultaneous determination of 10 bioactive compounds isolated from Cynanchum paniculatum Kitagawa, one of the herbal medicines. Materials and Methods: The chromatography analysis was performed on a SHISEIDO C18 column (S-5 ?m, 4.6 mm I.D. × 250 mm) at 35°C with a gradient elution of acetonitrile and water at a flow rate of 1ml/min and UV detection at 210, 230, and 280 nm. Results: The method was validated for linearity, precision, and accuracy. All calibration curves showed good linear regression (r2 > 0.9996). Limits of detection (LOD) and limits of quantification (LOQ) fell in the ranges 0.01 - 0.28 ?g/ml and 0.04 - 0.83 ?g/ml, respectively. The relative standard deviation (RSD) of the intra- and inter- day test, precision test were within 1.92% and 2.43%, respectively. The mean recovery of all ranged from 92.82 to 107.96% with RSD values 0.12 - 2.18%. Conclusion: The results of validation appeared that this established method was very accurate and stabilized for the quantification of 10 bioactive compounds isolated from C. paniculatum. PMID:23060698

Weon, Jin Bae; Lee, Bohyoung; Yun, Bo-Ra; Lee, Jiwoo; Ma, Choong Je

2012-01-01

310

Substitute technology for reference substances in the analysis of impurities in cefonicid for injection with HPLC using a diode array detector.  

PubMed

With HPLC using a diode array detector (DAD), a method of substitution for reference substances in impurity profiling control was developed that combined peak tracking by the correlation of spectra with application of correction factors for determination of each impurity. For qualitative analysis, two-dimensional (2D) standard spectrochromatographic data produced by HPLC-DAD were compared with sample data to develop 2D chromatographic spectral correlative maps so that the three target impurities were recognized without preparation and injection of reference solutions. For quantitative analysis, correction factors among cefonicid and the three impurities were established. The correction factors were 1.06 for 5-mercapto-1,2,3,4-tetrazole 1-methyl sulfonic acid detected at 255 nm, 0.77 for 7-aminocephalosporanic acid detected at 265 nm, and 0.97 for methoxycefonicid detected at 268 nm. The method could be used in analysis of related substances in cefonicid for injection without recourse to chemical reference standards of the three impurities. PMID:21563687

Li, Wei

2011-01-01

311

Comparative analysis of three Callicarpa herbs using high performance liquid chromatography with diode array detector and electrospray ionization-trap mass spectrometry method.  

PubMed

Three Callicarpa species, namely Callicarpa nudiflora Hook. et Arn., Callicarpa macrophylla Vahl. and Callicarpa kwangtungensis Chun. are astringency and hemostasis herbs in the traditional Chinese medical systems. Despite their wide use in Chinese medicine, no report on system comparison on their chemical constituents is available so far. High-performance liquid chromatography coupled with diode array detector and electrospray ionization trap mass spectrometry (HPLC-DAD-ESI-Trap MS) technique was used for qualitative and quantitative analyses of the three Callicarpa herbs. Phenylpropanoid glycosides, flavonoids and organic acids were identified by comparing with reference standards or according to their MS/MS fragmentation behaviors. A total of 33 compounds were identified identified or tentatively identified, and 23 of them were reported from these herbs for the first time. Phenylpropanoid glycosides were featured in the three species with their types and contents presenting significant differences. Furthermore, quantitative analysis was conducted by determining four marker phenylpropanoid glycosides (forsythoside B (14), acteoside (15), poliumoside (19), isoacteoside (21)) and two flavonoids (luteolin (30), apigenin (32)). Three flavonoid glucuronides (luteolin-diglucuronide-glucuronide (5), luteolin-diglucuronide (12), apigenin-7-O-?-glucuronide (24)) were semi-quantified according to their corresponding aglycones. The total contents of the nine major compounds in the three species varied significantly from 8.92 to 40.89 mg/g. PMID:23277156

Shi, Yatao; Wu, Chunyong; Chen, Yanhua; Liu, Wenyuan; Feng, Feng; Xie, Ning

2013-03-01

312

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

PubMed

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

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

2014-05-01

313

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

PubMed

Different extraction procedures and clean-up methods were compared in order to develop a sample preparation procedure for the multi-residue analysis of six post-emergence herbicides (metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium and cyhalofop butyl) in rice grains followed by liquid chromatography-diode array detection (LC-DAD). Optimum results were obtained dispersing milled rice grain in water, followed by the addition of 1% acetic acid in acetonitrile, MgSO(4) and sodium acetate as a modification of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method but no primary and secondary amine (PSA) sorbent was added due to the acidic nature of the herbicides. The method was further expanded to other post-emergence herbicides (quinclorac, clomazone and propanil). Except for quinclorac, which cannot be analysed with this method, the recoveries of the other eight herbicides were in the range 73-111%, with relative standard deviations lower than 12%. Limits of detection (LODs) ranged from 0.03 to 0.08 mg kg(-1). A single analyst can extract twelve samples in 4 h. The method presented here allows the simultaneous residue determination of the most common post-emergence herbicides employed in cultivating rice. It is simple, rapid, sensitive, and can be applied routinely to polished rice grain herbicide residue analysis. PMID:20013445

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

2010-02-01

314

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 0.01-0.5ngg(-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

315

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

PubMed

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 microg/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 microg/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 microg/l, whereas the LOQ using the HPLC/MS method was at 0.05 microg/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. PMID:10805235

Hostetler, K A; Thurman, E M

2000-04-01

316

Identification of protein binders in works of art by high-performance liquid chromatography-diode array detector analysis of their tryptic digests.  

PubMed

Proteins in works of art are generally determined by the relative amounts of amino acids. This method, however, implies a loss of information on the protein structure and its modifications. Consequently, we propose a method based on the analysis of trypsin digests using high-performance liquid chromatography (HPLC) UV diode array detection (DAD) for painting binder studies. All reaction steps are done in the same vial; no extraction methods or sample transfer is needed, reducing the risk of sample losses. A collection of pure binders (collagen, ovalbumin, yolk and casein) as well as homemade and historical paint samples have been investigated with this method. Chromatograms of unknowns at 214 nm and 280 nm are compared with those of the reference samples as a fingerprint. There is a good agreement between many peptides, but others seem to have been lost or their retention time shifted due to small compositional changes because of ageing and degradation of the paint. The results are comparable with the results of other techniques used for binder identification on the same samples, with the additional advantage of differentiation between egg yolk and glair. PMID:19259647

Fremout, Wim; Sanyova, Jana; Saverwyns, Steven; Vandenabeele, Peter; Moens, Luc

2009-04-01

317

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

PubMed

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

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

2014-01-15

318

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

PubMed

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

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

2006-01-20

319

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

320

Ultrasound-assisted extraction of phenolic compounds from strawberries prior to liquid chromatographic separation and photodiode array ultraviolet detection.  

PubMed

Ultrasound-assisted extraction was used for the determination of phenolic compounds present in strawberries. The optimization study of the extraction was carried out using spiked samples (100 mg/kg). The sample immersed in an aqueous solution containing hydrochloric acid (0.4 M) was sonicated for 2 min (duty cycle 0.2 s, output amplitude 20% of the nominal amplitude of the converter, applied power 100 W with the probe placed 1cm from the bottom of the water bath and 5 cm from the walls of the precipitate glass). Subsequent separation was carried out by liquid chromatography (LC) with photodiode array UV detection. Calibration curves using the standard addition in green strawberries typically gave linear dynamic ranges of 2-300 mg/l for all analytes; R(2) values exceeded 0.996 in all cases. The method was applied to two types of strawberries to demonstrate the applicability of the proposed method, which is much faster and produces less analyte degradation than methods as solid-liquid, subcritical water and microwave-assisted extraction. PMID:16203008

Herrera, M C; de Castro, M D Luque

2005-12-23

321

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

NASA Technical Reports Server (NTRS)

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

Albyn, K.; Finckenor, M.

2006-01-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

323

A p-silicon nanowire/n-ZnO thin film heterojunction diode prepared by thermal evaporation  

NASA Astrophysics Data System (ADS)

This paper represents the electrical and optical characteristics of a SiNW/ZnO heterojunction diode and subsequent studies on the photodetection properties of the diode in the ultraviolet (UV) wavelength region. In this work, silicon nanowire arrays were prepared on p-type (100)-oriented Si substrate by an electroless metal deposition and etching method with the help of ultrasonication. After that, catalyst-free deposition of zinc oxide (ZnO) nanowires on a silicon nanowire (SiNW) array substrate was done by utilizing a simple and cost-effective thermal evaporation technique without using a buffer layer. The SEM and XRD techniques are used to show the quality of the as-grown ZnO nanowire film. The junction properties of the diode are evaluated by measuring current—voltage and capacitance—voltage characteristics. The diode has a well-defined rectifying behavior with a rectification ratio of 190 at ±2 V, turn-on voltage of 0.5 V, and barrier height is 0.727 eV at room temperature under dark conditions. The photodetection parameters of the diode are investigated in the bias voltage range of ±2 V. The diode shows responsivity of 0.8 A/W at a bias voltage of 2 V under UV illumination (wavelength = 365 nm). The characteristics of the device indicate that it can be used for UV detection applications in nano-optoelectronic and photonic devices.

Hazra, Purnima; Jit, S.

2014-01-01

324

Combination of Indium-Tin Oxide and SiO2/AlN Dielectric Multilayer Reflective Electrodes for Ultraviolet-Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

We have investigated novel reflective electrodes by combining an indium-tin oxide (ITO) layer and a SiO2/AlN dielectric multilayer (DM) for UV-light-emitting diodes (LEDs). The reflectance of 10 pairs of SiO2/AlN DM reached 98.5% at 350 nm. As a result, the ITO/DM electrodes simultaneously satisfied the requirements of high reflectivity in the UV region, good contact characteristics, and current spreading. The light output power of the UV LED with an ITO/DM electrode is 1.2 and 1.6 times higher than those of LEDs with ITO/Al and Ni/Au electrodes, respectively.

Nakashima, Tsubasa; Takeda, Kenichiro; Shinzato, Hiroshi; Iwaya, Motoaki; Kamiyama, Satoshi; Takeuchi, Tetsuya; Akasaki, Isamu; Amano, Hiroshi

2013-08-01

325

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

326

Simultaneous determination of chromones and coumarins in Radix Saposhnikoviae by high performance liquid chromatography with diode array and tandem mass detectors.  

PubMed

Methods using high performance liquid chromatography with diode array detection (HPLC-DAD) and tandem mass spectrometry (HPLC-MS/MS) were developed and validated for the simultaneous determination of 5 chromones and 6 coumarins: prim-O-glucosylcimifugin (1), cimifugin (2), nodakenin (3), 4'-O-?-d-glucosyl-5-O-methylvisamminol (4), sec-O-glucosylhamaudol (5), psoralen (6), bergapten (7), imperatorin (8), phellopterin (9), 3'-O-angeloylhamaudol (10) and anomalin (11), in Radix Saposhnikoviae. The separation conditions for HPLC-DAD were optimized using an Ascentis Express C18 (4.6 mm×100 mm, 2.7 ?m particle size) fused-core column. The mobile phase was composed of 10% aqueous acetonitrile (A) and 90% acetonitrile (B) and the elution was performed under a gradient mode at a flow rate of 1.0 mL/min. The detection wavelength was set at 300 nm. The HPLC-DAD method yielded a base line separation of the 11 components in 50% methanol extract of Radix Saposhnikoviae with no interfering peaks detected. The HPLC-DAD method was validated in terms of linearity, accuracy and precision (intra- and inter-day), limit of quantification (LOQ), recovery, and robustness. Specific determination of the 11 components was also accomplished by a triple quadrupole tandem mass spectrometer equipped with an electrospray ionization (ESI) source. This HPLC-MS/MS method was also validated by determining the linearity, limit of quantification, accuracy, and precision. Quantification of the 11 components in 51 commercial Radix Saposhnikoviae samples was successfully performed using the developed HPLC-DAD method. The identity, batch-to-batch consistency, and authenticity of Radix Saposhnikoviae were successfully monitored by the proposed HPLC-DAD and HPLC-MS/MS methods. PMID:21807369

Kim, Min Kyung; Yang, Dong-Hyug; Jung, Mihye; Jung, Eun Ha; Eom, Han Young; Suh, Joon Hyuk; Min, Jung Won; Kim, Unyong; Min, Hyeyoung; Kim, Jinwoong; Han, Sang Beom

2011-09-16

327

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

PubMed

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

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

2011-01-01

328

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, Tania Regina; dos Santos, Andrea Karla Almeida; Uetanabaro, Ana Paula Trovatti; Branco, Alexsandro

2012-01-01

329

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

PubMed

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

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

2007-01-30

330

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

331

Nd Laser Pumped by Laser Diodes.  

National Technical Information Service (NTIS)

Performance data for laser diode pumped cw Nd:BEL and Nd :YAG lasers are presented. Two phased laser diode arrays are used as the pump source, each emitting 500 mW. The heat sink for the arrays is temperature controlled to allow for wavelength tunability....

R. Scheps

1989-01-01

332

BIN Diode For Submillimeter Wavelengths  

NASA Technical Reports Server (NTRS)

Diode formed by selective doping during epitaxial growth, starting with semi-insulating substrate. Use of high-mobility semiconductors like GaAs extends cutoff frequency. Either molecular-beam epitaxy (MBE) or organometallic chemical-vapor deposition used to form layers of diode. Planar growth process permits subsequent fabrication of arrays of diodes by standard photolithographic techniques, to achieve quasi-optical coupling of submillimeter radiation. Useful for generation of harmonics or heterodyne mixing in receivers for atmospheric and space spectroscopy operating at millimeter and submillimeter wavelengths. Used as frequency doublers or triplers, diodes of new type extend frequency range of present solid-state oscillators.

Maserjian, J.

1989-01-01

333

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

334

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

335

An enhanced multiwavelength ultraviolet biological trigger lidar  

NASA Astrophysics Data System (ADS)

A compact Ultraviolet Biological Trigger Lidar (UBTL) instrument for detection and discrimination of bio-warfare-agent (BWA) simulant aerosol clouds was developed by us [Prasad, et al, 2004] using a 5mW, 375nm semiconductor UV optical source (SUVOS) laser diode. It underwent successful field tests at Dugway Proving Ground and demonstrated measurement ranges of over 300m for elastic scattering and >100m for fluorescence. The UBTL was modified during mid-2004 to enhance its detection and discrimination performance with increased range of operation and sensitivity. The major optical modifications were: 1. increase in telescope collection aperture to 200 mm diameter: 2. addition of 266nm and 977nm laser transmitters: 3. addition of three detection channels for 266nm and 977nm elastic backscatter and fluorescence centered at 330nm. Also the commercial electronics of the original UBTL were replaced with a multi-channel field programmable gate array (FPGA) chip for laser diode modulation and data acquisition that allowed simultaneous and continuous operation of the UBTL sensor on all of its transmitter and receiver wavelengths. A notebook computer was added for data display and storage. Field tests were performed during July 2004 at the Edgewood Chemical and Biological Center in Maryland to establish the enhanced performance of UBTL subsystems. Results of these tests are presented and discussed.

Achey, Alexander; Bufton, Jack; Dawson, Jeffrey; Huang, Wen; Lee, Sangmin; Mehta, Nikhil; Prasad, Coorg R.

2004-12-01

336

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

337

Simple and rapid simultaneous profiling of minor components of honey by size exclusion chromatography (SEC) coupled to ultraviolet diode array detection (UV-DAD), combined with chemometric methods.  

PubMed

This paper discusses the importance of profiling UV-responsive components, properly integrated with chemometric techniques, in detecting indicative parameters for quality control of honey. The minor components in honeys of different botanical and geographical origins were investigated by size SEC-UV-DAD. We diluted honey with mobile phase before injection into the chromatographic apparatus and a single chromatographic run gave a fast profile of high- (proteins and enzymes), intermediate- (e.g. terpenoid glycosides in lime tree honey) and low-molecular-weight components (secondary metabolites, e.g. kynurenic acid in chestnut honey). The analysis of a total number of 32 honey samples from different regions (Italy, Western Balkan countries, Brazil, Cameroon, Kenya) and of different botanical origins (herbal flower and arboreal flower nectars/honeydews) showed peculiar and characteristic distribution of these markers, which were basically related to their floral origin. Chemometric examination carried out using principal component analysis (PCA) and hierarchical cluster analysis (HCA) of the chromatograms (RT vs. absorption) detected four main clusters in which the groups of (i) chestnut honeys, (ii) honeys from rain forests and (iii) counterfeit/adulterated honeys were clearly separated from the main group of flower nectar honeys. The method is fast, requiring minimal sample handling, and the chromatographic data can be analyzed by multivariate statistical techniques to obtain descriptive information about the honey's quality and composition. PMID:21962760

Beretta, Giangiacomo; Fermo, Paola; Maffei Facino, Roberto

2012-01-25

338

Fast separation and determination of tyrosol, hydroxytyrosol and other phenolic compounds in extra-virgin olive oil by capillary zone electrophoresis with ultraviolet-diode array detection  

Microsoft Academic Search

Olive oil is the main source of fat in the Mediterranean diet, and its consumption has been related to a low incidence of coronary heart disease and certain cancers. Recent findings demonstrate that olive oil phenolics are powerful in vitro and in vivo antioxidants and display other biological activities that could partially account for the observed healthful effects of the

Matteo Bonoli; Marina Montanucci; Tullia Gallina Toschi; Giovanni Lercker

2003-01-01

339

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

340

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

Microsoft Academic Search

The reliability and lifetime demanded by space- based 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. INTRODUCTION Laser diode array is a critical

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

341

Ultraviolet laser excitation source  

NASA Technical Reports Server (NTRS)

A new intense ultraviolet light source has been developed from an array of hypocycloidal pinch (HCP) devices. The basic unit of the array is constructed with three disk electrodes and is capable of producing dense plasmas at temperatures up to 10,000,000 K. Very high input power levels to the array are possible without significantly shortening its useful life, in strong contrast with conventional xenon flashlamps. The new light source, when operated with Ar and Xe gas mixtures at high pressures (approximately 5 x 10 to the 4th Pa), produced a light output of over 100 MW in the near-UV spectral range and successfully pumped an iodine photodissociation laser at 1.315 microns. A xenon recombination laser at 2.027 microns was also pumped in the HCP array.

Lee, J. H.; Mcfarland, D. R.; Hohl, F.

1980-01-01

342

Ultraviolet laser excitation source.  

PubMed

A new intense ultraviolet light source has been developed from an array of hypocycloidal pinch (HCP) devices. The basic unit of the array is constructed with three disk electrodes and is capable of producing dense plasmas at temperatures up to 10,000,000 K. Very high input power levels to the array are possible without significantly shortening its useful life, in strong contrast with conventional xenon flashlamps. The new light source, when operated with Ar and Xe gas mixtures at high pressures (~5 x 10(4) Pa), produced a light output of over 100 MW in the near-UV spectral range and successfully pumped an iodine photodissociation laser at 1.315 microm. A xenon recombination laser at 2.027 microm was also pumped in the HCP array. PMID:20234618

Lee, J H; McFarland, D R; Hohl, F

1980-10-01

343

Identification of major alkaloids and steroidal saponins in rat serum by HPLC-diode array detection-MS/MS following oral administration of Huangbai-Zhimu herb-pair Extract.  

PubMed

Huangbai-Zhimu herb-pair (HBZMHP) is a widely used Chinese traditional medicine formula in treating various diseases; however, its active components have remained unknown. In this paper, serum chemistry and combined high-performance liquid chromatography (HPLC), diode-array detection and mass-spectrometry (MS) techniques were used to study the constituents of HBZMHP extract absorbed into rat serum after oral administration. A total of nine characteristic HPLC peaks in the TIC chromatograms were identified as magnoflorine (1), menisperine (2), palmatine (3), berberine (4), timosaponin N or timosaponin E1 (5), timosaponin D (6), timosaponin BIII, anemarsaponin C or xilingsaponin B (7) timosaponin BII (8) and timosaponin AIII (9). All of the identified peaks were constituents of HBZMHP extract. The results narrow the range of active compounds to be found in HBZMHP extract, and pave the way for the follow-up action mechanism research. PMID:18318017

Ma, Chunhui; Fan, Mingsong; Tang, Yihong; Li, Zhixiong; Sun, Zhaolin; Ye, Guan; Huang, Chenggang

2008-08-01

344

Analysis of phenolic compounds in two blackberry species (Rubus glaucus and Rubus adenotrichus) by high-performance liquid chromatography with diode array detection and electrospray ion trap mass spectrometry.  

PubMed

High-performance liquid chromatography with diode array (LC-DAD) and electrospray ionization mass spectrometric detection (ESI-MS) was used to analyze phenolic compounds of two blackberry species ( Rubus glaucus Benth. and Rubus adenotrichus Schlech.) growing in South America. UV-visible spectrophotometry was a valuable tool for identifying the class of phenolic compound, whereas MS and MS ( n ) fragmentation data were useful for their structural characterization. Ellagitannins were the major compounds, with sanguiin H-6 and lambertianin C being the predominant ones. The anthocyanin composition as well as the presence or absence of kaempferol glycosides can be used to distinguish the Rubus species studied. Flavonol hexoside-malonates were identified in both berries. Hydroxycinnamic acids were minor compounds and found as ferulic, caffeic, and p-coumaric acid esters. Similar contents were obtained by analysis of soluble ellagitannins and ellagic acid glycosides as ellagic acid equivalents and by analysis of ellagic acid equivalents released after acid hydrolysis. PMID:17896814

Mertz, Christian; Cheynier, Veronique; Günata, Ziya; Brat, Pierre

2007-10-17

345

Diode-Laser Phase Conjugation 03FS030 Final Report  

Microsoft Academic Search

Arrays of lasers are often considered when a need exists to increase laser optical output power, for a variety of purposes. Similarly, individual semiconductor laser-diodes, generating 0.01-1.0 W each, are commonly placed in arrays in order to increase total optical power onto targeted objects. Examples of such usage are diode-laser pump arrays for solid-slab heat-capacity lasers, laser arrays for heat-treating

R H Page; R J Beach; S A Payne; J F Holzrichter

2005-01-01

346

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

347

Evaluation of a method based on liquid chromatography-diode array detector-tandem mass spectrometry for a rapid and comprehensive characterization of the fat-soluble vitamin and carotenoid profile of selected plant foods.  

PubMed

The feasibility of using reversed-phase liquid chromatography/diode array/tandem mass spectrometry (LC-DAD-MS/MS) for a rapid and comprehensive profiling of fat soluble vitamins and pigments in some foods of plant origin (maize flour, green and golden kiwi) was evaluated. The instrumental approach was planned for obtaining two main outcomes within the same chromatographic run: (i) the quantitative analysis of ten target analytes, whose standards are commercially available; (ii) the screening of pigments occurring in the selected matrices. The quantitative analysis was performed simultaneously for four carotenoids (lutein, zeaxanthin, ?-cryptoxanthin, and ?-carotene) and six compounds with fat-soluble activity (?-tocopherol, ?-tocopherol, ?-tocopherol, ergocalciferol, phylloquinone and menaquinone-4), separated on a C30 reversed-phase column and detected by atmospheric pressure chemical ionization (APCI) tandem mass spectrometry, operating in Selected Reaction Monitoring (SRM) mode. Extraction procedure was based on matrix solid-phase dispersion with recoveries of all compounds under study exceeding 78 and 60% from maize flour and kiwi, respectively. The method intra-day precision ranged between 3 and 7%, while the inter-day one was below 12%. The mild isolation conditions precluded artefacts creation, such as cis-isomerization phenomena for carotenoids. During the quantitative LC-SRM determination of the ten target analytes, the identification power of the diode array detector joined to that of the triple quadrupole (QqQ) allowed the tentatively identification of several pigments (chlorophylls and carotenoids), without the aid of standards, on the basis of: (i) the UV-vis spectra recorded in the range of 200-700nm; (ii) the expected retention time; (iii) the two SRM transitions, chosen for the target carotenoids but also common to many of isomeric carotenoids occurring in the selected foods. PMID:21190690

Gentili, Alessandra; Caretti, Fulvia

2011-02-01

348

Nd:BEL Laser Pumped by Laser Diodes.  

National Technical Information Service (NTIS)

Performance data for a laser diode pumped cw Nd:BEL laser is presented . Two phased laser diode arrays are used as the pump source, each emitting 500 mW. The heat sink for the arrays is temperature controlled to allow for wavelength tunability. A Nd:YAG r...

D. F. Heller, E. J. Schimitschek, J. Myers, R. Scheps

1988-01-01

349

Improved Light Extraction Efficiency in Blue Light-Emitting Diodes by SiO2-Coated ZnO Nanorod Arrays  

NASA Astrophysics Data System (ADS)

We report on the improved light extraction efficiency of blue light-emitting diodes (LEDs) by SiO2-coated ZnO nanorods (NRs) grown on indium-tin oxide (ITO). The optical output power of the LEDs with SiO2-coated ZnO NRs, which are grown on the patterned sapphire substrates, increases by 5% at 20 mA, compared with that of LEDs with bare ZnO NRs. This increase is attributed to the improved light extraction efficiency of LEDs because the SiO2 layer with a refractive index lower than that of ZnO NRs further reduces the Fresnel reflection.

Cho, Chu-Young; Kim, Na-Yeong; Kang, Jang-Won; Leem, Young-Chul; Hong, Sang-Hyun; Lim, Wantae; Kim, Sung-Tae; Park, Seong-Ju

2013-04-01

350

Microwave diode switchable metamaterial reflector/absorber  

NASA Astrophysics Data System (ADS)

We embed diodes as active circuit elements within a metamaterial to implement a switchable metamaterial reflector/absorber at microwave frequencies. Diodes are placed in series with the unit cells of the metamaterial array. This results in just a pair of control lines to actively tune all the diodes in a metamaterial. Diodes can be tuned on and off to switch the function of the metamaterial between a perfect absorber and a reflector. The design, simulation, and experimental results of a switchable reflector/absorber in 2-6 GHz range are presented.

Xu, Wangren; Sonkusale, Sameer

2013-07-01

351

High-power laser diodes at various wavelengths  

SciTech Connect

High power laser diodes at various wavelengths are described. First, performance and reliability of an optimized large transverse mode diode structure at 808 and 941 nm are presented. Next, data are presented on a 9.5 kW peak power array at 900 nm having a narrow emission bandwidth suitable for pumping Yb:S-FAP laser materials. Finally, results on a fiber-coupled laser diode array at {approx}730 nm are presented.

Emanuel, M.A.

1997-02-19

352

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

353

Modular radiation detector array and module  

SciTech Connect

A modular radiation detector array which allows improved spatial resolution and facilitates installation and replacement for repair. Each module includes two detachably assembled portions with one portion including a plurality of spaced plates for collimating radiation. The second portion includes a printed circuit board, a semiconductor diode array chip mounted on the printed circuit board, and a plurality of scintillator crystals mounted on the semiconductor chip with each crystal overlying a diode. Signals from the diodes are applied to signal processing means by a cable which is readily connected to and disconnected from the diode array.

Morehouse, C.C.; Shaw, R.H.

1982-07-06

354

Volume Bragg grating external-cavity designs for coherent emission of an array of tapered  

E-print Network

) 1 laser diode N incoherent laser diodes N coherent laser diodes IntroductionIntroduction Coherent designs Purpose : passive coherent combining of diode lasers to induce an efficient coupling between emitters p External cavity HR coating Diode laser array Output coupler Coherent high power laser beam

Boyer, Edmond

355

Simultaneous determination of carbonyl compounds and polycyclic aromatic hydrocarbons in atmospheric particulate matter by liquid chromatography–diode array detection–fluorescence detection  

Microsoft Academic Search

Simultaneous analysis of 24 carbonyl compounds (alkanals, unsaturated, dicarbonylic and aromatic aldehydes and ketones) derivatized with 2,4-dinitrophenylhydrazine and 16 polycyclic aromatic hydrocarbons (PAHs) using a photodiode-array (PDA) and a fluorescence (FL) detector in series is proposed.The separation is carried out with a reversed-phase column and gradient elution using four solvents (acetonitrile, water, tetrahydrofuran and methanol) in less than 35min. Several

M. C. Prieto-Blanco; M. Piñeiro Iglesias; P. López-Mahía; S. Muniategui Lorenzo; D. Prada Rodríguez

2010-01-01

356

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

357

Identification and quantitation of iodotyrosines and iodothyronines in proteins using high-performance liquid chromatography by photodiode-array ultraviolet-visible detection.  

PubMed

We describe a new method for the separation, identification and quantitation of iodotyrosines and iodothyronines [3-monoiodo-L-tyrosine (MIT), 3,5-diiodo-L-tyrosine (DIT), L-thyronine (T0), 3,5-diiodo-L-thyronine (T2), 3,5,3'-triiodo-L-thyronine (T3), reverse 3,3',5'-triiodo-L-thyronine (rT3) and 3,3',5,5'-tetraiodo-L-thyronine (T4)]. Reversed-phase high-performance liquid chromatography (RP-HPLC) was performed on a Nucleosil C8 column with photodiode-array UV-Vis detection. A clearly defined elution profile was obtained of each iodoamino acid (iodotyrosines and iodothyronines) using a linear gradient from 20 to 80% phase B (90% acetonitrile, 10% water, 0.1% TFA), phase A (water, 0.1% TFA, pH 2.0) eluted over 40 min. Iodoamino acid composition was determined, taking into account retention times and spectral characteristics. Thyroid protein samples were digested enzymatically and the complex mixture of IAA was then injected onto the RP-HPLC system. A photodiode-array detector with a dynamic range in the UV-Vis region was used in the HPLC system to monitor the absorbance at different wavelengths continuously, collecting data which were compared with standard samples. Each IAA was quantitated using linear calibration curves obtained at 280 nm. This method allowed identification and quantitation of iodoamino acids from diverse sources in the range 2-500 ng, avoiding the need to radiolabel samples. The technique was tested with in vitro iodinated and non-iodinated human thyroglobulin and the recoveries ranged from 84 to 91%. PMID:9029324

de la Vieja, A; Calero, M; Santisteban, P; Lamas, L

1997-01-10

358

Strong photonic crystal behavior in regular arrays of core-shell and quantum disc InGaN/GaN nanorod light-emitting diodes  

NASA Astrophysics Data System (ADS)

We show that arrays of emissive nanorod structures can exhibit strong photonic crystal behavior, via observations of the far-field luminescence from core-shell and quantum disc InGaN/GaN nanorods. The conditions needed for the formation of directional Bloch modes characteristic of strong photonic behavior are found to depend critically upon the vertical shape of the nanorod sidewalls. Index guiding by a region of lower volume-averaged refractive index near the base of the nanorods creates a quasi-suspended photonic crystal slab at the top of the nanorods which supports Bloch modes. Only diffractive behavior could be observed without this region. Slab waveguide modelling of the vertical structure shows that the behavioral regime of the emissive nanorod arrays depends strongly upon the optical coupling between the nanorod region and the planar layers below. The controlled crossover between the two regimes of photonic crystal operation enables the design of photonic nanorod structures formed on planar substrates that exploit either behavior depending on device requirements.

Lewins, C. J.; Le Boulbar, E. D.; Lis, S. M.; Edwards, P. R.; Martin, R. W.; Shields, P. A.; Allsopp, D. W. E.

2014-07-01

359

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

360

Rapid method for simultaneous determination of flavonoid, saponins and polyacetylenes in folium ginseng and radix ginseng by pressurized liquid extraction and high-performance liquid chromatography coupled with diode array detection and mass spectrometry.  

PubMed

A rapid pressurized liquid extraction (PLE) and high-performance liquid chromatography coupled with diode array detection and mass spectrometry (HPLC-DAD-MS) method for the simultaneous determination of one flavonoid (panasenoside), nine saponins (ginsenoside Rg1, Re, Rf, Rg2, Rb1, Rc, Rb2, Rb3 and Rd) and two polyacetylenes (panaxydol and panaxynol) in folium ginseng and radix ginseng was developed. A Prevail C(18) rocket column (33 mm x 7 mm, 3.0 microm) and gradient elution were used during the analysis. Flavonoid was quantified at 355 nm, and saponins and polyacetylenes were determined at 203 nm. The chromatographic peaks of 12 investigated compounds in samples were unambiguously identified by compared their UV spectra and/or MS data with the related reference compounds. All calibration curves showed good linearity (r>0.999) within the test ranges. The intra- and inter-day variations for 12 analytes were less than 1.17% and 2.17%, respectively. The developed method was successfully applied to determine the investigated compounds in 10 samples of radix ginseng and folium ginseng, respectively. The result showed that PLE combined with rocket column HPLC analysis could provide a rapid method for analysis of compounds in traditional Chinese medicines (TCMs), which is helpful to comprehensive evaluation of quality of radix ginseng and folium ginseng. PMID:19272605

Qian, Z M; Lu, J; Gao, Q P; Li, S P

2009-05-01

361

Discovery of xanthine oxidase inhibitors from a complex mixture using an online, restricted-access material coupled with column-switching liquid chromatography with a diode-array detection system.  

PubMed

To find potential lead compounds for antigout drug discovery, an automated online, restricted-access material coupled with column-switching liquid chromatography with a diode-array detection (RAM-LC-DAD) system was developed for screening of xanthine oxidase (XO) inhibitors and their affinity rankings in complex mixtures. The system was first evaluated by analyzing a mixture of six compounds with known inhibition of XO. Nonspecific binding to the denatured XO was investigated and used as the control for screening. Subsequently, the newly developed system was applied to screening of a natural product, Oroxylum indicum extract, and four compounds which could specifically interact with XO were found and identified as oroxin B, oroxin A, baicalin, and baicalein. The results were verified by a competitive binding test using the known competitive inhibitor allopurinol and were further validated by an inhibition assay in vitro. The online RAM-LC-DAD system developed was shown to be a simple and effective strategy for the rapid screening of bioactive compounds from a complex mixture. PMID:24510210

Li, De-qiang; Zhao, Jing; Li, Shao-ping; Zhang, Qing-wen

2014-03-01

362

A new ultrahigh performance liquid chromatography with diode array detection coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry analytical strategy for fast analysis and improved characterization of phenolic compounds in apple products.  

PubMed

A new, rapid, selective and sensitive ultrahigh performance liquid chromatography with diode array detection coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (UHPLC-DAD-ESI-Q-ToF-MS) strategy using automatic and simultaneous acquisition of exact mass at high and low collision energy, MS(E), has been developed to obtain polyphenolic profile of apples, apple pomace and apple juice from Asturian cider apples in a single run injection of 22 min. MS(E) spectral data acquisition overcomes chromatographic co-elution problems, performing simultaneous collection of precursor ions as well as other ions produced as a result of their fragmentation, which allows resolving complex spectra from mixtures of precursor ions in an unsupervised way and eases their interpretation. Using this technique, 52 phenolic compounds of five different classes were readily characterized in these apple extracts in both positive and negative ionization modes. The spectral data for phenolic compounds obtained using this acquisition mode are comparable to those obtained by conventional LC-MS/MS as exemplified in this work. Among the 52 phenolic compounds identified in this work, 2 dihydrochalcones and 3 flavonols have been tentatively identified for the first time in apple products. Moreover, 2 flavanols, 4 dihydrochalcones, 9 hydroxycinnamic acids and 4 flavonols had not been previously reported in apple by ToF analysis to our knowledge. PMID:24120027

Ramirez-Ambrosi, M; Abad-Garcia, B; Viloria-Bernal, M; Garmon-Lobato, S; Berrueta, L A; Gallo, B

2013-11-01

363

Schottky barrier diode and method thereof  

NASA Technical Reports Server (NTRS)

Pt/n.sup.-GaN Schottky barrier diodes are disclosed that are particularly suited to serve as ultra-violet sensors operating at wavelengths below 200 nm. The Pt/n.sup.-GaN Schottky barrier diodes have very large active areas, up to 1 cm.sup.2, which exhibit extremely low leakage current at low reverse biases. Very large area Pt/n.sup.-GaN Schottky diodes of sizes 0.25 cm.sup.2 and 1 cm.sup.2 have been fabricated from n.sup.-/n.sup.+ GaN epitaxial layers grown by vapor phase epitaxy on single crystal c-plane sapphire, which showed leakage currents of 14 pA and 2.7 nA, respectively for the 0.25 cm.sup.2 and 1 cm.sup.2 diodes both configured at a 0.5V reverse bias.

Aslam, Shahid (Inventor); Franz, David (Inventor)

2008-01-01

364

Determination of polymer additives-antioxidants and ultraviolet (UV) absorbers by high-performance liquid chromatography coupled with UV photodiode array detection in food simulants.  

PubMed

An analytical method for the quantitative determination of migration levels of polymer additives such as antioxidants and UV absorbers in food packages by high-performance liquid chromatography coupled with UV-vis photodiode array detection has been developed. The pretreatment step involved solid-phase extraction with silica C18 cartridges. The analytical method showed good linearity, presenting regression coefficients (R(2)) ? 0.9990 for all compounds. This optimized method was also validated with respect to precision, reproducibility, stability, and accuracy. The limits of detection and quantification were between 0.09 and 1.72 ?g mL(-1) and between 0.20 and 5.64 ?g mL(-1) for 12 analytes, respectively. Recoveries were in the range of 67.48 and 108.55%, with relative standard deviations between 2.76 and 9.81%. Migration levels of antioxidants and UV absorbers were determined. Butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol (BHT), 2,4-di-tert-butylphenol, Cyanox 2246, Irganox 1035, Tinuvin 326, Tinuvin 328, Irganox 1010, and Irganox 1330 were detected; BHT and Cyanox 2246 were at higher levels than the specific migration levels in some food simulants. PMID:22141443

Gao, Yali; Gu, Yanxiang; Wei, Yun

2011-12-28

365

[Studies on identification of drugs of abuse by diode array detection. I. Screening-test and identification of benzodiazepines by HPLC-DAD with ICOS software system].  

PubMed

For the establishment of screening-test and identification of 20 benzodiazepines (Alprazolam, Bromazepam, Chlordiazepoxide, Clonazepam, Clotiazepam, Cloxazolam, Diazepam, Estazolam, Fludiazepam, Flunitrazepam, Flurazepam, Lorazepam, Lormetazepam, Medazolam, Midazepam, Nimetazepam, Nitrazepam, Oxazepam, Prazepam, Triazolam), the optimum separation condition on HPLC was investigated by using Interactive Computer Optimization for HPLC Separation (ICOS) software. The two eluent systems of 0.02M KH2PO4 (pH 3.1)-methanol-acetonitrile (66.4:5.7:27.9) and 0.1% TFA-methanol-acetonitrile (61.6:16.1:22.3) were selected by HPLC analyses using ICOS. These optimum separation conditions enabled the screening test and identification of the 20 benzodiazepines on HPLC with photodiode array detection. PMID:7920567

Shimamine, M; Masunari, T; Nakahara, Y

1993-01-01

366

Coaxial In(x)Ga(1-x)N/GaN multiple quantum well nanowire arrays on Si(111) substrate for high-performance light-emitting diodes.  

PubMed

We report the growth of high-quality nonpolar (m-plane) and semipolar (r-plane) multiple quantum well (MQW) nanowires (NWs) for high internal quantum efficiency light emitting diodes (LEDs) without polarization. Highly aligned and uniform In(x)Ga(1-x)N/GaN MQW layers are grown coaxially on the {1-100} sidewalls of hexagonal c-axis n-GaN NWs on Si(111) substrates by a pulsed flow metal-organic chemical vapor deposition (MOCVD) technique. The photoluminescence (PL) measurements reveal that the wavelength and intensity of an MQW structure with various pairs (2-20) are very stable and possess composition-dependent emission ranging from 369 to 600 nm. The cathodoluminescence (CL) spectrum of individual In(x)Ga(1-x)N/GaN MQW NW is dominated by band-edge emission at 369 and 440 nm with a relatively homogeneous profile of parallel alignment. High-resolution transmission electron microscopy (HR-TEM) studies of coaxial InxGa1-xN/GaN MQW NWs measured along the [0001] and [2-1-10] zone axes reveal that the grown NWs are uniform with six nonpolar m-plane facets without any dislocations and stacking faults. The p-GaN/In(x)Ga(1-x)N/GaN MQW/n-GaN NW coaxial LEDs show a current rectification with a sharp onset voltage at 2.65 V in the forward bias. The linear enhancement of power output could be attributed to the elimination of piezoelectric fields in the In(x)Ga(1-x)N/GaN MQW active region. The superior performance of coaxial NW LEDs is observed in comparison with that of thin film LEDs. Overall, the feasibility of obtaining low defect and strain free m-plane coaxial NWs using pulsed MOCVD can be utilized for the realization of high-power LEDs without an efficiency droop. These kinds of coaxial NWs are viable high surface area MQW structures which can be used to enhance the efficiency of LEDs. PMID:23701263

Ra, Yong-Ho; Navamathavan, R; Park, Ji-Hyeon; Lee, Cheul-Ro

2013-08-14

367

Local nanotip arrays sculptured by atomic force microscopy to enhance the light-output efficiency of GaN-based light-emitting diode structures  

NASA Astrophysics Data System (ADS)

In this work, local nanotip arrays on GaN-based light-emitting (LED) structures were fabricated through nano-oxidation using an atomic force microscope (AFM). The photoluminescence (PL) intensity of the InGaN/GaN multiple quantum wells (MQWs) active layer and the light extraction efficiency of the LED structure were enhanced by forming this nanotips structure to serve as a graded-refractive index layer, which is further validated by the finite-difference time-domain analysis. The PL emission peak of the MQWs active layer has a blue-shift phenomenon that is caused by a partial reduction of the strain on the InGaN well. It is expected that our approach opens a promising route for simultaneously enhancing both the internal quantum efficiency and the light extraction efficiency of GaN-based LEDs. The proposed AFM-based method will be of importance for local patterning the light emitting components for optoelectronic applications.

Huang, Chun-Ying; Yao, Yung-Chi; Lee, Ya-Ju; Lin, Tai-Yuan; Kao, Wen-Jang; Hwang, Jih Shang; Yang, Ying-Jay; Shen, Ji-Lin

2014-05-01

368

Local nanotip arrays sculptured by atomic force microscopy to enhance the light-output efficiency of GaN-based light-emitting diode structures.  

PubMed

In this work, local nanotip arrays on GaN-based light-emitting (LED) structures were fabricated through nano-oxidation using an atomic force microscope (AFM). The photoluminescence (PL) intensity of the InGaN/GaN multiple quantum wells (MQWs) active layer and the light extraction efficiency of the LED structure were enhanced by forming this nanotips structure to serve as a graded-refractive index layer, which is further validated by the finite-difference time-domain analysis. The PL emission peak of the MQWs active layer has a blue-shift phenomenon that is caused by a partial reduction of the strain on the InGaN well. It is expected that our approach opens a promising route for simultaneously enhancing both the internal quantum efficiency and the light extraction efficiency of GaN-based LEDs. The proposed AFM-based method will be of importance for local patterning the light emitting components for optoelectronic applications. PMID:24763484

Huang, Chun-Ying; Yao, Yung-Chi; Lee, Ya-Ju; Lin, Tai-Yuan; Kao, Wen-Jang; Shang Hwang, Jih; Yang, Ying-Jay; Shen, Ji-Lin

2014-05-16

369

The Ultraviolet Spectrum of the Crab Pulsar  

Microsoft Academic Search

The time-averaged ultraviolet spectrum of the Crab pulsar will be measured with the FOS using the G160L grating in the ACCUM mode. The grating covers from 1150 A to 2510 A at a dispersion of 6.87 A\\/diode. The 0.3 arcsec diameter aperture will be used in order to exclude as much as possible of the surrounding nebula. The observed spectrum

Robert Bless

1995-01-01

370

Large-Area Vacuum Ultraviolet Sensors  

NASA Technical Reports Server (NTRS)

Pt/(n-doped GaN) Schottky-barrier diodes having active areas as large as 1 cm square have been designed and fabricated as prototypes of photodetectors for the vacuum ultraviolet portion (wavelengths approximately equal 200 nm) of the solar spectrum. In addition to having adequate sensitivity to photons in this wavelength range, these photodetectors are required to be insensitive to visible and infrared components of sunlight and to have relatively low levels of dark current.

Aslam, Shahid; Franz, David

2012-01-01

371

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

PubMed

Following preparative isolation and purification by high-speed counter-current chromatography (HSCCC), the collected fractions were generally analyzed by high-performance liquid chromatography (HPLC) to determine the relative purities of each fraction. Our paper reports for the first time a preparative isolation-purity detection hyphenated system: online coupling of HSCCC with high-performance liquid chromatography-diode array detection (HSCCC-HPLC-DAD). The introduction of online purity analysis in HSCCC has dramatically improved the efficiency of this technique by overcoming the drawbacks of post analysis in HSCCC isolation. The effluent from the outlet of HSCCC was splitted into two parts: one was collected, while the other was introduced directly into an HPLC-DAD system for purity analysis through a switch valve. Therefore, the purities of the obtained fractions from HSCCC were monitored, and fractions with high purities were collected. This strategy has been successfully demonstrated with the preparative isolation and purification of hyperoside from Hypericum perforatum (St. Jone's Wort); a model of TBE-300A HSCCC was used to isolate and separate hyperoside from H. perforatum with a two-phase solvent system composed of ethyl acetate-ethanol-water at the volume ratio of 5:1:5 (v/v) using online detection technique. The isolation was done in less than 3.5 h, and a total of 83.0-mg hyperoside at over 99.0% purity was yielded from 300 mg of the partially purified extract. This new strategy possesses general utility in the preparation of bioactive compounds from traditional Chinese medicine (TCM). PMID:16620843

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

2006-05-26

372

Identification of the Position of Mono-O-Glucuronide of Flavones and Flavonols by Analyzing Shift in Online UV Spectrum (?max) Generated from an Online Diode-arrayed Detector  

PubMed Central

The beneficial pharmacological effects of flavonoids such as chemo-prevention against cancer, aging and heart diseases are severely limited due to their extensive in vivo glucuronidation by UGTs. UGTs showed regiospecificity (i.e. position preference) in the glucuronidation of the flavonoids based on substrate’s chemical structure. In this paper, glucuronide(s) of 36 flavones and flavonols were generated using an in vitro glucuronidation reaction. UPLC/MS/MS was used to confirm the degree (mono- or di-) of glucuronidation in flavonoids with up to four hydroxyl group. UV spectra of flavonoids and their respective mono-O-glucuronides were generated using UPLC with an online diode-arrayed detector. Analysis of the extent of shift in spectra of glucuronides in Band I and Band II regions as reflected by changes in ?max value was used to identify the position of glucuronidation. The data showed that glucuronidation of 3- and 4’-hydroxyl resulted in Band I ?max hypsochromic shift (or blue shift) of 13–30 nm and 5–10 nm, respectively. And glucuronidation of 5-hydroxyl group caused Band II ?max hypsochromic shift of 5–10 nm. In contrast, glucuronidation of 7-hydroxyl group did not cause any ?max change in Band I or II ?max whereas glucuronidation of 6-hydroxyl group did not cause predictable changes in ?max values. The paper demonstrated for the first time that a rapid and robust analysis method using ?max changes in online UV spectra can be used to pinpoint region-specific glucuronidation of flavones and flavonols with hydroxyl groups at 4’, 3, 5, and/or 7 position(s). PMID:20687611

Singh, Rashim; Wu, Baojian; Tang, Lan; Liu, Zhongqiu; Hu, Ming

2012-01-01

373

Application of dispersive liquid-liquid microextraction and dispersive micro-solid-phase extraction for the determination of quinolones in swine muscle by high-performance liquid chromatography with diode-array detection.  

PubMed

Dispersive liquid-liquid microextraction (DLLME) and dispersive micro-solid-phase extraction (DMSPE) are two simple and low-cost sample preparation methods for liquid samples. In this work, these two methods were applied to solid tissue sample for the determination of seven quinolones by high-performance liquid chromatography with diode-array detection (HPLC-DAD). After the homogenization of the swine muscle with acetonitrile and salt-promoted partitioning, small amounts of the extract were used for the DLLME and DMSPE methods. In the DLLME approach, the target analytes in the extraction solvent were rapidly extracted into a small volume of dichloromethane for drying and the residue was reconstituted for HPLC-DAD analysis. In the DMSPE approach, the target analytes in the extraction solvent were trapped by dispersive silica-based PSA (primary and secondary amine) sorbents and desorbed into a small amount of desorption solution for HPLC-DAD analysis. Under the optimal conditions, relative recoveries were determined for swine muscle spiked 50-200 microg kg(-1) and quantification was achieved by matrix-matched calibration. The calibration curves of seven quinolones showed linearity with a correlation coefficient value above 0.998 for both approaches. Relative recoveries ranged from 93.0 to 104.7% and from 95.5 to 111.0% for DLLME and DMSPE, respectively. Limits of detection (LODs) ranged from 5.6 to 23.8 microg kg(-1) and from 7.5 to 26.3 microg kg(-1) for DLLME and DMSPE, respectively. PMID:19932815

Tsai, Wen-Hsien; Chuang, Hung-Yi; Chen, Ho-Hsien; Huang, Joh-Jong; Chen, Hwi-Chang; Cheng, Shou-Hsun; Huang, Tzou-Chi

2009-12-10

374

A multi-residue method for pesticide residue analysis in rice grains using matrix solid-phase dispersion extraction and high-performance liquid chromatography-diode array detection.  

PubMed

Pesticides are widely used in rice cultivation, often resulting in detection of their residues in rice grains. So far, no analytical method has been available for the simultaneous determination of most rice pesticides in rice grains. This paper reports the development and validation of such a method for the determination of eight rice pesticides (penoxsulam tricyclazole, propanil, azoxystrobin, molinate, profoxydim, cyhalofop-butyl, deltamethrin) and 3,4-dichloroaniline, the main metabolite of propanil. Pesticide extraction and clean-up was performed by an optimized matrix solid-phase dispersion (MSPD) protocol on neutral alumina (5 g) using acetonitrile as the elution solvent. Samples were analyzed in a high-performance liquid chromatography-diode array detection (HPLC-DAD) system. Pesticide separation was achieved with a mobile phase of acetonitrile/water in a linear elution gradient from 30:70% (v/v) to 100:0% (v/v) in 14 min at a flow rate of 0.8 mL min(-1). Method validation was performed by means of linearity, intra-day accuracy, inter-day precision and sensitivity. Linear regression coefficients (R(2)) were always above 0.9948. Limits of detection (LOD) and quantification (LOQ) varied from 0.002 to 0.200 mg kg(-1) and 0.006 to 0.600 mg kg(-1), respectively. Recoveries were investigated at three fortification levels and were found to be acceptable (74-127%) with relative standard deviations (RSD) below 12%. Application of the method for the analysis of five commercial rice grain samples showed that the pesticide levels were below the LOD. Overall, the method developed is suitable for the determination of residues of most rice pesticides in rice grains at levels below the established MRLs. PMID:20379813

Tsochatzis, Emmanouil D; Menkissoglu-Spiroudi, Urania; Karpouzas, Dimitrios G; Tzimou-Tsitouridou, Roxani

2010-07-01

375

An automated method for the simultaneous determination of pravastatin, 3-hydroxy isomeric metabolite, pravalactone and fenofibric acid in human plasma by sensitive liquid chromatography combined with diode array and tandem mass spectrometry detection.  

PubMed

In this study, a sensitive and selective method based on liquid chromatography combined with diode array and tandem mass spectrometry detection (LC-DAD-MS/MS) was developed for the simultaneous quantitative determination of fenofibric acid, pravastatin and its main metabolites in human plasma. In this method, an automated solid-phase extraction (SPE) on disposable extraction cartridges (DECs) is used to isolate the compounds from the biological matrix and to prepare a cleaner sample before injection and analysis in the LC-DAD-MS/MS system. On-line LC-DAD-MS/MS system using an atmospheric pressure ionization (TurboIonSpray) was then developed for the simultaneous determination of pravastatin, 3-hydroxy isomeric metabolite (3-OH metab), pravalactone and fenofibric acid. The separation is obtained on an endcapped dodecyl silica based stationary phase using a mobile phase consisting of a mixture of acetonitrile, methanol and 5mM ammonium acetate solution (30:30:40, v/v/v). Sulindac and triamcinolone were used as internal standards (ISs). The detection of the fenofibric acid and sulindac was achieved by means of a DAD system. The MS/MS ion transitions monitored were m/z 442.2-->269.1, 442.2-->269.1, 424.3-->183.0 and 435.2-->397.2 for pravastatin, 3-OH metab, pravalactone and triamcinolone, respectively. The method was validated regarding stability, selectivity, extraction efficiency, response function, trueness, precision lower limit of quantitation and matrix effect. The limits of quantitation (LOQs) were around 0.50 ng/ml for pravastatin, 0.25 ng/ml for 3-OH metab, 0.05 ng/ml for pravalactone and 0.25 microg/ml for fenofibric acid. PMID:18342321

Mertens, B; Cahay, B; Klinkenberg, R; Streel, B

2008-05-01

376

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 8min 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

377

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

378

A Comparison of Optical Detectors for the Visible and Ultraviolet.  

ERIC Educational Resources Information Center

Presents data for instructors on the current state of ultraviolet-visible detector technology and gives sources of further information. Described are the mechanisms and characteristics of photomultiplier tubes and array detectors. Lists 15 references. (YP)

Grossman, William E. L.

1989-01-01

379

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

380

deg-phase shift, single-lobe operation from wide-waveguide interferometric (WWI) phase-locked arrays of InGaAsP/InP (lambda = 1.3 microns) diode lasers  

NASA Astrophysics Data System (ADS)

A new type of interferometric-type phase-locked array is demonstrated which selects fundamental-mode operation to relatively high drive levels above threshold. The WWI array allows 10-11 elements to operate in a single, diffraction-limited beam to 70 percent above lasing threshold. In contrast to Y-junction arrays, the array does not have significant radiation losses.

Botez, D.; Pham, T.; Tran, D.

1987-04-01

381

deg-phase shift, single-lobe operation from wide-waveguide interferometric (WWI) phase-locked arrays of InGaAsP\\/InP (lambda = 1.3 microns) diode lasers  

Microsoft Academic Search

A new type of interferometric-type phase-locked array is demonstrated which selects fundamental-mode operation to relatively high drive levels above threshold. The WWI array allows 10-11 elements to operate in a single, diffraction-limited beam to 70 percent above lasing threshold. In contrast to Y-junction arrays, the array does not have significant radiation losses.

D. Botez; T. Pham; D. Tran

1987-01-01

382

Optical Spectroscopy Results for the Self-Magnetic Pinch Electron Beam Diode on the ITS-6 Accelerator.  

SciTech Connect

Experiments have been conducted at Sandia National Laboratories' RITS-6 accelerator facility [1] (operating at 7.5 MV and 180 kA) investigating plasma formation and propagation in relativistic electron beam diodes used for flash x-ray radiography. High resolution, visible and ultraviolet spectra were collected in the anode-cathode (A-K) vacuum gap of the Self-Magnetic Pinch (SMP) diode [2-4]. Time and space resolved spectra are compared with time-dependent, collisional-radiative (CR) calculations [5-7] and Lsp, hybrid particle-in-cell code simulations [8,9]. Results indicate the presence of a dense (>1x1017cm-3), low temperature (few eV), on-axis plasma, composed of hydrocarbon and metal ion species, which expands at a rate of several cm/s from the anode to the cathode. In addition, cathode plasmas are observed which extend several millimeters into the A-K gap [10]. It is believed that the interaction of these electrode plasmas cause premature impedance collapse of the diode and subsequent reduction in the total radiation output. Diagnostics include high speed imaging and spectroscopy using nanosecond gated ICCD cameras, streak cameras, and photodiode arrays.

Johnston, Mark D.; Oliver, Bryan V.; Hahn, Kelly; Droemer, Darryl W.; Crain, Marlon D.; Welch, Dale R.; Yitzhak, Maron

2012-06-01

383

Microreflectance inspection of diode laser front facets  

Microsoft Academic Search

We report on specular reflectivity measurements at the position of the waveguide at front facets of commercial diode laser arrays. Since the waveguide thickness is such semiconductor structures amounts about 1 micrometers an even better spatial resolution of the probe light spot is required. For this purpose, a micro-reflectance setup was designed and implemented. For re-locating the optically active region,

Fabian Doerfel; Stefan Nerreter; Jens W. Tomm; Ruediger Grunwald; R. Kunkel; Johann Luft

2002-01-01

384

Combined ultraviolet studies of astronomical sources  

NASA Technical Reports Server (NTRS)

Topics addressed include: Cygnus Loop; P Cygni profiles in dwarf novae; YY Gem; nova shells; HZ Herculis; activity cycles in cluster giants; Alpha Ori; metal deficient giant stars; ultraviolet spectra of symbiotic stars detected by the Very Large Array; time variability in symbiotic stars; blue galaxies; and quasistellar objects with X-ray spectra.

Baliunas, S. L.; Dupree, A. K.; Elvis, M.; Huchra, J. P.; Kenyon, S.; Raymond, J. C.

1986-01-01

385

Promoting Robust Design of Diode Lasers for Space: A National Initiative  

Microsoft Academic Search

The diode-laser array working group (DAWG) is a national-level consumer\\/provider forum for discussion of engineering and manufacturing issues which influence the reliability and survivability of high-power broad-area laser diode devices in space, with an emphasis on laser diode arrays (LDAs) for optical pumping of solid-state laser media. The goals of the group are to formulate and validate standardized test and

D. M. Tratt; F. Amzajerdian; N. B. Kashem; M. A. Stephen; A. A. Shapiro; A. T. Mense

2008-01-01

386

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

387

Method for extreme ultraviolet lithography  

DOEpatents

A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods.

Felter, T. E. (727 Clara St., Livermore, Alameda County, CA 94550); Kubiak, G. D. (475 Maple St., Livermore, Alameda County, CA 94550)

2000-01-01

388

Measurements of vector fields with diode array  

NASA Technical Reports Server (NTRS)

A polarimeter was designed for high spatial and spectral resolution. It consists of a quarter-wave plate alternately operating in two positions for Stoke-V measurements and an additional quarter-wave plate for Stokes-U and -Q measurements. The spatial range covers 75 arcsec, the spectral window of about 1.8 a allows the simultaneous observations of neighboring lines. The block diagram of the data processing and acquisition system consists of five memories each one having a capacity of 10 to the 4th power 16-bit words. The total time to acquire profiles of Stokes parameters can be chosen by selecting the number of successive measurements added in the memories, each individual measurement corresponding to an integration time of 0.5 sec. Typical values range between 2 and 60 sec depending on the brightness of the structure, the amount of polarization and a compromise between desired signal-to-noise ratio and spatial resolution.

Wiehr, E. J.; Scholiers, W.

1985-01-01

389

Line emission tomography for CDX-U using filtered diodes  

SciTech Connect

Electron density and temperature in the CDX-U low aspect ratio tokamak are too low to allow observation of fast magnetohydrodynamic activity using soft x-ray continuum emission. However, spectroscopic measurements show that extreme ultraviolet (XUV) line emission of intrinsic impurities is bright enough to observe such activity. In addition, a fast monitoring system for local temperature changes in the plasma core is required for planned auxiliary heating experiments. We present a spectrally resolved tomographic system for fast imaging of OVI 2s{endash}np, 2p{endash}nd (n{ge}3), CV 1s{sup 2}{endash}1s2p and CVI 1s{endash}2p XUV transitions. Using this emission, we can study both core and edge MHD activity, while the CVI to CV intensity ratio can indicate local changes in electron temperature. To achieve maximal throughput together with the needed spectral resolution, we use arrays of surface barrier diodes filtered with bandpass elemental filters. Using M edge filters (Zr, Pd, and Ag), we achieve both good discrimination between the above charge states and large transmission at the wavelengths of interest. Preliminary results obtained from CDX-U are presented. {copyright} {ital 1997 American Institute of Physics.}

Stutman, D.; Menard, J.; Hwang, Y.S.; Choe, W.; Ono, M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Finkenthal, M.; Soukhanovskii, V.; May, M.J.; Regan, S.P.; Moos, H.W. [Johns Hopkins University, Baltimore, Maryland 21218 (United States)] [Johns Hopkins University, Baltimore, Maryland 21218 (United States)

1997-01-01

390

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

391

Ba1.3Ca0.7SiO4: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

392

Long pulse compact and high-brightness near 1-kW QCW diode laser stack  

NASA Astrophysics Data System (ADS)

A custom designed compact, high brightness diode laser array stack was designed and manufactured using proprietary methods that are robust and suitable for low cost manufacturing. The diode laser stack consisted of four 10 mm-wide diode laser bars having lasing wavelength of 970 - 980 nm mounted onto high performance submounts separated by approximately 1mm. Each diode laser bar had a 50% fill factor. The cooling methodology employed used a combined passive and active scheme and not the traditional more expensive and more complicated standard microchannel coolers used for high duty cycle applications. The total combined optical power attained from the diode array stack was close to 1 kW for current levels up to 220 A, limited only by the capability of the power supply. In this paper, we summarize the performance results for this diode laser array and analyze the maximum expected optical performance as a function of operating current and pulse width and junction temperature limit.

Wilson, Stewart; Altshuler, Gregory; Erofeev, Andrey; Inochkin, Mikhail; Khloponin, Leonid; Khramov, Valery; Feldchtein, Felix

2012-03-01

393

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

394

Scalable pump source for diode pumped alkali laser  

NASA Astrophysics Data System (ADS)

External cavity diode laser systems are well-suited for diode pumped alkali laser (DPAL) systems due to their high power efficiency and excellent wavelength control under changing thermal loads. By conditioning the characteristics of feedback power, external cavities can narrow the spectral bandwidth and limit transverse modes of diode laser bars. Existing configurations typically use low-efficiency diffraction gratings at the Littrow angle to send back to the diodes a small fraction of the power, while directing the majority of the power forward in the output beam. We previously reported that a stepped mirror allows a single external cavity to condition the output beams of a stack of diode array bars. In this report, we describe a new approach that could use a single external cavity to condition the output beams of several hundred diode array bars. A high efficiency grating is used to feedback essentially all the power in the external cavity, and power splitters then distribute the power to multiple diode array stacks. A 384 bar module capable of 20 kW power output into a modelimited slowly diverging beam with a spectral width below 0.050 nm has been designed and proposed for use in a DPAL. A 50 bar 3 kW prototype is currently being assembled.

Hersman, F. W.; Distelbrink, J. H.; Ketel, J.; Sargent, D.; Watt, D. W.

2014-02-01

395

First identification of benzo[ ghi]naphtho[8,1,2- bcd]perylene as a product of fuel pyrolysis, using high-performance liquid chromatography with diode-array ultraviolet-visible absorbance detection and mass spectrometry  

Microsoft Academic Search

We present HPLC\\/UV\\/MS evidence to support the identification of benzo[ghi]naphtho[8,1,2-bcd]perylene as a product of supercritical toluene pyrolysis. Mass spectral data confirm that compound I—eluting in between co-eluting benzo[a]coronene\\/phenanthro[5,4,3,2-efghi]perylene and benzo[pqr]naphtho[8,1,2-bcd]perylene, all three of which have been unequivocally identified as C28H14 products of toluene pyrolysis—is also a C28H14 product component. The UV spectrum of compound I is presented, and indicates that

Jennifer W. McClaine; Xia Zhang; Mary J. Wornat

2006-01-01

396

Diode and Diode Circuits, a Programmed Text.  

ERIC Educational Resources Information Center

This programed text on diode and diode circuits was developed under contract with the United States Office of Education as Number 4 in a series of materials for use in an electrical engineering sequence. It is intended as a supplement to a regular text and other instructional material. (DH)

Balabanian, Norman; Kirwin, Gerald J.

397

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

398

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

399

Optimizing wire parameters in exploding wire arrays  

Microsoft Academic Search

Exploding wire arrays as fast switches are of interest for explosive pulsed power applications utilizing magnetic flux compression. This type of opening switch has proven effective in producing pulses of several hundred kilovolts into vacuum diode loads. The research presented here discusses an exploding wire array capable of producing single digit kilo- joules, 100 nanosecond pulses when driven by a

C. Davis; A. Neuber; J. Stephens; A. Young; J. Dickens; M. Kristiansen

2010-01-01

400

Compound semiconductor SPAD arrays  

NASA Astrophysics Data System (ADS)

Single photon avalanche diodes (SPADs) are revolutionizing ultra-sensitive photodetection applications, providing single photon sensitivity, high quantum efficiency and low dark noise at or near room temperature. When aggregated into arrays, these devices have demonstrated the ability to operate as photon number resolving detectors with wide dynamic range, or as single-photon imaging detectors. SPAD array performance has reached a point where replacing vacuum tube based MCP and PMT photodetectors for most applications is inevitable. Compound semiconductor SPAD arrays offer the unique proposition to tailor performance to match application specific wavelength, speed and radiation hardness requirements. We present a theoretical framework describing performance limits to compound semiconductor SPAD arrays and our latest experimental results detailing the performance of GaAs SPAD arrays. These devices achieve nanosecond rise and fall times, excellent photon number resolving capability, and low dark count rates. Single photon number resolving is demonstrated with 4% single photon detection efficiency at room temperature with dark count rates below 7 Mcps/mm2. Compound semiconductor SPAD arrays have the opportunity to provide orders of magnitude improvement in dark count rate and radiation hardness over silicon SPAD arrays, as well as the ability to detect wavelengths where silicon is blind.

Harmon, Eric S.; Naydenkov, Mikhail; Hyland, James T.

2013-06-01

401

Qualification of diode foil materials for excimer lasers  

SciTech Connect

The Aurora facility at Los Alamos National Laboratory uses KrF excimer lasers to produce 248 nm light for inertial confinement fusion applications. Diodes in each amplifier produce relativistic electron beams to pump a Kr-F-Ar gas mixture. A foil is necessary to separate the vacuum diode from the laser gas. High tensile strength, high electron transmission, low ultraviolet reflectivity, and chemical compatibility with fluorine have been identified as requisite foil properties. Several different materials were acquired and tested for use as diode foils. Transmission and fluorine compatibility tests were performed using the Electron Gun Test Facility (EGTF) at Los Alamos. Off-line tests of tensile strength and reflectivity were performed. Titanium foil, which is commonly used as a diode foil, was found to generate solid and gaseous fluoride compounds, some of which are highly reactive in contact with water vapor. 6 refs., 6 figs., 1 tab.

Anderson, R.G.; Shurter, R.P.; Rose, E.A.

1989-01-01

402

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

403

Studies of solution-processed organic light-emitting diodes and their materials  

NASA Astrophysics Data System (ADS)

The wide use of organic light-emitting diodes (OLEDs) is materializing as devices exhibit enhanced performance. Attention has been placed on finding quality solution-processable organic semiconducting materials amenable to low cost processing via solution-based fabrication methods. The high solubility and good film formability intrinsic to polymers have led to their use in the majority of solution-processed devices. Recently, attention has shifted to the incorporation of small molecules into solution-processed devices. With this focus, we gain the high efficiency of small molecules as well as the ease of fabrication by solution-processing. Research has also been aimed at developing materials with efficient and stable red, green, and blue emission necessary for full color displays. OLEDs in the ultraviolet are attractive for analytical applications, including compact sensors and on-chip spectrometers. Particularly of interest for analytical applications are narrow-band multi-color microcavity OLED arrays, which can be used in on-chip spectrometers or in multianalyte chemical or biological sensing. In this dissertation, novel solution-processed device structures are demonstrated, including the hitherto unexplored structure of polymer guest:small molecule host OLEDs and a UV-to-blue multi-color microcavity OLED array based on a mixed emitting layer. Also included are investigations into new materials and discussions on the origins of improvements.

Hellerich, Emily S.

404

n-ZnO nanorods/p+-Si (111) heterojunction light emitting diodes  

PubMed Central

In this study, we report the effects of thermal annealing in nitrogen ambient on the optical and electrical properties of zinc oxide (ZnO) nanorod (NR) arrays for the application in light emission diodes (LED). The single-crystalline ZnO NR array was synthesized on p+-Si (111) substrate without seed layer using simple, low-cost, and low-temperature hydrothermal method. The substrate surface was functionalized by hydrofluoric acid and self-assembled monolayer of octadecyltrimethoxysilane ((CH3 (CH2)17Si(OCH3)3). ZnO NRs were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and micro-photoluminescence (micro-PL). The results of FESEM and XRD indicate that single crystalline ZnO NRs with (002) preferred orientation along the substrate surface is successfully grown on functionalized p+-Si (111) substrate. The current–voltage and electroluminescence (EL) characteristics of the LED show that the most suitable annealing temperature ranges from 400°C to 600°C. Both PL and EL spectra show broadband emissions, ultraviolet and visible (green-yellow) light. The white-like light emission is able to be observed by naked eyes. PMID:23216651

2012-01-01

405

n-ZnO nanorods/p+-Si (111) heterojunction light emitting diodes  

NASA Astrophysics Data System (ADS)

In this study, we report the effects of thermal annealing in nitrogen ambient on the optical and electrical properties of zinc oxide (ZnO) nanorod (NR) arrays for the application in light emission diodes (LED). The single-crystalline ZnO NR array was synthesized on p+-Si (111) substrate without seed layer using simple, low-cost, and low-temperature hydrothermal method. The substrate surface was functionalized by hydrofluoric acid and self-assembled monolayer of octadecyltrimethoxysilane ((CH3 (CH2)17Si(OCH3)3). ZnO NRs were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and micro-photoluminescence (micro-PL). The results of FESEM and XRD indicate that single crystalline ZnO NRs with (002) preferred orientation along the substrate surface is successfully grown on functionalized p+-Si (111) substrate. The current-voltage and electroluminescence (EL) characteristics of the LED show that the most suitable annealing temperature ranges from 400°C to 600°C. Both PL and EL spectra show broadband emissions, ultraviolet and visible (green-yellow) light. The white-like light emission is able to be observed by naked eyes.

Tsai, Jenn Kai; Shih, Jun Hong; Wu, Tian Chiuan; Meen, Teen Hang

2012-12-01

406

Hair removal with an 800-nm pulsed diode laser  

Microsoft Academic Search

Background and Objective: Laser hair removal is a relatively new procedure. Our purpose was to study the efficacy and safety of a high-power, pulsed diode laser array for removing unwanted hair. Methods: A total of 38 subjects were treated with a prototype of the 800-nm diode laser system. Fluences ranging from 10 to 40 J\\/cm2 (mean, 33.4 J\\/cm2) were used

Valeria B. Campos; Christine C. Dierickx; William A. Farinelli; Tai-Yuan D. Lin; Woraphong Manuskiatti; R. Rox Anderson

2000-01-01

407

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

408

Double Light-Emitting Diode  

NASA Technical Reports Server (NTRS)

Two GaAs light-emitting diodes packaged as single unit offer greater reliability than conventional single-diode package. One diode is primary light source. If it fails, backup diode switched in. Each diode has separate power lead, so either or both switched on or off at same time.

Johnson, R. L.; Hall, T. C.

1985-01-01

409

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

410

A pn-SiC diode as a radiation detector  

Microsoft Academic Search

We evaluated pn-SiC (silicon carbide) particle detectors exposed to 5.486 MeV alpha particles from a sealed radioactive source of 241Am and 3.26 eV (380 nm) pulsed Ultra-Violet (UV) light at 100 Hz from a Light Emitting Diode (LED). The pn junction SiC diode was made by the implantation of phosphorus (P) ions (140, 60, 90 keV) into p-type 6H-SiC epitaxial

A. Kinoshita; M. Iwami; I. Nakano; R. Tanaka; T. Kamiya; A. Ohi; T. Ohshima; Y. Fukushima

2003-01-01

411

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

412

Diodes and Rectifiers  

NSDL National Science Digital Library

Written by Tony R. Kuphaldt, this chapter of All About Circuit's third volume on Semiconductors describes the physics behind diodes and rectifiers. The chapter is divided into fourteen sections on topics including diode ratings, voltage multipliers, and zener diodes. Each section has clear illustrations and examples, and most have a concise, bulleted review of what was covered at the end of the page. This is an excellent resource for educators in physics and electronic engineering classrooms to introduce lessons or units on semiconductors, diodes, and rectifiers. [ASC

Kuphaldt, Tony R.

2008-07-02

413

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.

Wnet

2011-11-14

414

Ultraviolet absorption spectrum of chlorine peroxide, ClOOCl.  

PubMed

The photolysis of chlorine peroxide (ClOOCl) is understood to be a key step in the destruction of polar stratospheric ozone. This study generated and purified ClOOCl in a novel fashion, which resulted in spectra with low impurity levels and high peak absorbances. The ClOOCl was generated by laser photolysis of Cl2 in the presence of ozone, or by photolysis of ozone in the presence of CF2Cl2. The product ClOOCl was collected, along with small amounts of impurities, in a trap at about -125 degrees C. Gas-phase ultraviolet spectra were recorded using a long path cell and spectrograph/diode array detector as the trap was slowly warmed. The spectrum of ClOOCl could be fit with two Gaussian-like expressions, corresponding to two different electronic transitions, having similar energies but different widths. The energies and band strengths of these two transitions compare favorably with previous ab initio calculations. The cross sections of ClOOCl at wavelengths longer than 300 nm are significantly lower than all previous measurements or estimates. These low cross sections in the photolytically active region of the solar spectrum result in a rate of photolysis of ClOOCl in the stratosphere that is much lower than currently recommended. For conditions representative of the polar vortex (solar zenith angle of 86 degrees, 20 km altitude, and O3 and temperature profiles measured in March 2000) calculated photolysis rates are a factor of 6 lower than the current JPL/NASA recommendation. This large discrepancy calls into question the completeness of present atmospheric models of polar ozone depletion. PMID:17474723

Pope, Francis D; Hansen, Jaron C; Bayes, Kyle D; Friedl, Randall R; Sander, Stanley P

2007-05-24

415

Photon-counting detector arrays based on microchannel array plates. [for image enhancement  

NASA Technical Reports Server (NTRS)

The recent development of the channel electron multiplier (CEM) and its miniaturization into the microchannel array plate (MCP) offers the possibility of fully combining the advantages of the photographic and photoelectric detection systems. The MCP has an image-intensifying capability and the potential of being developed to yield signal outputs superior to those of conventional photomultipliers. In particular, the MCP has a photon-counting capability with a negligible dark-count rate. Furthermore, the MCP can operate stably and efficiently at extreme-ultraviolet and soft X-ray wavelengths in a windowless configuration or can be integrated with a photo-cathode in a sealed tube for use at ultraviolet and visible wavelengths. The operation of one- and two-dimensional photon-counting detector arrays based on the MCP at extreme-ultraviolet wavelengths is described, and the design of sealed arrays for use at ultraviolet and visible wavelengths is briefly discussed.

Timothy, J. G.

1975-01-01

416

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

417

An aluminium nitride light-emitting diode with a wavelength of 210nanometres  

Microsoft Academic Search

Compact high-efficiency ultraviolet solid-state light sources-such as light-emitting diodes (LEDs) and laser diodes-are of considerable technological interest as alternatives to large, toxic, low-efficiency gas lasers and mercury lamps. Microelectronic fabrication technologies and the environmental sciences both require light sources with shorter emission wavelengths: the former for improved resolution in photolithography and the latter for sensors that can detect minute hazardous

Yoshitaka Taniyasu; Makoto Kasu; Toshiki Makimoto

2006-01-01

418

A strategy for the use of light emitting diodes by autonomous underwater vehicles  

E-print Network

Light Emitting Diode (LED) technology has advanced dramatically in a few short years. An expensive and difficult to manufacture LED array containing nearly 100 individual LEDs and measuring at least 5 cm² can now be replaced ...

Curran, Joseph R. (Joseph Robinson)

2004-01-01

419

120-W continuous-wave diode-pumped Tm:YAG laser.  

PubMed

We present a 120-W cw diode-pumped Tm:YAG laser. The Tm:YAG rod is side pumped by three diode arrays whose radiation is coupled through compound parabolic concentrators. The maximum optical-to-optical conversion efficiency of the 2.02-mum laser output is 25.2%, with a slope efficiency of 31.2%. PMID:18066286

Lai, K S; Phua, P B; Wu, R F; Lim, Y L; Lau, E; Toh, S W; Toh, B T; Chng, A

2000-11-01

420

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

421

Relativistic Bursian diode equilibria  

SciTech Connect

A comprehensive study of steady-states of a planar vacuum diode driven by a cold relativistic electron beam is presented. The emitter electric field as a characteristic function for their existence is evaluated in dependence of the diode length, the applied potential V, and the relativistic beam factor at injection {gamma}{sub 0}. It is used to classify the different branches of possible solutions, which encompass electron flows that are (i) transmitted through the diode completely, (ii) partially reflected from a virtual cathode (VC) either within the diode region or at the collector side, and (iii) reflected totally. As a byproduct, the V and {gamma}{sub 0} dependences of both bifurcation points of the minimum potential and of the transmitted current are obtained and the ultrarelativistic limit, {gamma}{sub 0}>>1, is performed. In this highly relativistic regime, the density of electrons appears to be constant across the diode region except for a small area around the VC.

Ender, A. Y.; Kuznetsov, V. I. [Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Schamel, H. [Physikalisches Institut, Universitaet Bayreuth, D-95466 Bayreuth (Germany)

2011-03-15

422

A novel red phosphor for white light emitting diodes  

Microsoft Academic Search

A novel red phosphor, CaMoO4:Eu3+, has been developed for white light emitting diodes (LEDs). The phosphor was prepared by using oxides in air and its luminescent properties have been investigated. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (UV) (394nm) and blue (464nm) light, and exhibits a satisfactory red performance (616nm), nicely fitting

Yunsheng Hu; Weidong Zhuang; Hongqi Ye; Donghui Wang; Shusheng Zhang; Xiaowei Huang

2005-01-01

423

Dual-band ultraviolet-short-wavelength infrared imaging via luminescent downshifting with colloidal quantum dots  

E-print Network

The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging ...

Geyer, Scott M.

424

Array Games  

NSDL National Science Digital Library

Arrays are very important in Computer Programming. An array is a way to store similar items in computer memory. The items may be numbers, words, pictures, or even sounds. Many games use an array because it is an easy way to keep track of the objects used to play the game. The Arrow Game uses an array to store arrow ...

Watts, Mrs.

2007-10-05

425

Magnetic arrays  

DOEpatents

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

426

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

427

Millimeter-Wave Diode-Grid Frequency Doubler,  

National Technical Information Service (NTIS)

Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analys...

C. F. Jou, W. W. Lam, D. B. Rutledge, H. Z. Chen, K. S. Stolt

1988-01-01

428

Multiple-Diode-Laser Gas-Detection Spectrometer  

NASA Technical Reports Server (NTRS)

Small concentrations of selected gases measured automatically. Proposed multiple-laser-diode spectrometer part of system for measuring automatically concentrations of selected gases at part-per-billion level. Array of laser/photodetector pairs measure infrared absorption spectrum of atmosphere along probing laser beams. Adaptable to terrestrial uses as monitoring pollution or control of industrial processes.

Webster, Christopher R.; Beer, Reinhard; Sander, Stanley P.

1988-01-01

429

Phase Conjugate Techniques for Diode Laser Brightness Enhancement.  

National Technical Information Service (NTIS)

Diode laser arrays provide a compact, high power, high efficiency source of monochromatic light and are finding many applications in all solid-state mini and micro-laser systems. Unfortunately, the preferred modes of operation of free-running, conventiona...

1992-01-01

430

Efficiency enhancement of UV\\/blue light emitting diodes via nanoscaled epitaxial lateral overgrowth of GaN on a SiO 2 nanorod-array patterned sapphire substrate  

Microsoft Academic Search

High-quality GaN layer was successfully grown on a SiO2 nanorod-array patterned sapphire substrate (NAPSS) using metal-organic chemical vapor deposition by a nanoscaled epitaxial lateral overgrowth (NELO) method. From tunneling electron microscope images, well coalescence and turned dislocations are parallel to the surface direction were clearly observed. The Raman shift measurement shows the residual stress in GaN was greatly reduced from

C. H. Chiu; Zhen-Yu Li; C. L. Chao; M. H. Lo; H. C. Kuo; P. C. Yu; T. C. Lu; S. C. Wang; K. M. Lau; S. J. Cheng

2008-01-01

431

Design of atmospheric composition monitor based on ultraviolet optical absorption technology  

Microsoft Academic Search

An open path atmospheric composition monitor is designed based on ultraviolet differential absorption technology. Dark current correction and diode response correction are used to improve the detection limit and Savitzky-Golay filter is used to improve the measurement accuracy. The experimental results show that the designed system has the ability to measure NO and NO2 in real time with reasonable accuracy.

Wen-Jun Li

2011-01-01

432

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

433

Simple Diode Rectifier Circuit  

NSDL National Science Digital Library

This website from the Thayer School of Engineering at Dartmouth College features an animation of a simple diode rectifier circuit. A rectifier is an electrical device that converts alternating current (AC) to direct current (DC), a process known as rectification.

2012-10-24

434

Inelastic tunnel diodes  

NASA Technical Reports Server (NTRS)

Power is extracted from plasmons, photons, or other guided electromagnetic waves at infrared to midultraviolet frequencies by inelastic tunneling in metal-insulator-semiconductor-metal diodes. Inelastic tunneling produces power by absorbing plasmons to pump electrons to higher potential. Specifically, an electron from a semiconductor layer absorbs a plasmon and simultaneously tunnels across an insulator into metal layer which is at higher potential. The diode voltage determines the fraction of energy extracted from the plasmons; any excess is lost to heat.

Anderson, L. M. (inventor)

1984-01-01

435

Scanning Led Array Based Volumetric Display  

Microsoft Academic Search

A novel quasi-holographic display concept is developed using light emitting diode (LED) arrays on scanning platform. The display system is capable of providing smooth motion parallax and solving the accommodation-vergence rivalry. Each scanner module contains 1D LED array mounted on a polymer scanner with a lens for imaging the LEDs onto a special diffuser screen. The scanning modules are actuated

M. Saymta; Serhan O. Isikman; Hakan Urey

2008-01-01