Lateral carrier diffusion and current gain in terahertz InGaAs/InP double-heterojunction bipolar transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiang, Han-Wei; Rode, Johann C.; Choudhary, Prateek

2014-01-21

The DC current gain in In{sub 0.53}Ga{sub 0.47}As/InP double-heterojunction bipolar transistors is computed based on a drift-diffusion model, and is compared with experimental data. Even in the absence of other scaling effects, lateral diffusion of electrons to the base Ohmic contacts causes a rapid reduction in DC current gain as the emitter junction width and emitter-base contact spacing are reduced. The simulation and experimental data are compared in order to examine the effect of carrier lateral diffusion on current gain. The impact on current gain due to device scaling and approaches to increase current gain are discussed.

Field ion microscopic studies of the CO oxidation on platinum: Bistability and oscillations

NASA Astrophysics Data System (ADS)

Gorodetskii, V.; Drachsel, W.; Ehsasi, M.; Block, J. H.

1994-05-01

The oscillating CO oxidation is investigated on a Pt-field emitter tip by using the field ion mode of surface imaging of Oad sites with O2 as imaging gas. Based on data of the titration reactions [V. Gorodetskii, W. Drachsel, and J. H. Block, J. Chem. Phys. 100, C. E. UPDATE (1994)], external control parameters for the regions of bistability and of self-sustained isothermal oscillations could be found. On a field emitter tip, oscillations can be generated in a rather large parameter space. The anticlockwise hysteresis of O+2 ion currents in temperature cycles occurs in agreement with results on single crystal planes. Unexpected regular oscillation sequences could occasionally be obtained on the small surface areas of a field emitter tip and measured as function of the CO partial pressure and of the temperature. Different stages within oscillating cycles were documented by field ion images. Oscillations of total ion currents are correlated with variations in the spatial brightness of field ion images. In the manifold of single crystal planes of a field emitter {331} planes around the {011} regions are starting points for oscillations which mainly proceed along [100] vicinals. This excludes the {111} regions from autonomous oscillations. With slightly increased CO partial pressures fast local oscillations at a few hundred surface sites of the Pt(001) plane display short-living CO islands of 40 to 50 Å diameter. Temporal oscillations of the total O+2 ion current are mainly caused by surface plane specific spatial oscillations. The synchronization is achieved by diffusion reaction fronts rather than by gas phase synchronization.

Effects of surface diffusion on high temperature selective emitters

DOE PAGES

Peykov, Daniel; Yeng, Yi Xiang; Celanovic, Ivan; ...

2015-01-01

Using morphological and optical simulations of 1D tantalum photonic crystals at 1200K, surface diffusion was determined to gradually reduce the efficiency of selective emitters. This was attributed to shifting resonance peaks and declining emissivity caused by changes to the cavity dimensions and the aperture width. Decreasing the structure’s curvature through larger periods and smaller cavity widths, as well as generating smoother transitions in curvature through the introduction of rounded cavities, was found to alleviate this degradation. An optimized structure, that shows both high efficiency selective emissivity and resistance to surface diffusion, was presented.

Quantifying fluorescence enhancement for slowly diffusing single molecules in plasmonic near fields

NASA Astrophysics Data System (ADS)

Caldarola, Martín; Pradhan, Biswajit; Orrit, Michel

2018-03-01

Gold nanorods are extensively used for single-molecule fluorescence enhancement as they are easy to synthesize, bio-compatible, and provide high light confinement at their nanometer-sized tips. The current way to estimate fluorescence enhancement relies on binned time traces or on fluorescence correlation spectroscopy. We report on novel ways to extract the enhancement factor in a single-molecule enhancement experiment, avoiding the arbitrary selection of one or a few high-intensity burst(s). These new estimates for the enhancement factor make use of the whole distribution of intensity bursts or of the interphoton delay distribution, which avoids the arbitrary binning of the fluorescence intensity time traces. We present experimental results on the bi-dimensional case, experimentally achieved using a lipid bilayer to support the diffusion of fluorophores. We support our findings with histograms of fluorescence bursts and with an analytical derivation of the interphoton delay distribution of (nearly) immobilized emitters from the fluorescence intensity profile.

Remote detection of single emitters via optical waveguides

NASA Astrophysics Data System (ADS)

Then, Patrick; Razinskas, Gary; Feichtner, Thorsten; Haas, Philippe; Wild, Andreas; Bellini, Nicola; Osellame, Roberto; Cerullo, Giulio; Hecht, Bert

2014-05-01

The integration of lab-on-a-chip technologies with single-molecule detection techniques may enable new applications in analytical chemistry, biotechnology, and medicine. We describe a method based on the reciprocity theorem of electromagnetic theory to determine and optimize the detection efficiency of photons emitted by single quantum emitters through truncated dielectric waveguides of arbitrary shape positioned in their proximity. We demonstrate experimentally that detection of single quantum emitters via such waveguides is possible, confirming the predicted behavior of the detection efficiency. Our findings blaze the trail towards efficient lensless single-emitter detection compatible with large-scale optofluidic integration.

Doping-free white organic light-emitting diodes without blue molecular emitter: An unexplored approach to achieve high performance via exciplex emission

NASA Astrophysics Data System (ADS)

Luo, Dongxiang; Xiao, Ye; Hao, Mingming; Zhao, Yu; Yang, Yibin; Gao, Yuan; Liu, Baiquan

2017-02-01

Doping-free white organic light-emitting diodes (DF-WOLEDs) are promising for the low-cost commercialization because of their simplified device structures. However, DF-WOLEDs reported thus far in the literature are based on the use of blue single molecular emitters, whose processing can represent a crucial point in device manufacture. Herein, DF-WOLEDs without the blue single molecular emitter have been demonstrated by managing a blue exciplex system. For the single-molecular-emitter (orange or yellow emitter) DF-WOLEDs, (i) a color rendering index (CRI) of 81 at 1000 cd/m2 can be obtained, which is one of the highest for the single-molecular-emitter WOLEDs, or (ii) a high efficiency of 35.4 lm/W can be yielded. For the dual-molecular-emitter (yellow/red emitters) DF-WOLED, a high CRI of 85 and low correlated color temperature of 2376 K at 1000 cd/m2 have been simultaneously achieved, which has not been reported by previous DF-WOLEDs. Such presented findings may unlock an alternative avenue to the simplified but high-performance WOLEDs.

Method of manufacturing a hybrid emitter all back contact solar cell

DOEpatents

Loscutoff, Paul; Rim, Seung

2017-02-07

A method of manufacturing an all back contact solar cell which has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. A second emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The method further includes forming contact holes that allow metal contacts to connect to corresponding emitters.

Diamond-based single-photon emitters

NASA Astrophysics Data System (ADS)

Aharonovich, I.; Castelletto, S.; Simpson, D. A.; Su, C.-H.; Greentree, A. D.; Prawer, S.

2011-07-01

The exploitation of emerging quantum technologies requires efficient fabrication of key building blocks. Sources of single photons are extremely important across many applications as they can serve as vectors for quantum information—thereby allowing long-range (perhaps even global-scale) quantum states to be made and manipulated for tasks such as quantum communication or distributed quantum computation. At the single-emitter level, quantum sources also afford new possibilities in terms of nanoscopy and bio-marking. Color centers in diamond are prominent candidates to generate and manipulate quantum states of light, as they are a photostable solid-state source of single photons at room temperature. In this review, we discuss the state of the art of diamond-based single-photon emitters and highlight their fabrication methodologies. We present the experimental techniques used to characterize the quantum emitters and discuss their photophysical properties. We outline a number of applications including quantum key distribution, bio-marking and sub-diffraction imaging, where diamond-based single emitters are playing a crucial role. We conclude with a discussion of the main challenges and perspectives for employing diamond emitters in quantum information processing.

Efficient room-temperature source of polarized single photons

DOEpatents

Lukishova, Svetlana G.; Boyd, Robert W.; Stroud, Carlos R.

2007-08-07

An efficient technique for producing deterministically polarized single photons uses liquid-crystal hosts of either monomeric or oligomeric/polymeric form to preferentially align the single emitters for maximum excitation efficiency. Deterministic molecular alignment also provides deterministically polarized output photons; using planar-aligned cholesteric liquid crystal hosts as 1-D photonic-band-gap microcavities tunable to the emitter fluorescence band to increase source efficiency, using liquid crystal technology to prevent emitter bleaching. Emitters comprise soluble dyes, inorganic nanocrystals or trivalent rare-earth chelates.

Dynamical theory of single-photon transport in a one-dimensional waveguide coupled to identical and nonidentical emitters

NASA Astrophysics Data System (ADS)

Liao, Zeyang; Nha, Hyunchul; Zubairy, M. Suhail

2016-11-01

We develop a general dynamical theory for studying a single-photon transport in a one-dimensional (1D) waveguide coupled to multiple emitters which can be either identical or nonidentical. In this theory, both the effects of the waveguide and non-waveguide vacuum modes are included. This theory enables us to investigate the propagation of an emitter excitation or an arbitrary single-photon pulse along an array of emitters coupled to a 1D waveguide. The dipole-dipole interaction induced by the non-waveguide modes, which is usually neglected in the literature, can significantly modify the dynamics of the emitter system as well as the characteristics of the output field if the emitter separation is much smaller than the resonance wavelength. Nonidentical emitters can also strongly couple to each other if their energy difference is less than or of the order of the dipole-dipole energy shift. Interestingly, if their energy difference is close but nonzero, a very narrow transparency window around the resonance frequency can appear which does not occur for identical emitters. This phenomenon may find important applications in quantum waveguide devices such as optical switches and ultranarrow single-photon frequency comb generator.

Long-Term Reliability of High Speed SiGe/Si Heterojunction Bipolar Transistors

NASA Technical Reports Server (NTRS)

Ponchak, George E. (Technical Monitor); Bhattacharya, Pallab

2003-01-01

Accelerated lifetime tests were performed on double-mesa structure Si/Si0.7Ge0.3/Si npn heterojunction bipolar transistors, grown by molecular beam epitaxy, in the temperature range of 175C-275C. Both single- and multiple finger transistors were tested. The single-finger transistors (with 5x20 micron sq m emitter area) have DC current gains approximately 40-50 and f(sub T) and f(sub MAX) of up to 22 GHz and 25 GHz, respectively. The multiple finger transistors (1.4 micron finger width, 9 emitter fingers with total emitter area of 403 micron sq m) have similar DC current gain but f(sub T) of 50 GHz. It is found that a gradual degradation in these devices is caused by the recombination enhanced impurity diffusion (REID) of boron atoms from the p-type base region and the associated formation of parasitic energy barriers to electron transport from the emitter to collector layers. This REID has been quantitatively modeled and explained, to the first order of approximation, and the agreement with the measured data is good. The mean time to failure (MTTF) of the devices at room temperature is estimated from the extrapolation of the Arrhenius plots of device lifetime versus reciprocal temperature. The results of the reliability tests offer valuable feedback for SiGe heterostructure design in order to improve the long-term reliability of the devices and circuits made with them. Hot electron induced degradation of the base-emitter junction was also observed during the accelerated lifetime testing. In order to improve the HBT reliability endangered by the hot electrons, deuterium sintered techniques have been proposed. The preliminary results from this study show that a deuterium-sintered HBT is, indeed, more resistant to hot-electron induced base-emitter junction degradation. SiGe/Si based amplifier circuits were also subjected to lifetime testing and we extrapolate MTTF is approximately 1.1_10(exp 6) hours at 125iC junction temperature from the circuit lifetime data.

Enhanced photon indistinguishability in pulse-driven quantum emitters

NASA Astrophysics Data System (ADS)

Fotso, Herbert F.

2017-04-01

Photon indistinguishability is an essential ingredient for the realization of scalable quantum networks. For quantum bits in the solid state, this is hindered by spectral diffusion, the uncontrolled random drift of the emission/absorption spectrum as a result of fluctuations in the emitter's environment. We study optical properties of a quantum emitter in the solid state when it is driven by a periodic sequence of optical pulses with finite detuning with respect to the emitter. We find that a pulse sequence can effectively mitigate spectral diffusion and enhance photon indistinguishability. The bulk of the emission occurs at a set target frequency; Photon indistinguishability is enhanced and is restored to its optimal value after every even pulse. Also, for moderate values of the sequence period and of the detuning, both the emission spectrum and the absorption spectrum have lineshapes with little dependence on the detuning. We describe the solution and the evolution of the emission/absorption spectrum as a function time.

Internal quantum efficiency mapping analysis for a >20%-efficiency n-type bifacial solar cell with front-side emitter formed by BBr3 thermal diffusion

NASA Astrophysics Data System (ADS)

Simayi, Shalamujiang; Mochizuki, Toshimitsu; Kida, Yasuhiro; Shirasawa, Katsuhiko; Takato, Hidetaka

2017-10-01

This paper presents a large-area (239-cm2) high-efficiency n-type bifacial solar cell that is processed using tube-furnace thermal diffusion employing liquid sources BBr3 for the front-side boron emitter and POCl3 for the rear-side phosphorus back surface field (BSF). The SiN x /Al2O3 stack was applied to the front-side boron emitter as a passivation layer. Both the front and rear-side electrodes are obtained using screen-printed contacts with H-patterns. The resulting highest-efficiency solar cell has front- and rear-side efficiencies of 20.3 and 18.7%, respectively, while the corresponding bifaciality is up to 92%. Finally, the passivation quality of the SiN x /Al2O3 stack on the front-side boron emitter and rear-side phosphorus BSF is investigated and visualized by measuring the internal quantum efficiency mapping of the bifacial solar cell.

Emittance measurements in low energy ion storage rings

NASA Astrophysics Data System (ADS)

Hunt, J. R.; Carli, C.; Resta-López, J.; Welsch, C. P.

2018-07-01

The development of the next generation of ultra-low energy antiproton and ion facilities requires precise information about the beam emittance to guarantee optimum performance. In the Extra-Low ENergy Antiproton storage ring (ELENA) the transverse emittances will be measured by scraping. However, this diagnostic measurement faces several challenges: non-zero dispersion, non-Gaussian beam distributions due to effects of the electron cooler and various systematic errors such as closed orbit offsets and inaccurate rms momentum spread estimation. In addition, diffusion processes, such as intra-beam scattering might lead to emittance overestimates. Here, we present algorithms to efficiently address the emittance reconstruction in presence of the above effects, and present simulation results for the case of ELENA.

In situ arsenic-doped polycrystalline silicon as a low thermal budget emitter contact for Si/Si1 - xGex heterojunction bipolar transistors

NASA Astrophysics Data System (ADS)

King, C. A.; Johnson, R. W.; Pinto, M. R.; Luftman, H. S.; Munanka, J.

1996-01-01

A low thermal budget emitter contact with low specific contact resistivity (ρc) with the absence of transient enhanced diffusion (TED) effects is essential to fabricate integratable high performance Si/SiGe heterojunction bipolar transistors (HBTs). We report the use of in situ As-doped polycrystalline silicon (polysilicon) from a low base pressure rapid thermal episystem for this purpose and find that it meets all the requirements. We used secondary ion mass spectrometry to find that 18 nm, heavily B-doped layers remain intact after implantation into the surface polysilicon and annealing at 800 °C for 40 s. Similar samples without the surface polylayer displayed extreme broadening of B profile. Kelvin crossbridge resistors together with 2D device simulations revealed that ρc is an extremely low value of 1.2×10-8 Ω cm2 in as-deposited material. Fabrication of simple 30×30 μm2 mesa isolated HBT devices showed IC to be more than two decades higher in devices with only an in situ As-doped polyemitter compared with devices that incorporated a surface implant into the single crystal portion of the emitter before polysilicon deposition. These results demonstrate that this doped polycrystalline silicon material is an excellent choice for emitter contacts to HBT devices.

Fabricating solar cells with silicon nanoparticles

DOEpatents

Loscutoff, Paul; Molesa, Steve; Kim, Taeseok

2014-09-02

A laser contact process is employed to form contact holes to emitters of a solar cell. Doped silicon nanoparticles are formed over a substrate of the solar cell. The surface of individual or clusters of silicon nanoparticles is coated with a nanoparticle passivation film. Contact holes to emitters of the solar cell are formed by impinging a laser beam on the passivated silicon nanoparticles. For example, the laser contact process may be a laser ablation process. In that case, the emitters may be formed by diffusing dopants from the silicon nanoparticles prior to forming the contact holes to the emitters. As another example, the laser contact process may be a laser melting process whereby portions of the silicon nanoparticles are melted to form the emitters and contact holes to the emitters.

Non-blinking single-photon emitters in silica

DOE PAGES

Rabouw, Freddy T.; Cogan, Nicole M. B.; Berends, Anne C.; ...

2016-02-19

Samples for single-emitter spectroscopy are usually prepared by spin-coating a dilute solution of emitters on a microscope cover slip of silicate based glass (such as quartz). Here, we show that both borosilicate glass and quartz contain intrinsic defect colour centres that fluoresce when excited at 532 nm. In a microscope image the defect emission is indistinguishable from spin-coated emitters. The emission spectrum is characterised by multiple peaks with the main peak between 2.05 and 2.20 eV, most likely due to coupling to a silica vibration with an energy that varies between 160 and 180 meV. The defects are single-photon emitters,more » do not blink, and have photoluminescence lifetimes of a few nanoseconds. Furthermore, photoluminescence from such defects may previously have been misinterpreted as originating from single nanocrystal quantum dots.« less

High-brightness 800nm fiber-coupled laser diodes

NASA Astrophysics Data System (ADS)

Berk, Yuri; Levy, Moshe; Rappaport, Noam; Tessler, Renana; Peleg, Ophir; Shamay, Moshe; Yanson, Dan; Klumel, Genadi; Dahan, Nir; Baskin, Ilya; Shkedi, Lior

2014-03-01

Fiber-coupled laser diodes have become essential sources for fiber laser pumping and direct energy applications. Single emitters offer reliable multi-watt output power from a 100 m lateral emission aperture. By their combination and fiber coupling, pump powers up to 100 W can be achieved from a low-NA fiber pigtail. Whilst in the 9xx nm spectral range the single emitter technology is very mature with <10W output per chip, at 800nm the reliable output power from a single emitter is limited to 4 W - 5 W. Consequently, commercially available fiber coupled modules only deliver 5W - 15W at around 800nm, almost an order of magnitude down from the 9xx range pumps. To bridge this gap, we report our advancement in the brightness and reliability of 800nm single emitters. By optimizing the wafer structure, laser cavity and facet passivation process we have demonstrated QCW device operation up to 19W limited by catastrophic optical damage to the 100 μm aperture. In CW operation, the devices reach 14 W output followed by a reversible thermal rollover and a complete device shutdown at high currents, with the performance fully rebounded after cooling. We also report the beam properties of our 800nm single emitters and provide a comparative analysis with the 9xx nm single emitter family. Pump modules integrating several of these emitters with a 105 μm / 0.15 NA delivery fiber reach 35W in CW at 808 nm. We discuss the key opto-mechanical parameters that will enable further brightness scaling of multi-emitter pump modules.

Deterministic strain-induced arrays of quantum emitters in a two-dimensional semiconductor

PubMed Central

Branny, Artur; Kumar, Santosh; Proux, Raphaël; Gerardot, Brian D

2017-01-01

An outstanding challenge in quantum photonics is scalability, which requires positioning of single quantum emitters in a deterministic fashion. Site positioning progress has been made in established platforms including defects in diamond and self-assembled quantum dots, albeit often with compromised coherence and optical quality. The emergence of single quantum emitters in layered transition metal dichalcogenide semiconductors offers new opportunities to construct a scalable quantum architecture. Here, using nanoscale strain engineering, we deterministically achieve a two-dimensional lattice of quantum emitters in an atomically thin semiconductor. We create point-like strain perturbations in mono- and bi-layer WSe2 which locally modify the band-gap, leading to efficient funnelling of excitons towards isolated strain-tuned quantum emitters that exhibit high-purity single photon emission. We achieve near unity emitter creation probability and a mean positioning accuracy of 120±32 nm, which may be improved with further optimization of the nanopillar dimensions. PMID:28530219

Impact of dopant concentrations on emitter formation with spin on dopant source in n-type crystalline silicon solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singha, Bandana; Solanki, Chetan Singh

Use of a suitable dopant source for emitter formation is an essential requirement in n-type crystalline silicon solar cells. Boron spin on dopant source, used as alternative to mostly used BBr{sub 3} liquid source, can yield an emitter with less diffusion induced defects under controlled conditions. Different concentrations of commercially available spin on dopant source is used and optimized in this work for sheet resistance values of the emitter ranging from 30 Ω/□ to 70 Ω/□ with emitter doping concentrations suitable for ohmic contacts. The dopant concentrations diluted with different ratios improves the carrier lifetime and thus improves the emittermore » performance. Hence use of suitable dopant source is essential in forming emitters in n-type crystalline silicon solar cells.« less

Wiring up pre-characterized single-photon emitters by laser lithography

NASA Astrophysics Data System (ADS)

Shi, Q.; Sontheimer, B.; Nikolay, N.; Schell, A. W.; Fischer, J.; Naber, A.; Benson, O.; Wegener, M.

2016-08-01

Future quantum optical chips will likely be hybrid in nature and include many single-photon emitters, waveguides, filters, as well as single-photon detectors. Here, we introduce a scalable optical localization-selection-lithography procedure for wiring up a large number of single-photon emitters via polymeric photonic wire bonds in three dimensions. First, we localize and characterize nitrogen vacancies in nanodiamonds inside a solid photoresist exhibiting low background fluorescence. Next, without intermediate steps and using the same optical instrument, we perform aligned three-dimensional laser lithography. As a proof of concept, we design, fabricate, and characterize three-dimensional functional waveguide elements on an optical chip. Each element consists of one single-photon emitter centered in a crossed-arc waveguide configuration, allowing for integrated optical excitation and efficient background suppression at the same time.

Quantum memory and gates using a Λ -type quantum emitter coupled to a chiral waveguide

NASA Astrophysics Data System (ADS)

Li, Tao; Miranowicz, Adam; Hu, Xuedong; Xia, Keyu; Nori, Franco

2018-06-01

By coupling a Λ -type quantum emitter to a chiral waveguide, in which the polarization of a photon is locked to its propagation direction, we propose a controllable photon-emitter interface for quantum networks. We show that this chiral system enables the swap gate and a hybrid-entangling gate between the emitter and a flying single photon. It also allows deterministic storage and retrieval of single-photon states with high fidelities and efficiencies. In short, this chirally coupled emitter-photon interface can be a critical building block toward a large-scale quantum network.

Massively parallel diffuse optical tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandusky, John V.; Pitts, Todd A.

Diffuse optical tomography systems and methods are described herein. In a general embodiment, the diffuse optical tomography system comprises a plurality of sensor heads, the plurality of sensor heads comprising respective optical emitter systems and respective sensor systems. A sensor head in the plurality of sensors heads is caused to act as an illuminator, such that its optical emitter system transmits a transillumination beam towards a portion of a sample. Other sensor heads in the plurality of sensor heads act as observers, detecting portions of the transillumination beam that radiate from the sample in the fields of view of themore » respective sensory systems of the other sensor heads. Thus, sensor heads in the plurality of sensors heads generate sensor data in parallel.« less

Biomimetic light-harvesting funnels for re-directioning of diffuse light.

PubMed

Pieper, Alexander; Hohgardt, Manuel; Willich, Maximilian; Gacek, Daniel Alexander; Hafi, Nour; Pfennig, Dominik; Albrecht, Andreas; Walla, Peter Jomo

2018-02-14

Efficient sunlight harvesting and re-directioning onto small areas has great potential for more widespread use of precious high-performance photovoltaics but so far intrinsic solar concentrator loss mechanisms outweighed the benefits. Here we present an antenna concept allowing high light absorption without high reabsorption or escape-cone losses. An excess of randomly oriented pigments collects light from any direction and funnels the energy to individual acceptors all having identical orientations and emitting ~90% of photons into angles suitable for total internal reflection waveguiding to desired energy converters (funneling diffuse-light re-directioning, FunDiLight). This is achieved using distinct molecules that align efficiently within stretched polymers together with others staying randomly orientated. Emission quantum efficiencies can be >80% and single-foil reabsorption <0.5%. Efficient donor-pool energy funneling, dipole re-orientation, and ~1.5-2 nm nearest donor-acceptor transfer occurs within hundreds to ~20 ps. Single-molecule 3D-polarization experiments confirm nearly parallel emitters. Stacked pigment selection may allow coverage of the entire solar spectrum.

Localization of Narrowband Single Photon Emitters in Nanodiamonds.

PubMed

Bray, Kerem; Sandstrom, Russell; Elbadawi, Christopher; Fischer, Martin; Schreck, Matthias; Shimoni, Olga; Lobo, Charlene; Toth, Milos; Aharonovich, Igor

2016-03-23

Diamond nanocrystals that host room temperature narrowband single photon emitters are highly sought after for applications in nanophotonics and bioimaging. However, current understanding of the origin of these emitters is extremely limited. In this work, we demonstrate that the narrowband emitters are point defects localized at extended morphological defects in individual nanodiamonds. In particular, we show that nanocrystals with defects such as twin boundaries and secondary nucleation sites exhibit narrowband emission that is absent from pristine individual nanocrystals grown under the same conditions. Critically, we prove that the narrowband emission lines vanish when extended defects are removed deterministically using highly localized electron beam induced etching. Our results enhance the current understanding of single photon emitters in diamond and are directly relevant to fabrication of novel quantum optics devices and sensors.

Solid-state single-photon emitters

NASA Astrophysics Data System (ADS)

Aharonovich, Igor; Englund, Dirk; Toth, Milos

2016-10-01

Single-photon emitters play an important role in many leading quantum technologies. There is still no 'ideal' on-demand single-photon emitter, but a plethora of promising material systems have been developed, and several have transitioned from proof-of-concept to engineering efforts with steadily improving performance. Here, we review recent progress in the race towards true single-photon emitters required for a range of quantum information processing applications. We focus on solid-state systems including quantum dots, defects in solids, two-dimensional hosts and carbon nanotubes, as these are well positioned to benefit from recent breakthroughs in nanofabrication and materials growth techniques. We consider the main challenges and key advantages of each platform, with a focus on scalable on-chip integration and fabrication of identical sources on photonic circuits.

High brightness fiber laser pump sources based on single emitters and multiple single emitters

NASA Astrophysics Data System (ADS)

Scheller, Torsten; Wagner, Lars; Wolf, Jürgen; Bonati, Guido; Dörfel, Falk; Gabler, Thomas

2008-02-01

Driven by the potential of the fiber laser market, the development of high brightness pump sources has been pushed during the last years. The main approaches to reach the targets of this market had been the direct coupling of single emitters (SE) on the one hand and the beam shaping of bars and stacks on the other hand, which often causes higher cost per watt. Meanwhile the power of single emitters with 100μm emitter size for direct coupling increased dramatically, which also pushed a new generation of wide stripe emitters or multi emitters (ME) of up to 1000μm emitter size respectively "minibars" with apertures of 3 to 5mm. The advantage of this emitter type compared to traditional bars is it's scalability to power levels of 40W to 60W combined with a small aperture which gives advantages when coupling into a fiber. We show concepts using this multiple single emitters for fiber coupled systems of 25W up to 40W out of a 100μm fiber NA 0.22 with a reasonable optical efficiency. Taking into account a further efficiency optimization and an increase in power of these devices in the near future, the EUR/W ratio pushed by the fiber laser manufacturer will further decrease. Results will be shown as well for higher power pump sources. Additional state of the art tapered fiber bundles for photonic crystal fibers are used to combine 7 (19) pump sources to output powers of 100W (370W) out of a 130μm (250μm) fiber NA 0.6 with nominal 20W per port. Improving those TFB's in the near future and utilizing 40W per pump leg, an output power of even 750W out of 250μm fiber NA 0.6 will be possible. Combined Counter- and Co-Propagated pumping of the fiber will then lead to the first 1kW fiber laser oscillator.

Axial diffusion barriers in near-infrared nanopillar LEDs.

PubMed

Scofield, Adam C; Lin, Andrew; Haddad, Michael; Huffaker, Diana L

2014-11-12

The growth of GaAs/GaAsP axial heterostructures is demonstrated and implemented as diffusion current barriers in nanopillar light-emitting diodes at near-infrared wavelengths. The nanopillar light-emitting diodes utilize an n-GaAs/i-InGaAs/p-GaAs axial heterostructure for current injection. Axial GaAsP segments are inserted into the n- and p-GaAs portions of the nanopillars surrounding the InGaAs emitter region, acting as diffusion barriers to provide enhanced carrier confinement. Detailed characterization of growth of the GaAsP inserts and electronic band-offset measurements are used to effectively implement the GaAsP inserts as diffusion barriers. The implementation of these barriers in nanopillar light-emitting diodes provides a 5-fold increase in output intensity, making this a promising approach to high-efficiency pillar-based emitters in the near-infrared wavelength range.

Generating a high brightness multi-kilowatt laser by dense spectral combination of VBG stabilized single emitter laser diodes

NASA Astrophysics Data System (ADS)

Fritsche, H.; Koch, Ralf; Krusche, B.; Ferrario, F.; Grohe, Andreas; Pflueger, S.; Gries, W.

2014-05-01

Generating high power laser radiation with diode lasers is commonly realized by geometrical stacking of diode bars, which results in high output power but poor beam parameter product (BPP). The accessible brightness in this approach is limited by the fill factor, both in slow and fast axis. By using a geometry that accesses the BPP of the individual diodes, generating a multi kilowatt diode laser with a BPP comparable to fiber lasers is possible. We will demonstrate such a modular approach for generating multi kilowatt lasers by combining single emitter diode lasers. Single emitter diodes have advantages over bars, mainly a simplified cooling, better reliability and a higher brightness per emitter. Additionally, because single emitters can be arranged in many different geometries, they allow building laser modules where the brightness of the single emitters is preserved. In order to maintain the high brightness of the single emitter we developed a modular laser design which uses single emitters in a staircase arrangement, then coupling two of those bases with polarization combination which is our basic module. Those modules generate up to 160 W with a BPP better than 7.5 mm*mrad. For further power scaling wavelength stabilization is crucial. The wavelength is stabilized with only one Volume Bragg Grating (VBG) in front of a base providing the very same feedback to all of the laser diodes. This results in a bandwidth of < 0.5 nm and a wavelength stability of better than 250 MHz over one hour. Dense spectral combination with dichroic mirrors and narrow channel spacing allows us to combine multiple wavelength channels, resulting in a 2 kW laser module with a BPP better than 7.5 mm*mrad, which can easily coupled into a 100 μm fiber and 0.15 NA.

Open-circuit voltage improvements in low-resistivity solar cells

NASA Technical Reports Server (NTRS)

Godlewski, M. P.; Klucher, T. M.; Mazaris, G. A.; Weizer, V. G.

1979-01-01

Mechanisms limiting the open-circuit voltage in 0.1 ohm-cm solar cells were investigated. It was found that a rather complicated multistep diffusion process could produce cells with significantly improved voltages. The voltage capabilities of various laboratory cells were compared independent of their absorption and collection efficiencies. This was accomplished by comparing the cells on the basis of their saturation currents or, equivalently, comparing their voltage outputs at a constant current-density level. The results show that for both the Lewis diffused emitter cell and the Spire ion-implanted emitter cell the base component of the saturation current is voltage controlling. The evidence for the University of Florida cells, although not very conclusive, suggests emitter control of the voltage in this device. The data suggest further that the critical voltage-limiting parameter for the Lewis cell is the electron mobility in the cell base.

Wavelength locking of single emitters and multi-emitter modules: simulation and experiments

NASA Astrophysics Data System (ADS)

Yanson, Dan; Rappaport, Noam; Peleg, Ophir; Berk, Yuri; Dahan, Nir; Klumel, Genady; Baskin, Ilya; Levy, Moshe

2016-03-01

Wavelength-stabilized high-brightness single emitters are commonly used in fiber-coupled laser diode modules for pumping Yb-doped lasers at 976 nm, and Nd-doped ones at 808 nm. We investigate the spectral behavior of single emitters under wavelength-selective feedback from a volume Bragg (or hologram) grating (VBG) in a multi-emitter module. By integrating a full VBG model as a multi-layer thin film structure with commercial raytracing software, we simulated wavelength locking conditions as a function of beam divergence and angular alignment tolerances. Good correlation between the simulated VBG feedback strength and experimentally measured locking ranges, in both VBG misalignment angle and laser temperature, is demonstrated. The challenges of assembling multi-emitter modules based on beam-stacked optical architectures are specifically addressed, where the wavelength locking conditions must be achieved simultaneously with high fiber coupling efficiency for each emitter in the module. It is shown that angular misorientation between fast and slow-axis collimating optics can have a dramatic effect on the spectral and power performance of the module. We report the development of our NEON-S wavelength-stabilized fiber laser pump module, which uses a VBG to provide wavelength-selective optical feedback in the collimated portion of the beam. Powered by our purpose-developed high-brightness single emitters, the module delivers 47 W output at 11 A from an 0.15 NA fiber and a 0.3 nm linewidth at 976 nm. Preliminary wavelength-locking results at 808 nm are also presented.

Brightness-enhanced high-efficiency single emitters for fiber laser pumping

NASA Astrophysics Data System (ADS)

Yanson, Dan; Rappaport, Noam; Shamay, Moshe; Cohen, Shalom; Berk, Yuri; Klumel, Genadi; Don, Yaroslav; Peleg, Ophir; Levy, Moshe

2013-02-01

Reliable single emitters delivering <10W in the 9xx nm spectral range, are common energy sources for fiber laser pumps. The brightness (radiance) of a single emitter, which connotes the angular concentration of the emitted energy, is just as important a parameter as the output power alone for fiber coupling applications. We report on the development of high-brightness single emitters that demonstrate <12W output with 60% wall-plug efficiency and a lateral emission angle that is compatible with coupling into 0.15 NA delivery fiber. Using a purpose developed active laser model, simulation of far-field patterns in the lateral (slow) axis can be performed for different epitaxial wafer structures. By optimizing both the wafer and chip designs, we have both increased the device efficiency and improved the slow-axis divergence in high-current operation. Device reliability data are presented. The next-generation emitters will be integrated in SCD's NEON fiber pump modules to upgrade the pump output towards higher ex-fiber powers with high efficiency.

Alpha-particle radiotherapy: For large solid tumors diffusion trumps targeting.

PubMed

Zhu, Charles; Sempkowski, Michelle; Holleran, Timothy; Linz, Thomas; Bertalan, Thomas; Josefsson, Anders; Bruchertseifer, Frank; Morgenstern, Alfred; Sofou, Stavroula

2017-06-01

Diffusion limitations on the penetration of nanocarriers in solid tumors hamper their therapeutic use when labeled with α-particle emitters. This is mostly due to the α-particles' relatively short range (≤100 μm) resulting in partial tumor irradiation and limited killing. To utilize the high therapeutic potential of α-particles against solid tumors, we designed non-targeted, non-internalizing nanometer-sized tunable carriers (pH-tunable liposomes) that are triggered to release, within the slightly acidic tumor interstitium, highly-diffusive forms of the encapsulated α-particle generator Actinium-225 ( 225 Ac) resulting in more homogeneous distributions of the α-particle emitters, improving uniformity in tumor irradiation and increasing killing efficacies. On large multicellular spheroids (400 μm-in-diameter), used as surrogates of the avascular areas of solid tumors, interstitially-releasing liposomes resulted in best growth control independent of HER2 expression followed in performance by (a) the HER2-targeting radiolabeled antibody or (b) the non-responsive liposomes. In an orthotopic human HER2-negative mouse model, interstitially-releasing 225 Ac-loaded liposomes resulted in the longest overall and median survival. This study demonstrates the therapeutic potential of a general strategy to bypass the diffusion-limited transport of radionuclide carriers in solid tumors enabling interstitial release from non-internalizing nanocarriers of highly-diffusing and deeper tumor-penetrating molecular forms of α-particle emitters, independent of cell-targeting. Copyright © 2017 Elsevier Ltd. All rights reserved.

Systems and Methods for Implementing Robust Carbon Nanotube-Based Field Emitters

NASA Technical Reports Server (NTRS)

Kristof, Valerie (Inventor); Manohara, Harish (Inventor); Toda, Risaku (Inventor)

2015-01-01

Systems and methods in accordance with embodiments of the invention implement carbon nanotube-based field emitters. In one embodiment, a method of fabricating a carbon nanotube field emitter includes: patterning a substrate with a catalyst, where the substrate has thereon disposed a diffusion barrier layer; growing a plurality of carbon nanotubes on at least a portion of the patterned catalyst; and heating the substrate to an extent where it begins to soften such that at least a portion of at least one carbon nanotube becomes enveloped by the softened substrate.

Single-Photon Emitters in Boron Nitride Nanococoons.

PubMed

Ziegler, Joshua; Blaikie, Andrew; Fathalizadeh, Aidin; Miller, David; Yasin, Fehmi S; Williams, Kerisha; Mohrhardt, Jordan; McMorran, Benjamin J; Zettl, Alex; Alemán, Benjamín

2018-04-11

Quantum emitters in two-dimensional hexagonal boron nitride (hBN) are attractive for a variety of quantum and photonic technologies because they combine ultra-bright, room-temperature single-photon emission with an atomically thin crystal. However, the emitter's prominence is hindered by large, strain-induced wavelength shifts. We report the discovery of a visible-wavelength, single-photon emitter (SPE) in a zero-dimensional boron nitride allotrope (the boron nitride nanococoon, BNNC) that retains the excellent optical characteristics of few-layer hBN while possessing an emission line variation that is lower by a factor of 5 than the hBN emitter. We determined the emission source to be the nanometer-size BNNC through the cross-correlation of optical confocal microscopy with high-resolution scanning and transmission electron microscopy. Altogether, this discovery enlivens color centers in BN materials and, because of the BN nanococoon's size, opens new and exciting opportunities in nanophotonics, quantum information, biological imaging, and nanoscale sensing.

Tunable and high-purity room temperature single-photon emission from atomic defects in hexagonal boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grosso, Gabriele; Moon, Hyowon; Lienhard, Benjamin

Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. Here, we demonstrate that strain control allows spectral tunability of hBN single photon emitters over 6 meV, and material processing sharply improves the single photon purity. We observe high single photon count rates exceeding 7 × 10 6 counts per second at saturation, after correcting for uncorrelated photonmore » background. Furthermore, these emitters are stable to material transfer to other substrates. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.« less

Tunable and high-purity room temperature single-photon emission from atomic defects in hexagonal boron nitride

DOE PAGES

Grosso, Gabriele; Moon, Hyowon; Lienhard, Benjamin; ...

2017-09-26

Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. Here, we demonstrate that strain control allows spectral tunability of hBN single photon emitters over 6 meV, and material processing sharply improves the single photon purity. We observe high single photon count rates exceeding 7 × 10 6 counts per second at saturation, after correcting for uncorrelated photonmore » background. Furthermore, these emitters are stable to material transfer to other substrates. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.« less

An integrated microcombustor and photonic crystal emitter for thermophotovoltaics

NASA Astrophysics Data System (ADS)

Chan, Walker R.; Stelmakh, Veronika; Allmon, William R.; Waits, Christopher M.; Soljacic, Marin; Joannopoulos, John D.; Celanovic, Ivan

2016-11-01

Thermophotovoltaic (TPV) energy conversion is appealing for portable millimeter- scale generators because of its simplicity, but it relies on a high temperatures. The performance and reliability of the high-temperature components, a microcombustor and a photonic crystal emitter, has proven challenging because they are subjected to 1000-1200°C and stresses arising from thermal expansion mismatches. In this paper, we adopt the industrial process of diffusion brazing to fabricate an integrated microcombustor and photonic crystal by bonding stacked metal layers. Diffusion brazing is simpler and faster than previous approaches of silicon MEMS and welded metal, and the end result is more robust.

Superresolution microscope image reconstruction by spatiotemporal object decomposition and association: application in resolving t-tubule structure in skeletal muscle

PubMed Central

Sun, Mingzhai; Huang, Jiaqing; Bunyak, Filiz; Gumpper, Kristyn; De, Gejing; Sermersheim, Matthew; Liu, George; Lin, Pei-Hui; Palaniappan, Kannappan; Ma, Jianjie

2014-01-01

One key factor that limits resolution of single-molecule superresolution microscopy relates to the localization accuracy of the activated emitters, which is usually deteriorated by two factors. One originates from the background noise due to out-of-focus signals, sample auto-fluorescence, and camera acquisition noise; and the other is due to the low photon count of emitters at a single frame. With fast acquisition rate, the activated emitters can last multiple frames before they transiently switch off or permanently bleach. Effectively incorporating the temporal information of these emitters is critical to improve the spatial resolution. However, majority of the existing reconstruction algorithms locate the emitters frame by frame, discarding or underusing the temporal information. Here we present a new image reconstruction algorithm based on tracklets, short trajectories of the same objects. We improve the localization accuracy by associating the same emitters from multiple frames to form tracklets and by aggregating signals to enhance the signal to noise ratio. We also introduce a weighted mean-shift algorithm (WMS) to automatically detect the number of modes (emitters) in overlapping regions of tracklets so that not only well-separated single emitters but also individual emitters within multi-emitter groups can be identified and tracked. In combination with a maximum likelihood estimator method (MLE), we are able to resolve low to medium density of overlapping emitters with improved localization accuracy. We evaluate the performance of our method with both synthetic and experimental data, and show that the tracklet-based reconstruction is superior in localization accuracy, particularly for weak signals embedded in a strong background. Using this method, for the first time, we resolve the transverse tubule structure of the mammalian skeletal muscle. PMID:24921337

Superresolution microscope image reconstruction by spatiotemporal object decomposition and association: application in resolving t-tubule structure in skeletal muscle.

PubMed

Sun, Mingzhai; Huang, Jiaqing; Bunyak, Filiz; Gumpper, Kristyn; De, Gejing; Sermersheim, Matthew; Liu, George; Lin, Pei-Hui; Palaniappan, Kannappan; Ma, Jianjie

2014-05-19

One key factor that limits resolution of single-molecule superresolution microscopy relates to the localization accuracy of the activated emitters, which is usually deteriorated by two factors. One originates from the background noise due to out-of-focus signals, sample auto-fluorescence, and camera acquisition noise; and the other is due to the low photon count of emitters at a single frame. With fast acquisition rate, the activated emitters can last multiple frames before they transiently switch off or permanently bleach. Effectively incorporating the temporal information of these emitters is critical to improve the spatial resolution. However, majority of the existing reconstruction algorithms locate the emitters frame by frame, discarding or underusing the temporal information. Here we present a new image reconstruction algorithm based on tracklets, short trajectories of the same objects. We improve the localization accuracy by associating the same emitters from multiple frames to form tracklets and by aggregating signals to enhance the signal to noise ratio. We also introduce a weighted mean-shift algorithm (WMS) to automatically detect the number of modes (emitters) in overlapping regions of tracklets so that not only well-separated single emitters but also individual emitters within multi-emitter groups can be identified and tracked. In combination with a maximum likelihood estimator method (MLE), we are able to resolve low to medium density of overlapping emitters with improved localization accuracy. We evaluate the performance of our method with both synthetic and experimental data, and show that the tracklet-based reconstruction is superior in localization accuracy, particularly for weak signals embedded in a strong background. Using this method, for the first time, we resolve the transverse tubule structure of the mammalian skeletal muscle.

Back-junction back-contact n-type silicon solar cell with diffused boron emitter locally blocked by implanted phosphorus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Müller, Ralph, E-mail: ralph.mueller@ise.fraunhofer.de; Schrof, Julian; Reichel, Christian

2014-09-08

The highest energy conversion efficiencies in the field of silicon-based photovoltaics have been achieved with back-junction back-contact (BJBC) silicon solar cells by several companies and research groups. One of the most complex parts of this cell structure is the fabrication of the locally doped p- and n-type regions, both on the back side of the solar cell. In this work, we introduce a process sequence based on a synergistic use of ion implantation and furnace diffusion. This sequence enables the formation of all doped regions for a BJBC silicon solar cell in only three processing steps. We observed that implantedmore » phosphorus can block the diffusion of boron atoms into the silicon substrate by nearly three orders of magnitude. Thus, locally implanted phosphorus can be used as an in-situ mask for a subsequent boron diffusion which simultaneously anneals the implanted phosphorus and forms the boron emitter. BJBC silicon solar cells produced with such an easy-to-fabricate process achieved conversion efficiencies of up to 21.7%. An open-circuit voltage of 674 mV and a fill factor of 80.6% prove that there is no significant recombination at the sharp transition between the highly doped emitter and the highly doped back surface field at the device level.« less

Fluorescence enhancement and strong-coupling in faceted plasmonic nanocavities

NASA Astrophysics Data System (ADS)

Kongsuwan, Nuttawut; Demetriadou, Angela; Chikkaraddy, Rohit; Baumberg, Jeremy J.; Hess, Ortwin

2018-06-01

Emission properties of a quantum emitter can be significantly modified inside nanometre-sized gaps between two plasmonic nanostructures. This forms a nanoscopic optical cavity which allows single-molecule detection and single-molecule strong-coupling at room temperature. However, plasmonic resonances of a plasmonic nanocavity are highly sensitive to the exact gap morphology. In this article, we shed light on the effect of gap morphology on the plasmonic resonances of a faceted nanoparticle-on-mirror (NPoM) nanocavity and their interaction with quantum emitters. We find that with increasing facet width the NPoM nanocavity provides weaker field enhancement and thus less coupling strength to a single quantum emitter since the effective mode volume increases with the facet width. However, if multiple emitters are present, a faceted NPoM nanocavity is capable of accommodating a larger number of emitters, and hence the overall coupling strength is larger due to the collective and coherent energy exchange from all the emitters. Our findings pave the way to more efficient designs of nanocavities for room-temperature light-matter strong-coupling, thus providing a big step forward to a non-cryogenic platform for quantum technologies.

Localised excitation of a single photon source by a nanowaveguide.

PubMed

Geng, Wei; Manceau, Mathieu; Rahbany, Nancy; Sallet, Vincent; De Vittorio, Massimo; Carbone, Luigi; Glorieux, Quentin; Bramati, Alberto; Couteau, Christophe

2016-01-29

Nowadays, integrated photonics is a key technology in quantum information processing (QIP) but achieving all-optical buses for quantum networks with efficient integration of single photon emitters remains a challenge. Photonic crystals and cavities are good candidates but do not tackle how to effectively address a nanoscale emitter. Using a nanowire nanowaveguide, we realise an hybrid nanodevice which locally excites a single photon source (SPS). The nanowire acts as a passive or active sub-wavelength waveguide to excite the quantum emitter. Our results show that localised excitation of a SPS is possible and is compared with free-space excitation. Our proof of principle experiment presents an absolute addressing efficiency ηa ~ 10(-4) only ~50% lower than the one using free-space optics. This important step demonstrates that sufficient guided light in a nanowaveguide made of a semiconductor nanowire is achievable to excite a single photon source. We accomplish a hybrid system offering great potentials for electrically driven SPSs and efficient single photon collection and detection, opening the way for optimum absorption/emission of nanoscale emitters. We also discuss how to improve the addressing efficiency of a dipolar nanoscale emitter with our system.

Localised excitation of a single photon source by a nanowaveguide

PubMed Central

Geng, Wei; Manceau, Mathieu; Rahbany, Nancy; Sallet, Vincent; De Vittorio, Massimo; Carbone, Luigi; Glorieux, Quentin; Bramati, Alberto; Couteau, Christophe

2016-01-01

Nowadays, integrated photonics is a key technology in quantum information processing (QIP) but achieving all-optical buses for quantum networks with efficient integration of single photon emitters remains a challenge. Photonic crystals and cavities are good candidates but do not tackle how to effectively address a nanoscale emitter. Using a nanowire nanowaveguide, we realise an hybrid nanodevice which locally excites a single photon source (SPS). The nanowire acts as a passive or active sub-wavelength waveguide to excite the quantum emitter. Our results show that localised excitation of a SPS is possible and is compared with free-space excitation. Our proof of principle experiment presents an absolute addressing efficiency ηa ~ 10−4 only ~50% lower than the one using free-space optics. This important step demonstrates that sufficient guided light in a nanowaveguide made of a semiconductor nanowire is achievable to excite a single photon source. We accomplish a hybrid system offering great potentials for electrically driven SPSs and efficient single photon collection and detection, opening the way for optimum absorption/emission of nanoscale emitters. We also discuss how to improve the addressing efficiency of a dipolar nanoscale emitter with our system. PMID:26822999

Importing super-resolution imaging into nanoscale puzzles of materials dynamics

NASA Astrophysics Data System (ADS)

King, John; Tsang, Chi Hang Boyce; Wilson, William; Granick, Steve

2014-03-01

A limitation of the exciting recent advances in sub-diffraction microscopy is that they focus on imaging rather than dynamical changes. We are engaged in extending this technique beyond the usual biological applications to address materials problems instead. To this end, we employ stimulated emission depletion (STED) microscopy, which relies on selectively turning off fluorescence emitters through stimulated emission, allowing only a small subset of emitters to be detected, such that the excitation spot size can be downsized to tens of nanometers. By coupling the STED excitation scheme to fluorescence correlation spectroscopy (FCS), diffusive processes are studied with nanoscale resolution. Here, we demonstrate the benefits of such experimental capabilities in a diverse range of complex systems, ranging from the diffusion of nano-objects in crowded 3D environments to the study of polymer diffusion on 2D surfaces.

Reliability study of high-brightness multiple single emitter diode lasers

NASA Astrophysics Data System (ADS)

Zhu, Jing; Yang, Thomas; Zhang, Cuipeng; Lang, Chao; Jiang, Xiaochen; Liu, Rui; Gao, Yanyan; Guo, Weirong; Jiang, Yuhua; Liu, Yang; Zhang, Luyan; Chen, Louisa

2015-03-01

In this study the chip bonding processes for various chips from various chip suppliers around the world have been optimized to achieve reliable chip on sub-mount for high performance. These chip on sub-mounts, for examples, includes three types of bonding, 8xx nm-1.2W/10.0W Indium bonded lasers, 9xx nm 10W-20W AuSn bonded lasers and 1470 nm 6W Indium bonded lasers will be reported below. The MTTF@25 of 9xx nm chip on sub-mount (COS) is calculated to be more than 203,896 hours. These chips from various chip suppliers are packaged into many multiple single emitter laser modules, using similar packaging techniques from 2 emitters per module to up to 7 emitters per module. A reliability study including aging test is performed on those multiple single emitter laser modules. With research team's 12 years' experienced packaging design and techniques, precise optical and fiber alignment processes and superior chip bonding capability, we have achieved a total MTTF exceeding 177,710 hours of life time with 60% confidence level for those multiple single emitter laser modules. Furthermore, a separated reliability study on wavelength stabilized laser modules have shown this wavelength stabilized module packaging process is reliable as well.

Coherent interaction of single molecules and plasmonic nanowires

NASA Astrophysics Data System (ADS)

Gerhardt, Ilja; Grotz, Bernhard; Siyushev, Petr; Wrachtrup, Jörg

2017-09-01

Quantum plasmonics opens the option to integrate complex quantum optical circuitry onto chip scale devices. In the past, often external light sources were used and nonclassical light was coupled in and out of plasmonic structures, such as hole arrays or waveguide structures. Another option to launch single plasmonic excitations is the coupling of single emitters in the direct proximity of, e.g., a silver or gold nanostructure. Here, we present our attempts to integrate the research of single emitters with wet-chemically grown silver nanowires. The emitters of choice are single organic dye molecules under cryogenic conditions, which are known to act as high-brightness and extremely narrow-band single photon sources. Another advantage is their high optical nonlinearity, such that they might mediate photon-photon interactions on the nanoscale. We report on the coupling of a single molecule fluorescence emission through the wire over the length of several wavelengths. The transmission of coherently emitted photons is proven by an extinction type experiment. As for influencing the spectral properties of a single emitter, we are able to show a remote change of the line-width of a single terrylene molecule, which is in close proximity to the nanowire.

Single photon emission from plasma treated 2D hexagonal boron nitride.

PubMed

Xu, Zai-Quan; Elbadawi, Christopher; Tran, Toan Trong; Kianinia, Mehran; Li, Xiuling; Liu, Daobin; Hoffman, Timothy B; Nguyen, Minh; Kim, Sejeong; Edgar, James H; Wu, Xiaojun; Song, Li; Ali, Sajid; Ford, Mike; Toth, Milos; Aharonovich, Igor

2018-05-03

Artificial atomic systems in solids are becoming increasingly important building blocks in quantum information processing and scalable quantum nanophotonic networks. Amongst numerous candidates, 2D hexagonal boron nitride has recently emerged as a promising platform hosting single photon emitters. Here, we report a number of robust plasma and thermal annealing methods for fabrication of emitters in tape-exfoliated hexagonal boron nitride (hBN) crystals. A two-step process comprising Ar plasma etching and subsequent annealing in Ar is highly robust, and yields an eight-fold increase in the concentration of emitters in hBN. The initial plasma-etching step generates emitters that suffer from blinking and bleaching, whereas the two-step process yields emitters that are photostable at room temperature with emission wavelengths greater than ∼700 nm. Density functional theory modeling suggests that the emitters might be associated with defect complexes that contain oxygen. This is further confirmed by generating the emitters via annealing hBN in air. Our findings advance the present understanding of the structure of quantum emitters in hBN and enhance the nanofabrication toolkit needed to realize integrated quantum nanophotonic circuits.

Multi-spectral investigation of bulk and facet failures in high-power single emitters at 980 nm

NASA Astrophysics Data System (ADS)

Yanson, Dan; Levy, Moshe; Shamay, Moshe; Cohen, Shalom; Shkedy, Lior; Berk, Yuri; Tessler, Renana; Klumel, Genadi; Rappaport, Noam; Karni, Yoram

2013-03-01

Reliable single emitters delivering >10W in the 9xx nm spectral range, are common building blocks for fiber laser pumps. As facet passivation techniques can suppress or delay catastrophic optical mirror damage (COMD) extending emitter reliability into hundreds of thousands of hours, other, less dominant, failure modes such as intra-chip catastrophic optical bulk damage (COBD) become apparent. Based on our failure statistics in high current operation, only ~52% of all failures can be attributed to COMD. Imaging through a window opened in the metallization on the substrate (n) side of a p-side down mounted emitter provides valuable insight into both COMD and COBD failure mechanisms. We developed a laser ablation process to define a window on the n-side of an InGaAs/AlGaAs 980nm single emitter that is overlaid on the pumped 90μm stripe on the p-side. The ablation process is compatible with the chip wire-bonding, enabling the device to be operated at high currents with high injection uniformity. We analyzed both COMD and COBD failed emitters in the electroluminescence and mid-IR domains supported by FIB/SEM observation. The ablated devices revealed branching dark line patterns, with a line origin either at the facet center (COMD case) or near the stripe edge away from the facet (COBD case). In both cases, the branching direction is always toward the rear facet (against the photon density gradient), with SEM images revealing a disordered active layer structure. Absorption levels between 0.22eV - 0.55eV were observed in disordered regions by FT-IR spectroscopy. Temperature mapping of a single emitter in the MWIR domain was performed using an InSb detector. We also report an electroluminescence study of a single emitter just before and after failure.

Progress in p(+)n InP solar cells fabricated by thermal diffusion

NASA Technical Reports Server (NTRS)

Faur, Mircea; Faur, Maria; Flood, D. J.; Brinker, D. J.; Weinberg, I.; Fatemi, N. S.; Vargas-Aburto, Carlos; Goradia, C.; Goradia, Manju

1992-01-01

In SPRAT XI, we proposed that p(sup +)n diffused junction InP solar cells should exhibit a higher conversion efficiency than their n(sup +)p counterparts. This was mainly due to the fact that our p(sup +)n (Cd,S) cell structures consistently showed higher V (sub OC) values than our n(sup +)p (S,Cd) structures. The highest V(sub OC) obtained with the p(sup +)n (Cd,S) cell configuration was 860 mV, as compared to the highest V(sub OC) 840 mV obtained with the n(sup +)p (S,Cd) configuration (AMO, 25 C). In this work, we present the performance results of our most recent thermally diffused cells using the p(sup +)n (Cd,S) structure. We have been able to fabricate cells with V(sub OC) values approaching 880 mV. Our best cell with an unoptimized front contact grid design (GS greater than or equal to 10%) showed a conversion efficiency of 13.4% (AMO, 25 C) without an AR coating layer. The emitter surface was passivated by a -50A P rich oxide. Achievement of such high V(sub OC) values was primarily due to the fabrication of emitter surfaces, having EPD densities as low as 2E2 cm(sup -2) and N(sub a)N(sub d) of about 3E18 cm (sup -3). In addition, our preliminary investigation of p(sup +)n structures seem to suggest that Cd-doped emitter cells are more radiation resistant than Zn-doped emitter cells against both high energy electron and proton irradiation.

Controlling the angular radiation of single emitters using dielectric patch nanoantennas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yuanqing; Li, Qiang; Qiu, Min, E-mail: minqiu@zju.edu.cn

2015-07-20

Dielectric nanoantennas have generated much interest in recent years owing to their low loss and optically induced electric and magnetic resonances. In this paper, we investigate the coupling between a single emitter and dielectric patch nanoantennas. For the coupled system involving non-spherical structures, analytical Mie theory is no longer applicable. A semi-analytical model is proposed instead to interpret the coupling mechanism and the radiation characteristics of the system. Based on the presented model, we demonstrate that the angular emission of the single emitter can be not only enhanced but also rotated using the dielectric patch nanoantennas.

Plasmon-Assisted Selective and Super-Resolving Excitation of Individual Quantum Emitters on a Metal Nanowire.

PubMed

Li, Qiang; Pan, Deng; Wei, Hong; Xu, Hongxing

2018-03-14

Hybrid systems composed of multiple quantum emitters coupled with plasmonic waveguides are promising building blocks for future integrated quantum nanophotonic circuits. The techniques that can super-resolve and selectively excite contiguous quantum emitters in a diffraction-limited area are of great importance for studying the plasmon-mediated interaction between quantum emitters and manipulating the single plasmon generation and propagation in plasmonic circuits. Here we show that multiple quantum dots coupled with a silver nanowire can be controllably excited by tuning the interference field of surface plasmons on the nanowire. Because of the period of the interference pattern is much smaller than the diffraction limit, we demonstrate the selective excitation of two quantum dots separated by a distance as short as 100 nm. We also numerically demonstrate a new kind of super-resolution imaging method that combines the tunable surface plasmon interference pattern on the NW with the structured illumination microscopy technique. Our work provides a novel high-resolution optical excitation and imaging method for the coupled systems of multiple quantum emitters and plasmonic waveguides, which adds a new tool for studying and manipulating single quantum emitters and single plasmons for quantum plasmonic circuitry applications.

InAlAs photovoltaic cell design for high device efficiency

DOE PAGES

Smith, Brittany L.; Bittner, Zachary S.; Hellstroem, Staffan D.; ...

2017-04-17

This study presents a new design for a single-junction InAlAs solar cell, which reduces parasitic absorption losses from the low band-gap contact layer while maintaining a functional window layer by integrating a selective etch stop. The etch stop is then removed prior to depositing an anti-reflective coating. The final cell had a 17.9% efficiency under 1-sun AM1.5 with an anti-reflective coating. Minority carrier diffusion lengths were extracted from external quantum efficiency data using physics-based device simulation software yielding 170 nm in the n-type emitter and 4.6 um in the p-type base, which is more than four times the diffusion lengthmore » previously reported for a p-type InAlAs base. In conclusion, this report represents significant progress towards a high-performance InAlAs top cell for a triple-junction design lattice-matched to InP.« less

Controlling the gain contribution of background emitters in few-quantum-dot microlasers

NASA Astrophysics Data System (ADS)

Gericke, F.; Segnon, M.; von Helversen, M.; Hopfmann, C.; Heindel, T.; Schneider, C.; Höfling, S.; Kamp, M.; Musiał, A.; Porte, X.; Gies, C.; Reitzenstein, S.

2018-02-01

We provide experimental and theoretical insight into single-emitter lasing effects in a quantum dot (QD)-microlaser under controlled variation of background gain provided by off-resonant discrete gain centers. For that purpose, we apply an advanced two-color excitation concept where the background gain contribution of off-resonant QDs can be continuously tuned by precisely balancing the relative excitation power of two lasers emitting at different wavelengths. In this way, by selectively exciting a single resonant QD and off-resonant QDs, we identify distinct single-QD signatures in the lasing characteristics and distinguish between gain contributions of a single resonant emitter and a countable number of off-resonant background emitters to the optical output of the microlaser. Our work addresses the important question whether single-QD lasing is feasible in experimentally accessible systems and shows that, for the investigated microlaser, the single-QD gain needs to be supported by the background gain contribution of off-resonant QDs to reach the transition to lasing. Interestingly, while a single QD cannot drive the investigated micropillar into lasing, its relative contribution to the emission can be as high as 70% and it dominates the statistics of emitted photons in the intermediate excitation regime below threshold.

Local Control of Lung Derived Tumors by Diffusing Alpha-Emitting Atoms Released From Intratumoral Wires Loaded With Radium-224

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooks, Tomer; Schmidt, Michael; Bittan, Hadas

2009-07-01

Purpose: Diffusing alpha-emitters radiation therapy (DART) is a new form of brachytherapy enabling the treatment of solid tumors with alpha radiation. The present study examines the antitumoral effects resulting from the release of alpha emitting radioisotopes into solid lung carcinoma (LL2, A427, and NCI-H520). Methods and Materials: An in vitro setup tested the dose-dependent killing of tumor cells exposed to alpha particles. In in vivo studies, radioactive wires (0.3 mm diameter, 5 mm long) with {sup 224}Ra activities in the range of 21-38 kBq were inserted into LL/2 tumors in C57BL/6 mice and into human-derived A427 or NCI-H520 tumors inmore » athymic mice. The efficacy of the short-lived daughters of {sup 224}Ra to produce tumor growth retardation and prolong life was assessed, and the spread of radioisotopes inside tumors was measured using autoradiography. Results: The insertion of a single DART wire into the center of 6- to 7-mm tumors had a pronounced retardation effect on tumor growth, leading to a significant inhibition of 49% (LL2) and 93% (A427) in tumor development and prolongations of 48% (LL2) in life expectancy. In the human model, more than 80% of the treated tumors disappeared or shrunk. Autoradiographic analysis of the treated sectioned tissue revealed the intratumoral distribution of the radioisotopes, and histological analysis showed corresponding areas of necrosis. In vitro experiments demonstrated a dose-dependent killing of tumors cells exposed to alpha particles. Conclusions: Short-lived diffusing alpha-emitters produced tumor growth retardation and increased survival in mice bearing lung tumor implants. These results justify further investigations with improved dose distributions.« less

On the Ionization and Ion Transmission Efficiencies of Different ESI-MS Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, Jonathan T.; Marginean, Ioan; Smith, Richard D.

2014-09-30

It is well known that the achievable sensitivity of electrospray ionization mass spectrometry (ESI-MS) is largely determined by the ionization efficiency in the ESI source and ion transmission efficiency through the ESI-MS interface. In this report we systematically study the ion transmission and ionization efficiencies in different ESI-MS interface configurations. The configurations under investigation include a single emitter/single inlet capillary, single emitter/multi-inlet capillary, and a subambient pressure ionization with nanoelectrospray (SPIN) MS interfaces with a single emitter and an emitter array, respectively. We present an effective method to evaluate the overall ion utilization efficiency of an ESI-MS interface by measuringmore » the total gas phase ion current transmitted through the interface and correlating it to the observed ion abundance measured in the corresponding mass spectrum. Our experimental results suggest that the overall ion utilization efficiency in the SPIN-MS interface configurations is better than that in the inlet capillary based ESI-MS interface configurations.« less

Measuring the number of independent emitters in single-molecule fluorescence images and trajectories using coincident photons.

PubMed

Weston, Kenneth D; Dyck, Martina; Tinnefeld, Philip; Müller, Christian; Herten, Dirk P; Sauer, Markus

2002-10-15

A simple new approach is described and demonstrated for measuring the number of independent emitters along with the fluorescence intensity, lifetime, and emission wavelength for trajectories and images of single molecules and multichromophoric systems using a single PC plug-in card for time-correlated single-photon counting. The number of independent emitters present in the detection volume can be determined using the interphoton times in a manner similar to classical antibunching experiments. In contrast to traditional coincidence analysis based on pulsed laser excitation and direct measurement of coincident photon pairs using a time-to-amplitude converter, the interphoton distances are retrieved afterward by recording the absolute arrival time of each photon with nanosecond time resolution on two spectrally separated detectors. Intensity changes that result from fluctuations of a photophysical parameter can be distinguished from fluctuations due to changes in the number of emitters (e.g., photobleaching) in single chromophore and multichromophore intensity trajectories. This is the first report to demonstrate imaging with contrast based on the number of independently emitting species within the detection volume.

Theoretical investigation of confocal microscopy using an elliptically polarized cylindrical vector laser beam: Visualization of quantum emitters near interfaces

NASA Astrophysics Data System (ADS)

Boichenko, Stepan

2018-04-01

We theoretically study laser-scanning confocal fluorescence microscopy using elliptically polarized cylindrical vector excitation light as a tool for visualization of arbitrarily oriented single quantum dipole emitters located (1) near planar surfaces enhancing fluorescence, (2) in a thin supported polymer film, (3) in a freestanding polymer film, and (4) in a dielectric planar microcavity. It is shown analytically that by using a tightly focused azimuthally polarized beam, it is possible to exclude completely the orientational dependence of the image intensity maximum of a quantum emitter that absorbs light as a pair of incoherent independent linear dipoles. For linear dipole quantum emitters, the orientational independence degree higher than 0.9 can normally be achieved (this quantity equal to 1 corresponds to completely excluded orientational dependence) if the collection efficiency of the microscope objective and the emitter's total quantum yield are not strongly orientationally dependent. Thus, the visualization of arbitrarily oriented single quantum emitters by means of the studied technique can be performed quite efficiently.

Distinguishing triplet energy transfer and trap-assisted recombination in multi-color organic light-emitting diode with an ultrathin phosphorescent emissive layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Qin, E-mail: xueqin19851202@163.com; Liu, Shouyin; Xie, Guohua

2014-03-21

An ultrathin layer of deep-red phosphorescent emitter tris(1-phenylisoquinoline) iridium (III) (Ir(piq){sub 3}) is inserted within different positions of the electron blocking layer fac-tris (1-phenylpyrazolato-N,C{sup 2′})-iridium(III) (Ir(ppz){sub 3}) to distinguish the contribution of the emission from the triplet exciton energy transfer/diffusion from the adjacent blue phosphorescent emitter and the trap-assisted recombination from the narrow band-gap emitter itself. The charge trapping effect of the narrow band-gap deep-red emitter which forms a quantum-well-like structure also plays a role in shaping the electroluminescent characteristics of multi-color organic light-emitting diodes. By accurately controlling the position of the ultrathin sensing layer, it is considerably easy tomore » balance the white emission which is quite challenging for full-color devices with multiple emission zones. There is nearly no energy transfer detectable if 7 nm thick Ir(ppz){sub 3} is inserted between the blue phosphorescent emitter and the ultrathin red emitter.« less

Fabrication and life testing of thermionic converters

NASA Technical Reports Server (NTRS)

Yang, L.; Bruce, R.

1973-01-01

An unfueled converter containing a chloride-fluoride duplex tungsten emitter of 4.78 eV vacuum work function was tested for 46,647 hours at an emitter temperature of 1973 K and an electrode power output of about 8 watts/sq cm. The test demonstrated the superior and stable performance of the (110) oriented tungsten emitter at high temperatures. Three 90 UC-10 ZrC(C/U = 1.04, tungsten additive = 4 wt %) fueled converters were fabricated and tested at an emitter temperature of 1873 K. Converter containing chloride-arc-cast duplex tungsten cladding showed temperature thermionic performance and slower rate of performance drop than converter containing chloride-fluoride duplex tungsten cladding. This is believed to be due to the superior fuel component diffusion resistance of the arc-cast tungsten substrate used in the fuel cladding. It was shown that a converter containing a carbide fueled chloride-arc-cast duplex tungsten emitter with an initial electrode power output of 6.80 watts/sq cm could still deliver an electrode power output of 6.16 watts/sq cm after 18,632 hours of operation at an emitter temperature of 1873 K.

Effect of rotational diffusion in an orientational potential well on the point spread function of electric dipole emitters.

PubMed

Stallinga, Sjoerd

2015-02-01

A study is presented of the point spread function (PSF) of electric dipole emitters that go through a series of absorption-emission cycles while the dipole orientation is changing due to rotational diffusion within the constraint of an orientational potential well. An analytical expression for the PSF is derived valid for arbitrary orientational potential wells in the limit of image acquisition times much larger than the rotational relaxation time. This framework is used to study the effects of the direction of incidence, polarization, and degree of coherence of the illumination. In the limit of fast rotational diffusion on the scale of the fluorescence lifetime the illumination influences only the PSF height, not its shape. In the limit of slow rotational diffusion on the scale of the fluorescence lifetime there is a significant effect on the PSF shape as well, provided the illumination is (partially) coherent. For oblique incidence, illumination asymmetries can arise in the PSF that give rise to position offsets in localization based on Gaussian spot fitting. These asymmetries persist in the limit of free diffusion in a zero orientational potential well.

Measurements of beam halo diffusion and population density in the Tevatron and in the Large Hadron Collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stancari, Giulio

2015-03-01

Halo dynamics influences global accelerator performance: beam lifetimes, emittance growth, dynamic aperture, and collimation efficiency. Halo monitoring and control are also critical for the operation of high-power machines. For instance, in the high-luminosity upgrade of the LHC, the energy stored in the beam tails may reach several megajoules. Fast losses can result in superconducting magnet quenches, magnet damage, or even collimator deformation. The need arises to measure the beam halo and to remove it at controllable rates. In the Tevatron and in the LHC, halo population densities and diffusivities were measured with collimator scans by observing the time evolution ofmore » losses following small inward or outward collimator steps, under different experimental conditions: with single beams and in collision, and, in the case of the Tevatron, with a hollow electron lens acting on a subset of bunches. After the LHC resumes operations, it is planned to compare measured diffusivities with the known strength of transverse damper excitations. New proposals for nondestructive halo population density measurements are also briefly discussed.« less

Emittance Measurements for a Thin Liquid Sheet Flow

NASA Technical Reports Server (NTRS)

Englehart, Amy N.; McConley, Marc W.; Chubb, Donald L.

1996-01-01

The Liquid Sheet Radiator (LSR) is an external flow radiator that uses a triangular-shaped flowing liquid sheet as the radiating surface. It has potentially much lower mass than solid wall radiators such as pumped loop and heat pipe radiators, along with being nearly immune to micrometeoroid penetration. The LSR has an added advantage of simplicity. Surface tension causes a thin (100-300 microns) liquid sheet to coalesce to a point, causing the sheet flow to have a triangular shape. Such a triangular sheet is desirable since it allows for simple collection of the flow at a single point. A major problem for all external flow radiators is the requirement that the working fluid be of very low (approx. 10(sup -8) torr) vapor pressure to keep evaporative losses low. As a result, working fluids are limited to certain oils (such as used in diffusion pumps) for low temperatures (300-400 K) and liquid metals for higher temperatures. Previous research on the LSR has been directed at understanding the fluid mechanics of thin sheet flows and assessing the stability of such flows, especially with regard to the formation of holes in the sheet. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. The latest research has been directed at determining the emittance of thin sheet flows. The emittance was calculated from spectral transmittance data for the Dow Corning 705 silicone oil. By experimentally setting up a sheet flow, the emittance was also determined as a function of measurable quantities, most importantly, the temperature drop between the top of the sheet and the temperature at the coalescence point of the sheet. Temperature fluctuations upstream of the liquid sheet were a potential problem in the analysis and were investigated.

Experimental Realization of Efficient, Room Temperature Single-Photon Sources with Definite Circular and Linear Polarizations

NASA Astrophysics Data System (ADS)

Boutsidis, Christos

In this thesis I present experimental demonstrations of room-temperature, single-photon sources with definite linear and circular polarizations. Definite photon polarization increases the efficiency of quantum communication systems. In contrast with cryogenic-temperature single-photon sources based on epitaxial quantum dots requiring expensive MBE and nanofabrication, my method utilizes a mature liquid crystal technology, which I made consistent with single-emitter fluorescence microscopy. The structures I have prepared are planar-aligned cholesteric liquid crystals forming 1-D photonic bandgaps for circularly-polarized light, which were used to achieve definite circularly-polarized fluorescence of single emitters doped in this environment. I also used planar-aligned nematic liquid crystals to align single molecules with linear dipole moments and achieved definite linearly-polarized fluorescence. I used single nanocrystal quantum dots, single nanodiamond color-centers, rare-earth-doped nanocrystals, and single terrylene and DiIC18(3) dye molecules as emitters. For nanocrystal quantum dots I observed circular polarization dissymmetry factors as large as ge = --1.6. In addition, I observed circularly-polarized resonances in the fluorescence of emitters within a cholesteric microcavity, with cavity quality factors of up to Q ˜ 250. I also showed that the fluorescence of DiIC18(3) dye molecules in planar-aligned nematic cells exhibits definite linear polarization, with a degree of polarization of rho = --0.58 +/- 0.03. Distributed Bragg reflectors form another type of microcavity that can be used to realize a single-photon source. I characterized the fluorescence from nanocrystal quantum dots doped in the defect layers of such microcavites, both organic and inorganic. Finally, to demonstrate the single-photon properties of single-emitter-doped cholesteric and nematic liquid crystal structures and distributed Bragg reflector microcavities, I present observations of photon antibunching from emitters doped in each of these structures. These experimental observations include photon antibunching from: nanocrystal quantum dots and nanodiamond color-centers doped in a cholesteric microcavity; terrylene and DiIC 18(3) dye molecules doped in nematic structures, and nanocrystal quantum dots doped in the distributed Bragg reflector microcavity. A value of the zero-time second-order coherence as low as g(2)(0) = 0.001 +/- 0.03 was measured. These results represent an important step forward in the realization of room temperature single-photon sources with definite polarization for secure quantum communication.

Highly efficient single-junction GaAs thin-film solar cell on flexible substrate.

PubMed

Moon, Sunghyun; Kim, Kangho; Kim, Youngjo; Heo, Junseok; Lee, Jaejin

2016-07-20

There has been much interest in developing a thin-film solar cell because it is lightweight and flexible. The GaAs thin-film solar cell is a top contender in the thin-film solar cell market in that it has a high power conversion efficiency (PCE) compared to that of other thin-film solar cells. There are two common structures for the GaAs solar cell: n (emitter)-on-p (base) and p-on-n. The former performs better due to its high collection efficiency because the electron diffusion length of the p-type base region is much longer than the hole diffusion length of the n-type base region. However, it has been limited to fabricate highly efficient n-on-p single-junction GaAs thin film solar cell on a flexible substrate due to technical obstacles. We investigated a simple and fast epitaxial lift-off (ELO) method that uses a stress originating from a Cr/Au bilayer on a 125-μm-thick flexible substrate. A metal combination of AuBe/Pt/Au is employed as a new p-type ohmic contact with which an n-on-p single-junction GaAs thin-film solar cell on flexible substrate was successfully fabricated. The PCE of the fabricated single-junction GaAs thin-film solar cells reached 22.08% under air mass 1.5 global illumination.

Nanodiamonds with photostable, sub-gigahertz linewidth quantum emitters

NASA Astrophysics Data System (ADS)

Tran, Toan Trong; Kianinia, Mehran; Bray, Kerem; Kim, Sejeong; Xu, Zai-Quan; Gentle, Angus; Sontheimer, Bernd; Bradac, Carlo; Aharonovich, Igor

2017-11-01

Single-photon emitters with narrow linewidths are highly sought after for applications in quantum information processing and quantum communications. In this letter, we report on a bright, highly polarized near infrared single photon emitter embedded in diamond nanocrystals with a narrow, sub-GHz optical linewidth at 10 K. The observed zero-phonon line at ˜780 nm is optically stable under low power excitation and blue shifts as the excitation power increases. Our results highlight the prospect for using new near infrared color centers in nanodiamonds for quantum applications.

High efficiency and stable white OLED using a single emitter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jian

2016-01-18

The ultimate objective of this project was to demonstrate an efficient and stable white OLED using a single emitter on a planar glass substrate. The focus of the project is on the development of efficient and stable square planar phosphorescent emitters and evaluation of such class of materials in the device settings. Key challenges included improving the emission efficiency of molecular dopants and excimers, controlling emission color of emitters and their excimers, and improving optical and electrical stability of emissive dopants. At the end of this research program, the PI has made enough progress to demonstrate the potential of excimer-basedmore » white OLED as a cost-effective solution for WOLED panel in the solid state lighting applications.« less

Advancements in high-power high-brightness laser bars and single emitters for pumping and direct diode application

NASA Astrophysics Data System (ADS)

An, Haiyan; Jiang, Ching-Long J.; Xiong, Yihan; Zhang, Qiang; Inyang, Aloysius; Felder, Jason; Lewin, Alexander; Roff, Robert; Heinemann, Stefan; Schmidt, Berthold; Treusch, Georg

2015-03-01

We have continuously optimized high fill factor bar and packaging design to increase power and efficiency for thin disc laser system pump application. On the other hand, low fill factor bars packaged on the same direct copper bonded (DCB) cooling platform are used to build multi-kilowatt direct diode laser systems. We have also optimized the single emitter designs for fiber laser pump applications. In this paper, we will give an overview of our recent advances in high power high brightness laser bars and single emitters for pumping and direct diode application. We will present 300W bar development results for our next generation thin disk laser pump source. We will also show recent improvements on slow axis beam quality of low fill factor bar and its application on performance improvement of 4-5 kW TruDiode laser system with BPP of 30 mm*mrad from a 600 μm fiber. Performance and reliability results of single emitter for multiemitter fiber laser pump source will be presented as well.

On the Ionization and Ion Transmission Efficiencies of Different ESI-MS Interfaces

PubMed Central

Cox, Jonathan T.; Marginean, Ioan; Smith, Richard D.; Tang, Keqi

2014-01-01

The achievable sensitivity of electrospray ionization mass spectrometry (ESI-MS) is largely determined by the ionization efficiency in the ESI source and ion transmission efficiency through the ESI-MS interface. These performance characteristics are difficult to evaluate and compare across multiple platforms as it is difficult to correlate electrical current measurements to actual analyte ions reaching the detector of a mass spectrometer. We present an effective method to evaluate the overall ion utilization efficiency of an ESI-MS interface by measuring the total gas phase ion current transmitted through the interface and correlating it to the observed ion abundance measured in the corresponding mass spectrum. Using this method we systematically studied the ion transmission and ionization efficiencies of different ESI-MS interface configurations, including a single emitter/single inlet capillary, single emitter/multi-inlet capillary, and a subambient pressure ionization with nanoelectrospray (SPIN) MS interface with a single emitter and an emitter array, respectively. Our experimental results indicate that the overall ion utilization efficiency of SPIN-MS interface configurations exceeds that of the inlet capillary-based ESI-MS interface configurations. PMID:25267087

On the ionization and ion transmission efficiencies of different ESI-MS interfaces.

PubMed

Cox, Jonathan T; Marginean, Ioan; Smith, Richard D; Tang, Keqi

2015-01-01

The achievable sensitivity of electrospray ionization mass spectrometry (ESI-MS) is largely determined by the ionization efficiency in the ESI source and ion transmission efficiency through the ESI-MS interface. These performance characteristics are difficult to evaluate and compare across multiple platforms as it is difficult to correlate electrical current measurements to actual analyte ions reaching the detector of a mass spectrometer. We present an effective method to evaluate the overall ion utilization efficiency of an ESI-MS interface by measuring the total gas-phase ion current transmitted through the interface and correlating it to the observed ion abundance measured in the corresponding mass spectrum. Using this method, we systematically studied the ion transmission and ionization efficiencies of different ESI-MS interface configurations, including a single emitter/single inlet capillary, single emitter/multi-inlet capillary, and a subambient pressure ionization with nanoelectrospray (SPIN) MS interface with a single emitter and an emitter array, respectively. Our experimental results indicate that the overall ion utilization efficiency of SPIN-MS interface configurations exceeds that of the inlet capillary-based ESI-MS interface configurations.

Ultrafast Room-Temperature Single Photon Emission from Quantum Dots Coupled to Plasmonic Nanocavities.

PubMed

Hoang, Thang B; Akselrod, Gleb M; Mikkelsen, Maiken H

2016-01-13

Efficient and bright single photon sources at room temperature are critical components for quantum information systems such as quantum key distribution, quantum state teleportation, and quantum computation. However, the intrinsic radiative lifetime of quantum emitters is typically ∼10 ns, which severely limits the maximum single photon emission rate and thus entanglement rates. Here, we demonstrate the regime of ultrafast spontaneous emission (∼10 ps) from a single quantum emitter coupled to a plasmonic nanocavity at room temperature. The nanocavity integrated with a single colloidal semiconductor quantum dot produces a 540-fold decrease in the emission lifetime and a simultaneous 1900-fold increase in the total emission intensity. At the same time, the nanocavity acts as a highly efficient optical antenna directing the emission into a single lobe normal to the surface. This plasmonic platform is a versatile geometry into which a variety of other quantum emitters, such as crystal color centers, can be integrated for directional, room-temperature single photon emission rates exceeding 80 GHz.

Switchable wavelength-selective and diffuse metamaterial absorber/emitter with a phase transition spacer layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hao; Yang, Yue; Wang, Liping, E-mail: liping.wang@asu.edu

2014-08-18

We numerically demonstrate a switchable metamaterial absorber/emitter by thermally turning on or off the excitation of magnetic resonance upon the phase transition of vanadium dioxide (VO{sub 2}). Perfect absorption peak exists around the wavelength of 5 μm when the excitation of magnetic resonance is supported with the insulating VO{sub 2} spacer layer. The wavelength-selective absorption is switched off when the magnetic resonance is disabled with metallic VO{sub 2} that shorts the top and bottom metallic structures. The resonance wavelength can be tuned with different geometry, and the switchable metamaterial exhibits diffuse behaviors at oblique angles. The results would facilitate the designmore » of switchable metamaterials for active control in energy and sensing applications.« less

Ground Motion Studies for Large Future Accelerator

NASA Astrophysics Data System (ADS)

Takeda, Shigeru; Oide, Katsunobu

1997-05-01

The future large accelerator, such as TeV linear collider, should have extremely small emittance to perform the required luminosity. Precise alignment of machine components is essential to prevent emittance dilution. The ground motion spoils alignment of accelerator elements and results in emittance growth. The ground motion in the frequency range of seismic vibration is mostly coherent in the related accelerator. But the incoherent diffusive or Brownian like motion becomes dominant at frequency region less than seismic vibration [1, 2, 3]. Slow ground motion with respect to the machine performance is discussed including the method of tunnel construction. Our experimental results and recent excavated results clarify that application of TBMs is better excavating method than NATM (Drill + Blast) for accelerator tunnel to prevent emittance dilution. ([1] V. Shiltsev, Proc. of IWAA95 Tsukuba, 1995. [2] Shigeru Takeda et al., Proc. of EPAC96, 1996. [3] A. Sery, Proc. of LINAC96, 1996.)

Deterministic Integration of Quantum Dots into on-Chip Multimode Interference Beamsplitters Using in Situ Electron Beam Lithography.

PubMed

Schnauber, Peter; Schall, Johannes; Bounouar, Samir; Höhne, Theresa; Park, Suk-In; Ryu, Geun-Hwan; Heindel, Tobias; Burger, Sven; Song, Jin-Dong; Rodt, Sven; Reitzenstein, Stephan

2018-04-11

The development of multinode quantum optical circuits has attracted great attention in recent years. In particular, interfacing quantum-light sources, gates, and detectors on a single chip is highly desirable for the realization of large networks. In this context, fabrication techniques that enable the deterministic integration of preselected quantum-light emitters into nanophotonic elements play a key role when moving forward to circuits containing multiple emitters. Here, we present the deterministic integration of an InAs quantum dot into a 50/50 multimode interference beamsplitter via in situ electron beam lithography. We demonstrate the combined emitter-gate interface functionality by measuring triggered single-photon emission on-chip with g (2) (0) = 0.13 ± 0.02. Due to its high patterning resolution as well as spectral and spatial control, in situ electron beam lithography allows for integration of preselected quantum emitters into complex photonic systems. Being a scalable single-step approach, it paves the way toward multinode, fully integrated quantum photonic chips.

Improving the Sensitivity of Mass Spectrometry by Using a New Sheath Flow Electrospray Emitter Array at Subambient Pressures

DOE PAGES

Cox, Jonathan T.; Marginean, Ioan; Kelly, Ryan T.; ...

2014-03-28

Arrays of chemically etched emitters with individualized sheath gas capillaries have been developed to enhance electrospray ionization (ESI) at subambient pressures. By including an emitter array in a subambient pressure ionization with nanoelectrospray (SPIN) source, ionization and transmission efficiency can be maximized allowing for increased sensitivity in mass spectrometric analyses. The SPIN source eliminates the major ion losses at conventional ESI-mass spectrometry (MS) interface by placing the emitter in the first vacuum region of the instrument. To facilitate stable electrospray currents in such conditions we have developed an improved emitter array with individualized sheath gas around each emitter. The utilitymore » of the new emitter arrays for generating stable multi-electrosprays at subambient pressures was probed by coupling the emitter array/SPIN source with a time of flight (TOF) mass spectrometer. The instrument sensitivity was compared between single emitter/SPIN-MS and multi-emitter/SPIN-MS configurations using an equimolar solution of 9 peptides. An increase in sensitivity correlative to the number of emitters in the array was observed.« less

Rare earth garnet selective emitter

NASA Technical Reports Server (NTRS)

Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

1994-01-01

Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approximately equal to 0.74, ((4)l(sub 15/2)) - ( (4)l(sub13/2)), for Er-YAG and epsilon(sub lambda) approximately equal to 0.65, ((5)l(sub 7))-((5)l(sub 8)) for Ho-YAG) at excellent candidates for high efficiency selective emitters in the thermophotovoltaics (TPV) systems operating at moderate temperatures (1200-1500K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. This paper presents normal spectral emittance, epsilon(sub lambda), measurements of holmium (Ho), and erbium (Er) doped YAG thin film selective emitters at 1500 K, and compares those results with the theoretical spectral emittance.

Improving the Sensitivity of Mass Spectrometry by Using a New Sheath Flow Electrospray Emitter Array at Subambient Pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, Jonathan T.; Marginean, Ioan; Kelly, Ryan T.

Arrays of chemically etched emitters with individualized sheath gas capillaries have been developed to enhance electrospray ionization (ESI) at subambient pressures. By including an emitter array in a subambient pressure ionization with nanoelectrospray (SPIN) source, ionization and transmission efficiency can be maximized allowing for increased sensitivity in mass spectrometric analyses. The SPIN source eliminates the major ion losses at conventional ESI-mass spectrometry (MS) interface by placing the emitter in the first vacuum region of the instrument. To facilitate stable electrospray currents in such conditions we have developed an improved emitter array with individualized sheath gas around each emitter. The utilitymore » of the new emitter arrays for generating stable multi-electrosprays at subambient pressures was probed by coupling the emitter array/SPIN source with a time of flight (TOF) mass spectrometer. The instrument sensitivity was compared between single emitter/SPIN-MS and multi-emitter/SPIN-MS configurations using an equimolar solution of 9 peptides. An increase in sensitivity correlative to the number of emitters in the array was observed.« less

Nonlinear theory of transverse beam echoes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Tanaji; Li, Yuan Shen

Transverse beam echoes can be excited with a single dipole kick followed by a single quadrupole kick. They have been used to measure diffusion in hadron beams and have other diagnostic capabilities. Here we develop theories of the transverse echo nonlinear in both the dipole and quadrupole kick strengths. The theories predict the maximum echo amplitudes and the optimum strength parameters. We find that the echo amplitude increases with smaller beam emittance and the asymptotic echo amplitude can exceed half the initial dipole kick amplitude. We show that multiple echoes can be observed provided the dipole kick is large enough.more » The spectrum of the echo pulse can be used to determine the nonlinear detuning parameter with small amplitude dipole kicks. Simulations are performed to check the theoretical predictions. In the useful ranges of dipole and quadrupole strengths, they are shown to be in reasonable agreement.« less

Nonlinear theory of transverse beam echoes

DOE PAGES

Sen, Tanaji; Li, Yuan Shen

2018-02-23

Transverse beam echoes can be excited with a single dipole kick followed by a single quadrupole kick. They have been used to measure diffusion in hadron beams and have other diagnostic capabilities. Here we develop theories of the transverse echo nonlinear in both the dipole and quadrupole kick strengths. The theories predict the maximum echo amplitudes and the optimum strength parameters. We find that the echo amplitude increases with smaller beam emittance and the asymptotic echo amplitude can exceed half the initial dipole kick amplitude. We show that multiple echoes can be observed provided the dipole kick is large enough.more » The spectrum of the echo pulse can be used to determine the nonlinear detuning parameter with small amplitude dipole kicks. Simulations are performed to check the theoretical predictions. In the useful ranges of dipole and quadrupole strengths, they are shown to be in reasonable agreement.« less

Recent Progress in Silicon-Based MEMS Field Emission Thrusters

NASA Astrophysics Data System (ADS)

Lenard, Roger X.; Kravitz, Stanley H.; Tajmar, Martin

2005-02-01

The Indium Field Emission Thruster (In-FET) is a highly characterized and space-proven device based on space-qualified liquid metal ion sources. There is also extensive experience with liquid metal ion sources for high-brightness semiconductor fabrications and inspection Like gridded ion engines, In-FETs efficiently accelerate ions through a series of high voltage electrodes. Instead of a plasma discharge to generate ions, which generates a mixture of singly and doubly charged ions as well as neutrals, indium metal is melted (157°C) and fed to the tip of a capillary tube where very high local electric fields perform more-efficient field emission ionization, providing nearly 100% singly charged species. In-FETs do not have the associated losses or lifetime concerns of a magnetically confined discharge and hollow cathode in ion thrusters. For In-FETs, propellant efficiencies ˜100% stipulate single-emitter currents ⩽10μA, perhaps as low as 5μA of current. This low emitter current results in ⩽0.5 W/emitter. Consequently, if the In-FET is to be used for future Human and Robotic missions under President Bush's Exploration plan, a mechanism to generate very high power levels is necessary. Efficient high-power operation requires many emitter/extractor pairs. Conventional fabrication techniques allow 1-10 emitters in a single module, with pain-staking precision required. Properly designed and fabricated In-FETs possess electric-to-jet efficiency >90% and a specific mass <0.25 kg/kWe. MEMS techniques allow reliable batch processing with ˜160,000 emitters in a 10×10-cm array. Developing a 1.5kW 10×10-cm module is a necessary stepping-stone for >500 kWe systems where groups of 9 or 16 modules, with a single PPU/feed system, form the building blocks for even higher-power exploration systems. In 2003, SNL and ARCS produced a MEMS-based In-FET 5×5 emitter module with individually addressable emitter/extractor pairs on a 15×15mm wafer. The first MEMS thruster prototype has already been tested to demonstrate the proof-of-concept in laboratory-scale testing. In this paper we discuss progress that has been achieved in the past year on fabricating silicon-based MEMS In-FETs.

Studies of silicon pn junction solar cells

NASA Technical Reports Server (NTRS)

Lindholm, F. A.; Neugroschel, A.

1977-01-01

Modifications of the basic Shockley equations that result from the random and nonrandom spatial variations of the chemical composition of a semiconductor were developed. These modifications underlie the existence of the extensive emitter recombination current that limits the voltage over the open circuit of solar cells. The measurement of parameters, series resistance and the base diffusion length is discussed. Two methods are presented for establishing the energy bandgap narrowing in the heavily-doped emitter region. Corrections that can be important in the application of one of these methods to small test cells are examined. Oxide-charge-induced high-low-junction emitter (OCI-HLE) test cells which exhibit considerably higher voltage over the open circuit than was previously seen in n-on-p solar cells are described.

Pure single-photon emission from In(Ga)As QDs in a tunable fiber-based external mirror microcavity

NASA Astrophysics Data System (ADS)

Herzog, T.; Sartison, M.; Kolatschek, S.; Hepp, S.; Bommer, A.; Pauly, C.; Mücklich, F.; Becher, C.; Jetter, M.; Portalupi, S. L.; Michler, P.

2018-07-01

Cavity quantum electrodynamics is widely used in many solid-state systems for improving quantum emitter performances or accessing specific physical regimes. For these purposes it is fundamental that the non-classical emitter, like a quantum dot or an NV center, matches the cavity mode, both spatially and spectrally. In the present work, we couple single photons stemming from In(Ga)As quantum dots into an open fiber-based Fabry–Pérot cavity. Such a system allows for reaching an optimal spatial and spectral matching for every present emitter and every optical transition, by precisely tuning the cavity geometry. In addition to that, the capability of deterministically and repeatedly locating a single quantum dot enables to compare the behavior of the quantum emitter inside the cavity with respect to before it is placed inside. The presented open-cavity system shows full flexibility by precisely tuning in resonance different QD transitions, namely excitons, biexcitons and trions. A measured Purcell enhancement of 4.4 ± 0.5 is obtained with a cavity finesse of about 140, while still demonstrating a single-photon source with vanishing multi-photon emission probability.

Measurement of Electron Beam Emittance Using Optical Transition Radiation and Development of a Diffuse Screen Electron Beam Monitor

DTIC Science & Technology

1990-12-01

Zerodur ,irror, 2" relfects light. 1OZ20BD.1; 20th wave zerodur mirror , 1" reflects light. LS-35; 3’ x 5’ optical breadboard; for mounting components...profile measurements using the diffuse screen were compared with measurements using a front surface mirror and a fluorescent screen. The 20 DISTRIBUTION...Beam current and profile measurements using the diffuse screen were compared with measurements using a front surface mirror and a fluorescent screen

Effect of phonon-bath dimensionality on the spectral tuning of single-photon emitters in the Purcell regime

NASA Astrophysics Data System (ADS)

Chassagneux, Yannick; Jeantet, Adrien; Claude, Théo; Voisin, Christophe

2018-05-01

We develop a theoretical frame to investigate the spectral dependence of the brightness of a single-photon source made of a solid-state nanoemitter embedded in a high-quality factor microcavity. This study encompasses the cases of localized excitons embedded in a one-, two-, or three-dimensional matrix. The population evolution is calculated based on a spin-boson model, using the noninteracting blip approximation. We find that the spectral dependence of the single-photon source brightness (hereafter called spectral efficiency) can be expressed analytically through the free-space emission and absorption spectra of the emitter, the vacuum Rabi splitting, and the loss rates of the system. In other words, the free-space spectrum of the emitter encodes all the relevant information on the interaction between the exciton and the phonon bath to obtain the dynamics of the cavity-coupled system. We compute numerically the spectral efficiency for several types of localized emitters differing by the phonon bath dimensionality. In particular, in low-dimensional systems where this interaction is enhanced, a pronounced asymmetric energy exchange between the emitter and the cavity on the phonon sidebands yields a considerable extension of the tuning range of the source through phonon-assisted cavity feeding, possibly surpassing that of a purely resonant system.

Single photon emitters in boron nitride: More than a supplementary material

NASA Astrophysics Data System (ADS)

Koperski, M.; Nogajewski, K.; Potemski, M.

2018-03-01

We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation.

SAPHIRE: A New Flat-Panel Digital Mammography Detector With Avalanche Photoconductor and High-Resolution Field Emitter Readout

DTIC Science & Technology

2006-06-01

work by Marshak et al.,9 who was studying neutron diffusion, and by Hamaker ,10 who had calculated the light emitted from a layer of x-ray fluorescent...diffusion and slowing down of neutrons,” Nucleonics 4, 10–22 1949. 10H. C. Hamaker , “Radiation and heat conduction in light scattering mate- rials

Direct experimental observation of nonclassicality in ensembles of single-photon emitters

NASA Astrophysics Data System (ADS)

Moreva, E.; Traina, P.; Forneris, J.; Degiovanni, I. P.; Ditalia Tchernij, S.; Picollo, F.; Brida, G.; Olivero, P.; Genovese, M.

2017-11-01

In this work we experimentally demonstrate a recently proposed criterion addressed to detect nonclassical behavior in the fluorescence emission of ensembles of single-photon emitters. In particular, we apply the method to study clusters of nitrogen-vacancy centers in diamond characterized with single-photon-sensitive confocal microscopy. Theoretical considerations on the behavior of the parameter at any arbitrary order in the presence of Poissonian noise are presented and, finally, the opportunity of detecting manifold coincidences is discussed.

High quality GaAs single photon emitters on Si substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bietti, S.; Sanguinetti, S.; Cavigli, L.

2013-12-04

We describe a method for the direct epitaxial growth of a single photon emitter, based on GaAs quantum dots fabricated by droplet epitaxy, working at liquid nitrogen temperatures on Si substrates. The achievement of quantum photon statistics up to T=80 K is directly proved by antibunching in the second order correlation function as measured with a H anbury Brown and Twiss interferometer.

Deterministic Integration of Quantum Dots into on-Chip Multimode Interference Beamsplitters Using in Situ Electron Beam Lithography

NASA Astrophysics Data System (ADS)

Schnauber, Peter; Schall, Johannes; Bounouar, Samir; Höhne, Theresa; Park, Suk-In; Ryu, Geun-Hwan; Heindel, Tobias; Burger, Sven; Song, Jin-Dong; Rodt, Sven; Reitzenstein, Stephan

2018-04-01

The development of multi-node quantum optical circuits has attracted great attention in recent years. In particular, interfacing quantum-light sources, gates and detectors on a single chip is highly desirable for the realization of large networks. In this context, fabrication techniques that enable the deterministic integration of pre-selected quantum-light emitters into nanophotonic elements play a key role when moving forward to circuits containing multiple emitters. Here, we present the deterministic integration of an InAs quantum dot into a 50/50 multi-mode interference beamsplitter via in-situ electron beam lithography. We demonstrate the combined emitter-gate interface functionality by measuring triggered single-photon emission on-chip with $g^{(2)}(0) = 0.13\\pm 0.02$. Due to its high patterning resolution as well as spectral and spatial control, in-situ electron beam lithography allows for integration of pre-selected quantum emitters into complex photonic systems. Being a scalable single-step approach, it paves the way towards multi-node, fully integrated quantum photonic chips.

Emittance of a finite scattering medium with refractive index greater than unity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crosbie, A.L.

1980-01-01

Refractive index and scattering can significantly influence the transfer of radiation in a semitransparent medium such as water, glass, plastics, or ceramics. In a recent article (1979), the author presented exact numerical results for the emittance of a semiinfinite scattering medium with a refractive index greater than unity. The present investigation extends the analysis to a finite medium. The physical situation consists of a finite planar layer. The isothermal layer emits, absorbs, and isotropically scatters thermal radiation. It is characterized by single scattering albedo, optical thickness, refractive index, and temperature. A formula for the directional emittance is derived, the directionalmore » emittance being the emittance of the medium multiplied by the interface transmittance. The ratio of hemispherical to normal emittance is tabulated and discussed.« less

Determination of lifetimes and recombination currents in p-n junction solar cells, diodes, and transistors

NASA Technical Reports Server (NTRS)

Neugroschel, A.

1981-01-01

New methods are presented and illustrated that enable the accurate determination of the diffusion length of minority carriers in the narrow regions of a solar cell or a diode. Other methods now available are inaccurate for the desired case in which the width of the region is less than the diffusion length. Once the diffusion length is determined by the new methods, this result can be combined with measured dark I-V characteristics and with small-signal admittance characteristics to enable determination of the recombination currents in each quasi-neutral region of the cell - for example, in the emitter, low-doped base, and high-doped base regions of the BSF (back-surface-field) cell. This approach leads to values for the effective surface recombination velocity of the high-low junction forming the back-surface field of BSF cells or the high-low emitter junction of HLE cells. These methods are also applicable for measuring the minority-carrier lifetime in thin epitaxial layers grown on substrates with opposite conductivity type.

Selective far-field addressing of coupled quantum dots in a plasmonic nanocavity.

PubMed

Tang, Jianwei; Xia, Juan; Fang, Maodong; Bao, Fanglin; Cao, Guanjun; Shen, Jianqi; Evans, Julian; He, Sailing

2018-04-27

Plasmon-emitter hybrid nanocavity systems exhibit strong plasmon-exciton interactions at the single-emitter level, showing great potential as testbeds and building blocks for quantum optics and informatics. However, reported experiments involve only one addressable emitting site, which limits their relevance for many fundamental questions and devices involving interactions among emitters. Here we open up this critical degree of freedom by demonstrating selective far-field excitation and detection of two coupled quantum dot emitters in a U-shaped gold nanostructure. The gold nanostructure functions as a nanocavity to enhance emitter interactions and a nanoantenna to make the emitters selectively excitable and detectable. When we selectively excite or detect either emitter, we observe photon emission predominantly from the target emitter with up to 132-fold Purcell-enhanced emission rate, indicating individual addressability and strong plasmon-exciton interactions. Our work represents a step towards a broad class of plasmonic devices that will enable faster, more compact optics, communication and computation.

Bias-free lateral terahertz emitters—A simulation study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Granzner, R., E-mail: ralf.granzner@tu-ilmenau.de; Schwierz, F.; Polyakov, V. M.

2015-07-28

The design and performance of bias-free InN-based THz emitters that exploit lateral photocurrents is studied by means of numerical simulations. We use a drift-diffusion model with adjusted carrier temperatures and mobilities. The applicability of this approach is demonstrated by a comparison with results from Monte-Carlo simulations. We consider a simple but robust lateral emitter concept using metal stripes with two different thicknesses with one of them being thin enough to be transparent for THz radiation. This arrangement can be easily multiplexed and the efficiency of this concept has already been demonstrated by experiment for GaAs substrates. In the present study,more » we consider InN, which is known to be an efficient photo-Dember emitter because of its superior transport properties. Our main focus is on the impact of the emitter design on the emission efficiency assuming different operation principles. Both the lateral photo-Dember (LPD) effect and built-in lateral field effects are considered. The appropriate choice of the metal stripe and window geometry as well as the impact of surface Fermi level pinning are investigated in detail, and design guidelines for efficient large area emitters using multiplexed structures are provided. We find that InN LPD emitters do not suffer from Fermi level pinning at the InN surface. The optimum emission efficiency is found for LPD emitter structures having 200 nm wide illumination windows and mask stripes. Emitter structures in which lateral electric fields are induced by the metal mask contacts can have a considerably higher efficiency than pure LPD emitters. In the best case, the THz emission of such structures is increased by one order of magnitude. Their optimum window size is 1 μm without the necessity of a partially transparent set of mask stripes.« less

Out-of-core Evaluations of Uranium Nitride-fueled Converters

NASA Technical Reports Server (NTRS)

Shimada, K.

1972-01-01

Two uranium nitride fueled converters were tested parametrically for their initial characterization and are currently being life-tested out of core. Test method being employed for the parametric and the diagnostic measurements during the life tests, and test results are presented. One converter with a rhenium emitter had an initial output power density of 6.9 W/ sq cm at the black body emitter temperature of 1900 K. The power density remained unchanged for the first 1000 hr of life test but degraded nearly 50% percent during the following 1000 hr. Electrode work function measurements indicated that the uranium fuel was diffusing out of the emitter clad of 0.635 mm. The other converter with a tungsten emitter had an initial output power density of 2.2 W/ sq cm at 1900 K with a power density of 3.9 W/sq cm at 4300 h. The power density suddenly degraded within 20 hr to practically zero output at 4735 hr.

Impact of boron rich layer on performance degradation in boric acid diffused emitters for n-type crystalline Si solar cells

NASA Astrophysics Data System (ADS)

Singha, Bandana; Singh Solanki, Chetan

2018-01-01

Boron rich layer (BRL) formed beneath the borosilicate glass layer during p-type emitter formation is an undesirable phenomenon. It influences different cell parameters and can degrade the device performance. In this work, the device degradation study is done for different BRL thicknesses produced with different concentrations of the boric acid dopant source. The bulk carrier lifetime reduces to more than 75% and emitter saturation current density becomes more than 10-12 mA cm-2 for 60 nm of BRL thickness. The observed J sc and V oc values become zero for BRL thicknesses higher than 40 nm as seen in this work and the device properties could not be enhanced. So, higher thicknesses of BRL should be avoided.

Coupling of individual quantum emitters to channel plasmons.

PubMed

Bermúdez-Ureña, Esteban; Gonzalez-Ballestero, Carlos; Geiselmann, Michael; Marty, Renaud; Radko, Ilya P; Holmgaard, Tobias; Alaverdyan, Yury; Moreno, Esteban; García-Vidal, Francisco J; Bozhevolnyi, Sergey I; Quidant, Romain

2015-08-07

Efficient light-matter interaction lies at the heart of many emerging technologies that seek on-chip integration of solid-state photonic systems. Plasmonic waveguides, which guide the radiation in the form of strongly confined surface plasmon-polariton modes, represent a promising solution to manipulate single photons in coplanar architectures with unprecedented small footprints. Here we demonstrate coupling of the emission from a single quantum emitter to the channel plasmon polaritons supported by a V-groove plasmonic waveguide. Extensive theoretical simulations enable us to determine the position and orientation of the quantum emitter for optimum coupling. Concomitantly with these predictions, we demonstrate experimentally that 42% of a single nitrogen-vacancy centre emission efficiently couples into the supported modes of the V-groove. This work paves the way towards practical realization of efficient and long distance transfer of energy for integrated solid-state quantum systems.

Overview of Lattice Design and Evaluation for the APS Upgrade

DOE PAGES

Borland, M.; Emery, L.; Lindberg, R.; ...

2017-08-01

The Advanced Photon Source (APS) is a 7-GeV synchrotron light source that has been in operation since 1996. Since that time, the effective emittance has been decreased from 8 nm to 3.1 nm, which is very competitive for a 3rd-generation light source. However, newer facilities such as PETRA-III, NSLS-II, and MAX-IV are pushing the emittance to significantly smaller values. MAX-IV in particular has set the current benchmark with an emittance of about 300 pm at 3 GeV. This was accomplished by use of a multi-bend achromat lattice, which takes advantage of the 1/M3 scaling of the emittance with respect tomore » the number of dipoles M. In order to ensure that our facility remains competitive, APS is pursuing a major upgrade, which involves replacement of the existing double-bend lattice with a seven-bend achromat lattice, promising a 40-fold reduction in emittance. This paper describes the process of developing and evaluating candidate lattice designs. Two candidate 6-GeV lattices are described: one providing a natural emittance of 67 pm and the other providing 41 pm. Our analysis includes single-particle dynamics as well as single- and multi-bunch collective effects.« less

Single-Photon Nanoantennas

PubMed Central

2017-01-01

Single-photon nanoantennas are broadband strongly scattering nanostructures placed in the near field of a single quantum emitter, with the goal to enhance the coupling between the emitter and far-field radiation channels. Recently, great strides have been made in the use of nanoantennas to realize fluorescence brightness enhancements, and Purcell enhancements, of several orders of magnitude. This perspective reviews the key figures of merit by which single-photon nanoantenna performance is quantified and the recent advances in measuring these metrics unambiguously. Next, this perspective discusses what the state of the art is in terms of fluoresent brightness enhancements, Purcell factors, and directivity control on the level of single photons. Finally, I discuss future challenges for single-photon nanoantennas. PMID:29354664

Experimental Demonstration of a Hybrid-Quantum-Emitter Producing Individual Entangled Photon Pairs in the Telecom Band

PubMed Central

Chen, Geng; Zou, Yang; Zhang, Wen-Hao; Zhang, Zi-Huai; Zhou, Zong-Quan; He, De-Yong; Tang, Jian-Shun; Liu, Bi-Heng; Yu, Ying; Zha, Guo-Wei; Ni, Hai-Qiao; Niu, Zhi-Chuan; Han, Yong-Jian; Li, Chuan-Feng; Guo, Guang-Can

2016-01-01

Quantum emitters generating individual entangled photon pairs (IEPP) have significant fundamental advantages over schemes that suffer from multiple photon emission, or schemes that require post-selection techniques or the use of photon-number discriminating detectors. Quantum dots embedded within nanowires (QD-NWs) represent one of the most promising candidate for quantum emitters that provide a high collection efficiency of photons. However, a quantum emitter that generates IEPP in the telecom band is still an issue demanding a prompt solution. Here, we demonstrate in principle that IEPPs in the telecom band can be created by combining a single QD-NW and a nonlinear crystal waveguide. The QD-NW system serves as the single photon source, and the emitted visible single photons are split into IEPPs at approximately 1.55 μm through the process of spontaneous parametric down conversion (SPDC) in a periodically poled lithium niobate (PPLN) waveguide. The compatibility of the QD-PPLN interface is the determinant factor in constructing this novel hybrid-quantum-emitter (HQE). Benefiting from the desirable optical properties of QD-NWs and the extremely high nonlinear conversion efficiency of PPLN waveguides, we successfully generate IEPPs in the telecom band with the polarization degree of freedom. The entanglement of the generated photon pairs is confirmed by the entanglement witness. Our experiment paves the way to producing HQEs inheriting the advantages of multiple systems. PMID:27225881

Experimental Demonstration of a Hybrid-Quantum-Emitter Producing Individual Entangled Photon Pairs in the Telecom Band.

PubMed

Chen, Geng; Zou, Yang; Zhang, Wen-Hao; Zhang, Zi-Huai; Zhou, Zong-Quan; He, De-Yong; Tang, Jian-Shun; Liu, Bi-Heng; Yu, Ying; Zha, Guo-Wei; Ni, Hai-Qiao; Niu, Zhi-Chuan; Han, Yong-Jian; Li, Chuan-Feng; Guo, Guang-Can

2016-05-26

Quantum emitters generating individual entangled photon pairs (IEPP) have significant fundamental advantages over schemes that suffer from multiple photon emission, or schemes that require post-selection techniques or the use of photon-number discriminating detectors. Quantum dots embedded within nanowires (QD-NWs) represent one of the most promising candidate for quantum emitters that provide a high collection efficiency of photons. However, a quantum emitter that generates IEPP in the telecom band is still an issue demanding a prompt solution. Here, we demonstrate in principle that IEPPs in the telecom band can be created by combining a single QD-NW and a nonlinear crystal waveguide. The QD-NW system serves as the single photon source, and the emitted visible single photons are split into IEPPs at approximately 1.55 μm through the process of spontaneous parametric down conversion (SPDC) in a periodically poled lithium niobate (PPLN) waveguide. The compatibility of the QD-PPLN interface is the determinant factor in constructing this novel hybrid-quantum-emitter (HQE). Benefiting from the desirable optical properties of QD-NWs and the extremely high nonlinear conversion efficiency of PPLN waveguides, we successfully generate IEPPs in the telecom band with the polarization degree of freedom. The entanglement of the generated photon pairs is confirmed by the entanglement witness. Our experiment paves the way to producing HQEs inheriting the advantages of multiple systems.

Progress in reliable single emitters and laser bars for efficient CW-operation in the near-infrared emission range

NASA Astrophysics Data System (ADS)

Zorn, Martin; Hülsewede, Ralf; Pietrzak, Agnieszka; Meusel, Jens; Sebastian, Jürgen

2015-03-01

Laser bars, laser arrays, and single emitters are highly-desired light sources e.g. for direct material processing, pump sources for solid state and fiber lasers or medical applications. These sources require high output powers with optimal efficiency together with good reliability resulting in a long lifetime of the device. Desired wavelengths range from 760 nm in esthetic skin treatment over 915 nm, 940 nm and 976 nm to 1030 nm for direct material processing and pumping applications. In this publication we present our latest developments for the different application-defined wavelengths in continuouswave operation mode. At 760nm laser bars with 30 % filling factor and 1.5 mm resonator length show optical output powers around 90-100 W using an optimized design. For longer wavelengths between 915 nm and 1030 nm laser bars with 4 mm resonator length and 50 % filling factor show reliable output powers above 200 W. The efficiency reached lies above 60% and the slow axis divergence (95% power content) is below 7°. Further developments of bars tailored for 940 nm emission wavelength reach output powers of 350 W. Reliable single emitters for effective fiber coupling having emitter widths of 90 μm and 195 μm are presented. They emit optical powers of 12 W and 24 W, respectively, at emission wavelengths of 915 nm, 940 nm and 976 nm. Moreover, reliability tests of 90 μm-single emitters at a power level of 12W currently show a life time over 3500 h.

Analyses of Transistor Punchthrough Failures

NASA Technical Reports Server (NTRS)

Nicolas, David P.

1999-01-01

The failure of two transistors in the Altitude Switch Assembly for the Solid Rocket Booster followed by two additional failures a year later presented a challenge to failure analysts. These devices had successfully worked for many years on numerous missions. There was no history of failures with this type of device. Extensive checks of the test procedures gave no indication for a source of the cause. The devices were manufactured more than twenty years ago and failure information on this lot date code was not readily available. External visual exam, radiography, PEID, and leak testing were performed with nominal results Electrical testing indicated nearly identical base-emitter and base-collector characteristics (both forward and reverse) with a low resistance short emitter to collector. These characteristics are indicative of a classic failure mechanism called punchthrough. In failure analysis punchthrough refers to an condition where a relatively low voltage pulse causes the device to conduct very hard producing localized areas of thermal runaway or "hot spots". At one or more of these hot spots, the excessive currents melt the silicon. Heavily doped emitter material diffuses through the base region to the collector forming a diffusion pipe shorting the emitter to base to collector. Upon cooling, an alloy junction forms between the pipe and the base region. Generally, the hot spot (punch-through site) is under the bond and no surface artifact is visible. The devices were delidded and the internal structures were examined microscopically. The gold emitter lead was melted on one device, but others had anomalies in the metallization around the in-tact emitter bonds. The SEM examination confirmed some anomalies to be cosmetic defects while other anomalies were artifacts of the punchthrough site. Subsequent to these analyses, the contractor determined that some irregular testing procedures occurred at the time of the failures heretofore unreported. These testing irregularities involved the use of a breakout box and were the likely cause of the failures. There was no evidence to suggest a generic failure mechanism was responsible for the failure of these transistors.

Method and apparatus for multispray emitter for mass spectrometry

DOEpatents

Smith, Richard D.; Tang, Keqi; Lin, Yuehe

2004-12-14

A method and apparatus that utilizes two or more emitters simultaneously to form an electrospray of a sample that is then directed into a mass spectrometer, thereby increasing the total ion current introduced into an electrospray ionization mass spectrometer, given a liquid flow rate of a sample. The method and apparatus are most conveniently constructed as an array of spray emitters fabricated on a single chip, however, the present invention encompasses any apparatus wherein two or more emitters are simultaneously utilized to form an electrospray of a sample that is then directed into a mass spectrometer.

The anodic emitter effect and its inversion demonstrated by temperature measurements at doped and undoped tungsten electrodes

NASA Astrophysics Data System (ADS)

Hoebing, T.; Bergner, A.; Hermanns, P.; Mentel, J.; Awakowicz, P.

2016-04-01

The admixture of a small amount of emitter oxides, e.g. \\text{Th}{{\\text{O}}2} , \\text{L}{{\\text{a}}2}{{\\text{O}}3} or \\text{C}{{\\text{e}}2}{{\\text{O}}3} to tungsten generates the so-called emitter effect. It reduces the work function of tungsten cathodes, that are applied in high intensity discharge (HID) lamps. After leaving the electrode bulk and moving to the surface, a monolayer of Th, La, or Ce atoms is formed on the surface, which reduces the effective work function ϕ. Depending on the coverage of the electrode, the effective reduction in ϕ is subjected to the thermal desorption of the monolayer from the hot electrode surface. The thermal desorption of emitter atoms from the cathode is compensated not only by the supply from the interior of the electrode and by surface diffusion of the emitter material to its tip, but also to a large extent by a repatriation of the emitter ions from the plasma by the strong electric field in front of the cathode. Yet, an emitter ion current from the arc discharge to the anode may only be present, if the anode is cold enough to refrain from thermionic emission. Therefore, the ability of emitter oxides to reduce the temperature of tungsten anodes is only given for a moderate temperature so that the thermal desorption is low and an additional ion current is present in front of the anode. A higher electrode temperature leads to their evaporation and to an inversion of the emitter effect, which increases the temperature of the respective anodes in comparison with pure tungsten anodes. Within this article, the emitter effect of doped tungsten anodes and the transition to its inversion is investigated for thoriated, lanthanated, and ceriated tungsten electrodes by measurements of the electrode temperature in dependence on the discharge current. It is shown for a lanthanated and a ceriated anode that the emitter effect is sustained by an ion current at anode temperatures at which the thermal evaporation of emitter material is completed.

The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

NASA Astrophysics Data System (ADS)

Mentel, Juergen

2018-01-01

A mono-layer of atoms, electropositive with respect to the substrate atoms, forms a dipole layer, reducing its work function. Such a layer is generated by diffusion of emitter material from the interior of the substrate, by vapour deposition or by deposition of emitter material onto arc electrodes by cataphoresis. This cataphoretic emitter effect is investigated within metal halide lamps with transparent YAG ceramic burners, and within model lamps. Within the YAG lamps, arcs are operated with switched-dc current between rod shaped tungsten electrodes in high pressure Hg vapour seeded with metal iodides. Within the model lamps, dc arcs are operated between rod-shaped tungsten electrodes—one doped—in atmospheric pressure Ar. Electrode temperatures are determined by 1λ -pyrometry, combined with simulation of the electrode heat balance. Plasma temperatures, atom and ion densities of emitter material are determined by emission and absorption spectroscopy. Phase resolved measurements in YAG lamps seeded with CeI3, CsI, DyI3, TmI3 and LaI3 show, within the cathodic half period, a reduction of the electrode temperature and an enhanced metal ion density in front of the electrode, and an opposite behavior after phase reversal. With increasing operating frequency, the state of the cathode overlaps onto the anodic phase—except for Cs, being low in adsorption energy. Generally, the phase averaged electrode tip temperature is reduced by seeding a lamp with emitter material; its height depends on admixtures. Measurements at tungsten electrodes doped with ThO2, La2O3 and Ce2O3 within the model lamp show that evaporated emitter material is redeposited by an emitter ion current onto the electrode surface. It reduces the work function of tungsten cathodes above the evaporation temperature of the emitter material, too; and also of cold anodes, indicating a field reversal in front of them. The formation of an emitter spot at low cathode temperature and high emitter material density is traced back to a locally reduced work function generated by a locally enhanced emitter ion current density.

Quantum Emitters in Two-Dimensional Structured Reservoirs in the Nonperturbative Regime

NASA Astrophysics Data System (ADS)

González-Tudela, A.; Cirac, J. I.

2017-10-01

We show that the coupling of quantum emitters to a two-dimensional reservoir with a simple band structure gives rise to exotic quantum dynamics with no analogue in other scenarios and which cannot be captured by standard perturbative treatments. In particular, for a single quantum emitter with its transition frequency in the middle of the band, we predict an exponential relaxation at a rate different from that predicted by Fermi's golden rule, followed by overdamped oscillations and slow relaxation decay dynamics. This is accompanied by directional emission into the reservoir. This directionality leads to a modification of the emission rate for few emitters and even perfect subradiance, i.e., suppression of spontaneous emission, for four quantum emitters.

Three-dimensional single-molecule localization with nanometer accuracy using Metal-Induced Energy Transfer (MIET) imaging

NASA Astrophysics Data System (ADS)

Karedla, Narain; Chizhik, Anna M.; Stein, Simon C.; Ruhlandt, Daja; Gregor, Ingo; Chizhik, Alexey I.; Enderlein, Jörg

2018-05-01

Our paper presents the first theoretical and experimental study using single-molecule Metal-Induced Energy Transfer (smMIET) for localizing single fluorescent molecules in three dimensions. Metal-Induced Energy Transfer describes the resonant energy transfer from the excited state of a fluorescent emitter to surface plasmons in a metal nanostructure. This energy transfer is strongly distance-dependent and can be used to localize an emitter along one dimension. We have used Metal-Induced Energy Transfer in the past for localizing fluorescent emitters with nanometer accuracy along the optical axis of a microscope. The combination of smMIET with single-molecule localization based super-resolution microscopy that provides nanometer lateral localization accuracy offers the prospect of achieving isotropic nanometer localization accuracy in all three spatial dimensions. We give a thorough theoretical explanation and analysis of smMIET, describe its experimental requirements, also in its combination with lateral single-molecule localization techniques, and present first proof-of-principle experiments using dye molecules immobilized on top of a silica spacer, and of dye molecules embedded in thin polymer films.

Vertically integrated (Ga, In)N nanostructures for future single photon emitters operating in the telecommunication wavelength range

NASA Astrophysics Data System (ADS)

Winden, A.; Mikulics, M.; Grützmacher, D.; Hardtdegen, H.

2013-10-01

Important technological steps are discussed and realized for future room-temperature operation of III-nitride single photon emitters. First, the growth technology of positioned single pyramidal InN nanostructures capped by Mg-doped GaN is presented. The optimization of their optical characteristics towards narrowband emission in the telecommunication wavelength range is demonstrated. In addition, a device concept and technology was developed so that the nanostructures became singularly addressable. It was found that the nanopyramids emit in the telecommunication wavelength range if their size is chosen appropriately. A p-GaN contacting layer was successfully produced as a cap to the InN pyramids and the top p-contact was achievable using an intrinsically conductive polymer PEDOT:PSS, allowing a 25% increase in light transmittance compared to standard Ni/Au contact technology. Single nanopyramids were successfully integrated into a high-frequency device layout. These decisive technology steps provide a promising route to electrically driven and room-temperature operating InN based single photon emitters in the telecommunication wavelength range.

Heralded quantum repeater based on the scattering of photons off single emitters using parametric down-conversion source.

PubMed

Song, Guo-Zhu; Wu, Fang-Zhou; Zhang, Mei; Yang, Guo-Jian

2016-06-28

Quantum repeater is the key element in quantum communication and quantum information processing. Here, we investigate the possibility of achieving a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We design the compact quantum circuits for nonlocal entanglement generation, entanglement swapping, and entanglement purification, and discuss the feasibility of our protocols with current experimental technology. In our scheme, we use a parametric down-conversion source instead of ideal single-photon sources to realize the heralded quantum repeater. Moreover, our protocols can turn faulty events into the detection of photon polarization, and the fidelity can reach 100% in principle. Our scheme is attractive and scalable, since it can be realized with artificial solid-state quantum systems. With developed experimental technique on controlling emitter-waveguide systems, the repeater may be very useful in long-distance quantum communication.

Heralded quantum repeater based on the scattering of photons off single emitters using parametric down-conversion source

PubMed Central

Song, Guo-Zhu; Wu, Fang-Zhou; Zhang, Mei; Yang, Guo-Jian

2016-01-01

Quantum repeater is the key element in quantum communication and quantum information processing. Here, we investigate the possibility of achieving a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We design the compact quantum circuits for nonlocal entanglement generation, entanglement swapping, and entanglement purification, and discuss the feasibility of our protocols with current experimental technology. In our scheme, we use a parametric down-conversion source instead of ideal single-photon sources to realize the heralded quantum repeater. Moreover, our protocols can turn faulty events into the detection of photon polarization, and the fidelity can reach 100% in principle. Our scheme is attractive and scalable, since it can be realized with artificial solid-state quantum systems. With developed experimental technique on controlling emitter-waveguide systems, the repeater may be very useful in long-distance quantum communication. PMID:27350159

Small slot waveguide rings for on-chip quantum optical circuits.

PubMed

Rotenberg, Nir; Türschmann, Pierre; Haakh, Harald R; Martin-Cano, Diego; Götzinger, Stephan; Sandoghdar, Vahid

2017-03-06

Nanophotonic interfaces between single emitters and light promise to enable new quantum optical technologies. Here, we use a combination of finite element simulations and analytic quantum theory to investigate the interaction of various quantum emitters with slot-waveguide rings. We predict that for rings with radii as small as 1.44 μm, with a Q-factor of 27,900, near-unity emitter-waveguide coupling efficiencies and emission enhancements on the order of 1300 can be achieved. By tuning the ring geometry or introducing losses, we show that realistic emitter-ring systems can be made to be either weakly or strongly coupled, so that we can observe Rabi oscillations in the decay dynamics even for micron-sized rings. Moreover, we demonstrate that slot waveguide rings can be used to directionally couple emission, again with near-unity efficiency. Our results pave the way for integrated solid-state quantum circuits involving various emitters.

Annual Progress Report of Research Activities that Occured in the Coordinated Science Laboratory for July 1, 1982 through Jun 30, 1983,

DTIC Science & Technology

1983-08-01

particular fabrication concerns, both the emitter and collector region were made of Al„ -Ga0 5As wide gap material. Devices with emitter area of 10 x 60...im and collector area of 50 x 60 (im exhi- bited current gains of 500 for a base doping of 10 cm and thickness of 500 A, and 1700 for a base...spreading over a large enough distance, it is usually necessary to heat the surface to a temperature at which not just diffusion, but also

Hybrid Integration of Solid-State Quantum Emitters on a Silicon Photonic Chip.

PubMed

Kim, Je-Hyung; Aghaeimeibodi, Shahriar; Richardson, Christopher J K; Leavitt, Richard P; Englund, Dirk; Waks, Edo

2017-12-13

Scalable quantum photonic systems require efficient single photon sources coupled to integrated photonic devices. Solid-state quantum emitters can generate single photons with high efficiency, while silicon photonic circuits can manipulate them in an integrated device structure. Combining these two material platforms could, therefore, significantly increase the complexity of integrated quantum photonic devices. Here, we demonstrate hybrid integration of solid-state quantum emitters to a silicon photonic device. We develop a pick-and-place technique that can position epitaxially grown InAs/InP quantum dots emitting at telecom wavelengths on a silicon photonic chip deterministically with nanoscale precision. We employ an adiabatic tapering approach to transfer the emission from the quantum dots to the waveguide with high efficiency. We also incorporate an on-chip silicon-photonic beamsplitter to perform a Hanbury-Brown and Twiss measurement. Our approach could enable integration of precharacterized III-V quantum photonic devices into large-scale photonic structures to enable complex devices composed of many emitters and photons.

Protein-Glass Surface Interactions and Ion Desalting in Electrospray Ionization with Submicron Emitters

NASA Astrophysics Data System (ADS)

Xia, Zije; Williams, Evan R.

2018-01-01

Theta glass electrospray emitters can rapidly mix solutions to investigate fast reactions that occur as quickly as 1 μs, but emitters with submicron tips have the unusual properties of desalting protein ions and affecting the observed abundances of some proteins as a result of protein-surface interactions. The role of protein physical properties on ion signal was investigated using 1.7 ± 0.1 μm and 269 ± 7 nm emitters and 100 mM aqueous ammonium acetate or ammonium bicarbonate solutions. Protein ion desalting occurs for both positive and negative ions. The signal of a mixture of proteins with the 269 nm tips is time-dependent and the order in which ions of each protein is observed is related to the expected strengths of the protein-surface interactions. These results indicate that it is not just the high surface-to-volume ratio that plays a role in protein adsorption and reduction or absence of initial ion signal, but the small diffusion distance and extremely low flow rates of the smaller emitters can lead to complete adsorption of some proteins and loss of signal until the adsorption sites are filled and the zeta potential is significantly reduced. After about 30 min, signals for a protein mixture from the two different size capillaries are similar. These results show the advantages of submicron emitters but also indicate that surface effects must be taken into account in experiments using such small tips or that coating the emitter surface to prevent adsorption should be considered. [Figure not available: see fulltext.

Diffusion-Driven Charge Transport in Light Emitting Devices

PubMed Central

Oksanen, Jani; Suihkonen, Sami

2017-01-01

Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses that arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT) emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN) based DDCT devices, and an outlook of potential DDCT has for opto- and microelectronics. PMID:29231900

Single-shot measurements of low emittance beams from laser-plasma accelerators comparing two triggered injection methods

NASA Astrophysics Data System (ADS)

van Tilborg, Jeroen

2017-10-01

The success of laser plasma accelerator (LPA) based applications, such as a compact x-ray free electron laser (FEL), relies on the ability to produce electron beams with excellent 6D brightness, where brightness is defined as the ratio of charge to the product of the three normalized emittances. As such, parametric studies of the emittance of LPA generated electron beams are essential. Profiting from a stable and tunable LPA setup, combined with a carefully designed single-shot energy-dispersed emittance diagnostic, we present a direct comparison of charge dependent emittance measurements of electron beams generated by two different injection mechanisms: ionization injection and shock-induced density down-ramp injection. Both injection mechanisms have gained in popularity in recent years due to their demonstrated stable LPA performance. For the down-ramp injection configuration, normalized emittances a factor of two lower were recorded: less than 1 micron at spectral charge densities up to 2 pC/MeV. For both injection mechanisms, a contributing correlation of space charge to the emittance was identified. This measurement technique in general, and these results specifically, are critical to the evaluation of LPA injection methods and development of high-quality LPA beam lines worldwide. This work is supported by the U.S. DOE under Contract No. DE-AC02-05CH11231, by the U.S. DOE NNSA, DNN R&D (NA22), by the National Science Foundation under Grant No. PHY-1415596, and by the Gordon and Betty Moore Foundation under Grant ID GBMF4898.

Electrically driven polarized single-photon emission from an InGaN quantum dot in a GaN nanowire.

PubMed

Deshpande, Saniya; Heo, Junseok; Das, Ayan; Bhattacharya, Pallab

2013-01-01

In a classical light source, such as a laser, the photon number follows a Poissonian distribution. For quantum information processing and metrology applications, a non-classical emitter of single photons is required. A single quantum dot is an ideal source of single photons and such single-photon sources in the visible spectral range have been demonstrated with III-nitride and II-VI-based single quantum dots. It has been suggested that short-wavelength blue single-photon emitters would be useful for free-space quantum cryptography, with the availability of high-speed single-photon detectors in this spectral region. Here we demonstrate blue single-photon emission with electrical injection from an In0.25Ga0.75N quantum dot in a single nanowire. The emitted single photons are linearly polarized along the c axis of the nanowire with a degree of linear polarization of ~70%.

High-efficiency, deep-junction, epitaxial InP solar cells on (100) and (111)B InP substrates

NASA Technical Reports Server (NTRS)

Venkatasubramanian, R.; Timmons, M. L.; Hutchby, J. A.; Walters, Robert J.; Summers, Geoffrey P.

1994-01-01

We report on the development and performance of deep-junction (approximately 0.25 micron), graded-emitter-doped, n(sup +)-p InP solar cells grown by metallorganic chemical vapor deposition (MOCVD). A novel, diffusion-transport process for obtaining lightly-doped p-type base regions of the solar cell is described. The I-V data and external quantum-efficiency response of these cells are presented. The best active-area AMO efficiency for these deep-junction cells on (100)-oriented InP substrates is 16.8 percent, with a J(sub SC) of 31.8 mA/sq cm, a V(sub OC) of 0.843 V, and a fill-factor of 0.85. By comparison, the best cell efficiency on the (111)B-oriented InP substrates was 15.0 percent. These efficiency values for deep-junction cells are encouraging and compare favorably with performance of thin-emitter (0.03 micron) epitaxial cells as well as that of deep-emitter diffused cells. The cell performance and breakdown voltage characteristics of a batch of 20 cells on each of the orientations are presented, indicating the superior breakdown voltage properties and other characteristics of InP cells on the (111)B orientation. Spectral response, dark I-V data, and photoluminescence (PL) measurements on the InP cells are presented with an analysis on the variation in J(sub SC) and V(sub OC) of the cells. It is observed, under open-circuit conditions, that lower-V(sub OC) cells exhibit higher band-edge PL intensity for both the (100) and (111)B orientations. This anomalous behavior suggests that radiative recombination in the heavily-doped n(sup +)-InP emitter may be detrimental to achieving higher V(sub OC) in n(sup +)-p InP solar cells.

Terahertz Focusing and Polarization Control in Large-Area Bias-Free Semiconductor Emitters

NASA Astrophysics Data System (ADS)

Carthy, Joanna L.; Gow, Paul C.; Berry, Sam A.; Mills, Ben; Apostolopoulos, Vasilis

2018-03-01

We show that, when large-area multiplex terahertz semiconductor emitters, that work on diffusion currents and Schottky potentials, are illuminated by ultrashort optical pulses they can radiate a directional electromagnetic terahertz pulse which is controlled by the angular spectrum of the incident optical beam. Using the lens that focuses the incident near-infrared pulse, we have demonstrated THz emission focusing in free space, at the same point where the optical radiation would focus. We investigated the beam waist and Gouy phase shift of the THz emission as a function of frequency. We also show that the polarization profile of the emitted THz can be tailored by the metallic patterning on the semiconductor, demonstrating radial polarization when a circular emitter design is used. Our techniques can be used for fast THz beam steering and mode control for efficiently coupling to waveguides without the need for THz lenses or parabolic mirrors.

Voltage controlling mechanisms in low resistivity silicon solar cells: A unified approach

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Swartz, C. K.; Hart, R. E.; Godlewski, M. P.

1984-01-01

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

Voltage controlling mechanisms in low resistivity silicon solar cells - A unified approach

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Swartz, C. K.; Hart, R. E.; Godlewski, M. P.

1984-01-01

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

Crystalline silicon solar cells with high resistivity emitter

NASA Astrophysics Data System (ADS)

Panek, P.; Drabczyk, K.; Zięba, P.

2009-06-01

The paper presents a part of research targeted at the modification of crystalline silicon solar cell production using screen-printing technology. The proposed process is based on diffusion from POCl3 resulting in emitter with a sheet resistance on the level of 70 Ω/□ and then, shaped by high temperature passivation treatment. The study was focused on a shallow emitter of high resistivity and on its influence on output electrical parameters of a solar cell. Secondary ion mass spectrometry (SIMS) has been employed for appropriate distinguishing the total donor doped profile. The solar cell parameters were characterized by current-voltage characteristics and spectral response (SR) methods. Some aspects playing a role in suitable manufacturing process were discussed. The situation in a photovoltaic industry with emphasis on silicon supply and current prices of solar cells, modules and photovoltaic (PV) systems are described. The economic and quantitative estimation of the PV world market is shortly discussed.

Energy transfer in PPV-based conjugated polymers: a defocused widefield fluorescence microscopy study.

PubMed

Hooley, E N; Tilley, A J; White, J M; Ghiggino, K P; Bell, T D M

2014-04-21

Both pendant and main chain conjugated MEH-PPV based polymers have been studied at the level of single chains using confocal and widefield fluorescence microscopy techniques. In particular, defocused widefield fluorescence is applied to reveal the extent of energy transfer in these polymers by identifying whether they act as single emitters. For main chain conjugated MEH-PPV, molecular weight and the surrounding matrix play a primary role in determining energy transport processes and whether single emitter behaviour is observed. Surprisingly in polymers with a saturated backbone but containing the same pendant MEH-PPV oligomer on each repeating unit, intra-chain energy transfer to a single emitter is also apparent. The results imply there is chromophore heterogeneity that can facilitate energy funneling to the emitting site. Both main chain conjugated and pendant MEH-PPV polymers exhibit changes in orientation of the emission dipole during a fluorescence trajectory of many seconds, whereas a model MEH-PPV oligomer does not. The results suggest that, in the polymers, the nature of the emitting chromophores can change during the time trajectory.

Limiting effects in double EEX beamline

NASA Astrophysics Data System (ADS)

Ha, G.; Power, J. G.; Conde, M.; Doran, D. S.; Gai, W.

2017-07-01

The double emittance exchange (EEX) beamline is suggested to overcome the large horizontal emittance and transverse jitter issues associated with the single EEX beamline while preserving its powerful phase-space manipulation capability. However, the double EEX beamline also has potential limitations due to coherent synchrotron radiation (CSR) and transverse jitter. The former limitation arises because double EEX uses twice as many bending magnets as single EEX which means stronger CSR effects degrading the beam quality. The latter limitation arises because a longitudinal jitter in front of the first EEX beamline is converted into a transverse jitter in the middle section (between the EEX beamlines) which can cause beam loss or beam degradation. In this paper, we numerically explore the effects of these two limitations on the emittance and beam transport.

Interplay between morphological and shielding effects in field emission via Schwarz-Christoffel transformation

NASA Astrophysics Data System (ADS)

Marcelino, Edgar; de Assis, Thiago A.; de Castilho, Caio M. C.

2018-03-01

It is well known that sufficiently strong electrostatic fields are able to change the morphology of Large Area Field Emitters (LAFEs). This phenomenon affects the electrostatic interactions between adjacent sites on a LAFE during field emission and may lead to several consequences, such as: the emitter's degradation, diffusion of absorbed particles on the emitter's surface, deflection due to electrostatic forces, and mechanical stress. These consequences are undesirable for technological applications, since they may significantly affect the macroscopic current density on the LAFE. Despite the technological importance, these processes are not completely understood yet. Moreover, the electrostatic effects due to the proximity between emitters on a LAFE may compete with the morphological ones. The balance between these effects may lead to a non trivial behavior in the apex-Field Enhancement Factor (FEF). The present work intends to study the interplay between proximity and morphological effects by studying a model amenable for an analytical treatment. In order to do that, a conducting system under an external electrostatic field, with a profile limited by two mirror-reflected triangular protrusions on an infinite line, is considered. The FEF near the apex of each emitter is obtained as a function of their shape and the distance between them via a Schwarz-Christoffel transformation. Our results suggest that a tradeoff between morphological and proximity effects on a LAFE may provide an explanation for the observed reduction of the local FEF and its variation at small distances between the emitter sites.

Efficient Generation of an Array of Single Silicon-Vacancy Defects in Silicon Carbide

NASA Astrophysics Data System (ADS)

Wang, Junfeng; Zhou, Yu; Zhang, Xiaoming; Liu, Fucai; Li, Yan; Li, Ke; Liu, Zheng; Wang, Guanzhong; Gao, Weibo

2017-06-01

Color centers in silicon carbide have increasingly attracted attention in recent years owing to their excellent properties such as single-photon emission, good photostability, and long spin-coherence time even at room temperature. As compared to diamond, which is widely used for hosting nitrogen-vacancy centers, silicon carbide has an advantage in terms of large-scale, high-quality, and low-cost growth, as well as an advanced fabrication technique in optoelectronics, leading to prospects for large-scale quantum engineering. In this paper, we report an experimental demonstration of the generation of a single-photon-emitter array through ion implantation. VSi defects are generated in predetermined locations with high generation efficiency (approximately 19 % ±4 % ). The single emitter probability reaches approximately 34 % ±4 % when the ion-implantation dose is properly set. This method serves as a critical step in integrating single VSi defect emitters with photonic structures, which, in turn, can improve the emission and collection efficiency of VSi defects when they are used in a spin photonic quantum network. On the other hand, the defects are shallow, and they are generated about 40 nm below the surface which can serve as a critical resource in quantum-sensing applications.

Role of constant value of surface diffuseness in alpha decay half-lives of superheavy nuclei

NASA Astrophysics Data System (ADS)

Dehghani, V.; Alavi, S. A.; Benam, Kh.

2018-05-01

By using WKB method and considering deformed Woods-Saxon nuclear potential, deformed Coulomb potential, and centrifugal potential, the alpha decay half-lives of 68 superheavy alpha emitters have been calculated. The effect of the constant value of surface diffuseness parameter in the range of 0.1 ≤ a ≤ 0.9 (fm) on the potential barrier, tunneling probability, assault frequency, and alpha decay half-lives has been investigated. Significant differences were observed for alpha decay half-lives and decay quantities in this range of surface diffuseness. Good agreement between calculated half-lives with fitted surface diffuseness parameter a = 0.54 (fm) and experiment was observed.

Self aligning electron beam gun having enhanced thermal and mechanical stability

DOEpatents

Scarpetti, Jr., Raymond D.; Parkison, Clarence D.; Switzer, Vernon A.; Lee, Young J.; Sawyer, William C.

1995-01-01

A compact, high power electron gun having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the "triple point" where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques.

Measured emittance dependence on injection method in laser plasma accelerators

NASA Astrophysics Data System (ADS)

Barber, Samuel; van Tilborg, Jeroen; Schroeder, Carl; Lehe, Remi; Tsai, Hai-En; Swanson, Kelly; Steinke, Sven; Nakamura, Kei; Geddes, Cameron; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

2017-10-01

The success of many laser plasma accelerator (LPA) based applications relies on the ability to produce electron beams with excellent 6D brightness, where brightness is defined as the ratio of charge to the product of the three normalized emittances. As such, parametric studies of the emittance of LPA generated electron beams are essential. Profiting from a stable and tunable LPA setup, combined with a carefully designed single-shot transverse emittance diagnostic, we present a direct comparison of charge dependent emittance measurements of electron beams generated by two different injection mechanisms: ionization injection and shock induced density down-ramp injection. Notably, the measurements reveal that ionization injection results in significantly higher emittance. With the down-ramp injection configuration, emittances less than 1 micron at spectral charge densities up to 2 pC/MeV were measured. This work was supported by the U.S. DOE under Contract No. DE-AC02-05CH11231, by the NSF under Grant No. PHY-1415596, by the U.S. DOE NNSA, DNN R&D (NA22), and by the Gordon and Betty Moore Foundation under Grant ID GBMF4898.

Diffusion of low-energy electrons in tissue-like liquids.

PubMed

Malamut, C; Paes-Leme, P J; Paschoa, A S

1992-11-01

The spatial-energetic distribution of low-energy electrons was studied for a source located in a liquid medium simulating biological tissue. A time-independent Boltzmann equation was used to model this distribution microscopically. Ionization was treated as a perturbation to a quasi-elastic collision process between the electron and the medium. A diffusion limit was obtained by using a scale parameter, leading to a sequence of recursive partial differential equations whose solutions, associated with a macroscopic scale, were obtained by numerical approximations. As an application, electron ranges were estimated based on these solutions and then compared with values reported in the open literature based on experimental results and on Monte Carlo calculation. Local dosimetry, i.e., the energy imparted to a volume of a sphere with radius equal to the range of low-energy electrons, of low-energy electrons from internal emitters can benefit by the knowledge of the ranges estimated for biological tissue. Auger electron emitters, for example, have been the object of a number of investigations because of their radiobiological significance.

Deterministic photon-emitter coupling in chiral photonic circuits.

PubMed

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Deterministic photon-emitter coupling in chiral photonic circuits

NASA Astrophysics Data System (ADS)

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Tuning the spectral emittance of α-SiC open-cell foams up to 1300 K with their macro porosity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousseau, B., E-mail: benoit.rousseau@univ-nantes.fr; Guevelou, S.; Mekeze-Monthe, A.

2016-06-15

A simple and robust analytical model is used to finely predict the spectral emittance under air up to 1300 K of α-SiC open-cell foams constituted of optically thick struts. The model integrates both the chemical composition and the macro-porosity and is valid only if foams have volumes higher than their Representative Elementary Volumes required for determining their emittance. Infrared emission spectroscopy carried out on a doped silicon carbide single crystal associated to homemade numerical tools based on 3D meshed images (Monte Carlo Ray Tracing code, foam generator) make possible to understand the exact role of the cell network in emittance.more » Finally, one can tune the spectral emittance of α-SiC foams up to 1300 K by simply changing their porosity.« less

High-Power Broad-Area Diode Lasers and Laser Bars

NASA Astrophysics Data System (ADS)

Erbert, Goetz; Baerwolff, Arthur; Sebastian, Juergen; Tomm, Jens

This review presents the basic ideas and some examples of the chip technology of high-power diode lasers ( λ= 650,-1060,) in connection with the achievements of mounted single-stripe emitters in recent years.In the first section the optimization of the epitaxial layer structure for a low facet load and high conversion efficiency is discussed. The so-called broadened waveguide Large Optical Cavity (LOC) concept is described and also some advantages and disadvantages of Al-free material. The next section deals with the processing steps of epitaxial wafers to make single emitters and bars. Several possibilities to realize contact windows (implantation, insulators, and wet chemical oxidation) and laser mirrors are presented. The impact of heating in the CW regime and some aspects of reliability are the following topics. The calculation of thermal distributions in diode lasers, which shows the need for sophisticated mounting, will be given. In the last part the current state-of-the-art of single-stripe emitters will be reviewed.

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

PubMed Central

Schröder, Tim; Trusheim, Matthew E.; Walsh, Michael; Li, Luozhou; Zheng, Jiabao; Schukraft, Marco; Sipahigil, Alp; Evans, Ruffin E.; Sukachev, Denis D.; Nguyen, Christian T.; Pacheco, Jose L.; Camacho, Ryan M.; Bielejec, Edward S.; Lukin, Mikhail D.; Englund, Dirk

2017-01-01

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ∼32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ∼2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ∼51 GHz and close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ∼1.4 times the natural linewidth. This method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors. PMID:28548097

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

DOE PAGES

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael; ...

2017-05-26

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

A universal formula for the field enhancement factor

NASA Astrophysics Data System (ADS)

Biswas, Debabrata

2018-04-01

The field enhancement factor (FEF) is an important quantity in field emission calculations since the tunneling electron current depends very sensitively on its magnitude. The exact dependence of FEF on the emitter height h, the radius of curvature at the apex Ra, as well as the shape of the emitter base are still largely unknown. In this work, a universal formula for the field enhancement factor is derived for a single emitter. It depends on the ratio h/Ra and has the form γ a = ( 2 h / R a ) / [ α 1 ln ( 4 h / R a ) - α 2 ] , where α1 and α2 depend on the charge distribution on the emitter. Numerical results show that a simpler form γ a = ( 2 h / R a ) / [ ln ( 4 h / R a ) - α ] is equally valid with α depending on the emitter-base. Thus, for the hyperboloid, conical, and ellipsoid emitters, the value of α is 0, 0.88, and 2, while for the cylindrical base, α ≃ 2.6.

Piezoresistance and solar cell efficiency

NASA Technical Reports Server (NTRS)

Weizer, Victor G.

1987-01-01

Diffusion-induced stresses in silicon are shown to result in large localized changes in the minority-carrier mobility which in turn can have a significant effect on cell output. Evidence is given that both compressive and tensile stresses can be generated in either the emitter or the base region. Tensile stresses in the base appear to be much more effective in altering cell performance than do compressive stresses. While most stress-related effects appear to degrade cell efficiency, this is not always the case. Evidence is presented showing that arsenic-induced stresses can result in emitter characteristics comparable to those found in the MINP cell without requiring a high degree of surface passivation.

The effect of internal stresses on solar cell efficiency

NASA Technical Reports Server (NTRS)

Weizer, Victor G.

1987-01-01

Diffusion induced stresses in silicon are shown to result in large localized changes in the minority carrier mobility which in turn have a significant effect on cell output. Evidence is given that both compressive and tensile stresses can be generated in either the emitter or the base region. Tensile stresses appear to be much more effective in altering cell performance. While most stress related effects appear to degrade cell efficiency, this is not always the case. Evidence is presented showing that arsenic induced stresses can result in emitter characteristics comparable to those found in the MINP cell without requiring a high degree of surface passivation.

Engineered Emitters for Improved Silicon Photovoltaics

NASA Astrophysics Data System (ADS)

Kamat, Ronak A.

In 2014, installation of 5.3GW of new Photovoltaic (PV) systems occurred in the United States, raising the total installed capacity to 16.36GW. Strong growth is predicted for the domestic PV market with analysts reporting goals of 696GW by 2020. Conventional single crystalline silicon cells are the technology of choice, accounting for 90% of the installations in the global commercial market. Cells made of GaAs offer higher efficiencies, but at a substantially higher cost. Thin film technologies such as CIGS and CdTe compete favorably with multi-crystalline Si (u-Si), but at 20% efficiency, still lag the c-Si cell in performance. The c-Si cell can be fabricated to operate at approximately 25% efficiency, but commercially the efficiencies are in the 18-21% range, which is a direct result of cost trade-offs between process complexity and rapid throughput. With the current cost of c-Si cell modules at nearly 0.60/W. The technology is well below the historic metric of 1/W for economic viability. The result is that more complex processes, once cost-prohibitive, may now be viable. An example is Panasonic's HIT cell which operates in the 22-24% efficiency range. To facilitate research and development of novel PV materials and techniques, RIT has developed a basic solar cell fabrication process. Student projects prior to this work had produced cells with 12.8% efficiency using p type substrates. This thesis reports on recent work to improve cell efficiencies while simultaneously expanding the capability of the rapid prototyping process. In addition to the p-Si substrates, cells have been produced using n-Si substrates. The cell emitter, which is often done with a single diffusion or implant has been re-engineered using a dual implant of the same dose. This dual-implanted emitter has been shown to lower contact resistance, increase Voc, and increase the efficiency. A p-Si substrate cell has been fabricated with an efficiency of 14.6% and n-Si substrate cell with a 13.5% efficiency. Further improvements could be made through the incorporation of a front-surface field, surface texturing and nitride ARC.

GPU-Accelerated Hybrid Algorithm for 3D Localization of Fluorescent Emitters in Dense Clusters

NASA Astrophysics Data System (ADS)

Jung, Yoon; Barsic, Anthony; Piestun, Rafael; Fakhri, Nikta

In stochastic switching-based super-resolution imaging, a random subset of fluorescent emitters are imaged and localized for each frame to construct a single high resolution image. However, the condition of non-overlapping point spread functions (PSFs) imposes constraints on experimental parameters. Recent development in post processing methods such as dictionary-based sparse support recovery using compressive sensing has shown up to an order of magnitude higher recall rate than single emitter fitting methods. However, the computational complexity of this approach scales poorly with the grid size and requires long runtime. Here, we introduce a fast and accurate compressive sensing algorithm for localizing fluorescent emitters in high density in 3D, namely sparse support recovery using Orthogonal Matching Pursuit (OMP) and L1-Homotopy algorithm for reconstructing STORM images (SOLAR STORM). SOLAR STORM combines OMP with L1-Homotopy to reduce computational complexity, which is further accelerated by parallel implementation using GPUs. This method can be used in a variety of experimental conditions for both in vitro and live cell fluorescence imaging.

Demonstration of cathode emittance dominated high bunch charge beams in a DC gun-based photoinjector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gulliford, Colwyn, E-mail: cg248@cornell.edu; Bartnik, Adam, E-mail: acb20@cornell.edu; Bazarov, Ivan

We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9–9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of deliveringmore » beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers.« less

Emittance studies of the 2.45 GHz permanent magnet ECR ion source

NASA Astrophysics Data System (ADS)

Zelenak, A.; Bogomolov, S. L.; Yazvitsky, N. Yu.

2004-05-01

During the past several years different types of permanent magnet 2.45 GHz (electron cyclotron resonance) ion sources were developed for production of singly charged ions. Ion sources of this type are used in the first stage of DRIBs project, and are planned to be used in the MASHA mass separator. The emittance of the beam provided by the source is one of the important parameters for these applications. An emittance scanner composed from a set of parallel slits and rotary wire beam profile monitor was used for the studying of the beam emittance characteristics. The emittance of helium and argon ion beams was measured with different shapes of the plasma electrode for several ion source parameters: microwave power, source potential, plasma aperture-puller aperture gap distance, gas pressure. The results of measurements are compared with previous simulations of ion optics.

Emitters of N-photon bundles

PubMed Central

Muñoz, C. Sánchez; del Valle, E.; Tudela, A. González; Müller, K.; Lichtmannecker, S.; Kaniber, M.; Tejedor, C.; Finley, J.J.; Laussy, F.P.

2014-01-01

Controlling the ouput of a light emitter is one of the basic tasks of photonics, with landmarks such as the laser and single-photon sources. The development of quantum applications makes it increasingly important to diversify the available quantum sources. Here, we propose a cavity QED scheme to realize emitters that release their energy in groups, or “bundles” of N photons, for integer N. Close to 100% of two-photon emission and 90% of three-photon emission is shown to be within reach of state of the art samples. The emission can be tuned with system parameters so that the device behaves as a laser or as a N-photon gun. The theoretical formalism to characterize such emitters is developed, with the bundle statistics arising as an extension of the fundamental correlation functions of quantum optics. These emitters will be useful for quantum information processing and for medical applications. PMID:25013456

Thermal management of microwave power heterojunction bipolar transistors

NASA Astrophysics Data System (ADS)

Bozada, C.; Cerny, C.; De Salvo, G.; Dettmer, R.; Ebel, J.; Gillespie, J.; Havasy, C.; Jenkins, T.; Ito, C.; Nakano, K.; Pettiford, C.; Quach, T.; Sewell, J.; Via, G. D.; Anholt, R.

1997-10-01

A comprehensive study of the device layout effects on thermal resistance in thermally-shunted heterojunction bipolar transistors (HBTs) was completed. The thermal resistance scales linearly with emitter dot diameter for single element HBTs. For multiple emitter element devices, the thermal resistance scales with area. HBTs with dot geometrics have lower thermal impedance than bar HBTs with equivalent emitter area. The thermal resistance of a 200 μm 2 emitter area device was reduced from 266°C/W to 146°C/W by increasing the shunt thickness from 3 μm to 20 μm and placing a thermal shunt landing between the fingers. Also, power-added efficiencies at 10 GHz were improved from 30% to 68% by this thermal resistance reduction.

Collaborative emitter tracking using Rao-Blackwellized random exchange diffusion particle filtering

NASA Astrophysics Data System (ADS)

Bruno, Marcelo G. S.; Dias, Stiven S.

2014-12-01

We introduce in this paper the fully distributed, random exchange diffusion particle filter (ReDif-PF) to track a moving emitter using multiple received signal strength (RSS) sensors. We consider scenarios with both known and unknown sensor model parameters. In the unknown parameter case, a Rao-Blackwellized (RB) version of the random exchange diffusion particle filter, referred to as the RB ReDif-PF, is introduced. In a simulated scenario with a partially connected network, the proposed ReDif-PF outperformed a PF tracker that assimilates local neighboring measurements only and also outperformed a linearized random exchange distributed extended Kalman filter (ReDif-EKF). Furthermore, the novel ReDif-PF matched the tracking error performance of alternative suboptimal distributed PFs based respectively on iterative Markov chain move steps and selective average gossiping with an inter-node communication cost that is roughly two orders of magnitude lower than the corresponding cost for the Markov chain and selective gossip filters. Compared to a broadcast-based filter which exactly mimics the optimal centralized tracker or its equivalent (exact) consensus-based implementations, ReDif-PF showed a degradation in steady-state error performance. However, compared to the optimal consensus-based trackers, ReDif-PF is better suited for real-time applications since it does not require iterative inter-node communication between measurement arrivals.

Self aligning electron beam gun having enhanced thermal and mechanical stability

DOEpatents

Scarpetti, R.D. Jr.; Parkison, C.D.; Switzer, V.A.; Lee, Y.J.; Sawyer, W.C.

1995-05-16

A compact, high power electron gun is disclosed having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the ``triple point`` where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques. 12 Figs.

Synthesis and optoelectronic properties of a heterobimetallic Pt(II)-Ir(III) complex used as a single-component emitter in white PLEDs.

PubMed

Li, Xiaoshuang; Liu, Yu; Luo, Jian; Zhang, Zhiyong; Shi, Danyan; Chen, Qing; Wang, Yafei; He, Juan; Li, Jianming; Lei, Gangtie; Zhu, Weiguo

2012-03-14

To tune aggregation/excimer emission and obtain a single active emitter for white polymer light-emitting devices (PLEDs), a heterobimetallic Pt(II)-Ir(III) complex of FIr(pic)-C(6)DBC(6)-(pic)PtF was designed and synthesized, in which C(6)DBC(6) is a di(phenyloxyhexyloxy) bridging group, FIr(pic) is an iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore and FPt(pic) is a platinum(II) [(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore. Its physical and opto-electronic properties were investigated. Interestingly, the excimer emission was efficiently controlled by this heterobimetallic Pt(II)-Ir(III) complex compared to the PL profile of the mononuclear FPt(pic) complex in the solid state. Near-white emissions were obtained in the single emissive layer (SEL) PLEDs using this heterobimetallic Pt(II)-Ir(III) complex as a single dopant and poly(vinylcarbazole) as a host matrix at dopant concentrations from 0.5 wt% to 2 wt%. This work indicates that incorporating a non-planar iridium(III) complex into the planar platinum(II) complex can control aggregation/excimer emissions and a single phosphorescent emitter can be obtained to exhibit white emission in SEL devices.

Analytical approach to Eigen-emittance evolution in storage rings

NASA Astrophysics Data System (ADS)

Nash, Boaz

This dissertation develops the subject of beam evolution in storage rings with nearly uncoupled symplectic linear dynamics. Linear coupling and dissipative/diffusive processes are treated perturbatively. The beam distribution is assumed Gaussian and a function of the invariants. The development requires two pieces: the global invariants and the local stochastic processes which change the emittances, or averages of the invariants. A map based perturbation theory is described, providing explicit expressions for the invariants near each linear resonance, where small perturbations can have a large effect. Emittance evolution is determined by the damping and diffusion coefficients. The discussion is divided into the cases of uniform and non-uniform stochasticity, synchrotron radiation an example of the former and intrabeam scattering the latter. For the uniform case, the beam dynamics is captured by a global diffusion coefficent and damping decrement for each eigen-invariant. Explicit expressions for these quantities near coupling resonances are given. In many cases, they are simply related to the uncoupled values. Near a sum resonance, it is found that one of the damping decrements becomes negative, indicating an anti-damping instability. The formalism is applied to a number of examples, including synchrobetatron coupling caused by a crab cavity, a case of current interest where there is concern about operation near half integer betatron tune. In the non-uniform case, the moment evolution is computed directly, which is illustrated through the example of intrabeam scattering. Our approach to intrabeam scattering damping and diffusion has the advantage of not requiring a loosely-defined Coulomb Logarithm. It is found that in some situations there is a small difference between our results and the standard approaches such as Bjorken-Mtingwa, which is illustrated by comparison of the two approaches and with a measurement of Au evolution in RHIC. Finally, in combining IBS with the global invariants some general statements about IBS equilibrium can be made. Specifically, it is emphasized that no such equilibrium is possible in a non-smooth lattice, even below transition. Near enough to a synchrobetatron coupling resonance, it is found that even for a smooth ring, no IBS equilibrium occurs.

Matching optics for Gaussian beams

NASA Technical Reports Server (NTRS)

Gunter, William D. (Inventor)

1991-01-01

A system of matching optics for Gaussian beams is described. The matching optics system is positioned between a light beam emitter (such as a laser) and the input optics of a second optics system whereby the output from the light beam emitter is converted into an optimum input for the succeeding parts of the second optical system. The matching optics arrangement includes the combination of a light beam emitter, such as a laser with a movable afocal lens pair (telescope) and a single movable lens placed in the laser's output beam. The single movable lens serves as an input to the telescope. If desired, a second lens, which may be fixed, is positioned in the beam before the adjustable lens to serve as an input processor to the movable lens. The system provides the ability to choose waist diameter and position independently and achieve the desired values with two simple adjustments not requiring iteration.

Progress in p(+)n InP solar cells fabricated by thermal diffusion

NASA Technical Reports Server (NTRS)

Flood, D. J.; Brinker, D. J.; Weinberg, I.; Vargas, C.; Faur, Mircea; Faur, Maria; Goradia, C.; Goradia, M.; Fatemi, N. S.

1993-01-01

The performance results of our most recently thermally diffused InP solar cells using the p(+)n (Cd,S) structures are presented. We have succeeded in fabricating cells with measured AMO, 25 C V(sub oc) exceeding 880 mV (bare cells) which to the best of our knowledge is higher than previously reported V(sub oc) values for any InP homojunction solar cells. The cells were fabricated by thinning the emitter, after Au-Zn front contacting, from its initial thickness of about 4.5 microns to about 0.6 microns. After thinning, the exposed surface of the emitter was passivated by a thin (approximately 50A) P-rich oxide. Based on the measured EQY and J(sub sc)-V(sub oc) characteristics of our experimental high V(sub oc) p(+)n InP solar cells, we project that reducing the emitter thickness to 0.3 microns, using an optimized AR coating, maintaining the surface hole concentration of 3 x 10(exp 18)cm(sup -3), reducing the grid shadowing from actual 10.55 percent to 6 percent and reducing the contact resistance will increase the actual measured 12.57 percent AMO 25 C efficiency to about 20.1 percent. By using our state-of-the-art p(+)n structures which have a surface hole concentration of 4 x 10(exp 18)cm(sup -3) and slightly improving the front surface passivation, an even higher practically achievable AMO, 25 C efficiency of 21.3 percent is projected.

Intrinsic delay of permeable base transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wenchao; Guo, Jing; So, Franky

2014-07-28

Permeable base transistors (PBTs) fabricated by vacuum deposition or solution process have the advantages of easy fabrication and low power operation and are a promising device structure for flexible electronics. Intrinsic delay of PBT, which characterizes the speed of the transistor, is investigated by solving the three-dimensional Poisson equation and drift-diffusion equation self-consistently using finite element method. Decreasing the emitter thickness lowers the intrinsic delay by improving on-current, and a thinner base is also preferred for low intrinsic delay because of fewer carriers in the base region at off-state. The intrinsic delay exponentially decreases as the emitter contact Schottky barriermore » height decreases, and it linearly depends on the carrier mobility. With an optimized emitter contact barrier height and device geometry, a sub-nano-second intrinsic delay can be achieved with a carrier mobility of ∼10 cm{sup 2}/V/s obtainable in solution processed indium gallium zinc oxide, which indicates the potential of solution processed PBTs for GHz operations.« less

Charge recombination in the muon collider cooling channel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernow, R. C.; Palmer, R. B.

2012-12-21

The final stage of the ionization cooling channel for the muon collider must transversely recombine the positively and negatively charged bunches into a single beam before the muons can be accelerated. It is particularly important to minimize any emittance growth in this system since no further cooling takes place before the bunches are collided. We have found that emittance growth could be minimized by using symmetric pairs of bent solenoids and careful matching. We show that a practical design can be found that has transmission {approx}99%, emittance growth less than 0.1%, and minimal dispersion in the recombined bunches.

Use of Wedge Absorbers in MICE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neuffer, D.; Summers, D.; Mohayai, T.

2017-03-01

Wedge absorbers are needed to obtain longitudinal cooling in ionization cooling. They also can be used to obtain emittance exchanges between longitudinal and transverse phase space. There can be large exchanges in emittance, even with single wedges. In the present note we explore the use of wedge absorbers in the MICE experiment to obtain transverse–longitudinal emittance exchanges within present and future operational conditions. The same wedge can be used to explore “direct” and “reverse” emittance exchange dynamics, where direct indicates a configuration that reduces momentum spread and reverse is a configuration that increases momentum spread. Analytical estimated and ICOOL andmore » G4BeamLine simulations of the exchanges at MICE parameters are presented. Large exchanges can be obtained in both reverse and direct configurations.« less

Photon scattering from a system of multilevel quantum emitters. II. Application to emitters coupled to a one-dimensional waveguide

NASA Astrophysics Data System (ADS)

Das, Sumanta; Elfving, Vincent E.; Reiter, Florentin; Sørensen, Anders S.

2018-04-01

In a preceding paper we introduced a formalism to study the scattering of low-intensity fields from a system of multilevel emitters embedded in a three-dimensional (3 D ) dielectric medium. Here we show how this photon-scattering relation can be used to analyze the scattering of single photons and weak coherent states from any generic multilevel quantum emitter coupled to a one-dimensional (1 D ) waveguide. The reduction of the photon-scattering relation to 1 D waveguides provides a direct solution of the scattering problem involving low-intensity fields in the waveguide QED regime. To show how our formalism works, we consider examples of multilevel emitters and evaluate the transmitted and reflected field amplitude. Furthermore, we extend our study to include the dynamical response of the emitters for scattering of a weak coherent photon pulse. As our photon-scattering relation is based on the Heisenberg picture, it is quite useful for problems involving photodetection in the waveguide architecture. We show this by considering a specific problem of state generation by photodetection in a multilevel emitter, where our formalism exhibits its full potential. Since the considered emitters are generic, the 1 D results apply to a plethora of physical systems such as atoms, ions, quantum dots, superconducting qubits, and nitrogen-vacancy centers coupled to a 1 D waveguide or transmission line.

Increase of intrinsic emittance induced by multiphoton photoemission from copper cathodes illuminated by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

An, Chenjie; Zhu, Rui; Xu, Jun; Liu, Yaqi; Hu, Xiaopeng; Zhang, Jiasen; Yu, Dapeng

2018-05-01

Electron sources driven by femtosecond laser have important applications in many aspects, and the research about the intrinsic emittance is becoming more and more crucial. The intrinsic emittance of polycrystalline copper cathode, which was illuminated by femtosecond pulses (FWHM of the pulse duration was about 100 fs) with photon energies above and below the work function, was measured with an extremely low bunch charge (single-electron pulses) based on free expansion method. A minimum emittance was obtained at the photon energy very close to the effective work function of the cathode. When the photon energy decreased below the effective work function, emittance increased rather than decreased or flattened out to a constant. By investigating the dependence of photocurrent density on the incident laser intensity, we found the emission excited by pulsed photons with sub-work-function energies contained two-photon photoemission. In addition, the portion of two-photon photoemission current increased with the reduction of photon energy. We attributed the increase of emittance to the effect of two-photon photoemission. This work shows that conventional method of reducing the photon energy of excited light source to approach the room temperature limit of the intrinsic emittance may be infeasible for femtosecond laser. There would be an optimized photon energy value near the work function to obtain the lowest emittance for pulsed laser pumped photocathode.

Bright Room-Temperature Single-Photon Emission from Defects in Gallium Nitride.

PubMed

Berhane, Amanuel M; Jeong, Kwang-Yong; Bodrog, Zoltán; Fiedler, Saskia; Schröder, Tim; Triviño, Noelia Vico; Palacios, Tomás; Gali, Adam; Toth, Milos; Englund, Dirk; Aharonovich, Igor

2017-03-01

Room-temperature quantum emitters in gallium nitride (GaN) are reported. The emitters originate from cubic inclusions in hexagonal lattice and exhibit narrowband luminescence in the red spectral range. The sources are found in different GaN substrates, and therefore are promising for scalable quantum technologies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum Optics with Near-Lifetime-Limited Quantum-Dot Transitions in a Nanophotonic Waveguide.

PubMed

Thyrrestrup, Henri; Kiršanskė, Gabija; Le Jeannic, Hanna; Pregnolato, Tommaso; Zhai, Liang; Raahauge, Laust; Midolo, Leonardo; Rotenberg, Nir; Javadi, Alisa; Schott, Rüdiger; Wieck, Andreas D; Ludwig, Arne; Löbl, Matthias C; Söllner, Immo; Warburton, Richard J; Lodahl, Peter

2018-03-14

Establishing a highly efficient photon-emitter interface where the intrinsic linewidth broadening is limited solely by spontaneous emission is a key step in quantum optics. It opens a pathway to coherent light-matter interaction for, e.g., the generation of highly indistinguishable photons, few-photon optical nonlinearities, and photon-emitter quantum gates. However, residual broadening mechanisms are ubiquitous and need to be combated. For solid-state emitters charge and nuclear spin noise are of importance, and the influence of photonic nanostructures on the broadening has not been clarified. We present near-lifetime-limited linewidths for quantum dots embedded in nanophotonic waveguides through a resonant transmission experiment. It is found that the scattering of single photons from the quantum dot can be obtained with an extinction of 66 ± 4%, which is limited by the coupling of the quantum dot to the nanostructure rather than the linewidth broadening. This is obtained by embedding the quantum dot in an electrically contacted nanophotonic membrane. A clear pathway to obtaining even larger single-photon extinction is laid out; i.e., the approach enables a fully deterministic and coherent photon-emitter interface in the solid state that is operated at optical frequencies.

Rare Earth Garnet Selective Emitter

NASA Technical Reports Server (NTRS)

Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

1994-01-01

Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approx. = 0.75, sup 4)|(sub 15/2) - (sup 4)|(sub 13/2),for Er-YAG and epsilon(sub lambda) approx. = 0.65, (sup 5)|(sub 7) - (sup 5)|(sub 8) for Ho-YAG) at 1500 K. In addition, low out-of-band spectral emittance, epsilon(sub lambda) less than 0.2, suggest these materials would be excellent candidates for high efficiency selective emitters in thermophotovoltaic (TPV) systems operating at moderate temperatures (1200-1500 K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. Selective emitters in the near IR are of special interest for thermophotovoltaic (TPV) energy conversion. The most promising solid selective emitters for use in a TPV system are rare earth oxides. Early spectral emittance work on rare earth oxides showed strong emission bands in the infrared (0.9 - 3 microns). However, the emittance outside the emission band was also significant and the efficiency of these emitters was low. Recent improvements in efficiency have been made with emitters fabricated from fine (5 - 10 microns) rare earth oxide fibers similar to the Welsbach mantle used in gas lanterns. However, the rare earth garnet emitters are more rugged than the mantle type emitters. A thin film selective emitter on a low emissivity substrate such as gold, platinum etc., is rugged and easily adapted to a wide variety of thermal sources. The garnet structure and its many subgroups have been successfully used as hosts for rare earth ions, introduced as substitutional impurities, in the development of solid state laser crystals. Doping, dependent on the particular ion and crystal structure, may be as high as 100 at. % (complete substitution of yttrium ion with the rare earth ion). These materials have high melting points, 1940 C for YAG (Yttrium Aluminum Garnet), and low emissivity in the near infrared making them excellent candidates for a thin film selective emitter. As previously stated, the spectral emittance of a rare earth emitter is characterized by one or more well defined emission bands. Outside the emission band the emittance(absorptance) is much lower. Therefore, it is expected that emission outside the band for a thin film selective emitter will be dominated by the emitter substrate. For an efficient emitter (power in the emission band/total emitted power) the substrate must have low emittance, epsilon(sub S). This paper presents normal spectral emittance, epsilon(sub lambda), measurements of holmium(Ho) and erbium (Er) doped YAG thin film selective emitters at (1500 K), and compares those results with the theoretical spectral emittance.

Effect of low-energy hydrogen ion implantation on dendritic web silicon solar cells

NASA Technical Reports Server (NTRS)

Rohatgi, A.; Meier, D. L.; Rai-Choudhury, P.; Fonash, S. J.; Singh, R.

1986-01-01

The effect of a low-energy (0.4 keV), short-time (2-min), heavy-dose (10 to the 18th/sq cm) hydrogen ion implant on dendritic web silicon solar cells and material was investigated. Such an implant was observed to improve the cell open-circuit voltage and short-circuit current appreciably for a number of cells. In spite of the low implant energy, measurements of internal quantum efficiency indicate that it is the base of the cell, rather than the emitter, which benefits from the hydrogen implant. This is supported by the observation that the measured minority-carrier diffusion length in the base did not change when the emitter was removed. In some cases, a threefold increase of the base diffusion length was observed after implantation. The effects of the hydrogen implantation were not changed by a thermal stress test at 250 C for 111 h in nitrogen. It is speculated that hydrogen enters the bulk by traveling along dislocations, as proposed recently for edge-defined film-fed growth silicon ribbon.

Superresolution Microscopy of Single Rare-Earth Emitters in YAG and H 3 Centers in Diamond

NASA Astrophysics Data System (ADS)

Kolesov, R.; Lasse, S.; Rothfuchs, C.; Wieck, A. D.; Xia, K.; Kornher, T.; Wrachtrup, J.

2018-01-01

We demonstrate superresolution imaging of single rare-earth emitting centers, namely, trivalent cerium, in yttrium aluminum garnet crystals by means of stimulated emission depletion (STED) microscopy. The achieved all-optical resolution is ≈50 nm . Similar results were obtained on H 3 color centers in diamond. In both cases, STED resolution is improving slower than the conventional inverse square-root dependence on the depletion beam intensity. In the proposed model of this effect, the anomalous behavior is caused by excited state absorption and the interaction of the emitter with nonfluorescing crystal defects in its local surrounding.

Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations

NASA Astrophysics Data System (ADS)

Crocker, Roland M.; Ruiter, Ashley J.; Seitenzahl, Ivo R.; Panther, Fiona H.; Sim, Stuart; Baumgardt, Holger; Möller, Anais; Nataf, David M.; Ferrario, Lilia; Eldridge, J. J.; White, Martin; Tucker, Brad E.; Aharonian, Felix

2017-06-01

Our Galaxy hosts the annihilation of a few 1043 low-energy positrons every second. Radioactive isotopes capable of supplying such positrons are synthesized in stars, stellar remnants and supernovae. For decades, however, there has been no positive identification of a main stellar positron source, leading to suggestions that many positrons originate from exotic sources like the Galaxy's central supermassive black hole or dark matter annihilation. Here we show that a single type of transient source, deriving from stellar populations of age 3-6 Gyr and yielding ∼0.03 M ⊙ of the positron emitter 44Ti, can simultaneously explain the strength and morphology of the Galactic positron annihilation signal and the Solar System abundance of the 44Ti decay product 44Ca. This transient is likely the merger of two low-mass white dwarfs, observed in external galaxies as the sub-luminous, thermonuclear supernova known as SN 1991bg-like.

A comparative study of p(+)n and n(+)p InP solar cells made by a closed ampoule diffusion

NASA Technical Reports Server (NTRS)

Faur, M.; Faur, M.; Flood, D. J.; Weinberg, I.; Brinker, D. J.; Goradia, C.; Fatemi, N.; Goradia, M.; Thesling, W.

1991-01-01

The purpose was to demonstrate the possibility of fabricating thermally diffused p(+)n InP solar cells having high open-circuit voltage without sacrificing the short circuit current. The p(+)n junctions were formed by closed-ampoule diffusion of Cd through a 3 to 5 nm thick anodic or chemical phosphorus-rich oxide cap layer grown on n-InP:S Czochralski LEC grown substrates. For solar cells made by thermal diffusion the p(+)n configuration is expected to have a higher efficiency than the n(+)p configuration. It is predicted that the AM0, BOL efficiencies approaching 19 percent should be readily achieved providing that good ohmic front contacts could be realized on the p(+) emitters of thickness lower than 1 micron.

Recent progress of 638-nm high-power broad area laser diodes in Mitsubishi Electric

NASA Astrophysics Data System (ADS)

Kuramoto, Kyosuke; Abe, Shinji; Miyashita, Motoharu; Nishida, Takehiro; Yagi, Tetsuya

2018-02-01

Laser based displays have gathered much attention because only the displays can express full color gamut of Ultra-HDTV, ITU-R BT.2020. One of the displays uses the lasers under pulse such as a single spatial light modulator (SLM) projector, and the other does ones under CW such as a multiple SLM projector and a liquid crystal display. Both types require high-power lasers because brightness is the most important factor in the market. We developed two types of 638-nm multi-emitter high-power BA-LDs assembled on Φ9.0-TO, that is, triple emitter for pulse and dual emitter for CW. The triple emitter LD emitted exceeding 6.0 W peak power under 25°C, frequency of 120 Hz, and duty of 30%. At high temperature, 55°C, the peak power was approximately 2.9W. The dual emitter emitted exceeding 3.0W under 25°C, CW. It emitted up to 1.7 W at 55°C. WPE of the dual emitter reached 40.5% at Tc of 25°C, which is the world highest in 638-nm LD under CW to the best of our knowledge, although that of the triple emitter was 38.1%. Both LDs may be suitable for laser based display applications.

Silicon cells made by self-aligned selective-emitter plasma-etchback process

DOEpatents

Ruby, Douglas S.; Schubert, William K.; Gee, James M.; Zaidi, Saleem H.

2000-01-01

Photovoltaic cells and methods for making them are disclosed wherein the metallized grids of the cells are used to mask portions of cell emitter regions to allow selective etching of phosphorus-doped emitter regions. The preferred etchant is SF.sub.6 or a combination of SF.sub.6 and O.sub.2. This self-aligned selective etching allows for enhanced blue response (versus cells with uniform heavy doping of the emitter) while preserving heavier doping in the region beneath the gridlines needed for low contact resistance. Embodiments are disclosed for making cells with or without textured surfaces. Optional steps include plasma hydrogenation and PECVD nitride deposition, each of which are suited to customized applications for requirements of given cells to be manufactured. The techniques disclosed could replace expensive and difficult alignment methodologies used to obtain selectively etched emitters, and they may be easily integrated with existing plasma processing methods and techniques of the invention may be accomplished in a single plasma-processing chamber.

Emittance and absorptance of the National Aeronautics and Space Administration ceramic thermal barrier coating. [for gas turbine engine components

NASA Technical Reports Server (NTRS)

Liebert, C. H.

1978-01-01

The spectral emittance of a NASA developed zirconia ceramic thermal barrier coating system, consisting of a metal substrate, a layer of Ni-Cr-Al-Y bond material and a layer of yttria-stabilized zirconia ceramic material, is analyzed. The emittance, needed for evaluation of radiant heat loads on cooled coated gas turbine components, was measured over a range of temperatures that would be typical of its use on such components. Emittance data were obtained with a spectrometer, a reflectometer and a radiation pyrometer at a single bond coating thickness of 0.010 cm and at a ceramic coating thickness of 0-0.076 cm. The data were transformed into the hemispherical total emittance and were correlated to the ceramic coating thickness and temperature using multiple-regression curve-fitting techniques. The system was found to be highly reflective, and, consequently, capable of significantly reducing radiation heat loads on cooled gas turbine engine components.

Waveguide transport mediated by strong coupling with atoms

NASA Astrophysics Data System (ADS)

Cheng, Mu-Tian; Xu, Jingping; Agarwal, Girish S.

2017-05-01

We investigate single-photon scattering properties in a one-dimensional waveguide coupled to a quantum emitter's chain with dipole-dipole interaction (DDI). The photon transport is extremely sensitive to the location of the evanescently coupled atoms. The analytical expressions of reflection and transmission amplitudes for the chain containing two emitters with DDI are deduced by using a real-space Hamiltonian. Two cases, where the two emitters symmetrically or asymmetrically couple to the waveguide, are discussed in detail. It shows that the reflection and transmission typical spectra split into two peaks due to the DDI. The Fano minimum in the spectra can be used to estimate the strength of the DDI. Furthermore, the DDI makes spectra strongly asymmetric and creates a transmission window in the region where there was zero transmission. The scattering spectra for the chain consisting of multiple emitters are also given. Our key finding is that DDI can broaden the frequency bandwidth for high reflection when the chain consists of many emitters.

Evidence of universal inverse-third power law for the shielding-induced fractional decrease in apex field enhancement factor at large spacings: a response via accurate Laplace-type calculations

NASA Astrophysics Data System (ADS)

de Assis, Thiago A.; Dall’Agnol, Fernando F.

2018-05-01

Numerical simulations are important when assessing the many characteristics of field emission related phenomena. In small simulation domains, the electrostatic effect from the boundaries is known to influence the calculated apex field enhancement factor (FEF) of the emitter, but no established dependence has been reported at present. In this work, we report the dependence of the lateral size, L, and the height, H, of the simulation domain on the apex-FEF of a single conducting ellipsoidal emitter. Firstly, we analyze the error, ε, in the calculation of the apex-FEF as a function of H and L. Importantly, our results show that the effects of H and L on ε are scale invariant, allowing one to predict ε for ratios L/h and H/h, where h is the height of the emitter. Next, we analyze the fractional change of the apex-FEF, δ, from a single emitter, , and a pair, . We show that small relative errors in (i.e. ), due to the finite domain size, are sufficient to alter the functional dependence , where c is the distance from the emitters in the pair. We show that obeys a recently proposed power law decay (Forbes 2016 J. Appl. Phys. 120 054302), at sufficiently large distances in the limit of infinite domain size (, say), which is not observed when using a long time established exponential decay (Bonard et al 2001 Adv. Mater. 13 184) or a more sophisticated fitting formula proposed recently by Harris et al (2015 AIP Adv. 5 087182). We show that the inverse-third power law functional dependence is respected for various systems like infinity arrays and small clusters of emitters with different shapes. Thus, , with m  =  3, is suggested to be a universal signature of the charge-blunting effect in small clusters or arrays, at sufficient large distances between emitters with any shape. These results improve the physical understanding of the field electron emission theory to accurately characterize emitters in small clusters or arrays.

Enhanced blue responses in nanostructured Si solar cells by shallow doping

NASA Astrophysics Data System (ADS)

Cheon, Sieun; Jeong, Doo Seok; Park, Jong-Keuk; Kim, Won Mok; Lee, Taek Sung; Lee, Heon; Kim, Inho

2018-03-01

Optimally designed Si nanostructures are very effective for light trapping in crystalline silicon (c-Si) solar cells. However, when the lateral feature size of Si nanostructures is comparable to the junction depth of the emitter, dopant diffusion in the lateral direction leads to excessive doping in the nanostructured emitter whereby poor blue responses arise in the external quantum efficiency (EQE). The primary goal of this study is to find the correlation of emitter junction depth and carrier collection efficiency in nanostructured c-Si solar cells in order to enhance the blue responses. We prepared Si nanostructures of nanocone shape by colloidal lithography, with silica beads of 520 nm in diameter, followed by a reactive ion etching process. c-Si solar cells with a standard cell architecture of an Al back surface field were fabricated varying the emitter junction depth. We varied the emitter junction depth by adjusting the doping level from heavy doping to moderate doping to light doping and achieved greatly enhanced blue responses in EQE from 47%-92% at a wavelength of 400 nm. The junction depth analysis by secondary ion mass-spectroscopy profiling and the scanning electron microscopy measurements provided us with the design guide of the doping level depending on the nanostructure feature size for high efficiency nanostructured c-Si solar cells. Optical simulations showed us that Si nanostructures can serve as an optical resonator to amplify the incident light field, which needs to be considered in the design of nanostructured c-Si solar cells.

Fabrication of a Cryogenic Terahertz Emitter for Bolometer Focal Plane Calibrations

NASA Technical Reports Server (NTRS)

Chervenak, James; Brown, Ari; Wollack, Edward

2012-01-01

A fabrication process is reported for prototype emitters of THz radiation, which operate cryogenically, and should provide a fast, stable blackbody source suitable for characterization of THz devices. The fabrication has been demonstrated and, at the time of this reporting, testing was underway. The emitter is similar to a monolithic silicon bolometer in design, using both a low-noise thermometer and a heater element on a thermally isolated stage. An impedance-matched, high-emissivity coat ing is also integrated to tune the blackbody properties. This emitter is designed to emit a precise amount of power as a blackbody spectrum centered on terahertz frequencies. The emission is a function of the blackbody temperature. An integrated resistive heater and thermometer system can control the temperature of the blackbody with greater precision than previous incarnations of calibration sources that relied on blackbody emission. The emitter is fabricated using a silicon- on-insulator substrate wafer. The buried oxide is chosen to be less than 1 micron thick, and the silicon device thickness is 1-2 microns. Layers of phosphorus compensated with boron are implanted into and diffused throughout the full thickness of the silicon device layer to create the thermometer and heater components. Degenerately doped wiring is implanted to connect the devices to wire-bondable contact pads at the edge of the emitter chip. Then the device is micromachined to remove the thick-handle silicon behind the thermometer and heater components, and to thermally isolate it on a silicon membrane. An impedance- matched emissive coating (ion assisted evaporated Bi) is applied to the back of the membrane to enable high-efficiency emission of the blackbody spectrum.

Modeling and optimal designs for dislocation and radiation tolerant single and multijunction solar cells

NASA Astrophysics Data System (ADS)

Mehrotra, A.; Alemu, A.; Freundlich, A.

2011-02-01

Crystalline defects (e.g. dislocations or grain boundaries) as well as electron and proton induced defects cause reduction of minority carrier diffusion length which in turn results in degradation of efficiency of solar cells. Hetro-epitaxial or metamorphic III-V devices with low dislocation density have high BOL efficiencies but electron-proton radiation causes degradation in EOL efficiencies. By optimizing the device design (emitter-base thickness, doping) we can obtain highly dislocated metamorphic devices that are radiation resistant. Here we have modeled III-V single and multi junction solar cells using drift and diffusion equations considering experimental III-V material parameters, dislocation density, 1 Mev equivalent electron radiation doses, thicknesses and doping concentration. Thinner device thickness leads to increment in EOL efficiency of high dislocation density solar cells. By optimizing device design we can obtain nearly same EOL efficiencies from high dislocation solar cells than from defect free III-V multijunction solar cells. As example defect free GaAs solar cell after optimization gives 11.2% EOL efficiency (under typical 5x1015cm-2 1 MeV electron fluence) while a GaAs solar cell with high dislocation density (108 cm-2) after optimization gives 10.6% EOL efficiency. The approach provides an additional degree of freedom in the design of high efficiency space cells and could in turn be used to relax the need for thick defect filtering buffer in metamorphic devices.

2.1 μm high-power laser diode beam combining(Conference Presentation)

NASA Astrophysics Data System (ADS)

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

2016-10-01

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 < 1.5 for slow axis and < 1.1 for fast axis). Then we characterized broad-area single emitter diodes (808 mW) with an electrical-to-optical efficiency of 19 %. The emitter width was 90 µm with a cavity length of 1.5 mm. In our experiments we found that the slow axis multimode output 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 focal length 100 mm for fully collimating the slow axis. Using D-shaped gold-coated mirrors, multiple single emitter beams are stacked in the fast axis direction with the objective that the combined beam has a beam propagation factor in the stacking direction close to the beam propagation factor of the slow axis of a single emitter, e.g. M2 of 20 to 25 in both axes. We further found that the output beam of a single emitter is highly linearly polarized along the slow axis, making it feasible to implement polarization beam combining techniques to increase the beam power by a factor two while maintaining the same beam quality. Along with full beam characterization, a power scaling strategy towards a multi-watt output power beam combining laser system will be presented.

Operating single quantum emitters with a compact Stirling cryocooler

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlehahn, A.; Krüger, L.; Gschrey, M.

2015-01-15

The development of an easy-to-operate light source emitting single photons has become a major driving force in the emerging field of quantum information technology. Here, we report on the application of a compact and user-friendly Stirling cryocooler in the field of nanophotonics. The Stirling cryocooler is used to operate a single quantum emitter constituted of a semiconductor quantum dot (QD) at a base temperature below 30 K. Proper vibration decoupling of the cryocooler and its surrounding enables free-space micro-photoluminescence spectroscopy to identify and analyze different charge-carrier states within a single quantum dot. As an exemplary application in quantum optics, wemore » perform a Hanbury-Brown and Twiss experiment demonstrating a strong suppression of multi-photon emission events with g{sup (2)}(0) < 0.04 from this Stirling-cooled single quantum emitter under continuous wave excitation. Comparative experiments performed on the same quantum dot in a liquid helium (LHe)-flow cryostat show almost identical values of g{sup (2)}(0) for both configurations at a given temperature. The results of this proof of principle experiment demonstrate that low-vibration Stirling cryocoolers that have so far been considered exotic to the field of nanophotonics are an attractive alternative to expensive closed-cycle cryostats or LHe-flow cryostats, which could pave the way for the development of high-quality table-top non-classical light sources.« less

Operating single quantum emitters with a compact Stirling cryocooler.

PubMed

Schlehahn, A; Krüger, L; Gschrey, M; Schulze, J-H; Rodt, S; Strittmatter, A; Heindel, T; Reitzenstein, S

2015-01-01

The development of an easy-to-operate light source emitting single photons has become a major driving force in the emerging field of quantum information technology. Here, we report on the application of a compact and user-friendly Stirling cryocooler in the field of nanophotonics. The Stirling cryocooler is used to operate a single quantum emitter constituted of a semiconductor quantum dot (QD) at a base temperature below 30 K. Proper vibration decoupling of the cryocooler and its surrounding enables free-space micro-photoluminescence spectroscopy to identify and analyze different charge-carrier states within a single quantum dot. As an exemplary application in quantum optics, we perform a Hanbury-Brown and Twiss experiment demonstrating a strong suppression of multi-photon emission events with g((2))(0) < 0.04 from this Stirling-cooled single quantum emitter under continuous wave excitation. Comparative experiments performed on the same quantum dot in a liquid helium (LHe)-flow cryostat show almost identical values of g((2))(0) for both configurations at a given temperature. The results of this proof of principle experiment demonstrate that low-vibration Stirling cryocoolers that have so far been considered exotic to the field of nanophotonics are an attractive alternative to expensive closed-cycle cryostats or LHe-flow cryostats, which could pave the way for the development of high-quality table-top non-classical light sources.

Low-NA fiber laser pumps powered by high-brightness single emitters

NASA Astrophysics Data System (ADS)

Yanson, Dan; Levy, Moshe; Peleg, Ophir; Rappaport, Noam; Shamay, Moshe; Dahan, Nir; Klumel, Genady; Berk, Yuri; Baskin, Ilya

2015-03-01

Fiber laser manufacturers demand high-brightness laser diode pumps delivering optical pump energy in both a compact fiber core and narrow angular content. A pump delivery fiber of a 105 μm core and 0.22 numerical aperture (NA) is typically used, where the fiber NA is under-filled to ease the launch of laser diode emission into the fiber and make the fiber tolerant to bending. At SCD, we have developed high-brightness NEON multi-emitter fiber-coupled pump modules that deliver 50 W output from a 105 μm, 0.15 NA fiber enabling low-NA power delivery to a customer's fiber laser network. Brightness-enhanced single emitters are engineered with ultra-low divergence for compatibility with the low-NA delivery fiber, with the latest emitters delivering 14 W with 95% of the slow-axis energy contained within an NA of 0.09. The reduced slow-axis divergence is achieved with an optimized epitaxial design, where the peak optical intensity is reduced to both lessen filamentation within the laser cavity and reduce the power density on the output facet thus increasing the emitter reliability. The low mode filling of the fiber allows it to be coiled with diameters down to 70 mm at full operating power despite the small NA and further eliminates the need for mode-stripping at fiber combiners and splices downstream from our pump modules. 50W fiber pump products at 915, 950 and 975 nm wavelengths are presented, including a wavelengthstabilized version at 976 nm.

Single-molecule strong coupling at room temperature in plasmonic nanocavities

NASA Astrophysics Data System (ADS)

Chikkaraddy, Rohit; de Nijs, Bart; Benz, Felix; Barrow, Steven J.; Scherman, Oren A.; Rosta, Edina; Demetriadou, Angela; Fox, Peter; Hess, Ortwin; Baumberg, Jeremy J.

2016-07-01

Photon emitters placed in an optical cavity experience an environment that changes how they are coupled to the surrounding light field. In the weak-coupling regime, the extraction of light from the emitter is enhanced. But more profound effects emerge when single-emitter strong coupling occurs: mixed states are produced that are part light, part matter, forming building blocks for quantum information systems and for ultralow-power switches and lasers. Such cavity quantum electrodynamics has until now been the preserve of low temperatures and complicated fabrication methods, compromising its use. Here, by scaling the cavity volume to less than 40 cubic nanometres and using host-guest chemistry to align one to ten protectively isolated methylene-blue molecules, we reach the strong-coupling regime at room temperature and in ambient conditions. Dispersion curves from more than 50 such plasmonic nanocavities display characteristic light-matter mixing, with Rabi frequencies of 300 millielectronvolts for ten methylene-blue molecules, decreasing to 90 millielectronvolts for single molecules—matching quantitative models. Statistical analysis of vibrational spectroscopy time series and dark-field scattering spectra provides evidence of single-molecule strong coupling. This dressing of molecules with light can modify photochemistry, opening up the exploration of complex natural processes such as photosynthesis and the possibility of manipulating chemical bonds.

Heterojunction solar cell

DOEpatents

Olson, Jerry M.

1994-01-01

A high-efficiency single heterojunction solar cell wherein a thin emitter layer (preferably Ga.sub.0.52 In.sub.0.48 P) forms a heterojunction with a GaAs absorber layer. The conversion effiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the emitter layer.

Mapping Nanoscale Hotspots with Single-Molecule Emitters Assembled into Plasmonic Nanocavities Using DNA Origami.

PubMed

Chikkaraddy, Rohit; Turek, V A; Kongsuwan, Nuttawut; Benz, Felix; Carnegie, Cloudy; van de Goor, Tim; de Nijs, Bart; Demetriadou, Angela; Hess, Ortwin; Keyser, Ulrich F; Baumberg, Jeremy J

2018-01-10

Fabricating nanocavities in which optically active single quantum emitters are precisely positioned is crucial for building nanophotonic devices. Here we show that self-assembly based on robust DNA-origami constructs can precisely position single molecules laterally within sub-5 nm gaps between plasmonic substrates that support intense optical confinement. By placing single-molecules at the center of a nanocavity, we show modification of the plasmon cavity resonance before and after bleaching the chromophore and obtain enhancements of ≥4 × 10 3 with high quantum yield (≥50%). By varying the lateral position of the molecule in the gap, we directly map the spatial profile of the local density of optical states with a resolution of ±1.5 nm. Our approach introduces a straightforward noninvasive way to measure and quantify confined optical modes on the nanoscale.

Space charge effects on the current-voltage characteristics of gated field emitter arrays

NASA Astrophysics Data System (ADS)

Jensen, K. L.; Kodis, M. A.; Murphy, R. A.; Zaidman, E. G.

1997-07-01

Microfabricated field emitter arrays (FEAs) can provide the very high electron current densities required for rf amplifier applications, typically on the order of 100 A/cm2. Determining the dependence of emission current on gate voltage is important for the prediction of emitter performance for device applications. Field emitters use high applied fields to extract current, and therefore, unlike thermionic emitters, the current densities can exceed 103A/cm2 when averaged over an array. At such high current densities, space charge effects (i.e., the influence of charge between cathode and collector on emission) affect the emission process or initiate conditions which can lead to failure mechanisms for field emitters. A simple model of a field emitter will be used to calculate the one-dimensional space charge effects on the emission characteristics by examining two components: charge between the gate and anode, which leads to Child's law, and charge within the FEA unit cell, which gives rise to a field suppression effect which can exist for a single field emitter. The predictions of the analytical model are compared with recent experimental measurements designed to assess space charge effects and predict the onset of gate current. It is shown that negative convexity on a Fowler-Nordheim plot of Ianode(Vgate) data can be explained in terms of field depression at the emitter tip in addition to reflection of electrons by a virtual cathode created when the anode field is insufficient to extract all of the current; in particular, the effects present within the unit cell constitute a newly described effect.

Emitter and absorber assembly for multiple self-dual operation and directional transparency

NASA Astrophysics Data System (ADS)

Kalozoumis, P. A.; Morfonios, C. V.; Kodaxis, G.; Diakonos, F. K.; Schmelcher, P.

2017-03-01

We demonstrate how to systematically design wave scattering systems with simultaneous coherent perfect absorbing and lasing operation at multiple and prescribed frequencies. The approach is based on the recursive assembly of non-Hermitian emitter and absorber units into self-dual emitter-absorber trimers at different composition levels, exploiting the simple structure of the corresponding transfer matrices. In particular, lifting the restriction to parity-time-symmetric setups enables the realization of emitter and absorber action at distinct frequencies and provides flexibility with respect to the choice of realistic parameters. We further show how the same assembled scatterers can be rearranged to produce unidirectional and bidirectional transparency at the selected frequencies. With the design procedure being generically applicable to wave scattering in single-channel settings, we demonstrate it with concrete examples of photonic multilayer setups.

Electrospray performance of interacting multi-capillary emitters in a linear array

NASA Astrophysics Data System (ADS)

Kumar, V.; Srivastava, A.; Shanbhogue, K. M.; Ingersol, S.; Sen, A. K.

2018-03-01

Here, we report electrospray performance of multiple emitters (of internal diameter 200 µm) arranged in a linear (inline) array. For a fixed flow rate Q , at higher voltages {{V}a} , multi-jet mode is observed, which leads to a rapid increase in the spray current (I∼ {{V}a} ) as compared to the single cone-jet case (I∼ Va0.8 ). A theoretical model is presented that predicts (within 10% of experimental data) the divergence of sprays g(x) issued from a pair of interacting emitters due to the mutual Columbic interaction of space charges. The variation of onset voltage {{V}o} and spray current I with spacing between the emitters p is studied and it is found that {{V}o}∼ {{p}-0.2} and I∼ {{p}0.8} . The effect of the flow rate Q , voltage V and number of emitters ~n~ on the spray current I is investigated and it is found that I∼ {{Q}0.5} , I∼ Va0.8 and I∼ \\sqrt{n} . The present work provides insight regarding the behavior of interacting sprays in an inline configuration and could be significant in the design of multiple emitter systems for electrospray applications.

A multiple-scattering polaritonic-operator method for hybrid arrays of metal nanoparticles and quantum emitters

NASA Astrophysics Data System (ADS)

Chatzidakis, Georgios D.; Yannopapas, Vassilios

2018-05-01

We present a new technique for the study of hybrid collections of quantum emitters (atoms, molecules, quantum dots) with nanoparticles. The technique is based on a multiple-scattering polaritonic-operator formalism in conjunction with an electromagnetic coupled dipole method. Apart from collections of quantum emitters and nanoparticles, the method can equally treat the interaction of a collection of quantum emitters with a single nano-object of arbitrary shape in which case the nano-object is treated as a finite three-dimensional lattice of point scatterers. We have applied our method to the case of linear array (chain) of dimers of quantum emitters and metallic nanoparticles wherein the corresponding (geometrical and physical) parameters of the dimers are chosen so as the interaction between the emitter and the nanoparticle lies in the strong-coupling regime in order to enable the formation of plexciton states in the dimer. In particular, for a linear chain of dimers, we show that the corresponding light spectra reveal a multitude of plexciton modes resulting from the hybridization of the plexciton resonances of each individual dimer in a manner similar to the tight-binding description of electrons in solids.

Optimization of manufacturing of emitter-coupled logic to decrease surface of chip

NASA Astrophysics Data System (ADS)

Pankratov, E. L.; Bulaeva, E. A.

2015-11-01

In this paper, we introduce an approach to increase integration rate of bipolar heterotransistors. The approach based on doping of required parts of heterostructure by diffusion or implantation and optimization of annealing of dopant and/or radiation defects. As simplification of the considered approach to increase integration rate we consider possibility to used common collector.

High reliability and high performance of 9xx-nm single emitter laser diodes

NASA Astrophysics Data System (ADS)

Bao, L.; Leisher, P.; Wang, J.; Devito, M.; Xu, D.; Grimshaw, M.; Dong, W.; Guan, X.; Zhang, S.; Bai, C.; Bai, J. G.; Wise, D.; Martinsen, R.

2011-03-01

Improved performance and reliability of 9xx nm single emitter laser diodes are presented. To date, over 15,000 hours of accelerated multi-cell lifetest reliability data has been collected, with drive currents from 14A to 18A and junction temperatures ranging from 60°C to 110°C. Out of 208 devices, 14 failures have been observed so far. Using established accelerated lifetest analysis techniques, the effects of temperature and power acceleration are assessed. The Mean Time to Failure (MTTF) is determined to be >30 years, for use condition 10W and junction temperature 353K (80°C), with 90% statistical confidence.

Visible high power fiber coupled diode lasers

NASA Astrophysics Data System (ADS)

Köhler, Bernd; Drovs, Simon; Stoiber, Michael; Dürsch, Sascha; Kissel, Heiko; Könning, Tobias; Biesenbach, Jens; König, Harald; Lell, Alfred; Stojetz, Bernhard; Löffler, Andreas; Strauß, Uwe

2018-02-01

In this paper we report on further development of fiber coupled high-power diode lasers in the visible spectral range. New visible laser modules presented in this paper include the use of multi single emitter arrays @ 450 nm leading to a 120 W fiber coupled unit with a beam quality of 44 mm x mrad, as well as very compact modules with multi-W output power from 405 nm to 640 nm. However, as these lasers are based on single emitters, power scaling quickly leads to bulky laser units with a lot of optical components to be aligned. We also report on a new approach based on 450 nm diode laser bars, which dramatically reduces size and alignment effort. These activities were performed within the German government-funded project "BlauLas": a maximum output power of 80 W per bar has been demonstrated @ 450 nm. We show results of a 200 μm NA0.22 fiber coupled 35 W source @ 450 nm, which has been reduced in size by a factor of 25 compared to standard single emitter approach. In addition, we will present a 200 μm NA0.22 fiber coupled laser unit with an output power of 135 W.

Vacancy-impurity centers in diamond: prospects for synthesis and applications

NASA Astrophysics Data System (ADS)

Ekimov, E. A.; Kondrin, M. V.

2017-06-01

The bright luminescence of impurity-vacancy complexes, combined with high chemical and radiation resistance, makes diamond an attractive platform for the production of single-photon emitters and luminescent biomarkers for applications in nanoelectronics and medicine. Two representatives of this kind of defects in diamond, silicon-vacancy (SiV) and germanium-vacancy (GeV) centers, are discussed in this review; their similarities and differences are demonstrated in terms of the more thoroughly studied nitrogen-vacancy (NV) complexes. The recent discovery of GeV luminescent centers opens a unique opportunity for the controlled synthesis of single-photon emitters in nanodiamonds. We demonstrate prospects for the high-pressure high-temperature (HPHT) technique to create single-photon emitters, not only as an auxiliary to chemical vapor deposition (CVD) and ion-implantation methods but also as a primary synthesis tool for producing color centers in nanodiamonds. Besides practical applications, comparative studies of these two complexes, which belong to the same structural class of defects, have a fundamental importance for deeper understanding of shelving levels, the electronic structure, and optical properties of these centers. In conclusion, we discuss several open problems regarding the structure, charge state, and practical application of these centers, which still require a solution.

Nanoscale probing of image-dipole interactions in a metallic nanostructure

PubMed Central

Ropp, Chad; Cummins, Zachary; Nah, Sanghee; Fourkas, John T.; Shapiro, Benjamin; Waks, Edo

2015-01-01

An emitter near a surface induces an image dipole that can modify the observed emission intensity and radiation pattern. These image-dipole effects are generally not taken into account in single-emitter tracking and super-resolved imaging applications. Here we show that the interference between an emitter and its image dipole induces a strong polarization anisotropy and a large spatial displacement of the observed emission pattern. We demonstrate these effects by tracking the emission of a single quantum dot along two orthogonal polarizations as it is deterministically positioned near a silver nanowire. The two orthogonally polarized diffraction spots can be displaced by up to 50 nm, which arises from a Young’s interference effect between the quantum dot and its induced image dipole. We show that the observed spatially varying interference fringe provides a useful measure for correcting image-dipole-induced distortions. These results provide a pathway towards probing and correcting image-dipole effects in near-field imaging applications. PMID:25790228

22 W coherent GaAlAs amplifier array with 400 emitters

NASA Technical Reports Server (NTRS)

Krebs, D.; Herrick, R.; No, K.; Harting, W.; Struemph, F.

1991-01-01

Greater than 22 W of optical power has been demonstrated from a multiple-emitter, traveling-wave semiconductor amplifier, with approximately 87 percent of the output at the frequency of the injection source. The device integrates, in AlGaAs graded-index separate-confinement heterostructure single quantum well (GRINSCH-SQW) epitaxy, 400 ridge waveguide amplifiers with a coherent optical signal distribution circuit on a 12 x 6 mm chip.

Heterojunction solar cell

DOEpatents

Olson, J.M.

1994-08-30

A high-efficiency single heterojunction solar cell is described wherein a thin emitter layer (preferably Ga[sub 0.52]In[sub 0.48]P) forms a heterojunction with a GaAs absorber layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the emitter layer. 1 fig.

Field ion microscopic studies of the CO oxidation on platinum: Field ion imaging and titration reactions

NASA Astrophysics Data System (ADS)

Gorodetskii, V.; Drachsel, W.; Block, J. H.

1994-05-01

Elementary steps of the CO oxidation—which are important for understanding the oscillatory behavior of this catalytic reaction—are investigated simultaneously on different Pt-single crystal surfaces by field ion microscopy. Due to preferential ionization probabilities of oxygen as imaging gas on those surface sites, which are adsorbed with oxygen, these sites can be imaged in a lateral resolution on the atomic scale. In the titration reaction a COad-precovered field emitter surface reacts with gaseous oxygen adsorbed from the gas phase or, vice versa, the Oad-precovered surface with carbon monoxide adsorbed from the gas phase. The competition of the manifold of single crystal planes exposed to the titration reaction at the field emitter tip is studied. The surface specificity can be documented in the specific reaction delay times of the different planes and in the propagation rates of the reaction-diffusion wave fronts measured on these individual planes during the titration reaction with a time resolution of 40 ms. At 300 K the COad-precovered surfaces display the {011} regions, precisely the {331} planes as the most active, followed by {012}, {122}, {001}, and finally by {111}. Reaction wave fronts move with a velocity of 8 Å/s at {012}, with ≊0.8 Å/s at {111}, and have a very fast ``switch-on'' reaction at the (001) plane with 500 Å/s. At higher temperature, T=350 K, an acceleration of reaction rates is combined with shorter delay times. The titration reaction of a precovered Oad surface with COgas at T=373 K shows the formation of CO islands starting in the {011} regions with a quickly moving reaction front into the other surface areas without showing particular delay times for different surface symmetries. The two reverse titration reactions have a largely different character. The titration of COad with oxygen adsorbed from the gas phase consists of three different steps, (i) the induction times, (ii) the highly surface specific reaction, and (iii) different rates of wave front propagation. The reaction of COgas with a precovered Oad layer on the other hand starts with nucleating islands around the {011} planes from where the whole emitter surface is populated with COad without pronounced surface specifity.

Design of 150W, 105-μm, 0.22NA, fiber coupled laser diode module by ZEMAX

NASA Astrophysics Data System (ADS)

Qi, Yunfei; Zhao, Pengfei; Chen, Qing; Wu, Yulong; Chen, Yongqi; Zou, Yonggang; Lin, Xuechun

2016-10-01

We represent a design of a high brightness, fiber coupled diode laser module based on 16 single emitters at 915nm. The module can produce more than 150 Watts output power from a standard fiber with core diameter of 105μm and numerical aperture (NA) of 0.22. To achieve a high power and high brightness laser beam, the spatial beam combination and polarization beam combination are used to combine output of 16 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation show that the total coupling efficiency is more than 95% and the highest brightness is estimated to be 11MW/ (cm2*sr).

Parametric emittance measurements of electron beams produced by a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Barber, S. K.; van Tilborg, J.; Schroeder, C. B.; Lehe, R.; Tsai, H.-E.; Swanson, K. K.; Steinke, S.; Nakamura, K.; Geddes, C. G. R.; Benedetti, C.; Esarey, E.; Leemans, W. P.

2018-05-01

Laser plasma accelerators (LPA) offer an exciting possibility to deliver high energy, high brightness electrons beams in drastically smaller distance scales than is typical for conventional accelerators. As such, LPAs draw considerable attention as potential drivers for next generation light sources and for a compact linear collider. In order to asses the viability of an LPA source for a particular application, the brightness of the source should be properly characterized. In this paper, we present charge dependent transverse emittance measurements of LPA sources using both ionization injection and shock induced density down ramp injection, with the latter delivering smaller transverse emittances by a factor of two when controlling for charge density. The single shot emittance method is described in detail with a discussion on limitations related to second order transport effects. The direct role of space charge is explored through a series of simulations and found to be consistent with experimental observations.

Mapping Nanoscale Hotspots with Single-Molecule Emitters Assembled into Plasmonic Nanocavities Using DNA Origami

PubMed Central

2017-01-01

Fabricating nanocavities in which optically active single quantum emitters are precisely positioned is crucial for building nanophotonic devices. Here we show that self-assembly based on robust DNA-origami constructs can precisely position single molecules laterally within sub-5 nm gaps between plasmonic substrates that support intense optical confinement. By placing single-molecules at the center of a nanocavity, we show modification of the plasmon cavity resonance before and after bleaching the chromophore and obtain enhancements of ≥4 × 103 with high quantum yield (≥50%). By varying the lateral position of the molecule in the gap, we directly map the spatial profile of the local density of optical states with a resolution of ±1.5 nm. Our approach introduces a straightforward noninvasive way to measure and quantify confined optical modes on the nanoscale. PMID:29166033

Self-Assembled Nanocrystals of Polycyclic Aromatic Hydrocarbons Show Photostable Single-Photon Emission.

PubMed

Pazzagli, Sofia; Lombardi, Pietro; Martella, Daniele; Colautti, Maja; Tiribilli, Bruno; Cataliotti, Francesco Saverio; Toninelli, Costanza

2018-05-22

Quantum technologies could largely benefit from the control of quantum emitters in sub-micrometric size crystals. These are naturally prone to integration in hybrid devices, including heterostructures and complex photonic devices. Currently available quantum emitters in nanocrystals suffer from spectral instability, preventing their use as single-photon sources for most quantum optics operations. In this work we report on the performances of single-photon emission from organic nanocrystals (average size of hundreds of nm), made of anthracene (Ac) and doped with dibenzoterrylene (DBT) molecules. The source has hours-long photostability with respect to frequency and intensity, both at room and at cryogenic temperature. When cooled to 3 K, the 00-zero phonon line shows linewidth values (50 MHz) close to the lifetime limit. Such optical properties in a nanocrystalline environment recommend the proposed organic nanocrystals as single-photon sources for integrated photonic quantum technologies.

Mapping Nanoscale Hotspots with Single-Molecule Emitters Assembled into Plasmonic Nanocavities Using DNA Origami

NASA Astrophysics Data System (ADS)

Chikkaraddy, Rohit; Turek, V. A.; Kongsuwan, Nuttawut; Benz, Felix; Carnegie, Cloudy; van de Goor, Tim; de Nijs, Bart; Demetriadou, Angela; Hess, Ortwin; Keyser, Ulrich F.; Baumberg, Jeremy J.

2018-01-01

Fabricating nanocavities in which optically-active single quantum emitters are precisely positioned, is crucial for building nanophotonic devices. Here we show that self-assembly based on robust DNA-origami constructs can precisely position single molecules laterally within sub-5nm gaps between plasmonic substrates that support intense optical confinement. By placing single-molecules at the center of a nanocavity, we show modification of the plasmon cavity resonance before and after bleaching the chromophore, and obtain enhancements of $\\geq4\\times10^3$ with high quantum yield ($\\geq50$%). By varying the lateral position of the molecule in the gap, we directly map the spatial profile of the local density of optical states with a resolution of $\\pm1.5$ nm. Our approach introduces a straightforward non-invasive way to measure and quantify confined optical modes on the nanoscale.

Single-photon non-linear optics with a quantum dot in a waveguide

NASA Astrophysics Data System (ADS)

Javadi, A.; Söllner, I.; Arcari, M.; Hansen, S. Lindskov; Midolo, L.; Mahmoodian, S.; Kiršanskė, G.; Pregnolato, T.; Lee, E. H.; Song, J. D.; Stobbe, S.; Lodahl, P.

2015-10-01

Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.

On the feasibility of sub-100 nm rad emittance measurement in plasma accelerators using permanent magnetic quadrupoles

NASA Astrophysics Data System (ADS)

Li, F.; Wu, Y. P.; Nie, Z.; Guo, B.; Zhang, X. H.; Huang, S.; Zhang, J.; Cheng, Z.; Ma, Y.; Fang, Y.; Zhang, C. J.; Wan, Y.; Xu, X. L.; Hua, J. F.; Pai, C. H.; Lu, W.; Gu, Y. Q.

2018-01-01

Low emittance (sub-100 nm rad) measurement of electron beams in plasma accelerators has been a challenging issue for a while. Among various measurement schemes, measurements based on single-shot quad-scan using permanent magnetic quadrupoles (PMQs) has been recently reported with emittance as low as ˜200 nm Weingartner (2012 Phys. Rev. Spec. Top. Accel. Beams 15 111302). However, the accuracy and reliability of this method have not been systematically analyzed. Such analysis is critical for evaluating the potential of sub-100 nm rad emittance measurement using any scheme. In this paper, we analyze the effects of various nonideal physical factors on the accuracy and reliability using the PMQ method. These factors include aberration induced by a high order field, PMQ misalignment and angular fluctuation of incoming beams. Our conclusions are as follows: (i) the aberrations caused by high order fields of PMQs are relatively weak for low emittance measurement as long as the PMQs are properly constructed. A series of PMQs were manufactured and measured at Tsinghua University, and using numerical simulations their high order field effects were found to be negligible . (ii) The largest measurement error of emittance is caused by the angular misalignment between PMQs. For low emittance measurement of ˜100 MeV beams, an angular alignment accuracy of 0.1° is necessary. This requirement can be eased for beams with higher energies. (iii) The transverse position misalignment of PMQs and angular fluctuation of incoming beams only cause a translational and rotational shift of measured signals, respectively, therefore, there is no effect on the measured value of emittance. (iv) The spatial resolution and efficiency of the detection system need to be properly designed to guarantee the accuracy of sub-100 nm rad emittance measurement.

20-mN Variable Specific Impulse (Isp) Colloid Thruster

NASA Technical Reports Server (NTRS)

Demmons, Nathaniel

2015-01-01

Busek Company, Inc., has designed and manufactured an electrospray emitter capable of generating 20 mN in a compact package (7x7x1.7 in). The thruster consists of nine porous-surface emitters operating in parallel from a common propellant supply. Each emitter is capable of supporting over 70,000 electrospray emission sites with the plume from each emitter being accelerated through a single aperture, eliminating the need for individual emission site alignment to an extraction grid. The total number of emission sites during operation is expected to approach 700,000. This Phase II project optimized and characterized the thruster fabricated during the Phase I effort. Additional porous emitters also were fabricated for full-scale testing. Propellant is supplied to the thruster via existing feed-system and microvalve technology previously developed by Busek, under the NASA Space Technology 7's Disturbance Reduction System (ST7-DRS) mission and via follow-on electric propulsion programs. This project investigated methods for extending thruster life beyond the previously demonstrated 450 hours. The life-extending capabilities will be demonstrated on a subscale version of the thruster.

Design and Development of Emittance Measurement Device by Using the Pepper-pot Technique

NASA Astrophysics Data System (ADS)

Pakluea, S.; Rimjaem, S.

2017-09-01

Transverse emittance of a charged particle beam is one of the most important properties that reveals the quality of the beam. It is related to charge density, transvers size and angular displacement of the beam in transverse phase space. There are several techniques to measure the transverse emittance value. One of practical methods is the pepper-pot technique, which can measure both horizontal and vertical emittance value in a single measurement. This research concentrates on development of a pepper-pot device to measure the transverse emittance of electron beam produced from an accelerator injector system, which consists of a thermionic cathode RF electron gun and an alpha magnet, at the Plasma and Beam Physics Research Facility, Chiang Mai University. Simulation of beam dynamics was conducted with programs PARMELA, ELEGANT and self-developed codes using C and MATLAB. The geometry, dimensions and location of the pepper-pot as well as its corresponding screen station position were included in the simulation. The result from this study will be used to design and develop a practical pepper-pot experimental station.

Variations in the concentration of plutonium, strontium-90 and total alpha-emitters in human teeth collected within the British Isles.

PubMed

O'Donnell, R G; Mitchell, P I; Priest, N D; Strange, L; Fox, A; Henshaw, D L; Long, S C

1997-08-18

Concentrations of plutonium-239, plutonium-240, strontium-90 and total alpha-emitters have been measured in children's teeth collected throughout Great Britain and Ireland. The concentrations of plutonium and strontium-90 were measured in batched samples, each containing approximately 50 teeth, using low-background radiochemical methods. The concentrations of total alpha-emitters were determined in single teeth using alpha-sensitive plastic track detectors. The results showed that the average concentrations of total alpha-emitters and strontium-90 were approximately one to three orders of magnitude greater than the equivalent concentrations of plutonium-239,240. Regression analyses indicated that the concentrations of plutonium, but not strontium-90 or total alpha-emitters, decreased with increasing distance from the Sellafield nuclear fuel reprocessing plant-suggesting that this plant is a source of plutonium contamination in the wider population of the British Isles. Nevertheless, the measured absolute concentrations of plutonium (mean = 5 +/- 4 mBq kg-1 ash wt.) were so low that they are considered to present an insignificant radiological hazard.

Coherent beam combining architectures for high power tapered laser arrays

NASA Astrophysics Data System (ADS)

Schimmel, G.; Janicot, S.; Hanna, M.; Decker, J.; Crump, P.; Erbert, G.; Witte, U.; Traub, M.; Georges, P.; Lucas-Leclin, G.

2017-02-01

Coherent beam combining (CBC) aims at increasing the spatial brightness of lasers. It consists in maintaining a constant phase relationship between different emitters, in order to combine them constructively in one single beam. We have investigated the CBC of an array of five individually-addressable high-power tapered laser diodes at λ = 976 nm, in two architectures: the first one utilizes the self-organization of the lasers in an interferometric extended-cavity, which ensures their mutual coherence; the second one relies on the injection of the emitters by a single-frequency laser diode. In both cases, the coherent combining of the phase-locked beams is ensured on the front side of the array by a transmission diffractive grating with 98% efficiency. The passive phase-locking of the laser bar is obtained up to 5 A (per emitter). An optimization algorithm is implemented to find the proper currents in the five ridge sections that ensured the maximum combined power on the front side. Under these conditions we achieve a maximum combined power of 7.5 W. In the active MOPA configuration, we can increase the currents in the tapered sections up to 6 A and get a combined power of 11.5 W, corresponding to a combining efficiency of 76%. It is limited by the beam quality of the tapered emitters and by fast phase fluctuations between emitters. Still, these results confirm the potential of CBC approaches with tapered lasers to provide a high-power and high-brightness beam, and compare with the current state-of-the-art with laser diodes.

Ultra-bright emission from hexagonal boron nitride defects as a new platform for bio-imaging and bio-labelling

NASA Astrophysics Data System (ADS)

Elbadawi, Christopher; Tran, Trong Toan; Shimoni, Olga; Totonjian, Daniel; Lobo, Charlene J.; Grosso, Gabriele; Moon, Hyowan; Englund, Dirk R.; Ford, Michael J.; Aharonovich, Igor; Toth, Milos

2016-12-01

Bio-imaging requires robust ultra-bright probes without causing any toxicity to the cellular environment, maintain their stability and are chemically inert. In this work we present hexagonal boron nitride (hBN) nanoflakes which exhibit narrowband ultra-bright single photon emitters1. The emitters are optically stable at room temperature and under ambient environment. hBN has also been noted to be noncytotoxic and seen significant advances in functionalization with biomolecules2,3. We further demonstrate two methods of engineering this new range of extremely robust multicolour emitters across the visible and near infrared spectral ranges for large scale sensing and biolabeling applications.

Evidence of universal inverse-third power law for the shielding-induced fractional decrease in apex field enhancement factor at large spacings: a response via accurate Laplace-type calculations.

PubMed

de Assis, Thiago A; Dall'Agnol, Fernando F

2018-05-16

Numerical simulations are important when assessing the many characteristics of field emission related phenomena. In small simulation domains, the electrostatic effect from the boundaries is known to influence the calculated apex field enhancement factor (FEF) of the emitter, but no established dependence has been reported at present. In this work, we report the dependence of the lateral size, L, and the height, H, of the simulation domain on the apex-FEF of a single conducting ellipsoidal emitter. Firstly, we analyze the error, ε, in the calculation of the apex-FEF as a function of H and L. Importantly, our results show that the effects of H and L on ε are scale invariant, allowing one to predict ε for ratios L/h and H/h, where h is the height of the emitter. Next, we analyze the fractional change of the apex-FEF, δ, from a single emitter, [Formula: see text], and a pair, [Formula: see text]. We show that small relative errors in [Formula: see text] (i.e. [Formula: see text]), due to the finite domain size, are sufficient to alter the functional dependence [Formula: see text], where c is the distance from the emitters in the pair. We show that [Formula: see text] obeys a recently proposed power law decay (Forbes 2016 J. Appl. Phys. 120 054302), at sufficiently large distances in the limit of infinite domain size ([Formula: see text], say), which is not observed when using a long time established exponential decay (Bonard et al 2001 Adv. Mater. 13 184) or a more sophisticated fitting formula proposed recently by Harris et al (2015 AIP Adv. 5 087182). We show that the inverse-third power law functional dependence is respected for various systems like infinity arrays and small clusters of emitters with different shapes. Thus, [Formula: see text], with m  =  3, is suggested to be a universal signature of the charge-blunting effect in small clusters or arrays, at sufficient large distances between emitters with any shape. These results improve the physical understanding of the field electron emission theory to accurately characterize emitters in small clusters or arrays.

Homojunction GaAs solar cells grown by close space vapor transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boucher, Jason W.; Ritenour, Andrew J.; Greenaway, Ann L.

2014-06-08

We report on the first pn junction solar cells grown by homoepitaxy of GaAs using close space vapor transport (CSVT). Cells were grown both on commercial wafer substrates and on a CSVT absorber film, and had efficiencies reaching 8.1%, open circuit voltages reaching 909 mV, and internal quantum efficiency of 90%. The performance of these cells is partly limited by the electron diffusion lengths in the wafer substrates, as evidenced by the improved peak internal quantum efficiency in devices fabricated on a CSVT absorber film. Unoptimized highly-doped n-type emitters also limit the photocurrent, indicating that thinner emitters with reduced doping,more » and ultimately wider band gap window or surface passivation layers, are required to increase the efficiency.« less

A straightforward approach for gated STED-FCS to investigate lipid membrane dynamics

PubMed Central

Clausen, Mathias P.; Sezgin, Erdinc; Bernardino de la Serna, Jorge; Waithe, Dominic; Lagerholm, B. Christoffer; Eggeling, Christian

2015-01-01

Recent years have seen the development of multiple technologies to investigate, with great spatial and temporal resolution, the dynamics of lipids in cellular and model membranes. One of these approaches is the combination of far-field super-resolution stimulated-emission-depletion (STED) microscopy with fluorescence correlation spectroscopy (FCS). STED-FCS combines the diffraction-unlimited spatial resolution of STED microscopy with the statistical accuracy of FCS to determine sub-millisecond-fast molecular dynamics with single-molecule sensitivity. A unique advantage of STED-FCS is that the observation spot for the FCS data recordings can be tuned to sub-diffraction scales, i.e. <200 nm in diameter, in a gradual manner to investigate fast diffusion of membrane-incorporated labelled entities. Unfortunately, so far the STED-FCS technology has mostly been applied on a few custom-built setups optimised for far-red fluorescent emitters. Here, we summarise the basics of the STED-FCS technology and highlight how it can give novel details into molecular diffusion modes. Most importantly, we present a straightforward way for performing STED-FCS measurements on an unmodified turnkey commercial system using a time-gated detection scheme. Further, we have evaluated the STED-FCS performance of different commonly used green emitting fluorescent dyes applying freely available, custom-written analysis software. PMID:26123184

Report on the CCT Supplementary Comparison S1 of Infrared Spectral Normal Emittance/Emissivity

PubMed Central

Hanssen, Leonard; Wilthan, B.; Monte, Christian; Hollandt, Jörg; Hameury, Jacques; Filtz, Jean-Remy; Girard, Ferruccio; Battuello, Mauro; Ishii, Juntaro

2016-01-01

The National Measurement Institutes (NMIs) of the United States, Germany, France, Italy and Japan, have joined in an inter-laboratory comparison of their infrared spectral emittance scales. This action is part of a series of supplementary inter-laboratory comparisons (including thermal conductivity and thermal diffusivity) sponsored by the Consultative Committee on Thermometry (CCT) Task Group on Thermophysical Quantities (TG-ThQ). The objective of this collaborative work is to strengthen the major operative National Measurement Institutes’ infrared spectral emittance scales and consequently the consistency of radiative properties measurements carried out worldwide. The comparison has been performed over a spectral range of 2 μm to 14 μm, and a temperature range from 23 °C to 800 °C. Artefacts included in the comparison are potential standards: oxidized inconel, boron nitride, and silicon carbide. The measurement instrumentation and techniques used for emittance scales are unique for each NMI, including the temperature ranges covered as well as the artefact sizes required. For example, all three common types of spectral instruments are represented: dispersive grating monochromator, Fourier transform and filter-based spectrometers. More than 2000 data points (combinations of material, wavelength and temperature) were compared. Ninety-eight percent (98%) of the data points were in agreement, with differences to weighted mean values less than the expanded uncertainties calculated from the individual NMI uncertainties and uncertainties related to the comparison process. PMID:28239193

Ultimate high power operation of 9xx-nm single emitter broad stripe laser diodes

NASA Astrophysics Data System (ADS)

Kaifuchi, Yoshikazu; Yamagata, Yuji; Nogawa, Ryozaburo; Morohashi, Rintaro; Yamada, Yumi; Yamaguchi, Masayuki

2017-02-01

Design optimization of single emitter broad stripe 9xx-nm laser diodes was studied to achieve ultimate high power and high efficiency operation for a use in fiber laser pumping and other industrial applications. We tuned laser vertical layer design and stripe width in terms of optical confinement as well as electrical resistance. As a result, newly designed LDs with 4mm-long cavity and 220 μm-wide stripe successfully demonstrate maximum CW output power as high as 33 W and high efficiency operation of more than 60 % PCE even at 27 W output power. In pulse measurement, the maximum output of 68 W was obtained.

Status of Diffused Junction p(+)n InP Solar Cells for Space Applications

NASA Technical Reports Server (NTRS)

Faur, Mircea; Faur, Maria; Flood, D. J.; Brinker, D. J.; Goradia, C.; Fatemi, N. S.; Jenkins, P. P.; Wilt, D. M.; Bailey, S.

1994-01-01

Recently, we have succeeded in fabricating diffused junction p(+)n(Cd,S) InP solar cells with measured AMO, 25 C open circuit voltage (V(sub OC)) of 887.6 mV, which, to the best of our knowledge, is higher than previously reported V(sub OC) values for any InP homojunction solar cells. The experiment-based projected achievable efficiency of these cells using LEC grown substrates is 21.3%. The maximum AMO, 25 C efficiency recorded to date on bare cells is, however, only 13.2%. This is because of large external and internal losses due to non-optimized front grid design, antireflection (AR) coating and emitter thickness. This paper summarizes recent advances in the technology of fabrication of p(+)n InP diffused structures and solar cells, resulted from a study undertaken in an effort to increase the cell efficiency. The topics discussed in this paper include advances in: 1) the formation of thin p(+) InP:Cd emitter layers, 2) electroplated front contacts, 3) surface passivation and 4) the design of a new native oxide/AI203/MgF2 three layer AR coating using a chemically-grown P-rich passivating oxide as a first layer. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.

Photon pair source via two coupling single quantum emitters

NASA Astrophysics Data System (ADS)

Peng, Yong-Gang; Zheng, Yu-Jun

2015-10-01

We study the two coupling two-level single molecules driven by an external field as a photon pair source. The probability of emitting two photons, P2, is employed to describe the photon pair source quality in a short time, and the correlation coefficient RAB is employed to describe the photon pair source quality in a long time limit. The results demonstrate that the coupling single quantum emitters can be considered as a stable photon pair source. Project supported by the National Natural Science Foundation of China (Grand Nos. 91021009, 21073110, and 11374191), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2013AQ020), the Postdoctoral Science Foundation of China (Grant No. 2013M531584), the Doctoral Program of Higher Education of China (Grant Nos. 20130131110005 and 20130131120006), and the Taishan Scholarship Project of Shandong Province, China.

Processes for producing low cost, high efficiency silicon solar cells

DOEpatents

Rohatgi, Ajeet; Chen, Zhizhang; Doshi, Parag

1996-01-01

Processes which utilize rapid thermal processing (RTP) are provided for inexpensively producing high efficiency silicon solar cells. The RTP processes preserve minority carrier bulk lifetime .tau. and permit selective adjustment of the depth of the diffused regions, including emitter and back surface field (bsf), within the silicon substrate. Silicon solar cell efficiencies of 16.9% have been achieved. In a first RTP process, an RTP step is utilized to simultaneously diffuse phosphorus and aluminum into the front and back surfaces, respectively, of a silicon substrate. Moreover, an in situ controlled cooling procedure preserves the carrier bulk lifetime .tau. and permits selective adjustment of the depth of the diffused regions. In a second RTP process, both simultaneous diffusion of the phosphorus and aluminum as well as annealing of the front and back contacts are accomplished during the RTP step. In a third RTP process, the RTP step accomplishes simultaneous diffusion of the phosphorus and aluminum, annealing of the contacts, and annealing of a double-layer antireflection/passivation coating SiN/SiO.sub.x.

Microstructure and thermal stability of Cu/Zr0.3Al0.7N/Zr0.2Al0.8N/Al34O60N6 cermet-based solar selective absorbing coatings

NASA Astrophysics Data System (ADS)

Meng, Jian-ping; Guo, Rui-rui; Li, Hu; Zhao, Lu-ming; Liu, Xiao-peng; Li, Zhou

2018-05-01

Solar selective absorbing coatings play a valuable role in photo-thermal conversion for high efficiency concentrating solar power systems (CSP). In this paper, a novel Cu/Zr0.3Al0.7N/Zr0.2Al0.8N/Al34O60N6 cermet-based solar selective absorbing coating was successfully deposited by ion beam assisted deposition. The optical properties, microstructure and element distribution in depth were investigated by spectroscopic ellipsometry, UV-vis-NIR spectrophotometer, transmission electron microscope (TEM) and Auger electron spectroscopy (AES), respectively. A high absorptance of 0.953 and a low thermal emittance of 0.079 at 400 °C are obtained by the integral computation according to the whole reflectance from 300 nm to 28,800 nm. After annealing treatment at 400 °C (in vacuum) for 192 h, the deposited coating exhibits the high thermal stability. Whereas, the photothermal conversion efficiency decreases from 12.10 to 6.86 due to the emittance increase after annealing at 600 °C for 192 h. Meanwhile, the nitrogen atom in the Zr0.3Al0.7N sub-layer diffuses toward the adjacent sub-layer due to the spinodal decomposition of metastable c-ZrAlN and the phase transition from c-AlN to h-AlN, which leads to the composition of the Zr0.3Al0.7N sub-layer deviates the initial design. This phenomenon has a guide effect for the thermal-stability improvement of cermet coatings. Additionally, a serious diffusion between copper and silicon substrate also contributes to the emittance increase.

Studies in High Current Density Ion Sources for Heavy Ion Fusion Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacon-Golcher, Edwin

This dissertation develops diverse research on small (diameter ~ few mm), high current density (J ~ several tens of mA/cm 2) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield () at different operating conditions are presented for K + and Cs + contact ionization sources and potassium aluminum silicate sources. Maximum valuesmore » for a K + beam of ~90 mA/cm 2 were observed in 2.3 μs pulses. Measurements of beam intensity profiles and emittances are included. Measurements of neutral particle desorption are presented at different operating conditions which lead to a better understanding of the underlying atomic diffusion processes that determine the lifetime of the emitter. Estimates of diffusion times consistent with measurements are presented, as well as estimates of maximum repetition rates achievable. Diverse studies performed on the composition and preparation of alkali aluminosilicate ion sources are also presented. In addition, this work includes preliminary work carried out exploring the viability of an argon plasma ion source and a bismuth metal vapor vacuum arc (MEVVA) ion source. For the former ion source, fast rise-times (~ 1 μs), high current densities (~ 100 mA/cm +) and low operating pressures (< 2 mtorr) were verified. For the latter, high but acceptable levels of beam emittance were measured (ε n ≤ 0.006 π· mm · mrad) although measured currents differed from the desired ones (I ~ 5mA) by about a factor of 10.« less

Novel high-brightness fiber coupled diode laser device

NASA Astrophysics Data System (ADS)

Haag, Matthias; Köhler, Bernd; Biesenbach, Jens; Brand, Thomas

2007-02-01

High brightness becomes more and more important in diode laser applications for fiber laser pumping and materials processing. For OEM customers fiber coupled devices have great advantages over direct beam modules: the fiber exit is a standardized interface, beam guiding is easy with nearly unlimited flexibility. In addition to the transport function the fiber serves as homogenizer: the beam profile of the laser radiation emitted from a fiber is symmetrical with highly repeatable beam quality and pointing stability. However, efficient fiber coupling requires an adaption of the slow-axis beam quality to the fiber requirements. Diode laser systems based on standard 10mm bars usually employ beam transformation systems to rearrange the highly asymmetrical beam of the laser bar or laser stack. These beam transformation systems (prism arrays, lens arrays, fiber bundles etc.) are expensive and become inefficient with increasing complexity. This is especially true for high power devices with small fiber diameters. On the other hand, systems based on single emitters are claimed to have good potential in cost reduction. Brightness of the inevitable fiber bundles, though, is limited due to inherent fill-factor losses. At DILAS a novel diode laser device has been developed combining the advantages of diode bars and single emitters: high brightness at high reliability with single emitter cost structure. Heart of the device is a specially tailored laser bar (T-Bar), which epitaxial and lateral structure was designed such that only standard fast- and slow-axis collimator lenses are required to couple the beam into a 200μm fiber. Up to 30 of these T-Bars of one wavelength can be combined to reach a total of > 500W ex fiber in the first step. Going to a power level of today's single emitter diodes even 1kW ex 200μm fiber can be expected.

Effect of increased crystallinity of single-walled carbon nanotubes used as field emitters on their electrical properties

NASA Astrophysics Data System (ADS)

Shimoi, Norihiro

2015-12-01

Single-walled carbon nanotubes (SWCNTs) synthesized by arc discharge are expected to exhibit good field emission (FE) properties at a low driving voltage. We used a coating containing homogeneously dispersed highly crystalline SWCNTs produced by a high-temperature annealing process to fabricate an FE device by a wet-coating process at a low cost. Using the coating, we succeeded in reducing the power consumption of field emitters for planar lighting devices. SWCNTs synthesized by arc discharge have crystal defects in the carbon network, which are considered to induce inelastic electron tunneling that deteriorates the electrical conductivity of the SWCNTs. In this study, the blocking of the transport of electrons in SWCNTs with crystal defects is simulated using an inelastic electron tunneling model. We succeeded in clarifying the mechanism underlying the electrical conductivity of SWCNTs by controlling their crystallinity. In addition, it was confirmed that field emitters using highly crystalline SWCNTs can lead to new applications operating with low power consumption and new devices that may change our daily lives in the future.

High-power laser diodes with high polarization purity

NASA Astrophysics Data System (ADS)

Rosenkrantz, Etai; Yanson, Dan; Peleg, Ophir; Blonder, Moshe; Rappaport, Noam; Klumel, Genady

2017-02-01

Fiber-coupled laser diode modules employ power scaling of single emitters for fiber laser pumping. To this end, techniques such as geometrical, spectral and polarization beam combining (PBC) are used. For PBC, linear polarization with high degree of purity is important, as any non-perfectly polarized light leads to losses and heating. Furthermore, PBC is typically performed in a collimated portion of the beams, which also cancels the angular dependence of the PBC element, e.g., beam-splitter. However, we discovered that single emitters have variable degrees of polarization, which depends both on the operating current and far-field divergence. We present data to show angle-resolved polarization measurements that correlate with the ignition of high-order modes in the slow-axis emission of the emitter. We demonstrate that the ultimate laser brightness includes not only the standard parameters such as power, emitting area and beam divergence, but also the degree of polarization (DoP), which is a strong function of the latter. Improved slow-axis divergence, therefore, contributes not only to high brightness but also high beam combining efficiency through polarization.

Effect of increased crystallinity of single-walled carbon nanotubes used as field emitters on their electrical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimoi, Norihiro, E-mail: shimoi@mail.kankyo.tohoku.ac.jp

2015-12-07

Single-walled carbon nanotubes (SWCNTs) synthesized by arc discharge are expected to exhibit good field emission (FE) properties at a low driving voltage. We used a coating containing homogeneously dispersed highly crystalline SWCNTs produced by a high-temperature annealing process to fabricate an FE device by a wet-coating process at a low cost. Using the coating, we succeeded in reducing the power consumption of field emitters for planar lighting devices. SWCNTs synthesized by arc discharge have crystal defects in the carbon network, which are considered to induce inelastic electron tunneling that deteriorates the electrical conductivity of the SWCNTs. In this study, themore » blocking of the transport of electrons in SWCNTs with crystal defects is simulated using an inelastic electron tunneling model. We succeeded in clarifying the mechanism underlying the electrical conductivity of SWCNTs by controlling their crystallinity. In addition, it was confirmed that field emitters using highly crystalline SWCNTs can lead to new applications operating with low power consumption and new devices that may change our daily lives in the future.« less

Single Spatial-Mode Room-Temperature-Operated 3.0 to 3.4 micrometer Diode Lasers

NASA Technical Reports Server (NTRS)

Frez, Clifford F.; Soibel, Alexander; Belenky, Gregory; Shterengas, Leon; Kipshidze, Gela

2010-01-01

Compact, highly efficient, 3.0 to 3.4 m light emitters are in demand for spectroscopic analysis and identification of chemical substances (including methane and formaldehyde), infrared countermeasures technologies, and development of advanced infrared scene projectors. The need for these light emitters can be currently addressed either by bulky solid-state light emitters with limited power conversion efficiency, or cooled Interband Cascade (IC) semiconductor lasers. Researchers here have developed a breakthrough approach to fabrication of diode mid-IR lasers that have several advantages over IC lasers used for the Mars 2009 mission. This breakthrough is due to a novel design utilizing the strain-engineered quantum-well (QW) active region and quinternary barriers, and due to optimization of device material composition and growth conditions (growth temperatures and rates). However, in their present form, these GaSb-based laser diodes cannot be directly used as a part of sensor systems. The device spectrum is too broad to perform spectroscopic analysis of gas species, and operating currents and voltages are too high. In the current work, the emitters were fabricated as narrow-ridge waveguide index-guided lasers rather than broad stripe-gain guided multimode Fabry-Perot (FP) lasers as was done previously. These narrow-ridge waveguide mid-IR lasers exhibit much lower power consumptions, and can operate in a single spatial mode that is necessary for demonstration of single-mode distributed feedback (DBF) devices for spectroscopic applications. These lasers will enable a new generation of compact, tunable diode laser spectrometers with lower power consumption, reduced complexity, and significantly reduced development costs. These lasers can be used for the detection of HCN, C2H2, methane, and ethane.

Highly efficient and stable white organic light emitting diode base on double recombination zones of phosphorescent blue/orange emitters.

PubMed

Lee, Seok Jae; Koo, Ja Ryong; Lim, Dong Hwan; Park, Hye Rim; Kim, Young Kwan; Ha, Yunkyoung

2011-08-01

We demonstrated efficient and stable white phosphorescent organic light-emitting diodes (OLEDs) with double-emitting layers (D-EMLs), which were comprised of two emissive layers with a hole transport-type host of N,N'-dicarbazolyl-3,5-benzene (mCP) and a electron transport-type host of 2,2',2"-(1,3,5-benzenetryl)tris(1-phenyl)-1H-benzimidazol (TPBi) with blue/orange emitters, respectively. We fabricated two type white devices with single emitting layer (S-EML) and D-EML of orange emitter, maintaining double recombination zone of blue emitter. In addition, the device architecture was developed to confine excitons inside the D-EMLs and to manage triplet excitons by controlling the charge injection. As a result, light-emitting performances of white OLED with D-EMLs were improved and showed the steady CIE coordinates compared to that with S-EML of orange emitter, which demonstrated the maximum luminous efficiency and external quantum efficiency were 21.38 cd/A and 11.09%. It also showed the stable white emission with CIE(x,y) coordinates from (x = 0.36, y = 0.37) at 6 V to (x = 0.33, y = 0.38) at 12 V.

Electrical characterisation of SiGe heterojunction bipolar transistors and Si pseudo-HBTS

NASA Astrophysics Data System (ADS)

De Barros, O.; Le Tron, B.; Woods, R. C.; Giroult-Matlakowski, G.; Vincent, G.; Brémond, G.

1996-08-01

This paper reports an electrical characterisation of the emitter-base junction of Si pseudo-HBTs and SiGe HBTs fabricated in a CMOS compatible single polysilicon self-aligned process. From the reverse characteristics it appears that the definition of the emitter-base junction by plasma etching induces peripheral defects that increase the base current of the transistors. Deep level transient spectroscopy measurements show a deep level in the case of SiGe base, whose spatial origin is not fully determinate up to now.

Cooperative emission of light by an ensemble of dipoles near a metal nanoparticle: the plasmonic Dicke effect.

PubMed

Pustovit, Vitaliy N; Shahbazyan, Tigran V

2009-02-20

We identify a new mechanism for cooperative emission of light by an ensemble of N dipoles near a metal nanostructure supporting a surface plasmon. The cross talk between emitters due to the virtual plasmon exchange leads to the formation of three plasmonic superradiant modes whose radiative decay rates scale with N, while the total radiated energy is thrice that of a single emitter. Our numerical simulations indicate that the plasmonic Dicke effect survives nonradiative losses in the metal.

A study of process-related electrical defects in SOI lateral bipolar transistors fabricated by ion implantation

NASA Astrophysics Data System (ADS)

Yau, J.-B.; Cai, J.; Hashemi, P.; Balakrishnan, K.; D'Emic, C.; Ning, T. H.

2018-04-01

We report a systematic study of process-related electrical defects in symmetric lateral NPN transistors on silicon-on-insulator (SOI) fabricated using ion implantation for all the doped regions. A primary objective of this study is to see if pipe defects (emitter-collector shorts caused by locally enhanced dopant diffusion) are a show stopper for such bipolar technology. Measurements of IC-VCE and Gummel currents in parallel-connected transistor chains as a function of post-fabrication rapid thermal anneal cycles allow several process-related electrical defects to be identified. They include defective emitter-base and collector-base diodes, pipe defects, and defects associated with a dopant-deficient region in an extrinsic base adjacent its intrinsic base. There is no evidence of pipe defects being a major concern in SOI lateral bipolar transistors.

Microcavity enhanced single photon emission from two-dimensional WSe2

NASA Astrophysics Data System (ADS)

Flatten, L. C.; Weng, L.; Branny, A.; Johnson, S.; Dolan, P. R.; Trichet, A. A. P.; Gerardot, B. D.; Smith, J. M.

2018-05-01

Atomically flat semiconducting materials such as monolayer WSe2 hold great promise for novel optoelectronic devices. Recently, quantum light emission has been observed from bound excitons in exfoliated WSe2. As part of developing optoelectronic devices, the control of the radiative properties of such emitters is an important step. Here, we report the coupling of a bound exciton in WSe2 to open microcavities. We use a range of radii of curvature in the plano-concave cavity geometry with mode volumes in the λ3 regime, giving Purcell factors of up to 8 while increasing the photon flux five-fold. Additionally, we determine the quantum efficiency of the single photon emitter to be η=0.46 ±0.03 . Our findings pave the way to cavity-enhanced monolayer based single photon sources for a wide range of applications in nanophotonics and quantum information technologies.

Design of 20 W fiber-coupled green laser diode by Zemax

NASA Astrophysics Data System (ADS)

Qi, Yunfei; Zhao, Pengfei; Wu, Yulong; Chen, Yongqi; Zou, Yonggang

2017-09-01

We represent a design of a 20 W, fiber-coupled diode laser module based on 26 single emitters at 520 nm. The module can produce more than 20 W output power from a standard fiber with core diameter of 400 μm and numerical aperture (NA) of 0.22. To achieve a 20 W laser beam, the spatial beam combination and polarization beam combination by polarization beam splitter are used to combine output of 26 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation shows that the total coupling efficiency is more than 95%. Project supported by the National Key R& D Program of China (No. 2016YFB0402105), the Key Deployment Program of the Chinese Academy of Sciences (No. KGZD-SW-T01-2), and the National Natural Science Foundation of China (No. 61404135).

Heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Guo-Zhu; Zhang, Mei; Ai, Qing

We propose a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We show the details by implementing nonlocal entanglement generation, entanglement swapping, and entanglement purification modules with atoms in waveguides, and discuss the feasibility of the repeater with currently achievable technology. In our scheme, the faulty events can be discarded by detecting the polarization of the photons. That is, our protocols are accomplished with a fidelity of 100% in principle, which is advantageous for implementing realistic long-distance quantum communication. Moreover, additional atomic qubits are not required, but only a single-photon medium. Our schememore » is scalable and attractive since it can be realized in solid-state quantum systems. With the great progress on controlling atom-waveguide systems, the repeater may be very useful in quantum information processing in the future.« less

Nullspace MUSIC and Improved Radio Frequency Emitter Geolocation from a Mobile Antenna Array

NASA Astrophysics Data System (ADS)

Kintz, Andrew L.

This work advances state-of-the-art Radio Frequency (RF) emitter geolocation from an airborne or spaceborne antenna array. With an antenna array, geolocation is based on Direction of Arrival (DOA) estimation algorithms such as MUSIC. The MUSIC algorithm applies to arbitrary arrays of polarization sensitive antennas and yields high resolution. However, MUSIC fails to obtain its theoretical resolution for simultaneous, closely spaced, co-frequency signals. We propose the novel Nullspace MUSIC algorithm, which outperforms MUSIC and its existing modifications while maintaining MUSIC(apostrophe)s fundamental orthogonality test. Nullspace MUSIC applies a divide-and-conquer approach and estimates a single DOA at a time. Additionally, an antenna array on an aircraft cannot be perfectly calibrated. RF waves are blocked, reflected, and scattered in a time-varying fashion by the platform around the antenna array. Consequently, full-wave electromagnetics simulations or demanding measurements of the entire platform cannot eliminate the mismatch between the true, in-situ antenna patterns and the antenna patterns that are available for DOA estimation (the antenna array manifold). Platform-induced manifold mismatch severely degrades MUSIC(apostrophe)s resolution and accuracy. We show that Nullspace MUSIC improves DOA accuracy for well separated signals that are incident on an airborne antenna array. Conventionally, geolocation from a mobile platform draws Lines of Bearing (LOB) from the antenna array along the DOAs to find the locations where the DOAs intersect with the ground. However, averaging the LOBs in the global coordinate system yields large errors due to geometric dilution of precision. Since averaging positions fails, a single emitter is typically located by finding the position on the ground that yields the Minimum Apparent Angular Error (MAAE) for the DOA estimates over a flight. We extend the MAAE approach to cluster LOBs from multiple emitters. MAAE clustering geolocates multiple simultaneous and co-frequency emitters in spite of highly erratic DOA estimates. We also mitigate manifold mismatch by applying the Direct Mapping Method (DMM). DMM averages DOA spectra on the earth(apostrophe)s surface and estimates the emitter locations directly from the composite spectrum. In the example results presented, our goal is to geolocate four diversely polarized emitters with a seven-element antenna array. This is too challenging for MAAE and DMM. We fuse Nullspace MUSIC and DMM into the novel Nullspace DMM algorithm and demonstrate that Nullspace DMM locates all emitters. Finally, we apply the proposed geolocation algorithms to real-world experimental data. A six-element antenna array and Data Collection System (DCS) were installed on a small aircraft. The DCS recorded signals from four live transmitters during a three-hour flight over Columbus, Ohio. The four emitters were geolocated from various segments of the flight. As expected, individual DOA estimates were erratic and widespread due to the airplane(apostrophe)s perturbations of the measured array manifold. MAAE and DMM locate at most three of the four emitters. On the other hand, Nullspace DMM yields unambiguous estimates for every emitter in every flight segment. The successful experimental trials show that Nullspace DMM could significantly enhance airborne emitter geolocation in missions such as RF spectrum enforcement, locating unknown transmitters for defense, and search and rescue operations.

Optical tracking of nanoscale particles in microscale environments

NASA Astrophysics Data System (ADS)

Mathai, P. P.; Liddle, J. A.; Stavis, S. M.

2016-03-01

The trajectories of nanoscale particles through microscale environments record useful information about both the particles and the environments. Optical microscopes provide efficient access to this information through measurements of light in the far field from nanoparticles. Such measurements necessarily involve trade-offs in tracking capabilities. This article presents a measurement framework, based on information theory, that facilitates a more systematic understanding of such trade-offs to rationally design tracking systems for diverse applications. This framework includes the degrees of freedom of optical microscopes, which determine the limitations of tracking measurements in theory. In the laboratory, tracking systems are assemblies of sources and sensors, optics and stages, and nanoparticle emitters. The combined characteristics of such systems determine the limitations of tracking measurements in practice. This article reviews this tracking hardware with a focus on the essential functions of nanoparticles as optical emitters and microenvironmental probes. Within these theoretical and practical limitations, experimentalists have implemented a variety of tracking systems with different capabilities. This article reviews a selection of apparatuses and techniques for tracking multiple and single particles by tuning illumination and detection, and by using feedback and confinement to improve the measurements. Prior information is also useful in many tracking systems and measurements, which apply across a broad spectrum of science and technology. In the context of the framework and review of apparatuses and techniques, this article reviews a selection of applications, with particle diffusion serving as a prelude to tracking measurements in biological, fluid, and material systems, fabrication and assembly processes, and engineered devices. In so doing, this review identifies trends and gaps in particle tracking that might influence future research.

An analytical study of double bend achromat lattice.

PubMed

Fakhri, Ali Akbar; Kant, Pradeep; Singh, Gurnam; Ghodke, A D

2015-03-01

In a double bend achromat, Chasman-Green (CG) lattice represents the basic structure for low emittance synchrotron radiation sources. In the basic structure of CG lattice single focussing quadrupole (QF) magnet is used to form an achromat. In this paper, this CG lattice is discussed and an analytical relation is presented, showing the limitation of basic CG lattice to provide the theoretical minimum beam emittance in achromatic condition. To satisfy theoretical minimum beam emittance parameters, achromat having two, three, and four quadrupole structures is presented. In this structure, different arrangements of QF and defocusing quadruple (QD) are used. An analytical approach assuming quadrupoles as thin lenses has been followed for studying these structures. A study of Indus-2 lattice in which QF-QD-QF configuration in the achromat part has been adopted is also presented.

Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

PubMed Central

Kappaun, Stefan; Slugovc, Christian; List, Emil J. W.

2008-01-01

Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo- and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers. PMID:19325819

A compact time reversal emitter-receiver based on a leaky random cavity

PubMed Central

Luong, Trung-Dung; Hies, Thomas; Ohl, Claus-Dieter

2016-01-01

Time reversal acoustics (TRA) has gained widespread applications for communication and measurements. In general, a scattering medium in combination with multiple transducers is needed to achieve a sufficiently large acoustical aperture. In this paper, we report an implementation for a cost-effective and compact time reversal emitter-receiver driven by a single piezoelectric element. It is based on a leaky cavity with random 3-dimensional printed surfaces. The random surfaces greatly increase the spatio-temporal focusing quality as compared to flat surfaces and allow the focus of an acoustic beam to be steered over an angle of 41°. We also demonstrate its potential use as a scanner by embedding a receiver to detect an object from its backscatter without moving the TRA emitter. PMID:27811957

A chip-scale, telecommunications-band frequency conversion interface for quantum emitters.

PubMed

Agha, Imad; Ates, Serkan; Davanço, Marcelo; Srinivasan, Kartik

2013-09-09

We describe a chip-scale, telecommunications-band frequency conversion interface designed for low-noise operation at wavelengths desirable for common single photon emitters. Four-wave-mixing Bragg scattering in silicon nitride waveguides is used to demonstrate frequency upconversion and downconversion between the 980 nm and 1550 nm wavelength regions, with signal-to-background levels > 10 and conversion efficiency of ≈ -60 dB at low continuous wave input pump powers (< 50 mW). Finite element simulations and the split-step Fourier method indicate that increased input powers of ≈ 10 W (produced by amplified nanosecond pulses, for example) will result in a conversion efficiency > 25 % in existing geometries. Finally, we present waveguide designs that can be used to connect shorter wavelength (637 nm to 852 nm) quantum emitters with 1550 nm.

The treatment of solid tumors by alpha emitters released from 224Ra-loaded sources—internal dosimetry analysis

NASA Astrophysics Data System (ADS)

Arazi, L.; Cooks, T.; Schmidt, M.; Keisari, Y.; Kelson, I.

2010-02-01

Diffusing alpha-emitters radiation therapy (DART) is a proposed new form of brachytherapy, allowing the treatment of solid tumors by alpha particles. DART utilizes implantable sources carrying small activities of radium-224, which continually release into the tumor radon-220, polonium-216 and lead-212 atoms, while radium-224 itself remains fixed to the source. The released atoms disperse inside the tumor by diffusive and convective processes, creating, through their alpha emissions, a high-dose region measuring several mm in diameter about each source. The efficacy of DART has been demonstrated in preclinical studies on mice-borne squamous cell carcinoma and lung tumors and the method is now being developed toward clinical trials. This work studies DART safety with respect to the dose delivered to distant organs as a result of lead-212 leakage from the tumor through the blood, relying on a biokinetic calculation coupled to internal dose assessments. It is found that the dose-limiting organs are the kidneys and red bone marrow. Assuming a typical source spacing of ~5 mm and a typical radium-224 activity density of 0.4-0.8 MBq g-1 of tumor tissue, it is predicted that tumors weighing up to several hundred grams may be treated without reaching the tolerance dose in any organ.

Status of diffused junction p+n InP solar cells for space applications

NASA Technical Reports Server (NTRS)

Faur, Mircea; Goradia, C.; Faur, Maria; Fatemi, N. S.; Jenkins, P. P.; Flood, D. J.; Brinker, D. J.; Wilt, D. M.; Bailey, S.; Goradia, M.

1994-01-01

Recently, we have succeeded in fabricating diffused junction p(sup +)n(Cd,S) InP solar cells with measured AMO, 25 C open circuit voltage (V(sub OC)) of 887.6 mV, which, to the best of our knowledge, is higher than previously reported V(sub OC) values for any InP homojunction solar cells. The experiment-based projected achievable efficiency of these cells using LEC grown substrates is 21.3 percent. The maximum AMO, 25 C internal losses due to date on bare cells is, however, only 13.2 percent. This is because of large external and internal losses due to non-optimized front grid design, antireflection (AR) coating and emitter thickness. This paper summarizes recent advances in the technology of fabrication of p(sup +)n InP diffused structures and solar cells, resulted from a study undertaken in an effort to increase the cell efficiency. The topics discussed in this paper include advances in: (1) the formation on thin p(sup +) InP:Cd emitter layers, (2) electroplated front contacts, (3) surface passivation and (4) the design of a new native oxide/Al2O3/MgF2 tree layer AR coating using a chemically-grown P-rich passivating oxide as a first layer. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.

Status of diffused junction p+n InP solar cells for space applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faur, M.; Goradia, C.; Faur, M.

1994-09-01

Recently, the authors have succeeded in fabricating diffused junction p{sup +}n(Cd,S) InP solar cells with measured AMO, 25 C open circuit voltage (V{sub OC}) of 887.6 mV, which, to the best of their knowledge, is higher than previously reported V{sub OC} values for any InP homojunction solar cells. The experiment-based projected achievable efficiency of these cells using LEC grown substrates is 21.3 percent. The maximum AMO, 25 C internal losses due to date on bare cells is, however, only 13.2 percent. This is because of large external and internal losses due to non-optimized front grid design, antireflection (AR) coating andmore » emitter thickness. This paper summarizes recent advances in the technology of fabrication of p{sup +}n InP diffused structures and solar cells, resulted from a study undertaken in an effort to increase the cell efficiency. The topics discussed in this paper include advances in: (1) the formation on thin p{sup +} InP:Cd emitter layers, (2) electroplated front contacts, (3) surface passivation and (4) the design of a new native oxide/Al2O3/MgF2 tree layer AR coating using a chemically-grown P-rich passivating oxide as a first layer. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.« less

Superresolution imaging in live Caulobacter crescentus cells using photoswitchable enhanced yellow fluorescent protein

NASA Astrophysics Data System (ADS)

Biteen, Julie S.; Thompson, Michael A.; Tselentis, Nicole K.; Shapiro, Lucy; Moerner, W. E.

2009-02-01

Recently, photoactivation and photoswitching were used to control single-molecule fluorescent labels and produce images of cellular structures beyond the optical diffraction limit (e.g., PALM, FPALM, and STORM). While previous live-cell studies relied on sophisticated photoactivatable fluorescent proteins, we show in the present work that superresolution imaging can be performed with fusions to the commonly used fluorescent protein EYFP. Rather than being photoactivated, however, EYFP can be reactivated with violet light after apparent photobleaching. In each cycle after initial imaging, only a sparse subset fluorophores is reactivated and localized, and the final image is then generated from the measured single-molecule positions. Because these methods are based on the imaging nanometer-sized single-molecule emitters and on the use of an active control mechanism to produce sparse sub-ensembles, we suggest the phrase "Single-Molecule Active-Control Microscopy" (SMACM) as an inclusive term for this general imaging strategy. In this paper, we address limitations arising from physiologically imposed upper boundaries on the fluorophore concentration by employing dark time-lapse periods to allow single-molecule motions to fill in filamentous structures, increasing the effective labeling concentration while localizing each emitter at most once per resolution-limited spot. We image cell-cycle-dependent superstructures of the bacterial actin protein MreB in live Caulobacter crescentus cells with sub-40-nm resolution for the first time. Furthermore, we quantify the reactivation quantum yield of EYFP, and find this to be 1.6 x 10-6, on par with conventional photoswitchable fluorescent proteins like Dronpa. These studies show that EYFP is a useful emitter for in vivo superresolution imaging of intracellular structures in bacterial cells.

Scalable Quantum Information Processing and Applications

DTIC Science & Technology

2008-01-19

qubit logic gates, and finally emitting an entangled photon from the single- photon emitter. For the program, we proposed to demonstrate the...coherent, single photon transmitter/receiver system. These requirements included careful tailoring of the g factor for conduction band electrons in...physics required for the realization of a spin-coherent, single photon transmitter/receiver system. These requirements included careful tailoring of

Nearly Blinking-Free, High-Purity Single-Photon Emission by Colloidal InP/ZnSe Quantum Dots.

PubMed

Chandrasekaran, Vigneshwaran; Tessier, Mickaël D; Dupont, Dorian; Geiregat, Pieter; Hens, Zeger; Brainis, Edouard

2017-10-11

Colloidal core/shell InP/ZnSe quantum dots (QDs), recently produced using an improved synthesis method, have a great potential in life-science applications as well as in integrated quantum photonics and quantum information processing as single-photon emitters. Single-particle spectroscopy of 10 nm QDs with 3.2 nm cores reveals strong photon antibunching attributed to fast (70 ps) Auger recombination of multiple excitons. The QDs exhibit very good photostability under strong optical excitation. We demonstrate that the antibunching is preserved when the QDs are excited above the saturation intensity of the fundamental-exciton transition. This result paves the way toward their usage as high-purity on-demand single-photon emitters at room temperature. Unconventionally, despite the strong Auger blockade mechanism, InP/ZnSe QDs also display very little luminescence intermittency ("blinking"), with a simple on/off blinking pattern. The analysis of single-particle luminescence statistics places these InP/ZnSe QDs in the class of nearly blinking-free QDs, with emission stability comparable to state-of-the-art thick-shell and alloyed-interface CdSe/CdS, but with improved single-photon purity.

Continued advances in high brightness fiber-coupled laser modules for efficient pumping of fiber and solid-state lasers

NASA Astrophysics Data System (ADS)

Hemenway, M.; Chen, Z.; Urbanek, W.; Dawson, D.; Bao, L.; Kanskar, M.; DeVito, M.; Martinsen, R.

2018-02-01

Both the fibber laser and diode-pumped solid-state laser market continue to drive advances in pump diode module brightness. We report on the continued progress by nLIGHT to develop and deliver the highest brightness diode-laser pumps using single-emitter technology. Continued advances in multimode laser diode technology [13] and fiber-coupling techniques have enabled higher emitter counts in the element packages, enabling us to demonstrate 305 W into 105 μm - 0.16 NA. This brightness improvement is achieved by leveraging our prior-reported package re-optimization, allowing an increase in the emitter count from two rows of nine emitters to two rows of twelve emitters. Leveraging the two rows off twelve emitter architecture,, product development has commenced on a 400 W into 200 μm - 00.16 NA package. Additionally, the advances in pump technology intended for CW Yb-doped fiber laser pumping has been leveraged to develop the highest brightness 793 nm pump modules for 2 μm Thulium fiber laser pumping, generating 150 W into 200 μm - 0.18 NA and 100 W into 105 μm - 0.15 NA. Lastly, renewed interest in direct diode materials processing led us to experiment with wavelength multiplexing our existing state of the art 200 W, 105 μm - 00.15 NA package into a combined output of 395 WW into 105 μm - 0.16 NA.

Effect of the fabrication conditions of SiGe LEDs on their luminescence and electrical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyadin, A. E.; Sobolev, N. A., E-mail: nick@sobolev.ioffe.rssi.ru; Strel’chuk, A. M.

2016-02-15

SiGe-based n{sup +}–p–p{sup +} light-emitting diodes (LEDs) with heavily doped layers fabricated by the diffusion (of boron and phosphorus) and CVD (chemical-vapor deposition of polycrystalline silicon layers doped with boron and phosphorus) techniques are studied. The electroluminescence spectra of both kinds of LEDs are identical, but the emission intensity of CVD diodes is ∼20 times lower. The reverse and forward currents in the CVD diodes are substantially higher than those in diffusion-grown diodes. The poorer luminescence and electrical properties of the CVD diodes are due to the formation of defects at the interface between the emitter and base layers.

The effect of plasma density and emitter geometry on space charge limits for field emitter array electron charge emission into a space plasma

NASA Astrophysics Data System (ADS)

Morris, Dave; Gilchrist, Brian; Gallimore, Alec

2001-02-01

Field Emitter Array Cathodes (FEACs) are a new technology being developed for several potential spacecraft electron emission and charge control applications. Instead of a single hot (i.e., high powered) emitter, or a gas dependant plasma contactor, FEAC systems consist of many (hundreds or thousands) of small (micron level) cathode/gate pairs printed on a semiconductor wafer that effect cold field emission at relatively low voltages. Each individual cathode emits only micro-amp level currents, but a functional array is capable of amp/cm2 current densities. It is hoped that thus FEAC offers the possibility of a relatively low-power, simple to integrate, and inexpensive technique for the high level of current emissions that are required for an electrodynamic tether (EDT) propulsion mission. Space charge limits are a significant concern for the EDT application. Vacuum chamber tests and PIC simulations are being performed at the University of Michigan Plasmadynamics and Electric Propulsion Laboratory and Space Physics Research Laboratory to determine the effect of plasma density and emitter geometry on space charge limitations. The results of this work and conclusions to date of how to best mitigate space charge limits will be presented. .

Modelling of hydrogen transport in silicon solar cell structures under equilibrium conditions

NASA Astrophysics Data System (ADS)

Hamer, P.; Hallam, B.; Bonilla, R. S.; Altermatt, P. P.; Wilshaw, P.; Wenham, S.

2018-01-01

This paper presents a model for the introduction and redistribution of hydrogen in silicon solar cells at temperatures between 300 and 700 °C based on a second order backwards difference formula evaluated using a single Newton-Raphson iteration. It includes the transport of hydrogen and interactions with impurities such as ionised dopants. The simulations lead to three primary conclusions: (1) hydrogen transport across an n-type emitter is heavily temperature dependent; (2) under equilibrium conditions, hydrogen is largely driven by its charged species, with the switch from a dominance of negatively charged hydrogen (H-) to positively charged hydrogen (H+) within the emitter region critical to significant transport across the junction; and (3) hydrogen transport across n-type emitters is critically dependent upon the doping profile within the emitter, and, in particular, the peak doping concentration. It is also observed that during thermal processes after an initial high temperature step, hydrogen preferentially migrates to the surface of a phosphorous doped emitter, drawing hydrogen out of the p-type bulk. This may play a role in several effects observed during post-firing anneals in relation to the passivation of recombination active defects and even the elimination of hydrogen-related defects in the bulk of silicon solar cells.

Single Fluorescent Molecules as Nano-Illuminators for Biological Structure and Function

NASA Astrophysics Data System (ADS)

Moerner, W. E.

2011-03-01

Since the first optical detection and spectroscopy of a single molecule in a solid (Phys. Rev. Lett. {62}, 2535 (1989)), much has been learned about the ability of single molecules to probe local nanoenvironments and individual behavior in biological and nonbiological materials in the absence of ensemble averaging that can obscure heterogeneity. Because each single fluorophore acts a light source roughly 1 nm in size, microscopic imaging of individual fluorophores leads naturally to superlocalization, or determination of the position of the molecule with precision beyond the optical diffraction limit, simply by digitization of the point-spread function from the single emitter. For example, the shape of single filaments in a living cell can be extracted simply by allowing a single molecule to move through the filament (PNAS {103}, 10929 (2006)). The addition of photoinduced control of single-molecule emission allows imaging beyond the diffraction limit (super-resolution) and a new array of acronyms (PALM, STORM, F-PALM etc.) and advances have appeared. We have used the native blinking and switching of a common yellow-emitting variant of green fluorescent protein (EYFP) reported more than a decade ago (Nature {388}, 355 (1997)) to achieve sub-40 nm super-resolution imaging of several protein structures in the bacterium Caulobacter crescentus: the quasi-helix of the actin-like protein MreB (Nat. Meth. {5}, 947 (2008)), the cellular distribution of the DNA binding protein HU (submitted), and the recently discovered division spindle composed of ParA filaments (Nat. Cell Biol. {12}, 791 (2010)). Even with these advances, better emitters would provide more photons and improved resolution, and a new photoactivatable small-molecule emitter has recently been synthesized and targeted to specific structures in living cells to provide super-resolution images (JACS {132}, 15099 (2010)). Finally, a new optical method for extracting three-dimensional position information based on a double-helix point spread function enables quantitative tracking of single mRNA particles in living yeast cells with 15 ms time resolution and 25-50 nm spatial precision (PNAS {107}, 17864 (2010)). These examples illustrate the power of single-molecule optical imaging in extracting new structural and functional information in living cells.

Mode Matching for Optical Antennas

NASA Astrophysics Data System (ADS)

Feichtner, Thorsten; Christiansen, Silke; Hecht, Bert

2017-11-01

The emission rate of a point dipole can be strongly increased in the presence of a well-designed optical antenna. Yet, optical antenna design is largely based on radio-frequency rules, ignoring, e.g., Ohmic losses and non-negligible field penetration in metals at optical frequencies. Here, we combine reciprocity and Poynting's theorem to derive a set of optical-frequency antenna design rules for benchmarking and optimizing the performance of optical antennas driven by single quantum emitters. Based on these findings a novel plasmonic cavity antenna design is presented exhibiting a considerably improved performance compared to a reference two-wire antenna. Our work will be useful for the design of high-performance optical antennas and nanoresonators for diverse applications ranging from quantum optics to antenna-enhanced single-emitter spectroscopy and sensing.

Feasibility of efficient room-temperature solid-state sources of indistinguishable single photons using ultrasmall mode volume cavities

NASA Astrophysics Data System (ADS)

Wein, Stephen; Lauk, Nikolai; Ghobadi, Roohollah; Simon, Christoph

2018-05-01

Highly efficient sources of indistinguishable single photons that can operate at room temperature would be very beneficial for many applications in quantum technology. We show that the implementation of such sources is a realistic goal using solid-state emitters and ultrasmall mode volume cavities. We derive and analyze an expression for photon indistinguishability that accounts for relevant detrimental effects, such as plasmon-induced quenching and pure dephasing. We then provide the general cavity and emitter conditions required to achieve efficient indistinguishable photon emission and also discuss constraints due to phonon sideband emission. Using these conditions, we propose that a nanodiamond negatively charged silicon-vacancy center combined with a plasmonic-Fabry-Pérot hybrid cavity is an excellent candidate system.

Eye safe high power laser diode in the 1410-1550nm range

NASA Astrophysics Data System (ADS)

Boucart, Julien; de Largy, Brian; Kearley, Mark; Lichtenstein, Norbert

2010-02-01

The demand for high power lasers emitting in the 14xx-15xxnm range is growing for applications in fields such as medical or homeland security. We demonstrate high power laser diodes with emission at 1430, 1470 and 1560 nm. Single multimode emitters at 1470nm emit about 3.5W in CW operation. Power conversion efficiency can reach values as high as 38.5%. With this base material, single and multi-emitter fiber coupled modules are built. Additionally, bars on passive and microchannel coolers are fabricated that deliver 25W and 38W respectively in CW mode, while obtaining more than 80 W in pulsed mode. All reliability tests show an outstanding stability of the material with no signs of wearout after 3750 hrs under strong acceleration conditions.

Generic conditions for suppressing the coherent synchrotron radiation induced emittance growth in a two-dipole achromat

NASA Astrophysics Data System (ADS)

Jiao, Yi; Cui, Xiaohao; Huang, Xiyang; Xu, Gang

2014-06-01

The effect of the coherent synchrotron radiation (CSR) becomes evident, and leads to increased beam energy spread and transverse emittance dilution, as both the emittance and bunch length of the electron beams are continuously pushed down in present and forthcoming high-brightness light sources and linear colliders. Suppressing this effect is important to preserve the expected machine performance. Methods of the R-matrix analysis and the Courant-Snyder formalism analysis have been proposed to evaluate and to suppress the emittance growth due to CSR in achromatic cells. In this paper a few important modifications are made on these two methods, which enable us to prove that these two methods are equivalent to each other. With the modified analysis, we obtain explicit and generic conditions of cancelling the CSR-driven emittance excitation in a single achromat consisting of two dipoles of arbitrary bending angles. In spite of the fact that the analysis constrains itself in a linear regime, based on the assumption that CSR-induced particle energy deviation is proportional to both θ and ρ1/3, with θ being the bending angle and ρ the bending radius, it is demonstrated through ELEGANT simulations that the conditions derived from this analysis are still effective in suppressing the emittance growth when a more detailed one-dimensional CSR model is considered. In addition, it illustrates that the emittance growth can be reduced to a lower level with the proposed conditions than with the other two approaches, such as matching the beam envelope to the CSR kick and setting the cell-to-cell betatron phase advance to an appropriate value.

Carrier transport and sensitivity issues in heterojunction with intrinsic thin layer solar cells on N-type crystalline silicon: A computer simulation study

NASA Astrophysics Data System (ADS)

Rahmouni, M.; Datta, A.; Chatterjee, P.; Damon-Lacoste, J.; Ballif, C.; Roca i Cabarrocas, P.

2010-03-01

Heterojunction with intrinsic thin layer or "HIT" solar cells are considered favorable for large-scale manufacturing of solar modules, as they combine the high efficiency of crystalline silicon (c-Si) solar cells, with the low cost of amorphous silicon technology. In this article, based on experimental data published by Sanyo, we simulate the performance of a series of HIT cells on N-type crystalline silicon substrates with hydrogenated amorphous silicon (a-Si:H) emitter layers, to gain insight into carrier transport and the general functioning of these devices. Both single and double HIT structures are modeled, beginning with the initial Sanyo cells having low open circuit voltages but high fill factors, right up to double HIT cells exhibiting record values for both parameters. The one-dimensional numerical modeling program "Amorphous Semiconductor Device Modeling Program" has been used for this purpose. We show that the simulations can correctly reproduce the electrical characteristics and temperature dependence for a set of devices with varying I-layer thickness. Under standard AM1.5 illumination, we show that the transport is dominated by the diffusion mechanism, similar to conventional P/N homojunction solar cells, and tunneling is not required to describe the performance of state-of-the art devices. Also modeling has been used to study the sensitivity of N-c-Si HIT solar cell performance to various parameters. We find that the solar cell output is particularly sensitive to the defect states on the surface of the c-Si wafer facing the emitter, to the indium tin oxide/P-a-Si:H front contact barrier height and to the band gap and activation energy of the P-a-Si:H emitter, while the I-a-Si:H layer is necessary to achieve both high Voc and fill factor, as it passivates the defects on the surface of the c-Si wafer. Finally, we describe in detail for most parameters how they affect current transport and cell properties.

Improved Rare-Earth Emitter Hollow Cathode

NASA Technical Reports Server (NTRS)

Goebel, Dan M.

2011-01-01

An improvement has been made to the design of the hollow cathode geometry that was created for the rare-earth electron emitter described in Compact Rare Earth Emitter Hollow Cathode (NPO-44923), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 52. The original interior assembly was made entirely of graphite in order to be compatible with the LaB6 material, which cannot be touched by metals during operation due to boron diffusion causing embrittlement issues in high-temperature refractory materials. Also, the graphite tube was difficult to machine and was subject to vibration-induced fracturing. This innovation replaces the graphite tube with one made out of refractory metal that is relatively easy to manufacture. The cathode support tube is made of molybdenum or molybdenum-rhenium. This material is easily gun-bored to near the tolerances required, and finish machined with steps at each end that capture the orifice plate and the mounting flange. This provides the manufacturability and robustness needed for flight applications, and eliminates the need for expensive e-beam welding used in prior cathodes. The LaB6 insert is protected from direct contact with the refractory metal tube by thin, graphite sleeves in a cup-arrangement around the ends of the insert. The sleeves, insert, and orifice plate are held in place by a ceramic spacer and tungsten spring inserted inside the tube. To heat the cathode, an insulating tube is slipped around the refractory metal hollow tube, which can be made of high-temperature materials like boron nitride or aluminum nitride. A screw-shaped slot, or series of slots, is machined in the outside of the ceramic tube to constrain a refractory metal wire wound inside the slot that is used as the heater. The screw slot can hold a single heater wire that is then connected to the front of the cathode tube by tack-welding to complete the electrical circuit, or it can be a double slot that takes a bifilar wound heater with both leads coming out the back. This configuration replaces the previous sheathed heater design that limited the cycling-life of the cathode.

A Single RF Emitter-Based Indoor Navigation Method for Autonomous Service Robots.

PubMed

Sherwin, Tyrone; Easte, Mikala; Chen, Andrew Tzer-Yeu; Wang, Kevin I-Kai; Dai, Wenbin

2018-02-14

Location-aware services are one of the key elements of modern intelligent applications. Numerous real-world applications such as factory automation, indoor delivery, and even search and rescue scenarios require autonomous robots to have the ability to navigate in an unknown environment and reach mobile targets with minimal or no prior infrastructure deployment. This research investigates and proposes a novel approach of dynamic target localisation using a single RF emitter, which will be used as the basis of allowing autonomous robots to navigate towards and reach a target. Through the use of multiple directional antennae, Received Signal Strength (RSS) is compared to determine the most probable direction of the targeted emitter, which is combined with the distance estimates to improve the localisation performance. The accuracy of the position estimate is further improved using a particle filter to mitigate the fluctuating nature of real-time RSS data. Based on the direction information, a motion control algorithm is proposed, using Simultaneous Localisation and Mapping (SLAM) and A* path planning to enable navigation through unknown complex environments. A number of navigation scenarios were developed in the context of factory automation applications to demonstrate and evaluate the functionality and performance of the proposed system.

A Single RF Emitter-Based Indoor Navigation Method for Autonomous Service Robots

PubMed Central

Sherwin, Tyrone; Easte, Mikala; Wang, Kevin I-Kai; Dai, Wenbin

2018-01-01

Location-aware services are one of the key elements of modern intelligent applications. Numerous real-world applications such as factory automation, indoor delivery, and even search and rescue scenarios require autonomous robots to have the ability to navigate in an unknown environment and reach mobile targets with minimal or no prior infrastructure deployment. This research investigates and proposes a novel approach of dynamic target localisation using a single RF emitter, which will be used as the basis of allowing autonomous robots to navigate towards and reach a target. Through the use of multiple directional antennae, Received Signal Strength (RSS) is compared to determine the most probable direction of the targeted emitter, which is combined with the distance estimates to improve the localisation performance. The accuracy of the position estimate is further improved using a particle filter to mitigate the fluctuating nature of real-time RSS data. Based on the direction information, a motion control algorithm is proposed, using Simultaneous Localisation and Mapping (SLAM) and A* path planning to enable navigation through unknown complex environments. A number of navigation scenarios were developed in the context of factory automation applications to demonstrate and evaluate the functionality and performance of the proposed system. PMID:29443906

Using a multi-scale approach to identify and quantify oil and gas emissions: a case study for GHG emissions verification

NASA Astrophysics Data System (ADS)

Sweeney, C.; Kort, E. A.; Rella, C.; Conley, S. A.; Karion, A.; Lauvaux, T.; Frankenberg, C.

2015-12-01

Along with a boom in oil and natural gas production in the US, there has been a substantial effort to understand the true environmental impact of these operations on air and water quality, as well asnet radiation balance. This multi-institution effort funded by both governmental and non-governmental agencies has provided a case study for identification and verification of emissions using a multi-scale, top-down approach. This approach leverages a combination of remote sensing to identify areas that need specific focus and airborne in-situ measurements to quantify both regional and large- to mid-size single-point emitters. Ground-based networks of mobile and stationary measurements provide the bottom tier of measurements from which process-level information can be gathered to better understand the specific sources and temporal distribution of the emitters. The motivation for this type of approach is largely driven by recent work in the Barnett Shale region in Texas as well as the San Juan Basin in New Mexico and Colorado; these studies suggest that relatively few single-point emitters dominate the regional emissions of CH4.

Parallel mapping of optical near-field interactions by molecular motor-driven quantum dots.

PubMed

Groß, Heiko; Heil, Hannah S; Ehrig, Jens; Schwarz, Friedrich W; Hecht, Bert; Diez, Stefan

2018-04-30

In the vicinity of metallic nanostructures, absorption and emission rates of optical emitters can be modulated by several orders of magnitude 1,2 . Control of such near-field light-matter interaction is essential for applications in biosensing 3 , light harvesting 4 and quantum communication 5,6 and requires precise mapping of optical near-field interactions, for which single-emitter probes are promising candidates 7-11 . However, currently available techniques are limited in terms of throughput, resolution and/or non-invasiveness. Here, we present an approach for the parallel mapping of optical near-field interactions with a resolution of <5 nm using surface-bound motor proteins to transport microtubules carrying single emitters (quantum dots). The deterministic motion of the quantum dots allows for the interpolation of their tracked positions, resulting in an increased spatial resolution and a suppression of localization artefacts. We apply this method to map the near-field distribution of nanoslits engraved into gold layers and find an excellent agreement with finite-difference time-domain simulations. Our technique can be readily applied to a variety of surfaces for scalable, nanometre-resolved and artefact-free near-field mapping using conventional wide-field microscopes.

Impact of a boron rich layer on minority carrier lifetime degradation in boron spin-on dopant diffused n-type crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Singha, Bandana; Singh Solanki, Chetan

2016-03-01

In the production of n-type crystalline silicon solar cells with boron diffused emitters, the formation of a boron rich layer (BRL) is a common phenomenon and is largely responsible for bulk lifetime degradation. The phenomenon of BRL formation during diffusion of boron spin-on dopant and its impact on bulk lifetime degradation are investigated in this work. The BRL formed beneath the borosilicate glass layer has thicknesses varying from 10 nm-150 nm depending on the diffusion conditions. The effective and bulk minority carrier lifetimes, measured with Al2O3 deposited layers and a quinhydron-methanol solution, show that carrier lifetime degradation is proportional to the BRL thicknesses and their surface recombination velocities. The controlled diffusion processes and different oxidation techniques used in this work can partially reduce the BRL thickness and improve carrier lifetime by more than 10%. But for BRL thicknesses higher than 50 nm, different etching techniques further lower the carrier lifetime and the degradation in the device cannot be recovered.

Space-charge-limited solid-state triode

NASA Technical Reports Server (NTRS)

Shumka, A. (Inventor)

1975-01-01

A solid-state triode is provided from a wafer of nearinstrinsic semiconductor material sliced into filaments of rectangular cross section. Before slicing, emitter and collector regions are formed on the narrow sides of the filaments, and after slicing gate regions are formed in arrow strips extending longitudinally along the midsections of the wide sides of the filaments. Contacts are then formed on the emitter, collector and gate regions of each filament individually for a single filament device, or in parallel for an array of filament devices to increase load current.

Single-Molecule Spectroscopy and Imaging Over the Decades

PubMed Central

Moerner, W. E.; Shechtman, Yoav; Wang, Quan

2016-01-01

As of 2015, it has been 26 years since the first optical detection and spectroscopy of single molecules in condensed matter. This area of science has expanded far beyond the early low temperature studies in crystals to include single molecules in cells, polymers, and in solution. The early steps relied upon high-resolution spectroscopy of inhomogeneously broadened optical absorption profiles of molecular impurities in solids at low temperatures. Spectral fine structure arising directly from the position-dependent fluctuations of the number of molecules in resonance led to the attainment of the single-molecule limit in 1989 using frequency-modulation laser spectroscopy. In the early 1990's, a variety of fascinating physical effects were observed for individual molecules, including imaging of the light from single molecules as well as observations of spectral diffusion, optical switching and the ability to select different single molecules in the same focal volume simply by tuning the pumping laser frequency. In the room temperature regime, researchers showed that bursts of light from single molecules could be detected in solution, leading to imaging and microscopy by a variety of methods. Studies of single copies of the green fluorescent protein also uncovered surprises, especially the blinking and photoinduced recovery of emitters, which stimulated further development of photoswitchable fluorescent protein labels. All of these early steps provided important fundamentals underpinning the development of super-resolution microscopy based on single-molecule localization and active control of emitting concentration. Current thrust areas include extensions to three-dimensional imaging with high precision, orientational analysis of single molecules, and direct measurements of photodynamics and transport properties for single molecules trapped in solution by suppression of Brownian motion. Without question, a huge variety of studies of single molecules performed by many talented scientists all over the world have extended our knowledge of the nanoscale and microscopic mechanisms previously hidden by ensemble averaging. PMID:26616210

Plasmon-emitter interaction using integrated ring grating-nanoantenna structures.

PubMed

Rahbany, Nancy; Geng, Wei; Bachelot, Renaud; Couteau, Christophe

2017-05-05

Overcoming the diffraction limit to achieve high optical resolution is one of the main challenges in the fields of plasmonics, nanooptics and nanophotonics. In this work, we introduce novel plasmonic structures consisting of nanoantennas (nanoprisms, single bowtie nanoantennas and double bowtie nanoantennas) integrated in the center of ring diffraction gratings. Propagating surface plasmon polaritons (SPPs) are generated by the ring grating and coupled with localized surface plasmons (LSPs) at the nanoantennas exciting emitters placed in their gap. SPPs are widely used for optical waveguiding but provide low resolution due to their weak spatial confinement. In contrast, LSPs provide excellent sub-wavelength confinement but induce large losses. The phenomenon of SPP-LSP coupling witnessed in our structures allows for achieving more precise focusing at the nanoscale, causing an increase in the fluorescence emission of the emitters. Finite-difference time-domain simulations as well as experimental fabrication and optical characterization results are presented to study plasmon-emitter coupling between an ensemble of dye molecules and our integrated plasmonic structures. A comparison is given to highlight the importance of each structure on the photoluminescence and radiative decay enhancement of the molecules.

Intrinsic beam emittance of laser-accelerated electrons measured by x-ray spectroscopic imaging.

PubMed

Golovin, G; Banerjee, S; Liu, C; Chen, S; Zhang, J; Zhao, B; Zhang, P; Veale, M; Wilson, M; Seller, P; Umstadter, D

2016-04-19

The recent combination of ultra-intense lasers and laser-accelerated electron beams is enabling the development of a new generation of compact x-ray light sources, the coherence of which depends directly on electron beam emittance. Although the emittance of accelerated electron beams can be low, it can grow due to the effects of space charge during free-space propagation. Direct experimental measurement of this important property is complicated by micron-scale beam sizes, and the presence of intense fields at the location where space charge acts. Reported here is a novel, non-destructive, single-shot method that overcame this problem. It employed an intense laser probe pulse, and spectroscopic imaging of the inverse-Compton scattered x-rays, allowing measurement of an ultra-low value for the normalized transverse emittance, 0.15 (±0.06) π mm mrad, as well as study of its subsequent growth upon exiting the accelerator. The technique and results are critical for designing multi-stage laser-wakefield accelerators, and generating high-brightness, spatially coherent x-rays.

Intrinsic beam emittance of laser-accelerated electrons measured by x-ray spectroscopic imaging

DOE PAGES

Golovin, G.; Banerjee, S.; Liu, C.; ...

2016-04-19

Here, the recent combination of ultra-intense lasers and laser-accelerated electron beams is enabling the development of a new generation of compact x-ray light sources, the coherence of which depends directly on electron beam emittance. Although the emittance of accelerated electron beams can be low, it can grow due to the effects of space charge during free-space propagation. Direct experimental measurement of this important property is complicated by micron-scale beam sizes, and the presence of intense fields at the location where space charge acts. Reported here is a novel, non-destructive, single-shot method that overcame this problem. It employed an intense lasermore » probe pulse, and spectroscopic imaging of the inverse-Compton scattered x-rays, allowing measurement of an ultra-low value for the normalized transverse emittance, 0.15 (±0.06) π mm mrad, as well as study of its subsequent growth upon exiting the accelerator. The technique and results are critical for designing multi-stage laser-wakefield accelerators, and generating high-brightness, spatially coherent x-rays.« less

Plasmon-emitter interaction using integrated ring grating-nanoantenna structures

NASA Astrophysics Data System (ADS)

Rahbany, Nancy; Geng, Wei; Bachelot, Renaud; Couteau, Christophe

2017-05-01

Overcoming the diffraction limit to achieve high optical resolution is one of the main challenges in the fields of plasmonics, nanooptics and nanophotonics. In this work, we introduce novel plasmonic structures consisting of nanoantennas (nanoprisms, single bowtie nanoantennas and double bowtie nanoantennas) integrated in the center of ring diffraction gratings. Propagating surface plasmon polaritons (SPPs) are generated by the ring grating and coupled with localized surface plasmons (LSPs) at the nanoantennas exciting emitters placed in their gap. SPPs are widely used for optical waveguiding but provide low resolution due to their weak spatial confinement. In contrast, LSPs provide excellent sub-wavelength confinement but induce large losses. The phenomenon of SPP-LSP coupling witnessed in our structures allows for achieving more precise focusing at the nanoscale, causing an increase in the fluorescence emission of the emitters. Finite-difference time-domain simulations as well as experimental fabrication and optical characterization results are presented to study plasmon-emitter coupling between an ensemble of dye molecules and our integrated plasmonic structures. A comparison is given to highlight the importance of each structure on the photoluminescence and radiative decay enhancement of the molecules.

Room temperature solid-state quantum emitters in the telecom range.

PubMed

Zhou, Yu; Wang, Ziyu; Rasmita, Abdullah; Kim, Sejeong; Berhane, Amanuel; Bodrog, Zoltán; Adamo, Giorgio; Gali, Adam; Aharonovich, Igor; Gao, Wei-Bo

2018-03-01

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies.

MicroSPE-nanoLC-ESI-MS/MS Using 10-μm-i.d. Silica-Based Monolithic Columns for Proteomics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Quanzhou; Page, Jason S.; Tang, Keqi

2007-01-01

Silica-based monolithic narrow bore capillary columns (25 cm x 10 µm i.d.) with an integrated nanoESI emitter has been developed to provide high quality and robust microSPE-nanoLC-ESI-MS analyses. The integrated nanoESI emitter adds no dead volume to the LC separation, allowing stable electrospray performance to be obtained at flow rates of ~10 nL/min. In an initial application we identified 5510 unique peptides covering 1443 distinct Shewanella oneidensis proteins from a 300 ng tryptic digest sample in a single 4-h LC-MS/MS analysis using a linear ion trap MS (LTQ). We found the use of an integrated monolithic ESI emitter provided enhancedmore » resistance to clogging and good run-to-run reproducibility.« less

Ultralow mode-volume photonic crystal nanobeam cavities for high-efficiency coupling to individual carbon nanotube emitters

PubMed Central

Miura, R.; Imamura, S.; Ohta, R.; Ishii, A.; Liu, X.; Shimada, T.; Iwamoto, S.; Arakawa, Y.; Kato, Y. K.

2014-01-01

The unique emission properties of single-walled carbon nanotubes are attractive for achieving increased functionality in integrated photonics. In addition to being room-temperature telecom-band emitters that can be directly grown on silicon, they are ideal for coupling to nanoscale photonic structures. Here we report on high-efficiency coupling of individual air-suspended carbon nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence images of dielectric- and air-mode cavities reflect their distinctly different mode profiles and show that fields in the air are important for coupling. We find that the air-mode cavities couple more efficiently, and estimated spontaneous emission coupling factors reach a value as high as 0.85. Our results demonstrate advantages of ultralow mode-volumes in air-mode cavities for coupling to low-dimensional nanoscale emitters. PMID:25420679

Two-dimensional numerical simulation of boron diffusion for pyramidally textured silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Fa-Jun, E-mail: Fajun.Ma@nus.edu.sg; Duttagupta, Shubham; Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117576

2014-11-14

Multidimensional numerical simulation of boron diffusion is of great relevance for the improvement of industrial n-type crystalline silicon wafer solar cells. However, surface passivation of boron diffused area is typically studied in one dimension on planar lifetime samples. This approach neglects the effects of the solar cell pyramidal texture on the boron doping process and resulting doping profile. In this work, we present a theoretical study using a two-dimensional surface morphology for pyramidally textured samples. The boron diffusivity and segregation coefficient between oxide and silicon in simulation are determined by reproducing measured one-dimensional boron depth profiles prepared using different boronmore » diffusion recipes on planar samples. The established parameters are subsequently used to simulate the boron diffusion process on textured samples. The simulated junction depth is found to agree quantitatively well with electron beam induced current measurements. Finally, chemical passivation on planar and textured samples is compared in device simulation. Particularly, a two-dimensional approach is adopted for textured samples to evaluate chemical passivation. The intrinsic emitter saturation current density, which is only related to Auger and radiative recombination, is also simulated for both planar and textured samples. The differences between planar and textured samples are discussed.« less

High-efficiency screen-printed belt co-fired solar cells on cast multicrystalline silicon

NASA Astrophysics Data System (ADS)

Upadhyaya, Ajay; Sheoran, Manav; Rohatgi, Ajeet

2005-01-01

High-efficiency 4cm2 untextured screen-printed solar cells were achieved on cast multicrystalline silicon. These cells were fabricated using a simple manufacturable process involving POCl3 diffusion for emitter, PECVD SiNx:H deposition for a single-layer antireflection coating and rapid co-firing of Ag grid, Al backcontact, and Al-BSF in a belt furnace. An optimized process sequence contributed to effective impurity gettering and defect passivation, resulting in high average bulk lifetimes in the range of 100-250 μs after the cell processing. The contact firing contributed to good ohmic contacts with low series resistance of <1Ωcm2, low backsurface recombination velocity of <500cm/s, and high fill factors of ˜0.78. These parameters resulted in 16.9% and 16.8% efficient untextured screen-printed cells with a single layer AR coating on heat exchanger method (HEM) and Baysix mc-Si. The identical process applied to the untextured float zone wafers gave an efficiency of 17.2%. The same optimized co-firing cycle, when applied to HEM mc-Si wafers with starting lifetimes varying over a wide range of 4-70 μs, resulted in cell efficiencies in the range of 16.5%-17%.

Laser doping of boron-doped Si paste for high-efficiency silicon solar cells

NASA Astrophysics Data System (ADS)

Tomizawa, Yuka; Imamura, Tetsuya; Soeda, Masaya; Ikeda, Yoshinori; Shiro, Takashi

2015-08-01

Boron laser doping (LD) is a promising technology for high-efficiency solar cells such as p-type passivated locally diffused solar cells and n-type Si-wafer-based solar cells. We produced a printable phosphorus- or boron-doped Si paste (NanoGram® Si paste/ink) for use as a diffuser in the LD process. We used the boron LD process to fabricate high-efficiency passivated emitter and rear locally diffused (PERL) solar cells. PERL solar cells on Czochralski Si (Cz-Si) wafers yielded a maximum efficiency of 19.7%, whereas the efficiency of a reference cell was 18.5%. Fill factors above 79% and open circuit voltages above 655 mV were measured. We found that the boron-doped area effectively performs as a local boron back surface field (BSF). The characteristics of the solar cell formed using NanoGram® Si paste/ink were better than those of the reference cell.

Suppressing spectral diffusion of emitted photons with optical pulses

DOE PAGES

Fotso, H. F.; Feiguin, A. E.; Awschalom, D. D.; ...

2016-01-22

In many quantum architectures the solid-state qubits, such as quantum dots or color centers, are interfaced via emitted photons. However, the frequency of photons emitted by solid-state systems exhibits slow uncontrollable fluctuations over time (spectral diffusion), creating a serious problem for implementation of the photon-mediated protocols. Here we show that a sequence of optical pulses applied to the solid-state emitter can stabilize the emission line at the desired frequency. We demonstrate efficiency, robustness, and feasibility of the method analytically and numerically. Taking nitrogen-vacancy center in diamond as an example, we show that only several pulses, with the width of 1more » ns, separated by few ns (which is not difficult to achieve) can suppress spectral diffusion. As a result, our method provides a simple and robust way to greatly improve the efficiency of photon-mediated entanglement and/or coupling to photonic cavities for solid-state qubits.« less

Long-Term Reliability of SiGe/Si HBTs From Accelerated Lifetime Testing

NASA Technical Reports Server (NTRS)

Bhattacharya, Pallab

2001-01-01

Accelerated lifetime tests were performed on double-mesa structure Si(0.7)Ge(0.3)/Si npn heterojunction bipolar transistors, grown by molecular beam epitaxy, in the temperature range of 175 C-275 C. The transistors (with 5x20 sq micron emitter area) have DC current gains approx. 40-50 and f(sub T) and f(sub max) of up to 22 GHz and 25 GHz, respectively. It is found that a gradual degradation in these devices is caused by the recombination enhanced impurity diffusion (REID) of boron atoms from the p-type base region and the associated formation of parasitic energy barriers to electron transport from the emitter to collector layers. This REED has been quantitatively modeled and explained, to the first order of approximation, and the agreement with the measured data is good. The mean time to failure (MTTF) of these devices at room temperature under 1.35 x 10(exp 4) A/sq cm current density operation is estimated from the extrapolation of the Arrhenius plots of device lifetime versus reciprocal temperature. The results of the reliability tests offer valuable feedback for SiGe heterostructure design in order to improve the long-term reliability of the devices and circuits made with them. Hot electron induced degradation of the base-emitter junction was also observed during the accelerated lifetime testing. In order to improve the HBT reliability endangered by the hot electrons, deuterium sintered techniques have been proposed. The preliminary results from this study show that a deuterium-sintered HBT is, indeed, more resistant to hot-electron induced base-emitter junction degradation.

Understanding and development of manufacturable screen-printed contacts on high sheet-resistance emitters for low-cost silicon solar cells

NASA Astrophysics Data System (ADS)

Hilali, Mohamed M.

2005-11-01

A simple cost-effective approach was proposed and successfully employed to fabricate high-quality screen-printed (SP) contacts to high sheet-resistance emitters (100 O/sq) to improve the Si solar cell efficiency. Device modeling was used to quantify the performance enhancement possible from the high sheet-resistance emitter for various cell designs. It was found that for performance enhancement from the high sheet-resistance emitter, certain cell design criteria must be satisfied. Model calculations showed that in order to achieve any performance enhancement over the conventional ˜40 O/sq emitter, the high sheet resistance emitter solar cell must have a reasonably good (<120,000 cm/s) or low front-surface recombination velocity (FSRV). Model calculations were also performed to establish requirements for high fill factors (FFs). The results showed that the series resistance should be less than 0.8 O-cm2, the shunt resistance should be greater than 1000 O-cm2, and the junction leakage current should be less than 25 nA/cm2. Analytical microscopy and surface analysis techniques were used to study the Ag-Si contact interface of different SP Ag pastes. Physical and electrical properties of SP Ag thick-film contacts were studied and correlated to understand and achieve good-quality ohmic contacts to high sheet-resistance emitters for solar cells. This information was then used to define the criteria for high-quality screen-printed contacts. The role of paste constituents and firing scheme on contact quality were investigated to tailor the high-quality screen-printed contact interface structure that results in high performance solar cells. Results indicated that small particle size, high glass transition temperature, rapid firing and less aggressive glass frit help in producing high-quality contacts. Based on these results high-quality SP contacts with high FFs > 0.78 on high sheet-resistance emitters were achieved for the first time using a simple single-step firing process. This technology was applied to different substrates (monocrystalline and multicrystalline) and surfaces (textured and planar). Cell efficiencies of ˜16.2% on low-cost EFG ribbon substrates were achieved on high sheet-resistance emitters with SP contacts. A record high-efficiency SP solar cell of 19% with textured high sheet-resistance emitter was also fabricated and modeled.

Multi-junction solar cell device

DOEpatents

Friedman, Daniel J.; Geisz, John F.

2007-12-18

A multi-junction solar cell device (10) is provided. The multi-junction solar cell device (10) comprises either two or three active solar cells connected in series in a monolithic structure. The multi-junction device (10) comprises a bottom active cell (20) having a single-crystal silicon substrate base and an emitter layer (23). The multi-junction device (10) further comprises one or two subsequent active cells each having a base layer (32) and an emitter layer (23) with interconnecting tunnel junctions between each active cell. At least one layer that forms each of the top and middle active cells is composed of a single-crystal III-V semiconductor alloy that is substantially lattice-matched to the silicon substrate (22). The polarity of the active p-n junction cells is either p-on-n or n-on-p. The present invention further includes a method for substantially lattice matching single-crystal III-V semiconductor layers with the silicon substrate (22) by including boron and/or nitrogen in the chemical structure of these layers.

Transport and collective radiance in a basic quantum chiral optical model

NASA Astrophysics Data System (ADS)

Kornovan, D. F.; Petrov, M. I.; Iorsh, I. V.

2017-09-01

In our work, we theoretically study the dynamics of a single excitation in a one-dimensional array of two-level systems, which are chirally coupled through a single mode waveguide. The chirality is achieved owing to a strong optical spin-locking effect, which in an ideal case gives perfect unidirectional excitation transport. We obtain a simple analytical solution for a single excitation dynamics in the Markovian limit, which directly shows the tolerance of the system with respect to the fluctuations of emitters position. We also show that the Dicke state, which is well known to be superradiant, has twice lower emission rate in the case of unidirectional quantum interaction. Our model is supported and verified with the numerical computations of quantum emitters coupled via surface plasmon modes in a metallic nanowire. The obtained results are based on a very general model and can be applied to any chirally coupled system that gives a new outlook on quantum transport in chiral nanophotonics.

System providing limit switch function with simultaneous absolute position output

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

2006-01-01

A limit and position sensing system includes a sensor assembly and an emitter. The sensor assembly includes first and second electrical conductors arranged in opposing parallel planes. The first electrical conductor is coiled outwardly from either end thereof in a clockwise fashion to form a first coil region and a second coil region. The second electrical conductor forms a single coil with portions of the single coil's rings lying between the first end and second end of the first electrical conductor being parallel to an axis of the first electrical conductor's plane. Ferromagnetic material is aligned with the first and second electrical conductors and spans beyond (a) the first and second ends of the first electrical conductor, and (b) the portions of the rings of the second electrical conductor's single coil that lie between the first end and second end of the first electrical conductor. The emitter is spaced apart from the sensor assembly and transmits a periodic electromagnetic wave towards the sensor assembly.

Metal Photocathodes for Free Electron Laser Applications

NASA Astrophysics Data System (ADS)

Greaves, Corin Michael Ricardo

Synchrotron x-ray radiation sources have revolutionized many areas of science from elucidating the atomic structure of proteins to understanding the electronic structure of complex materials such as the cuprate superconductors. In a Free Electron Laser (FEL), the main difference to the synchrotron radiation mechanism is that the light field acts on the electron beam, over a long distance in an undulator, and causes electron bunching at the optical wavelength. Electrons in different parts of the electron bunch are therefore correlated, and so emit coherently, with a brightness that scales as the square of the number of electrons. In order to lase, the electron beam in a FEL must have a transverse geometric emittance less than the wavelength of the light to be produced. For the generation of x-ray wavelengths, this is one of the most difficult challenges in the design and construction of a FEL. The geometric emittance can be "compressed" by acceleration to very high energy, but with the penalty of very large physical size and very large cost. The motivation for this work was provided by the desire to investigate the fundamental origin of the emittance of an electron beam as it is born at a photocathode. If this initial, or "thermal" emittance can be reduced, the energy, scale and cost of accelerators potentially would be reduced. As the LCLS used copper as its photocathode, this material was the one studied in this work. Copper was used in the LCLS as it represented a "robust" material that could stand the very high accelerating gradients used in the photoinjector of the FEL. Metals are also prompt photoemitters, and so can be used to produce very short electron bunches. This can be a useful property for creation of extremely short FEL pulses, and also for creation of beams that are allowed to expand under space charge forces, but in a way that results in linear fields, allowing subsequent recompression. An ideal photocathode for FEL photoinjector should have high quantum efficiency (QE), small emittance, fast temporal response, long lifetime, and minimal complexity. High QE of cathodes require less power for driving laser and also reduce the risk of damaging the cathode materials. Small emittance reduce the scale of the accelerator, therefore, the cost. Metal photocathodes such as copper exhibit long lifetime and fast response, but have quite low quantum efficiency ( < 10-4). The aim in this work was to understand the quantum yield of the metal, and the transverse momentum spectrum, as the product of the latter and the cathode beam spot size gives the transverse emittance. Initial x-ray diffraction work provided evidence that the LCLS photocathode consisted of large low index single crystal grains, and so work focused on the study of single crystals that could be produced with atomically ordered surfaces, rather than a polycrystalline material. Present theories of quantum yield and transverse emittance assume the basic premise that the metal is entirely disordered, and work here shows that this is fundamentally incorrect, and that the order of the surface plays a critical role in determining the characteristics of emission. In order to investigate these surfaces, I constructed a laser-based ultra-low energy angle resolved photoemission system, capable of measuring the momentum spectrum of the emission and wavelength and angle dependent electron yield. This system has been commissioned, and data taken on low index surfaces of copper. Results from this work on single crystal copper demonstrates that emitted electrons from the band structure of a material can exhibit small emittance and high quantum efficiency. We show that the emission from the Cu(111) surface state is highly correlated between angle of incidence and excitation energy. This manifests itself in the form of a truncated emission cone, rather than the isotropic emission predicted from the normal model. This clearly then reduces the emittance from the normal values. It also results in extremely strong polarization dependence, with p-s asymmetry of up to 16 at low photon energy. It also directly suggests ways through changing materials, or by material design to significantly reduce emittance, at the same time increasing electron yield. These results show the benefits that could be gained from electronic engineering of cathodes and should have direct impact in the design of future FEL photoinjectors. (Abstract shortened by UMI.)

Optical steam quality measurement system and method

DOEpatents

Davidson, James R.; Partin, Judy K.

2006-04-25

An optical measurement system is presented that offers precision on-line monitoring of the quality of steam. Multiple wavelengths of radiant energy are passed through the steam from an emitter to a detector. By comparing the amount of radiant energy absorbed by the flow of steam for each wavelength, a highly accurate measurement of the steam quality can be determined on a continuous basis in real-time. In an embodiment of the present invention, the emitter, comprises three separate radiant energy sources for transmitting specific wavelengths of radiant energy through the steam. In a further embodiment, the wavelengths of radiant energy are combined into a single beam of radiant energy for transmission through the steam using time or wavelength division multiplexing. In yet a further embodiment, the single beam of radiant energy is transmitted using specialized optical elements.

Integrated nanoplasmonic quantum interfaces for room-temperature single-photon sources

NASA Astrophysics Data System (ADS)

Peyskens, Frédéric; Englund, Dirk; Chang, Darrick

2017-12-01

We describe a general analytical framework of a nanoplasmonic cavity-emitter system interacting with a dielectric photonic waveguide. Taking into account emitter quenching and dephasing, our model directly reveals the single-photon extraction efficiency η as well as the indistinguishability I of photons coupled into the waveguide mode. Rather than minimizing the cavity modal volume, our analysis predicts an optimum modal volume to maximize η that balances waveguide coupling and spontaneous emission rate enhancement. Surprisingly, our model predicts that near-unity indistinguishability is possible, but this requires a much smaller modal volume, implying a fundamental performance trade-off between high η and I at room temperature. Finally, we show that maximizing η I requires that the system has to be driven in the weak coupling regime because quenching effects and decreased waveguide coupling drastically reduce η in the strong coupling regime.

Multi-ball and one-ball geolocation

NASA Astrophysics Data System (ADS)

Nelson, D. J.; Townsend, J. L.

2017-05-01

We present analysis methods that may be used to geolocate emitters using one or more moving receivers. While some of the methods we present may apply to a broader class of signals, our primary interest is locating and tracking ships from short pulsed transmissions, such as the maritime Automatic Identification System (AIS.) The AIS signal is difficult to process and track since the pulse duration is only 25 milliseconds, and the pulses may only be transmitted every six to ten seconds. In this article, we address several problems including accurate TDOA and FDOA estimation methods that do not require searching a two dimensional surface such as the cross-ambiguity surface. As an example, we apply these methods to identify and process AIS pulses from a single emitter, making it possible to geolocate the AIS signal using a single moving receiver.

High brightness diode lasers controlled by volume Bragg gratings

NASA Astrophysics Data System (ADS)

Glebov, Leonid

2017-02-01

Volume Bragg gratings (VBGs) recorded in photo-thermo-refractive (PTR) glass are holographic optical elements that are effective spectral and angular filters withstanding high power laser radiation. Reflecting VBGs are narrow-band spectral filters while transmitting VBGs are narrow-band angular filters. The use of these optical elements in external resonators of semiconductor lasers enables extremely resonant feedback that provides dramatic spectral and angular narrowing of laser diodes radiation without significant power and efficiency penalty. Spectral narrowing of laser diodes by reflecting VBGs demonstrated in wide spectral region from near UV to 3 μm. Commercially available VBGs have spectral width ranged from few nanometers to few tens of picometers. Efficient spectral locking was demonstrated for edge emitters (single diodes, bars, modules, and stacks), vertical cavity surface emitting lasers (VCSELs), grating coupled surface emitting lasers (GCSELs), and interband cascade lasers (ICLs). The use of multiplexed VBGs provides multiwavelength emission from a single emitter. Spectrally locked semiconductor lasers demonstrated CW power from milliwatts to a kilowatt. Angular narrowing by transmitting VBGs enables single transverse mode emission from wide aperture diode lasers having resonators with great Fresnel numbers. This feature provides close to diffraction limit divergence along a slow axis of wide stripe edge emitters. Radiation exchange between lasers by means of spatially profiled or multiplexed VBGs enables coherent combining of diode lasers. Sequence of VBGs or multiplexed VBGs enable spectral combining of spectrally narrowed diode lasers or laser modules. Thus the use of VBGs for diode lasers beam control provides dramatic increase of brightness.

970-nm ridge waveguide diode laser bars for high power DWBC systems

NASA Astrophysics Data System (ADS)

Wilkens, Martin; Erbert, Götz; Wenzel, Hans; Knigge, Andrea; Crump, Paul; Maaßdorf, Andre; Fricke, Jörg; Ressel, Peter; Strohmaier, Stephan; Schmidt, Berthold; Tränkle, Günther

2018-02-01

de lasers are key components in material processing laser systems. While mostly used as pump sources for solid state or fiber lasers, direct diode laser systems using dense wavelength multiplexing have come on the market in recent years. These systems are realized with broad area lasers typically, resulting in beam quality inferior to disk or fiber lasers. We will present recent results of highly efficient ridge waveguide (RW) lasers, developed for dense-wavelength-beamcombining (DWBC) laser systems expecting beam qualities comparable to solid state laser systems and higher power conversion efficiencies (PCE). The newly developed RW lasers are based on vertical structures with an extreme double asymmetric large optical cavity. Besides a low vertical divergence these structures are suitable for RW-lasers with (10 μm) broad ridges, emitting in a single mode with a good beam quality. The large stripe width enables a lateral divergence below 10° (95 % power content) and a high PCE by a comparably low series resistance. We present results of single emitters and small test arrays under different external feedback conditions. Single emitters can be tuned from 950 nm to 975 nm and reach 1 W optical power with more than 55 % PCE and a beam quality of M2 < 2 over the full wavelength range. The spectral width is below 30 pm FWHM. 5 emitter arrays were stabilized using the same setup. Up to now we reached 3 W optical power, limited by power supply, with 5 narrow spectral lines.

Two-dimensional and 3-D images of thick tissue using time-constrained times-of-flight and absorbance spectrophotometry

NASA Astrophysics Data System (ADS)

Benaron, David A.; Lennox, M.; Stevenson, David K.

1992-05-01

Reconstructing deep-tissue images in real time using spectrophotometric data from optically diffusing thick tissues has been problematic. Continuous wave applications (e.g., pulse oximetry, regional cerebral saturation) ignore both the multiple paths traveled by the photons through the tissue and the effects of scattering, allowing scalar measurements but only under limited conditions; interferometry works poorly in thick, highly-scattering media; frequency- modulated approaches may not allow full deconvolution of scattering and absorbance; and pulsed-light techniques allow for preservation of information regarding the multiple paths taken by light through the tissue, but reconstruction is both computation intensive and limited by the relative surface area available for detection of photons. We have developed a picosecond times-of-flight and absorbance (TOFA) optical system, time-constrained to measure only photons with a narrow range of path lengths and arriving within a narrow angel of the emitter-detector axis. The delay until arrival of the earliest arriving photons is a function of both the scattering and absorbance of the tissues in a direct line between the emitter and detector, reducing the influence of surrounding tissues. Measurement using a variety of emitter and detector locations produces spatial information which can be analyzed in a standard 2-D grid, or subject to computer reconstruction to produce tomographic images representing 3-D structure. Using such a technique, we have been able to demonstrate the principles of tc-TOFA, detect and localize diffusive and/or absorptive objects suspended in highly scattering media (such as blood admixed with yeast), and perform simple 3-D reconstructions using phantom objects. We are now attempting to obtain images in vivo. Potential future applications include use as a research tool, and as a continuous, noninvasive, nondestructive monitor in diagnostic imaging, fetal monitoring, neurologic and cardiac assessment. The technique may lead to real-time optical imaging and quantitation of tissues oxygen delivery.

Passivation of phosphorus diffused silicon surfaces with Al2O3: Influence of surface doping concentration and thermal activation treatments

NASA Astrophysics Data System (ADS)

Richter, Armin; Benick, Jan; Kimmerle, Achim; Hermle, Martin; Glunz, Stefan W.

2014-12-01

Thin layers of Al2O3 are well known for the excellent passivation of p-type c-Si surfaces including highly doped p+ emitters, due to a high density of fixed negative charges. Recent results indicate that Al2O3 can also provide a good passivation of certain phosphorus-diffused n+ c-Si surfaces. In this work, we studied the recombination at Al2O3 passivated n+ surfaces theoretically with device simulations and experimentally for Al2O3 deposited with atomic layer deposition. The simulation results indicate that there is a certain surface doping concentration, where the recombination is maximal due to depletion or weak inversion of the charge carriers at the c-Si/Al2O3 interface. This pronounced maximum was also observed experimentally for n+ surfaces passivated either with Al2O3 single layers or stacks of Al2O3 capped by SiNx, when activated with a low temperature anneal (425 °C). In contrast, for Al2O3/SiNx stacks activated with a short high-temperature firing process (800 °C) a significant lower surface recombination was observed for most n+ diffusion profiles without such a pronounced maximum. Based on experimentally determined interface properties and simulation results, we attribute this superior passivation quality after firing to a better chemical surface passivation, quantified by a lower interface defect density, in combination with a lower density of negative fixed charges. These experimental results reveal that Al2O3/SiNx stacks can provide not only excellent passivation on p+ surfaces but also on n+ surfaces for a wide range of surface doping concentrations when activated with short high-temperature treatments.

'Squeezing' near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion.

PubMed

Karalis, Aristeidis; Joannopoulos, J D

2016-07-01

We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm(2) with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm(2) with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm(2) with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a 'squeezed' narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells.

‘Squeezing’ near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion

PubMed Central

Karalis, Aristeidis; Joannopoulos, J. D.

2016-01-01

We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm2 with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm2 with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm2 with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a ‘squeezed’ narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells. PMID:27363522

Optical tracking of nanoscale particles in microscale environments

PubMed Central

Mathai, P. P.; Liddle, J. A.; Stavis, S. M.

2016-01-01

The trajectories of nanoscale particles through microscale environments record useful information about both the particles and the environments. Optical microscopes provide efficient access to this information through measurements of light in the far field from nanoparticles. Such measurements necessarily involve trade-offs in tracking capabilities. This article presents a measurement framework, based on information theory, that facilitates a more systematic understanding of such trade-offs to rationally design tracking systems for diverse applications. This framework includes the degrees of freedom of optical microscopes, which determine the limitations of tracking measurements in theory. In the laboratory, tracking systems are assemblies of sources and sensors, optics and stages, and nanoparticle emitters. The combined characteristics of such systems determine the limitations of tracking measurements in practice. This article reviews this tracking hardware with a focus on the essential functions of nanoparticles as optical emitters and microenvironmental probes. Within these theoretical and practical limitations, experimentalists have implemented a variety of tracking systems with different capabilities. This article reviews a selection of apparatuses and techniques for tracking multiple and single particles by tuning illumination and detection, and by using feedback and confinement to improve the measurements. Prior information is also useful in many tracking systems and measurements, which apply across a broad spectrum of science and technology. In the context of the framework and review of apparatuses and techniques, this article reviews a selection of applications, with particle diffusion serving as a prelude to tracking measurements in biological, fluid, and material systems, fabrication and assembly processes, and engineered devices. In so doing, this review identifies trends and gaps in particle tracking that might influence future research. PMID:27213022

Room temperature solid-state quantum emitters in the telecom range

PubMed Central

Bodrog, Zoltán; Adamo, Giorgio; Gali, Adam

2018-01-01

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies. PMID:29670945

High-power VCSELs for smart munitions

NASA Astrophysics Data System (ADS)

Geske, Jon; MacDougal, Michael; Cole, Garrett; Snyder, Donald

2006-08-01

The next generation of low-cost smart munitions will be capable of autonomously detecting and identifying targets aided partly by the ability to image targets with compact and robust scanning rangefinder and LADAR capabilities. These imaging systems will utilize arrays of high performance, low-cost semiconductor diode lasers capable of achieving high peak powers in pulses ranging from 5 to 25 nanoseconds in duration. Aerius Photonics is developing high-power Vertical-Cavity Surface-Emitting Lasers (VCSELs) to meet the needs of these smart munitions applications. The authors will report the results of Aerius' development program in which peak pulsed powers exceeding 60 Watts were demonstrated from single VCSEL emitters. These compact packaged emitters achieved pulse energies in excess of 1.5 micro-joules with multi kilo-hertz pulse repetition frequencies. The progress of the ongoing effort toward extending this performance to arrays of VCSEL emitters and toward further improving laser slope efficiency will be reported.

Deterministic Generation of All-Photonic Quantum Repeaters from Solid-State Emitters

NASA Astrophysics Data System (ADS)

Buterakos, Donovan; Barnes, Edwin; Economou, Sophia E.

2017-10-01

Quantum repeaters are nodes in a quantum communication network that allow reliable transmission of entanglement over large distances. It was recently shown that highly entangled photons in so-called graph states can be used for all-photonic quantum repeaters, which require substantially fewer resources compared to atomic-memory-based repeaters. However, standard approaches to building multiphoton entangled states through pairwise probabilistic entanglement generation severely limit the size of the state that can be created. Here, we present a protocol for the deterministic generation of large photonic repeater states using quantum emitters such as semiconductor quantum dots and defect centers in solids. We show that arbitrarily large repeater states can be generated using only one emitter coupled to a single qubit, potentially reducing the necessary number of photon sources by many orders of magnitude. Our protocol includes a built-in redundancy, which makes it resilient to photon loss.

C-history method: rapid measurement of the initial emittable concentration, diffusion and partition coefficients for formaldehyde and VOCs in building materials.

PubMed

Xiong, Jianyin; Yao, Yuan; Zhang, Yinping

2011-04-15

The initial emittable concentration (C(m,0)), the diffusion coefficient (D(m)), and the material/air partition coefficient (K) are the three characteristic parameters influencing emissions of formaldehyde and volatile organic compounds (VOCs) from building materials or furniture. It is necessary to determine these parameters to understand emission characteristics and how to control them. In this paper we develop a new method, the C-history method for a closed chamber, to measure these three parameters. Compared to the available methods of determining the three parameters described in the literature, our approach has the following salient features: (1) the three parameters can be simultaneously obtained; (2) it is time-saving, generally taking less than 3 days for the cases studied (the available methods tend to need 7-28 days); (3) the maximum relative standard deviations of the measured C(m,0), D(m) and K are 8.5%, 7.7%, and 9.8%, respectively, which are acceptable for engineering applications. The new method was validated by using the characteristic parameters determined in the closed chamber experiment to predict the observed emissions in a ventilated full scale chamber experiment, proving that the approach is reliable and convincing. Our new C-history method should prove useful for rapidly determining the parameters required to predict formaldehyde and VOC emissions from building materials as well as for furniture labeling.

Research on Electrically Driven Single Photon Emitter by Diamond for Quantum Cryptography

DTIC Science & Technology

2015-03-24

by diamond for quantum cryptography 5a. CONTRACT NUMBER FA2386-14-1-4037 5b. GRANT NUMBE R Grant 14IOA093_144037 5c. PROGRAM ELEMENT...emerged as a highly competitive platform for applications in quantum cryptography , quantum computing, spintronics, and sensing or metrology...15. SUBJECT TERMS Diamond LED, Nitrogen Vacancy Complex, Quantum Computing, Quantum Cryptography , Single Spin Single Photon 16. SECURITY

Measurements of optical properties of some molten oxides

NASA Astrophysics Data System (ADS)

Nason, D. O.; Yen, C. T.; Tiller, W. A.

1990-11-01

A method based on a fine-focussed optical laser has been developed to measure the spectral reflectance and the transmittance of small ( ∽ 1 mm) liquid or single crystal materials. The measured normal spectral emittance for 633 nm light is about 0.9 for several molten refractory oxides, 0.8 for lithium niobate and 0.7 for molten sapphire. Sapphire and YAG experience a several-fold increase in emittance on melting. The absorption coefficient and the thickness for opaqueness are calculated and some consequences of the partial transparency of small hot materials, when their temperatures are measured by optical pyrometry, are discussed.

Applications using high-Tc superconducting terahertz emitters

PubMed Central

Nakade, Kurama; Kashiwagi, Takanari; Saiwai, Yoshihiko; Minami, Hidetoshi; Yamamoto, Takashi; Klemm, Richard A.; Kadowaki, Kazuo

2016-01-01

Using recently-developed THz emitters constructed from single crystals of the high-Tc superconductor Bi2Sr2CaCu2O8+δ, we performed three prototype tests of the devices to demonstrate their unique characteristic properties for various practical applications. The first is a compact and simple transmission type of THz imaging system using a Stirling cryocooler. The second is a high-resolution Michelson interferometer used as a phase-sensitive reflection-type imaging system. The third is a system with precise temperature control to measure the liquid absorption coefficient. The detailed characteristics of these systems are discussed. PMID:26983905

Stable two-plane focusing for emittance-dominated sheet-beam transport

NASA Astrophysics Data System (ADS)

Carlsten, B. E.; Earley, L. M.; Krawczyk, F. L.; Russell, S. J.; Potter, J. M.; Ferguson, P.; Humphries, S.

2005-06-01

Two-plane focusing of sheet electron beams will be an essential technology for an emerging class of high-power, 100 to 300 GHz rf sources [Carlsten et al., IEEE Trans. Plasma Sci. 33, 85 (2005), ITPSBD, 0093-3813, 10.1109/TPS.2004.841172]. In these devices, the beam has a unique asymmetry in which the transport is emittance dominated in the sheet’s thin dimension and space-charge dominated in the sheet’s wide dimension. Previous work has studied the stability of the transport of beams in the emittance-dominated regime for both wiggler and periodic permanent magnet (PPM) configurations with single-plane focusing, and has found that bigger envelope scalloping occurs for equilibrium transport, as compared to space-charge dominated beams [Carlsten et al., this issue, Phys. Rev. ST Accel. Beams 8, 062001 (2005), PRABFM, 1098-4402]. In this paper, we describe the differences in transport stability when two-plane focusing is included. Two-plane wiggler focusing degrades the transport stability slightly, whereas two-plane PPM focusing greatly compromises the transport. On the other hand, single-plane PPM focusing can be augmented with external quadrupole fields to provide weak focusing in the sheet’s wide dimension, which has stability comparable to two-plane wiggler transport.

Microfluidic White Organic Light-Emitting Diode Based on Integrated Patterns of Greenish-Blue and Yellow Solvent-Free Liquid Emitters

NASA Astrophysics Data System (ADS)

Kobayashi, Naofumi; Kasahara, Takashi; Edura, Tomohiko; Oshima, Juro; Ishimatsu, Ryoichi; Tsuwaki, Miho; Imato, Toshihiko; Shoji, Shuichi; Mizuno, Jun

2015-10-01

We demonstrated a novel microfluidic white organic light-emitting diode (microfluidic WOLED) based on integrated sub-100-μm-wide microchannels. Single-μm-thick SU-8-based microchannels, which were sandwiched between indium tin oxide (ITO) anode and cathode pairs, were fabricated by photolithography and heterogeneous bonding technologies. 1-Pyrenebutyric acid 2-ethylhexyl ester (PLQ) was used as a solvent-free greenish-blue liquid emitter, while 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb)-doped PLQ was applied as a yellow liquid emitter. In order to form the liquid white light-emitting layer, the greenish-blue and yellow liquid emitters were alternately injected into the integrated microchannels. The fabricated electro-microfluidic device successfully exhibited white electroluminescence (EL) emission via simultaneous greenish-blue and yellow emissions under an applied voltage of 100 V. A white emission with Commission Internationale de l’Declairage (CIE) color coordinates of (0.40, 0.42) was also obtained; the emission corresponds to warm-white light. The proposed device has potential applications in subpixels of liquid-based microdisplays and for lighting.

Thermo-electronic solar power conversion with a parabolic concentrator

NASA Astrophysics Data System (ADS)

Olukunle, Olawole C.; De, Dilip K.

2016-02-01

We consider the energy dynamics of the power generation from the sun when the solar energy is concentrated on to the emitter of a thermo-electronic converter with the help of a parabolic mirror. We use the modified Richardson-Dushman equation. The emitter cross section is assumed to be exactly equal to the focused area at a height h from the base of the mirror to prevent loss of efficiency. We report the variation of output power with solar insolation, height h, reflectivity of the mirror, and anode temperature, initially assuming that there is no space charge effect. Our methodology allows us to predict the temperature at which the anode must be cooled in order to prevent loss of efficiency of power conversion. Novel ways of tackling the space charge problem have been discussed. The space charge effect is modeled through the introduction of a parameter f (0 < f < 1) in the thermos-electron emission equation. We find that the efficiency of the power conversion depends on solar insolation, height h, apart from radii R of the concentrator aperture and emitter, and the collector material properties. We have also considered solar thermos electronic power conversion by using single atom-layer graphene as an emitter.

Improving Defect-Based Quantum Emitters in Silicon Carbide via Inorganic Passivation.

PubMed

Polking, Mark J; Dibos, Alan M; de Leon, Nathalie P; Park, Hongkun

2018-01-01

Defect-based color centers in wide-bandgap crystalline solids are actively being explored for quantum information science, sensing, and imaging. Unfortunately, the luminescent properties of these emitters are frequently degraded by blinking and photobleaching that arise from poorly passivated host crystal surfaces. Here, a new method for stabilizing the photoluminescence and charge state of color centers based on epitaxial growth of an inorganic passivation layer is presented. Specifically, carbon antisite-vacancy pairs (CAV centers) in 4H-SiC, which serve as single-photon emitters at visible wavelengths, are used as a model system to demonstrate the power of this inorganic passivation scheme. Analysis of CAV centers with scanning confocal microscopy indicates a dramatic improvement in photostability and an enhancement in emission after growth of an epitaxial AlN passivation layer. Permanent, spatially selective control of the defect charge state can also be achieved by exploiting the mismatch in spontaneous polarization at the AlN/SiC interface. These results demonstrate that epitaxial inorganic passivation of defect-based quantum emitters provides a new method for enhancing photostability, emission, and charge state stability of these color centers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical levitation of a microdroplet containing a single quantum dot.

PubMed

Minowa, Yosuke; Kawai, Ryoichi; Ashida, Masaaki

2015-03-15

We demonstrate the optical levitation or trapping in helium gas of a single quantum dot (QD) within a liquid droplet. Bright single photon emission from the levitated QD in the droplet was observed for more than 200 s. The observed photon count rates are consistent with the value theoretically estimated from the two-photon-action cross section. This Letter presents the realization of an optically levitated solid-state quantum emitter.

Innovative single-shot diagnostics for electrons accelerated through laser-plasma interaction at FLAME

NASA Astrophysics Data System (ADS)

Bisesto, F. G.; Anania, M. P.; Chiadroni, E.; Cianchi, A.; Costa, G.; Curcio, A.; Ferrario, M.; Galletti, M.; Pompili, R.; Schleifer, E.; Zigler, A.

2017-05-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (> 100 GV/m), enabling acceleration of electrons to GeV energy in few centimeters. Here we present all the plasma related activities currently underway at SPARC LAB exploiting the high power laser FLAME. In particular, we will give an overview of the single shot diagnostics employed: Electro Optic Sampling (EOS) for temporal measurement and optical transition radiation (OTR) for an innovative one shot emittance measurements. In detail, the EOS technique has been employed to measure for the first time the longitudinal profile of electric field of fast electrons escaping from a solid target, driving the ions and protons acceleration, and to study the impact of using different target shapes. Moreover, a novel scheme for one shot emittance measurements based on OTR, developed and tested at SPARC LAB LINAC, will be shown.

APS-U LATTICE DESIGN FOR OFF-AXIS ACCUMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yipeng; Borland, M.; Lindberg, R.

2017-06-25

A 67-pm hybrid-seven-bend achromat (H7BA) lattice is being proposed for a future Advanced Photon Source (APS) multi-bend-achromat (MBA) upgrade project. This lattice design pushes for smaller emittance and requires use of a swap-out (on-axis) injection scheme due to limited dynamic acceptance. Alternate lattice design work has also been performed for the APS upgrade to achieve better beam dynamics performance than the nominal APS MBA lattice, in order to allow off-axis accumulation. Two such alternate H7BA lattice designs, which target a still-low emittance of 90 pm, are discussed in detail in this paper. Although the single-particle-dynamics performance is good, simulations ofmore » collective effects indicate that surprising difficulty would be expected accumulating high single-bunch charge in this lattice. The brightness of the 90-pm lattice is also a factor of two lower than the 67-pm H7BA lattice.« less

Marshak Lectureship: Vibrational properties of isolated color centers in diamond

NASA Astrophysics Data System (ADS)

Alkauskas, Audrius

In this talk we review our recent work on first-principles calculations of vibrational properties of isolated defect spin qubits and single photon emitters in diamond. These properties include local vibrational spectra, luminescence lineshapes, and electron-phonon coupling. They are key in understanding physical mechanisms behind spin-selective optical initialization and read-out, quantum efficiency of single-photon emitters, as well as in the experimental identification of as yet unknown centers. We first present the methodology to calculate and analyze vibrational properties of effectively isolated defect centers. We then apply the methodology to the nitrogen-vacancy and the silicon-vacancy centers in diamond. First-principles calculations yield important new insights about these important defects. Work performed in collaboration with M. W. Doherty, A. Gali, E. Londero, L. Razinkovas, and C. G. Van de Walle. Supported by the Research Council of Lithuania (Grant M-ERA.NET-1/2015).

Direct determination of minority carrier diffusion lengths at axial GaAs nanowire p-n junctions.

PubMed

Gutsche, Christoph; Niepelt, Raphael; Gnauck, Martin; Lysov, Andrey; Prost, Werner; Ronning, Carsten; Tegude, Franz-Josef

2012-03-14

Axial GaAs nanowire p-n diodes, possibly one of the core elements of future nanowire solar cells and light emitters, were grown via the Au-assisted vapor-liquid-solid mode, contacted by electron beam lithography, and investigated using electron beam induced current measurements. The minority carrier diffusion lengths and dynamics of both, electrons and holes, were determined directly at the vicinity of the p-n junction. The generated photocurrent shows an exponential decay on both sides of the junction and the extracted diffusion lengths are about 1 order of magnitude lower compared to bulk material due to surface recombination. Moreover, the observed strong diameter-dependence is well in line with the surface-to-volume ratio of semiconductor nanowires. Estimating the surface recombination velocities clearly indicates a nonabrupt p-n junction, which is in essential agreement with the model of delayed dopant incorporation in the Au-assisted vapor-liquid-solid mechanism. Surface passivation using ammonium sulfide effectively reduces the surface recombination and thus leads to higher minority carrier diffusion lengths. © 2012 American Chemical Society

Infrared spectral normal emittance/emissivity comparison

NASA Astrophysics Data System (ADS)

Hanssen, L.; Wilthan, B.; Filtz, J.-R.; Hameury, J.; Girard, F.; Battuello, M.; Ishii, J.; Hollandt, J.; Monte, C.

2016-01-01

The National Measurement Institutes (NMIs) of the United States, Germany, France, Italy and Japan, have joined in an inter-laboratory comparison of their infrared spectral emittance scales. This action is part of a series of supplementary inter-laboratory comparisons (including thermal conductivity and thermal diffusivity) sponsored by the Consultative Committee on Thermometry (CCT) Task Group on Thermophysical Quantities (TG-ThQ). The objective of this collaborative work is to strengthen the major operative National Measurement Institutes' infrared spectral emittance scales and consequently the consistency of radiative properties measurements carried out worldwide. The comparison has been performed over a spectral range of 2 μm to 14 μm, and a temperature range from 23 °C to 800 °C. Artefacts included in the comparison are potential standards: oxidized Inconel, boron nitride, and silicon carbide. The measurement instrumentation and techniques used for emittance scales are unique for each NMI, including the temperature ranges covered as well as the artefact sizes required. For example, all three common types of spectral instruments are represented: dispersive grating monochromator, Fourier transform and filter-based spectrometers. More than 2000 data points (combinations of material, wavelength and temperature) were compared. Ninety-eight percent (98%) of the data points were in agreement, with differences to weighted mean values less than the expanded uncertainties calculated from the individual NMI uncertainties and uncertainties related to the comparison process. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

High temperature fuel/emitter system for advanced thermionic fuel elements

NASA Astrophysics Data System (ADS)

Moeller, Helen H.; Bremser, Albert H.; Gontar, Alexander; Fiviesky, Evgeny

1997-01-01

Specialists in space applications are currently focusing on bimodal power systems designed to provide both electric power and thermal propulsion (Kennedy, 1994 and Houts, 1995). Our work showed that thermionics is a viable technology for nuclear bimodal power systems. We demonstrated that materials for a thermionic fuel-emitter combination capable of performing at operating temperatures of 2473 K are not only possible but available. The objective of this work, funded by the US Department of Energy, Office of Space and Defense Power Systems, was to evaluate the compatibility of fuel material consisting of an uranium carbide/tantalum carbide solid solution with an emitter material consisting of a monocrystalline tungsten-niobium alloy. The uranium loading of the fuel material was 70 mole% uranium carbide. The program was successfully accomplished by a B&W/SIA LUTCH team. Its workscope was integrated with tasks being performed at both Babcock & Wilcox, Lynchburg Research Center, Lynchburg, Virginia, and SIA LUTCH, Podolsk, Russia. Samples were fabricated by LUTCH and seven thermal tests were performed in a hydrogen atmosphere. The first preliminary test was performed at 2273 K by LUTCH, and the remaining six tests were performed At B&W. Three tests were performed at 2273 K, two at 2373 K, and the final test at 2473 K. The results showed that the fuel and emitter materials were compatible in the presence of hydrogen. No evidence of liquid formation, dissolution of the uranium carbide from the uranium carbide/tantalum carbide solid solution, or diffusion of the uranium into the monocrystalline tungsten alloy was observed. Among the highlights of the program was the successful export of the fuel samples from Russia and their import into the US by commercial transport. This paper will discuss the technical aspects of this work.

Spectroscopy of Single AlInAs Quantum Dots

NASA Astrophysics Data System (ADS)

Derebezov, I. A.; Gaisler, A. V.; Gaisler, V. A.; Dmitriev, D. V.; Toropov, A. I.; Kozhukhov, A. S.; Shcheglov, D. V.; Latyshev, A. V.; Aseev, A. L.

2018-03-01

A system of quantum dots based on Al x In1- x As/Al y Ga1- y As solid solutions is investigated. The use of Al x In1- x As wide-gap solid solutions as the basis of quantum dots substantially extends the spectral emission range to the short-wavelength region, including the wavelength region near 770 nm, which is of interest for the development of aerospace systems of quantum cryptography. The optical characteristics of Al x In1- x As single quantum dots grown by the Stranski-Krastanov mechanism were studied by cryogenic microphotoluminescence. The statistics of the emission of single quantum dot excitons was studied using a Hanbury Brown-Twiss interferometer. The pair photon correlation function indicates the sub-Poissonian nature of the emission statistics, which directly confirms the possibility of developing single-photon emitters based on Al x In1- x As quantum dots. The fine structure of quantum dot exciton states was investigated at wavelengths near 770 nm. The splitting of the exciton states is found to be similar to the natural width of exciton lines, which is of great interest for the development of entangled photon pair emitters based on Al x In1- x As quantum dots.

Use of low energy hydrogen ion implants in high efficiency crystalline silicon solar cells

NASA Technical Reports Server (NTRS)

Fonash, S. J.; Singh, R.

1985-01-01

This program is a study of the use of low energy hydrogen ion implantation for high efficiency crystalline silicon solar cells. The first quarterly report focuses on two tasks of this program: (1) an examination of the effects of low energy hydrogen implants on surface recombination speed; and (2) an examination of the effects of hydrogen on silicon regrowth and diffusion in silicon. The first part of the project focussed on the measurement of surface properties of hydrogen implanted silicon. Low energy hydrogen ions when bombarded on the silicon surface will create structural damage at the surface, deactivate dopants and introduce recombination centers. At the same time the electrically active centers such as dangling bonds will be passivated by these hydrogen ions. Thus hydrogen is expected to alter properties such as the surface recombination velocity, dopant profiles on the emitter, etc. In this report the surface recombination velocity of a hydrogen emplanted emitter was measured.

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells

PubMed Central

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n+ emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion. PMID:25520602

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

PubMed

Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire.

PubMed

Li, Qiang; Wei, Hong; Xu, Hongxing

2015-12-09

The interactions between surface plasmons (SPs) in metal nanostructures and excitons in quantum emitters (QEs) lead to many interesting phenomena and potential applications that are strongly dependent on the quantum yield of SPs. The difficulty in distinguishing all the possible exciton recombination channels hinders the experimental determination of SP quantum yield. Here, we experimentally measured for the first time the quantum yield of single SPs generated by the exciton-plasmon coupling in a system composed of a single quantum dot and a silver nanowire (NW). By utilizing the SP guiding property of the NW, the decay rates of all the exciton recombination channels, i.e., direct free space radiation channel, SP generation channel, and nonradiative damping channel, are quantitatively obtained. It is determined that the optimum emitter-NW coupling distance for the largest SP quantum yield is about 10 nm, resulting from the different distance-dependent decay rates of the three channels. These results are important for manipulating the coupling between plasmonic nanostructures and QEs and developing on-chip quantum plasmonic devices for potential nanophotonic and quantum information applications.

High-brightness 9xxnm fiber coupled diode lasers

NASA Astrophysics Data System (ADS)

Liu, Rui; Jiang, Xiaochen; Yang, Thomas; He, Xiaoguang; Gao, Yanyan; Zhu, Jing; Zhang, Tujia; Guo, Weirong; Wang, Baohua; Guo, Zhijie; Zhang, Luyan; Chen, Louisa

2015-03-01

We developed a high brightness fiber coupled diode laser module providing more than 140W output power from a 105μm NA 0.15 fiber at the wavelength of 915nm.The high brightness module has an electrical to optical efficiency better than 45% and power enclosure more than 90% within NA 0.13. It is based on multi-single emitters using optical and polarization beam combining and fiber coupling technique. With the similar technology, over 100W of optical power into a 105μm NA 0.15 fiber at 976nm is also achieved which can be compatible with the volume Bragg gratings to receive narrow and stabilized spectral linewidth. The light within NA 0.12 is approximately 92%. The reliability test data of single and multiple single emitter laser module under high optical load are also presented and analyzed using a reliability model with an emitting aperture optimized for coupling into 105μm core fiber. The total MTTF shows exceeding 100,000 hours within 60% confidence level. The packaging processes and optical design are ready for commercial volume production.

The role of upstream distal electrodes in mitigating electrochemical degradation of ionic liquid ion sources

NASA Astrophysics Data System (ADS)

Brikner, Natalya; Lozano, Paulo C.

2012-11-01

Ionic liquid ion sources produce molecular ions from micro-tip emitters wetted with room-temperature molten salts. When a single ion polarity is extracted, counterions accumulate and generate electrochemical reactions that limit the source lifetime. The dynamics of double layer formation are reviewed and distal electrode contacts are introduced to resolve detrimental electrochemical decomposition effects at the micro-tip apex. By having the emitter follow the ionic liquid potential, operation can be achieved for an extended period of time with no apparent degradation of the material, indicating that electrochemistry can be curtailed and isolated to the upstream distal electrode.

Characterisation of the muon beams for the Muon Ionisation Cooling Experiment

DOE PAGES

Adams, D.; Adey, D.; Alekou, A.; ...

2013-10-01

A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.2-2.3 π mm-rad horizontally and 0.6-1.0 π mm-rad vertically, a horizontal dispersion of 90-190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE.

LC-oscillator with automatic stabilized amplitude via bias current control. [power supply circuit for transducers

NASA Technical Reports Server (NTRS)

Hamlet, J. F. (Inventor)

1974-01-01

A stable excitation supply for measurement transducers is described. It consists of a single-transistor oscillator with a coil connected to the collector and a capacitor connected from the collector to the emitter. The output of the oscillator is rectified and the rectified signal acts as one input to a differential amplifier; the other input being a reference potential. The output of the amplifier is connected at a point between the emitter of the transistor and ground. When the rectified signal is greater than the reference signal, the differential amplifier produces a signal of polarity to reduce bias current and, consequently, amplification.

Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method

PubMed Central

Van Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Héroux, M È; Gibson, M D; Guernsey, J R; Kindzierski, W; Wheeler, A J

2015-01-01

Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER1z). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER2z). In total, 287 daily pairs of AER2z and AER1z estimates were made from 35 homes across three cities. In 87% of the cases, AER2z was higher than AER1z. Overall, the AER1z estimates underestimated AER2z by approximately 16% (IQR: 5–32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. PMID:25399878

Excitation-dependent local symmetry reversal in single host lattice Ba2A(BO3)2:Eu3+ [A = Mg and Ca] phosphors with tunable emission colours.

PubMed

Jayakiruba, S; Chandrasekaran, S Selva; Murugan, P; Lakshminarasimhan, N

2017-07-05

Eu 3+ activated phosphors are widely used as red emitters in various display devices and light emitting diodes (LEDs). The emission characteristics of Eu 3+ depend on the local site symmetry. The present study demonstrates the role of excitation-dependent local symmetry changes due to the structural reorganization on the emission colour tuning of Eu 3+ from orange-red to orange in single host lattices, Ba 2 Mg(BO 3 ) 2 and Ba 2 Ca(BO 3 ) 2 . The choice of these lattices was based on the difference in the extent of strain experienced by the oxygen atoms. The samples with Eu 3+ at Ba or Mg (Ca) sites were synthesized using the conventional high-temperature solid-state reaction method. The samples were characterized using powder XRD, 11 B MAS-NMR, FT-IR, and diffuse reflectance UV-Vis spectroscopic techniques. The room temperature photoluminescence (PL) recorded using different excitation wavelengths revealed a clear difference in the PL emission features due to symmetry reversal from non-inversion to inversion symmetry around Eu 3+ . The reorganization of highly strained oxygen atoms leads to such symmetry reversal. First-principles calculations were used to deduce the optimized structures of the two borate host lattices, and local geometries and their distortions upon Eu 3+ substitution. The outcomes of these calculations support the experimental findings.

Performance, Defect Behavior and Carrier Enhancement in Low Energy, Proton Irradiated p(+)nn(+) InP Solar Cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Rybicki, G. C.; Vargas-Aburto, C.; Jain, R. K.; Scheiman, D.

1994-01-01

InP p(+)nn(+) cells, processed by MOCVD, were irradiated by 0.2 MeV protons and their performance and defect behavior observed to a maximum fluence of 10(exp 13)/sq cm. Their radiation induced degradation, over this fluence range, was considerably+less than observed for similarly irradiated, diffused junction n p InP cells. Significant degradation occurred in both the cell's emitter and base regions the least degradation occurring in the depletion region. A significant increase in series resistance occurs at the highest fluenc.e. Two majority carrier defect levels, E7 and E10, are observed by DLTS with activation energies at (E(sub C) - 0.39)eV and (E(sub C) - 0.74)eV respectively. The relative concentration of these defects differs considerably from that observed after 1 MeV electron irradiation. An increased carrier concentration in the cell's n-region was observed at the highest proton fluence, the change in carrier concentration being insignificant at the lower fluences. In agreement with previous results, for 1 and 1.5 MeV electron irradiated InP p(+)n junctions, the defect level E10 is attributed to a complex between zinc, diffused into the n-region from the zinc doped emitter, and a radiation induced defect. The latter is assumed to be either a phosphorus vacancy or interstitial. The increased, or enhanced carrier concentration is attributed to this complex acting as a donor.

Rayleigh scattering in an emitter-nanofiber-coupling system

NASA Astrophysics Data System (ADS)

Tang, Shui-Jing; Gao, Fei; Xu, Da; Li, Yan; Gong, Qihuang; Xiao, Yun-Feng

2017-04-01

Scattering is a general process in both fundamental and applied physics. In this paper, we investigate Rayleigh scattering of a solid-state-emitter coupled to a nanofiber, by S -matrix-like theory in k -space description. Under this model, both Rayleigh scattering and dipole interaction are studied between a two-level artificial atom embedded in a nanocrystal and fiber modes (guided and radiation modes). It is found that Rayleigh scattering plays a critical role in the transport properties and quantum statistics of photons. On the one hand, Rayleigh scattering produces the transparency in the optical transmitted field of the nanofiber, accompanied by the change of atomic phase, population, and frequency shift. On the other hand, the interference between two kinds of scattering fields by Rayleigh scattering and dipole transition modifies the photon statistics (second-order autocorrelation function) of output fields, showing a strong wavelength dependence. This study provides guidance for the solid-state emitter acting as a single-photon source and can be extended to explore the scattering effect in many-body physics.

Measuring true localization accuracy in super resolution microscopy with DNA-origami nanostructures

NASA Astrophysics Data System (ADS)

Reuss, Matthias; Fördős, Ferenc; Blom, Hans; Öktem, Ozan; Högberg, Björn; Brismar, Hjalmar

2017-02-01

A common method to assess the performance of (super resolution) microscopes is to use the localization precision of emitters as an estimate for the achieved resolution. Naturally, this is widely used in super resolution methods based on single molecule stochastic switching. This concept suffers from the fact that it is hard to calibrate measures against a real sample (a phantom), because true absolute positions of emitters are almost always unknown. For this reason, resolution estimates are potentially biased in an image since one is blind to true position accuracy, i.e. deviation in position measurement from true positions. We have solved this issue by imaging nanorods fabricated with DNA-origami. The nanorods used are designed to have emitters attached at each end in a well-defined and highly conserved distance. These structures are widely used to gauge localization precision. Here, we additionally determined the true achievable localization accuracy and compared this figure of merit to localization precision values for two common super resolution microscope methods STED and STORM.

Exploring quantum thermodynamics in continuous measurement of superconducting qubits

NASA Astrophysics Data System (ADS)

Murch, Kater

The extension of thermodynamics into the realm of quantum mechanics, where quantum fluctuations dominate and systems need not occupy definite states, poses unique challenges. Superconducting quantum circuits offer exquisite control over the environment of simple quantum systems allowing the exploration of thermodynamics at the quantum level through measurement and feedback control. We use a superconducting transmon qubit that is resonantly coupled to a waveguide cavity as an effectively one-dimensional quantum emitter. By driving the emitter and detecting the fluorescence with a near-quantum-limited Josephson parametric amplifier, we track the evolution of the quantum state and characterize the work and heat along single quantum trajectories. By using quantum feedback control to compensate for heat exchanged with the emitter's environment we are able to extract the work statistics associated with the quantum evolution and examine fundamental fluctuation theorems in non-equilibrium thermodynamics. This work was supported by the Alfred P. Sloan Foundation, the National Science Foundation, and the Office of Naval Research.

Infrared Organic Light-Emitting Diodes with Carbon Nanotube Emitters.

PubMed

Graf, Arko; Murawski, Caroline; Zakharko, Yuriy; Zaumseil, Jana; Gather, Malte C

2018-03-01

While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum are widespread, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter is demonstrated. By using a multilayer stacked architecture with matching charge blocking and charge-transport layers, narrow-band electroluminescence at wavelengths between 1000 and 1200 nm is achieved, with spectral features characteristic of excitonic and trionic emission of the employed (6,5) SWCNTs. Here, the OLED performance is investigated in detail and it is found that local conduction hot-spots lead to pronounced trion emission. Analysis of the emissive dipole orientation shows a strong horizontal alignment of the SWCNTs with an average inclination angle of 12.9° with respect to the plane, leading to an exceptionally high outcoupling efficiency of 49%. The SWCNT-based OLEDs represent a highly attractive platform for emission across the entire nIR. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phonon-Assisted Two-Photon Interference from Remote Quantum Emitters.

PubMed

Reindl, Marcus; Jöns, Klaus D; Huber, Daniel; Schimpf, Christian; Huo, Yongheng; Zwiller, Val; Rastelli, Armando; Trotta, Rinaldo

2017-07-12

Photonic quantum technologies are on the verge of finding applications in everyday life with quantum cryptography and quantum simulators on the horizon. Extensive research has been carried out to identify suitable quantum emitters and single epitaxial quantum dots have emerged as near-optimal sources of bright, on-demand, highly indistinguishable single photons and entangled photon-pairs. In order to build up quantum networks, it is essential to interface remote quantum emitters. However, this is still an outstanding challenge, as the quantum states of dissimilar "artificial atoms" have to be prepared on-demand with high fidelity and the generated photons have to be made indistinguishable in all possible degrees of freedom. Here, we overcome this major obstacle and show an unprecedented two-photon interference (visibility of 51 ± 5%) from remote strain-tunable GaAs quantum dots emitting on-demand photon-pairs. We achieve this result by exploiting for the first time the full potential of a novel phonon-assisted two-photon excitation scheme, which allows for the generation of highly indistinguishable (visibility of 71 ± 9%) entangled photon-pairs (fidelity of 90 ± 2%), enables push-button biexciton state preparation (fidelity of 80 ± 2%) and outperforms conventional resonant two-photon excitation schemes in terms of robustness against environmental decoherence. Our results mark an important milestone for the practical realization of quantum repeaters and complex multiphoton entanglement experiments involving dissimilar artificial atoms.

Synchrotron radiation-based quasi-elastic scattering using time-domain interferometry with multi-line gamma rays.

PubMed

Saito, Makina; Masuda, Ryo; Yoda, Yoshitaka; Seto, Makoto

2017-10-02

We developed a multi-line time-domain interferometry (TDI) system using 14.4 keV Mössbauer gamma rays with natural energy widths of 4.66 neV from 57 Fe nuclei excited using synchrotron radiation. Electron density fluctuations can be detected at unique lengths ranging from 0.1 nm to a few nm on time scales from several nanoseconds to the sub-microsecond order by quasi-elastic gamma-ray scattering (QGS) experiments using multi-line TDI. In this report, we generalize the established expression for a time spectrum measured using an identical single-line gamma-ray emitter pair to the case of a nonidentical pair of multi-line gamma-ray emitters by considering the finite energy width of the incident synchrotron radiation. The expression obtained illustrates the unique characteristics of multi-line TDI systems, where the finite incident energy width and use of a nonidentical emitter pair produces further information on faster sub-picosecond-scale dynamics in addition to the nanosecond dynamics; this was demonstrated experimentally. A normalized intermediate scattering function was extracted from the spectrum and its relaxation form was determined for a relaxation time of the order of 1 μs, even for relatively large momentum transfer of ~31 nm -1 . The multi-line TDI method produces a microscopic relaxation picture more rapidly and accurately than conventional single-line TDI.

Optical-nanofiber-based interface for single molecules

NASA Astrophysics Data System (ADS)

Skoff, Sarah M.; Papencordt, David; Schauffert, Hardy; Bayer, Bernhard C.; Rauschenbeutel, Arno

2018-04-01

Optical interfaces for quantum emitters are a prerequisite for implementing quantum networks. Here, we couple single molecules to the guided modes of an optical nanofiber. The molecules are embedded within a crystal that provides photostability and, due to the inhomogeneous broadening, a means to spectrally address single molecules. Single molecules are excited and detected solely via the nanofiber interface without the requirement of additional optical access. In this way, we realize a fully fiber-integrated system that is scalable and may become a versatile constituent for quantum hybrid systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huamg, C. W., E-mail: huang.zw@nsrrc.org.tw; Hwang, C. S., E-mail: cshwang@nsrrc.org.tw; Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan

The Taiwan Photon Source (TPS) has been successfully commissioned. However, the minimum emittance in the TPS lattice is 1.6 nm rad. In the existing TPS storage ring lattice, it is imperative to reduce the emittance to below 1 nm rad. Therefore, a feasibility study for reducing the effective emittance of the TPS storage ring by using a Robinson wiggler was launched; the reduction is necessary to enhance the photon brilliance. In this study, a permanent-magnet multiperiod Robinson wiggler (MRW) was developed for use instead of the single-period Robinson wiggler. In general, the quadruple field of a combined function magnet inmore » the storage ring is approximately few tesla per meter. According to beam dynamic analysis, we found that it is necessary to adopt a high gradient (40 T/m) combined-function MRW magnet to reduce the emittance effectively. Therefore, a high gradient field strength is required in the combined function MRW magnet. In this study, the quadrupole field strength of the MRW magnet was allowed to be approximately 40 T/m at a magnet gap of 20 mm. The period length of the MRW magnet was 300 mm and the period number was 16. The of MRWs is discussed in regard to the possibility of increasing the photon brilliance from IU22.« less

Fabrication and optimization of phosphorescent organic light emitting diodes for solid-state lighting applications

NASA Astrophysics Data System (ADS)

Bhansali, Unnat S.

Organic Light Emitting Diodes (OLEDs) have made tremendous progress over the last decade and are under consideration for use as solid-state lighting sources to replace the existing incandescent and fluorescent technology. Use of metal-organic phosphorescent complexes as bright emitters and efficient charge transporting organic semiconductors has resulted in OLEDs with internal quantum efficiency ˜ 100% and power efficiency ˜100 lm/W (green OLEDs) at 1000 cd/m2. For lighting applications, white OLEDs (WOLEDs) are required to have a color rendering index (CRI) > 80, correlated color temperature (CCT) (2700 ≤ WOLEDs ≤ 6500 °K), power efficiency > 100 lm/W and a lifetime > 25,000 hrs (at 70% of its original lumen value) at a brightness of 1000 cd/m2. Typically, high CRIs and high power efficiencies are obtained by either a combination of a blue fluorescent emitter with green and red phosphorescent emitters or a stack of blue, green and red phosphorescent emitters doped in a host material. In this work, we implement a single-emitter WOLEDs (SWOLEDs) approach by using monomer (blue) and broad excimer emissions (green and orange) from a self-sensitizing Pt-based phosphorescent complex, designed and synthesized by Prof. M.A. Omary's group. We have optimized and demonstrated high efficiency turquoise-blue OLEDs from monomer emission of Pt(ptp)2-bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) doped in a phosphine-oxide based host molecule and an electron transport molecule. The device peak power efficiency and external quantum efficiency were maintained >40 lm/W and >11%, respectively throughout the wide range of dopant concentrations (1% to 10%). A monotonic increase in the excimer/monomer emission intensity ratio is observed at the higher doping concentrations within 1%-10%, causing a small green-shift in the color. The peak performance of 60 -- 70 lm/W for the best optimized device represents the highest power efficiency known to date for blue OLEDs. Typically, the commercially available and most commonly used Ir-based emitters suffer from triplet-triplet annihilation and self-quenching issues due to their long triplet excited lifetimes (˜1 mus). The performance of these OLEDs is hence very sensitive to the dopant concentration. On the other hand, Pt(ptp)2 is a self-sensitizing, fast phosphor with triplet lifetimes ~100 ns and near unity quantum yield at room temperature. We have demonstrated high peak efficiency yellow OLEDs from undoped (neat) thin films of the emitter complex (>30 lm/W) and near 100% Internal Quantum Efficiency (IQE) with faster radiative recombination rate than doped films, thus proving the existence of self-sensitization in electroluminescence. We have successfully combined the monomer emission (low dopant concentrations) and excimer emission of Pt(ptp)2 to achieve high CRI SWOLEDs using a 2-layer and a 3-layer graded-doping design. The best color metrics were a CRI=62 and a CCT = 3452 K for a WOLED with the highest power efficiency = 31.3 lm/W and EQE = 17.4%, representing excellent performance for single-emitter WOLEDs.

Development of a model using the MATLAB System identification toolbox to estimate (222)Rn equilibrium factor from CR-39 based passive measurements.

PubMed

Abo-Elmagd, M; Sadek, A M

2014-12-01

Can and Bare method is a widely used passive method for measuring the equilibrium factor F through the determination of the track density ratio between bare (D) and filtered (Do) detectors. The dimensions of the used diffusion chamber are altering the deposition ratios of Po-isotopes on the chamber walls as well as the ratios of the existing alpha emitters in air. Then the measured filtered track density and therefore the resultant equilibrium factor is changed according to the diffusion chamber dimensions. For this reason, high uncertainty was expected in the measured F using different diffusion chambers. In the present work, F is derived as a function of both track density ratio (D/Do) and the dimensions of the used diffusion chambers (its volume to the total internal surface area; V/A). The accuracy of the derived formula was verified using the black-box modeling technique via the MATLAB System identification toolbox. The results show that the uncertainty of the calculated F by using the derived formula of F (D/Do, V/A) is only 5%. The obtained uncertainty ensures the quality of the derived function to calculate F using diffusion chambers with wide range of dimensions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Processes for producing low cost, high efficiency silicon solar cells

DOEpatents

Rohatgi, Ajeet; Doshi, Parag; Tate, John Keith; Mejia, Jose; Chen, Zhizhang

1998-06-16

Processes which utilize rapid thermal processing (RTP) are provided for inexpensively producing high efficiency silicon solar cells. The RTP processes preserve minority carrier bulk lifetime .tau. and permit selective adjustment of the depth of the diffused regions, including emitter and back surface field (bsf), within the silicon substrate. In a first RTP process, an RTP step is utilized to simultaneously diffuse phosphorus and aluminum into the front and back surfaces, respectively, of a silicon substrate. Moreover, an in situ controlled cooling procedure preserves the carrier bulk lifetime .tau. and permits selective adjustment of the depth of the diffused regions. In a second RTP process, both simultaneous diffusion of the phosphorus and aluminum as well as annealing of the front and back contacts are accomplished during the RTP step. In a third RTP process, the RTP step accomplishes simultaneous diffusion of the phosphorus and aluminum, annealing of the contacts, and annealing of a double-layer antireflection/passivation coating SiN/SiO.sub.x. In a fourth RTP process, the process of applying front and back contacts is broken up into two separate respective steps, which enhances the efficiency of the cells, at a slight time expense. In a fifth RTP process, a second RTP step is utilized to fire and adhere the screen printed or evaporated contacts to the structure.

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ubnoske, Stephen M.; Radauscher, Erich J.; Meshot, Eric R.

The growth of carbon nanotubes (CNTs) on polycrystalline silicon substrates was studied to improve the design of CNT field emission sources for microelectromechanical systems (MEMS) applications and vacuum microelectronic devices (VMDs). Microwave plasma-enhanced chemical vapor deposition (PECVD) was used for CNT growth, resulting in CNTs that incorporate the catalyst particle at their base. The kinetics of CNT growth on polysilicon were compared to growth on Si (100) using the model of Deal and Grove, finding activation energies of 1.61 and 1.54 eV for the nucleation phase of growth and 1.90 and 3.69 eV for the diffusion-limited phase on Si (100)more » and polysilicon, respectively. Diffusivity values for growth on polysilicon were notably lower than the corresponding values on Si (100) and the growth process became diffusion-limited earlier. Evidence favors a surface diffusion growth mechanism involving diffusion of carbon precursor species along the length of the CNT forest to the catalyst at the base. Explanations for the differences in activation energies and diffusivities were elucidated by SEM analysis of the catalyst nanoparticle arrays and through wide-angle X-ray scattering (WAXS) of CNT forests. As a result, methods are presented to improve adhesion of CNT films during operation as field emitters, resulting in a 2.5× improvement.« less

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

DOE PAGES

Ubnoske, Stephen M.; Radauscher, Erich J.; Meshot, Eric R.; ...

2016-11-19

The growth of carbon nanotubes (CNTs) on polycrystalline silicon substrates was studied to improve the design of CNT field emission sources for microelectromechanical systems (MEMS) applications and vacuum microelectronic devices (VMDs). Microwave plasma-enhanced chemical vapor deposition (PECVD) was used for CNT growth, resulting in CNTs that incorporate the catalyst particle at their base. The kinetics of CNT growth on polysilicon were compared to growth on Si (100) using the model of Deal and Grove, finding activation energies of 1.61 and 1.54 eV for the nucleation phase of growth and 1.90 and 3.69 eV for the diffusion-limited phase on Si (100)more » and polysilicon, respectively. Diffusivity values for growth on polysilicon were notably lower than the corresponding values on Si (100) and the growth process became diffusion-limited earlier. Evidence favors a surface diffusion growth mechanism involving diffusion of carbon precursor species along the length of the CNT forest to the catalyst at the base. Explanations for the differences in activation energies and diffusivities were elucidated by SEM analysis of the catalyst nanoparticle arrays and through wide-angle X-ray scattering (WAXS) of CNT forests. As a result, methods are presented to improve adhesion of CNT films during operation as field emitters, resulting in a 2.5× improvement.« less

On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits.

PubMed

Elshaari, Ali W; Zadeh, Iman Esmaeil; Fognini, Andreas; Reimer, Michael E; Dalacu, Dan; Poole, Philip J; Zwiller, Val; Jöns, Klaus D

2017-08-30

Quantum light plays a pivotal role in modern science and future photonic applications. Since the advent of integrated quantum nanophotonics different material platforms based on III-V nanostructures-, colour centers-, and nonlinear waveguides as on-chip light sources have been investigated. Each platform has unique advantages and limitations; however, all implementations face major challenges with filtering of individual quantum states, scalable integration, deterministic multiplexing of selected quantum emitters, and on-chip excitation suppression. Here we overcome all of these challenges with a hybrid and scalable approach, where single III-V quantum emitters are positioned and deterministically integrated in a complementary metal-oxide-semiconductor-compatible photonic circuit. We demonstrate reconfigurable on-chip single-photon filtering and wavelength division multiplexing with a foot print one million times smaller than similar table-top approaches, while offering excitation suppression of more than 95 dB and efficient routing of single photons over a bandwidth of 40 nm. Our work marks an important step to harvest quantum optical technologies' full potential.Combining different integration platforms on the same chip is currently one of the main challenges for quantum technologies. Here, Elshaari et al. show III-V Quantum Dots embedded in nanowires operating in a CMOS compatible circuit, with controlled on-chip filtering and tunable routing.

Emittance growth due to multiple passes through H-minus stripping foil in Booster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardner, C. J.

Expressions for transverse emittance growth due to turn-by-turn passes through the H-minus stripping foil in Booster are developed here from simple principles of statistics and simple assumptions about the initial distribution of particles incident on the foil. These are meant to complement work already presented by Zeno [1, 2, 3] and Brown [4]. The expressions show that while the average emittance hEi of the distribution simply increases linearly with turn number, the emittance E based on the mean square particle position does so with an additional oscillatory term that depends on the machine tune. It is shown that this termmore » can be ignored as long as the turn number is su ciently large and the tune is su ciently far from integer and half-integer values. Under these conditions the relation between hEi and E is simply hEi = 2 E. This relation is shown to hold for a Gaussian distribution that is matched to the machine lattice. Two symmetry conditions which help characterize the particle distribution are identi ed. These provide justi cation for calling E an emittance. It is shown that if the conditions are satis ed by the initial distribution, they will not be satis ed after a single traversal of the foil and one turn around the machine. However, on subsequent turns the distribution can (and does) return to satisfying the conditions. Moreover, for su ciently large turn number, the symmetry conditions are approximately satis ed. As already noted in [4], the emittance growth per turn is proportional to the lattice beta at the foil and the mean square angular kick received by protons passing through the foil. We take the former to be 5 m. The latter is obtained from simulations performed with the code TRIM [5]. Having these numbers in hand, actual numbers for emittance growth are presented. The reader may wish to start with Section 11 and refer to previous sections as needed or desired.« less

A topological quantum optics interface

NASA Astrophysics Data System (ADS)

Barik, Sabyasachi; Karasahin, Aziz; Flower, Christopher; Cai, Tao; Miyake, Hirokazu; DeGottardi, Wade; Hafezi, Mohammad; Waks, Edo

2018-02-01

The application of topology in optics has led to a new paradigm in developing photonic devices with robust properties against disorder. Although considerable progress on topological phenomena has been achieved in the classical domain, the realization of strong light-matter coupling in the quantum domain remains unexplored. We demonstrate a strong interface between single quantum emitters and topological photonic states. Our approach creates robust counterpropagating edge states at the boundary of two distinct topological photonic crystals. We demonstrate the chiral emission of a quantum emitter into these modes and establish their robustness against sharp bends. This approach may enable the development of quantum optics devices with built-in protection, with potential applications in quantum simulation and sensing.

Local effects of partly-cloudy skies on solar and emitted radiation

NASA Technical Reports Server (NTRS)

Whitney, D. A.; Venable, D. D.

1982-01-01

A computer automated data acquisition system for atmospheric emittance, and global solar, downwelled diffuse solar, and direct solar irradiances is discussed. Hourly-integrated global solar and atmospheric emitted radiances were measured continuously from February 1981 and hourly-integrated diffuse solar and direct solar irradiances were measured continuously from October 1981. One-minute integrated data are available for each of these components from February 1982. The results of the correlation of global insolation with fractional cloud cover for the first year's data set. A February data set, composed of one-minute integrated global insolation and direct solar irradiance, cloud cover fractions, meteorological data from nearby weather stations, and GOES East satellite radiometric data, was collected to test the theoretical model of satellite radiometric data correlation and develop the cloud dependence for the local measurement site.

Innovative single-shot diagnostics for electrons from laser wakefield acceleration at FLAME

NASA Astrophysics Data System (ADS)

Bisesto, F. G.; Anania, M. P.; Cianchi, A.; Chiadroni, E.; Curcio, A.; Ferrario, M.; Pompili, R.; Zigler, A.

2017-07-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (> 100 GV/m), enabling acceleration of electrons to GeV energy in few centimeters. Here we present all the plasma related activities currently underway at SPARC_LAB exploiting the high power laser FLAME. In particular, we will give an overview of the single shot diagnostics employed: Electro Optic Sampling (EOS) for temporal measurement and Optical Transition Radiation (OTR) for an innovative one shot emittance measurements. In detail, the EOS technique has been employed to measure for the first time the longitudinal profile of electric field of fast electrons escaping from a solid target, driving the ions and protons acceleration, and to study the impact of using different target shapes. Moreover, a novel scheme for one shot emittance measurements based on OTR, developed and tested at SPARC_LAB LINAC, used in an experiment on electrons from laser wakefield acceleration still undergoing, will be shown.

Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts.

PubMed

Wu, Xiaojian; Kim, Mijin; Kwon, Hyejin; Wang, YuHuang

2018-01-15

Quantum defects are an emerging class of synthetic single-photon emitters that hold vast potential for near-infrared imaging, chemical sensing, materials engineering, and quantum information processing. Herein, we show that it is possible to optically direct the synthetic creation of molecularly tunable fluorescent quantum defects in semiconducting single-walled carbon nanotube hosts through photochemical reactions. By exciting the host semiconductor with light that resonates with its electronic transition, we find that halide-containing aryl groups can covalently bond to the sp 2 carbon lattice. The introduced quantum defects generate bright photoluminescence that allows tracking of the reaction progress in situ. We show that the reaction is independent of temperature but correlates strongly with the photon energy used to drive the reaction, suggesting a photochemical mechanism rather than photothermal effects. This type of photochemical reactions opens the possibility to control the synthesis of fluorescent quantum defects using light and may enable lithographic patterning of quantum emitters with electronic and molecular precision. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single-spin stochastic optical reconstruction microscopy

PubMed Central

Pfender, Matthias; Aslam, Nabeel; Waldherr, Gerald; Neumann, Philipp; Wrachtrup, Jörg

2014-01-01

We experimentally demonstrate precision addressing of single-quantum emitters by combined optical microscopy and spin resonance techniques. To this end, we use nitrogen vacancy (NV) color centers in diamond confined within a few ten nanometers as individually resolvable quantum systems. By developing a stochastic optical reconstruction microscopy (STORM) technique for NV centers, we are able to simultaneously perform sub–diffraction-limit imaging and optically detected spin resonance (ODMR) measurements on NV spins. This allows the assignment of spin resonance spectra to individual NV center locations with nanometer-scale resolution and thus further improves spatial discrimination. For example, we resolved formerly indistinguishable emitters by their spectra. Furthermore, ODMR spectra contain metrology information allowing for sub–diffraction-limit sensing of, for instance, magnetic or electric fields with inherently parallel data acquisition. As an example, we have detected nuclear spins with nanometer-scale precision. Finally, we give prospects of how this technique can evolve into a fully parallel quantum sensor for nanometer resolution imaging of delocalized quantum correlations. PMID:25267655

Development of New Front Side Metallization Method of Aluminum Electroplating for Silicon Solar Cell

NASA Astrophysics Data System (ADS)

Willis, Megan D.

In this thesis, the methods of aluminum electroplating in an ionic liquid for silicon solar cell front side metallization were studied. It focused on replacing the current silver screen printing with an alternative metallization technology using a low-cost Earth-abundant metal for mass production, due to the high cost and limited availability of silver. A conventional aluminum electroplating method was employed for silicon solar cells fabrication on both p-type and n-type substrates. The highest efficiency of 17.9% was achieved in the n-type solar cell with a rear junction, which is comparable to that of the same structure cell with screen printed silver electrodes from industrial production lines. It also showed better spiking resistant performance than the common structure p-type solar cell. Further efforts were put on the development of a novel light-induced plating of aluminum technique. The aluminum was deposited directly on a silicon substrate without the assistance of a conductive seed layer, thus simplified and reduced the process cost. The plated aluminum has good adhesion to the silicon surface with the resistivity as low as 4x10-6 Ω-cm. A new demo tool was designed and set up for the light-induced plating experiment, aiming to utilize this technique in large-size solar cells fabrication and mass production. Besides the metallization methods, a comprehensive sensitivity analysis for the efficiency dispersion in the production of crystalline-Si solar cells was presented based on numerical simulations. Temperature variation in the diffusion furnace was the most significant cause of the efficiency dispersion. It was concluded that a narrow efficiency range of +/-0.5% absolute is achievable if the emitter diffusion temperature is confined to a 13°C window, while other cell parameters vary within their normal windows. Possible methods to minimize temperature variation in emitter diffusion were proposed.

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

PubMed Central

Neculaes, V. Bogdan; Caiafa, Antonio; Cao, Yang; De Man, Bruno; Edic, Peter M.; Frutschy, Kristopher; Gunturi, Satish; Inzinna, Lou; Reynolds, Joseph; Vermilyea, Mark; Wagner, David; Zhang, Xi; Zou, Yun; Pelc, Norbert J.; Lounsberry, Brian

2016-01-01

Purpose: This paper summarizes the development of a high-power distributed x-ray source, or “multisource,” designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., “Multisource inverse-geometry CT. Part I. System concept and development,” Med. Phys. 43, 4607–4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks—one anode block per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 μs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations. PMID:27487878

Sensitivity of Beam Parameters to a Station C Solenoid Scan on Axis II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulze, Martin E.

Magnet scans are a standard technique for determining beam parameters in accelerators. Beam parameters are inferred from spot size measurements using a model of the beam optics. The sensitivity of the measured beam spot size to the beam parameters is investigated for typical DARHT Axis II beam energies and currents. In a typical S4 solenoid scan, the downstream transport is tuned to achieve a round beam at Station C with an envelope radius of about 1.5 cm with a very small divergence with S4 off. The typical beam energy and current are 16.0 MeV and 1.625 kA. Figures 1-3 showmore » the sensitivity of the bean size at Station C to the emittance, initial radius and initial angle respectively. To better understand the relative sensitivity of the beam size to the emittance, initial radius and initial angle, linear regressions were performed for each parameter as a function of the S4 setting. The results are shown in Figure 4. The measured slope was scaled to have a maximum value of 1 in order to present the relative sensitivities in a single plot. Figure 4 clearly shows the beam size at the minimum of the S4 scan is most sensitive to emittance and relatively insensitive to initial radius and angle as expected. The beam emittance is also very sensitive to the beam size of the converging beam and becomes insensitive to the beam size of the diverging beam. Measurements of the beam size of the diverging beam provide the greatest sensitivity to the initial beam radius and to a lesser extent the initial beam angle. The converging beam size is initially very sensitive to the emittance and initial angle at low S4 currents. As the S4 current is increased the sensitivity to the emittance remains strong while the sensitivity to the initial angle diminishes.« less

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neculaes, V. Bogdan, E-mail: neculaes@ge.com; Caia

2016-08-15

Purpose: This paper summarizes the development of a high-power distributed x-ray source, or “multisource,” designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., “Multisource inverse-geometry CT. Part I. System concept and development,” Med. Phys. 43, 4607–4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks—one anode blockmore » per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 μs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations.« less

Intense, carrier frequency and bandwidth tunable quasi single-cycle pulses from an organic emitter covering the Terahertz frequency gap

PubMed Central

Vicario, C.; Monoszlai, B.; Jazbinsek, M.; Lee, S. -H.; Kwon, O. -P.; Hauri, C. P.

2015-01-01

In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1–15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light. PMID:26400005

Single Crystal Diamond Needle as Point Electron Source.

PubMed

Kleshch, Victor I; Purcell, Stephen T; Obraztsov, Alexander N

2016-10-12

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Single Crystal Diamond Needle as Point Electron Source

NASA Astrophysics Data System (ADS)

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-10-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Arrays of Bundles of Carbon Nanotubes as Field Emitters

NASA Technical Reports Server (NTRS)

Manohara, Harish; Bronkowski, Michael

2007-01-01

Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

Focused X-ray source

DOEpatents

Piestrup, Melvin A.; Boyers, David G.; Pincus, Cary I.; Maccagno, Pierre

1990-01-01

An intense, relatively inexpensive X-ray source (as compared to a synchrotron emitter) for technological, scientific, and spectroscopic purposes. A conical radiation pattern produced by a single foil or stack of foils is focused by optics to increase the intensity of the radiation at a distance from the conical radiator.

Single Platform Geolocation of Radio Frequency Emitters

DTIC Science & Technology

2015-03-26

Error SNR Signal to Noise Ratio SOI Signal of Interest STK Systems Tool Kit UCA Uniform Circular Array WGS World Geodetic System xv SINGLE PLATFORM...Section 2.6 describes a method to visualize the confidence of estimated parameters. 2.1 Coordinate Systems and Reference Frames The following...be used to visualize the confidence surface using the method developed in Section 2.6. The NLO method will be shown to be the minimization of the

Emitter formation in dendritic web silicon solar cells

NASA Technical Reports Server (NTRS)

Meier, D. L.; Rohatgi, A.; Campbell, R. B.; Alexander, P.; Fonash, S. J.; Singh, R.

1984-01-01

The use of liquid dopants and liquid masks for p-n junction formation in dendritic web solar cells was investigated and found to be equivalent to the use of gaseous dopants and CVD SiO2 masks previously used. This results in a projected cost reduction of 0.02 1980$/Watt for a 25 MW/year production line, and makes possible junction formation processes having a higher throughput than more conventional processes. The effect of a low-energy (0.4 keV) hydrogen ion implant on dendritic web solar cells was also investigated. Such an implant was observed to improve Voc and Jsc substantially. Measurements of internal quantum efficiency suggest that it is the base of the cell, rather than the emitter, which benefits from the hydrogen implant. The diffusion length for electrons in the p-type base increased from 53 microns to 150 microns in one case, with dendritic web cell efficiency being boosted to 15.2 percent. The mechanism by which low-energy hydrogen ions can penetrate deeply into the silicon to effect the observed improvement is not known at this time.

Cu gettering by phosphorus-doped emitters in p-type silicon: Effect on light-induced degradation

NASA Astrophysics Data System (ADS)

Inglese, Alessandro; Laine, Hannu S.; Vähänissi, Ville; Savin, Hele

2018-01-01

The presence of copper (Cu) contamination is known to cause relevant light-induced degradation (Cu-LID) effects in p-type silicon. Due to its high diffusivity, Cu is generally regarded as a relatively benign impurity, which can be readily relocated during device fabrication from the wafer bulk, i.e. the region affected by Cu-LID, to the surface phosphorus-doped emitter. This contribution examines in detail the impact of gettering by industrially relevant phosphorus layers on the strength of Cu-LID effects. We find that phosphorus gettering does not always prevent the occurrence of Cu-LID. Specifically, air-cooling after an isothermal anneal at 800°C results in only weak impurity segregation to the phosphorus-doped layer, which turns out to be insufficient for effectively mitigating Cu-LID effects. Furthermore, we show that the gettering efficiency can be enhanced through the addition of a slow cooling ramp (-4°C/min) between 800°C and 600°C, resulting in the nearly complete disappearance of Cu-LID effects.

Engine Systems Ownership Cost Reduction - Aircraft Propulsion Subsystems Integration (APSI)

DTIC Science & Technology

1975-08-01

compreusor fabrication costs. Hybrid Radial Compresscr Diffuser - Combining both the radial and axial sections of a standard diffuser into a single cascade...compressor diffuser by using a single mixed-flow diffuser instead of the separate radial and axial diffuser stator rows. The proposed mixed-flow diffuser...to an axial diffuser. A cost analyses of the hybrid radial diffuser was made and compared to baseline configuration ( radial and axial diffusers). The

Treatment of solid tumors by interstitial release of recoiling short-lived alpha emitters

NASA Astrophysics Data System (ADS)

Arazi, L.; Cooks, T.; Schmidt, M.; Keisari, Y.; Kelson, I.

2007-08-01

A new method utilizing alpha particles to treat solid tumors is presented. Tumors are treated with interstitial radioactive sources which continually release short-lived alpha emitting atoms from their surface. The atoms disperse inside the tumor, delivering a high dose through their alpha decays. We implement this scheme using thin wire sources impregnated with 224Ra, which release by recoil 220Rn, 216Po and 212Pb atoms. This work aims to demonstrate the feasibility of our method by measuring the activity patterns of the released radionuclides in experimental tumors. Sources carrying 224Ra activities in the range 10-130 kBq were used in experiments on murine squamous cell carcinoma tumors. These included gamma spectroscopy of the dissected tumors and major organs, Fuji-plate autoradiography of histological tumor sections and tissue damage detection by Hematoxylin-Eosin staining. The measurements focused on 212Pb and 212Bi. The 220Rn/216Po distribution was treated theoretically using a simple diffusion model. A simplified scheme was used to convert measured 212Pb activities to absorbed dose estimates. Both physical and histological measurements confirmed the formation of a 5-7 mm diameter necrotic region receiving a therapeutic alpha-particle dose around the source. The necrotic regions shape closely corresponded to the measured activity patterns. 212Pb was found to leave the tumor through the blood at a rate which decreased with tumor mass. Our results suggest that the proposed method, termed DART (diffusing alpha-emitters radiation therapy), may potentially be useful for the treatment of human patients.

Bulk single crystal ternary substrates for a thermophotovoltaic energy conversion system

DOEpatents

Charache, Greg W.; Baldasaro, Paul F.; Nichols, Greg J.

1998-01-01

A thermophotovoltaic energy conversion device and a method for making the device. The device includes a substrate formed from a bulk single crystal material having a bandgap (E.sub.g) of 0.4 eV

Bulk single crystal ternary substrates for a thermophotovoltaic energy conversion system

DOEpatents

Charache, G.W.; Baldasaro, P.F.; Nichols, G.J.

1998-06-23

A thermophotovoltaic energy conversion device and a method for making the device are disclosed. The device includes a substrate formed from a bulk single crystal material having a bandgap (E{sub g}) of 0.4 eV < E{sub g} < 0.7 eV and an emitter fabricated on the substrate formed from one of a p-type or an n-type material. Another thermophotovoltaic energy conversion device includes a host substrate formed from a bulk single crystal material and lattice-matched ternary or quaternary III-V semiconductor active layers. 12 figs.

SU-E-J-03: A Comprehensive Comparison Between Alpha and Beta Emitters for Cancer Radioimmunotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, C.Y.; Guatelli, S; Oborn, B

2014-06-01

Purpose: The purpose of this study is to perform a comprehensive comparison of the therapeutic efficacy and cytotoxicity of alpha and beta emitters for Radioimmunotherapy (RIT). For each stage of cancer development, specific models were built for the separate objectives of RIT to be addressed:a) kill isolated cancer cells in transit in the lymphatic and vascular circulation,b) regress avascular cell clusters,c) regress tumor vasculature and tumors. Methods: Because of the nature of short range, high LET alpha and long energy beta radiation and heterogeneous antigen expression among cancer cells, the microdosimetric approach is essential for the RIT assessment. Geant4 basedmore » microdosimetric models are developed for the three different stages of cancer progression: cancer cells, cell clusters and tumors. The energy deposition, specific energy resulted from different source distribution in the three models was calculated separately for 4 alpha emitting radioisotopes ({sup 211}At, {sup 213}Bi, {sup 223}Ra and {sup 225}Ac) and 6 beta emitters ({sup 32}P, {sup 33}P, {sup 67}Cu, {sup 90}Y, {sup 131}I and {sup 177}Lu). The cell survival, therapeutic efficacy and cytotoxicity are determined and compared between alpha and beta emitters. Results: We show that internal targeted alpha radiation has advantages over beta radiation for killing isolated cancer cells, regressing small cell clusters and also solid tumors. Alpha particles have much higher dose specificity and potency than beta particles. They can deposit 3 logs more dose than beta emitters to single cells and solid tumor. Tumor control probability relies on deep penetration of radioisotopes to cancer cell clusters and solid tumors. Conclusion: The results of this study provide a quantitative understanding of the efficacy and cytotoxicity of RIT for each stage of cancer development.« less

Multiple emitters in a waveguide: Nonreciprocity and correlated photons at perfect elastic transmission

NASA Astrophysics Data System (ADS)

Fang, Yao-Lung L.; Baranger, Harold U.

2017-07-01

We investigate interference and correlation effects when several detuned emitters are placed along a one-dimensional photonic waveguide. Such a setup allows multiple interactions between the photons and the strongly coupled emitters, and underlies proposed devices for quantum information processing. We show, first, that a pair of detuned two-level systems (2LS) separated by a half wavelength mimic a driven Λ -type three-level system (3LS) in both the single- and two-photon sectors. There is an interference-induced transparency peak at which the fluorescence is quenched, leaving the transmitted photons completely uncorrelated. Slightly away from this separation, we find that the inelastic scattering (fluorescence) is large, leading to nonlinear effects such as nonreciprocity (rectification). We connect this nonreciprocity to inelastic scattering caused by driving a dark pole and so derive a condition for maximum rectification. Finally, by placing a true 3LS midway between the two 2LS, we show that elastic scattering produces only transmission, but inelastic scattering nevertheless occurs (the fluorescence is not quenched) causing substantial photon correlations.

"Sizing" the oligomers of Azami Green fluorescent protein with FCS and antibunching

NASA Astrophysics Data System (ADS)

Temirov, Jamshid; Werner, James H.; Goodwin, Peter M.; Bradbury, Andrew R. M.

2012-02-01

Fluorescent proteins are invaluable molecules in fluorescence microscopy and spectroscopy. The size and brightness of fluorescent proteins often dictates the application they may be used for. While a monomeric protein may be the least perturbative structure for labeling a protein in a cell, often oligomers (dimers and tetramers) of fluorescent proteins can be more stable. However, from a quantitative microscopy standpoint, it is important to realize the photophysical properties of monomers do not necessarily multiply by their number when they form oligomers. In this work we studied oligomerization states of the Azami Green (AG) protein with fluorescence correlation spectroscopy (FCS) and photon antibunching or photon pair correlation spectroscopy (PPCS). FCS was used to measure the hydrodynamic size of the oligomers, whereas antibunching was used to count the number of fluorescent emitters in the oligomers. The results exhibited that the dimers of AG were single emitters and the tetramers were dual-emitters, indicative of dipole-dipole interactions and energy transfer between the monomeric units. We also used these methods to estimate the number of fluorescent proteins displayed on T7 phage molecules.

The rise and fall of star formation in z ~ 0.2 merging galaxy clusters

DOE PAGES

Stroe, Andra; Sobral, David; Dawson, William; ...

2015-04-20

CIZA J2242.8+5301 (‘Sausage’) and 1RXS J0603.3+4213 (‘Toothbrush’) are two low-redshift (z ~ 0.2), massive (~2 × 10 15 M ⊙), post-core passage merging clusters, which host-shock waves traced by diffuse radio emission. To study their star formation properties, we uniformly survey the ‘Sausage’ and ‘Toothbrush’ clusters in broad- and narrow-band filters and select a sample of 201 and 463 line emitters, down to a rest-frame equivalent width (13 Å). Here, we robustly separate between Hα and higher redshift emitters using a combination of optical multiband (B, g, V, r, i, z) and spectroscopic data. We build Hα luminosity functions formore » the entire cluster region, near the shock fronts, and away from the shock fronts and find striking differences between the two clusters. In the dynamically younger, 1 Gyr old ‘Sausage’ cluster we find numerous (59) Hα emitters above a star formation rate (SFR) of 0.17 M ⊙ yr -1 surprisingly located in close proximity to the shock fronts, embedded in very hot intracluster medium plasma. The SFR density for the cluster population is at least at the level of typical galaxies at z ~ 2. Down to the same SFR, the possibly dynamically more evolved ‘Toothbrush’ cluster has only nine Hα galaxies. The cluster Hα galaxies fall on the SFR–stellar mass relation z ~ 0.2 for the field. However, the ‘Sausage’ cluster has an Hα emitter density >20 times that of blank fields. If the shock passes through gas-rich cluster galaxies, the compressed gas could collapse into dense clouds and excite star formation for a few 100 Myr. Finally, this process ultimately leads to a rapid consumption of the molecular gas, accelerating the transformation of gas-rich field spirals into cluster S0s or ellipticals.« less

Passivation of phosphorus diffused silicon surfaces with Al{sub 2}O{sub 3}: Influence of surface doping concentration and thermal activation treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, Armin, E-mail: armin.richter@ise.fraunhofer.de; Benick, Jan; Kimmerle, Achim

2014-12-28

Thin layers of Al{sub 2}O{sub 3} are well known for the excellent passivation of p-type c-Si surfaces including highly doped p{sup +} emitters, due to a high density of fixed negative charges. Recent results indicate that Al{sub 2}O{sub 3} can also provide a good passivation of certain phosphorus-diffused n{sup +} c-Si surfaces. In this work, we studied the recombination at Al{sub 2}O{sub 3} passivated n{sup +} surfaces theoretically with device simulations and experimentally for Al{sub 2}O{sub 3} deposited with atomic layer deposition. The simulation results indicate that there is a certain surface doping concentration, where the recombination is maximal duemore » to depletion or weak inversion of the charge carriers at the c-Si/Al{sub 2}O{sub 3} interface. This pronounced maximum was also observed experimentally for n{sup +} surfaces passivated either with Al{sub 2}O{sub 3} single layers or stacks of Al{sub 2}O{sub 3} capped by SiN{sub x}, when activated with a low temperature anneal (425 °C). In contrast, for Al{sub 2}O{sub 3}/SiN{sub x} stacks activated with a short high-temperature firing process (800 °C) a significant lower surface recombination was observed for most n{sup +} diffusion profiles without such a pronounced maximum. Based on experimentally determined interface properties and simulation results, we attribute this superior passivation quality after firing to a better chemical surface passivation, quantified by a lower interface defect density, in combination with a lower density of negative fixed charges. These experimental results reveal that Al{sub 2}O{sub 3}/SiN{sub x} stacks can provide not only excellent passivation on p{sup +} surfaces but also on n{sup +} surfaces for a wide range of surface doping concentrations when activated with short high-temperature treatments.« less

Focused X-ray source

DOEpatents

Piestrup, M.A.; Boyers, D.G.; Pincus, C.I.; Maccagno, P.

1990-08-21

Disclosed is an intense, relatively inexpensive X-ray source (as compared to a synchrotron emitter) for technological, scientific, and spectroscopic purposes. A conical radiation pattern produced by a single foil or stack of foils is focused by optics to increase the intensity of the radiation at a distance from the conical radiator. 8 figs.

Monolithic multinozzle emitters for nanoelectrospray mass spectrometry

DOEpatents

Wang, Daojing [Daly City, CA; Yang, Peidong [Kensington, CA; Kim, Woong [Seoul, KR; Fan, Rong [Pasadena, CA

2011-09-20

Novel and significantly simplified procedures for fabrication of fully integrated nanoelectrospray emitters have been described. For nanofabricated monolithic multinozzle emitters (NM.sup.2 emitters), a bottom up approach using silicon nanowires on a silicon sliver is used. For microfabricated monolithic multinozzle emitters (M.sup.3 emitters), a top down approach using MEMS techniques on silicon wafers is used. The emitters have performance comparable to that of commercially-available silica capillary emitters for nanoelectrospray mass spectrometry.

Asymmetrical field emitter

DOEpatents

Fleming, J.G.; Smith, B.K.

1995-10-10

A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

Photovoltaic investigation of minority carrier lifetime in the heavily-doped emitter layer of silicon junction solar cell

NASA Technical Reports Server (NTRS)

Ho, C.-T.

1982-01-01

The results of experiments on the recombination lifetime in a phosphorus diffused N(+) layer of a silicon solar cell are reported. The cells studied comprised three groups of Czochralski grown crystals: boron doped to one ohm-cm, boron doped to 6 ohm-cm, and aluminum doped to one ohm-cm, all with a shunt resistance exceeding 500 kilo-ohms. The characteristic bulk diffusion length of a cell sample was determined from the short circuit current response to light at a wavelength of one micron. The recombination rates were obtained by measurement of the open circuit voltage as a function of the photogeneration rate. The recombination rate was found to be dependent on the photoinjection level, and is positive-field controlled at low photoinjection, positive-field influence Auger recombination at a medium photoinjection level, and negative-field controlled Auger recombination at a high photoinjection level.

Processes for producing low cost, high efficiency silicon solar cells

DOEpatents

Rohatgi, A.; Doshi, P.; Tate, J.K.; Mejia, J.; Chen, Z.

1998-06-16

Processes which utilize rapid thermal processing (RTP) are provided for inexpensively producing high efficiency silicon solar cells. The RTP processes preserve minority carrier bulk lifetime {tau} and permit selective adjustment of the depth of the diffused regions, including emitter and back surface field (bsf), within the silicon substrate. In a first RTP process, an RTP step is utilized to simultaneously diffuse phosphorus and aluminum into the front and back surfaces, respectively, of a silicon substrate. Moreover, an in situ controlled cooling procedure preserves the carrier bulk lifetime {tau} and permits selective adjustment of the depth of the diffused regions. In a second RTP process, both simultaneous diffusion of the phosphorus and aluminum as well as annealing of the front and back contacts are accomplished during the RTP step. In a third RTP process, the RTP step accomplishes simultaneous diffusion of the phosphorus and aluminum, annealing of the contacts, and annealing of a double-layer antireflection/passivation coating SiN/SiO{sub x}. In a fourth RTP process, the process of applying front and back contacts is broken up into two separate respective steps, which enhances the efficiency of the cells, at a slight time expense. In a fifth RTP process, a second RTP step is utilized to fire and adhere the screen printed or evaporated contacts to the structure. 28 figs.

Single-photon emitting diode in silicon carbide.

PubMed

Lohrmann, A; Iwamoto, N; Bodrog, Z; Castelletto, S; Ohshima, T; Karle, T J; Gali, A; Prawer, S; McCallum, J C; Johnson, B C

2015-07-23

Electrically driven single-photon emitting devices have immediate applications in quantum cryptography, quantum computation and single-photon metrology. Mature device fabrication protocols and the recent observations of single defect systems with quantum functionalities make silicon carbide an ideal material to build such devices. Here, we demonstrate the fabrication of bright single-photon emitting diodes. The electrically driven emitters display fully polarized output, superior photon statistics (with a count rate of >300 kHz) and stability in both continuous and pulsed modes, all at room temperature. The atomic origin of the single-photon source is proposed. These results provide a foundation for the large scale integration of single-photon sources into a broad range of applications, such as quantum cryptography or linear optics quantum computing.

Preliminary investigation of single-file diffusion in complex plasma rings

NASA Astrophysics Data System (ADS)

Theisen, W. L.; Sheridan, T. E.

2010-04-01

Particles in one-dimensional (1D) systems cannot pass each other. However, it is still possible to define a diffusion process where the mean-squared displacement (msd) of an ensemble of particles in a 1D chain increases with time t. This process is called single-file diffusion. In contrast to diffusive processes that follow Fick's law, msdt, single-file diffusion is sub-Fickean and the msd is predicted to increase as t^1/2. We have recently created 1D dusty (complex) plasma rings in the DONUT (Dusty ONU experimenT) apparatus. Particle position data from these rings will be analyzed to determine the scaling of the msd with time and results will be compared with predictions of single-file diffusion theory.

Communication: Coordinate-dependent diffusivity from single molecule trajectories

NASA Astrophysics Data System (ADS)

Berezhkovskii, Alexander M.; Makarov, Dmitrii E.

2017-11-01

Single-molecule observations of biomolecular folding are commonly interpreted using the model of one-dimensional diffusion along a reaction coordinate, with a coordinate-independent diffusion coefficient. Recent analysis, however, suggests that more general models are required to account for single-molecule measurements performed with high temporal resolution. Here, we consider one such generalization: a model where the diffusion coefficient can be an arbitrary function of the reaction coordinate. Assuming Brownian dynamics along this coordinate, we derive an exact expression for the coordinate-dependent diffusivity in terms of the splitting probability within an arbitrarily chosen interval and the mean transition path time between the interval boundaries. This formula can be used to estimate the effective diffusion coefficient along a reaction coordinate directly from single-molecule trajectories.

Characterization of single-file diffusion in one-dimensional dusty plasma

NASA Astrophysics Data System (ADS)

Theisen, W. L.; Sheridan, T. E.

2010-11-01

Single-file diffusion occurs in one-dimensional systems when particles cannot pass each other and the mean-squared displacement (msd) of these particles increases with time t. Diffusive processes that follow Ficks law predict that the msd increases as t, however, single-file diffusion is sub-Fickean meaning that the msd is predicted to increase as t^1/2. One-dimensional dusty plasma rings have been created under strongly coupled, over-damped conditions. Particle position data from these rings will be analyzed to determine the scaling of the msd with time. Results will be compared with predictions of single-file diffusion theory.

MaRIE X-Ray Free-Electron Laser Pre-Conceptual Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlsten, Bruce E.; Barnes, Cris W.; Bishofberger, Kip A.

2011-01-01

The proposed Matter-Radiation Interactions in Extremes (MaRIE) facility at the Los Alamos National Laboratory will include a 50-keV X-Ray Free-Electron Laser (XFEL), a significant extension from planned and existing XFEL facilities. To prevent an unacceptably large energy spread arsing from energy diffusion, the electron beam energy should not exceed 20 GeV, which puts a significant constraint on the beam emittance. A 100-pC baseline design is presented along with advanced technology options to increase the photon flux and to decrease the spectral bandwidth through pre-bunching the electron beam.

Heavy doping effects in high efficiency silicon solar cells

NASA Technical Reports Server (NTRS)

Lindholm, F. A.; Neugroschel, A.

1985-01-01

The use of a (silicon)/(heavily doped polysilicon)/(metal) structure to replace the conventional high-low junction (or back-surface-field, BSF) structure of silicon solar cells was examined. The results of an experimental study designed to explore both qualitatively and quantitatively the mechanism of the improved current gain in bipolar transistors with polysilicon emitter contact are presented. A reciprocity theorem is presented that relates the short circuit current of a device, induced by a carrier generation source, to the minority carrier Fermi level in the dark. A method for accurate measurement of minority-carrier diffusion coefficients in silicon is described.

Use of low-energy hydrogen ion implants in high-efficiency crystalline-silicon solar cells

NASA Technical Reports Server (NTRS)

Fonash, S. J.; Sigh, R.; Mu, H. C.

1986-01-01

The use of low-energy hydrogen implants in the fabrication of high-efficiency crystalline silicon solar cells was investigated. Low-energy hydrogen implants result in hydrogen-caused effects in all three regions of a solar cell: emitter, space charge region, and base. In web, Czochralski (Cz), and floating zone (Fz) material, low-energy hydrogen implants reduced surface recombination velocity. In all three, the implants passivated the space charge region recombination centers. It was established that hydrogen implants can alter the diffusion properties of ion-implanted boron in silicon, but not ion-implated arsenic.

Reappraisal of solid selective emitters

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1990-01-01

New rare earth oxide emitters show greater efficiency than previous emitters. As a result, based on a simple model the efficiency of these emitters was calculated. Results indicate that the emission band of the selective emitter must be at relatively low energy (less than or equal to .52 eV) to obtain maximum efficiency at moderate emitter temperatures (less than or equal to 1500 K). Thus low bandgap energy PV materials are required to obtain an efficient thermophotovoltaic (TPV) system. Of the 4 specific rare earths (Nd, Ho, Er, Yb) studied Ho has the largest efficiency at moderate temperatures (72 percent at 1500 K). A comparison was made between a selective emitter TPV system and a TPV system that uses a thermal emitter plus a band pass filter to make the thermal emitter behave like a selective emitter. Results of the comparison indicate that only for very optimistic filter and thermal emitter properties will the filter TPV system have a greater efficiency than the selective emitter system.

Generation of Single Photons and Entangled Photon Pairs from a Quantum Dot

NASA Astrophysics Data System (ADS)

Yamamoto, Y.; Pelton, M.; Santori, C.; Solomon, G. S.

2002-10-01

Current quantum cryptography systems are limited by the Poissonian photon statistics of a standard light source: a security loophole is opened up by the possibility of multiple-photon pulses. By replacing the source with a single-photon emitter, transmission rates of secure information can be improved. A single photon source is also essential to implement a linear optics quantum computer. We have investigated the use of single self-assembled InAs/GaAs quantum dots as such single-photon sources, and have seen a hundred-fold reduction in the multi-photon probability as compared to Poissonian pulses. An extension of our experiment should also allow for the generation of triggered, polarizationentangled photon pairs.

On the role of adhesion in single-file dynamics

NASA Astrophysics Data System (ADS)

Fouad, Ahmed M.; Noel, John A.

2017-08-01

For a one-dimensional interacting system of Brownian particles with hard-core interactions (a single-file model), we study the effect of adhesion on both the collective diffusion (diffusion of the entire system with respect to its center of mass) and the tracer diffusion (diffusion of the individual tagged particles). For the case with no adhesion, all properties of these particle systems that are independent of particle labeling (symmetric in all particle coordinates and velocities) are identical to those of non-interacting particles (Lebowitz and Percus, 1967). We clarify this last fact twice. First, we derive our analytical predictions that show that the probability-density functions of single-file (ρsf) and ordinary (ρord) diffusion are identical, ρsf =ρord, predicting a nonanomalous (ordinary) behavior for the collective single-file diffusion, where the average second moment with respect to the center of mass, < x(t) 2 > , is calculated from ρ for both diffusion processes. Second, for single-file diffusion, we show, both analytically and through large-scale simulations, that < x(t) 2 > grows linearly with time, confirming the nonanomalous behavior. This nonanomalous collective behavior comes in contrast to the well-known anomalous sub-diffusion behavior of the individual tagged particles (Harris, 1965). We introduce adhesion to single-file dynamics as a second inter-particle interaction rule and, interestingly, we show that adding adhesion does reduce the magnitudes of both < x(t) 2 > and the mean square displacement per particle Δx2; but the diffusion behavior remains intact independent of adhesion in both cases. Moreover, we study the dependence of both the collective diffusion constant D and the tracer diffusion constant DT on the adhesion coefficient α.

Single-image diffusion coefficient measurements of proteins in free solution.

PubMed

Zareh, Shannon Kian; DeSantis, Michael C; Kessler, Jonathan M; Li, Je-Luen; Wang, Y M

2012-04-04

Diffusion coefficient measurements are important for many biological and material investigations, such as studies of particle dynamics and kinetics, and size determinations. Among current measurement methods, single particle tracking (SPT) offers the unique ability to simultaneously obtain location and diffusion information about a molecule while using only femtomoles of sample. However, the temporal resolution of SPT is limited to seconds for single-color-labeled samples. By directly imaging three-dimensional diffusing fluorescent proteins and studying the widths of their intensity profiles, we were able to determine the proteins' diffusion coefficients using single protein images of submillisecond exposure times. This simple method improves the temporal resolution of diffusion coefficient measurements to submilliseconds, and can be readily applied to a range of particle sizes in SPT investigations and applications in which diffusion coefficient measurements are needed, such as reaction kinetics and particle size determinations. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Shielding in ungated field emitter arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, J. R.; Jensen, K. L.; Shiffler, D. A.

Cathodes consisting of arrays of high aspect ratio field emitters are of great interest as sources of electron beams for vacuum electronic devices. The desire for high currents and current densities drives the cathode designer towards a denser array, but for ungated emitters, denser arrays also lead to increased shielding, in which the field enhancement factor β of each emitter is reduced due to the presence of the other emitters in the array. To facilitate the study of these arrays, we have developed a method for modeling high aspect ratio emitters using tapered dipole line charges. This method can bemore » used to investigate proximity effects from similar emitters an arbitrary distance away and is much less computationally demanding than competing simulation approaches. Here, we introduce this method and use it to study shielding as a function of array geometry. Emitters with aspect ratios of 10{sup 2}–10{sup 4} are modeled, and the shielding-induced reduction in β is considered as a function of tip-to-tip spacing for emitter pairs and for large arrays with triangular and square unit cells. Shielding is found to be negligible when the emitter spacing is greater than the emitter height for the two-emitter array, or about 2.5 times the emitter height in the large arrays, in agreement with previously published results. Because the onset of shielding occurs at virtually the same emitter spacing in the square and triangular arrays, the triangular array is preferred for its higher emitter density at a given emitter spacing. The primary contribution to shielding in large arrays is found to come from emitters within a distance of three times the unit cell spacing for both square and triangular arrays.« less

Silicon-nitride/oxynitride wavelength demultiplexer and resonators for quantum photonics

NASA Astrophysics Data System (ADS)

Lim, Soon Thor; Gandhi, Alagappan; Ong, Jun Rong; Ang, Thomas; Png, Ching Eng; Lu, Ding; Ang, Norman Soo Seng; Teo, Ee Jin; Teng, Jinghua

2018-02-01

SiOxNy shows promises for bright emitters of single photons. We successfully fabricated ultra-low-loss SiOxNy waveguide and AWG with low insertion loss <1dB and <3dB total loss (<2dB on-chip loss and <1dB coupling loss) at 1310nm.

The Next Generation Photoinjector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, Dennis Thomas; /Stanford U., Appl. Phys. Dept.

2005-09-12

This dissertation will elucidate the design, construction, theory, and operation of the Next Generation Photoinjector (NGP). This photoinjector is comprised of the BNL/SLAC/UCLA 1.6 cell symmetrized S-band photocathode radio frequency (rf) electron gun and a single emittance-compensation solenoidal magnet. This photoinjector is a prototype for the Linear Coherent Light Source X-ray Free Electron Laser operating in the 1.5 {angstrom} range. Simulations indicate that this photoinjector is capable of producing a 1nC electron bunch with transverse normalized emittance less than 1 {pi} mm mrad were the cathode is illuminated with a 10 psec longitudinal flat top pulse. Using a Gaussian longitudinalmore » laser profile with a full width half maximum (FWHM) of 10 psec, simulation indicates that the NGP is capable of producing a normalized rms emittance of 2.50 {pi} mm mrad at 1 nC. Using the removable cathode plate we have studied the quantum efficiency (QE) of both copper and magnesium photo-cathodes. The Cu QE was found to be 4.5 x 10{sup -5} with a 25% variation in the QE across the emitting surface of the cathode, while supporting a field gradient of 125 MV/m. At low charge, the transverse normalized rms emittance, {epsilon}{sub n,rms}, produced by the NGP is {epsilon}{sub n,rms} = 1.2 {pi} mm mrad for Q{sub T} = 0.3 nC. The 95% electron beam bunch length was measured to 10.9 psec. The emittance due to the finite magnetic field at the cathode has been studied. The scaling of this magnetic emittance term as a function of cathode magnetic field was found to be 0.01 {pi} mm mrad per Gauss. The 1.6 cell rf gun has been designed to reduce the dipole field asymmetry of the longitudinal accelerating field. Low level rf measurements show that this has in fact been accomplished, with an order of magnitude decrease in the dipole field. High power beam studies also show that the dipole field has been decreased. An upper limit of the intrinsic non-reducible thermal emittance of a photocathode under high field gradient was found to be {epsilon}{sub n,rms} = 0.8 {pi} mm mrad. Agreement is found between the theoretical calculation of the thermal emittance, {epsilon}{sub 0} = 0.62 {pi} mm mrad, and the experimental results, after taking into account all of the emittance contribution terms. The 1 nC emittance was found to be {epsilon}{sub n,rms} = 4.75 {pi} mm mrad with a 95% electron beam bunch length of 14.7 psec. Systematic bunch length measurements showed electron beam bunch lengthening due the electron beam charge. They will show that the discrepancy between measurement and simulation is due to three effects. The major effect is due to the variation of the QE in the photo-emitting area of the Cu cathode. Also, space charge emittance blowup in the transport line will be shown to be a significant effect because the electron beam is still in the space charge dominated regime. The last effect, which has been observed experimentally, is the electron bunch lengthening as a function of total electron bunch charge.« less

Single Crystal Diamond Needle as Point Electron Source

PubMed Central

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-01-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2–0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics. PMID:27731379

Electrical and Optical Performance Characteristics of 0.74-eV p/n InGaAs Monolithic Interconnected Modules

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Jain, Raj K.; Murray, Christopher S.; Riley, David R.

1997-01-01

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74-eV InGaAs, have demonstrated V(sub oc) = 3.2 volts, J(sub sc) = 70 mA/sq cm, and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (greater than 2 micron) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55-eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

InGaAs/InP Monolithic Interconnected Modules (MIM) for Thermophotovoltaic Applications

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Scheiman, David A.; Murray, Christopher S.; Riley, David R.

2004-01-01

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between systems efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) devices series -connected on a single semi-insulating indium phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight series interconnected cells. MIM devices, produced from 0,74 eV InGAAs, have demonstrated V(sub infinity) = 3.23 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurement (less than 2 microns) of these devices indicate a reflectivity of less than 82%. MIM devices produced from 0.55 eV InGaAs have also been den=monstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM1) have been demonstrated.

Thermal Ablation by High-Intensity-Focused Ultrasound Using a Toroid Transducer Increases the Coagulated Volume and Allows Coagulation Near Portal and Hepatic veins in Pigs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melodelima, D.; N'Djin, W. A.; Parmentier, H.

2009-04-14

A new geometry of HIFU transducer is described to enlarge the coagulated volume. The geometry of the transducer was not spherical. The surface of the transducer was built based on a toroid geometry. The transducer was generated by the revolution of a circle about an axis lying in its plane. Eight emitters operating at a frequency of 3 MHz were diced out of a single toroid piezocomposite element. Each of the eight emitters was divided into 32 transducers. The focal zone is conical and located at 70 mm from the transducer. A 7.5 MHz ultrasound imaging probe is placed inmore » the centre of the device for guiding the treatment. Our long-term objective is to develop a device that can be used during surgery. In vivo trials have been performed on 13 pigs to demonstrate this new principle and to evaluate the vascular tolerance of the treatment. This new geometry combined with consecutive activation of the eight emitters around the toroid allows achieving a mean thermal ablation of 7.0{+-}2.5 cm3 in 40 seconds. All lesions were visible with high contrast on sonograms. The correlation between the size of lesions observed on sonograms and during gross examination was 92%. This allows the user to easily enlarge the coagulated volume by juxtaposing single lesions. The pigs tolerate the treatment well over the experimental period even when coagulation was produced through portal and/or hepatic veins.« less

Xenon gas field ion source from a single-atom tip

NASA Astrophysics Data System (ADS)

Lai, Wei-Chiao; Lin, Chun-Yueh; Chang, Wei-Tse; Li, Po-Chang; Fu, Tsu-Yi; Chang, Chia-Seng; Tsong, T. T.; Hwang, Ing-Shouh

2017-06-01

Focused ion beam (FIB) systems have become powerful diagnostic and modification tools for nanoscience and nanotechnology. Gas field ion sources (GFISs) built from atomic-size emitters offer the highest brightness among all ion sources and thus can improve the spatial resolution of FIB systems. Here we show that the Ir/W(111) single-atom tip (SAT) can emit high-brightness Xe+ ion beams with a high current stability. The ion emission current versus extraction voltage was analyzed from 150 K up to 309 K. The optimal emitter temperature for maximum Xe+ ion emission was ˜150 K and the reduced brightness at the Xe gas pressure of 1 × 10-4 torr is two to three orders of magnitude higher than that of a Ga liquid metal ion source, and four to five orders of magnitude higher than that of a Xe inductively coupled plasma ion source. Most surprisingly, the SAT emitter remained stable even when operated at 309 K. Even though the ion current decreased with increasing temperature, the current at room temperature (RT) could still reach over 1 pA when the gas pressure was higher than 1 × 10-3 torr, indicating the feasibility of RT-Xe-GFIS for application to FIB systems. The operation temperature of Xe-SAT-GFIS is considerably higher than the cryogenic temperature required for the helium ion microscope (HIM), which offers great technical advantages because only simple or no cooling schemes can be adopted. Thus, Xe-GFIS-FIB would be easy to implement and may become a powerful tool for nanoscale milling and secondary ion mass spectroscopy.

Highly Efficient Simplified Single-Emitting-Layer Hybrid WOLEDs with Low Roll-off and Good Color Stability through Enhanced Förster Energy Transfer.

PubMed

Zhang, Dongdong; Cai, Minghan; Zhang, Yunge; Zhang, Deqiang; Duan, Lian

2015-12-30

Single-emitting layer hybrid white organic light-emitting diodes (SEL-hybrid-WOLEDs) usually suffer from low efficiency, significant roll-off, and poor color stability, attributed to the incomplete energy transfer from the triplet states of the blue fluorophores to the phosphors. Here, we demonstrate highly efficient SEL-hybrid-WOLEDs with low roll-off and good color-stability utilizing blue thermally activated delayed fluorescence (TADF) materials as the host emitters. The triplet states of the blue TADF host emitter can be up-converted into its singlet states, and then the energy is transferred to the complementary phosphors through the long-range Förster energy transfer, enhancing the energy transfer from the host to the dopant. Simplified SEL-hybrid-WOLEDs achieve the highest forward-viewing external quantum efficiency (EQE) of 20.8% and power efficiency of 51.2 lm/W with CIE coordinates of (0.398, 0.456) at a luminance of 500 cd/m(2). The device EQE only slightly drops to 19.6% at a practical luminance of 1000 cd/m(2) with a power efficiency of 38.7 lm/W. Furthermore, the spectra of the device are rather stable with the raising voltage. The reason can be assigned to the enhanced Förster energy transfer, wide charge recombination zone, as well as the bipolar charge transporting ability of the host emitter. We believe that our work may shed light on the future development of highly efficient SEL-hybrid-WOLEDs with simultaneous low roll-off and good color stability.

Chemical regeneration of emitter surface increases thermionic diode life

NASA Technical Reports Server (NTRS)

Breiteieser, R.

1966-01-01

Chemical regeneration of sublimated emitter electrode increases the operating efficiency and life of thermionic diodes. A gas which forms chemical compounds with the sublimated emitter material is introduced into the space between the emitter and the collector. The compounds migrate to the emitter where they decompose and redeposit the emitter material.

Single-shot diffusion measurement in laser-polarized Gas

NASA Technical Reports Server (NTRS)

Peled, S.; Tseng, C. H.; Sodickson, A. A.; Mair, R. W.; Walsworth, R. L.; Cory, D. G.

1999-01-01

A single-shot pulsed gradient stimulated echo sequence is introduced to address the challenges of diffusion measurements of laser polarized 3He and 129Xe gas. Laser polarization enhances the NMR sensitivity of these noble gases by >10(3), but creates an unstable, nonthermal polarization that is not readily renewable. A new method is presented which permits parallel acquisition of the several measurements required to determine a diffusive attenuation curve. The NMR characterization of a sample's diffusion behavior can be accomplished in a single measurement, using only a single polarization step. As a demonstration, the diffusion coefficient of a sample of laser-polarized 129Xe gas is measured via this method. Copyright 1999 Academic Press.

Experimental demonstration of a single-spike hard-X-ray free-electron laser starting from noise

DOE PAGES

Marinelli, A.; MacArthur, J.; Emma, P.; ...

2017-10-09

In this letter, we report the experimental demonstration of single-spike hard-X-ray free-electron laser pulses starting from noise with multi-eV bandwidth. Here, this is accomplished by shaping a low-charge electron beam with a slotted emittance spoiler and by adjusting the transport optics to optimize the beam-shaping accuracy. Based on elementary free-electron laser scaling laws, we estimate the pulse duration to be less than 1 fs full-width at half-maximum.

Experimental demonstration of a single-spike hard-X-ray free-electron laser starting from noise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marinelli, A.; MacArthur, J.; Emma, P.

In this letter, we report the experimental demonstration of single-spike hard-X-ray free-electron laser pulses starting from noise with multi-eV bandwidth. Here, this is accomplished by shaping a low-charge electron beam with a slotted emittance spoiler and by adjusting the transport optics to optimize the beam-shaping accuracy. Based on elementary free-electron laser scaling laws, we estimate the pulse duration to be less than 1 fs full-width at half-maximum.

Single-photon interconnector composed of two individual one-dimensional nano-waveguides and a single emitter

NASA Astrophysics Data System (ADS)

Zhang, Xin-Qin; Xia, Xiu-Wen; Xu, Jing-Ping; Yang, Ya-Ping

2017-05-01

Not Available Project supported by the National Natural Science Foundation of China (Grant Nos. 11274242, 11474221, and 11574229), the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (Grant No. U1330203), the National Key Basic Research Special Foundation of China (Grant Nos. 2011CB922203 and 2013CB632701), and the Doctor Startup Fund of the Natural Science of Jinggangshan University, China (Grant No. JZB16003).

Ultrahigh resolution multicolor colocalization of single fluorescent probes

DOEpatents

Weiss, Shimon; Michalet, Xavier; Lacoste, Thilo D.

2005-01-18

A novel optical ruler based on ultrahigh-resolution colocalization of single fluorescent probes is described. Two unique families of fluorophores are used, namely energy-transfer fluorescent beads and semiconductor nanocrystal (NC) quantum dots, that can be excited by a single laser wavelength but emit at different wavelengths. A novel multicolor sample-scanning confocal microscope was constructed which allows one to image each fluorescent light emitter, free of chromatic aberrations, by scanning the sample with nanometer scale steps using a piezo-scanner. The resulting spots are accurately localized by fitting them to the known shape of the excitation point-spread-function of the microscope.

Photon antibunching from a single quantum-dot-microcavity system in the strong coupling regime.

PubMed

Press, David; Götzinger, Stephan; Reitzenstein, Stephan; Hofmann, Carolin; Löffler, Andreas; Kamp, Martin; Forchel, Alfred; Yamamoto, Yoshihisa

2007-03-16

We observe antibunching in the photons emitted from a strongly coupled single quantum dot and pillar microcavity in resonance. When the quantum dot was spectrally detuned from the cavity mode, the cavity emission remained antibunched, and also anticorrelated from the quantum dot emission. Resonant pumping of the selected quantum dot via an excited state enabled these observations by eliminating the background emitters that are usually coupled to the cavity. This device demonstrates an on-demand single-photon source operating in the strong coupling regime, with a Purcell factor of 61+/-7 and quantum efficiency of 97%.

Visible-to-telecom quantum frequency conversion of light from a single quantum emitter.

PubMed

Zaske, Sebastian; Lenhard, Andreas; Keßler, Christian A; Kettler, Jan; Hepp, Christian; Arend, Carsten; Albrecht, Roland; Schulz, Wolfgang-Michael; Jetter, Michael; Michler, Peter; Becher, Christoph

2012-10-05

We demonstrate efficient (>30%) quantum frequency conversion of visible single photons (711 nm) emitted by a quantum dot to a telecom wavelength (1313 nm). Analysis of the first- and second-order coherence before and after wavelength conversion clearly proves that pivotal properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with quantum frequency conversion as a promising technique that may pave the way for a number of new applications in quantum technology.

A Yellow-Emitting Homoleptic Iridium(III) Complex Constructed from a Multifunctional Spiro Ligand for Highly Efficient Phosphorescent Organic Light-Emitting Diodes.

PubMed

Ren, Bao-Yi; Guo, Run-Da; Zhong, Dao-Kun; Ou, Chang-Jin; Xiong, Gang; Zhao, Xiang-Hua; Sun, Ya-Guang; Jurow, Matthew; Kang, Jun; Zhao, Yi; Li, Sheng-Biao; You, Li-Xin; Wang, Lin-Wang; Liu, Yi; Huang, Wei

2017-07-17

To suppress concentration quenching and to improve charge-carrier injection/transport in the emission layer (EML) of phosphorescent organic light-emitting diodes (PhOLEDs), a facial homoleptic iridium(III) complex emitter with amorphous characteristics was designed and prepared in one step from a multifunctional spiro ligand containing spiro[fluorene-9,9'-xanthene] (SFX) unit. Single-crystal X-ray analysis of the resulting fac-Ir(SFXpy) 3 complex revealed an enlarged Ir···Ir distance and negligible intermolecular π-π interactions between the spiro ligands. The emitter exhibits yellow emission and almost equal energy levels compared to the commercial phosphor iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C 2 ')acetylacetonate (PO-01). Dry-processed devices using a common host, 4,4'-bis(N-carbazolyl)-1,1'-biphenyl, and the fac-Ir(SFXpy) 3 emitter at a doping concentration of 15 wt % exhibited a peak performance of 46.2 cd A -1 , 36.3 lm W -1 , and 12.1% for the current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE), respectively. Compared to control devices using PO-01 as the dopant, the fac-Ir(SFXpy) 3 -based devices remained superior in the doping range between 8 and 15 wt %. The current densities went up with increasing doping concentration at the same driving voltage, while the roll-offs remain relatively low even at high doping levels. The superior performance of the new emitter-based devices was ascribed to key roles of the spiro ligand for suppressing aggregation and assisting charge-carrier injection/transport. Benefiting from the amorphous stability of the emitter, the wet-processed device also exhibited respectful CE, PE, and EQE of 32.2 cd A -1 , 22.1 lm W -1 , and 11.3%, respectively, while the EQE roll-off was as low as 1.7% at the luminance of 1000 cd m -2 . The three-dimensional geometry and binary-conjugation features render SFX the ideal multifunctional module for suppressing concentration quenching, facilitating charge-carrier injection/transport, and improving the amorphous stability of iridium(III)-based phosphorescent emitters.

Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles

NASA Astrophysics Data System (ADS)

Li, F.; Nie, Z.; Wu, Y. P.; Guo, B.; Zhang, X. H.; Huang, S.; Zhang, J.; Cheng, Z.; Ma, Y.; Fang, Y.; Zhang, C. J.; Wan, Y.; Xu, X. L.; Hua, J. F.; Pai, C. H.; Lu, W.; Mori, W. B.

2018-04-01

We report the transverse phase space diagnostics for electron beams generated through ionization injection in a laser-plasma accelerator. Single-shot measurements of both ultimate emittance and Twiss parameters are achieved by means of permanent magnetic quadrupole. Beams with emittance of μm rad level are obtained in a typical ionization injection scheme, and the dependence on nitrogen concentration and charge density is studied experimentally and confirmed by simulations. A key feature of the transverse phase space, matched beams with Twiss parameter α T ≃ 0, is identified according to the measurement. Numerical simulations that are in qualitative agreement with the experimental results reveal that a sufficient phase mixing induced by an overlong injection length leads to the matched phase space distribution.

Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, F.; Nie, Z.; Wu, Y. P.

We report the transverse phase space diagnostics for electron beams generated through ionization injection in a laser-plasma accelerator. Single-shot measurements of both ultimate emittance and Twiss parameters are achieved by means of permanent magnetic quadrupole. Beams with emittance of μm rad level are obtained in a typical ionization injection scheme, and the dependence on nitrogen concentration and charge density is studied experimentally and confirmed by simulations. A key feature of the transverse phase space, matched beams with Twiss parameter α T ≃ 0, is identified according to the measurement. Lastly, numerical simulations that are in qualitative agreement with the experimentalmore » results reveal that a sufficient phase mixing induced by an overlong injection length leads to the matched phase space distribution.« less

Reflection and emission models for deserts derived from Nimbus-7 ERB scanner measurements

NASA Technical Reports Server (NTRS)

Staylor, W. F.; Suttles, J. T.

1986-01-01

Broadband shortwave and longwave radiance measurements obtained from the Nimbus-7 Earth Radiation Budget scanner were used to develop reflectance and emittance models for the Sahara-Arabian, Gibson, and Saudi Deserts. The models were established by fitting the satellite measurements to analytic functions. For the shortwave, the model function is based on an approximate solution to the radiative transfer equation. The bidirectional-reflectance function was obtained from a single-scattering approximation with a Rayleigh-like phase function. The directional-reflectance model followed from integration of the bidirectional model and is a function of the sum and product of cosine solar and viewing zenith angles, thus satisfying reciprocity between these angles. The emittance model was based on a simple power-law of cosine viewing zenith angle.

Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles

DOE PAGES

Li, F.; Nie, Z.; Wu, Y. P.; ...

2018-02-22

We report the transverse phase space diagnostics for electron beams generated through ionization injection in a laser-plasma accelerator. Single-shot measurements of both ultimate emittance and Twiss parameters are achieved by means of permanent magnetic quadrupole. Beams with emittance of μm rad level are obtained in a typical ionization injection scheme, and the dependence on nitrogen concentration and charge density is studied experimentally and confirmed by simulations. A key feature of the transverse phase space, matched beams with Twiss parameter α T ≃ 0, is identified according to the measurement. Lastly, numerical simulations that are in qualitative agreement with the experimentalmore » results reveal that a sufficient phase mixing induced by an overlong injection length leads to the matched phase space distribution.« less

Reproduction of mouse-pup ultrasonic vocalizations by nanocrystalline silicon thermoacoustic emitter

NASA Astrophysics Data System (ADS)

Kihara, Takashi; Harada, Toshihiro; Kato, Masahiro; Nakano, Kiyoshi; Murakami, Osamu; Kikusui, Takefumi; Koshida, Nobuyoshi

2006-01-01

As one of the functional properties of ultrasound generator based on efficient thermal transfer at the nanocrystalline silicon (nc-Si) layer surface, its potential as an ultrasonic simulator of vocalization signals is demonstrated by using the acoustic data of mouse-pup calls. The device composed of a surface-heating thin-film electrode, an nc-Si layer, and a single-crystalline silicon (c-Si) wafer, exhibits an almost completely flat frequency response over a wide range without any mechanical surface vibration systems. It is shown that the fabricated emitter can reproduce digitally recorded ultrasonic mouse-pups vocalizations very accurately in terms of the call duration, frequency dispersion, and sound pressure level. The thermoacoustic nc-Si device provides a powerful physical means for the understanding of ultrasonic communication mechanisms in various living animals.

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

NASA Astrophysics Data System (ADS)

Nanni, E. A.; Graves, W. S.; Moncton, D. E.

2018-01-01

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately ten meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.

Unraveling mirror properties in time-delayed quantum feedback scenarios

NASA Astrophysics Data System (ADS)

Faulstich, Fabian M.; Kraft, Manuel; Carmele, Alexander

2018-06-01

We derive in the Heisenberg picture a widely used phenomenological coupling element to treat feedback effects in quantum optical platforms. Our derivation is based on a microscopic Hamiltonian, which describes the mirror-emitter dynamics based on a dielectric, a mediating fully quantized electromagnetic field and a single two-level system in front of the dielectric. The dielectric is modelled as a system of identical two-state atoms. The Heisenberg equation yields a system of describing differential operator equations, which we solve in the Weisskopf-Wigner limit. Due to a finite round-trip time between emitter and dielectric, we yield delay differential operator equations. Our derivation motivates and justifies the typical phenomenologicalassumed coupling element and allows, furthermore, a generalization to a variety of mirrors, such as dissipative mirrors or mirrors with gain dynamics.

Polarizability tensor retrieval for magnetic and plasmonic antenna design

NASA Astrophysics Data System (ADS)

Bernal Arango, Felipe; Femius Koenderink, A.

2013-07-01

A key quantity in the design of plasmonic antennas and metasurfaces, as well as metamaterials, is the electrodynamic polarizability of a single scattering building block. In particular, in the current merging of plasmonics and metamaterials, subwavelength scatterers are judged by their ability to present a large, generally anisotropic electric and magnetic polarizability, as well as a bi-anisotropic magnetoelectric polarizability. This bi-anisotropic response, whereby a magnetic dipole is induced through electric driving, and vice versa, is strongly linked to the optical activity and chiral response of plasmonic metamolecules. We present two distinct methods to retrieve the polarizibility tensor from electrodynamic simulations. As a basis for both, we use the surface integral equation (SIE) method to solve for the scattering response of arbitrary objects exactly. In the first retrieval method, we project scattered fields onto vector spherical harmonics with the aid of an exact discrete spherical harmonic Fourier transform on the unit sphere. In the second, we take the effective current distributions generated by SIE as a basis to calculate dipole moments. We verify that the first approach holds for scatterers of any size, while the second is only approximately correct for small scatterers. We present benchmark calculations, revisiting the zero-forward scattering paradox of Kerker et al (1983 J. Opt. Soc. Am. 73 765-7) and Alù and Engheta (2010 J. Nanophoton. 4 041590), relevant in dielectric scattering cancelation and sensor cloaking designs. Finally, we report the polarizability tensor of split rings, and show that split rings will strongly influence the emission of dipolar single emitters. In the context of plasmon-enhanced emission, split rings can imbue their large magnetic dipole moment on the emission of simple electric dipole emitters. We present a split ring antenna array design that is capable of converting the emission of a single linear dipole emitter in forward and backward beams of directional emission of opposite handedness. This design can, for instance, find application in the spin angular momentum encoding of quantum information.

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

NASA Technical Reports Server (NTRS)

Eegholm, Niels; Ott, Melanie; Stephen, Mark; Leidecker, Henning

2005-01-01

Semiconductor laser diodes emit coherent light by simulated emission generated inside the cavity formed by the cleaved end facets of a slab of semiconductor that is typically less than a millimeter in any dimension for single emitters. The diode is pumped by current injection in the p-n junction through the metallic contacts. Laser diodes emitting in the range of 0.8 micron to 1.06 micron have a wide variety of applications from pumping erbium doped fiber amplifiers, dual-clad fiber lasers, solid-state lasers used in telecom, aerospace, military, medical purposes and all the way to CD players, laser printers and other consumer and industrial products. Laser diode bars have many single emitters side by side and spaced approximately .5 mm on a single slab of semiconductor material approximately .5 mm x 10 mm. The individual emitters are connected in parallel maintaining the voltage at -2V but increasing the current to 50-100A/bar. Stacking these laser diode bars in multiple layers, 2 to 20+ high, yields high power laser diode arrays capable of emitting several hundreds of Watts. Electrically the bars are wired in series increasing the voltage by 2V/bar but maintaining the total current at 50-100A. These arrays are one of the enabling technologies for efficient, high power solid-state lasers. Traditionally these arrays are operated in QCW (Quasi CW) mode with pulse widths 10-200 (mu)s and with repetition rates of 10-200Hz. In QCW mode the wavelength and the output power of the laser reaches steady-state but the temperature does not. The advantage is a substantially higher output power than in CW mode, where the output power would be limited by the internal heating and hence the thermal and heat sinking properties of the device. The down side is a much higher thermal induced mechanical stress caused by the constant heating and cooling cycle inherent to the QCW mode.

Use of probabilistic neural networks for emitter correlation

NASA Astrophysics Data System (ADS)

Maloney, P. S.

1990-08-01

The Probabilistic Neural Network (PNN) as described by Specht''3 has been successfully applied to a number of emitter correlation problems involving operational data for training and testing of the neural net work. The PNN has been found to be a reliable classification tool for determining emitter type or even identifying specific emitter platforms given appropriate representative data sets for training con sisting only of parametric data from electronic intelligence (ELINT) reports. Four separate feasibility studies have been conducted to prove the usefulness of PNN in this application area: . Hull-to-emitter correlation (HULTEC) for identification of seagoing emitter platforms . Identification of landbased emitters from airborne sensors . Pulse sorting according to emitter of origin . Emitter typing based on a dynamically learning neural network. 1 .

Inferring diffusion in single live cells at the single-molecule level

PubMed Central

Robson, Alex; Burrage, Kevin; Leake, Mark C.

2013-01-01

The movement of molecules inside living cells is a fundamental feature of biological processes. The ability to both observe and analyse the details of molecular diffusion in vivo at the single-molecule and single-cell level can add significant insight into understanding molecular architectures of diffusing molecules and the nanoscale environment in which the molecules diffuse. The tool of choice for monitoring dynamic molecular localization in live cells is fluorescence microscopy, especially so combining total internal reflection fluorescence with the use of fluorescent protein (FP) reporters in offering exceptional imaging contrast for dynamic processes in the cell membrane under relatively physiological conditions compared with competing single-molecule techniques. There exist several different complex modes of diffusion, and discriminating these from each other is challenging at the molecular level owing to underlying stochastic behaviour. Analysis is traditionally performed using mean square displacements of tracked particles; however, this generally requires more data points than is typical for single FP tracks owing to photophysical instability. Presented here is a novel approach allowing robust Bayesian ranking of diffusion processes to discriminate multiple complex modes probabilistically. It is a computational approach that biologists can use to understand single-molecule features in live cells. PMID:23267182

High spectral selectivity for solar absorbers using a monolayer transparent conductive oxide coated on a metal substrate

NASA Astrophysics Data System (ADS)

Shimizu, Makoto; Suzuki, Mari; Iguchi, Fumitada; Yugami, Hiroo

2017-05-01

A spectrally selective absorber composed of a monolayer transparent conductive oxide (TCO) coated on a metal substrate is investigated for use in solar systems operating at temperatures higher (>973 K) than the operation temperature of conventional systems ( ˜ 673 K). This method is different from the currently used solar-selective coating technologies, such as those using multilayered and cermet materials. The spectral selective absorption property can be attributed to the inherent optical property of TCO owing to the plasma frequency and interferences between the substrates. Since spectral selectivity can be achieved using monolayered materials, the effect of atomic diffusion occurring at each layer boundary in a multilayer or cermet coatings under high-temperature conditions can be reduced. In addition, since this property is attributed to the inherent property of TCO, the precise control of the layer thickness can be omitted if the layer is sufficiently thick (>0.5 μm). The optimum TCO properties, namely, carrier density and mobility, required for solar-selective absorbers are analyzed to determine the cutoff wavelength and emittance in the infrared range. A solar absorptance of 0.95 and hemispherical emittance of 0.10 at 973 K are needed for achieving the optimum TCO properties, i.e., a carrier density of 5.5 × 1020 cm-3 and mobility of 90 cm2 V-1 s-1 are required. Optical simulations indicate that the spectrally selective absorption weakly depends on the incident angle and film thickness. The thermal stability of the fabricated absorber treated at temperatures up to 973 K for 10 h is verified in vacuum by introducing a SiO2 interlayer, which plays an important role as a diffusion barrier.

High temperature bias line stabilized current sources

DOEpatents

Patterson, III, Raymond B.

1984-01-01

A compensation device for the base of emitter follower configured bipolar transistors becoming operable at elevated temperatures including a bipolar transistor of a geometry of not more than half the geometry of the bipolar emitter follower having its collector connected to the base of the emitter follower and its base and emitter connected together and to the emitter of the emitter follower.

High temperature bias line stabilized current sources

DOEpatents

Patterson, R.B. III.

1984-09-11

A compensation device for the base of emitter follower configured bipolar transistors becoming operable at elevated temperatures including a bipolar transistor of a geometry of not more than half the geometry of the bipolar emitter follower having its collector connected to the base of the emitter follower and its base and emitter connected together and to the emitter of the emitter follower. 1 fig.

A transistor based on 2D material and silicon junction

NASA Astrophysics Data System (ADS)

Kim, Sanghoek; Lee, Seunghyun

2017-07-01

A new type of graphene-silicon junction transistor based on bipolar charge-carrier injection was designed and investigated. In contrast to many recent studies on graphene field-effect transistor (FET), this device is a new type of bipolar junction transistor (BJT). The transistor fully utilizes the Fermi level tunability of graphene under bias to increase the minority-carrier injection efficiency of the base-emitter junction in the BJT. Single-layer graphene was used to form the emitter and the collector, and a p-type silicon was used as the base. The output of this transistor was compared with a metal-silicon junction transistor ( i.e. surface-barrier transistor) to understand the difference between a graphene-silicon junction and metal-silicon Schottky junction. A significantly higher current gain was observed in the graphene-silicon junction transistor as the base current was increased. The graphene-semiconductor heterojunction transistor offers several unique advantages, such as an extremely thin device profile, a low-temperature (< 110 °C) fabrication process, low cost (no furnace process), and high-temperature tolerance due to graphene's stability. A transistor current gain ( β) of 33.7 and a common-emitter amplifier voltage gain of 24.9 were achieved.

Nonlinear optical effects in semi-polar GaN micro-cavity emitter

NASA Astrophysics Data System (ADS)

Butler, Sween; Jiang, Hongxing; Lin, Jingyu; Neogi, Arup

Nonlinear optical (NLO) response of low dimensional emitters is of current interest because of the need for active elements in photonic applications. NLO effects in a selectively grown array of semi-polar GaN microcavity structures offer a promising route toward devices for integrated optical circuitry in optoelectronics and photonics field. Localized spatial excitation of a single hexagonal GaN microcavity with semipolar facets formed by selective area growth was optimized for nonlinear optical light generation due to second harmonic generation (SHG) and multi-photon luminescence(MPL). Multi-photon transition induced by tightly focused femtosecond NIR incident field results in ultra-violet and yellow luminescence for excitations above and below half bandgap energy, whereas SHG was observed for below half bandgap energy. We show that color and coherence of the light generation from the emitter can be controlled by selective onset of the nonlinear process which depends not only on the incident laser energy and intensity but also on the geometry of the microcavity. Quasi-WGM like modes were observed for off-resonant excitations from the GaN microcavity resulting in enhanced SHG. The directionality of MPL and SHG will be presented as a function of the pump polarization.

Emitter location errors in electronic recognition system

NASA Astrophysics Data System (ADS)

Matuszewski, Jan; Dikta, Anna

2017-04-01

The paper describes some of the problems associated with emitter location calculations. This aspect is the most important part of the series of tasks in the electronic recognition systems. The basic tasks include: detection of emission of electromagnetic signals, tracking (determining the direction of emitter sources), signal analysis in order to classify different emitter types and the identification of the sources of emission of the same type. The paper presents a brief description of the main methods of emitter localization and the basic mathematical formulae for calculating their location. The errors' estimation has been made to determine the emitter location for three different methods and different scenarios of emitters and direction finding (DF) sensors deployment in the electromagnetic environment. The emitter has been established using a special computer program. On the basis of extensive numerical calculations, the evaluation of precise emitter location in the recognition systems for different configuration alignment of bearing devices and emitter was conducted. The calculations which have been made based on the simulated data for different methods of location are presented in the figures and respective tables. The obtained results demonstrate that calculation of the precise emitter location depends on: the number of DF sensors, the distances between emitter and DF sensors, their mutual location in the reconnaissance area and bearing errors. The precise emitter location varies depending on the number of obtained bearings. The higher the number of bearings, the better the accuracy of calculated emitter location in spite of relatively high bearing errors for each DF sensor.

Visualizing repetitive diffusion activity of double-strand RNA binding proteins by single molecule fluorescence assays.

PubMed

Koh, Hye Ran; Wang, Xinlei; Myong, Sua

2016-08-01

TRBP, one of double strand RNA binding proteins (dsRBPs), is an essential cofactor of Dicer in the RNA interference pathway. Previously we reported that TRBP exhibits repetitive diffusion activity on double strand (ds)RNA in an ATP independent manner. In the TRBP-Dicer complex, the diffusion mobility of TRBP facilitates Dicer-mediated RNA cleavage. Such repetitive diffusion of dsRBPs on a nucleic acid at the nanometer scale can be appropriately captured by several single molecule detection techniques. Here, we provide a step-by-step guide to four different single molecule fluorescence assays by which the diffusion activity of dsRBPs on dsRNA can be detected. One color assay, termed protein induced fluorescence enhancement enables detection of unlabeled protein binding and diffusion on a singly labeled RNA. Two-color Fluorescence Resonance Energy Transfer (FRET) in which labeled dsRBPs is applied to labeled RNA, allows for probing the motion of protein along the RNA axis. Three color FRET reports on the diffusion movement of dsRBPs from one to the other end of RNA. The single molecule pull down assay provides an opportunity to collect dsRBPs from mammalian cells and examine the protein-RNA interaction at single molecule platform. Copyright © 2016 Elsevier Inc. All rights reserved.

Silicon MINP solar cells

NASA Technical Reports Server (NTRS)

Olsen, L. C.; Addis, F. W.; Miller, W. A.

1985-01-01

The MINP solar cell concept refers to a cell structure designed to be a base region dominated device. Thus, it is desirable that recombination losses are reduced to the point that they occur only in the base region. The most unique feature of the MINP cell design is that a tunneling contact is utilized for the metallic contact on the front surface. The areas under the collector grid and bus bar are passivated by a thin oxide of tunneling thickness. Efforts must also be taken to minimize recombination at the surface between grid lines, at the junction periphery and within the emitter. Results of both theoretical and experimental studies of silicon MINP cells are given. Performance calculations are described which give expected efficiencies as a function of base resistivity and junction depth. Fabrication and characterization of cells are discussed which are based on 0.2 ohm-cm substrates, diffused emitters on the order of 0.15 to 0.20 microns deep, and with Mg MIS collector grids. A total area AM 1 efficiency of 16.8% was achieved. Detailed analyses of photocurrent and current loss mechanisms are presented and utilized to discuss future directions of research. Finally, results reported by other workers are discussed.

Demonstration and properties of a planar heterojunction bipolar transistor with lateral current flow

NASA Astrophysics Data System (ADS)

Thornton, Robert L.; Mosby, William J.; Chung, Harlan F.

1989-10-01

The authors present fabrication techniques and device performance for a novel transistor structure, the lateral heterojunction bipolar transistor. The lateral heterojunctions are formed by impurity-induced disordering of a GaAs base layer sandwiched between two AlGaAs layers. These transistor structures exhibit current gains of 14 for base widths of 0.74 micron. Transistor action in this device occurs parallel to the surface of the device structure. The active base region of the structure is completely submerged, resulting in a reduction of surface recombination as a mechanism for gain reduction in the device. Impurity-induced disordering is used to widen the bandgap of the alloy in the emitter and collector, resulting in an improvement of the emitter injection efficiency. Since the device is based entirely on a surface diffusion process, the device is completely planar and has no steps involving etching of the III-V alloy material. These advantages lead this device to be considered as a candidate for optoelectronic integration applications. The transistor device functions as a buried heterostructure laser, with a threshold current as low as 6 mA for a 1.4-micron stripe.

Determination of the efficiency of commercially available dose calibrators for beta-emitters.

PubMed

Valley, Jean-François; Bulling, Shelley; Leresche, Michel; Wastiel, Claude

2003-03-01

The goals of this investigation are to determine whether commercially available dose calibrators can be used to measure the activity of beta-emitting radionuclides used in pain palliation and to establish whether manufacturer-supplied calibration factors are appropriate for this purpose. Six types of commercially available dose calibrators were studied. Dose calibrator response was controlled for 5 gamma-emitters used for calibration or typically encountered in routine use. For the 4 most commonly used beta-emitters ((32)P, (90)Sr, (90)Y, and (169)Er) dose calibrator efficiency was determined in the syringe geometry used for clinical applications. Efficiency of the calibrators was also measured for (153)Sm and (186)Re, 2 beta-emitters with significant gamma-contributions. Source activities were traceable to national standards. All calibrators measured gamma-emitters with a precision of +/-10%, in compliance with Swiss regulatory requirements. For beta-emitters, dose calibrator intrinsic efficiency depends strongly on the maximal energy of the beta-spectrum and is notably low for (169)Er. Manufacturer-supplied calibration factors give accurate results for beta-emitters with maximal beta-energy in the middle-energy range (1 MeV) but are not appropriate for use with low-energy ((169)Er) or high-energy ((90)Y) beta-emitters. beta-emitters with significant gamma-contributions behave like gamma-emitters. Commercially available dose calibrators have an intrinsic efficiency that is sufficient for the measurement of beta-emitters, including beta-emitters with a low maximum beta-energy. Manufacturer-supplied calibration factors are reliable for gamma-emitters and beta-emitters in the middle-energy range. For low- and high-energy beta-emitters, the use of manufacturer-supplied calibration factors introduces significant measurement inaccuracy.

Multinozzle emitter arrays for ultrahigh-throughput nanoelectrospray mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Daojing; Mao, Pan; Wang, Hung-Ta

The present invention provides for a structure comprising a plurality of emitters, wherein a first nozzle of a first emitter and a second nozzle of a second emitter emit in two directions that are not or essentially not in the same direction; wherein the walls of the nozzles and the emitters form a monolithic whole. The present invention also provides for a structure comprising an emitter with a sharpened end from which the emitter emits; wherein the emitters forms a monolithic whole. The present invention also provides for a fully integrated separation of proteins and small molecules on a siliconmore » chip before the electrospray mass spectrometry analysis.« less

Strong Coupling of Single Emitters to Surface Plasmons

DTIC Science & Technology

2007-07-01

however, we can make an eikonal approximation,39 assuming that the plas- mons are emitted completely into the end of the tip z=0 and that the propagative...restricts the re- gimes of validity to ki w, ki d1. An additional set of as- sumptions is made in using the eikonal approximation to arrive at Eq. 49

Polarized muon beams for muon collider

NASA Astrophysics Data System (ADS)

Skrinsky, A. N.

1996-11-01

An option for the production of intense and highly polarized muon beams, suitable for a high-luminosity muon collider, is described briefly. It is based on a multi-channel pion-collection system, narrow-band pion-to-muon decay channels, proper muon spin gymnastics, and ionization cooling to combine all of the muon beams into a single bunch of ultimately low emittance.

Video-rate nanoscopy enabled by sCMOS camera-specific single-molecule localization algorithms

PubMed Central

Huang, Fang; Hartwich, Tobias M. P.; Rivera-Molina, Felix E.; Lin, Yu; Duim, Whitney C.; Long, Jane J.; Uchil, Pradeep D.; Myers, Jordan R.; Baird, Michelle A.; Mothes, Walther; Davidson, Michael W.; Toomre, Derek; Bewersdorf, Joerg

2013-01-01

Newly developed scientific complementary metal–oxide–semiconductor (sCMOS) cameras have the potential to dramatically accelerate data acquisition in single-molecule switching nanoscopy (SMSN) while simultaneously increasing the effective quantum efficiency. However, sCMOS-intrinsic pixel-dependent readout noise substantially reduces the localization precision and introduces localization artifacts. Here we present algorithms that overcome these limitations and provide unbiased, precise localization of single molecules at the theoretical limit. In combination with a multi-emitter fitting algorithm, we demonstrate single-molecule localization super-resolution imaging at up to 32 reconstructed images/second (recorded at 1,600–3,200 camera frames/second) in both fixed and living cells. PMID:23708387

Hot electron light emission in gallium arsenide/aluminium(x) gallium(1-x) arsenic heterostructures

NASA Astrophysics Data System (ADS)

Teke, Ali

In this thesis we have demonstrated the operation of a novel tunable wavelength surface light emitting device. The device is based on a p-GaAs, and n-Ga1- xAlxAs heterojunction containing an inversion layer on the p- side, and GaAs quantum wells on the n- side, and, is referred to as HELLISH-2 (Hot Electron Light Emitting and Lasing in Semiconductor Heterostructure-Type 2). The devices utilise hot electron longitudinal transport and, therefore, light emission is independent of the polarity of the applied voltage. The wavelength of the emitted light can be tuned with the applied bias from GaAs band-to-band transition in the inversion layer to e1-hh1 transition in the quantum wells. In this work tunable means that the device can be operated at either single or multiple wavelength emission. The operation of the device requires only two diffused in point contacts. In this project four HELLISH-2 samples coded as ES1, ES2, ES6 and QT919 have been studied. First three samples were grown by MBE and the last one was grown by MOVPE techniques. ES1 was designed for single and double wavelength operation. ES2 was a control sample used to compare our results with previous work on HELLISH-2 and ES6 was designed for single, double and triple wavelength operation. Theoretical modelling of the device operation was carried out and compared with the experimental results. HELLISH-2 structure was optimised for low threshold and high efficiency operation as based on our model calculations. The last sample QT919 has been designed as an optimised device for single and double wavelength operation like ES1. HELLISH-2 has a number of advantages over the conventional light emitters, resulting in some possible applications, such as light logic gates and wavelength division multiplexing in optoelectronic.

Parallel nanomanufacturing via electrohydrodynamic jetting from microfabricated externally-fed emitter arrays

NASA Astrophysics Data System (ADS)

Ponce de Leon, Philip J.; Hill, Frances A.; Heubel, Eric V.; Velásquez-García, Luis F.

2015-06-01

We report the design, fabrication, and characterization of planar arrays of externally-fed silicon electrospinning emitters for high-throughput generation of polymer nanofibers. Arrays with as many as 225 emitters and with emitter density as large as 100 emitters cm-2 were characterized using a solution of dissolved PEO in water and ethanol. Devices with emitter density as high as 25 emitters cm-2 deposit uniform imprints comprising fibers with diameters on the order of a few hundred nanometers. Mass flux rates as high as 417 g hr-1 m-2 were measured, i.e., four times the reported production rate of the leading commercial free-surface electrospinning sources. Throughput increases with increasing array size at constant emitter density, suggesting the design can be scaled up with no loss of productivity. Devices with emitter density equal to 100 emitters cm-2 fail to generate fibers but uniformly generate electrosprayed droplets. For the arrays tested, the largest measured mass flux resulted from arrays with larger emitter separation operating at larger bias voltages, indicating the strong influence of electrical field enhancement on the performance of the devices. Incorporation of a ground electrode surrounding the array tips helps equalize the emitter field enhancement across the array as well as control the spread of the imprints over larger distances.

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films.

PubMed

Cusnir, Ruslan; Steinmann, Philipp; Christl, Marcus; Bochud, François; Froidevaux, Pascal

2015-11-09

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

Quantitative single-particle digital autoradiography with α-particle emitters for targeted radionuclide therapy using the iQID camera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Brian W., E-mail: brian.miller@pnnl.gov; Frost, Sofia H. L.; Frayo, Shani L.

2015-07-15

Purpose: Alpha-emitting radionuclides exhibit a potential advantage for cancer treatments because they release large amounts of ionizing energy over a few cell diameters (50–80 μm), causing localized, irreparable double-strand DNA breaks that lead to cell death. Radioimmunotherapy (RIT) approaches using monoclonal antibodies labeled with α emitters may thus inactivate targeted cells with minimal radiation damage to surrounding tissues. Tools are needed to visualize and quantify the radioactivity distribution and absorbed doses to targeted and nontargeted cells for accurate dosimetry of all treatment regimens utilizing α particles, including RIT and others (e.g., Ra-223), especially for organs and tumors with heterogeneous radionuclidemore » distributions. The aim of this study was to evaluate and characterize a novel single-particle digital autoradiography imager, the ionizing-radiation quantum imaging detector (iQID) camera, for use in α-RIT experiments. Methods: The iQID camera is a scintillator-based radiation detection system that images and identifies charged-particle and gamma-ray/x-ray emissions spatially and temporally on an event-by-event basis. It employs CCD-CMOS cameras and high-performance computing hardware for real-time imaging and activity quantification of tissue sections, approaching cellular resolutions. In this work, the authors evaluated its characteristics for α-particle imaging, including measurements of intrinsic detector spatial resolutions and background count rates at various detector configurations and quantification of activity distributions. The technique was assessed for quantitative imaging of astatine-211 ({sup 211}At) activity distributions in cryosections of murine and canine tissue samples. Results: The highest spatial resolution was measured at ∼20 μm full width at half maximum and the α-particle background was measured at a rate as low as (2.6 ± 0.5) × 10{sup −4} cpm/cm{sup 2} (40 mm diameter detector area). Simultaneous imaging of multiple tissue sections was performed using a large-area iQID configuration (ø 11.5 cm). Estimation of the {sup 211}At activity distribution was demonstrated at mBq/μg-levels. Conclusions: Single-particle digital autoradiography of α emitters has advantages over traditional film-based autoradiographic techniques that use phosphor screens, in terms of spatial resolution, sensitivity, and activity quantification capability. The system features and characterization results presented in this study show that the iQID is a promising technology for microdosimetry, because it provides necessary information for interpreting alpha-RIT outcomes and for predicting the therapeutic efficacy of cell-targeted approaches using α emitters.« less

Quantitative single-particle digital autoradiography with α-particle emitters for targeted radionuclide therapy using the iQID camera.

PubMed

Miller, Brian W; Frost, Sofia H L; Frayo, Shani L; Kenoyer, Aimee L; Santos, Erlinda; Jones, Jon C; Green, Damian J; Hamlin, Donald K; Wilbur, D Scott; Fisher, Darrell R; Orozco, Johnnie J; Press, Oliver W; Pagel, John M; Sandmaier, Brenda M

2015-07-01

Alpha-emitting radionuclides exhibit a potential advantage for cancer treatments because they release large amounts of ionizing energy over a few cell diameters (50-80 μm), causing localized, irreparable double-strand DNA breaks that lead to cell death. Radioimmunotherapy (RIT) approaches using monoclonal antibodies labeled with α emitters may thus inactivate targeted cells with minimal radiation damage to surrounding tissues. Tools are needed to visualize and quantify the radioactivity distribution and absorbed doses to targeted and nontargeted cells for accurate dosimetry of all treatment regimens utilizing α particles, including RIT and others (e.g., Ra-223), especially for organs and tumors with heterogeneous radionuclide distributions. The aim of this study was to evaluate and characterize a novel single-particle digital autoradiography imager, the ionizing-radiation quantum imaging detector (iQID) camera, for use in α-RIT experiments. The iQID camera is a scintillator-based radiation detection system that images and identifies charged-particle and gamma-ray/x-ray emissions spatially and temporally on an event-by-event basis. It employs CCD-CMOS cameras and high-performance computing hardware for real-time imaging and activity quantification of tissue sections, approaching cellular resolutions. In this work, the authors evaluated its characteristics for α-particle imaging, including measurements of intrinsic detector spatial resolutions and background count rates at various detector configurations and quantification of activity distributions. The technique was assessed for quantitative imaging of astatine-211 ((211)At) activity distributions in cryosections of murine and canine tissue samples. The highest spatial resolution was measured at ∼20 μm full width at half maximum and the α-particle background was measured at a rate as low as (2.6 ± 0.5) × 10(-4) cpm/cm(2) (40 mm diameter detector area). Simultaneous imaging of multiple tissue sections was performed using a large-area iQID configuration (ø 11.5 cm). Estimation of the (211)At activity distribution was demonstrated at mBq/μg-levels. Single-particle digital autoradiography of α emitters has advantages over traditional film-based autoradiographic techniques that use phosphor screens, in terms of spatial resolution, sensitivity, and activity quantification capability. The system features and characterization results presented in this study show that the iQID is a promising technology for microdosimetry, because it provides necessary information for interpreting alpha-RIT outcomes and for predicting the therapeutic efficacy of cell-targeted approaches using α emitters.

A combined emitter threat assessment method based on ICW-RCM

NASA Astrophysics Data System (ADS)

Zhang, Ying; Wang, Hongwei; Guo, Xiaotao; Wang, Yubing

2017-08-01

Considering that the tradition al emitter threat assessment methods are difficult to intuitively reflect the degree of target threaten and the deficiency of real-time and complexity, on the basis of radar chart method(RCM), an algorithm of emitter combined threat assessment based on ICW-RCM (improved combination weighting method, ICW) is proposed. The coarse sorting is integrated with fine sorting in emitter combined threat assessment, sequencing the emitter threat level roughly accordance to radar operation mode, and reducing task priority of the low-threat emitter; On the basis of ICW-RCM, sequencing the same radar operation mode emitter roughly, finally, obtain the results of emitter threat assessment through coarse and fine sorting. Simulation analyses show the correctness and effectiveness of this algorithm. Comparing with classical method of emitter threat assessment based on CW-RCM, the algorithm is visual in image and can work quickly with lower complexity.

Effect of zone size on the convergence of exact solutions for diffusion in single phase systems with planar, cylindrical or spherical geometry

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.

1981-01-01

Exact solutions for diffusion in single phase binary alloy systems with constant diffusion coefficient and zero-flux boundary condition have been evaluated to establish the optimum zone size of applicability. Planar, cylindrical and spherical interface geometry, and finite, singly infinite, and doubly infinite systems are treated. Two solutions are presented for each geometry, one well suited to short diffusion times, and one to long times. The effect of zone-size on the convergence of these solutions is discussed. A generalized form of the diffusion solution for doubly infinite systems is proposed.

A spin echo sequence with a single-sided bipolar diffusion gradient pulse to obtain snapshot diffusion weighted images in moving media

NASA Astrophysics Data System (ADS)

Freidlin, R. Z.; Kakareka, J. W.; Pohida, T. J.; Komlosh, M. E.; Basser, P. J.

2012-08-01

In vivo MRI data can be corrupted by motion. Motion artifacts are particularly troublesome in Diffusion Weighted MRI (DWI), since the MR signal attenuation due to Brownian motion can be much less than the signal loss due to dephasing from other types of complex tissue motion, which can significantly degrade the estimation of self-diffusion coefficients, diffusion tensors, etc. This paper describes a snapshot DWI sequence, which utilizes a novel single-sided bipolar diffusion sensitizing gradient pulse within a spin echo sequence. The proposed method shortens the diffusion time by applying a single refocused bipolar diffusion gradient on one side of a refocusing RF pulse, instead of a set of diffusion sensitizing gradients, separated by a refocusing RF pulse, while reducing the impact of magnetic field inhomogeneity by using a spin echo sequence. A novel MRI phantom that can exhibit a range of complex motions was designed to demonstrate the robustness of the proposed DWI sequence.

Improving low-level plasma protein mass spectrometry-based detection for candidate biomarker discovery and validation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Page, Jason S.; Kelly, Ryan T.; Camp, David G.

2008-09-01

Methods. To improve the detection of low abundance protein candidate biomarker discovery and validation, particularly in complex biological fluids such as blood plasma, increased sensitivity is desired using mass spectrometry (MS)-based instrumentation. A key current limitation on the sensitivity of electrospray ionization (ESI) MS is due to the fact that many sample molecules in solution are never ionized, and the vast majority of the ions that are created are lost during transmission from atmospheric pressure to the low pressure region of the mass analyzer. Two key technologies, multi-nanoelectrospray emitters and the electrodynamic ion funnel have recently been developed and refinedmore » at Pacific Northwest National Laboratory (PNNL) to greatly improve the ionization and transmission efficiency of ESI MS based analyses. Multi-emitter based ESI enables the flow from a single source (typically a liquid chromatography [LC] column) to be divided among an array of emitters (Figure 1). The flow rate delivered to each emitter is thus reduced, allowing the well-documented benefits of nanoelectrospray 1 for both sensitivity and quantitation to be realized for higher flow rate separations. To complement the increased ionization efficiency afforded by multi-ESI, tandem electrodynamic ion funnels have also been developed at PNNL, and shown to greatly improve ion transmission efficiency in the ion source interface.2, 3 These technologies have been integrated into a triple quadrupole mass spectrometer for multiple reaction monitoring (MRM) of probable biomarker candidates in blood plasma and show promise for the identification of new species even at low level concentrations.« less

Multilayer-Grown Ultrathin Nanostructured GaAs Solar Cells as a Cost-Competitive Materials Platform for III-V Photovoltaics.

PubMed

Gai, Boju; Sun, Yukun; Lim, Haneol; Chen, Huandong; Faucher, Joseph; Lee, Minjoo L; Yoon, Jongseung

2017-01-24

Large-scale deployment of GaAs solar cells in terrestrial photovoltaics demands significant cost reduction for preparing device-quality epitaxial materials. Although multilayer epitaxial growth in conjunction with printing-based materials assemblies has been proposed as a promising route to achieve this goal, their practical implementation remains challenging owing to the degradation of materials properties and resulting nonuniform device performance between solar cells grown in different sequences. Here we report an alternative approach to circumvent these limitations and enable multilayer-grown GaAs solar cells with uniform photovoltaic performance. Ultrathin single-junction GaAs solar cells having a 300-nm-thick absorber (i.e., emitter and base) are epitaxially grown in triple-stack releasable multilayer assemblies by molecular beam epitaxy using beryllium as a p-type impurity. Microscale (∼500 × 500 μm 2 ) GaAs solar cells fabricated from respective device layers exhibit excellent uniformity (<3% relative) of photovoltaic performance and contact properties owing to the suppressed diffusion of p-type dopant as well as substantially reduced time of epitaxial growth associated with ultrathin device configuration. Bifacial photon management employing hexagonally periodic TiO 2 nanoposts and a vertical p-type metal contact serving as a metallic back-surface reflector together with specialized epitaxial design to minimize parasitic optical losses for efficient light trapping synergistically enable significantly enhanced photovoltaic performance of such ultrathin absorbers, where ∼17.2% solar-to-electric power conversion efficiency under simulated AM1.5G illumination is demonstrated from 420-nm-thick single-junction GaAs solar cells grown in triple-stack epitaxial assemblies.

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

DOE PAGES

Nanni, E. A.; Graves, W. S.; Moncton, D. E.

2018-01-19

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately tenmore » meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.« less

Radiative damping and synchronization in a graphene-based terahertz emitter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moskalenko, A. S., E-mail: andrey.moskalenko@physik.uni-augsburg.de; Mikhailov, S. A., E-mail: sergey.mikhailov@physik.uni-augsburg.de

2014-05-28

We investigate the collective electron dynamics in a recently proposed graphene-based terahertz emitter under the influence of the radiative damping effect, which is included self-consistently in a molecular dynamics approach. We show that under appropriate conditions synchronization of the dynamics of single electrons takes place, leading to a rise of the oscillating component of the charge current. The synchronization time depends dramatically on the applied dc electric field and electron scattering rate and is roughly inversely proportional to the radiative damping rate that is determined by the carrier concentration and the geometrical parameters of the device. The emission spectra inmore » the synchronized state, determined by the oscillating current component, are analyzed. The effective generation of higher harmonics for large values of the radiative damping strength is demonstrated.« less

Atom-atom interactions around the band edge of a photonic crystal waveguide.

PubMed

Hood, Jonathan D; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E; Kimble, H J

2016-09-20

Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields [Formula: see text] outside the bandgap to localized fields [Formula: see text] within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the [Formula: see text] line of atomic cesium for [Formula: see text] atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom-atom interactions with low dissipation into the guided mode.

A topological quantum optics interface.

PubMed

Barik, Sabyasachi; Karasahin, Aziz; Flower, Christopher; Cai, Tao; Miyake, Hirokazu; DeGottardi, Wade; Hafezi, Mohammad; Waks, Edo

2018-02-09

The application of topology in optics has led to a new paradigm in developing photonic devices with robust properties against disorder. Although considerable progress on topological phenomena has been achieved in the classical domain, the realization of strong light-matter coupling in the quantum domain remains unexplored. We demonstrate a strong interface between single quantum emitters and topological photonic states. Our approach creates robust counterpropagating edge states at the boundary of two distinct topological photonic crystals. We demonstrate the chiral emission of a quantum emitter into these modes and establish their robustness against sharp bends. This approach may enable the development of quantum optics devices with built-in protection, with potential applications in quantum simulation and sensing. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nanni, E. A.; Graves, W. S.; Moncton, D. E.

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately tenmore » meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.« less

Near-field levitated quantum optomechanics with nanodiamonds

NASA Astrophysics Data System (ADS)

Juan, M. L.; Molina-Terriza, G.; Volz, T.; Romero-Isart, O.

2016-08-01

We theoretically show that the dipole force of an ensemble of quantum emitters embedded in a dielectric nanosphere can be exploited to achieve near-field optical levitation. The key ingredient is that the polarizability from the ensemble of embedded quantum emitters can be larger than the bulk polarizability of the sphere, thereby enabling the use of repulsive optical potentials and consequently the levitation using optical near fields. In levitated cavity quantum optomechanics, this could be used to boost the single-photon coupling by combining larger polarizability to mass ratio, larger field gradients, and smaller cavity volumes while remaining in the resolved sideband regime and at room temperature. A case study is done with a nanodiamond containing a high density of silicon-vacancy color centers that is optically levitated in the evanescent field of a tapered nanofiber and coupled to a high-finesse microsphere cavity.

Optical polarization properties of InAs/InP quantum dot and quantum rod nanowires.

PubMed

Anufriev, Roman; Barakat, Jean-Baptiste; Patriarche, Gilles; Letartre, Xavier; Bru-Chevallier, Catherine; Harmand, Jean-Christophe; Gendry, Michel; Chauvin, Nicolas

2015-10-02

The emission polarization of single InAs/InP quantum dot (QD) and quantum rod (QR) nanowires is investigated at room temperature. Whereas the emission of the QRs is mainly polarized parallel to the nanowire axis, the opposite behavior is observed for the QDs. These optical properties can be explained by a combination of dielectric effects related to the nanowire geometry and to the configuration of the valence band in the nanostructure. A theoretical model and finite difference in time domain calculations are presented to describe the impact of the nanowire and the surroundings on the optical properties of the emitter. Using this model, the intrinsic degree of linear polarization of the two types of emitters is extracted. The strong polarization anisotropies indicate a valence band mixing in the QRs but not in the QDs.

High efficient white organic light-emitting diodes with single emissive layer using phosphorescent red, green, and blue dopants

NASA Astrophysics Data System (ADS)

Kim, You-Hyun; Wai Cheah, Kok; Young Kim, Woo

2013-07-01

Phosphorescent white organic light-emitting diodes (PHWOLEDs) with single emissive layer were fabricated by co-doping phosphorescent blue, green, and red emitters with different concentrations. WOLEDs using Ir(piq)3 and Ir(ppy)3 as red and green dopants along with 8% of Firpic as blue dopant with host materials of 4CzPBP in the emissive layer were compared under various doping ratio between Ir(piq)3 and Ir(ppy)3. Triplet-triplet Dexter energy transfer in single emissive PHWOLEDs including three primary colors was saturated from higher triplet energy levels to lower triplet energy levels directly.

Single-crystalline δ-Ni2Si nanowires with excellent physical properties

PubMed Central

2013-01-01

In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

Single-pass BPM system of the Photon Factory storage ring.

PubMed

Honda, T; Katoh, M; Mitsuhashi, T; Ueda, A; Tadano, M; Kobayashi, Y

1998-05-01

At the 2.5 GeV ring of the Photon Factory, a single-pass beam-position monitor (BPM) system is being prepared for the storage ring and the beam transport line. In the storage ring, the injected beam position during the first several turns can be measured with a single injection pulse. The BPM system has an adequate performance, useful for the commissioning of the new low-emittance lattice. Several stripline BPMs are being installed in the beam transport line. The continuous monitoring of the orbit in the beam transport line will be useful for the stabilization of the injection energy as well as the injection beam orbit.

High precision wavefront control in point spread function engineering for single emitter localization

NASA Astrophysics Data System (ADS)

Siemons, M.; Hulleman, C. N.; Thorsen, R. Ø.; Smith, C. S.; Stallinga, S.

2018-04-01

Point Spread Function (PSF) engineering is used in single emitter localization to measure the emitter position in 3D and possibly other parameters such as the emission color or dipole orientation as well. Advanced PSF models such as spline fits to experimental PSFs or the vectorial PSF model can be used in the corresponding localization algorithms in order to model the intricate spot shape and deformations correctly. The complexity of the optical architecture and fit model makes PSF engineering approaches particularly sensitive to optical aberrations. Here, we present a calibration and alignment protocol for fluorescence microscopes equipped with a spatial light modulator (SLM) with the goal of establishing a wavefront error well below the diffraction limit for optimum application of complex engineered PSFs. We achieve high-precision wavefront control, to a level below 20 m$\\lambda$ wavefront aberration over a 30 minute time window after the calibration procedure, using a separate light path for calibrating the pixel-to-pixel variations of the SLM, and alignment of the SLM with respect to the optical axis and Fourier plane within 3 $\\mu$m ($x/y$) and 100 $\\mu$m ($z$) error. Aberrations are retrieved from a fit of the vectorial PSF model to a bead $z$-stack and compensated with a residual wavefront error comparable to the error of the SLM calibration step. This well-calibrated and corrected setup makes it possible to create complex `3D+$\\lambda$' PSFs that fit very well to the vectorial PSF model. Proof-of-principle bead experiments show precisions below 10~nm in $x$, $y$, and $\\lambda$, and below 20~nm in $z$ over an axial range of 1 $\\mu$m with 2000 signal photons and 12 background photons.

Packaging of wavelength stabilized 976nm 100W 105µm 0.15 NA fiber coupled diode lasers

NASA Astrophysics Data System (ADS)

Jiang, Xiaochen; Liu, Rui; Gao, Yanyan; Zhang, Tujia; He, Xiaoguang; Zhu, Jing; Zhang, Qiang; Yang, Thomas; Zhang, Cuipeng

2016-03-01

Fiber coupled diode lasers are widely used in many fields now especially as pumps in fiber laser systems. In many fiber laser applications, high brightness pumps are essential to achieve high brightness fiber lasers. Furthermore, 976nm wavelength absorption band is narrow with Yb3+ doped fiber lasers which is more challenging for controlling wavelength stabilized in diode laser modules. This study designed and implemented commercial available high brightness and narrow wavelength width lasers to be able to use in previous mentioned applications. Base on multiple single emitters using spatial and polarization beam combining as well as fiber coupling techniques, we report a wavelength stabilized, 105μm NA 0.15 fiber coupled diode laser package with 100W of optical output power at 976 nm, which are 14 emitters inside each multiple single emitter module. The emitting aperture of the combined lasers output are designed and optimized for coupling light into a 105μm core NA 0.15 fiber. Volume Bragg grating technology has been used to improve spectral characteristics of high-power diode lasers. Mechanical modular design and thermal simulation are carried out to optimize the package. The spectral width is roughly 0.5 nm (FWHM) and the wavelength shift per °C < 0.02nm. The output spectrum is narrowed and wavelength is stabilized using Volume Bragg gratings (VBGs). The high brightness package has an electrical to optical efficiency better than 45% and power enclosure more than 90% within NA 0.12. Qualification tests have been included on this kind of package. Mechanical shock, vibration and accelerated aging tests show that the package is reliability and the MTTF is calculated to be more than 100k hours at 25°C.

Thermionic converter

DOEpatents

Rasor, Ned S.; Britt, Edward J.

1976-01-01

A gas-filled thermionic converter is provided with a collector and an emitter having a main emitter region and an auxiliary emitter region in electrical contact with the main emitter region. The main emitter region is so positioned with respect to the collector that a main gap is formed therebetween and the auxiliary emitter region is so positioned with respect to the collector that an auxiliary gap is formed therebetween partially separated from the main gap with access allowed between the gaps to allow ionizable gas in each gap to migrate therebetween. With heat applied to the emitter the work function of the auxiliary emitter region is sufficiently greater than the work function of the collector so that an ignited discharge occurs in the auxiliary gap and the work function of the main emitter region is so related to the work function of the collector that an unignited discharge occurs in the main gap sustained by the ions generated in the auxiliary gap. A current flows through a load coupled across the emitter and collector due to the unignited discharge in the main gap.

Field emission characteristics of a small number of carbon fiber emitters

NASA Astrophysics Data System (ADS)

Tang, Wilkin W.; Shiffler, Donald A.; Harris, John R.; Jensen, Kevin L.; Golby, Ken; LaCour, Matthew; Knowles, Tim

2016-09-01

This paper reports an experiment that studies the emission characteristics of small number of field emitters. The experiment consists of nine carbon fibers in a square configuration. Experimental results show that the emission characteristics depend strongly on the separation between each emitter, providing evidence of the electric field screening effects. Our results indicate that as the separation between the emitters decreases, the emission current for a given voltage also decreases. The authors compare the experimental results to four carbon fiber emitters in a linear and square configurations as well as to two carbon fiber emitters in a paired array. Voltage-current traces show that the turn-on voltage is always larger for the nine carbon fiber emitters as compared to the two and four emitters in linear configurations, and approximately identical to the four emitters in a square configuration. The observations and analysis reported here, based on Fowler-Nordheim field emission theory, suggest the electric field screening effect depends critically on the number of emitters, the separation between them, and their overall geometric configuration.

Electrochemical formation of field emitters

DOEpatents

Bernhardt, Anthony F.

1999-01-01

Electrochemical formation of field emitters, particularly useful in the fabrication of flat panel displays. The fabrication involves field emitting points in a gated field emitter structure. Metal field emitters are formed by electroplating and the shape of the formed emitter is controlled by the potential imposed on the gate as well as on a separate counter electrode. This allows sharp emitters to be formed in a more inexpensive and manufacturable process than vacuum deposition processes used at present. The fabrication process involves etching of the gate metal and the dielectric layer down to the resistor layer, and then electroplating the etched area and forming an electroplated emitter point in the etched area.

Spectrally-engineered solar thermal photovoltaic devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lenert, Andrej; Bierman, David; Chan, Walker

A solar thermal photovoltaic device, and method of forming same, includes a solar absorber and a spectrally selective emitter formed on either side of a thermally conductive substrate. The solar absorber is configured to absorb incident solar radiation. The solar absorber and the spectrally selective emitter are configured with an optimized emitter-to-absorber area ratio. The solar thermal photovoltaic device also includes a photovoltaic cell in thermal communication with the spectrally selective emitter. The spectrally selective emitter is configured to permit high emittance for energies above a bandgap of the photovoltaic cell and configured to permit low emittance for energies belowmore » the bandgap.« less

Ultra-high Temperature Emittance Measurements for Space and Missile Applications

NASA Technical Reports Server (NTRS)

Rogers, Jan; Crandall, David

2009-01-01

Advanced modeling and design efforts for many aerospace components require high temperature emittance data. Applications requiring emittance data include propulsion systems, radiators, aeroshells, heatshields/thermal protection systems, and leading edge surfaces. The objective of this work is to provide emittance data at ultra-high temperatures. MSFC has a new instrument for the measurement of emittance at ultra-high temperatures, the Ultra-High Temperature Emissometer System (Ultra-HITEMS). AZ Technology Inc. developed the instrument, designed to provide emittance measurements over the temperature range 700-3500K. The Ultra-HITEMS instrument measures the emittance of samples, heated by lasers, in vacuum, using a blackbody source and a Fourier Transform Spectrometer. Detectors in a Nicolet 6700 FT-IR spectrometer measure emittance over the spectral range of 0.4-25 microns. Emitted energy from the specimen and output from a Mikron M390S blackbody source at the same temperature with matched collection geometry are measured. Integrating emittance over the spectral range yields the total emittance. The ratio provides a direct measure of total hemispherical emittance. Samples are heated using lasers. Optical pyrometry provides temperature data. Optical filters prevent interference from the heating lasers. Data for Inconel 718 show excellent agreement with results from literature and ASTM 835. Measurements taken from levitated spherical specimens provide total hemispherical emittance data; measurements taken from flat specimens mounted in the chamber provide near-normal emittance data. Data from selected characterization studies will be presented. The Ultra-HITEMS technique could advance space and missile technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials.

Universal photonic quantum computation via time-delayed feedback

PubMed Central

Pichler, Hannes; Choi, Soonwon; Zoller, Peter; Lukin, Mikhail D.

2017-01-01

We propose and analyze a deterministic protocol to generate two-dimensional photonic cluster states using a single quantum emitter via time-delayed quantum feedback. As a physical implementation, we consider a single atom or atom-like system coupled to a 1D waveguide with a distant mirror, where guided photons represent the qubits, while the mirror allows the implementation of feedback. We identify the class of many-body quantum states that can be produced using this approach and characterize them in terms of 2D tensor network states. PMID:29073057

Self-aligned gated field emission devices using single carbon nanofiber cathodes

NASA Astrophysics Data System (ADS)

Guillorn, M. A.; Melechko, A. V.; Merkulov, V. I.; Hensley, D. K.; Simpson, M. L.; Lowndes, D. H.

2002-11-01

We report on the fabrication and operation of integrated gated field emission devices using single vertically aligned carbon nanofiber (VACNF) cathodes where the gate aperture has been formed using a self-aligned technique based on chemical mechanical polishing. We find that this method for producing gated cathode devices easily achieves structures with gate apertures on the order of 2 mum that show good concentric alignment to the VACNF emitter. The operation of these devices was explored and field emission characteristics that fit well to the Fowler-Nordheim model of emission was demonstrated.

Emittance Theory for Thin Film Selective Emitter

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Lowe, Roland A.; Good, Brian S.

1994-01-01

Thin films of high temperature garnet materials such as yttrium aluminum garnet (YAG) doped with rare earths are currently being investigated as selective emitters. This paper presents a radiative transfer analysis of the thin film emitter. From this analysis the emitter efficiency and power density are calculated. Results based on measured extinction coefficients for erbium-YAG and holmium-YAG are presented. These results indicated that emitter efficiencies of 50 percent and power densities of several watts/sq cm are attainable at moderate temperatures (less than 1750 K).

A state space based approach to localizing single molecules from multi-emitter images.

PubMed

Vahid, Milad R; Chao, Jerry; Ward, E Sally; Ober, Raimund J

2017-01-28

Single molecule super-resolution microscopy is a powerful tool that enables imaging at sub-diffraction-limit resolution. In this technique, subsets of stochastically photoactivated fluorophores are imaged over a sequence of frames and accurately localized, and the estimated locations are used to construct a high-resolution image of the cellular structures labeled by the fluorophores. Available localization methods typically first determine the regions of the image that contain emitting fluorophores through a process referred to as detection. Then, the locations of the fluorophores are estimated accurately in an estimation step. We propose a novel localization method which combines the detection and estimation steps. The method models the given image as the frequency response of a multi-order system obtained with a balanced state space realization algorithm based on the singular value decomposition of a Hankel matrix, and determines the locations of intensity peaks in the image as the pole locations of the resulting system. The locations of the most significant peaks correspond to the locations of single molecules in the original image. Although the accuracy of the location estimates is reasonably good, we demonstrate that, by using the estimates as the initial conditions for a maximum likelihood estimator, refined estimates can be obtained that have a standard deviation close to the Cramér-Rao lower bound-based limit of accuracy. We validate our method using both simulated and experimental multi-emitter images.

Anisotropic electrical transport of flexible tungsten carbide nanostructures: towards nanoscale interconnects and electron emitters

NASA Astrophysics Data System (ADS)

Sun, Bo; Sun, Yong; Wang, Chengxin

2017-11-01

Due to the coexistence of metal- and ionic-bonds in a hexagonal tungsten carbide (WC) lattice, disparate electron behaviors were found in the basal plane and along the c-axial direction, which may create an interesting anisotropic mechanical and electrical performance. To demonstrate this, low-dimensional nanostructures such as nanowires and nanosheets are suitable for investigation because they usually grow in single crystals with special orientations. Herein, we report the experimental research regarding the anisotropic conductivity of [0001] grown WC nanowires and basal plane-expanded nanosheets, which resulted in a conductivity of 7.86 × 103 Ω-1 · m-1 and 7.68 × 104 Ω-1 · m-1 respectively. This conforms to the fact that the highly localized W d state aligns along the c direction, while there is little intraplanar directional bonding in the W planes. With advanced micro-manipulation technology, the conductivity of a nanowire was tested to be approximately constant, even under a considerable bending state. Moreover, the field electron emission of WC was evaluated based on large area emission and single nanowire (nanosheet) emission. A single nanowire exhibits a stable electron emission performance, which can output emission currents >3 uA before fusing. These results provide useful references to assess low-dimensional WC nanostructures as electronic materials in flexible devices, such as nanoscale interconnects and electron emitters.

Search for diffuse neutrino flux from astrophysical sources with MACRO

NASA Astrophysics Data System (ADS)

MACRO Collaboration; Ambrosio, M.; Antolini, R.; Auriemma, G.; Bakari, D.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Becherini, Y.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bloise, C.; Bower, C.; Brigida, M.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Carboni, M.; Caruso, R.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; Cozzi, M.; de Cataldo, G.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Grillo, A.; Guarino, F.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Iarocci, E.; Katsavounidis, E.; Katsavounidis, I.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lipari, P.; Longley, N. P.; Longo, M. J.; Loparco, F.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Margiotta, A.; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Michael, D. G.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicolò, D.; Nolty, R.; Orth, C.; Osteria, G.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Perrone, L.; Petrera, S.; Pistilli, P.; Popa, V.; Rainò, A.; Reynoldson, J.; Ronga, F.; Rrhioua, A.; Satriano, C.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra, P.; Sioli, M.; Sirri, G.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarlè, G.; Togo, V.; Vakili, M.; Walter, C. W.; Webb, R.

2003-04-01

Many galactic and extragalactic astrophysical sources are currently considered promising candidates as high-energy neutrino emitters. Astrophysical neutrinos can be detected as upward-going muons produced in charged-current interactions with the medium surrounding the detector. The expected neutrino fluxes from various models start to dominate on the atmospheric neutrino background at neutrino energies above some tens of TeV. We present the results of a search for an excess of high-energy upward-going muons among the sample of data collected by MACRO during ~5.8 years of effective running time. No significant evidence for this signal was found. As a consequence, an upper limit on the flux of upward-going muons from high-energy neutrinos was set at the level of 1.7×10-14 cm-2s-1sr-1. The corresponding upper limit for the diffuse neutrino flux was evaluated assuming a neutrino power law spectrum. Our result was compared with theoretical predictions and upper limits from other experiments.

Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

NASA Technical Reports Server (NTRS)

Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

1988-01-01

Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

Evidence of low injection efficiency for implanted p-emitters in bipolar 4H-SiC high-voltage diodes

NASA Astrophysics Data System (ADS)

Matthus, Christian D.; Huerner, Andreas; Erlbacher, Tobias; Bauer, Anton J.; Frey, Lothar

2018-06-01

In this study, the influence of the emitter efficiency on the forward current-voltage characteristics, especially the conductivity modulation of bipolar SiC-diodes was analyzed. It was determined that the emitter efficiency of p-emitters formed by ion implantation is significantly lower compared to p-emitters formed by epitaxy. In contrast to comparable studies, experimental approach was arranged that the influence of the quality of the drift-layer or the thickness of the emitter on the conductivity modulation could be excluded for the fabricated bipolar SiC-diodes of this work. Thus, it can be established that the lower emitter injection efficiency is mainly caused by the reduced electron lifetime in p-emitters formed by ion implantation. Therefore, a significant enhancement of the electron lifetime in implanted p-emitters is mandatory for e.g. SiC-MPS-diodes where the functionality of the devices depends significantly on the injection efficiency.

Measurement of transverse emittance and coherence of double-gate field emitter array cathodes

PubMed Central

Tsujino, Soichiro; Das Kanungo, Prat; Monshipouri, Mahta; Lee, Chiwon; Miller, R.J. Dwayne

2016-01-01

Achieving small transverse beam emittance is important for high brightness cathodes for free electron lasers and electron diffraction and imaging experiments. Double-gate field emitter arrays with on-chip focussing electrode, operating with electrical switching or near infrared laser excitation, have been studied as cathodes that are competitive with photocathodes excited by ultraviolet lasers, but the experimental demonstration of the low emittance has been elusive. Here we demonstrate this for a field emitter array with an optimized double-gate structure by directly measuring the beam characteristics. Further we show the successful application of the double-gate field emitter array to observe the low-energy electron beam diffraction from suspended graphene in minimal setup. The observed low emittance and long coherence length are in good agreement with theory. These results demonstrate that our all-metal double-gate field emitters are highly promising for applications that demand extremely low-electron bunch-phase space volume and large transverse coherence. PMID:28008918

Measurement of transverse emittance and coherence of double-gate field emitter array cathodes

NASA Astrophysics Data System (ADS)

Tsujino, Soichiro; Das Kanungo, Prat; Monshipouri, Mahta; Lee, Chiwon; Miller, R. J. Dwayne

2016-12-01

Achieving small transverse beam emittance is important for high brightness cathodes for free electron lasers and electron diffraction and imaging experiments. Double-gate field emitter arrays with on-chip focussing electrode, operating with electrical switching or near infrared laser excitation, have been studied as cathodes that are competitive with photocathodes excited by ultraviolet lasers, but the experimental demonstration of the low emittance has been elusive. Here we demonstrate this for a field emitter array with an optimized double-gate structure by directly measuring the beam characteristics. Further we show the successful application of the double-gate field emitter array to observe the low-energy electron beam diffraction from suspended graphene in minimal setup. The observed low emittance and long coherence length are in good agreement with theory. These results demonstrate that our all-metal double-gate field emitters are highly promising for applications that demand extremely low-electron bunch-phase space volume and large transverse coherence.

Beta/alpha continuous air monitor

DOEpatents

Becker, Gregory K.; Martz, Dowell E.

1989-01-01

A single deep layer silicon detector in combination with a microcomputer, recording both alpha and beta activity and the energy of each pulse, distinguishing energy peaks using a novel curve fitting technique to reduce the natural alpha counts in the energy region where plutonium and other transuranic alpha emitters are present, and using a novel algorithm to strip out radon daughter contribution to actual beta counts.

High-precision Q EC -value measurement of the superallowed β + emitter Mg 22 and an ab initio evaluation of the A = 22 isobaric triplet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiter, M. P.; Leach, K. G.; Drozdowski, O. M.

The direct atomic mass difference between 22Mg and 22Na was measured using TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) and was determined to be Q=4781.40(22) keV. This measurement represents the most precise single measurement of this quantity to date.

High-precision Q EC -value measurement of the superallowed β + emitter Mg 22 and an ab initio evaluation of the A = 22 isobaric triplet

DOE PAGES

Reiter, M. P.; Leach, K. G.; Drozdowski, O. M.; ...

2017-11-06

The direct atomic mass difference between 22Mg and 22Na was measured using TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) and was determined to be Q=4781.40(22) keV. This measurement represents the most precise single measurement of this quantity to date.

Advances in 7xx-nm fiber-coupled modules with application to Tm fiber laser pumping and DPAL (Conference Presentation)

NASA Astrophysics Data System (ADS)

Patterson, Steven G.; Guiney, Tina; Stapleton, Dean; Braker, Joseph; Alegria, Kim; Irwin, David A.; Ebert, Christopher

2017-02-01

DILAS has leveraged its industry-leading work in manufacturing low SWaP fiber-coupled modules extending the wavelength range to 793nm for Tm fiber laser pumping. Ideal for medical, industrial and military applications, modules spanning from single emitter-based 9W to TBar-based 200W of 793nm pump power will be discussed. The highlight is a lightweight module capable of <200W of 793nm pump power out of a package weighing < 400 grams. In addition, other modules spanning from single emitter-based 9W to TBar-based 200W of 793nm pump power will be presented. In addition, advances in DPAL modules, emitting at the technologically important wavelengths near 766nm and 780nm, will be detailed. Highlights include a fully microprocessor controlled fiber-coupled module that produces greater than 400W from a 600 micron core fiber and a line width of only 56.3pm. The micro-processor permits the automated center wavelength and line width tuning of the output over a range of output powers while retaining excellent line center and line width stability over time.

Nanophotonic enhanced quantum emitters

NASA Astrophysics Data System (ADS)

Li, Xin; Zhou, Zhang-Kai; Yu, Ying; Gather, Malte; Di Falco, Andrea

2017-08-01

Quantum dots are excellent solid-state quantum sources, because of their stability, their narrow spectral linewidth, and radiative lifetime in the range of 1ns. Most importantly, they can be integrated into more complex nanophononics devices, to realize high quality quantum emitters of single photons or entangled photon sources. Recent progress in nanotechnology materials and devices has opened a number of opportunities to increase, optimize and ultimately control the emission property of single quantum dot. In this work, we present an approach that combines the properties of quantum dots with the flexibility of light control offered by nanoplasmonics and metamaterials structuring. Specifically, we show the nanophotonic enhancement of two types of quantum dots devices. The quantum dots are inserted into optical-positioned micropillar cavities, or decorated on the facets of core-shell GaAs/AlGaAs nanowires, fabricated with a bottom-up approach. In both cases, the metallic nanofeatures, which are designed to control the emission and the polarization state of the emitted light, are realized via direct electron-beam-induced deposition. This approach permits to create three-dimensional features with nanometric resolution and positional accuracy, and does not require wet lithographic steps and previous knowledge of the exact spatial arrangement of the quantum devices.

Photonic engineering of highly linearly polarized quantum dot emission at telecommunication wavelengths

NASA Astrophysics Data System (ADS)

Mrowiński, P.; Emmerling, M.; Schneider, C.; Reithmaier, J. P.; Misiewicz, J.; Höfling, S.; Sek, G.

2018-04-01

In this work, we discuss a method to control the polarization anisotropy of spontaneous emission from neutral excitons confined in quantum-dot-like nanostructures, namely single epitaxial InAs quantum dashes emitting at telecom wavelengths. The nanostructures are embedded inside lithographically defined, in-plane asymmetric photonic mesa structures, which generate polarization-dependent photonic confinement. First, we study the influence of the photonic confinement on the polarization anisotropy of the emission by photoluminescence spectroscopy, and we find evidence of different contributions to a degree of linear polarization (DOLP), i.e., from the quantum dash and the photonic mesa, in total giving rise to DOLP =0.85 . Then, we perform finite-difference time-domain simulations of photonic confinement, and we calculate the DOLP in a dipole approximation showing well-matched results for the established model. Furthermore, by using numerical calculations, we demonstrate several types of photonic confinements where highly linearly polarized emission with DOLP of about 0.9 is possible by controlling the position of a quantum emitter inside the photonic structure. Then, we elaborate on anisotropic quantum emitters allowing for exceeding DOLP =0.95 in an optimized case, and we discuss the ways towards efficient linearly polarized single photon source at telecom bands.

NuSTAR results from the Galactic Center - diffuse emission

NASA Astrophysics Data System (ADS)

Hailey, Charles

2016-03-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) was launched in June 2012. It carried the first true, hard X-ray (>~10 keV-79 keV) focusing telescopes into orbit. Its twin telescopes provide 10 times better angular resolution and 100 times better sensitivity than previously obtainable in the hard X-ray band. Consequently NuSTAR is able to resolve faint diffuse structures whose hard X-rays offer insight into some of the most energetic processes in the Galactic Center. One of the surprising discoveries that NuSTAR made in the Galactic Center is the central hard X-ray emission (CHXE). The CHXE is a diffuse emission detected from ~10 keV to beyond 50 keV in X-ray energy, and extending spatially over a region ~8 parsecs x ~4 parsecs in and out of the plane of the galaxy respectively, and centered on the supermassive black hole Sgr A*. The CHXE was speculated to be due to a large population of unresolved black hole X-ray binaries, millisecond pulsars (MSP), a class of highly magnetized white dwarf binaries called intermediate polars, or to particle outflows from Sgr A*. The presence of an unexpectedly large population of MSP in the Galactic Center would be particularly interesting, since MSP emitting at higher energies and over a much larger region have been posited to be the origin of the gamma-ray emission that is also ascribed to dark matter annihilation in the galaxy. In addition, the connection of the CHXE to the ~9000 unidentified X-ray sources in the central the the ~100 pc detected by the Chandra Observatory, to the soft X-ray emission detected by the Chandra and XMM/Newton observatories in the Galactic Center, and to the hard X-ray emission detected by both the RXTE and INTEGRAL observatories in the Galactic Ridge, is unclear. I review these results and present recent NuSTAR observations that potentially resolve the origin of the CHXE and point to a unified origin for all these X-ray emissions. Two other noteworthy classes of diffuse structures in the Galactic Center will be discussed. The first class are the giant molecular clouds, which are strong hard X-ray emitters. These hard X-rays are believed to be produced when one or more giant outbursts from the supermassive black hole Sgr A*, more than a century ago, resulted in hard X-rays being reflected from the clouds, and detected only today. I discuss how these hard X-rays are used to elucidate the past history of the supermassive black hole, and to compare and contrast these past giant outbursts with those observed from the supermassive black hole more recently. The second class are non-thermal filaments, magnetized structures with both radio and soft X-ray emission that have now been shown by NuSTAR to be hard X-ray emitters. The electrons generating the hard X-rays observed in one of these filaments are the most energetic that have been observed in the galaxy. The filaments are a heterogeneous class of hard X-ray emitters, and the various mechanisms by which they produce hard X-ray emission will be discussed. Future NuSTAR observations of the Galactic Center with NuSTAR will also be discussed.

Single-molecule diffusion and conformational dynamics by spatial integration of temporal fluctuations

PubMed Central

Serag, Maged F.; Abadi, Maram; Habuchi, Satoshi

2014-01-01

Single-molecule localization and tracking has been used to translate spatiotemporal information of individual molecules to map their diffusion behaviours. However, accurate analysis of diffusion behaviours and including other parameters, such as the conformation and size of molecules, remain as limitations to the method. Here, we report a method that addresses the limitations of existing single-molecular localization methods. The method is based on temporal tracking of the cumulative area occupied by molecules. These temporal fluctuations are tied to molecular size, rates of diffusion and conformational changes. By analysing fluorescent nanospheres and double-stranded DNA molecules of different lengths and topological forms, we demonstrate that our cumulative-area method surpasses the conventional single-molecule localization method in terms of the accuracy of determined diffusion coefficients. Furthermore, the cumulative-area method provides conformational relaxation times of structurally flexible chains along with diffusion coefficients, which together are relevant to work in a wide spectrum of scientific fields. PMID:25283876

Anomalous diffusion of single metal atoms on a graphene oxide support

DOE PAGES

Furnival, Tom; Leary, Rowan K.; Tyo, Eric C.; ...

2017-04-21

Recent studies of single-atom catalysts open up the prospect of designing exceptionally active and environmentally efficient chemical processes. The stability and durability of such catalysts is governed by the strength with which the atoms are bound to their support and their diffusive behaviour. Here we use aberration-corrected STEM to image the diffusion of single copper adatoms on graphene oxide. As a result, we discover that individual atoms exhibit anomalous diffusion as a result of spatial and energetic disorder inherent in the support, and interpret the origins of this behaviour to develop a physical picture for the surface diffusion of singlemore » metal atoms.« less

Electrochemical formation of field emitters

DOEpatents

Bernhardt, A.F.

1999-03-16

Electrochemical formation of field emitters, particularly useful in the fabrication of flat panel displays is disclosed. The fabrication involves field emitting points in a gated field emitter structure. Metal field emitters are formed by electroplating and the shape of the formed emitter is controlled by the potential imposed on the gate as well as on a separate counter electrode. This allows sharp emitters to be formed in a more inexpensive and manufacturable process than vacuum deposition processes used at present. The fabrication process involves etching of the gate metal and the dielectric layer down to the resistor layer, and then electroplating the etched area and forming an electroplated emitter point in the etched area. 12 figs.

Emittance measurements of Space Shuttle orbiter reinforced carbon-carbon

NASA Technical Reports Server (NTRS)

Caram, Jose M.; Bouslog, Stanley A.; Cunnington, George R., Jr.

1992-01-01

The spectral and total normal emittance of the Reinforced Carbon-Carbon (RCC) used on Space Shuttle nose cap and wing leading edges has been measured at room temperature and at surface temperatures of 1200 to 2100 K. These measurements were made on virgin and two flown RCC samples. Room temperature directional emittance data were also obtained and were used to determine the total hemispherical emittance of RCC as a function of temperature. Results of the total normal emittance for the virgin samples showed good agreement with the current RCC emittance design curve; however, the data from the flown samples showed an increase in the emittance at high temperature possibly due to exposure from flight environments.

Emittance Theory for Cylindrical Fiber Selective Emitter

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1998-01-01

A fibrous rare earth selective emitter is approximated as an infinitely long cylinder. The spectral emittance, epsilon(lambda), is obtained by solving the radiative transfer equations with appropriate boundary conditions and uniform temperature. For optical depths, Kappa(R) = alpha(lambda)R, where alpha(lambda) is the extinction coefficient and R is the cylinder radius, greater than 1 the spectral emittance is nearly at its maximum value. There is an optimum cylinder radius, R(opt), for maximum emitter efficiency, eta(E). Values for R(opt) are strongly dependent on the number of emission bands of the material. The optimum radius decreases slowly with increasing emitter temperature, while the maximum efficiency and useful radiated power increase rapidly with increasing temperature.

Radial arrays of nano-electrospray ionization emitters and methods of forming electrosprays

DOEpatents

Kelly, Ryan T [West Richland, WA; Tang, Keqi [Richland, WA; Smith, Richard D [Richland, WA

2010-10-19

Electrospray ionization emitter arrays, as well as methods for forming electrosprays, are described. The arrays are characterized by a radial configuration of three or more nano-electrospray ionization emitters without an extractor electrode. The methods are characterized by distributing fluid flow of the liquid sample among three or more nano-electrospray ionization emitters, forming an electrospray at outlets of the emitters without utilizing an extractor electrode, and directing the electrosprays into an entrance to a mass spectrometry device. Each of the nano-electrospray ionization emitters can have a discrete channel for fluid flow. The nano-electrospray ionization emitters are circularly arranged such that each is shielded substantially equally from an electrospray-inducing electric field.

Simultaneous, accurate measurement of the 3D position and orientation of single molecules

PubMed Central

Backlund, Mikael P.; Lew, Matthew D.; Backer, Adam S.; Sahl, Steffen J.; Grover, Ginni; Agrawal, Anurag; Piestun, Rafael; Moerner, W. E.

2012-01-01

Recently, single molecule-based superresolution fluorescence microscopy has surpassed the diffraction limit to improve resolution to the order of 20 nm or better. These methods typically use image fitting that assumes an isotropic emission pattern from the single emitters as well as control of the emitter concentration. However, anisotropic single-molecule emission patterns arise from the transition dipole when it is rotationally immobile, depending highly on the molecule’s 3D orientation and z position. Failure to account for this fact can lead to significant lateral (x, y) mislocalizations (up to ∼50–200 nm). This systematic error can cause distortions in the reconstructed images, which can translate into degraded resolution. Using parameters uniquely inherent in the double-lobed nature of the Double-Helix Point Spread Function, we account for such mislocalizations and simultaneously measure 3D molecular orientation and 3D position. Mislocalizations during an axial scan of a single molecule manifest themselves as an apparent lateral shift in its position, which causes the standard deviation (SD) of its lateral position to appear larger than the SD expected from photon shot noise. By correcting each localization based on an estimated orientation, we are able to improve SDs in lateral localization from ∼2× worse than photon-limited precision (48 vs. 25 nm) to within 5 nm of photon-limited precision. Furthermore, by averaging many estimations of orientation over different depths, we are able to improve from a lateral SD of 116 (∼4× worse than the photon-limited precision; 28 nm) to 34 nm (within 6 nm of the photon limit). PMID:23129640

Thermal emittance from ionization-induced trapping in plasma accelerators

DOE PAGES

Schroeder, C.  B.; Vay, J. -L.; Esarey, E.; ...

2014-10-03

The minimum obtainable transverse emittance (thermal emittance) of electron beams generated and trapped in plasma-based accelerators using laser ionization injection is examined. The initial transverse phase space distribution following ionization and passage through the laser is derived, and expressions for the normalized transverse beam emittance, both along and orthogonal to the laser polarization, are presented. Results are compared to particle-in-cell simulations. Ultralow emittance beams can be generated using laser ionization injection into plasma accelerators, and examples are presented showing normalized emittances on the order of tens of nm.

A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems

NASA Astrophysics Data System (ADS)

Rauch, Michael; Haehnelt, Martin; Bunker, Andrew; Becker, George; Marleau, Francine; Graham, James; Cristiani, Stefano; Jarvis, Matt; Lacey, Cedric; Morris, Simon; Peroux, Celine; Röttgering, Huub; Theuns, Tom

2008-07-01

We have conducted a long-slit search for low surface brightness Lyα emitters at redshift 2.67 < z < 3.75. A 92 hr long exposure with the ESO VLT FORS2 instrument down to a 1 σ surface brightness detection limit of 8 × 10-20 erg cm-2 s-1 arcsec-2 per arcsec2 aperture yielded a sample of 27 single line emitters with fluxes of a few × 10-18 erg s-1 cm-2. We present arguments that most objects are indeed Lyα. The large comoving number density, 3 × 10-2 h370 Mpc-3, the large covering factor, dN/dz ~ 0.2-1, and the often extended Lyα emission suggest that the emitters can be identified with the elusive host population of damped Lyα systems (DLAS) and high column density Lyman limit systems (LLS). A small inferred star formation rate, perhaps supplemented by cooling radiation, appears to energetically dominate the Lyα emission, and is consistent with the low metallicity, low dust content, and theoretically inferred low masses of DLAS, and with the relative lack of success of earlier searches for their optical counterparts. Some of the line profiles show evidence for radiative transfer in galactic outflows. Stacking surface brightness profiles, we find emission out to at least 4''. The centrally concentrated emission of most objects appears to light up the outskirts of the emitters (where LLS arise) down to a column density where the conversion from UV to Lyα photon becomes inefficient. DLAS, high column density LLS, and the emitter population discovered in this survey appear to be different observational manifestations of the same low-mass, protogalactic building blocks of present-day L* galaxies. Based partly on observations made with ESO Telescopes at the Paranal Observatories under Program ID LP173.A-0440, and partly on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil) and CONICET (Argentina).

Detection of Single Molecules Illuminated by a Light-Emitting Diode

PubMed Central

Gerhardt, Ilja; Mai, Lijian; Lamas-Linares, Antía; Kurtsiefer, Christian

2011-01-01

Optical detection and spectroscopy of single molecules has become an indispensable tool in biological imaging and sensing. Its success is based on fluorescence of organic dye molecules under carefully engineered laser illumination. In this paper we demonstrate optical detection of single molecules on a wide-field microscope with an illumination based on a commercially available, green light-emitting diode. The results are directly compared with laser illumination in the same experimental configuration. The setup and the limiting factors, such as light transfer to the sample, spectral filtering and the resulting signal-to-noise ratio are discussed. A theoretical and an experimental approach to estimate these parameters are presented. The results can be adapted to other single emitter and illumination schemes. PMID:22346610

Highly Simplified Tandem Organic Light-Emitting Devices Incorporating a Green Phosphorescence Ultrathin Emitter within a Novel Interface Exciplex for High Efficiency.

PubMed

Xu, Ting; Zhou, Jun-Gui; Huang, Chen-Chao; Zhang, Lei; Fung, Man-Keung; Murtaza, Imran; Meng, Hong; Liao, Liang-Sheng

2017-03-29

Herein we report a novel design philosophy of tandem OLEDs incorporating a doping-free green phosphorescent bis[2-(2-pyridinyl-N)phenyl-C](acetylacetonato)iridium(III) (Ir(ppy) 2 (acac)) as an ultrathin emissive layer (UEML) into a novel interface-exciplex-forming structure of 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and 1,3,5-tri(p-pyrid-3-yl-phenyl)benzene (TmPyPB). Particularly, relatively low working voltage and remarkable efficiency are achieved and the designed tandem OLEDs exhibit a peak current efficiency of 135.74 cd/A (EQE = 36.85%) which is two times higher than 66.2 cd/A (EQE = 17.97%) of the device with a single emitter unit. This might be one of the highest efficiencies of OLEDs applying ultrathin emitters without light extraction. Moreover, with the proposed structure, the color gamut of the displays can be effectively increased from 76% to 82% NTSC if the same red and blue emissions as those in the NTSC are applied. A novel form of harmonious fusion among interface exciplex, UEML, and tandem structure is successfully realized, which sheds light on further development of ideal OLED structure with high efficiency, simplified fabrication, low power consumption, low cost, and improved color gamut, simultaneously.

High-quality beam generation using an RF gun and a 150 MeV microtron

NASA Astrophysics Data System (ADS)

Kuroda, R.; Washio, M.; Kashiwagi, S.; Kobuki, T.; Ben-Zvi, I.; Wang, X. J.; Hori, T.; Sakai, F.; Tsunemi, A.; Urakawa, J.; Hirose, T.

2000-11-01

Low-emittance sub-picosecond electron pulses are expected to be used in a wide field, such as free electron laser, laser acceleration, femtosecond X-ray generation by Inverse Compton scattering, pulse radiolysis, etc. In order to produce the low-emittance sub-picosecond electron pulse, we are developing a compact Racetrack Microtron (RTM) with a new 5 MeV injection system adopting a laser photo cathode RF gun (Washio et al., Seventh China-Japan Bilateral Symposium on Radiation Chemistry, October 28, Cengdu, China, 1996). The operation of RTM has been kept under a steady state of beam loading for long pulse mode so far (Washio et al., J. Surf. Sci. Soc. Jpn. 19 (2) (1998) 23). In earlier work (Washio et al., PAC99, March 31, New York, USA, 1999), we have succeeded in the numerical simulation for the case of single short pulse acceleration. Finally, the modified RTM was demonstrated as a useful accelerator for a picosecond electron pulse generation under a transient state of beam loading. In the simulation, a picosecond electron pulse was accelerated to 149.6 MeV in RTM for the injection of 5 MeV electron bunch with a pulse length of 10 ps (FWHM), a charge of 1 nC per pulse, and an emittance of 3 πmm mrad.

Chemical nature of the light emitter of the Aequorea green fluorescent protein

PubMed Central

Niwa, Haruki; Inouye, Satoshi; Hirano, Takashi; Matsuno, Tatsuki; Kojima, Satoshi; Kubota, Masayuki; Ohashi, Mamoru; Tsuji, Frederick I.

1996-01-01

The jellyfish Aequorea victoria possesses in the margin of its umbrella a green fluorescent protein (GFP, 27 kDa) that serves as the ultimate light emitter in the bioluminescence reaction of the animal. The protein is made up of 238 amino acid residues in a single polypeptide chain and produces a greenish fluorescence (λmax = 508 nm) when irradiated with long ultraviolet light. The fluorescence is due to the presence of a chromophore consisting of an imidazolone ring, formed by a post-translational modification of the tripeptide -Ser65-Tyr66-Gly67-. GFP has been used extensively as a reporter protein for monitoring gene expression in eukaryotic and prokaryotic cells, but relatively little is known about the chemical mechanism by which fluorescence is produced. To obtain a better understanding of this problem, we studied a peptide fragment of GFP bearing the chromophore and a synthetic model compound of the chromophore. The results indicate that the GFP chromophore consists of an imidazolone ring structure and that the light emitter is the singlet excited state of the phenolate anion of the chromophore. Further, the light emission is highly dependent on the microenvironment around the chromophore and that inhibition of isomerization of the exo-methylene double bond of the chromophore accounts for its efficient light emission. PMID:8942983

Surface hydration amplifies single-well protein atom diffusion propagating into the macromolecular core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Liang; Cheng, Xiaolin; Glass, Dennis C.

2012-06-05

The effect of surface hydration water on internal protein motion is of fundamental interest in molecular biophysics. Here, by decomposing the picosecond to nanosecond atomic motion in molecular dynamics simulations of lysozyme at different hydration levels into three components localized single-well diffusion, methyl group rotation, and nonmethyl jumps we show that the effect of surface hydration is mainly to increase the volume of the localized single-well diffusion. As a result, these diffusive motions are coupled in such a way that the hydration effect propagates from the protein surface into the dry core.

Design of a three-layer antireflection coating for high efficiency indium phosphide solar cells using a chemical oxide as first layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moulot, J.; Faur, M.; Faur, M.

1995-10-01

It is well known that the behavior of III-V compound based solar cells is largely controlled by their surface, since the majority of light generated carriers (63% for GaAs and 79% for InP) are created within 0.2 mu m of the surface of the illuminated cell. Consequently, the always observed high surface recombination velocity (SRV) on these cells is a serious limiting factor for their high efficiency performance, especially for those with p-n junction made by either thermal diffusion or ion implantation. A good surface passivation layer, ideally a grown oxide as opposed to a deposited one, will cause amore » significant reduction in the SRV without adding interface problems, thus improving the performance of III-V compound based solar cells. Another significant benefit to the overall performance of the solar cells can be achieved by a substantial reduction of their large surface optical reflection by the use of a well designed antireflection (AR) coating. In this paper, the authors demonstrate the effectiveness of using a chemically grown thermally and chemically stable oxide, not only for surface passivation but also as an integral part of a 3-layer AR coating for thermally diffused p+n InP solar cells. A phosphorus-rich interfacial oxide, In(PO3)3, is grown at the surface of the p+ emitter using an etchant based on HNO3, o-H3PO4 and H2O2. This oxide has the unique properties of passivating the surface as well as serving as an efficient antireflective layer yielding a measured record high AMO open-circuit voltage of 890.3 mV on a thermally diffused InP(Cd,S) solar cell. Unlike conventional single layer AR coatings such as ZnS, Sb2O3, SiO or double layer AR coatings such as ZnS/MgF2 deposited by e-beam or resistive evaporation, this oxide preserves the stoichiometry of the InP surface.« less

Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method.

PubMed

Van Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Héroux, M È; Gibson, M D; Guernsey, J R; Kindzierski, W; Wheeler, A J

2015-12-01

Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER(1z)). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER(2z)). In total, 287 daily pairs of AER(2z) and AER(1z) estimates were made from 35 homes across three cities. In 87% of the cases, AER(2z) was higher than AER(1z). Overall, the AER(1z) estimates underestimated AER(2z) by approximately 16% (IQR: 5-32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. The results of this study suggest that the long-standing assumption that a home represents a single well-mixed air zone may result in a substantial negative bias in air exchange estimates. Indoor air quality professionals should take this finding into consideration when developing study designs or making decisions related to the recommendation and installation of residential ventilation systems. © 2014 Her Majesty the Queen in Right of Canada. Indoor Air published by John Wiley & Sons Ltd Reproduced with the permission of the Minister of Health Canada.

Reconfigurable visible nanophotonic switch for optogenetic applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Mohanty, Aseema; Li, Qian; Tadayon, Mohammad Amin; Bhatt, Gaurang R.; Cardenas, Jaime; Miller, Steven A.; Kepecs, Adam; Lipson, Michal

2017-02-01

High spatiotemporal resolution deep-brain optical excitation for optogenetics would enable activation of specific neural populations and in-depth study of neural circuits. Conventionally, a single fiber is used to flood light into a large area of the brain with limited resolution. The scalability of silicon photonics could enable neural excitation over large areas with single-cell resolution similar to electrical probes. However, active control of these optical circuits has yet to be demonstrated for optogenetics. Here we demonstrate the first active integrated optical switch for neural excitation at 473 nm, enabling control of multiple beams for deep-brain neural stimulation. Using a silicon nitride waveguide platform, we develop a cascaded Mach-Zehnder interferometer (MZI) network located outside the brain to direct light to 8 different grating emitters located at the tip of the neural probe. We use integrated platinum microheaters to induce a local thermo-optic phase shift in the MZI to control the switch output. We measure an ON/OFF extinction ratio of >8dB for a single switch and a switching speed of 20 microseconds. We characterize the optical output of the switch by imaging its excitation of fluorescent dye. Finally, we demonstrate in vivo single-neuron optical activation from different grating emitters using a fully packaged device inserted into a mouse brain. Directly activated neurons showed robust spike firing activities with low first-spike latency and small jitter. Active switching on a nanophotonic platform is necessary for eventually controlling highly-multiplexed reconfigurable optical circuits, enabling high-resolution optical stimulation in deep-brain regions.

Single-photon superradiance and cooperative Lamb shift in an optoelectronic device (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sirtori, Carlo

2017-02-01

Superradiance is one of the many fascinating phenomena predicted by quantum electrodynamics that have first been experimentally demonstrated in atomic systems and more recently in condensed matter systems like quantum dots, superconducting q-bits, cyclotron transitions and plasma oscillations in quantum wells (QWs). It occurs when a dense collection of N identical two-level emitters are phased via the exchange of photons, giving rise to enhanced light-matter interaction, hence to a faster emission rate. Of great interest is the regime where the ensemble interacts with one photon only and therefore all of the atoms, but one, are in the ground state. In this case the quantum superposition of all possible configurations produces a symmetric state that decays radiatively with a rate N times larger than that of the individual oscillators. This phenomenon, called single photon superradiance, results from the exchange of real photons among the N emitters. Yet, to single photon superradiance is also associated another collective effect that renormalizes the emission frequency, known as cooperative Lamb shift. In this work, we show that single photon superradiance and cooperative Lamb shift can be engineered in a semiconductor device by coupling spatially separated plasma resonances arising from the collective motion of confined electrons in QWs. These resonances hold a giant dipole along the growth direction z and have no mutual Coulomb coupling. They thus behave as a collection of macro-atoms on different positions along the z axis. Our device is therefore a test bench to simulate the low excitation regime of quantum electrodynamics.

High performance incandescent lighting using a selective emitter and nanophotonic filters

NASA Astrophysics Data System (ADS)

Leroy, Arny; Bhatia, Bikram; Wilke, Kyle; Ilic, Ognjen; Soljačić, Marin; Wang, Evelyn N.

2017-09-01

Previous approaches for improving the efficiency of incandescent light bulbs (ILBs) have relied on tailoring the emitted spectrum using cold-side interference filters that reflect the infrared energy back to the emitter while transmitting the visible light. While this approach has, in theory, potential to surpass light-emitting diodes (LEDs) in terms of luminous efficiency while conserving the excellent color rendering index (CRI) inherent to ILBs, challenges such as low view factor between the emitter and filter, high emitter (>2800 K) and filter temperatures and emitter evaporation have significantly limited the maximum efficiency. In this work, we first analyze the effect of non-idealities in the cold-side filter, the emitter and the view factor on the luminous efficiency. Second, we theoretically and experimentally demonstrate that the loss in efficiency associated with low view factors can be minimized by using a selective emitter (e.g., high emissivity in the visible and low emissivity in the infrared) with a filter. Finally, we discuss the challenges in achieving a high performance and long-lasting incandescent light source including the emitter and filter thermal stability as well as emitter evaporation.

Close proximity electrostatic effect from small clusters of emitters

NASA Astrophysics Data System (ADS)

Dall'Agnol, Fernando F.; de Assis, Thiago A.

2017-10-01

Using a numerical simulation based on the finite-element technique, this work investigates the field emission properties from clusters of a few emitters at close proximity, by analyzing the properties of the maximum local field enhancement factor (γm ) and the corresponding emission current. At short distances between the emitters, we show the existence of a nonintuitive behavior, which consists of the increasing of γm as the distance c between the emitters decreases. Here we investigate this phenomenon for clusters with 2, 3, 4 and 7 identical emitters and study the influence of the proximity effect in the emission current, considering the role of the aspect ratio of the individual emitters. Importantly, our results show that peripheral emitters with high aspect-ratios in large clusters can, in principle, significantly increase the emitted current as a consequence only of the close proximity electrostatic effect (CPEE). This phenomenon can be seen as a physical mechanism to produce self-oscillations of individual emitters. We discuss new insights for understanding the nature of self-oscillations in emitters based on the CPEE, including applications to nanometric oscillators.

Sharpening of field emitter tips using high-energy ions

DOEpatents

Musket, Ronald G.

1999-11-30

A process for sharpening arrays of field emitter tips of field emission cathodes, such as found in field-emission, flat-panel video displays. The process uses sputtering by high-energy (more than 30 keV) ions incident along or near the longitudinal axis of the field emitter to sharpen the emitter with a taper from the tip or top of the emitter down to the shank of the emitter. The process is particularly applicable to sharpening tips of emitters having cylindrical or similar (e.g., pyramidal) symmetry. The process will sharpen tips down to radii of less than 12 nm with an included angle of about 20 degrees. Because the ions are incident along or near the longitudinal axis of each emitter, the tips of gated arrays can be sharpened by high-energy ion beams rastered over the arrays using standard ion implantation equipment. While the process is particularly applicable for sharpening of arrays of field emitters in field-emission flat-panel displays, it can be effectively utilized in the fabrication of other vacuum microelectronic devices that rely on field emission of electrons.

Analysis of InP-based single photon avalanche diodes based on a single recess-etching process

NASA Astrophysics Data System (ADS)

Lee, Kiwon

2018-04-01

Effects of the different etching techniques have been investigated by analyzing electrical and optical characteristics of two-types of single-diffused single photon avalanche diodes (SPADs). The fabricated two-types of SPADs have no diffusion depth variation by using a single diffusion process at the same time. The dry-etched SPADs show higher temperature dependence of a breakdown voltage, larger dark-count-rate (DCR), and lower photon-detection-efficiency (PDE) than those of the wet-etched SPADs due to plasma-induced damage of dry-etching process. The results show that the dry etching damages can more significantly affect the performance of the SPADs based on a single recess-etching process.

Delay-induced wave instabilities in single-species reaction-diffusion systems

NASA Astrophysics Data System (ADS)

Otto, Andereas; Wang, Jian; Radons, Günter

2017-11-01

The Turing (wave) instability is only possible in reaction-diffusion systems with more than one (two) components. Motivated by the fact that a time delay increases the dimension of a system, we investigate the presence of diffusion-driven instabilities in single-species reaction-diffusion systems with delay. The stability of arbitrary one-component systems with a single discrete delay, with distributed delay, or with a variable delay is systematically analyzed. We show that a wave instability can appear from an equilibrium of single-species reaction-diffusion systems with fluctuating or distributed delay, which is not possible in similar systems with constant discrete delay or without delay. More precisely, we show by basic analytic arguments and by numerical simulations that fast asymmetric delay fluctuations or asymmetrically distributed delays can lead to wave instabilities in these systems. Examples, for the resulting traveling waves are shown for a Fisher-KPP equation with distributed delay in the reaction term. In addition, we have studied diffusion-induced instabilities from homogeneous periodic orbits in the same systems with variable delay, where the homogeneous periodic orbits are attracting resonant periodic solutions of the system without diffusion, i.e., periodic orbits of the Hutchinson equation with time-varying delay. If diffusion is introduced, standing waves can emerge whose temporal period is equal to the period of the variable delay.

Patterned growth of carbon nanotubes over vertically aligned silicon nanowire bundles for achieving uniform field emission.

PubMed

Hung, Yung-Jr; Huang, Yung-Jui; Chang, Hsuan-Chen; Lee, Kuei-Yi; Lee, San-Liang

2014-01-01

A fabrication strategy is proposed to enable precise coverage of as-grown carbon nanotube (CNT) mats atop vertically aligned silicon nanowire (VA-SiNW) bundles in order to realize a uniform bundle array of CNT-SiNW heterojunctions over a large sample area. No obvious electrical degradation of as-fabricated SiNWs is observed according to the measured current-voltage characteristic of a two-terminal single-nanowire device. Bundle arrangement of CNT-SiNW heterojunctions is optimized to relax the electrostatic screening effect and to maximize the field enhancement factor. As a result, superior field emission performance and relatively stable emission current over 12 h is obtained. A bright and uniform fluorescent radiation is observed from CNT-SiNW-based field emitters regardless of its bundle periodicity, verifying the existence of high-density and efficient field emitters on the proposed CNT-SiNW bundle arrays.