Sample records for broad area diode

  1. V-shaped resonators for addition of broad-area laser diode arrays (United States)

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


    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.

  2. In-phase output beam from broad-area diode array using Talbot cavity

    Institute of Scientific and Technical Information of China (English)

    Pengfei Zhao; Qiang Li; Weirong Guo; Bo Liu; Tiechuan Zuo


    The robust phase locking of a linear diode array consisting of 49 broad-area emitters was demonstrated.The single lobe in the far field with output power of 0.83 W was observed. The far-field divergence was reduced to 2.0 mrad. The spectral bandwidth was reduced from 1.7 to 0.13 nm.

  3. Near-field dynamics of broad area diode laser at very high pump levels

    Directory of Open Access Journals (Sweden)

    Martin Hempel


    Full Text Available Near-field properties of the emission of broad area semiconductor diode lasers under extremely high pumping of up to ∼50 times the threshold are investigated. A transition from a gain to thermally-induced index guiding is shown under operation with single pulses of 300 ns duration. At highest output powers, catastrophic optical damage is observed which is studied in conjunction with the evolution of time-averaged filamentary near-field properties. Dynamics of the process is resolved on a picosecond time scale.

  4. Improved spectral characteristics of 980 nm broad area slotted Fabry-Perot diode lasers

    Institute of Scientific and Technical Information of China (English)

    Gao Zhuo; Wang Jun; Xiong Cong; Liu Yuanyuan; Liu Suping; Ma Xiaoyu


    A novel broad area slotted Fabry-Perot diode laser is designed and fabricated.Using a new semianalytical method,we introduce effective refractive index perturbations in the form of etched slot features into a conventional 980 nm broad area Fabry-Perot cavity,and the spectral characteristics of the device are expected to be noticeably improved.A low density of slot features is formed by using standard optical lithography and inductively coupled plasma dry etching.The experimental results show that the full spectral width at half-maximum is less than 0.4 nm,meanwhile,the thermal shift of the emission spectrum is decreased from 0.26 to 0.07 nm/℃ over a temperature range of 10 to 60 ℃.The improved spectral characteristics of the device are proved to be attributed to such slotted Fabry-Perot laser structures.

  5. Near-diffraction-limited segmented broad area diode laser based on off-axis spectral beam combining

    DEFF Research Database (Denmark)

    Jensen, O.B.; Thestrup Nielsen, Birgitte; Andersen, Peter E.;


    The beam quality of a 500-mu m-wide broad area diode laser with five active segments has been improved beyond the beam quality of the individual segments. The principle of this new laser system is based on off-axis feedback in combination with spectral beam combining. By using a double......-feedback scheme we are able to improve the beam quality of the laser by a factor of 23 from M-2 = 55 for the free-running diode laser to M-2 = 2.4 for the laser with feedback at a drive current of 2.2 A. The improved M-2 value is a factor of 3.4 below M-2 = 8.2 for a single free-running segment. This is the first...... time that the beam quality of a segmented broad area diode laser has been improved beyond the beam quality of the individual segments....

  6. Achieving single-lobed far-field patterns of broad area laser diode with external cavity feedback

    Institute of Scientific and Technical Information of China (English)

    Jianhong Ge(葛剑虹); Jun Chen(陈军); Andreas Hermerschmidt; H.J.Eichler


    We demonstrate a technique for single transverse mode operation of high-power broad area laser diode(BAL). In the experiment, the HR mirror is used as an external cavity mirror and the grating is used as a wavelength selective component. By tiling the HR mirror and the grating, the number of transverse modes oscillating in the cavity can be limited and the spectral bandwidth of the laser diode can be reduced. A single-lobed near diffraction-limited laser beam with the beam divergence (FWHM) of 0.43°, the spectral line-width of 0.7 nm and the output power of 350 mW are obtained. With the feedback, the power density of the output laser beam is increased 6 times in comparison with the free running.

  7. Dynamic behaviors of a broad-area diode laser with lateral-mode-selected external feedback

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael


    behavior disappears in some case; when the zero-order mode is selected, periodic dynamics corresponding to a double roundtrip external-cavity loop is observed. When the stripe mirror is not aligned perfectly, a dynamic behavior like pulse-package oscillations is observed: a periodic oscillated output...... with a frequency of the single roundtrip external-cavity loop modulated by periodic low-frequency fluctuation. This is the first observation of pulse-package oscillation in a diode laser with long-cavity feedback, to our knowledge....

  8. Multiple and broad frequency response Gunn diodes (United States)

    Pilgrim, N. J.; Macpherson, R. F.; Khalid, A.; Dunn, G. M.; Cumming, D. R. S.


    Gunn diodes, operating in transit time mode, are usually thought of as incapable of generating power at multiple frequencies or over a broad frequency range. In this paper, we report experimental results showing that these diodes can generate power at several frequencies and, using Monte Carlo simulations of both planar and vertical devices, we offer an explanation of how this unusual behaviour may come into being and suggest possible applications for this novel device.

  9. Coherent beam combination of broad-area laser diode array using off-axis external cavity with double feedback

    Institute of Scientific and Technical Information of China (English)

    Zhouping Su; Zhicheng Ji; Lizhi Que; Zhuowei Zhu


    In this letter,we demonstrate coherent beam combination of laser diode array using the external Talbot cavity with double feedback.The double feedback elements consist of grating and high-reflection plane mirror.Compared with single high-reflection plane mirror feedback,the external Talbot cavity with double feedback reduce the number of interference strips in the far-field pattern and narrow spectral line-width of the laser diode array.The results indicate that the application of the external Talbot cavity with double feedback produces a clear far-field interference pattern.In addition,line-width is reduced to 0.15 nm full-width at half-maximum (FWHM).

  10. Dynamics of a broad-area diode laser with lateral-mode-selected long-cavity feedback

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael


    of the cases, the output of the laser shows a periodic oscillation corresponding to a single roundtrip external-cavity loop, but the dynamic behavior disappears in some case; when the zero-order lateral-mode is selected, periodic oscillation corresponding to a double roundtrip external-cavity loop is observed....... When the feedback mirror is aligned non-perfectly, pulse-package oscillation is observed, for the first time to our knowledge, in a diode laser with long-cavity feedback....

  11. Innovation in Broad-Area Diode Laser Array Architecture: Coupling Grating-Confined Zigzag Modes for High Power, High Brightness Applications (United States)


    arrays [16-18]; 3) leaky wave coupled (anti- guided ) laser arrays [7, 19-21]; 4) unstable resonators, e.g., curved mirror or tapered lasers [22-26...amplifiers. The phase of each individual amplified beam is controlled by a discrete optical phase modulator. The phase difference among the array elements...overlap area of the two gratings defines a two dimensional coupling region. The phase locking of two emitters is obtained by the wave coupling through

  12. 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


    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.

  13. Folded cavity angled-grating broad-area lasers. (United States)

    Zhao, Yunsong; Zhu, Lin


    The angled-grating broad-area laser is a promising candidate for high power, high brightness diode laser source. The key point in the design is the angled gratings which can simultaneously support the unique snake-like zigzag lasing mode and eliminate the direct Fabry-Perot (FP) feedback. Unlike a conventional laser waveguide mode, the phase front of the zigzag mode periodically changes along the propagation direction. By use of the mirror symmetry of the zigzag mode, we propose and demonstrate the folded cavity angled-grating broad-area lasers. One benefit of this design is to reduce the required wafer space compared to a regular angled-grating broad-area laser, especially in a long cavity laser for high power operation. Experimental results show that the folded cavity laser exhibits good beam quality in far field with a slightly larger threshold and smaller slope efficiency due to the additional interface loss.

  14. Rapid and broad wavelength sweeping of standard telecommunication distributed feedback laser diode. (United States)

    Njegovec, Matej; Donlagic, Denis


    This Letter presents a method for the fast and broad wavelength sweeping of a standard setup of a diode's active region and its immediate vicinity, which contain the diode's optical feedback system. The selective and rapid heating of the active region is possible due to the confinement of the voltage drop to the active diode's region that has submicrometer thickness. Using the presented method and an off-the-shelf telecommunication distributed feedback laser diode, we demonstrate wavelength sweeps in excess of 10 nm that were completed in about 200 ns, while generating average optical power in excess of 50 mW. In spite of high-amplitude current-drive pulses, 6000 h continuous operation of the diode within such an operational regime did not show any significant degradation of the diode's performance.

  15. Broad Spectrum Photoelectrochemical Diodes for Solar Hydrogen Generation

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, Craig A.


    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.

  16. A low-temperature external cavity diode laser for broad wavelength tuning (United States)

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


    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 the 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 °C, more than 85 °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 is 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 and extending the wavelength coverage of commercial laser diodes.

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

    CERN Document Server

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


    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 ...

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

    Institute of Scientific and Technical Information of China (English)


    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.

  19. Near-infrared broad-band cavity enhanced absorption spectroscopy using a superluminescent light emitting diode. (United States)

    Denzer, W; Hamilton, M L; Hancock, G; Islam, M; Langley, C E; Peverall, R; Ritchie, G A D


    A fibre coupled near-infrared superluminescent light emitting diode that emits approximately 10 mW of radiation between 1.62 and 1.7 microm is employed in combination with a broad-band cavity enhanced spectrometer consisting of a linear optical cavity with mirrors of reflectivity approximately 99.98% and either a dispersive near-infrared spectrometer or a Fourier transform interferometer. Results are presented on the absorption of 1,3-butadiene, and sensitivities are achieved of 6.1 x 10(-8) cm(-1) using the dispersive spectrometer in combination with phase-sensitive detection, and 1.5 x 10(-8) cm(-1) using the Fourier transform interferometer (expressed as a minimum detectable absorption coefficient) over several minutes of acquisition time.

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

    KAUST Repository

    Dimas, Clara E.


    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.

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

    KAUST Repository

    Khan, Mohammed Zahed Mustafa


    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.

  2. Spontaneous pattern formation in broad-area lasers (United States)

    Krents, Anton; Anchikov, Dmitry; Molevich, Nonna; Pakhomov, Anton


    The paper studies the spontaneous formation of nonlinear optical patterns in broad area lasers. Spatiotemporal transverse dynamics of the laser is described by the Maxwell-Bloch equations (MBE). The instability of the steady-state solution leads to pattern formation. Two different types of instabilities were observed analytically (Hopf and wave). 2D numerical simulation of the MBE with the random initial conditions has been performed using a split-step Fourier method and periodic boundary conditions. Hopf instability leads to homogeneous oscillations, spatiotemporal chaos and spiral waves. In the case of wave instability, the direct numerical simulation showed that space-time (periodic, quasi-periodic, or chaotic) modulation of the uniform profile is observed. The characteristic sizes of excited patterns are in good agreement with analytical predictions. The nonlinear interaction of four travelling waves forms a square optical vortex lattice similar to the vortex lattices observed in superconductors and Bose Einstein condensate.

  3. A broad area electrospray generated by a piezoelectric transformer (United States)

    Ramshani, Zeinab; Johnson, Michael J.; Atashbar, Massood Z.; Go, David B.


    Electrosprays are typically formed by the application of a high (kilovolt) voltage to the flow exiting a small diameter capillary, and they have been used in applications ranging from material synthesis to spray coating because of the finely controlled plume of micron-sized droplets they produce. In this work, we report a similar but distinct spray directly off the surface of a piezoelectric transformer. Using a paper wick to deliver liquid to the surface of the piezoelectric crystal, a continuous, broad area spray is generated from the wick in contact with the transformer surface, only requiring input voltages on the order of 20 Vamp. Systematic variation of critical parameters indicate that this piezoelectric transformer-generated spray is similar to a conventional electrospray, with the spray current exhibiting a non-linear dependence on the solution conductivity, but distinct, as the spray exhibits little dependence on the solution surface tension. This innovative spray could potentially lead to uniform, large area spray coverage from a single device for a wide variety of applications.

  4. Selective-area nanoheteroepitaxy for light emitting diode (LED) applications (United States)

    Wildeson, Isaac H.

    Over 20% of the electricity in the United States is consumed for lighting, and the majority of this energy is wasted as heat during the lighting process. A solid-state (or light emitting diode (LED)-based) light source has the potential of saving the United States billions of dollars in electricity and reducing megatons of global CO2 emissions annually. While white light LEDs are currently on the market with efficiencies that are superior to incandescent and fluorescent light sources, their high up-front cost is inhibiting mass adoption. One reason for the high cost is the inefficiency of green and amber LEDs that can used to make white light. The inefficiency of green and amber LEDs results in more of these chips being required, and thus a higher cost. Improvements in the performance of green and amber LEDs is also required in order to realize the full potential of solid-state lighting. Nanoheteroepitaxy is an interesting route towards achieving efficient green and amber LEDs as it resolves major challenges that are currently plaguing III-nitride LEDs such as high dislocation densities and limited active region critical thicknesses. A method for fabricating III-nitride nanopyramid LEDs is presented that employs conventional processing used in industry. The present document begins with an overview of the current challenges in III-nitride LEDs and the benefits of nanoheteroepitaxy. A process for controlled selective-area growth of nanopyramid LEDs by organometallic vapor phase epitaxy has been developed throughout the course of this work. Dielectric templates used for the selective-area growth are patterned by two methods, namely porous anodic alumina and electron-beam lithography. The dielectric templates serve as efficient dislocation filters; however, planar defects are initiated during lower temperature growth on the nanopyramids. The quantum wells outline six semipolar planes that form each hexagonal pyramid. Quantum wells grown on these semipolar planes

  5. High packing density laser diode stack arrays using Al-free active region laser bars with a broad waveguide and discrete copper microchannel-cooled heatsinks

    Institute of Scientific and Technical Information of China (English)

    Zhigang Liu; Gaozhan Fang; Kecheng Feng


    A high packing density laser diode stack array is developed utilizing Al-free active region laser bars with a broad waveguide and discrete copper microchannel-cooled heatsinks. The microchannel cooling technology leads to a 10-bar laser diode stack array having the thermal resistance of 0.199 ℃/W, and enables the device to be operated under continuous-wave (CW) condition at an output power of 1200 W. The thickness of the discrete copper heatsink is only 1.5 mm, which results in a high packing density and a small bar pitch of 1.8 mm.

  6. A two-stage series diode for intense large-area moderate pulsed X rays production (United States)

    Lai, Dingguo; Qiu, Mengtong; Xu, Qifu; Su, Zhaofeng; Li, Mo; Ren, Shuqing; Huang, Zhongliang


    This paper presents a method for moderate pulsed X rays produced by a series diode, which can be driven by high voltage pulse to generate intense large-area uniform sub-100-keV X rays. A two stage series diode was designed for Flash-II accelerator and experimentally investigated. A compact support system of floating converter/cathode was invented, the extra cathode is floating electrically and mechanically, by withdrawing three support pins several milliseconds before a diode electrical pulse. A double ring cathode was developed to improve the surface electric field and emission stability. The cathode radii and diode separation gap were optimized to enhance the uniformity of X rays and coincidence of the two diode voltages based on the simulation and theoretical calculation. The experimental results show that the two stage series diode can work stably under 700 kV and 300 kA, the average energy of X rays is 86 keV, and the dose is about 296 rad(Si) over 615 cm2 area with uniformity 2:1 at 5 cm from the last converter. Compared with the single diode, the average X rays' energy reduces from 132 keV to 88 keV, and the proportion of sub-100-keV photons increases from 39% to 69%.

  7. Selective-area growth of periodic nanopyramid light-emitting diode arrays on GaN/sapphire templates patterned by multiple-exposure colloidal lithography (United States)

    Xiong, Zhuo; Wei, Tongbo; Zhang, Yonghui; Zhang, Xiang; Yang, Chao; Liu, Zhiqiang; Yuan, Guodong; Li, Jinmin; Wang, Junxi


    Gallium nitride-based nanopyramid light-emitting diodes are a promising technology to achieve highly efficient solid-state lighting and beyond. Here, periodic nanopyramid light-emitting diode arrays on gallium nitride/sapphire templates were fabricated by selective-area metalorganic chemical vapor deposition and multiple-exposure colloidal lithography. The electric field intensity distribution of incident light going through polystyrene microspheres and photoresist are simulated using finite-different time-domain method. Nitrogen as the carrier gas and a low V/III ratio (ratio of molar flow rate of group-V to group-III sources) are found to be important in order to form gallium nitride nanopyramid. In addition, a broad yellow emission in photoluminescence and cathodoluminescence spectra were observed. This phenomena showed the potential of nanopyramid light-emitting diodes to realize long wavelength visible emissions.

  8. Extracting fundamental transverse mode operation in broad area quantum cascade lasers (United States)

    Kaspi, R.; Luong, S.; Yang, C.; Lu, C.; Newell, T. C.; Bate, T.


    Power scaling in broad area quantum cascade lasers results in the operation of high order transverse modes with a far-field profile consisting of two lobes propagating at large angles relative to the optical axis. We report a method of suppressing the high order transverse modes that can extract the fundamental mode and provide emission along the optical axis. By generating a lateral constriction in the waveguide in the form of short trenches defined by the focused ion beam milling technique, we report broad area devices in which most of the power is contained in a near diffraction-limited beam that provides high brightness.

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

    DEFF Research Database (Denmark)

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


    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 differ......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...

  10. 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.;


    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...

  11. Broad Area Distributed Gain, Distributed Index Profile GaAlAs Semiconductor Laser Diodes (United States)


    time-zero char- "’S. D. Offsey, W. J. Schaff , P. J. Tasker. H. Ennen. and L. F. Eastman, acterization of strained-layer In. Ga, - . As-GaAs quantum...35 11. S.D. Offsey, W.J. Schaff , P.J. Tasker, H. Ennen, and L.F. Eastman, Appi. Phys. Lett. 54, 2527 (1989). 12. S.E. Fischer, D. Fekete, G.B. Feak...setting up wave Technol.. vol. LT-5. pp 305-315. Mar. 1987 the software package iSMILE and for many technical dis- [24) M. J. Adams et al.. -Analysis

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

    CERN Document Server

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


    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.

  13. High power coherent polarization locked laser diode. (United States)

    Purnawirman; Phua, P B


    We have coherently combined a broad area laser diode array to obtain high power single-lobed output by using coherent polarization locking. The single-lobed coherent beam is achieved by spatially combining four diode emitters using walk-off crystals and waveplates while their phases are passively locked via polarization discrimination. While our previous work focused on coherent polarization locking of diode in Gaussian beams, we demonstrate in this paper, the feasibility of the same polarization discrimination for locking multimode beams from broad area diode lasers. The resonator is designed to mitigate the loss from smile effect by using retro-reflection feedback in the cavity. In a 980 nm diode array, we produced 7.2 W coherent output with M2 of 1.5x11.5. The brightness of the diode is improved by more than an order of magnitude.

  14. Stabilization of class-B broad-area lasers emission by external optical injection

    CERN Document Server

    Pakhomov, A V


    We theoretically examine the effect of external optical injection on the spatio-temporal dynamics of class-B broad-area lasers. We demonstrate that optical injection can efficiently stabilize the intrinsic transverse instabilities in such lasers associated with both the boundaries of the pumping area and with the bulk nonlinearities of the active medium. Stabilizing action of optical injection is shown to be closely related to the suppression of inherent relaxation oscillations behavior.

  15. Spatiospectral and picosecond spatiotemporal properties of a broad area operating channeled-substrate-planar laser array (United States)

    Yu, NU; Defreez, Richard K.; Bossert, David J.; Wilson, Geoffrey A.; Elliott, Richard A.


    Spatiospectral and spatiotemporal properties of an eight-element channeled-substrate-planar laser array are investigated in both CW and pulsed operating conditions. The closely spaced CSP array with strong optical coupling between array elements is characterized by a broad area laserlike operation determined by its spatial mode spectra. The spatiotemporal evolution of the near and far field exhibits complex dynamic behavior in the picosecond to nanosecond domain. Operating parameters for the laser device have been experimentally determined. These results provide important information for the evaluation of the dynamic behavior of coherent semiconductor laser arrays.

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

    DEFF Research Database (Denmark)

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


    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...

  17. Control of lateral divergence in high-power, broad-area photonic crystal lasers (United States)

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


    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%.

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

    DEFF Research Database (Denmark)

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

    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 complex......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...

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

    CERN Document Server

    Stipčević, Mario; Ursin, Rupert


    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.

  20. Beam shaping in high-power broad-area quantum cascade lasers using optical feedback (United States)

    Ferré, Simon; Jumpertz, Louise; Carras, Mathieu; Ferreira, Robson; Grillot, Frédéric


    Broad-area quantum cascade lasers with high output powers are highly desirable sources for various applications including infrared countermeasures. However, such structures suffer from strongly deteriorated beam quality due to multimode behavior, diffraction of light and self-focusing. Quantum cascade lasers presenting high performances in terms of power and heat-load dissipation are reported and their response to a nonlinear control based on optical feedback is studied. Applying optical feedback enables to efficiently tailor its near-field beam profile. The different cavity modes are sequentially excited by shifting the feedback mirror angle. Further control of the near-field profile is demonstrated using spatial filtering. The impact of an inhomogeneous gain as well as the influence of the cavity width are investigated. Compared to existing technologies, that are complex and costly, beam shaping with optical feedback is a more flexible solution to obtain high-quality mid-infrared sources. PMID:28287175

  1. Beam shaping in high-power broad-area quantum cascade lasers using optical feedback (United States)

    Ferré, Simon; Jumpertz, Louise; Carras, Mathieu; Ferreira, Robson; Grillot, Frédéric


    Broad-area quantum cascade lasers with high output powers are highly desirable sources for various applications including infrared countermeasures. However, such structures suffer from strongly deteriorated beam quality due to multimode behavior, diffraction of light and self-focusing. Quantum cascade lasers presenting high performances in terms of power and heat-load dissipation are reported and their response to a nonlinear control based on optical feedback is studied. Applying optical feedback enables to efficiently tailor its near-field beam profile. The different cavity modes are sequentially excited by shifting the feedback mirror angle. Further control of the near-field profile is demonstrated using spatial filtering. The impact of an inhomogeneous gain as well as the influence of the cavity width are investigated. Compared to existing technologies, that are complex and costly, beam shaping with optical feedback is a more flexible solution to obtain high-quality mid-infrared sources.

  2. Broad-area search for targets in SAR imagery with context-adaptive algorithms (United States)

    Patterson, Tim J.; Fairchild, Scott R.


    This paper describes an ATR system based on gray scale morphology which has proven very effective in performing broad area search for targets of interest. Gray scale morphology is used to extract several distinctive sets of features which combine intensity and spatial information. Results of direct comparisons with other algorithms are presented. In a series of tests which were scored independently the morphological approach has shown superior results. An automated training systems based on a combination of genetic algorithms and classification and regression trees is described. Further performance gains are expected by allowing context sensitive selection of parameter sets for the morphological processing. Context is acquired from the image using texture measures to identify the local clutter environment. The system is designed to be able to build new classifiers on the fly to match specific image to image variations.

  3. Above room temperature continuous wave operation of a broad-area quantum-cascade laser (United States)

    Semtsiv, M. P.; Masselink, W. T.


    We describe the design and implementation of a broad-area (w ≈ 30 μm) quantum-cascade laser operating in a continuous wave mode up to heat-sink temperatures beyond +100 °C. The room-temperature emission wavelength is 4.6 μm. The temperature gradient in the active region of such a wide laser stripe is essentially perpendicular to the epitaxial layers and the resulting steady-state active region temperature offset scales approximately with the square of the number of cascades. With only 10 cascades in the active region, the threshold electrical power density in the current quantum-cascade laser in the continuous-wave mode is as low as Vth × Ith = 3.8 V × 0.9 kA/cm2 = 3.4 kW/cm2 at room temperature for 2 mm-long two-side high-reflectivity coated laser stripe. A 4 mm-long one-side high-reflectivity coated laser stripe delivers in continuous-wave mode above 0.6 W at +20 °C and above 1.3 W at -27 °C (cooled with a single-stage Peltier element). A 2 mm-long two-side high-reflectivity coated laser stripe demonstrates continuous-wave lasing up to at least +102 °C (375 K). The thermal conductance, Gth, ranges between 235 W/K cm2 and 140 W/K cm2 for temperatures between -33 °C and +102 °C. This demonstration opens the route for continuous-wave power scaling of quantum-cascade lasers via broad-area laser ridges.

  4. Thermal investigation on high power dfb broad area lasers at 975 nm, with 60% efficiency (United States)

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


    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 (new measurement based on the pulse electrical method and using the T3STERequipment. This method is well known for electronic 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

  5. Design, fabrication and test of Load Bearing multilayer insulation to support a broad area cooled shield (United States)

    Dye, S. A.; Johnson, W. L.; Plachta, D. W.; Mills, G. L.; Buchanan, L.; Kopelove, A. B.


    Improvements in cryogenic propellant storage are needed to achieve reduced or Zero Boil Off of cryopropellants, critical for long duration missions. Techniques for reducing heat leak into cryotanks include using passive multi-layer insulation (MLI) and vapor cooled or actively cooled thermal shields. Large scale shields cannot be supported by tank structural supports without heat leak through the supports. Traditional MLI also cannot support shield structural loads, and separate shield support mechanisms add significant heat leak. Quest Thermal Group and Ball Aerospace, with NASA SBIR support, have developed a novel Load Bearing multi-layer insulation (LBMLI) capable of self-supporting thermal shields and providing high thermal performance. We report on the development of LBMLI, including design, modeling and analysis, structural testing via vibe and acoustic loading, calorimeter thermal testing, and Reduced Boil-Off (RBO) testing on NASA large scale cryotanks. LBMLI uses the strength of discrete polymer spacers to control interlayer spacing and support the external load of an actively cooled shield and external MLI. Structural testing at NASA Marshall was performed to beyond maximum launch profiles without failure. LBMLI coupons were thermally tested on calorimeters, with superior performance to traditional MLI on a per layer basis. Thermal and structural tests were performed with LBMLI supporting an actively cooled shield, and comparisons are made to the performance of traditional MLI and thermal shield supports. LBMLI provided a 51% reduction in heat leak per layer over a previously tested traditional MLI with tank standoffs, a 38% reduction in mass, and was advanced to TRL5. Active thermal control using LBMLI and a broad area cooled shield offers significant advantages in total system heat flux, mass and structural robustness for future Reduced Boil-Off and Zero Boil-Off cryogenic missions with durations over a few weeks.

  6. Analytical model for current distribution in large-area organic light emitting diodes with parallel metal grid lines

    NARCIS (Netherlands)

    Barink, M.; Harkema, S.


    In this study, an analytical solution for the current distribution of a large-area organic light emitting diodes (OLEDs) with parallel equidistant gridlines is derived. In contrast to numerical methods, this analytical solution allows for a very quick scan of the OLED design space, even for very lar

  7. Large-area broad band saturable Bragg reflectors using oxidized AlAs in the circular and inverted mesa geometries (United States)

    Nabanja, Sheila P.; Kolodziejski, Leslie A.; Petrich, Gale S.; Sander, Michelle Y.; Morse, Jonathan L.; Shtyrkova, Katia; Ippen, Erich P.; Kärtner, Franz X.


    A semiconductor Saturable Bragg Reflector (SBR) is a mirror structure comprising alternating layers of high and low refractive index materials with an incorporated saturable absorber. SBRs can be used to initiate and sustain ultra-short pulses in various laser systems. In order to form ultra-short pulses, SBRs with high reflectivity over a broad wavelength range are required. Furthermore, large-area SBRs facilitate easy integration in a laser cavity. One of the key elements for the realization of broad band SBRs is the development of the thermal oxidation process that creates buried low-index AlxOy layers over large areas. The design, fabrication, characterization, and implementation of broad band, high index contrast III-V/AlxOy SBRs in the form of circular mesas, as well as inverted mesa structures, is presented.

  8. Rosin-enabled ultraclean and damage-free transfer of graphene for large-area flexible organic light-emitting diodes (United States)

    Zhang, Zhikun; Du, Jinhong; Zhang, Dingdong; Sun, Hengda; Yin, Lichang; Ma, Laipeng; Chen, Jiangshan; Ma, Dongge; Cheng, Hui-Ming; Ren, Wencai


    The large polymer particle residue generated during the transfer process of graphene grown by chemical vapour deposition is a critical issue that limits its use in large-area thin-film devices such as organic light-emitting diodes. The available lighting areas of the graphene-based organic light-emitting diodes reported so far are usually square with about 1% deviation over a large area. Such clean, damage-free graphene has produced the four-inch monolithic flexible graphene-based organic light-emitting diode with a high brightness of about 10,000 cd m-2 that can already satisfy the requirements for lighting sources and displays.

  9. Ion-exchanged Er3+/Yb3+ co-doped waveguide amplifiers longitudinally pumped by broad area lasers. (United States)

    Donzella, V; Toccafondo, V; Faralli, S; Di Pasquale, F; Cassagnettes, C; Barbier, D; Figueroa, H Hernandez


    A multimode pumping scheme for Er(3+)/Yb(3+) co-doped waveguide amplifiers based on broad area lasers at around 980 nm is presented. The proposed amplifier is fabricated by ion-exchange (IE) technique on silicate and phosphate glasses. The highly efficient energy transfer from Yb(3+) to Er(3+) ions, combined with the use of low cost and high power broad area laser, allows the realization of high performance and cost-effective integrated amplifiers. The structure has been designed and numerically studied using a 3D finite element modelling tool, and over 3 dB/cm small signal gain has been predicted for an optimized amplifier. Preliminary characterization of an amplifier structure provides a first experimental evidence of the novel multimode longitudinal pumping.

  10. Green high-power tunable external-cavity GaN diode laser at 515 nm

    DEFF Research Database (Denmark)

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael


    A 480 mW green tunable diode laser system is demonstrated for the first time to our knowledge. The laser system is based on a GaN broad-area diode laser and Littrow external-cavity feedback. The green laser system is operated in two modes by switching the polarization direction of the laser beam ...

  11. 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


    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...

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

    Directory of Open Access Journals (Sweden)

    Moloney Kirk A


    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

  13. Minimum sampling area and a biodiversity of riparian broad-leaved/Korean pine forest in Erdaobaihe forested watershed, Changbai Mountain

    Institute of Scientific and Technical Information of China (English)


    Riparian zone is an important component of forested watershed. Species component, structure, and distribution pattern of plant community in riparian zone are different from those of forest far away from the riparian zone because of edge effect and influence of river, and their minimum sampling areas are also different. To study the minimum area and a biodiversity of broad-leaved/Korean pine forest in riparian zone, three 8 m × 32 m sampling belts were selected and distributed at elevation of 800 m, 900 m, and 1000 m. In the riparian broad-leaved/Korean pine forest, mean minimum sampling areas including 60%, 80%, and 90% of total species were 80 m2 (8 m×10 m), 180 m2 (12 m×15 m), and 320 m2 (16 m × 20 m) respectively; The corresponding mean minimum areas of non-riparian forest were about 260 m2, 380 m2, and 480 m2; and the former were smaller than the latter. In the riparian zone, species richness, Shannon-Weiner index and species evenness were also higher than those in non-riparian forest. On the contrary, species dominance in forest community was higher than that in riparian zone.

  14. Clonally Related Forebrain Interneurons Disperse Broadly across Both Functional Areas and Structural Boundaries. (United States)

    Mayer, Christian; Jaglin, Xavier H; Cobbs, Lucy V; Bandler, Rachel C; Streicher, Carmen; Cepko, Constance L; Hippenmeyer, Simon; Fishell, Gord


    The medial ganglionic eminence (MGE) gives rise to the majority of mouse forebrain interneurons. Here, we examine the lineage relationship among MGE-derived interneurons using a replication-defective retroviral library containing a highly diverse set of DNA barcodes. Recovering the barcodes from the mature progeny of infected progenitor cells enabled us to unambiguously determine their respective lineal relationship. We found that clonal dispersion occurs across large areas of the brain and is not restricted by anatomical divisions. As such, sibling interneurons can populate the cortex, hippocampus striatum, and globus pallidus. The majority of interneurons appeared to be generated from asymmetric divisions of MGE progenitor cells, followed by symmetric divisions within the subventricular zone. Altogether, our findings uncover that lineage relationships do not appear to determine interneuron allocation to particular regions. As such, it is likely that clonally related interneurons have considerable flexibility as to the particular forebrain circuits to which they can contribute.

  15. Nonlinear gain amplification due to two-wave mixing in a broad-area semiconductor amplifier with moving gratings

    DEFF Research Database (Denmark)

    Chi, Mingjun; Huignard, J.-P.; Petersen, Paul Michael


    . The results show that the optical gain of the amplifier is affected by both the moving phase grating and the moving gain grating, and there is energy exchange between the pump and signal beams. Depending on the moving direction of the gratings and the anti-guiding parameter, the optical gain may increase......The two-wave mixing in a broad-area semiconductor amplifier with moving gratings is investigated theoretically, where a pump beam and a signal beam with different frequencies are considered, thus both a moving phase grating and a moving gain grating are induced in the amplifier. The coupled...

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

    Energy Technology Data Exchange (ETDEWEB)

    Karmakar, Prasanta, E-mail: [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700064 (India); Satpati, Biswarup [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)


    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{sup +} 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.

  17. Synthesis and luminescence properties of a broad-band red phosphor Ca{sub 3}Si{sub 2}O{sub 7}:Eu{sup 2+} for warm white light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Qian Fengjiao [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Fu Renli, E-mail: [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Agathopoulos, Simeon [Materials Science and Engineering Department, University of Ioannina, GR-451 10 Ioannina (Greece); Gu Xiguang; Song Xiufeng [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)


    Single-phase broad-band red-emitting Ca{sub 3}Si{sub 2}O{sub 7}:Eu{sup 2+} 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 H{sub 3}BO{sub 3} 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 Eu{sup 2+}. The discussion of the results shows that Eu{sup 2+} 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 {approx}31 A. - Highlights: > Pure Ca{sub 3}Si{sub 2}O{sub 7}:Eu{sup 2+} phosphor was successfully synthesized by adding H{sub 3}BO{sub 3} . > Effects of H{sub 3}BO{sub 3} on phase formation and emission intensity were presented. > Luminescence properties in conjunction with Ca{sub 3}Si{sub 2}O{sub 7} structure were studied. > Energy transfer mechanism of Eu{sup 2+} and its critical distance were proposed.

  18. Rosin-enabled ultraclean and damage-free transfer of graphene for large-area flexible organic light-emitting diodes (United States)

    Zhang, Zhikun; Du, Jinhong; Zhang, Dingdong; Sun, Hengda; Yin, Lichang; Ma, Laipeng; Chen, Jiangshan; Ma, Dongge; Cheng, Hui-Ming; Ren, Wencai


    The large polymer particle residue generated during the transfer process of graphene grown by chemical vapour deposition is a critical issue that limits its use in large-area thin-film devices such as organic light-emitting diodes. The available lighting areas of the graphene-based organic light-emitting diodes reported so far are usually graphene, good solubility and sufficient strength enable ultraclean and damage-free transfer. The transferred graphene has a low surface roughness with an occasional maximum residue height of about 15 nm and a uniform sheet resistance of 560 Ω per square with about 1% deviation over a large area. Such clean, damage-free graphene has produced the four-inch monolithic flexible graphene-based organic light-emitting diode with a high brightness of about 10,000 cd m−2 that can already satisfy the requirements for lighting sources and displays. PMID:28233778

  19. Advanced image collection, information extraction, and change detection in support of NN-20 broad area search and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Petrie, G.M.; Perry, E.M.; Kirkham, R.R.; Slator, D.E. [and others


    This report describes the work performed at the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy`s Office of Nonproliferation and National Security, Office of Research and Development (NN-20). The work supports the NN-20 Broad Area Search and Analysis, a program initiated by NN-20 to improve the detection and classification of undeclared weapons facilities. Ongoing PNNL research activities are described in three main components: image collection, information processing, and change analysis. The Multispectral Airborne Imaging System, which was developed to collect georeferenced imagery in the visible through infrared regions of the spectrum, and flown on a light aircraft platform, will supply current land use conditions. The image information extraction software (dynamic clustering and end-member extraction) uses imagery, like the multispectral data collected by the PNNL multispectral system, to efficiently generate landcover information. The advanced change detection uses a priori (benchmark) information, current landcover conditions, and user-supplied rules to rank suspect areas by probable risk of undeclared facilities or proliferation activities. These components, both separately and combined, provide important tools for improving the detection of undeclared facilities.

  20. Application of a process-based shallow landslide hazard model over a broad area in Central Italy (United States)

    Gioia, Eleonora; Speranza, Gabriella; Ferretti, Maurizio; Godt, Jonathan W.; Baum, Rex L.; Marincioni, Fausto


    Process-based models are widely used for rainfall-induced shallow landslide forecasting. Previous studies have successfully applied the U.S. Geological Survey’s Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model (Baum et al. 2002) to compute infiltration-driven changes in the hillslopes’ factor of safety on small scales (i.e., tens of square kilometers). Soil data input for such models are difficult to obtain across larger regions. This work describes a novel methodology for the application of TRIGRS over broad areas with relatively uniform hydrogeological properties. The study area is a 550-km2 region in Central Italy covered by post-orogenic Quaternary sediments. Due to the lack of field data, we assigned mechanical and hydrological property values through a statistical analysis based on literature review of soils matching the local lithologies. We calibrated the model using rainfall data from 25 historical rainfall events that triggered landslides. We compared the variation of pressure head and factor of safety with the landslide occurrence to identify the best fitting input conditions. Using calibrated inputs and a soil depth model, we ran TRIGRS for the study area. Receiver operating characteristic (ROC) analysis, comparing the model’s output with a shallow landslide inventory, shows that TRIGRS effectively simulated the instability conditions in the post-orogenic complex during historical rainfall scenarios. The implication of this work is that rainfall-induced landslides over large regions may be predicted by a deterministic model, even where data on geotechnical and hydraulic properties as well as temporal changes in topography or subsurface conditions are not available.

  1. White LEDs as broad spectrum light sources for spectrophotometry: demonstration in the visible spectrum range in a diode-array spectrophotometric detector. (United States)

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


    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.

  2. High Power Diode Lasers with External Feedback: Overview and Prospects

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael


    In summary, different external-cavity feedback techniques to improve the spatial beam quality and narrow the linewidth of the output beam from both BALs and TDLs are presented. Broad-area diode laser system with external-cavity feedback around 800 nm can produce several Watts of output power...

  3. Monolithic active quenching and picosecond timing circuit suitable for large-area single-photon avalanche diodes. (United States)

    Gallivanoni, A; Rech, I; Resnati, D; Ghioni, M; Cova, S


    A new integrated active quenching circuit (i-AQC) designed in a standard CMOS process is presented, capable of operating with any available single photon avalanche diode (SPAD) over wide temperature range. The circuit is suitable for attaining high photon timing resolution also with wide-area SPADs. The new i-AQC integrates the basic active-quenching loop, a patented low-side timing circuit comprising a fast pulse pick-up scheme that substantially improves time-jitter performance, and a novel active-load passive quenching mechanism (consisting of a current mirror rather than a traditional high-value resistor) greatly improves the maximum counting rate. The circuit is also suitable for portable instruments, miniaturized detector modules and SPAD-array detectors. The overall features of the circuit may open the way to new developments in diversified applications of time-correlated photon counting in life sciences and material sciences.

  4. Coaxial foilless diode

    Directory of Open Access Journals (Sweden)

    Long Kong


    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.

  5. Computer Simulations of Edge Effects in a Small-Area Mesa N-P Junction Diodes: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Appel, J.; Sopori, B.; Ravindra, N. M.


    In this work, computer simulations are used to determine the influence of edge conditions on the overall performance of mesa diodes under dark and illuminated conditions. In particular, we examine the effect of edge shape on the I-V characteristics of the diode.

  6. Quantum-Dot Light-Emitting Diodes for Large-Area Displays: Towards the Dawn of Commercialization. (United States)

    Dai, Xingliang; Deng, Yunzhou; Peng, Xiaogang; Jin, Yizheng


    Quantum dots are a unique class of emitters with size-tunable emission wavelengths, saturated emission colors, near-unity luminance efficiency, inherent photo- and thermal- stability and excellent solution processability. Quantum dots have been used as down-converters for back-lighting in liquid-crystal displays to improve color gamut, leading to the booming of quantum-dot televisions in consumer market. In the past few years, efficiency and lifetime of electroluminescence devices based on quantum dots achieved tremendous progress. These encouraging facts foreshadow the commercialization of quantum-dot light-emitting diodes (QLEDs), which promises an unprecedented generation of cost-effective, large-area, energy-saving, wide-color-gamut, ultra-thin and flexible displays. Here we provide a Progress Report, covering interdisciplinary aspects including material chemistry of quantum dots and charge-transporting layers, optimization and mechanism studies of prototype devices and processing techniques to produce large-area and high-resolution red-green-blue pixel arrays. We also identify a few key challenges facing the development of active-matrix QLED displays.

  7. Electrical and Optical Properties of a High-Voltage Large Area Blue Light-Emitting Diode (United States)

    Wang; Wei; Cai; Yong; Huang; Wei; Li; Hai-ou; Zhang; Bao-shun


    In this paper, we report a single-chip large area (5×5 mm2) InGaN/GaN blue LED with the optical output power of 4.3 W. This device consists of 24-stages small LED-cells that are connected in series. Driven at 500 mA, the forward voltage is measured to be 87.2 V with a reverse current of 2.63×10-9 A at -120 V. The comparison of two different cooling schemes, i.e., with/without fan cooling, was made; the results suggest that the thermal convection between the heat sink and air is more critical. A simple white LED package was also tried by covering silicone gel mixed with yttrium aluminum garnet (YAG) phosphor. The luminous flux and the correlated color temperature (CCT) were measured to be 1090 lm and 5082 K, when the device was driven at 500 mA. This report also demonstrated the feasibility of the application for camera flash.

  8. 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


    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.

  9. Degradation Processes in High-Power Diode Lasers under External Optical Feedback

    DEFF Research Database (Denmark)

    Tomm, Jens. W.; Hempel, Martin; Petersen, Paul Michael;


    The effect of moderate external feedback on the gradual degradation of 808 nm emitting AlGaAs-based high-power broad-area diode lasers is analyzed. Eventually the quantum well that actually experiences the highest total optical load remains unaffected by the aging, while severe impact...

  10. Coupling of polarization and spatial degrees of freedom of highly divergent emission in broad-area square vertical-cavity surface-emitting lasers. (United States)

    Babushkin, I V; Schulz-Ruhtenberg, M; Loiko, N A; Huang, K F; Ackemann, T


    The polarization of highly divergent modes of broad-area square vertical-cavity surface-emitting lasers is shown to be only marginally affected by material anisotropies but determined by an interplay of the polarization properties of the Bragg cavity mirrors and of the transverse boundary conditions. This leads to a locking of the polarization direction to the boundaries and its indeterminacy for wave vectors oriented along the diagonal. We point out a non-Poissonian character of nearest-neighbor frequency spacing distribution and the impossibility of single-wave number solutions.

  11. Theory of mind broad and narrow: reasoning about social exchange engages ToM areas, precautionary reasoning does not. (United States)

    Ermer, Elsa; Guerin, Scott A; Cosmides, Leda; Tooby, John; Miller, Michael B


    Baron-Cohen (1995) proposed that the theory of mind (ToM) inference system evolved to promote strategic social interaction. Social exchange--a form of co-operation for mutual benefit--involves strategic social interaction and requires ToM inferences about the contents of other individuals' mental states, especially their desires, goals, and intentions. There are behavioral and neuropsychological dissociations between reasoning about social exchange and reasoning about equivalent problems tapping other, more general content domains. It has therefore been proposed that social exchange behavior is regulated by social contract algorithms: a domain-specific inference system that is functionally specialized for reasoning about social exchange. We report an fMRI study using the Wason selection task that provides further support for this hypothesis. Precautionary rules share so many properties with social exchange rules--they are conditional, deontic, and involve subjective utilities--that most reasoning theories claim they are processed by the same neurocomputational machinery. Nevertheless, neuroimaging shows that reasoning about social exchange activates brain areas not activated by reasoning about precautionary rules, and vice versa. As predicted, neural correlates of ToM (anterior and posterior temporal cortex) were activated when subjects interpreted social exchange rules, but not precautionary rules (where ToM inferences are unnecessary). We argue that the interaction between ToM and social contract algorithms can be reciprocal: social contract algorithms requires ToM inferences, but their functional logic also allows ToM inferences to be made. By considering interactions between ToM in the narrower sense (belief-desire reasoning) and all the social inference systems that create the logic of human social interaction--ones that enable as well as use inferences about the content of mental states--a broader conception of ToM may emerge: a computational model embodying

  12. Current-Sensing and Voltage-Feedback Driving Method for Large-Area High-Resolution Active Matrix Organic Light Emitting Diodes (United States)

    In, Hai‑Jung; Choi, Byong‑Deok; Chung, Ho‑Kyoon; Kwon, Oh‑Kyong


    There is the problem of picture quality nonuniformity due to thin film transistor (TFT) characteristic variations throughout a panel of large-area high-resolution active matrix organic light emitting diodes. The current programming method could solve this issue, but it also requires very long charging time of a data line at low gray shades. Therefore, we propose a new driving method and a pixel circuit with emission-current sensing and feedback operation in order to resolve these problems. The proposed driving method and pixel circuit successfully compensate threshold voltage and mobility variations of TFTs and overcome the data line charging problem. Simulation results show that emission current deviations of the proposed driving method are less than 1.7% with ± 10.0% mobility and ± 0.3 V threshold voltage variations of pixel-driving TFTs, which means the proposed driving method is applicable to large-area high-resolution applications.

  13. Compact high brightness diode laser emitting 500W from a 100μm fiber (United States)

    Heinemann, Stefan; Fritsche, Haro; Kruschke, Bastian; Schmidt, Torsten; Gries, Wolfgang


    High power, high brightness diode lasers are beginning to compete with solid state lasers, i.e. disk and fiber lasers. The core technologies for brightness scaling of diode lasers are optical stacking and dense spectral combining (DSC), as well as improvements of the diode material. Diode lasers have the lowest cost of ownership, highest efficiency and most compact design among all lasers. Multiple Single Emitter (MSE) modules allow highest power and highest brightness diode lasers based on standard broad area diodes. Multiple single emitters, each rated at 12 W, are stacked in the fast axis with a monolithic slow axis collimator (SAC) array. Volume Bragg Gratings (VBG) stabilizes the wavelength and narrow the linewidth to less than 1 nm. Dichroic mirrors are used for dense wavelength multiplexing of 4 channels within 12 nm. Subsequently polarization multiplexing generates 450 W with a beam quality of 4.5 mm*mrad. Fast control electronics and miniaturized switched power supplies enable pulse rise times of less than 10 μs, with pulse widths continuously adjustable from 20 μs to cw. Further power scaling up to multi-kilowatts can be achieved by multiplexing up to 16 channels. The power and brightness of these systems enables the use of direct diode lasers for cutting and welding. The technologies can be transferred to other wavelengths to include 793 nm and 1530 nm. Optimized spectral combining enables further improvements in spectral brightness and power.

  14. 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;


    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...

  15. The improved output performance of a broad-area vertical-cavity surface-emitting laser with an optimized electrode diameter

    Institute of Scientific and Technical Information of China (English)

    Zhang Xing; Ning Yong-Qiang; Qin Li; Tong Cun-Zhu; Liu Yun; Wang Li-Jun


    The output performance of a 980-nm broad-area vertical-cavity surface-emitting laser (VCSEL) is improved by optimizing the p-electrode diameter in this study.Based on a three-dimensional finite-element method,the current density distribution within the active region of the VCSEL is optimized through the appropriate adjustment of the p-electrode diameter,and uniform current-density distribution is achieved.Then,the effects of this optimization are studied experimentally.The L-I-V characteristics under different temperatures of the VCSELs with different p-electrode diameters are investigated,and better temperature stability is demonstrated in the VCSEL with an optimized p-electrode diameter.The far-field measurements show that with an injected current of 2 A,the far-field divergence angle of the VCSEL with an optimized p-electrode diameter is 9°,which is much lower than the far-field angle of the VCSEL without this optimization.Also the VCSEL with an optimized p-electrode diameter shows a better near-field distribution.

  16. Variability in radial sap flux density patterns and sapwood area among seven co-occurring temperate broad-leaved tree species. (United States)

    Gebauer, Tobias; Horna, Viviana; Leuschner, Christoph


    Forest transpiration estimates are frequently based on xylem sap flux measurements in the outer sections of the hydro-active stem sapwood. We used Granier's constant-heating technique with heating probes at various xylem depths to analyze radial patterns of sap flux density in the sapwood of seven broad-leaved tree species differing in wood density and xylem structure. Study aims were to (1) compare radial sap flux density profiles between diffuse- and ring-porous trees and (2) analyze the relationship between hydro-active sapwood area and stem diameter. In all investigated species except the diffuse-porous beech (Fagus sylvatica L.) and ring-porous ash (Fraxinus excelsior L.), sap flux density peaked at a depth of 1 to 4 cm beneath the cambium, revealing a hump-shaped curve with species-specific slopes. Beech and ash reached maximum sap flux densities immediately beneath the cambium in the youngest annual growth rings. Experiments with dyes showed that the hydro-active sapwood occupied 70 to 90% of the stem cross-sectional area in mature trees of diffuse-porous species, whereas it occupied only about 21% in ring-porous ash. Dendrochronological analyses indicated that vessels in the older sapwood may remain functional for 100 years or more in diffuse-porous species and for up to 27 years in ring-porous ash. We conclude that radial sap flux density patterns are largely dependent on tree species, which may introduce serious bias in sap-flux-derived forest transpiration estimates, if non-specific sap flux profiles are assumed.

  17. On-chip coherent combining of angled-grating diode lasers toward bar-scale single-mode lasers. (United States)

    Zhao, Yunsong; Zhu, Lin


    Single mode operation of broad-area diode lasers, which is the key to obtain high power, high brightness sources, is difficult due to highly nonlinear materials and strong coupling between gain and index. Conventional broad-area lasers usually operate with multiple modes and have poor beam quality. Laser bars usually consist of incoherently combined broad-area single emitters placed side by side. In this article, we have demonstrated a novel integrated laser architecture in which Bragg diffraction is used to realize simultaneous modal control and coherent combining of broad-area diode lasers. Our experimental results show that two 100 μm wide, 1.3mm long InP broad-area lasers provide near-diffraction-limited output beam and are coherently combined at the same time without any external optical components. Furthermore, our design can be expanded to a coherently combined broad-area laser array that turns a laser bar into a coherent single mode laser with diffraction-limited beam quality.

  18. Promoting Robust Design of Diode Lasers for Space: A National Initiative (United States)

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


    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

  19. Optimized high-power diode laser, laser arrays, and bars for pump applications (United States)

    Hülsewede, R.; Schulze, H.; Sebastian, J.; Schröder, D.; Meusel, J.; Wolf, J.; Hennig, P.


    Broad area diode laser and diode laser bars are the most efficient light sources. In comparison to solid state laser or gas laser systems the over all beam quality of the diode laser is poor. Thus most application of diode laser bars is high efficient pumping of solid state lasers converting the beam quality and scaling the power of laser systems within the kW range. The pump efficiency and the beam coupling efficiency of the diode laser pumped systems has to be increased to meet the increasing laser market demands for reduced costs. JENOPTIK Diode Lab GmbH (JDL) has optimized their high power brilliance bars to enable reliable high power operation especially, for the 9xx nm wavelength range and low far field divergences. Superior reliability with long operation time of 13,000 hours and high power operation of 200 W are demonstrated for high power bars high filling factor mounted on passively cooled heat sinks. Smaller far field divergence at high power levels requires longer cavity length and higher efficiencies in the beam coupling needs requires lower filling factors. The new high brilliance bars and arrays with 20% filling factor are showing high power operation up to 95 W and a slow axis beam divergence of less than 8° (95% power content).

  20. 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.;


    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...... lasers are 29+/-1 and 34+/-1, respectively. (C) 2003 American Institute of Physics.......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...

  1. Large area inkjet printing for organic photovoltaics and organic light emitting diodes using non-halogenated ink formulations

    NARCIS (Netherlands)

    Eggenhuisen, T.M.; Coenen, M.J.J.; Slaats, M.W.L.; Groen, W.A.


    The transfer of laboratory scale solution processing of organic electronics to large area roll-to-roll production requires the use of up-scalable deposition techniques. Furthermore, industrial production demands the omission of halogenated and other harmful solvents. Here, the authors discuss large

  2. Advances in high power semiconductor diode lasers (United States)

    Ma, Xiaoyu; Zhong, Li


    High power semiconductor lasers have broad applications in the fields of military and industry. Recent advances in high power semiconductor lasers are reviewed mainly in two aspects: improvements of diode lasers performance and optimization of packaging architectures of diode laser bars. Factors which determine the performance of diode lasers, such as power conversion efficiency, temperature of operation, reliability, wavelength stabilization etc., result from a combination of new semiconductor materials, new diode structures, careful material processing of bars. The latest progress of today's high-power diode lasers at home and abroad is briefly discussed and typical data are presented. The packaging process is of decisive importance for the applicability of high-power diode laser bars, not only technically but also economically. The packaging techniques include the material choosing and the structure optimizing of heat-sinks, the bonding between the array and the heat-sink, the cooling and the fiber coupling, etc. The status of packaging techniques is stressed. There are basically three different diode package architectural options according to the integration grade. Since the package design is dominated by the cooling aspect, different effective cooling techniques are promoted by different package architectures and specific demands. The benefit and utility of each package are strongly dependent upon the fundamental optoelectronic properties of the individual diode laser bars. Factors which influence these properties are outlined and comparisons of packaging approaches for these materials are made. Modularity of package for special application requirements is an important developing tendency for high power diode lasers.

  3. Diode lasers with asymmetric barriers for 850 nm spectral range: experimental studies of power characteristics


    Zubov, F. I.; Zhukov, A. E.; Shernyakov, Yu. M.; M. V. Maximov; Semenova, Elizaveta; Asryan, L. V.


    It is demonstrated that the use of asymmetric barrier layers in a waveguide of a diode laser suppress non-linearity of light-current characteristic and thus improve its power characteristics under high current injection. The results are presented for 850-nm AlGaAs/GaAs broad-area lasers with GaInP and AlInGaAs asymmetric barriers.

  4. High power pump laser diodes for 2μm fibre laser (United States)

    Pawlik, S.; Todt, R.; Moser, M.; Romero, O.; Lichtenstein, N.


    We report on our recent developments at II-VI Laser Enterprise of laser diode sources for the 79x nm range. High power conversion efficiency in excess of 62% was demonstrated. For high power applications like Thulium fiber laser pumping we have achieved an output power of more than 12.5W in CW operation for 94 μm wide broad-area single-emitters. We added the functionality of wavelength stabilization to the laser diodes by using a distributed feedback grating (DFB). Locking has been obtained over the full current range between 1A and 4A tested so far with some margin for temperature variation. For efficient fiber laser pumping the laser diodes were integrated in a multi-emitter platform, achieving 38 W out of a 105 μm fiber within 0.15 NA.

  5. High-power narrow-vertical-divergence photonic band crystal laser diodes with optimized epitaxial structure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lei; Qu, Hongwei; Liu, Yun; Zhang, Yejin; Zheng, Wanhua, E-mail: [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, CAS, Beijing 100083 (China); Laboratory of Solid State Optoelectronics Information Technology, Institute of Semiconductors, CAS, Beijing 100083 (China); Wang, Yufei; Qi, Aiyi [Laboratory of Solid State Optoelectronics Information Technology, Institute of Semiconductors, CAS, Beijing 100083 (China)


    900 nm longitudinal photonic band crystal (PBC) laser diodes with optimized epitaxial structure are fabricated. With a same calculated fundamental-mode divergence, stronger mode discrimination is achieved by a quasi-periodic index modulation in the PBC waveguide than a periodic one. Experiments show that the introduction of over 5.5 μm-thick PBC waveguide contributes to only 10% increment of the internal loss for the laser diodes. For broad area PBC lasers, output powers of 5.75 W under continuous wave test and over 10 W under quasi-continuous wave test are reported. The vertical divergence angles are 10.5° at full width at half maximum and 21.3° with 95% power content, in conformity with the simulated angles. Such device shows a prospect for high-power narrow-vertical-divergence laser emission from single diode laser and laser bar.

  6. Physics and Applications of Laser Diode Chaos

    CERN Document Server

    Sciamanna, Marc


    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.

  7. Effect of Top-Region Area of Flat-Top Pyramid Patterned Sapphire Substrate on the Optoelectronic Performance of GaN-Based Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Hsu-Hung Hsueh


    Full Text Available The flat-top pyramid patterned sapphire substrates (FTP-PSSs have been prepared for the growth of GaN epilayers and the fabrication of lateral-type light-emitting diodes (LEDs with an emission wavelength of approximately 470 nm. Three kinds of FTP-PSSs, which were denoted as FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C, respectively, were formed through the sequential wet etching processes. The diameters of circle areas on the top regions of these three FTP-PSSs were 1, 2, and 3 μm, respectively. Based on the X-ray diffraction results, the full-width at half-maximum values of rocking curves at (002 plane for the GaN epilayers grown on conventional sapphire substrate (CSS, FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 412, 238, 346, and 357 arcsec, while these values at (102 plane were 593, 327, 352, and 372 arcsec, respectively. The SpeCLED-Ratro simulation results reveal that the LED prepared on FTP-PSS-A has the highest light extraction efficiency than that of the other devices. At an injection current of 350 mA, the output powers of LEDs fabricated on CSS, FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 157, 254, 241, and 233 mW, respectively. The results indicate that both the crystal quality of GaN epilayer and the light extraction of LED can be improved via the use of FTP-PSS, especially for the FTP-PSS-A.

  8. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    DEFF Research Database (Denmark)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.;


    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...

  9. Coaxial foilless diode


    Long Kong; QingXiang Liu; XiangQiang Li; ShaoMeng Wang


    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...

  10. Header For Laser Diode (United States)

    Rall, Jonathan A. R.; Spadin, Paul L.


    Header designed to contain laser diode. Output combined incoherently with outputs of other laser diodes in grating laser-beam combiner in optical communication system. Provides electrical connections to laser diode, cooling to thermally stabilize laser operation, and optomechanical adjustments that steer and focus laser beam. Range of adjustments provides for correction of worst-case decentering and defocusing of laser beam encountered with laser diodes. Mechanical configuration made simple to promote stability and keep cost low.

  11. Laser Diode Ignition (LDI) (United States)

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


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

  12. An all-silicon passive optical diode. (United States)

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


    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.

  13. The 2010 Broad Prize (United States)

    Education Digest: Essential Readings Condensed for Quick Review, 2011


    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…

  14. Scaling the spectral beam combining channel by multiple diode laser stacks in an external cavity (United States)

    Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao; Lei, Fuchuan; Yu, Junhong; Tan, Hao


    Spectral beam combining of a broad area diode laser is a promising technique for direct diode laser applications. We present an experimental study of three mini-bar stacks in an external cavity on spectral beam combining in conjunction with spatial beam combining. At the pump current of 70 A, a CW output power of 579 W, spectral bandwidth of 18.8 nm and electro-optical conversion efficiency of 47% are achieved. The measured M 2 values of spectral beam combining are 18.4 and 14.7 for the fast and the slow axis, respectively. The brightness of the spectral beam combining output is 232 MW · cm‑2 · sr‑1.

  15. Efficient, high-brightness wavelength-beam-combined commercial off-the-shelf diode stacks achieved by use of a wavelength-chirped volume Bragg grating. (United States)

    Chann, B; Goyal, A K; Fan, T Y; Sanchez-Rubio, A; Volodin, B L; Ban, V S


    We report a method of scaling the spatial brightness from commercial off-the-shelf diode laser stacks through wavelength beam combining, by use of a linearly wavelength-chirped volume Bragg grating (VBG). Using a three-bar commercial stack of broad-area lasers and a VBG, we demonstrate 89.5 W cw of beam-combined output with a beam-combining efficiency of 75%. The output beam has a propagation factor M2 approximately 26 on the slow axis and M2 approximately 21 on the fast axis. This corresponds to a brightness of approximately 20 MW/cm2 sr. To our knowledge, this is the highest brightness broad-area diode laser system. We achieve 81% coupling efficiency into a 100 microm, 0.22 N.A. fiber.

  16. Terahertz Diode Development (United States)


    Gunn Diode , Negative Differential Resistance, Ballistic Transport, GaN, THz, Co-planar Resonator 16. SECURITY CLASSIFICATION OF: REPORT U b...Report DATES COVERED (From - Jo) 1 January 2004- 31 December 2008 4. TITLE AND SUBTITLE Terahertz Diode Development 5a. CONTRACT NUMBER N00014...current-voltage oscillations at the terminals of the diode at a frequency which is, to first order, determined by the average transit time of the EAL

  17. Comparison of Diode and Argon Laser Lesions in Rabbit Retina

    Institute of Scientific and Technical Information of China (English)

    Hui Zhang; Xiaoxin Li; Bin Li; Jiping Da


    Purpose: To compare the histological alteration of retina with various spot intensities between diode and argon lasers in order to instruct the clinical use of 810 nm diode laser.Methods: Transpupillary retinal photocoagulations were performed on 42 eyes of 27pigmented rabbits. Histopathologic alteration of lesions in different intensities and different time intervals after irradiation produced by diode and argon laser was observed and compared using light microscopy. Areas of various lesions measured by image analysis system (CMIAS) were compared quantitatively.Results: Histopathologically, two-week-old grade 2 lesions produced by diode laser induced the disappearance of outer nuclear cells. More than a half of all showed reduction in number of outer nuclear layer cells in argon. Fibroblasts appeared in the diode grade 3lesions 5 days after irradiation. CMIAS data showed that all the areas of diode lesions immediately after photocoagulation were to be larger than those of argon laser lesions in the same spot intensity (P < 0.05). However, twenty-four hours after photocoagulation, the area of the diode lesions increased less than that of the argon laser lesions (8%vs.23%).Conclusion: The acute histological effect caused by 810 nm diode laser and argon green laser is similar,while the expansion of lesion area 24 hours after photocoagulation was less with the diode laser compared to the argon. This may be the first report in the literature regarding quantitative analysis of the delayed reaction of argon green lasers.

  18. Versatile light-emitting-diode-based spectral response measurement system for photovoltaic device characterization. (United States)

    Hamadani, Behrang H; Roller, John; Dougherty, Brian; Yoon, Howard W


    An absolute differential spectral response measurement system for solar cells is presented. The system couples an array of light emitting diodes with an optical waveguide to provide large area illumination. Two unique yet complementary measurement methods were developed and tested with the same measurement apparatus. Good agreement was observed between the two methods based on testing of a variety of solar cells. The first method is a lock-in technique that can be performed over a broad pulse frequency range. The second method is based on synchronous multifrequency optical excitation and electrical detection. An innovative scheme for providing light bias during each measurement method is discussed.

  19. Improve the Performance of Integrated Diode Laser Beam Combining Through Grating Regrowth (United States)


    well suitable for high power diode lasers due to its excellent optical and electrical properties . However, AlGaAs is not ideal for the grating regrowth...combined lasers. However, the optical and electrical losses induced by the surface grating still limit the laser output power and efficiency. 3. in GaAs We will demonstrate the buried grating design for integrated broad area laser beam combining in AlGaAs -GaAs materials to obtain high power

  20. Advanced laser diodes for sensing applications

    Energy Technology Data Exchange (ETDEWEB)



    The authors have developed diode lasers for short pulse duration and high peak pulse power in the 0.01--100.0 m pulsewidth regime. A primary goal of the program was producing up to 10 W while maintaining good far-field beam quality and ease of manufacturability for low cost. High peak power, 17 W, picosecond pulses have been achieved by gain switching of flared geometry waveguide lasers and amplifiers. Such high powers area world record for this type of diode laser. The light emission pattern from diode lasers is of critical importance for sensing systems such as range finding and chemical detection. They have developed a new integrated optical beam transformer producing rib-waveguide diode lasers with a symmetric, low divergence, output beam and increased upper power limits for irreversible facet damage.

  1. 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


    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.

  2. An All-Silicon Passive Optical Diode


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


    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...

  3. The Broad Foundations, 2006 (United States)

    Broad Foundation, 2006


    The mission of the Broad Foundations is to transform K-12 urban public education through better governance, management, labor relations and competition; make significant contributions to advance major scientific and medical research; foster public appreciation of contemporary art by increasing access for audiences worldwide; and lead and…

  4. Powerful infrared emitting diodes

    Directory of Open Access Journals (Sweden)

    Kogan L. M.


    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.

  5. Chemically Modulated Graphene Diodes


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


    PUBLISHED 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 biocom...

  6. Diode lasers and photonic integrated circuits

    CERN Document Server

    Coldren, Larry A; Mashanovitch, Milan L


    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

  7. Planar jumping-drop thermal diodes (United States)

    Boreyko, Jonathan B.; Zhao, Yuejun; Chen, Chuan-Hua


    Phase-change thermal diodes rectify heat transport much more effectively than solid-state ones, but are limited by either the gravitational orientation or one-dimensional configuration. Here, we report a planar phase-change diode scalable to large areas with an orientation-independent diodicity of over 100, in which water/vapor is enclosed by parallel superhydrophobic and superhydrophilic plates. The thermal rectification is enabled by spontaneously jumping dropwise condensate which only occurs when the superhydrophobic surface is colder than the superhydrophilic surface.

  8. Barrier inhomogeneities limited current and 1/f noise transport in GaN based nanoscale Schottky barrier diodes. (United States)

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


    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.

  9. Barrier inhomogeneities limited current and 1/f noise transport in GaN based nanoscale Schottky barrier diodes (United States)

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


    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

  10. Deterministic polarization chaos from a laser diode

    CERN Document Server

    Virte, Martin; Thienpont, Hugo; Sciamanna, Marc


    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.

  11. Physical based Schottky barrier diode modeling for THz applications

    DEFF Research Database (Denmark)

    Yan, Lei; Krozer, Viktor; Michaelsen, Rasmus Schandorph;


    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...

  12. Growth of laser diode structures with emission wavelength beyond 1100 nm for yellow-green emission by frequency conversion (United States)

    Bugge, F.; Paschke, K.; Blume, G.; Feise, D.; Zeimer, U.; Weyers, M.


    Laser structures for emission wavelengths of 1120 nm and 1180 nm, suitable for non-linear frequency conversion to yellow-green and yellow-orange, were developed. At 1120 nm emission wavelength different active regions and structures were investigated. The introduction of a GaAs spacer layer between GaAsP barriers and InGaAs QWs reduces threshold and transparency current density significantly. Lifetime measurements were done successfully over 1700 h for broad area and 10 000 h for ridge waveguide tapered lasers. Broad area laser diodes with a partly strain-compensated 6 nm InGaAs QW, emitting at 1180 nm, show lifetimes above 1000 h at an output power of 1.5 W. The required beam quality was achieved by processing a ridge waveguide laser with an included distributed Bragg reflector. Such a laser emits up to 200 mW in single mode output power.

  13. Organic reprogrammable circuits based on electrochemically formed diodes. (United States)

    Liu, Jiang; Engquist, Isak; Berggren, Magnus


    We report a method to construct reprogrammable circuits based on organic electrochemical (EC) p-n junction diodes. The diodes are built up from the combination of the organic conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] and a polymer electrolyte. The p-n diodes are defined by EC doping performed at 70 °C, and then stabilized at -30 °C. The reversible EC reaction allows for in situ reprogramming of the polarity of the organic p-n junction, thus enabling us to reconfigure diode circuits. By combining diodes of specific polarities dedicated circuits have been created, such as various logic gates, a voltage limiter and an AC/DC converter. Reversing the EC reaction allows in situ reprogramming of the p-n junction polarity, thus enabling reconfiguration of diode circuits, for example, from an AND gate to an OR gate. The reprogrammable circuits are based on p-n diodes defined from only two layers, the electrodes and then the active semiconductor:electrolyte composite material. Such simple device structures are promising for large-area and fully printed reconfigurable circuits manufactured using common printing tools. The structure of the reported p-n diodes mimics the architecture of and is based on identical materials used to construct light-emitting electrochemical cells (LEC). Our findings thus provide a robust signal routing technology that is easily integrated with traditional LECs.

  14. Hyperchaos via X-Diode

    DEFF Research Database (Denmark)

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


    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 simulation...

  15. Wavelength stabilized multi-kW diode laser systems (United States)

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


    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.

  16. 100 years of the physics of diodes (United States)

    Zhang, Peng; Valfells, Ágúst; Ang, L. K.; Luginsland, J. W.; Lau, Y. Y.


    The Child-Langmuir Law (CL), discovered a century 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 nanoscale quantum diodes and nano gap based 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 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 photoemission) to the space charge limited state (CL) will be addressed, especially highlighting the important simulation and experimental developments in selected contemporary areas of study. We 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.

  17. Silicon Schottky Diode Safe Operating Area (United States)

    Casey, Megan C.; Lauenstein, Jean-Marie; Ladbury, Raymond L.; Wilcox, Edward P.; Phan, Anthony M.; Label, Kenneth A.


    Vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacementdamage is studied. Devices tested include optoelectronics, digital, analog, linear bipolar devices, and hybrid devices.

  18. High net modal gain (>100 cm(-1)) in 19-stacked InGaAs quantum dot laser diodes at 1000 nm wavelength band. (United States)

    Tanoue, Fumihiko; Sugawara, Hiroharu; Akahane, Kouichi; Yamamoto, Naokatsu


    An InGaAs quantum dot (QD) laser diode with 19-stacked QDs separated by 20 nm-thick GaAs spacers was fabricated using an ultrahigh-rate molecular beam epitaxial growth technique, and the laser characteristics were evaluated. A 19-stacked simple broad area QD laser diode was lased at the 1000 nm waveband. A net modal gain of 103 cm(-1) was obtained at 2.25 kA/cm(2), and the saturated modal gain was 145.6 cm(-1); these are the highest values obtained to our knowledge. These results indicate that using this technique to highly stack QDs is effective for improving the net modal gain of QD lasers.

  19. "Diode Pumped Solid State Lasers At 2 And 3 µm" (United States)

    Esterowitz, Leon


    The most attractive alternative to flashlamp pumping of solid state lasers is the diode laser. In the past two decades numerous laboratory devices have been assembled which incorporated single diode lasers, small laser diode arrays or LED's for pumping of Nd:YAG, Nd:glass and a host of other Nd lasers. The low power output, low packaging density, and extremely high cost of diode lasers prevented any serious applications for laser pumping in the past. The reason for the continued interest in this area stems from the potential dramatic increase in system efficiency and component lifetime, and reduction of thermal load of the solid-state laser material. The latter not only will reduce thereto-optic effects and therefore lead to better beam quality but also will enable an increase in pulse repetition frequency. The attractive operating parameters combined with low voltage operation and the compactness of an all solid-state laser system have a potential high payoff. The high pumping efficiency compared to flashlamps stems from the good spectral match between the laser diode emission and the rare earth activator absorption bands. A significant advantage of laser diode pumping compared to arc lamps is system lifetime and reliability. Laser diode arrays have exhibited lifetimes on the order of 10,000 hours in cw operation and 109 shots in the pulsed mode. Flashlamp life is on the order of 107 shots, and about 200 hours for cw operation. In addition, the high pump flux combined with a substantial UV content in lamp pumped systems causes material degradation in the pump cavity and in the coolant. Such problems are virtually eliminated with laser diode pump sources. The absence of high voltage pulses, high temperatures and UV radiation encountered with arc lamps leads to much more benign operating features for solid state laser systems employing laser diode pumps. Laser diode technology dates back to 1962 when laser action in GaAs diodes was first demonstrated. However, it

  20. Diode, transistor & fet circuits manual

    CERN Document Server

    Marston, R M


    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

  1. A comparative investigation on sub-micrometer InN and GaN Gunn diodes working at terahertz frequency (United States)

    Yang, Lin'an; Long, Shuang; Guo, Xin; Hao, Yue


    We report on a simulation for wurtzite-InN and GaN Gunn diodes with notch-doping and uniform-doping structural transit regions. Results show that 0.3-1.0 μm Gunn diodes with a diode area of 500 μm2 can generate fundamental frequencies of around 0.2-0.8 THz and rf currents of several hundred mA. InN diodes exhibit more stable oscillations, whereas GaN diodes generate higher oscillation frequencies at both dipole-domain mode and accumulation-domain mode due to different negative differential resistance (NDR) characteristics of high-field transport. The sharp NDR region of InN makes it more suitable for short transit region Gunn diode. Higher Irf/Iav and lower bias voltage in InN Gunn diode imply its conversion efficiency significantly higher than GaN diode.

  2. Rational Chebyshev Spectral Transform for the dynamics of high-power laser diodes

    CERN Document Server

    Javaloyes, J


    This manuscript details the use of the rational Chebyshev transform for describing the transverse dynamics of high-power laser diodes, either broad area lasers, index guided lasers or monolithic master oscillator power amplifier devices. This spectral method can be used in combination with the delay algebraic equation approach developed in \\cite{JB-OE-12}, which allows to substantially reduce the computation time. The theory is presented in such a way that it encompasses the case of the Fourier spectral transform presented in \\cite{PJB-JSTQE-13} as a particular case. It is also extended to the consideration of index guiding with an arbitrary 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 method. As practical examples, we solve the beam propagation problem with and without index guiding: we obtain excellent results and an improvement of th...

  3. Broad-spectrum antiviral agents

    Directory of Open Access Journals (Sweden)

    Jun-Da eZhu


    Full Text Available Development of highly effective, broad-spectrum antiviral agents is the major objective shared by the fields of virology and pharmaceutics. Antiviral drug development has focused on targeting viral entry and replication, as well as modulating cellular defense system. High throughput screening of molecules, genetic engineering of peptides, and functional screening of agents have identified promising candidates for development of optimal broad-spectrum antiviral agents to intervene in viral infection and control viral epidemics. This review discusses current knowledge, prospective applications, opportunities, and challenges in the development of broad-spectrum antiviral agents.

  4. Broad resonances in transport theory

    CERN Document Server

    Leupold, S


    The extension of the transport theoretical framework to include states with a broad mass distribution is discussed. The proper life-time and cross sections for a state with an arbitrarily given invariant mass is discussed in detail. (author)

  5. Diode laser applications in urology (United States)

    Sam, Richard C.; Esch, Victor C.


    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. Gallium phosphide high temperature diodes (United States)

    Chaffin, R. J.; Dawson, L. R.


    High temperature (300 C) diodes for geothermal and other energy applications were developed. A comparison of reverse leakage currents of Si, GaAs, and GaP was made. Diodes made from GaP should be usable to 500 C. A Liquid Phase Epitaxy (LPE) process for producing high quality, grown junction GaP diodes is described. This process uses low vapor pressure Mg as a dopant which allows multiple boat growth in the same LPE run. These LPE wafers were cut into die and metallized to make the diodes. These diodes produce leakage currents below ten to the -9th power A/sq cm at 400 C while exhibiting good high temperature rectification characteristics. High temperature life test data is presented which shows exceptional stability of the V-I characteristics.

  7. An Analysis of the Equivalent Resistance of PIN Diodes at Microwave Frequencies

    Institute of Scientific and Technical Information of China (English)

    YANG Guo-yu; SONG Kai-jun; MAO Rui-jie; LU Shi-qiang


    The forward bias equivalent resistance of PIN diodes, an important parameter in applications, is usually measured at lower frequencies. But in fact, due to skin effect the effective conduction area of the region I of a PIN diode decreases as the frequency increases. In this paper, the affection of skin effect to forward bias equivalent resistance is considered and an analytic expression of the equivalent resistance of the region I is presented. In result, the forward bias resistance ora PIN diode at microwave frequencies is much higher than that at DC and low frequencies. It is necessary, therefore,to consider the skin effect of PIN diodes in high frequency applications.

  8. 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


    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.

  9. 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) (United States)

    Ambrosius, I.; Mann, P.


    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

  10. Wavelength beam combining of a 980-nm tapered diode laser bar in an external cavity (United States)

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


    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.

  11. The Broad Autism Phenotype Questionnaire (United States)

    Hurley, Robert S. E.; Losh, Molly; Parlier, Morgan; Reznick, J. Steven; Piven, Joseph


    The broad autism phenotype (BAP) is a set of personality and language characteristics that reflect the phenotypic expression of the genetic liability to autism, in non-autistic relatives of autistic individuals. These characteristics are milder but qualitatively similar to the defining features of autism. A new instrument designed to measure the…

  12. Diode-pumped dye laser (United States)

    Burdukova, O. A.; Gorbunkov, M. V.; Petukhov, V. A.; Semenov, M. A.


    This letter reports diode pumping for dye lasers. We offer a pulsed dye laser with an astigmatism-compensated three-mirror cavity and side pumping by blue laser diodes with 200 ns pulse duration. Eight dyes were tested. Four dyes provided a slope efficiency of more than 10% and the highest slope efficiency (18%) was obtained for laser dye Coumarin 540A in benzyl alcohol.

  13. Broad Diphotons from Narrow States

    CERN Document Server

    An, Haipeng; Zhang, Yue


    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.

  14. 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. (United States)

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


    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

  15. 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 (United States)

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


    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.

  16. Al-free active region laser diodes at 894 nm for compact Cesium atomic clocks (United States)

    Von Bandel, N.; Bébé Manga Lobé, J.; Garcia, M.; Larrue, A.; Robert, Y.; Vinet, E.; Lecomte, M.; Drisse, O.; Parillaud, O.; Krakowski, M.


    Time-frequency applications are in need of high accuracy and high stability clocks. Compact industrial Cesium atomic clocks optically pumped is a promising area that could satisfy these demands. However, the stability of these clocks relies, among others, on the performances of laser diodes that are used for atomic pumping. This issue has led the III-V Lab to commit to the European Euripides-LAMA project that aims to provide competitive compact optical Cesium clocks for earth applications. This work will provide key experience for further space technology qualification. We are in charge of the design, fabrication and reliability of Distributed-Feedback diodes (DFB) at 894nm (D1 line of Cesium) and 852nm (D2 line). The use of D1 line for pumping will provide simplified clock architecture compared to D2 line pumping thanks to simpler atomic transitions and larger spectral separation between lines in the 894nm case. Also, D1 line pumping overcomes the issue of unpumped "dark states" that occur with D2 line. The modules should provide narrow linewidth (<1MHz), very good reliability in time and, crucially, be insensitive to optical feedback. The development of the 894nm wavelength is grounded on our previous results for 852nm DFB. Thus, we show our first results from Al-free active region with InGaAsP quantum well broad-area lasers (100μm width, with lengths ranging from 2mm to 4mm), for further DFB operation at 894nm. We obtained low internal losses below 2cm-1, the external differential efficiency is 0.49W/A with uncoated facets and a low threshold current density of 190A/cm², for 2mm lasers at 20°C.

  17. Broad-spectrum antiviral therapeutics.

    Directory of Open Access Journals (Sweden)

    Todd H Rider

    Full Text Available Currently there are relatively few antiviral therapeutics, and most which do exist are highly pathogen-specific or have other disadvantages. We have developed a new broad-spectrum antiviral approach, dubbed Double-stranded RNA (dsRNA Activated Caspase Oligomerizer (DRACO that selectively induces apoptosis in cells containing viral dsRNA, rapidly killing infected cells without harming uninfected cells. We have created DRACOs and shown that they are nontoxic in 11 mammalian cell types and effective against 15 different viruses, including dengue flavivirus, Amapari and Tacaribe arenaviruses, Guama bunyavirus, and H1N1 influenza. We have also demonstrated that DRACOs can rescue mice challenged with H1N1 influenza. DRACOs have the potential to be effective therapeutics or prophylactics for numerous clinical and priority viruses, due to the broad-spectrum sensitivity of the dsRNA detection domain, the potent activity of the apoptosis induction domain, and the novel direct linkage between the two which viruses have never encountered.

  18. Laser Diode Beam Basics, Manipulations and Characterizations

    CERN Document Server

    Sun, Haiyin


    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...

  19. 2.1 μm high-power laser diode beam combining(Conference Presentation) (United States)

    Berrou, Antoine P. C.; Elder, Ian F.; Lamb, Robert A.; Esser, M. J. Daniel


    Laser power and brightness scaling, in "eye safe" atmospheric transmission windows, is driving laser system research and development. High power lasers with good beam quality, at wavelength around 2.1 µm, are necessary for optical countermeasure applications. For such applications, focusing on efficiency and compactness of the system is mandatory. In order to cope with these requirements, one must consider the use of laser diodes which emit directly in the desired spectral region. The challenge for these diodes is to maintain a good beam quality factor as the output power increases. 2 µm diodes with excellent beam quality in both axes are available with output powers of 100 mW. Therefore, in order to reach multi-watt of average output power, broad-area single emitters and beam combining becomes relevant. Different solutions have been implemented in the 1.9 to 2 µm wavelength range, one of which is to stack multiple emitter bars reaching more than one hundred watt, while another is a fibre coupled diode module. The beam propagation factor of these systems is too high for long atmospheric propagation applications. Here we describe preliminary results on non-coherent beam combining of 2.1 µm high power Fabry-Perot GaSb laser diodes supplied by Brolis Semiconductors Ltd. First we evaluated single mode diodes (143 mW) with good beam quality (M2 beam consisted of two symmetric lobes with a total full width at half maximum (FWHM) divergence angle of 25 degrees, corresponding to a calculated beam quality factor of M2 = 25. The fast axis divergence was specified to be 44 degrees, with an expected beam quality factor close to the diffraction limit, which informed our selection of collimation lenses used in the experiment. We evaluated two broadband (1.8 - 3 µm) AR coated Geltech aspheric lenses with focal lengths of 1.87 mm and 4 mm, with numerical apertures of 0.85 and 0.56, respectively, as an initial collimation lens, followed by an additional cylindrical lens of

  20. Few-photon optical diode

    CERN Document Server

    Roy, Dibyendu


    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.

  1. Few-photon optical diode


    Roy, Dibyendu


    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...

  2. 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


    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.

  3. Scaling of nano-Schottky-diodes

    NARCIS (Netherlands)

    Smit, G.D.J.; Rogge, S.; Klapwijk, T.M.


    A generally applicable model is presented to describe the potential barrier shape in ultrasmall Schottky diodes. It is shown that for diodes smaller than a characteristic length lc (associated with the semiconductor doping level) the conventional description no longer holds. For such small diodes th

  4. 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


    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.

  5. Broad Area Wireless Networking Via High Altitude Platforms (United States)


    Multiplexing ORS Operationally Responsive Space OSINT Open-Source Intelligence PTMP Point To Multi-Point PTP Point To Point QOS Quality Of...Intelligence (SIGINT), Measurement and Signature Intelligence (MASINT), Human Resources Intelligence (HUMINT), and Open-Source Intelligence ( OSINT ) [34

  6. Broad Area Review of the Enhanced Flight Screening Program (United States)


    Kirkbymoorside, York, England. The aircraft is a Glass Reinforced Plastic ( GRP ) structure, low-wing monoplane with: a single Textron Lycoming, low pressure lines with compression pipe fittings, new calipers, new brake pads, and an improved fluid reservoir system. AETC/LGM reviewed the front of the engine via a 3/16 inch stainless steel pipe to the oil pressure indicator in the cockpit. A containment system consisting of a

  7. Spin-photon entangling diode

    DEFF Research Database (Denmark)

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


    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 t...

  8. Thermal-Diode Sandwich Panel (United States)

    Basiulis, A.


    Thermal diode sandwich panel transfers heat in one direction, but when heat load reversed, switches off and acts as thermal insulator. Proposed to control temperature in spacecraft and in supersonic missiles to protect internal electronics. In combination with conventional heat pipes, used in solar panels and other heat-sensitive systems.

  9. Handbook of distributed feedback laser diodes

    CERN Document Server

    Morthier, Geert


    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. Clinical analysis results of 1 857 cases different areas of female in hair removal with diode laser in xinjiang%新疆地区1857例女性不同部位激光脱毛效果临床分析

    Institute of Scientific and Technical Information of China (English)

    朱淑萍; 陈梅; 张曼鑫; 马玲


    目的:评价半导体激光脱毛仪对新疆地区女性不同部位激光脱毛效果的疗效.方法:采用半导体激光脱毛仪为1 857例新疆地区女性全身不同部位脱毛,其中维吾尔族32例,哈萨克族9例,蒙古族16例,其余均为汉族女性,毛发生长部位无明显的种族差异.包括面部绒毛、唇部、鬓角、前后发际、腋下、上臂、前臂、手背、腰骶部、腹部、大腿、小腿、足背、比基尼等部位行脱毛治疗,并对脱毛结果进行分析.结果:脱毛治疗次数最少3次,最多20次,总有效率:面部86.46%、上唇93.22%、发际99.78%、鬓角98.67%、腋下98.22%、上臂96.79%、小臂96.54%、手背94.65%、腰骶部99.32%、下腹部97.56%、大腿93.29%、小腿98.54%、足背部97.34%、比基尼100%.结论:半导体激光脱毛仪对新疆地区女性不同部位脱毛疗效安全、可靠,值得进一步推广应用.%Objective To evaluate the efficiency of hair removal of female different part with diode laser. Methods Diode laser was used to remove hairs of 1857 cases women, including uygur 32 cases, hazak 9 cases, Mongolia 16 cases, and Han population 1800 cases. Different areas of female, including face, lips, hairlines, temples, armpit, upper arms, antebrachiums, opisthenar, lumbosacral area .abdominal part, thighs, shanks, instep .bikinis areas. Results At least three times, the maximum 20 times, were needed to achieve satisfactory results. Total effective ratio increased with the treatment times but depended on the area: face86.46%,lips93.22%,hairlines99.78%,temples98.67%,armpit98.22%, upper arms96.79%,antebrachiums96.54%,opisthenar94.65%, lumbosacral area99.32%.abdominal part97.56%,thighs93.29%, shanks98.54%, instep 97.34%, bikinis areas 100%. Conclusions Diode laser is a safe and efficient method of hair removal, and is worthy to application.

  11. Broad Leaves in Strong Flow

    CERN Document Server

    Miller, Laura


    Flexible broad leaves are thought to reconfigure in the wind and water to reduce the drag forces that act upon them. Simple mathematical models of a flexible beam immersed in a two-dimensional flow will also exhibit this behavior. What is less understood is how the mechanical properties of a leaf in a three-dimensional flow will passively allow roll up into a cone shape and reduce both drag and vortex induced oscillations. In this fluid dynamics video, the flows around the leaves are compared with those of simplified sheets using 3D numerical simulations and physical models. For some reconfiguration shapes, large forces and oscillations due to strong vortex shedding are produced. In the actual leaf, a stable recirculation zone is formed within the wake of the reconfigured cone. In physical and numerical models that reconfigure into cones, a similar recirculation zone is observed with both rigid and flexible tethers. These results suggest that the three-dimensional cone structure in addition to flexibility is ...

  12. Influence of laser diode red beams on germination rate of tomato seeds (United States)

    Niculita, P.; Danaila-Guidea, Silvana; Livadariu, Oana; Popa, M.; Ristici, M.; Ristici, Esofina


    Laser diodes are lighting devices in which the light is generated by stimulated emission rather than spontaneous emission, with high generation efficiency. A device using 20 red laser diodes is presented. Emission wavelengths are in the 650-670 nm range. Emission power for each laser diode is about 4 mW. This device is used to irradiate the tomato seeds with three different irradiating doses. There were three Petri vessels for each dose having 25 seeds each of them. Results show that the germination rate increases for irradiated seeds. The red light has a positive effect for vegetable cultivated in protected area.

  13. Operational characteristics and analysis of the immersed-Bz diode on RITS-3.

    Energy Technology Data Exchange (ETDEWEB)

    Bruner, Nichelle " Nicki" ; Oliver, Bryan Velten; Portillo, Salvador; Puetz, Elizabeth A.; Johnston, Mark D.; Welch, Dale Robert; Rose, David Vincent; Cooper, G.M. (AWE, Aldermaston, Reading, United Kingdom); McLean, John (AWE, Aldermaston, Reading, United Kingdom); Rovang, Dean Curtis; Maenchen, John Eric


    The immersed-B{sub z} diode is being developed as a high-brightness, flash x-ray radiography source. This diode is a foil-less electron-beam diode with a long, thin, needle-like cathode inserted into the bore of a solenoid. The solenoidal magnetic field guides the electron beam emitted from the cathode to the anode while maintaining a small beam radius. The electron beam strikes a thin, high-atomic-number anode and produces bremsstrahlung. We report on an extensive series of experiments where an immersed-B{sub z} diode was fielded on the RITS-3 pulsed power accelerator, a 3-cell inductive voltage generator that produced peak voltages between 4 and 5 MV, {approx}140 kA of total current, and power pulse widths of {approx}50 ns. The diode is a high impedance device that, for these parameters, nominally conducts {approx}30 kA of electron beam current. Diode operating characteristics are presented and two broadly characterized operating regimes are identified: a nominal operating regime where the total diode current is characterized as classically bipolar and an anomalous impedance collapse regime where the total diode current is in excess of the bipolar limit and up to the full accelerator current. The operating regimes are approximately separated by cathode diameters greater than {approx}3 mm for the nominal regime and less than {approx} 3 mm for the anomalous impedance collapse regime. This report represents a compilation of data taken on RITS-3. Results from key parameter variations are presented in the main body of the report and include cathode diameter, anode-cathode gap, and anode material. Results from supporting parameter variations are presented in the appendices and include magnetic field strength, prepulse, pressure and accelerator variations.

  14. 76 FR 34087 - Broad Stakeholder Survey (United States)


    ... 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...

  15. 78 FR 20119 - Broad Stakeholder Survey (United States)


    ... 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...

  16. 77 FR 50144 - Broad Stakeholder Survey (United States)


    ... 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...

  17. Destructive Single-Event Failures in Diodes (United States)

    Casey, Megan C.; Gigliuto, Robert A.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Kim, Hak; Chen, Dakai; Phan, Anthony M.; LaBel, Kenneth A.


    In this summary, we have shown that diodes are susceptible to destructive single-event effects, and that these failures occur along the guard ring. By determining the last passing voltages, a safe operating area can be derived. By derating off of those values, rather than by the rated voltage, like what is currently done with power MOSFETs, we can work to ensure the safety of future missions. However, there are still open questions about these failures. Are they limited to a single manufacturer, a small number, or all of them? Is there a threshold rated voltage that must be exceeded to see these failures? With future work, we hope to answer these questions. In the full paper, laser results will also be presented to verify that failures only occur along the guard ring.

  18. Ultrafast and nanoscale diodes (United States)

    Zhang, Peng; Lau, Y. Y.


    Charge carrier transport across interfaces of dissimilar materials (including vacuum) is the essence of all electronic devices. Ultrafast charge transport across a nanometre length scale is of fundamental importance in the miniaturization of vacuum and plasma electronics. With the combination of recent advances in electronics, photonics and nanotechnology, these miniature devices may integrate with solid-state platforms, achieving superior performance. This paper reviews recent modelling efforts on quantum tunnelling, ultrafast electron emission and transport, and electrical contact resistance. Unsolved problems and challenges in these areas are addressed.

  19. Megahertz organic/polymer diodes (United States)

    Katz, Howard Edan; Sun, Jia; Pal, Nath Bhola


    Featured is an organic/polymer diode having a first layer composed essentially of one of an organic semiconductor material or a polymeric semiconductor material and a second layer formed on the first layer and being electrically coupled to the first layer such that current flows through the layers in one direction when a voltage is applied in one direction. The second layer is essentially composed of a material whose characteristics and properties are such that when formed on the first layer, the diode is capable of high frequency rectifications on the order of megahertz rectifications such as for example rectifications at one of above 100KHz, 500KhZ, IMHz, or 10 MHz. In further embodiments, the layers are arranged so as to be exposed to atmosphere.


    Directory of Open Access Journals (Sweden)

    Aririguzo Marvis Ijeaku


    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.

  1. Enhanced Light Extraction from a GaN-based Light Emitting Diode with Triangle Grating Structure

    Directory of Open Access Journals (Sweden)

    Li Cheng


    Full Text Available We propose a simple method to improve the light extraction in GaN based light emitting diode. Conventional light emitting diode has an extraction limitation due to the total internal reflection which occurs at the interface between GaN and air. By using periodic grating etched at the GaN layer, we can couple more emitting light out of the active layer. Tapering the grating structure would facilitate the impedance matching between GaN light emitting diode and air, which can enhance broadband light extraction. We use finite difference time domain method to numerically find the best tapering grating structure. The numerical experiment demonstrate an enhance factor 4 of our proposed structure compared with the conventional one over broad band specctrum.

  2. Visible electroluminescence from p-n junction porous Si diode with a polyaniline film contact

    Institute of Scientific and Technical Information of China (English)

    Hongjian Li (李宏建); Baiyun Huang (黄伯云); Danqing Yi (易丹青); Haoyang Gui (崔昊杨); Jingcui Peng (彭景翠)


    We have fabricated a light emitting diode using a p-type conducting polyaniline layer deposited on a n-type porous silicon (PS) layer. The contact formed between a p-type conducting polyaniline layer and a n-type PS wafer has rectified behaviour demonstrated clearly by the I-V curves. The series resistance Rs in the p-type conducting polyaniline/n-PS diode is reduced greatly and has a lower onset voltage compared with ITO/n-PS diode. The PS has an orange photoluminescence (PL) band after coating with polyaniline.Visible electroluminescence (EL) has been obtained from this junction when a forward bias is applied. The emission band is very broad extending from 600 - 803 nm with a peak at 690 nm.

  3. P-N junction and metal contact reliability of SiC diode in high temperature (873 K) environment (United States)

    Chand, R.; Esashi, M.; Tanaka, S.


    This paper reports the high temperature test results of SiC p-n junction diode up to 873 K. No significant change in diode series resistance (Rs) and a diode ideality factor of 1.02 were confirmed in air. We used the 4H-SiC diode which had a contact pad area of 300 μm × 300 μm and a junction area of 220 μm × 220 μm. Ohmic contact on both p and n (i.e. front and back) sides were made by Ni, because nickel silicide (NiSi) provides good ohmic contact for high temperature applications. The electrical contact pads of the SiC diode were made by sputter-depositing Ni or Pt on the NiSi ohmic contact. High temperature aging tests at 673 K, 773 K and 873 K were carried out in air, and the forward current-voltage (I-V) characteristics of the SiC diodes were measured at different time intervals to observe change in the junction and series resistance. Stable p-n junction characteristic and constant series resistance were confirmed for the Pt-metalized diodes at 673 K, 773 K and 873 K. However, the Ni-metallized diodes showed marginal increase in series resistance due to the oxidation of Ni metal contacts.

  4. Electromagnetic wave analogue of electronic diode


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


    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 ...

  5. Effects of radiation on laser diodes.

    Energy Technology Data Exchange (ETDEWEB)

    Phifer, Carol Celeste


    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.

  6. All-carbon nanotube diode and solar cell statistically formed from macroscopic network

    Institute of Scientific and Technical Information of China (English)

    Albert G. Nasibulin[1,2,3; Adinath M. Funde[3,4; Ilya V. Anoshkin[3; Igor A. Levitskyt[5,6


    Schottky diodes and solar cells are statistically created in the contact area between two macroscopic films of single-walled carbon nanotubes (SWNTs) at the junction of semiconducting and quasi-metallic bundles consisting of several high quality tubes. The n-doping of one of the films allows for photovoltaic action, owing to an increase in the built-in potential at the bundle-to-bundle interface. Statistical analysis demonstrates that the Schottky barrier device contributes significantly to the I-V characteristics, compared to the p-n diode. The upper limit of photovoltaic conversion efficiency has been estimated at N20%, demonstrating that the light energy conversion is very efficient for such a unique solar cell. While there have been multiple studies on rectifying SWNT diodes in the nanoscale environment, this is the first report of a macroscopic all-carbon nanotube diode and solar cell.

  7. Broad Prize: Do the Successes Spread? (United States)

    Samuels, Christina A.


    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…

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

    KAUST Repository

    Majid, M. A.


    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.

  9. Temperature dependence of commercially available diode detectors. (United States)

    Saini, Amarjit S; Zhu, Timothy C


    Temperature dependence of commercially available n- and p-type diodes were studied experimentally under both high instantaneous dose rate (pulsed) and low dose rate (continuous) radiation. The sensitivity versus temperature was measured at SSD = 80 or 100 cm, 10 x 10 cm2, and 5 cm depth in a 30 x 30 x 30 cm3 water phantom between 10 degrees C and 35 degrees C. The response was linear for all the diode detectors. The temperature coefficient (or sensitivity variation with temperature, svwt) was dose rate independent for preirradiated diodes. They were (0.30 +/- 0.01)%/degrees C, (0.36 +/- 0.03)%/degrees C, and (0.29 +/- 0.08)%/degrees C for QED p-type, EDP p-type, and Isorad n-type diodes, respectively. The temperature coefficient for unirradiated n-type diodes was different under low dose rate [(0.16 to 0.45)%/degrees C, continuous, cobalt] and high instantaneous dose rate [(0.07 +/- 0.02)%/degrees C, pulsed radiation]. Moreover, the temperature coefficient varies among individual diodes. Similarly, the temperature coefficient for a special unirradiated QED p-type diode was different under low dose rate (0.34%/degrees C, cobalt) and high instantaneous dose rate [(0.26 +/- 0.01)%/degrees C, pulsed radiation]. Sufficient preirradiation can eliminate dose rate dependence of the temperature coefficient. On the contrary, preirradiation cannot eliminate dose rate dependence of the diode sensitivity itself.

  10. Materials for diode pumped solid state lasers (United States)

    Chase, L. L.; Davis, L. E.; Krupke, W. F.; Payne, S. A.


    The advantages of semiconductor diode lasers and laser arrays as pump sources for solid state lasers are reviewed. The properties that are desirable in solid state laser media for various diode pumping applications are discussed, and the characteristics of several promising media are summarized.

  11. Laser diode package with enhanced cooling (United States)

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


    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.

  12. Electromagnetic wave analogue of electronic diode

    CERN Document Server

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


    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.

  13. Hermetic diode laser transmitter module (United States)

    Ollila, Jyrki; Kautio, Kari; Vahakangas, Jouko; Hannula, Tapio; Kopola, Harri K.; Oikarinen, Jorma; Sivonen, Matti


    In very demanding optoelectronic sensor applications it is necessary to encapsulate semiconductor components hermetically in metal housings to ensure reliable operation of the sensor. In this paper we report on the development work to package a laser diode transmitter module for a time- off-light distance sensor application. The module consists of a lens, laser diode, electronic circuit and optomechanics. Specifications include high acceleration, -40....+75 degree(s)C temperature range, very low gas leakage and mass-production capability. We have applied solder glasses for sealing optical lenses and electrical leads hermetically into a metal case. The lens-metal case sealing has been made by using a special soldering glass preform preserving the optical quality of the lens. The metal housings are finally sealed in an inert atmosphere by welding. The assembly concept to retain excellent optical power and tight optical axis alignment specifications is described. The reliability of the laser modules manufactured has been extensively tested using different aging and environmental test procedures. Sealed packages achieve MIL- 883 standard requirements for gas leakage.

  14. Optical mode engineering and high power density per facet length (>8.4 kW/cm) in tilted wave laser diodes (United States)

    Ledentsov, N. N.; Shchukin, V. A.; Maximov, M. V.; Gordeev, N. Y.; Kaluzhniy, N. A.; Mintairov, S. A.; Payusov, A. S.; Shernyakov, Yu. M.


    Tilted Wave Lasers (TWLs) based on optically coupled thin active waveguide and thick passive waveguide offer an ultimate solution for thick-waveguide diode laser, preventing catastrophic optical mirror damage and thermal smile in laser bars, providing robust operation in external cavity modules thus enabling wavelength division multiplexing and further increase in brightness enabling direct applications of laser diodes in the mainstream material processing. We show that by proper engineering of the waveguide one can realize high performance laser diodes at different tilt angles of the vertical lobes. Two vertical lobes directed at various angles (namely, +/-27° or +/-9°) to the junction plane are experimentally realized by adjusting the compositions and the thicknesses of the active and the passive waveguide sections. The vertical far field of a TWL with the two +/-9° vertical beams allows above 95% of all the power to be concentrated within a vertical angle below 25°, the fact which is important for laser stack applications using conventional optical coupling schemes. The full width at half maximum of each beam of the value of 1.7° evidences diffraction- limited operation. The broad area (50 μm) TWL chips at the cavity length of 1.5 mm reveal a high differential efficiency ~90% and a current-source limited pulsed power >42W for as-cleaved TWL device. Thus the power per facet length in a laser bar in excess of 8.4 kW/cm can be realized. Further, an ultimate solution for the smallest tilt angle is that where the two vertical lobes merge forming a single lobe directed at the zero angle is proposed.

  15. Study on photon sensitivity of silicon diodes related to materials used for shielding (United States)

    Moiseev, T.


    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.

  16. 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


    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.

  17. Influenza virus antigenicity and broadly neutralizing epitopes. (United States)

    Air, Gillian M


    A vaccine formulation that would be effective against all strains of influenza virus has long been a goal of vaccine developers, but antibodies after infection or vaccination were seen to be strain specific and there was little evidence of cross-reactive antibodies that neutralized across subtypes. Recently a number of broadly neutralizing monoclonal antibodies have been characterized. This review describes the different classes of broadly neutralizing antibodies and discusses the potential of their therapeutic use or for design of immunogens that induce a high proportion of broadly neutralizing antibodies.

  18. Measuring Prevention More Broadly, An Empirical... (United States)

    U.S. Department of Health & Human Services — Measuring Prevention More Broadly, An Empirical Assessment of CHIPRA Core Measures Differences in CHIP design and structure, across states and over time, may limit...

  19. 946 nm Diode Pumped Laser Produces 100mJ (United States)

    Axenson, Theresa J.; Barnes, Norman P.; Reichle, Donald J., Jr.


    An innovative approach to obtaining high energy at 946 nm has yielded 101 mJ of laser energy with an optical-to-optical slope efficiency of 24.5%. A single gain module resonator was evaluated, yielding a maximum output energy of 50 mJ. In order to obtain higher energy a second gain module was incorporated into the resonator. This innovative approach produced un-surprised output energy of 101 mJ. This is of utmost importance since it demonstrates that the laser output energy scales directly with the number of gain modules. Therefore, higher energies can be realized by simply increasing the number of gain modules within the laser oscillator. The laser resonator incorporates two gain modules into a folded "M-shaped" resonator, allowing a quadruple pass gain within each rod. Each of these modules consists of a diode (stack of 30 microlensed 100 Watt diode array bars, each with its own fiber lens) end-pumping a Nd:YAG laser rod. The diode output is collected by a lens duct, which focuses the energy into a 2 mm diameter flat to flat octagonal pump area of the laser crystal. Special coatings have been developed to mitigate energy storage problems, including parasitic lasing and amplified spontaneous emission (ASE), and encourage the resonator to operate at the lower gain transition at 946 nm.

  20. Nickel-gallium arsenide high-voltage power Schottky diodes (United States)

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


    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.


    Directory of Open Access Journals (Sweden)

    Subba Rao


    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

  2. Liquid metal heat sink for high-power laser diodes (United States)

    Vetrovec, John; Litt, Amardeep S.; Copeland, Drew A.; Junghans, Jeremy; Durkee, Roger


    We report on the development of a novel, ultra-low thermal resistance active heat sink (AHS) for thermal management of high-power laser diodes (HPLD) and other electronic and photonic components. AHS uses a liquid metal coolant flowing at high speed in a miniature closed and sealed loop. The liquid metal coolant receives waste heat from an HPLD at high flux and transfers it at much reduced flux to environment, primary coolant fluid, heat pipe, or structure. Liquid metal flow is maintained electromagnetically without any moving parts. Velocity of liquid metal flow can be controlled electronically, thus allowing for temperature control of HPLD wavelength. This feature also enables operation at a stable wavelength over a broad range of ambient conditions. Results from testing an HPLD cooled by AHS are presented.

  3. 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


    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.

  4. Full-quantum light diode

    CERN Document Server

    Ghobadi, Roohollah


    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.

  5. Bilayer avalanche spin-diode logic

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Joseph S., E-mail:; 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)


    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. Diamond based light-emitting diode for visible single-photon emission at room temperature (United States)

    Lohrmann, A.; Pezzagna, S.; Dobrinets, I.; Spinicelli, P.; Jacques, V.; Roch, J.-F.; Meijer, J.; Zaitsev, A. M.


    Diamond-based p-i-n light-emitting diodes capable of single-photon emission in the visible spectral region at room temperature are discussed. The diodes were fabricated on a high quality single crystal diamond grown by chemical vapor deposition. Implantation of boron and phosphorus ions followed by annealing at a temperature of 1600 °C has been used for doping p-type and n-type areas, respectively. Electrical characterization of the devices demonstrates clear diode behavior. Spectra of electroluminescence generated in the i-area reveal sole emission from the neutral nitrogen-vacancy (NV) defects. Photon antibunching implies single-photon character of this emission when generated by individual NV defects.

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


    Cappuccio, Joseph C., Jr.


    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. Arbitrary waveform generator to improve laser diode driver performance (United States)

    Fulkerson, Jr, Edward Steven


    An arbitrary waveform generator modifies the input signal to a laser diode driver circuit in order to reduce the overshoot/undershoot and provide a "flat-top" signal to the laser diode driver circuit. The input signal is modified based on the original received signal and the feedback from the laser diode by measuring the actual current flowing in the laser diode after the original signal is applied to the laser diode.

  9. 33 CFR 110.27 - Lynn Harbor in Broad Sound, Mass. (United States)


    ... 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...

  10. 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


    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.

  11. Temperature change during non-contact diode laser irradiation of implant surfaces. (United States)

    Geminiani, Alessandro; Caton, Jack G; Romanos, Georgios E


    A temperature increase of more than 10°C can compromise bone vitality. Laser radiation with different wavelengths has been used for the treatment of peri-implantitis, but little is known about the effect of laser irradiation on temperature rise on the implant surface. In this study, the temperature gradient (∆T) generated by laser irradiation of implant surface using two diode lasers (810 nm and a 980 nm) with 2 W of power has been recorded by two thermocouples (one in the cervical area and one in the apical area) and studied. The 810-nm diode laser showed the following results: after 60 s of irradiation with 2 W of continuous mode the temperature gradient in the cervical area of the implant (∆Tc) was 37.2°C, while in the apical area (∆Ta) was 27.2°C. The 980-nm diode laser showed the following results: after 60 s of irradiation with 2 W continuous mode ∆Tc was 41.1°C, and ∆Ta was 30.6°C. The 810-nm diode laser with 2 W continuous mode generated a temperature increase of 10°C after only 14 s. The 980-nm diode lasers groups produced a much more rapid temperature increase. In only 12 s, the continuous wave of 980 nm reached the 10°C temperature rise. From the present in vitro study it was concluded that the irradiation of implant surfaces with diode lasers may produce a temperature increase above the critical threshold (10°C ) after only 10 s.

  12. A Criterion for Rating the Usability and Accuracy of the One-Diode Models for Photovoltaic Modules


    Aldo Orioli; Alessandra Di Gangi


    In selecting a mathematical model for simulating physical behaviours, it is important to reach an acceptable compromise between analytical complexity and achievable precision. With the aim of helping researchers and designers working in the area of photovoltaic systems to make a choice among the numerous diode-based models, a criterion for rating both the usability and accuracy of one-diode models is proposed in this paper. A three-level rating scale, which considers the ease of finding the d...

  13. High Power Diode Lasers Technology and Applications

    CERN Document Server

    Bachmann, Friedrich; Poprawe, Reinhart


    In a very comprehensive way this book covers all aspects of high power diode laser technology for materials processing. Basics as well as new application oriented results obtained in a government funded national German research project are described in detail. Along the technological chain after a short introduction in the second chapter diode laser bar technology is discussed regarding structure, manufacturing technology and metrology. The third chapter illuminates all aspects of mounting and cooling, whereas chapter four gives wide spanning details on beam forming, beam guiding and beam combination, which are essential topics for incoherently coupled multi-emitter based high power diode lasers. Metrology, standards and safety aspects are the theme of chapter five. As an outcome of all the knowledge from chapter two to four various system configurations of high power diode lasers are described in chapter six; not only systems focussed on best available beam quality but especially also so called "modular" set...

  14. I-V characteristics of foilless diodes

    Institute of Scientific and Technical Information of China (English)

    Liu Guo-Zhi; Huang Wen-Hua; Yang Zhan-Feng


    Some physical characteristics of foilless diodes are obtained and analysed by numerical simulations. Relations between diode current andconfiguration parameters, i.e. diode voltage and external magnetic field, are investigated.Employing these relations and assuming that the external magnetic field is strong enough, the diode current can be approximately written as Ib=(7.5/x)(x+(0.81-x)/(1+0.7Ld2/δr))(γ0 2/3-1)3/2, in which Ld is the Anode-Cathode(AK) gap, Rc the outer radius of cathode, and Rp the radius of drifting tube; x=ln(Rp/Rc), δr=Rp- Rc. This expression is comparatively accurate for different configuration parameters and voltages; results obtained from this expression are consistent with that of numerical simulations within an error of 10%.

  15. Diode laser (980nm) cartilage reshaping (United States)

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


    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. 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


    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.

  17. Interferometry and Holography With Diode Laser Light

    CERN Document Server

    Lunazzi, Jose Joaquin


    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.

  18. Phase Noise Reduction of Laser Diode (United States)

    Zhang, T. C.; Poizat, J.-Ph.; Grelu, P.; Roch, J.-F.; Grangier, P.; Marin, F.; Bramati, A.; Jost, V.; Levenson, M. D.; Giacobino, E.


    Phase noise of single mode laser diodes, either free-running or using line narrowing technique at room temperature, namely injection-locking, has been investigated. It is shown that free-running diodes exhibit very large excess phase noise, typically more than 80 dB above shot-noise at 10 MHz, which can be significantly reduced by the above-mentioned technique.

  19. Bypass diode for a solar cell (United States)

    Rim, Seung Bum; Kim, Taeseok; Smith, David D.; Cousins, Peter J.


    Bypass diodes for solar cells are described. In one embodiment, a bypass diode for a solar cell includes a substrate of the solar cell. A first conductive region is disposed above the substrate, the first conductive region of a first conductivity type. A second conductive region is disposed on the first conductive region, the second conductive region of a second conductivity type opposite the first conductivity type.

  20. Varactor diodes for millimeter and submillimeter wavelengths (United States)

    Rizzi, Brian J.; Hesler, Jeffrey L.; Dossal, Hasan; Crowe, Thomas W.


    Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.

  1. Giant Broad Line Regions in Dwarf Seyferts

    CERN Document Server

    Devereux, Nick


    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, ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xianmei; Wang, Yilin; Gule, Teri; Luo, Qiang [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China); Zhou, Liya, E-mail: [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China); Gong, Fuzhong [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China)


    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. Modelling Demand for Broad Money in Australia


    Abbas Valadkhani


    The existence of a stable demand for money is very important for the conduct of monetary policy. It is argued that previous work on the demand for money in Australia has not been very satisfactory in a number of ways. This paper examines the long- and short-run determinants of the demand for broad money employing the Johansen cointegration technique and a short-run dynamic model. Using quarterly data for the period 1976:3-2002:2, this paper finds, inter alia, that the demand for broad money i...

  4. Mutual phase locking of a coupled laser diode-Gunn diode pair


    Izadpanah, S.H; Rav-Noy, Z.; Mukai, S.; Margalit, S.; Yariv, Amnon


    Mutual phase locking has been achieved through series connection of a semiconductor laser and a Gunn diode oscillator. Experimental results obtained demonstrate a mutual interaction between the two oscillators which results in a short term Gunn diode oscillator stability and improved spectral purity of its output. We also observe a narrowing of laser pulses and an improvement in regularity.

  5. 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


    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...

  6. Teaching the Broad, Interdisciplinary Impact of Evolution (United States)

    Benson, David; Atlas, Pierre; Haberski, Raymond; Higgs, Jamie; Kiley, Patrick; Maxwell, Michael, Jr.; Mirola, William; Norton, Jamey


    As perhaps the most encompassing idea in biology, evolution has impacted not only science, but other academic disciplines as well. The broad, interdisciplinary impact of evolution was the theme of a course taught at Marian College, Indianapolis, Indiana in 2002, 2004, and 2006. Using a strategy that could be readily adopted at other institutions,…

  7. The GREGOR Broad-Band Imager (United States)

    von der Lühe, O.; Volkmer, R.; Kentischer, T. J.; Geißler, R.


    The design and characteristics of the Broad-Band Imager (BBI) of GREGOR are described. BBI covers the visible spectral range with two cameras simultaneously for a large field and with critical sampling at 390 nm, and it includes a mode for observing the pupil in a Foucault configuration. Samples of first-light observations are shown.

  8. Nitride superluminescent diodes with broadened emission spectrum fabricated using laterally patterned substrate. (United States)

    Kafar, A; Stanczyk, S; Sarzynski, M; Grzanka, S; Goss, J; Targowski, G; Nowakowska-Siwinska, A; Suski, T; Perlin, P


    We demonstrate InGaN/GaN superluminescent diodes with broadened emission spectra fabricated on surface-shaped bulk GaN (0001) substrates. The patterning changes the local vicinal angle linearly along the device waveguide, which results in an indium incorporation profile in InGaN quantum wells. The structure was investigated by microphotoluminescence mapping, showing a shift of central emission wavelength from 413 nm to 430 nm. Spectral full width at half maximum of processed superluminescent diodes is equal to 6.1 nm, while the reference chips show 3.4 nm. This approach may open the path for using nitride devices in applications requiring broad emission spectrum and high beam quality, such as optical coherence tomography.

  9. SiC-Based Schottky Diode Gas Sensors (United States)

    Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai


    Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one can affect the diode stability as well as the diode sensitivity to various gases. It is concluded that the ability of SiC to operate as a high temperature semiconductor significantly enhances the versatility of the Schottky diode gas sensing structure and will potentially allow the fabrication of a SiC-based gas sensor arrays for versatile high temperature gas sensing applications.

  10. Tunable diode laser control by a stepping Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Valentin, A.; Nicolas, C.; Henry, L.; Mantz, A.W.


    A tunable diode laser beam is sent through a Michelson interferometer and is locked to a fringe of the diode laser interferometer pattern by controlling the diode laser polarization current. The path difference change of the Michelson interferometer is controlled step by step by a stabilized He--Ne red laser. When the interferometer path differences increases or decreases, the polarization current of the diode is forced to change in order to preserve the interference order of the diode beam. At every step the diode frequency is accurately fixed and its phase noise significantly reduced.

  11. The design and manufacture of a notch structure for a planar InP Gunn diode (United States)

    Bai, Yang; Jia, Rui; Wu, De-Qi; Jin, Zhi; Liu, Xin-Yu


    A planar InP-based Gunn diode with a notch doping structure is designed and fabricated for integration into millimeter-wave and terahertz integrated circuits. We design two kinds of InP-based Gunn diodes. One has a fixed diameter of cathode area, but has variable spacing between anode and cathode; the other has fixed spacing, but a varying diameter. The threshold voltage and saturated current exhibit their strong dependences on the spacing (10 μm-20 μm) and diameter (40 μm-60 μm) of the InP Gunn diode. The threshold voltage is approximately 4.5 V and the saturated current is in a range of 293 mA-397 mA. In this work, the diameter of the diode and the space between anode and cathode are optimized. The devices are fabricated using a wet etching technique and show excellent performances. The results strongly suggest that low-cost and reliable InP planar Gunn diodes can be used as single chip terahertz sources.

  12. The design and manufacture of a notch structure for a planar InP Gunn diode

    Institute of Scientific and Technical Information of China (English)

    Bai Yang; Jia Rui; Wu De-Qi; Jin Zhi; Liu Xin-Yu


    A planar InP-based Gunn diode with a notch doping structure is designed and fabricated for integration into millimeter-wave and terahertz integrated circuits.We design two kinds of InP-based Gunn diodes.One has a fixed diameter of cathode area,but has variable spacing between anode and cathode; the other has fixed spacing,but a varying diameter.The threshold voltage and saturated current exhibit their strong dependences on the spacing (10 μm-20 μm) and diameter (40 μm-60 μm) of the InP Gunn diode.The threshold voltage is approximately 4.5 V and the saturated current is in a range of 293 mA-397 mA.In this work,the diameter of the diode and the space between anode and cathode are optimized.The devices are fabricated using a wet etching technique and show excellent performances.The results strongly suggest that low-cost and reliable InP planar Gunn diodes can be used as single chip terahertz sources.

  13. Assessment of the Usability and Accuracy of the Simplified One-Diode Models for Photovoltaic Modules

    Directory of Open Access Journals (Sweden)

    Vincenzo Franzitta


    Full Text Available Models for photovoltaic (PV cells and panels, based on the diode equivalent circuit, have been widely used because they are effective tools for system design. Many authors have presented simplified one-diode models whose three or four parameters are calculated using the data extracted from the datasheets issued by PV panel manufactures and adopting some simplifying hypotheses and numerical solving techniques. Sometimes it may be difficult to make a choice among so many models. To help researchers and designers working in the area of photovoltaic systems in selecting the model that is fit for purpose, a criterion for rating both the usability and accuracy of simplified one-diode models is proposed in this paper. The paper minutely describes the adopted hypotheses, analytical procedures and operative steps to calculate the parameters of the most famous simplified one-diode equivalent circuits. To test the achievable accuracy of the models, a comparison between the characteristics of some commercial PV modules issued by PV panel manufacturers and the calculated current-voltage (I-V curves, at constant solar irradiance and/or cell temperature, is carried out. The study shows that, even if different usability ratings and accuracies are observed, the simplified one-diode models can be considered very effective tools.

  14. All-optical diode effect of a nonlinear photonic crystal with a defect

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-jiang; ZHOU Jin-yun; XIAO Wan-neng


    An all-optical diode behavior that uses a nonlinear one-dimensional photonic crystal (NPC) with a defect Kerr medium is numerically simulated by the use of a nonlinear finite-difference time-domain (NFDTD) method.The numerical results show that for an incident pulse with appropriate intensity and temporal width,the transmittance can be several times greater in one direction of NPC than in the opposite direction at the pulse carrier frequency. This behaves like an all-optical diode and has promising applications in some areas such as optical isolation and all-optical processing.The ways to obtain low threshold of pulse field strength to realize an all-optical diode are also analyzed in detail.

  15. Diode-pumped laser altimeter (United States)

    Welford, D.; Isyanova, Y.


    TEM(sub 00)-mode output energies up to 22.5 mJ with 23 percent slope efficiencies were generated at 1.064 microns in a diode-laser pumped Nd:YAG laser using a transverse-pumping geometry. 1.32-micron performance was equally impressive at 10.2 mJ output energy with 15 percent slope efficiency. The same pumping geometry was successfully carried forward to several complex Q-switched laser resonator designs with no noticeable degradation of beam quality. Output beam profiles were consistently shown to have greater than 90 percent correlation with the ideal TEM(sub 00)-order Gaussian profile. A comparison study on pulse-reflection-mode (PRM), pulse-transmission-mode (PTM), and passive Q-switching techniques was undertaken. The PRM Q-switched laser generated 8.3 mJ pulses with durations as short as 10 ns. The PTM Q-switch laser generated 5 mJ pulses with durations as short as 5 ns. The passively Q-switched laser generated 5 mJ pulses with durations as short as 2.4 ns. Frequency doubling of both 1.064 microns and 1.32 microns with conversion efficiencies of 56 percent in lithium triborate and 10 percent in rubidium titanyl arsenate, respectively, was shown. Sum-frequency generation of the 1.064 microns and 1.32 microns radiations was demonstrated in KTP to generate 1.1 mJ of 0.589 micron output with 11.5 percent conversion efficiency.

  16. Broadly Neutralizing Antibodies for HIV Eradication. (United States)

    Stephenson, Kathryn E; Barouch, Dan H


    Passive transfer of antibodies has long been considered a potential treatment modality for infectious diseases, including HIV. Early efforts to use antibodies to suppress HIV replication, however, were largely unsuccessful, as the antibodies that were studied neutralized only a relatively narrow spectrum of viral strains and were not very potent. Recent advances have led to the discovery of a large portfolio of human monoclonal antibodies that are broadly neutralizing across many HIV-1 subtypes and are also substantially more potent. These antibodies target multiple different epitopes on the HIV envelope, thus allowing for the development of antibody combinations. In this review, we discuss the application of broadly neutralizing antibodies (bNAbs) for HIV treatment and HIV eradication strategies. We highlight bNAbs that target key epitopes, such as the CD4 binding site and the V2/V3-glycan-dependent sites, and we discuss several bNAbs that are currently in the clinical development pipeline.

  17. 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)


    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.

  18. Low-leakage diode-triggered silicon controlled rectifier for electrostatic discharge protection in 0.18-μm CMOS process

    Institute of Scientific and Technical Information of China (English)

    Xiao-yang DU; Shu-rong DONG; Yan HAN; Ming-xu HUO; Da-hai HUANG


    A diode-triggered silicon controlled rectifier (DTSCR) is being developed as an electrostatic discharge (ESD) protection device for low voltage applications. However, DTSCR leaks high current during normal operation due to the Darlington effect of the triggering-assist diode string. In this study, two types of diode string triggered SCRs are designed for low leakage consideration; the modified diode string and composite polysilicon diode string triggered SCRs (MDTSCR & PDTSCR). Compared with the conventional DTSCR (CDTSCR), the MDTSCR has a much lower substrate leakage current with a relatively large silicon cost, and the PDTSCR has a much lower substrate leakage current with similar area and shows good leakage performance at a high temperature. Other DTSCR ESD properties are also investigated, especially regarding their layout, triggering voltage and failure current.

  19. Destructive Single-Event Failures in Schottky Diodes (United States)

    Casey, Megan C.; Lauenstein, Jean-Marie; Gigliuto, Robert A.; Wilcox, Edward P.; Phan, Anthony M.; Kim, Hak; Chen, Dakai; LaBel, Kenneth A.


    This presentation contains test results for destructive failures in DC-DC converters. We have shown that Schottky diodes are susceptible to destructive single-event effects. Future work will be completed to identify parameter that determines diode susceptibility.

  20. Optical communications. V - Light emitting diodes /LED/ (United States)

    Best, S. W.


    The process of assembling diode chips is discussed, along with their application in optical communications. Metal plating is performed with an evaporation technique using primarily AuGe on the back side and Al or AuZn on the front side. The assembling of LED-chips with metal casings is illustrated. The chip is mounted on a flat bottom plate and electrical contact is established by means of an alloying or adhesion procedure. A glass fiber can be attached to the diode and then fitted with a casing, or the diode can be assembled with a metal cap and a lense, or with an open cap that is sealed with a clear synthetic resin plastic. The typical emission spectra of an LED and a semiconductor laser are compared. Limitations in the operation of an LED in a photoconductor are examined, taking into account spectral line width and radiated power criteria.

  1. Diode laser and endoscopic laser surgery. (United States)

    Sullins, Kenneth E


    Two functionally important differences exist between the diode laser and the carbon dioxide (CO2) laser (used more commonly in small animal surgery). Diode laser energy is delivered through a quartz fiber instead of being reflected through an articulated arm or waveguide. Quartz fibers are generally more flexible and resilient than waveguides and can be inserted through an endoscope for minimally invasive procedures. Laser-tissue interaction is the other significant difference. The CO2 laser is completely absorbed by water, which limits the effect to visible tissue. The diode wavelength is minimally absorbed by water and may affect tissue as deep as 10 mm below the surface in the free-beam mode. With proper respect for the tissue effect, these differences can be used to the advantage of the patient.

  2. Thermal diode made by nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Djair, E-mail: [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Fernandes, Ivna [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Moraes, Fernando [Departamento de Física, CCEN, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa, PB (Brazil); Departamento de Física, Universidade Federal Rural de Pernambuco, 52171-900 Recife, PE (Brazil); Fumeron, Sébastien [Institut Jean Lamour, Université de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre les Nancy (France); Pereira, Erms [Escola Politécnica de Pernambuco, Universidade de Pernambuco, Rua Benfíca, 455, Madalena, 50720-001 Recife, PE (Brazil)


    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. - Highlights: • An escaped radial disclination as a thermal diode made by a nematic liquid crystal. • Rectifying effects comparable to those caused by carbon and boron nitride nanotubes. • Thermal rectification increasing with radius and decreasing with height of the tube. • Asymmetric BCs cause rectification from the spatial asymmetry produced by the escape. • Symmetric BCs provide rectifications smaller than those yields by asymmetric BCs.

  3. Drivers for High Power Laser Diodes

    Institute of Scientific and Technical Information of China (English)

    Yankov P; Todorov D; Saramov E


    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.

  4. Logarithmic current electrometer using light emitting diodes (United States)

    Acharya, Y. B.; Aggarwal, A. K.


    The limit of low current measurement using logarithmic current to voltage converter is improved by 6 - 7 orders of magnitude with the use of diodes of large band gap as compared with silicon diodes. Low cost commercially available light emitting diodes (LEDs) have been used for this purpose. A theoretical study and experimental measurement of device constant and reverse saturation currents of the whole class of commercially available LEDs has been carried out. A circuit has been developed which makes use of a new technique for temperature compensation and its performance is compared with the technique in common use. The performance of the amplifier is found to be stable in the temperature range 5 - 600957-0233/7/2/005/img5 for both polarity of signals from 0957-0233/7/2/005/img6 to 0957-0233/7/2/005/img7 A.

  5. Semiconductor diode characterization for total skin electron irradiation. (United States)

    Madrid González, O A; Rivera Montalvo, T


    In this paper, a semiconductor diode characterization was performed. The diode characterization was completed using an electron beam with 4 MeV of energy. The semiconductor diode calibration used irradiation with an electron beam in an ion chamber. "In vivo" dosimetry was also conducted. The dosimetry results revealed that the semiconductor diode was a good candidate for use in the total skin electron therapy (TSET) treatment control.

  6. Diode laser based light sources for biomedical applications

    DEFF Research Database (Denmark)

    Müller, André; Marschall, Sebastian; Jensen, Ole Bjarlin;


    Diode lasers are by far the most efficient lasers currently available. With the ever-continuing improvement in diode laser technology, this type of laser has become increasingly attractive for a wide range of biomedical applications. Compared to the characteristics of competing laser systems, diode...... imaging. This review provides an overview of the latest development of diode laser technology and systems and their use within selected biomedical applications....

  7. Investigation of radial temperature gradients in diode pumped alkali lasers using tunable diode laser absorption spectroscopy (United States)

    Fox, Charles D.; Perram, Glen P.


    Heat loads in Diode Pumped Alkali Lasers (DPAL) have been investigated using a diode laser to probe the radial dependence of the absorbance. A TiS pump laser heats the medium in a T=50-100°C cesium heat pipe with 5 Torr nitrogen used for quenching. A tunable diode laser probes the spectral absorbance of the cesium cell. Local alkali concentration, temperature, and saturation broadening modify Voigt lineshapes in the wing of the hyperfine split lines. The temperature within the pumped volume exceeds the wall temperature by almost 200 C.

  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)


    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. To Broad-Match or Not to Broad-Match : An Auctioneer's Dilemma ?

    CERN Document Server

    Singh, Sudhir Kumar


    We initiate the study of an interesting aspect of sponsored search advertising, namely the consequences of broad match-a feature where an ad of an advertiser can be mapped to a broader range of relevant queries, and not necessarily to the particular keyword(s) that ad is associated with. Starting with a very natural setting for strategies available to the advertisers, and via a careful look through algorithmic and complexity theoretic glasses, we first propose a solution concept called broad match equilibrium(BME) for the game originating from the strategic behavior of advertisers as they try to optimize their budget allocation across various keywords. Next, we consider two broad match scenarios based on factors such as information asymmetry between advertisers and the auctioneer, and the extent of auctioneer's control on the budget splitting. In the first scenario, the advertisers have the full information about broad match and relevant parameters, and can reapportion their own budgets to utilize the extra i...

  10. Investigation of MIM Diodes for RF Applications

    KAUST Repository

    Khan, Adnan


    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

  11. Thermal diode made by nematic liquid crystal (United States)

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


    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.

  12. Phase-change radiative thermal diode

    CERN Document Server

    Ben-Abdallah, Philippe


    A thermal diode transports heat mainly in one preferential direction rather than in the opposite direction. This behavior is generally due to the non-linear dependence of certain physical properties with respect to the temperature. Here we introduce a radiative thermal diode which rectifies heat transport thanks to the phase transitions of materials. Rectification coefficients greater than 70% and up to 90% are shown, even for small temperature differences. This result could have important applications in the development of futur contactless thermal circuits or in the conception of radiative coatings for thermal management.

  13. Laser diode initiated detonators for space applications (United States)

    Ewick, David W.; Graham, J. A.; Hawley, J. D.


    Ensign Bickford Aerospace Company (EBAC) has over ten years of experience in the design and development of laser ordnance systems. Recent efforts have focused on the development of laser diode ordnance systems for space applications. Because the laser initiated detonators contain only insensitive secondary explosives, a high degree of system safety is achieved. Typical performance characteristics of a laser diode initiated detonator are described in this paper, including all-fire level, function time, and output. A finite difference model used at EBAC to predict detonator performance, is described and calculated results are compared to experimental data. Finally, the use of statistically designed experiments to evaluate performance of laser initiated detonators is discussed.

  14. External cavity diode laser around 657 nm

    Institute of Scientific and Technical Information of China (English)

    Desheng Lǖ (吕德胜); Kaikai Huang (黄凯凯); Fengzhi Wang (王凤芝); DonghaiYang (杨东海)


    Operating a laser diode in an external cavity, which provides frequency-selective feedback, is a very effective method to tune the laser frequency to a range far from its free running frequency. For the Ca atomic Ramsey spectroscopy experiment, we have constructed a 657-nm laser system based on the LittmanMetcalf configuration with a 660-nm commercial laser diode. Continuously 10-GHz tuning range was achieved with about 100-kHz spectral linewidth, measured with beat-note spectrum of two identical laser systems.

  15. A 640 GHz Planar-Diode Fundamental Mixer/Receiver (United States)

    Siegel, P.; Mehdi, I.; Dengler, R.; Lee, T.; Humphrey, D.; Pease, A.


    The design and performance of a 640 GHz solid-state receiver using a fundamental planar-Schottky-diode mixer, InP Gunn diode oscillator, whisker-contacted Schottky-varactor-diode sextupler and folded-Fabry-Perot diplexer are reported.

  16. Linear variable voltage diode capacitor and adaptive matching networks

    NARCIS (Netherlands)

    Larson, L.E.; De Vreede, L.C.N.


    An integrated variable voltage diode capacitor topology applied to a circuit providing a variable voltage load for controlling variable capacitance. The topology includes a first pair of anti-series varactor diodes, wherein the diode power-law exponent n for the first pair of anti-series varactor di

  17. Crx broadly modulates the pineal transcriptome

    DEFF Research Database (Denmark)

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


    Cone-rod homeobox (Crx) encodes Crx, a transcription factor expressed selectively in retinal photoreceptors and pinealocytes, the major cell type of the pineal gland. In this study, the influence of Crx on the mammalian pineal gland was studied by light and electron microscopy and by use......-regulation of 745 genes (p pineal glands of wild......-type animals; only eight of these were also day/night expressed in the Crx-/- pineal gland. However, in the Crx-/- pineal gland 41 genes exhibited differential night/day expression that was not seen in wild-type animals. These findings indicate that Crx broadly modulates the pineal transcriptome and also...

  18. Broad spectrum antibiotic compounds and use thereof

    Energy Technology Data Exchange (ETDEWEB)

    Koglin, Alexander; Strieker, Matthias


    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.

  19. Analysis of nanosecond breaking of a high-density current in SOS diodes (United States)

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


    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.

  20. End-pumped 1.5 microm monoblock laser for broad temperature operation. (United States)

    Schilling, Bradley W; Chinn, Stephen R; Hays, A D; Goldberg, Lew; Trussell, C Ward


    We describe a next-generation monoblock laser capable of a greater than 10 mJ, 1.5 microm output at 10 pulses/s (pps) over broad ambient temperature extremes with no active temperature control. The transmitter design is based on a Nd:YAG laser with a Cr4+ passive Q switch and intracavity potassium titanyl phosphate optical parametric oscillator. To achieve the repetition rate and efficiency goals of this effort, but still have wide temperature capability, the Nd:YAG slab is end pumped with a 12-bar stack of 100 W (each) diode bars. Different techniques for focusing the pump radiation into the 4.25 mmx4.25 mm end of the slab are compared, including a lensed design, a reflective concentrator, and a lens duct. A wide temperature operation (-20 degrees C to 50 degrees C) for each end-pumped configuration is demonstrated.

  1. 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


    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.

  2. Final report for EDI energy conservation with diode light; Slutrapport for EDI energibesparelser med diodelys

    Energy Technology Data Exchange (ETDEWEB)



    The aim of this project has been to develop technological knowledge and a competence platform for utilization of new light emitting diode technology for general lighting purposes. Furthermore the project has aimed at developing a 3 W light diode bulb to replace 15-20 W filament bulbs and halogen spotlights, and thereby demonstrating a large energy conservation potential in the use of LED technology for lighting purposes. (BA)

  3. XMM-Newton and Broad Iron Lines

    CERN Document Server

    Fabian, A C


    Iron line emission is common in the X-ray spectra of accreting black holes. When the line emission is broad or variable then it is likely to originate from close to the black hole. X-ray irradiation of the accretion flow by the power-law X-ray continuum produces the X-ray 'reflection' spectrum which includes the iron line. The shape and variability of the iron lines and reflection can be used as a diagnostic of the radius, velocity and nature of the flow. The inner radius of the dense flow corresponds to the innermost stable circular orbit and thus can be used to determine the spin of the black hole. Studies of broad iron lines and reflection spectra offer much promise for understanding how the inner parts of accretion flows (and outflows) around black holes operate. There remains great potential for XMM-Newton to continue to make significant progress in this work. The need for high quality spectra and thus for long exposure times is paramount.

  4. A CW Gunn Diode Switching Element. (United States)

    Hurtado, Marco; Rosenbaum, Fred J.

    As part of a study of the application of communication satellites to educational development, certain technical aspects of such a system were examined. A current controlled bistable switching element using a CW Gunn diode is reported on here. With modest circuits switching rates of the order of 10 MHz have been obtained. Switching is initiated by…

  5. A CW Gunn diode bistable switching element. (United States)

    Hurtado, M.; Rosenbaum, F. J.


    Experiments with a current-controlled bistable switching element using a CW Gunn diode are reported. Switching rates of the order of 10 MHz have been obtained. Switching is initiated by current pulses of short duration (5-10 ns). Rise times of the order of several nanoseconds could be obtained.

  6. Diode pumped Nd:YAG laser development (United States)

    Reno, C. W.; Herzog, D. G.


    A low power Nd:YAG laser was constructed which employs GaAs injection lasers as a pump source. Power outputs of 125 mW TEM CW with the rod at 250 K and the pump at 180 K were achieved for 45 W input power to the pump source. Operation of the laser, with array and laser at a common heat sink temperature of 250 K, was inhibited by difficulties in constructing long-life GaAs LOC laser arrays. Tests verified pumping with output power of 20 to 30 mW with rod and pump at 250 K. Although life tests with single LOC GaAs diodes were somewhat encouraging (with single diodes operating as long as 9000 hours without degradation), failures of single diodes in arrays continue to occur, and 50 percent power is lost in a few hundred hours at 1 percent duty factor. Because of the large recent advances in the state of the art of CW room temperature AlGaAs diodes, their demonstrated lifetimes of greater than 5,000 hours, and their inherent advantages for this task, it is recommended that these sources be used for further CW YAG injection laser pumping work.

  7. Light-Emitting Diodes: A Hidden Treasure (United States)

    Planinšic, Gorazd; Etkina, Eugenia


    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…

  8. Phosphorescent Nanocluster Light-Emitting Diodes. (United States)

    Kuttipillai, Padmanaban S; Zhao, Yimu; Traverse, Christopher J; Staples, Richard J; Levine, Benjamin G; Lunt, Richard R


    Devices utilizing an entirely new class of earth abundant, inexpensive phosphorescent emitters based on metal-halide nanoclusters are reported. Light-emitting diodes with tunable performance are demonstrated by varying cation substitution to these nanoclusters. Theoretical calculations provide insight about the nature of the phosphorescent emitting states, which involves a strong pseudo-Jahn-Teller distortion.

  9. Achromatic optical diode in fiber optics

    CERN Document Server

    Berent, Michal; Vitanov, Nikolay V


    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.

  10. Superluminescent Diode Light Sources for OCT (United States)

    Shidlovski, Vladimir R.

    Contrary to laser diodes, the path of superluminescent diodes (SLDs) to widespread practical use was much longer. There was always a scientific interest in "superluminescent" light output from laser diode structures slightly below threshold that might be considerably enhanced by "damping" of the laser resonator. SLD design efforts were intensified in early 1980s when it was proved that they are "light sources of choice" for fiber-optic gyroscopes. The next wave of interest to SLDs as a "stand-alone" type of semiconductor emitters was related to advances in OCT technologies. Challenging OCT requirements, e.g. simultaneous high-power, high brightness and very low coherence length of a light source, resulted in the development of new generation of SLDs characterized by output power and brightness the same as that of medium-to-high power laser diodes, but with the spectral width and flatness of edge-emitting LEDs. In this chapter, the main principles of the development of powerful broadband SLDs and ultra-low-coherence SLD-based light sources in 650-1600 nm spectral range, and the main parameters reported to date, are reviewed. Important aspects of SLD use in practice are discussed.

  11. Tunnel Diode Discriminator with Fixed Dead Time

    DEFF Research Database (Denmark)

    Diamond, J. M.


    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...

  12. 2-D Design of Schottky Diodes (United States)


    Schottky diode with- Lb, rse = 2.5 ,im as can be observed in figure 3. 25 ........... ...... ..... Series roi~ttarce for *ý,,,,-io irm. Ii bsai.10in 0...epitaxial layer Wp ( rse < 𔃽 -4), which is typical 4D0 ............. . . for submillimeter varactors. Of course, the influence of the .............. ~ L

  13. Light-Emitting Diodes: Learning New Physics (United States)

    Planinšic, Gorazd; Etkina, Eugenia


    This is the third paper in our Light-Emitting Diodes series. The series aims to create a systematic library of LED-based materials and to provide the readers with the description of experiments and pedagogical treatment that would help their students construct, test, and apply physics concepts and mathematical relations. The first paper, published…

  14. Determining Extinction Ratio Of A Laser Diode (United States)

    Unger, Glenn L.


    Improved technique to determine extinction ratio of pulsed laser diode based partly on definition of extinction ratio applicable to nonideal laser pulses. Heretofore, determinations involved assumption of ideal laser pulses, and neglected optical power from background light. Because power fluctuates during real pulse, more realistic to define extinction ratio in terms of energy obtained.

  15. Microring Diode Laser for THz Generation

    DEFF Research Database (Denmark)

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


    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...

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

    Institute of Scientific and Technical Information of China (English)

    GAO Chunqing; WEI Guanghui


    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.

  17. Electronically controlled heat sink for high-power laser diodes (United States)

    Vetrovec, John


    We report on a novel electronically controlled active heat sink for high-power laser diodes offering unparalleled capacity in high-heat flux handling and temperature control. The heat sink receives diode waste heat at high flux and transfers it at reduced flux to environment, coolant fluid, heat pipe, or structure. Thermal conductance of the heat sink is electronically adjustable, allowing for precise control of diode temperature and the diode light wavelength. When pumping solid-state or alkaline vapor lasers, diode wavelength can be precisely temperature-tuned to the gain medium absorption features. This paper presents the heat sink physics, engineering design, and performance modeling.

  18. Coherent polarization locking of a diode emitter array. (United States)

    Ng, S P; Phua, P B


    We present our work on the coherent combining of an array of diode emitters in a conventional diode bar configuration using the coherent polarization locking technique. An external laser cavity is designed so that the diode emissions from four diode emitters are spatially overlapped and passively phase locked via a series of birefringent walk-off crystals and a polarizing beam splitter. This concept was experimentally demonstrated up to 1030 mW of coherently combined power and was shown to increase the laser brightness of the diode bar by approximately 50 times.

  19. 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: [Batman University, Faculty of Sciences and Arts, Department of Physics, 72060 Batman (Turkey)


    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}.

  20. Gigahertz frequency comb from a diode-pumped solid-state laser. (United States)

    Klenner, Alexander; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula


    We present the first stabilization of the frequency comb offset from a diode-pumped gigahertz solid-state laser oscillator. No additional external amplification and/or compression of the output pulses is required. The laser is reliably modelocked using a SESAM and is based on a diode-pumped Yb:CALGO gain crystal. It generates 1.7-W average output power and pulse durations as short as 64 fs at a pulse repetition rate of 1 GHz. We generate an octave-spanning supercontinuum in a highly nonlinear fiber and use the standard f-to-2f carrier-envelope offset (CEO) frequency fCEO detection method. As a pump source, we use a reliable and cost-efficient commercial diode laser. Its multi-spatial-mode beam profile leads to a relatively broad frequency comb offset beat signal, which nevertheless can be phase-locked by feedback to its current. Using improved electronics, we reached a feedback-loop-bandwidth of up to 300 kHz. A combination of digital and analog electronics is used to achieve a tight phase-lock of fCEO to an external microwave reference with a low in-loop residual integrated phase-noise of 744 mrad in an integration bandwidth of [1 Hz, 5 MHz]. An analysis of the laser noise and response functions is presented which gives detailed insights into the CEO stabilization of this frequency comb.

  1. Qualification and Selection of Flight Diode Lasers for Space Applications (United States)

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


    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

  2. Broad-band acoustic hyperbolic metamaterial

    CERN Document Server

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


    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.

  3. Magnetohydrodynamic stability of broad line region clouds

    CERN Document Server

    Krause, Martin; Burkert, Andreas


    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...

  4. Spectrophotometry of six broad absorption line QSOs (United States)

    Junkkarinen, Vesa T.; Burbidge, E. Margaret; Smith, Harding E.


    Spectrophotometric observations of six broad absorption-line QSOs (BALQSOs) are presented. The continua and emission lines are compared with those in the spectra of QSOs without BALs. A statistically significant difference is found in the emission-line intensity ratio for (N V 1240-A)/(C IV 1549-A). The median value of (N V)/(C IV) for the BALQSOs is two to three times the median for QSOs without BALs. The absorption features of the BALQSOs are described, and the column densities and limits on the ionization structure of the BAL region are discussed. If the dominant ionization mechanism is photoionization, then it is likely that either the ionizing spectrum is steep or the abundances are considerably different from solar. Collisional ionization may be a significant factor, but it cannot totally dominate the ionization rate.

  5. 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


    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 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).

  6. 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.


    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...

  7. More Is Better: Selecting for Broad Host Range Bacteriophages. (United States)

    Ross, Alexa; Ward, Samantha; Hyman, Paul


    Bacteriophages are viruses that infect bacteria. In this perspective, we discuss several aspects of a characteristic feature of bacteriophages, their host range. Each phage has its own particular host range, the range of bacteria that it can infect. While some phages can only infect one or a few bacterial strains, other phages can infect many species or even bacteria from different genera. Different methods for determining host range may give different results, reflecting the multiple mechanisms bacteria have to resist phage infection and reflecting the different steps of infection each method depends on. This makes defining host range difficult. Another difficulty in describing host range arises from the inconsistent use of the words "narrow" and especially "broad" when describing the breadth of the host range. Nearly all bacteriophages have been isolated using a single host strain of bacteria. While this procedure is fairly standard, it may more likely produce narrow rather than broad host range phage. Our results and those of others suggest that using multiple host strains during isolation can more reliably produce broader host range phages. This challenges the common belief that most bacteriophages have a narrow host range. We highlight the implications of this for several areas that are affected by host range including horizontal gene transfer and phage therapy.

  8. Generation of 3.5 W of diffraction-limited green light from SHG of a single tapered diode laser in a cascade of nonlinear crystals

    DEFF Research Database (Denmark)

    Hansen, Anders Kragh; Jensen, Ole Bjarlin; Sumpf, Bernd;


    Many applications, e.g., within biomedicine stand to benefit greatly from the development of diode laser-based multi- Watt efficient compact green laser sources. The low power of existing diode lasers in the green area (about 100 mW) means that the most promising approach remains nonlinear......, such as optical coherence tomography or multimodal imaging devices, e.g., FTCARS-OCT, based on a strongly pumped ultrafast Ti:Sapphire laser....

  9. The evaluation of dose of TSEI with TLD and diode detector of the uterine cervix cancer

    Energy Technology Data Exchange (ETDEWEB)

    Je, Young Wan; Na, Keyung Su; Yoon, Il Kyu; Park, Heung Deuk [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of)


    To evaluate radiation dose and accuracy with TLD and diode detector when treat total skin with electron beam. Using Stanford Technique, we treated patient with Mycosis Fungoides. 6 MeV electron beam of LINAC was used and the SSD was 300 cm. Also, acrylic speller(0.8 cm) was used. The patient position was 6 types and the gantry angle was 64, 90 and 116 degree. The patient's skin dose and the output were detected 5 to 6 times with TLD and diode. The deviations of dose detected with TLD from tumor dose were CA + 6%, thigh + 8%, umbilicus + 4%, calf - 8%, vertex - 74.4%, deep axillae - 10.2%, anus and testis - 87%, sole - 86% and nails shielded with 4 mm lead + 4%. The deviations of dose detected with diode were - 4.5% {approx} + 5% at the patient center and - 1.1% {approx} + 1% at the speller. The deviation of total skin dose was + 8% {approx} - 8% and that deviation was within the acceptable range({+-}10%). The boost dose was irradiated for the low dose areas(vertex, anus, sole). The electron beam output detected at the sootier was stable. It is thought that the deviation of dose at patient center detected with diode was induced by detection point and patient position.

  10. Betavoltaic and photovoltaic energy conversion in three-dimensional macroporous silicon diodes

    Energy Technology Data Exchange (ETDEWEB)

    Clarkson, J.P. [Materials Science Program, University of Rochester, Rochester, New York 14627 (United States); Sun, W. [Dept. of Biomedical Engineering, University of Rochester, Rochester, New York 14627 (United States); Hirschman, K.D. [Microelectronic Engineering Dept., Rochester Institute of Technology, Rochester, NY 14623 (United States); Gadeken, L.L. [BetaBatt, Inc., 12819 Westleigh Drive, Houston, Texas 77077 (United States); Fauchet, P.M. [Dept. of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627 (United States)


    A three-dimensional p-n diode structure is presented for the generation of energy via photovoltaic and betavoltaic modes of operation. Macroporous Silicon (MPS) has a large degree of internal surface area and its vertically oriented pores, which extend deep into the bulk of the Si substrate, allow for the creation of three-dimensional structures. In this device the MPS will not only serve as a means for creating 3D diode structures, it will also serve as a host matrix for a tritium isotope which emits energetic beta particles. By varying electrochemical etching conditions and using a prepatterning technique, 1.1 {mu}m diameter pores with a spacing of 2.5 {mu}m were achieved. The p-n junction was created using a rapid thermal process (RTP) which relies on the diffusion from an n-type solid source into the MPS. To ensure the quality of the diode structure, devices were tested using a light source which resulted in a photovoltaic response. Finally, betavoltaic operation was demonstrated by exposing devices to a tritium gas source. The average energy conversion efficiency of the first generation 3D diode was one order of magnitude higher than that of a similar planar device. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. 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


    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.

  12. A Pair of Light Emitting Diodes for Absorbance Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Dongyong; Eom, Inyong [Catholic Univ. of Daegu, Gyeongsan (Korea, Republic of)


    Two same wavelength LEDs (i. e. an emitter LED and a detector LED, respectively) were successfully used to measure absorbance of BTB solution. A linear calibration with r-squared value of 0.9945 was achieved. 0.03 μM of LOD was observed with a noise level of 2 Χ 10{sup -4} absorbance unit. We are now examining relative sensitivities of different LEDs with distinct wavelength. In the future, building a spectrophotometer equipped with LEDs is quite interesting both in scientifically and pedagogically (i. e. undergraduate lab course). Light emitting diodes (LEDs) have a semiconductor chip (∼1 mm{sup 2} area) mounted on a concave mirror and emit narrow band of wavelengths when forward biased. LEDs have been widely used in many fields. Conventional light bulbs are being replaced by LED bulbs.

  13. Diode-coupled Ag nanoantennas for nanorectenna energy conversion (United States)

    Osgood, Richard, III; Giardini, Stephen; Carlson, Joel; Fernandes, Gustavo E.; Kim, Jin Ho; Xu, Jimmy; Chin, Matthew; Nichols, Barbara; Dubey, Madan; Parilla, Philip; Berry, Joseph; Ginley, David; Periasamy, Prakash; Guthrey, Harvey; O'Hayre, Ryan; Buchwald, Walter


    Arrays of "nanorectennas" consist of diode-coupled nanoantennas with plasmonic resonances in the visible/near-infrared (vis/nir) regime, and are expected to convert vis/nir radiative power into useful direct current. We study plasmonic resonances in large format (~ 1 mm2 area) arrays, consisting of electron beam-patterned horizontal (e.g., parallel to the substrate) Ag lines patterned on ultrathin (afore-mentioned barrier layers and different metals for the ground plane, are experimentally characterized and compared to our conduction model. We observe ~ 1 mV signals from NiO-based nanorectenna arrays illuminated by 532 nm and 1064 nm laser pulses, and discuss the origin of these signals.

  14. Seven broad absorption line quasars with excess broad band absorption near 2250

    CERN Document Server

    Zhang, Shaohua; Jiang, Peng; Zhou, Hongyan; Ma, Jingzhe; Brandt, W N; York, Donald G; Noterdaeme, P; Schneider, Donald P


    We report the discovery of excess broad band absorption near 2250 A (EBBA) in the spectra of seven broad absorption line (BAL) quasars. By comparing with the statistical results from the control quasar sample, the significance for the detections are all above the > 4{\\sigma} level, with five above > 5{\\sigma}. The detections have also been verified by several other independent methods. The EBBAs present broader and weaker bumps at smaller wavenumbers than the Milky Way, and similar to the Large Magellanic Cloud. The EBBA bump may be related to the 2175 A bump seen in the Local Group and may be a counterpart of the 2175 A bump under different conditions in the early Universe. Furthermore, five objects in this sample show low-ionization broad absorption lines (LoBALs), such as Mg II and Al III, in addition to the high-ionization broad absorption lines (HiBALs) of C IV and Si IV. The fraction of LoBALs in our sample, ~70%, is surprisingly high compared to that of general BAL quasars, ~10%. Although the origin of...

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

    Energy Technology Data Exchange (ETDEWEB)


    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.

  16. Application of spherical micro diodes for brachytherapy dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Broisman, Andrey, E-mail: [Medical Physics, Ariel University Center, Ariel 40700 (Israel); Shani, Gad [Biomedical Engineering, Ben Gurion University, P.O. Box 653, Beer Sheva 84105 (Israel)


    The research presented in this paper demonstrates the feasibility and the advantages of using spherical micro diodes for radiation dosimetry. The spherical symmetry of the diode response is demonstrated, compared to that of planar diodes. The application of the spherical diode described here is for radiotherapy dosimetry, particularly brachytherapy. Measurements were done in PMMA phantoms. The advantage of the spherical diode is that it can be used for radiation measurement in a 4{pi} geometry, it was demonstrated by measurements in both axial and azimuthal planes. The diodes were found to respond equally to radiation coming from all directions, directly from the source or due to scattered radiation within the medium. In the present work 1.8 mm diameter silicone diodes were used. The small size of these spherical diodes provides local dose measurement and can be used for in situ dosimetry while treatment takes place. Treatment planning correction can be made accordingly. Commercially available seeds of the isotopes I{sup 125} and Pd{sup 103} were used as radiation sources. The spherical diodes response was compared with that of planar diodes XRB generally used for UV and X-ray dosimetry, and with TLD measurements. We have also compared the measured results with Monte Carlo simulation, applying the MCNP code and with calculations shown in the TG-43 report.

  17. Method for detection and imaging over a broad spectral range (United States)

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


    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.

  18. Broadly neutralizing antibodies: An approach to control HIV-1 infection. (United States)

    Yaseen, Mahmoud Mohammad; Yaseen, Mohammad Mahmoud; Alqudah, Mohammad Ali


    Although available antiretroviral therapy (ART) has changed human immunodeficiency virus (HIV)-1 infection to a non-fatal chronic disease, the economic burden of lifelong therapy, severe adverse ART effects, daily ART adherence, and emergence of ART-resistant HIV-1 mutants require prospecting for alternative therapeutic modalities. Indeed, a growing body of evidence suggests that broadly neutralizing anti-HIV-1 antibodies (BNAbs) may offer one such feasible alternative. To evaluate their therapeutic potential in established HIV-1 infection, we sought to address recent advances in pre-clinical and clinical investigations in this area of HIV-1 research. In addition, we addressed the obstacles that may impede the success of such immunotherapeutic approach, suggested strategic solutions, and briefly compared this approach with the currently used ART to open new insights for potential future passive immunotherapy for HIV-1 infection.

  19. Diode-quad bridge circuit means (United States)

    Harrison, D. R.; Dimeff, J. (Inventor)


    A transducer and frequency discriminator circuit is described including a four-terminal circulating diode bridge, a first pair of capacitors connected in series across two terminals of the bridge, and a second pair of capacitors, or other impedance elements, connected in series across the other two terminals of the bridge. A source of balanced alternating electrical energy for energizing the circuit is coupled between the commonly connected plates of the first pair of capacitors and the commonly connected plates of the second pair of capacitors. Due to the operation of the diode bridge, the sum of the resultant charges developed on the first pair of capacitors is proportional to the relationship between the respective capacitors of the second pair, and consequently, an output voltage taken across the first pair of capacitors will be proportional to that relationship.

  20. Schottky diodes from 2D germanane (United States)

    Sahoo, Nanda Gopal; Esteves, Richard J.; Punetha, Vinay Deep; Pestov, Dmitry; Arachchige, Indika U.; McLeskey, James T.


    We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe2 framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.

  1. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

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


    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 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications.......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 27...

  2. Diode-pumped optical parametric oscillator. (United States)

    Geiger, A R; Hemmati, H; Farr, W H; Prasad, N S


    Diode-pumped optical parametric oscillation has been demonstrated for the first time to our knowledge in a single Nd:MgO:LiNbO(3) nonlinear crystal. The crystal is pumped by a semiconductor diode laser array at 812 nm. The Nd(3+) ions absorb the 812-nm radiation to generate 1084-nm laser oscillation. On internal Q switching the 1084-nm radiation pumps the LiNbO(3) host crystal that is angle cut at 46.5 degrees and generates optical parametric oscillation. The oscillation threshold that is due to the 1084-nm laser pump with a pulse length of 80 ns in a 1-mm-diameter beam was measured to be approximately 1 mJ and produced 0.5-mJ output at 3400-nm signal wavelength.

  3. Photoionisation modelling of the broad line region (United States)

    King, Anthea


    Two of the most fundamental questions regarding the broad line region (BLR) are "what is its structure?" and "how is it moving?" Baldwin et al. (1995) showed that by summing over an ensemble of clouds at differing densities and distances from the ionising source we can easily and naturally produce a spectrum similar to what is observed for AGN. This approach is called the `locally optimally emitting clouds' (LOC) model. This approach can also explain the well-observed stratification of emission lines in the BLR (e.g. Clavel et al. 1991, Peterson et al. 1991, Kollatschny et al. 2001) and `breathing' of BLR with changes in the continuum luminosity (Netzer & Mor 1990, Peterson et al. 2014) and is therefore a generally accepted model of the BLR. However, LOC predictions require some assumptions to be made about the distribution of the clouds within the BLR. By comparing photoionization predictions, for a distribution of cloud properties, with observed spectra we can infer something about the structure of the BLR and distribution of clouds. I use existing reverberation mapping data to constrain the structure of the BLR by observing how individual line strengths and ratios of different lines change in high and low luminosity states. I will present my initial constraints and discuss the challenges associated with the method.

  4. Comparison between rad-hard standard float zone (FZ) and magnetic Czochralski (MCZ) silicon diodes in radiotherapy electron beam dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Santos, T.C. dos; Goncalves, J.A.C.; Vasques, M.M.; Tobias, C.C.B. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Tecnologia das Radiacoes; Neves-Junior, W.F.P.; Haddad, C.M.K. [Hospital Sirio Libanes, Sao Paulo, SP (Brazil). Sociedade Beneficente de Senhoras; Harkonen, J. [Helsinki University of Technology (Denmark). Helsinki Inst. of Physics


    Full text. The use of semiconductor detectors has increased in radiotherapy practice since 1980s due to mainly their fast processing time, small sensitive volume and high relative sensitivity to ionizing radiation. Other major advantages of Si devices are excellent repeatability, good mechanical stability, high spatial resolution and the energy independence of mass collision stopping powers ratios (between silicon and water for electron beams with energy from 4 up to 20 MeV). However, ordinary silicon devices are very prone to radiation damage effects. In the last years, the development of radiation tolerant silicon detectors for High Energy Physics experiments has overcome this drawback. In this work we present the preliminary results obtained with a rad-hard epitaxial silicon diode as on-line clinical electron beam dosimeter. The diodes with 25 mm{sup 2} active area, were housed in a PMMA probe and connected, in a photovoltaic mode, to a Keithley 6517B electrometer. During all measurements, the diodes were held between PMMA plates, placed at Zref and centered in a radiation field of 10 cm x 10 cm, with the SSD kept at 100 cm. The devices dosimetric response was evaluated for 6, 9, 12, 15, 18 e 21 MeV electron beams from a Siemens KD 2 Radiotherapy Linear Accelerator, located at Sirio-Libanes Hospital. The radiation induced current in the diodes was registered as a function of the exposure time during 60 s for a fixed 300 MU. To study the short term repeatability, current signals were registered for the same radiation dose, for all energies. The dose-response of the diodes was achieved through the integration of the current signals as a function of the exposure time. The results obtained in the energy range of 6 up to 21 MeV evidenced that, for the same average dose rate of 5.0 cGy/s, the current signals are very stable and repeatable in both cases. For all energies, data shows good instantaneous repeatability with a percentage variation coefficient better than 2

  5. Stability theory of Knudsen plasma diodes

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  6. Diode Laser Sensor for Scramjet Inlet (United States)


    Conference’. 1.2 O’Byrne, S., Huynh, L., Wittig, S. M. and Smith, N. S. A. (2009), Non- intrusive water vapour absorp- tion measurements in a simulated...O’Byrne, L. Huynh, S. M. Wittig and N. S. A. Smith, “Non- intrusive Water Vapour Absorp- tion Measurements in a Simulated Helicopter Exhaust”, Proceedings...rather than at a surface. The measurement techniques used at these hypersonic flow conditions should also be non- intrusive . Tuneable diode laser

  7. Safety of light emitting diodes in toys. (United States)

    Higlett, M P; O'Hagan, J B; Khazova, M


    Light emitting diodes (LEDs) are increasingly being used in toys. An assessment methodology is described for determining the accessible emission limits for the optical radiation from the toys, which takes account of expected use and reasonably foreseeable misuse of toys. Where data are available, it may be possible to assess the toy from the data sheet alone. If this information is not available, a simple measurement protocol is proposed.

  8. Reconfigurable nonreciprocity with nonlinear Fano diode


    Xu, Yi; Miroshnichenko, Andrey E.


    We propose a dynamically tunable nonreciprocal response for wave propagations by employing nonlinear Fano resonances. We demonstrate that transmission contrast of waves propagation in opposite directions can be controlled by excitation signal. In particular, the unidirectional transmission can be flipped at different times of a pulse, resembling a diode operation with {\\em dynamical reconfigurable nonreciprocity}. The key mechanism is the interaction between the linear and nonlinear Fano reso...

  9. Diode having trenches in a semiconductor region (United States)

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


    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.

  10. Rugged, Tunable Extended-Cavity Diode Laser (United States)

    Moore, Donald; Brinza, David; Seidel, David; Klipstein, William; Choi, Dong Ho; Le, Lam; Zhang, Guangzhi; Iniguez, Roberto; Tang, Wade


    A rugged, tunable extended-cavity diode laser (ECDL) has been developed to satisfy stringent requirements for frequency stability, notably including low sensitivity to vibration. This laser is designed specifically for use in an atomic-clock experiment to be performed aboard the International Space Station (ISS). Lasers of similar design would be suitable for use in terrestrial laboratories engaged in atomic-clock and atomic-physics research.

  11. Diode-pumped Yb,Y:CaF2 laser mode-locked by monolayer graphene (United States)

    Zhu, Hongtong; Liu, Jie; Jiang, Shouzhen; Xu, Shicai; Su, Liangbi; Jiang, Dapeng; Qian, Xiaobo; Xu, Jun


    The large-area and high-quality monolayer graphene saturable absorber with a sandwich structure is prepared by the chemical vapor deposition technique. Using graphene saturable absorber, the mode locking operation of a diode-pumped Yb,Y:CaF2 laser is demonstrated. Without extra negative dispersion elements, 4.8 ps pulses are yielded at 1051 nm. The pulse repetition rate is 60 MHz.

  12. Integrated software package for laser diodes characterization (United States)

    Sporea, Dan G.; Sporea, Radu A.


    The characteristics of laser diodes (wavelength of the emitted radiation, output optical power, embedded photodiode photocurrent, threshold current, serial resistance, external quantum efficiency) are strongly influenced by their driving circumstances (forward current, case temperature). In order to handle such a complex investigation in an efficient and objective manner, the operation of several instruments (a laser diode driver, a temperature controller, a wavelength meter, a power meter, and a laser beam analyzer) is synchronously controlled by a PC, through serial and GPIB communication. For each equipment, instruments drivers were designed using the industry standards graphical programming environment - LabVIEW from National Instruments. All the developed virtual instruments operate under the supervision of a managing virtual instrument, which sets the driving parameters for each unit under test. The manager virtual instrument scans as appropriate the driving current and case temperature values for the selected laser diode. The software enables data saving in Excel compatible files. In this way, sets of curves can be produced according to the testing cycle needs.

  13. New laser materials for laser diode pumping (United States)

    Jenssen, H. P.


    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.

  14. Evaluation of laser diode based optical switches for optical processors (United States)

    Swanson, Paul D.; Parker, Michael A.; Libby, Stuart I.


    Three optical switching elements have been designed, fabricated, and tested for use in an integrated, optical signal processor. The first, an optical NOR logic gate, uses gain quenching as a means of allowing one (or more) light beam(s) to control the output light. This technique, along with the use of a two pad bistable output laser, is used in demonstrating the feasibility of the second device, an all optical RS flip flop. The third device consists of a broad area orthogonal model switching laser, whose corollary outputs correspond to the sign of the voltage difference between its two high impedance electrical inputs. This device also has possible memory applications if bistable mode switching within the broad area laser can be achieved.

  15. Blue laser diode (LD) and light emitting diode (LED) applications (United States)

    Bergh, Arpad A.


    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.


    Institute of Scientific and Technical Information of China (English)

    Jun-hua Fan; Mei-xiang Wan; Dao-ben Zhu


    Two kinds of heterojunction diodes of porous silicon (PS) with soluble polyaniline (PANI) were fabricated. One is a heterojunction diode of PS with water-soluble copolymer of polyaniline(PAOABSA),Al/PS-PAOABSA/Au cell as rectifying diode. Another is a heterojunction diode of PS with soluble polyaniline doped with DBSA, Al/PS-PANI (DBSA)/Au cell as light emitting diode (LED). The rectifying characteristics of the rectifying diodes were measured as a function of the degree of sulfonation and thickness of the copolymers, as well as oxidation of PS. The rectifying ratio of the heterojunction can reach 5.0×104 at ±3 V bias. For the LED, the photoluminescence (PL) and electroluminescence (EL) spectra were measured and discussed.

  17. Design and manufacture of planar GaAs Gunn diode for millimeter wave application (United States)

    Huang, Jie; Yang, Hao; Tian, Chao; Dong, Jun-Rong; Zhang, Hai-Ying; Guo, Tian-Yi


    GaAs-based planar Gunn diodes with AlGaAs hot electron injector have been successfully developed to be used as a local oscillator of 76 GHz in monolithic millimeter-wave integrated circuits. We designed two kinds of structure diode, one has a fixed distance between the anode and cathode, but has variational cathode area, the other has a fixed cathode area, but has different distances between two electrodes. The fabrication of Gunn diode is performed in accordance with the order of operations: cathode defining, mesa etching, anode defining, isolation, passivation, via hole and electroplating. A peak current density of 29.5 kA/cm2 is obtained. And the characteristics of negative differential resistance and the asymmetry of the current—voltage curve due to the AlGaAs hot electron injector are discussed in detail. It is demonstrated that the smaller size of active area corresponds to the smaller current, and the shorter distance between anode and cathode also corresponds to the lower threshold voltage and higher peak current, and hot electron injector can effectively enhance the radio frequency conversion efficiency and output power.

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

    NARCIS (Netherlands)

    Bael, Cristophe Patrick Jan Van


    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

  19. Broad spectrum anthelmintic potential of Cassia plants

    Institute of Scientific and Technical Information of China (English)

    Suman Kundu; Saptarshi Roy; Larisha Mawkhleing Lyndem


    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.

  20. Arctic Change Information for a Broad Audience (United States)

    Soreide, N. N.; Overland, J. E.; Calder, J.


    Demonstrable environmental changes have occurred in the Arctic over the past three decades. NOAA's Arctic Theme Page is a rich resource web site focused on high latitude studies and the Arctic, with links to widely distributed data and information focused on the Arctic. Included is a collection of essays on relevant topics by experts in Arctic research. The website has proven useful to a wide audience, including scientists, students, teachers, decision makers and the general public, as indicated through recognition by USA Today, Science magazine, etc. ( Working jointly with NSF and the University of Washington's Polar Science Center as part of the Study of Environmental Arctic Change (SEARCH) program, NOAA has developed a website for access to pan-Arctic time series spanning diverse data types including climate indices, atmospheric, oceanic, sea ice, terrestrial, biological and fisheries. Modest analysis functions and more detailed analysis results are provided. ( This paper will describe development of an Artic Change Detection status website to provide a direct and comprehensive view of previous and ongoing change in the Arctic for a broad climate community. For example, composite metrics are developed using principal component analysis based on 86 multivariate pan-Arctic time series for seven data types. Two of these metrics can be interpreted as a regime change/trend component and an interdecadal component. Changes can also be visually observed through tracking of 28 separate biophysical indicators. Results will be presented in the form of a web site with relevant, easily understood, value-added knowledge backed by peer review from Arctic scientists and scientific journals.

  1. Plasma opening switch studies of an applied Bz ion diode (United States)

    Struckman, C. K.; Kusse, B. R.; Meyerhofer, D. D.; Rondeau, G.


    The light ion accelerator (1.5 MV, 4 ohms) at Cornell University is being used to study the characteristics of an applied Bz, or 'barrel', diode. The results of a series of experiments utilizing a plasma opening switch are reported. With a magnetically insulated ion diode load, the peak diode voltage increase from 1.5 to 1.8 MV and the ion power increased from 50 to 80 GW when a plasma opening switch was used.

  2. Innovative Facet Passivation for High-Brightness Laser Diodes (United States)


    minimal growth initiation sites. 11 Modern laser diode structures are separate confinement, double heterostructures. The optical field is confined...Low magnification cross section of laser diode front facet showing the quantum well (QW) and the epitaxial passivation layer grown by MBE. 22...Figure 4.10 Cross section of laser diode A) front facet and B) rear facet showing the epitaxial passivation GaAs/AlGaAs layers grown by MBE. 9

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

    Energy Technology Data Exchange (ETDEWEB)

    Goncalves, J.A.C.; Santos, T.C. dos; Barbosa, R.F.; Pascoalino, K.C.S.; Bueno, C.C. [Instituto de Pesquisas Energeticas e Nucleares (CTR/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Tecnologia das Radiacoes


    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 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

  4. Underwater Chaotic Lidar using Blue Laser Diodes (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

  5. A novel diode laser system for photodynamic therapy

    DEFF Research Database (Denmark)

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


    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...... 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...

  6. Laboratory diode laser spectroscopy in molecular planetary astronomy (United States)

    Jennings, D. E.


    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.

  7. 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)


    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.

  8. Plasma-filled diode based on the coaxial gun (United States)

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


    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.

  9. Plasma-filled diode based on the coaxial gun. (United States)

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


    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.

  10. 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


    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‰.

  11. Planar GaAs diodes for THz frequency mixing applications (United States)

    Bishop, William L.; Crowe, Thomas W.; Mattauch, Robert J.; Dossal, Hasan


    Schottky barrier diodes for terahertz applications are typically fabricated as a micron to sub-micron circular anode metallization on GaAs which is contacted with a sharp wire (whisker). This structure has the benefits of the simplicity of the fabrication of the diode chip, the minimal shunt capacitance of the whisker contact and the ability of the whisker wire to couple energy to the diode. However, whisker-contacted diodes are costly to assembly and difficult to qualify for space applications. Also, complex receiver systems which require many diodes are difficult to assemble. The objective of this paper is to discuss the advantages of planar Schottky diodes for high frequency receiver applications and to summarize the problems of advancing the planar technology to the terahertz frequency range. Section 2 will discuss the structure, fabrication and performance of state-of-the-art planar Schottky diodes. In Section 3 the problems of designing and fabricating planar diodes for terahertz frequency operation are discussed along with a number of viable solutions. Section 4 summarizes the need for further research and cooperation between diode designers and RF engineers.

  12. Broad-Spectrum Solution-Processed Photovoltaics (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

  13. Bright light-emitting diodes based on organometal halide perovskite. (United States)

    Tan, Zhi-Kuang; Moghaddam, Reza Saberi; Lai, May Ling; Docampo, Pablo; Higler, Ruben; Deschler, Felix; Price, Michael; Sadhanala, Aditya; Pazos, Luis M; Credgington, Dan; Hanusch, Fabian; Bein, Thomas; Snaith, Henry J; Friend, Richard H


    Solid-state light-emitting devices based on direct-bandgap semiconductors have, over the past two decades, been utilized as energy-efficient sources of lighting. However, fabrication of these devices typically relies on expensive high-temperature and high-vacuum processes, rendering them uneconomical for use in large-area displays. Here, we report high-brightness light-emitting diodes based on solution-processed organometal halide perovskites. We demonstrate electroluminescence in the near-infrared, green and red by tuning the halide compositions in the perovskite. In our infrared device, a thin 15 nm layer of CH3NH3PbI(3-x)Cl(x) perovskite emitter is sandwiched between larger-bandgap titanium dioxide (TiO2) and poly(9,9'-dioctylfluorene) (F8) layers, effectively confining electrons and holes in the perovskite layer for radiative recombination. We report an infrared radiance of 13.2 W sr(-1) m(-2) at a current density of 363 mA cm(-2), with highest external and internal quantum efficiencies of 0.76% and 3.4%, respectively. In our green light-emitting device with an ITO/PEDOT:PSS/CH3NH3PbBr3/F8/Ca/Ag structure, we achieved a luminance of 364 cd m(-2) at a current density of 123 mA cm(-2), giving external and internal quantum efficiencies of 0.1% and 0.4%, respectively. We show, using photoluminescence studies, that radiative bimolecular recombination is dominant at higher excitation densities. Hence, the quantum efficiencies of the perovskite light-emitting diodes increase at higher current densities. This demonstration of effective perovskite electroluminescence offers scope for developing this unique class of materials into efficient and colour-tunable light emitters for low-cost display, lighting and optical communication applications.

  14. Position and mode dependent coupling of terahertz quantum cascade laser fields to an integrated diode (United States)

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


    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.

  15. 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


    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.

  16. Photon Reabsorption in Mixed CsPbCl3:CsPbI3 Perovskite Nanocrystal Films for Light-Emitting Diodes (United States)


    Cesium lead halide nanocrystals, CsPbX3 (X = Cl, Br, I), exhibit photoluminescence quantum efficiencies approaching 100% without the core–shell structures usually used in conventional semiconductor nanocrystals. These high photoluminescence efficiencies make these crystals ideal candidates for light-emitting diodes (LEDs). However, because of the large surface area to volume ratio, halogen exchange between perovskite nanocrystals of different compositions occurs rapidly, which is one of the limiting factors for white-light applications requiring a mixture of different crystal compositions to achieve a broad emission spectrum. Here, we use mixtures of chloride and iodide CsPbX3 (X = Cl, I) perovskite nanocrystals where anion exchange is significantly reduced. We investigate samples containing mixtures of perovskite nanocrystals with different compositions and study the resulting optical and electrical interactions. We report excitation transfer from CsPbCl3 to CsPbI3 in solution and within a poly(methyl methacrylate) matrix via photon reabsorption, which also occurs in electrically excited crystals in bulk heterojunction LEDs. PMID:28316756

  17. Control of GaAs Microwave Schottky Diode Electrical Characteristics by Contact Geometry: The Gap Diode. (United States)


    versus incident RF power of a Gap diode (V- bO ) .. . . . Ii i.... .. l -- _ _ __ll .. . I -82- c"-)) IZDn UU Figure 36. Single-ended mixer conversion...267 (1970). (12] C.J. Madams , D.V. Morgan, J.M. Howes, "Outmigratlon of Gallium from Au-GaAs Interfaces", Electronic Letters, Vol. 11(24), 574 (1975

  18. Photon-Phonon-Enhanced Infrared Rectification in a Two-Dimensional Nanoantenna-Coupled Tunnel Diode (United States)

    Kadlec, Emil A.; Jarecki, Robert L.; Starbuck, Andrew; Peters, David W.; Davids, Paul S.


    The interplay of strong infrared photon-phonon coupling with electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast photon-assisted tunneling in metal-oxide-semiconductor (MOS) structures. Infrared active optical phonon modes in polar oxides lead to strong dispersion and enhanced electric fields at material interfaces. We find that the infrared dispersion of SiO2 near a longitudinal optical phonon mode can effectively impedance match a photonic surface mode into a nanoscale tunnel gap that results in large transverse-field confinement. An integrated 2D nanoantenna structure on a distributed large-area MOS tunnel-diode rectifier is designed and built to resonantly excite infrared surface modes and is shown to efficiently channel infrared radiation into nanometer-scale gaps in these MOS devices. This enhanced-gap transverse-electric field is converted to a rectified tunneling displacement current resulting in a dc photocurrent. We examine the angular and polarization-dependent spectral photocurrent response of these 2D nanoantenna-coupled tunnel diodes in the photon-enhanced tunneling spectral region. Our 2D nanoantenna-coupled infrared tunnel-diode rectifier promises to impact large-area thermal energy harvesting and infrared direct detectors.

  19. Substrate-Free InGaN/GaN Nanowire Light-Emitting Diodes. (United States)

    Neplokh, Vladimir; Messanvi, Agnes; Zhang, Hezhi; Julien, Francois H; Babichev, Andrey; Eymery, Joel; Durand, Christophe; Tchernycheva, Maria


    We report on the demonstration of substrate-free nanowire/polydimethylsiloxane (PDMS) membrane light-emitting diodes (LEDs). Metal-organic vapour-phase epitaxy (MOVPE)-grown InGaN/GaN core-shell nanowires were encapsulated into PDMS layer. After metal deposition to p-GaN, a thick PDMS cap layer was spin-coated and the membrane was manually peeled from the sapphire substrate, flipped upside down onto a steel holder, and transparent indium tin oxide (ITO) contact to n-GaN was deposited. The fabricated LEDs demonstrate rectifying diode characteristics. For the electroluminescence (EL) measurements, the samples were manually bonded using silver paint. The EL spectra measured at different applied voltages demonstrate a blue shift with the current increase. This shift is explained by the current injection into the InGaN areas of the active region with different average indium content.

  20. Deciduous teeth occlusal caries detection with 655-nm diode laser confirmed by surface scanning electron microscopy (United States)

    Duarte, Danilo; Fonseca, Yara P. C.; Zanin, Fatima A. A.; Brugnera, Aldo, Jr.


    The morphological complexity of the occlusal surface of deciduous molar teeth is considered as a factor to increase vulnerability to caries lesion. Occlusal surface of these teeth shows sulcus, pits and fissures which allow retention of both micro-organisms and food debris which make them more susceptible to caries. In the last decades there was a significant reduction on caries of smooth surface but not on the occlusal surface where dentinal caries develops under fissures which are apparently caries-free under eye observation. This is known as a hidden caries. The occlusal surface of sound extracted deciduous molar teeth were examined using a 655 nm diode laser (DIAGNOdent - KaVo) in order to detect hidden caries. When there was indication of a hidden caries, the area was examined using SEM and confirm or not the diagnosis. The authors concludes that the diagnosis of caries using 655 diode laser is reliable and precise method.

  1. Laser Diode Pumped Solid State Lasers (United States)


    CRYSTAL ._____ ____ &m? * Deuterated • Potassium Dihydrogen . Phosphate - ’ KD PO (KD*P) ~ .~ ,_ .i-; Deuterated Ceslum 43ssI6 1 .. r., Dihydrogen a buffer layer to absorb the thermal strain differential between the diode and a copper heatsink has also been suggested in the past and a recent...Potassium Titanium d33829-3 0.16 *; . ~ Penta- Phosphate - ’(20 na) ;A.: KTiOPOi (KTP) - Barium Sodium d33 8 43 .0j 4 eNilhatsh RA.NaNhO

  2. Efficient organic light emitting-diodes (OLEDs)

    CERN Document Server

    Chang, Yi-Lu


    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

  3. Method for partially coating laser diode facets (United States)

    Dholakia, Anil R. (Inventor)


    Bars of integral laser diode devices cleaved from a wafer are placed with their p regions abutting and n regions abutting. A thin BeCu mask having alternate openings and strips of the same width as the end facets is used to mask the n region interfaces so that multiple bars can be partially coated over their exposed p regions with a reflective or partial reflective coating. The partial coating permits identification of the emitting facet from the fully coated back facet during a later device mounting procedure.

  4. Deep ultraviolet light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Hu, X.; Deng, J.; Zhang, J.P.; Lunev, A.; Bilenko, Y.; Katona, T.; Gaska, R. [Sensor Electronic Technology, Inc., 1195 Atlas Road, Columbia, SC 29209 (United States); Shur, M.S. [Department of Electrical Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Shatalov, M.; Khan, A. [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States)


    We report on the development of AlGaN-based deep UV light emitting diodes (LEDs) with emission wavelengths from 254 to 340 nm, focusing on the improvement of 280 nm LEDs efficiency. Under optimal device structure the UV LEDs efficiency was found to strongly depend on the AlGaN material quality. Milliwatt-power level LEDs were demonstrated for the 254-340 nm spectral range, and for 280 nm LEDs powers reaching 2.5 mW was achieved at 20 mA DC. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Neutron Detection Using Gadolinium-Based Diodes (United States)


    U Uranium UNL The University of Nebraska, Lincoln XRD X-Ray Diffraction 1 NEUTRON DETECTION USING GADOLINIUM-BASED DIODES I...detector volume of approximately 3.46x10-6 cm3. 6 4 2 0 2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Applied BiasV De ple tio nW idt hm  Si SiC 22...Layer deposition on the SiC substrate was confirmed by x-ray diffraction ( XRD ), however, no ellipsometry or other characterization measurements were

  6. Atomically thin quantum light-emitting diodes (United States)

    Palacios-Berraquero, Carmen; Barbone, Matteo; Kara, Dhiren M.; Chen, Xiaolong; Goykhman, Ilya; Yoon, Duhee; Ott, Anna K.; Beitner, Jan; Watanabe, Kenji; Taniguchi, Takashi; Ferrari, Andrea C.; Atatüre, Mete


    Transition metal dichalcogenides are optically active, layered materials promising for fast optoelectronics and on-chip photonics. We demonstrate electrically driven single-photon emission from localized sites in tungsten diselenide and tungsten disulphide. To achieve this, we fabricate a light-emitting diode structure comprising single-layer graphene, thin hexagonal boron nitride and transition metal dichalcogenide mono- and bi-layers. Photon correlation measurements are used to confirm the single-photon nature of the spectrally sharp emission. These results present the transition metal dichalcogenide family as a platform for hybrid, broadband, atomically precise quantum photonics devices.

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

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


    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.

  8. Diode pumped solid-state laser oscillators for spectroscopic applications (United States)

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


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

  9. Spectral control of diode lasers using external waveguide circuits

    NARCIS (Netherlands)

    Oldenbeuving, R.M.


    We investigated spectral control of diode lasers using external waveguide circuits. The purpose of this work is to investigate such external control for providing a new class of diode lasers with technologically interesting properties, such as a narrow spectral bandwidth and spectrally tunable outpu

  10. Suitability of integrated protection diodes from diverse semiconductor technologies

    NARCIS (Netherlands)

    Wanum, van Maurice; Lebouille, Tom; Visser, Guido; Vliet, van Frank E.


    Abstract In this article diodes from three different semiconductor technologies are compared based on their suitability to protect a receiver. The semiconductor materials involved are silicon, gallium arsenide and gallium nitride. The diodes in the diverse semiconductor technologies themselves are c

  11. Suitability of integrated protection diodes from diverse semiconductor technologies

    NARCIS (Netherlands)

    Wanum, M. van; Lebouille, T.T.N.; Visser, G.C.; Vliet, F.E. van


    In this article diodes from three different semiconductor technologies are compared based on their suitability to protect a receiver. The semiconductor materials involved are Silicon, Gallium Arsenide and Gallium Nitride. The diodes in the diverse semiconductor technologies themselves are close in p

  12. Compact green-diode-based lasers for biophotonic bioimaging

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Hansen, Anders Kragh; Petersen, Paul Michael;


    Diode lasers simultaneously offer tunability, high-power emission, and compact size at fairly low cost and are increasingly preferred for pumping titanium:sapphire lasers.......Diode lasers simultaneously offer tunability, high-power emission, and compact size at fairly low cost and are increasingly preferred for pumping titanium:sapphire lasers....

  13. Operation of AC Adapters Visualized Using Light-Emitting Diodes (United States)

    Regester, Jeffrey


    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…

  14. IMPATT diodes. Citations from the NTIS data base (United States)

    Reed, W. E.


    Government sponsored research reports are cited covering the design, characterization, and applications of IMPATT diodes. Topics include reliability, power handling, properties, noise, fabrication, and radiation effects. The use of silicon and gallium arsenide IMPATT diodes for microwave generation and amplification is included. This updated bibliography contains 182 abstracts, 14 of which are new entries to the previous edition.

  15. Diode-Assisted Buck-Boost Voltage-Source Inverters

    DEFF Research Database (Denmark)

    Gao, Feng; Loh, Poh Chiang; Teodorescu, Remus;


    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...

  16. Digital control of diode laser for atmospheric spectroscopy (United States)

    Menzies, R. T.; Rutledge, C. W. (Inventor)


    A system is described for remote absorption spectroscopy of trace species using a diode laser tunable over a useful spectral region of 50 to 200 cm(-1) by control of diode laser temperature over range from 15 K to 100 K, and tunable over a smaller region of typically 0.1 to 10 cm(-1) by control of the diode laser current over a range from 0 to 2 amps. Diode laser temperature and current set points are transmitted to the instrument in digital form and stored in memory for retrieval under control of a microprocessor during measurements. The laser diode current is determined by a digital to analog converter through a field effect transistor for a high degree of ambient temperature stability, while the laser diode temperature is determined by set points entered into a digital to analog converter under control of the microprocessor. Temperature of the laser diode is sensed by a sensor diode to provide negative feedback to the temperature control circuit that responds to the temperature control digital to analog converter.

  17. On the Operational Meaning of Broad-Spectrum Philosophy Methodology

    Directory of Open Access Journals (Sweden)

    Miao Yi


    Full Text Available This study analyze the Broad-spectrum Philosophy Methodology on the operational meaning, and discusses three relatively primary methods of Broad-spectrum Philosophy Methodologies. The methodology of Broad-spectrum philosophy cannot pursuit of accuracy of numerical sense, but it pursuits of the exact nature of the research questions, the accuracy of the sense of set theory and sums up the experience which we solve problems in real life and make it up to the generalized quantization and procedural level and thus the methodology of Broad-spectrum philosophy has a general guide and it is a broad operations research. We gets the results that along with deep exploration and development of Broad-spectrum Philosophy Methodology, its function as generalized operation research can be more powerful.

  18. Patterning of flexible organic light emitting diode (FOLED) stack using an ultrafast laser. (United States)

    Mandamparambil, Rajesh; Fledderus, Henri; Van Steenberge, Geert; Dietzel, Andreas


    A femtosecond laser has been successfully utilized for patterning thin Flexible Organic Light Emitting Diode (FOLED) structures of individual layer thickness around 100nm. The authors report in this paper a step-like ablation behavior at the layer interfaces which accounts for a local removal of entire layers. Various surface analyzing techniques are used to investigate the morphologies and chemical compositions within and in the vicinity of the ablation areas. This study opens a new avenue in selectively ablating different layers from a multilayer stack on flexible substrates using fs lasers allowing post deposition structuring of large area flexible organic electronic devices.

  19. Future Solid State Lighting using LEDs and Diode Lasers

    DEFF Research Database (Denmark)

    Petersen, Paul Michael


    significant savings. Solid state lighting (SSL) based on LEDs is today the most efficient light source for generation of high quality white light. Diode lasers, however, have the potential of being more efficient than LEDs for the generation of white light. A major advantage using diode lasers for solid state...... applications. Within the coming years, it is expected that the efficiency of blue laser diodes will approach the efficiency of infrared diode lasers. This will enable high efficiency white light generation with very high lumen per watt values. SSL today is mainly based on phosphor converted blue light emitting...... diodes (LEDs). Blue emitting 445-460 nm LED chips with conversion in phosphorescent materials have undergone tremendous development in the last decade with ultra high efficiencies. However, the technology suffers from a decrease in efficiency at high input current densities, known as the “efficiency...

  20. Stacked, Filtered Multi-Channel X-Ray Diode Array

    Energy Technology Data Exchange (ETDEWEB)

    MacNeil, Lawrence P. [National Security Technologies, LLC; Dutra, Eric C. [National Security Technologies, LLC; Raphaelian, Mark; Compton, Steven [Lawrence Livermore National Laboratory; Jacoby, Barry [Lawrence Livermore National Laboratory


    This system meets the need for a low-cost, robust X-ray diode array to use for experiments in hostile environments on multiple platforms, and for experiments utilizing forces that may destroy the diode(s). Since these uses require a small size with a minimal single line-of-sight, a parallel array often cannot be used. So a stacked, filtered multi-channel X-ray diode array was developed that was called the MiniXRD. The design was modeled, built, and tested at National Security Technologies, LLC (NSTec) Livermore Operations (LO) to determine fundamental characteristics. Then, several different systems were fielded as ancillary “ridealong” diagnostics at several national facilities to allow us to iteratively improve the design and usability. Presented here are design considerations and experimental results. This filtered diode array is currently at Technical Readiness Level (TRL) 6.

  1. 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


    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.

  2. Cross-reactive broadly neutralizing antibodies: timing is everything


    Euler, Zelda; Schuitemaker, Hanneke


    The recent surge of research into new broadly neutralizing antibodies in HIV-1 infection has recharged the field of HIV-1 vaccinology. In this review we discuss the currently known broadly neutralizing antibodies and focus on factors that may shape these antibodies in natural infection. We further discuss the role of these antibodies in the clinical course of the infection and consider immunological obstacles in inducing broadly neutralizing antibodies with a vaccine.

  3. Cross-reactive broadly neutralizing antibodies: timing is everything. (United States)

    Euler, Zelda; Schuitemaker, Hanneke


    The recent surge of research into new broadly neutralizing antibodies in HIV-1 infection has recharged the field of HIV-1 vaccinology. In this review we discuss the currently known broadly neutralizing antibodies and focus on factors that may shape these antibodies in natural infection. We further discuss the role of these antibodies in the clinical course of the infection and consider immunological obstacles in inducing broadly neutralizing antibodies with a vaccine.

  4. Diode and Final Focus Simulations for DARHT (United States)

    Hughes, Thomas P.; Welch, Dale R.; Carlson, Randolph L.


    We have used the numerical simulation codes uc(ivory,) uc(iprop) and uc(pbguns) to simulate beam dynamics in the diode and final focus of the 4 kA, 20 MV DARHT linear accelerator. A low emittance 4 MV, 4 kA source for a 4-pulse injector was designed using uc(ivory) and uc(pbguns.) Due to the long pulse length (four 70 ns pulses over 1 μsec), we have kept the field stress to stacks. The normalized edge emittance produced by the diode optics is only ≈ 130 mm-mrad. In the final-focus region, we have used uc(iprop) to model the effect of ion emission from the target. The intense electric field of the beam at the 1 mm diameter focal spot produces substantial ion velocities, and, if the space-charge-limited current density can be supplied, significant focal spot degradation may occur due to ion space-charge. Calculations for the ITS test stand, which has a larger focal spot, show that the effect should be observable for H^+ and C^+ ion species. The effect may be lessened if there is insufficient ion density on the target to supply the space-charge-limited current density, or if the ion charge-to-mass ratio is sufficiently large.

  5. Sensitivity of resonant tunneling diode photodetectors (United States)

    Pfenning, Andreas; Hartmann, Fabian; Langer, Fabian; Kamp, Martin; Höfling, Sven; Worschech, Lukas


    We have studied the sensitivity of AlGaAs/GaAs double barrier resonant tunneling diode photodetectors with an integrated GaInNAs absorption layer for light sensing at the telecommunication wavelength of λ = 1.3 μm for illumination powers from pico- to microwatts. The sensitivity decreases nonlinearly with power. An illumination power increase of seven orders of magnitude leads to a reduction of the photocurrent sensitivity from S I = 5.82 × 103 A W-1 to 3.2 A W-1. We attribute the nonlinear sensitivity-power dependence to an altered local electrostatic potential due to hole-accumulation that on the one hand tunes the tunneling current, but on the other hand affects the lifetime of photogenerated holes. In particular, the lifetime decreases exponentially with increasing hole population. The lifetime reduction results from an enhanced electrical field, a rise of the quasi-Fermi level, and an increased energy splitting within the triangular potential well. The non-constant sensitivity is a direct result of the non-constant lifetime. Based on these findings, we provide an expression that allows us to calculate the sensitivity as a function of illumination power and bias voltage, show a way to model the time-resolved photocurrent, and determine the critical power up to which the resonant tunneling diode photodetector sensitivity can be assumed constant.

  6. Charge Transport in Resonant Tunneling Double - Diodes (United States)

    Diff, Karim

    With the advent of semiconductor devices with typical lengths of the order of a few nanometers and response times of a few picoseconds, the conventional methods used in device modeling have reached their limits of validity. Modern devices based on heterostructures fabricated by Molecular Beam Epitaxy (MBE) require more fundamental approaches based entirely on quantum mechanics. These generally necessitate numerical solutions and are computationally intensive. This dissertation focuses on Resonant Tunneling Double-Barrier (RTDB) diodes as the prototype of "quantum devices". A one-electron model and the effective mass approximation are used. By solving numerically the time-dependent Schrodinger equation for Gaussian wavepackets, the various time characteristics of resonant tunneling are probed. These characteristics are usually overlooked in other treatments based on the time-independent Schrodinger equation. The transit time, the build-up time and the exponential decay time are studied. The difference between these various time scales and their relative importance are discussed. A new method that takes into account the finite extent of the electron wavefunction, is proposed to compute the I-V characteristics of such devices. Results indicate a possible explanation for the discrepancy observed between experimental results and previous analyses. The effect of high frequency fields on resonant tunneling is also studied, and a method to determine the intrinsic cut-off frequency is suggested. The role of the effective mass in the determination of the characteristics of RTDB diodes is emphasized throughout this work.

  7. Broadband tunable external cavity laser using a bent-waveguide quantum-dot superluminescent diode as gain device

    Institute of Scientific and Technical Information of China (English)

    Wu Jian; Lü Xue-Qin; Jin Peng; Meng Xian-Quan; Wang Zhan-Guo


    A broadband tunable grating-coupled external cavity laser is realized by employing a self-assembled InAs/GaAs quantum-dot (QD) superluminescent diode (SLD) as the gain device. The SLD device is processed with a bent-waveguide structure and facet antireflection (AR) coating. Tuning bandwidths of 106 nm and 117 nm are achieved under 3-A and 3.5-A injection currents, respectively. The large tuning range originates essentially from the broad gain spectrum of self-assembled QDs. The bent waveguide structure combined with the facet AR coating plays a role in suppressing the inner-cavity lasing under a large injection current.

  8. High-efficiency and low-jitter Silicon single-photon avalanche diodes based on nanophotonic absorption enhancement

    CERN Document Server

    Ma, Jian; Yu, Zongfu; Jiang, Xiao; Huo, Yijie; Zang, Kai; Zhang, Jun; Harris, James S; Jin, Ge; Zhang, Qiang; Pan, Jian-Wei


    Silicon single-photon avalanche diode (SPAD) is a core device for single-photon detection in the visible and the near-infrared range, and widely used in many applications. However, due to limits of the structure design and device fabrication for current silicon SPADs, the key parameters of detection befficiency and timing jitter are often forced to compromise. Here, we propose a nanostructured silicon SPAD, which achieves high detection efficiency with excellent timing jitter simultaneously over a broad spectral range. The optical and electric simulations show significant performance enhancement compared with conventional silicon SPAD devices. This nanostructured devices can be easily fabricated and thus well suited for practical applications.

  9. Inclination of Broad Line Region in Narrow Line and Broad Line Seyfert 1 Galaxies

    Institute of Scientific and Technical Information of China (English)


    The sizes of the Broad Line Region (BLR) of some Seyfert 1 galax-ies and nearby quasars can be determined by the reverberation mapping method.Combining with the observed FWHM of Hβ emission line and assuming that themotion of BLR clouds is virialized, the black hole masses of these objects have beenestimated. However, this method strongly depends on the poorly-understood geom-etry and inclination of the BLR. On the other hand, a tight correlation between theblack hole mass and the bulge velocity dispersion was recently found for both activeand nearby inactive galaxies. This may provide another method, independent of theBLR geometry, for estimating the black hole mass. Using this method for estimatingthe black hole mass and combining with the measured BLR size and FWHM of Hβemission line, we derived the BLR inclination angles for 20 Seyfert I galaxies underthe assumption that the BLR is disk-like. The derived inclination angles agree wellwith those derived previously by fitting the UV continuum and Hβ emission lineprofiles. Adopting a relation between the FWHMs of [OⅢ]λ5007 forbidden line andthe stellar velocity dispersion, we also estimated the BLR inclinations for 50 nar-row line Seyfert 1 galaxies (NLSls). We found that the inclinations of broad LineSeyfert 1 galaxies (BLS1s) are systematically greater than those of NLS1s, whichseldom exceed 30. This may be an important factor that leads to the differencesbetween NLS1s and BLS1s if the BLR of NLS1s is really disk-like.

  10. Wavelength optimization using available laser diodes in spectral near-infrared optical tomography. (United States)

    Chen, Liang-Yu; Pan, Min-Cheng; Yan, Chung-Chen; Pan, Min-Chun


    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.

  11. More Is Better: Selecting for Broad Host Range Bacteriophages (United States)

    Ross, Alexa; Ward, Samantha; Hyman, Paul


    Bacteriophages are viruses that infect bacteria. In this perspective, we discuss several aspects of a characteristic feature of bacteriophages, their host range. Each phage has its own particular host range, the range of bacteria that it can infect. While some phages can only infect one or a few bacterial strains, other phages can infect many species or even bacteria from different genera. Different methods for determining host range may give different results, reflecting the multiple mechanisms bacteria have to resist phage infection and reflecting the different steps of infection each method depends on. This makes defining host range difficult. Another difficulty in describing host range arises from the inconsistent use of the words “narrow” and especially “broad” when describing the breadth of the host range. Nearly all bacteriophages have been isolated using a single host strain of bacteria. While this procedure is fairly standard, it may more likely produce narrow rather than broad host range phage. Our results and those of others suggest that using multiple host strains during isolation can more reliably produce broader host range phages. This challenges the common belief that most bacteriophages have a narrow host range. We highlight the implications of this for several areas that are affected by host range including horizontal gene transfer and phage therapy. PMID:27660623

  12. An Alkane-Soluble Dendrimer as Electron-Transport Layer in Polymer Light-Emitting Diodes. (United States)

    Zhong, Zhiming; Zhao, Sen; Pei, Jian; Wang, Jian; Ying, Lei; Peng, Junbiao; Cao, Yong


    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.

  13. Assessing Eli Broad's Assault on Public School System Leadership (United States)

    English, Fenwick W.; Crowder, Zan


    Eli Broad's approach to reforming urban public education does not recognize his own self-interest in promoting changes within such educational systems, a classic problem of misrecognition. The Broad agenda is an assault on the notion of the mission of public education as a service instead of a for-profit enterprise concerned with making money for…

  14. Social Cognition, Social Skill, and the Broad Autism Phenotype (United States)

    Sasson, Noah J.; Nowlin, Rachel B.; Pinkham, Amy E.


    Social-cognitive deficits differentiate parents with the "broad autism phenotype" from non-broad autism phenotype parents more robustly than other neuropsychological features of autism, suggesting that this domain may be particularly informative for identifying genetic and brain processes associated with the phenotype. The current study…

  15. Broadly protective influenza vaccines: Redirecting the antibody response through adjuvation

    NARCIS (Netherlands)

    Cox, F.


    Influenza virus infections are responsible for significant morbidity worldwide and current vaccines have limited coverage, therefore it remains a high priority to develop broadly protective vaccines. With the discovery of broadly neutralizing antibodies (bnAbs) against influenza these vaccines becam

  16. Boot Camp for Education CEOs: The Broad Foundation Superintendents Academy (United States)

    Jehlen, Alain


    The Broad Foundation Superintendents Academy is the most prominent and most controversial training institute for school chiefs. The Academy is the flagship program of the Eli and Edythe Broad Foundation, the smallest of a triumvirate of corporate foundations that are at the heart of the billionaire campaign to remake public education in the image…

  17. Inverse I-V Injection Characteristics of ZnO Nanoparticle-Based Diodes. (United States)

    Mundt, Paul; Vogel, Stefan; Bonrad, Klaus; von Seggern, Heinz


    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.

  18. Influence of Preparation Conditions on Electrical Properties of the Al/Alq3/Si Diode Structures

    Directory of Open Access Journals (Sweden)

    Irina ČERNIUKĖ


    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:

  19. Solar-energy conversion and light emission in an atomic monolayer p-n diode. (United States)

    Pospischil, Andreas; Furchi, Marco M; Mueller, Thomas


    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.

  20. Single-molecule diodes with high rectification ratios through environmental control. (United States)

    Capozzi, Brian; Xia, Jianlong; Adak, Olgun; Dell, Emma J; Liu, Zhen-Fei; Taylor, Jeffrey C; Neaton, Jeffrey B; Campos, Luis M; Venkataraman, Latha


    Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40 years ago and consisted of an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule-electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.

  1. Pulse Shape Characterization of Silicon Diodes for HGCal with data from Beam Test at CERN

    CERN Document Server

    De Silva, Malinda


    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...

  2. A practical guide to handling laser diode beams

    CERN Document Server

    Sun, Haiyin


    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...

  3. Additional electric field in real trench MOS barrier Schottky diode (United States)

    Mamedov, R. K.; Aslanova, A. R.


    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.

  4. Respiratory complications after diode-laser-assisted tonsillotomy. (United States)

    Fischer, Miloš; Horn, Iris-Susanne; Quante, Mirja; Merkenschlager, Andreas; Schnoor, Jörg; Kaisers, Udo X; Dietz, Andreas; Kluba, Karsten


    Children with certain risk factors, such as comorbidities or severe obstructive sleep apnea syndrome (OSAS) are known to require extended postoperative monitoring after adenotonsillectomy. However, there are no recommendations available for diode-laser-assisted tonsillotomy. A retrospective chart review of 96 children who underwent diode-laser-assisted tonsillotomy (07/2011-06/2013) was performed. Data for general and sleep apnea history, power of the applied diode-laser (λ = 940 nm), anesthesia parameters, the presence of postoperative respiratory complications and postoperative healing were evaluated. After initially uncomplicated diode-laser-assisted tonsillotomy, an adjustment of post-anesthesia care was necessary in 16 of 96 patients due to respiratory failure. Respiratory complications were more frequent in younger children (3.1 vs. 4.0 years, p = 0.049, 95 % CI -1.7952 to -0.0048) and in children who suffered from nocturnal apneas (OR = 5.00, p diode-laser power higher than 13 W could be identified as a risk factor for the occurrence of a postoperative oropharyngeal edema (OR = 3.45, p diode-laser-assisted tonsillotomy. We recommend a reduced diode-laser power (<13 W) to reduce oropharyngeal edema.

  5. Light-Emitting Diodes: Phosphorescent Nanocluster Light-Emitting Diodes (Adv. Mater. 2/2016). (United States)

    Kuttipillai, Padmanaban S; Zhao, Yimu; Traverse, Christopher J; Staples, Richard J; Levine, Benjamin G; Lunt, Richard R


    On page 320, R. R. Lunt and co-workers demonstrate electroluminescence from earth-abundant phosphorescent metal halide nanoclusters. These inorganic emitters, which exhibit rich photophysics combined with a high phosphorescence quantum yield, are employed in red and near-infrared light-emitting diodes, providing a new platform of phosphorescent emitters for low-cost and high-performance light-emission applications.

  6. Developing Quantum Dot Phosphor-Based Light-Emitting Diodes for Aviation Lighting Applications

    Directory of Open Access Journals (Sweden)

    Fengbing Wu


    Full Text Available We have investigated the feasibility of employing quantum dot (QD phosphor-based light-emitting diodes (LEDs in aviation applications that request Night Vision Imaging Systems (NVIS compliance. Our studies suggest that the emerging QD phosphor-based LED technology could potentially be superior to conventional aviation lighting technology by virtue of the marriage of tight spectral control and broad wavelength tunability. This largely arises from the fact that the optical properties of semiconductor nanocrystal QDs can be tailored by varying the nanocrystal size without any compositional changes. It is envisioned that the QD phosphor-based LEDs hold great potentials in cockpit illumination, back light sources of monitor screens, as well as the LED indicator lights of aviation panels.

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

    KAUST Repository

    Shen, Chao


    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 (τ<0.35 ns) through the amplified spontaneous emission, the SLD exhibits a significantly large 3-dB bandwidth of 807 MHz. A data rate of 1.3 Gbps with a bit-error rate of 2.9 × 10 was obtained using on-off keying modulation scheme, suggesting the SLD being a high-speed transmitter for VLC applications.

  8. Heat generation and thermo-mechanical effect modeling in longitudinally diode-pumped solid state lasers (United States)

    Lakhdari, Fouad; Osmani, Ismahen; Tabet, Saida


    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.

  9. IR detection and energy harvesting using antenna coupled MIM tunnel diodes (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

  10. Role of electron blocking layer in III-nitride laser diodes and light-emitting diodes (United States)

    Kuo, Yen-Kuang; Chang, Jih-Yuan; Chen, Mei-Ling


    A high energy bandgap electron blocking layer (EBL) just behind the active region is conventionally used in the nitride-based laser diodes (LDs) and light-emitting diodes (LEDs) to improve the confinement capability of electrons within the quantum wells. Nevertheless, the EBL may also act as a potential barrier for the holes and cause non-uniform distribution of holes among quantum wells. A most recent study by Han et al. (Appl. Phys. Lett. 94, 231123, 2009) reported that, because of the blocking effect for holes, the InGaN LED device without an EBL has slighter efficiency droop and higher light output at high level of current injection when compared with the LED device with an EBL. This result seems to contradict with the original intention of using the EBL. Furthermore, findings from our previous studies (IEEE J. Lightwave Technol. 26, 329, 2008; J. Appl. Phys. 103, 103115, 2008; Appl. Phys. Lett. 91, 201118, 2007) indicated that the utilization of EBL is essential for the InGaN laser diodes. Thus, in this work, the optical properties of the InGaN LDs and LEDs are explored numerically with the LASTIP simulation program and APSYS simulation program, respectively. The analyses focus particularly on the light output power, energy band diagrams, recombination rates, distribution of electrons and holes in the active region, and electron overflow. This study will then conclude with a discussion of the effect of EBL on the optical properties of the InGaN LDs and LEDs.

  11. Current transport mechanisms in mercury cadmium telluride diode (United States)

    Gopal, Vishnu; Li, Qing; He, Jiale; He, Kai; Lin, Chun; Hu, Weida


    This paper reports the results of modelling of the current-voltage characteristics (I-V) of a planar mid-wave Mercury Cadmium Telluride photodiode in a gate controlled diode experiment. It is reported that the diode exhibits nearly ideal I-V characteristics under the optimum surface potential leading to the minimal surface leakage current. Deviations from the optimum surface potential lead to non ideal I-V characteristics, indicating a strong relationship between the ideality factor of the diode with its surface leakage current. Diode's I-V characteristics have been modelled over a range of gate voltages from -9 V to -2 V. This range of gate voltages includes accumulation, flat band, and depletion and inversion conditions below the gate structure of the diode. It is shown that the I-V characteristics of the diode can be very well described by (i) thermal diffusion current, (ii) ohmic shunt current, (iii) photo-current due to background illumination, and (iv) excess current that grows by the process of avalanche multiplication in the gate voltage range from -3 V to -5 V that corresponds to the optimum surface potential. Outside the optimum gate voltage range, the origin of the excess current of the diode is associated with its high surface leakage currents. It is reported that the ohmic shunt current model applies to small surface leakage currents. The higher surface leakage currents exhibit a nonlinear shunt behaviour. It is also shown that the observed zero-bias dynamic resistance of the diode over the entire gate voltage range is the sum of ohmic shunt resistance and estimated zero-bias dynamic resistance of the diode from its thermal saturation current.

  12. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells. (United States)

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J


    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance.

  13. Light-emitting diodes for analytical chemistry. (United States)

    Macka, Mirek; Piasecki, Tomasz; Dasgupta, Purnendu K


    Light-emitting diodes (LEDs) are playing increasingly important roles in analytical chemistry, from the final analysis stage to photoreactors for analyte conversion to actual fabrication of and incorporation in microdevices for analytical use. The extremely fast turn-on/off rates of LEDs have made possible simple approaches to fluorescence lifetime measurement. Although they are increasingly being used as detectors, their wavelength selectivity as detectors has rarely been exploited. From their first proposed use for absorbance measurement in 1970, LEDs have been used in analytical chemistry in too many ways to make a comprehensive review possible. Hence, we critically review here the more recent literature on their use in optical detection and measurement systems. Cloudy as our crystal ball may be, we express our views on the future applications of LEDs in analytical chemistry: The horizon will certainly become wider as LEDs in the deep UV with sufficient intensity become available.

  14. Terahertz optoelectronics with surface plasmon polariton diode. (United States)

    Vinnakota, Raj K; Genov, Dentcho A


    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 exceedingly large signal modulation rates. The SPPD uses heavily doped p-n junction where surface plasmon polaritons propagate at the interface between n and p-type GaAs and can be switched by an external voltage. The devices can operate at transmission modulation higher than 98% and depending on the doping and applied voltage can achieve switching rates of up to 1 THz. The proposed switch is compatible with the current semiconductor fabrication techniques and could lead to nanoscale semiconductor-based optoelectronics.

  15. Active coherent beam combining of diode lasers. (United States)

    Redmond, Shawn M; Creedon, Kevin J; Kansky, Jan E; Augst, Steven J; Missaggia, Leo J; Connors, Michael K; Huang, Robin K; Chann, Bien; Fan, Tso Yee; Turner, George W; Sanchez-Rubio, Antonio


    We have demonstrated active coherent beam combination (CBC) of up to 218 semiconductor amplifiers with 38.5 W cw output using up to eleven one-dimensional 21-element individually addressable diode amplifier arrays operating at 960 nm. The amplifier array elements are slab-coupled-optical-waveguide semiconductor amplifiers (SCOWAs) set up in a master-oscillator-power-amplifier configuration. Diffractive optical elements divide the master-oscillator beam to seed multiple arrays of SCOWAs. A SCOWA was phase actuated by adjusting the drive current to each element and controlled using a stochastic-parallel-gradient-descent (SPGD) algorithm for the active CBC. The SPGD is a hill-climbing algorithm that maximizes on-axis intensity in the far field, providing phase locking without needing a reference beam.

  16. Contact Whiskers for Millimeter Wave Diodes (United States)

    Kerr, A. R.; Grange, J. A.; Lichtenberger, J. A.


    Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

  17. High-power green diode laser systems for biomedical applications

    DEFF Research Database (Denmark)

    Müller, André

    in conjunction with optical coherence tomography, two-photon microscopy or coherent anti-Stokes Raman scattering microscopy. In order to provide high-power green diode laser emission, nonlinear frequency conversion of state-of-the-art near-infrared diode lasers represents a necessary means. However, the obtained...... output power of frequency doubled single emitters is limited by thermal effects potentially resulting in laser degradation and failure. In this work new concepts for power scaling of visible diode laser systems are introduced that help to overcome current limitations and enhance the application potential...

  18. Tapered diode laser pumped 946 nm Nd:YAG laser

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay; Jensen, Ole Bjarlin; Petersen, Paul Michael


    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....

  19. 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


    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.

  20. Bipolar Host Materials for Organic Light-Emitting Diodes. (United States)

    Yook, Kyoung Soo; Lee, Jun Yeob


    It is important to balance holes and electrons in the emitting layer of organic light-emitting diodes to maximize recombination efficiency and the accompanying external quantum efficiency. Therefore, the host materials of the emitting layer should transport both holes and electrons for the charge balance. From this perspective, bipolar hosts have been popular as the host materials of thermally activated delayed fluorescent devices and phosphorescent organic light-emitting diodes. In this review, we have summarized recent developments of bipolar hosts and suggested perspectives of host materials for organic light-emitting diodes.

  1. A transient model of a cesium-barium diode

    Energy Technology Data Exchange (ETDEWEB)

    Luke, J.R.; El-Genk, M.S.


    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.

  2. Optical monitoring of high power direct diode laser cladding (United States)

    Liu, Shuang; Farahmand, Parisa; Kovacevic, Radovan


    Laser cladding is one of the most advanced surface modification techniques which can be used to build and repair high-value components. High power direct diode laser (HPDDL) offers unique quality and cost advantages over other lasers (CO2, Nd:YAG). Especially its rectangular laser beam with top-hat intensity distribution makes HPDDL an ideal tool for large area cladding. In order to utilize this technique successfully, the development of on-line monitoring and process control is necessary. In this study, an optical monitoring system consisting of a high-speed CCD camera, a pyrometer, and an infrared camera was used to analyze the mass- and heat-transfer in the cladding process. The particle transport in flight was viewed by a high-speed CCD camera; the interaction between powder flow and laser beam was observed by an infrared camera; and the thermal behavior of the molten pool was recorded by the pyrometer and the infrared camera. The effects of the processing parameters on the laser attenuation, particle heating and clad properties were investigated based on the obtained signals. The optical monitoring method improved the understanding about mutual interrelated phenomena in the cladding process.

  3. Titanium-dioxide nanotube p-n homojunction diode

    Energy Technology Data Exchange (ETDEWEB)

    Alivov, Yahya, E-mail:, E-mail:; Ding, Yuchen; Singh, Vivek [Department of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, Colorado 80303 (United States); Nagpal, Prashant, E-mail:, E-mail: [Department of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, Colorado 80303 (United States); Materials Science and Engineering, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, Colorado 80303 (United States); Renewable and Sustainable Energy Institute, University of Colorado Boulder, 2445 Kittredge Loop, Boulder, Colorado 80309 (United States)


    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 (TiO{sub 2}) nanotubes doped with nitrogen (N) and niobium (Nb) as acceptors and donors, respectively, and formation of TiO{sub 2} nanotubes p-n homojunction. This TiO{sub 2}:N/TiO{sub 2}: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.

  4. Ultra-broad bandwidth parametric amplification at degeneracy. (United States)

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


    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.

  5. Enhanced performance thermal diode via thermal boundary resistance at nanoscale (United States)

    Tovar-Padilla, M.; Licea-Jimenez, L.; Pérez-Garcia, S. A.; Alvarez-Quintana, J.


    Hypothetically, a thermal rectifier is a device which leads a greater heat flux in one direction than another one, similarly as the electrical diode works for the electrical flux. Here, a drastic increment in the rectification factor has been obtained in nanoscale layered thermal diodes due to the effect of thermal boundary resistance present on an asymmetrical stack of nanofilms. Measurements show a thermal rectification factor as large as 3.3 under a temperature bias well below 1 K, which is the biggest thermal rectification factor reported at room temperature compared to previously reported thermal diodes so far. According to the direction of the applied heat flux, the observed impact of the thermal boundary resistance on the device is manifested through the presence of an asymmetric temperature rise along the heat transfer axis. Such effect provides an alternative route for the development of high performance thermal diodes.

  6. Theoretical studies on ionospheric irregularities and ion diode performance (United States)

    Sudan, R. N.


    Work accomplished is divided into three parts: ionospheric physics; ion diodes, magnetic insulation, and plasma opening switches; and subgrid modeling in numerical computations and other research. Abstracts of published and conference papers are presented.

  7. Active graphene-silicon hybrid diode for terahertz waves (United States)

    Li, Quan; Tian, Zhen; Zhang, Xueqian; Singh, Ranjan; Du, Liangliang; Gu, Jianqiang; Han, Jiaguang; Zhang, Weili


    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.

  8. An all MMIC Replacement for Gunn Diode Oscillators Project (United States)

    National Aeronautics and Space Administration — We propose to replace the Gunn Diode Oscillators (GDOs) in NASA?s millimeter- and submillimeter-wave sensing instruments. Our new solution will rely on modern and...

  9. Femtosecond soliton diode on heterojunction Bragg-grating structure

    CERN Document Server

    Deng, Zhigui; Li, Hongji; Fu, Shenhe; Liu, Yikun; Xiang, Ying; Li, Yongyao


    We numerically propose a scheme for realizing an all-optical femtosecond soliton diode based on a tailored heterojunction Bragg grating, which is designed by two spatially asymmetric chirped cholesteric liquid crystals. Our simulations demonstrate that with the consideration of optical nonlinearity, not only the femtosecond diode effect with nonreciprocal transmission ratio up to 120 can be achieved, but also the optical pulse evolving into soliton which maintains its shape during propagation through the sample is observed. Further, the influence of pulse width and the carrier wavelength to the femtosecond diode effect is also discussed in detail. Our demonstrations might suggest a new direction for experimentally realizing the femtosecond soliton diode based on the cholesteric liquid crystals.

  10. Active Stabilization of a Diode Laser Injection Lock

    CERN Document Server

    Saxberg, Brendan; Gupta, Subhadeep


    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.

  11. Active graphene-silicon hybrid diode for terahertz waves. (United States)

    Li, Quan; Tian, Zhen; Zhang, Xueqian; Singh, Ranjan; Du, Liangliang; Gu, Jianqiang; Han, Jiaguang; Zhang, Weili


    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.

  12. Active stabilization of a diode laser injection lock (United States)

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep


    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.

  13. Giant Thermal Rectification from Polyethylene Nanofiber Thermal Diodes

    CERN Document Server

    Zhang, Teng


    The realization of phononic computing is held hostage by the lack of high performance thermal devices. Here we show through theoretical analysis and molecular dynamics simulations that unprecedented thermal rectification factors (as large as 1.20) can be achieved utilizing the phase dependent thermal conductivity of polyethylene nanofibers. More importantly, such high thermal rectifications only need very small temperature differences (< 20 oC) across the device, which is a significant advantage over other thermal diodes which need temperature biases on the order of the operating temperature. Taking this into consideration, we show that the dimensionless temperature-scaled rectification factors of the polymer nanofiber diodes range from 12 to 25 - much larger than other thermal diodes (< 8). The polymer nanofiber thermal diode consists of a crystalline portion whose thermal conductivity is highly phase-sensitive and a cross-linked portion which has a stable phase. Nanoscale size effect can be utilized t...

  14. Differential Diode Laser Sensor for High-Purity Oxygen Project (United States)

    National Aeronautics and Space Administration — A compact portable sensor for determining the purity of oxygen concentrations near 100 percent is proposed based on differential absorption of two beams from a diode...

  15. Organic light-emitting diodes: High-throughput virtual screening (United States)

    Hirata, Shuzo; Shizu, Katsuyuki


    Computer networks, trained with data from delayed-fluorescence materials that have been successfully used in organic light-emitting diodes, facilitate the high-speed prediction of good emitters for display and lighting applications.

  16. Response time of light emitting diode-logarithmic electrometer (United States)

    Acharya, Y. B.; Vyavahare, P. D.


    In a logarithmic electrometer which uses a transistor as a nonlinear element, a capacitance is generally connected across the feedback element of the operational amplifier. This stabilizes the loop but degrades the response at low current levels. However the stability problem is not so serious when a junction diode is used. In the present work an attempt was made to study the response time of a logarithmic electrometer which uses a light emitting diode (LED) as a nonlinear element and without external capacitance. The calculated values of rise time are based on an equivalent circuit with a depletion layer capacitance and voltage dependent conductance. These values are found to be in reasonable agreement with the experimentally measured values. This study will be useful in the estimation of dynamical errors in logarithmic electrometers using junction diode/LED, LED photometers and will be helpful in the techniques for improvements of the response time of logarithmic electrometers using a junction diode, particularly at low currents.

  17. Pulse-Width Jitter Measurement for Laser Diode Pulses

    Institute of Scientific and Technical Information of China (English)

    TANG Jun-Hua; WANG Yun-Cai


    @@ Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced.

  18. Unmanned Aerial Vehicle Diode Laser Sensor for Methane Project (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...

  19. Efficient potassium diode pumped alkali laser operating in pulsed mode. (United States)

    Zhdanov, Boris V; Rotondaro, Matthew D; Shaffer, Michael K; Knize, Randall J


    This paper presents the results of our experiments on the development of an efficient hydrocarbon free diode pumped alkali laser based on potassium vapor buffered by He gas at 600 Torr. A slope efficiency of more than 50% was demonstrated with a total optical conversion efficiency of 30%. This result was achieved by using a narrowband diode laser stack as the pump source. The stack was operated in pulsed mode to avoid limiting thermal effects and ionization.

  20. Stacked, filtered multi-channel X-ray diode array (United States)

    MacNeil, L. P.; Dutra, E. C.; Compton, S. M.; Jacoby, B. A.; Raphaelian, M. L.


    There are many types of X-ray diodes that are used for X-ray flux or spectroscopic measurements and for estimating the spectral shape of the VUV to soft X-ray spectrum. However, a need arose for a low cost, robust X-ray diode to use for experiments in hostile environments on multiple platforms, and for experiments that utilize forces that may destroy the diode(s). Since the typical proposed use required a small size with a minimal single line-of-sight, a parallel array could not be used. So, a stacked, filtered multi-channel X-ray diode array was developed, called the MiniXRD. To achieve significant cost savings while maintaining robustness and ease of field setup, repair, and replacement, we designed the system to be modular. The filters were manufactured in-house and cover the range from 450 eV to 5000 eV. To achieve the line-of-sight accuracy needed, we developed mounts and laser alignment techniques. We modeled and tested elements of the diode design at NSTec Livermore Operations (NSTec / LO) to determine temporal response and dynamic range, leading to diode shape and circuitry changes to optimize impedance and charge storage. We fielded individual and stacked systems at several national facilities as ancillary `ride-along' diagnostics to test and improve the design usability. We present the MiniXRD system performance which supports consideration as a viable low-cost alternative for multiple-channel low-energy X-ray measurements. This diode array is currently at Technical Readiness Level (TRL) 6.

  1. Stacked, filtered multi-channel X-ray diode array

    Energy Technology Data Exchange (ETDEWEB)

    MacNeil, Lawrence [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Dutra, Eric [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Raphaelian, Mark [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Compton, Steve [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jacoby, Barry [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)


    There are many types of X-ray diodes used for X-ray flux or spectroscopic measurements and for estimating the spectral shape of the VUV to soft X-ray spectrum. However, a need exists for a low-cost, robust X-ray diode to use for experiments in hostile environments on multiple platforms, and for experiments that utilize forces that may destroy the diode(s). Since the typical proposed use required a small size with a minimal single line-of-sight, a parallel array could not be used. So, a stacked, filtered multi-channel X-ray diode array was developed, called the MiniXRD. To achieve significant cost savings while maintaining robustness and ease of field setup, repair, and replacement, we designed the system to be modular. The filters were manufactured in-house and cover the range from 450 eV to 5000 eV. To achieve the line-of-sight accuracy needed, we developed mounts and laser alignment techniques. We modeled and tested elements of the diode design at NSTec Livermore Operations (NSTec / LO) to determine temporal response and dynamic range, leading to diode shape and circuitry changes to optimize impedance and charge storage. The authors fielded individual and stacked systems at several national facilities as ancillary "ride-along" diagnostics to test and improve the design usability. This paper presents the MiniXRD system performance, which supports consideration as a viable low-costalternative for multiple-channel low-energy X-ray measurements. This diode array is currently at Technical Readiness Level (TRL) 6.

  2. Active Stabilization of a Diode Laser Injection Lock


    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep


    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 sudde...

  3. Active graphene–silicon hybrid diode for terahertz waves


    Li, Quan; Tian, Zhen; Zhang, Xueqian; Singh, Ranjan; Du, Liangliang; Gu, Jianqiang; Han, Jiaguang; Zhang, Weili


    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 di...

  4. Spectral beam combining of diode lasers with high efficiency

    DEFF Research Database (Denmark)

    Müller, André; Vijayakumar, Deepak; Jensen, Ole Bjarlin;


    Based on spectral beam combining we obtain 16 W of output power, combining two 1063 nm DBR-tapered diode lasers. The spectral separation within the combined beam can be used for subsequent sum-frequency generation.......Based on spectral beam combining we obtain 16 W of output power, combining two 1063 nm DBR-tapered diode lasers. The spectral separation within the combined beam can be used for subsequent sum-frequency generation....

  5. AGN Broad Line Regions Scale with Bolometric Luminosity

    CERN Document Server

    Trippe, Sascha


    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.

  6. Broad Spectrum Sanitizing Wipes with Food Additives Project (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...

  7. Phosphor-free white light-emitting diode with laterally distributed multiple quantum wells (United States)

    Park, Il-Kyu; Kim, Ja-Yeon; Kwon, Min-Ki; Cho, Chu-Young; Lim, Jae-Hong; Park, Seong-Ju


    A phosphor-free white light-emitting diode (LED) was fabricated with laterally distributed blue and green InGaN /GaN multiple quantum wells (MQWs) grown by a selective area growth method. Photoluminescence and electroluminescence (EL) spectra of the LED showed emission peaks corresponding to the individual blue and green MQWs. The integrated EL intensity ratio of green to blue emission varied from 2.5 to 6.5 with the injection current below 300mA, but remained constant at high injection currents above 300mA. The stability of the emission color at high currents is attributed to parallel carrier injection into both MQWs.

  8. Transient surface modifications during singular heating events at diode laser facets (United States)

    Hempel, Martin; Tomm, Jens W.; Bachmann, Alexander; Lauer, Christian; Furitsch, Michael; Strauß, Uwe; Elsaesser, Thomas


    Surface morphology changes and transient reflectance changes at diode laser facets are monitored during the catastrophic optical damage (COD) process in a single pulse operation. Time-resolved micro-reflectance spectroscopy with a streak-camera (time resolution ˜20 ns) allows us to observe the creation sequence of up to four distinct degradation seed points at a device facet within <300 ns. The shape of the COD seeds is created within <30-40 ns. Creation of non-planar facet areas by local melting represents the main mechanism behind the observed reflectivity changes. Subsequently the surface temperature decreases within the pulse which caused the COD.

  9. A Flight-like Integrated Circulator for Broad Area Cooling Project (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...

  10. Clues to Quasar Broad Line Region Geometry and Kinematics

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Wilkes, B. J.; Barthel, P. D.


    width to show significant inverse correlations with the fractional radio core-flux density, R, the radio axis inclination indicator. Highly inclined systems have broader line wings, consistent with a high-velocity field perpendicular to the radio axis. By contrast, the narrow line-core shows...... and with an accretion disk-wind emitting the broad lines. A spherical distribution of randomly orbiting broad-line clouds and a polar high-ionization outflow are ruled out....

  11. Identification and specificity of broadly neutralizing antibodies against HIV


    McCoy, Laura E.; Burton, Dennis R.


    Summary Beginning in 2009, studies of the humoral responses of HIV‐positive individuals have led to the identification of scores, if not hundreds, of antibodies that are both broadly reactive and potently neutralizing. This development has provided renewed impetus toward an HIV vaccine and led directly to the development of novel immunogens. Advances in identification of donors with the most potent and broad anti‐HIV serum neutralizing responses were crucial in this effort. Equally, developme...

  12. Design and Fabrication of Planar GaAs Gunn Diodes (United States)

    Kim, Mi-Ra; Lee, Seong-Dae; Chae, Yeon-Sik; Rhee, Jin-Koo

    We studied planar graded-gap injector GaAs Gunn diodes designed for operation at 94GHz. Two types of planar Gunn diodes were designed and fabricated. In the first diode, a cathode was situated inside a circular anode with a diameter of 190μm. The distance between the anode and cathode varied from 60μm to 68μm depending on the cathode size. Also, we designed a structure with a constant distance between the anode and cathode of 10μm. In the second diode, the anode was situated inside the cathode for the flip-chip mounting on the oscillator circuits. The fabrication of the Gunn diode was based on ohmic contact metallization, mesa etching, and air-bridge and overlay metallization. DC measurements were carried out, and the nature of the negative differential resistance, the operating voltage, and the peak current in the graded-gap injector GaAs Gunn diodes are discussed for different device structures. It is shown that the structure with the shorter distance between the cathode and anode has a higher peak current, higher breakdown voltage, and lower threshold voltage than those of the structure with the larger distance between the cathode and anode.

  13. Coherent and noncoherent low-power diodes in clinical practice (United States)

    Antipa, Ciprian; Pascu, Mihail-Lucian; Stanciulescu, Viorica; Vlaiculescu, Mihaela; Ionescu, Elena; Bordea, Daniel


    Clinical efficacy of the low power laser (LPL) in medical treatments is still not well established. In a double blind, placebo controlled study, we tried to find out first which type of LPL is more efficient, and second if coherence is an important character for clinical efficacy. We treated 1228 patients having different rheumatic diseases, with low power diode, used as follows: A group: IR coherent diode, continuous emission, 3 mW power; B group: IR coherent diode, pulsed emission, output power about 3 mW; C group: IR noncoherent diode continuous emission 9 mW power; D group: both IR diode lasers (continuous or pulsed) and HeNe laser, continuous emission, 2 mW power; E group: placebo laser as control group. The energy dose used for every group was the same, as well as the clinical protocols. The positive results were: 66.16% for A group; 64.06% for B group; 48.87% for C group; 76.66% for D group, and 39.07% for E group. Finally, we showed that LPL is really efficient in the treatment of some rheumatic diseases, especially when red and IR diode laser were used in combination. The type of emission (continuous or pulsed) is not important, but coherence is obviously necessary for clinical efficacy.

  14. Transition metal dichalcogenide heterojunction PN diode toward ultimate photovoltaic benefits (United States)

    Ahn, Jongtae; Jeon, Pyo Jin; Raza, Syed Raza Ali; Pezeshki, Atiye; Min, Sung-Wook; Hwang, Do Kyung; Im, Seongil


    Recently, two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors as van der Waals (vdW) materials have attracted much attention from researchers. Among many 2D TMDC materials, a few layer-thin molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) have been most intensively studied respectively as 2D n- and p-type semiconductors. Here, we have fabricated vertical vdW heterojunction n-MoS2/p-WSe2 diode with a few tens nm-thick layers by using vertically-sandwiched ohmic terminals, so that no quasi neutral region may exist between two terminals. As a result, we obtained high photo responsivity at zero volt without any electric power, and it appears comparable to those of commercially-optimized Si PN diode. Photo-voltage output of 0.3 V was easily obtained from our vdW PN diode as open circuit voltage, and can be doubled up to 0.6 V by using two PN diodes. These beneficial photovoltaic results from vdW PN diode were directly applied to PV switching dynamics and transistor photo gating, for the first time. We regard that our vdW n-MoS2/p-WSe2 heterojunction diode could maximize its photovoltaic energy benefits with optimized TMDC thicknesses.

  15. Clinical comparison between the bleaching efficacy of light-emitting diode and diode laser with sodium perborate. (United States)

    Koçak, Sibel; Koçak, Mustafa Murat; Sağlam, Baran Can


    The aim of this clinical study was to test the efficacy of a light-emitting diode (LED) light and a diode laser, when bleaching with sodium perborate. Thirty volunteers were selected to participate in the study. The patients were randomly divided into two groups. The initial colour of each tooth to be bleached was quantified with a spectrophotometer. In group A, sodium perborate and distilled water were mixed and placed into the pulp chamber, and the LED light was source applied. In group B, the same mixture was used, and the 810 nm diode laser was applied. The final colour of each tooth was quantified with the same spectrophotometer. Initial and final spectrophotometer values were recorded. Mann-Whitney U-test and Wicoxon tests were used to test differences between both groups. Both devices successfully whitened the teeth. No statistical difference was found between the efficacy of the LED light and the diode laser.

  16. Investigation of Diode Pumped Alkali Laser Atmospheric Transmission Using Tunable Diode Laser Absorption Spectroscopy (United States)


    House Appropriations hearing on May 20th, 2010 where Robert Gates, then U.S. Secretary of Defense, said the following in answer to a question from Rep...Henry, B. P. Wert, T. Gilpin , and J. R. Drummond. “Tunable diode laser absorption spectrometer for ground-based measurements of formaldehyde”. Journal...spectroscopy (TDLAS) at 1.37 µm”. Applied Physics B: Lasers and Optics, 92(3):393–401, 2008. 43. Kormann, Robert , Horst Fischer, and Frank G. Wienhold

  17. FTIR Study of White and Green Broad Beans Based on Curve-fitting

    Institute of Scientific and Technical Information of China (English)

    Xiaohua; WANG; Gang; LIU; Quanhong; OU; Xingxiang; ZHAO; Jianming; HAO; Xiangping; ZHOU


    Fourier transform infrared(FTIR)spectroscopy was used to study two kinds of broad beans with white and green cotyledons respectively.The results show that the infrared spectra of the two kinds of broad beans are similar and mainly made up of the absorption bands of protein,and polysaccharides.The second derivative infrared spectra amplified the differences and revealed that there were some obvious differences in the range of 1 800-700 cm-1and 1 200-700 cm-1.Hierarchical cluster analysis(HCA)were used for the discrimination of the two kinds broad beans based on the second derivative spectral data in the region of 1 611-1 100 cm-1,and yielded 88.9%accuracy.The spectra in the range from 1 700 to 1 600 cm-1were used to perform Fourier self-deconvolution and curve fitting,which obtained nine peaks.The ratios of relative areas of the bands atα-helix,β-sheet,β-turn and the unordered structure of protein in white beans were 67.71%,35.6%,35.6%and 21.09%respectively,while the ratios in green beans were 8.02%,31.59%,37.12%and 23.27%respectively.The results indicate that the secondary structure of protein was different in the two kinds of broad beans.

  18. MMIC Replacement for Gunn Diode Oscillators (United States)

    Crowe, Thomas W.; Porterfield, David


    An all-solid-state replacement for high-frequency Gunn diode oscillators (GDOs) has been proposed for use in NASA s millimeter- and submillimeter-wave sensing instruments. Highly developed microwave oscillators are used to achieve a low-noise and highly stable reference signal in the 10-40-GHz band. Compact amplifiers and high-power frequency multipliers extend the signal to the 100-500-GHz band with minimal added phase noise and output power sufficient for NASA missions. This technology can achieve improved output power and frequency agility, while maintaining phase noise and stability comparable to other GDOs. Additional developments of the technology include: a frequency quadrupler to 145 GHz with 18 percent efficiency and 15 percent fixed tuned bandwidth; frequency doublers featuring 124, 240, and 480 GHz; an integrated 874-GHz subharmonic mixer with a mixer noise temperature of 3,000 K DSB (double sideband) and mixer conversion loss of 11.8 dB DSB; a high-efficiency frequency tripler design with peak output power of 23 mW and 14 mW, and efficiency of 16 and 13 percent, respectively; millimeter-wave integrated circuit (MMIC) power amplifiers to the 30-40 GHz band with high DC power efficiency; and an 874-GHz radiometer suitable for airborne observation with state-of-the-art sensitivity at room temperature and less than 5 W of total power consumption.

  19. Design of drive circuit of laser diode (United States)

    Ran, Yingying; Huang, Xuegong; Xu, Xiaobin


    Aiming at the difficult problem of high precision frequency stabilization of semiconductor laser diode, the laser frequency control is realized through the design of the semiconductor drive system. Above all, the relationship between the emission frequency and the temperature of LD is derived theoretically. Then the temperature corresponding to the stable frequency is obtained. According to the desired temperature stability of LD, temperature control system is designed, which is composed of a temperature setting circuit, temperature gathering circuit, the temperature display circuit, analog PID control circuit and a semiconductor refrigerator control circuit module. By sampling technology, voltage of platinum resistance is acquired, and the converted temperature is display on liquid crystal display. PID analog control circuit controls speed stability and precision of temperature control. The constant current source circuit is designed to provide the reference voltage by a voltage stabilizing chip, which is buffered by an operational amplifier. It is connected with the MOSFET to drive the semiconductor laser to provide stable current for the semiconductor laser. PCB circuit board was finished and the experimental was justified. The experimental results show that: the design of the temperature control system could achieve the goal of temperature monitoring. Meanwhile, temperature can be stabilized at 40°C +/- 0.1°C. The output voltage of the constant current source is 2 V. The current is 35 mA.

  20. Diode laser absorption spectroscopy of lithium isotopes (United States)

    Olivares, Ignacio E.; González, Iván A.


    We study Doppler-limited laser intensity absorption, in a thermal lithium vapor containing 7Li and 6Li atoms in a 9 to 1 ratio, using a narrow-linewidth single-longitudinal-mode tunable external cavity diode laser at the wavelength of 670.8 nm. The lithium vapor was embedded in helium or argon buffer gas. The spectral lineshapes were rigorously predicted for D_1 and D_2 for the lithium 6 and 7 isotope lines using reduced optical Bloch equations, specifically derived, from a density matrix analysis. Here, a detailed comparison is provided of the predicted lineshapes with the measured 7Li-D_2, 7Li-D_1, 6Li-D_2 and 6Li-D_1 lines, in the case of high vapor density and with intensity above the saturation intensity. To our knowledge, this is the first time that such detailed comparison is reported in the open literature. The calculations were also extended to saturated absorption spectra and compared to measured Doppler-free 7Li-D_2 and 6Li-D_2 hyperfine lines.

  1. Comparison between blue lasers and light-emitting diodes for future solid-state lighting: Comparison between blue lasers and light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wierer, Jonathan J. [Sandia National Laboratories, Albuquerque NM 87185 USA; Tsao, Jeffrey Y. [Sandia National Laboratories, Albuquerque NM 87185 USA; Sizov, Dmitry S. [Corning Incorporated, One Science Center Dr., Corning NY 14831 USA


    Solid-state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light-emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state-of-the-art input-power-density-dependent power-conversion efficiencies; potential improvements both in their peak power-conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL.

  2. Development of a Broadly Tunable Mid-Infrared Laser Source for Highly Sensitive Multiple Trace Gas Detection

    Institute of Scientific and Technical Information of China (English)

    Xiao-Juan Cui; Feng-Zhong Dong; Yu-Jun Zhang; Rui-Feng Kan; Yi-Ben Cui; Min Wang; Dong Chen; Jian-Guo Liu; Wen-Qing Liu


    A room-temperature broadly tunable mid-infrared difference frequency laser source for highly sensitive trace gas detection has been developed recently in our laboratory. The mid-infrared laser system is based on quasi-phase-matched (QPM) difference frequency generation (DFG) in a multi-grating, temperature-controlled periodically poled LiNbO3 (PPLN) crystal and employs two near-infrared diode lasers as pump sources. The mid-infrared coherent radiation generated is tunable from 3.2 μm to 3.7 μm with an output power of about 100 μW. By changing one of the pump laser head with another wavelength range, we can readily obtain other needed mid-infrared wavelength range cover. The performance of the mid-infrared laser system and its application to highly sensitive spectroscopic detection of CH4, HCI, CH2O, and NO2 has been carried out. A multi-reflection White cell was used in the experiment gaining ppb-level sensitivity. The DFG laser system has the features of compact, room-temperature operation, narrow line-width, and broadly continuous tunable range for potential applications in industry and environmental monitoring.

  3. Ablation of dentin by irradiation of violet diode laser (United States)

    Hatayama, H.; Kato, J.; Akashi, G.; Hirai, Y.; Inoue, A.


    Several lasers have been used for clinical treatment in dentistry. Among them, diode lasers are attractive because of their compactness compared with other laser sources. Near-infrared diode lasers have been practically used for cutting soft tissues. Because they penetrate deep to soft tissues, they cause sufficiently thick coagulation layer. However, they aren't suitable for removal of carious dentin because absorption by components in dentin is low. Recently, a violet diode laser with a wavelength of 405nm has been developed. It will be effective for cavity preparation because dentin contains about 20% of collagen whose absorption coefficient at a violet wavelength is larger than that at a near-infrared wavelength. In this paper, we examined cutting performance of the violet diode laser for dentin. To our knowledge, there have been no previous reports on application of a violet laser to dentin ablation. Bovine teeth were irradiated by continuous wave violet diode laser with output powers in a range from 0.4W to 2.4W. The beam diameter on the sample was about 270μm and an irradiation time was one second. We obtained the crater ablated at more than an output power of 0.8W. The depth of crater ranged from 20μm at 0.8W to 90μm at 2.4W. Furthermore, the beam spot with an output power of 1.7W was scanned at a speed of 1mm/second corresponding to movement of a dentist's hand in clinical treatment. Grooves with the depth of more than 50μm were also obtained. From these findings, the violet diode laser has good potential for cavity preparation. Therefore, the violet diode laser may become an effective tool for cavity preparation.

  4. Applications of microlens-conditioned laser diode arrays

    Energy Technology Data Exchange (ETDEWEB)

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


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

  5. Bid Optimization in Broad-Match Ad auctions

    CERN Document Server

    Even-dar, Eyal; Mirrokni, Vahab; Muthukrishnan, S; Nadav, Uri


    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 ...

  6. Antiviral Therapy by HIV-1 Broadly Neutralizing and Inhibitory Antibodies

    Directory of Open Access Journals (Sweden)

    Zhiqing Zhang


    Full Text Available Human immunodeficiency virus type 1 (HIV-1 infection causes acquired immune deficiency syndrome (AIDS, a global epidemic for more than three decades. HIV-1 replication is primarily controlled through antiretroviral therapy (ART but this treatment does not cure HIV-1 infection. Furthermore, there is increasing viral resistance to ART, and side effects associated with long-term therapy. Consequently, there is a need of alternative candidates for HIV-1 prevention and therapy. Recent advances have discovered multiple broadly neutralizing antibodies against HIV-1. In this review, we describe the key epitopes on the HIV-1 Env protein and the reciprocal broadly neutralizing antibodies, and discuss the ongoing clinical trials of broadly neutralizing and inhibitory antibody therapy as well as antibody combinations, bispecific antibodies, and methods that improve therapeutic efficacy by combining broadly neutralizing antibodies (bNAbs with latency reversing agents. Compared with ART, HIV-1 therapeutics that incorporate these broadly neutralizing and inhibitory antibodies offer the advantage of decreasing virus load and clearing infected cells, which is a promising prospect in HIV-1 prevention and treatment.

  7. Antiviral Therapy by HIV-1 Broadly Neutralizing and Inhibitory Antibodies. (United States)

    Zhang, Zhiqing; Li, Shaowei; Gu, Ying; Xia, Ningshao


    Human immunodeficiency virus type 1 (HIV-1) infection causes acquired immune deficiency syndrome (AIDS), a global epidemic for more than three decades. HIV-1 replication is primarily controlled through antiretroviral therapy (ART) but this treatment does not cure HIV-1 infection. Furthermore, there is increasing viral resistance to ART, and side effects associated with long-term therapy. Consequently, there is a need of alternative candidates for HIV-1 prevention and therapy. Recent advances have discovered multiple broadly neutralizing antibodies against HIV-1. In this review, we describe the key epitopes on the HIV-1 Env protein and the reciprocal broadly neutralizing antibodies, and discuss the ongoing clinical trials of broadly neutralizing and inhibitory antibody therapy as well as antibody combinations, bispecific antibodies, and methods that improve therapeutic efficacy by combining broadly neutralizing antibodies (bNAbs) with latency reversing agents. Compared with ART, HIV-1 therapeutics that incorporate these broadly neutralizing and inhibitory antibodies offer the advantage of decreasing virus load and clearing infected cells, which is a promising prospect in HIV-1 prevention and treatment.

  8. Coexistence of diode-like volatile and multilevel nonvolatile resistive switching in a ZrO2/TiO2 stack structure (United States)

    Li, Yingtao; Yuan, Peng; Fu, Liping; Li, Rongrong; Gao, Xiaoping; Tao, Chunlan


    Diode-like volatile resistive switching as well as nonvolatile resistive switching behaviors in a Cu/ZrO2/TiO2/Ti stack are investigated. Depending on the current compliance during the electroforming process, either volatile resistive switching or nonvolatile resistive switching is observed. With a lower current compliance (diode-like volatile resistive switching with a rectifying ratio over 106. The permanent transition from volatile to nonvolatile resistive switching can be obtained by applying a higher current compliance of 100 μA. Furthermore, by using different reset voltages, the Cu/ZrO2/TiO2/Ti device exhibits multilevel memory characteristics with high uniformity. The coexistence of nonvolatile multilevel memory and diode-like volatile resistive switching behaviors in the same Cu/ZrO2/TiO2/Ti device opens areas of applications in high-density storage, logic circuits, neural networks, and passive crossbar memory selectors.

  9. PG 1411 + 442 - The nearest broad absorption line quasar (United States)

    Malkan, Matthew A.; Green, Richard F.; Hutchings, John B.


    IUE observations reveal strong, moderately broad absorption troughs in the blue wings of the C IV and N V emission lines of the quasar PG 1411 + 442. No absorption from weakly ionized gas is detected. The emission-line strengths and overall shape of the ultraviolet/optical/near-infrared/far-infrared continuum of the new broad absorption line quasar are within the range normally measured in quasars. Its redshift is low enough to allow the morphology of the host galaxy to be studied in deep broad-band and intermediate-band CCD images. The galaxy appears to be a large spiral with a very long arm or tail. The inclination angle is 57 deg, which rules out the possibility that the line of sight to the nucleus intersects a large path length in a galactic disk.

  10. Surface Roughness Effects on Discharge Coefficient of Broad Crested Weir

    Directory of Open Access Journals (Sweden)

    Shaker A. Jalil


    Full Text Available The aim of this study is to investigate the effects of surface roughness sizes on the discharge coefficient for a broad crested weirs. For this purpose, three models having different lengths of broad crested weirs were tested in a horizontal flume. In each model, the surface was roughed four times. Experimental results of all models showed that the logical negative effect of roughness increased on the discharge (Q for different values of length. The performance of broad crested weir improved with decrease ratio of roughness to the weir height (Ks/P and with the increase of the total Head to the Length (H/L. An empirical equation was obtained to estimate the variation of discharge coefficient Cd in terms total head to length ratio, with total head to roughness ratio.

  11. Broad ligament pregnancy a diagnostic dilemma: a case report

    Directory of Open Access Journals (Sweden)

    Amit Gupta


    Full Text Available Broad ligament pregnancy is one of the rarest forms of ectopic pregnancy with high risk of maternal mortality. Although ultrasonography is usually helpful in making the diagnosis but it is mostly established during laparotomy. 34 year old G2P1 with previous caesarean section reported at 8th month of pregnancy with inability to perceive foetal movements. Ultrasonography confirmed intrauterine fetal demise. Patient was taken for caesarean section after failed induction. Intraoperative diagnosis of broad ligament pregnancy was made and broad ligament along with fetus, sac, fallopian tube and ovary was excised. Post-operative period was uneventful. [Int J Reprod Contracept Obstet Gynecol 2016; 5(7.000: 2478-2480

  12. Micro thermal diode with glass thermal insulation structure embedded in a vapor chamber (United States)

    Tsukamoto, Takashiro; Hirayanagi, Takashi; Tanaka, Shuji


    This paper reports a micro thermal diode based on one-way working fluid circulation driven by surface tension force. In forward mode, working fluid evaporates and condenses at a heated and cooled area, respectively, and the condensed liquid returns to the evaporation area due to the wettability difference. By this vapor-liquid phase change mechanism, the overall heat transfer coefficient becomes high. On the other hand, in reverse mode, no continuous evaporation-condensation cycle exists. The conductive heat loss in reverse mode was minimized by an embedded glass thermal isolation structure, which makes overall heat transfer coefficient low. The test device was made by a standard MEMS process combined with glass reflow and gold bump sealing. The overall heat transfer coefficients of 13 300 \\text{W}~{{\\text{m}}-2}~\\text{K} for forward mode and 4790 \\text{W}~{{\\text{m}}-2}~\\text{K} for reverse mode were measured. The performance index of the micro thermal diode was about 2.8.

  13. Reliability of high power laser diodes with external optical feedback (United States)

    Bonsendorf, Dennis; Schneider, Stephan; Meinschien, Jens; Tomm, Jens W.


    Direct diode laser systems gain importance in the fields of material processing and solid-state laser pumping. With increased output power, also the influence of strong optical feedback has to be considered. Uncontrolled optical feedback is known for its spectral and power fluctuation effects, as well as potential emitter damage. We found that even intended feedback by use of volume Bragg gratings (VBG) for spectral stabilization may result in emitter lifetime reduction. To provide stable and reliable laser systems design, guidelines and maximum feedback ratings have to be found. We present a model to estimate the optical feedback power coupled back into the laser diode waveguide. It includes several origins of optical feedback and wide range of optical elements. The failure thresholds of InGaAs and AlGaAs bars have been determined not only at standard operation mode but at various working points. The influence of several feedback levels to laser diode lifetime is investigated up to 4000h. The analysis of the semiconductor itself leads to a better understanding of the degradation process by defect spread. Facet microscopy, LBIC- and electroluminescence measurements deliver detailed information about semiconductor defects before and after aging tests. Laser diode protection systems can monitor optical feedback. With this improved understanding, the emergency shutdown threshold can be set low enough to ensure laser diode reliability but also high enough to provide better machine usability avoiding false alarms.

  14. In vivo dosimetry with silicon diodes in total body irradiation (United States)

    Oliveira, F. F.; Amaral, L. L.; Costa, A. M.; Netto, T. G.


    The aim of this work is the characterization and application of silicon diode detectors for in vivo dosimetry in total body irradiation (TBI) treatments. It was evaluated the diode response with temperature, dose rate, gantry angulations and field size. A maximum response variation of 2.2% was obtained for temperature dependence. The response variation for dose rate and angular was within 1.2%. For field size dependence, the detector response increased with field until reach a saturation region, where no more primary radiation beam contributes for dose. The calibration was performed in a TBI setup. Different lateral thicknesses from one patient were simulated and then the calibration factors were determined by means of maximum depth dose readings. Subsequent to calibration, in vivo dosimetry measurements were performed. The response difference between diode readings and the prescribed dose for all treatments was below 4%. This difference is in agreement as recommended by the International Commission on Radiation Units and Measurements (ICRU), which is ±5%. The present work to test the applicability of a silicon diode dosimetry system for performing in vivo dose measurements in TBI techniques presented good results. These measurements demonstrated the value of diode dosimetry as a treatment verification method and its applicability as a part of a quality assurance program in TBI treatments.

  15. Diode laser power module for beamed power transmission (United States)

    Choi, S. H.; Williams, M. D.; Lee, J. H.; Conway, E. J.


    Recent progress with powerful, efficient, and coherent monolithic diode master-oscillator/power-amplifier (M-MOPA) systems is promising for the development of a space-based diode laser power station. A conceptual design of a 50-kW diode laser power module was made for space-based power stations capable of beaming coherent power to the moon, Martian rovers, or other satellites. The laser diode power module consists of a solar photovoltaic array or nuclear power source, diode laser arrays (LDAs), a phase controller, beam-steering optics, a thermal management unit, and a radiator. Thermal load management and other relevant aspects of the system (such as power requirements and system mass) are considered. The 50-kW power module described includes the highest available efficiency of LD M-MOPA system to date. However, the overall efficiency of three amplifier stages, including the coupling efficiency, turns out to be 55.5 percent. Though a chain of PA stages generates a high-power coherent beam, there is a penalty due to the coupling loss between stages. The specific power of the 50-kW module using solar power is 6.58 W/kg.

  16. Method and system for homogenizing diode laser pump arrays

    Energy Technology Data Exchange (ETDEWEB)

    Bayramian, Andrew James


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

  17. High-average-power diode-pumped Yb: YAG lasers

    Energy Technology Data Exchange (ETDEWEB)

    Avizonis, P V; Beach, R; Bibeau, C M; Emanuel, M A; Harris, D G; Honea, E C; Monroe, R S; Payne, S A; Skidmore, J A; Sutton, S B


    A scaleable diode end-pumping technology for high-average-power slab and rod lasers has been under development for the past several years at Lawrence Livermore National Laboratory (LLNL). This technology has particular application to high average power Yb:YAG lasers that utilize a rod configured gain element. Previously, this rod configured approach has achieved average output powers in a single 5 cm long by 2 mm diameter Yb:YAG rod of 430 W cw and 280 W q-switched. High beam quality (M{sup 2} = 2.4) q-switched operation has also been demonstrated at over 180 W of average output power. More recently, using a dual rod configuration consisting of two, 5 cm long by 2 mm diameter laser rods with birefringence compensation, we have achieved 1080 W of cw output with an M{sup 2} value of 13.5 at an optical-to-optical conversion efficiency of 27.5%. With the same dual rod laser operated in a q-switched mode, we have also demonstrated 532 W of average power with an M{sup 2} < 2.5 at 17% optical-to-optical conversion efficiency. These q-switched results were obtained at a 10 kHz repetition rate and resulted in 77 nsec pulse durations. These improved levels of operational performance have been achieved as a result of technology advancements made in several areas that will be covered in this manuscript. These enhancements to our architecture include: (1) Hollow lens ducts that enable the use of advanced cavity architectures permitting birefringence compensation and the ability to run in large aperture-filling near-diffraction-limited modes. (2) Compound laser rods with flanged-nonabsorbing-endcaps fabricated by diffusion bonding. (3) Techniques for suppressing amplified spontaneous emission (ASE) and parasitics in the polished barrel rods.

  18. 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


    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.

  19. Plasma-filled applied B ion diode experiments using a plasma opening switch (United States)

    Renk, T. J.


    In order for a plasma opening switch (POS) to open quickly and transfer power efficiently from an inductively charged vacuum transmission line to an applied B ion diode, the load impedance of the ion diode may be required to have an initial low impedance phase. A plasma-filled diode has such an impedance history. To test the effect of a plasma-filled diode on POS-diode coupling, a drifting plasma was introduced from the cathode side of an applied B ion diode operated on the LION accelerator (1.5 MV, 4 Ohm, 40 ns) at Cornell University. This plasma readily crossed the 2.1 T magnetic insulation field of the diode, and resulted in both increased diode electrical power, and an increased ability of the ion beam to remove material from a target. The plasma did not appear to have a noticeable effect on local beam steering angle.

  20. Fazostabilny RF attenuator on the р—і—n diods

    Directory of Open Access Journals (Sweden)

    A. S. Makarenko


    Full Text Available Considered agreed attenuator р—і—n diods low uneven phase response when you change the insertion loss is achieved by separate compensation of reactive elements diodes. Calculated characteristics.

  1. The electrical characterization and response to hydrogen of Schottky diodes with a resistive metal electrode-rectifying an oversight in Schottky diode investigation

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, P; Feng, L; Penate-Quesada, L [Centre for Nanostructured Media, School of Maths and Physics, Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom); Hill, G [EPSRC National Centre for III-V Technologies, Mappin Street, University ofSheffield, Sheffield S1 3JD (United Kingdom); Mitra, J, E-mail:


    Schottky-barrier structures with a resistive metal electrode are examined using the 4-point probe method where the probes are connected to the metal electrode only. The observation of a significant decrease in resistance with increasing temperature (over a range of {approx}100 K) in the diode resistance-temperature (R{sub D}-T) characteristic is considered due to charge carrier confinement to the metal electrode at low temperature (high resistance), with the semiconductor progressively opening up as a parallel current carrying channel (low resistance) with increasing temperature due to increasing thermionic emission across the barrier. A simple model is constructed, based on thermionic emission at quasi-zero bias, that generates good fits to the experimental data. The negative differential resistance (NDR) region in the R{sub D}-T characteristic is a general effect and is demonstrated across a broad temperature range for a variety of Schottky structures grown on Si-, GaAs- and InP-substrates. In addition the NDR effect is harnessed in micro-scaled Pd/n-InP devices for the detection of low levels of hydrogen in an ambient atmosphere of nitrogen.

  2. 1-D array of perforated diode neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    McNeil, Walter J. [Kansas State University, Mechanical and Nuclear Engineering Department, Manhattan, KS 66506 (United States)], E-mail:; Bellinger, Steven L.; Unruh, Troy C.; Henderson, Chris M.; Ugorowski, Phil; Morris-Lee, Bryce [Kansas State University, Mechanical and Nuclear Engineering Department, Manhattan, KS 66506 (United States); Taylor, Russell D. [Electronics Design Laboratory, Kansas State University, Manhattan, KS 66506 (United States); McGregor, Douglas S. [Kansas State University, Mechanical and Nuclear Engineering Department, Manhattan, KS 66506 (United States)], E-mail:


    Performance of a 4 cm long 64-pixel perforated diode neutron detector array is compared with an identical array of thin-film coated diodes. The perforated neutron detector design has been adapted to a 1-D pixel array capable of 120 {mu}m spatial resolution and counting efficiency greater than 12%. Deep vertical trenches filled with {sup 6}LiF provide outstanding improvement in efficiency over thin-film coated diode designs limited to only 4.5%. This work marks the final step towards the construction of a much larger array consisting of 1024 pixels spanning 10 cm. The larger detector array will be constructed with a sub-array of 64-pixel sensors, and will be used for small-angle neutron scattering experiments at the Spallation Neutron Source of Oak Ridge National Laboratory.

  3. Space-charge limiting current in spherical cathode diodes

    Institute of Scientific and Technical Information of China (English)

    刘国治; 邵浩


    The results of the investigation on the space-charge limiting current for a spherical-cathode diode in the nonrelativistic situation are presented in this paper. The results show that the current enhancement factor equals the square of E-field enhancement factor on the cathode surface. The generated space-charge limiting current is deduced.In the case of a pin-shaped-cathode diode, the space-charge limiting current is also obtained, indicating that the current is independent of the geometric parameters of the diode. Analyses of the shielding effects and the conditions for generation of the uniform space-charge limiting beam show that, for pin-arrayed cathodes, the distance between pins should be in the range from 1.2D to 1.5D, where D is the distance between the two electrodes.

  4. Photoporation and cell transfection using a violet diode laser (United States)

    Paterson, L.; Agate, B.; Comrie, M.; Ferguson, R.; Lake, T. K.; Morris, J. E.; Carruthers, A. E.; Brown, C. T. A.; Sibbett, W.; Bryant, P. E.; Gunn-Moore, F.; Riches, A. C.; Dholakia, Kishan


    The introduction and subsequent expression of foreign DNA inside living mammalian cells (transfection) is achieved by photoporation with a violet diode laser. We direct a compact 405 nm laser diode source into an inverted optical microscope configuration and expose cells to 0.3 mW for 40 ms. The localized optical power density of ~1200 MW/m2 is six orders of magnitude lower than that used in femtosecond photoporation (~104 TW/m2). The beam perforates the cell plasma membrane to allow uptake of plasmid DNA containing an antibiotic resistant gene as well as the green fluorescent protein (GFP) gene. Successfully transfected cells then expand into clonal groups which are used to create stable cell lines. The use of the violet diode laser offers a new and simple poration technique compatible with standard microscopes and is the simplest method of laser-assisted cell poration reported to date.

  5. Dose rate and SDD dependence of commercially available diode detectors. (United States)

    Saini, Amarjit S; Zhu, Timothy C


    The dose-rate dependence of commercially available diode detectors was measured under both high instantaneous dose-rate (pulsed) and low dose rate (continuous, Co-60) radiation. The dose-rate dependence was measured in an acrylic miniphantom at a 5-cm depth in a 10 x 10 cm2 collimator setting, by varying source-to-detector distance (SDD) between at least 80 and 200 cm. The ratio of a normalized diode reading to a normalized ion chamber reading (both at SDD=100 cm) was used to determine diode sensitivity ratio for pulsed and continuous radiation at different SDD. The inverse of the diode sensitivity ratio is defined as the SDD correction factor (SDD CF). The diode sensitivity ratio increased with increasing instantaneous dose rate (or decreasing SDD). The ratio of diode sensitivity, normalized to 4000 cGy/s, varied between 0.988 (1490 cGy/s)-1.023 (38,900 cGy/s) for unirradiated n-type Isorad Gold, 0.981 (1460 cGy/s)-1.026 (39,060 cGy/s) for unirradiated QED Red (n type), 0.972 (1490 cGy/s)-1.068 (38,900 cGy/s) for preirradiated Isorad Red (n type), 0.985 (1490 cGy/s)-1.012 (38,990 cGy/s) for n-type Pt-doped Isorad-3 Gold, 0.995 (1450 cGy/s)-1.020 (21,870 cGy/s) for n-type Veridose Green, 0.978 (1450 cGy/s)-1.066 (21,870 cGy/s) for preirradiated Isorad-p Red, 0.994 (1540 cGy/s)-1.028 (17,870 cGy/s) for p-type preirradiated QED, 0.998 (1450 cGy/s)-1.003 (21,870 cGy/s) for the p-type preirradiated Scanditronix EDP20(3G), and 0.998 (1490 cGy/s)-1.015 (38,880 cGy/s) for Scanditronix EDP10(3G) diodes. The p-type diodes do not always show less dose-rate dependence than the n-type diodes. Preirradiation does not always reduce diode dose-rate dependence. A comparison between the SDD dependence measured at the surface of a full scatter phantom and that in a miniphantom was made. Using a direct adjustment of radiation pulse height, we concluded that the SDD dependence of diode sensitivity can be explained by the instantaneous dose-rate dependence if sufficient buildup is

  6. Practical applications of the diode in dental practice (United States)

    Moldoveanu, Lucia E.; Odor, Alin A.


    Introduction: The use of lasers has become a practice in modern periodontology and it is a fact that the use of diodes in the dental office can bring a real benefit in periodontal surgery. Material and method: These case reports describe few of various soft tissue procedures that were performed with diode laser 940 nm (Epic 10, Biolase Inc., USA). Discussions: There are a few immediate benefits of the intervention: the "periodontal bandage" belongs to the patient, the procedure is painless, performed under a superficial anesthesia and the psychological impact on the patient, as well as the acceptance, are superior to conventional methods of dentistry. Conclusions: Diode lasers at the level of periodontium have become a significant part of the dentistry, reducing the patient's stress and giving satisfaction to practitioners as well.

  7. A Direct Diode Laser System Using a Planar Lightwave Circuit (United States)

    Hasegawa, Kazuo; Matsubara, Hiroyuki; Ichikawa, Tadashi; Maeda, Mitsutoshi; Ito, Hiroshi


    In this paper we propose a direct diode laser (DDL) system consisting of laser diode (LD) bars, a planar lightwave circuit (PLC), and an optical fiber. We have developed a PLC as an optical power combiner and an LD mounting technology that is suitable for coupling to the PLC. A DDL system is presented that consists of six LD-PLC optical modules for the laser-welding of highly heat-resistant plastics. The total output power is in the 200 W class, with a spot diameter of 5.52 mm for the major axis and 5.00 mm for the minor axis at a focal length of 50 mm. The total output efficiency is 60.9% from the laser diode to the welding torch.

  8. Gate Modulation of Graphene-ZnO Nanowire Schottky Diode. (United States)

    Liu, Ren; You, Xu-Chen; Fu, Xue-Wen; Lin, Fang; Meng, Jie; Yu, Da-Peng; Liao, Zhi-Min


    Graphene-semiconductor interface is important for the applications in electronic and optoelectronic devices. Here we report the modulation of the electric transport properties of graphene/ZnO nanowire Schottky diode by gate voltage (Vg). The ideality factor of the graphene/ZnO nanowire Schottky diode is ~1.7, and the Schottky barrier height is ~0.28 eV without external Vg. The Schottky barrier height is sensitive to Vg due to the variation of Fermi level of graphene. The barrier height increases quickly with sweeping Vg towards the negative value, while decreases slowly towards the positive Vg. Our results are helpful to understand the fundamental mechanism of the electric transport in graphene-semiconductor Schottky diode.

  9. Enhancement in performance of polycarbazole-graphene nanocomposite Schottky diode

    Directory of Open Access Journals (Sweden)

    Rajiv K. Pandey


    Full Text Available We report formation of polycarbazole (PCz–graphene nanocomposite over indium tin oxide (ITO coated glass substrate using electrochemical technique for fabrication of high performance Schottky diodes. The synthesized nanocomposite is characterized before fabrication of devices for confirmation of uniform distribution of graphene nanosheets in the polymer matrix. Pure PCz and PCz-graphene nanocomposites based Schottky diodes are fabricated of configuration Al/PCz/ITO and Al/PCz-graphene nanocomposite/ITO, respectively. The current density–voltage (J-V characteristics and diode performance parameters (such as the ideality factor, barrier height, and reverse saturation current density are compared under ambient condition. Al/PCz-graphene nanocomposite/ITO device exhibits better ideality factor in comparison to the device formed using pure PCz. It is also observed that the Al/PCz-graphene nanocomposite/ITO device shows large forward current density and low turn on voltage in comparison to Al/PCz/ITO device.

  10. Experimental study of the diode pumped alkali laser (DPAL) (United States)

    Endo, Masamori; Nagaoka, Ryuji; Nagaoka, Hiroki; Nagai, Toru; Wani, Fumio


    A small-scale cesium diode-pumped alkali laser (DPAL) apparatus has been developed for fundamental researches. A commercial laser diode with volume Bragg grating outcoupler is used to pump the gain cell longitudinally. Both windows of the gain cell are set at Brewster's angle for minimum loss and maximum durability. Output coupling coefficient is continuously variable from 13% to 85% by the slanted quartz plate outcoupler inserted in the optical resonator. Small signal gain is measured with a laser diode probe at various gain cell temperatures. A 6.5 W continuouswave output with 56% optical-to-optical conversion efficiency (based on the absorbed power) has been achieved. A numerical simulation code is developed and its calculation results are in good agreement with the experiments.

  11. Silver Nanoparticles with Broad Multiband Linear Optical Absorption

    KAUST Repository

    Bakr, Osman M.


    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.

  12. Broad Band Photometric Reverberation Mapping of NGC 4395

    CERN Document Server

    Edri, Haim; Chelouche, Doron; Kaspi, Shai; Behar, Ehud


    We present results of broad band photometric reverberation mapping (RM) to measure the radius of the broad line region, and subsequently the black hole mass (M$_{\\rm BH}$), in the nearby, low luminosity active galactic nuclei (AGN) NGC 4395. Using the Wise Observatory's 1m telescope equipped with the SDSS g$'$, r$'$ and i$'$ broad band filters, we monitored NGC 4395 for 9 consecutive nights and obtained 3 light curves each with over 250 data points. The g$'$ and r$'$ bands include time variable contributions from H$\\beta$ and H$\\alpha$ (respectively) plus continuum. The i$'$ band is free of broad lines and covers exclusively continuum. We show that by looking for a peak in the difference between the cross-correlation and the auto-correlation functions for all combinations of filters, we can get a reliable estimate of the time lag necessary to compute M$_{\\rm BH}$. We measure the time lag for H$\\alpha$ to be $3.6 \\pm 0.8 $ hours, comparable to previous studies using the line resolved spectroscopic RM method. W...

  13. Mathematical Development: The Role of Broad Cognitive Processes (United States)

    Calderón-Tena, Carlos O.


    This study investigated the role of broad cognitive processes in the development of mathematics skills among children and adolescents. Four hundred and forty-seven students (age mean [M] = 10.23 years, 73% boys and 27% girls) from an elementary school district in the US southwest participated. Structural equation modelling tests indicated that…

  14. PRINCIPAR An Efficient, Broad-coverage, Principle-based Parser

    CERN Document Server

    Lin, D


    We present an efficient, broad-coverage, principle-based parser for English. The parser has been implemented in C++ and runs on SUN Sparcstations with X-windows. It contains a lexicon with over 90,000 entries, constructed automatically by applying a set of extraction and conversion rules to entries from machine readable dictionaries.

  15. Model Invariance across Genders of the Broad Autism Phenotype Questionnaire (United States)

    Broderick, Neill; Wade, Jordan L.; Meyer, J. Patrick; Hull, Michael; Reeve, Ronald E.


    ASD is one of the most heritable neuropsychiatric disorders, though comprehensive genetic liability remains elusive. To facilitate genetic research, researchers employ the concept of the broad autism phenotype (BAP), a milder presentation of traits in undiagnosed relatives. Research suggests that the BAP Questionnaire (BAPQ) demonstrates…

  16. Broad-band hard X-ray reflectors

    DEFF Research Database (Denmark)

    Joensen, K.D.; Gorenstein, P.; Hoghoj, P.;


    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 ...

  17. Broad-Band Spectroscopy of Hercules X-1 with Suzaku (United States)

    Asami, Fumi; Enoto, Teruaki; Iwakiri, Wataru; Yamada, Shin'ya; Tamagawa, Toru; Mihara, Tatehiro; Nagase, Fumiaki


    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.

  18. Broad spectral range synchronized flat-top arrayed waveguide grating

    NARCIS (Netherlands)

    Akca, B. Imran; Doerr, Christopher R.; Pollnau, Markus; Ridder, de René M.


    A broad-band Mach-Zehnder-interferometer-synchronized flat-top arrayed waveguide grating is presented with a 0.5-dB bandwidth of 12 nm over 90 nm of spectral range and a central excess loss value of -0.5 dB.

  19. Broad-band spectrophotometry of HAT-P-32 b

    DEFF Research Database (Denmark)

    Mallonn, M.; Bernt, I.; Herrero, E.


    Multicolour broad-band transit observations offer the opportunity to characterize the atmosphere of an extrasolar planet with small- to medium-sized telescopes. One of the most favourable targets is the hot Jupiter HAT-P-32 b. We combined 21 new transit observations of this planet with 36 previou...

  20. Radio frequency diodes and circuits fabricated via adhesion lithography (Conference Presentation) (United States)

    Georgiadou, Dimitra G.; Semple, James; Wyatt-Moon, Gwenhivir; Anthopoulos, Thomas D.


    The commercial interest in Radio Frequency Identification (RFID) tags keeps growing, as new application sectors, spanning from healthcare to electronic article surveillance (EAS) and personal identification, are constantly emerging for these types of electronic devices. The increasing demand for the so-called "smart labels" necessitates their high throughput manufacturing, and indeed on thin flexible substrates, that will reduce the cost and render them competitive to the currently widely employed barcodes. Adhesion Lithography (a-Lith) is a novel patterning technique that allows the facile high yield fabrication of co-planar large aspect ratio (<100,000) metal electrodes separated by a sub-20 nm gap on large area substrates of any type. Deposition of high mobility semiconductors from their solution at low, compatible with plastic substrates, temperatures and application of specific processing protocols can dramatically improve the performance of the fabricated Schottky diodes. It will be shown that in this manner both organic and inorganic high speed diodes and rectifiers can be obtained, operating at frequencies much higher than the 13.56 MHz benchmark, currently employed in passive RFID tags and near filed communications (NFC). This showcases the universality of this method towards fabricating high speed p- and n-type diodes, irrespective of the substrate, simply based on the extreme downscaling of key device dimensions obtained in these nanoscale structures. The potential for scaling up this technique at low cost, combined with the significant performance optimisation and improved functionality that can be attained through intelligent material selection, render a-Lith unique within the field of plastic electronics.

  1. Experimental evidence of energetic neutrals production in an ion diode

    Energy Technology Data Exchange (ETDEWEB)

    Pushkarev, A.I., E-mail:; Isakova, Y.I.; Khaylov, I.P.


    The paper presents several experimental proofs of the formation of energetic charge-exchange neutrals in a self-magnetically insulated ion diode with a graphite cathode. The energetic neutrals are thought to be produced as a result of charge exchange process between accelerated ions and stationary neutral molecules. The experiments have been carried out using both a diode with externally applied magnetic insulation (single-pulse mode: 100 ns, 250–300 kV) and a diode with self-magnetic insulation (double-pulse mode: 300–500 ns, 100–150 kV (negative pulse); 120 ns, 250–300 kV (positive pulse)). The motivation for looking at the neutral component of the ion beam came when we compared two independent methods to measure the energy density of the beam. A quantitative comparison of infrared measurements with signals from Faraday cups and diode voltage was made to assess the presence of neutral atoms in the ion beam. As another proof of charge-exchange effects in ion diode we present the results of statistical analysis of diode performance. It was found that the shot-to shot variation of the energy density in a set of 50–100 shots does not exceed 11%, whilst the same variation for ion current density was 20–30%; suggesting the presence of neutrals in the beam. Moreover, the pressure in the zone of ion beam energy dissipation exceeds the results stated in cited references. The difference between our experimental data and results stated by other authors we attribute to the presence of a low-energy charge-exchange neutral component in the ion beam.

  2. Hyper NRD guide oscillator with Gunn diodes mounted in the dielectric strip


    Sanagi, Minoru; Nogi, Shigeji


    Hyper NRD guide oscillators mounted with a single and multiple Gunn diodes have been investigated. The operating mode of the hyper NRD guide can be lower order by optimizing the structure of the guide. The Gunn diodes were arranged in the dielectric strip of the guide. In experiments at X-band, the oscillation frequencies could be varied by a movable shorting plane for the single diode case and an almost perfect power combining was obtained for the double diode case

  3. Stimulated Brillouin Scattering Suppression in Fiber Amplifiers via Chirped Diode Lasers (United States)


    1.55-µm diode laser at 1014 Hz/s using a phase-locked loop and a fiber -optic Michelson interferometer (9). The chirp has now been extended to 5×1015...diode lasers. By incorporating a fiber interferometer , the technique has been extended to chirp a (single) laser diode at 1015 Hz/s in an extremely...Stimulated Brillouin Scattering Suppression in Fiber Amplifiers via Chirped Diode Lasers by Jeffrey O. White, George Rakuljic, and Carl E

  4. Planar Schottky barrier mixer diodes for space applications at submillimeter wavelengths (United States)

    Bishop, W. L.; Crowe, T. W.; Mattauch, R. J.; Ostdiek, P. H.


    Available planar diodes for space-based applications at submillimeter wavelengths have not achieved either the required low junction capacitance or the low series resistance-junction capacitance product. Here, the development of a novel planar diode structure that overcomes both of these difficulties is outlined. The characteristics of these Schottky barrier mixer diodes are presented and electron micrographs are shown. The diode structure will allow planar technology to be extended throughout the submillimeter wavelength range.

  5. C. W. GaAs Diode Laser (United States)


    laser fabrication , assembly, and evaluation. The principal personnel responsible for the BeO materials effort at Rockwell International were Dr...principal areas. The first area was the optimization of the semiconductor growth and laser fabrication techniques to achieve lasers with low

  6. Wild coastline birds as reservoirs of broad-spectrum-β-lactamase-producing Enterobacteriaceae in Miami Beach, Florida. (United States)

    Poirel, Laurent; Potron, Anaïs; De La Cuesta, Carolina; Cleary, Timothy; Nordmann, Patrice; Munoz-Price, L Silvia


    A high rate of broad-spectrum-β-lactamase-producing Escherichia coli isolates was identified from seagull and pelican feces collected in the Miami Beach, Florida, area. The most commonly identified resistance determinants were CMY-2 and CTX-M-15. Those wild birds might be therefore considered vehicles for wide dissemination of multidrug-resistant Enterobacteriaceae in the United States.

  7. Management of gingival hyperpigmentation by semiconductor diode laser. (United States)

    Gupta, Geeti


    Gingival hyperpigmentation is caused by excessive deposition of melanin in the basal and suprabasal cell layers of the epithelium. Although melanin pigmentation of the gingiva is completely benign, cosmetic concerns are common, particularly in patients having a very high smile line (gummy smile). Various depigmentation techniques have been employed, such as scalpel surgery, gingivectomy, gingivectomy with free gingival autografting, cryosurgery, electrosurgery, chemical agents such as 90% phenol and 95% alcohol, abrasion with diamond burs, Nd:YAG laser, semiconductor diode laser, and CO(2) laser. The present case report describes simple and effective depigmentation technique using semiconductor diode laser surgery - for gingival depigmentation, which have produced good results with patient satisfaction.

  8. Radiation hardness of n-GaN schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, A. A., E-mail:; Belov, S. V.; Mynbaeva, M. G.; Strel’chuk, A. M.; Bogdanova, E. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Makarov, Yu. N. [Nitride Crystals Group (Russian Federation); Usikov, A. S. [Nitride Crystals Inc. (United States); Kurin, S. Yu.; Barash, I. S.; Roenkov, A. D. [Nitride Crystals Group (Russian Federation); Kozlovski, V. V. [St. Petersburg State Polytechnic University (Russian Federation)


    Schottky-barrier diodes with a diameter of ∼10 µm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier removal rate was found to be 130–145 cm{sup –1}. The linear nature of the dependence N = f(D) (N is the carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transitions of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

  9. Mode locking and spatiotemporal chaos in periodically driven Gunn diodes

    DEFF Research Database (Denmark)

    Mosekilde, Erik; Feldberg, Rasmus; Knudsen, Carsten;


    Numerical simulation is applied to study the highly nonlinear-dynamic phenomena that can arise in Gunn diodes by interaction between the internally generated domain mode and an external microwave signal. By adjusting the time of domain formation and the speed of propagation, the internal...... oscillation entrains with the external signal. This produces a devil’s staircase of frequency-locked solutions. At higher microwave amplitudes, period doubling and other forms of mode-converting bifurcations can be seen. In this interval the diode also exhibits spatiotemporal chaos. At still higher microwave...

  10. Electrically driven surface plasmon light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke;

    We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  11. Daily check of the electron beams with a diode system

    Energy Technology Data Exchange (ETDEWEB)

    Pilette, P. [Hospital Civil de Charleroi (Belgium). Centre for Radiotherapy


    A fast systems to check all the accelerator beams on a daily basis has been developed. A cheap home-made detector, based on non-medical diodes (type 1N5408), has been used since July 1992 to verify all the electron beams every day. The relative energy and Top-cGy correspondence is verified with one single irradiation of less than 1 minute by 6 diodes fixed in a polystyrene phantom. The principle of construction, software implementation and results are presented.

  12. Characteristic of laser diode beam propagation through a collimating lens. (United States)

    Xu, Qiang; Han, Yiping; Cui, Zhiwei


    A mathematical model of a laser diode beam propagating through a collimating lens is presented. Wave propagation beyond the paraxial approximation is studied. The phase delay of the laser diode wave in passing through the lens is analyzed in detail. The propagation optical field after the lens is obtained from the diffraction integral by the stationary phase method. The model is employed to predict the light intensity at various beam cross sections, and the computed intensity distributions are in a good agreement with the corresponding measurements.

  13. Computer Processing Of Tunable-Diode-Laser Spectra (United States)

    May, Randy D.


    Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.

  14. Gummy Smile Correction with Diode Laser: Two Case Reports (United States)

    Narayanan, Mahesh; Laju, S; Erali, Susil M; Erali, Sunil M; Fathima, Al Zainab; Gopinath, P V


    Beautification of smiles is becoming an everyday requirement in dental practice. Apart from teeth, gingiva also plays an important role in smile esthetics. Excessive visualization of gingiva is a common complaint among patients seeking esthetic treatment. A wide variety of procedures are available for correction of excessive gum display based on the cause of the condition. Soft tissue diode laser contouring of gingiva is a common procedure that can be undertaken in a routine dental setting with excellent patient satisfaction and minimal post-operative sequale. Two cases of esthetic crown lengthening with diode laser 810 nm are presented here. PMID:26668491

  15. Degradation of light emitting diodes: a proposed methodology*

    Institute of Scientific and Technical Information of China (English)

    Sau Koh; Willem Van Driel; G.Q.Zhang


    Due to their long lifetime and high efficacy, light emitting diodes have the potential to revolutionize the illumination industry. However, self heat and high environmental temperature which will lead to increased junction temperature and degradation due to electrical overstress can shorten the life of the light emitting diode. In this research, a methodology to investigate the degradation of the LED emitter has been proposed. The epoxy lens of the emitter can be modelled using simplified Eyring methods whereas an equation has been proposed for describing the degradation of the LED emitters.

  16. Three-phase bridge rectifiers with freewheeling diodes

    CERN Document Server

    Hausler, M


    Freewheeling diodes are used in controlled rectifiers working in one quadrant only in order to reduce the reactive power and the d.c.- voltage ripple. In addition the freewheeling diodes allow a higher d.c.-current at low d.c.-voltages. The mean value of the freewheeling current depends on the d.c.-current, the load, and the stray-reactance of the rectifier transformer. This paper describes how the freewheeling current can be determined with these parameters. Results for some typical cases are shown in diagrams. (2 refs).

  17. Combless broadband terahertz generation with conventional laser diodes. (United States)

    Molter, D; Wagner, A; Weber, S; Jonuscheit, J; Beigang, R


    We present a novel technique to generate a continuous, combless broadband Terahertz spectrum with conventional low-cost laser diodes. A standard time-domain spectroscopy system using photoconductive antennas is pumped by the output of two tunable diode lasers. Using fine tuning for one laser and fine and coarse tuning for the second laser, difference frequency generation results in a continuous broadband THz spectrum. Fast coarse-tuning is achieved by a simple spatial light modulator introduced in an external cavity. The results are compared to multi-mode operation for THz generation.

  18. Gate Modulation of Graphene-ZnO Nanowire Schottky Diode


    Liu, Ren; You, Xu-Chen; Fu, Xue-Wen; Lin, Fang; Meng, Jie; Yu, Da-Peng; Liao, Zhi-Min


    Graphene-semiconductor interface is important for the applications in electronic and optoelectronic devices. Here we report the modulation of the electric transport properties of graphene/ZnO nanowire Schottky diode by gate voltage (Vg). The ideality factor of the graphene/ZnO nanowire Schottky diode is ~1.7, and the Schottky barrier height is ~0.28 eV without external Vg. The Schottky barrier height is sensitive to Vg due to the variation of Fermi level of graphene. The barrier height increa...

  19. Performance characteristics and optimal analysis of a nonlinear diode refrigerator

    Institute of Scientific and Technical Information of China (English)

    Wang Xiu-Mei; He Ji-Zhou; Liang Hong-Ni


    This paper establishes a model of a nonlinear diode refrigerator consisting of two diodes switched in the opposite directions and located in two heat reservoirs with different temperatures. Based on the theory of thermal fluctuations, the expressions of the heat flux absorbed from the heat reservoirs are derived. After the heat leak between the two reservoirs is considered, the cooling rate and the coefficient of performance are obtained analytically. The influence of the heat leak and the temperature ratio on the performance characteristics of the refrigerator is analysed in detail.

  20. Millimeter Wave Metal-Insulator-Metal Detector/Mixer Diode. (United States)



  1. System and method for high power diode based additive manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    El-Dasher, Bassem S.; Bayramian, Andrew; Demuth, James A.; Farmer, Joseph C.; Torres, Sharon G.


    A system is disclosed for performing an Additive Manufacturing (AM) fabrication process on a powdered material forming a substrate. The system may make use of a diode array for generating an optical signal sufficient to melt a powdered material of the substrate. A mask may be used for preventing a first predetermined portion of the optical signal from reaching the substrate, while allowing a second predetermined portion to reach the substrate. At least one processor may be used for controlling an output of the diode array.

  2. Electrical and optical study of semiconductor laser diodes and materials (United States)

    Albin, Sacharia


    The characterization of a 2-D diode laser array from McDonald Douglas has been completed. The array consisted of 8 linear arrays of approximately 11 mm x 0.18 mm. Each array has between 7 and 8 diodes per mm. The threshold current is approximately 15 amps. The power output vs drive current (above threshold) of the array was measured. A peak power of 50 W was obtained at a drive current of 26 amps. Its far field pattern has a double lobe.

  3. Theory of piezo-phototronics for light-emitting diodes. (United States)

    Zhang, Yan; Wang, Zhong Lin


    Devices fabricated by using the inner-crystal piezopotential as a "gate" voltage to tune/control the carrier generation, transport, and recombination processes at the vicinity of a p-n junction are named piezo-phototronics. Here, the theory of the photon emission and carrier transport behavior in piezo-phototronic devices is investigated as a p-n junction light-emitting diode. Numerical calculations are given for predicting the photon emission and current-voltage characteristics of a general piezo-phototronic light-emitting diode.

  4. Gravure printed PEDOT:PSS as anode for flexible ITO-free organic light emitting diodes

    Directory of Open Access Journals (Sweden)

    M. Montanino


    Full Text Available Roll-to-roll gravure printing is considered as potential leading manufacturing technology for flexible, low cost and large area optoelectronics. However, solution processed multilayer organic electronics are still challenging to be produced, especially in the case of electrodes. In this work, the gravure printing technique was successfully employed to realize the highly conductive poly(3,4ethylenedioxythiophene:poly(styrene sulfonate (PEDOT:PSS polymeric anode and tested for the first time in flexible ITO-free (Indium Thin Oxide organic light emitting diodes (OLEDs. The device performances were found to be similar to those of a reference device containing a spin-coated polymeric anode. A gravure printed dimethyl sulfoxide (DMSO post-treatment was successfully tried to improve the printed anode characteristics. The obtained results show the way for future development for processing flexible ITO-free devices using the most attractive printing technology for roll-to-roll large area manufacturing.

  5. Light extraction from organic light-emitting diodes for lighting applications by sand-blasting substrates. (United States)

    Chen, Shuming; Kwok, Hoi Sing


    Light extraction from organic light-emitting diodes (OLEDs) by scattering the light is one of the effective methods for large-area lighting applications. In this paper, we present a very simple and cost-effective method to rough the substrates and hence to scatter the light. By simply sand-blasting the edges and back-side surface of the glass substrates, a 20% improvement of forward efficiency has been demonstrated. Moreover, due to scattering effect, a constant color over all viewing angles and uniform light pattern with Lambertian distribution has been obtained. This simple and cost-effective method may be suitable for mass production of large-area OLEDs for lighting applications.

  6. Whole device printing for full colour displays with organic light emitting diodes (United States)

    Choi, Jun-ho; Kim, Kyung-Ho; Choi, Se-Jin; Lee, Hong H.


    Whole device printing is presented for realizing full colour displays with red (R), green (G) and blue (B) organic light emitting diodes (OLEDs). In this process, the whole OLED structure is transferred from a patterned mould to a glass substrate. Therefore, a simple step and repeat of the transfer of each of R, G and B OLED for RGB pixels completes the fabrication of the full colour display over a given area. A difference in the work of adhesion at two interfaces enables the transfer. A 'rigiflex' mould is used for the printing. It is rigid enough to allow sub-100 nm resolution and yet flexible enough for intimate contact with the glass substrate, which permits large area application.

  7. Investigating Bandgap Energies, Materials, and Design of Light-Emitting Diodes (United States)

    Wagner, Eugene P., II


    A student laboratory experiment to investigate the intrinsic and extrinsic bandgaps, dopant materials, and diode design in light-emitting diodes (LEDs) is presented. The LED intrinsic bandgap is determined by passing a small constant current through the diode and recording the junction voltage variation with temperature. A second visible…

  8. A Novel Current-Mode Full-Wave Rectifier Based on One CDTA and Two Diodes

    Directory of Open Access Journals (Sweden)

    F. Khateb


    Full Text Available Precision rectifiers are important building blocks for analog signal processing. The traditional approach based on diodes and operational amplifiers (OpAmps exhibits undesirable effects caused by limited OpAmp slew rate and diode commutations. In the paper, a full-wave rectifier based on one CDTA and two Schottky diodes is presented. The PSpice simulation results are included.

  9. Estimating p-n Diode Bulk Parameters, Bandgap Energy and Absolute Zero by a Simple Experiment (United States)

    Ocaya, R. O.; Dejene, F. B.


    This paper presents a straightforward but interesting experimental method for p-n diode characterization. The method differs substantially from many approaches in diode characterization by offering much tighter control over the temperature and current variables. The method allows the determination of important diode constants such as temperature…

  10. Strain tunable light emitting diodes with germanium P-I-N heterojunctions (United States)

    Lagally, Max G; Sanchez Perez, Jose Roberto


    Tunable p-i-n diodes comprising Ge heterojunction structures are provided. Also provided are methods for making and using the tunable p-i-n diodes. Tunability is provided by adjusting the tensile strain in the p-i-n heterojunction structure, which enables the diodes to emit radiation over a range of wavelengths.

  11. Dichromatic InGaN-based white light emitting diodes by using laser lift-off and wafer-bonding schemes (United States)

    Lee, Y. J.; Lin, P. C.; Lu, T. C.; Kuo, H. C.; Wang, S. C.


    An InGaN-based dual-wavelength blue/green (470nm/550nm) light emitting diode (LED) with three terminal operations has been designed and fabricated by using sapphire laser lift-off and wafer-bonding schemes. The device is equivalent to a parallel connection of blue and green LEDs; thus the effective electrical resistance of the device could be reduced. The luminous efficiency is 40lm/W at 20mA, accompanied by a broad electroluminescence emission with a combination of blue and green colors. This monolithically integrated dichromatic lighting structure has great potential in the application of the solid-state lighting.

  12. Evaluation of light-emitting diodes for signage applications (United States)

    Freyssinier, Jean Paul; Zhou, Yutao; Ramamurthy, Vasudha; Bierman, Andrew; Bullough, John D.; Narendran, Nadarajah


    This paper outlines two parts of a study designed to evaluate the use of light-emitting diodes (LEDs) in channel-letter signs. The first part of the study evaluated the system performance of red LED signs and white LED signs against reference neon and cold-cathode signs. The results show a large difference between the actual performance and potential savings from red and white LEDs. Depending on the configuration, a red LED sign could use 20% to 60% less power than a neon sign at the same light output. The light output of the brightest white LED sign tested was 15% lower than the cold-cathode reference, but its power was 53% higher. It appears from this study that the most efficient white LED system is still 40% less efficient than the cold-cathode system tested. One area that offers a great potential for further energy savings is the acrylic diffuser of the signs. The acrylic diffusers measured absorb between 60% and 66% of the light output produced by the sign. Qualitative factors are also known to play an important role in signage systems. One of the largest issues with any new lighting technology is its acceptance by the end user. Consistency of light output and color among LEDs, even from the same manufacturing batch, and over time, are two of the major issues that also could affect the advantages of LEDs for signage applications. To evaluate different signage products and to identify the suitability of LEDs for this application, it is important to establish a criterion for brightness uniformity. Building upon this information, the second part of the study used human factors evaluations to determine a brightness-uniformity criterion for channel-letter signs. The results show that the contrast modulation between bright and dark areas within a sign seems to elicit the strongest effect on how people perceive uniformity. A strong monotonic relationship between modulation and acceptability was found in this evaluation. The effect of contrast seems to be stronger

  13. [Tree uprooting of coniferous-broad leaved Korean pine mixed forest in Lesser Khingan Mountains, China]. (United States)

    Ge, Xiao-wen; Hou, Jie-jian; Wang, Li-hai; Wang, Xing-long; Rong, Bin-bin


    The morphological parameters, root wad indexes and site conditions of 127 uprooting trees from 76 plots (20 mx20 m) in Lesser Khingan coniferous-broad leaved Korean pine mixed forest were measured. Then the influencing factors of uprooting differences and the relationship between uprooting trees and disturbed soil were analyzed. Results showed that the number of uprooting trees varied significantly among species. Abies nephrolepis suffered the most serious uprooting damage, then Pinus koraiensis, and Ulmus spp. the least. Deciduous species had a stronger uprooting-resistant capacity than broad-leaved species. With the increase of tree DBH and height, tree' s uprooting resistance declined rapidly first and then was gradually enhanced, and finally reached the minimum at diameter class of 20 cm and height class of 14 m, respectively. The smaller the taper degree and projected area of crown were, the stronger the uprooting resistance was. Uprooting rate was negatively correlated with stand density. Trees lying in wet ground, flat terrain, medium low altitude area and windward slope had a greater risk of uprooting. There were significant positive correlation between the depth, area and volume of disturbed soil and the DBH, height, volume of uprooting trees.

  14. High-performance planar green light-emitting diodes based on a PEDOT:PSS/CH3NH3PbBr3/ZnO sandwich structure (United States)

    Shi, Zhi-Feng; Sun, Xu-Guang; Wu, Di; Xu, Ting-Ting; Zhuang, Shi-Wei; Tian, Yong-Tao; Li, Xin-Jian; Du, Guo-Tong


    Recently, perovskite-based light-emitting diodes based on organometal halide emitters have attracted much attention because of their excellent properties of high color purity, tunable emission wavelength and a low-temperature processing technique. As is well-known, organic light-emitting diodes have shown powerful capabilities in this field; however, the fabrication of these devices typically relies on high-temperature and high-vacuum processes, which increases the final cost of the product and renders them uneconomical for use in large-area displays. Organic/inorganic hybrid halide perovskites match with these material requirements, as it is possible to prepare such materials with high crystallinity through solution processing at low temperature. Herein, we demonstrated a high-brightness green light-emitting diode based on PEDOT:PSS/CH3NH3PbBr3/ZnO sandwich structures by a spin-coating method combined with a sputtering system. Under forward bias, a dominant emission peak at ~530 nm with a low full width of half-maximum (FWHM) of 30 nm can be achieved at room temperature. Owing to the high surface coverage of the CH3NH3PbBr3 layer and a device design based on carrier injection and a confinement configuration, the proposed diode exhibits good electroluminescence performance, with an external quantum efficiency of 0.0645%. More importantly, we investigated the working stability of the studied diode under continuous operation to verify the sensitivity of the electroluminescence performance to ambient atmosphere and to assess the suitability of the diode for practical applications. Moreover, the underlying reasons for the undesirable emission decay are tentatively discussed. This demonstration of an effective green electroluminescence based on CH3NH3PbBr3 provides valuable information for the design and development of perovskites as efficient emitters, thus facilitating their use in existing applications and suggesting new potential applications.

  15. Permissiveness of soil microbial communities towards broad host range plasmids

    DEFF Research Database (Denmark)

    Klümper, Uli

    larger than previously assumed. I was able to show abundant plasmid transfer from the Gram negative donor strains to a wide diversity of Gram positive soil bacteria, formerly thought to constitute distinct clusters of gene transfer. Moreover, among the observed transconjugants, I identified a core super...... environmental factors that modulate plasmid transfer in soil microbial communities. In order to attain these goals, I developed a high-throughput method that enabled me to evaluate the permissiveness of bacterial communities towards introduced plasmids. This new approach is based on the introduction...... fraction of soil the bacteria (up to 1 in 10,000) were able to take up any of these broad host range conjugal plasmids. The transconjugal pools comprised 11 bacterial phyla. This finding indicates that the realized transfer range of broad host range plasmids in environmental microbial communities is much...

  16. 30 GHz monitoring of broad absorption line (BAL) quasars

    CERN Document Server

    Ceglowski, Maciej; Pazderska, Bogna; Gawronski, Marcin


    Broad absorption line (BAL) quasars have been studied for over thirty years. Yet it is still unclear why and when we observe broad absorption lines in quasars. Is this phenomenon caused by geometry or is it connected with the evolution process? Variability of the BAL quasars, if present, can give us information about their orientation, namely it can indicate whether they are oriented more pole-on. Using the Torun 32-metre dish equipped with the One Centimetre Receiver Array (OCRA) we have started a monitoring campaign of a sample of compact radio-loud BAL quasars. This 30 GHz variability monitoring program supplements the high-resolution interferometric observations of these objects we have carried out with the EVN and VLBA.

  17. Flow characteristics at trapezoidal broad-crested side weir

    Directory of Open Access Journals (Sweden)

    Říha Jaromír


    Full Text Available Broad-crested side weirs have been the subject of numerous hydraulic studies; however, the flow field at the weir crest and in front of the weir in the approach channel still has not been fully described. Also, the discharge coefficient of broad-crested side weirs, whether slightly inclined towards the stream or lateral, still has yet to be clearly determined. Experimental research was carried out to describe the flow characteristics at low Froude numbers in the approach flow channel for various combinations of in- and overflow discharges. Three side weir types with different oblique angles were studied. Their flow characteristics and discharge coefficients were analyzed and assessed based on the results obtained from extensive measurements performed on a hydraulic model. The empirical relation between the angle of side weir obliqueness, Froude numbers in the up- and downstream channels, and the coefficient of obliqueness was derived.

  18. Evolution of Broad-line Emission from Active Galactic Nuclei

    CERN Document Server

    Elitzur, Moshe; Trump, Jonathan R


    Apart from viewing-dependent obscuration, intrinsic broad-line emission from active galactic nuclei (AGNs) follows an evolutionary sequence: Type $1 \\to 1.2/1.5 \\to 1.8/1.9 \\to 2$ as the accretion rate onto the central black hole is decreasing. This spectral evolution is controlled, at least in part, by the parameter $L_{\\rm bol}/M^{2/3}$, where $L_{\\rm bol}$ is the AGN bolometric luminosity and $M$ is the black hole mass. Both this dependence and the double-peaked profiles that emerge along the sequence arise naturally in the disk-wind scenario for the AGN broad-line region.

  19. Diverse Broad Line Region Kinematic Signatures From Reverberation Mapping

    CERN Document Server

    Denney, K D; Pogge, R W; Adair, A; Atlee, D W; Au-Yong, K; Bentz, M C; Bird, J C; Brokofsky, D J; Chisholm, E; Comins, M L; Dietrich, M; Doroshenko, V T; Eastman, J D; Efimov, Y S; Ewald, S; Ferbey, S; Gaskell, C M; Hedrick, C H; Jackson, K; Klimanov, S A; Klimek, E S; Kruse, A K; Ladéroute, A; Lamb, J B; Leighly, K; Minezaki, T; Nazarov, S V; Onken, C A; Petersen, E A; Peterson, P; Poindexter, S; Sakata, Y; Schlesinger, K J; Sergeev, S G; Skolski, N; Stieglitz, L; Tobin, J J; Unterborn, C; Vestergaard, M; Watkins, A E; Watson, L C; Yoshii, Y


    A detailed analysis of the data from a high sampling rate, multi-month reverberation mapping campaign, undertaken primarily at MDM Observatory with supporting observations from telescopes around the world, reveals that the Hbeta emission region within the broad line regions (BLRs) of several nearby AGNs exhibit a variety of kinematic behaviors. While the primary goal of this campaign was to obtain either new or improved Hbeta reverberation lag measurements for several relatively low luminosity AGNs (presented in a separate work), we were also able to unambiguously reconstruct velocity-resolved reverberation signals from a subset of our targets. Through high cadence spectroscopic monitoring of the optical continuum and broad Hbeta emission line variations observed in the nuclear regions of NGC 3227, NGC 3516, and NGC 5548, we clearly see evidence for outflowing, infalling, and virialized BLR gas motions, respectively.

  20. The broad autism phenotype: findings from an epidemiological survey. (United States)

    Micali, N; Chakrabarti, S; Fombonne, E


    This study aimed to determine if relatives of children with autism and less severe pervasive developmental disorders (PDDs) have higher rates of various components of the broad autistic phenotype. Psychiatric and medical disorders were investigated. Parents of children with PDDs were selected from an epidemiological survey and compared with parents of control children with non-autistic developmental problems. Rates of abnormalities and disorders were compared in relatives of 79 cases and 61 controls. Medical and autoimmune disorders in both groups were endorsed by few relatives. Specific developmental disorders were commoner in parents of controls. Depression and anxiety were significantly more prevalent in mothers of children with PDDs. Significantly more PDD children had at least one first-degree relative with anxiety and one second-degree relative with OCD. PDDs were commoner in first-degree relatives. The implications of the findings for the definition of the broad phenotype of autism are discussed.