WorldWideScience

Sample records for broad area diode

  1. Broad-Area Laser Diode With Fiber-Optic Injection

    Science.gov (United States)

    Hazel, Geoffrey; Mead, Patricia; Davis, Christopher; Cornwell, Donald

    1992-01-01

    Fiber-optic injection-locked broad-area laser diode features single-mode output via fiber-optic injection and serves as compact, rugged, high-power near-infrared source. Useful in free-space and fiber-optic communication links, as communication-receiver preamplifier, and pump source for solid-state lasers.

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

    Science.gov (United States)

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

    2012-12-25

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

  3. A new approach to assymmetric feedback in a segmented broad area diode laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Thestrup Nielsen, Birgitte; Petersen, Paul Michael

    2009-01-01

    We present the demonstration of a non-critical setup for asymmetric feedback in a segmented broad area diode laser. We compare the dependence of the beam quality on the position of the dispersive element for standard spectral beam combining and our new non-critical setup. We find that our new...

  4. A comprehensive model of catastrophic optical-damage in broad-area laser diodes

    Science.gov (United States)

    Chin, A. K.; Bertaska, R. K.; Jaspan, M. A.; Flusberg, A. M.; Swartz, S. D.; Knapczyk, M. T.; Petr, R.; Smilanski, I.; Jacob, J. H.

    2009-02-01

    The present model of formation and propagation of catastrophic optical-damage (COD), a random failure-mode in laser diodes, was formulated in 1974 and has remained substantially unchanged. We extend the model of COD phenomena, based on analytical studies involving EBIC (electron-beam induced current), STEM (scanning transmission-electron microscopy) and sophisticated optical-measurements. We have determined that a ring-cavity mode, whose presence has not been previously reported, significantly contributes to COD initiation and propagation in broad-area laser-diodes.

  5. Rational Chebyshev spectral transform for the dynamics of broad-area laser diodes

    International Nuclear Information System (INIS)

    This manuscript details the use of the rational Chebyshev transform for describing the transverse dynamics of broad-area laser diodes and amplifiers. This spectral method can be used in combination with the delay algebraic equations approach developed in [1], which substantially reduces the computation time. The theory is presented in such a way that it encompasses the case of the Fourier spectral transform presented in [2] as a particular case. It is also extended to the consideration of index guiding with an arbitrary transverse profile. Because their domain of definition is infinite, the convergence properties of the Chebyshev rational functions allow handling the boundary conditions with higher accuracy than with the previously studied Fourier transform method. As practical examples, we solve the beam propagation problem with and without index guiding: we obtain excellent results and an improvement of the integration time between one and two orders of magnitude as compared with a fully distributed two dimensional model

  6. Rational Chebyshev spectral transform for the dynamics of broad-area laser diodes

    Energy Technology Data Exchange (ETDEWEB)

    Javaloyes, J., E-mail: julien.javaloyes@uib.es [Universitat de les Illes Balears, C/Valldemossa, km 7.5, E-07122 Palma de Mallorca (Spain); Balle, S. [Institut Mediterrani d' Estudis Avançats, CSIC-UIB, E-07071 Palma de Mallorca (Spain)

    2015-10-01

    This manuscript details the use of the rational Chebyshev transform for describing the transverse dynamics of broad-area laser diodes and amplifiers. This spectral method can be used in combination with the delay algebraic equations approach developed in [1], which substantially reduces the computation time. The theory is presented in such a way that it encompasses the case of the Fourier spectral transform presented in [2] as a particular case. It is also extended to the consideration of index guiding with an arbitrary transverse profile. Because their domain of definition is infinite, the convergence properties of the Chebyshev rational functions allow handling the boundary conditions with higher accuracy than with the previously studied Fourier transform method. As practical examples, we solve the beam propagation problem with and without index guiding: we obtain excellent results and an improvement of the integration time between one and two orders of magnitude as compared with a fully distributed two dimensional model.

  7. Spectral properties of a broad-area diode laser with off-axis external-cavity feedback

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael

    2013-01-01

    intensity noise spectrum of the diode laser shows that the intensity noise is increased strongly by the external-cavity feedback. External-cavity modes are excited in the external cavity even in the off-axis configuration. The peak spacing of the intensity noise spectrum shows that single roundtrip external......Spectral properties, both the optical spectrum and the intensity noise spectrum, of a broad-area diode laser with off-axis external-cavity feedback are presented. We show that the optical spectrum of the diode laser system is shifted to longer wavelengths due to the external-cavity feedback. The......-cavity modes are excited. We believe that the four-wave mixing process in the broad-area diode laser is responsible for the establishment of the external-cavity mode....

  8. Experimental investigation of factors limiting slow axis beam quality in 9xx nm high power broad area diode lasers

    International Nuclear Information System (INIS)

    GaAs-based broad-area diode lasers are needed with improved lateral beam parameter product (BPPlat) at high power. An experimental study of the factors limiting BPPlat is therefore presented, using extreme double-asymmetric (EDAS) vertical structures emitting at 910 nm. Continuous wave, pulsed and polarization-resolved measurements are presented and compared to thermal simulation. The importance of thermal and packaging-induced effects is determined by comparing junction -up and -down devices. Process factors are clarified by comparing diodes with and without index-guiding trenches. We show that in all cases studied, BPPlat is limited by a non-thermal BPP ground-level and a thermal BPP, which depends linearly on self-heating. Measurements as a function of pulse width confirm that self-heating rather than bias-level dominates. Diodes without trenches show low BPP ground-level, and a thermal BPP which depends strongly on mounting, due to changes in the temperature profile. The additional lateral guiding in diodes with trenches strongly increases the BPP ground-level, but optically isolates the stripe from the device edges, suppressing the influence of the thermal profile, leading to a BPP-slope that is low and independent of mounting. Trenches are also shown to initiate strain fields that cause parasitic TM-polarized emission with large BPPlat, whose influence on total BPPlat remains small, provided the overall polarization purity is >95%

  9. Experimental investigation of factors limiting slow axis beam quality in 9xx nm high power broad area diode lasers

    Energy Technology Data Exchange (ETDEWEB)

    Winterfeldt, M., E-mail: martin.winterfeldt@fbh-berlin.de; Crump, P.; Wenzel, H.; Erbert, G.; Tränkle, G. [Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2014-08-14

    GaAs-based broad-area diode lasers are needed with improved lateral beam parameter product (BPP{sub lat}) at high power. An experimental study of the factors limiting BPP{sub lat} is therefore presented, using extreme double-asymmetric (EDAS) vertical structures emitting at 910 nm. Continuous wave, pulsed and polarization-resolved measurements are presented and compared to thermal simulation. The importance of thermal and packaging-induced effects is determined by comparing junction -up and -down devices. Process factors are clarified by comparing diodes with and without index-guiding trenches. We show that in all cases studied, BPP{sub lat} is limited by a non-thermal BPP ground-level and a thermal BPP, which depends linearly on self-heating. Measurements as a function of pulse width confirm that self-heating rather than bias-level dominates. Diodes without trenches show low BPP ground-level, and a thermal BPP which depends strongly on mounting, due to changes in the temperature profile. The additional lateral guiding in diodes with trenches strongly increases the BPP ground-level, but optically isolates the stripe from the device edges, suppressing the influence of the thermal profile, leading to a BPP-slope that is low and independent of mounting. Trenches are also shown to initiate strain fields that cause parasitic TM-polarized emission with large BPP{sub lat}, whose influence on total BPP{sub lat} remains small, provided the overall polarization purity is >95%.

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

    International Nuclear Information System (INIS)

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

  11. Highly efficient broad-area blue and white light-emitting diodes on bulk GaN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Vampola, Kenneth J.; Fellows, Natalie N.; Masui, Hisashi; Chung, Roy B.; Sato, Hitoshi; Sonoda, Junichi; Hirasawa, Hirohiko; Iza, Michael; Nakamura, Shuji [Materials Department, University of California, Santa Barbara, California (United States); Brinkley, Stuart E.; Furukawa, Motoko [Electrical and Computer Engineering Department, University of California, Santa Barbara, California (United States); DenBaars, Steven P. [Materials Department, University of California, Santa Barbara, California (United States)]|[Electrical and Computer Engineering Department, University of California, Santa Barbara, California (United States)

    2009-02-15

    Highly efficient light emitting diodes (LEDs) with peak emission wavelengths of nominally 450 nm were grown, fabricated and tested. The growth was performed by metal organic chemical vapour deposition. The LEDs were grown on c-plane (0001) bulk GaN substrates and fabricated into broad-area devices with active area 0.01 cm{sup 2}. Considerations were made to improve extraction efficiency, including transparent contacts, suspended mirror-less packaging and encapsulation in a truncated pyramid optic. These factors resulted in LEDs with high peak external quantum efficiency and reduced efficiency droop. The output power and external quantum efficiency at 20 mA were 38.5 mW and 68.9%. At 100 mA, they were 170 mW and 60.9%. White LEDs were fabricated by application of a yellow phosphor to the blue LEDs. The white LED luminous flux and efficacy at 20 mA was 9.6 lm and 128 lm/W. The chromaticity coordinates and correlated colour temperature were (0.348 K, 0.378 K) and 4998 K. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. 55 W peak power from 1100 nm wavelength 60 µm broad-area laser diodes enabled by reduced carrier accumulation in the waveguide

    International Nuclear Information System (INIS)

    Optical power from 1100 nm broad-area laser diodes is found to be limited by the accumulation of minority carriers in the waveguide layer, caused by a small effective barrier between the quantum wells and the GaAs waveguide. This effect is visible as enhanced spontaneous emission at high currents. We show that increasing the number of QWs mitigates this effect and leads to higher emitted powers. Optimized devices deliver more than 55 W per 60 µm stripe width under 300 ns pulse operation. In this paper we present the experimental results of our study

  13. Assessing the influence of the vertical epitaxial layer design on the lateral beam quality of high-power broad area diode lasers

    Science.gov (United States)

    Winterfeldt, M.; Rieprich, J.; Knigge, S.; Maaßdorf, A.; Hempel, M.; Kernke, R.; Tomm, J. W.; Erbert, G.; Crump, P.

    2016-03-01

    GaAs-based high-power broad-area diode lasers deliver optical output powers Popt > 10W with efficiency > 60%. However, their application is limited due to poor in-plane beam parameter product BPPlat=0.25×Θ95%×w95% (Θ95% and w95% are emission angle and aperture, 95% power content). We present experimental investigations on λ = 9xx nm broad area lasers that aim to identify regulating factors of the BPPlat connected to the epitaxial layer design. First, we assess the thermal lens of vertical designs with varying asymmetry, using thermal camera images to determine its strength. Under study are an extreme-double-asymmetric (EDAS) vertical structure and a reference (i.e. more symmetric) design. The lateral thermal profiles clearly show that BPPlat increase is correlated to the bowing of the thermal lens. The latter is derived out of a quadratic temperature fit in the active region beneath the current injection of the laser device and depends on the details of the epitaxial layers. Second, we test the benefit of low modal gain factor Γg0, predicted to improve BPPlat via a suppression of filamentation. EDAS-based lasers with single quantum well (SQW) and double quantum well (DQW) active regions were compared, with 2.5x reduced Γg0, for 2.2x reduced filament gain. However, no difference is seen in measured BPPlat, giving evidence that filamentary processes are no longer a limit. In contrast, devices with lower Γg0 demonstrate an up to twofold reduced near field modulation depth, potentially enabling higher facet loads and increased device facet reliability, when operated near to the COD limit.

  14. High Power 940 nm Al-free Active Region Laser Diodes and Bars with a Broad Waveguide

    Institute of Scientific and Technical Information of China (English)

    FANG Gaozhan; XIAO Jianwei; MA Xiaoyu; XU Zuntu; ZHANG Jinming; TAN Manqing; LIU Zongshun; LIU Suping; FENG Xiaoming

    2002-01-01

    The 940 nm Al-free active region laser diodes and bars with a broad waveguide were designed and fabricated. The stuctures were grown by metal organic chemical vapour deposition. The devices show excellent performances. The maximum output power of 6.7 W in the 100 μm broad-area laser diodes has been measured, and is 2.5 times higher than that in the Al-containing active region laser diodes with a narrow waveguide and 1.7 times higher than that in Al-free active region laser diodes with a narrow waveguide. The 19% fill-factor laser diode bars emit 33 W, and they can operate at 15W with low degradation rates.

  15. A low-temperature external cavity diode laser for broad wavelength tuning

    OpenAIRE

    Tobias, William G.; Rosenberg, Jason S.; Hutzler, Nicholas R.; Ni, Kang-Kuen

    2016-01-01

    We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64{\\deg}C, more than ...

  16. A nonlinear theory of a coherent generation in the resonant tunnel diodes within a broad frequency range

    International Nuclear Information System (INIS)

    Numerical solution to the Schroedinger equation with open boundary conditions is found out, which makes it possible to describe coherent generation in resonant-tunneling diodes in a broad interval of frequencies and field amplitudes. Within the linear field area approximation results obtained coincide with a high degree of accuracy with analytical results. The power of generation is calculated as a function of the current and other parameters of the resonant-tunneling diode. It is demonstrated that the high-power generation is possible in the quantum regime at frequencies exceeding the level width, i. e. within the THz range

  17. Broad Spectrum Photoelectrochemical Diodes for Solar Hydrogen Generation

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, Craig A.

    2014-11-26

    Under program auspices we have investigated material chemistries suitable for the solar generation of hydrogen by water photoelectrolysis. We have built upon, and extended, our knowledge base on the synthesis and application of TiO2 nanotube arrays, a material architecture that appears ideal for water photoelectrolysis. To date we have optimized, refined, and greatly extended synthesis techniques suitable for achieving highly ordered TiO2 nanotube arrays of given length, wall thickness, pore diameter, and tube-to-tube spacing for use in water photoelectrolysis. We have built upon this knowledge based to achieve visible light responsive, photocorrosion stable n-type and p-type ternary oxide nanotube arrays for use in photoelectrochemical diodes.

  18. A low-temperature external cavity diode laser for broad wavelength tuning

    CERN Document Server

    Tobias, William G; Hutzler, Nicholas R; Ni, Kang-Kuen

    2016-01-01

    We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64{\\deg}C, more than 85{\\deg}C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation was achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers ...

  19. Large area electron beam diode development

    International Nuclear Information System (INIS)

    A large area annular electron beam diode has been tested at Physics International Co. on the multi-terawatt PITHON generator. A twelve element post hole convolute converted the coaxial MITL into a triaxial arrangement of anode current return structures both inside and outside the cathode structure. The presence of both inner and outer current return paths provide magnetic pressure balance for the beam, as determined by diode current measurements. X-ray pinhole photographs indicated uniform emission with intensity maxima between the post positions. Current losses in the post hole region were negligible, as evidenced by the absence of damage to the aluminum hardware. Radial electron flow near the cathode ring however did damage the inner anode cylinder between the post positions. Cutting away these regions prevented further damage of the transmission lines

  20. Packaging and Performance of 980nm Broad Area Semiconductor Lasers

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    High power broad area semiconductor lasers have found increasing applications in pumping of solid state laser systems and fiber amplifiers, frequency doubling, medical systems and material processing.Packaging including the assembly design, process and thermal management, has a significant impact on the optical performance and reliability of a high power broad area laser. In this paper, we introduce the package structures and assembling process of 980nm broad area lasers and report the performances including output power, thermal behavior and far fields.We will report two types of high power broad area laser assemblies.One is a microchannel liquid cooled assembly and the other is a conduction cooled CT-mount assembly. Optical powers of 15W and 10W were achieved from a 980nm broad area laser with a 120 μ m stripe width in a microchannel liquid cooled assembly and conduction cooled CT-mount assembly, respectively.Furthermore,a high power of 6.5W out of fiber was demonstrated from a pigtailed, fully packaged butterfly-type module without TEC (Thermoelectric cooler).The measurement results showed that thermal management is the key in not only improving output power, but also significantly improving beam divergence and far field distribution.The results also showed that the die attach solder can significant impact the reliability of high power broad area lasers and that indium solder is not suitable for high power laser applications due to electromigration at high current densities and high temperatures.

  1. Gain optimization method of a DQW superluminescent diode with broad multi-state emission

    KAUST Repository

    Dimas, Clara E.

    2010-01-01

    Optimizing gain through systematic methods of varying current injection schemes analytically is significant to maximize experimentally device yield and evaluation. Various techniques are used to calculate the amplified spontaneous emission (ASE) gain for light emitting devices consisting of single-section and multiple-sections of even length. Recently double quantum well (DQW) superluminescent diodes (SLD) have shown a broad multi-state emission due to mutlielectrodes of non-equal lengths and at high non-equal current densities. In this study, we adopt an improved method utilizing an ASE intensity ratio to calibrate a gain curve based on the sum of the measured ASE spectra to efficiently estimate the gain. Although the laser gain for GaAs/AlGaAs material is well studied, the ASE gain of SLD devices has not been systematically studied particular to further explain the multiple-state emission observed in fabricated devices. In addition a unique gain estimate was achieved where the excited state gain clamps prior to the ground state due to approaching saturation levels. In our results, high current densities in long sectioned active regions achieved sufficient un-truncated gain that show evidence of excited state emission has been observed.

  2. Variable-area resonant tunnelling diodes using implanted gates

    International Nuclear Information System (INIS)

    A new fabrication technique is reported for variable-area resonant tunnelling diodes in which control is achieved by means of a reverse-biased, implanted pn junction surrounding the device. The characteristics of such devices are shown and interpreted. (author)

  3. High-Performance 1.55-µm Superluminescent Diode Based on Broad Gain InAs/InGaAlAs/InP Quantum Dash Active Region

    KAUST Repository

    Khan, Mohammed Zahed Mustafa

    2014-08-01

    We report on the high-performance characteristics from superluminescent diodes (SLDs) based on four-stack InAs/InGaAlAs chirped-barrier thickness quantum dash (Qdash) in a well structure. The active region exhibits a measured broad gain spectrum of 140 nm, with a peak modal gain of ~41 cm-1. The noncoated two-section gainabsorber broad-area and ridge-waveguide device configuration exhibits an output power of > 20 mW and > 12 mW, respectively. The corresponding -3-dB bandwidths span ~82 nm and ~72 nm, with a small spectral ripple of <; 0.2 dB, related largely to the contribution from dispersive height dash ensembles of the highly inhomogeneous active region. These C-L communication band devices will find applications in various cross-disciplinary fields of optical metrology, optical coherent tomography, etc.

  4. An asymmetric broad waveguide structure for a 0.98-μm high-conversion-efficiency diode laser

    Institute of Scientific and Technical Information of China (English)

    Chong Feng; Wang Jun; Xiong Cong; Wang Cuiluan; Han Lin; Wu Peng; Wang Guan; Ma Xiaoyu

    2009-01-01

    A novel asymmetric broad waveguide diode laser structure was designed for high power conversion efficiency (PCE). The internal quantum efficiency, the series resistance, and the thermal resistance were theoretically optimized. The series resistance and the thermal resistance were greatly decreased by optimizing the thickness of the P-waveguide and the P-cladding layers. The internal quantum efficiency was increased by introducing a novel strain-compensated GaAs0.9P0.1/InGaAs quantum well. Experimentally, a single 1-cm bar with 20% fill factor and 900 μm cavity length was mounted P-side down on a microchannel-cooled heatsink, and a peak PCE of 60% is obtained at 26.3-W continuous wave output power. The results prove that this novel asymmetric waveguide structure design is an efficient approach to improve the PCE.

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

    Science.gov (United States)

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

    2015-12-01

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

  6. Highly-reliable operation of 638-nm broad stripe laser diode with high wall-plug efficiency for display applications

    Science.gov (United States)

    Yagi, Tetsuya; Shimada, Naoyuki; Nishida, Takehiro; Mitsuyama, Hiroshi; Miyashita, Motoharu

    2013-03-01

    Laser based displays, as pico to cinema laser projectors have gathered much attention because of wide gamut, low power consumption, and so on. Laser light sources for the displays are operated mainly in CW, and heat management is one of the big issues. Therefore, highly efficient operation is necessitated. Also the light sources for the displays are requested to be highly reliable. 638 nm broad stripe laser diode (LD) was newly developed for high efficiency and highly reliable operation. An AlGaInP/GaAs red LD suffers from low wall plug efficiency (WPE) due to electron overflow from an active layer to a p-cladding layer. Large optical confinement factor (Γ) design with AlInP cladding layers is adopted to improve the WPE. The design has a disadvantage for reliable operation because the large Γ causes high optical density and brings a catastrophic optical degradation (COD) at a front facet. To overcome the disadvantage, a window-mirror structure is also adopted in the LD. The LD shows WPE of 35% at 25°C, highest record in the world, and highly stable operation at 35°C, 550 mW up to 8,000 hours without any catastrophic optical degradation.

  7. Spatially nondegenerate four-wave mixing in a broad area semiconductor laser: Modeling

    DEFF Research Database (Denmark)

    Jensen, Søren Blaaberg; Tromborg, Bjarne; Petersen, P. M.

    We present a numerical model of spatially nondegenerate four-wave mixing in a bulk broad area semiconductor laser with an external reflector and a spatial filter. The external reflector provides a feedback with an off-aixs direction of propagation. Such a configuration has experimentally been seen...... to improve the coherence of the output of a broad area laser. While the far-field of a broad area laser is often double-lobed. the reflector feeds only one of the lobes back into the cavity in the same angle as the emission angle. As our model assumes only four waves inside the cavity it consists of...... four coupled equations for the field components in the cavity and a rate equation is used to describe the carrier density of the semiconductor material. The interference pattern of the four field components inside the cavity induces a periodic spatial modulation of the carrier density and thus of the...

  8. Quantum dot resonant tunneling diode single photon detector with aluminum oxide aperture defined tunneling area

    OpenAIRE

    Li, H W; Kardynal, Beata; Ellis, D. J. P.; Shields, A.J.; Farrer, I.; Ritchie, D. A.

    2008-01-01

    Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality resonant tunneling diodes. A single photon detection efficiency of 2.1%+/- 0.1% at 685 nm was measured corresponding to an internal quantum efficiency of 14%. The devices are simple to fabricate, robust,...

  9. Resistance-area product of diodes in a long-wavelength infrared HgCdTe mosaic array

    Science.gov (United States)

    Gopal, Vishnu; Dhar, Vikram

    2002-02-01

    A long wavelength infrared (LWIR) 2D (mosaic) diode array has been studied by numerically solving the diffusion equation in terms of thermally generated carriers in a n +-on-p HgCdTe diode in an array environment. The results are presented in terms of the resistance-area ( RA) product, in the diffusion-limited case. The results are compared with analytical expressions in the limiting case of the infinite diode. For a finite diode, with a definite junction depth, and a diode size that is smaller than the pitch, the RA, obtained from quasi-3D calculations, is smaller than that expected for the infinite diode case, the deviation being greater for small diodes. Commonly in the literature, the theoretical values of the infinite (1D) diode - which are overestimates - are stated as experimental targets. In the present calculations, the volume of the diode is considered to consist of two parts: one that contributes to the lateral diffusion current that is collected by the four lateral faces of the diode junction, and another that is the `normal' diffusion current, collected by the planar part of the junction from the volume `under' the diode. For the infinite diode case, only the latter component exists. The effect of the perimeter-to-area ratio on the RA in an array environment has been studied. The effective diffusion length associated with the finite diode geometry in an array differs from the standard diffusion length.

  10. Observation of electro-activated localized structures in broad area VCSELs

    OpenAIRE

    Parravicini, J.; Brambilla, M; Columbo, L.; Prati, F.; C. Rizza; Tissoni, G.; Agranat, A. J.; DelRe, E.

    2014-01-01

    We demonstrate experimentally the electro-activation of a localized optical structure in a coherently driven broad-area vertical-cavity surface-emitting laser (VCSEL) operated below threshold. Control is achieved by electro-optically steering a writing beam through a pre-programmable switch based on a photorefractive funnel waveguide.

  11. Structure, stability, and spectra of lateral modes of a broad-area semiconductor laser

    DEFF Research Database (Denmark)

    Blaaberg, Søren; Petersen, Paul Michael; Tromborg, Bjarne

    2007-01-01

    We present a theoretical analysis of the lateral modes of a broad-area semiconductor laser. The structure of the modes are classified into four categories and the modes are traced in the frequency versus pump rate diagram. It is shown how the branches of the frequency tuning curves for the...

  12. A micrometer-size movable light emitting area in a resonant tunneling light emitting diode

    International Nuclear Information System (INIS)

    We report on the fabrication of a micrometer-size movable light emitting area in a GaAs/AlAs quantum well resonant tunneling p-i-n diode. The spatial position of the micrometer-size light emitting area shifts linearly with increasing applied bias, up to 30 μm for a bias increment of 0.2 V. Also, the simultaneous resonant tunneling injection of both electrons and holes into the quantum well states is achieved at specific positions of the diode, thus resulting in a tenfold increase of the electroluminescence intensity

  13. A micrometer-size movable light emitting area in a resonant tunneling light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Pettinari, G., E-mail: giorgio.pettinari@cnr.it [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); National Research Council (CNR), Institute for Photonics and Nanotechnologies (IFN-CNR), Via Cineto Romano 42, 00156 Roma (Italy); Balakrishnan, N.; Makarovsky, O.; Campion, R. P.; Patanè, A. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Polimeni, A.; Capizzi, M. [CNISM-Dipartimento di Fisica, Sapienza Università di Roma, P.le A. Moro 2, 00185 Roma (Italy)

    2013-12-09

    We report on the fabrication of a micrometer-size movable light emitting area in a GaAs/AlAs quantum well resonant tunneling p-i-n diode. The spatial position of the micrometer-size light emitting area shifts linearly with increasing applied bias, up to 30 μm for a bias increment of 0.2 V. Also, the simultaneous resonant tunneling injection of both electrons and holes into the quantum well states is achieved at specific positions of the diode, thus resulting in a tenfold increase of the electroluminescence intensity.

  14. A micrometer-size movable light emitting area in a resonant tunneling light emitting diode

    Science.gov (United States)

    Pettinari, G.; Balakrishnan, N.; Makarovsky, O.; Campion, R. P.; Polimeni, A.; Capizzi, M.; Patanè, A.

    2013-12-01

    We report on the fabrication of a micrometer-size movable light emitting area in a GaAs/AlAs quantum well resonant tunneling p-i-n diode. The spatial position of the micrometer-size light emitting area shifts linearly with increasing applied bias, up to 30 μm for a bias increment of 0.2 V. Also, the simultaneous resonant tunneling injection of both electrons and holes into the quantum well states is achieved at specific positions of the diode, thus resulting in a tenfold increase of the electroluminescence intensity.

  15. Intrinsic performance-limiting instabilities in two-level class-B broad-area lasers

    Science.gov (United States)

    Pakhomov, A. V.; Molevich, N. E.; Krents, A. A.; Anchikov, D. A.

    2016-08-01

    The present paper is concerned with the analytical and numerical investigation of the transverse spatio-temporal instabilities in two-level broad-area lasers for the specific class-B case. We show that the two-level class-B broad-area laser tends to naturally operate in the filamentary state. This is revealed to be provided with two causes. First of them is related with the homogeneous output profile being intrinsically unstable due to the traveling-wave instability, independently from the boundary conditions. Secondly, high sensitivity to the boundaries of the pumping region was found for the commonly used top-hat-like profile leading to boundaries-induced filamentary dynamics. Spatio-temporal properties of both instability mechanisms are studied and their effects on the resulting laser dynamical behavior are analyzed.

  16. Cavity solitons in broad-area vertical-cavity surface-emitting lasers below threshold

    International Nuclear Information System (INIS)

    Cavity solitons are stationary self-organized bright intensity peaks which form over a homogeneous background in the section of broad area radiation beams. They are generated by shining a writing/erasing laser pulse into a nonlinear optical cavity, driven by a holding beam. The ability to control their location and their motion by introducing phase or amplitude gradients in the holding beam makes them interesting as mobile pixels for all-optical processing units. We show the generation of a number of cavity solitons in broad-area vertical cavity semiconductor microresonators electrically pumped above transparency but slightly below threshold. We analyze the switching process in details. The observed spots can be written, erased, and manipulated as independent objects, as predicted by the theoretical model. An especially tailored one is used to simulate the studied phenomena and to compare our simulations to the experimental findings with good agreement

  17. An electron beam-heater with a broad-area plasma cathode

    International Nuclear Information System (INIS)

    An electron-beam heater with a broad-area plasma cathode was designed for thermal treatment of large surfaces in vacuum. Using the plasma electron source of broad cross-section beams instead of a hot-cathode gun generating thin scanning beams allows simultaneous heating all the surface as well as lengthening the service life and raising the reliability of the heater. A broad-area emitting plasma surface is produced in a special electrode cavity by injection into it, through a small hole, of charged particles from a reflex discharge with cold electrodes. Such a principle of design of the plasma cathode allows to obtain an electron beam of the required current density in the pressure range of 10-2 to 1 Pa. The heater can be operated with He, Ar, air and other gases. Using a multiaperture accelerating system comprising emitting and accelerating electrodes, an electron beam up to 150 mm in diameter with an energy up to 15 keV, a current up to 0.5 A, and a nonuniformity of the cross-sectional distribution of the current density not more than +- 6% on the area of 100 cm2 could be generated. The efficiency of the heater at the accelerating voltage of 11 to 13 kV equals to about 90%. (author)

  18. Quantum dot resonant tunneling diode single photon detector with aluminum oxide aperture defined tunneling area

    DEFF Research Database (Denmark)

    Li, H.W.; Kardynal, Beata; Ellis, D.J.P.;

    2008-01-01

    Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality res...

  19. Area-dependent electrical characteristics of Schottky diodes fabricated on n-type GaN

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yunju; Kim, Yangsoo [Korea Basic Science Institute, Suncheon (Korea, Republic of); Jung, Eunjin; Oh, Munsik; Kim, Hyunsoo [Chonbuk National University, Jeonju (Korea, Republic of)

    2014-05-15

    The electrical characteristics of Schottky diodes fabricated on n-type GaN were investigated as a function of the contact area. A strong areal dependence was observed for all Schottky diodes, e.g., the larger the contact area, the smaller the Schottky barrier height, while the ideality factor retained a large value as high as 2.0 for all contact areas, likely due to the randomly-distributed threading dislocations observed via atomic force microscopy and/or to the plasma-induced surface states. A strong area-dependent Schottky barrier height could, therefore, be explained in terms of the barrier inhomogeneity model. In this transport regime, the Schottky characteristics exhibited an insignificant dependence on the work function of the Schottky metals; namely, Fermi level pinning occurred.

  20. Area-dependent electrical characteristics of Schottky diodes fabricated on n-type GaN

    International Nuclear Information System (INIS)

    The electrical characteristics of Schottky diodes fabricated on n-type GaN were investigated as a function of the contact area. A strong areal dependence was observed for all Schottky diodes, e.g., the larger the contact area, the smaller the Schottky barrier height, while the ideality factor retained a large value as high as 2.0 for all contact areas, likely due to the randomly-distributed threading dislocations observed via atomic force microscopy and/or to the plasma-induced surface states. A strong area-dependent Schottky barrier height could, therefore, be explained in terms of the barrier inhomogeneity model. In this transport regime, the Schottky characteristics exhibited an insignificant dependence on the work function of the Schottky metals; namely, Fermi level pinning occurred.

  1. 5.5-MeV proton irradiation of a strained quantum-well laser diode and a multiple quantum-well broad-band LED

    International Nuclear Information System (INIS)

    The degradation under 5.5-MeV proton irradiation of two classes of quantum-well-based fiber-optic light sources was evaluated for satellite applications. The first was an InGaAs/GaAs strained-layer quantum-well (QW) laser; the second was a broad-band light-emitting diode (LED) based on dual asymmetric quantum wells in the InGaAs/GaAs/AlGaAs system. In contrast to earlier reports comparing bulk active-region heterostructure LEDs with similarly structured laser diodes, these QW LEDs were more tolerant of proton irradiation (-3dB power at ∼3x1013 protons/cm2) than the QW lasers (-3dB power at ∼3x1012 protons/cm2). The LEDs were operated far into gain saturation with a high-loss cavity structure, while the lasers were operated in a region where gain was more sensitive to current density. Therefore atomic displacement-related recombination sites had a greater detrimental effect upon the lasers than the LEDs. The lasers held constant slope efficiency, and current thresholds increased linearly with proton fluence, while both LED power and slope efficiency decreased with proton fluence. Similar damage factors were found to those predicted from a universal damage factor versus non-ionizing energy deposition relation reported by others, and appears to extend that relation to include these QW photonic devices

  2. Broad gain of the Er/Al-doped fiber amplifier by pumping with a white light-emitting diode

    International Nuclear Information System (INIS)

    Broad gain of 88 nm from 1511 to 1599 nm upon pumping of an Er/Al-doped fiber amplifier with a white LED was demonstrated. The multiple absorption bands located in visible wavelength of Er3+ ions were simultaneously excited with the white LED. Optical gains of 13 dB and 12 dB, respectively, were obtained in the Er/Al-doped fiber and the Er-doped fiber. The 3 dB gain bandwidth of the Er/Al-doped fiber amplifier was 46 nm broader than that of the Er-doped fiber amplifier -- Highlights: • Broad gain characteristic around 1550 nm of the Er/Al-doped fiber was investigated upon pumping with white LED. • Optical gain of 13 dB at 1550 nm with 3 dB gain bandwidth of 88 nm was obtained. • Gain bandwidth of the Er/Al-doped fiber amplifier was twice as broad as that of the Er-doped fiber amplifier. • White LED-pumped Er/Al-doped fiber amplifier not only provides the required gain bandwidth but also reduces the manufacturing cost

  3. Vector cavity solitons in broad area Vertical-Cavity Surface-Emitting Lasers.

    Science.gov (United States)

    Averlant, Etienne; Tlidi, Mustapha; Thienpont, Hugo; Ackemann, Thorsten; Panajotov, Krassimir

    2016-01-01

    We report the experimental observation of two-dimensional vector cavity solitons in a Vertical-Cavity Surface-Emitting Laser (VCSEL) under linearly polarized optical injection when varying optical injection linear polarization direction. The polarization of the cavity soliton is not the one of the optical injection as it acquires a distinct ellipticity. These experimental results are qualitatively reproduced by the spin-flip VCSEL model. Our findings open the road to polarization multiplexing when using cavity solitons in broad-area lasers as pixels in information technology. PMID:26847004

  4. Enlargement of the inversionless lasing domain by using broad-area cavities

    International Nuclear Information System (INIS)

    We investigate analytically and numerically the role of diffraction in the operation of a broad-area inversionless laser in a cascade three-level configuration. Through a linear stability analysis of the trivial non-lasing solution and numerical integration of the corresponding Maxwell-Schroedinger equations, we show that off-axis emission allows stationary inversionless lasing over a cavity detuning range much larger than in small-aspect-ratio cavities and in conventionally inverted three-level lasers. In addition, we investigate inversionless lasing in a self-pulsing regime in the presence of diffraction, which leads to rich spatiotemporal dynamics

  5. Enlargement of the inversionless lasing domain by using broad-area cavities

    CERN Document Server

    Mompart, J; Ahufinger, V; García-Ojalvo, J; Corbalán, R; Vilaseca, R

    2003-01-01

    We investigate analytically and numerically the role of diffraction in the operation of a broad-area inversionless laser in a cascade three-level configuration. Through a linear stability analysis of the trivial non-lasing solution and numerical integration of the corresponding Maxwell-Schroedinger equations, we show that off-axis emission allows stationary inversionless lasing over a cavity detuning range much larger than in small-aspect-ratio cavities and in conventionally inverted three-level lasers. In addition, we investigate inversionless lasing in a self-pulsing regime in the presence of diffraction, which leads to rich spatiotemporal dynamics.

  6. Two-wave mixing in a broad-area semiconductor amplifier

    DEFF Research Database (Denmark)

    Chi, M.; Jensen, S.B.; Huignard, J.P.; Petersen, P.M.

    2006-01-01

    The two-wave mixing in the broad-area semiconductor amplifier was investigated, both theoretically and experimentally. In detail we investigated how the optical gain is affected by the presence of the two-wave mixing interference grating. In the experimental setup we are able to turn on and off the...... interference pattern in the semiconductor amplifier. This arrangement allows us to determine the two-wave mixing gain. The coupled-wave equations of two-wave mixing were derived based on the Maxwell’s wave equation and rate equation of the carrier density. The analytical solutions of the coupled-wave equations...

  7. A Broad Band and Large Area X-Ray Omni Sky Monitor (BLOSM)

    OpenAIRE

    Zhang, W.; Petre, R; Peele, A. N.; Jahoda, K.; Marshall, F. E.; Soong, Y.; White, N.E.

    1997-01-01

    We present a conceptual design for a new X-ray all sky monitor (ASM). Compared with previous ASMs, its salient features are: (1) it has a focusing capability that increases the signal to background ratio by a factor of 3; (2) it has a broad-band width: 200 eV to 15 keV; (3) it has a large X-ray collection area: ~100 square cm; (4) it has a duty cycle of nearly 100%, and (5) it can measure the position of a new source with an accuracy of a few minutes of arc. These features combined open up an...

  8. Control of lateral divergence in high-power, broad-area photonic crystal lasers

    Science.gov (United States)

    Rong, Jiamin; Xing, Enbo; Wang, Lijie; Shu, Shili; Tian, Sicong; Tong, Cunzhu; Wang, Lijun

    2016-07-01

    One-dimensional photonic bandgap crystal (PBC) lasers have demonstrated ultra-low vertical divergence and record brightness; however, their future development is limited by their lateral beam quality. In this paper, a fishbone microstructure is proposed to control the lateral modes in broad-area PBC lasers. The findings reveal that the introduction of the microstructure improves the full width at half maximum of the lateral far field by 22.2% and increases the output power to a small extent. The detailed measurements show that the lateral beam parameter product decreases by 15.9%.

  9. Synthesis and luminescence properties of a broad-band red phosphor Ca3Si2O7:Eu2+ for warm white light-emitting diodes

    International Nuclear Information System (INIS)

    Single-phase broad-band red-emitting Ca3Si2O7:Eu2+ phosphors, with photoluminescence features that qualify them as candidates for white light-emitting diodes applications, were successfully synthesized via a modified solid-state reaction method that employed H3BO3 as a flux. The phosphors produced have an intense broad red emission band, with a peak at 603 nm, a full width at half maximum of 110 nm, and color coordinates of (0.550, 0.438). Concentration quenching occurred at 0.01 mol Eu2+. The discussion of the results shows that Eu2+ ions should be accommodated at the Ca-sites of the lattice, dipole-dipole interactions should predominantly govern the energy transfer mechanism among them, and the critical distance between them is ∼31 A. - Highlights: → Pure Ca3Si2O7:Eu2+ phosphor was successfully synthesized by adding H3BO3 . → Effects of H3BO3 on phase formation and emission intensity were presented. → Luminescence properties in conjunction with Ca3Si2O7 structure were studied. → Energy transfer mechanism of Eu2+ and its critical distance were proposed.

  10. A reflex glow discharge as a plasma source for broad area electron beam generation

    International Nuclear Information System (INIS)

    The authors demonstrated an electron beam generation scheme in which two glow discharge electron guns are used in a reflex configuration to create a dense and cold plasma in a large volume. The thermal electrons from this plasma, created mainly by electron beam ionization, are subsequently accelerated in the gap between two grids by an externally applied electric field to produce a broad area electron beam. This electron beam current density and energy are independently controlled by the voltage applied to the glow discharge guns and by the electric field sustained between the grids respectively. They present a schematic representation of the electron gun used in the experimental demonstration of the concept reported here

  11. The Global Evidence Mapping Initiative: Scoping research in broad topic areas

    Directory of Open Access Journals (Sweden)

    Tavender Emma

    2011-06-01

    Full Text Available Abstract Background Evidence mapping describes the quantity, design and characteristics of research in broad topic areas, in contrast to systematic reviews, which usually address narrowly-focused research questions. The breadth of evidence mapping helps to identify evidence gaps, and may guide future research efforts. The Global Evidence Mapping (GEM Initiative was established in 2007 to create evidence maps providing an overview of existing research in Traumatic Brain Injury (TBI and Spinal Cord Injury (SCI. Methods The GEM evidence mapping method involved three core tasks: 1. Setting the boundaries and context of the map: Definitions for the fields of TBI and SCI were clarified, the prehospital, acute inhospital and rehabilitation phases of care were delineated and relevant stakeholders (patients, carers, clinicians, researchers and policymakers who could contribute to the mapping were identified. Researchable clinical questions were developed through consultation with key stakeholders and a broad literature search. 2. Searching for and selection of relevant studies: Evidence search and selection involved development of specific search strategies, development of inclusion and exclusion criteria, searching of relevant databases and independent screening and selection by two researchers. 3. Reporting on yield and study characteristics: Data extraction was performed at two levels - 'interventions and study design' and 'detailed study characteristics'. The evidence map and commentary reflected the depth of data extraction. Results One hundred and twenty-nine researchable clinical questions in TBI and SCI were identified. These questions were then prioritised into high (n = 60 and low (n = 69 importance by the stakeholders involved in question development. Since 2007, 58 263 abstracts have been screened, 3 731 full text articles have been reviewed and 1 644 relevant neurotrauma publications have been mapped, covering fifty-three high priority

  12. Thermal investigation on high power dfb broad area lasers at 975 nm, with 60% efficiency

    Science.gov (United States)

    Mostallino, R.; Garcia, M.; Deshayes, Y.; Larrue, A.; Robert, Y.; Vinet, E.; Bechou, L.; Lecomte, M.; Parillaud, O.; Krakowski, M.

    2016-03-01

    The demand of high power diode lasers in the range of 910-980nm is regularly growing. This kind of device for many applications, such as fiber laser pumping [1], material processing [1], solid-state laser pumping [1], defense and medical/dental. The key role of this device lies in the efficiency (𝜂𝐸) of converting input electrical power into output optical power. The high value of 𝜂𝐸 allows high power level and reduces the need in heat dissipation. The requirement of wavelength stabilization with temperature is more obvious in the case of multimode 975nm diode lasers used for pumping Yb, Er and Yb/Er co-doped solid-state lasers, due to the narrow absorption line close to this wavelength. Such spectral width property (devices and LEDs but is weakly developed for the high power diodes laser. This crucial measurement compared to spectral one is critical for understand the thermal management of diode laser device and improve the structure based on design for reliability. To have a perfect relation between structure, and their modification, and temperature, FEM simulations are performed using COMSOL software. In this case, we can understand the impact of structure on the isothermal distribution and then reveal the sensitive zones in the diode laser. To validate the simulation, we compare the simulation results to the experimental one and develop an analytical model to determine the different contributions of the thermal heating. This paper reports on the development laser structure and the process techniques required to write the gratings. Performances are particularly characterized in terms of experimental electro-optical characterization and spectral response. The extraction of thermal resistance (Rth) is particularly difficult, because of the implicit low value (Rth ≈ 2𝐾/𝑊) and the multimodal nature of the diode laser. In such a context, thermal resistance has been measured using a dedicated equipment namely T3STER

  13. Acoustic and Thermal Testing of an Integrated Multilayer Insulation and Broad Area Cooling Shield System

    Science.gov (United States)

    Wood, Jessica J.; Foster, Lee W.

    2013-01-01

    A Multilayer Insulation (MLI) and Broad Area Cooling (BAC) shield thermal control system shows promise for long-duration storage of cryogenic propellant. The NASA Cryogenic Propellant Storage and Transfer (CPST) project is investigating the thermal and structural performance of this tank-applied integrated system. The MLI/BAC Shield Acoustic and Thermal Test was performed to evaluate the MLI/BAC shield's structural performance by subjecting it to worst-case launch acoustic loads. Identical thermal tests using Liquid Nitrogen (LN2) were performed before and after the acoustic test. The data from these tests was compared to determine if any degradation occurred in the thermal performance of the system as a result of exposure to the acoustic loads. The thermal test series consisted of two primary components: a passive boil-off test to evaluate the MLI performance and an active cooling test to evaluate the integrated MLI/BAC shield system with chilled vapor circulating through the BAC shield tubes. The acoustic test used loads closely matching the worst-case envelope of all launch vehicles currently under consideration for CPST. Acoustic test results yielded reasonable responses for the given load. The thermal test matrix was completed prior to the acoustic test and successfully repeated after the acoustic test. Data was compared and yielded near identical results, indicating that the MLI/BAC shield configuration tested in this series is an option for structurally implementing this thermal control system concept.

  14. Broad-area detection of structural irregularities in composites using fibre Bragg gratings

    Science.gov (United States)

    Davis, Claire E.; Norman, Patrick; Moss, Scott; Ratcliffe, Colin; Crane, Roger

    2010-04-01

    The Structural Irregularity and Damage Evaluation Routine (SIDER) is a broadband vibration-based technique that uses features in complex curvature operating shapes to locate damage and other areas with structural stiffness variations. It is designed for the inspection of large-scale composite structures not amenable to more conventional inspection methods. The current SIDER methodology relies on impact excitation at a series of grid points on the structure and records the response using a small number of accelerometers to determine the operational curvature shapes. This paper reports on a modification to the SIDER technique whereby the acceleration measurements are replaced with in-plane strain measurements using Fibre Bragg Gratings (FBGs). One of the major challenges associated with using Bragg gratings for this type of response measurement is that the strains induced by structural vibrations tend to be low, particularly at higher frequencies. This paper also reports on the development of an intensity-based, swept wavelength interrogation system to facilitate these measurements. The modified SIDER system was evaluated on an E-glass/vinyl ester composite test beam containing a machined notch. The measurements accurately detected the presence and location of the notch. The distributive capacity of FBGs means that these sensors have the potential to replace the excitation grid with a measurement grid, allowing for single point or environmental excitation. The spatially separated measurements of strain can be used to provide the curvature shapes directly. This change in approach could potentially transition SIDER from an interval-based, broad-area inspection tool to an in-service structural health monitoring system.

  15. Characterization of a commercially available large area, high detection efficiency single-photon avalanche diode

    CERN Document Server

    Stipčević, Mario; Ursin, Rupert

    2013-01-01

    We characterize a new commercial, back-illuminated reach-through silicon single-photon avalanche photo diode (SPAD) SAP500 (Laser Components. Inc.), operated in Geiger-mode for purpose of photon counting. We show that for this sensor a significant interplay exists between dark counts, detection efficiency, afterpulsing, excess voltage and operating temperature, sometimes requiring a careful optimization tailored for a specific application. We find that a large flat plateau of sensitive area of about 0.5 mm in diameter, a peak quantum efficiency of 73% at 560 nm and timing precision down to 150 ps FWHM are the main distinguishing characteristics of this SPAD.

  16. Large area buried nanopatterning by broad ion implantation without any mask or direct writing

    OpenAIRE

    Karmakar, Prasanta; Satpati, Biswarup

    2013-01-01

    We have introduced here a simple, single step and cost effective broad ion beam technique for preparation of nanoscale electronic, magnetic, optical and mechanical devices without the need of resist, mask, or focused electron and ion beams. In this approach, broad beam ion implantation of desired atom on a prefabricated ion beam patterned surface promotes site selective deposition by adjusting the local angle of ion implantation. We show that implantation of Fe ions on an O+ induced pre fabri...

  17. 20 000 h reliable operation of 100 µm stripe width 650 nm broad area lasers at more than 1.1 W output power

    International Nuclear Information System (INIS)

    Reliability tests for highly efficient high-power 650 nm broad area diode lasers will be presented. The devices have a 5 nm thick single GaInP quantum well as an active layer, which is embedded in AlGaInP waveguide layers and n-AlInP and p-AlGaAs cladding layers. The devices with a stripe width of 100 µm and a cavity length of 1.5 mm were soldered on diamond submounts and mounted on standard C-mounts for an efficient heat removal. The test was performed at a temperature of 15 °C over a first period of 10 000 h at 1.1 W followed by a second period of 10 000 h at 1.2 W. Based on the aging test and assuming a 60% confidence level, the lower limit of the mean time to failure of 87 000 h was determined for the devices

  18. Area-Effective Inductive Peaking with Interwoven Inductor for High-Speed Laser-Diode Driver for Optical Communication System

    OpenAIRE

    KUBOKI, Takeshi; OHTOMO, Yusuke; TSUCHIYA, Akira; KISHINE, Keiji; Onodera, Hidetoshi

    2012-01-01

    This paper presents an area-effective bandwidth enhancement technique using interwoven inductors. Inductive peaking is a common practice for bandwidth enhancement, however the area overhead of inductors is a serious issue. We implement six or four inductors into an interwoven inductor. Furthermore parasitics of the inductors can be reduced. The proposed inductor is applied to a laser-diode driver in a 0.18µm CMOS. Compared to conventional shunt-peaking, the proposed circuit achieves 1.6 times...

  19. Current models broadly neglect specific needs of biodiversity conservation in protected areas under climate change

    Directory of Open Access Journals (Sweden)

    Moloney Kirk A

    2011-05-01

    Full Text Available Abstract Background Protected areas are the most common and important instrument for the conservation of biological diversity and are called for under the United Nations' Convention on Biological Diversity. Growing human population densities, intensified land-use, invasive species and increasing habitat fragmentation threaten ecosystems worldwide and protected areas are often the only refuge for endangered species. Climate change is posing an additional threat that may also impact ecosystems currently under protection. Therefore, it is of crucial importance to include the potential impact of climate change when designing future nature conservation strategies and implementing protected area management. This approach would go beyond reactive crisis management and, by necessity, would include anticipatory risk assessments. One avenue for doing so is being provided by simulation models that take advantage of the increase in computing capacity and performance that has occurred over the last two decades. Here we review the literature to determine the state-of-the-art in modeling terrestrial protected areas under climate change, with the aim of evaluating and detecting trends and gaps in the current approaches being employed, as well as to provide a useful overview and guidelines for future research. Results Most studies apply statistical, bioclimatic envelope models and focus primarily on plant species as compared to other taxa. Very few studies utilize a mechanistic, process-based approach and none examine biotic interactions like predation and competition. Important factors like land-use, habitat fragmentation, invasion and dispersal are rarely incorporated, restricting the informative value of the resulting predictions considerably. Conclusion The general impression that emerges is that biodiversity conservation in protected areas could benefit from the application of modern modeling approaches to a greater extent than is currently reflected in the

  20. Broad Band Optical Properties of Large Area Monolayer CVD Molybdenum Disulfide

    OpenAIRE

    Li, Wei; Birdwell, A. Glen; Amani, Matin; Burke, Robert A.; Ling, Xi; Lee, Yi-Hsien; Liang, Xuelei; Peng, Lianmao; Richter, Curt A.; Kong, Jing; Gundlach, David J.; Nguyen, N.V.

    2014-01-01

    Recently emerging large-area single-layer MoS2 grown by chemical vapor deposition has triggered great interest due to its exciting potential for applications in advanced electronic and optoelectronic devices. Unlike gapless graphene, MoS2 has an intrinsic band gap in the visible which crosses over from an indirect to a direct gap when reduced to a single atomic layer. In this article, we report a comprehensive study of fundamental optical properties of MoS2 revealed by optical spectroscopy of...

  1. A high-frequency response and a nonlinear coherent generation in resonant-tunneling diodes within a broad frequency range with electron-electron interaction

    International Nuclear Information System (INIS)

    Within the framework of a sequential quantum mechanical model, the response and the power of a coherent generation have been obtained numerically in a resonant-tunneling diode in a wide range of frequencies with the electron-electron interaction. The quantum regime of generation is shown to be sustained under the electron-electron interaction. Thus, a high-power generation is probable under frequencies exceeding the width of the resonant level

  2. Gain-guided broad area quantum cascade lasers emitting 23.5 W peak power at room temperature.

    Science.gov (United States)

    Sergachev, Ilia; Maulini, Richard; Bismuto, Alfredo; Blaser, Stephane; Gresch, Tobias; Muller, Antoine

    2016-08-22

    We report gain-guided broad area quantum cascade lasers at 4.55 μm. The devices were processed in a buried heterostructure configuration with a current injector section much narrower than the active region. They demonstrate 23.5 W peak power at a temperature of 20°C and duty cycle of 1%, while their far field consists of a single symmetric lobe centered on the optical axis. These experimental results are supported well by 2D numerical simulations of electric currents and optical fields in a device cross-section. PMID:27557186

  3. High-power, low-lateral divergence broad area quantum cascade lasers with a tilted front facet

    International Nuclear Information System (INIS)

    We introduce a simple technique to improve the beam quality of broad area quantum cascade lasers. Moderately tilted front facets of the laser provide suppression of higher order lateral waveguide modes. A device with a width of 60 μm and a front facet angle of 17° shows a nearly diffraction limited beam profile. In addition, the peak output power and the slope efficiency of the device are increased since most of the light inside the cavity is emitted through the tilted front facet by an asymmetric light intensity distribution along the cavity

  4. Analyzing charge distribution in the termination area of 4H-SiC diodes by measuring depletion-layer capacitance

    Science.gov (United States)

    Matsushima, Hiroyuki; Okino, Hiroyuki; Mochizuki, Kazuhiro; Yamada, Renichi

    2016-04-01

    The distribution of positive-charge density at the SiO2/SiC interface of the termination area (Q TM) was analyzed by measuring the depletion-layer capacitance of 4H-SiC PN diodes with different termination structures. A change in Q TM induced by reverse-bias stressing (ΔQ TM) caused a change in the breakdown voltage of the diodes. By comparing the measured depletion-layer capacitance to the simulated value, the initial Q TM (Q\\text{TM}\\text{o}) and the distribution of ΔQ TM were clarified. It is concluded from these results that the distribution of ΔQ TM was not uniform but that positive charges mostly accumulated in the termination area under a high applied electric field.

  5. Design and fabrication of 1.55 μm broad area slotted single-mode Fabry–Perot lasers

    Science.gov (United States)

    Mengke, Li; Lijun, Yuan; Hongyan, Yu; Qiang, Kan; Shiyan, Li; Junping, Mi; Jiaoqing, Pan

    2016-03-01

    We present a single-mode laser on a p-InP substrate suitable for bonding on silicon-on-insulator (SOI) wafer. The laser can realize single mode lasing with etching perturbing slots by standard photolithography and an inductively coupled-plasma (ICP) etching technique without any regrowth steps. The parameters were designed using the simulation tool “cavity modeling framework” (CAMFR). The single mode of 1539 nm wavelength at the threshold current of 130 mA with the maximum output power of 3.9 mW was obtained at 10 °C in continuous-wave operation. The simple technology, low cost and the single-mode characteristics make the broad area slotted single-mode FP laser a promising light source on the silicon-based optical interconnection applications.

  6. Site specific isolated nanostructure array formation on a large area by broad ion beam without any mask and resist

    Science.gov (United States)

    Karmakar, Prasanta; Satpati, Biswarup

    2014-06-01

    We report the formation of isolated nanostructure arrays on a large area via broad ion beam implantation without the aid of any mask or resist. Desired ions have been implanted at specific locations of the prefabricated silicon ripple or triangular structures by exploiting the variation of local ion impact angles. We have shown that the implantation of Fe ions on an O+ ions induced pre fabricated triangular shaped patterned Si surface results in a self-organized periodic array of striped magnetic nanostructures having several micron length and about 50 nm width arranged with a spacial separation of ˜200 nm. The morphology, composition, crystalline structure, and magnetic property of these nanopatterns have been analyzed using high-resolution cross-sectional transmission electron microscopy and atomic force microscopy. A geometrical model has been proposed to explain the fundamental features of such ion-induced nanopattern structures.

  7. Site specific isolated nanostructure array formation on a large area by broad ion beam without any mask and resist

    International Nuclear Information System (INIS)

    We report the formation of isolated nanostructure arrays on a large area via broad ion beam implantation without the aid of any mask or resist. Desired ions have been implanted at specific locations of the prefabricated silicon ripple or triangular structures by exploiting the variation of local ion impact angles. We have shown that the implantation of Fe ions on an O+ ions induced pre fabricated triangular shaped patterned Si surface results in a self-organized periodic array of striped magnetic nanostructures having several micron length and about 50 nm width arranged with a spacial separation of ∼200 nm. The morphology, composition, crystalline structure, and magnetic property of these nanopatterns have been analyzed using high-resolution cross-sectional transmission electron microscopy and atomic force microscopy. A geometrical model has been proposed to explain the fundamental features of such ion-induced nanopattern structures.

  8. Production of uniform ion beam of large area in a magnetically-insulatd diode

    International Nuclear Information System (INIS)

    The results of experimental investigation of a magnetically insulated diode generating a powerful ribbon ion beam with 100x10 cm cross section are presented. Modification of the known diode designs allowed to provide the constancy of the electric and magnetic field by the anode length and uniform generation of the ion beam over the larger part of its length. At the same time these measures have decreased considerably electron losses in the anode up to 1-2 A/cm2 that reduces the efficiency of anode plasma formation during the first part of a high-voltage pulse. At 500 kV anode voltage the ion current amplitude is 18 kA, the beam-out energy - 460 J, the efficiency of ion generation - 85%

  9. White LEDs as broad spectrum light sources for spectrophotometry: demonstration in the visible spectrum range in a diode-array spectrophotometric detector.

    Science.gov (United States)

    Piasecki, Tomasz; Breadmore, Michael C; Macka, Mirek

    2010-11-01

    Although traditional lamps, such as deuterium lamps, are suitable for bench-top instrumentation, their compatibility with the requirements of modern miniaturized instrumentation is limited. This study investigates the option of utilizing solid-state light source technology, namely white LEDs, as a broad band spectrum source for spectrophotometry. Several white light LEDs of both RGB and white phosphorus have been characterized in terms of their emission spectra and energy output and a white phosphorus Luxeon LED was then chosen for demonstration as a light source for visible-spectrum spectrophotometry conducted in CE. The Luxeon LED was fixed onto the base of a dismounted deuterium (D(2) ) lamp so that the light-emitting spot was geometrically positioned exactly where the light-emitting spot of the original D(2) lamp is placed. In this manner, the detector of a commercial CE instrument equipped with a DAD was not modified in any way. As the detector hardware and electronics remained the same, the change of the deuterium lamp for the Luxeon white LED allowed a direct comparison of their performances. Several anionic dyes as model analytes with absorption maxima between 450 and 600 nm were separated by CE in an electrolyte of 0.01 mol/L sodium tetraborate. The absorbance baseline noise as the key parameter was 5 × lower for the white LED lamp, showing clearly superior performance to the deuterium lamp in the available, i.e. visible part of the spectrum. PMID:21077241

  10. Coaxial foilless diode

    Directory of Open Access Journals (Sweden)

    Long Kong

    2014-05-01

    Full Text Available A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves.

  11. Low lateral divergence 2 μm InGaSb/ AlGaAsSb broad-area quantum well lasers.

    Science.gov (United States)

    Rong, Jiamin; Xing, Enbo; Zhang, Yu; Wang, Lijie; Shu, Shili; Tian, Sicong; Tong, Cunzhu; Chai, Xiaoli; Xu, Yingqiang; Ni, Haiqiao; Niu, Zhichuan; Wang, Lijun

    2016-04-01

    High power and high brightness mid-infrared GaSb based lasers are desired for many applications, however, the high lateral divergence is still the influence factor for practical application. In this paper, a simple and effective approach based on the fishbone-shape microstructure was proposed, the effective improvement on both the lateral divergence and output power of 2 μm GaSb based broad-area lasers was demonstrated. The lateral divergence is reduced averagely by 55% and 15.8° for 95% power content is realized. The continuous-wave emission power is increased about 19% with the decreased threshold current. The other merits for this microstructure are the unchanged intrinsic characteristic of broad-area lasers and the low cost fabrication. PMID:27137016

  12. A Novel Passive Millimeter Imager for Broad-Area Search - Final Report on Project PL09-NPMI-PD07 (PNNL-55180)

    Energy Technology Data Exchange (ETDEWEB)

    Tedeschi, Jonathan R.; Bernacki, Bruce E.; Kelly, James F.; Sheen, David M.; Harris, Robert V.; Hall, Thomas E.; Hatchell, Brian K.; Knopik, Clint D.; Lechelt, Wayne M.; McMakin, Douglas L.; Mendoza, Albert; Severtsen, Ronald H.; Valdez, Patrick LJ

    2011-12-31

    This report describes research and development efforts toward a novel passive millimeter-wave (mm-wave) electromagnetic imaging device for broad-area search. It addresses the technical challenge of detecting anomalies that occupy a small fraction of a pixel. The purpose of the imager is to pinpoint suspicious locations for cuing subsequent higher-resolution imaging. The technical basis for the approach is to exploit thermal and polarization anomalies that distinguish man-made features from natural features.

  13. Mercury levels in fish, invertebrates and sediment in a recently recorded polluted area (Nissum Broad, western Limfjord, Denmark)

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Møhlenberg, Flemming; Ulrik Riisgård, Hans

    1983-01-01

    High concentrations of mercury were measured in sediment and animals collected in the immediate vicinity of a closed-down chemical factory. Sediment contained up to 22 ppm (dry wt) of mercury, deposit-feeding bivalves between 1.4 and 4.4 ppm (wet wt), suspension-feeding bivalves between 0.9 and 1.......9 ppm and predatory fish between 0.3 and 0.8 ppm. Outside the ‘hot spot’ area, the mercury concentration in sediment and mussels (Mytilus edulis) rapidly decreased with increasing distance from the former factory. Mercury concentration in flounders (Platichthys flesus) also decreased with distance from...

  14. Suppression of roll-off characteristics of organic light-emitting diodes by narrowing current injection/transport area to 50 nm

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Kyohei, E-mail: k-hayashi@bioorg.rcast.u-tokyo.ac.jp; Inoue, Munetomo; Yoshida, Kou [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Nakanotani, Hajime [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); JST, ERATO, Adachi Molecular Exciton Engineering Project, c/o OPERA, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Innovative Organic Device Laboratory, Institute of Systems, Information Technologies and Nanotechnologies (ISIT), 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Mikhnenko, Oleksandr; Nguyen, Thuc-Quyen, E-mail: quyen@chem.ucsb.edu, E-mail: adachi@cstf.kyushu-u.ac.jp [Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-9510 (United States); Adachi, Chihaya, E-mail: quyen@chem.ucsb.edu, E-mail: adachi@cstf.kyushu-u.ac.jp [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); JST, ERATO, Adachi Molecular Exciton Engineering Project, c/o OPERA, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Innovative Organic Device Laboratory, Institute of Systems, Information Technologies and Nanotechnologies (ISIT), 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)

    2015-03-02

    Using e-beam nanolithography, the current injection/transport area in organic light-emitting diodes (OLEDs) was confined into a narrow linear structure with a minimum width of 50 nm. This caused suppression of Joule heating and partial separation of polarons and excitons, so the charge density where the electroluminescent efficiency decays to the half of the initial value (J{sub 0}) was significantly improved. A device with a narrow current injection width of 50 nm exhibited a J{sub 0} that was almost two orders of magnitude higher compared with that of the unpatterned OLED.

  15. Fabrication of Fe3Si/CaF2 heterostructures ferromagnetic resonant tunneling diode by selected-area molecular beam epitaxy

    International Nuclear Information System (INIS)

    We have fabricated 200-nm-diameter ferromagnetic resonant tunneling diodes (FM-RTDs) using CaF2/Fe3Si heterostructures on Si(111) substrates, by selected-area molecular beam epitaxy (MBE) using electron-beam (EB) lithography. Clear negative differential resistances (NDRs) were observed in the current-voltage (I-V) characteristics at room temperature (RT). The reproducibility of the I-V characteristics was greatly improved, and approximately 40% of the FM-RTDs showed clear NDRs at RT.

  16. Fabrication of Fe{sub 3}Si/CaF{sub 2} heterostructures ferromagnetic resonant tunneling diode by selected-area molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Sadakuni-Makabe, Kenji; Suzuno, Mitsushi; Harada, Kazunori [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8573 (Japan); Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8573 (Japan); Akinaga, Hiro [Nanodevice Innovation Research Center and Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2011-10-03

    We have fabricated 200-nm-diameter ferromagnetic resonant tunneling diodes (FM-RTDs) using CaF{sub 2}/Fe{sub 3}Si heterostructures on Si(111) substrates, by selected-area molecular beam epitaxy (MBE) using electron-beam (EB) lithography. Clear negative differential resistances (NDRs) were observed in the current-voltage (I-V) characteristics at room temperature (RT). The reproducibility of the I-V characteristics was greatly improved, and approximately 40% of the FM-RTDs showed clear NDRs at RT.

  17. High brightness laser source based on polarization coupling of two diode lasers with asymmetric feedback

    DEFF Research Database (Denmark)

    Thestrup, B.; Chi, M.; Sass, B.; Petersen, P.M.

    2003-01-01

    In this letter, we show that polarization coupling and asymmetric diode-laser feedback can be used to combine two diode-laser beams with low spatial coherence into a single beam with high spatial coherence. The coupled laser source is based on two similar laser systems each consisting of a 1 mumx......200 mum broad area laser diode applied with a specially designed feedback circuit. When operating at two times threshold, 50% of the freely running system output power is obtained in a single beam with an M-2 beam quality factor of 1.6+/-0.1, whereas the M-2 values of the two freely running diode...... lasers are 29+/-1 and 34+/-1, respectively. (C) 2003 American Institute of Physics....

  18. Color-conversion efficiency enhancement of quantum dots via selective area nano-rods light-emitting diodes.

    Science.gov (United States)

    Liu, Che-Yu; Chen, Tzu-Pei; Kao, Tsung Sheng; Huang, Jhih-Kai; Kuo, Hao-Chung; Chen, Yang-Fang; Chang, Chun-Yen

    2016-08-22

    A large enhancement of color-conversion efficiency of colloidal quantum dots in light-emitting diodes (LEDs) with novel structures of nanorods embedded in microholes has been demonstrated. Via the integration of nano-imprint and photolithography technologies, nanorods structures can be fabricated at specific locations, generating functional nanostructured LEDs for high-efficiency performance. With the novel structured LED, the color-conversion efficiency of the existing quantum dots can be enhanced by up to 32.4%. The underlying mechanisms can be attributed to the enhanced light extraction and non-radiative energy transfer, characterized by conducting a series of electroluminescence and time-resolved photoluminescence measurements. This hybrid nanostructured device therefore exhibits a great potential for the application of multi-color lighting sources. PMID:27557273

  19. Mechanically Q-switched co-doped Er-Yb glass laser under Ti:Sapphire and laser diode pumping

    OpenAIRE

    Tanguy, Eric; Pocholle, Jean-Paul; Feugnet, Gilles; Larat, Christian; Schwartz, M.; Brun, Alain; Georges, Patrick

    1995-01-01

    A simple Q-switched TEMoo Er3+. Yb3+ glass laser end-pumped by a Ti:Al203 laser or by a broad-area high-power laser diode is demonstrated. In both cases the FWHM pulse duration is about 50ns and the peak power is > lOOW

  20. Efficient quasi-three-level Nd:YAG laser at 946 nm pumped by a tunable external cavity tapered diode laser

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter;

    2010-01-01

    Using a tunable external cavity tapered diode laser (ECDL) pumped quasi-three-level Nd:YAG laser, a fivefold reduction in threshold and twofold increase in slope efficiency is demonstrated when compared to a traditional broad area diode laser pump source. A TEM00 power of 800 mW with 65% slope...... efficiency is obtained, the highest reported TEM00 power from any 946 nm Nd:YAG laser pumped by a single emitter diode laser pump source. A quantum efficiency of 0.85 has been estimated from experimental data using a simple quasi-three-level model. The reported value is in good agreement with published...... values, suggesting that the model is adequate. Improvement of the 946 nm laser due to the ECDL's narrow spectrum proves to be less significant when compared to its spatial quality, inferring a broad spectrum tapered diode laser pump source may be most practical. Experimental confirmation of such setup is...

  1. Unveiling laser diode “fossil” and the dynamic analysis for heliotropic growth of catastrophic optical damage in high power laser diodes

    OpenAIRE

    Qiang Zhang; Yihan Xiong; Haiyan An; Konstantin Boucke; Georg Treusch

    2016-01-01

    Taking advantage of robust facet passivation, we unveil a laser “fossil” buried within a broad area laser diode (LD) cavity when the LD was damaged by applying a high current. For the first time, novel physical phenomena have been observed at these dramatically elevated energy densities within the nanoscale LD waveguide. The observation of the laser “fossil” is interpreted with different mechanisms, including: the origination of bulk catastrophic optical damage (COD) due to locally high energ...

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

    Science.gov (United States)

    Tratt, David M.; Amzajerdian, Farzin; Kashem, Nasir B.; Shapiro, Andrew A.; Mense, Allan T.

    2007-01-01

    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 qualification protocols, operational control recommendations, and consensus manufacturing and certification standards. The group is using reliability and lifetime data collected by laser diode manufacturers and the user community to develop a set of standardized guidelines for specifying and qualifying laser diodes for long-duration operation in space, the ultimate goal being to promote an informed U.S. Government investment and procurement strategy for assuring the availability and durability of space-qualified LDAs. The group is also working to establish effective implementation of statistical design techniques at the supplier design, development, and manufacturing levels to help reduce product performance variability and improve product reliability for diodes employed in space applications

  3. Approaches of output improvement for a cesium vapor laser pumped by a volume-Bragg-grating coupled laser-diode-array

    International Nuclear Information System (INIS)

    We report the approaches of output improvement for a cesium vapor laser, which was pumped by a volume-Bragg-grating (VBG) coupled broad-area laser-diode-array (LDA) with the quasi-continuous-wave (QCW) drive mode, in adopting an appropriate heating procedure and improving the pump configuration

  4. Leaf area expansion and dry matter accumulation during establishment of broad bean and sorghum at different temperatures and soil water contents in two types of soil in mediterranean Portugal

    OpenAIRE

    Andrade, José; Abreu, Francisco

    2005-01-01

    Crop establishment is a major factor determining crop productivity in the field and is strongly controlled by soil temperature and soil moisture. Fast leaf expansion and dry matter accumulation during crop establishment are required for an adequate establishment. Leaf area expansion and accumulation of dry matter during the establishment of broad bean (Vicia faba L.) and sorghum (Sorghum vulgare L.) were studied at different soil temperatures and soil moisture contents in a Vertisol (Lisbo...

  5. Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Broad Creek site, 2006 - 2007 (NODC Accession 0039880)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

  6. Compatibility of the selective area growth of GaN nanowires on AlN-buffered Si substrates with the operation of light emitting diodes

    International Nuclear Information System (INIS)

    AlN layers with thicknesses between 2 and 14 nm were grown on Si(111) substrates by molecular beam epitaxy. The effect of the AlN layer thickness on the morphology and nucleation time of spontaneously formed GaN nanowires (NWs) was investigated by scanning electron microscopy and line-of-sight quadrupole mass spectrometry, respectively. We observed that the alignment of the NWs grown on these layers improves with increasing layer thickness while their nucleation time decreases. Our results show that 4 nm is the smallest thickness of the AlN layer that allows the growth of well-aligned NWs with short nucleation time. Such an AlN buffer layer was successfully employed, together with a patterned SiOx mask, for the selective-area growth (SAG) of vertical GaN NWs. In addition, we fabricated light-emitting diodes (LEDs) from NW ensembles that were grown by means of self-organization phenomena on bare and on AlN-buffered Si substrates. A careful characterization of the optoelectronic properties of the two devices showed that the performance of NW-LEDs on bare and AlN-buffered Si is similar. Electrical conduction across the AlN buffer is facilitated by a high number of grain boundaries that were revealed by transmission electron microscopy. These results demonstrate that grainy AlN buffer layers on Si are compatible both with the SAG of GaN NWs and LED operation. Therefore, this study is a first step towards the fabrication of LEDs on Si substrates based on homogeneous NW ensembles. (paper)

  7. Physics and Applications of Laser Diode Chaos

    CERN Document Server

    Sciamanna, Marc

    2015-01-01

    An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.

  8. Augmenting saturated LTP by broadly spaced episodes of theta-burst stimulation in hippocampal area CA1 of adult rats and mice

    OpenAIRE

    Cao, Guan; Harris, Kristen M.

    2014-01-01

    Hippocampal long-term potentiation (LTP) is a model system for studying cellular mechanisms of learning and memory. Recent interest in mechanisms underlying the advantage of spaced over massed learning has prompted investigation into the effects of distributed episodes of LTP induction. The amount of LTP induced in hippocampal area CA1 by one train (1T) of theta-burst stimulation (TBS) in young Sprague-Dawley rats was further enhanced by additional bouts of 1T given at 1-h intervals. However,...

  9. The world's high background natural radiation areas (HBNRAs) revisited: A broad overview of the dosimetric, epidemiological and radiobiological issues

    International Nuclear Information System (INIS)

    The residents of the world's high background natural radiation areas (HBNRAs), such as Ramsar (in Iran), Guarapari (in Brazil), Orissa and Kerala (in India) and Yangjiang (in China) have lived in these areas for generations under extraordinary radiation fields. The failure of earlier epidemiological studies to report any substantial increase in cancer incidence in HBNRAs has raised some controversy regarding the validity of the linear no-threshold hypothesis. This paper reviews some of the most recent studies of HBNRAs with the intent of stimulating greater research interest in the dosimetric, epidemiological and radiobiological issues related to the world's HBNRAs and proposes solutions to the challenges facing HBNRA studies. This paper may serve as a useful reference for some of the harder-to-find literature. - Highlights: • Some of the challenging issues of HBNRAs have not been resolved. • A literature review of the most recent studies of HBNRAs has been conducted. • An overview of some of the challenging issues and viable solutions are presented

  10. The 2010 Broad Prize

    Science.gov (United States)

    Education Digest: Essential Readings Condensed for Quick Review, 2011

    2011-01-01

    A new data analysis, based on data collected as part of The Broad Prize process, provides insights into which large urban school districts in the United States are doing the best job of educating traditionally disadvantaged groups: African-American, Hispanics, and low-income students. Since 2002, The Eli and Edythe Broad Foundation has awarded The…

  11. Augmenting saturated LTP by broadly spaced episodes of theta-burst stimulation in hippocampal area CA1 of adult rats and mice.

    Science.gov (United States)

    Cao, Guan; Harris, Kristen M

    2014-10-15

    Hippocampal long-term potentiation (LTP) is a model system for studying cellular mechanisms of learning and memory. Recent interest in mechanisms underlying the advantage of spaced over massed learning has prompted investigation into the effects of distributed episodes of LTP induction. The amount of LTP induced in hippocampal area CA1 by one train (1T) of theta-burst stimulation (TBS) in young Sprague-Dawley rats was further enhanced by additional bouts of 1T given at 1-h intervals. However, in young Long-Evans (LE) rats, 1T did not initially saturate LTP. Instead, a stronger LTP induction paradigm using eight trains of TBS (8T) induced saturated LTP in hippocampal slices from both young and adult LE rats as well as adult mice. The saturated LTP induced by 8T could be augmented by another episode of 8T following an interval of at least 90 min. The success rate across animals and slices in augmenting LTP by an additional episode of 8T increased significantly with longer intervals between the first and last episodes, ranging from 0% at 30- and 60-min intervals to 13-66% at 90- to 180-min intervals to 90-100% at 240-min intervals. Augmentation above initially saturated LTP was blocked by the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist D-2-amino-5-phosphonovaleric acid (D-APV). These findings suggest that the strength of induction and interval between episodes of TBS, as well as the strain and age of the animal, are important components in the augmentation of LTP. PMID:25057146

  12. Coaxial foilless diode

    OpenAIRE

    Long Kong; QingXiang Liu; XiangQiang Li; ShaoMeng Wang

    2014-01-01

    A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode par...

  13. TP Diode Laser

    OpenAIRE

    Lamine, Brahim; Maître, Agnès; Schwob, Catherine

    2011-01-01

    Master Ce TP consiste à étudier des éléments optoélectroniques courants (diode laser, diode électro-luminescente, photodiode, capteur CCD). Il est axé sur les diodes laser et leurs caractéristiques utilisées dans les télécommunications et la spectroscopie.

  14. An all-silicon passive optical diode.

    Science.gov (United States)

    Fan, Li; Wang, Jian; Varghese, Leo T; Shen, Hao; Niu, Ben; Xuan, Yi; Weiner, Andrew M; Qi, Minghao

    2012-01-27

    A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input power is higher than the forward input. The silicon optical diode is ultracompact and is compatible with current complementary metal-oxide semiconductor processing. PMID:22194410

  15. Schottky barrier diode and method thereof

    Science.gov (United States)

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

    2008-01-01

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

  16. Wavelength beam combining of a 980-nm tapered diode laser bar in an external cavity

    DEFF Research Database (Denmark)

    Vijayakumar, Deepak; Jensen, Ole Bjarlin; Thestrup Nielsen, Birgitte

    2010-01-01

    4.0 nm between the emitters. An output power of 9 W has been achieved at an operating current of 30 A. The combined beam had an M2 value (1/e2) of 5.3 along the slow axis which is comparable to that of a single tapered emitter on the laser bar. The overall beam combining efficiency was measured to......High power diode lasers are used in a large number of applications. A limiting factor for more widespread use of broad area lasers is the poor beam quality. Gain guided tapered diode lasers are ideal candidates for industrial applications that demands watt level output power with good beam quality...

  17. Security Applications of Diodes with Unique Current-Voltage Characteristics

    Science.gov (United States)

    Rührmair, Ulrich; Jaeger, Christian; Hilgers, Christian; Algasinger, Michael; Csaba, György; Stutzmann, Martin

    Diodes are among the most simple and inexpensive electric components. In this paper, we investigate how random diodes with irregular I(U) curves can be employed for crypto and security purposes. We show that such diodes can be used to build Strong Physical Unclonable Functions (PUFs), Certificates of Authenticity (COAs), and Physically Obfuscated Keys (POKs), making them a broadly usable security tool. We detail how such diodes can be produced by an efficient and inexpensive method known as ALILE process. Furthermore, we present measurement data from real systems and discuss prototypical implementations. This includes the generation of helper data as well as efficient signature generation by elliptic curves and 2D barcode generation for the application of the diodes as COAs.

  18. Silicon diode dosimetry

    International Nuclear Information System (INIS)

    The theory of silicon dosimetry is briefly reviewed with respect to operation of these diodes without reverse bias in the short-circuit current mode. The problems of temperature dependence, radiation damage, and the dependence on photon energy are discussed. Various applications of the diodes to practical radiation dosimetry are then described with a view toward pointing out the pitfalls as well as the advantages of using these diodes for dosimetry. (author)

  19. Silicon diode dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, R.L.; Ekstrand, K.E. (Wake Forest Univ., Winston-Salem, NC (USA). Bowman Gray School of Medicine)

    1982-11-01

    The theory of silicon dosimetry is briefly reviewed with respect to operation of these diodes without reverse bias in the short-circuit current mode. The problems of temperature dependence, radiation damage, and the dependence on photon energy are discussed. Various applications of the diodes to practical radiation dosimetry are then described with a view toward pointing out the pitfalls as well as the advantages of using these diodes for dosimetry.

  20. Generation of incoherent light from a laser diode based on the injection of an emission from a superluminescent diode

    CERN Document Server

    Takamizawa, Akifumi; Ikegami, Takeshi

    2013-01-01

    In this study, incoherent light with a spectral linewidth of 7 nm and 140 mW of power was generated from a laser diode into which incoherent light emitted from a superluminescent diode was injected with 2.7 mW of power. The spectral linewidth of the light from the laser diode was broadened to 12 nm when the diode's output power was reduced to 15 mW. In the process of transformation from single-mode laser light to incoherent light with a broad spectrum by increasing injection-light power, multimode laser oscillation and a noisy spectrum were found in the light from the laser diode. This optical system can be used not only for amplification of incoherent light but also as a coherence-convertible light source.

  1. High repetition rate intense ion beam diode

    International Nuclear Information System (INIS)

    A magnetically insulated ion beam diode with a gas-breakdown plasma anode has been successfully developed recently. In this paper, the authors report the experiment results of operating a version of this diode at a 1-Hz repetition rate. Intense ion beams (100ns, 200Kv and 20kA per pulse) are generated by using an inductive voltage to breakdown an annular hydrogen gas puff (8.5cm mean radius, and 160cm2 in area), and magnetically driving the resulting plasma toward a magnetically insulated accelerating gap. The high voltage pulses on the accelerating gap are supplied using two thyratron switch chassises which are connected to the diode through a series of capacitors coupled with saturable inductors. To understand the operation of the diode, the anode plasma source and the extracted ion beams are characterized by using various diagnostics

  2. Dual-Wavelength Internal-Optically-Pumped Semiconductor Laser Diodes

    Science.gov (United States)

    Green, Benjamin

    Dual-wavelength laser sources have various existing and potential applications in wavelength division multiplexing, differential techniques in spectroscopy for chemical sensing, multiple-wavelength interferometry, terahertz-wave generation, microelectromechanical systems, and microfluidic lab-on-chip systems. In the drive for ever smaller and increasingly mobile electronic devices, dual-wavelength coherent light output from a single semiconductor laser diode would enable further advances and deployment of these technologies. The output of conventional laser diodes is however limited to a single wavelength band with a few subsequent lasing modes depending on the device design. This thesis investigates a novel semiconductor laser device design with a single cavity waveguide capable of dual-wavelength laser output with large spectral separation. The novel dual-wavelength semiconductor laser diode uses two shorter- and longer-wavelength active regions that have separate electron and hole quasi-Fermi energy levels and carrier distributions. The shorter-wavelength active region is based on electrical injection as in conventional laser diodes, and the longer-wavelength active region is then pumped optically by the internal optical field of the shorter-wavelength laser mode, resulting in stable dual-wavelength laser emission at two different wavelengths quite far apart. Different designs of the device are studied using a theoretical model developed in this work to describe the internal optical pumping scheme. The carrier transport and separation of the quasi-Fermi distributions are then modeled using a software package that solves Poisson's equation and the continuity equations to simulate semiconductor devices. Three different designs are grown using molecular beam epitaxy, and broad-area-contact laser diodes are processed using conventional methods. The modeling and experimental results of the first generation design indicate that the optical confinement factor of the

  3. Frequency Comb Assisted Broadband Precision Spectroscopy with Cascaded Diode Lasers

    CERN Document Server

    Liu, Junqiu; Pfeiffer, Martin H P; Kordts, Arne; Kamel, Ayman N; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J

    2016-01-01

    Frequency comb assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this letter we present a novel method using cascaded frequency agile diode lasers, which allows extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy and in particular it enables to characterize the dispersion of integrated microresonators up to the fourth order.

  4. An All-Silicon Passive Optical Diode

    OpenAIRE

    Fan, Li; Wang, Jian; Varghese, Leo T.; Shen, Hao; Niu, Ben; Xuan, Yi; Weiner, Andrew M.; Qi, Minghao

    2012-01-01

    A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input pow...

  5. Smooth bumps in H/V curves over a broad area from single-station ambient noise recordings are meaningful and reveal the importance of Q in array processing: The Boumerdes (Algeria) case

    Science.gov (United States)

    Guillier, B.; Chatelain, J.-L.; Hellel, M.; Machane, D.; Mezouer, N.; Ben Salem, R.; Oubaiche, E. H.

    2005-12-01

    Single-station H/V curves from ambient noise recordings in Boumerdes (Algeria) show smooth bumps around 1 and 3 Hz. A complementary microtremor study, based on two 34 and 134-meter aperture arrays, evidences that these bumps are indeed real peaks produced by two strong VS contrasts at 37 and 118 meters depth, strongly smoothed by very high S-wave attenuation in the two sedimentary layers. These two H/V bumps, observed over a broad area, are meaningful and reveal the importance of Q in S-wave velocity modeling from microtremor array data processing. It also appears that Tertiary rocks should be, at least in some cases, taken into account, together with the Quaternary sediments, to explain single-station H/V frequency peaks, and therefore that considering only the first 30 m of soil for VS amplification evaluation, as usually recommended, sometimes leads to flaky results by artificially eliminating non-explained low-frequency peaks from the analysis.

  6. Triaxial diode on HYDRAMITE

    International Nuclear Information System (INIS)

    In 1982, members of Sandia National Laboratories' Department 1230 performed triaxial diode experiments on the HYDRAMITE accelerator. These experiments demonstrated the viability of the triaxial concept, and established the multiple, concentric diode (several, nested, triaxial diodes) as the leading candidate for the radiation-production diode for the Saturn accelerator. A triaxial diode consists of three, coaxial cylinders and a perpendicular, planar anode connecting the downstream ends of the inner and outer cylinders. The intermediate cylinder is the cathode, and the space between the end of the cathode and the planar anode is the axial, anode-cathode gap. HYDRAMITE, with a long self-magnetically-insulated transmission line, provided the electrical pulse to drive the triaxial diode. A post-hole convolute inside the diode housing split the incoming, electromagnetic wave into the two waves needed to feed the triaxial diode. An inductively-corrected, vacuum-voltage monitor measured the diode voltage, and B dot probes and Rogowski coils measured all the anode and cathode currents. Nuclear activation measurements indicated that less than 0.5% of the diode current consisted of protons moving from the anode to the cathode, and particle-in-cell computer simulations support this measurement. Moreover, the impedance was consistent with the cathode tip emitting in the one-dimensional, space-charge-limited mode with unipolar flow. Although the beam deposited enough energy in the anode to generate an anode plasma, probably the electrical pulse was too short for the plasma to form and begin emitting ions into the anode-cathode gap. Finally, no charge flowed in the inner radial gap, and the outer gap current, which was constant from shot to shot, probably originated from the post-hole convolute. 35 refs., 40 figs

  7. Powerful infrared emitting diodes

    Directory of Open Access Journals (Sweden)

    Kogan L. M.

    2012-02-01

    Full Text Available Powerful infrared LEDs with emission wavelength 805 ± 10, 870 ± 20 and 940 ± 10 nm developed at SPC OED "OPTEL" are presented in the article. The radiant intensity of beam diode is under 4 W/sr in the continuous mode and under 100 W/sr in the pulse mode. The radiation power of wide-angle LEDs reaches 1 W in continuous mode. The external quantum efficiency of emission IR diodes runs up to 30%. There also has been created infrared diode modules with a block of flat Fresnel lenses with radiant intensity under 70 W/sr.

  8. The influence of edge effects on the determination of the doping profile of silicon pad diodes

    OpenAIRE

    Hufschmidt, M.; Fretwurst, E.; Garutti, E.; Klanner, R.; Kopsalis, I.; Schwandt, J.

    2016-01-01

    Edge effects for square p+n pad diodes with guard rings, fabricated on high-ohmic silicon, are investigated. Using capacitance-voltage measurements of two pad diodes with different areas, the planar and the edge contributions to the diode capacitance are determined separately. It is shown that the doping concentration derived from the capacitance-voltage measurements with and without edge corrections differ significantly. After the edge correction, the bulk doping of the pad diodes is found t...

  9. Chemically modulated graphene diodes.

    Science.gov (United States)

    Kim, Hye-Young; Lee, Kangho; McEvoy, Niall; Yim, Chanyoung; Duesberg, Georg S

    2013-05-01

    We report the manufacture of novel graphene diode sensors (GDS), which are composed of monolayer graphene on silicon substrates, allowing exposure to liquids and gases. Parameter changes in the diode can be correlated with charge transfer from various adsorbates. The GDS allows for investigation and tuning of extrinsic doping of graphene with great reliability. The demonstrated recovery and long-term stability qualifies the GDS as a new platform for gas, environmental, and biocompatible sensors. PMID:23547771

  10. Precision UV laser scribing for cleaving mirror facets of GaN-based laser diodes

    Science.gov (United States)

    Krüger, O.; Kang, J.-H.; Spevak, M.; Zeimer, U.; Einfeldt, S.

    2016-04-01

    Laser scribing with a nanosecond-pulsed UV laser operating at 355 nm was used to create precise perforation for die separation of GaN-based laser diodes. Machining depth of single- and multiple-pass scribing was investigated. For pulse energies between 1 and 45 µJ at a pulse repetition frequency of 20 kHz and single scan at 100 mm/min, scribe depths from 15 to 180 µm were obtained. Processing parameters were adjusted to minimize the formation of microcracks due to laser-induced local heating. By using the laser skip-and-scribe technique, the propagation of the cleavage plane could be controlled, irregular breaking could be minimized, and die yield could be improved. Smooth mirror facets with low density of terraces were formed by cleaving. In the vicinity of the laser-treated zone, no detrimental effects on the crystal quality of the multi-quantum wells could be detected by cathodoluminescence. The electro-optical characteristics of broad-area laser diodes fabricated by the laser-assisted process were similar to the ones fabricated using the conventional diamond-tip edge-scribing technique that suffers from low die yield. Our results demonstrate that nanosecond-pulsed UV laser scribing followed by cleaving is a powerful technique for the formation of mirror facets of GaN-based laser diodes.

  11. Magnetically insulated H- diodes

    International Nuclear Information System (INIS)

    At the Univ. of California, Irvine, the authors have been studying the production of intense H- beams using pulse power techniques for the past 7 years. Previously, current densities of H- ions for various diode designs at UCI have been a few A/cm2. Recently, they have developed diodes similar to the coaxial design of the Lebedev Physical Institute, Moscow, USSR, where current densities of up to 200 A/cm2 were reported using nuclear activation of a carbon target. In experiments at UCI employing the coaxial diode, current densities of up to 35 A/cm2 from a passive polyethylene cathode loaded with TiH2 have been measured using a pinhole camera and CR-39 track recording plastic. The authors have also been working on a self-insulating, annular diode which can generate a directed beam of H- ions. In the annular diode experiments a plasma opening switch was used to provide a prepulse and a current path which self-insulated the diode. These experiments were done on the machine APEX, a 1 MV, 50 ns, 7 Ω pulseline with a unipolar negative prepulse of ∼ 100 kV and 400 ns duration. Currently, the authors are modifying the pulseline to include an external LC circuit which can generate a bipolar, 150 kV, 1 μs duration prepulse (similar prepulse characteristic as in the Lebedev Institute experiments cited above)

  12. Light-emitting Diodes

    Science.gov (United States)

    Opel, Daniel R.; Hagstrom, Erika; Pace, Aaron K.; Sisto, Krisanne; Hirano-Ali, Stefanie A.; Desai, Shraddha

    2015-01-01

    Background: In the early 1990s, the biological significance of light-emitting diodes was realized. Since this discovery, various light sources have been investigated for their cutaneous effects. Study design: A Medline search was performed on light-emitting diode lights and their therapeutic effects between 1996 and 2010. Additionally, an open-label, investigator-blinded study was performed using a yellow light-emitting diode device to treat acne, rosacea, photoaging, alopecia areata, and androgenetic alopecia. Results: The authors identified several case-based reports, small case series, and a few randomized controlled trials evaluating the use of four different wavelengths of light-emitting diodes. These devices were classified as red, blue, yellow, or infrared, and covered a wide range of clinical applications. The 21 patients the authors treated had mixed results regarding patient satisfaction and pre- and post-treatment evaluation of improvement in clinical appearance. Conclusion: Review of the literature revealed that differing wavelengths of light-emitting diode devices have many beneficial effects, including wound healing, acne treatment, sunburn prevention, phototherapy for facial rhytides, and skin rejuvenation. The authors’ clinical experience with a specific yellow light-emitting diode device was mixed, depending on the condition being treated, and was likely influenced by the device parameters. PMID:26155326

  13. Diode lasers and photonic integrated circuits

    CERN Document Server

    Coldren, Larry A; Mashanovitch, Milan L

    2011-01-01

    Diode Lasers and Photonic Integrated Circuits, Second Edition provides a comprehensive treatment of optical communication technology, its principles and theory, treating students as well as experienced engineers to an in-depth exploration of this field. Diode lasers are still of significant importance in the areas of optical communication, storage, and sensing. Using the the same well received theoretical foundations of the first edition, the Second Edition now introduces timely updates in the technology and in focus of the book. After 15 years of development in the field, this book wil

  14. Barrier inhomogeneities limited current and 1/f noise transport in GaN based nanoscale Schottky barrier diodes.

    Science.gov (United States)

    Kumar, Ashutosh; Heilmann, M; Latzel, Michael; Kapoor, Raman; Sharma, Intu; Göbelt, M; Christiansen, Silke H; Kumar, Vikram; Singh, Rajendra

    2016-01-01

    The electrical behaviour of Schottky barrier diodes realized on vertically standing individual GaN nanorods and array of nanorods is investigated. The Schottky diodes on individual nanorod show highest barrier height in comparison with large area diodes on nanorods array and epitaxial film which is in contrast with previously published work. The discrepancy between the electrical behaviour of nanoscale Schottky diodes and large area diodes is explained using cathodoluminescence measurements, surface potential analysis using Kelvin probe force microscopy and 1ow frequency noise measurements. The noise measurements on large area diodes on nanorods array and epitaxial film suggest the presence of barrier inhomogeneities at the metal/semiconductor interface which deviate the noise spectra from Lorentzian to 1/f type. These barrier inhomogeneities in large area diodes resulted in reduced barrier height whereas due to the limited role of barrier inhomogeneities in individual nanorod based Schottky diode, a higher barrier height is obtained. PMID:27282258

  15. Design of a large-area CsI(Tl) photo-diode array for explosives detection by neutron-activation gamma-ray spectroscopy

    International Nuclear Information System (INIS)

    A design for a large area, position-sensitive gamma-ray spectrometer for use in imaging explosive materials is described. The design has been optimised for use in the energy range from 2 to 12 MeV. At 5 MeV, the spectral resolution of each CsI(Tl)-photodiode pixel is better than 3% FWHM. The multi-element detector system, when used in conjunction with a coded-aperture mask, is able to provide a 'multi-colour' image of the scene when illuminated by a neutron source. The feasibility of using such a system to identify the unique elemental composition and location of the explosive materials is discussed

  16. Deterministic polarization chaos from a laser diode

    CERN Document Server

    Virte, Martin; Thienpont, Hugo; Sciamanna, Marc

    2014-01-01

    Fifty years after the invention of the laser diode and fourty years after the report of the butterfly effect - i.e. the unpredictability of deterministic chaos, it is said that a laser diode behaves like a damped nonlinear oscillator. Hence no chaos can be generated unless with additional forcing or parameter modulation. Here we report the first counter-example of a free-running laser diode generating chaos. The underlying physics is a nonlinear coupling between two elliptically polarized modes in a vertical-cavity surface-emitting laser. We identify chaos in experimental time-series and show theoretically the bifurcations leading to single- and double-scroll attractors with characteristics similar to Lorenz chaos. The reported polarization chaos resembles at first sight a noise-driven mode hopping but shows opposite statistical properties. Our findings open up new research areas that combine the high speed performances of microcavity lasers with controllable and integrated sources of optical chaos.

  17. Physical based Schottky barrier diode modeling for THz applications

    DEFF Research Database (Denmark)

    Yan, Lei; Krozer, Viktor; Michaelsen, Rasmus Schandorph; Djurhuus, Torsten; Johansen, Tom Keinicke

    2013-01-01

    In this work, a physical Schottky barrier diode model is presented. The model is based on physical parameters such as anode area, Ohmic contact area, doping profile from epitaxial (EPI) and substrate (SUB) layers, layer thicknesses, barrier height, specific contact resistance, and device...... temperature. The effects of barrier height lowering, nonlinear resistance from the EPI layer, and hot electron noise are all included for accurate characterization of the Schottky diode. To verify the diode model, measured I-V and C-V characteristics are compared with the simulation results. Due to the lack...

  18. Integrating Hot and Cool Intelligences: Thinking Broadly about Broad Abilities

    Directory of Open Access Journals (Sweden)

    W. Joel Schneider

    2016-01-01

    Full Text Available Although results from factor-analytic studies of the broad, second-stratum abilities of human intelligence have been fairly consistent for decades, the list of broad abilities is far from complete, much less understood. We propose criteria by which the list of broad abilities could be amended and envision alternatives for how our understanding of the hot intelligences (abilities involving emotionally-salient information and cool intelligences (abilities involving perceptual processing and logical reasoning might be integrated into a coherent theoretical framework.

  19. Coaxial diode and vircator

    Science.gov (United States)

    Liu, Guozhi; Qiu, Shi; Wang, Hongjun; Huang, Wenhua; Wang, Feng

    1997-10-01

    The experimental and theoretical results of coaxial diode and the theoretical results of coaxial vircator are presented in this paper. The cathode is a cold, field- emitting graphite ring and needle-shaped copper applied to a grounded cylinder. The anode is a semi-transparent cylinder located inside of, and concentric to the cathode cylinder. The anode cylinder is pulsed positive. The coaxial vircator generates microwave by injecting a radial electron beam into cylinder such that the space-charge limited current is exceeded. A virtual cathode forms and oscillates in radial position and amplitude, generating microwaves which are extracted by an attached waveguide with a circular cross- section. Analytic and PIC simulations were used to study coaxial diode and vircator, with aid of the two dimensional PIC code, KARAT. The comparisons between the theoretical and the experimental results for a coaxial diode are presented.

  20. Pyrolyzed carbon film diodes.

    Science.gov (United States)

    Morton, Kirstin C; Tokuhisa, Hideo; Baker, Lane A

    2013-11-13

    We have previously reported pyrolyzed parylene C (PPC) as a conductive carbon electrode material for use with micropipets, atomic force microscopy probes, and planar electrodes. Advantages of carbon electrode fabrication from PPC include conformal coating of high-aspect ratio micro/nanoscale features and the benefits afforded by chemical vapor deposition of carbon polymers. In this work, we demonstrate chemical surface doping of PPC through the use of previously reported methods. Chemically treated PPC films are characterized by multiple spectroscopic and electronic measurements. Pyrolyzed parylene C and doped PPC are used to construct diodes that are examined as both p-n heterojunction and Schottky barrier diodes. Half-wave rectification is achieved with PPC diodes and demonstrates the applicability of PPC as a conductive and semiconductive material in device fabrication. PMID:24090451

  1. Hyperchaos via X-Diode

    DEFF Research Database (Denmark)

    Lindberg, Erik; Tamasevicius, A.; Cenys, A.;

    1998-01-01

    A Chaos diode (X-diode) with a hysteric current-voltage characteristic has been used to generate hyperchaotic oscillations characterized with multiple positive Lyapunov exponents. The hyperchaotic oscillators comprise a X-diode in parallel with an M'th order LC loop (M.GE.4). Numerical simulations...

  2. A photon thermal diode.

    Science.gov (United States)

    Chen, Zhen; Wong, Carlaton; Lubner, Sean; Yee, Shannon; Miller, John; Jang, Wanyoung; Hardin, Corey; Fong, Anthony; Garay, Javier E; Dames, Chris

    2014-01-01

    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

  3. Wavelength stabilized multi-kW diode laser systems

    Science.gov (United States)

    Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

    2015-03-01

    We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

  4. 100 Years of the Physics of Diodes

    Science.gov (United States)

    Luginsland, John

    2013-10-01

    The Child-Langmuir Law (CL), discovered 100 years ago, gives the maximum current that can be transported across a planar diode in the steady state. As a quintessential example of the impact of space-charge shielding near a charged surface, it is central to the studies of high current diodes, such as high power microwave sources, vacuum microelectronics, electron and ion sources, and high current drivers used in high-energy density physics experiments. CL remains a touchstone of fundamental sheath physics, including contemporary studies of nano-scale quantum diodes and plasmonic devices. Its solid state analog is the Mott-Gurney law, governing the maximum charge injection in solids, such as organic materials and other dielectrics, which is important to energy devices, such as solar cells and light-emitting diodes. This paper reviews the important advances in the physics of diodes since the discovery of CL, including virtual cathode formation and extension of CL to multiple dimensions, to the quantum regime, and to ultrafast processes. We will review the influence of magnetic fields, multiple species in bipolar flow, electromagnetic and time dependent effects in both short pulse and high frequency THz limits, and single electron regimes. Transitions from various emission mechanisms (thermionic, field, and photo-emission) to the space charge limited state (CL) will be addressed, especially highlighting important simulation and experimental developments in selected contemporary areas of study. This talk will stress the fundamental physical links between the physics of beams to limiting currents in other areas, such as low temperature plasmas, laser plasmas, and space propulsion. Also emphasized is the role of non-equilibrium phenomena associated with materials and plasmas in close contact. Work supported by the Air Force Office of Scientific Research.

  5. Fast-Recovery, High-Voltage Power Diode

    Science.gov (United States)

    Sundberg, G.; Berman, A.; Balodis, V.; Gaugh, C.; Duffin, J.; Karatnicki, H.; Larson, E.

    1985-01-01

    New family of fast-recovery high-voltage power diodes compatible with D60T and D7ST transistors developed. Have wide range of applications in spacecraft and aircraft electrical distribution equipment, dc/dc inverters, and ac motor controllers for high-horsepower electric motors operating from 480-volt ac lines. Fast-Recovery 1,200-V Power Diodes use chip of hexagonal geometry to maximize effective silicon area.

  6. The use of diode laser in dentistry - two cases report

    OpenAIRE

    Papakoca, Kiro; Dimova, Cena; Kovacevska, Ivona; Papakoca, Gordana; Radeska, Ana

    2012-01-01

    Introduction: We present our clinical cases, the use of diode laser in patients with gingival hypertrophy and lower semi impact third molar. An indication for application of our diode laser as in our cases is: At first – periodontal surgery, gingival depigmentation and decontamination and curettage of the sulcus, In the other case, in the area of the third molar, we made operculectomy, circumcision and we got excellent hemostasis. Methods: The patient, a 64 year ...

  7. Properties of high ν/γ diodes using thin foil anodes

    International Nuclear Information System (INIS)

    Properties of high ν/γ diodes using thin anode foils have been studied both experimentally and theoretically. It has been demonstrated that these diodes are very useful in accelerating the pinch formation, in production of intense ion beams from the pinch area and in enhanced energy deposition in the focal area of the electron beam

  8. Theoretical motivation of indented-anode diode for HERMES III

    International Nuclear Information System (INIS)

    HERMES III is an accelerator being designed as a uniform source of flash γ-rays. Diode designs are needed that efficiently convert electrical energy to γ-ray energy and that distribute that γ-ray energy uniformly over a large area. Code simulations of coaxial diode designs show that the electron beam in the anode-cathode gap forms a weak pinch, which results in excessive on-axis radiation. In this report, a diode concept is developed that can reduce the pinch at the anode converter and thus can improve the uniformity of the radiation. This concept employs an indentation in the anode to passively control the beam. For this diode, electron flow, impedance models, and scaling laws of the diode behavior as a function of the geometric parameters of the diode, voltage, and current are developed. We evaluate the subsequent radiation output and improvement in radiation uniformity relative to diodes with planar anodes. The analysis shows that not only is the indented-anode capable of significantly improving radiation uniformity, but that it is also capable of reducing the width of the radiation pulse

  9. Spin-Wave Diode

    Science.gov (United States)

    Lan, Jin; Yu, Weichao; Wu, Ruqian; Xiao, Jiang

    2015-10-01

    A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound states in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. Our findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.

  10. Biointegrated flexible inorganic light emitting diodes

    OpenAIRE

    Lee, Keon Jae

    2012-01-01

    Min Koo, So Young Park, Keon Jae LeeDepartment of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon, Republic of KoreaAbstract: The use of light-emitting diodes (LEDs) as therapeutic tools has been actively studied over the past few decades due to their advantages of high safety, low cost, excellent portability, and wide bandwidth. In addition, their application in biomedical fields has been expanded to such areas as nerve stimulation, ...

  11. Study on Light Extraction from GaN-based Green Light-Emitting Diodes Using Anodic Aluminum Oxide Pattern and Nanoimprint Lithography

    OpenAIRE

    Shengxiang Jiang; Yulong Feng; Zhizhong Chen; Lisheng Zhang; Xianzhe Jiang; Qianqian Jiao; Junze Li; Yifan Chen; Dongsan Li; Lijian Liu; Tongjun Yu; Bo Shen; Guoyi Zhang

    2016-01-01

    An anodic aluminum oxide (AAO) patterned sapphire substrate, with the lattice constant of 520 ± 40 nm, pore dimension of 375 ± 50 nm, and height of 450 ± 25 nm was firstly used as a nanoimprint lithography (NIL) stamp and imprinted onto the surface of the green light-emitting diode (LED). A significant light extraction efficiency (LEE) was improved by 116% in comparison to that of the planar LED. A uniform broad protrusion in the central area and some sharp lobes were also obtained in the ang...

  12. Diamond Schottky barrier diodes

    OpenAIRE

    Brezeanu, Mihai

    2008-01-01

    Research on wide band gap semiconductors suitable for power electronic devices has spread rapidly in the last decade. The remarkable results exhibited by silicon carbide (SiC) Schottky batTier diodes (SBDs), commercially available since 2001, showed the potential of wide band gap semiconductors for replacing silicon (Si) in the range of medium to high voltage applications, where high frequency operation is required. With superior physical and electrical properties, diamond beca...

  13. Graphite based Schottky diodes

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Grym, Jan

    Bratislava: Slovak Expert Group of Solid State Chemistry and Physics , 2011 - (Koman, M.; Mikloš, D.), s. 74-75 ISBN 978-80-8134-002-4. [21th Joint Seminar Development of Materials Science in Research and Education . Kežmarské Žlaby (SK), 29.08.2011-02.09.2011] Institutional research plan: CEZ:AV0Z20670512 Keywords : Schottky diode * Graphite * InP Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  14. Areas of Active Tectonic Uplift Are Sensitive to Small Changes in Fold Orientations within a Broad Zone of Left-lateral Transpression and Shearing, Dominican Republic and Haiti (Hispaniola)

    Science.gov (United States)

    Ambrosius, I.; Mann, P.

    2014-12-01

    Previous GPS studies have shown that the island of Hispaniola is a 250 km-wide zone of active, east-west, left-lateral shearing along two major strike-slip zones: the Septentrional-Oriente fault zone through the northern part of the island and the Enriquillo-Plantain Garden fault zone (EPGFZ) through the southern part of the island. The total interplate rate distributed on both faults is 21 mm/yr. Using a high-resolution DEM, we constructed fluvial channel profiles across transpression-related folds of late Miocene to recent age in the area of central and southern Dominican Republic and Haiti to determine controls of areas of relatively high, moderate, and slow uplift inferred from fluvial channel profiles. Fold axes in this area extend for 50-150 km and exhibit two different trends: 1) folds that occupy the area of the Sierra de Neiba-Chaine des Matheux north of the Enriquillo-Cul-de-Sac Valley and EPGFZ and folds that occupy the area of the Sierra de Bahoruco-Massif de la Selle all exhibit more east-west fold axes trending 110; 2) folds that occupy the area northwest of the EPGFZ in the western Chaine des Matheux and Sierra de Neiba all exhibit fold axes with more northwest trends of 125. River channel profiles show that the second group of more northwesterly-trending fold axes show relatively higher rates of tectonic uplift based on their convex-upward river profiles. Our interpretation for regional variations in river profiles and inferred uplift is that uplift is more pronounced on fold axes trending 15 degrees more to the northwest because their axes are more oblique to the interplate direction of east-west shearing. Longterm uplift rates previously measured from a stairstep of late Quaternary coral terraces at the plunging nose of the westernmost Chaine des Matheux have been previously shown to be occurring at a rate of 0.19 mm/yr. Onland exposures of Holocene corals are found only on one locality within the southern area of folds 30 km west of the epicenter

  15. Diode, transistor & fet circuits manual

    CERN Document Server

    Marston, R M

    2013-01-01

    Diode, Transistor and FET Circuits Manual is a handbook of circuits based on discrete semiconductor components such as diodes, transistors, and FETS. The book also includes diagrams and practical circuits. The book describes basic and special diode characteristics, heat wave-rectifier circuits, transformers, filter capacitors, and rectifier ratings. The text also presents practical applications of associated devices, for example, zeners, varicaps, photodiodes, or LEDs, as well as it describes bipolar transistor characteristics. The transistor can be used in three basic amplifier configuration

  16. Magnetically insulated helium ion diode

    International Nuclear Information System (INIS)

    A gas-puff magnetically insulated ion diode is under development as a pulsed source of high-energy alpha particles for magnetic fusion experiments. The diode is patterned after the Cornell gas-puff diode [J. B. Greenly, M. Ueda, G. D. Rondeau, and D. A. Hammer, J. Appl. Phys. 63, 1872 (1988)], but with modifications to accomodate higher voltages (2 one meter downstream from the source; in our first test of the new source, a helium beam was obtained

  17. Compact, efficient, scalable neodymium laser co-doped with activator ions and pumped by visible laser diodes

    Science.gov (United States)

    Scheps, Richard

    1994-02-01

    Efficient, low threshold laser emission from a laser crystal doped with chromium and neodymium ions is obtained when pumped by visible laser diodes in the range of 610 nm to 680 nm. A typical laser Cr,Nd:GSGG crystal having an extraordinarily broad absorption bandwidth allows high pump efficiencies when using visible laser diodes, particularly in comparison to the Nd:YAG laser. The broad absorption bandwidth tolerance of the Cr,Nd:GSGG crystal to the pumping wavelengths allows visible diode pumping of the neodymium transition without regard to the wavelength of the visible diodes. Longitudinal or end-pumping to take advantage of the emission properties of the visible laser diodes, a nearly hemispherical laser resonator configuration and other co-doped Cr,Nd laser host materials are disclosed.

  18. Magnetically insulated helium ion diode

    Energy Technology Data Exchange (ETDEWEB)

    Wessel, F.J.; Heidbrink, W.W.; Drum, S.; Hoang, K.; Layton, P. (Physics Department, University of California, Irvine, California 92717 (US))

    1990-01-01

    A gas-puff magnetically insulated ion diode is under development as a pulsed source of high-energy alpha particles for magnetic fusion experiments. The diode is patterned after the Cornell gas-puff diode (J. B. Greenly, M. Ueda, G. D. Rondeau, and D. A. Hammer, J. Appl. Phys. {bold 63}, 1872 (1988)), but with modifications to accomodate higher voltages ({lt}1 MeV) and operation in helium. The diode is designed to yield current densities approaching 200 A/cm{sup 2} one meter downstream from the source; in our first test of the new source, a helium beam was obtained.

  19. Overview on new diode lasers for defense applications

    Science.gov (United States)

    Neukum, Joerg

    2012-11-01

    Diode lasers have a broad wavelength range, from the visible to beyond 2.2μm. This allows for various applications in the defense sector, ranging from classic pumping of DPSSL in range finders or target designators, up to pumping directed energy weapons in the 50+ kW range. Also direct diode applications for illumination above 1.55μm, or direct IR countermeasures are of interest. Here an overview is given on some new wavelengths and applications which are recently under discussion. In this overview the following aspects are reviewed: • High Power CW pumps at 808 / 880 / 940nm • Pumps for DPAL - Diode Pumped Alkali Lasers • High Power Diode Lasers in the range Mini-Bar concept for high brightness fiber coupled modules • The Light Weight Fiber Coupled module based on the Mini-Bar concept Overall, High Power Diode Lasers offer many ways to be used in new applications in the defense market.

  20. ND laser with co-doped ion(s) pumped by visible laser diodes

    Science.gov (United States)

    Scheps, Richard

    1993-04-01

    The 1.06 microns Nd transition in a co-doped Cr,Nd:Gd3Sc2Ga3O12 (Cr,Nd:GSGG) gain element is obtained by diode pumping Cr(3+) at 670 run and produces efficient, low threshold laser operation. Although co-doped Cr,Nd:GSGG was developed for more efficient flashlamp pumping, it has the desirable property of having an extraordinarily broad absorption to allow for efficient diode pumping relative to the ND:YAG laser. The consequent broad bandwidth tolerance of the Cr,Nd:GSGG for the diode pumping radiation allows diode pumping of the 1.06 microns transition without regard to the wavelength of the visible diodes which has the potential for reducing the cost of the semiconductor pump and also demonstrates the extended versatility of these diodes which previously had been restricted to pump the Cr(3+) tunable vibronic lasers. CW and long pulse diode pumping provided pump power levels as high as 300 mW CW and 1 W pulsed. The lowest threshold power was measured at 938 micron W and the highest output power was obtained at 43 mW CW and 173 mW pulsed. The best slope efficiency obtained was 42.1%, 78% of the theoretical maximum. Loss measurements indicate a value of 0.4%/cm.

  1. Broad Diphotons from Narrow States

    CERN Document Server

    An, Haipeng; Zhang, Yue

    2015-01-01

    ATLAS and CMS have each reported a modest diphoton excess consistent with the decay of a broad resonance at ~ 750 GeV. We show how this signal can arise in a weakly coupled theory comprised solely of narrow width particles. In particular, if the decaying particle is produced off-shell, then the associated diphoton resonance will have a broad, adjustable width. We present simplified models which explain the diphoton excess through the three-body decay of a scalar or fermion. Our minimal ultraviolet completion is a weakly coupled and renormalizable theory of a singlet scalar plus a heavy vector-like quark and lepton. The smoking gun of this mechanism is an asymmetric diphoton peak recoiling against missing transverse energy, jets, or leptons.

  2. Cochlear microphonic broad tuning curves

    Science.gov (United States)

    Ayat, Mohammad; Teal, Paul D.; Searchfield, Grant D.; Razali, Najwani

    2015-12-01

    It is known that the cochlear microphonic voltage exhibits much broader tuning than does the basilar membrane motion. The most commonly used explanation for this is that when an electrode is inserted at a particular point inside the scala media, the microphonic potentials of neighbouring hair cells have different phases, leading to cancelation at the electrodes location. In situ recording of functioning outer hair cells (OHCs) for investigating this hypothesis is exceptionally difficult. Therefore, to investigate the discrepancy between the tuning curves of the basilar membrane and those of the cochlear microphonic, and the effect of phase cancellation of adjacent hair cells on the broadness of the cochlear microphonic tuning curves, we use an electromechanical model of the cochlea to devise an experiment. We explore the effect of adjacent hair cells (i.e., longitudinal phase cancellation) on the broadness of the cochlear microphonic tuning curves in different locations. The results of the experiment indicate that active longitudinal coupling (i.e., coupling with active adjacent outer hair cells) only slightly changes the broadness of the CM tuning curves. The results also demonstrate that there is a π phase difference between the potentials produced by the hair bundle and the soma near the place associated with the characteristic frequency based on place-frequency maps (i.e., the best place). We suggest that the transversal phase cancellation (caused by the phase difference between the hair bundle and the soma) plays a far more important role than longitudinal phase cancellation in the broadness of the cochlear microphonic tuning curves. Moreover, by increasing the modelled longitudinal resistance resulting the cochlear microphonic curves exhibiting sharper tuning. The results of the simulations suggest that the passive network of the organ of Corti determines the phase difference between the hair bundle and soma, and hence determines the sharpness of the

  3. Broad-scale sampling of primary freshwater fish populations reveals the role of intrinsic traits, inter-basin connectivity, drainage area and latitude on shaping contemporary patterns of genetic diversity.

    Science.gov (United States)

    Sousa-Santos, Carla; Robalo, Joana I; Pereira, Ana M; Branco, Paulo; Santos, José Maria; Ferreira, Maria Teresa; Sousa, Mónica; Doadrio, Ignacio

    2016-01-01

    Background. Worldwide predictions suggest that up to 75% of the freshwater fish species occurring in rivers with reduced discharge could be extinct by 2070 due to the combined effect of climate change and water abstraction. The Mediterranean region is considered to be a hotspot of freshwater fish diversity but also one of the regions where the effects of climate change will be more severe. Iberian cyprinids are currently highly endangered, with over 68% of the species raising some level of conservation concern. Methods. During the FISHATLAS project, the Portuguese hydrographical network was extensively covered (all the 34 river basins and 47 sub-basins) in order to contribute with valuable data on the genetic diversity distribution patterns of native cyprinid species. A total of 188 populations belonging to 16 cyprinid species of Squalius, Luciobarbus, Achondrostoma, Iberochondrostoma, Anaecypris and Pseudochondrostoma were characterized, for a total of 3,678 cytochrome b gene sequences. Results. When the genetic diversity of these populations was mapped, it highlighted differences among populations from the same species and between species with identical distribution areas. Factors shaping the contemporary patterns of genetic diversity were explored and the results revealed the role of latitude, inter-basin connectivity, migratory behaviour, species maximum size, species range and other species intrinsic traits in determining the genetic diversity of sampled populations. Contrastingly, drainage area and hydrological regime (permanent vs. temporary) seem to have no significant effect on genetic diversity. Species intrinsic traits, maximum size attained, inter-basin connectivity and latitude explained over 30% of the haplotype diversity variance and, generally, the levels of diversity were significantly higher for smaller sized species, from connected and southerly river basins. Discussion. Targeting multiple co-distributed species of primary freshwater fish allowed

  4. Numerical simulations of novel high-power high-brightness diode laser structures

    Science.gov (United States)

    Boucke, Konstantin; Rogg, Joseph; Kelemen, Marc T.; Poprawe, Reinhart; Weimann, Guenter

    2001-07-01

    One of the key topics in today's semiconductor laser development activities is to increase the brightness of high-power diode lasers. Although structures showing an increased brightness have been developed specific draw-backs of these structures lead to a still strong demand for investigation of alternative concepts. Especially for the investigation of basically novel structures easy-to-use and fast simulation tools are essential to avoid unnecessary, cost and time consuming experiments. A diode laser simulation tool based on finite difference representations of the Helmholtz equation in 'wide-angle' approximation and the carrier diffusion equation has been developed. An optimized numerical algorithm leads to short execution times of a few seconds per resonator round-trip on a standard PC. After each round-trip characteristics like optical output power, beam profile and beam parameters are calculated. A graphical user interface allows online monitoring of the simulation results. The simulation tool is used to investigate a novel high-power, high-brightness diode laser structure, the so-called 'Z-Structure'. In this structure an increased brightness is achieved by reducing the divergency angle of the beam by angular filtering: The round trip path of the beam is two times folded using internal total reflection at surfaces defined by a small index step in the semiconductor material, forming a stretched 'Z'. The sharp decrease of the reflectivity for angles of incidence above the angle of total reflection leads to a narrowing of the angular spectrum of the beam. The simulations of the 'Z-Structure' indicate an increase of the beam quality by a factor of five to ten compared to standard broad-area lasers.

  5. Diode laser applications in urology

    Science.gov (United States)

    Sam, Richard C.; Esch, Victor C.

    1995-05-01

    Diode lasers are air-cooled, efficient, compact devices which have the potential of very low cost when produced in quantity. The characteristics of diode lasers are discussed. Their applications in interstitial thermal treatment of the prostate, and laser ablation of prostate tissues, will be presented.

  6. Prepared and Characteristics of ZnO:YAG/Silicon Nanostructure Diodes Prepared by Ultrasonic Spraying

    OpenAIRE

    Chih-Hung Hsu; Lung-Chien Chen; Jia-Ren Wu

    2014-01-01

    This work presents a novel white light source. An yttrium aluminum garnet (YAG) phosphor incorporated zinc oxide (ZnO) (ZnO:YAG) film is deposited on a silicon substrate by ultrasonic spray pyrolysis to form a nanostructure diode. A nanoflower consisting of a hexagonal nanopetal is formed on the surfaces of the silicon substrate. A white broad band at the room temperature photoluminescence ranging from 420 to 650 nm for the ZnO:YAG/silicon nanostructure diode was observed. The white broad ban...

  7. Light Emitting Diode (LED)

    Science.gov (United States)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique called photodynamic therapy, requires the surgeon to use tiny pinhead-size Light Emitting Diodes (LEDs) (a source releasing long wavelengths of light) to activate light-sensitive, tumor-treating drugs. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can also be used for hours at a time while still remaining cool to the touch. The LED probe consists of 144 tiny pinhead-size diodes, is 9-inches long, and about one-half-inch in diameter. The small balloon aids in even distribution of the light source. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The probe was developed for photodynamic cancer therapy by the Marshall Space Flight Center under a NASA Small Business Innovative Research program grant.

  8. Personal neutron diode dosemeter

    International Nuclear Information System (INIS)

    The control and management of neutron doses, received by workers in nuclear power or research facilities, requires a knowledge of cumulated dose equivalent or dose equivalent rate in real time. Individual dosemeters so far developed for this purpose are scarce and not very satisfactory. Passive dosemeters such as TLD systems based on the albedo effect, nuclear emulsions or solid track detectors, do not give sufficiently accurate measurements. Furthermore, the increase in the quality factor and the more restrictive new ICRP recommendations diminish the maximum admissible threshold making currently used systems obsolete. Other than bubble dosemeter systems, based on thermodynamic effects of a superheated gel, no simple electronic device is available at the present time. The development of diode based dosimetric gamma badges, having a size similar to that of credit cards, has stimulated us to design and develop a personal neutron dosemeter based on a double diode system. The results obtained are very encouraging and practical models should become available in the near future. (author)

  9. Polymer light emitting diodes

    International Nuclear Information System (INIS)

    We study sandwich type semiconducting polymer light emitting diodes; anode/polymer/cathode. ITO is selected as anode, this polymer is a blend of a commercially available polymer with a high hole transport ability: polyvinyl-carbazole and a laser dye: coumarin-515. Magnesium covered with silver is chosen for the anode. We study the influence of polymer thickness and coumarin doping ratio on electroluminescence spectrum, electric characteristics and quantum efficiency. An important drawback is that diodes lifetime remains low. In the second part of our study we determine degradations causes with X-Ray reflectivity experiments. It may be due to ITO very high roughness. We realize a new type of planar electroluminescent device: a channel type electroluminescent device in which polymer layer is inserted into an aluminium channel. Such a device is by far more stable than using classical sandwich structures with the same polymer composition: indeed, charges are generated by internal-field ionization and there is no injection from the electrode to the polymer. This avoids electrochemical reactions at electrodes, thus reducing degradations routes. (author)

  10. A broad-application microchannel-plate detector system for advanced particle or photon detection tasks: large area imaging, precise multi-hit timing information and high detection rate

    International Nuclear Information System (INIS)

    New applications for single particle and photon detection in many fields require both large area imaging performance and precise time information on each detected particle. Moreover, a very high data acquisition rate is desirable for most applications and eventually the detection and imaging of more than one particle arriving within a microsecond is required. Commercial CCD systems lack the timing information whereas other electronic microchannel plate (MCP) read-out schemes usually suffer from a low acquisition rate and complicated and sometimes costly read-out electronics. We have designed and tested a complete imaging system consisting of an MCP position readout with helical wire delay-lines, single-unit amplifier box and PC-controlled time-to-digital converter (TDC) readout. The system is very flexible and can detect and analyse position and timing information at single particle rates beyond 1 MHz. Alternatively, multi-hit events can be collected and analysed at about 20 kHz rate. We discuss the advantages and applications of this technique and then focus on the detector's ability to detect and analyse multiple hits

  11. A broad-application microchannel-plate detector system for advanced particle or photon detection tasks large area imaging, precise multi-hit timing information and high detection rate

    CERN Document Server

    Jagutzki, O; Mergel, V; Schmidt-Böcking, H; Spielberger, L; Spillmann, U; Ullmann-Pfleger, K

    2002-01-01

    New applications for single particle and photon detection in many fields require both large area imaging performance and precise time information on each detected particle. Moreover, a very high data acquisition rate is desirable for most applications and eventually the detection and imaging of more than one particle arriving within a microsecond is required. Commercial CCD systems lack the timing information whereas other electronic microchannel plate (MCP) read-out schemes usually suffer from a low acquisition rate and complicated and sometimes costly read-out electronics. We have designed and tested a complete imaging system consisting of an MCP position readout with helical wire delay-lines, single-unit amplifier box and PC-controlled time-to-digital converter (TDC) readout. The system is very flexible and can detect and analyse position and timing information at single particle rates beyond 1 MHz. Alternatively, multi-hit events can be collected and analysed at about 20 kHz rate. We discuss the advantage...

  12. The influence of edge effects on the determination of the doping profile of silicon pad diodes

    CERN Document Server

    Hufschmidt, M; Garutti, E; Klanner, R; Kopsalis, I; Schwandt, J

    2016-01-01

    Edge effects for square p+n pad diodes with guard rings, fabricated on high-ohmic silicon, are investigated. Using capacitance-voltage measurements of two pad diodes with different areas, the planar and the edge contributions to the diode capacitance are determined separately. It is shown that the doping concentration derived from the capacitance-voltage measurements with and without edge corrections differ significantly. After the edge correction, the bulk doping of the pad diodes is found to be uniform within +/- 1.5%. The voltage dependence of the edge capacitance is compared to the predictions of two simple models.

  13. Built-in hyperspectral camera for smartphone in visible, near-infrared and middle-infrared lights region (third report): spectroscopic imaging for broad-area and real-time componential analysis system against local unexpected terrorism and disasters

    Science.gov (United States)

    Hosono, Satsuki; Kawashima, Natsumi; Wollherr, Dirk; Ishimaru, Ichiro

    2016-05-01

    The distributed networks for information collection of chemical components with high-mobility objects, such as drones or smartphones, will work effectively for investigations, clarifications and predictions against unexpected local terrorisms and disasters like localized torrential downpours. We proposed and reported the proposed spectroscopic line-imager for smartphones in this conference. In this paper, we will mention the wide-area spectroscopic-image construction by estimating 6 DOF (Degrees Of Freedom: parallel movements=x,y,z and rotational movements=θx, θy, θz) from line data to observe and analyze surrounding chemical-environments. Recently, smartphone movies, what were photographed by peoples happened to be there, had worked effectively to analyze what kinds of phenomenon had happened around there. But when a gas tank suddenly blew up, we did not recognize from visible-light RGB-color cameras what kinds of chemical gas components were polluting surrounding atmospheres. Conventionally Fourier spectroscopy had been well known as chemical components analysis in laboratory usages. But volatile gases should be analyzed promptly at accident sites. And because the humidity absorption in near and middle infrared lights has very high sensitivity, we will be able to detect humidity in the sky from wide field spectroscopic image. And also recently, 6-DOF sensors are easily utilized for estimation of position and attitude for UAV (Unmanned Air Vehicle) or smartphone. But for observing long-distance views, accuracies of angle measurements were not sufficient to merge line data because of leverage theory. Thus, by searching corresponding pixels between line spectroscopic images, we are trying to estimate 6-DOF in high accuracy.

  14. Wavelength beam combining of a 980-nm tapered diode laser bar in an external cavity

    Science.gov (United States)

    Vijayakumar, Deepak; Jensen, Ole Bjarlin; Thestrup, Birgitte

    2010-04-01

    High power diode lasers are used in a large number of applications. A limiting factor for more widespread use of broad area lasers is the poor beam quality. Gain guided tapered diode lasers are ideal candidates for industrial applications that demands watt level output power with good beam quality. By adapting a bar geometry, the output power could be scaled even up to several tens of watts. Unfortunately, the high divergence which is a characteristic feature of the bar geometry could lead to a degradation of the overall beam quality of the laser bar. However, spectral beam combining is an effective solution for preserving the beam quality of the bar in the range of that of a single emitter and at the same time, enabling the power scaling. We report spectral beam combining applied to a 12 emitter tapered laser bar at 980 nm. The external cavity has been designed for a wavelength separation of 4.0 nm between the emitters. An output power of 9 W has been achieved at an operating current of 30 A. The combined beam had an M2 value (1/e2) of 5.3 along the slow axis which is comparable to that of a single tapered emitter on the laser bar. The overall beam combining efficiency was measured to be 63%. The output spectrum of the individual emitters was narrowed considerably. In the free running mode, the individual emitters displayed a broad spectrum of the order of 0.5-1.0 nm while the spectral width has been reduced to 30-100 pm in the spectral beam combining mode.

  15. Laser diode array and transmission optics

    Science.gov (United States)

    Kwon, Jin H.

    1989-01-01

    Information on laser diode array and transmission optics is given in viewgraph form. Information is given on coherent combining of laser diode arrays, amplification through a laser diode array, the far field pattern of a laser diode transmitter, and beam diameter at receiver vs. transmission distance.

  16. Ghost imaging with broad distance

    Institute of Scientific and Technical Information of China (English)

    段德洋; 张路; 杜少将; 夏云杰

    2015-01-01

    We present a scheme that is able to achieve the ghost imaging with broad distance. The physical nature of our scheme is that the different wavelength beams are separated in free space by an optical media according to the slow light or dispersion principle. Meanwhile, the equality of the optical distance of the two light arms is not violated. The photon correlation is achieved by the rotating ground glass plate (RGGP) and spatial light modulator (SLM), respectively. Our work shows that a monochromic ghost image can be obtained in the case of RGGP. More importantly, the position (or distance) of the object can be ascertained by the color of the image. Thus, the imaging and ranging processes are combined as one process for the first time to the best of our knowledge. In the case of SLM, we can obtain a colored image regardless of where the object is.

  17. Diode Laser Arrays

    Science.gov (United States)

    Botez, Dan; Scifres, Don R.

    1994-08-01

    This book provides a comprehensive overview of the fundamental principles and applications of semiconductor diode laser arrays. All of the major types of arrays are discussed in detail, including coherent, incoherent, edge- and surface-emitting, horizontal- and vertical-cavity, individually addressed, lattice- matched and strained-layer systems. The initial chapters cover such topics as lasers, amplifiers, external-cavity control, theoretical modeling, and operational dynamics. Spatially incoherent arrays are then described in detail, and the uses of vertical-cavity surface emitter and edge-emitting arrays in parallel optical-signal processing and multi-channel optical recording are discussed. Researchers and graduate students in solid state physics and electrical engineering studying the properties and applications of such arrays will find this book invaluable.

  18. Diagnosing light ion beam diodes

    International Nuclear Information System (INIS)

    This lecture begins with a discussion of diagnostics in ion-beam diodes. This will include electromagnetic measurements, measurements of the electron cloud, and measurements of anode plasmas. A few minutes will be spent on diagnostics of distributed ion sources required for one class of ion diodes, the plasma-filled versions, which require high-density, highly ionized sources of very uniform plasma. The measurements of the beam characteristics will then be discussed. This will be broken into two regions; the region near the diode where diagnostics are generally extensions of those used in other fields; and the region near focus where new diagnostics have been developed

  19. Enhanced vbasis laser diode package

    Energy Technology Data Exchange (ETDEWEB)

    Deri, Robert J.; Chen, Diana; Bayramian, Andy; Freitas, Barry; Kotovsky, Jack

    2014-08-19

    A substrate having an upper surface and a lower surface is provided. The substrate includes a plurality of v-grooves formed in the upper surface. Each v-groove includes a first side and a second side perpendicular to the first side. A laser diode bar assembly is disposed within each of the v-grooves and attached to the first side. The laser diode bar assembly includes a first adhesion layer disposed on the first side of the v-groove, a metal plate attached to the first adhesion layer, a second adhesion layer disposed over the metal plate, and a laser diode bar attached to the second adhesion layer. The laser diode bar has a coefficient of thermal expansion (CTE) substantially similar to that of the metal plate.

  20. Ghost imaging with broad distance

    Science.gov (United States)

    Duan, De-Yang; Zhang, Lu; Du, Shao-Jiang; Xia, Yun-Jie

    2015-10-01

    We present a scheme that is able to achieve the ghost imaging with broad distance. The physical nature of our scheme is that the different wavelength beams are separated in free space by an optical media according to the slow light or dispersion principle. Meanwhile, the equality of the optical distance of the two light arms is not violated. The photon correlation is achieved by the rotating ground glass plate (RGGP) and spatial light modulator (SLM), respectively. Our work shows that a monochromic ghost image can be obtained in the case of RGGP. More importantly, the position (or distance) of the object can be ascertained by the color of the image. Thus, the imaging and ranging processes are combined as one process for the first time to the best of our knowledge. In the case of SLM, we can obtain a colored image regardless of where the object is. Project supported by the National Natural Science Foundation of China (Grant Nos. 61178012, 11204156, 11304179, and 11247240), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20133705110001 and 20123705120002), the Scientific Research Foundation for Outstanding Young Scientists of Shandong Province, China (Grant No. BS2013DX034), and the Natural Science Foundation of Shandong Province, China (Grant No. ZR2012FQ024).

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

    Science.gov (United States)

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

    2016-04-01

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

  2. Spectral narrowing of a 980 nm tapered diode laser bar

    DEFF Research Database (Denmark)

    Vijayakumar, Deepak; Jensen, Ole Bjarlin; Lucas Leclin, Gaëlle;

    2011-01-01

    in wavelength specific applications and hence, it is vital to stabilize the emission spectrum of these devices. In our experiment, we describe the wavelength narrowing of a 12 element 980 nm tapered diode laser bar using a simple Littman configuration. The tapered laser bar which suffered from a big......High power diode laser bars are interesting in many applications such as solid state laser pumping, material processing, laser trapping, laser cooling and second harmonic generation. Often, the free running laser bars emit a broad spectrum of the order of several nanometres which limit their scope...... smile has been "smile corrected" using individual phase masks for each emitter. The external cavity consists of the laser bar, both fast and slow axis micro collimators, smile correcting phase mask, 6.5x beam expanding lens combination, a 1200 lines/mm reflecting grating with 85% efficiency in the first...

  3. Utilization of pulsed diode lasers to lidar remote sensing

    Science.gov (United States)

    Penchev, S.; Pencheva, Vasilka H.; Naboko, Vassily N.; Naboko, Sergei V.; Simeonov, P.

    2001-04-01

    Investigation of new aspects of application of pulsed quantum well (In)GaAs/AlGaAs diode lasers to atmospheric spectroscopy and lidar remote sensing is reported. The presented method utilizing these powerful multichipstack diode lasers of broad radiation line is approved theoretically and experimentally for monitoring of atmospheric humidity. Molecular absorption of gas species in the investigated spectral band 0.85 - 0.9 micrometer implemented by laser technology initiates further development of prospective DIAL analysis. A mobile lidar system is realized, employing optimal photodetection based on computer-operated boxcar and adaptive digital filter processing of the lidar signal in the analytical system. Aerosol profile exhibiting cloud strata in open atmosphere by testing of the sensor is demonstrative of the efficiency and high sensitivity of long-range sounding.

  4. 77 FR 50144 - Broad Stakeholder Survey

    Science.gov (United States)

    2012-08-20

    ... SECURITY Broad Stakeholder Survey AGENCY: National Protection and Programs Directorate, DHS. ACTION: 60-day... comments concerning the Broad Stakeholder Survey. DATES: Comments are encouraged and will be accepted until... across the Nation. The Broad Stakeholder Survey is designed to gather stakeholder feedback on...

  5. 76 FR 34087 - Broad Stakeholder Survey

    Science.gov (United States)

    2011-06-10

    ... SECURITY Broad Stakeholder Survey AGENCY: National Protection and Programs Directorate, DHS. ACTION: 60-day... comments concerning the Broad Stakeholder Survey. DATES: Comments are encouraged and will be accepted until.... The Broad Stakeholder Survey is designed to gather stakeholder feedback on the effectiveness of...

  6. 78 FR 20119 - Broad Stakeholder Survey

    Science.gov (United States)

    2013-04-03

    ... SECURITY Broad Stakeholder Survey AGENCY: National Protection and Programs Directorate, DHS. ACTION: 30-day... soliciting comments concerning the Broad Stakeholder Survey. DHS previously published this ICR in the Federal... responders across the Nation. The Broad Stakeholder Survey is designed to gather stakeholder feedback on...

  7. Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source

    International Nuclear Information System (INIS)

    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 μW of ultraviolet light at 266 nm. (fundamental areas of phenomenology (including applications))

  8. Light Emitting Diodes (LEDs)

    Science.gov (United States)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique, called Photodynamic Therapy, requires the surgeon to use tiny, pinhead-size Light Emitting Diodes (LEDs) (a source that releases long wavelengths of light ) to activate light-sensitive, tumor-treating drugs. 'A young woman operated on in May 1999 has fully recovered with no complications and no evidence of the tumor coming back,' said Dr. Harry Whelan, a pediatric neurologist at the Medical Hospital of Wisconsin in Milwaukee. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can be used for hours at a time while still remaining cool to the touch. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The LEDs, developed and managed by NASA's Marshall Space Flight Center, have been used on seven Space Shuttle flights inside the Microgravity Astroculture Facility. This technology has also been successfully used to further commercial research in crop growth.

  9. A laser-diode-pumped Nd:glass laser mode-locked, high power and single frequency performance

    OpenAIRE

    Hughes, D W; Phillips, M. W.; Barr, J.R.M.; Hanna, D.C.

    1992-01-01

    The authors report the performance of a laser-diode-pumped Nd:glass laser. Using the AM active mode-locking technique, pulses as short as 9 ps were obtained. The development of a high-power (415 mW), high-optical-slope-efficiency (32.4%) laser-diode-pumped Nd:glass laser using high-power, broad stripe laser diodes as the pump source is described. Single-frequency operation of the Nd:glass laser using an acoustooptic modulator to ensure unidirectional operation in a ring laser configuration wa...

  10. Broad and focused ion beams Ga+ implantation damage in the fabrication of p+-n Si shallow junctions

    International Nuclear Information System (INIS)

    The use of focused and broad beam Ga+ implantation for the fabrication of p+-n Si shallow junctions is explored. In particular, the issue of ion induced damage and its effect on diode electrical properties is explored. FIB-fabricated junctions exhibit a deeper junction with lower sheet resistance and higher leakage current than the BB-implanted diodes. TEM analysis exhibits similar amorphization and recrystallization behavior for both implantation techniques with the BB case generating a higher dislocation loop density after a 900 degree C anneal. 6 refs., 5 figs., 1 tab

  11. Laser Diode Beam Basics, Manipulations and Characterizations

    CERN Document Server

    Sun, Haiyin

    2012-01-01

    Many optical design technical books are available for many years which mainly deal with image optics design based on geometric optics and using sequential raytracing technique. Some books slightly touched laser beam manipulation optics design. On the other hand many books on laser diodes have been published that extensively deal with laser diode physics with little touching on laser diode beam manipulations and characterizations. There are some internet resources dealing with laser diode beams. However, these internet resources have not covered enough materials with enough details on laser diode beam manipulations and characterizations. A technical book concentrated on laser diode beam manipulations and characterizations can fit in to the open and provide useful information to laser diode users. Laser Diode Beam Basics, Manipulations and  Characterizations is concentrated on the very practical side of the subject, it only discusses the basic physics and mathematics that are necessary for the readers in order...

  12. A multi-source portable light emitting diode spectrofluorometer.

    Science.gov (United States)

    Obeidat, Safwan; Bai, Baolong; Rayson, Gary D; Anderson, Dean M; Puscheck, Adam D; Landau, Serge Y; Glasser, Tzach

    2008-03-01

    A portable luminescence spectrofluorometer weighing only 1.5 kg that uses multiple light emitting diodes (LEDs) as excitation sources was developed and evaluated. Excitation using a sequence of seven individual broad-band LED emission sources enabled the generation of excitation-emission spectra using a light weight (pistache or Mastic) and Philyria latifolia, and the herbaceous species Medicago sativa (alfalfa), Trifolium spp. (clover), and a feed concentrate. Application of multi-way principal component analysis (MPCA) to the resulting three-dimensional data sets enabled discernment among these various diet constituents. PMID:18339242

  13. Terahertz Emission from Resonant Tunneling Diodes without Satisfying Oscillation Condition

    Science.gov (United States)

    Asada, Masahiro; Kanaya, Hidetoshi; Suzuki, Safumi

    2013-10-01

    Terahertz (THz) emission from resonant tunneling diodes (RTDs) is normally obtained under the oscillation condition in which the negative differential conductance (NDC) exceeds the circuit loss. In this study, we show that a relatively broad band THz emission was observed even for RTDs with an NDC smaller than the circuit loss. The observed output power was on the order of 1-10 nW at 1.2-1.9 THz with spectral widths of 50-100 GHz. The observation was reasonably explained by the theoretical calculation based on the shot noise amplified by the NDC. This emission corresponds to the amplified spontaneous emission in optical devices.

  14. The art in dentistry using Diode laser

    OpenAIRE

    Bojkovska, Dijana; Dimova, Cena

    2010-01-01

    The aim of our work was to present the use of diode laser in clinical practice and to underline the benefits of laser application in the treatment of soft tissue. For achieving the aim of the study Laser Diode AlGaAs Galbiaty was used. Diode laser application approved our expectations of achieving immediate efficiency result. The benefits of diode laser treatment were equal because of saving treatment time in the procedure.

  15. Case studies of industrial applications of high-power diode laser in Finland

    Science.gov (United States)

    Hovikorpi, Jari; Jansson, Anssi; Salminen, Antti

    2003-06-01

    The high power diode laser is a new industrial tool. It has several advantages and disadvantages compared to the conventional industrially used CO2 and Nd:YAG laser. The most promising areas of application of diode laser have been considered to be thin sheet welding and hardening. Quite a few feasibility studies of the use of diode laser have been carried out in Finland. So far there has been some application in which diode laser is the most suitable laser. Typically, the HPDL is integrated to an industrial robot. The welding of stainless steel housing, car door lock and catalytic converters are typical examples of applications in which diode laser has technological as well as economical advantages over the conventional laser and welding techniques. The welding of these products requires good control over the heat input, short through put time and low investment. The weld cross-section of a diode laser weld is, because of conduction limited welding process, more suitable for these applications than the keyhole welding. Hardening of a large gear wheel presents also a good example of an application in which the diode laser makes it possible to economically produce structures that have not earlier been possible. Hardening requires a special form of heat delivery in order to ensure evenly hardened zone and acceptable quality. The application was performed with two high power diode lasers. The case studies of these four applications are presented and discussed in details in this paper.

  16. High power collimated diode laser stack

    Institute of Scientific and Technical Information of China (English)

    LIU Yuan-yuan; FANG Gao-zhan; MA Xiao-yu; LIU Su-ping; FENG Xiao-ming

    2006-01-01

    A high power collimated diode laser stack is carried out based on fast-axis collimation and stack packaging techniques.The module includes ten typical continuous wave (cw) bars and the total output power can be up to 368W at 48.6A.Using a cylindrical lens as the collimation elements,we can make the fast-axis divergence and the slow-axis divergence are 0.926 40 and 8.2060 respectively.The light emitting area is limited in a square area of 18.3 mm×11 mm.The module has the advantage of high power density and offers a wide potential applications in pumping and material processing.

  17. Few-photon optical diode

    OpenAIRE

    Roy, Dibyendu

    2010-01-01

    We propose a novel scheme of realizing an optical diode at the few-photon level. The system consists of a one-dimensional waveguide coupled asymmetrically to a two-level system. The two or multi-photon transport in this system is strongly correlated. We derive exactly the single and two-photon current and show that the two-photon current is asymmetric for the asymmetric coupling. Thus the system serves as an optical diode which allows transmission of photons in one direction much more efficie...

  18. Few-photon optical diode

    CERN Document Server

    Roy, Dibyendu

    2010-01-01

    We propose a novel scheme of realizing an optical diode at the few-photon level. The system consists of a one-dimensional waveguide coupled asymmetrically to a two-level system. The two or multi-photon transport in this system is strongly correlated. We derive exactly the single and two-photon current and show that the two-photon current is asymmetric for the asymmetric coupling. Thus the system serves as an optical diode which allows transmission of photons in one direction much more efficiently than the opposite.

  19. Method of making diode structures

    Science.gov (United States)

    Compaan, Alvin D.; Gupta, Akhlesh

    2006-11-28

    A method of making a diode structure includes the step of depositing a transparent electrode layer of any one or more of the group ZnO, ZnS and CdO onto a substrate layer, and depositing an active semiconductor junction having an n-type layer and a p-type layer onto the transparent electrode layer under process conditions that avoid substantial degradation of the electrode layer. A back electrode coating layer is applied to form a diode structure.

  20. Few-photon optical diode

    International Nuclear Information System (INIS)

    We propose a scheme of realizing an optical diode at the few-photon level. The system consists of a one-dimensional waveguide coupled asymmetrically to a two-level system. The two or multiphoton transport in this system is strongly correlated. We derive exactly the single and two-photon current and show that the two-photon current is asymmetric for the asymmetric coupling. Thus the system serves as an optical diode which allows transmission of photons in one direction much more efficiently than the opposite.

  1. Spin-photon entangling diode

    DEFF Research Database (Denmark)

    Flindt, Christian; Sørensen, A. S.; Lukin, M. D.;

    2007-01-01

    We propose a semiconductor device that can electrically generate entangled electron spin-photon states, providing a building block for entanglement of distant spins. The device consists of a p-i-n diode structure that incorporates a coupled double quantum dot. We show that electronic control of the...... diode bias and local gating allow for the generation of single photons that are entangled with a robust quantum memory based on the electron spins. Practical performance of this approach to controlled spin-photon entanglement is analyzed....

  2. A broad view of arsenic.

    Science.gov (United States)

    Jones, F T

    2007-01-01

    In the mind of the general public, the words "arsenic" and "poison" have become almost synonymous. Yet, As is a natural metallic element found in low concentrations in virtually every part of the environment, including foods. Mining and smelting activities are closely associated with As, and the largest occurrence of As contamination in the United States is near the gold mines of northern Nevada. Inhabitants of Bangladesh and surrounding areas have been exposed to water that is naturally and heavily contaminated with As, causing what the World Health Organization has described as the worst mass poisoning in history. Although readily absorbed by humans, most inorganic As (>90%) is rapidly cleared from the blood with a half-life of 1 to 2 h, and 40 to 70% of the As intake is absorbed, metabolized, and excreted within 48 h. Arsenic does not appreciably bioaccumulate, nor does it biomagnify in the food chain. The United States has for some time purchased more As than any other country in the world, but As usage is waning, and further reductions appear likely. Arsenic is used in a wide variety of industrial applications, from computers to fireworks. All feed additives used in US poultry feeds must meet the strict requirements of the US Food and Drug Administration Center for Veterinary Medicine (Rockville, MD) before use. Although some public health investigators have identified poultry products as a potentially significant source of total As exposure for Americans, studies consistently demonstrate that <1% of samples tested are above the 0.5 ppm limit established by the US Food and Drug Administration Center for Veterinary Medicine. Although laboratory studies have demonstrated the possibility that As in poultry litter could pollute ground waters, million of tons of litter have been applied to the land, and no link has been established between litter application and As contamination of ground water. Yet, the fact that <2% of the United States population is involved in

  3. Advances in Diode-Laser-Based Water Vapor Differential Absorption Lidar

    Science.gov (United States)

    Spuler, Scott; Repasky, Kevin; Morley, Bruce; Moen, Drew; Weckwerth, Tammy; Hayman, Matt; Nehrir, Amin

    2016-06-01

    An advanced diode-laser-based water vapor differential absorption lidar (WV-DIAL) has been developed. The next generation design was built on the success of previous diode-laser-based prototypes and enables accurate measurement of water vapor closer to the ground surface, in rapidly changing atmospheric conditions, and in daytime cloudy conditions up to cloud base. The lidar provides up to 1 min resolution, 150 m range resolved measurements of water vapor in a broad range of atmospheric conditions. A description of the instrument and results from its initial field test in 2014 are discussed.

  4. DIAL monitoring of atmospheric climate-determining gases employing high-power pulsed laser diodes

    Science.gov (United States)

    Penchev, Stoyan P.; Naboko, Sergei V.; Naboko, Vassily N.; Pencheva, Vasilka H.; Donchev, T.; Pavlov, Lyubomir Y.; Simeonov, P.

    2003-11-01

    High-power pulsed laser diodes are employed for determining atmospheric humidity and methane. The proposed DIAL method optimizes the spectral properties of laser radiation within the molecular absorption bands of 0.86 - 0.9 μm of these major greenhouse gases. The explicit absorption spectrum is explored by computational convolution method based on reference data on spectral linestrengths modulated by the characteristic broad laser line of the selected laser diodes. The lidar scheme is ultimately compact, of low-energy consumption and suggests a large potential for ecological monitoring.

  5. Neutralization of low energy broad ion beam

    International Nuclear Information System (INIS)

    The paper is devoted to experimental and theoretical investigation of a low energy broad ion beam space charge and current compensation and ion-beam plasma (IBP), which would be created in transport space of the beam. The beam had cylindrical symmetry. The continuous uniform and hole tube like ion beams are used in the experiments. Different channels of electron appearing have been investigated for cases of neutralization due to secondary γ-electrons from the target and by electrons from glow cathode-neutralizer with metal or dielectric target. Results of neutralizing electrons energy distributions function measurements are presented as well as dependences of electron temperature and self-consisted plasma potential vs. beam parameters, ambient gas pressure, neutralizer parameters. Role of the thermoelectrons and dependence of IBP parameters on neutralizer area, location and potential are discussed. Significant role in neutralization of spatial collisional processes has been revealed even in neutralization by thermocathode. On the base of the experimental results self-consistent theoretical model have been developed, which describes the behavior of intense ion beam passing through the neutral gas at low pressure within conductive walls. The collisionless approach is used which means absence of collisional relaxation of the beam. This theory is used to derive the plasma potential and electron temperature within the beam

  6. Laser diode technology and applications

    International Nuclear Information System (INIS)

    This book covers a wide range of semiconductor laser technology, from new laser structures and laser design to applications in communications, remote sensing, and optoelectronics. The authors report on new laser diode physics and applications and present a survey of the state of the art as well as progress in new developments

  7. Directly diode-pumped femtosecond laser based on an Yb:KYW crystal

    Science.gov (United States)

    Kim, G. H.; Yang, J.; Lee, D. S.; Kulik, A. V.; Sall', E. G.; Chizhov, S. A.; Yashin, V. E.; Kang, U.

    2012-01-01

    Ultrashort pulse laser systems are widely used in many areas such as microprocessing of various materials, the generation of terahertz radiation, nonlinear optics, medical tomography, chemistry, and biology due to the high peak power and large spectral width. For a practical usage of the femtosecond lasers, they must be fairly compact and stable. These conditions are most fully met when laser media are used that allow direct pumping with the radiation from semiconductor injection lasers, which are more compact, reliable, and inexpensive than pumping with solid-state lasers. Since Ytterbium-doped crystals have a broad luminescence band for generating femtosecond pulses less than 500 fs wide, they are attractive as materials for lasers with direct diode pumping. Moreover, the position of the central luminescence wavelength of Yb:KGW and Yb:KYW crystals makes them promising priming sources of femtosecond pulses for amplifiers that operate at wavelengths close to 1 μm (Yb:KGW, Yb-glass, Nd-glass, Yb:YAG, etc.) We developed a femtosecond generator based on the Yb:KYW crystal with direct pumping by the radiation of a laser diode with fiber output of the pump radiation. The use of such pumping, as well as of chirped mirrors to compensate intracavity dispersion, made it possible to generate a continuous sequence of optical pulses 90 fs wide at a frequency of 87.8 MHz with a mean radiation power of more than 1 W. The product of the pulse width by the spectral width is close to the theoretical limit, and this indicates that there is no frequency modulation.

  8. Characterization of Stock Blu-ray diodes

    Science.gov (United States)

    Cunningham, Mark; Archibald, James; Erickson, Christopher; Durfee, Dallin

    2010-10-01

    I am developing a process to test and characterize diodes of unknown wavelengths. using a B&WTEK Spectrometer we are characterizing the wavelength of 405 nm blu-ray diodes purchased in bulk. With the known error in production of the Diode Lasers we are hoping to find a diode at 408 nm to use in driving a raman transition between hyperfine states of strontium 87 ions. The bulk of the project is a java program that communicates with the spectrometer and graphically displays the intensities of the wavelengths from the laser diodes.

  9. Handbook of distributed feedback laser diodes

    CERN Document Server

    Morthier, Geert

    2013-01-01

    Since the first edition of this book was published in 1997, the photonics landscape has evolved considerably and so has the role of distributed feedback (DFB) laser diodes. Although tunable laser diodes continue to be introduced in advanced optical communication systems, DFB laser diodes are still widely applied in many deployed systems. This also includes wavelength tunable DFB laser diodes and DFB laser diode arrays, usually integrated with intensity or phase modulators and semiconductor optical amplifiers.This valuable resource gives professionals a comprehensive description of the differen

  10. Broad Prize: Do the Successes Spread?

    Science.gov (United States)

    Samuels, Christina A.

    2011-01-01

    When the Broad Prize for Urban Education was created in 2002, billionaire philanthropist Eli Broad said he hoped the awards, in addition to rewarding high-performing school districts, would foster healthy competition; boost the prestige of urban education, long viewed as dysfunctional; and showcase best practices. Over the 10 years the prize has…

  11. Pulsed power supply system of magnetic field coils of ion diode

    International Nuclear Information System (INIS)

    The pulsed power system of magnetic coils of an ion diode with external magnetic insulation (IDM), which ensures operation of the diode in the frequency mode, is described. Demands are formulated for the IDM magnetic field in which the electronic cloud acting as a cathode in the diode is formed as well as for storage conditions of the negative charge in the magnetic field for neutralizing the ion beam in the ion-beam drift area. The basic relationships required for engineering calculations of the IDM coils and a pulsed power system in the frequency mode are given

  12. New Two-Diode Model for Detailed Analysis of Multicrystalline Silicon Solar Cells

    Science.gov (United States)

    Kurobe, Ken-ichi; Matsunami, Hiroyuki

    2005-12-01

    In order to extract electrical properties of multicrystalline silicon (Mx-Si) solar cells precisely, current-voltage (I-V) measurement in the dark condition was carried out. A new two-diode model, which includes a diffusion-current dominant area (DCA) and a recombination-current dominant area (RCA), with nonequivalent series resistances, was proposed as a new equivalent circuit. Electrical properties as fitting parameters were successfully extracted using a successive approximation method. This characterization derived J01 and J02, which are the diode saturation current densities for n=1 and 2 diodes, respectively. To ensure this diode model, temperature characteristics were measured, and the validity of this model was shown through calculation of the energy band gap from J01. J01 and J02 indicate a power factor and a loss factor of solar cells, respectively, which are newly proposed to classify solar cell performance.

  13. Finite Element Analysis Of Thermal Transients In Multi-Stripe Laser Diode Arrays

    Science.gov (United States)

    Lippincott, Wendy L.; Clement, Anne E.

    1989-05-01

    The NASTRAN finite element code was used to simulate the temperature transients in the active area of laser diode arrays caused by driving the array with a pulsed waveform. A ten-stripe multi-quantum-well (MQW) structure was used. The thermal impedance of the array was also determined and compared to experimental values obtained by monitoring the threshold dependance of the device during pulsed and cw operation. The single-stripe diode was also modeled for comparison purposes.

  14. Microlens frames for laser diode arrays

    Science.gov (United States)

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

    1999-07-13

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

  15. Design and evaluation of the XBT diode

    International Nuclear Information System (INIS)

    This paper describes the design and experimental results achieved with the 440 kV, microperveance 1.9, XBT (X-band Beam Tester) diode. The Pierce gun was developed for the 100 MW X-band klystron; the high power RF source to be used on the NLC (Next Linear Collider). The gun is electrostatically focused (no magnetic compression) to a beam diameter of 6.35 mm, with an area convergence of 110:1. Maximum cathode loading is approximately 25 A/cm2, with a beam power density of 770 MW/cm2. The measured beam current was within 2% of the value predicted by simulation with EGUN. Transmission through the highly instrumented beam tester was 99.98%. Some novel techniques were used to achieve near perfect beam transmission, which include the use of a reentrant-floating input pole piece

  16. Microlens frames for laser diode arrays

    Science.gov (United States)

    Skidmore, Jay A.; Freitas, Barry L.

    1999-01-01

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

  17. Operation of a high repetition rate intense ion beam diode

    International Nuclear Information System (INIS)

    A magnetically insulated diode has been developed that is capable of pulsing at high repetition rate for short bursts. This diode has a plasma-anode ion source which originates as an annular puff of H2 or some other gas. The gas puff is preionized and then inductively broken down by a 1 μs rise time magnetic field coil. This same field coil magnetically drives the resulting plasma toward a magnetically insulated acceleration gap. Finally, a ∼ 100 kV, 20--40 kA, approx-lt 100 ns acceleration voltage pulse is applied to the gap to generate the beam. The annular plasma has a mean radius of 8.5 cm, and the ion beam is extracted from an area of approx-lt 200 cm2. The pulsed power systems that drive this diode at high repetition rates are based upon saturable inductor switching. The anode plasma's temperature and density, as measured by spectroscopic techniques, is reported as a function of repetition rate and shot number within a burst. How the plasma parameters vary with diode operating conditions, such as gas puff pressure or insulating field strength, are also presented. In addition, these plasma parameters are compared with the parameters of the extracted beam

  18. Optimization of Quantum-Dot Molecular Beam Epitaxy for Broad Spectral Bandwidth Devices

    KAUST Repository

    Majid, M. A.

    2012-12-01

    The optimization of the key growth parameters for broad spectral bandwidth devices based on quantum dots is reported. A combination of atomic force microscopy, photoluminescence of test samples, and optoelectronic characterization of superluminescent diodes (SLDs) is used to optimize the growth conditions to obtain high-quality devices with large spectral bandwidth, radiative efficiency (due to a reduced defective-dot density), and thus output power. The defective-dot density is highlighted as being responsible for the degradation of device performance. An SLD device with 160 nm of bandwidth centered at 1230 nm is demonstrated.

  19. Changes in Cell Viability of Wounded Fibroblasts following Laser Irradiation in Broad-Spectrum or Infrared Light

    OpenAIRE

    Hawkins, Denise; Abrahamse, Heidi

    2007-01-01

    Objective. This study aimed to establish if broad-spectrum or infrared (IR) light in combination with laser therapy can assist phototherapy to improve the cell function of wounded cells. Background. The effect of laser light may be partly or completely reduced by broad-spectrum light. Methods. Wounded human skin fibroblasts were irradiated with 5 J/cm2 using a helium-neon laser, a diode laser, or an Nd:YAG laser in the dark, in the light, or in IR. Changes in cell viability were evaluated by ...

  20. Stability of high current diode under 100-nanosecond-pulse voltage

    International Nuclear Information System (INIS)

    Stability of high current diode under pulse voltage with 80 ns and 34 ns rise time was studied on the flash Ⅱ accelerator. Influence of rise time of diode voltage on startup time and cathode emission uniformity and repeatability of diode impedance was analyzed by comparing the experimental results with numerically simulated results, and the influence mechanism was discussed. The startup time of diode increases with the increasing of rise time of voltage, and the repeatability of diode impedance decreases. Discal plane cathode is prone to emit rays intensely in the center area, the time that plasma covers the surface of the cathode increases and the shielding effect has more impact on cathode emission according to the increase of rise time. Local intense emission on the cathode increases expansion speed of plasma and reduces the effective emission area. The stability of characteristic impedance of diode under a pulse voltage with slow rise time is decreased by the combined action of expansion speed of plasma and the effective emission area. (authors)

  1. ORGANIC LIGHT EMITTING DIODE (OLED

    Directory of Open Access Journals (Sweden)

    Aririguzo Marvis Ijeaku

    2015-09-01

    Full Text Available An Organic Light Emitting Diode (OLED is a device composed of an organic layer that emits lights in response to an electrical current. Organic light emitting diodes have advanced tremendously over the past decades. The different manufacturing processes of the OLED itself to several advantages over flat panel displays made with LCD technology which includes its light weight and flexible plastic substrates, wider viewing angles, improved brightness, better power efficiency and quicker response time. However, its drawbacks include shorter life span, poor color balance, poor outdoor performance, susceptibility to water damage etc.The application of OLEDs in electronics is on the increase on daily basics from cameras to cell phones to OLED televisions, etc. Although OLEDs provides prospects for thinner, smarter, lighter and ultraflexible electronics displays, however, due to high cost of manufacturing, it is not yet widely used.

  2. Single-electron heat diode

    OpenAIRE

    Ruokola, Tomi; Ojanen, Teemu

    2011-01-01

    We introduce a new functional nanoscale device, a single-electron heat diode, consisting of two quantum dots or metallic islands coupled to electronic reservoirs by tunnel contacts. Electron transport through the system is forbidden but the capacitive coupling between the two dots allows electronic fluctuations to transmit heat between the reservoirs. When the reservoir temperatures are biased in the forward direction, heat flow is enabled by a four-step sequential tunneling cycle, while in t...

  3. Mapping plant functional types over broad mountainous regions

    OpenAIRE

    Danlu Cai; Yanning Guan; Shan Guo; Chunyan Zhang; Klaus Fraedrich

    2014-01-01

    Research on global climate change requires plant functional type (PFT) products. Although several PFT mapping procedures for remote sensing imagery are being used, none of them appears to be specifically designed to map and evaluate PFTs over broad mountainous areas which are highly relevant regions to identify and analyze the response of natural ecosystems. We present a methodology for generating soft classifications of PFTs from remotely sensed time series that are based on a hierarchical s...

  4. The Simulation of Resonant Tunneling Diodes

    OpenAIRE

    Gilbertson, Woodrow A; Long, Pengyu; Fonseca, Jim; Klimeck, Gerhard

    2014-01-01

    The goal of this project is to improve the simulation of an electrical device known as a Resonant Tunneling Diode (RTD). Diodes are in most electronic devices today, but RTDs have 10 times greater switching speeds than regular diodes. This increase in efficiency would have impacts from supercomputers to the next big cell phone. The increased functionality of the simulation tool will come from implementing more recent mathematical solvers and modeling techniques. The simulation tool makes use ...

  5. Electromagnetic wave analogue of electronic diode

    OpenAIRE

    Shadrivov, Ilya V.; Powell, David A.; Kivshar, Yuri S.; Fedotov, Vassili A.; Zheludev, Nikolay I.

    2010-01-01

    An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of the polarization state rotation and is also a key component of optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by ...

  6. Quantum optical diode with semiconductor microcavities

    OpenAIRE

    Shen, H. Z.; Zhou, Y.H.; Yi, X. X.

    2014-01-01

    The semiconductor diode, which acts as an electrical rectifier and allows unidirectional electronic transports, is the key to information processing in integrated circuits. Analogously, an optical rectifier (or diode) working at specific target wavelengths has recently becomes a dreaming device in optical communication and signal processing. In this paper, we propose a scheme to realize an optical diode for photonic transport at the level of few photons. The system consists of two spatially o...

  7. Numerical simulation of spherical plasma focus diode

    International Nuclear Information System (INIS)

    A self-magnetically insulated, three-dimensionally-focused ion-beam diode, spherical plasma focus diode (SPFD), is studied by numerical simulation using a two-dimensional, electromagnetic, relativistic particle-in-cell computer code. The calculated results of the diode impedance, the ion-current efficiency, and the focusing characteristics of the ion beam are presented. These results, except the data of the ion-beam current, are in good agreement with the experimental results. (author)

  8. Schlieren with a laser diode source

    Science.gov (United States)

    Burner, A. W.; Franke, J. M.

    1981-01-01

    The use of a laser diode as a light source for a schlieren system designed to study phase objects such as a wind-tunnel flow is explored. A laser diode schlieren photograph and a white light schlieren photograph (zirconium arc source) are presented for comparison. The laser diode has increased sensitivity, compared with light schlieren, without appreciable image degradiation, and is an acceptable source for schlieren flow visualization.

  9. Thermal (Silicon Diode) Data Acquisition Systems

    Science.gov (United States)

    Wright, Ernest; Kegley, Jeff

    2008-01-01

    Marshall Space Flight Center s X-ray Cryogenic Facility (XRCF) has been performing cryogenic testing to 20 Kelvin since 1999. Two configurations for acquiring data from silicon diode temperature sensors have been implemented at the facility. The facility's environment is recorded via a data acquisition system capable of reading up to 60 silicon diodes. Test article temperature is recorded by a second data acquisition system capable of reading 150+ silicon diodes. The specifications and architecture of both systems will be presented.

  10. Thermal (Silicon Diode) Data Acquisition System

    Science.gov (United States)

    Kegley, Jeffrey

    2008-01-01

    Marshall Space Flight Center's X-ray Calibration Facility (XRCF) has been performing cryogenic testing to 20 Kelvin since 1999. Two configurations for acquiring data from silicon diode temperature sensors have been implemented at the facility. The facility's environment is recorded via a data acquisition system capable of reading up to 60 silicon diodes. Test article temperature is recorded by a second data acquisition system capable of reading 150+ silicon diodes. The specifications and architecture of both systems will be presented.

  11. Effects of radiation on laser diodes.

    Energy Technology Data Exchange (ETDEWEB)

    Phifer, Carol Celeste

    2004-09-01

    The effects of ionizing and neutron radiation on the characteristics and performance of laser diodes are reviewed, and the formation mechanisms for nonradiative recombination centers, the primary type of radiation damage in laser diodes, are discussed. Additional topics include the detrimental effects of aluminum in the active (lasing) volume, the transient effects of high-dose-rate pulses of ionizing radiation, and a summary of ways to improve the radiation hardness of laser diodes. Radiation effects on laser diodes emitting in the wavelength region around 808 nm are emphasized.

  12. Focusing experiments with light ion diodes

    International Nuclear Information System (INIS)

    A review of recent experimental and theoretical work at Sandia Laboratories on magnetically insulated single stage ion diodes for inertial confinement fusion experiments is presented. The production, focusing, and numerical simulation of a 0.5 TW annular proton beam using the Proto I dual transmission line generator is described. The modular magnetically insulated ion diode for the Hydra generator is also described along with recent experimental results. A brief description of how an array of modular diodes similar to the Hydra magnetically insulated diode could be used on the EBFA I generator for breakeven fusion experiments is presented

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

    Science.gov (United States)

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

    2004-01-01

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

  14. 33 CFR 110.27 - Lynn Harbor in Broad Sound, Mass.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Lynn Harbor in Broad Sound, Mass. 110.27 Section 110.27 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY ANCHORAGES ANCHORAGE REGULATIONS Special Anchorage Areas § 110.27 Lynn Harbor in Broad Sound, Mass. North...

  15. BROAD PHONEME CLASSIFICATION USING SIGNAL BASED FEATURES

    Directory of Open Access Journals (Sweden)

    Deekshitha G

    2014-12-01

    Full Text Available Speech is the most efficient and popular means of human communication Speech is produced as a sequence of phonemes. Phoneme recognition is the first step performed by automatic speech recognition system. The state-of-the-art recognizers use mel-frequency cepstral coefficients (MFCC features derived through short time analysis, for which the recognition accuracy is limited. Instead of this, here broad phoneme classification is achieved using features derived directly from the speech at the signal level itself. Broad phoneme classes include vowels, nasals, fricatives, stops, approximants and silence. The features identified useful for broad phoneme classification are voiced/unvoiced decision, zero crossing rate (ZCR, short time energy, most dominant frequency, energy in most dominant frequency, spectral flatness measure and first three formants. Features derived from short time frames of training speech are used to train a multilayer feedforward neural network based classifier with manually marked class label as output and classification accuracy is then tested. Later this broad phoneme classifier is used for broad syllable structure prediction which is useful for applications such as automatic speech recognition and automatic language identification.

  16. Giant Broad Line Regions in Dwarf Seyferts

    CERN Document Server

    Devereux, Nick

    2015-01-01

    High angular resolution spectroscopy obtained with the Hubble Space Telescope (HST) has revealed a remarkable population of galaxies hosting dwarf Seyfert nuclei with an unusually large broad-line region (BLR). These objects are remarkable for two reasons. Firstly, the size of the BLR can, in some cases, rival those seen in the most luminous quasars. Secondly, the size of the BLR is not correlated with the central continuum luminosity, an observation that distinguishes them from their reverberating counterparts. Collectively, these early results suggest that non-reverberating dwarf Seyferts are a heterogeneous group and not simply scaled versions of each other. Careful inspection reveals broad H Balmer emission lines with single peaks, double peaks, and a combination of the two, suggesting that the broad emission lines are produced in kinematically distinct regions centered on the black hole (BH). Because the gravitational field strength is already known for these objects, by virtue of knowing their BH mass, ...

  17. Plasma Redshift in the Broad Line Region

    CERN Document Server

    Hansen, Peter M

    2013-01-01

    Astronomical properties of the broad line emission region (BLR) of active galactic nuclei (AGN) and quasi-stellar objects (QSO) are used to formulate a model of dynamic and electromagnetic scattering characteristics. The results of this modeling show that the observed redshift of these objects may be more complex than that from recession alone due to ionization or plasma effects.

  18. Broad resonances and beta-decay

    DEFF Research Database (Denmark)

    Riisager, K.; Fynbo, H. O. U.; Hyldegaard, S.;

    2015-01-01

    Beta-decay into broad resonances gives a distorted lineshape in the observed energy spectrum. Part of the distortion arises from the phase space factor, but we show that the beta-decay matrix element may also contribute. Based on a schematic model for p-wave continuum neutron states it is argued...

  19. Electromagnetic wave analogue of electronic diode

    CERN Document Server

    Shadrivov, Ilya V; Kivshar, Yuri S; Fedotov, Vassili A; Zheludev, Nikolay I

    2010-01-01

    An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of the polarization state rotation and is also a key component of optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by an extraordinary strong nonlinear wave propagation effect in the same way as electronic diode function is provided by a nonlinear current characteristic of a semiconductor junction. The effect exploited in this new electromagnetic diode is an intensity-dependent polarization change in an artificial chiral metamolecule. This microwave effect exceeds a similar optical effect previously observed in natural crystals by more than 12 orders of magnitude and a direction-dependent transmission that differing by a factor of 65.

  20. Laser diode package with enhanced cooling

    Science.gov (United States)

    Deri, Robert J.; Kotovsky, Jack; Spadaccini, Christopher M.

    2011-09-13

    A laser diode package assembly includes a reservoir filled with a fusible metal in close proximity to a laser diode. The fusible metal absorbs heat from the laser diode and undergoes a phase change from solid to liquid during the operation of the laser. The metal absorbs heat during the phase transition. Once the laser diode is turned off, the liquid metal cools off and resolidifies. The reservoir is designed such that that the liquid metal does not leave the reservoir even when in liquid state. The laser diode assembly further includes a lid with one or more fin structures that extend into the reservoir and are in contact with the metal in the reservoir.

  1. Electromagnetic wave analogue of an electronic diode

    International Nuclear Information System (INIS)

    An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of rotation of the polarization state and is also a key component in optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by an extraordinarily strong nonlinear wave propagation effect in the same way as the electronic diode function is provided by the nonlinear current characteristic of a semiconductor junction. The effect exploited in this new electromagnetic diode is an intensity-dependent polarization change in an artificial chiral metamolecule. This microwave effect exceeds a similar optical effect previously observed in natural crystals by more than 12 orders of magnitude and a direction-dependent transmission that differs by a factor of 65.

  2. Laser diode package with enhanced cooling

    Science.gov (United States)

    Deri, Robert J.; Kotovsky, Jack; Spadaccini, Christopher M.

    2012-06-12

    A laser diode package assembly includes a reservoir filled with a fusible metal in close proximity to a laser diode. The fusible metal absorbs heat from the laser diode and undergoes a phase change from solid to liquid during the operation of the laser. The metal absorbs heat during the phase transition. Once the laser diode is turned off, the liquid metal cools off and resolidifies. The reservoir is designed such that that the liquid metal does not leave the reservoir even when in liquid state. The laser diode assembly further includes a lid with one or more fin structures that extend into the reservoir and are in contact with the metal in the reservoir.

  3. Spectroscopic amplifier for pin diode

    International Nuclear Information System (INIS)

    The photodiode remains the basic choice for the photo-detection and is widely used in optical communications, medical diagnostics and field of corpuscular radiation. In detecting radiation it has been used for monitoring radon and its progeny and inexpensive spectrometric systems. The development of a spectroscopic amplifier for Pin diode is presented which has the following characteristics: canceler Pole-Zero (P/Z) with a time constant of 8 μs; constant gain of 57, suitable for the acquisition system; 4th integrator Gaussian order to waveform change of exponential input to semi-Gaussian output and finally a stage of baseline restorer which prevents Dc signal contribution to the next stage. The operational amplifier used is the TLE2074 of BiFET technology of Texas Instruments with 10 MHz bandwidth, 25 V/μs of slew rate and a noise floor of 17 nv/(Hz)1/2. The integrated circuit has 4 operational amplifiers and in is contained the total of spectroscopic amplifier that is the goal of electronic design. The results show like the exponential input signal is converted to semi-Gaussian, modifying only the amplitude according to the specifications in the design. The total system is formed by the detector, which is the Pin diode, a sensitive preamplifier to the load, the spectroscopic amplifier that is what is presented and finally a pulse height analyzer (Mca) which is where the spectrum is shown. (Author)

  4. Study on Photon Sensitivity of Silicon Diodes Related to Materials Used for Shielding

    International Nuclear Information System (INIS)

    Large area Silicon diodes used in electronic neutron dosemeters have a significant over-response to X and gamma rays, highly non-linear at photon energies below 200 keV. This over-response to photons is proportional to the diodes active area and strongly affects the neutron sensitivity of such dosemeters. Since Silicon diodes are sensitive to light and electromagnetic fields, most diode detector assemblies are provided with a shielding, sometimes also used as radiation filter. In this paper, the influence of materials covering the diode's active area is investigated using the MCNP-4A code by estimating the photon induced pulses in a typical silicon wafer (300 μm thickness and 1 cm diameter) when provided with a front case cover. There have been simulated small-size diode front covers made of several materials with low neutron interaction cross-sections like aluminium, TEFLON, iron and lead. The estimated number of induced pulses in the silicon wafer is calculated for each type of shielding at normal photon incidence for several photon energies from 9.8 keV up to 1.15 MeV and compared with that in a bare silicon wafer. The simulated pulse height spectra show the origin of the photon induced pulses in silicon for each material used as protective cover: the photoelectric effect for low Z front case materials at low energy incident photons (up to about 65 keV) and the Compton and build-up effects for high Z case materials at higher photon energies. A simple means to lower and flatten the photon response of silicon diodes over an extended X and gamma rays energy range is proposed by designing a composed photon filter. (author)

  5. Study on photon sensitivity of silicon diodes related to materials used for shielding

    International Nuclear Information System (INIS)

    Large area silicon diodes used in electronic neutron dosemeters have a significant over-response to X- and gamma-rays, highly non-linear at photon energies below 200 keV. This over-response to photons is proportional to the diode's active area and strongly affects the neutron sensitivity of such dosemeters. Since silicon diodes are sensitive to light and electromagnetic fields, most diode detector assemblies are provided with a shielding, sometimes also used as radiation filter. In this paper, the influence of materials covering the diode's active area is investigated using the MCNP-4A code by estimating the photon induced pulses in a typical silicon wafer (300 μm thickness and 1 cm diameter) when provided with a front case cover. There have been simulated small-size diode front covers made of several materials with low neutron interaction cross-sections like aluminium, TEFLON, iron and lead. The estimated number of induced pulses in the silicon wafer is calculated for each type of shielding at normal photon incidence for several photon energies from 9.8 keV up to 1.15 MeV and compared with that in a bare silicon wafer. The simulated pulse height spectra show the origin of the photon-induced pulses in silicon for each material used as protective cover: the photoelectric effect for low Z front case materials at low-energy incident photons (up to about 65 keV) and the Compton and build-up effects for high Z case materials at higher photon energies. A simple means to lower and flatten the photon response of silicon diodes over an extended X- and gamma rays energy range is proposed by designing a composed photon filter. (author)

  6. Electrical and thermal finite element modeling of arc faults in photovoltaic bypass diodes.

    Energy Technology Data Exchange (ETDEWEB)

    Bower, Ward Isaac; Quintana, Michael A.; Johnson, Jay

    2012-01-01

    Arc faults in photovoltaic (PV) modules have caused multiple rooftop fires. The arc generates a high-temperature plasma that ignites surrounding materials and subsequently spreads the fire to the building structure. While there are many possible locations in PV systems and PV modules where arcs could initiate, bypass diodes have been suspected of triggering arc faults in some modules. In order to understand the electrical and thermal phenomena associated with these events, a finite element model of a busbar and diode was created. Thermoelectrical simulations found Joule and internal diode heating from normal operation would not normally cause bypass diode or solder failures. However, if corrosion increased the contact resistance in the solder connection between the busbar and the diode leads, enough voltage potentially would be established to arc across micron-scale electrode gaps. Lastly, an analytical arc radiation model based on observed data was employed to predicted polymer ignition times. The model predicted polymer materials in the adjacent area of the diode and junction box ignite in less than 0.1 seconds.

  7. Semiconductor diodes as cryogenic temperature sensors

    International Nuclear Information System (INIS)

    The diode temperature sensor makes use of the fact that, under conditions of constant forward current, the forward voltage of the diode junction increases with decreasing temperature. Some results in developing some types of semiconductor diodes, designed to act as cryogenic temperature sensors, were achieved since 1981, first in USA. All these sensors were of Ga-As type. Our first attempt in using semiconductor diodes as cryogenic sensors was in automatising the filling of a liquid nitrogen tank, where we used a germanium diode, EFD 106, made by IPRS Baneasa, as level sensor. Then we noticed the pronounced temperature dependence of the internal resistance of the diode and also the fact that the device has a sufficient mechanical stability at cryogenic temperatures. On this basis and taking into account the fact that the cryogenic temperature sensors (platinum, carbon or semiconductor thermo resistors and some sorts of special thermocouples) are expensive, we try to find out whether and how ordinary diodes could be used in low temperature thermometry. Using a Cryostat with EDWARDS Cryogenerator and ITC temperature regulator, an YEW Constant Current Source, a HP 3458A Programmable Multimeter, a Tektronix 576 Curve Tracer and a PC, we studied the temperature dependence of the BANEASA SA 1N4148 silicon diode forward tension in the range of 20 to 300 K. Two temperature characteristics were measured, at 10 μA and 100 μA bias current. The characteristics show a linear dependence of the forward tension of diode junction on temperature and also a good sensitivity, which decreases from 3 mV/K at 300 K, to 2 mV/K at 20 K, which is higher than the sensitivity of platinum thermo resistance at 1 mA bias current. We investigated also the diode sensitivity to bias current variations and we found a change of less than 0.1 K at 10% change in bias current, what is better than the same parameter in platinum thermo resistors. So, the constant current source for biasing a diode

  8. Spin injection in a ferromagnet/resonant tunneling diode heterostructure

    Institute of Scientific and Technical Information of China (English)

    Jin Bao; Fang Wan; Yu Wang; Xiaoguang Xu; Yong Jiang

    2008-01-01

    The spin transport property of a ferromagnet (FM)/insulator (I)/resonant tunneling diode (RTD) heterostructure was stud-ied. The transmission coefficient and spin polarization in a multilayered heterostructure was calculated by a Scbr(o)dinger wave equa-tion. An Airy function formalism approach was used to solve this equation. Based on the transfer matrix approach, the transmittivity of the structure was determined as a function of the Feimi energy and other parameters. The result shows that the spin polarization induced by the structure oscillates with the increasing Fermi energy of the FM layer. While the thickness of the RTD is reduced, the resonant peaks become broad. In the heterostructure, the spin polarization reaches as high as 40% and can be easily controlled by the external bias voltage.

  9. Flow over an Erodible Broad Crested Weir

    Directory of Open Access Journals (Sweden)

    Dr. K. C.Sahu

    2015-01-01

    Full Text Available The overtopping flow of water over an earthen embankment causes erosion of soil from its surfaces and the eroded surface of the embankment acts as a Broad crest weir. But the longitudinal profile of the weir goes on changing with time of erosion. Hence crest height of the weir goes changing in accelerated flow condition. In this paper, the discharge equation for this type of flow situation is established for different types of soils used in the embankment. Then, the experiments have been carried out as the analogous rigid beds of the captured eroded profiles at any time of erosion of the broad crested weir to compare the discharge equation and to study the energy loss in dislodging the soil from the surface of the weir and transporting them down stream.

  10. Broad line regions in Seyfert-1 galaxies

    International Nuclear Information System (INIS)

    To reproduce observed emission profiles of Seyfert galaxies, rotation in an accretion disk has been proposed. In this thesis, the profiles emitted by such an accretion disk are investigated. Detailed comparison with the observed profiles yields that a considerable fraction can be fitted with a power-law function, as predicted by the model. The author analyzes a series of high quality spectra of Seyfert galaxies, obtained with the 2.5m telescope at Las Campanas. He presents detailed analyses of two objects: Mkn335 and Akn120. In both cases, strong evidence is presented for the presence of two separate broad line zones. These zones are identified with an accretion disk and an outflowing wind. The disk contains gas with very high densities and emits predominantly the lower ionization lines. He reports on the discovery of very broad wings beneath the strong forbidden line 5007. (Auth.)

  11. Broad iron lines in Active Galactic Nuclei

    CERN Document Server

    Fabian, A C; Reynolds, C S; Young, A J

    2000-01-01

    An intrinsically narrow line emitted by an accretion disk around a black hole appears broadened and skewed as a result of the Doppler effect and gravitational redshift. The fluorescent iron line in the X-ray band at 6.4-6.9keV is the strongest such line and is seen in the X-ray spectrum of many active galactic nuclei and, in particular, Seyfert galaxies. It is an important diagnostic with which to study the geometry and other properties of the accretion flow very close to the central black hole. The broad iron line indicates the presence of a standard thin accretion disk in those objects, often seen at low inclination. The broad iron line has opened up strong gravitational effects around black holes to observational study with wide-reaching consequences for both astrophysics and physics.

  12. INFRARED DIODE LASER RETINAL TREATMENT FOR CHRONIC HEADACHE

    Directory of Open Access Journals (Sweden)

    Subba Rao

    2013-12-01

    Full Text Available ABSTRACT: Nearly 60 to 70 crores of people all over the world are suffering from various types of chronic headache. This is one of the commonest medical problems. To get relief from headache various medical treatments are used with little success. The aim of our study is to give permanent treatment to chronic headache patients by using infrared diode laser selective retinal photocoagulati on. NIDEK infrared diode laser with NIDEK SL40 slit - lamp and NIDEK digital fundus camera for retinal evaluation, MAINSTER 135D lens for laser beam focusing and retinal examination and TOPCON non - contact tonometer for intra ocular pressure measurements are used. Diode laser is chosen because of its deep penetration into all the layers of retina and choroid. 500 cases of chronic headache were studied. Laser photocoagulation was given in selective areas of retina in 2 to 3 sessions with 15 days interval. 10 to 60 years age group were studied. 90% of patients who got laser treatment are relieved from their headache in severity and in frequency. 80% of patients needed 2 sittings and 20% of patients needed 3 sittings. 70% of patients got relief from headache by fi rst sitting itself. 50% of patients are not only relieved from their headaches but also noticed visual clarity improvement. Retinal ischaemia is one of the main cause for ocular pain and headache. Laser treatment will improve circulation by reducing ischae mia thereby relieves ocular pain and headache

  13. Nickel-gallium arsenide high-voltage power Schottky diodes

    Science.gov (United States)

    Ashkinazi, G.; Hadas, Tz.; Meyler, B.; Nathan, M.; Zolotarevski, L.; Zolotarevski, O.

    1993-01-01

    A power GaAs Schottky diode (SD) with a chemically deposited Ni barrier was designed, fabricated and tested. The diode has a reverse breakdown voltage VBR of 140 V, forward voltage drop VF (at 50 A/cm 2) of 0.7 V at 23°C, 0.5 V at 150°C and 0.3 V at 250°C, and reverse leakage current densities jR (at -50 V) of 0.1 μA/cm 2 at 23°C and 1 mA/cm 2 at 150°C. Calculated forward and reverse I- V characteristics using a simple self-consistent computer model are in good agreement with measured values. Calculated characteristics of a silicon SD with identical structure parameters, using the same model, show much poorer VBR, VF and jR values. The theoretical maximum value of VBR is physically limited by the largest allowed VF. For a V Fof ⋍1.6 V, V BR.maxis ⋍200 V in Si and ⋍800 simple technology allows manufacturing of large area GaAs Schottky diodes with average currents up to V in GaAs SDs. Our relatively 100 A.

  14. Fourier evaluation of broad Moessbauer spectra

    International Nuclear Information System (INIS)

    It is shown by the Fourier analysis of broad Moessbauer spectra that the even part of the distribution of the dominant hyperfine interaction (hyperfine field or quadrupole splitting) can be obtained directly without using least-square fitting procedures. Also the odd part of this distribution correlated with other hyperfine parameters (e.g. isomer shift) can be directly determined. Examples for amorphous magnetic and paramagnetic iron-based alloys are presented. (author)

  15. A Broad View of Macroeconomic Stability

    OpenAIRE

    José Antonio Ocampo

    2005-01-01

    This paper recommends a broad concept of macroeconomic stability, whereby “sound macroeconomic frameworks” include not only price stability and sound fiscal policies, but also a well-functioning real economy, sustainable debt ratios and healthy public and private sector balance sheets. These multiple dimensions imply using multiple policy instruments. The paper elaborates a framework for developing countries that involves active use of counter-cyclical macroeconomic policies (exchange rate, m...

  16. Crx broadly modulates the pineal transcriptome

    OpenAIRE

    Rovsing, Louise; Clokie, Samuel; Bustos, Diego M.; Rohde, Kristian; Steven L Coon; Litman, Thomas; Rath, Martin F.; Møller, Morten; Klein, David C.

    2011-01-01

    Cone-rod homeobox (Crx) encodes Crx, a transcription factor expressed selectively in retinal photoreceptors and pinealocytes, the major cell type of the pineal gland. Here, the influence of Crx on the mammalian pineal gland was studied by light and electron microscopy and by use of microarray and qRTPCR technology, thereby extending previous studies on selected genes (Furukawa et al. 1999). Deletion of Crx was not found to alter pineal morphology, but was found to broadly modulate the mouse p...

  17. Report on broad reconsiderations. Part 1. Energy and Climate

    International Nuclear Information System (INIS)

    In twenty policy areas various working groups have studied variants that can lead to a 20% budget cut in the government budgets of the Netherlands, which must be realized in 2015. The aim of the reconsiderations is to use less government means to realize the same results, or even better results if possible. The broad reconsideration in the field of energy and climate focuses on the expenditure for renewable energy and energy efficiency, mitigating (inter)national climate policy and fiscal benefits. This report addresses six policy variants.

  18. Relativistic redshifts in quasar broad lines

    International Nuclear Information System (INIS)

    The broad emission lines commonly seen in quasar spectra have velocity widths of a few percent of the speed of light, so special- and general-relativistic effects have a significant influence on the line profile. We have determined the redshift of the broad Hβ line in the quasar rest frame (determined from the core component of the [O III] line) for over 20,000 quasars from the Sloan Digital Sky Survey Data Release 7 quasar catalog. The mean redshift as a function of line width is approximately consistent with the relativistic redshift that is expected if the line originates in a randomly oriented Keplerian disk that is obscured when the inclination of the disk to the line of sight exceeds ∼30°-45°, consistent with simple active galactic nucleus unification schemes. This result also implies that the net line-of-sight inflow/outflow velocities in the broad-line region are much less than the Keplerian velocity when averaged over a large sample of quasars with a given line width.

  19. Relativistic redshifts in quasar broad lines

    CERN Document Server

    Tremaine, Scott; Liu, Xin; Loeb, Abraham

    2014-01-01

    The broad emission lines commonly seen in quasar spectra have velocity widths of a few per cent of the speed of light, so special- and general-relativistic effects have a significant influence on the line profile. We have determined the redshift of the broad H-beta line in the quasar rest frame (determined from the core component of the [OIII] line) for over 20,000 quasars from the Sloan Digital Sky Survey DR7 quasar catalog. The mean redshift as a function of line width is approximately consistent with the relativistic redshift that is expected if the line originates in a randomly oriented Keplerian disk that is obscured when the inclination of the disk to the line of sight exceeds ~30-45 degrees, consistent with simple AGN unification schemes. This result also implies that the net line-of-sight inflow/outflow velocities in the broad-line region are much less than the Keplerian velocity when averaged over a large sample of quasars with a given line width.

  20. Fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Dong Chen; Wenqing Liu; Yujun Zhang; Jianguo Liu; Ruifeng Kan; Min Wang; Xi Fang; Yiben Cui

    2007-01-01

    Tunable diode laser based gas detectors are now being used in a wide variety of applications for safety and environmental interest. A fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy (TDLAS) is developed, the laser used is a telecommunication near infrared distributed feed-back (DFB) tunable diode laser, combining with wavelength modulation specby combining optical fiber technique. An on-board reference cell provides on-line sensor calibration and almost maintenance-free operation. The sensor is suitable for large area field H2S monitoring application.

  1. Plasma-filled diode experiments on PBFA-II

    International Nuclear Information System (INIS)

    The PBFA-II accelerator is designed to use a Plasma Opening Switch (POS) for pulse shaping and voltage multiplication using inductive storage. The vacuum section of the machine consists of a set of short magnetically insulated transmission lines (MITLs) that both act as a voltage adder for series stacking of the pulses out of the 72 parallel plate water lines, and as a 100 nH (total) storage inductor upstream of a biconically shaped POS region. There are two POS plasma injection areas, located above and below an equatorial load, which has consisted of either a short circuit, a blade (electron beam) diode, or an Applied B magnetically insulated ion diode. The POS is designed to conduct up to 6 MA, and open into a 5 ohm diode load in 10 ns or less. Under these conditions, the voltage at the load is predicted to exceed 24 MV. Initial POS experiments using these loads have produced 1) opening times of typically 20 ns or longer, 2) poor current transfer efficiency (less than 50%) when load impedances averaged 2 ohms or more, and 3) differential switch opening in azimuthal segments of the power feed, thought to be caused by poor plasma uniformity across the flashboard plasma source. One possible explanation for 2) is that efficient transfer out of the POS requires that the current carried to the load be magnetically insulated, or else considerable energy will be deposited in the feed region between the POS and load. This had indeed been observed. The problem is further exacerbated by the longer current turn-on times that occur when an ion diode is used as the load

  2. Full-quantum light diode

    CERN Document Server

    Ghobadi, Roohollah

    2015-01-01

    Unidirectional light transport in one-dimensional nanomaterials at the quantum level is a crucial goal to achieve for upcoming computational devices. We here employ a full-quantum mechanical approach based on master equation to describe unidirectional light transport through a pair of two-level systems coupled to a one-dimensional waveguide. By comparing with published semi-classical results, we find that the nonlinearity of the system is reduced, thereby reducing also the unidirectional light transport efficiency. Albeit not fully efficient, we find that the considered quantum system can work as a light diode with an efficiency of approximately 60%. Our results may be used in quantum computation with classical and quantized light.

  3. Bilayer avalanche spin-diode logic

    International Nuclear Information System (INIS)

    A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing

  4. Diode-pumped CW molecular lasers

    Science.gov (United States)

    Wellegehausen, B.; Luhs, W.

    2016-05-01

    First continuous laser oscillation on many lines in the range of 533-635 nm on different transitions of Na2 and Te2 molecules has been obtained, optically pumped with common cw blue emitting InGaN diode lasers operating around 445 and 460 nm. Spectral narrowing of the diode laser is achieved with a beamsplitter and grating setup, allowing use of more than 50 % of the diode power. Operation conditions and properties of the laser systems are presented, and perspectives for the realization of compact low cost molecular lasers are discussed.

  5. Bilayer avalanche spin-diode logic

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Joseph S., E-mail: joseph.friedman@u-psud.fr; Querlioz, Damien [Institut d’Electronique Fondamentale, Univ. Paris-Sud, CNRS, 91405 Orsay (France); Fadel, Eric R. [Department of Materials Science, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wessels, Bruce W. [Department of Electrical Engineering & Computer Science, Northwestern University, Evanston, IL 60208 (United States); Department of Materials Science & Engineering, Northwestern University, Evanston, IL 60208 (United States); Sahakian, Alan V. [Department of Electrical Engineering & Computer Science, Northwestern University, Evanston, IL 60208 (United States); Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208 (United States)

    2015-11-15

    A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing.

  6. Bilayer avalanche spin-diode logic

    Directory of Open Access Journals (Sweden)

    Joseph S. Friedman

    2015-11-01

    Full Text Available A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing.

  7. Semiconductor laser diodes and the design of a D.C. powered laser diode drive unit

    OpenAIRE

    Cappuccio, Joseph C., Jr.

    1988-01-01

    Approved for public release; distribution is unlimited This thesis addresses the design, development and operational analysis of a D.C. powered semiconductor laser diode drive unit. A laser diode requires an extremely stable power supply since a picosecond spike of current or power supply switching transient could result in permanent damage. The design offers stability and various features for operational protection of the laser diode. The ability to intensity modulate (analog) and pulse m...

  8. Dosimetric evaluation using the diode measurements for total skin electron therapy technique

    Institute of Scientific and Technical Information of China (English)

    Ehab M.Attalla; Nashaat A.Deiab; Walaa S.Abd Elgawad

    2014-01-01

    The purpose of this study was to present the dosimetric study and evaluation the dose delivered to the skin tumor by using diode detector with total skin electron therapy (TSET).Methods: The total skin electron irradiation (TSEI) technique was used to treat ten patients with histological confirmed mycosis fungoides according to the Stanford staging system at the Radiotherapy Department, National Cancer Institute, Cairo University, Egypt. High dose rate electron beams with low electron energy 5 MeV from a Siemens linear accelerator were used for treatment. Diodes were calibrated at TSET distance 300 cm and field size (35 x 35) cm2.Results:The result of diodes measurements showed the dose to flat surface of the body was within ±10 % from the prescribed dose. Special areas of the body such as the perineum & eyelid showed large deviation up to 30% variation from the prescription dose.Conclusion:The diode results of this study wil be used as a quality assurance check for al new patients treated with TSET and to compare it to the prescribed dose delivered to the patients. It is recommends to evaluate the diodes measurements for al patients throughout the ful treatment cycle and to identify individu-aly the boost dose areas.

  9. Performance of the cold powered diodes and diode leads in the main magnets of the LHC

    Science.gov (United States)

    Willering, G. P.; Giloux, C.; Bajko, M.; Bednarek, M.; Bottura, L.; Charifoulline, Z.; Dahlerup-Petersen, K.; Dib, G.; D'Angelo, G.; Gharib, A.; Grand-Clement, L.; Izquierdo Bermudez, S.; Prin, H.; Roger, V.; Rowan, S.; Savary, F.; Tock, J.-Ph; Verweij, A.

    2015-12-01

    During quench tests in 2011 variations in resistance of an order of magnitude were found in the diode by-pass circuit of the main LHC magnets. An investigation campaign was started to understand the source, the occurrence and the impact of the high resistances. Many tests were performed offline in the SM18 test facility with a focus on the contact resistance of the diode to heat sink contact and the diode wafer temperature. In 2014 the performance of the diodes and diode leads of the main dipole bypass systems in the LHC was assessed during a high current qualification test. In the test a current cycle similar to a magnet circuit discharge from 11 kA with a time constant of 100 s was performed. Resistances of up to 600 μΩ have been found in the diode leads at intermediate current, but in general the high resistances decrease at higher current levels and no sign of overheating of diodes has been seen and the bypass circuit passed the test. In this report the performance of the diodes and in particular the contact resistances in the diode leads are analysed with available data acquired over more than 10 years from acceptance test until the main dipole training campaign in the LHC in 2015.

  10. Broad spectrum antibiotic compounds and use thereof

    Energy Technology Data Exchange (ETDEWEB)

    Koglin, Alexander; Strieker, Matthias

    2016-07-05

    The discovery of a non-ribosomal peptide synthetase (NRPS) gene cluster in the genome of Clostridium thermocellum that produces a secondary metabolite that is assembled outside of the host membrane is described. Also described is the identification of homologous NRPS gene clusters from several additional microorganisms. The secondary metabolites produced by the NRPS gene clusters exhibit broad spectrum antibiotic activity. Thus, antibiotic compounds produced by the NRPS gene clusters, and analogs thereof, their use for inhibiting bacterial growth, and methods of making the antibiotic compounds are described.

  11. Near infrared polymer light-emitting diodes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong; YANG Jian; HOU Qiong; MO Yueqi; PENG Junbiao; CAO Yong

    2005-01-01

    High efficiency of near infrared polymer light-emitting diodes with bilayer structure was obtained. The diode structure is ITO/PEDOT/L1/L2/Ba/Al, where L1 is phenyl-substituted poly [p-phenylphenylene vinylene] derivative (P-PPV), L2 is 9,9-dioctylfluorene (DOF) and 4,7- bis(3-hexylthiophen)-2-yl-2,1,3-naphthothiadiazole (HDNT) copolymer (PFHDNT10). The electroluminescence (EL) spectrum of diodes from PFHDNT10 is at 750 nm located in the range of near infrared. The maximum external quantum efficiency is up to 2.1% at the current density of 35 mA/cm2. The improvement of the diode's performances was considered to be the irradiative excitons confined in the interface between L1 and L2 layers.

  12. Defect assessment of irradiated STI diodes

    Energy Technology Data Exchange (ETDEWEB)

    Ohyama, H. E-mail: ohyama@cc.knct.ac.jp; Hayama, K.; Miura, T.; Simoen, E.; Claeys, C.; Poyai, A.; Nakabayashi, M.; Kobayashi, K

    2002-01-01

    The device performance degradation and the induced lattice defects of shallow trench isolation (STI) n{sup +}p diodes, subjected to different high energy particle irradiations will be described. The diodes were irradiated with 1-MeV neutrons, 2-MeV electrons and 20-MeV protons. Insight into the displacement damage mechanisms is obtained by analyzing the relation between the current damage coefficient, and the calculated non-ionizing energy loss. Deep level transient spectroscopy is used to detect the radiation-induced electron capture levels. Some levels are thought to be related to the degradation of the STI interfaces. The degradation of the electrical performance results from the induced defects. A different degradation behavior in dependence of the irradiation particle is found for meander diodes compared with square diodes.

  13. Diode lasers applied to element spectrometry

    International Nuclear Information System (INIS)

    The radiation of continuous-wave single mode laser diodes is narrow-banded and tunable either by current or by temperature variations. Such laser diodes are available up to an output power of several hundred mW. Due to these properties, in the last decade laser diodes were increasingly used for applications in analytical spectrochemistry. It is shown which wavelength ranges are of special interest for the atomic absorption spectrometry and achievable for the fundamental as well as the frequency doubled wavelength of commercially available laser diodes. Besides the frequency doubling another nonlinear technique, the sum frequency generation, is presented and demonstrated, for example, the generation of the wavelengths 365 nm and 283 nm.

  14. Diode lasers applied to element spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Franzke, Joachim [Institute for Spectrochemistry and Applied Spectroscopy, Dortmund (Germany)

    2001-11-15

    The radiation of continuous-wave single mode laser diodes is narrow-banded and tunable either by current or by temperature variations. Such laser diodes are available up to an output power of several hundred mW. Due to these properties, in the last decade laser diodes were increasingly used for applications in analytical spectrochemistry. It is shown which wavelength ranges are of special interest for the atomic absorption spectrometry and achievable for the fundamental as well as the frequency doubled wavelength of commercially available laser diodes. Besides the frequency doubling another nonlinear technique, the sum frequency generation, is presented and demonstrated, for example, the generation of the wavelengths 365 nm and 283 nm.

  15. Diode laser (980nm) cartilage reshaping

    Science.gov (United States)

    El Kharbotly, A.; El Tayeb, T.; Mostafa, Y.; Hesham, I.

    2011-03-01

    Loss of facial or ear cartilage due to trauma or surgery is a major challenge to the otolaryngologists and plastic surgeons as the complicated geometric contours are difficult to be animated. Diode laser (980 nm) has been proven effective in reshaping and maintaining the new geometric shape achieved by laser. This study focused on determining the optimum laser parameters needed for cartilage reshaping with a controlled water cooling system. Harvested animal cartilages were angulated with different degrees and irradiated with different diode laser powers (980nm, 4x8mm spot size). The cartilage specimens were maintained in a deformation angle for two hours after irradiation then released for another two hours. They were serially measured and photographed. High-power Diode laser irradiation with water cooling is a cheep and effective method for reshaping the cartilage needed for reconstruction of difficult situations in otorhinolaryngologic surgery. Key words: cartilage,diode laser (980nm), reshaping.

  16. Proto-I switching and diode studies

    International Nuclear Information System (INIS)

    Proto-I is a 3 MV, 800 kA, 24 ns electron beam accelerator that is under development at Sandia Laboratories. It represents an initial effort to develop a scalable technology that is applicable to accelerators for electron beam driven, inertial confinement fusion studies. Energy is supplied to each of the two diodes from six oil-dielectric Blumlein transmission lines (PFL) operating in parallel. A Marx generator charges three intermediate storage, water-dielectric capacitors which subsequently transfer the stored energy to the PFL. The discharge of the PFL is initiated by the simultaneous closure of 12 triggered oil-dielectric rail switches. Data will be presented on the operation of these multichannel switches. The two diodes have a common anode. Cathode diameters can be varied from 10 to 60 cm. Results of initial diode experiments and comparisons with theory are discussed. Plasma filled diode experiments are also reported, indicating pinch collapse velocities in excess of 109 cm/s

  17. Proto-I switching and diode studies

    International Nuclear Information System (INIS)

    Proto-I is a 3 MV, 800 kA, 24 ns electron beam accelerator that is under development as an initial effort to develop a scalable technology that is applicable to accelerators for electron beam driven, inertial confinement fusion studies. Energy is supplied to each of the two diodes from six oil-dielectric Blumlein transmission lines (PFL) operating in parallel. A Marx generator charges three intermediate storage, water-dielectric capacitors which subsequently transfer the stored energy to the PFL. The discharge of the PFL is initiated by the simultaneous closure of 12 triggered oil-dielectric rail switches. Data are presented on the operation of these multichannel switches. The two diodes have a common anode. Cathode diameters can be varied from 10 to 60 cm. Results of initial diode experiments and comparisons with theory are discussed. Plasma filled diode experiments are also reported, indicating pinch collapse velocities in excess of 109 cm/s

  18. Varactor diode assembly with low parasitic reactances

    Science.gov (United States)

    Dickens, L. E.

    1975-01-01

    Development of varactor diode assembly overcomes parasitic reactances of conventional varactor packages. In specially constructed assembly very high idler-frequency to signal-frequency ratios are used to obtain low-noise operation over maximum bandwidth.

  19. Blood sugar monitoring with laser diode

    Science.gov (United States)

    Zhang, Xiqin; Chen, Jianhong; Yeo, Joon Hock

    2006-09-01

    In this paper, the non-invasive measurement of blood sugar level was studied by use of near infrared laser diode. The in-vivo experiments were carried out using laser diodes with wavelength 1625nm and 1650nm. Several volunteers were tested before and after drinking glucose solution. We took blood from a fingertip and measured its concentration with a glucose meter while taking signal voltage from laser diode system. The signal voltage was processed by using a computer and blood absorption was obtained. The results show that blood sugar level and blood absorption have similar trends before and after drinking glucose solution. We also compared the trends of drinking glucose solution and pure water and the results show that the difference of blood absorption is obvious. From the results we can see that laser diode is suitable for blood glucose monitoring.

  20. Diode Based on Amorphous SiC

    Directory of Open Access Journals (Sweden)

    V.S. Zakhvalinskii

    2013-12-01

    Full Text Available Diode structure on the basis of amorphous silicon carbide and p-type polycrystalline silicon (Eurosolar were obtained with magnetron RF-nonreactive sputtering method from solid-phase target in argon atmosphere.

  1. Diode Based on Amorphous SiC

    OpenAIRE

    V.S. Zakhvalinskii; L.V. Borisenko; A.J. Aleynikov; E.A. Piljuk; I. Goncharov; S.V. Taran

    2013-01-01

    Diode structure on the basis of amorphous silicon carbide and p-type polycrystalline silicon (Eurosolar) were obtained with magnetron RF-nonreactive sputtering method from solid-phase target in argon atmosphere.

  2. Synthesis and optical properties of cadmium selenide quantum dots for white light-emitting diode application

    International Nuclear Information System (INIS)

    Highlights: ► Stable CdSe QDs were synthesized by the one-step and two-level process respectively. ► The fabricated white LEDs show good white balance. ► CdSe QDs present well green to yellow band luminescence. ► CdSe QDs displayed a broad excitation band. - Abstract: Yellow light-emitting cadmium selenide quantum dots were synthesized using one-step and two-step methods in an aqueous medium. The structural luminescent properties of these quantum dots were investigated. The obtained cadmium selenide quantum dots displayed a broad excitation band suitable for blue or near-ultraviolet light-emitting diode applications. White light-emitting diodes were fabricated by coating the cadmium selenide samples onto a 460 nm-emitting indium gallium nitrite chip. Both samples exhibited good white balance. Under a 20 mA working current, the white light-emitting diode fabricated via the one-step and two-step methods showed Commission Internationale de l’Éclairage coordinates at (0.27, 0.23) and (0.27, 0.33), respectively, and a color rendering index equal to 41 and 37, respectively. The one-step approach was simpler, greener, and more effective than the two-step approach. The one-step approach can be enhanced by combining cadmium selenide quantum dots with proper phosphors

  3. High Current Density 2D/3D Esaki Tunnel Diodes

    OpenAIRE

    Krishnamoorthy, Sriram; Lee II, Edwin W.; Lee, Choong Hee; Zhang, Yuewei; McCulloch, William D.; Johnson, Jared M.; Hwang, Jinwoo; Wu, Yiying; Rajan, Siddharth

    2016-01-01

    The integration of two-dimensional materials such as transition metal dichalcogenides with bulk semiconductors offer interesting opportunities for 2D/3D heterojunction-based novel device structures without any constraints of lattice matching. By exploiting the favorable band alignment at the GaN/MoS2 heterojunction, an Esaki interband tunnel diode is demonstrated by transferring large area, Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current density of 446 A/cm2 with repeatable roo...

  4. Light-emitting diodes - Their potential in biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Naichia Gary; Wu, Chia-Hao [College of Applied Sciences, MingDao University, 369 Wen-Hua Road, Peetou, Changhua 52345 (China); Cheng, Ta Chih [Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, 1 Hseuh-Fu Rd., Nei-Pu Hsiang, Pingtung 91201 (China)

    2010-10-15

    The rapid development of high brightness light-emitting diodes (LEDs) makes feasible the use of LEDs, among other light sources (such as laser, intense pulse light and other incoherent light systems), for medical treatment and light therapy. This paper provides a general review on red, green, blue, ultraviolet LED applications in photo rejuvenation and medical treatments of a variety of physical abnormalities, as well as the relief of stress, circadian rhythm disorders, and seasonal affective disorder. The review, concentrated in the papers published after 1990, intends to show that LEDs are well qualified to succeed its more energy demanding counterparts in the named areas and beyond. (author)

  5. Laser semiconductor diode integrated with frequency doubler

    International Nuclear Information System (INIS)

    The invention relates to the technology of optoelectronic semiconductor devices and may be used in the production of laser semiconductor diodes integrated with optical nonlinear elements. The laser semiconductor diode integrated with frequency doubler includes a semiconductor substrate, a laser structure with waveguide. metal contacts in the waveguide of the laser structure it is formed a nanostructured field so that the nanostructure provides for the fulfillment of the phase synchronism conditions

  6. Organic Schottky diode: Characterization of traps

    Science.gov (United States)

    Rani, Varsha; Yadav, Sarita; Ghosh, Subhasis

    2015-06-01

    We have demonstrated the formation and characterization of Schottky junction in metal/organic/metal sandwiched devices based on organic molecular semiconductors, using current-voltage (J-V) and capacitance-voltage (C-V) characteristics, in particular how traps affect the device performance. Ideality factor of organic Schottky diode is always greater than unity and increases with decreasing the temperature. Diffusion coefficient has been determined from current density -voltage characteristic in Schottky diodes.

  7. Interferometry and Holography With Diode Laser Light

    CERN Document Server

    Lunazzi, Jose Joaquin

    2016-01-01

    We made an interferometric Michelson type setup and a simple holographic setup to demonstrate the feasibility of interferometric and holographic techniques by means of a diode laser. The laser was made by using a common diode available as a penlight element (less than R$ 15,00 value) and a simple stabilized 110 VCA- 3 VCC power supply. Interference fringes and holograms of small objects where obtained very similar to those of a helium-neon laser based setup.

  8. Dynamics of resonant tunneling diode optoelectronic oscillators

    OpenAIRE

    Romeira, Bruno

    2012-01-01

    The nonlinear dynamics of optoelectronic integrated circuit (OEIC) oscillators comprising semiconductor resonant tunneling diode (RTD) nanoelectronic quantum devices has been investigated. The RTD devices used in this study oscillate in the microwave band frequency due to the negative di erential conductance (NDC) of their nonlinear current voltage characteristics, which is preserved in the optoelectronic circuit. The aim was to study RTD circuits incorporating laser diodes and...

  9. Design and construction of a broad-band electric field probe

    International Nuclear Information System (INIS)

    The design of a broad-band electric field probe based on a resistive film diode antenna on RT/Duroid substrate to measure the electric RF/MW fields as constructed at the National Radiation Protection Department (NRPD) of the Atomic Energy Organization of Iran (AEOI) are described in this paper. A square law diode detector with a matching circuit and also low pass filter have been used to produce a dc current proportional to the square RF voltage across the resistive antenna gap. A double-strip coplanar waveguide has also been designed to transfer this dc current to an amplifier with an output signal showing the electric field intensity in one direction. By using three mutually orthogonal resistive antennas, an isotropic electric field probe was made. All parts of this probe have been completely modeled and solved by the MATLAB computer program to determine the optimum values of the elements of the probe. The frequency response of the probe has also been theoretically found to be flat in the range 0.8 to 3 GHz. It was found to be quite satisfactory compared with those of similar probes commercially available. The probe is being used routinely in practice. (author)

  10. Microwave emission from pulsed, relativistic e-beam diodes. I. The smooth-bore magnetron

    International Nuclear Information System (INIS)

    Measurements of intense magnetron oscillations in pulsed, field-emission diodes (approx.350 kV, 30 nsec) subjected to crossed externally applied fields (< or approx. =16 kG) are reported. The oscillations set in as soon as the magnetic field exceeds the critical field necessary for cutting off the diode current. The oscilations are diagnosed by the microwave emission which is studied in the range from 7 to 40 GHz. The radiation is emitted in broad frequency bands, it is strongly polarized, and can be tuned by the magnetic field; the power levels are typically 1 to 5 kW. The observations are consistent with the onset of the slipping stream instability in the Brillouin space charge flow of the electron cloud

  11. Diode-based microbolometer with performance enhanced by broadband metamaterial absorber.

    Science.gov (United States)

    Ma, Wei; Jia, Delin; Wen, Yongzheng; Yu, Xiaomei; Feng, Yun; Zhao, Yuejin

    2016-07-01

    This Letter reports a microbolometer integrated with a broadband metamaterial absorber (MMA) to enhance its performance, which contains series-connected silicon diodes as the temperature sensor. The broadband MMA is readily integrated into the device by introducing an array of different-sized square resonators on the silicon nitride structural layer, while the widened titanium interconnecting wires between individual diodes serve as the ground plane. In a comparative experiment, the broadband MMA was demonstrated to be superior to the ordinary silicon nitride absorber in a broad spectra range, especially in a long-wavelength IR regime, which directly leads to an increase in IR responsivity by 60%. More importantly, this enhancement in responsivity was achieved with no sacrifice of the response time due to the negligible thermal mass of the introduced resonator array. PMID:27367079

  12. Polarization-engineered GaN/InGaN/GaN tunnel diodes

    International Nuclear Information System (INIS)

    We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density and low tunneling turn-on voltage. Wentzel-Kramers-Brillouin calculations were used to model and design tunnel junctions with narrow band gap InGaN-based barrier layers. N-polar p-GaN/In0.33Ga0.67N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient interband tunneling was achieved close to zero bias with a high current density of 118 A/cm2 at a reverse bias of 1 V, reaching a maximum current density up to 9.2 kA/cm2. These results represent the highest current density reported in III-nitride tunnel junctions and demonstrate the potential of III-nitride tunnel devices for a broad range of optoelectronic and electronic applications.

  13. Study on the interfacial layer in ZnO/GaN heterostructure light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Seung-Ho; Chung, Tae-Hoon [Department of Materials Science and Engineering, Photonic and Electronic Thin Film Laboratory, Chonnam National University, 300 Yong-bong dong, Gwangju 500-757 (Korea, Republic of); Lee, Byung-Teak [Department of Materials Science and Engineering, Photonic and Electronic Thin Film Laboratory, Chonnam National University, 300 Yong-bong dong, Gwangju 500-757 (Korea, Republic of)], E-mail: btlee@jnu.ac.kr

    2009-02-15

    Heterostructure light-emitting diodes (LEDs) were fabricated by growing Ga-doped n-ZnO and undoped ZnO layers on p-GaN/Al{sub 2}O{sub 3} templates. The p-n junction showed a diode like I-V characteristic and emitted electroluminescence (EL) peaks at 430 nm, 440 nm and 480 nm along with a broad band of yellow light. An interfacial layer was observed between ZnO and GaN, identified as ZnGa{sub 2}O{sub 4} by transmission electron microscopy and X-ray diffraction analysis. It was observed that thickness of the interfacial layer did not significantly affect EL characteristics of the ZnO/GaN heterostructure LED.

  14. Study on the interfacial layer in ZnO/GaN heterostructure light-emitting diode

    International Nuclear Information System (INIS)

    Heterostructure light-emitting diodes (LEDs) were fabricated by growing Ga-doped n-ZnO and undoped ZnO layers on p-GaN/Al2O3 templates. The p-n junction showed a diode like I-V characteristic and emitted electroluminescence (EL) peaks at 430 nm, 440 nm and 480 nm along with a broad band of yellow light. An interfacial layer was observed between ZnO and GaN, identified as ZnGa2O4 by transmission electron microscopy and X-ray diffraction analysis. It was observed that thickness of the interfacial layer did not significantly affect EL characteristics of the ZnO/GaN heterostructure LED

  15. Generation of single-frequency tunable green light in a coupled ring tapered diode laser cavity

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Petersen, Paul Michael

    2013-01-01

    the broad wavelength range from 1049 nm to 1093 nm and the beam propagation factor is improved from M2 = 2.8 to below 1.1. The laser frequency is automatically locked to the cavity resonance frequency using optical feedback. Furthermore, we show that this adaptive external cavity approach leads to......We report the realization of a tapered diode laser operated in a coupled ring cavity that significantly improves the coherence properties of the tapered laser and efficiently generates tunable light at the second harmonic frequency. The tapered diode laser is tunable with single-frequency output in...... efficient frequency doubling. More than 500 mW green output power is obtained by placing a periodically poled LiNbO3 crystal in the external cavity. The single frequency green output from the laser system is tunable in the 530 nm to 533 nm range limited by the LiNbO3 crystal. The optical to optical...

  16. Active differential optical absorption spectroscopy for NO2 gas pollution using blue light emitting diodes

    Science.gov (United States)

    Aljalal, Abdulaziz; Gasmi, Khaled; Al-Basheer, Watheq

    2015-05-01

    Availability of high intensity light emitting diodes in the blue region offer excellent opportunity for using them in active Differential Optical Absorption Spectroscopy (DOAS) to detect air pollution. Their smooth and relatively broad spectral emissions as well as their long life make them almost ideal light sources for active DOAS. In this study, we report the usage of a blue light emitting diode in an active DOAS setup to measure traces of NO2 gas and achieving few parts per billion detection limit for a path length of 300 m. Details of the setup will be presented along with the effects on measurement accuracy due to shifts in the measured spectra calibration and due to using theoretical instrument Gaussian function instead of the measured instrument function.

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

    International Nuclear Information System (INIS)

    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. (fundamental areas of phenomenology(including applications))

  18. A p-i-n junction diode based on locally doped carbon nanotube network

    OpenAIRE

    Xiaodong Liu; Changxin Chen; Liangming Wei; Nantao Hu; Chuanjuan Song; Chenghao Liao; Rong He; Xusheng Dong; Ying Wang; Qinran Liu; Yafei Zhang

    2016-01-01

    A p-i-n junction diode constructed by the locally doped network of single-walled carbon nanotubes (SWNTs) was investigated. In this diode, the two opposite ends of the SWNT-network channel were selectively doped by triethyloxonium hexachloroantimonate (OA) and polyethylenimine (PEI) to obtain the air-stable p- and n-type SWNTs respectively while the central area of the SWNT-network remained intrinsic state, resulting in the formation of a p-i-n junction with a strong built-in electronic field...

  19. Performance of the cold powered diodes and diode leads in the main magnets of the LHC

    CERN Document Server

    Willering, G P; Bajko, M; Bednarek, M; Bottura, L; Charifoulline, Z; Dahlerup-Petersen, K; Dib, G; D'Angelo, G; Gharib, A; Grand-Clement, L; Izquierdo Bermudez, S; Prin, H; Roger, V; Rowan, S; Savary, F; Tock, J-Ph; Verweij, A

    2015-01-01

    During quench tests in 2011 variations in resistance of an order of magnitude were found in the diode by-pass circuit of the main LHC magnets. An investigation campaign was started to understand the source, the occurrence and the impact of the high resistances. Many tests were performed offline in the SM18 test facility with a focus on the contact resistance of the diode to heat sink contact and the diode wafer temperature. In 2014 the performance of the diodes and diode leads of the main dipole bypass systems in the LHC was assessed during a high current qualification test. In the test a current cycle similar to a magnet circuit discharge from 11 kA with a time constant of 100 s was performed. Resistances of up to 600 μΩ have been found in the diode leads at intermediate current, but in general the high resistances decrease at higher current levels and no sign of overheating of diodes has been seen and the bypass circuit passed the test. In this report the performance of the diodes and in particular the co...

  20. Operation and maintenance manual for diode performance analysis program DIODE0

    International Nuclear Information System (INIS)

    This program computes diode performance parameters for the e beam fusion accelerators HYDRA, PROTO I and PROTO II. The program works in conjunction with other programs in the data acquisition facility library. It reads the input data produced by the Tekronix R7012 Transient Digitizers off the disc. It then computes and plots the diode corrected voltages, impedances, powers, and energies

  1. A broad view of model validation

    International Nuclear Information System (INIS)

    The safety assessment of a nuclear waste repository requires the use of models. Such models need to be validated to ensure, as much as possible, that they are a good representation of the actual processes occurring in the real system. In this paper we attempt to take a broad view by reviewing step by step the modeling process and bringing out the need to validating every step of this process. This model validation includes not only comparison of modeling results with data from selected experiments, but also evaluation of procedures for the construction of conceptual models and calculational models as well as methodologies for studying data and parameter correlation. The need for advancing basic scientific knowledge in related fields, for multiple assessment groups, and for presenting our modeling efforts in open literature to public scrutiny is also emphasized. 16 refs

  2. Buildup factors for broad gamma beams

    International Nuclear Information System (INIS)

    The paper deals with buildup factors for the photon number and the exposure in broad conical beams penetrating through iron slabs. Using the Monte Carlo method, the dependence on the thickness of the slabs is calculated for various geometrical configurations of the 137Cs radiation source, the slab and the detector. The same dependence has also been measured for 137Cs and 60Co. The results show the dependence of the buildup factor B on the collimation angle α (B increases with increasing α), on the distance a between the source and the slab (B increases with increasing a), and on the distance b between the detector and the slab (B decreases with increasing b). Comparison of the obtained results with those from model configurations shows that in the latter case errors may range up to nearly 100%. (author)

  3. Broad-band acoustic hyperbolic metamaterial

    CERN Document Server

    Shen, Chen; Sui, Ni; Wang, Wenqi; Cummer, Steven A; Jing, Yun

    2015-01-01

    Acoustic metamaterials (AMMs) are engineered materials, made from subwavelength structures, that exhibit useful or unusual constitutive properties. There has been intense research interest in AMMs since its first realization in 2000 by Liu et al. A number of functionalities and applications have been proposed and achieved using AMMs. Hyperbolic metamaterials are one of the most important types of metamaterials due to their extreme anisotropy and numerous possible applications, including negative refraction, backward waves, spatial filtering, and subwavelength imaging. Although the importance of acoustic hyperbolic metamaterials (AHMMs) as a tool for achieving full control of acoustic waves is substantial, the realization of a broad-band and truly hyperbolic AMM has not been reported so far. Here, we demonstrate the design and experimental characterization of a broadband AHMM that operates between 1.0 kHz and 2.5 kHz.

  4. Crx broadly modulates the pineal transcriptome

    DEFF Research Database (Denmark)

    Rovsing, Louise; Clokie, Samuel; Bustos, Diego M;

    2011-01-01

    microarray and qRTPCR technology, thereby extending previous studies on selected genes (Furukawa et al. 1999). Deletion of Crx was not found to alter pineal morphology, but was found to broadly modulate the mouse pineal transcriptome, characterized by a > 2-fold down-regulation of 543 genes and a > 2-fold up-regulation...... of 745 genes (p < 0.05). Of these, one of the most highly up-regulated (18-fold) was Hoxc4, a member of the Hox gene family, members of which are known to control gene expression cascades. During a 24-h period, a set of 51 genes exhibited differential day/night expression in pineal glands of wild...... influences differential night/day gene expression in this tissue. Some effects of Crx deletion on the pineal transcriptome might be mediated by Hoxc4 up-regulation....

  5. Magnetohydrodynamic stability of broad line region clouds

    CERN Document Server

    Krause, Martin; Burkert, Andreas

    2012-01-01

    Hydrodynamic stability has been a longstanding issue for the cloud model of the broad line region in active galactic nuclei. We argue that the clouds may be gravitationally bound to the supermassive black hole. If true, stabilisation by thermal pressure alone becomes even more difficult. We further argue that if magnetic fields should be present in such clouds at a level that could affect the stability properties, they need to be strong enough to compete with the radiation pressure on the cloud. This would imply magnetic field values of a few Gauss for a sample of Active Galactic Nuclei we draw from the literature. We then investigate the effect of several magnetic configurations on cloud stability in axi-symmetric magnetohydrodynamic simulations. For a purely azimuthal magnetic field which provides the dominant pressure support, the cloud first gets compressed by the opposing radiative and gravitational forces. The pressure inside the cloud then increases, and it expands vertically. Kelvin-Helmholtz and colu...

  6. Computational study of magnetic-dam effects in a high-impedance diode

    International Nuclear Information System (INIS)

    Computer simulations have been conducted to test the magnetic dam concept as a means for boosting the overall ion efficiency of high impedance diodes. The dam consists of a cell located immediately behind the anode foil containing a wire along its central axis which carries a current flowing in a direction opposite to that in the diode gap. The azimuthal magnetic field generated by the wire current, I/sub w/, reflects the electrons crossing the foil back into the A-K gap at higher radii where their space charge can enhance ion emission over relatively large areas. Significant increases in the ion current were observed for several values of I/sub w/ but a simultaneous increase in electron current prevented gains in overall ion efficiency. Instead, only decreased impedances were observed. The cause of this phenomenon is explained and indicates solutions which could benefit a wide range of future diode designs

  7. Schottky Barrier mapping of the W/Si diode using ballistic electron emission microscopy

    Science.gov (United States)

    Durcan, Christopher; Balsano, Robert; Pieniazek, Nicholas; Labella, Vincent

    2015-03-01

    The Schottky barrier of the W/Si(001) diode was investigated and spatially mapped at the nanoscale using ballistic electron emission microscopy (BEEM) and ballistic hole emission microscopy (BHEM). The miscibility of tungsten and silicon creates a thin silicide upon deposition with transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) showing the changes in the silicide over several weeks. Using standard current voltage measurements there is no change in the charge transport across the diode during this time period. However, BEEM measurements do show dramatic changes to the transport of ballistic electrons over time with nanoscale resolution. Time dependent Schottky barrier maps are generated over a 1 μm x 1 μm area and provide valuable insight to the barrier height homogeneity, defect formation, and interfacial effects occurring in the diode.

  8. Optical polarization of m-plane In-GaN/GaN light-emitting diodes characterized via confocal microscope

    Energy Technology Data Exchange (ETDEWEB)

    Masui, Hisashi; Yamada, Hisashi; Iso, Kenji; Hirasawa, Hirohiko; Fellows, Natalie N.; Speck, James S.; Nakamura, Shuji; DenBaars, Steven P. [Solid-State Lighting and Display Center, Materials Department, College of Engineering, University of California, Santa Barbara, California 93106-5055 (United States)

    2008-05-15

    A confocal microscope was applied to characterize near-field optical polarization of light emission from InGaN-based light-emitting diodes prepared on a nonpolar orientation. Detection of stray light was significantly reduced as a result of the confocal technique compared to broad-area measurements. The confocal measurement required no special sample preparation and obtained data was directly interpretable. A polarization ratio of 0.83 was measured on long-wavelength emitting devices and was sustained over two orders of magnitude of low current range. Energy shifts and separation of emission peaks for the two polarization components were evaluated to discuss the valence-band structure. Energy shifts indicated that the topmost band vertical stroke X right angle had a heavier effective mass than the lower band vertical stroke Z right angle. Splitting energy of InGaN was estimated to be 30 meV. Results were consistent with the past reports, thus it was confirmed that the confocal microscope is a valid technique to characterize near-field optical polarization. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Change in Species Diversity during Recovering Process of Evergreen Broad-leaved Fo rest

    Institute of Scientific and Technical Information of China (English)

    WenYuanguang; LiuShirong; ChenFang; HeTatping; LiangHongwen

    2005-01-01

    Evergreen broad-leaved forest is one of the most important vegetation types in China. Because of the human activities, evergreen broad-leaved forest has been destroyed extensively, leading to degraded ecosystem. It is urgent to conserve and restore these natural forests in China.tn this paper, the tendency and rate of species diversity restoration of the evergreen broad-lea ved forest in Darning Mountain has been studied. The main results are as follows:(a) in subtropical mid-mountain area, species diversity in degraded evergreen broad-leaved forest can be restored. Through analyzing b diversity index of communities in different time and space, it was found that the species composition of communities tend to be the same as that in the zonal evergreen broad-leaved forest. (b) The restoration rate of evergreen broad-leaved forest was very fast. Planting Chinese fir after clear-cutting and controlled burning of the forest 178 species appeared in a 60Om2, sample area after 20 years"" natural recovering. Among these species, 58 were tree layer and the height of community reached 18m, The survey suggested that it would take only 20 years for the degraded forest to develop into community composed of light demanding broad-leaved pioneer trees and rain-tolerance broad-leaved trees, and it need another 40-80 years to reach the stage consisting of min-tulerance evergreen broad-leaved trees, (c) Species number increased quickly at the early stage (2-20 years) during vegetation recovering process toward the climax, and decreased at the min-stage (50-60 years ), then maintained a relatively stable level at the late-stage (over 150 years).

  10. The influence of interlayer exchange coupling in giant-magnetoresistive devices on spin diode effect in wide frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Ziętek, Sławomir, E-mail: zietek@agh.edu.pl; Skowroński, Witold; Wiśniowski, Piotr; Czapkiewicz, Maciej; Stobiecki, Tomasz [Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków (Poland); Ogrodnik, Piotr [Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków (Poland); Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warszawa (Poland); Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego 17, 60-179 Poznań (Poland); Barnaś, Józef [Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego 17, 60-179 Poznań (Poland); Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań (Poland)

    2015-09-21

    Spin diode effect in a giant magnetoresistive strip is measured in a broad frequency range, including resonance and off-resonance frequencies. The off-resonance dc signal is relatively strong and also significantly dependent on the exchange coupling between magnetic films through the spacer layer. The measured dc signal is described theoretically by taking into account magnetic dynamics induced by Oersted field created by an ac current flowing through the system.

  11. The influence of interlayer exchange coupling in giant-magnetoresistive devices on spin diode effect in wide frequency range

    International Nuclear Information System (INIS)

    Spin diode effect in a giant magnetoresistive strip is measured in a broad frequency range, including resonance and off-resonance frequencies. The off-resonance dc signal is relatively strong and also significantly dependent on the exchange coupling between magnetic films through the spacer layer. The measured dc signal is described theoretically by taking into account magnetic dynamics induced by Oersted field created by an ac current flowing through the system

  12. Scalable Light Module for Low-Cost, High-Efficiency Light- Emitting Diode Luminaires

    Energy Technology Data Exchange (ETDEWEB)

    Tarsa, Eric [Cree, Inc., Goleta, CA (United States)

    2015-08-31

    During this two-year program Cree developed a scalable, modular optical architecture for low-cost, high-efficacy light emitting diode (LED) luminaires. Stated simply, the goal of this architecture was to efficiently and cost-effectively convey light from LEDs (point sources) to broad luminaire surfaces (area sources). By simultaneously developing warm-white LED components and low-cost, scalable optical elements, a high system optical efficiency resulted. To meet program goals, Cree evaluated novel approaches to improve LED component efficacy at high color quality while not sacrificing LED optical efficiency relative to conventional packages. Meanwhile, efficiently coupling light from LEDs into modular optical elements, followed by optimally distributing and extracting this light, were challenges that were addressed via novel optical design coupled with frequent experimental evaluations. Minimizing luminaire bill of materials and assembly costs were two guiding principles for all design work, in the effort to achieve luminaires with significantly lower normalized cost ($/klm) than existing LED fixtures. Chief project accomplishments included the achievement of >150 lm/W warm-white LEDs having primary optics compatible with low-cost modular optical elements. In addition, a prototype Light Module optical efficiency of over 90% was measured, demonstrating the potential of this scalable architecture for ultra-high-efficacy LED luminaires. Since the project ended, Cree has continued to evaluate optical element fabrication and assembly methods in an effort to rapidly transfer this scalable, cost-effective technology to Cree production development groups. The Light Module concept is likely to make a strong contribution to the development of new cost-effective, high-efficacy luminaries, thereby accelerating widespread adoption of energy-saving SSL in the U.S.

  13. High power laser diodes at 14xx nm wavelength range for industrial and medical applications

    Science.gov (United States)

    Telkkälä, Jarkko; Boucart, Julien; Krejci, Martin; Crum, Trevor; Lichtenstein, Norbert

    2014-03-01

    We report on the development of the latest generation of high power laser diodes at 14xx nm wavelength range suitable for industrial applications such as plastics welding and medical applications including acne treatment, skin rejuvenation and surgery. The paper presents the newest chip generation developed at II-VI Laser Enterprise, increasing the output power and the power conversion efficiency while retaining the reliability of the initial design. At an emission wavelength around 1440 nm we applied the improved design to a variety of assemblies exhibiting maximum power values as high as 7 W for broad-area single emitters. For 1 cm wide bars on conductive coolers and for bars on active micro channel coolers we have obtained 50 W and 72 W in continuous wave (cw) operation respectively. The maximum power measured for a 1 cm bar operated with 50 μs pulse width and 0.01% duty cycle was 184 W, demonstrating the potential of the chip design for optimized cooling. Power conversion efficiency values as high as 50% for a single emitter device and over 40% for mounted bars have been demonstrated, reducing the required power budget to operate the devices. Both active and conductive bar assembly configurations show polarization purity greater than 98%. Life testing has been conducted at 95 A, 50% duty cycle and 0.5 Hz hard pulsed operation for bars which were soldered to conductive copper CS mounts using our hard solder technology. The results after 5500 h, or 10 million "on-off" cycles show stable operation.

  14. Peculiar Broad Absorption Line Quasars found in DPOSS

    CERN Document Server

    Brunner, R J; Djorgovski, S G; Gal, R R; Mahabal, A A; Lopes, P A A; De Carvalho, R R; Odewahn, S C; Castro, S; Thompson, D; Chaffee, F; Darling, J; Desai, V; Brunner, Robert J.; Hall, Patrick B.

    2003-01-01

    With the recent release of large (i.e., > hundred million objects), well-calibrated photometric surveys, such as DPOSS, 2MASS, and SDSS, spectroscopic identification of important targets is no longer a simple issue. In order to enhance the returns from a spectroscopic survey, candidate sources are often preferentially selected to be of interest, such as brown dwarfs or high redshift quasars. This approach, while useful for targeted projects, risks missing new or unusual species. We have, as a result, taken the alternative path of spectroscopically identifying interesting sources with the sole criterion being that they are in low density areas of the g - r and r - i color-space defined by the DPOSS survey. In this paper, we present three peculiar broad absorption line quasars that were discovered during this spectroscopic survey, demonstrating the efficacy of this approach. PSS J0052+2405 is an Iron LoBAL quasar at a redshift z = 2.4512 with very broad absorption from many species. PSS J0141+3334 is a reddened...

  15. Automatic and controlled processing and the Broad Autism Phenotype.

    Science.gov (United States)

    Camodeca, Amy; Voelker, Sylvia

    2016-01-30

    Research related to verbal fluency in the Broad Autism Phenotype (BAP) is limited and dated, but generally suggests intact abilities in the context of weaknesses in other areas of executive function (Hughes et al., 1999; Wong et al., 2006; Delorme et al., 2007). Controlled processing, the generation of search strategies after initial, automated responses are exhausted (Spat, 2013), has yet to be investigated in the BAP, and may be evidenced in verbal fluency tasks. One hundred twenty-nine participants completed the Delis-Kaplan Executive Function System Verbal Fluency test (D-KEFS; Delis et al., 2001) and the Broad Autism Phenotype Questionnaire (BAPQ; Hurley et al., 2007). The BAP group (n=53) produced significantly fewer total words during the 2nd 15" interval compared to the Non-BAP (n=76) group. Partial correlations indicated similar relations between verbal fluency variables for each group. Regression analyses predicting 2nd 15" interval scores suggested differentiation between controlled and automatic processing skills in both groups. Results suggest adequate automatic processing, but slowed development of controlled processing strategies in the BAP, and provide evidence for similar underlying cognitive constructs for both groups. Controlled processing was predictive of Block Design score for Non-BAP participants, and was predictive of Pragmatic Language score on the BAPQ for BAP participants. These results are similar to past research related to strengths and weaknesses in the BAP, respectively, and suggest that controlled processing strategy use may be required in instances of weak lower-level skills. PMID:26652842

  16. Laser diode pumped solid state laser driver

    International Nuclear Information System (INIS)

    Technical and economical feasibility of a diode pumped solid state laser driver for the fusion reactor is presented. Nd-doped solid state laser materials of lasing wavelengths at 1 μm are selected. We discuss the total efficiency of the laser driver in detail and then show that a total efficiency of 12 % can be achieved in the diode pumped solid state laser driver. We design the diode pumped solid state laser drivers with five typical solid state materials using a conceptual design technique. Designing conditions are the output energy of 4MJ per pulse at the wavelength of 0.35 μm, total efficiency of 12 % and repetition rate of 12 Hz. From the results of design, it is concluded the some diode pumped solid state laser drivers have large potentiality from both technical and economical points of view. Based on the conclusion, the items to be investigated for the quicker realization of the diode pumped solid state laser driver are also presented. (author)

  17. Study of Coda Qc According to Broad Band Seismic Data

    International Nuclear Information System (INIS)

    The coda wave attenuation quality factor Qc at the Javakheti plateau and at the area located at the north of Tbilisi from 11 local earthquakes recorded by broad band seismograph have been estimated. The Qc was estimated using the single-scattering attenuation model in the frequency range from 0.62 to 40 Hz. The analyzed events were recorded at epicentral distances up to 80 km and their magnitudes vary from 2.5 to 4.3. In the north of Tbilisi we found that Qc=(100±15)f0.6 in the indicated frequency range and Qc=(100±15)f0.4 for the Javakheti Plateau in the frequency range from 40 to 10 Hz. (author)

  18. Method for detection and imaging over a broad spectral range

    Science.gov (United States)

    Yefremenko, Volodymyr; Gordiyenko, Eduard; Pishko, legal representative, Olga; Novosad, Valentyn; Pishko, deceased; Vitalii

    2007-09-25

    A method of controlling the coordinate sensitivity in a superconducting microbolometer employs localized light, heating or magnetic field effects to form normal or mixed state regions on a superconducting film and to control the spatial location. Electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y--Ba--Cu--O films. Two different sensor designs were tested: (i) a 3 millimeter long and 40 micrometer wide stripe and (ii) a 1.25 millimeters long, and 50 micron wide meandering-like structure. Scanning the laser beam along the stripe leads to physical displacement of the sensitive area, and, therefore, may be used as a basis for imaging over a broad spectral range. Forming the superconducting film as a meandering structure provides the equivalent of a two-dimensional detector array. Advantages of this approach are simplicity of detector fabrication, and simplicity of the read-out process requiring only two electrical terminals.

  19. Self-magnetically insulated ion diode

    International Nuclear Information System (INIS)

    Light ion diodes for producing 1--100 TW ion beams are required for inertial confinement fusion. The theory, numerical simulations, and experiments on a self-magnetically insulated ion diode are presented. The treatment is from the point of view of a self-magnetically insulated transmission line with an ion loss current and differs from the usual treatment of the pinched electron beam diode. The simulations show that the ratio V/IZ0=0.25 in such a structure with voltage V, local total current I, and local vacuum wave impedance Z0. The ion current density is enhanced by a factor of approximately 2 over the simple space-charge limited value. The simulation results are verified in an experiment. An analytical theory is then presented for scaling the results to produce a focused beam of protons with a power of up to 1013 W

  20. Drivers for High Power Laser Diodes

    Institute of Scientific and Technical Information of China (English)

    Yankov P; Todorov D; Saramov E

    2006-01-01

    During the last year the high power laser diodes jumped over the 1 kW level of CW power for a stack,and the commercial 1 cm bars reached 100 W output optical power at the standard wavelengths around 800 nm and 980 nm. The prices are reaching the industry acceptable levels. All Nd:YAG and fiber industrial lasers manufacturers have developed kW prototypes. Those achievements have set new requirements for the power supplies manufactuers-high and stable output current, and possibilities for fast control of the driving current, keeping safe the expensive laser diode. The fast switching frequencies also allow long range free space communications and optical range finding. The high frequencies allow the design of a 3D laser radar with high resolution and other military applications. The prospects for direct laser diode micro machining are also attractive.

  1. Approaches to a broad range of high performance PDT sensitizers

    Science.gov (United States)

    d'A. Rocha Gonsalves, António M.; Serra, Arménio C.; Pineiro, Marta; Botelho, M. Filomena

    2009-02-01

    Starting from expertise in the area of chemical synthesis, particularly in tetrapyrrolic macrocycles and an interest in modelling structures for particular objectives, we came to the point of aiming at modelling photochemical sensitizers designed for photodynamic therapy (PDT) purposes. Our endeavours were gratifying when it was proved that our synthetic methodologies allowed for the easy availability of properly halogenated porphyrins with high quantum yield singlet oxygen efficiency. Joining the presence of this heavy atom and other functionalities as substituents in selected positions of macrocyclic structures we were able to generate novel porphyrin structures whose photophysical and photochemical properties, singlet oxygen formation quantum yields, photobleaching and logP were measured. Cellular uptake measurements and cytotoxicity assays on WiDr adenocarcinoma and A375 tumor cell lines were carried out and some of our porphyrins demonstrated very high performance as PDT sensitizers comparatively to known compounds approved for clinical use and in the market. Further developments of our studies allowed for the generation of different and more efficient structures, easily made available by our own synthetic methodologies. Our studies in this area allowed us to reach a stage which we believe to correspond to a significant knowledge and capacity to synthesise a broad range of simple structures, whose selectivity and efficiency as PDT sensitizers can be modulated for different cellular and tissue specificities. Our most recent developments in this area will be presented in this communication.

  2. Analog+digital phase and frequency detector for phase locking of diode lasers

    OpenAIRE

    Cacciapuoti, L.; M. De Angelis; Fattori, M.; Lamporesi, G.; Petelski, T.; Prevedelli, M.; Stuhler, J.; Tino, G. M.

    2005-01-01

    We describe a type of phase and frequency detector employing both an analog phase detector and a digital phase and frequency detector. The analog and digital detectors are mutually exclusive so that only one of them is active at any given time, resulting in a phase detector with both the broad capture range of digital circuits and the high speed and low noise of analog mixers. The detector has been used for phase locking the diode lasers generating the sequence of Raman pulses in an atom inte...

  3. A Flexible Blue Light-Emitting Diode Based on ZnO Nanowire/Polyaniline Heterojunctions

    OpenAIRE

    Liu, Y Y; Wang, X. Y.; Cao, Y; X. D. Chen; Xie, S. F.; X. J. ZHENG; Zeng, H. D.

    2013-01-01

    An organic/inorganic light-emitting diode (LED) consisting of n-type vertically aligned ZnO nanowires (NWs) and p-type proton acid doped polyaniline (PANi) is reported. The device was fabricated on flexible indium-tin-oxide (ITO) coated polyethylene terephthalate (PET) substrate. A broad blue light emission band ranging from 390 nm to 450 nm was observed in the electroluminescence (EL) spectra of the device, which was related to the interface recombination of electrons in the conduction band ...

  4. High-speed 405-nm superluminescent diode (SLD) with 807-MHz modulation bandwidth.

    Science.gov (United States)

    Shen, Chao; Lee, Changmin; Ng, Tien Khee; Nakamura, Shuji; Speck, James S; DenBaars, Steven P; Alyamani, Ahmed Y; El-Desouki, Munir M; Ooi, Boon S

    2016-09-01

    III-nitride LEDs are fundamental components for visible-light communication (VLC). However, the modulation bandwidth is inherently limited by the relatively long carrier lifetime. In this letter, we present the 405 nm emitting superluminescent diode (SLD) with tilted facet design on semipolar GaN substrate, showing a broad emission of ~9 nm at 20 mW optical power. Owing to the fast recombination (τe-3 was obtained using on-off keying modulation scheme, suggesting the SLD being a high-speed transmitter for VLC applications. PMID:27607634

  5. Determining internal screening electric field of working polymer light emitting diodes

    Science.gov (United States)

    Kanemoto, Katsuichi; Takahashi, Takahiro; Hashimoto, Hideki

    2016-07-01

    This study provides a method of determining the internal electric field of polymer light emitting diodes (LEDs) in the working condition. The method employs Stark signals induced by triangular shaped pulse biases and enables estimates of the internal field in a broad voltage region. The internal field under forward bias is shown to be determined by the screening effect caused by injected carriers. Spatial distribution calculated for the LED suggests the presence of strong electric field formed by accumulated carriers near the electrodes. The proposed method is applicable to a variety of devices and can promote understanding of veiled roles of internal fields on device operation.

  6. Quantum chaos with non-periodic, complex orbits in the Resonant Tunneling Diode

    OpenAIRE

    Saraga, D. S.; Monteiro, T. S.

    1998-01-01

    We show that a special type of orbits, which are non-periodic and complex, 'Saddle Orbits' (SOs) describe accurately the quantal and experimental current oscillations in the Resonant Tunneling Diode in tilted fields. This is the first demonstration that one needs to abandon the periodic orbits (POs) paradigm in favour of this new and peculiar type of orbit. The SOs solve the puzzle of broad regions of experimental oscillations where we find no real or complex PO that can explain the data. The...

  7. Quantum chaos with non-periodic, complex orbits in the Resonant Tunneling Diode

    CERN Document Server

    Saraga, D S

    1998-01-01

    We show that a special type of orbits, which are non-periodic and complex, 'Saddle Orbits' (SOs) describe accurately the quantal and experimental current oscillations in the Resonant Tunneling Diode in tilted fields. This is the first demonstration that one needs to abandon the periodic orbits (POs) paradigm in favour of this new and peculiar type of orbit. The SOs solve the puzzle of broad regions of experimental oscillations where we find no real or complex PO that can explain the data. The SOs succeeds in regimes involving several non-isolated POs, where PO formulas fail.

  8. Laser-diode pumped Nd:YAG lasers; Laser diode reiki Nd:YAG lasear

    Energy Technology Data Exchange (ETDEWEB)

    Yuasa, H.; Akiyama, Y.; Nakayama, M. [Toshiba Corp., Tokyo (Japan)

    2000-04-01

    Laser-diode pumped Nd:YAG lasers are expected to be applied to laser processing fields such as welding, cutting, drilling, and marking due to their potential for high efficiency and compactness. We are designing and developing laser-diode pumped Nd:YAG lasers using numerical analysis simulation techniques such as ray tracing and thermal analysis. We have succeeded in achieving a laser power of more than 3 kW with 20% efficiency, which is the best ever obtained. In addition, we have developed a laser-diode pumped green laser by second harmonic generation, for precision machining on silicon wafers. (author)

  9. Investigation of MIM Diodes for RF Applications

    KAUST Repository

    Khan, Adnan

    2015-05-01

    Metal Insulator Metal (MIM) diodes that work on fast mechanism of tunneling have been used in a number of very high frequency applications such as (Infra-Red) IR detectors and optical Rectennas for energy harvesting. Their ability to operate under zero bias condition as well as the possibility of realizing them through printing makes them attractive for (Radio Frequency) RF applications. However, MIM diodes have not been explored much for RF applications. One reason preventing their widespread RF use is the requirement of a very thin oxide layer essential for the tunneling operation that requires sophisticated nano-fabrication processes. Another issue is that the reliability and stable performance of MIM diodes is highly dependent on the surface roughness of the metallic electrodes. Finally, comprehensive RF characterization has not been performed for MIM diodes reported in the literature, particularly from the perspective of their integration with antennas as well as their rectification abilities. In this thesis, various metal deposition methods such as sputtering, electron beam evaporation, and Atomic Layer Deposition (ALD) are compared in pursuit of achieving low surface roughness. It is worth mentioning here that MIM diodes realized through ALD method have been presented for the first time in this thesis. Amorphous metal alloy have also been investigated in terms of their low surface roughness. Zinc-oxide has been investigated for its suitability as a thin dielectric layer for MIM diodes. Finally, comprehensive RF characterization of MIM diodes has been performed in two ways: 1) by standard S-parameter methods, and 2) by investigating their rectification ability under zero bias operation. It is concluded from the Atomic Force Microscopy (AFM) imaging that surface roughness as low as sub 1 nm can be achieved reliably from crystalline metals such as copper and platinum. This value is comparable to surface roughness achieved from amorphous alloys, which are non

  10. Thermal diode made by nematic liquid crystal

    Science.gov (United States)

    Melo, Djair; Fernandes, Ivna; Moraes, Fernando; Fumeron, Sébastien; Pereira, Erms

    2016-09-01

    This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed.

  11. Broad spectrum anthelmintic potential of Cassia plants

    Institute of Scientific and Technical Information of China (English)

    Suman Kundu; Saptarshi Roy; Larisha Mawkhleing Lyndem

    2014-01-01

    Objective: To study the in vitro anthelmintic efficacy of Cassia alata (C. alata), Cassia(C. angustifolia) and Cassia occidentalis (C. occidentalis). angustifolia Methods: Crude ethanol extract from leaves of the three plants were prepared in rotary evaporator and different concentrations (10, 20 and 40 mg/mL) of leaf extracts were used for treatment on different representatives of helminthes (Heterakis gallinarum, Raillietina tetragona and Catatropis sp.) from domestic fowl (Gallus gallus domesticus). Loss of motility and death were monitored frequently.Results: C. alata showed early paralysis in all worms treated followed by C. angustifolia. C. occidentalis in combination with C. alata together caused early paralysis in all treated worms than the combination of C. alata with C. angustfolia. While Heterakis gallinarum in control survived for (81.33±2.07) h, treated worms lost their motility at (5.71±0.10) h, (6.60±0.86) h and (13.95±0.43) h with C. angustifolia, C. alata and C. occidentalis respectively at a concentration of 40 mg/mL which showed better efficacy than albendazole. Catatropis sp. survival period was (26.49±1.38) h in control, but with plant treatment, it lost its motility in just (0.57±0.08) h, (1.00±0.12) h and (1.47±0.40) h at 40 mg/mL concentration of C. alata, C. angustifolia and C. occidentalis respectively.Raillietina tetragona on the other hand became paralysed at (1.68±0.27) h, (2.95±0.29) h and (4.13±0.31) h with above concentrations treated with three plants respectively, however in control it survived up to (81.93±4.71) h.Conclusions:This present study indicated broad spectrum vermifugal activity of all plants tested.

  12. Microlensing of Quasar Broad Emission Lines: Constraints on Broad Line Region Size

    CERN Document Server

    Guerras, E; Jimenez-Vicente, J; Kochanek, C S; Muñoz, J A; Falco, E; Motta, V

    2012-01-01

    We measure the differential microlensing of the broad emission lines between 18 quasar image pairs in 16 gravitational lenses. We find that high ionization lines such as CIV are more strongly microlensed than low ionization lines, indicating that the high ionization line emission regions are more compact. If we statistically model the distribution of microlensing magnifications, we obtain estimates for the broad line region radius of 24 (-15/+22) and 55 (-35/+150) light-days (90% confidence) for the high and low ionization lines, respectively. When the sample is divided attending to quasar luminosity, we find that the line emission regions of more luminous quasars are larger, with a slope consistent with the expected scaling from photoionization models. Our estimates also agree well with the results from local reveberation mapping studies.

  13. Relativistic Brillouin flow in the high ν/γ diode

    International Nuclear Information System (INIS)

    Relativistic Brillouin solutions have been derived for electron flow in crossed electric and magnetic fields. The application of these solutions to the high ν/γ diode is discussed and an approximate analytical expression for the anode current is derived. Measurements of diode current are compared to the theoretical and empirical expressions for diode current which have been developed

  14. Validation, automatic generation and use of broad phonetic transcriptions

    NARCIS (Netherlands)

    Bael, Cristophe Patrick Jan Van

    2007-01-01

    Broad phonetic transcriptions represent the pronunciation of words as strings of characters from specifically designed symbol sets. In everyday life, broad phonetic transcriptions are often used as aids to pronounce (foreign) words. In addition, broad phonetic transcriptions are often used for lingu

  15. Analysis of nanosecond breaking of a high-density current in SOS diodes

    Science.gov (United States)

    Grekhov, I. V.; Lyublinskii, A. G.; Smirnova, I. A.

    2015-11-01

    Effect of a sharp (nanosecond) breaking of the reverse current with a density on the order of 103-104 A/cm2 in a silicon diode upon switching from direct to reverse bias voltage (so-called silicon opening switch, or SOS effect) is widely used in nanosecond technologies of gigawatt powers. For detailed analysis of the SOS effect, we constructed a special setup with small stray inductance, which makes it possible to test single SOS diodes with a working area of 1-2 mm2 in a wide range of current densities. Our experiments show, in particular, that the numerical model of the SOS effect developed at the Institute of Electrophysics, Ural Branch, Russian Academy of Sciences successfully described the experimental results. It is also shown that the charge extracted from the diode structure by the reverse current exceeds the charge introduced by a direct current pulse by not more than 10%, indicating a relatively small role of ionization processes. The possibility to carry out experiments on single samples with a small surface area allows us to study the SOS effect and considerably facilitates investigations aimed at the perfection of the design of SOS diodes.

  16. Runoff erosion in Portugal: A broad overview

    OpenAIRE

    Figueiredo, Tomás

    2013-01-01

    Soils are generally a scarce natural resource in Portugal as far as productivity is concerned (CNROA, 1983; Agroconsultores e Coba, 1991; Agroconsultores e Geometral, 1995). In fact, the major part of the territory is potentially not suitable for agriculture, corresponding to areas with misuse and over-exploitation of the soil resource in cropland, and to typical marginal land cover by forests and shrubs. The soils with moderate and high suitability are under agricultural use, more or less in...

  17. Charge transfer and transient processes in silicon diodes irradiated by bismuth ions with energy of 700 MeV

    International Nuclear Information System (INIS)

    Silicon p+ n-diodes irradiated with bismuth ions with energy of 700 MeV were studied. Irradiation fluence was from 5×107 to 1010 cm-2. Current-voltage characteristics of the initial and irradiated diodes were registered and transient processes in diodes were studied when they switching from forward bias (forward current If ≤ 1 A) to reverse one (voltage Ur = -2 B). It is shown that the irradiation with bismuth ions with energy of 700 MeV with fluence of 5×107 cm-2 is sufficient to reduce the reverse recovery time from 30 μs (for the virgin diodes) to 0.33 μs (for the irradiated ones). It is established that a fundamental change in dependences of the differential conductance of the diodes with respect to the reverse bias is observed for the irradiation fluences 109 cm-2. For these fluences the formation of a continuous radiation-damaged layer is complete, which allows to estimate 0.1-0.2 μm2 as an upper limit of cross-section area of the defect created by the passage of a single ion. It is shown that the fluence Φ ≈ 5×108 cm-2 of irradiation with bismuth ions with energy of 700 MeV is preferable in the design of fast diodes. (authors)

  18. Factors affecting the energy resolution in alpha particle spectrometry with silicon diodes

    International Nuclear Information System (INIS)

    In this work are presented the studies about the response of a multi-structure guard rings silicon diode for detection and spectrometry of alpha particles. This ion-implanted diode (Al/p+/n/n+/Al) was processed out of 300 μm thick, n type substrate with a resistivity of 3 kΩ·cm and an active area of 4 mm2. In order to use this diode as a detector, the bias voltage was applied on the n+ side, the first guard ring was grounded and the electrical signals were readout from the p+ side. These signals were directly sent to a tailor made preamplifier, based on the hybrid circuit A250 (Amptek), followed by a conventional nuclear electronic. The results obtained with this system for the direct detection of alpha particles from 241Am showed an excellent response stability with a high detection efficiency (≅ 100 %). The performance of this diode for alpha particle spectrometry was studied and it was prioritized the influence of the polarization voltage, the electronic noise, the temperature and the source-diode distance on the energy resolution. The results showed that the major contribution for the deterioration of this parameter is due to the diode dead layer thickness (1 μm). However, even at room temperature, the energy resolution (FWHM = 18.8 keV) measured for the 5485.6 MeV alpha particles (241Am) is comparable to those obtained with ordinary silicon barrier detectors frequently used for these particles spectrometry. (author)

  19. Coupling of an applied field magnetically insulated ion diode to a high power magnetically insulated transmission line system

    International Nuclear Information System (INIS)

    The coupling of energy from a high power pulsed accelerator through a long triplate magnetically insulated transmission line (MITL) in vacuum to an annular applied magnetic field insulated extraction ion diode is examined. The narrow power transport window and the wave front erosion of the MITL set stringent impedance history conditions on the diode load. A new ion diode design developed to satisfy these criteria with marginal electron insulation is presented. The LION accelerator is used to provide a positive polarity 1.5 MV, 350 kA, 40 ns FWHM pulse with a 30 kA/ns current rate from a triplate MITL source. A transition converts the triplate into a cylindrical cross section which flares into the ion diode load. Extensive current and voltage measurements performed along this structure and on the extracted ion beam provide conclusive evidence that the self insulation condition of the MITL is maintained in the transition by current loss alone. The ion diode utilizes a radial magnetic field between a grounded cathode annular emission tip and a disk anode. A 50 cm2 dielectric/metal anode area serves as the ion plasma source subject to direct electron bombardment from the opposing cathode tip under marginal magnetic insulation conditions. The ions extracted cross the radial magnetic field and exit the diode volume as an annular cross section beam of peak current about 100 kA. The diode current gradually converts from the initial electron flow to nearly 100% ion current after 30 ns, coupling 60% of the diode energy into ions

  20. Broad-Spectrum Solution-Processed Photovoltaics

    Science.gov (United States)

    Ip, Alexander Halley

    High global demand for energy coupled with dwindling fossil fuel supply has driven the development of sustainable energy sources such as solar photovoltaics. Emerging solar technologies aim for low-cost, solution-processable materials which would allow wide deployment. Colloidal quantum dots (CQDs) are such a materials system which exhibits the ability to absorb across the entire solar spectrum, including in the infrared where many technologies cannot harvest photons. However, due to their nanocrystalline nature, CQDs are susceptible to surface-associated electronic traps which greatly inhibit performance. In this thesis, surface engineering of CQDs is presented through a combined ligand approach which improves the passivation of surface trap states. A metal halide treatment is found to passivate quantum dot surfaces in solution, while bifunctional organic ligands produce a dense film in solid state. This approach reduced midgap trap states fivefold compared with conventional passivation strategies and led to solar cells with a record certified 7.0% power conversion efficiency. The effect of this process on the electronic structure is studied through photoelectron spectroscopy. It is found that while the halide provides deep trap passivation, the nature of the metal cation on the CQD surface affects the density of band tail states. This effect is explored further through a wide survey of materials, and it is found that the coordination ability of the metal cation is responsible for the suppression of shallow traps. With this understanding of CQD surface passivation, broad spectral usage is then explored through a study of visible-absorbing organolead halide perovskite materials as well as narrow-bandgap CQD solar cells. Control over growth conditions and modification of electrode interfaces resulted in efficient perovskite devices with effective usages of visible photons. For infrared-absorbing CQDs, it is found that, in addition to providing surface trap

  1. Temperature control during diode laser welding in a human cornea

    Science.gov (United States)

    Rossi, Francesca; Matteini, Paolo; Pini, Roberto; Menabuoni, Luca

    2007-07-01

    Diode laser welding is a technique proposed in ophthalmic surgery to induce immediate sealing of clear corneal wounds. The welding effect is achieved irradiating the area, previously treated with a chromophore, by the use of a low power diode laser: the resulting thermal effect induces structural modifications in the stromal collagen, that welds upon cooling. We present a study on the temperature dynamics developing during welding in a human eye. An infrared thermocamera was used to measure the temperature variations on the surface of the cornea during clinical penetrating keratoplasty (corneal transplant). The experimental data were used as a starting point for a theoretical investigation of the temperature rising inside the ocular structures: we developed a mathematical model based on the bio-heat equation and solved by the use of the Finite Element Method (FEM). The predictive accuracy was verified by comparing the temperature post-processing description with the results obtained from the thermographic data. The model was then used to study the temperature rise and heat propagation inside the eye. Experimental results and model analysis indicated the occurrence of heat confinement during the treatment procedure and a modest enhancement of the temperature (reaching about 55°C inside the laser treated wound), thus evidencing the safety of the procedure in clinical applications.

  2. High Current Density 2D/3D Esaki Tunnel Diodes

    CERN Document Server

    Krishnamoorthy, Sriram; Lee, Choong Hee; Zhang, Yuewei; McCulloch, William D; Johnson, Jared M; Hwang, Jinwoo; Wu, Yiying; Rajan, Siddharth

    2016-01-01

    The integration of two-dimensional materials such as transition metal dichalcogenides with bulk semiconductors offer interesting opportunities for 2D/3D heterojunction-based novel device structures without any constraints of lattice matching. By exploiting the favorable band alignment at the GaN/MoS2 heterojunction, an Esaki interband tunnel diode is demonstrated by transferring large area, Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current density of 446 A/cm2 with repeatable room temperature negative differential resistance, peak to valley current ratio of 1.2, and minimal hysteresis was measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of 1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk semiconductor, and the electrostatics at the 2D/3D interface was found to be crucial in explaining the experimentally observed device characteristics.

  3. Tunnel Diode Discriminator with Fixed Dead Time

    DEFF Research Database (Denmark)

    Diamond, J. M.

    1965-01-01

    A solid state discriminator for the range 0.4 to 10 V is described. Tunnel diodes are used for the discriminator element and in a special fixed dead time circuit. An analysis of temperature stability is presented. The regulated power supplies are described, including a special negative resistance...

  4. Achromatic optical diode in fiber optics

    CERN Document Server

    Berent, Michal; Vitanov, Nikolay V

    2013-01-01

    We propose a broadband optical diode, which is composed of one achromatic reciprocal quarter-wave plate and one non-reciprocal quarter-wave plate, both placed between two crossed polarizers. The presented design of achromatic wave plates relies on an adiabatic evolution of the Stokes vector, thus, the scheme is robust and efficient. The possible simple implementation using fiber optics is suggested.

  5. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal;

    2010-01-01

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 2...

  6. Light-Emitting Diodes: A Hidden Treasure

    Science.gov (United States)

    Planinšic, Gorazd; Etkina, Eugenia

    2014-01-01

    LEDs, or light-emitting diodes, are cheap, easy to purchase, and thus commonly used in physics instruction as indicators of electric current or as sources of light (Fig. 1). In our opinion LEDs represent a unique piece of equipment that can be used to collect experimental evidence, and construct and test new ideas in almost every unit of a general…

  7. Flexoelectric MEMS: towards an electromechanical strain diode.

    Science.gov (United States)

    Bhaskar, U K; Banerjee, N; Abdollahi, A; Solanas, E; Rijnders, G; Catalan, G

    2016-01-21

    Piezoelectricity and flexoelectricity are two independent but not incompatible forms of electromechanical response exhibited by nanoscale ferroelectrics. Here, we show that flexoelectricity can either enhance or suppress the piezoelectric response of the cantilever depending on the ferroelectric polarity and lead to a diode-like asymmetric (two-state) electromechanical response. PMID:26676467

  8. The Fuge Tube Diode Array Spectrophotometer

    Science.gov (United States)

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

    2008-01-01

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

  9. Entangled Light Emission From a Diode

    International Nuclear Information System (INIS)

    Electrically-driven entangled photon generation is demonstrated for the first time using a single semiconductor quantum dot embedded in a light emitting diode structure. The entanglement fidelity is shown to be of sufficient quality for applications such as quantum key distribution.

  10. Optical diodes. [primary mechanism is electronic tunneling

    Science.gov (United States)

    Gustafson, T. K.

    1976-01-01

    Research on metal-barrier-metal structures is reviewed. Topics discussed include: demonstration of antenna coupling and rectification characteristics with high resistance evaporated structures at a wavelength of 10 microns; application of these devices to coherent conversion of laser radiation and infrared and optical circuit elements; and comparison of the point-contact type of diode structure and the newly developed photolithographic structures.

  11. Study on the Beam Quality of Uncoupled Laser Diode Arrays

    Institute of Scientific and Technical Information of China (English)

    GAO Chunqing; WEI Guanghui

    2001-01-01

    The beam quality of uncoupled laser diode array is studied theoretically and experimentally. By calculating the second order moments of the beam emitted from the laser diode array, the dependence of the M2-factor of the laser diode array on the M2-factor of the single emitter, the ratio of the emitting region to the non-emitting space, and the number of emitters, has been deduced. From the measurement of the beam propagation the M2-factor of a laser diode bar is experimentally determined. The measured M2-factor of the laser diode bar agrees with the theoretical prediction.

  12. Spin-current diode with a ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Qing-Feng, E-mail: sunqf@pku.edu.cn; Xie, X. C. [International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China and Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2015-05-04

    Diode is a key device in electronics: the charge current can flow through the device under a forward bias, while almost no current flows under a reverse bias. Here, we propose a corresponding device in spintronics: the spin-current diode, in which the forward spin current is large but the reversed one is negligible. We show that the lead/ferromagnetic quantum dot/lead system and the lead/ferromagnetic semiconductor/lead junction can work as spin-current diodes. The spin-current diode, a low dissipation device, may have important applications in spintronics, as the conventional charge-current diode does in electronics.

  13. Application of commercial semiconductor diodes as gamma radiation detectors

    International Nuclear Information System (INIS)

    The possibility of using silicon and germanium diodes for the registration of photons with the energy of 662 keV is considered. To this end, the dose sensitivity of the diodes has been measured, the counting characteristics and the integral spectra recorded. It has been found that the dose instability in the temperature range of from 20 to 35 deg C is +-5% for germanium diodes and remains constant in the temperature range of from 20 to 110 deg C for silicon diodes. The results allow to conclude that it is generally possible to use germanium and silicon diodes in gamma-radiation detection units

  14. Black phosphorus-monolayer MoS2 van der Waals heterojunction p-n diode.

    Science.gov (United States)

    Deng, Yexin; Luo, Zhe; Conrad, Nathan J; Liu, Han; Gong, Yongji; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Xu, Xianfan; Ye, Peide D

    2014-08-26

    Phosphorene, a elemental 2D material, which is the monolayer of black phosphorus, has been mechanically exfoliated recently. In its bulk form, black phosphorus shows high carrier mobility (∼10,000 cm(2)/V·s) and a ∼0.3 eV direct band gap. Well-behaved p-type field-effect transistors with mobilities of up to 1000 cm(2)/V·s, as well as phototransistors, have been demonstrated on few-layer black phosphorus, showing its promise for electronics and optoelectronics applications due to its high hole mobility and thickness-dependent direct band gap. However, p–n junctions, the basic building blocks of modern electronic and optoelectronic devices, have not yet been realized based on black phosphorus. In this paper, we demonstrate a gate-tunable p–n diode based on a p-type black phosphorus/n-type monolayer MoS2 van der Waals p–n heterojunction. Upon illumination, these ultrathin p–n diodes show a maximum photodetection responsivity of 418 mA/W at the wavelength of 633 nm and photovoltaic energy conversion with an external quantum efficiency of 0.3%. These p–n diodes show promise for broad-band photodetection and solar energy harvesting. PMID:25019534

  15. Optical and structural properties of CuO nanofilm: Its diode application

    Energy Technology Data Exchange (ETDEWEB)

    Erdogan, Ibrahim Y. [Bingoel University, Faculty of Sciences and Arts, Department of Chemistry, 12000 Bingoel (Turkey); Guellue, O., E-mail: omergullu@gmail.co [Batman University, Faculty of Sciences and Arts, Department of Physics, 72060 Batman (Turkey)

    2010-03-04

    The high crystalline CuO nanofilms have been prepared by spin coating and annealing combined with a simple chemical method. The obtained films have been characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-vis (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy. Structural analysis results demonstrate that the single phase CuO on Si (1 0 0) substrate is of high a crystalline structure with a dominant in monoclinic (1 1 1) orientation. FT-IR results confirm the formation of pure CuO phase. UV-vis absorption measurements indicate that the band gap of the CuO films is 2.64 eV. The PL spectrum of the CuO films shows a broad emission band centered at 467 nm, which is consistent with absorption measurement. Also, Au/CuO/p-Si metal/interlayer/semiconductor (MIS) diodes have been fabricated. Electronic properties (current-voltage) of these structures were investigated. In addition, the interfacial state properties of the MIS diode were obtained. The interface-state density of the MIS diode was found to vary from 6.21 x 10{sup 12} to 1.62 x 10{sup 12} eV{sup -1} cm{sup -2}.

  16. The Pierce-diode approximation to the single-emitter plasma diode

    International Nuclear Information System (INIS)

    The possibility of modeling fast processes in the collisionless single-emitter plasma diode (Knudsen diode with surface ionization, KDSI) by means of the Pierce-diode is studied. The KDSI is of practical importance in that it is an almost exact model of thermionic energy converters (TICs) in the collisionless regime and can also be used to model low-density Q-machines. At high temperatures, the Knudsen TIC comes close to the efficiency of the Carnot cycle and hence is the most promising converter of thermal to electric energy. TICs can be applied as component parts in high-temperature electronics. It is shown that normalizations must be chosen appropriately in order to compare the plasma characteristics of the two models: the KDSI and the Pierce-diode. A linear eigenmode theory of the KDSI is developed. For both nonlinear time-independent states and linear eigenmodes without electron reflection, excellent agreement is found between the analytical potential distributions for the Pierce-diode and the corresponding numerical ones for the KDSI. For the states with electron reflection, the agreement is satisfactory in a qualitative sense. A full classification of states of both diodes for the regimes with and without electron reflection is presented. The effect of the thermal spread in electron velocities on the potential distributions and the (ε,η) diagrams is analyzed. Generally speaking, the methodology developed is usefully applicable to a variety of systems in which the electrons have beam-like distributions

  17. An investigation of laser oscillators and amplifiers using high intensity diode-pumping

    OpenAIRE

    Moore, Nicholas

    1998-01-01

    The work presented in this thesis is split into two related areas. The first area of research was the construction of high gain, high power, all-solid-state laser amplifiers for use in master oscillator, power amplifier (MOPA) systems. The second area was the operation of solid-state lasers on low gain transitions. The two areas are related by the fact that the primary aim in each was to maximise the available gain on a given laser transition. Two diode-pumped travelling wave amplifiers a...

  18. Qualification and Selection of Flight Diode Lasers for Space Applications

    Science.gov (United States)

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

    2010-01-01

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

  19. Monolithically integrated broad-band Mach-Zehnder interferometers for highly sensitive label-free detection of biomolecules through dual polarization optics.

    Science.gov (United States)

    Psarouli, A; Salapatas, A; Botsialas, A; Petrou, P S; Raptis, I; Makarona, E; Jobst, G; Tukkiniemi, K; Sopanen, M; Stoffer, R; Kakabakos, S E; Misiakos, K

    2016-01-01

    Protein detection and characterization based on Broad-band Mach-Zehnder Interferometry is analytically outlined and demonstrated through a monolithic silicon microphotonic transducer. Arrays of silicon light emitting diodes and monomodal silicon nitride waveguides forming Mach-Zehnder interferometers were integrated on a silicon chip. Broad-band light enters the interferometers and exits sinusoidally modulated with two distinct spectral frequencies characteristic of the two polarizations. Deconvolution in the Fourier transform domain makes possible the separation of the two polarizations and the simultaneous monitoring of the TE and the TM signals. The dual polarization analysis over a broad spectral band makes possible the refractive index calculation of the binding adlayers as well as the distinction of effective medium changes into cover medium or adlayer ones. At the same time, multi-analyte detection at concentrations in the pM range is demonstrated. PMID:26825114

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

    Science.gov (United States)

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

    2003-01-01

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

  1. Femtosecond laser enhanced current in a thermionic diode with barium vapor

    International Nuclear Information System (INIS)

    We studied the signal from a thermionic diode when a femtosecond laser beam was spatially overlapped by an excimer pumped dye laser beam. The nanosecond dye laser was scanned from 435 to 438 nm in order to excite the autoionizing levels of barium by two photon absorption. The broadband ultrashort laser light was centered at 427 nm, which is also above the first ionization limit of barium. The bias voltage between the cell body and the tungsten rod (set at either 9 or 0 V) was used to collect electrons after the barium ions had been created by multiphoton (auto) ionization. The overall background of the thermionic signal was appreciably elevated due to the two photon ionization by the broadband femtosecond laser. We measured the thermionic signal with and without femtosecond laser overlap, and with a biasless and biased thermionic diode. The effect of the femtosecond laser was appreciable enhancement of the background ionization continuum. This was especially visible in the presence of noble gases at pressure of 50 mbar. Argon produced the largest and helium produced the smallest enhancement in the background continuum. In addition, we observed a few broad spectral features of a presumably collision induced nature. - Highlights: • Femtosecond laser beam spatially overlapped by excimer pumped dye laser beam. • The nanosecond dye laser scanned from 435 to 438 nm for two photon absorption. • Thermionic signal detection of Ba autoionizing levels. • The femtosecond laser enhanced the background ionization continuum. • Broad spectral features of presumably collision induced nature have been observed

  2. Neoplasms treatment by diode laser with and without real time temperature control on operation zone

    Science.gov (United States)

    Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Sosenkova, Svetlana A.; Lazareva, Anastasia A.; Semyashkina, Yulia V.

    2016-04-01

    Results of nevus, papilloma, dermatofibroma, and basal cell skin cancer in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and automatic power control (APC) mode are presented. The collateral damage width and width of graze wound area around the collateral damage area were demonstrated. The total damage area width was calculated as sum of collateral damage width and graze wound area width. The mean width of total damage area reached 1.538+/-0.254 mm for patient group with nevus removing by 980 nm diode laser operating in CW mode, papilloma - 0.586+/-0.453 mm, dermatofibroma - 1.568+/-0.437 mm, and basal cell skin cancer - 1.603+/-0.613 mm. The mean width of total damage area reached 1.201+/-0.292 mm for patient group with nevus removing by 980 nm diode laser operating in APC mode, papilloma - 0.413+/-0.418 mm, dermatofibroma - 1.240+/-0.546 mm, and basal cell skin cancer - 1.204+/-0.517 mm. It was found that using APC mode decreases the total damage area width at removing of these nosological neoplasms of human skin, and decreases the width of graze wound area at removing of nevus and basal cell skin cancer. At the first time, the dynamic of output laser power and thermal signal during laser removal of nevus in CW and APC mode is presented. It was determined that output laser power during nevus removal for APC mode was 1.6+/-0.05 W and for CW mode - 14.0+/-0.1 W. This difference can explain the decrease of the total damage area width and width of graze wound area for APC mode in comparison with CW mode.

  3. Organic Light-Emitting Diodes Driven by Organic Transistors

    Institute of Scientific and Technical Information of China (English)

    胡远川; 董桂芳; 王立铎; 梁琰; 邱勇

    2004-01-01

    Organic thin-film field-effect transistors (OTFTs) with pentacene as the semiconductor have been fabricated for driving an organic light-emitting diode (OLED). The driving circuit includes two OTFTs and one storage capacitor. The field-effect mobility of the transistors in the driving circuit is more than 0.3 cm2/Vs, and the on/off ratio is larger than 104. The light-emission area of the OLED is 0. 04mm2 and the brightness is larger than 400cd/m2 when the selected line voltage, data line voltage and drive voltage all are -40 V. The responding characteristics and holding characteristics are also researched when the selected line voltage and the date line voltage are changed.

  4. Improved field geometries for SABRE extraction ion diode operation with passive ion sources

    International Nuclear Information System (INIS)

    The SABRE Facility at Sandia National Laboratories is an integrated testbed for the study of high voltage ion beam production and transport in extraction geometry for inertial confinement fusion. Our major emphasis is on the development of active ion sources, but several techniques are under investigation to improve diode performance with passive hydrocarbon and LiF ion sources. The operation of passive sources is particularly sensitive to details of the magnetic and electric field geometries and can provide insight into divergence and parasitic load mechanisms which also affect high voltage diode performance with active sources. We demonstrate that an outer cathode lip extension can eliminate cathode feed electron participation in source turn-on and virtual cathode evolution. Experimental data and TWOQUICK PIC code simulations indicate that instability-induced cross-field diffusion of cathode tip electrons at small radius plays a dominant role in diode operation with a passive source. An improved diode geometry is presented with reduced feed electrode participation and better electron confinement at the anode emission area for lithium sources

  5. 640 x 480 pixel uncooled infrared FPA with SOI diode detectors

    Science.gov (United States)

    Ueno, Masashi; Kosasayama, Yasuhiro; Sugino, Takaki; Nakaki, Yoshiyuki; Fujii, Yoshio; Inoue, Hiromoto; Kama, Keisuke; Seto, Toshiki; Takeda, Munehisa; Kimata, Masafumi

    2005-05-01

    This paper describes the structure and performance of a 25-micron pitch 640 x 480 pixel uncooled infrared focal plane array (IR FPA) with silicon-on-insulator (SOI) diode detectors. The uncooled IR FPA is a thermal type FPA that has a temperature sensor of single crystal PN junction diodes formed in an SOI layer. In the conventional pixel structure, the temperature sensor and two support legs for thermal isolation are made in the lower level of the pixel, and an IR absorbing structure is made in the upper pixel level to cover almost the entire pixel area. The IR absorption utilizes IR reflections from the lower level. Since the reflection from the support leg portions is not perfect due to the slits in the metal reflector, the reflection becomes smaller as the support leg section increases in reduced pixel pitches. In order to achieve high thermal isolation and high IR absorption simultaneously, we have developed a new pixel structure that has an independent IR reflector between the lower and upper levels. The structure assures perfect IR reflection and thus improves IR absorption. The FPA shows a noise equivalent temperature difference (NETD) of 40 mK (f/1.0) and a responsivity non-uniformity of less than 0.9%. The good uniformity is due to the high uniformity of the electrical characteristics of SOI diodes made of single crystal silicon (Si). We have confirmed that the SOI diodes architecture is suitable for large format uncooled IR FPAs.

  6. A p-i-n junction diode based on locally doped carbon nanotube network

    Science.gov (United States)

    Liu, Xiaodong; Chen, Changxin; Wei, Liangming; Hu, Nantao; Song, Chuanjuan; Liao, Chenghao; He, Rong; Dong, Xusheng; Wang, Ying; Liu, Qinran; Zhang, Yafei

    2016-01-01

    A p-i-n junction diode constructed by the locally doped network of single-walled carbon nanotubes (SWNTs) was investigated. In this diode, the two opposite ends of the SWNT-network channel were selectively doped by triethyloxonium hexachloroantimonate (OA) and polyethylenimine (PEI) to obtain the air-stable p- and n-type SWNTs respectively while the central area of the SWNT-network remained intrinsic state, resulting in the formation of a p-i-n junction with a strong built-in electronic field in the SWNTs. The results showed that the forward current and the rectification ratio of the diode increased as the doping degree increased. The forward current of the device could also be increased by decreasing the channel length. A high-performance p-i-n junction diode with a high rectification ratio (~104), large forward current (~12.2 μA) and low reverse saturated current (~1.8 nA) was achieved with the OA and PEI doping time of 5 h and 18 h for a channel length of ~6 μm. PMID:26996610

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

    International Nuclear Information System (INIS)

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

  8. Photovoltaic-module bypass-diode encapsulation. Annual report

    Energy Technology Data Exchange (ETDEWEB)

    1983-06-20

    The design and processing techniques necessary to incorporate bypass diodes within the module encapsulant are presented in this annual report. A comprehensive survey of available pad-mounted PN junction and Schottky diodes led to the selection of Semicon PN junction diode cells for this application. Diode junction-to-heat spreader thermal resistance measurements, performed on a variety of mounted diode chip types and sizes, have yielded values which are consistently below 1/sup 0/C per watt, but show some instability when thermally cycled over the temperature range from -40 to 150/sup 0/C. Based on the results of a detailed thermal analysis, which covered the range of bypass currents from 2 to 20 amperes, three representative experimental modules, each incorporating integral bypass diode/heat spreader assemblies of various sizes, were designed and fabricated. Thermal testing of these modules has enabled the formation of a recommended heat spreader plate sizing relationship. The production cost of three encapsulated bypass diode/heat spreader assemblies were compared with similarly rated externally-mounted packaged diodes. An assessment of bypass diode reliability, which relies heavily on rectifying diode failure rate data, leads to the general conclusion that, when proper designed and installed, these devices will improve the overall reliability of a terrestrial array over a 20 year design lifetime.

  9. Pulsed diode source of polarized ions

    International Nuclear Information System (INIS)

    The advantages of polarized nuclei for fusion reactors have recently been described. We propose a pulsed source of polarized nuclei that consists of an ion diode with a polarized anode. With magnetic resonance techniques the nuclear spins of the protons of solid NH3 can be made about 90 to 95% polarized. This material would be used for the anode. The diode would be pulsed with a voltage of 1-200K-volts for 1-2 μ sec. Flashover of the anode produces a surface plasma from which the polarized protons would be extracted to form a beam. Depolarization could be detected by comparing reaction cross sections and/or distribution of reaction products with similar results for unpolarized beams

  10. Photon recycling and Shockley's diode equation

    Science.gov (United States)

    Martí, A.; Balenzategui, J. L.; Reyna, R. F.

    1997-10-01

    The Shockley's diode equation predicts a current-voltage characteristic different from that used by Shockley and Queisser to compute the limiting efficiency of photovoltaic energy conversion under the assumptions of the detailed balance theory. The reasons for such discrepancy are discussed being the neglect of photon recycling effects in Shockley's diode equation the main cause. This interpretation is crucial to understand the fundamentals on which the computation of the limiting efficiency of solar cells is based. Without photon recycling effects, it can be concluded that the limiting efficiency (one sun) of a gallium arsenide solar cell is 26.8% (with the sun assumed as blackbody at 6000 K) while the true figure is 30.7%, 38.7% as long as the angle of emission of photons from the cell is fully restricted.

  11. Cover slip external cavity diode laser

    CERN Document Server

    Carr, Adra V; Waitukaitis, Scott R; Perreault, John D; Lonij, Vincent P A; Cronin, Alexander D

    2007-01-01

    The design of a 671 nm diode laser with a mode-hop-free tuning range of 40 GHz is described. This long tuning range is achieved by simultaneously ramping the external cavity length with the laser injection current. The external cavity consists of a microscope cover slip mounted on piezoelectric actuators. In such a configuration the laser output pointing remains fixed, independent of its frequency. Using a diode with an output power of 5-7 mW, the laser linewidth was found to be smaller than 30 MHz. This cover slip cavity and feedforward laser current control system is simple, economical, robust, and easy to use for spectroscopy, as we demonstrate with lithium vapor and lithium atom beam experiments.

  12. SU-E-P-34: Dose Perturbation Caused by Sun Nuclear QED Diode When Used for Very Small Electron Fields

    International Nuclear Information System (INIS)

    Purpose: Diodes are utilized by radiotherapy departments to help verify that treatment fields are being delivered correctly to the patient. Some treatment fields utilize electron beams along with a cerrobend cutout to shape the beam to the area to be treated. Cerrobend cutouts can sometimes be very small < 2×2-cm2. Some published work has addressed diode perturbation for cutout sizes down to 1.5-cm, this work addresses the diode perturbation of the Sun Nuclear QEDTM diode for cutouts as small as 0.5-cm in diameter. Methods: Measurements were taken with an A16 Exradin micro-chamber in Solid Water to 100-cm SSD. Dmax was determined for each cutout using various amounts of Solid Water in 1–2 mm increments to account for the dmax shifting in small fields. The diode was placed on top of the solid water to 100-cm SSD in the center of the cutout. Measurements were taken with no diode for comparison. The cutouts ranged in diameter from 0.5-cm to 5.0-cm and included the open 6×6 insert. Measurements were made for energies 6, 9, 12, 15,&18 MeV. Results: For 6 MeV, the percent dose reduction from the diode in the cutout field compared to the field without the diode ranged from 35% to 25% as a function of cutout size. For higher energies, this percentage decreased and generally was 25% to 15%. It was observed that dmax shifts significantly upstream for very small cutouts (<2-cm diameter) to less than 1 cm for all energies. Conclusion: The presence of diodes in small electron fields is enough to cause significant dose perturbation to the target volume. It is recommended that diodes for very small electron fields be used sparingly or possibly with a dose correction per treatment fraction(s), if the total projected delivered dose is going to be significantly different from that prescribed by the physician

  13. Non-linearity correction of Schottky diode THz detector system using CSR burst from storage ring

    International Nuclear Information System (INIS)

    We show a practical method to calibrate non-linearity of Schottky diode detector for the short-pulsed THz radiation from the electron storage ring. A frequency distribution of pulse area was measured at three distances of the detector from the radiation source. Non-linearity correction function was obtained by a condition that the three distribution should be the same with non-linearity correction and reduction factor by the distance. (author)

  14. Model, design, and fabrication of antenna coupled metal-insulator-metal diodes for IR sensing

    OpenAIRE

    İnaç, Mesut; Inac, Mesut; Shafique, Atia; Özcan, Meriç; Ozcan, Meric; Gürbüz, Yaşar; Gurbuz, Yasar

    2015-01-01

    There is increasing demand for devices operating at room temperature for IR sensing and imaging. Antenna coupled metal-insulator-metal (MIM) diodes are potential candidates in this field. The reasons are miniaturizing features and femtosecond operation of these devices: smaller sizes lead to more pixels in limited areas and quantum tunneling phenomenon leads to faster operation. In this work, it is aimed to design and develop a device that can act as IR detector at room temperature.

  15. Microring Diode Laser for THz Generation

    DEFF Research Database (Denmark)

    Mariani, S.; Andronico, A.; Favero, I.;

    2013-01-01

    We report on the modeling and optical characterization of AlGaAs/InAs quantum-dot microring diode lasers designed for terahertz (THz) difference frequency generation (DFG) between two whispering gallery modes (WGMs) around 1.3 $\\mu$m. In order to investigate the spectral features of this active d...... identical double-metal microcylinders. The good agreement that we demonstrate between experimental results and design parameters is crucial towards the achievement of active phase-matched THz emitters....

  16. Terahertz Optoelectronics with Surface Plasmon Polariton Diode

    OpenAIRE

    Vinnakota, Raj K.; Genov, Dentcho A

    2014-01-01

    The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons, i.e. the collective electron oscillations at the interface of a metal/semiconductor and a dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we demonstrate a surface plasmon-polariton diode (SPPD) an optoelectronic switch that can operate at exceeding...

  17. Renormalized field theory of resistor diode percolation

    OpenAIRE

    Stenull, Olaf; Janssen, Hans-Karl

    2001-01-01

    We study resistor diode percolation at the transition from the non-percolating to the directed percolating phase. We derive a field theoretic Hamiltonian which describes not only geometric aspects of directed percolation clusters but also their electric transport properties. By employing renormalization group methods we determine the average two-port resistance of critical clusters, which is governed by a resistance exponent $\\phi$. We calculate $\\phi$ to two-loop order.

  18. A silicon diode dosimeter with a memory

    International Nuclear Information System (INIS)

    An integrating dosimeter using a silicon diode has been developed which can be used to check the calibration of radiation therapy treatment units at remote facilities by mail. The dose reading is retained indefinitely in a battery-operated CMOS digital counter. The accuracy of the device is at least +-0.6% standard deviation, as determined by 60Co irradiations over a two month period. (orig.)

  19. Bioinspired Hybrid White Light-Emitting Diodes.

    Science.gov (United States)

    Weber, Michael D; Niklaus, Lukas; Pröschel, Marlene; Coto, Pedro B; Sonnewald, Uwe; Costa, Rubén D

    2015-10-01

    The first bioinspired hybrid white-light-emitting diodes (bio-HLEDs) featuring protein cascade coatings are presented. For easy fabrication a new strategy to stabilize proteins in rubber-like material was developed. The synergy between the excellent features of fluorescent proteins and the easily processed rubber produces bio-HLEDs with less than 10% loss in luminous efficiency over 100 hours. PMID:26271025

  20. Stability theory of Knudsen plasma diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, V. I., E-mail: victor.kuznetsov@mail.ioffe.ru; Ender, A. Ya. [Ioffe Institute, Russian Academy of Sciences (Russian Federation)

    2015-11-15

    A stability theory is developed for a plasma diode in which an electron beam supplied from the emitter propagates without collisions in the self-consistent electric field against the immobile ion background. An integral equation for the amplitude of the perturbed field is deduced using the Q,G method for the regime without electron reflection from a potential barrier. Analytic solutions to this equation are obtained for a number of important particular cases, and the plasma dispersion properties are examined.

  1. Diode having trenches in a semiconductor region

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2016-03-22

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  2. Stability theory of Knudsen plasma diodes

    International Nuclear Information System (INIS)

    A stability theory is developed for a plasma diode in which an electron beam supplied from the emitter propagates without collisions in the self-consistent electric field against the immobile ion background. An integral equation for the amplitude of the perturbed field is deduced using the Q,G method for the regime without electron reflection from a potential barrier. Analytic solutions to this equation are obtained for a number of important particular cases, and the plasma dispersion properties are examined

  3. Simulation of double barrier resonant tunneling diodes

    OpenAIRE

    Porter, Roy M.

    1996-01-01

    The double barrier resonant tunneling diode (DBRTD) is one of several devices currently being considered by the semiconductor industry as a replacement for conventional very large scale integrated (VLSI) circuit technology when the latter reaches its currently perceived scaling limits. The DBRTD was one of the first and remains one of the most promising devices to exhibit a room temperature negative differential resistance (NDR); this non-linear device characteristic has innovative circuit ap...

  4. Resonant tunneling diode with spin polarized injector

    OpenAIRE

    Slobodskyy, A.; Gould, C.; Slobodskyy, T.; Schmidt, G.; Molenkamp, L. W.; Sanchez, D

    2007-01-01

    We investigate the current-voltage characteristics of a II-VI semiconductor resonant-tunneling diode coupled to a diluted magnetic semiconductor injector. As a result of an external magnetic field, a giant Zeeman splitting develops in the injector, which modifies the band structure of the device, strongly affecting the transport properties. We find a large increase in peak amplitude accompanied by a shift of the resonance to higher voltages with increasing fields. We discuss a model which sho...

  5. Materials engineering for polarized light emitting diodes

    Czech Academy of Sciences Publication Activity Database

    Wegner, G.; Neher, D.; Remmers, M.; Cimrová, Věra; Schulze, M.

    Keystone: Materials Research Society, 1995 - (Lee, C.; Dalton, L.), s. 23-34 ISBN 1-55899-316-9. [Materials Research Society Fall Meeting: Electrical, Optical, and Magnetic Properties of Organic Solid State Materials. Boston (US), 26.11.1995-1.12.1995] Institutional research plan: CEZ:AV0Z4050913 Keywords : soluble poly(p-phenylene) * polarized emission * light emitting diodes(LED) Subject RIV: CD - Macromolecular Chemistry

  6. Blue laser diode (LD) and light emitting diode (LED) applications

    Science.gov (United States)

    Bergh, Arpad A.

    2004-09-01

    The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography.As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc.Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity.Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care.

  7. Blue laser diode (LD) and light emitting diode (LED) applications

    International Nuclear Information System (INIS)

    The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography. As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc. Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity. Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Cross-field diode sputtering target assembly

    International Nuclear Information System (INIS)

    An improved cross-field diode sputtering target assembly adapted for sputtering a selected material having an ion target wherein a selected surface is formed of a selected material in a predetermined closed loop pattern having a central opening therein, and wherein the selected surface has spaced edges and is formed of a material adapted to be controllably eroded in a diode sputtering process, walls positioned contiguous or adjacent to each of the spaced edges of the selected surface wherein each of the walls extend substantially normal from and beyond each spaced edge of the selected surface of the ion target and a magnetic member having poles positioned in an opposed spaced relationship to each other and enclosing the walls and the ion target for providing a linear magnetic field through the walls, over the selected surface and through the ion target and wherein the magnetic member has a linear magnetic field of sufficient strength for plasma entrapment between the walls and over the selected surface wherein the selected surface is adapted to have an electric field applied thereacross at a direction substantially normal to the magnetic field to develop a BXE field and to entrap secondary electrons at the selected surface to control the erosion pattern thereof is shown. A method for utilizing the improved cross-field diode sputtering target assembly is also shown

  9. New laser materials for laser diode pumping

    Science.gov (United States)

    Jenssen, H. P.

    1990-01-01

    The potential advantages of laser diode pumped solid state lasers are many with high overall efficiency being the most important. In order to realize these advantages, the solid state laser material needs to be optimized for diode laser pumping and for the particular application. In the case of the Nd laser, materials with a longer upper level radiative lifetime are desirable. This is because the laser diode is fundamentally a cw source, and to obtain high energy storage, a long integration time is necessary. Fluoride crystals are investigated as host materials for the Nd laser and also for IR laser transitions in other rare earths, such as the 2 micron Ho laser and the 3 micron Er laser. The approach is to investigate both known crystals, such as BaY2F8, as well as new crystals such as NaYF8. Emphasis is on the growth and spectroscopy of BaY2F8. These two efforts are parallel efforts. The growth effort is aimed at establishing conditions for obtaining large, high quality boules for laser samples. This requires numerous experimental growth runs; however, from these runs, samples suitable for spectroscopy become available.

  10. Fine tuning power diodes with irradiation

    International Nuclear Information System (INIS)

    Diodes of a particular type are fine tuned with irradiation to optimize the reverse recovery time while minimizing forward voltage drop and providing more uniform electrical characcteristics. The initial and desired minority carrier lifetimes in the anode region of the type are determined as a function of forward voltage drop and reverse recovery time, and the minority carrier radiation damage factor is determined for a desired type of diode and radiation source. The radiation dosage to achieve the desired carrier lifetime with the radiation source is thereafter determined from the function 1/tau = 1/tau0 + K phi, where tau is the desired minority carrier lifetime, tau0 is the initial minority carrier lifetime, K is the determined minority carrier radiation damage factor and phi is the radiation dosage. A major surface and preferably the major surface adjoining the anode region of the diodes is then irradiated with the radiation source to the determined radiation dosage. Preferably, the radiation dosage is between about 1 X 1012 and 5 X 1013 e/cm2, with electron radiation of intensity between 1 and 3 MeV

  11. A novel diode laser system for photodynamic therapy

    DEFF Research Database (Denmark)

    Samsøe, E.; Andersen, P. E.; Petersen, P.;

    2001-01-01

    In this paper a novel diode laser system for photodynamic therapy is demonstrated. The system is based on linear spatial filtering and optical phase conjugate feedback from a photorefractive BaTiO3 crystal. The spatial coherence properties of the diode laser are significantly improved. The system...... provides an almost diffraction limited output which is efficiently coupled into a 50 mum core diameter fiber. The optical power transmitted through the fiber is increased by a factor of six when the feedback is applied to the diode laser. 85 percent of the power from the freely running laser diode...... is extracted in a high-quality beam and 80 percent of the output power is extracted through the fiber. The power transmitted through tile fiber scales linearly with the power of the laser diode. which means that a laser diode emitting 1.7 W multi-mode radiation would provide 1 W of optical power through a 50...

  12. Influence of 2 MeV electrons irradiation on gallium phosphide light-emitting diodes reverse currents

    International Nuclear Information System (INIS)

    Results of reverse electrophysical characteristics study of red and green LED's, initial and irradiated with 2 MeV electrons were given. It was found that reverse current was predominantly caused by carriers tunneling at Urev <- 9 V, and by the avalanche multiplication at Urev >- 13 V, in the range U = 9-13 V both mechanisms are available. Current increase at high voltage areas (Urev > 19 V) is limited by the base resistance of diode. In the case of significant reverse currents (I > 1 mA) irradiation of diodes leads to the shift of reverse current-voltage characteristics into the high voltages direction

  13. Diode laser absorption sensors for combustion control

    Science.gov (United States)

    Xin, Zhou

    Combustion is the most widely used energy conversion technique in the world. Diode-laser absorption sensors offer significant opportunities and advantages for in situ measurements of multiple combustion parameters such as temperature and species concentration due to their high sensitivity, high spectral resolution, fast time response, robustness and non-intrusive character. The overall objective of this thesis is to design and develop time-resolved and real-time tunable diode laser sensors with the potential for combustion control. A crucial element in the design of a tunable-diode-laser optical-absorption-based sensor is the selection of optimum transitions. The strategy and spectroscopic criteria for selecting optimum wavelength regions and absorption line combinations are developed. The development of this design-rule approach establishes a new paradigm to optimize tunable diode laser sensors for target applications. The water vapor spectrum in the 1-2 mum near-infrared region is systematically analyzed to find the best absorption transition pairs for sensitive measurement of temperature in the target combustion environment using a single tunable diode laser. Two sensors are developed in this work. The first sensor is a 1.8 mum, single-laser temperature sensor based on direct absorption scans. Successful time-resolved measurements in a variety of laboratory and practical devices are presented and used to identify potential improvements, and design rules for a second-generation sensor are developed based on the lessons learned. The second generation sensor is a 1.4 mum, single-laser temperature sensor using water vapor absorption detected by wavelength-modulation spectroscopy (WMS), which facilitates rapid data analysis and a 2 kHz real-time data rate in the combustion experiments reported here. Demonstration experiments in a heated cell and a forced Hencken burner confirm the sensitivity and accuracy of the sensors. The first application of TDL thermometry to a

  14. Silicon Diode Dose Response Correction in Small Photon Fields

    OpenAIRE

    Omar, Artur

    2010-01-01

    Silicon diodes compared to other types of dosimeters have several attractive properties, such as an excellent spatial resolution, a high sensitivity, and clinically practical to use. These properties make silicon diodes a preferred dosimeter for relative dosimetry for several types of measurements in small field dosimetry, e.g., stereotactic treatments and intensity modulated radiotherapy (IMRT). Silicon diodes are, however, limited by an energy dependent response variation in photon beams, r...

  15. Silicon diodes as detectors in relative dosimetry of heavy ions

    International Nuclear Information System (INIS)

    In this study, the characteristics of the diodes are described for heavy-ion beams, such as the effect of radiation damage, linearity for dose rate and directional dependence of sensitivity. The Bragg curves measured by the silicon diodes are compared with those by ionization chamber and calculations. The availability of the silicon diodes as detectors in relative dosimetry of heavy ions are discussed. (J.P.N.)

  16. Laser diagnostics on magnetically insulated flashover pulsed ion diodes

    International Nuclear Information System (INIS)

    Our recent experimental results on the characteristics of a flashover-type applied-B magnetically insulated pulsed ion diode are described. The main issues are to investigate the cause of impurity of the extracted beam and to examine the effect of neutral particles on the diode characteristics. In the experiment, our main efforts were placed on laser diagnostics of the diode gap behavior. (author)

  17. A XOR Threshold Logic Implementation Through Resonant Tunneling Diode

    OpenAIRE

    Nitesh Kumar Dixit; Vinod Kumari

    2012-01-01

    Resonant tunneling diodes (RTDs) have functional versatility and high speed switching capability. The integration of resonant tunneling diodes and MOS transistor makes threshold gates and logics. The design and fabrication of linear threshold gates will be presented based on a mono stable bis table transition logic element. Each of its input terminals consist out of a resonant tunnelling diode merged with a transistor device. The circuit models of RTD and MOSFET are simulated in HSPICE. Two i...

  18. Theory of digital magneto resistance in ferromagnetic resonant tunneling diodes

    OpenAIRE

    Ertler, Christian; Fabian, Jaroslav

    2006-01-01

    We propose a ferromagnetic spintronic system, which consists of two serial connected resonant tunneling diodes. One diode is nonmagnetic whereas the other comprises a ferromagnetic emitter and quantum well. Using a selfconsistent coherent transport model we show that the current-voltage characteristic of the ferromagnetic diode can be strongly modulated by changing the relative orientation of the magnetizations in the emitter and quantum well, respectively. By a continuous change of the relat...

  19. Thermal lens diagnostics and mitigation in diode end pumped lasers

    OpenAIRE

    Stučinskas, Darius

    2010-01-01

    In this thesis, analysis of thermal effects and various approaches for their mitigation in diode end pumped ultrafast lasers is presented. Experimental investigations were performed by employing Shack-Hartmann wavefront sensor which was adapted for measurements of thermal lens in diode end pumped lasers. During research, operation of high average power, diode-pumped, Nd:YVO4 laser with aspheric aberration corrector was investigated. Actual thermal lens measurements were conducted in order to ...

  20. Dose-rate dependence of epitaxial diodes response for gamma dosimetry

    International Nuclear Information System (INIS)

    Full text: In this work, we present the preliminary results about the evaluation of dose-rate influence on the response of rad-hard epitaxial (EPI) diodes for on-line gamma-ray dosimetry using Co-60 irradiators. The diodes used were processed at University of Hamburg on n-type 75 micrometer thick epitaxial silicon layer (nominal resistivity of 69 Ohm.cm) grown on a highly doped n-type 300 micrometer thick Czochralski (Cz) silicon substrate. Two samples of EPI diodes were investigated: EPI-08 and EPI-10 - both non-irradiated previously. These devices, with 5mm x 5mm active area, were housed in a PMMA probe and connected, in a photovoltaic mode, to a Keithley 617 electrometer. The EPI-10 device irradiation was performed in the Radiation Technology Center at IPEN-CNEN/SP using a Co-60 irradiator (Gammacell 220 - Nordion) which delivers a dose rate of 2.16 kGy/h, while the EPI-08 device irradiation was performed in Nuclear Energy Department at UFPE/PE using the same model Co-60 irradiator, but with a dose-rate of 7.47 kGy/h. During the irradiation, the devices photocurrents were monitored as a function of the exposure time. The diodes were irradiated at room temperature. The dose-response curves of the EPI diodes were achieved through the integration of the current signals as a function of the exposure time. The normalized current signals as a function of the dose evidenced a decrease of about 60 percent from the initial current for the first 100 kGy dose received. After 500 kGy of exposure, the current signals stabilize (ou maintain stable). The dose-response curves behave as a second order polynomial fit, with correlation coefficients of about 0.99991 and 0.99995, respectively to EPI-10 and EPI-08 diodes. The preliminary results obtained evinced that the EPI diodes response are not dose-rate dependent within the range of 2.16 kGy/h up to 7.47 kGy/h. On the other hand, the devices studied are tolerant to radiation damages for total absorbed doses of approximately 550

  1. Underwater Chaotic Lidar using Blue Laser Diodes

    Science.gov (United States)

    Rumbaugh, Luke K.

    The thesis proposes and explores an underwater lidar system architecture based on chaotic modulation of recently introduced, commercially available, low cost blue laser diodes. This approach is experimentally shown to allow accurate underwater impulse response measurements while eliminating the need for several major components typically found in high-performance underwater lidar systems. The proposed approach is to: 1. Generate wideband, noise-like intensity modulation signals using optical chaotic modulation of blue-green laser diodes, and then 2. Use this signal source to develop an underwater chaotic lidar system that uses no electrical signal generator, no electro-optic modulator, no optical frequency doubler, and no large-aperture photodetector. The outcome of this thesis is the demonstration of a new underwater lidar system architecture that could allow high resolution ranging, imaging, and water profiling measurements in turbid water, at a reduced size, weight, power and cost relative to state-of-the-art high-performance underwater lidar sensors. This work also makes contributions to the state of the art in optics, nonlinear dynamics, and underwater sensing by demonstrating for the first time: 1. Wideband noise-like intensity modulation of a blue laser diode using no electrical signal generator or electro-optic modulator. Optical chaotic modulation of a 462 nm blue InGaN laser diode by self-feedback is explored for the first time. The usefulness of the signal to chaotic lidar is evaluated in terms of bandwidth, modulation depth, and autocorrelation peak-to-sidelobe-ratio (PSLR) using both computer and laboratory experiments. In laboratory experiments, the optical feedback technique is shown to be effective in generating wideband, noise-like chaotic signals with strong modulation depth when the diode is operated in an external-cavity dominated state. The modulation signal strength is shown to be limited by the onset of lasing within the diode's internal

  2. Plasma-filled diode based on the coaxial gun

    Energy Technology Data Exchange (ETDEWEB)

    Zherlitsyn, A. A.; Kovalchuk, B. M.; Pedin, N. N. [Institute of High Current Electronics, 2/3 Academichesky Avenue, 634055 Tomsk (Russian Federation)

    2012-10-15

    The paper presents the results of studies of a coaxial gun for a plasma-filled electron diode. Effects of the discharge channel diameter and gun current on characteristics of the plasma and pulse generated in the diode were investigated. The electron beam with maximum energy of {>=}1 MeV at the current of Almost-Equal-To 100 kA was obtained in the experiments with a plasma-filled diode. The energy of Almost-Equal-To 5 kJ with the peak power of {>=}100 GW dissipated in the diode.

  3. Plasma-filled diode based on the coaxial gun

    Science.gov (United States)

    Zherlitsyn, A. A.; Kovalchuk, B. M.; Pedin, N. N.

    2012-10-01

    The paper presents the results of studies of a coaxial gun for a plasma-filled electron diode. Effects of the discharge channel diameter and gun current on characteristics of the plasma and pulse generated in the diode were investigated. The electron beam with maximum energy of ≥1 MeV at the current of ≈100 kA was obtained in the experiments with a plasma-filled diode. The energy of ≈5 kJ with the peak power of ≥100 GW dissipated in the diode.

  4. Plasma-filled diode based on the coaxial gun

    International Nuclear Information System (INIS)

    The paper presents the results of studies of a coaxial gun for a plasma-filled electron diode. Effects of the discharge channel diameter and gun current on characteristics of the plasma and pulse generated in the diode were investigated. The electron beam with maximum energy of ≥1 MeV at the current of ≈100 kA was obtained in the experiments with a plasma-filled diode. The energy of ≈5 kJ with the peak power of ≥100 GW dissipated in the diode.

  5. Laboratory diode laser spectroscopy in molecular planetary astronomy

    Science.gov (United States)

    Jennings, D. E.

    1988-01-01

    Infrared spectroscopy of planetary atmospheres is performed at high spectral resolution comparable to that in the laboratory. This requires that laboratory spectroscopy use the highest resolution and the most accurate techniques. Tunable diode laser spectroscopy can supply many of the spectroscopic parameters needed by astronomers. In particular, line positions, line strengths, and collisional line widths are measured with diode lasers, and these are often among the best values available. Diode laser spectra are complimentary to lower resolution, broader-coverage Fourier transform spectra. Certain procedures must be adopted, however, when using diode lasers, for determining their output characteristics and for calibrating each spectrum against quality references.

  6. Plasma-filled diode based on the coaxial gun.

    Science.gov (United States)

    Zherlitsyn, A A; Kovalchuk, B M; Pedin, N N

    2012-10-01

    The paper presents the results of studies of a coaxial gun for a plasma-filled electron diode. Effects of the discharge channel diameter and gun current on characteristics of the plasma and pulse generated in the diode were investigated. The electron beam with maximum energy of ≥1 MeV at the current of ≈100 kA was obtained in the experiments with a plasma-filled diode. The energy of ≈5 kJ with the peak power of ≥100 GW dissipated in the diode. PMID:23126788

  7. High stable power control of a laser diode

    Institute of Scientific and Technical Information of China (English)

    YANG Jiu-ru; LI Cheng; YE Hong-an; L(U) Guo-hui; JIA Shi-lou

    2006-01-01

    In this paper,the low and the high frequency noises of a laser diode have been analyzed. Based on the analysis a novel scheme that adapts analog and digital hybrid techniques is proposed to stabilize the output power of a laser diode. With the hybrid controller,the low and the high frequency noises of a laser diode are conspicuously reduced.By accurate calculation,the short-term stability of the output power of laser diode reaches ±0.55‰, and the long-term stability is ±0.7‰.

  8. Three-dimensional, tight focusing of intense pulsed light-ion beam by spherical plasma focus diode

    International Nuclear Information System (INIS)

    A new type of ion-beam diode, self-magnetically insulated, spherica plasma focus diode (SPFD), was developed. With the SPFD, three-dimensional focusing of an intense pulsed light-ion beam was obtained. Experiments and simulations were carried out to study the behavior of the SPFD. In the experiments, diagnostic results of the Rutherford scattering pinhole camera and the shadow-box showed that the ion beam was focused into a small cylindrical area with ∼ 0.5mm in diameter and ∼ 2.5 mm in length. The average ion-beam current density at the anode surface was found to be ∼ 2 kA/cm2. In the simulations, it was observed that most of the diode gap is well insulated by the self-magnetic field induced by the diode current. The electron sheath in the diode gap significantly enhances the ion flow from the anode. As a result, the ion current density is several times higher than the single-species space-charge limited value. (author)

  9. Increased efficiency of silicon light-emitting diodes in a standard 1.2-um silicon complementary metal oxide semiconductor technology

    Science.gov (United States)

    Snyman, Lukas W.; Aharoni, Herzl; du Plessis, Monuko; Gouws, Rudolph B.

    1998-07-01

    Scaled versions of a variety of silicon light-emitting diode elements (Si LEDs) have been realized using a standard 1.2- micrometers , double-polysilicon, double-metal, n-well CMOS fabrication process. The devices operated with a n+p junction biased in the avalanche breakdown mode and were realized by using standard features of the ORBIT FORESIGHT design rules. The elements emit optical radiation in a broad band in the 450- to 850-nm range. An emitted intensity of up to 7.1 (mu) W/cm2 has been obtained with 5 mA of current at an operating voltage of 18.5 V. Excellent uniformity in emission intensity of better than 1 percent variation was obtained over areas as large as 100 X 500 micrometers . A best power conversion efficiency of 8.7 X 10-8 and a quantum efficiency of 7.8 X 10-7 were measured. All of these values are about one order of magnitude better than previously reported values for Si LED avalanche devices. Coupling between the elements as well as electro- optical coupling between an element and an optical fiber was realized.

  10. Power Conversion Efficiency of AlGaAs/GaAs Schottky Diode for Low-Power On-Chip Rectenna Device Application

    International Nuclear Information System (INIS)

    A Schottky diode has been designed and fabricated on n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I-V) measurements show good device rectification with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences of Schottky barrier height from theoretical value are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are well rectified by the fabricated Schottky diodes and stable DC output voltage is obtained. Power conversion efficiency up to 50% is obtained at 1 GHz with series connection between diode and load. The fabricated the n-AlGaAs/GaAs Schottky diode provide conduit for breakthrough designs for ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

  11. Effects of heavy ion impact on power diodes

    International Nuclear Information System (INIS)

    At the sea level a significant amount of muons, pions, protons and neutrons coming from the outer space, can impact a semiconductor device with a significant probability. This impact may result in the production of a cascade of highly ionizing ions within the device, mainly silicon or aluminium, which is the main responsible of its single event burn-out (SEB). Many authors have, then, proposed to study the effects of cosmic rays on power devices, both at the sea level and into the space, by irradiating them with heavy ions reproducing this cascade. The aim of this paper is to present the experimental results of the bombardment with high-energy 28Si ions (108 MeV. 156 MeV) on 1700 V power diodes. In particular, it is shown that a multiplication mechanism enhances the charge generated during the ion impact by a large amount. This mechanism is strongly affected by the applied reverse voltage and the charge increases even, more than 10 times as the applied voltage rises from 50% to 65% of the device blocking voltage. For larger values the diode breaks-down (the destruction took place at only 1200 V during irradiation with 156 MeV ions). The paper presents a complete collection of the observed waveforms during the ion impact and shows that the multiplication mechanism causes an enormous increase of the peak current flowing through the device. Due to the very small area involved into the generation process, the local current density reaches so high values to trigger instabilities, like double injection, which can cause the device failure in a similar manner as during Second-Breakdown of power devices. The 15 MV Tandem of the Laboratori Nazionali di Legnaro was used for the experiment reported in this paper. (authors)

  12. Interstitial laser photocoagulation with diode laser unit in bovine liver

    International Nuclear Information System (INIS)

    To evaluate the extent of tissue coagulation during interstitial laser photocoagulation (ILP) in normal bovine liver, using a diode laser unit and various parameters, and to determine whether the procedure is applicable to clinical practice. Using an 18-gauge needle, experimental interstitial laser photocoagulation (ILP) was carried out in normal bovine liver. On the basis of differing parameters, three groups were established. For group 1, a single photofiber with laser power of 1, 3 and 5 watts and an exposure time of 60, 180, 300, 420 or 600 seconds was used. For groups 2 and 3, four needles were fixed at a distance of 1cm and 1.5cm ; in each case a needle fixation device was used, as well as a laser distributor for simultaneous laser exposure of photofibers. As a control, four photofibers were placed as for group 3, but to compare groups 2 and 3, each photofiber was exposed to a laser of 3 watts 300 seconds, without using a laser distributor. To evaluate the range of tissue coagulation, specimens were analyzed both with regard to cross-sectional gross findings and histopathologically. The largest diameter of thermal coagulation necrosis in Group 1 was 15 X 15mm, and this was ball-shaped. Coalescence of coagulation between each photofiber was observed in Group 2, and this was up to 25mm in diameter. In Group 3 and controls, coalescence was not found, though the extent of tissue coagulation increased with increasing wattage and exposure time. The extent of charring at the center of coagulation also increased with increasing wattage. Smoke bubbles emanating from the coagulation area were observed, and during ILP involving a single photofiber, increased from 3 watts, applied for 300 seconds. Using an 8-gauge needle and a diode laser ILP, we have shown that a range of tissue coagulation acutely ablates normal bovine liver. In selective cases, the procedure could be applied to clinical trials

  13. High-resolution Schottky CdTe diode for hard X-ray and gamma-ray astronomy

    International Nuclear Information System (INIS)

    We report a significant improvement of the spectral properties of cadmium telluride (CdTe) detectors, fabricated in the form of a Schottky CdTe diode. With the use of high quality CdTe wafer, we formed a Schottky junction by evaporating indium on the Te-face and operated the detector as a diode. This allows us to apply much higher bias voltage than was possible with the previous CdTe detectors. A 2 mmx2 mm detector of thickness 0.5 mm, when operated at a temperature of 5 deg. C, shows leakage current of only 0.2 and 0.4 nA for an operating voltage of 400 and 800 V, respectively. We found that, at a high-electric field of several kV cm-1, the Schottky CdTe diode has very good energy resolution and stability, suitable for astronomical applications. The broad low-energy tail, often observed in CdTe detectors due to the low mobility and short lifetime of holes, was significantly reduced by the application of a higher bias voltage which improves the charge collection efficiency. We achieved very good FWHM energy resolution of 1.1% and 0.8% at energies 122 and 511 keV, respectively, without any rise time discrimination or pulse height correction electronics. For the detection of hard X-rays and gamma-rays above 100 keV, we have improved the detection efficiency by stacking a number of thin CdTe diodes. Using individual readout electronics for each layer, we obtained high detection efficiency without sacrificing the energy resolution. In this paper, we report the performance of the new CdTe diode and discuss its proposed applications in future hard X-ray and gamma-ray astronomy missions

  14. High-resolution Schottky CdTe diode for hard X-ray and gamma-ray astronomy

    Science.gov (United States)

    Takahashi, T.; Paul, B.; Hirose, K.; Matsumoto, C.; Ohno, R.; Ozaki, T.; Mori, K.; Tomita, Y.

    1999-10-01

    We report a significant improvement of the spectral properties of cadmium telluride (CdTe) detectors, fabricated in the form of a Schottky CdTe diode. With the use of high quality CdTe wafer, we formed a Schottky junction by evaporating indium on the Te-face and operated the detector as a diode. This allows us to apply much higher bias voltage than was possible with the previous CdTe detectors. A /2 mm/×2 mm detector of thickness 0.5 mm, when operated at a temperature of /5°C, shows leakage current of only 0.2 and 0.4 nA for an operating voltage of 400 and 800 V, respectively. We found that, at a high-electric field of several kV cm-1, the Schottky CdTe diode has very good energy resolution and stability, suitable for astronomical applications. The broad low-energy tail, often observed in CdTe detectors due to the low mobility and short lifetime of holes, was significantly reduced by the application of a higher bias voltage which improves the charge collection efficiency. We achieved very good FWHM energy resolution of /1.1% and /0.8% at energies 122 and 511 keV, respectively, without any rise time discrimination or pulse height correction electronics. For the detection of hard X-rays and gamma-rays above 100 keV, we have improved the detection efficiency by stacking a number of thin CdTe diodes. Using individual readout electronics for each layer, we obtained high detection efficiency without sacrificing the energy resolution. In this paper, we report the performance of the new CdTe diode and discuss its proposed applications in future hard X-ray and gamma-ray astronomy missions.

  15. Anatomical features of pepper plants (Capsicum annuum L.) grown under red light-emitting diodes supplemented with blue or far-red light

    Science.gov (United States)

    Schuerger, A. C.; Brown, C. S.; Stryjewski, E. C.

    1997-01-01

    Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves and stems. One LED (660) array supplied 90% red light at 660 nm (25nm band-width at half-peak height) and 1% far-red light between 700-800nm. A second LED (660/735) array supplied 83% red light at 660nm and 17% far-red light at 735nm (25nm band-width at half-peak height). A third LED (660/blue) array supplied 98% red light at 660nm, 1% blue light between 350-550nm, and 1% far-red light between 700-800nm. Control plants were grown under broad spectrum metal halide lamps. Plants were gron at a mean photon flux (300-800nm) of 330 micromol m-2 s-1 under a 12 h day-night photoperiod. Significant anatomical changes in stem and leaf morphologies were observed in plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of choloplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660/blue LED array, and lowest in peppers grown under the 660 or 660/735 LED arrays. Most anatomical features of pepper stems and leaves were similar among plants grown under 660 or 660/735 LED arrays. The effects of spectral quality on anatomical changes in stem and leaf tissues of peppers generally correlate to the amount of blue light present in the primary light source.

  16. Broad-spectrum light versus blue light for phototherapy in neonatal hyperbilirubinemia: a randomized controlled trial.

    Science.gov (United States)

    Pratesi, Simone; Di Fabio, Sandra; Bresci, Cecilia; Di Natale, Cecilia; Bar, Shahar; Dani, Carlo

    2015-07-01

    Phototherapy is standard care for treatment of neonatal hyperbilirubinemia. Our aim was to compare the effectiveness of broad-spectrum light (BSL) to that of blue light emitting diodes (LED) phototherapy for the treatment of jaundiced late preterm and term infants. Infants with gestational age from 35(+0) to 41(+6) weeks of gestation and nonhemolytic hyperbilirubinemia were randomized to treatment with BSL phototherapy or blue LED phototherapy. A total of 20 infants were included in the blue LED phototherapy group and 20 in the BSL phototherapy group. The duration of phototherapy was lower in the BSL than in the blue LED phototherapy group (15.8 ± 4.9 vs. 20.6 ± 6.0 hours; p = 0.009), and infants in the former group had a lower probability (p = 0.015) of remaining in phototherapy than infants in the latter. We concluded that BSL phototherapy is more effective than blue LED phototherapy for the treatment of hyperbilirubinemia in late preterm and term infants. Our data suggest that these results are not due to the different irradiance of the two phototherapy systems, but probably depend on their different peak light emissions. PMID:25545446

  17. Simulation of broad spectral bandwidth emitters at 1060 nm for optical coherence tomography

    Science.gov (United States)

    Tooley, I. G.; Childs, D. T. D.; Stevens, B. J.; Groom, K. M.; Hogg, R. A.

    2016-03-01

    The simulation of broad spectral bandwidth light sources (semiconductor optical amplifiers (SOA) and superluminescent diodes (SLD)) for application in ophthalmic optical coherence tomography is reported. The device requirements and origin of key device parameters are outlined, and a range of single and double InGaAs/GaAs quantum well (QW) active elements are simulated with a view to application in different OCT embodiments. We confirm that utilising higher order optical transitions is beneficial for single QW SOAs, but may introduce deleterious spectral modulation in SLDs. We show how an addition QW may be introduced to eliminate this spectral modulation, but that this results in a reduction of the gain spectrum width. We go on to explore double QW structures where the roles of the two QWs are reversed, with the narrow QW providing long wavelength emission and gain. We show how this modification in the density of states results in a significant increase in gain-spectrum width for a given current.

  18. Discharge ratio of the broad-crested weir flowin the low head area КОЭФФИЦИЕНТ РАСХОДА ВОДОСЛИВА С ШИРОКИМ ПОРОГОМВ ОБЛАСТИ МАЛЫХ НАПОРОВ

    OpenAIRE

    Medzveliya Manana Levanovna; Pipiya Valeriy Valerianovich

    2013-01-01

    The authors consider the influence of the Reynolds number on the discharge ratio of the broad-crested weir. The authors provide an overview of their experiment in thearticle. They provide the equation that takes account of each factor of influence, including H — pressure over the broad-crested weir, P — weir height above the bottom, v — liquid velocity, ρ — liquid density, μ — dynamic viscosity, g — superficial tension, σ — gravity acceleration, q — per-unit weir flow, B — width of the weir, ...

  19. Position and mode dependent coupling of terahertz quantum cascade laser fields to an integrated diode

    CERN Document Server

    Dyer, Gregory C; Cich, Michael J; Ribaudo, Troy; Grine, Albert D; Fuller, Charles T; Reno, John L; Wanke, Michael C

    2016-01-01

    A Schottky diode integrated into a terahertz quantum cascade laser waveguide couples directly to the internal laser fields. In a multimode laser, the diode response is correlated with both the instantaneous power and the coupling strength to the diode of each lasing mode. Measurements of the rectified response of diodes integrated in two quantum cascade laser cavities at different locations indicate that the relative diode position strongly influences the laser-diode coupling.

  20. Ultra-broad bandwidth parametric amplification at degeneracy.

    Science.gov (United States)

    Limpert, J; Aguergaray, C; Montant, S; Manek-Hönninger, I; Petit, S; Descamps, D; Cormier, E; Salin, F

    2005-09-19

    We report on a novel approach of ultra-broad bandwidth parametric amplification around degeneracy. A bandwidth of up to 400 nm centered around 800 nm is amplified in a BBO crystal by using chirped pump pulses with a bandwitdth as broad as 10 nm. A supercontinuum signal is generated in a microstructured fiber, having to first order a quadratic chirp, which is necessary to ensure temporal overlap of the interacting waves over this broad bandwidth. Furthermore, we discuss the potential of this approach for an octave-spanning parametric amplification. PMID:19498762

  1. Thin-layer black phosphorous/GaAs heterojunction p-n diodes

    International Nuclear Information System (INIS)

    Owing to its high carrier mobility and thickness-tunable direct band gap, black phosphorous emerges as a promising component of optoelectronic devices. Here, we evaluate the device characteristics of p-n heterojunction diodes wherein thin black phosphorous layers are interfaced with an underlying, highly n-doped GaAs substrate. The p-n heterojunctions exhibit close-to-ideal diode behavior at low bias, while under illumination they display a photoresponse that is evenly distributed over the entire junction area, with an external quantum efficiency of up to 10% at zero bias. Moreover, the observed maximum open circuit voltage of 0.6 V is consistent with the band gap estimated for a black phosphorous sheet with a thickness on the order of 10 nm. Further analysis reveals that the device performance is limited by the structural quality of the black phosphorous surface

  2. Broad Spectrum Sanitizing Wipes with Food Additives Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Microcide proposes to develop novel multipurpose non-toxic sanitizing wipes that are aqueous based, have shelf life of 3-5 years, have broad spectrum microbicidal...

  3. AGN Broad Line Regions Scale with Bolometric Luminosity

    CERN Document Server

    Trippe, Sascha

    2015-01-01

    The masses of supermassive black holes in active galactic nuclei (AGN) can be derived spectroscopically via virial mass estimators based on selected broad optical/ultraviolet emission lines. These estimates commonly use the line width as a proxy for the gas speed and the monochromatic continuum luminosity as a proxy for the radius of the broad line region. However, if the size of the broad line region scales with bolometric rather than monochromatic AGN luminosity, mass estimates based on different emission lines will show a systematic discrepancy which is a function of the color of the AGN continuum. This has actually been observed in mass estimates based on H-alpha / H-beta and C IV lines, indicating that AGN broad line regions indeed scale with bolometric luminosity. Given that this effect seems to have been overlooked as yet, currently used single-epoch mass estimates are likely to be biased.

  4. Advancements in flowing diode pumped alkali lasers

    Science.gov (United States)

    Pitz, Greg A.; Stalnaker, Donald M.; Guild, Eric M.; Oliker, Benjamin Q.; Moran, Paul J.; Townsend, Steven W.; Hostutler, David A.

    2016-03-01

    Multiple variants of the Diode Pumped Alkali Laser (DPAL) have recently been demonstrated at the Air Force Research Laboratory (AFRL). Highlights of this ongoing research effort include: a) a 571W rubidium (Rb) based Master Oscillator Power Amplifier (MOPA) with a gain (2α) of 0.48 cm-1, b) a rubidium-cesium (Cs) Multi-Alkali Multi-Line (MAML) laser that simultaneously lases at both 795 nm and 895 nm, and c) a 1.5 kW resonantly pumped potassium (K) DPAL with a slope efficiency of 50%. The common factor among these experiments is the use of a flowing alkali test bed.

  5. High Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal;

    planar growth, many new materials combinations can be grown in a single NW. This opens up exciting opportunities for NW-based high-performance solar cells, where previously inaccessible materials combinations can now be chosen to match the solar spectrum. A key component of a multi-junction solar cell is......, individual NWs were contacted in a NW-FET setup. Electrical measurements at room temperature display typical tunnel diode behavior, with a Peak-to-Valley Current Ratio (PVCR) as high as 8.2 and a peak current density as high as 329 A/cm2. Low temperature measurements show improved PVCR of up to 27.6....

  6. Evaluation of automatic densitometer with laser diode

    International Nuclear Information System (INIS)

    The evaluation of a prototype of an automatic transmission scanning densitometer is presented. It contains a semiconductor diode laser as a light source, and is mainly oriented to the analysis of protein electrophoresis. It was developed on the Center for Technological Applications and Nuclear Development (CEADEN). Its technical specifications were established and certified by the National Institute of Researches on Metrology (INIMET), and also the equipment was submitted for assays to the Process Control Laboratory, that belongs to the 'Adalberto Pesant' Enterprise for Sera and Hemo derivatives Products, in Havana city, where it was employed to the partial quality control of products that are made there, achieving satisfactory results. (Author)

  7. Efficient organic light emitting-diodes (OLEDs)

    CERN Document Server

    Chang, Yi-Lu

    2015-01-01

    Following two decades of intense research globally, the organic light-emitting diode (OLED) has steadily emerged as the ultimate display technology of choice for the coming decades. Portable active matrix OLED displays have already become prevalent, and even large-sized ultra-high definition 4K TVs are being mass-produced. More exotic applications such as wearable displays have been commercialized recently. With the burgeoning success in displays, researchers are actively bringing the technology forward into the exciting solid-state lighting market. This book presents the knowledge needed for

  8. Wave guide optimization for homoepitaxial laser diodes

    Energy Technology Data Exchange (ETDEWEB)

    Figge, S.; Dennemarck, J.; Aschenbrenner, T.; Zargham, A.; Hommel, D. [Institute of Solid State Physics, University of Bremen, 28359 Bremen (Germany)

    2007-06-15

    GaN-based high power laser diodes in the violet spectral range are demanding for conductive substrates with a lower thermal resistance than the commonly used sapphire. The only feasible approach to this goal is homoepitaxy on GaN wafers produced from thick GaN layers grown by hydride vapour phase epitaxy. One drawback of GaN substrates is the high refractive index and therefore it acts as an parasitic wave guide. In this paper we discuss the optimization of the wave guide and the n-side cladding layer. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Wheat Under LED's (Light Emitting Diodes)

    Science.gov (United States)

    2004-01-01

    Astroculture is a suite of technologies used to produce and maintain a closed controlled environment for plant growth. The two most recent missions supported growth of potato, dwarf wheat, and mustard plants, and provided scientists with the first opportunity to conduct true plant research in space. Light emitting diodes have particular usefulness for plant growth lighting because they emit a much smaller amount of radiant heat than do conventional lighting sources and because they have potential of directing a higher percentage of the emitted light onto plants surfaces. Furthermore, the high output LED's have emissions in the 600-700 nm waveband, which is of highest efficiency for photosynthesis by plants.

  10. Piezoresistive properties of resonant tunneling diodes

    Institute of Scientific and Technical Information of China (English)

    MAO Haiyang; XIONG Jijun; ZHANG Wendong; XUE Chenyang; SANG Shengbo; BAO Aida

    2007-01-01

    A measurement system was designed and established to test the piezoresistive properties of resonant tunneling diodes(RTDs).The current-voltage characteristic shifts of RTD at different stress states were detected.The experimental results demonstrate that the piezoresistive sensitivity Of RTD is larger than 1×10-8 Pa-1.To accurately represent the piezoresistive properties of RtD.the current-voltage characteristic coherence of the same RTD was tested.According to the experimental results,the largest relative resistance shift of an RTD in the same measurement environment is less than 3%,of which 1%is caused by the testing apparatuses.

  11. InP-base resonant tunneling diodes

    International Nuclear Information System (INIS)

    We have fabricated In0.53Ga0.47As/AlAs/InP resonant tunneling diodes (RTDs) based on the air-bridge technology by using electron beam lithography processing. The epitaxial layers of the RTD were grown on semiinsulating (100) InP substrates by molecular beam epitaxy. RTDs with a peak current density of 24.6 kA/cm2 and a peak-to-valley current ratio of 8.6 at room temperature have been demonstrated.

  12. Resonant-tunnelling diodes for THz applications

    Science.gov (United States)

    Feiginov, Michael; Sydlo, Cezary; Cojocari, Oleg; Meissner, Peter

    2012-10-01

    We investigate experimentally resonant-tunnelling-diode (RTD) oscillators, which are based on RTDs with heavily doped collector. We demonstrate that such RTD oscillators can work at frequencies, which are far beyond the limitations imposed by resonant-state lifetime and relaxation time. Exploiting further such RTDs, we have achieved the record operating frequency of 1.1 THz and show that substantially higher frequencies should be also achievable with RTD oscillators. RTD oscillators are extremely compact (less than a square millimeter) room-temperature sources of coherent cw THz radiation. Such sources should enable plenty of real-world THz applications.

  13. InP-base resonant tunneling diodes

    Institute of Scientific and Technical Information of China (English)

    Han Chunlin; Chen Chen; Zou Penghui; Zhang Yang; Zeng Yiping; Xue Fangshi; Gao Jianfeng; Zhang Zheng; Geng Tao

    2009-01-01

    We have fabricated Ino.53Ga0.47As/AlAs/InP resonant tunneling diodes (RTDs) based on the air-bridge technology by using electron beam lithography processing. The epitaxial layers of the RTD were grown on semiinsulating (100) InP substrates by molecular beam epitaxy. RTDs with a peak current density of 24.6 kA/cm2 and a peak-to-valley current ratio of 8.6 at room temperature have been demonstrated.

  14. Large white organic light-emitting diode lighting panel on metal foils

    OpenAIRE

    Guaino, Philippe; Mazeri, Fabrizo; Hofmann, Michael; Birnstock, Jan; Avril, Ludovic; Viville, Pascal; Kanaan, Hani; Lazzaroni, Roberto; Loicq, Jerôme; Rotheudt, Frank; Pans, Christian

    2011-01-01

    Large-area top-emitting PIN structure (highly p- and n- type doped transport layers for electrons and holes and an undoped emitter layer)–organic light-emitting diode (OLED) on advanced metal foils were fabricated for lighting applications. ArcelorMittal has developed a new surface treatment on metal foils, suitable for roll-to-roll production and dedicated to large-area device integration. Both monochromatic and white devices are realized on advanced metal foils. Power efficiencies at 1000 c...

  15. Thermal Reliability Study of Bypass Diodes in Photovoltaic Modules (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.; Wohlgemuth, J.; Kurtz, S.

    2013-05-01

    This paper presents the result of high-temperature durability and thermal cycling testing and analysis for the selected diodes to study the detail of the thermal design and relative long-term reliability of the bypass diodes used to limit the detrimental effects of module hot-spot susceptibility.

  16. Low-inductance, dual-feed diode development

    International Nuclear Information System (INIS)

    We have tested three low-inductance, sub-ohm impedance diode configurations on the SNLA SPEED pulse generator at power levels above 1 TW. SPEED is a single module, approx. = 20 nsec FWHM accelerator with a .4 ohm triaxial power flow transmission line in the water section and a double-sided vacuum-water insulator at a radius of 53 cm. In these experiments, the dual feed was continued with a triplate disk arrangement down to a diode radius of 4 cm, resulting in a load inductance of 5 nH. The diodes were configured to operate in a Langmuir-Childe's bipolar mode, a paravector potential mode, and a double pinched beam mode. We observed pulses with V = 900 kV, I = 1.5 MA, and pulse width = 19 nsec FWHM at the diode. Diode impedance was governed by plasma gap closure; closure velocities of approx. 7 cm/μsec can be inferred from the data. In addition, a 4 nsec difference in the arrival time of the waves at the diode from the two feed lines was found to significantly perturb the expected diode performance. Diode performance improved markedly when the two feed lines were isolated from each other

  17. Integral bypass diodes in an amorphous silicon alloy photovoltaic module

    Science.gov (United States)

    Hanak, J. J.; Flaisher, H.

    1991-01-01

    Thin-film, tandem-junction, amorphous silicon (a-Si) photovoltaic modules were constructed in which a part of the a-Si alloy cell material is used to form bypass protection diodes. This integral design circumvents the need for incorporating external, conventional diodes, thus simplifying the manufacturing process and reducing module weight.

  18. Use of tunnel diode for nanosecond pulse amplification

    International Nuclear Information System (INIS)

    In a first part, after a brief review of tunnel diode properties, the paper presents graphic and analytic investigations of series, shunt and compound connected tunnel diode amplifiers. A study of the noise problem is given. In a second part, practical realizations are described and results of measurements of their gain and noise characteristics are presented. (author)

  19. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    Science.gov (United States)

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  20. The Switch from Low-Pressure Sodium to Light Emitting Diodes Does Not Affect Bat Activity at Street Lights

    OpenAIRE

    Rowse, Elizabeth G.; Harris, Stephen; Jones, Gareth

    2016-01-01

    We used a before-after-control-impact paired design to examine the effects of a switch from low-pressure sodium (LPS) to light emitting diode (LED) street lights on bat activity at twelve sites across southern England. LED lights produce broad spectrum ‘white’ light compared to LPS street lights that emit narrow spectrum, orange light. These spectral differences could influence the abundance of insects at street lights and thereby the activity of the bats that prey on them. Most of the bats f...

  1. Graded tensile-strained bulk InGaAs/InP superluminescent diode with very wide emission spectrum

    Institute of Scientific and Technical Information of China (English)

    Shurong Wang(王书荣); Wei Wang(王圩); Hongliang Zhu(朱洪亮); Zhihong Liu(刘志宏); Ruiving Zhang(张瑞英); Ying Ding(丁颖); Lingjuan Zhao(赵玲娟); Fan Zhou(周帆); Jing Bian(边静); Lufeng Wang(王鲁峰)

    2004-01-01

    A kind of novel broad-band superluminescent diodes (SLDs) using graded tensile-strained bulk InGaAs is developed. The graded tensile-strained bulk InGaAs is obtained by changing only group-Ⅲ trimethylgallium source flow during low-pressure metal organic vapor-phase epitaxy. At the injection current of 200mA, the fabricated SLDs with such structure demonstrate full-width at half-maximum spectral width of 106 nm and the output light power of 13.6 mW, respectively.

  2. Multi-Watt, diffraction-limited CW and Q-switched, diode-end-pumped, double-clad waveguide lasers

    OpenAIRE

    Mackenzie, J.I.; Wang, J.; Shepherd, D

    2003-01-01

    We demonstrate that double-clad waveguides can be used to obtain multiWatt, CW and Q-switched, diffraction-limited output when end-pumped by broad-stripe diodes. The waveguide geometry is shown to be especially favourable for efficient laser operation of low gain and quasithree-level transitions. The performance of the Nd:YAG system at several operating wavelengths. The quasithree-level 946 nm performance appears particularly impressive. The passively Q-switched Yb:YAG double-clad waveguide l...

  3. Structure, stability properties, and nonlinear dynamics of lateral modes of a broad area semiconductor laser

    DEFF Research Database (Denmark)

    Blaaberg, Søren

    2007-01-01

    Bred-areal halvlederlasere er kompakte lasere designet til at levere høj udgangseffekt (>1 Watt). Den høje effekt opnås ved at gøre laserens aktive område bredt (>100 mikrometer) samt laserspejlene endnu bredere. I det aktive område pumpes laseren elektrisk. Langs laserens ene tværstillede akse l...

  4. A Flight-like Integrated Circulator for Broad Area Cooling Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future instruments and platforms for NASA space applications will require increasingly sophisticated thermal control technology, and cryogenic applications will...

  5. Proviruses selected for high and stable expression of transduced genes accumulate in broadly transcribed genome areas

    Czech Academy of Sciences Publication Activity Database

    Plachý, Jiří; Kotáb, Jan; Divina, Petr; Reinišová, Markéta; Šenigl, Filip; Hejnar, Jiří

    2010-01-01

    Roč. 84, č. 9 (2010), s. 4204-4211. ISSN 0022-538X R&D Projects: GA ČR(CZ) GA204/07/1030; GA ČR GP301/09/P667 Institutional research plan: CEZ:AV0Z50520514 Keywords : avian sarcoma virus * retrovirus integration * position effects Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.189, year: 2010

  6. Fiber Optic Coupling of CW Linear Laser Diode Array

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaowei; XIAO Jianwei; MA Xiaoyu; WANG Zhongming; FANG Gaozhan

    2002-01-01

    Based on a set of microoptics the output radiation from a continuous wave (CW) linear laser diode array is coupled into a multi-mode optical fiber of 400 μm diameter.The CW linear laser diode array is a 1 cm laser diode bar with 19 stripes with 100 μm aperture spaced on 500 μm centers.The coupling system contains packaged laser diode bar,fast axis collimator,slow axis collimation array,beam transformation system and focusing system.The high brightness,high power density and single fiber output of a laser diode bar is achieved.The coupling efficiency is 65% and the power density is up to 1.03×104 W/cm2.

  7. Equivalent circuit model of semiconductor nanowire diode by SPICE.

    Science.gov (United States)

    Lee, SeHan; Yu, YunSeop; Hwang, SungWoo; Ahn, Doyeol

    2007-11-01

    An equivalent circuit model of nanowire diodes is introduced. Because nanowire diodes inevitably involve a metal-semiconductor-metal structure, they consist of two metal-semiconductor contacts and one resistor in between these contacts. Our equivalent circuit consists of two Schottky diodes and one resistor. The current through the reverse-biased Schottky diode is calculated from the thermionic field emission (TFE) theory and that of the forward-biased Schottky diode is obtained from the classical thermionic emission (TE) equation. Our model is integrated into the conventional circuit simulator SPICE by a sub-circuit with TFE and TE routines. The results simulated with our model by SPICE are in good agreement with various, previously reported experimental results. PMID:18047126

  8. High-power green diode laser systems for biomedical applications

    DEFF Research Database (Denmark)

    Müller, André

    beam propagation parameters and therefore efficiently increases the brightness of compact and cost-effective diode laser systems. The condition of overlapping beams is an ideal scenario for subsequent frequency conversion. Based on sum-frequency generation of two beam combined diode lasers a 3.2 fold....... The underlying principle is spectral beam combining of multiple, comparable diode lasers with subsequent nonlinear frequency conversion. In the former approach multiple lasers are incoherently combined with an external optical component. With two 1062 nm tapered diode lasers and a reflecting volume...... Bragg grating more than 16 W of output power at combining efficiencies > 93% are obtained. Utilizing the wavelength tunability of diode lasers enables less critical optical alignment compared to lasers limited to specific atomic transitions. It is shown that spectral beam combining does not affect the...

  9. Electron beam diodes using ferroelectric cathodes

    International Nuclear Information System (INIS)

    A new high current density electron source is investigated. The source consists of a polarized ceramic disk with aluminum electrodes coated on both faces. The front electrode is etched in a periodic grid to expose the ceramic beneath. A rapid change in the polarization state of the ceramic results in the emission of a high density electron cloud into a 1 to 10mm diode gap. The anode potential is maintained by a charged transmission line. Some of the emitted electrons traverse the gap and an electron current flows. The emitted electron current has been measured as a function of the gap spacing and the anode potential. Current densities in excess of 70 A/cm2 have been measured. The current is found to vary linearly with the anode voltage for gaps < 10 mm, and exceeds the Child-Langmuir current by at least two orders of magnitude. The experimental data will be compared with predictions from a model based on the emission of a cloud of electrons from the ferroelectric which in turn reflex in the diode gap

  10. Processes governing pinch formation in diodes

    International Nuclear Information System (INIS)

    The process of pinch formation in large aspect ratio diodes has been studied by means of streak photography and time-resolved x-ray detectors. A tight pinch is formed at the anode center by a collapsing thin hollow electron beam. The collapse velocity depends, among other things, on the type of material in the top 1 μm layer of the anode. In a tentative model it is assumed that an anode plasma is at least partially created from gases released from the surface layer of the anode by the heating action of the beam. These gases are ionized by primary, backscattered, and secondary electrons. Ions emitted from this plasma modify the electron trajectories in the diode leading to a radial collapse of the hollow electron beam. The observed monotonic dependence of the collapse velocity on the atomic number of the anode material can be explained by the smooth dependence on Z of both the specific heat and the electron backscatter coefficient. In the case of high-Z anodes the ion expansion time appears to be the factor limiting the collapse velocity. Detailed experimental data are presented

  11. Studies on 405nm blue-violet diode laser with external grating cavity

    Science.gov (United States)

    Li, Bin; Gao, Jun; Zhao, Jun; Yu, Anlan; Luo, Shiwen; Xiong, Dongsheng; Wang, Xinbing; Zuo, Duluo

    2016-03-01

    Spectroscopy applications of free-running laser diodes (LD) are greatly restricted as its broad band spectral emission. And the power of a single blue-violet LD is around several hundred milliwatts by far, it is of great importance to obtain stable and narrow line-width laser diodes with high efficiency. In this paper, a high efficiency external cavity diode laser (ECDL) with high output power and narrow band emission at 405 nm is presented. The ECDL is based on a commercially available LD with nominal output power of 110 mW at an injection current of 100 mA. The spectral width of the free-running LD is about 1 nm (FWHM). A reflective holographic grating which is installed on a home-made compact adjustable stage is utilized for optical feedback in Littrow configuration. In this configuration, narrow line-width operation is realized and the effects of grating groove density as well as the groove direction related to the beam polarization on the performances of the ECDL are experimentally investigated. In the case of grating with groove density of 3600 g/mm, the threshold is reduced from 21 mA to 18.3 mA or 15.6 mA and the tuning range is 3.95 nm or 6.01 nm respectively when the grating is orientated in TE or TM polarization. In addition, an output beam with a line-width of 30 pm and output power of 92.7 mW is achieved in TE polarization. With these narrow line-width and high efficiency, the ECDL is capable to serve as a light source for spectroscopy application such as Raman scattering and laser induced fluorescence.

  12. Wavelength optimization using available laser diodes in spectral near-infrared optical tomography.

    Science.gov (United States)

    Chen, Liang-Yu; Pan, Min-Cheng; Yan, Chung-Chen; Pan, Min-Chun

    2016-07-20

    For employing optimized wavelengths, a near-infrared (NIR) tomographic imaging system with multiwavelengths in a continuous wave (CW) enables us to provide accurate information of chromophores. In this paper, we discuss wavelength optimization with a selection from commercial laser diodes. Through theoretical analysis, the residual norm (R) and the condition number (κ) represent the uniqueness of a matrix problem and the smooth singular-value distribution of each chromophore, respectively. The optimum wavelengths take place for large R and small κ. We considered a total of 38 wavelengths of laser diodes in the range of 633-980 nm commercially available to discover optimum sets for a broad range of chromophore combinations. In the 38 wavelengths, there exists 501,942 (C538), 2,760,681 (C638), and 12,620,256 (C738) combinations of five, six, and seven wavelength sets, respectively, for accurately estimating chromophores (HbO2, HbR, H2O, and lipids), water, lipids, and the scattering prefactor A. With the numerical calculation, the top 10 wavelength sets were selected based on the principle of large R and small κ. In the study, the chromophore concentration for young and elderly women are investigated; finally, choosing the laser diodes with a wavelength of 650, 690, 705, 730, 870/880, 915, and 937 nm is recommended either for young or elderly women to construct a spectral NIR tomographic imaging system in the CW domain. Simulated data were used to validate the claims. PMID:27463930

  13. A study of signal generation and charge collection in a-Si:H diodes for radiation imaging

    International Nuclear Information System (INIS)

    Its high radiation resistivity and large-area capability are the expected advantages of this material together with its ability to provide a front-end readout electronics in the vicinity of the sensor element. Electrons and holes created by incoming charged particles, X-rays, γ rays, are drifted by the electric field inside a-Si:H diodes and this carrier movement induces signal charges on electrodes. Charge collection and signal generation process are analyzed in terms of carrier mobilities, lifetimes and electric field. Charge collection in thick a-Si:H diodes is often limited by deep-level trapping of carriers during transit and a finite charge integration time required for single particle counting in some applications and sometimes by volume recombination of carriers for detecting heavily-ionizing particles such as α particles. The charge collection process is also strongly affected by the non-uniform electric field profiles in a-Si:H diodes caused by the fixed space charges inside the material under reverse-bias. Signal generation due to a weak light pulse irradiating each end of a thick diode is measured as a function of a reverse-bias and it gives a valuable information about the fixed space charges. Field profiles can be manipulated by either doping, electrode geometry, or combination of both to improve the charge collection process. One can apply a higher reverse-bias on a diode with an equivalent thickness by providing buffer layers at each end of the diode and thus suppressing soft breakdown phenomena. X-ray detection with a good sensitivity is demonstrated by an a-Si:H photodiode coupled to an evaporated CsI scintillator. The scintillation quality of evaporated CsI layers can be made almost identical to its single crystal counterpart. Fields of a-Si:H radiation detector application include high energy physics, medical imaging, materials science and life science. 78 refs., 68 figs., 11 tabs

  14. Efficiency of the magnetic treatment of broad bean seeds cultivated under experimental plot conditions

    Directory of Open Access Journals (Sweden)

    Podleśna A.

    2004-03-01

    Full Text Available The tests were carried out in the Institute of Soil Science and Plant Cultivation in Puławy under experimental plot conditions in the years 2000-2001. The factor of the first order were two varieties of broad bean: Nadwiślański - a traditional form and Tim - a self-determining form, while the second factor was - 3 exposure doses of magnetic induction intensity. The magnetic treatment of the seed was done in the Department of Physics at the University of Agriculture in Lublin using a specially constructed device for the magnetic treatment of seeds prior to sowing equipped with an electromagnet with fluent regulation of magnetic induction. The research confirmed the positive effect of the magnetic treatment on the germination and emergence of both broad bean cultivars. Plant emergence was more regular after the use of the aforementioned treatment and occured 2-3 days earlier in com- parison to the control plants. The magnetic treatment of broad bean seeds prior to sowing exerted a significant influence on the increase of seed yield. However, the efficiency of this treatment was dependent on the weather. The gain in seed yield resulting from the pre-sowing treatment of seeds with a magnetic field for both forms of broad bean was due to the higher number of pods per plant and the fewer plant losses in the unit area in the growing season.

  15. An Alkane-Soluble Dendrimer as Electron-Transport Layer in Polymer Light-Emitting Diodes.

    Science.gov (United States)

    Zhong, Zhiming; Zhao, Sen; Pei, Jian; Wang, Jian; Ying, Lei; Peng, Junbiao; Cao, Yong

    2016-08-10

    Polymer light-emitting diodes (PLEDs) have attracted broad interest due to their solution-processable properties. It is well-known that to achieve better performance, organic light-emitting diodes require multilayer device structures. However, it is difficult to realize multilayer device structures by solution processing for PLEDs. Because most semiconducting polymers have similar solubility in common organic solvents, such as toluene, xylene, chloroform, and chlorobenzene, the deposition of multilayers can cause layers to mix together and damage each layer. Herein, a novel semiorthogonal solubility relationship was developed and demonstrated. For the first time, an alkane-soluble dendrimer is utilized as the electron-transport layer (ETL) in PLEDs via a solution-based process. With the dendrimer ETL, the external quantum efficiency increases more than threefold. This improvement in the device performance is attributed to better exciton confinement, improved exciton energy transfer, and better charge carrier balance. The semiorthogonal solubility provided by alkane offers another process dimension in PLEDs. By combining them with water/alcohol-soluble polyelectrolytes, more exquisite multilayer devices can be fabricated to achieve high device performance, and new device structures can be designed and realized. PMID:27435357

  16. Bid Optimization in Broad-Match Ad auctions

    CERN Document Server

    Even-dar, Eyal; Mirrokni, Vahab; Muthukrishnan, S; Nadav, Uri

    2009-01-01

    Ad auctions in sponsored search support ``broad match'' that allows an advertiser to target a large number of queries while bidding only on a limited number. While giving more expressiveness to advertisers, this feature makes it challenging to optimize bids to maximize their returns: choosing to bid on a query as a broad match because it provides high profit results in one bidding for related queries which may yield low or even negative profits. We abstract and study the complexity of the {\\em bid optimization problem} which is to determine an advertiser's bids on a subset of keywords (possibly using broad match) so that her profit is maximized. In the query language model when the advertiser is allowed to bid on all queries as broad match, we present an linear programming (LP)-based polynomial-time algorithm that gets the optimal profit. In the model in which an advertiser can only bid on keywords, ie., a subset of keywords as an exact or broad match, we show that this problem is not approximable within any ...

  17. Near-infrared Raman spectroscopy using a diode laser and CCD detector for tissue diagnostics

    International Nuclear Information System (INIS)

    This paper surveys the possibility to observe high-quality NIR Raman spectra of both fluorescent and non-fluorescent samples with the use of a diode laser, a fibre optic sample, a single spectrometer and a charge-coupled device (CCD) detector. A shifted excitation difference technique was implemented for removing the broad-band fluorescence emission from Raman spectra of the highly fluorescent samples. Raman spectra of 1.4-dioxane, toluene, rhodamine 6G, and HITCI in the 640 to 1840 cm-1 spectral region and 1.4-dioxane and toluene in the 400 to 3400 cm-1 spectral region have been recorded. The results open the field of sensitive tissue characterisation and the possibility of optical biopsy in vivo by using NIR Raman spectroscopy with fibre optic sampling, a single spectrometer, and a CCD detector

  18. Heat generation and thermo-mechanical effect modeling in longitudinally diode-pumped solid state lasers

    Science.gov (United States)

    Lakhdari, Fouad; Osmani, Ismahen; Tabet, Saida

    2015-09-01

    Thermal management in solid state laser is a challenge to the high power laser industry's ability to provide continued improvements in device and system performance. In this work an investigation of heat generation and thermo-mechanical effect in a high-power Nd:YAG and Yb:YAG cylindrical-type solid state laser pumped longitudinally with different power by fibre coupled laser diode is carried out by numerical simulation based on the finite element method (FEM). Impact of the dopant concentration on the power conversion efficiency is included in the simulation. The distribution of the temperature inside the lasing material is resolute according to the thermal conductivity. The thermo-mechanical effect is explored as a function of pump power in order to determine the maximum pumping power allowed to prevent the crystal's fracture. The presented simulations are in broad agreement with analytical solutions; provided that the boundary condition of the pump induced heat generation is accurately modelled.

  19. Broadband Light Source Based on Four-Color Self-Assembled InAs Quantum Dot Ensembles Monolithically Grown in Selective Areas

    Science.gov (United States)

    Ozaki, Nobuhiko; Takeuchi, Koichi; Ohkouchi, Shunsuke; Ikeda, Naoki; Sugimoto, Yoshimasa; Asakawa, Kiyoshi; Hogg, Richard A.

    We developed advanced techniques for the growth of self-assembled quantum dots (QDs) for fabricating a broadband light source that can be applied to optical coherence tomography (OCT). Four QD ensembles and strain reducing layers (SRLs) were grown in selective areas on a wafer by the use of a 90° rotational metal mask. The SRL thickness was varied to achieve appropriate shifts in the peak wavelength of the QD emission spectrum of up to 120nm. The four-color QD ensembles were expected to have a broad bandwidth of more than 160nm due to the combination of excited state emissions when introduced in a current-induced broadband light source such as a superluminescent diode (SLD). Furthermore, a desired shape of the SLD spectrum can be obtained by controlling the injection current applied to each QD ensemble. The broadband and spectrum shape controlled light source is promising for high-resolution and low-noise OCT systems.

  20. Study on the luminescence properties of n-ZnO/p-Si hetero-junction diode grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiangping [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Zhang Baolin [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Zhu Huichao [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Dong Xin [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Department of Physics, Dalian University of Technology, Dalian 116023 (China); Xia Xiaochuan [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Cui Yongguo [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Department of Physics, Dalian University of Technology, Dalian 116023 (China); Ma Yan [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Du Guotong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China)

    2008-02-07

    n-ZnO/p-Si hetero-junction light emitting diodes were fabricated using a metal organic chemical vapour deposition (MOCVD) technique. Room temperature (RT) photoluminescence (PL) spectrum showed an intense main peak at 377 nm and a weak deep-level emission. The I-V characteristics of the n-ZnO/p-Si hetero-junction showed rectifying diode behaviour at different temperatures. At a low bias voltage, typical values of the ideality factors were determined to be 2.84 at 77 K and 1.94 at 300 K, indicating that the junction had good diode characteristics. RT electroluminescence (EL) was detected under forward bias, which covered a broad visible range (400-600 nm) corresponding to defect-related emission. The remarkable difference between the PL and EL spectra was ascribed to their different excitation and recombination processes. Infrared EL emission at Si band gap energy based on the n-ZnO/p-Si hetero-junction structure was also detected.

  1. Study on the luminescence properties of n-ZnO/p-Si hetero-junction diode grown by MOCVD

    International Nuclear Information System (INIS)

    n-ZnO/p-Si hetero-junction light emitting diodes were fabricated using a metal organic chemical vapour deposition (MOCVD) technique. Room temperature (RT) photoluminescence (PL) spectrum showed an intense main peak at 377 nm and a weak deep-level emission. The I-V characteristics of the n-ZnO/p-Si hetero-junction showed rectifying diode behaviour at different temperatures. At a low bias voltage, typical values of the ideality factors were determined to be 2.84 at 77 K and 1.94 at 300 K, indicating that the junction had good diode characteristics. RT electroluminescence (EL) was detected under forward bias, which covered a broad visible range (400-600 nm) corresponding to defect-related emission. The remarkable difference between the PL and EL spectra was ascribed to their different excitation and recombination processes. Infrared EL emission at Si band gap energy based on the n-ZnO/p-Si hetero-junction structure was also detected

  2. Inverse I-V Injection Characteristics of ZnO Nanoparticle-Based Diodes.

    Science.gov (United States)

    Mundt, Paul; Vogel, Stefan; Bonrad, Klaus; von Seggern, Heinz

    2016-08-10

    Simple Al/ZnO(NP)/Au diodes produced by spin coating of ZnO nanoparticle dispersions (ZnO(NP)) on Al/Al2O3 and Au substrates and subsequent Au deposition have been investigated to understand electron injection properties of more complex devices, incorporating ZnO(NP) as injection layer. Inverse I-V characteristics have been observed compared to conventional Al/ZnO(SP)/Au diodes produced by reactive ion sputtering of ZnO. SEM micrographs reveal that the void-containing contact of ZnO(NP) with the bottom Al electrode and the rough morphology of the top Au electrode are likely to be responsible for the observed injection and ejection probabilities of electrons. A simple tunneling model, incorporating the voids, explains the strongly reduced injection currents from Al whereas the top electrode fabricated by vapor deposition of Au onto the nanoparticle topology adopts the inverse ZnO(NP) morphology leading to enlarged injection areas combined with Au-tip landscapes. These tips in contrast to the smooth sputtered ZnO(SP) lead to electric field enhancement and strongly increased injection of electrons in reverse direction. The injected charge piles up at the barrier generated by voids between ZnO(NP) and the bottom electrode forcing a change in the barrier shape and therefore allowing for higher ejection rates. Both effects in combination explain the inverse I-V characteristic of nanoparticle based diodes. PMID:27443793

  3. Influence of Preparation Conditions on Electrical Properties of the Al/Alq3/Si Diode Structures

    Directory of Open Access Journals (Sweden)

    Irina ČERNIUKĖ

    2013-12-01

    Full Text Available Hybrid organic-inorganic diode structures, Al/Alq3/n-Si and Al/Alq3/p-Si based on thin films of tris(8-hydroxyquinoline aluminum (Alq3 have been investigated. The Alq3 films were evaporated in vacuum and spin coated onto patterned areas of crystalline n- and p-type Si substrates with chemically removed native SiO2 layer. Current-voltage characteristics of the diode structures demonstrated improved rectification property compared to similar Al/n-Si and Al/p-Si device structures. Increased barrier height values (0.90 eV ÷ 1.1 eV and 0.77 eV ÷ 0.91 eV for the Al/Alq3/n-Si and Al/Alq3/p-Si device structures, respectively certified presence of an interface dipole induced by the organic interlayer. Non-ideal behavior of forward current-voltage characteristics has been explained assuming non-uniformity of barrier height, presence of interface states, and influence of the organic film on diode series resistance and space charge limited current. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2733

  4. Solar-energy conversion and light emission in an atomic monolayer p-n diode

    Science.gov (United States)

    Pospischil, Andreas; Furchi, Marco M.; Mueller, Thomas

    2014-04-01

    The limitations of the bulk semiconductors currently used in electronic devices--rigidity, heavy weight and high costs--have recently shifted the research efforts to two-dimensional atomic crystals such as graphene and atomically thin transition-metal dichalcogenides. These materials have the potential to be produced at low cost and in large areas, while maintaining high material quality. These properties, as well as their flexibility, make two-dimensional atomic crystals attractive for applications such as solar cells or display panels. The basic building blocks of optoelectronic devices are p-n junction diodes, but they have not yet been demonstrated in a two-dimensional material. Here, we report a p-n junction diode based on an electrostatically doped tungsten diselenide (WSe2) monolayer. We present applications as a photovoltaic solar cell, a photodiode and a light-emitting diode, and obtain light-power conversion and electroluminescence efficiencies of ~0.5% and ~0.1%, respectively. Given recent advances in the large-scale production of two-dimensional crystals, we expect them to profoundly impact future developments in solar, lighting and display technologies.

  5. Improving Metal-Oxide-Metal (MOM) Diode Performance Via the Optimization of the Oxide Layer

    Science.gov (United States)

    Dodd, Linzi E.; Shenton, Samantha A.; Gallant, Andrew J.; Wood, David

    2015-05-01

    Small area metal-oxide-metal (MOM) diodes are being investigated in many research groups for the detection of THz frequency radiation. In order to create a high-speed rectifying device, the central oxide layer of the MOM structure must be thin and have known physical characteristics. The thickness, structure and uniformity of the oxide can be controlled during the fabrication process. In the work presented here, the effects of both oxygen plasma concentration and annealing temperature during fabrication of MOM diodes have been explored. It has been found that, by reducing the oxygen gas concentration from previous work, the layer can be more repeatable and uniform. Furthermore, for an anneal temperature up to a threshold temperature in the to range, the performance of the diodes is excellent, with a value of zero-bias curvature coefficient (CCZB) that can be up to . For higher temperature treatments, the value of CCZB decreases to a maximum of . Similar trends in AC tests can be seen for voltage and current responsivity values.

  6. Pulse Shape Characterization of Silicon Diodes for HGCal with data from Beam Test at CERN

    CERN Document Server

    De Silva, Malinda

    2016-01-01

    The High Luminosity phase of the LHC (starting operation in 2025) will provide unprecedented instantaneous and integrated luminosity, with 25 ns bunch crossing intervals and up to 140 pileup events. A challenge is to provide excellent physics performance in such a harsh environment to fully exploit the HL-LHC potentialities and explore new physics frontiers. In this context, the High Granularity Calorimeter is the detector designed to provide electromagnetic and hadronic energy coverage and reconstruction in the forward direction of the upgraded CMS. In April 2016 and June 2016, a set of 36 diodes were tested in order to understand various characteristics of its performance, in order to use them in the upgraded HG Calorimeter. Here, the silicon diodes were mounted onto a test bench at CERN’s beam test area and exposed to electron showers. Data received from these diodes were acquired and analysed separately. The objective of this report is to show the variation of Time Rise, Time Over Threshold with various...

  7. IR detection and energy harvesting using antenna coupled MIM tunnel diodes

    Science.gov (United States)

    Yesilkoy, Filiz

    The infrared (IR) spectrum lies between the microwave and optical frequency ranges, which are well suited for communication and energy harvesting purposes, respectively. The long wavelength IR (LWIR) spectrum, corresponding to wavelengths from 8microm to 15microm, includes the thermal radiation emitted by objects at room temperature and the Earth's terrestrial radiation. Therefore, LWIR detectors are very appealing for thermal imaging purposes. Thermal detectors developed so far either demand cryogenic operation for fast detection, or they rely on the accumulation of thermal energy in their mass and subsequent measurable changes in material properties. Therefore, they are relatively slow. Quantum detectors allow for tunable and instantaneous detection but are expensive and require complex processes for fabrication. Bolometer detectors are simple and cheap but do not allow for tunability or for rapid detection. Harvesting the LWIR radiation energy sourced by the Earth's heating/cooling cycle is very important for the development of mobile energy resources. While speed is not as significant an issue here, conversion efficiency is an eminent problem for cheap, large area energy transduction. This dissertation addresses the development of tunable, fast, and low cost wave detectors that can operate at room temperature and, when produced in large array format, can harvest Earth's terrestrial radiation energy. This dissertation demonstrates the design, fabrication and testing of Antenna Coupled Metal-Insulator-Metal (ACMIM) tunnel diodes optimized for 10microm wavelength radiation detection. ACMIM tunnel diodes operate as electromagnetic wave detectors: the incident radiation is coupled by an antenna and converted into a 30 terahertz signal that is rectified by a fast tunneling MIM diode. For efficient IR radiation coupling, the antenna geometry and its critical dimensions are studied using a commercial finite-element based multi-physics simulation tool, and the half

  8. A practical guide to handling laser diode beams

    CERN Document Server

    Sun, Haiyin

    2015-01-01

    This book offers the reader a practical guide to the control and characterization of laser diode beams.  Laser diodes are the most widely used lasers, accounting for 50% of the global laser market.  Correct handling of laser diode beams is the key to the successful use of laser diodes, and this requires an in-depth understanding of their unique properties. Following a short introduction to the working principles of laser diodes, the book describes the basics of laser diode beams and beam propagation, including Zemax modeling of a Gaussian beam propagating through a lens.  The core of the book is concerned with laser diode beam manipulations: collimating and focusing, circularization and astigmatism correction, coupling into a single mode optical fiber, diffractive optics and beam shaping, and manipulation of multi transverse mode beams.  The final chapter of the book covers beam characterization methods, describing the measurement of spatial and spectral properties, including wavelength and linewidth meas...

  9. Additional electric field in real trench MOS barrier Schottky diode

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2016-04-01

    In real trench MOS barrier Schottky diode (TMBS diode) additional electric field (AEF) the whole is formed in the near contact region of the semiconductor and its propagation space is limited with the barrier metal and the metallic electrodes of MOS structures. Effective potential barrier height TMBS diode is formed via resulting electric field of superposition AEF and electric field of space charge region (SCR) semiconductor. The dependence of the resulting electric field intensity of the distance towards the inside the semiconductor is nonlinear and characterized by a peak at a certain distance from the interface. The thickness of the SCR in TMBS diode becomes equal to the trench depth. Force and energy parameters of the AEF, and thus resulting electric field in the SCR region, become dependent on the geometric design parameters TMBS diode. The forward I-V characteristic TMBS diode is described by the thermionic emission theory as in conventional flat Scottky diode, and in the reverse bias, current is virtually absent at initial voltage, appears abruptly at a certain critical voltage.

  10. Changes in Cell Viability of Wounded Fibroblasts following Laser Irradiation in Broad-Spectrum or Infrared Light

    International Nuclear Information System (INIS)

    Objective. This study aimed to establish if broad-spectrum or infrared (IR) light in combination with laser therapy can assist phototherapy to improve the cell function of wounded cells. Background. The effect of laser light may be partly or completely reduced by broad-spectrum light. Methods. Wounded human skin fibroblasts were irradiated with 5 J/cm2 using a helium-neon laser, a diode laser, or an Nd:YAG laser in the dark, in the light, or in IR. Changes in cell viability were evaluated by cell morphology, ATP cell viability, LDH membrane integrity, and caspase 3/7 as an early marker of apoptosis. Results. Wounded cells exposed to 5 J/cm2 using 632.8 nm in the dark or 830 nm in the light or 1064 nm in the dark showed an increase in ATP viability, an increase in cytokine expression, and a decrease in LDH cytotoxicity indicating that the metabolic activity of the wounded cells was stimulated. Conclusion. Wounded cells irradiated in IR light showed an undesirable thermal effect that was proportional to the duration of exposure.

  11. In vitro study of the diode laser effect on artificial demineralized surface of human dental enamel

    International Nuclear Information System (INIS)

    In scientific literature there are many reports about fusion and resolidification of dental enamel after laser irradiation and their capability to generate surfaces with increased resistance to demineralization compared to non-irradiated areas. The use of high power diode laser on demineralized surfaces of human dental enamel is presented as a good alternative in caries prevention. The purpose of this study is to investigate the morphological changes produced by the use of one high power diode laser on human dental enamel surface after demineralization treatment with lactic acid, under chosen parameters. Fifteen samples of human dental molars were used and divided in four groups: control - demineralization treatment with lactic acid and no irradiation, and demineralization treatment with lactic acid followed of irradiation with 212,20 mJ/cm2, 282,84 mJ/cm2 and 325,38 mJ/cm2, respectively. The samples were irradiated with high power diode laser (808 nm) with a 300 μm diameter fiber optics. Black ink was used on enamel surface to enhance the superficial absorption. The samples were studied by optical microscopy and scanning electron microscopy. Modifications on the enamel surfaces were observed. Such modifications were characterized by melted and re-solidified region of the enamel. According with our results the best parameter was 2.0 W, presenting the most uniform surface. The use of high power diode laser as demonstrated in this study is able to promote melting and re-solidification on human dental enamel. (author)

  12. The sub-millimeter properties of broad absorption line quasars

    OpenAIRE

    Willott, Chris J.; Rawlings, Steve; Grimes, Jennifer A.

    2003-01-01

    We have carried out the first systematic survey of the sub-millimeter properties of broad absorption line (BAL) quasars. 30 BAL quasars drawn from a homogeneously selected sample from the Sloan Digital Sky Survey at redshifts 2 3 sigma significance. The far-infrared luminosities of these quasars are > 10^{13} L_solar. There is no correlation of sub-millimeter flux with either the strength of the broad absorption feature or with absolute magnitude in our sample. We compare the sub-millimeter f...

  13. Analysis of fuel system technology for broad property fuels

    Science.gov (United States)

    Coffinberry, G. A.

    1984-01-01

    An analytical study was performed in order to assess relative performance and economic factors involved with alternative advanced fuel systems for future commercial aircraft operating with broad property fuels. Significant results, with emphasis on design practicality from the engine manufacturer' standpoint, are highlighted. Several advanced fuel systems were modeled to determine as accurately as possible the relative merits of each system from the standpoint of compatibility with broad property fuel. Freezing point, thermal stability, and lubricity were key property issues. A computer model was formulated to determine the investment incentive for each system. Results are given.

  14. Broad-band hard X-ray reflectors

    DEFF Research Database (Denmark)

    Joensen, K.D.; Gorenstein, P.; Hoghoj, P.;

    1997-01-01

    Interest in optics for hard X-ray broad-band application is growing. In this paper, we compare the hard X-ray (20-100 keV) reflectivity obtained with an energy-dispersive reflectometer, of a standard commercial gold thin-film with that of a 600 bilayer W/Si X-ray supermirror. The reflectivity of...... that of the gold, Various other design options are discussed, and we conclude that continued interest in the X-ray supermirror for broad-band hard X-ray applications is warranted....

  15. Development of broad-view camera unit for laparoscopic surgery.

    Science.gov (United States)

    Kawahara, Tomohiro; Takaki, Takeshi; Ishii, Idaku; Okajima, Masazumi

    2009-01-01

    A disadvantage of laparoscopic surgery is the narrow operative field provided by the endoscope camera. This paper describes a newly developed broad-view camera unit for use with the Broad-View Camera System, which is capable of providing a wider view of the internal organs during laparoscopic surgery. The developed camera unit is composed of a miniature color CMOS camera, an indwelling needle, and an extra-thin connector. The specific design of the camera unit and the method for positioning it are shown. The performance of the camera unit has been confirmed through basic and animal experiments. PMID:19963983

  16. Performance of EPI diodes as dosimeters for photon beam radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Thais C. dos; Bizetto, Cesar A., E-mail: ccbueno@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Neves-Junior, Wellington F.P.; Haddad, Cecilia M.K. [Hospital Sirio Libanes (HSL), Sao Paulo, SP (Brazil); Goncalves, Josemary A.C.; Bueno, Carmen C. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Pontificia Universidade Catolica de Sao Paulo (PUC-SP), SP (Brazil)

    2011-07-01

    In this work we present the preliminary results about the performance of an epitaxial (EPI) diode as on-line dosimeter for photon beam radiotherapy. The diode used was processed at University of Hamburg on n-type 75 {mu}m thick epitaxial silicon layer grown on a highly doped n-type 300 {mu}m thick Czochralski (Cz) silicon substrate. The measurements were performed with a diode which not received any type of pre-dose. In order to use this device as a dosimeter, it was enclosed in a black polymethylmethacrylate (PMMA) probe. The diode was connected to an electrometer Keithley 6517B in the photovoltaic mode. During all measurements, the diode was held between PMMA plates, placed at 10.0 cm depth and centered in a radiation field of 10 x 10 cm{sup 2}, with the source-to-surface distance (SSD) kept at 100 cm. The short-term repeatability was measured with photon beams of 6 and 18 MV energy by registering five consecutive current signals for the same radiation dose. The current signals induced showed good instantaneous repeatability of the diode, characterized by a smallest coefficient of variation (CV) of 0.21%. Furthermore, the dose-response curves of the diode were quite linear with the highest charge sensitivity achieved of 5.0 {mu}C/Gy. It worth noting that still remains to be investigated the pre-dose influence on epitaxial silicon diode response in radiotherapy photon beam dosimetry, the long term stability and the radiation hardness of these diodes for absorbed doses higher than that investigated in this work. All these studies are under way. (author)

  17. Role of diode lasers in metrology

    Science.gov (United States)

    Muthukrishnan, Kris

    1995-01-01

    The field of noncontact metrology is maturing as the video camera based and the laser probe based measurements are finding wide acceptance in the fields of semiconductor, micro electronics, disk drive, biomedical, chemical and aerospace industries. Some manufactures of conventional touch-probe based CMMs (Coordinated Measuring Machines) have started integrating video cameras and laser probes to compliment the measurements made by the touch-probe. The delicate nature of the parts and the extremely small feature sizes have fuelled the growing need for the multisensor technology to be incorporated into a single coordinate measuring machine. The laser probes compliment the video based metrology systems in providing the dynamic Z-height capabilities due to their faster data rate and increased resolution and accuracy. This paper highlights the pros and cons of different diode laser based sensors, drawn from the experience of applying them for measurements in different fields.

  18. Ion source diodes with magnetic mirror

    International Nuclear Information System (INIS)

    This device includes a grid anode, a first cathode set in front cf the anode, and a magnetic mirror behind the anode. It is a winding coaxial to the anode and the cathode. Anode and cathode have spherical cap shapes whose concavity is directed towards a target. Then the ion beam has some focusing. Electrons, emitted by cathode, are accelerated towards the anode and cross through it. These electrons are submitted to the winding magnetic field. Their trajectories curved around the field lines and lie on the diode axis. Then electrons go backwards through again the anode. Electrons oscillate thus a great number a time. At each passage, they give energy to the anode, that creates plasma round it. Ions are extracted from that plasma and accelerated by interelectrode field. As there is no electric field in the back of the anode, there is an ion beam emitted only foreward

  19. A high precision silicon diode dosimetry system

    International Nuclear Information System (INIS)

    An integrating dosimetry system using a silicon diode detector for use in routine spot checks of radiation therapy treatment machines is described. The system is a micropower, battery operated, dosemeter with a digital dose readout. It can contain the results of two irradiations in memory for the life of the batteries (approx. 4 months), and hence can be used to check the output of a treatment unit at a remote facility by main in lieu of TLD, with the advantage over TLD of higher precision and an immediate digital readout so that it is much less labour intensive. The dosemeter is designed to be completely automatic (radiation reset) for ease of use by the radiographer/technician. Stability over a three year period on a 60Co treatment machine was + -35% standard deviation with all readings being within 1.2% of the initial reading. (author)

  20. Low-cost laser diode array

    Science.gov (United States)

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

    1999-06-01

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

  1. Kinetics of current formation in molecular diode

    International Nuclear Information System (INIS)

    Based on the kinetic theory of election transfer in low-dimensional molecular systems, the formation of transient and stationary currents in a system 'electrode l-molecule-electrode 2' (molecular diode) is studied for different regimes of charge transmission. In the framework of the HOMO-LUMO molecular model, a situation is considered where the current formation is initiated either by molecule photoexcitation or by change of interelectrode voltage bias. It is found that the distant (tunnel) inelastic electron transfer plays a crucial role in changing molecular electronic states and, as a result, in generating transmission channels for hopping (sequential) and distant (direct) current components. The effect of inelastic tunneling is especially pronounced in the condition of resonant electron transmission.

  2. Terahertz imaging system with resonant tunneling diodes

    Science.gov (United States)

    Miyamoto, Tomoyuki; Yamaguchi, Atsushi; Mukai, Toshikazu

    2016-03-01

    We report a feasibility study of a terahertz imaging system with resonant tunneling diodes (RTDs) that oscillate at 0.30 THz. A pair of RTDs acted as an emitter and a detector in the system. Terahertz reflection images of opaque samples were acquired with our RTD imaging system. A spatial resolution of 1 mm, which is equal to the wavelength of the RTD emitter, was achieved. The signal-to-noise ratio (SNR) of the reflection image was improved by 6 dB by using polarization optics that reduced interference effects. Additionally, the coherence of the RTD enabled a depth resolution of less than 3 µm to be achieved by an interferometric technique. Thus, RTDs are an attractive candidate for use in small THz imaging systems.

  3. Resonant tunneling diode photodetector with nonconstant responsivity

    Science.gov (United States)

    Dong, Yu; Wang, Guanglong; Ni, Haiqiao; Chen, Jianhui; Gao, Fengqi; Li, Baochen; Pei, Kangming; Niu, Zhichuan

    2015-11-01

    Resonant tunneling diode with an In0.53Ga0.47As absorption layer is designed for light detection at 1550 nm. The responsivity of the detector is simulated by solving the Tsu-Esaki equation. The simulation results show that the responsivity of the detector is nonconstant. It decreases with the increment of the power density of the incident light. Samples of the detector are fabricated by molecular beam epitaxy. The experimental results show that the responsivity increases while the power density of the incident light decreases which agree with the simulation results. The responsivity reaches 4.8×108 A/(W/μm2) at room temperature and 5.0×109 A/(W/μm2) at 77 K when the power density of the incident light is 1×10-13 W/μm2.

  4. Light-Emitting Diodes: A Hidden Treasure

    Science.gov (United States)

    Planinšič, Gorazd; Etkina, Eugenia

    2014-02-01

    LEDs, or light-emitting diodes, are cheap, easy to purchase, and thus commonly used in physics instruction as indicators of electric current or as sources of light (Fig. 1). In our opinion LEDs represent a unique piece of equipment that can be used to collect experimental evidence, and construct and test new ideas in almost every unit of a general physics course (and in many advanced courses) either (I) as "black boxes" that allow students to study certain properties of a system of interest, (II) as physical systems that allow students to learn an astonishing amount of physics that they usually do not encounter in a regular introductory physics course, and (III) as non-traditional devices that allow students to construct concepts that are traditionally a part of a general physics course.

  5. A single blue nanorod light emitting diode

    Science.gov (United States)

    Hou, Y.; Bai, J.; Smith, R.; Wang, T.

    2016-05-01

    We report a light emitting diode (LED) consisting of a single InGaN/GaN nanorod fabricated by a cost-effective top-down approach from a standard LED wafer. The device demonstrates high performance with a reduced quantum confined Stark effect compared with a standard planar counterpart fabricated from the same wafer, confirmed by optical and electrical characterization. Current density as high as 5414 A cm‑2 is achieved without significant damage to the device due to the high internal quantum efficiency. The efficiency droop is mainly ascribed to Auger recombination, which was studied by an ABC model. Our work provides a potential method for fabricating compact light sources for advanced photonic integrated circuits without involving expensive or time-consuming fabrication facilities.

  6. Geoconservation and protected areas

    OpenAIRE

    Brilha, J. B.

    2002-01-01

    Conservation will fail if nature conservation policies impose artificial boundaries on the natural world. The protected area manager’s main task is biodiversity preservation. Nevertheless, nature conservation requires a broad perspective. Incorporating geology into conservation policies at the same level as biology is urgent. The slow rate of many geological processes leads to the misconception that geological resources are inexhaustible and immutable. Geologists know that this is not true an...

  7. Diode-Assisted Buck-Boost Voltage-Source Inverters

    DEFF Research Database (Denmark)

    Gao, Feng; Loh, Poh Chiang; Teodorescu, Remus;

    2009-01-01

    This paper proposes a number of diode-assisted buck-boost voltage-source inverters with a unique X-shaped diode-capacitor network inserted between the inverter circuitry and dc source for producing a voltage gain that is comparatively higher than those of other buck-boost conversion techniques....... Using the diode-assisted network, the proposed inverters can naturally configure themselves to perform capacitive charging in parallel and discharging in series to give a higher voltage multiplication factor without compromising waveform quality. In addition, by adopting different front-end circuitries...

  8. A transient model of a cesium-barium diode

    International Nuclear Information System (INIS)

    In this work a transient model of a Cs-Ba diode is developed, and a series of experiments is performed using a diode equipped with Langmuir probes. The Langmuir probe data show that the electron energy distribution is non-Maxwellian at low discharge currents, indicating the presence of an electron beam from the emitter. Experimental results also showed that the plasma properties are non-homogeneous across the 1 mm diode gap; the electron temperature and plasma potential were higher near the emitter and the plasma density was higher near the collector. Experimental evidence is presented to show that the discharge contracts to a filament below the maximum thermal emission current

  9. Tapered diode laser pumped 946 nm Nd:YAG laser

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay; Jensen, Ole Bjarlin; Petersen, Paul Michael;

    2009-01-01

    We successfully implemented a 946 nm Nd:YAG laser based on a 808 nm tapered diode pump laser. The tapered diode is developed at the Ferdinand-Braun-Institute fur Hochstfrequenztechnik in Germany. Figure 2 shows the experimental setup and results of each pump source coupled into a 1.5 mm crystal...... laser, we show that tapered diode laser pumping potentially increase the power of 946 nm lasers by a factor of two and reduce the threshold by a factor of three....

  10. Diode laser sensor for process control and environmental monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Zaatar, Y.; Bechara, J.; Khoury, A.; Zaouk, D. [Lebanese Univ., Physics Dept., Fanar (Lebanon); Charles, J.-P. [Metz Univ., L.I.C.M., Metz, 57 (France)

    2000-04-01

    Absorption spectroscopy with tunable diode lasers (TDLAS) in the infrared region is a well-known technique for the chemical analysis of gas mixtures. The laser provides a high selectivity, which is important in industrial environments such as in-line stack monitoring, where complex gas mixtures are present. A wavelength tunable diode laser in the near infrared region has been utilised as a light source in absorption measurements of air pollution resulting from energy usage for industry. The emission frequency can be varied over a relatively wide spectral range by changing the current and temperature of the diode. (Author)

  11. The tunnel diode as a threshold device: theory and application

    International Nuclear Information System (INIS)

    Due to the interesting properties of the tunnel diode, the device is extensively studied concerning its circuit behaviour. An empirical formula, approximating the diode's V-I characteristics, has been obtained. This allows calculations of rise time, delay time, jitter, etc., to be carried out in certain instances; theoretical predictions based on this approximation are in good agreement with experimental results. Stability considerations and curve-plotting circuits are also studied. A high-speed discriminatorcoincidence circuit using transistors and tunnel diodes is presented. (author)

  12. Construction of Tunnel Diode Oscillator for AC Impedance Measurement

    Science.gov (United States)

    Shin, J. H.; Kim, E.

    2014-03-01

    We construct a tunnel diode oscillator (TDO) to study electromagnetic response of a superconducting thin film. Highly sensitive tunnel diode oscillators allow us to detect extremely small changes in electromagnetic properties such as dielectric constant, ac magnetic susceptibility and magnetoresistance. A tunnel diode oscillator is a self-resonant oscillator of which resonance frequency is primarily determined by capacitance and inductance of a resonator. Amplitude of the signal depends on the quality factor of the resonator. The change in the impedance of the sample electromagnetic coupled to one of inductors in the resonator alters impedance of the inductor, and leads to the shift in the resonance frequency and the change of the amplitude.

  13. A XOR Threshold Logic Implementation Through Resonant Tunneling Diode

    Directory of Open Access Journals (Sweden)

    Nitesh Kumar Dixit

    2012-10-01

    Full Text Available Resonant tunneling diodes (RTDs have functional versatility and high speed switching capability. The integration of resonant tunneling diodes and MOS transistor makes threshold gates and logics. The design and fabrication of linear threshold gates will be presented based on a mono stable bis table transition logic element. Each of its input terminals consist out of a resonant tunnelling diode merged with a transistor device. The circuit models of RTD and MOSFET are simulated in HSPICE. Two input XOR gate is designed and tested.

  14. A XOR Threshold Logic Implementation Through Resonant Tunneling Diode

    Directory of Open Access Journals (Sweden)

    Nitesh Kumar Dixit

    2012-11-01

    Full Text Available Resonant tunneling diodes (RTDs have functional versatility and high speed switching capability. The integration of resonant tunneling diodes and MOS transistor makes threshold gates and logics. The design and fabrication of linear threshold gates will be presented based on a monostable bistable transition logic element. Each of its input terminals consist out of a resonant tunnelling diode merged with a transistor device. The circuit models of RTD and MOSFET are simulated in HSPICE. Two input XOR gate is designed and tested.

  15. Forward gated-diode method for parameter extraction of MOSFETs*

    Institute of Scientific and Technical Information of China (English)

    Zhang Chenfei; Ma Chenyue; Guo Xinjie; Zhang Xiufang; He Jin; Wang Guozeng; Yang Zhang; Liu Zhiwei

    2011-01-01

    The forward gated-diode method is used to extract the dielectric oxide thickness and body doping concentration of MOSFETs, especially when both of the variables are unknown previously. First, the dielectric oxide thickness and the body doping concentration as a function of forward gated-diode peak recombination-generation (R-G) current are derived from the device physics. Then the peak R-G current characteristics of the MOSFETs with different dielectric oxide thicknesses and body doping concentrations are simulated with ISE-Dessis for parameter extraction. The results from the simulation data demonstrate excellent agreement with those extracted from the forward gated-diode method.

  16. Activation of C-fiber nociceptors by low-power diode laser.

    Science.gov (United States)

    Azevedo, Eduardo; Silva, Andressa; Martins, Raquel; Andersen, Monica L; Tufik, Sergio; Manzano, Gilberto M

    2016-03-01

    Objective The evaluation of selective activation of C-fibers to record evoked potentials using the association of low-power diode laser (810 nm), tiny-area stimulation and skin-blackening. Method Laser-evoked potentials (LEPs) were obtained from 20 healthy young subjects. An aluminum plate with one thin hole was attached to the laser probe to provide tiny-area stimulation of the hand dorsum and the stimulated area was covered with black ink. Results The mean intensity used for eliciting the ultra-late laser-evoked potential (ULEP) was 70 ± 32 mW. All subjects showed a clear biphasic potential that comprised a negative peak (806 ± 61 ms) and a positive deflection (1033 ± 60 ms), corresponding to the ULEP related to C-fiber activation. Conclusion C-fiber-evoked responses can be obtained using a very low-power diode laser when stimulation is applied to tiny areas of darkened skin. This strategy offers a non-invasive and easy methodology that minimizes damage to the tissue. PMID:27050852

  17. Activation of C-fiber nociceptors by low-power diode laser

    Directory of Open Access Journals (Sweden)

    Eduardo Azevedo

    2016-03-01

    Full Text Available ABSTRACT Objective The evaluation of selective activation of C-fibers to record evoked potentials using the association of low-power diode laser (810 nm, tiny-area stimulation and skin-blackening. Method Laser-evoked potentials (LEPs were obtained from 20 healthy young subjects. An aluminum plate with one thin hole was attached to the laser probe to provide tiny-area stimulation of the hand dorsum and the stimulated area was covered with black ink. Results The mean intensity used for eliciting the ultra-late laser-evoked potential (ULEP was 70 ± 32 mW. All subjects showed a clear biphasic potential that comprised a negative peak (806 ± 61 ms and a positive deflection (1033 ± 60 ms, corresponding to the ULEP related to C-fiber activation. Conclusion C-fiber-evoked responses can be obtained using a very low-power diode laser when stimulation is applied to tiny areas of darkened skin. This strategy offers a non-invasive and easy methodology that minimizes damage to the tissue.

  18. Investigation of temperature feedback signal parameters during neoplasms treatment by diode laser radiation

    Science.gov (United States)

    Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Semyashkina, Yulia V.

    2016-04-01

    Dynamics of temperature signal in operation area and laser power at nevus, papilloma, and keratoma in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and with temperature feedback (APC) mode are presented. Feedback allows maintaining temperature in the area of laser treatment at a preset level by regulating power of diode laser radiation (automatic power control). Temperature in the area of laser treatment was controlled by measuring the amplitude of thermal radiation, which occurs when tissue is heated by laser radiation. Removal of neoplasm was carried out in CW mode with laser radiation average power of 12.5+/-0.5 W; mean temperature in the area of laser treatment was 900+/-10°C for nevus, 800+/-15°C for papilloma, and 850+/-20°C for keratoma. The same laser radiation maximal power (12.5 W) and targeted temperature (900°C) were set for nevus removal in APC mode. The results of investigation are real time oscillograms of the laser power and temperature in the area of laser treatment at neoplasms removal in two described above modes. Simultaneously with the measurement of laser power and the temperature in the area of laser treatment video recording of surgeon manipulations was carried out. We discuss the correlation between the power of the laser radiation, the temperature in the area of laser treatment and consistency of surgeon manipulation. It is shown that the method of removal (excision with or without traction, scanning) influences the temperature in the area of laser treatment. It was found, that at removal of nevus with temperature feedback (APC) mode to achieve comparable with CW mode temperature in the area of laser treatment (900+/-10°C) 20-50% less laser power is required. Consequently, removing these neoplasms in temperature feedback mode can be less traumatic than the removal in CW mode.

  19. Characterization of a radiographic system with broad energy band X-ray source

    International Nuclear Information System (INIS)

    High energy X-ray beams with broad band energy spectra allow performing radiographic analysis on different materials and objects of relevant interest that cannot be investigated with conventional X-ray sources. The quality of a radiographic image strongly depends on the characteristics of radiation source as the size of the X-ray emitting area, or focal spot, and the energy spectrum of the radiation. In this work the characterization of a broad-band energy Bremsstrahlung source obtained from a linac providing a 5.5 MeV electron beam colliding with a tungsten target is presented. In order to measure the focal-spot size an ad hoc slit camera has been designed and built and a specific technique was used. Furthermore an analysis of the energy spectrum of the beam was performed using a method based on X-ray diffraction by a mosaic crystal.

  20. Efficiency roll-off in organic light-emitting diodes.

    Science.gov (United States)

    Murawski, Caroline; Leo, Karl; Gather, Malte C

    2013-12-17

    Organic light-emitting diodes (OLEDs) have attracted much attention in research and industry thanks to their capability to emit light with high efficiency and to deliver high-quality white light that provides good color rendering. OLEDs feature homogeneous large area emission and can be produced on flexible substrates. In terms of efficiency, OLEDs can compete with highly efficient conventional light sources but their efficiency typically decreases at high brightness levels, an effect known as efficiency roll-off. In recent years, much effort has been undertaken to understand the underlying processes and to develop methods that improve the high-brightness performance of OLEDs. In this review, we summarize the current knowledge and provide a detailed description of the relevant principles, both for phosphorescent and fluorescent emitter molecules. In particular, we focus on exciton-quenching mechanisms, such as triplet-triplet annihilation, quenching by polarons, or field-induced quenching, but also discuss mechanisms such as changes in charge carrier balance. We further review methods that may reduce the roll-off and thus enable OLEDs to be used in high-brightness applications. PMID:24019178

  1. Titanium-dioxide nanotube p-n homojunction diode

    Science.gov (United States)

    Alivov, Yahya; Ding, Yuchen; Singh, Vivek; Nagpal, Prashant

    2014-12-01

    Application of semiconductors in functional optoelectronic devices requires precise control over their doping and formation of junction between p- and n-doped semiconductors. While doped thin films have led to several semiconductor devices, need for high-surface area nanostructured devices for photovoltaic, photoelectrochemical, and photocatalytic applications has been hindered by lack of desired doping in nanostructures. Here, we show titanium-dioxide (TiO2) nanotubes doped with nitrogen (N) and niobium (Nb) as acceptors and donors, respectively, and formation of TiO2 nanotubes p-n homojunction. This TiO2:N/TiO2:Nb homojunction showed distinct diode-like behaviour with rectification ratio of 1115 at ±5 V and exhibited good photoresponse for ultraviolet light (λ = 365 nm) with sensitivity of 0.19 A/W at reverse bias of -5 V. These results can have important implications for development of nanostructured metal-oxide solar-cells, photodiodes, LED's, photocatalysts, and photoelectrochemical devices.

  2. Titanium-dioxide nanotube p-n homojunction diode

    International Nuclear Information System (INIS)

    Application of semiconductors in functional optoelectronic devices requires precise control over their doping and formation of junction between p- and n-doped semiconductors. While doped thin films have led to several semiconductor devices, need for high-surface area nanostructured devices for photovoltaic, photoelectrochemical, and photocatalytic applications has been hindered by lack of desired doping in nanostructures. Here, we show titanium-dioxide (TiO2) nanotubes doped with nitrogen (N) and niobium (Nb) as acceptors and donors, respectively, and formation of TiO2 nanotubes p-n homojunction. This TiO2:N/TiO2:Nb homojunction showed distinct diode-like behaviour with rectification ratio of 1115 at ±5 V and exhibited good photoresponse for ultraviolet light (λ = 365 nm) with sensitivity of 0.19 A/W at reverse bias of −5 V. These results can have important implications for development of nanostructured metal-oxide solar-cells, photodiodes, LED's, photocatalysts, and photoelectrochemical devices

  3. Interface-driven magnetocapacitance in a broad range of materials

    International Nuclear Information System (INIS)

    Triggered by the revival of multiferroic materials, a lot of effort is presently underway to find a coupling between a capacitance and a magnetic field. We show in this paper that interfaces are the right way of increasing such a coupling provided free charges are localized on these two-dimensional defects. Starting from commercial diodes at room temperature and going to grain boundaries in giant permittivity materials and to ferroelectric domain walls, a clear magnetocapacitance is reported which is all the time more than a few per cent for a magnetic field of 90 kOe. The only tuning parameter for such strong coupling to arise is the dielectric relaxation time which is reached on tuning the operating frequency and the temperature in many different materials. (fast track communication)

  4. Broad-Band Spectroscopy of Hercules X-1 with Suzaku

    Science.gov (United States)

    Asami, Fumi; Enoto, Teruaki; Iwakiri, Wataru; Yamada, Shin'ya; Tamagawa, Toru; Mihara, Tatehiro; Nagase, Fumiaki

    2014-01-01

    Hercules X-1 was observed with Suzaku in the main-on state from 2005 to 2010. The 0.4- 100 keV wide-band spectra obtained in four observations showed a broad hump around 4-9 keV in addition to narrow Fe lines at 6.4 and 6.7 keV. The hump was seen in all the four observations regardless of the selection of the continuum models. Thus it is considered a stable and intrinsic spectral feature in Her X-1. The broad hump lacked a sharp structure like an absorption edge. Thus it was represented by two different spectral models: an ionized partial covering or an additional broad line at 6.5 keV. The former required a persistently existing ionized absorber, whose origin was unclear. In the latter case, the Gaussian fitting of the 6.5-keV line needs a large width of sigma = 1.0-1.5 keV and a large equivalent width of 400-900 eV. If the broad line originates from Fe fluorescence of accreting matter, its large width may be explained by the Doppler broadening in the accretion flow. However, the large equivalent width may be inconsistent with a simple accretion geometry.

  5. Document understanding for a broad class of documents

    NARCIS (Netherlands)

    Aiello, Marco; Monz, Christof; Todoran, Leon; Worring, Marcel

    2002-01-01

    We present a document analysis system able to assign logical labels and extract the reading order in a broad set of documents. All information sources, from geometric features and spatial relations to the textual features and content are employed in the analysis. To deal effectively with these infor

  6. Silver Nanoparticles with Broad Multiband Linear Optical Absorption

    KAUST Repository

    Bakr, Osman M.

    2009-07-06

    A simple one-pot method produces silver nanoparticles coated with aryl thiols that show intense, broad nonplasmonic optical properties. The synthesis works with many aryl-thiol capping ligands, including water-soluble 4-mercaptobenzoic acid. The nanoparticles produced show linear absorption that is broader, stronger, and more structured than most conventional organic and inorganic dyes.

  7. Children and trauma : a broad perspective on exposure and recovery

    NARCIS (Netherlands)

    Alisic, E.

    2011-01-01

    The purpose of this dissertation was to generate a broad overview of children’s exposure to and recovery from trauma in order to promote theory building and the design of prevention and intervention activities. First, a general population study was conducted in 1770 primary school children. They fil

  8. Dusty origin of the Broad Line Region in active galaxies

    CERN Document Server

    Czerny, Bozena; Kaluzny, Janusz; Maity, Ishita

    2012-01-01

    The most characteristic property of active galaxies, including quasars, are prominent broad emission lines. I will discuss an interesting possibility that dust is responsible for this phenomenon. The dust is known to be present in quasars in the form of a dusty/molecular torus which results in complexity of the appearance of active galaxies. However, this dust is located further from the black hole than the Broad Line Region. We propose that the dust is present also closer in and it is actually responsible for formation of the broad emission lines. The argument is based on determination of the temperature of the disk atmosphere underlying the Broad Line Region: it is close to 1000 K, independently from the black hole mass and accretion rate of the object. The mechanism is simple and universal but leads to a considerable complexity of the active nucleus surrounding. The understanding the formation of BLR opens a way to use it reliably - in combination with reverberation measurement of its size - as standard ca...

  9. Discharge ratio of the broad-crested weir flowin the low head area КОЭФФИЦИЕНТ РАСХОДА ВОДОСЛИВА С ШИРОКИМ ПОРОГОМВ ОБЛАСТИ МАЛЫХ НАПОРОВ

    Directory of Open Access Journals (Sweden)

    Medzveliya Manana Levanovna

    2013-04-01

    Full Text Available The authors consider the influence of the Reynolds number on the discharge ratio of the broad-crested weir. The authors provide an overview of their experiment in thearticle. They provide the equation that takes account of each factor of influence, including H — pressure over the broad-crested weir, P — weir height above the bottom, v — liquid velocity, ρ — liquid density, μ — dynamic viscosity, g — superficial tension, σ — gravity acceleration, q — per-unit weir flow, B — width of the weir, L — length of the weir. Superficial tension and liquid density values have minor differences for different fluids.A broad-crested weir flow was organized in the rectangular tray (6,000×100×200. The flow had the following dimensions: weir length L = 40 mm, weir height P = 50 mm, weir width B = 100 mm. The findings of the experiment have proven that the increase in the Reynolds number causes the increase in the broad-crested weir flow discharge ratio (at the pre-set relative pressure and it approaches the constant value at Re ≈ 2000.Рассмотрен вопрос о влиянии числа Рейнольдса на коэффициент расхода водослива с широким порогом. Показано, что коэффициент расхода водослива увеличивается с ростом числа Рейнольдса (при заданном относительном напоре, приближаясь к постоянному значению при Re ≈ 2000.

  10. Single Spatial-Mode Room-Temperature-Operated 3.0 to 3.4 micrometer Diode Lasers

    Science.gov (United States)

    Frez, Clifford F.; Soibel, Alexander; Belenky, Gregory; Shterengas, Leon; Kipshidze, Gela

    2010-01-01

    Compact, highly efficient, 3.0 to 3.4 m light emitters are in demand for spectroscopic analysis and identification of chemical substances (including methane and formaldehyde), infrared countermeasures technologies, and development of advanced infrared scene projectors. The need for these light emitters can be currently addressed either by bulky solid-state light emitters with limited power conversion efficiency, or cooled Interband Cascade (IC) semiconductor lasers. Researchers here have developed a breakthrough approach to fabrication of diode mid-IR lasers that have several advantages over IC lasers used for the Mars 2009 mission. This breakthrough is due to a novel design utilizing the strain-engineered quantum-well (QW) active region and quinternary barriers, and due to optimization of device material composition and growth conditions (growth temperatures and rates). However, in their present form, these GaSb-based laser diodes cannot be directly used as a part of sensor systems. The device spectrum is too broad to perform spectroscopic analysis of gas species, and operating currents and voltages are too high. In the current work, the emitters were fabricated as narrow-ridge waveguide index-guided lasers rather than broad stripe-gain guided multimode Fabry-Perot (FP) lasers as was done previously. These narrow-ridge waveguide mid-IR lasers exhibit much lower power consumptions, and can operate in a single spatial mode that is necessary for demonstration of single-mode distributed feedback (DBF) devices for spectroscopic applications. These lasers will enable a new generation of compact, tunable diode laser spectrometers with lower power consumption, reduced complexity, and significantly reduced development costs. These lasers can be used for the detection of HCN, C2H2, methane, and ethane.

  11. Wavelength-agile diode-laser sensing strategies for monitoring gas properties in optically harsh flows: application in cesium-seeded pulse detonation.

    Science.gov (United States)

    Sanders, Scott; Mattison, Daniel; Ma, Lin; Jeffries, Jay; Hanson, Ronald

    2002-06-17

    The rapid, broad wavelength scanning capabilities of advanced diode lasers allow extension of traditional diode-laser absorption techniques to high pressure, transient, and generally hostile environments. Here, we demonstrate this extension by applying a vertical cavity surface-emitting laser (VCSEL) to monitor gas temperature and pressure in a pulse detonation engine (PDE). Using aggressive injection current modulation, the VCSEL is scanned through a 10 cm-1 spectral window at megahertz rates - roughly 10 times the scanning range and 1000 times the scanning rate of a conventional diode laser. The VCSEL probes absorption lineshapes of the ~ 852 nm D2 transition of atomic Cs, seeded at ~ 5 ppm into the feedstock gases of a PDE. Using these lineshapes, detonated-gas temperature and pressure histories, spanning 2000 - 4000 K and 0.5 - 30 atm, respectively, are recorded with microsecond time response. The increasing availability of wavelength-agile diode lasers should support the development of similar sensors for other harsh flows, using other absorbers such as native H2O. PMID:19436388

  12. Unmanned Aerial Vehicle Diode Laser Sensor for Methane Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A compact, lightweight, and low power diode laser sensor will be developed for atmospheric methane detection on small unmanned aerial vehicles (UAVs). The physical...

  13. Active graphene-silicon hybrid diode for terahertz waves

    Science.gov (United States)

    Li, Quan; Tian, Zhen; Zhang, Xueqian; Singh, Ranjan; Du, Liangliang; Gu, Jianqiang; Han, Jiaguang; Zhang, Weili

    2015-05-01

    Controlling the propagation properties of the terahertz waves in graphene holds great promise in enabling novel technologies for the convergence of electronics and photonics. A diode is a fundamental electronic device that allows the passage of current in just one direction based on the polarity of the applied voltage. With simultaneous optical and electrical excitations, we experimentally demonstrate an active diode for the terahertz waves consisting of a graphene-silicon hybrid film. The diode transmits terahertz waves when biased with a positive voltage while attenuates the wave under a low negative voltage, which can be seen as an analogue of an electronic semiconductor diode. Here, we obtain a large transmission modulation of 83% in the graphene-silicon hybrid film, which exhibits tremendous potential for applications in designing broadband terahertz modulators and switchable terahertz plasmonic and metamaterial devices.

  14. Particle-in-cell simulation of spherical plasma focus diode

    International Nuclear Information System (INIS)

    A self-magnetically insulated, three-dimensionally focused ion-beam diode, spherical plasma focus diode (SPFD), is studied by numerical simulation using a two-dimensional, electromagnetic, relativistic particle-in-cell computer code. The calculated results of the diode impedance, the ion-current efficiency, and the focusing characteristics of the ion beam are presented. These results, except the data of the ion-beam current, are in good agreement with the experimental results. Since the major ion deflection direction observed experimentally is also obtained in the simulation, it is attempted to optimize the SPFD by correcting the ion deflection with the shape of the diode gap by means of simulations. copyright 1995 American Institute of Physics

  15. Passive fluidic diode for simple fluids using nested nanochannel structures

    Science.gov (United States)

    Mo, Jingwen; Li, Long; Wang, Jun; Li, Zhigang

    2016-03-01

    In this paper, we propose a moving part-free fluidic diode for simple fluids using nested nanochannels, which contain inner and outer channels of different lengths. Molecular dynamics simulations show that the fluidic diode accepts water flows in the forward direction and blocks flows in the backward direction in a wide range of pressure drops. The anisotropic flow rates are generated by the distinct activation pressures in different directions. In the forward direction, the activation pressure is low, which is determined by the infiltration pressure of the inner channel. In the backward direction, the activation pressure is quite high due to the capillary effects when flows are released from the inner to the outer channel. The pressure drop range for the fluidic diode can be varied by changing the channel size or surface wettability. The fluidic diode offers an alternative way for flow control in integrated micro- and nanofluidic devices.

  16. Active Stabilization of a Diode Laser Injection Lock

    CERN Document Server

    Saxberg, Brendan; Gupta, Subhadeep

    2016-01-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  17. Active stabilization of a diode laser injection lock

    Science.gov (United States)

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-06-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  18. Magnetically insulated ion diodes for synthesis of advanced materials

    International Nuclear Information System (INIS)

    Magnetically insulated ion diode technology has been used to generate intense ion beams. We have used such beams to form ablation plasmas from solid targets. Initial experiments have studied congruent deposition of complex stoichiometric thin films. Typical ion diode parameters are 400 kV and 50 kA ion beams over a pulse length of 0.5--1.0 μs. Diode operation has been modeled with 2.5-D particle-in-cell simulations. These calculations allow us to unfold the dynamics of electron flow, ion flow, and their interactions to recover time-dependent impedance behavior which is in good agreement with data. Transport of the dense ion flow through an extraction section of the diode requires a high degree of charge neutralization. Self-consistent neutralization dynamics have been modeled with the simulations. We present the latest numerical results and compare them with data from the ongoing experiments

  19. Silver-Rutile Schottky Diode Fabricated on Oxidized Titanium Foil

    International Nuclear Information System (INIS)

    The fabrication and characterization of a gas sensing Ag-TiO2 Schottky diode are reported. The fabricated Ag-TiO2-Ti structure, formed by sintering silver nanoparticles on the thermally oxidized titanium foil, demonstrated I-V characteristics of a typical Schottky diode at elevated temperatures up to 500 deg. C. The I-V characteristics of these devices strongly depended on the concentration level of the reducing gas contaminants in the surrounding atmosphere. The samples performed like high-barrier Schottky diodes in clean air, while behaved as ohmic contacts in highly reducing atmospheres. Different concentration levels of the examined alcohol vapours could increase the reverse current of the diodes up to 5 orders of magnitude. The measured electronic features of the device were described via an energy band diagram model.

  20. Diode-quad bridge for reactive transducers and FM discriminators

    Science.gov (United States)

    Harrison, D. R.; Dimeff, J.

    1972-01-01

    Diode-quad bridge circuit was developed for use with pressure-sensitive capacitive transducers, liquid-level measuring devices, proximity deflection sensors, and inductive displacement sensors. It may also be used as FM discriminator and as universal impedance bridge.