WorldWideScience

Sample records for prototype quantum cascade

  1. Cascade quantum teleportation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Nan-run; GONG Li-hua; LIU Ye

    2006-01-01

    In this letter a cascade quantum teleportation scheme is proposed. The proposed scheme needs less local quantum operations than those of quantum multi-teleportation. A quantum teleportation scheme based on entanglement swapping is presented and compared with the cascade quantum teleportation scheme. Those two schemes can effectively teleport quantum information and extend the distance of quantum communication.

  2. Integrated Broadband Quantum Cascade Laser

    Science.gov (United States)

    Mansour, Kamjou (Inventor); Soibel, Alexander (Inventor)

    2016-01-01

    A broadband, integrated quantum cascade laser is disclosed, comprising ridge waveguide quantum cascade lasers formed by applying standard semiconductor process techniques to a monolithic structure of alternating layers of claddings and active region layers. The resulting ridge waveguide quantum cascade lasers may be individually controlled by independent voltage potentials, resulting in control of the overall spectrum of the integrated quantum cascade laser source. Other embodiments are described and claimed.

  3. Lens Coupled Quantum Cascade Laser

    Science.gov (United States)

    Hu, Qing (Inventor); Lee, Alan Wei Min (Inventor)

    2013-01-01

    Terahertz quantum cascade (QC) devices are disclosed that can operate, e.g., in a range of about 1 THz to about 10 THz. In some embodiments, QC lasers are disclosed in which an optical element (e.g., a lens) is coupled to an output facet of the laser's active region to enhance coupling of the lasing radiation from the active region to an external environment. In other embodiments, terahertz amplifier and tunable terahertz QC lasers are disclosed.

  4. Modeling techniques for quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Jirauschek, Christian [Institute for Nanoelectronics, Technische Universität München, D-80333 Munich (Germany); Kubis, Tillmann [Network for Computational Nanotechnology, Purdue University, 207 S Martin Jischke Drive, West Lafayette, Indiana 47907 (United States)

    2014-03-15

    Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency, and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation of quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schrödinger equation and Schrödinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures.

  5. Modeling techniques for quantum cascade lasers

    Science.gov (United States)

    Jirauschek, Christian; Kubis, Tillmann

    2014-03-01

    Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency, and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation of quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schrödinger equation and Schrödinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures.

  6. How periodic are terahertz quantum cascade lasers?

    International Nuclear Information System (INIS)

    Kubis, T; Vogl, P

    2009-01-01

    We apply a novel non-equilibrium Green's function method for open quantum devices to analyze quantum cascade lasers. We find the carrier distribution in typical resonant phonon THz-QCLs to develop a periodicity that differs from the geometric periodicity of the QCL. We propose a design improvement that thermalizes electrons at threshold bias and thereby pins the electron density to the QCL periodicity.

  7. How periodic are terahertz quantum cascade lasers?

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, T; Vogl, P, E-mail: tillmann.kubis@wsi.tum.d [Walter Schottky Institute, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany)

    2009-11-15

    We apply a novel non-equilibrium Green's function method for open quantum devices to analyze quantum cascade lasers. We find the carrier distribution in typical resonant phonon THz-QCLs to develop a periodicity that differs from the geometric periodicity of the QCL. We propose a design improvement that thermalizes electrons at threshold bias and thereby pins the electron density to the QCL periodicity.

  8. Interferometric modulation of quantum cascade interactions

    Science.gov (United States)

    Cusumano, Stefano; Mari, Andrea; Giovannetti, Vittorio

    2018-05-01

    We consider many-body quantum systems dissipatively coupled by a cascade network, i.e., a setup in which interactions are mediated by unidirectional environmental modes propagating through a linear optical interferometer. In particular we are interested in the possibility of inducing different effective interactions by properly engineering an external dissipative network of beam splitters and phase shifters. In this work we first derive the general structure of the master equation for a symmetric class of translation-invariant cascade networks. Then we show how, by tuning the parameters of the interferometer, one can exploit interference effects to tailor a large variety of many-body interactions.

  9. Quantum Cascade Lasers Modulation and Applications

    Science.gov (United States)

    Luzhansky, Edward

    The mid-wave IR (MWIR) spectral band, extending from 3 to 5 microns, is considered to be a low loss atmospheric window. There are several spectral sub-bands with relatively low atmospheric attenuation in this region making it popular for various commercial and military applications. Relatively low thermal and solar background emissions, effective penetration through the natural and anthropogenic obscurants and eye safety add to the long list of advantages of MWIR wavelengths. Quantum Cascade Lasers are compact semiconductor devices capable of operating in MWIR spectrum. They are based on inter-subband transitions in a multiple-quantum-well (QW) hetero-structure, designed by means of band-structure engineering. The inter-subband nature of the optical transition has several key advantages. First, the emission wavelength is primarily a function of the QW thickness. This characteristic allows choosing well-understood and reliable semiconductors for the generation of light in a wavelength range of interest. Second, a cascade process in which tens of photons are generated per injected electron. This cascading process is behind the intrinsic high-power capabilities of QCLs. This dissertation is focused on modulation properties of Quantum Cascade Lasers. Both amplitude and phase/frequency modulations were studied including modulation bandwidth, modulation efficiency and chirp linearity. Research was consisted of the two major parts. In the first part we describe the theory of frequency modulation (FM) response of Distributed Feedback Quantum Cascade Lasers (DFB QCL). It includes cascading effect on the QCL's maximum modulation frequency. The "gain levering" effect for the maximum FM response of the two section QCLs was studied as well. In the second part of research we concentrated on the Pulse Position Amplitude Modulation of a single section QCL. The low complexity, low size, weight and power Mid-Wavelength Infra-Red optical communications transceiver concept is

  10. A prototype quantum cryptography system

    Energy Technology Data Exchange (ETDEWEB)

    Surasak, Chiangga

    1998-07-01

    In this work we have constructed a new secure quantum key distribution system based on the BB84 protocol. Many current state-of-the-art quantum cryptography systems encounter major problems concerning low bit rate, synchronization, and stabilization. Our quantum cryptography system utilizes only laser diodes and standard passive optical components, to enhance the stability and also to decrease the space requirements. The development of this demonstration for a practical quantum key distribution system is a consequence of our previous work on the quantum cryptographic system using optical fiber components for the transmitter and receiver. There we found that the optical fiber couplers should not be used due to the problems with space, stability and alignment. The goal of the synchronization is to use as little transmission capacities as possible. The experimental results of our quantum key distribution system show the feasibility of getting more than 90 % transmission capacities with the approaches developed in this work. Therefore it becomes feasible to securely establish a random key sequence at a rate of 1 to {approx} 5K bit/s by using our stable, compact, cheap, and user-friendly modules for quantum cryptography. (author)

  11. A prototype quantum cryptography system

    International Nuclear Information System (INIS)

    Chiangga Surasak

    1998-07-01

    In this work we have constructed a new secure quantum key distribution system based on the BB84 protocol. Many current state-of-the-art quantum cryptography systems encounter major problems concerning low bit rate, synchronization, and stabilization. Our quantum cryptography system utilizes only laser diodes and standard passive optical components, to enhance the stability and also to decrease the space requirements. The development of this demonstration for a practical quantum key distribution system is a consequence of our previous work on the quantum cryptographic system using optical fiber components for the transmitter and receiver. There we found that the optical fiber couplers should not be used due to the problems with space, stability and alignment. The goal of the synchronization is to use as little transmission capacities as possible. The experimental results of our quantum key distribution system show the feasibility of getting more than 90 % transmission capacities with the approaches developed in this work. Therefore it becomes feasible to securely establish a random key sequence at a rate of 1 to ∼ 5K bit/s by using our stable, compact, cheap, and user-friendly modules for quantum cryptography. (author)

  12. Generalizing Prototype Theory: A Formal Quantum Framework

    Science.gov (United States)

    Aerts, Diederik; Broekaert, Jan; Gabora, Liane; Sozzo, Sandro

    2016-01-01

    Theories of natural language and concepts have been unable to model the flexibility, creativity, context-dependence, and emergence, exhibited by words, concepts and their combinations. The mathematical formalism of quantum theory has instead been successful in capturing these phenomena such as graded membership, situational meaning, composition of categories, and also more complex decision making situations, which cannot be modeled in traditional probabilistic approaches. We show how a formal quantum approach to concepts and their combinations can provide a powerful extension of prototype theory. We explain how prototypes can interfere in conceptual combinations as a consequence of their contextual interactions, and provide an illustration of this using an intuitive wave-like diagram. This quantum-conceptual approach gives new life to original prototype theory, without however making it a privileged concept theory, as we explain at the end of our paper. PMID:27065436

  13. Generalizing Prototype Theory: A Formal Quantum Framework

    Directory of Open Access Journals (Sweden)

    Diederik eAerts

    2016-03-01

    Full Text Available Theories of natural language and concepts have been unable to model the flexibility, creativity, context-dependence, and emergence, exhibited by words, concepts and their combinations. The mathematical formalism of quantum theory has instead been successful in capturing these phenomena such as graded membership, situational meaning, composition of categories, and also more complex decision making situations, which cannot be modeled in traditional probabilistic approaches. We show how a formal quantum approach to concepts and their combinations can provide a powerful extension of prototype theory. We explain how prototypes can interfere in conceptual combinations as a consequence of their contextual interactions, and provide an illustration of this using an intuitive wave-like diagram. This quantum-conceptual approach gives new life to original prototype theory, without however making it a privileged concept theory, as we explain at the end of our paper.

  14. Quantum cascade laser infrared spectroscopy of single cancer cells

    KAUST Repository

    Patel, Imran

    2017-03-27

    Quantum cascade laser infrared spectroscopy is a next generation novel imaging technique allowing high resolution spectral imaging of cells. We show after spectral pre-processing, identification of different cancer cell populations within minutes.

  15. Quantum cascade laser infrared spectroscopy of single cancer cells

    KAUST Repository

    Patel, Imran; Rajamanickam, Vijayakumar Palanisamy; Bertoncini, Andrea; Pagliari, Francesca; Tirinato, Luca; Laptenok, Sergey P.; Liberale, Carlo

    2017-01-01

    Quantum cascade laser infrared spectroscopy is a next generation novel imaging technique allowing high resolution spectral imaging of cells. We show after spectral pre-processing, identification of different cancer cell populations within minutes.

  16. Linewidth and tuning characteristics of terahertz quantum cascade lasers.

    Science.gov (United States)

    Barkan, A; Tittel, F K; Mittleman, D M; Dengler, R; Siegel, P H; Scalari, G; Ajili, L; Faist, J; Beere, H E; Linfield, E H; Davies, A G; Ritchie, D A

    2004-03-15

    We have measured the spectral linewidths of three continuous-wave quantum cascade lasers operating at terahertz frequencies by heterodyning the free-running quantum cascade laser with two far-infrared gas lasers. Beat notes are detected with a GaAs diode mixer and a microwave spectrum analyzer, permitting very precise frequency measurements and giving instantaneous linewidths of less than -30 kHz. Characteristics are also reported for frequency tuning as the injection current is varied.

  17. Mode structure of a quantum cascade laser

    Science.gov (United States)

    Bogdanov, A. A.; Suris, R. A.

    2011-03-01

    We analyze the mode structure of a quantum cascade laser (QCL) cavity considering the surface plasmon-polariton modes and familiar modes of hollow resonator jointly, within a single model. We present a comprehensive mode structure analysis of the laser cavity, varying its geometric parameters and free electron concentration inside cavity layers within a wide range. Our analysis covers, in particular, the cases of metal-insulator-metal and insulator-metal-insulator waveguides. We discuss the phenomenon of negative dispersion for eigenmodes in detail and explain the nature of this phenomenon. We specify a waveguide parameters domain in which negative dispersion exists. The mode structure of QCL cavity is considered in the case of the anisotropic electrical properties of the waveguide materials. We show that anisotropy of the waveguide core results in propagation of Langmuir modes that are degenerated in the case of the isotropic core. Comparative analysis of optical losses due to free carrier absorption is presented for different modes within the frequency range from terahertz to ultraviolet frequencies.

  18. Chemical sensors based on quantum cascade lasers

    Science.gov (United States)

    Tittel, Frank K.; Kosterev, Anatoliy A.; Rochat, Michel; Beck, Mattias; Faist, Jerome

    2002-09-01

    There is an increasing need in many chemical sensing applications ranging from industrial process control to environmental science and medical diagnostics for fast, sensitive, and selective gas detection based on laser spectroscopy. The recent availability of novel pulsed and cw quantum cascade distributed feedback (QC-DFB) lasers as mid-infrared spectroscopic sources address this need. A number of spectroscopic techniques have been demonstrated. For example, the authors have employed QC-DFB lasers for the monitoring and quantification of several trace gases and isotopic species in ambient air at ppmv and ppbv levels by means of direct absorption, wavelength modulation, cavity enhanced and cavity ringdown spectroscopy. In this work, pulsed thermoelectrically cooled QC-DFB lasers operating at ~15.6 μm were characterized for spectroscopic gas sensing applications. A new method for wavelength scanning based on the repetition rate modulation was developed. A non-wavelength-selective pyroelectric detector was incorporated in the gas sensor giving an advantage of room-temperature operation and low cost. Absorption lines of CO2 and H2O were observed in ambient air providing information about the concentration of these species.

  19. Optical dynamics in low-dimensional semiconductor heterostructures. Quantum dots and quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Carsten

    2008-07-01

    This work is focused on the optical dynamics of mesoscopic semiconductor heterostructures, using as prototypes zero-dimensional quantum dots and quantum cascade lasers which consist of quasitwo- dimensional quantum wells. Within a density matrix theory, a microscopic many-particle theory is applied to study scattering effects in these structures: the coupling to external as well as local fields, electron-phonon coupling, coupling to impurities, and Coulomb coupling. For both systems, the investigated effects are compared to experimentally observed results obtained during the past years. In quantum dots, the three-dimensional spatial confinement leads to the necessity to consider a quantum kinetic description of the dynamics, resulting in non-Markovian electron-phonon effects. This can be seen in the spectral phonon sidebands due to interaction with acoustic phonons as well as a damping of nonlinear Rabi oscillations which shows a nonmonotonous intensity and pulse duration dependence. An analysis of the inclusion of the self-interaction of the quantum dot shows that no dynamical local field terms appear for the simple two-level model. Considering local fields which have their origin in many quantum dots, consequences for a two-level quantum dot such as a zero-phonon line broadening and an increasing signal in photon echo experiments are found. For the use of quantum dots in an optical spin control scheme, it is found that the dephasing due to the electron-phonon interaction can be dominant in certain regimes. Furthermore, soliton and breather solutions are studied analytically in nonlinear quantum dot ensembles. Generalizing to quasi-two-dimensional structures, the intersubband dynamics of quantum cascade laser structures is investigated. A dynamical theory is considered in which the temporal evolution of the subband populations and the current density as well as the influence of scattering effects is studied. In the nonlinear regime, the scattering dependence and

  20. Spectrally high performing quantum cascade lasers

    Science.gov (United States)

    Toor, Fatima

    Quantum cascade (QC) lasers are versatile semiconductor light sources that can be engineered to emit light of almost any wavelength in the mid- to far-infrared (IR) and terahertz region from 3 to 300 mum [1-5]. Furthermore QC laser technology in the mid-IR range has great potential for applications in environmental, medical and industrial trace gas sensing [6-10] since several chemical vapors have strong rovibrational frequencies in this range and are uniquely identifiable by their absorption spectra through optical probing of absorption and transmission. Therefore, having a wide range of mid-IR wavelengths in a single QC laser source would greatly increase the specificity of QC laser-based spectroscopic systems, and also make them more compact and field deployable. This thesis presents work on several different approaches to multi-wavelength QC laser sources that take advantage of band-structure engineering and the uni-polar nature of QC lasers. Also, since for chemical sensing, lasers with narrow linewidth are needed, work is presented on a single mode distributed feedback (DFB) QC laser. First, a compact four-wavelength QC laser source, which is based on a 2-by-2 module design, with two waveguides having QC laser stacks for two different emission wavelengths each, one with 7.0 mum/11.2 mum, and the other with 8.7 mum/12.0 mum is presented. This is the first design of a four-wavelength QC laser source with widely different emission wavelengths that uses minimal optics and electronics. Second, since there are still several unknown factors that affect QC laser performance, results on a first ever study conducted to determine the effects of waveguide side-wall roughness on QC laser performance using the two-wavelength waveguides is presented. The results are consistent with Rayleigh scattering effects in the waveguides, with roughness effecting shorter wavelengths more than longer wavelengths. Third, a versatile time-multiplexed multi-wavelength QC laser system that

  1. Efficient method for transport simulations in quantum cascade lasers

    Directory of Open Access Journals (Sweden)

    Maczka Mariusz

    2017-01-01

    Full Text Available An efficient method for simulating quantum transport in quantum cascade lasers is presented. The calculations are performed within a simple approximation inspired by Büttiker probes and based on a finite model for semiconductor superlattices. The formalism of non-equilibrium Green’s functions is applied to determine the selected transport parameters in a typical structure of a terahertz laser. Results were compared with those obtained for a infinite model as well as other methods described in literature.

  2. Surface plasmon quantum cascade lasers as terahertz local oscillators

    NARCIS (Netherlands)

    Hajenius, M.; Khosropanah, P.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Barbieri, S.; Dhillon, S.; Filloux, P.; Sirtori, C.; Ritchie, D. A.; Beere, H. E.

    2008-01-01

    We characterize a heterodyne receiver based on a surface-plasmon waveguide quantum cascade laser (QCL) emitting at 2.84 THz as a local oscillator, and an NbN hot electron bolometer as a mixer. We find that the envelope of the far-field pattern of the QCL is diffraction-limited and superimposed onto

  3. Multicomponent gas analysis using broadband quantum cascade laser spectroscopy

    NARCIS (Netherlands)

    Reyes Reyes, A.; Hou, Z.; Van Mastrigt, E.; Horsten, R.C.; De Jongste, J.C.; Pijnenburg, M.W.; Urbach, H.P.; Bhattacharya, N.

    2014-01-01

    We present a broadband quantum cascade laser-based spectroscopic system covering the region between 850 and 1250 cm?1. Its robust multipass cavity ensures a constant interaction length over the entire spectral region. The device enables the detection and identification of numerous molecules present

  4. Mid-infrared quantum cascade laser spectroscopy probing of the ...

    Indian Academy of Sciences (India)

    Aparajeo Chattopadhyay

    2018-05-07

    May 7, 2018 ... cm3 molecule. −1 s. −1 ... Quantum cascade laser; time-resolved mid-infrared spectroscopy; transient absorption; peroxy radicals .... peak of the laser emission profile. .... cal with O2 is a termolecular reaction (Eq. 3) and the.

  5. Quantum cascade laser combs: effects of modulation and dispersion.

    Science.gov (United States)

    Villares, Gustavo; Faist, Jérôme

    2015-01-26

    Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs2 mm-1) but disappears when much larger values are used (30'000 fs2 mm-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs.

  6. Atomic-cascade photons and quantum-mechanical nonlocality

    International Nuclear Information System (INIS)

    Bell, J.S.

    1995-01-01

    In recent years there have been several experiments on polarization correlation between photons emitted in atomic cascades. They are supposed to bear on the notion that the consequences of events do not propagate faster than light. This notion is difficult to reconcile with quantum-mechanical predictions for idealized versions of the experiments in question. The present Comment offers a brief introduction to the situation. (author)

  7. Quantum steering in cascaded four-wave mixing processes.

    Science.gov (United States)

    Wang, Li; Lv, Shuchao; Jing, Jietai

    2017-07-24

    Quantum steering is used to describe the "spooky action-at-a-distance" nonlocality raised in the Einstein-Podolsky-Rosen (EPR) paradox, which is important for understanding entanglement distribution and constructing quantum networks. Here, in this paper, we study an experimentally feasible scheme for generating quantum steering based on cascaded four-wave-mixing (FWM) processes in hot rubidium (Rb) vapor. Quantum steering, including bipartite steering and genuine tripartite steering among the output light fields, is theoretically analyzed. We find the corresponding gain regions in which the bipartite and tripartite steering exist. The results of bipartite steering can be used to establish a hierarchical steering model in which one beam can steer the other two beams in the whole gain region; however, the other two beams cannot steer the first beam simultaneously. Moreover, the other two beams cannot steer with each other in the whole gain region. More importantly, we investigate the gain dependence of the existence of the genuine tripartite steering and we find that the genuine tripartite steering exists in most of the whole gain region in the ideal case. Also we discuss the effect of losses on the genuine tripartite steering. Our results pave the way to experimental demonstration of quantum steering in cascaded FWM process.

  8. Design strategy for terahertz quantum dot cascade lasers.

    Science.gov (United States)

    Burnett, Benjamin A; Williams, Benjamin S

    2016-10-31

    The development of quantum dot cascade lasers has been proposed as a path to obtain terahertz semiconductor lasers that operate at room temperature. The expected benefit is due to the suppression of nonradiative electron-phonon scattering and reduced dephasing that accompanies discretization of the electronic energy spectrum. We present numerical modeling which predicts that simple scaling of conventional quantum well based designs to the quantum dot regime will likely fail due to electrical instability associated with high-field domain formation. A design strategy adapted for terahertz quantum dot cascade lasers is presented which avoids these problems. Counterintuitively, this involves the resonant depopulation of the laser's upper state with the LO-phonon energy. The strategy is tested theoretically using a density matrix model of transport and gain, which predicts sufficient gain for lasing at stable operating points. Finally, the effect of quantum dot size inhomogeneity on the optical lineshape is explored, suggesting that the design concept is robust to a moderate amount of statistical variation.

  9. Terahertz Quantum Cascade Laser With Efficient Coupling and Beam Profile

    Science.gov (United States)

    Chattopadhyay, Goutam; Kawamura, Jonathan H.; Lin, Robert H.; Williams, Benjamin

    2012-01-01

    Quantum cascade lasers (QCLs) are unipolar semiconductor lasers, where the wavelength of emitted radiation is determined by the engineering of quantum states within the conduction band in coupled multiple-quantum-well heterostructures to have the desired energy separation. The recent development of terahertz QCLs has provided a new generation of solid-state sources for radiation in the terahertz frequency range. Terahertz QCLs have been demonstrated from 0.84 to 5.0 THz both in pulsed mode and continuous wave mode (CW mode). The approach employs a resonant-phonon depopulation concept. The metal-metal (MM) waveguide fabrication is performed using Cu-Cu thermo-compression bonding to bond the GaAs/AlGaAs epitaxial layer to a GaAs receptor wafer.

  10. Widely tunable quantum cascade laser-based terahertz source.

    Science.gov (United States)

    Danylov, Andriy A; Light, Alexander R; Waldman, Jerry; Erickson, Neal; Qian, Xifeng

    2014-07-10

    A compact, tunable, ultranarrowband terahertz source, Δν∼1  MHz, is demonstrated by upconversion of a 2.324 THz, free-running quantum cascade laser with a THz Schottky-diode-balanced mixer using a swept, synthesized microwave source to drive the nonlinearity. Continuously tunable radiation of 1 μW power is demonstrated in two frequency regions: ν(Laser) ± 0 to 50 GHz and ν(Laser) ± 70 to 115 GHz. The sideband spectra were characterized with a Fourier-transform spectrometer, and the radiation was tuned through CO, HDO, and D2O rotational transitions.

  11. Coherent quantum cascade laser micro-stripe arrays

    Directory of Open Access Journals (Sweden)

    G. M. de Naurois

    2011-09-01

    Full Text Available We have fabricated InP-based coherent quantum cascade laser micro-stripe arrays. Phase-locking is provided by evanescent coupling between adjacent stripes. Stripes are buried into semi-insulating iron doped InP. Lasing at room temperature is obtained at 8.4μm for stripe arrays comprising up to 16 emitters. Pure supermode emission is demonstrated via farfield measurements and simulations. The farfield pattern shows a dual-lobe emission, corroborating the predicted phase-locked antisymmetric supermode emission.

  12. Surface emitting ring quantum cascade lasers for chemical sensing

    Science.gov (United States)

    Szedlak, Rolf; Hayden, Jakob; Martín-Mateos, Pedro; Holzbauer, Martin; Harrer, Andreas; Schwarz, Benedikt; Hinkov, Borislav; MacFarland, Donald; Zederbauer, Tobias; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Acedo, Pablo; Lendl, Bernhard; Strasser, Gottfried

    2018-01-01

    We review recent advances in chemical sensing applications based on surface emitting ring quantum cascade lasers (QCLs). Such lasers can be implemented in monolithically integrated on-chip laser/detector devices forming compact gas sensors, which are based on direct absorption spectroscopy according to the Beer-Lambert law. Furthermore, we present experimental results on radio frequency modulation up to 150 MHz of surface emitting ring QCLs. This technique provides detailed insight into the modulation characteristics of such lasers. The gained knowledge facilitates the utilization of ring QCLs in combination with spectroscopic techniques, such as heterodyne phase-sensitive dispersion spectroscopy for gas detection and analysis.

  13. Hot-phonon generation in THz quantum cascade lasers

    Science.gov (United States)

    Spagnolo, V.; Vitiello, M. S.; Scamarcio, G.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.

    2007-12-01

    Observation of non-equilibrium optical phonons population associated with electron transport in THz quantum cascade lasers is reported. The phonon occupation number was measured by using a combination of micro-probe photoluminescence and Stokes/Anti-Stokes Raman spectroscopy. Energy balance analysis allows us to estimate the phonon relaxation rate, that superlinearly increases with the electrical power in the range 1.5 W - 1.95 W, above laser threshold. This observation suggests the occurrence of stimulated emission of optical phonons.

  14. Fast gas spectroscopy using pulsed quantum cascade lasers

    Science.gov (United States)

    Beyer, T.; Braun, M.; Lambrecht, A.

    2003-03-01

    Laser spectroscopy has found many industrial applications, e.g., control of automotive exhaust and process monitoring. The midinfrared region is of special interest because it has stronger absorption lines compared to the near infrared (NIR). However, in the NIR high quality reliable laser sources, detectors, and passive optical components are available. A quantum cascade laser could change this situation if fundamental advantages can be exploited with compact and reliable systems. It will be shown that, using pulsed lasers and available fast detectors, lower residual sensitivity levels than in corresponding NIR systems can be achieved. The stability is sufficient for industrial applications.

  15. Influence of interface roughness in quantum cascade lasers

    International Nuclear Information System (INIS)

    Krivas, K. A.; Winge, D. O.; Franckié, M.; Wacker, A.

    2015-01-01

    We use a numerical model based on non-equilibrium Green's functions to investigate the influence of interface roughness (IFR) scattering in terahertz quantum cascade lasers. We confirm that IFR is an important phenomenon that affects both current and gain. The simulations indicate that IFR causes a leakage current that transfers electrons from the upper to the lower laser state. In certain cases, this current can greatly reduce gain. In addition, individual interfaces and their impact on the renormalized single particle energies are studied and shown to give both blue- and red-shifts of the gain spectrum

  16. Development of an Exploration-Class Cascade Distillation System: Flight Like Prototype Preliminary Design

    Science.gov (United States)

    Callahan, Michael R.; Sargusingh, Miriam J.

    2015-01-01

    The ability to recover and purify water through physiochemical processes is crucial for realizing long-term human space missions, including both planetary habitation and space travel. Because of their robust nature, distillation systems have been actively pursued as one of the technologies for water recovery. One such technology is the Cascade Distillation System (CDS) a multi-stage vacuum rotary distiller system designed to recover water in a microgravity environment. Its rotating cascading distiller operates similarly to the state of the art (SOA) vapor compressor distiller (VCD), but its control scheme and ancillary components are judged to be straightforward and simpler to implement into a successful design. Through the Advanced Exploration Systems (AES) Life Support Systems (LSS) Project, the NASA Johnson Space Center (JSC) in collaboration with Honeywell International is developing a second generation flight forward prototype (CDS 2.0). The key objectives for the CDS 2.0 design task is to provide a flight forward ground prototype that demonstrates improvements over the SOA system in the areas of increased reliability and robustness, and reduced mass, power and volume. It will also incorporate exploration-class automation. The products of this task are a preliminary flight system design and a high fidelity prototype of an exploration class CDS. These products will inform the design and development of the third generation CDS which is targeted for on-orbit DTO. This paper details the preliminary design of the CDS 2.0.

  17. Quantum cascade lasers as metrological tools for space optics

    Science.gov (United States)

    Bartalini, S.; Borri, S.; Galli, I.; Mazzotti, D.; Cancio Pastor, P.; Giusfredi, G.; De Natale, P.

    2017-11-01

    A distributed-feedback quantum-cascade laser working in the 4.3÷4.4 mm range has been frequency stabilized to the Lamb-dip center of a CO2 ro-vibrational transition by means of first-derivative locking to the saturated absorption signal, and its absolute frequency counted with a kHz-level precision and an overall uncertainty of 75 kHz. This has been made possible by an optical link between the QCL and a near-IR Optical Frequency Comb Synthesizer, thanks to a non-linear sum-frequency generation process with a fiber-amplified Nd:YAG laser. The implementation of a new spectroscopic technique, known as polarization spectroscopy, provides an improved signal for the locking loop, and will lead to a narrower laser emission and a drastic improvement in the frequency stability, that in principle is limited only by the stability of the optical frequency comb synthesizer (few parts in 1013). These results confirm quantum cascade lasers as reliable sources not only for high-sensitivity, but also for highprecision measurements, ranking them as optimal laser sources for space applications.

  18. Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection

    Directory of Open Access Journals (Sweden)

    Gaetano Scamarcio

    2006-10-01

    Full Text Available Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 109 (ppb and sub-ppb range.The recent development of quantum-cascade lasers (QCLs has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process.

  19. A hybrid plasmonic waveguide terahertz quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Degl' Innocenti, Riccardo, E-mail: rd448@cam.ac.uk; Shah, Yash D.; Wallis, Robert; Klimont, Adam; Ren, Yuan; Jessop, David S.; Beere, Harvey E.; Ritchie, David A. [Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-02-23

    We present the realization of a quantum cascade laser emitting at around 2.85 THz, based on a hybrid plasmonic waveguide with a low refractive index dielectric cladding. This hybrid waveguide design allows the performance of a double-metal waveguide to be retained, while improving the emission far-field. A set of lasers based on the same active region material were fabricated with different metal layer thicknesses. A detailed characterization of the performance of these lasers revealed that there is an optimal trade-off that yields the best far-field emission and the maximum temperature of operation. By exploiting the pure plasmonic mode of these waveguides, the standard operation conditions of a double-metal quantum cascade laser were retrieved, such that the maximum operating temperature of these devices is not affected by the process. These results pave the way to realizing a class of integrated devices working in the terahertz range which could be further exploited to fabricate terahertz on-chip circuitry.

  20. Spectral behavior of a terahertz quantum-cascade laser.

    Science.gov (United States)

    Hensley, J M; Montoya, Juan; Allen, M G; Xu, J; Mahler, L; Tredicucci, A; Beere, H E; Ritchie, D A

    2009-10-26

    In this paper, the spectral behavior of two terahertz (THz) quantum cascade lasers (QCLs) operating both pulsed and cw is characterized using a heterodyne technique. Both lasers emitting around 2.5 THz are combined onto a whisker contact Schottky diode mixer mounted in a corner cube reflector. The resulting difference frequency beatnote is recorded in both the time and frequency domain. From the frequency domain data, we measure the effective laser linewidth and the tuning rates as a function of both temperature and injection current and show that the current tuning behavior cannot be explained by temperature tuning mechanisms alone. From the time domain data, we characterize the intrapulse frequency tuning behavior, which limits the effective linewidth to approximately 5 MHz.

  1. Surface plasmon quantum cascade lasers as terahertz local oscillators.

    Science.gov (United States)

    Hajenius, M; Khosropanah, P; Hovenier, J N; Gao, J R; Klapwijk, T M; Barbieri, S; Dhillon, S; Filloux, P; Sirtori, C; Ritchie, D A; Beere, H E

    2008-02-15

    We characterize a heterodyne receiver based on a surface-plasmon waveguide quantum cascade laser (QCL) emitting at 2.84 THz as a local oscillator, and an NbN hot electron bolometer as a mixer. We find that the envelope of the far-field pattern of the QCL is diffraction-limited and superimposed onto interference fringes, which are similar to those found in narrow double-metal waveguide QCLs. Compared to the latter, a more directional beam allows for better coupling of the radiation power to the mixer. We obtain a receiver noise temperature of 1050 K when the mixer is at 2 K, which, to our knowledge, is the highest sensitivity reported at frequencies beyond 2.5 THz.

  2. Frequency modulation spectroscopy with a THz quantum-cascade laser.

    Science.gov (United States)

    Eichholz, R; Richter, H; Wienold, M; Schrottke, L; Hey, R; Grahn, H T; Hübers, H-W

    2013-12-30

    We report on a terahertz spectrometer for high-resolution molecular spectroscopy based on a quantum-cascade laser. High-frequency modulation (up to 50 MHz) of the laser driving current produces a simultaneous modulation of the frequency and amplitude of the laser output. The modulation generates sidebands, which are symmetrically positioned with respect to the laser carrier frequency. The molecular transition is probed by scanning the sidebands across it. In this way, the absorption and the dispersion caused by the molecular transition are measured. The signals are modeled by taking into account the simultaneous modulation of the frequency and amplitude of the laser emission. This allows for the determination of the strength of the frequency as well as amplitude modulation of the laser and of molecular parameters such as pressure broadening.

  3. Integration of quantum cascade lasers and passive waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Montoya, Juan, E-mail: juan.montoya@ll.mit.edu; Wang, Christine; Goyal, Anish; Creedon, Kevin; Connors, Michael; Daulton, Jeffrey; Donnelly, Joseph; Missaggia, Leo; Aleshire, Chris; Sanchez-Rubio, Antonio; Herzog, William [MIT Lincoln Laboratory, 244 Wood St, Lexington, Massachusetts 02420 (United States)

    2015-07-20

    We report on monolithic integration of active quantum cascade laser (QCL) materials with passive waveguides formed by using proton implantation. Proton implantation reduces the electron concentration in the QCL layers by creating deep levels that trap carriers. This strongly reduces the intersubband absorption and the free-carrier absorption in the gain region and surrounding layers, thus significantly reducing optical loss. We have measured loss as low as α = 0.33 cm{sup −1} in λ = 9.6 μm wavelength proton-implanted QCL material. We have also demonstrated lasing in active-passive integrated waveguides. This simple integration technique is anticipated to enable low-cost fabrication in infrared photonic integrated circuits in the mid-infrared (λ ∼ 3–16 μm)

  4. Integration of quantum cascade lasers and passive waveguides

    International Nuclear Information System (INIS)

    Montoya, Juan; Wang, Christine; Goyal, Anish; Creedon, Kevin; Connors, Michael; Daulton, Jeffrey; Donnelly, Joseph; Missaggia, Leo; Aleshire, Chris; Sanchez-Rubio, Antonio; Herzog, William

    2015-01-01

    We report on monolithic integration of active quantum cascade laser (QCL) materials with passive waveguides formed by using proton implantation. Proton implantation reduces the electron concentration in the QCL layers by creating deep levels that trap carriers. This strongly reduces the intersubband absorption and the free-carrier absorption in the gain region and surrounding layers, thus significantly reducing optical loss. We have measured loss as low as α = 0.33 cm −1 in λ = 9.6 μm wavelength proton-implanted QCL material. We have also demonstrated lasing in active-passive integrated waveguides. This simple integration technique is anticipated to enable low-cost fabrication in infrared photonic integrated circuits in the mid-infrared (λ ∼ 3–16 μm)

  5. Free-space communication based on quantum cascade laser

    International Nuclear Information System (INIS)

    Liu Chuanwei; Zhai Shenqiang; Zhang Jinchuan; Zhou Yuhong; Jia Zhiwei; Liu Fengqi; Wang Zhanguo

    2015-01-01

    A free-space communication based on a mid-infrared quantum cascade laser (QCL) is presented. A room-temperature continuous-wave distributed-feedback (DFB) QCL combined with a mid-infrared detector comprise the basic unit of the communication system. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. Our research has provided a proof-of-concept demonstration of space optical communication application with QCL. The highest operation frequency of our setup was determined by the circuit-limited modulation bandwidth. A high performance communication system can be obtained with improved modulation circuit system. (paper)

  6. Quantum cascade lasers, systems, and applications in Europe

    Science.gov (United States)

    Lambrecht, Armin

    2005-03-01

    Since the invention of the Quantum Cascade Laser (QCL) a decade ago an impressive progress has been achieved from first low temperature pulsed laser emission to continuous wave operation at room temperature. Distributed feedback (DFB) lasers working in pulsed mode at ambient temperatures and covering a broad spectral range in the mid infrared (MIR) are commercially available now. For many industrial applications e.g. automotive exhaust control and process monitoring, laser spectroscopy is an established technique, generally using near infrared (NIR) diode lasers. However, the mid infrared (MIR) spectral region is of special interest because of much stronger absorption lines compared to NIR. The status of QCL devices, system development and applications is reviewed. Special emphasis is given to the situation in Europe where a remarkable growth of QCL related R&D can be observed.

  7. Continuous wave room temperature external ring cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Revin, D. G., E-mail: d.revin@sheffield.ac.uk; Hemingway, M.; Vaitiekus, D.; Cockburn, J. W. [Physics and Astronomy Department, The University of Sheffield, S3 7RH Sheffield (United Kingdom); Hempler, N.; Maker, G. T.; Malcolm, G. P. A. [M Squared Lasers Ltd., G20 0SP Glasgow (United Kingdom)

    2015-06-29

    An external ring cavity quantum cascade laser operating at ∼5.2 μm wavelength in a continuous-wave regime at the temperature of 15 °C is demonstrated. Out-coupled continuous-wave optical powers of up to 23 mW are observed for light of one propagation direction with an estimated total intra-cavity optical power flux in excess of 340 mW. The uni-directional regime characterized by the intensity ratio of more than 60 for the light propagating in the opposite directions was achieved. A single emission peak wavelength tuning range of 90 cm{sup −1} is realized by the incorporation of a diffraction grating into the cavity.

  8. Continuous wave room temperature external ring cavity quantum cascade laser

    International Nuclear Information System (INIS)

    Revin, D. G.; Hemingway, M.; Vaitiekus, D.; Cockburn, J. W.; Hempler, N.; Maker, G. T.; Malcolm, G. P. A.

    2015-01-01

    An external ring cavity quantum cascade laser operating at ∼5.2 μm wavelength in a continuous-wave regime at the temperature of 15 °C is demonstrated. Out-coupled continuous-wave optical powers of up to 23 mW are observed for light of one propagation direction with an estimated total intra-cavity optical power flux in excess of 340 mW. The uni-directional regime characterized by the intensity ratio of more than 60 for the light propagating in the opposite directions was achieved. A single emission peak wavelength tuning range of 90 cm −1 is realized by the incorporation of a diffraction grating into the cavity

  9. Applications of quantum cascade lasers in plasma diagnostics: a review

    International Nuclear Information System (INIS)

    Röpcke, J; Lang, N; Davies, P B; Rousseau, A; Welzel, S

    2012-01-01

    Over the past few years mid-infrared absorption spectroscopy based on quantum cascade lasers operating over the region from 3 to 12 µm and called quantum cascade laser absorption spectroscopy or QCLAS has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, nitrogen oxides and organo-silicon compounds has led to further applications of QCLAS because most of these compounds and their decomposition products are infrared active. QCLAS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species at time resolutions below a microsecond, which is of particular importance for the investigation of reaction kinetics and dynamics. Information about gas temperature and population densities can also be derived from QCLAS measurements. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of QCLAS techniques to industrial requirements including the development of new diagnostic equipment. The recent availability of external cavity (EC) QCLs offers a further new option for multi-component detection. The aim of this paper is fourfold: (i) to briefly review spectroscopic issues arising from applying pulsed QCLs, (ii) to report on recent achievements in our understanding of molecular phenomena in plasmas and at surfaces, (iii) to describe the current status of industrial process monitoring in the mid-infrared and (iv) to discuss the potential of advanced instrumentation based on EC-QCLs for plasma diagnostics. (topical review)

  10. Development of an Exploration-Class Cascade Distillation System: Flight Like Prototype Design Status

    Science.gov (United States)

    Sargusingh, Miriam C.; Callahan, Michael R.

    2016-01-01

    The ability to recover and purify water through physiochemical processes is crucial for realizing long-term human space missions, including both planetary habitation and space travel. Because of their robust nature, distillation systems have been actively pursued as one of the technologies for water recovery. One such technology is the Cascade Distillation System (CDS) a multi-stage vacuum rotary distiller system designed to recover water in a microgravity environment. The CDS provides a similar function to the state of the art (SOA) vapor compressor distiller (VCD) currently employed on the International Space Station, but its control scheme and ancillary components are judged to be more straightforward and simpler to implement into a more reliable and efficient system. Through the Advanced Exploration Systems (AES) Life Support Systems (LSS) Project, the NASA Johnson Space Center (JSC) in collaboration with Honeywell International is developing a second generation flight forward prototype (CDS 2.0). A preliminary design fo the CDS 2.0 was presented to the project in September 2014. Following this review, detailed design of the system continued. The existing ground test prototype was used as a platform to demonstrate key 2.0 design and operational concepts to support this effort and mitigate design risk. A volumetric prototype was also developed to evaluate the packaging design for operability and maintainability. The updated system design was reviewed by the AES LSS Project and other key stakeholders in September 2015. This paper details the status of the CDS 2.0 design.

  11. Defence and security applications of quantum cascade lasers

    Science.gov (United States)

    Grasso, Robert J.

    2016-09-01

    Quantum Cascade Lasers (QCL) have seen tremendous recent application in the realm of Defence and Security. And, in many instances replacing traditional solid state lasers as the source of choice for Countermeasures, Remote Sensing, In-situ Sensing, Through-Barrier Sensing, and many others. Following their development and demonstration in the early 1990's, QCL's reached some maturity and specific defence and security application prior to 2005; with much initial development fostered by DARPA initiatives in the US, dstl, MoD, and EOARD funding initiatives in the UK, and University level R&D such as those by Prof Manijeh Razeghi at Northwestern University [1], and Prof Ted Masselink at Humboldt University [2]. As QCL's provide direct mid-IR laser output for electrical input, they demonstrate high quantum efficiency compared with diode pumped solid state lasers with optical parametric oscillators (OPOs) to generate mid-Infrared output. One particular advantage of QCL's is their very broad operational bandwidth, extending from the terahertz to the near-infrared spectral regions. Defence and Security areas benefiting from QCL's include: Countermeasures, Remote Sensing, Through-the-Wall Sensing, and Explosive Detection. All information used to construct this paper obtained from open sources.

  12. Terahertz quantum cascade laser as local oscillator in a heterodyne receiver.

    Science.gov (United States)

    Hübers, Heinz-Wilhelm; Pavlov, S; Semenov, A; Köhler, R; Mahler, L; Tredicucci, A; Beere, H; Ritchie, D; Linfield, E

    2005-07-25

    Terahertz quantum cascade lasers have been investigated with respect to their performance as a local oscillator in a heterodyne receiver. The beam profile has been measured and transformed in to a close to Gaussian profile resulting in a good matching between the field patterns of the quantum cascade laser and the antenna of a superconducting hot electron bolometric mixer. Noise temperature measurements with the hot electron bolometer and a 2.5 THz quantum cascade laser yielded the same result as with a gas laser as local oscillator.

  13. Terahertz Heterodyne Receiver with an Electron-Heating Mixer and a Heterodyne Based on the Quantum-Cascade Laser

    Science.gov (United States)

    Seliverstov, S. V.; Anfertyev, V. A.; Tretyakov, I. V.; Ozheredov, I. A.; Solyankin, P. M.; Revin, L. S.; Vaks, V. L.; Rusova, A. A.; Goltsman, G. N.; Shkurinov, A. P.

    2017-12-01

    We study characteristics of the laboratory prototype of a terahertz heterodyne receiver with an electron-heating mixer and a heterodyne based on the quantum-cascade laser. The results obtained demonstrate the possibility to use this receiver as a basis for creation of a high-sensitivity terahertz spectrometer, which can be used in many basic and practical applications. A significant advantage of this receiver will be the possibility of placing the mixer and heterodyne in the same cryostat, which will reduce the device dimensions considerably. The obtained experimental results are analyzed, and methods of optimizing the parameters of the receiver are proposed.

  14. Experimental characterization of quantum correlated triple beams generated by cascaded four-wave mixing processes

    Science.gov (United States)

    Qin, Zhongzhong; Cao, Leiming; Jing, Jietai

    2015-05-01

    Quantum correlations and entanglement shared among multiple modes are fundamental ingredients of most continuous-variable quantum technologies. Recently, a method used to generate multiple quantum correlated beams using cascaded four-wave mixing (FWM) processes was theoretically proposed and experimentally realized by our group [Z. Qin et al., Phys. Rev. Lett. 113, 023602 (2014)]. Our study of triple-beam quantum correlation paves the way to showing the tripartite entanglement in our system. Our system also promises to find applications in quantum information and precision measurement such as the controlled quantum communications, the generation of multiple quantum correlated images, and the realization of a multiport nonlinear interferometer. For its applications, the degree of quantum correlation is a crucial figure of merit. In this letter, we experimentally study how various parameters, such as the cell temperatures, one-photon, and two-photon detunings, influence the degree of quantum correlation between the triple beams generated from the cascaded two-FWM configuration.

  15. Novel High Power Type-I Quantum Well Cascade Diode Lasers

    Science.gov (United States)

    2017-08-30

    Novel High Power Type-I Quantum Well Cascade Diode Lasers The views, opinions and/or findings contained in this report are those of the author(s...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6... High Power Type-I Quantum Well Cascade Diode Lasers Report Term: 0-Other Email: leon.shterengas@stonybrook.edu Distribution Statement: 1-Approved

  16. Terahertz GaAs/AlAs quantum-cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Schrottke, L., E-mail: lutz@pdi-berlin.de; Lü, X.; Rozas, G.; Biermann, K.; Grahn, H. T. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin (Germany)

    2016-03-07

    We have realized GaAs/AlAs quantum-cascade lasers operating at 4.75 THz exhibiting more than three times higher wall plug efficiencies than GaAs/Al{sub 0.25}Ga{sub 0.75}As lasers with an almost identical design. At the same time, the threshold current density at 10 K is reduced from about 350 A/cm{sup 2} for the GaAs/Al{sub 0.25}Ga{sub 0.75}As laser to about 120 A/cm{sup 2} for the GaAs/AlAs laser. Substituting AlAs for Al{sub 0.25}Ga{sub 0.75}As barriers leads to a larger energy separation between the subbands reducing the probability for leakage currents through parasitic states and for reabsorption of the laser light. The higher barriers allow for a shift of the quasi-continuum of states to much higher energies. The use of a binary barrier material may also reduce detrimental effects due to the expected composition fluctuations in ternary alloys.

  17. Quantum cascade laser-based photoacoustic sulfuryl fluoride sensing

    Science.gov (United States)

    Minini, Kariza Mayra Silva; Bueno, Sâmylla Cristina Espécie; da Silva, Marcelo Gomes; Sthel, Marcelo Silva; Vargas, Helion; Angster, Judit; Miklós, András

    2017-02-01

    Although sulfuryl fluoride (SO2F2) is an efficient fumigant that does not react with the surface of indoor materials and does not reduce the stratospheric ozone shield, there are some concerns about its use. It is a toxic gas that attacks the central nervous system, and its global warming potential (GWP) value is 4780 for 100 years' time. Therefore, it is a clear necessity of implementing detection methods for tracing such a molecule. In this work a sensitive photoacoustic setup was built to detect SO2F2 at concentrations of parts per billion by volume (ppbv). The symmetric S-O stretching mode was excited by a continuous-wave quantum cascade laser with radiation wavenumber ranging from 1275.7 to 1269.3 cm-1. The photoacoustic signal was generated by modulating the laser wavenumber at the first longitudinal mode of the photoacoustic cell with amplitude depth of 5 × 10-3 cm-1. The detection of a minimum SO2F2 concentration of 20 ppbv was achieved.

  18. Heat flux and quantum correlations in dissipative cascaded systems

    Science.gov (United States)

    Lorenzo, Salvatore; Farace, Alessandro; Ciccarello, Francesco; Palma, G. Massimo; Giovannetti, Vittorio

    2015-02-01

    We study the dynamics of heat flux in the thermalization process of a pair of identical quantum systems that interact dissipatively with a reservoir in a cascaded fashion. Despite that the open dynamics of the bipartite system S is globally Lindbladian, one of the subsystems "sees" the reservoir in a state modified by the interaction with the other subsystem and hence it undergoes a non-Markovian dynamics. As a consequence, the heat flow exhibits a nonexponential time behavior which can greatly deviate from the case where each party is independently coupled to the reservoir. We investigate both thermal and correlated initial states of S and show that the presence of correlations at the beginning can considerably affect the heat-flux rate. We carry out our study in two paradigmatic cases—a pair of harmonic oscillators with a reservoir of bosonic modes and two qubits with a reservoir of fermionic modes—and compare the corresponding behaviors. In the case of qubits and for initial thermal states, we find that the trace distance discord is at any time interpretable as the correlated contribution to the total heat flux.

  19. Applying Quantum Cascade Laser Spectroscopy in Plasma Diagnostics

    Directory of Open Access Journals (Sweden)

    Jürgen Röpcke

    2016-07-01

    Full Text Available The considerably higher power and wider frequency coverage available from quantum cascade lasers (QCLs in comparison to lead salt diode lasers has led to substantial advances when QCLs are used in pure and applied infrared spectroscopy. Furthermore, they can be used in both pulsed and continuous wave (cw operation, opening up new possibilities in quantitative time resolved applications in plasmas both in the laboratory and in industry as shown in this article. However, in order to determine absolute concentrations accurately using pulsed QCLs, careful attention has to be paid to features like power saturation phenomena. Hence, we begin with a discussion of the non-linear effects which must be considered when using short or long pulse mode operation. More recently, cw QCLs have been introduced which have the advantage of higher power, better spectral resolution and lower fluctuations in light intensity compared to pulsed devices. They have proved particularly useful in sensing applications in plasmas when very low concentrations have to be monitored. Finally, the use of cw external cavity QCLs (EC-QCLs for multi species detection is described, using a diagnostics study of a methane/nitrogen plasma as an example. The wide frequency coverage of this type of QCL laser, which is significantly broader than from a distributed feedback QCL (DFB-QCL, is a substantial advantage for multi species detection. Therefore, cw EC-QCLs are state of the art devices and have enormous potential for future plasma diagnostic studies.

  20. Fast automotive diesel exhaust measurement using quantum cascade lasers

    Science.gov (United States)

    Herbst, J.; Brunner, R.; Lambrecht, A.

    2013-12-01

    Step by step, US and European legislations enforce the further reduction of atmospheric pollution caused by automotive exhaust emissions. This is pushing automotive development worldwide. Fuel efficient diesel engines with SCRtechnology can impede NO2-emission by reduction with NH3 down to the ppm range. To meet the very low emission limits of the Euro6 resp. US NLEV (National Low Emission Vehicle) regulations, automotive manufacturers have to optimize continuously all phases of engine operation and corresponding catalytic converters. Especially nonstationary operation holds a high potential for optimizing gasoline consumption and further reducing of pollutant emissions. Test equipment has to cope with demanding sensitivity and speed requirements. In the past Fraunhofer IPM has developed a fast emission analyzer called DEGAS (Dynamic Exhaust Gas Analyzer System), based on cryogenically cooled lead salt lasers. These systems have been used at Volkswagen AG`s test benches for a decade. Recently, IPM has developed DEGAS-Next which is based on cw quantum cascade lasers and thermoelectrically cooled detectors. The system is capable to measure three gas components (i.e. NO, NO2, NH3) in two channels with a time resolution of 20 ms and 1 ppm detection limits. We shall present test data and a comparison with fast FTIR measurements.

  1. Experimental investigation of terahertz quantum cascade laser with variable barrier heights

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Aiting; Vijayraghavan, Karun; Belkin, Mikhail A., E-mail: mbelkin@ece.utexas.edu [Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758 (United States); Matyas, Alpar; Jirauschek, Christian [Institute for Nanoelectronics, Technische Universität München, D-80333 Munich (Germany); Wasilewski, Zbig R. [Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G (Canada)

    2014-04-28

    We report an experimental study of terahertz quantum cascade lasers with variable barrier heights based on the Al{sub x}Ga{sub 1–x}As/GaAs material system. Two new designs are developed based on semiclassical ensemble Monte Carlo simulations using state-of-the-art Al{sub 0.15}Ga{sub 0.85}As/GaAs three-quantum-well resonant phonon depopulation active region design as a reference. The new designs achieved maximum lasing temperatures of 188 K and 172 K, as compared to the maximum lasing temperature of 191 K for the reference structure. These results demonstrate that terahertz quantum cascade laser designs with variable barrier heights provide a viable alternative to the traditional active region designs with fixed barrier composition. Additional design space offered by using variable barriers may lead to future improvements in the terahertz quantum cascade laser performance.

  2. Enhancement of optical Kerr effect in quantum-cascade lasers with multiple resonance levels.

    Science.gov (United States)

    Bai, Jing; Citrin, D S

    2008-08-18

    In this paper, we investigated the optical Kerr lensing effect in quantum-cascade lasers with multiple resonance levels. The Kerr refractive index n2 is obtained through the third-order susceptibility at the fundamental frequency chi(3)( omega; omega, omega,-omega). Resonant two-photon processes are found to have almost equal contributions to chi(3)( omega; omega, omega,-omega) as the single-photon processes, which result in the predicted enhancement of the positive nonlinear (Kerr) refractive index, and thus may enhance mode-locking of quantum-cascade lasers. Moreover, we also demonstrate an isospectral optimization strategy for further improving n2 through the band-structure design, in order to boost the multimode performance of quantum-cascade lasers. Simulation results show that the optimized stepwise multiple-quantum-well structure has n2 approximately 10-8 cm2/W, a twofold enhancement over the original flat quantum-well structure. This leads to a refractive-index change (delta)n of about 0.01, which is at the upper bound of those reported for typical Kerr medium. This stronger Kerr refractive index may be important for quantum-cascade lasers ultimately to demonstrate self-mode-locking.

  3. Estimating optical feedback from a chalcogenide fiber in mid-infrared quantum cascade lasers

    Directory of Open Access Journals (Sweden)

    L. Jumpertz

    2016-10-01

    Full Text Available The amount of optical feedback originating from a chalcogenide fiber used to couple light from a mid-infrared quantum cascade laser is evaluated experimentally. Threshold reduction measurements on the fibered laser, combined with an analytical study of a rate equations model of the laser under optical feedback, allow estimating the feedback strength between 11% and 15% depending on the fiber cleavage quality. While this remains below the frontier of the chaotic regime, it is sufficient to deeply modify the optical spectrum of a quantum cascade laser. Hence for applications such as gas spectroscopy, where the shape of the optical spectrum is of prime importance, the use of mid-infrared optical isolators may be necessary for fibered quantum cascade lasers to be fully exploited.

  4. Multimode analysis of highly tunable, quantum cascade powered, circular graphene spaser

    Energy Technology Data Exchange (ETDEWEB)

    Jayasekara, Charith, E-mail: charith.jayasekara@monash.edu; Premaratne, Malin [Advanced Computing and Simulation Laboratory (A chi L), Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Victoria 3800 (Australia); Stockman, Mark I. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Gunapala, Sarath D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

    2015-11-07

    We carried out a detailed analysis of a circular graphene spaser made of a circular graphene flake and a quantum cascade well structure. Owing to unique properties of graphene and quantum cascade well structure, the proposed design shows high mechanical and thermal stability and low optical losses. Additionally, operation characteristics of the model are analysed and tunability of the device is demonstrated. Some advantages of the proposed design include compact size, lower power operation, and the ability to set the operating wavelength over a wide range from Mid-IR to Near-IR. Thus, it can have wide spread applications including designing of ultracompact and ultrafast devices, nanoscopy and biomedical applications.

  5. Quantum Transport Simulation of High-Power 4.6-μm Quantum Cascade Lasers

    Directory of Open Access Journals (Sweden)

    Olafur Jonasson

    2016-06-01

    Full Text Available We present a quantum transport simulation of a 4.6- μ m quantum cascade laser (QCL operating at high power near room temperature. The simulation is based on a rigorous density-matrix-based formalism, in which the evolution of the single-electron density matrix follows a Markovian master equation in the presence of applied electric field and relevant scattering mechanisms. We show that it is important to allow for both position-dependent effective mass and for effective lowering of very thin barriers in order to obtain the band structure and the current-field characteristics comparable to experiment. Our calculations agree well with experiments over a wide range of temperatures. We predict a room-temperature threshold field of 62 . 5 kV/cm and a characteristic temperature for threshold-current-density variation of T 0 = 199 K . We also calculate electronic in-plane distributions, which are far from thermal, and show that subband electron temperatures can be hundreds to thousands of degrees higher than the heat sink. Finally, we emphasize the role of coherent tunneling current by looking at the size of coherences, the off-diagonal elements of the density matrix. At the design lasing field, efficient injection manifests itself in a large injector/upper lasing level coherence, which underscores the insufficiency of semiclassical techniques to address injection in QCLs.

  6. Theory of the multiphoton cascade transitions with two photon links: comparison of quantum electrodynamical and quantum mechanical approaches

    International Nuclear Information System (INIS)

    Zalialiutdinov, T; Baukina, Yu; Solovyev, D; Labzowsky, L

    2014-01-01

    The theory of multiphoton cascade transitions with two-photon links is considered within two different approaches: quantum electrodynamical (QED) and phenomenological quantum mechanical (QM). A problem of regularization of the cascade contributions is investigated in detail. It is argued that the correct regularization should include both initial and intermediate level widths in the singular energy denominators. This result follows both from the QED and from the QM approach. Particular transitions nl → 1s + 2γ with nl = 3s, 4s, 3d, 4d and nl → 1s + 3γ with nl = 3p, 4p are considered as examples. The importance of the proper cascade regularization is also demonstrated. (paper)

  7. Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?

    International Nuclear Information System (INIS)

    Matyas, A; Jirauschek, C; Kubis, T; Lugli, P

    2009-01-01

    We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.

  8. Phase locking and spectral linewidth of a two-mode terahertz quantum cascade laser

    NARCIS (Netherlands)

    Baryshev, A.; Hovenier, J.N.; Adam, A.J.L.; Kašalynas, I.; Gao, J.R.; Klaassen, T.O.; Williams, B.S.; Kumar, S.; Hu, Q.; Reno, J.L.

    2006-01-01

    We have studied the phase locking and spectral linewidth of an ? 2.7?THz quantum cascade laser by mixing its two lateral lasing modes. The beat signal at about 8?GHz is compared with a microwave reference by applying conventional phase lock loop circuitry with feedback to the laser bias current.

  9. Phase locking of a 2.7 THz quantum cascade laser to a microwave reference

    NARCIS (Netherlands)

    Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J.N.; Gao, J.R.; Klapwijk, T.M.; Paveliev, D.G.; Williams, B.S.; Kumar, S.; Hu, Q.; Reno, J.L.; Klein, B.; Hesler, J.L.

    2009-01-01

    We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain

  10. Phase locking and spectral linewidth of a two-mode terahertz quantum cascade laser

    NARCIS (Netherlands)

    Baryshev, A.; Hovenier, J. N.; Adam, A. J. L.; Kašalynas, I.; Gao, J. R.; Klaassen, T. O.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.

    2006-01-01

    We have studied the phase locking and spectral linewidth of an ˜2.7THz quantum cascade laser by mixing its two lateral lasing modes. The beat signal at about 8GHz is compared with a microwave reference by applying conventional phase lock loop circuitry with feedback to the laser bias current. Phase

  11. Phase locking of a 2.7 THz quantum cascade laser to a microwave reference

    NARCIS (Netherlands)

    Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.; Klein, B.; Hesler, J. L.

    2009-01-01

    We demonstrate the phase locking of a 2.7 THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain

  12. Study of optical confinement of quantum cascade lasers and applications to detection

    International Nuclear Information System (INIS)

    Moreau, Virginie

    2008-01-01

    Quantum cascade lasers have been invented in 1994 and they have already established themselves as the semiconductor laser source of choice in the mid- and far-infrared ranges of the electromagnetic spectrum. As most molecules of chemical interest exhibit roto-vibrational transitions in these spectral ranges, quantum cascade lasers are especially suited for applications such as spectroscopy, trace gas detection or medical imaging. One of the current leading research axis targets the device optimization and miniaturization, with possible applications in detection microsystems. This PhD thesis work focused on the study and optimization of the vertical optical confinement in quantum cascade lasers featuring optical waveguides without top cladding layers. These structures are interesting because they are compatible with two different guiding mechanisms at the same time, i.e. surface-plasmons and air confinement. The study of the characteristics of the optical mode and of the electrical current dispersion allowed us to conceive original structures which open new perspectives, for instance in the domain of analytic detection in a fluidic environment. Furthermore, we have shown that the observation by near field microscopy is a powerful tool to characterize and understand quantum cascade lasers. Finally, we have laid the foundations for the optimization of miniaturized arrays of single-mode lasers based on photonic crystal technology. (author) [fr

  13. Applications of cw quantum cascade laser near 8 μm in gas sensing research

    KAUST Repository

    Sajid, Muhammad Bilal; Farooq, Aamir

    2014-01-01

    Quantum cascade laser based sensors operating near 8 μm to detect H2O2, C2H2, CH4, N2O and H2O are discussed and demonstrated for applications in chemical kinetics, combustion and spectroscopic measurements.

  14. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot

    DEFF Research Database (Denmark)

    Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal

    2016-01-01

    . We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising...

  15. Dispersion compensated mid-infrared quantum cascade laser frequency comb with high power output

    Directory of Open Access Journals (Sweden)

    Q. Y. Lu

    2017-04-01

    Full Text Available Chromatic dispersion control plays an underlying role in optoelectronics and spectroscopy owing to its enhancement to nonlinear interactions by reducing the phase mismatching. This is particularly important to optical frequency combs based on quantum cascade lasers which require negligible dispersions for efficient mode locking of the dispersed modes into equally spaced comb modes. Here, we demonstrated a dispersion compensated mid-IR quantum cascade laser frequency comb with high power output at room temperature. A low-loss dispersive mirror has been engineered to compensate the device’s dispersion residue for frequency comb generation. Narrow intermode beating linewidths of 40 Hz in the comb-working currents were identified with a high power output of 460 mW and a broad spectral coverage of 80 cm-1. This dispersion compensation technique will enable fast spectroscopy and high-resolution metrology based on QCL combs with controlled dispersion and suppressed noise.

  16. Active mode locking of quantum cascade lasers in an external ring cavity.

    Science.gov (United States)

    Revin, D G; Hemingway, M; Wang, Y; Cockburn, J W; Belyanin, A

    2016-05-05

    Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents.

  17. A sulfur hexafluoride sensor using quantum cascade and CO2 laser-based photoacoustic spectroscopy.

    Science.gov (United States)

    Rocha, Mila; Sthel, Marcelo; Lima, Guilherme; da Silva, Marcelo; Schramm, Delson; Miklós, András; Vargas, Helion

    2010-01-01

    The increase in greenhouse gas emissions is a serious environmental problem and has stimulated the scientific community to pay attention to the need for detection and monitoring of gases released into the atmosphere. In this regard, the development of sensitive and selective gas sensors has been the subject of several research programs. An important greenhouse gas is sulphur hexafluoride, an almost non-reactive gas widely employed in industrial processes worldwide. Indeed it is estimated that it has a radiative forcing of 0.52 W/m(2). This work compares two photoacoustic spectrometers, one coupled to a CO(2) laser and another one coupled to a Quantum Cascade (QC) laser, for the detection of SF(6). The laser photoacoustic spectrometers described in this work have been developed for gas detection at small concentrations. Detection limits of 20 ppbv for CO(2) laser and 50 ppbv for quantum cascade laser were obtained.

  18. Quantum critical dynamics for a prototype class of insulating antiferromagnets

    Science.gov (United States)

    Wu, Jianda; Yang, Wang; Wu, Congjun; Si, Qimiao

    2018-06-01

    Quantum criticality is a fundamental organizing principle for studying strongly correlated systems. Nevertheless, understanding quantum critical dynamics at nonzero temperatures is a major challenge of condensed-matter physics due to the intricate interplay between quantum and thermal fluctuations. The recent experiments with the quantum spin dimer material TlCuCl3 provide an unprecedented opportunity to test the theories of quantum criticality. We investigate the nonzero-temperature quantum critical spin dynamics by employing an effective O (N ) field theory. The on-shell mass and the damping rate of quantum critical spin excitations as functions of temperature are calculated based on the renormalized coupling strength and are in excellent agreement with experiment observations. Their T lnT dependence is predicted to be dominant at very low temperatures, which will be tested in future experiments. Our work provides confidence that quantum criticality as a theoretical framework, which is being considered in so many different contexts of condensed-matter physics and beyond, is indeed grounded in materials and experiments accurately. It is also expected to motivate further experimental investigations on the applicability of the field theory to related quantum critical systems.

  19. Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?

    Energy Technology Data Exchange (ETDEWEB)

    Matyas, A; Jirauschek, C [Emmy Noether Research Group ' Modeling of Quantum Cascade Devices' , TU Muenchen, D-80333 Muenchen (Germany); Kubis, T [Walter Schottky Institute, TU Muenchen, D-85748 Garching (Germany); Lugli, P, E-mail: alparmat@mytum.d [Institute of Nanoelectronics, TU Muenchen, D-80333 Muenchen (Germany)

    2009-11-15

    We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.

  20. High performance 5.6μm quantum cascade lasers

    Science.gov (United States)

    Suttinger, M.; Go, R.; Figueiredo, P.; Todi, A.; Shu, Hong; Lyakh, A.

    2017-02-01

    5.6 μm quantum cascade lasers based on Al 0.78 In 0.22 As/In 0.69 Ga 0.31 As active region composition with measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured for the new design by testing devices with variable cavity length. Threshold current density of 1.7kA/cm2 and slope efficiency of 4.9W/A were measured for uncoated 3.15mm × 9μm lasers. Threshold current density and slope efficiency dependence on temperature in the range from 288K to 348K for the new structure can be described by characteristic temperatures T0 140K and T1 710K, respectively. Experimental data for inverse slope efficiency dependence on cavity length for 15-stage quantum cascade lasers with the same design are also presented. When combined with the 40-stage device data, the new data allowed for separate evaluation of the losses originating from the active region and from the cladding layers of the laser structure. Specifically, the active region losses for the studied design were found to be 0.77 cm-1, while cladding region losses - 0.33 cm-1. The data demonstrate that active region losses in mid wave infrared quantum cascade lasers largely define total waveguide losses and that their reduction should be one of the main priorities in the quantum cascade laser design.

  1. Thermal Management of Quantum Cascade Lasers in an individually Addressable Array Architecture

    Science.gov (United States)

    2016-02-08

    diode arrays, along with access to both front and rear facets. Hence, both laser and single-pass amplifier arrays can be accommodated. A module was... CW conditions at an emission wavelength of 9 m. OCIS codes: Semiconductor lasers , quantum cascade (140.5965), Laser arrays (140.3290) 1...Rubio, "Active coherent beam combining of diode lasers ," Opt. Lett. 36, 999-1001 (2011). 2. B. G. Saar, K. Creedon, L. Missaggia, C. A. Wang, M. K

  2. Mode-locked terahertz quantum cascade laser by direct phase synchronization

    International Nuclear Information System (INIS)

    Maussang, K.; Maysonnave, J.; Jukam, N.; Freeman, J. R.; Cavalié, P.; Dhillon, S. S.; Tignon, J.; Khanna, S. P.; Linfield, E. H.; Davies, A. G.; Beere, H. E.; Ritchie, D. A.

    2013-01-01

    Mode-locking of a terahertz quantum cascade laser is achieved using multimode injection seeding. Contrary to standard methods that rely on gain modulation, here a fixed phase relationship is directly imprinted to the laser modes. In this work, we demonstrate the generation of 9 ps phase mode-locked pulses around 2.75 THz. A direct measurement of the emitted field phase shows that it results from the phase of the initial injection

  3. Quantum-cascade laser photoacoustic detection of methane emitted from natural gas powered engines

    Science.gov (United States)

    Rocha, M. V.; Sthel, M. S.; Silva, M. G.; Paiva, L. B.; Pinheiro, F. W.; Miklòs, A.; Vargas, H.

    2012-03-01

    In this work we present a laser photoacoustic arrangement for the detection of the important greenhouse gas methane. A quantum-cascade laser and a differential photoacoustic cell were employed. A detection limit of 45 ppbv in nitrogen was achieved as well as a great selectivity. The same methodology was also tested in the detection of methane issued from natural gas powered vehicles (VNG) in Brazil, which demonstrates the excellent potential of this arrangement for greenhouse gas detection emitted from real sources.

  4. Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers

    International Nuclear Information System (INIS)

    Wójcik, Aleksander K.; Belyanin, Alexey; Malara, Pietro; Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico

    2013-01-01

    We propose a robust and reliable method of active mode locking of mid-infrared quantum cascade lasers and develop its theoretical description. Its key element is the use of an external ring cavity, which circumvents fundamental issues undermining the stability of mode locking in quantum cascade lasers. We show that active mode locking can give rise to the generation of picosecond pulses and phase-locked frequency combs containing thousands of the ring cavity modes

  5. Realization of a Tunable Dissipation Scale in a Turbulent Cascade using a Quantum Gas

    Science.gov (United States)

    Navon, Nir; Eigen, Christoph; Zhang, Jinyi; Lopes, Raphael; Smith, Robert; Hadzibabic, Zoran

    2017-04-01

    Many turbulent flows form so-called cascades, where excitations injected at large length scales, are transported to gradually smaller scales until they reach a dissipation scale. We initiate a turbulent cascade in a dilute Bose fluid by pumping energy at the container scale of an optical box trap using an oscillating magnetic force. In contrast to classical fluids where the dissipation scale is set by the viscosity of the fluid, the turbulent cascade of our quantum gas finishes when the particles kinetic energy exceeds the laser-trap depth. This mechanism thus allows us to effectively tune the dissipation scale where particles (and energy) are lost, and measure the particle flux in the cascade at the dissipation scale. We observe a unit power-law decay of the particle-dissipation rate with trap depth, which confirms the surprising prediction that in a wave-turbulent direct energy cascade, the particle flux vanishes in the ideal limit where the dissipation length scale tends to zero.

  6. Cascade Type-I Quantum Well GaSb-Based Diode Lasers

    Directory of Open Access Journals (Sweden)

    Leon Shterengas

    2016-05-01

    Full Text Available Cascade pumping of type-I quantum well gain sections was utilized to increase output power and efficiency of GaSb-based diode lasers operating in a spectral region from 1.9 to 3.3 μm. Carrier recycling between quantum well gain stages was realized using band-to-band tunneling in GaSb/AlSb/InAs heterostructure complemented with optimized electron and hole injector regions. Coated devices with an ~100-μm-wide aperture and a 3-mm-long cavity demonstrated continuous wave (CW output power of 1.96 W near 2 μm, 980 mW near 3 μm, 500 mW near 3.18 μm, and 360 mW near 3.25 μm at 17–20 °C—a nearly or more than twofold increase compared to previous state-of-the-art diode lasers. The utilization of the different quantum wells in the cascade laser heterostructure was demonstrated to yield wide gain lasers, as often desired for tunable laser spectroscopy. Double-step etching was utilized to minimize both the internal optical loss and the lateral current spreading penalties in narrow-ridge lasers. Narrow-ridge cascade diode lasers operate in a CW regime with ~100 mW of output power near and above 3 μm and above 150 mW near 2 μm.

  7. Pseudorandom dynamics of frequency combs in free-running quantum cascade lasers

    Science.gov (United States)

    Henry, Nathan; Burghoff, David; Yang, Yang; Hu, Qing; Khurgin, Jacob B.

    2018-01-01

    Recent research has shown that free-running quantum cascade lasers are capable of producing frequency combs in midinfrared and THz regions of the spectrum. Unlike familiar frequency combs originating from mode-locked lasers, these do not require any additional optical elements inside the cavity and have temporal characteristics that are dramatically different from the periodic pulse train of conventional combs. Frequency combs from quantum cascade lasers are characterized by the absence of sharp pulses and strong frequency modulation, periodic with the cavity round trip time but lacking any periodicity within that period. To explicate for this seemingly perplexing behavior, we develop a model of the gain medium using optical Bloch equations that account for hole burning in spectral, spatial, and temporal domains. With this model, we confirm that the most efficient mode of operation of a free-running quantum cascade laser is indeed a pseudorandom frequency-modulated field with nearly constant intensity. We show that the optimum modulation period is commensurate with the gain recovery time of the laser medium and the optimum modulation amplitude is comparable to the gain bandwidth, behavior that has been observed in the experiments.

  8. Long-range energy transfer in self-assembled quantum dot-DNA cascades

    Science.gov (United States)

    Goodman, Samuel M.; Siu, Albert; Singh, Vivek; Nagpal, Prashant

    2015-11-01

    The size-dependent energy bandgaps of semiconductor nanocrystals or quantum dots (QDs) can be utilized in converting broadband incident radiation efficiently into electric current by cascade energy transfer (ET) between layers of different sized quantum dots, followed by charge dissociation and transport in the bottom layer. Self-assembling such cascade structures with angstrom-scale spatial precision is important for building realistic devices, and DNA-based QD self-assembly can provide an important alternative. Here we show long-range Dexter energy transfer in QD-DNA self-assembled single constructs and ensemble devices. Using photoluminescence, scanning tunneling spectroscopy, current-sensing AFM measurements in single QD-DNA cascade constructs, and temperature-dependent ensemble devices using TiO2 nanotubes, we show that Dexter energy transfer, likely mediated by the exciton-shelves formed in these QD-DNA self-assembled structures, can be used for efficient transport of energy across QD-DNA thin films.The size-dependent energy bandgaps of semiconductor nanocrystals or quantum dots (QDs) can be utilized in converting broadband incident radiation efficiently into electric current by cascade energy transfer (ET) between layers of different sized quantum dots, followed by charge dissociation and transport in the bottom layer. Self-assembling such cascade structures with angstrom-scale spatial precision is important for building realistic devices, and DNA-based QD self-assembly can provide an important alternative. Here we show long-range Dexter energy transfer in QD-DNA self-assembled single constructs and ensemble devices. Using photoluminescence, scanning tunneling spectroscopy, current-sensing AFM measurements in single QD-DNA cascade constructs, and temperature-dependent ensemble devices using TiO2 nanotubes, we show that Dexter energy transfer, likely mediated by the exciton-shelves formed in these QD-DNA self-assembled structures, can be used for efficient

  9. Field test of a continuous-variable quantum key distribution prototype

    International Nuclear Information System (INIS)

    Fossier, S; Debuisschert, T; Diamanti, E; Villing, A; Tualle-Brouri, R; Grangier, P

    2009-01-01

    We have designed and realized a prototype that implements a continuous-variable quantum key distribution (QKD) protocol based on coherent states and reverse reconciliation. The system uses time and polarization multiplexing for optimal transmission and detection of the signal and phase reference, and employs sophisticated error-correction codes for reconciliation. The security of the system is guaranteed against general coherent eavesdropping attacks. The performance of the prototype was tested over preinstalled optical fibres as part of a quantum cryptography network combining different QKD technologies. The stable and automatic operation of the prototype over 57 h yielded an average secret key distribution rate of 8 kbit s -1 over a 3 dB loss optical fibre, including the key extraction process and all quantum and classical communication. This system is therefore ideal for securing communications in metropolitan size networks with high-speed requirements.

  10. Room-temperature operation of quantum cascade lasers at a wavelength of 5.8 μm

    Energy Technology Data Exchange (ETDEWEB)

    Babichev, A. V. [Connector Optics LLC (Russian Federation); Bousseksou, A. [University Paris Saclay, Institut d’Electronique Fondamentale, UMR 8622 CNRS (France); Pikhtin, N. A.; Tarasov, I. S. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Nikitina, E. V. [Russian Academy of Sciences, Saint Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation); Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E. [Peter-the-Great Saint-Petersburg Polytechnic University (Russian Federation); Novikov, I. I.; Karachinsky, L. Ya.; Egorov, A. Yu., E-mail: anton.egorov@connector-optics.com [Connector Optics LLC (Russian Federation)

    2016-10-15

    The room-temperature generation of multiperiod quantum-cascade lasers (QCL) at a wavelength of 5.8 μm in the pulsed mode is demonstrated. The heterostructure of a quantum-cascade laser based on a heterojunction of InGaAs/InAlAs alloys is grown by molecular-beam epitaxy and incorporates 60 identical cascades. The threshold current density of the stripe laser 1.4 mm long and 22 μm wide is ~4.8 kA/cm{sup 2} at a temperature of 303 K. The maximum power of the optical-radiation output from one QCL face, recorded by a detector, is 88 mW. The actual optical-power output from one QCL face is no less than 150 mW. The results obtained and possible ways of optimizing the structure of the developed quantum-cascade lasers are discussed.

  11. Optical feedback in dfb quantum cascade laser for mid-infrared cavity ring-down spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Terabayashi, Ryohei, E-mail: terabayashi.ryouhei@h.mbox.nagoya-u.ac.jp; Sonnenschein, Volker, E-mail: volker@nagoya-u.jp; Tomita, Hideki, E-mail: tomita@nagoya-u.jp; Hayashi, Noriyoshi, E-mail: hayashi.noriyoshi@h.mbox.nagoya-u.ac.jp; Kato, Shusuke, E-mail: katou.shuusuke@f.mbox.nagoya-u.ac.jp; Jin, Lei, E-mail: kin@nuee.nagoya-u.ac.jp; Yamanaka, Masahito, E-mail: yamanaka@nuee.nagoya-u.ac.jp; Nishizawa, Norihiko, E-mail: nishizawa@nuee.nagoya-u.ac.jp [Nagoya University, Department of Quantum Engineering, Graduate School of Engineering (Japan); Sato, Atsushi, E-mail: atsushi.sato@sekisui.com; Nozawa, Kohei, E-mail: kohei.nozawa@sekisui.com; Hashizume, Kenta, E-mail: kenta.hashizume@sekisui.com; Oh-hara, Toshinari, E-mail: toshinari.ohara@sekisui.com [Sekisui Medical Co., Ltd., Drug Development Solutions Center (Japan); Iguchi, Tetsuo, E-mail: t-iguchi@nucl.nagoya-u.ac.jp [Nagoya University, Department of Quantum Engineering, Graduate School of Engineering (Japan)

    2017-11-15

    A simple external optical feedback system has been applied to a distributed feedback quantum cascade laser (DFB QCL) for cavity ring-down spectroscopy (CRDS) and a clear effect of feedback was observed. A long external feedback path length of up to 4m can decrease the QCL linewidth to around 50kHz, which is of the order of the transmission linewidth of our high finesse ring-down cavity. The power spectral density of the transmission signal from high finesse cavity reveals that the noise at frequencies above 20kHz is reduced dramatically.

  12. Progress in Rapidly-Tunable External Cavity Quantum Cascade Lasers with a Frequency-Shifted Feedback

    Directory of Open Access Journals (Sweden)

    Arkadiy Lyakh

    2016-04-01

    Full Text Available The recent demonstration of external cavity quantum cascade lasers with optical feedback, controlled by an acousto-optic modulator, paves the way to ruggedized infrared laser systems with the capability of tuning the emission wavelength on a microsecond scale. Such systems are of great importance for various critical applications requiring ultra-rapid wavelength tuning, including combustion and explosion diagnostics and standoff detection. In this paper, recent research results on these devices are summarized and the advantages of the new configuration are analyzed in the context of practical applications.

  13. A terahertz heterodyne receiver based on a quantum cascade laser and a superconducting bolometer.

    Energy Technology Data Exchange (ETDEWEB)

    Klaassen, T. O. (Delft University of Technology, Lorentzweg, Delft, The Netherlands); Hajenius, M. (Delft University of Technology, Lorentzweg, Delft, The Netherlands); Adam, A. J. L. (Delft University of Technology, Lorentzweg, Delft, The Netherlands); Klapwijk, T. M. (Delft University of Technology, Lorentzweg, Delft, The Netherlands); Baryshev, A. (SRON National Institute for Space Research, Sorbonnelaan, Utrecht, The Netherlands); Kumar, Sushil (Massachusetts Institute of Technology, Cambridge, MA); Baselmans, J. J. A. (SRON National Institute for Space Research, Sorbonnelaan, Utrecht, The Netherlands); Hu, Qing (Massachusetts Institute of Technology, Cambridge, MA); Yang, Z. Q. (SRON National Institute for Space Research, Sorbonnelaan, Utrecht, The Netherlands); Hovenier, J. N. (Delft University of Technology, Lorentzweg, Delft, The Netherlands); Williams, Benjamin S. (Massachusetts Institute of Technology, Cambridge, MA); Gao, J. R. (Delft University of Technology, Lorentzweg, Delft, The Netherlands); Reno, John Louis

    2005-03-01

    We report the first demonstration of an all solid-state heterodyne receiver that can be used for high-resolution spectroscopy above 2 THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8 THz as local oscillator. We measure a double sideband receiver noise temperature of 1400 K at 2.8 THz and 4.2 K, and find that the free-running QCL has sufficient power stability for a practical receiver, demonstrating an unprecedented combination of sensitivity and stability.

  14. Indirect absorption spectroscopy using quantum cascade lasers: mid-infrared refractometry and photothermal spectroscopy.

    Science.gov (United States)

    Pfeifer, Marcel; Ruf, Alexander; Fischer, Peer

    2013-11-04

    We record vibrational spectra with two indirect schemes that depend on the real part of the index of refraction: mid-infrared refractometry and photothermal spectroscopy. In the former, a quantum cascade laser (QCL) spot is imaged to determine the angles of total internal reflection, which yields the absorption line via a beam profile analysis. In the photothermal measurements, a tunable QCL excites vibrational resonances of a molecular monolayer, which heats the surrounding medium and changes its refractive index. This is observed with a probe laser in the visible. Sub-monolayer sensitivities are demonstrated.

  15. Terahertz near-field imaging using subwavelength plasmonic apertures and a quantum cascade laser source.

    Science.gov (United States)

    Baragwanath, Adam J; Freeman, Joshua R; Gallant, Andrew J; Zeitler, J Axel; Beere, Harvey E; Ritchie, David A; Chamberlain, J Martyn

    2011-07-01

    The first demonstration, to our knowledge, of near-field imaging using subwavelength plasmonic apertures with a terahertz quantum cascade laser source is presented. "Bull's-eye" apertures, featuring subwavelength circular apertures flanked by periodic annular corrugations were created using a novel fabrication method. A fivefold increase in intensity was observed for plasmonic apertures over plain apertures of the same diameter. Detailed studies of the transmitted beam profiles were undertaken for apertures with both planarized and corrugated exit facets, with the former producing spatially uniform intensity profiles and subwavelength spatial resolution. Finally, a proof-of-concept imaging experiment is presented, where an inhomogeneous pharmaceutical drug coating is investigated.

  16. Integration of a terahertz quantum cascade laser with a hollow waveguide

    Science.gov (United States)

    Wanke, Michael C [Albuquerque, NM; Nordquist, Christopher D [Albuquerque, NM

    2012-07-03

    The present invention is directed to the integration of a quantum cascade laser with a hollow waveguide on a chip to improve both the beam pattern and manufacturability. By coupling the QCL output into a single-mode rectangular waveguide the radiation mode structure can be known and the propagation, manipulation, and broadcast of the QCL radiation can then be entirely controlled by well-established rectangular waveguide techniques. By controlling the impedance of the interface, enhanced functions, such as creating amplifiers, efficient coupling to external cavities, and increasing power output from metal-metal THz QCLs, are also enabled.

  17. Phase-locked, high power, mid-infrared quantum cascade laser arrays

    Science.gov (United States)

    Zhou, W.; Slivken, S.; Razeghi, M.

    2018-04-01

    We demonstrate phase-locked, high power quantum cascade laser arrays, which are combined using a monolithic, tree array multimode interferometer, with emission wavelengths around 4.8 μm. A maximum output power of 15 W was achieved from an eight-element laser array, which has only a slightly higher threshold current density and a similar slope efficiency compared to a Fabry-Perot laser of the same length. Calculated multimode interferometer splitting loss is on the order of 0.27 dB for the in-phase supermode. In-phase supermode operation with nearly ideal behavior is demonstrated over the working current range of the array.

  18. Fast continuous tuning of terahertz quantum-cascade lasers by rear-facet illumination

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Martin, E-mail: hempel@pdi-berlin.de; Röben, Benjamin; Schrottke, Lutz; Grahn, Holger T. [Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5–7, 10117 Berlin (Germany); Hübers, Heinz-Wilhelm [Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstr. 2, 12489 Berlin (Germany); Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany)

    2016-05-09

    GaAs-based terahertz quantum-cascade lasers (QCLs) are continuously tuned in their emission frequency by illuminating the rear facet with a near-infrared, high-power diode laser. For QCLs emitting around 3.1 THz, the maximum tuning range amounts to 2.8 GHz for continuous-wave operation at a heat sink temperature of 55 K, while in pulsed mode 9.1 and 8.0 GHz are achieved at 35 and 55 K, respectively.

  19. An experimental study of noise in midinfrared quantum cascade lasers of different designs

    OpenAIRE

    Schilt, Stéphane; Tombez, Lionel; Tardy, Camille; Bismuto, Alfredo; Blaser, Stéphane; Maulini, Richard; Terazzi, Romain; Rochat, Michel; Südmeyer, Thomas

    2015-01-01

    We present an experimental study of noise in mid-infrared quantum cascade lasers (QCLs) of differ-ent designs. By quantifying the high degree of correlation occurring between fluctuations of the optical frequency and voltage between the QCL terminals, we show that electrical noise is a powerful and simple mean to study noise in QCLs. Based on this outcome, we investigated the electrical noise in a large set of 22 QCLs emitting in the range of 7.6–8 μm and consisting of both ridge-waveguide and...

  20. Low-Loss Hollow Waveguide Fibers for Mid-Infrared Quantum Cascade Laser Sensing Applications

    Directory of Open Access Journals (Sweden)

    James A. Harrington

    2013-01-01

    Full Text Available We report on single mode optical transmission of hollow core glass waveguides (HWG coupled with an external cavity mid-IR quantum cascade lasers (QCLs. The QCL mode results perfectly matched to the hybrid HE11 waveguide mode and the higher losses TE-like modes have efficiently suppressed by the deposited inner dielectric coating. Optical losses down to 0.44 dB/m and output beam divergence of ~5 mrad were measured. Using a HGW fiber with internal core size of 300 µm we obtained single mode laser transmission at 10.54 µm and successful employed it in a quartz enhanced photoacoustic gas sensor setup.

  1. Quantum Cascade Laser-Based Photoacoustic Sensor for Trace Detection of Formaldehyde Gas

    Directory of Open Access Journals (Sweden)

    Pietro Mario Lugarà

    2009-04-01

    Full Text Available We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 mm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm-1 is selected for CH2O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters.

  2. Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser

    International Nuclear Information System (INIS)

    Hangauer, Andreas; Nikodem, Michal; Wysocki, Gerard; Spinner, Georg

    2013-01-01

    Chirped laser dispersion spectroscopy (CLaDS) utilizing direct modulation of a quantum cascade laser (QCL) is presented. By controlling the laser bias nearly single- and dual-sideband CLaDS operation can be realized in an extremely simplified optical setup with no external optical modulators. Capability of direct single-sideband modulation is a unique feature of QCLs that exhibit a low linewidth enhancement factor. The developed analytical model shows excellent agreement with the experimental, directly modulated CLaDS spectra. This method overcomes major technical limitations of mid-infrared CLaDS systems by allowing significantly higher modulation frequencies and eliminating optical fringes introduced by external modulators

  3. Real-time terahertz imaging through self-mixing in a quantum-cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Wienold, M., E-mail: martin.wienold@dlr.de; Rothbart, N.; Hübers, H.-W. [Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstr. 2, 12489 Berlin (Germany); Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Hagelschuer, T. [Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstr. 2, 12489 Berlin (Germany); Schrottke, L.; Biermann, K.; Grahn, H. T. [Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2016-07-04

    We report on a fast self-mixing approach for real-time, coherent terahertz imaging based on a quantum-cascade laser and a scanning mirror. Due to a fast deflection of the terahertz beam, images with frame rates up to several Hz are obtained, eventually limited by the mechanical inertia of the employed scanning mirror. A phase modulation technique allows for the separation of the amplitude and phase information without the necessity of parameter fitting routines. We further demonstrate the potential for transmission imaging.

  4. Extended electrical tuning of quantum cascade lasers with digital concatenated gratings

    Energy Technology Data Exchange (ETDEWEB)

    Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Lu, Q. Y.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu [Center for Quantum Devices, Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, Illinois 60208 (United States)

    2013-12-02

    In this report, the sampled grating distributed feedback laser architecture is modified with digital concatenated gratings to partially compensate for the wavelength dependence of optical gain in a standard high efficiency quantum cascade laser core. This allows equalization of laser threshold over a wide wavelength range and demonstration of wide electrical tuning. With only two control currents, a full tuning range of 500 nm (236 cm{sup −1}) has been demonstrated. Emission is single mode, with a side mode suppression of >20 dB.

  5. Influence of screening on longitudinal-optical phonon scattering in quantum cascade lasers

    International Nuclear Information System (INIS)

    Ezhov, Ivan; Jirauschek, Christian

    2016-01-01

    We theoretically investigate the influence of screening on electron-longitudinal optical phonon scattering in quantum cascade lasers. By employing ensemble Monte Carlo simulations, an advanced screening model based on the random-phase approximation is compared to the more elementary Thomas-Fermi and Debye models. For mid-infrared structures, and to a lesser extent also for terahertz designs, the inclusion of screening is shown to affect the simulated current and optical output power. Furthermore, it is demonstrated that by using the electron temperature rather than the lattice temperature, the Debye model can be significantly improved

  6. Sub-nanometrically resolved chemical mappings of quantum-cascade laser active regions

    International Nuclear Information System (INIS)

    Pantzas, Konstantinos; Beaudoin, Grégoire; Patriarche, Gilles; Largeau, Ludovic; Mauguin, Olivia; Sagnes, Isabelle; Pegolotti, Giulia; Vasanelli, Angela; Calvar, Ariane; Amanti, Maria; Sirtori, Carlo

    2016-01-01

    A procedure that produces sub-nanometrically resolved chemical mappings of MOCVD-grown InGaAs/InAlAs/InP quantum cascade lasers is presented. The chemical mappings reveal that, although the structure is lattice-matched to InP, the InAlAs barriers do not attain the nominal aluminum content—48%—and are, in fact, InGaAlAs quaternaries. This information is used to adjust the aluminum precursor flow and fine-tune the composition of the barriers, resulting in a significant improvement of the fabricated lasers. (paper)

  7. Widely tunable terahertz source based on intra-cavity frequency mixing in quantum cascade laser arrays

    International Nuclear Information System (INIS)

    Jiang, Aiting; Jung, Seungyong; Jiang, Yifan; Kim, Jae Hyun; Belkin, Mikhail A.; Vijayraghavan, Karun

    2015-01-01

    We demonstrate a compact monolithic terahertz source continuously tunable from 1.9 THz to 3.9 THz with the maximum peak power output of 106 μW at 3.46 THz at room temperature. The source consists of an array of 10 electrically tunable quantum cascade lasers with intra-cavity terahertz difference-frequency generation. To increase fabrication yield and achieve high THz peak power output in our devices, a dual-section current pumping scheme is implemented using two electrically isolated grating sections to independently control gain for the two mid-IR pumps

  8. Development of an Exploration-Class Cascade Distillation Subsystem: Performance Testing of the Generation 1.0 Prototype

    Science.gov (United States)

    Callahan, Michael R.; Sargusingh, Miriam J.

    2015-01-01

    The ability to recover and purify water is crucial for realizing long-term human space missions. The National Aeronautics and Space Admininstration and Honeywell co-developed a five-stage vacuum rotary distillation water recovery system referred to as the Cascade Distillation Subsystem (CDS). Over the past three years, NASA's Advanced Exploration Systems (AES) Water Recovery Project (WRP) has been working toward the development of a flight-forward CDS design. In 2012 the original CDS prototype underwent a series of incremental upgrades and tests intened to both demonstrate the feasibility of a on-orbit demonstration of the system and to collect operational and performance data to be used to inform a second generation design. The latest testing of the CDS Generation 1.0 prototype was conducted May 29 through July 2, 2014. Initial system performance was benchmarked by processing deionized water and sodium chloride. Following, the system was challenged with analogue urine waste stream solutions stabilized with an Oxone-based and the two International Space Station baseline and alternative pretreatment solutions. During testing, the system processed more than 160 kilograms of wastewater with targeted water recoveries between 75 and 85% depending on the specific waste stream tested. For all wastewater streams, contaminant removals from wastewater feed to product water distillate, were estimated at greater than 99%. The average specific energy of the system was less than 120 Watt-hours/kilogram. The following paper provides detailed information and data on the performance of the CDS as challenged per the WRP test objectives.

  9. Investigations of the polarization behavior of quantum cascade lasers by Stokes parameters.

    Science.gov (United States)

    Janassek, Patrick; Hartmann, Sébastien; Molitor, Andreas; Michel, Florian; Elsäßer, Wolfgang

    2016-01-15

    We experimentally investigate the full polarization behavior of mid-infrared emitting quantum cascade lasers (QCLs) in terms of measuring the complete Stokes parameters, instead of only projecting them on a linear polarization basis. We demonstrate that besides the pre-dominant linear TM polarization of the emitted light as governed by the selection rules of the intersubband transition, small non-TM contributions, e.g., circularly polarized light, are present reflecting the birefringent behavior of the semiconductor quantum well waveguide. Surprisingly unique is the persistence of these polarization properties well below laser threshold. These investigations give further insight into understanding, manipulating, and exploiting the polarization properties of QCLs, both from a laser point of view and with respect toward applications.

  10. Continuous wave power scaling in high power broad area quantum cascade lasers

    Science.gov (United States)

    Suttinger, M.; Leshin, J.; Go, R.; Figueiredo, P.; Shu, H.; Lyakh, A.

    2018-02-01

    Experimental and model results for high power broad area quantum cascade lasers are presented. Continuous wave power scaling from 1.62 W to 2.34 W has been experimentally demonstrated for 3.15 mm-long, high reflection-coated 5.6 μm quantum cascade lasers with 15 stage active region for active region width increased from 10 μm to 20 μm. A semi-empirical model for broad area devices operating in continuous wave mode is presented. The model uses measured pulsed transparency current, injection efficiency, waveguide losses, and differential gain as input parameters. It also takes into account active region self-heating and sub-linearity of pulsed power vs current laser characteristic. The model predicts that an 11% improvement in maximum CW power and increased wall plug efficiency can be achieved from 3.15 mm x 25 μm devices with 21 stages of the same design but half doping in the active region. For a 16-stage design with a reduced stage thickness of 300Å, pulsed roll-over current density of 6 kA/cm2 , and InGaAs waveguide layers; optical power increase of 41% is projected. Finally, the model projects that power level can be increased to 4.5 W from 3.15 mm × 31 μm devices with the baseline configuration with T0 increased from 140 K for the present design to 250 K.

  11. Corneal tissue ablation using 6.1 μm quantum cascade laser

    Science.gov (United States)

    Huang, Yong; Kang, Jin U.

    2012-03-01

    High absorption property of tissues in the IR range (λ> 2 μm) results in effective tissue ablation, especially near 3 μm. In the mid-infrared range, wavelengths of 6.1 μm and 6.45 μm fall into the absorption bands of the amide protein groups Amide-I and Amide-II, respectively. They also coincide with the deformation mode of water, which has an absorption peak at 6.1 μm. This coincidence makes 6.1 μm laser a better ablation tool that has promising effectiveness and minimum collateral damages than 3 μm lasers. In this work, we performed bovine corneal ablation test in-vitro using high-power 6.1μm quantum cascade laser (QCL) operated at pulse mode. Quantum cascade laser has the advantages of low cost, compact size and tunable wavelength, which makes it great alternative Mid-IR light source to conventional tunable free-electron lasers (FEL) for medical applications. Preliminary results show that effective corneal stroma craters were achieved with much less collateral damage in corneal tissue that contains less water. Future study will focus on optimizing the control parameters of QCL to attain neat and precise ablation of corneal tissue and development of high peak power QCL.

  12. External amplitude and frequency modulation of a terahertz quantum cascade laser using metamaterial/graphene devices.

    Science.gov (United States)

    Kindness, S J; Jessop, D S; Wei, B; Wallis, R; Kamboj, V S; Xiao, L; Ren, Y; Braeuninger-Weimer, P; Aria, A I; Hofmann, S; Beere, H E; Ritchie, D A; Degl'Innocenti, R

    2017-08-09

    Active control of the amplitude and frequency of terahertz sources is an essential prerequisite for exploiting a myriad of terahertz applications in imaging, spectroscopy, and communications. Here we present a optoelectronic, external modulation technique applied to a terahertz quantum cascade laser which holds the promise of addressing a number of important challenges in this research area. A hybrid metamaterial/graphene device is implemented into an external cavity set-up allowing for optoelectronic tuning of feedback into a quantum cascade laser. We demonstrate powerful, all-electronic, control over the amplitude and frequency of the laser output. Full laser switching is performed by electrostatic gating of the metamaterial/graphene device, demonstrating a modulation depth of 100%. External control of the emission spectrum is also achieved, highlighting the flexibility of this feedback method. By taking advantage of the frequency dispersive reflectivity of the metamaterial array, different modes of the QCL output are selectively suppressed using lithographic tuning and single mode operation of the multi-mode laser is enforced. Side mode suppression is electrically modulated from ~6 dB to ~21 dB, demonstrating active, optoelectronic modulation of the laser frequency content between multi-mode and single mode operation.

  13. Freedom from band-gap slavery: from diode lasers to quantum cascade lasers

    Science.gov (United States)

    Capasso, Federico

    2010-02-01

    Semiconductor heterostructure lasers, for which Alferov and Kromer received part of the Nobel Prize in Physics in 2000, are the workhorse of technologies such as optical communications, optical recording, supermarket scanners, laser printers and fax machines. They exhibit high performance in the visible and near infrared and rely for their operation on electrons and holes emitting photons across the semiconductor bandgap. This mechanism turns into a curse at longer wavelengths (mid-infrared) because as the bandgap, shrinks laser operation becomes much more sensitive to temperature, material defects and processing. Quantum Cascade Laser (QCL), invented in 1994, rely on a radically different process for light emission. QCLs are unipolar devices in which electrons undergo transitions between quantum well energy levels and are recycled through many stages emitting a cascade of photons. Thus by suitable tailoring of the layers' thickness, using the same heterostructure material, they can lase across the molecular fingerprint region from 3 to 25 microns and beyond into the far-infrared and submillimiter wave spectrum. High power cw room temperature QCLs and QCLs with large continuous single mode tuning range have found many applications (infrared countermeasures, spectroscopy, trace gas analysis and atmospheric chemistry) and are commercially available. )

  14. Optimizing optical nonlinearities in GaInAs/AlInAs quantum cascade lasers

    Directory of Open Access Journals (Sweden)

    Gajić Aleksandra D.

    2014-01-01

    Full Text Available Regardless of the huge advances made in the design and fabrication of mid-infrared and terahertz quantum cascade lasers, success in accessing the ~3-4 mm region of the electromagnetic spectrum has remained limited. This fact has brought about the need to exploit resonant intersubband transitions as powerful nonlinear oscillators, consequently enabling the occurrence of large nonlinear optical susceptibilities as a means of reaching desired wavelengths. In this work, we present a computational model developed for the optimization of second-order optical nonlinearities in In0.53Ga0.47As/Al0.48In0.52As quantum cascade laser structures based on the implementation of the Genetic algorithm. The carrier transport and the power output of the structure were calculated by self-consistent solutions to the system of rate equations for carriers and photons. Both stimulated and simultaneous double-photon absorption processes occurring between the second harmonic generation-relevant levels are incorporated into rate equations and the material-dependent effective mass and band non-parabolicity are taken into account, as well. The developed method is quite general and can be applied to any higher order effect which requires the inclusion of the photon density equation. [Projekat Ministarstva nauke Republike Srbije, br. III 45010

  15. Frequency locking of single-mode 3.5-THz quantum cascade lasers using a gas cell

    NARCIS (Netherlands)

    Ren, Y.; Hovenier, J.N.; Cui, M.; Hayton, D.J.; Gao, J.R.; Klapwijk, T.M.; Shi, S.C.; Kao, T.Y.; Hu, Q.; Reno, J.L.

    2012-01-01

    We report frequency locking of two 3.5-THz third-order distributed feedback (DFB) quantum cascade lasers (QCLs) by using methanol molecular absorption lines, a proportional-integral-derivative controller, and a NbN bolometer. We show that the free-running linewidths of the QCLs are dependent on the

  16. Phase locking of 2.324 and 2.959 terahertz quantum cascade lasers using a Schottky diode harmonic mixer.

    Science.gov (United States)

    Danylov, Andriy; Erickson, Neal; Light, Alexander; Waldman, Jerry

    2015-11-01

    The 23rd and 31st harmonics of a microwave signal generated in a novel THz balanced Schottky diode mixer were used as a frequency stable reference source to phase lock solid-nitrogen-cooled 2.324 and 2.959 THz quantum cascade lasers. Hertz-level frequency stability was achieved, which was maintained for several hours.

  17. Absolute spectroscopy near 7.8 {\\mu} m with a comb-locked extended-cavity quantum-cascade-laser

    KAUST Repository

    Lamperti, Marco; Alsaif, Bidoor; Gatti, Davide; Fermann, Martin; Laporta, Paolo; Farooq, Aamir; Marangoni, Marco

    2017-01-01

    We report the first experimental demonstration of frequency-locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locking scheme is applied to carry out absolute spectroscopy of N2O lines near 7.87 {\\mu

  18. Time-resolved study of a pulsed dc discharge using quantum cascade laser absorption spectroscopy : NO and gas temperature kinetics

    NARCIS (Netherlands)

    Welzel, S.; Gatilova, L.; Röpcke, J.; Rousseau, A.

    2007-01-01

    In a pulsed dc discharge of an Ar–N2 mixture containing 0.91% of NO the kinetics of the destruction of NO has been studied under static and flowing conditions, i.e. in a closed and open discharge tube (p = 266 Pa). For this purpose quantum cascade laser absorption spectroscopy (QCLAS) in the

  19. A calibration-free ammonia breath sensor using a quantum cascade laser with WMS 2f/1f

    KAUST Repository

    Owen, Kyle; Farooq, Aamir

    2013-01-01

    modulation spectroscopy with second harmonic normalized by the first harmonic (WMS 2f/1f) is a sensitive technique used in the development of calibration-free sensors. An ammonia gas sensor is designed and developed that uses a quantum cascade laser operating

  20. Time-resolved temperature measurements in a rapid compression machine using quantum cascade laser absorption in the intrapulse mode

    KAUST Repository

    Nasir, Ehson Fawad; Farooq, Aamir

    2016-01-01

    A temperature sensor based on the intrapulse absorption spectroscopy technique has been developed to measure in situ temperature time-histories in a rapid compression machine (RCM). Two quantum-cascade lasers (QCLs) emitting near 4.55μm and 4.89μm

  1. NO kinetics in pulsed low-pressure nitrogen plasmas studied by time resolved quantum cascade laser absorption spectroscopy

    NARCIS (Netherlands)

    Welzel, S.; Guaitella, O.; Lazzaroni, C.; Pintassilgo, C.; Rousseau, A.; Röpcke, J.

    2011-01-01

    Time-resolved quantum cascade laser absorption spectroscopy at 1897 cm-1 (5.27 µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the

  2. Strain-free Ge/GeSiSn Quantum Cascade Lasers Based on L-Valley Intersubband Transitions

    National Research Council Canada - National Science Library

    Soret, R. A; Sun, G; Cheng, H; Menendez, J; Khurgin, J

    2007-01-01

    The authors propose a Ge/Ge0.76Si0.19Sn0.05 quantum cascade laser using intersubband transitions at L valleys of the conduction band which has a clean offset of 150 meV situated below other energy valleys Gamma and X...

  3. Hot electron bolometer heterodyne receiver with a 4.7-THz quantum cascade laser as a local oscillator

    NARCIS (Netherlands)

    Kloosterman, J.L.; Hayton, D.J.; Ren, Y.; Kao, T.Y.; Hovenier, J.N.; Gao, J.R.; Klapwijk, T.M.; Hu, Q.; Walker, C.K.; Reno, J.L.

    2013-01-01

    We report on a heterodyne receiver designed to observe the astrophysically important neutral atomic oxygen [OI] line at 4.7448?THz. The local oscillator is a third-order distributed feedback quantum cascade laser operating in continuous wave mode at 4.741?THz. A quasi-optical, superconducting NbN

  4. Optical feedback effects on terahertz quantum cascade lasers: modelling and applications

    Science.gov (United States)

    Rakić, Aleksandar D.; Lim, Yah Leng; Taimre, Thomas; Agnew, Gary; Qi, Xiaoqiong; Bertling, Karl; Han, She; Wilson, Stephen J.; Kundu, Iman; Grier, Andrew; Ikonić, Zoran; Valavanis, Alexander; Demić, Aleksandar; Keeley, James; Li, Lianhe H.; Linfield, Edmund H.; Davies, A. Giles; Harrison, Paul; Ferguson, Blake; Walker, Graeme; Prow, Tarl; Indjin, Dragan; Soyer, H. Peter

    2016-11-01

    Terahertz (THz) quantum cascade lasers (QCLs) are compact sources of radiation in the 1-5 THz range with significant potential for applications in sensing and imaging. Laser feedback interferometry (LFI) with THz QCLs is a technique utilizing the sensitivity of the QCL to the radiation reflected back into the laser cavity from an external target. We will discuss modelling techniques and explore the applications of LFI in biological tissue imaging and will show that the confocal nature of the QCL in LFI systems, with their innate capacity for depth sectioning, makes them suitable for skin diagnostics with the well-known advantages of more conventional confocal microscopes. A demonstration of discrimination of neoplasia from healthy tissue using a THz, LFI-based system in the context of melanoma is presented using a transgenic mouse model.

  5. Common mode frequency instability in internally phase-locked terahertz quantum cascade lasers.

    Science.gov (United States)

    Wanke, M C; Grine, A D; Fuller, C T; Nordquist, C D; Cich, M J; Reno, J L; Lee, Mark

    2011-11-21

    Feedback from a diode mixer integrated into a 2.8 THz quantum cascade laser (QCL) was used to phase lock the difference frequencies (DFs) among the Fabry-Perot (F-P) longitudinal modes of a QCL. Approximately 40% of the DF power was phase locked, consistent with feedback loop bandwidth of 10 kHz and phase noise bandwidth ~0.5 MHz. While the locked DF signal has ≤ 1 Hz linewidth and negligible drift over ~30 min, mixing measurements between two QCLs and between a QCL and molecular gas laser show that the common mode frequency stability is no better than a free-running QCL. © 2011 Optical Society of America

  6. Planar integrated metasurfaces for highly-collimated terahertz quantum cascade lasers

    Science.gov (United States)

    Liang, Guozhen; Dupont, Emmanuel; Fathololoumi, Saeed; Wasilewski, Zbigniew R.; Ban, Dayan; Liang, Hou Kun; Zhang, Ying; Yu, Siu Fung; Li, Lianhe H.; Davies, Alexander Giles; Linfield, Edmund H.; Liu, Hui Chun; Wang, Qi Jie

    2014-01-01

    We report planar integration of tapered terahertz (THz) frequency quantum cascade lasers (QCLs) with metasurface waveguides that are designed to be spoof surface plasmon (SSP) out-couplers by introducing periodically arranged SSP scatterers. The resulting surface-emitting THz beam profile is highly collimated with a divergence as narrow as ~4° × 10°, which indicates a good waveguiding property of the metasurface waveguide. In addition, the low background THz power implies a high coupling efficiency for the THz radiation from the laser cavity to the metasurface structure. Furthermore, since all the structures are in-plane, this scheme provides a promising platform where well-established surface plasmon/metasurface techniques can be employed to engineer the emitted beam of THz QCLs controllably and flexibly. More importantly, an integrated active THz photonic circuit for sensing and communication applications could be constructed by incorporating other optoelectronic devices such as Schottky diode THz mixers, and graphene modulators and photodetectors. PMID:25403796

  7. Cascade of Quantum Transitions and Magnetocaloric Anomalies in an Open Nanowire

    Science.gov (United States)

    Val'kov, V. V.; Mitskan, V. A.; Shustin, M. S.

    2017-12-01

    A sequence of magnetocaloric anomalies occurring with the change in a magnetic field H is predicted for an open nanowire with the Rashba spin-orbit coupling and the induced superconducting pairing potential. The nature of such anomalies is due to the cascade of quantum transitions related to the successive changes in the fermion parity of the nanowire ground state with the growth of the magnetic field. It is shown that the critical H c values fall within the parameter range corresponding to the nontrivial values of the Z 2 topological invariant of the corresponding 1D band Hamiltonian characteristic of the D symmetry class. It is demonstrated that such features in the behavior of the open nanowire are retained even in the presence of Coulomb interactions.

  8. Quantum cascade laser photoacoustic detection of nitrous oxide released from soils for biofuel production

    Science.gov (United States)

    Couto, F. M.; Sthel, M. S.; Castro, M. P. P.; da Silva, M. G.; Rocha, M. V.; Tavares, J. R.; Veiga, C. F. M.; Vargas, H.

    2014-12-01

    In order to investigate the generation of greenhouse gases in sugarcane ethanol production chain, a comparative study of N2O emission in artificially fertilized soils and soils free from fertilizers was carried out. Photoacoustic spectroscopy using quantum cascade laser with an emission ranging from 7.71 to 7.88 µm and differential photoacoustic cell were applied to detect nitrous oxide (N2O), an important greenhouse gas emitted from soils cultivated with sugar cane. Owing to calibrate the experimental setup, an initial N2O concentration was diluted with pure nitrogen and detection limit of 50 ppbv was achieved. The proposed methodology was selective and sensitive enough to detect N2O from no fertilized and artificially fertilized soils. The measured N2O concentration ranged from ppmv to ppbv.

  9. Active mode-locking of mid-infrared quantum cascade lasers with short gain recovery time.

    Science.gov (United States)

    Wang, Yongrui; Belyanin, Alexey

    2015-02-23

    We investigate the dynamics of actively modulated mid-infrared quantum cascade lasers (QCLs) using space- and time-domain simulations of coupled density matrix and Maxwell equations with resonant tunneling current taken into account. We show that it is possible to achieve active mode locking and stable generation of picosecond pulses in high performance QCLs with a vertical laser transition and a short gain recovery time by bias modulation of a short section of a monolithic Fabry-Perot cavity. In fact, active mode locking in QCLs with a short gain recovery time turns out to be more robust to the variation of parameters as compared to previously studied lasers with a long gain recovery time. We investigate the effects of spatial hole burning and phase locking on the laser output.

  10. Phase Locking of a 2.7 THz Quantum Cascade Laser to a Microwave Reference

    Science.gov (United States)

    Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; Williams, B. S.; Hu, Q.; hide

    2009-01-01

    We demonstrate the phase locking of a 2.7 THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x 12) from a microwave synthesizer at approx. 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.

  11. Injection-locking of terahertz quantum cascade lasers up to 35GHz using RF amplitude modulation.

    Science.gov (United States)

    Gellie, Pierre; Barbieri, Stefano; Lampin, Jean-François; Filloux, Pascal; Manquest, Christophe; Sirtori, Carlo; Sagnes, Isabelle; Khanna, Suraj P; Linfield, Edmund H; Davies, A Giles; Beere, Harvey; Ritchie, David

    2010-09-27

    We demonstrate that the cavity resonance frequency - the round-trip frequency - of Terahertz quantum cascade lasers can be injection-locked by direct modulation of the bias current using an RF source. Metal-metal and single-plasmon waveguide devices with roundtrip frequencies up to 35GHz have been studied, and show locking ranges above 200MHz. Inside this locking range the laser round-trip frequency is phase-locked, with a phase noise determined by the RF-synthesizer. We find a square-root dependence of the locking range with RF-power in agreement with classical injection-locking theory. These results are discussed in the context of mode-locking operation.

  12. Spectrally resolved modal characteristics of leaky-wave-coupled quantum cascade phase-locked laser arrays

    Science.gov (United States)

    Sigler, Chris; Gibson, Ricky; Boyle, Colin; Kirch, Jeremy D.; Lindberg, Donald; Earles, Thomas; Botez, Dan; Mawst, Luke J.; Bedford, Robert

    2018-01-01

    The modal characteristics of nonresonant five-element phase-locked arrays of 4.7-μm emitting quantum cascade lasers (QCLs) have been studied using spectrally resolved near- and far-field measurements and correlated with results of device simulation. Devices are fabricated by a two-step metal-organic chemical vapor deposition process and operate predominantly in an in-phase array mode near threshold, although become multimode at higher drive levels. The wide spectral bandwidth of the QCL's core region is found to be a factor in promoting multispatial-mode operation at high drive levels above threshold. An optimized resonant-array design is identified to allow sole in-phase array-mode operation to high drive levels above threshold, and indicates that for phase-locked laser arrays full spatial coherence to high output powers does not require full temporal coherence.

  13. Extended and quasi-continuous tuning of quantum cascade lasers using superstructure gratings and integrated heaters

    Energy Technology Data Exchange (ETDEWEB)

    Bidaux, Yves, E-mail: yves.bidaux@alpeslasers.ch [Alpes Lasers SA, 1-3 Passsage Max Meuron, CH-2001 Neuchâtel (Switzerland); Institute for Quantum Electronics, ETH-Zurich, CH-8093 Zurich (Switzerland); Bismuto, Alfredo, E-mail: alfredo.bismuto@alpeslasers.ch; Tardy, Camille; Terazzi, Romain; Gresch, Tobias; Blaser, Stéphane; Muller, Antoine [Alpes Lasers SA, 1-3 Passsage Max Meuron, CH-2001 Neuchâtel (Switzerland); Faist, Jerome [Institute for Quantum Electronics, ETH-Zurich, CH-8093 Zurich (Switzerland)

    2015-11-30

    In this work, we demonstrate broad electrical tuning of quantum cascade lasers at 9.25 μm, 8.5 μm, and 4.4 μm in continuous wave operation using Vernier-effect distributed Bragg reflectors based on superstructure gratings. Integrated micro-heaters allow to switch from one Vernier channel to the other, while predictable and mode-hop free tuning can be obtained in each channel modulating the laser current with a side mode suppression ratio as high as 30 dB. The resulting device behaves effectively as a switchable multicolour tunable source. Tuning up to 6.5% of the central wavelength is observed. To prove the importance of the developed devices for high resolution molecular spectroscopy, a N{sub 2}O absorption spectrum has been measured.

  14. Frequency and Phase-lock Control of a 3 THz Quantum Cascade Laser

    Science.gov (United States)

    Betz, A. L.; Boreiko, R. T.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.

    2005-01-01

    We have locked the frequency of a 3 THz quantum cascade laser (QCL) to that of a far-infrared gas laser with a tunable microwave offset frequency. The locked QCL line shape is essentially Gaussian, with linewidths of 65 and 141 kHz at the -3 and -10 dB levels, respectively. The lock condition can be maintained indefinitely, without requiring temperature or bias current regulation of the QCL other than that provided by the lock error signal. The result demonstrates that a terahertz QCL can be frequency controlled with l-part-in-lO(exp 8) accuracy, which is a factor of 100 better than that needed for a local oscillator in a heterodyne receiver for atmospheric and astronomic spectroscopy.

  15. Terahertz imaging using quantum cascade lasers—a review of systems and applications

    International Nuclear Information System (INIS)

    Dean, P; Valavanis, A; Keeley, J; Alhathlool, R; Burnett, A D; Li, L H; Khanna, S P; Indjin, D; Linfield, E H; Davies, A G; Bertling, K; Lim, Y L; Rakić, A D; Taimre, T

    2014-01-01

    The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of THz radiation offering high power, high spectral purity and moderate tunability. As such, these sources are particularly suited to the application of THz frequency imaging across a range of disciplines, and have motivated significant research interest in this area over the past decade. In this paper we review the technological approaches to THz QCL-based imaging and the key advancements within this field. We discuss in detail a number of imaging approaches targeted to application areas including multiple-frequency transmission and diffuse reflection imaging for the spectral mapping of targets; as well as coherent approaches based on the self-mixing phenomenon in THz QCLs for long-range imaging, three-dimensional imaging, materials analysis, and high-resolution inverse synthetic aperture radar imaging. (paper)

  16. Methane concentration and isotopic composition measurements with a mid-infrared quantum-cascade laser

    Science.gov (United States)

    Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.

    1999-01-01

    A quantum-cascade laser operating at a wavelength of 8.1 micrometers was used for high-sensitivity absorption spectroscopy of methane (CH4). The laser frequency was continuously scanned with current over more than 3 cm-1, and absorption spectra of the CH4 nu 4 P branch were recorded. The measured laser linewidth was 50 MHz. A CH4 concentration of 15.6 parts in 10(6) ( ppm) in 50 Torr of air was measured in a 43-cm path length with +/- 0.5-ppm accuracy when the signal was averaged over 400 scans. The minimum detectable absorption in such direct absorption measurements is estimated to be 1.1 x 10(-4). The content of 13CH4 and CH3D species in a CH4 sample was determined.

  17. Detection of acrolein and acrylonitrile with a pulsed room temperature quantum cascade laser

    Science.gov (United States)

    Manne, J.; Jäger, W.; Tulip, J.

    2010-06-01

    We investigated the use of a pulsed, distributed feedback quantum cascade laser centered at 957 cm-1 in combination with an astigmatic Herriot cell with 250 m path length for the detection of acrolein and acrylonitrile. These molecules have been identified as hazardous air-pollutants because of their adverse health effects. The spectrometer utilizes the intra-pulse method, where a linear frequency down-chirp, that is induced when a top-hat current pulse is applied to the laser, is used for sweeping across the absorption line. Up to 450 ns long pulses were used for these measurements which resulted in a spectral window of ~2.2 cm-1. A room temperature mercury-cadmium-telluride detector was used, resulting in a completely cryogen free spectrometer. We demonstrated detection limits of ~3 ppb for acrylonitrile and ~6 ppb for acrolein with ~10 s averaging time. Laser characterization and optimization of the operational parameters for sensitivity improvement are discussed.

  18. Enhanced modeling of band nonparabolicity with application to a mid-IR quantum cascade laser structure

    International Nuclear Information System (INIS)

    Vukovic, N; Radovanovic, J; Milanovic, V

    2014-01-01

    We analyze the influence of conduction-band nonparabolicity on bound electronic states in the active region of a quantum cascade laser (QCL). Our model assumes expansion of the conduction-band dispersion relation up to a fourth order in wavevector and use of a suitable second boundary condition at the interface of two III-V semiconductor layers. Numerical results, obtained by the transfer matrix method, are presented for two mid-infrared GaAs/Al 0.33 Ga 0.67 As QCL active regions, and they are in very good agreement with experimental data found in the literature. Comparison with a different nonparabolicity model is presented for the example of a GaAs/Al 0.38 Ga 0.62 As-based mid-IR QCL. Calculations have also been carried out for one THz QCL structure to illustrate the possible application of the model in the terahertz part of the spectrum. (paper)

  19. Broadband external cavity quantum cascade laser based sensor for gasoline detection

    Science.gov (United States)

    Ding, Junya; He, Tianbo; Zhou, Sheng; Li, Jinsong

    2018-02-01

    A new type of tunable diode spectroscopy sensor based on an external cavity quantum cascade laser (ECQCL) and a quartz crystal tuning fork (QCTF) were used for quantitative analysis of volatile organic compounds. In this work, the sensor system had been tested on different gasoline sample analysis. For signal processing, the self-established interpolation algorithm and multiple linear regression algorithm model were used for quantitative analysis of major volatile organic compounds in gasoline samples. The results were very consistent with that of the standard spectra taken from the Pacific Northwest National Laboratory (PNNL) database. In future, The ECQCL sensor will be used for trace explosive, chemical warfare agent, and toxic industrial chemical detection and spectroscopic analysis, etc.

  20. Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings

    Science.gov (United States)

    Wang, Dong-Bo; Zhang, Jin-Chuan; Cheng, Feng-Min; Zhao, Yue; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

    2018-02-01

    In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al2O3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.

  1. Advances in quantum cascade lasers for security and crime-fighting

    Science.gov (United States)

    Normand, Erwan L.; Stokes, Robert J.; Hay, Kenneth; Foulger, Brian; Lewis, Colin

    2010-10-01

    Advances in the application of Quantum Cascade Lasers (QCL) to trace gas detection will be presented. The solution is real time (~1 μsec per scan), is insensitive to turbulence and vibration, and performs multiple measurements in one sweep. The QCL provides a large dynamic range, which is a linear response from ppt to % level. The concentration can be derived with excellent immunity from cross interference. Point sensing sensors developed by Cascade for home made and commercial explosives operate by monitoring key constituents in real time and matching this to a spatial event (i.e. sniffer device placed close to an object or person walking through portal (overt or covert). Programmable signature detection capability allows for detection of multiple chemical compounds along the most likely array of explosive chemical formulation. The advantages of configuration as "point sensing" or "stand off" will be discussed. In addition to explosives this method is highly applicable to the detection of mobile drugs labs through volatile chemical release.

  2. A novel electrochemical sensor for lead ion based on cascade DNA and quantum dots amplification

    International Nuclear Information System (INIS)

    Tang, Shurong; Lu, Wei; Gu, Fang; Tong, Ping; Yan, Zhiming; Zhang, Lan

    2014-01-01

    A new enzyme-free and ultrasensitive electrochemical Pb 2+ biosensor was developed. By coupling the DNA-assisted cascade of hybridization reaction with the quantum dots (QDs) for signal amplification, a detection limit as low as 6.1 pM can be obtained for Pb 2+ . In this study, the “8-17” DNAzyme was used for specific recognition of Pb 2+ . In the presence of Pb 2+ , the DNAzyme was activated and cleaved the substrate strand. And then, the hybridization between the linker probe and signal probe was initiated, which resulted in formation of a long cascade DNA structure as well as assemble of numerous QDs at last. By the use of magnetic beads, the free signal probe can be easily removed by external magnetic field. After acid lysis, a great amount of redox cations can be released from the QDs and eventually result in significantly amplified electrochemical signals. This method is highly sensitive, selective and simple without the participation of any protein based enzyme (nuclease), thereby holds great potential for real sample analysis

  3. Voltage tunable two-band MIR detection based on Si/SiGe quantum cascade injector structures

    International Nuclear Information System (INIS)

    Grydlik, M.; Rauter, P.; Meduna, M.; Fromherz, T.; Bauer, G.; Falub, C.; Dehlinger, G.; Sigg, H.; Gruetzmacher, D.

    2004-01-01

    We report the results of photocurrent spectroscopy in the mid-infrared (MIR) spectral region performed on p-type Si/SiGe cascade structures. The samples were grown by MBE and consist of a series of five SiGe quantum wells with ground states that can be coupled through thin Si barriers by aligning them in energy with an externally applied electric field E bi . Quantum wells and barriers are Boron doped to a level of 2.5 10 17 cm -3 . Our samples contain 10 sequences of the 5 quantum wells separated by 500 nm thick, undoped Si barriers. Vertical photocurrent spectroscopy has been performed for various electric fields applied perpendicular to the quantum wells at temperatures between 10 K and 100 K. Depending on the direction of the externally applied electric field relative to E bi , the photoresponse of our samples can be switched between two MIR detection bands with maxima at 230 meV and 400 meV. Due to the inversion asymmetry of the samples, at 0 V external voltage the samples deliver a short circuit current in the high-energy spectral band. Since the quantum cascades are formed in the valence band of the Si/SiGe structures, the quantum well transitions responsible for the observed photocurrents are allowed for radiation polarized parallel to the quantum wells. Therefore, these structures appear to be suitable for voltage tuneable MIR detection under normal incident radiation. By comparing the experimental results to model calculations, design strategies to optimize the responsivity of the Si/SiGe cascade structures are discussed. (author)

  4. Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing

    Directory of Open Access Journals (Sweden)

    Simone Borri

    2016-02-01

    Full Text Available The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF2 microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

  5. Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing.

    Science.gov (United States)

    Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

    2016-02-17

    The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF₂ microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

  6. Energy spectrum and thermal properties of a terahertz quantum-cascade laser based on the resonant-phonon depopulation scheme

    Energy Technology Data Exchange (ETDEWEB)

    Khabibullin, R. A., E-mail: khabibullin@isvch.ru; Shchavruk, N. V.; Klochkov, A. N.; Glinskiy, I. A.; Zenchenko, N. V.; Ponomarev, D. S.; Maltsev, P. P. [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation); Zaycev, A. A. [National Research University of Electronic Technology (MIET) (Russian Federation); Zubov, F. I.; Zhukov, A. E.; Cirlin, G. E.; Alferov, Zh. I. [Russian Academy of Sciences, Saint Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation)

    2017-04-15

    The dependences of the electronic-level positions and transition oscillator strengths on an applied electric field are studied for a terahertz quantum-cascade laser (THz QCL) with the resonant-phonon depopulation scheme, based on a cascade consisting of three quantum wells. The electric-field strengths for two characteristic states of the THz QCL under study are calculated: (i) “parasitic” current flow in the structure when the lasing threshold has not yet been reached; (ii) the lasing threshold is reached. Heat-transfer processes in the THz QCL under study are simulated to determine the optimum supply and cooling conditions. The conditions of thermocompression bonding of the laser ridge stripe with an n{sup +}-GaAs conductive substrate based on Au–Au are selected to produce a mechanically stronger contact with a higher thermal conductivity.

  7. Interband cascade light emitting devices based on type-II quantum wells

    International Nuclear Information System (INIS)

    Yang, Rui Q.; Lin, C.H.; Murry, S.J.

    1997-01-01

    The authors discuss physical processes in the newly developed type-II interband cascade light emitting devices, and review their recent progress in the demonstration of the first type-II interband cascade lasers and the observation of interband cascade electroluminescence up to room temperature in a broad mid-infrared wavelength region (extended to 9 μm)

  8. High sensitivity detection of NO2 employing cavity ringdown spectroscopy and an external cavity continuously tunable quantum cascade laser.

    Science.gov (United States)

    Rao, Gottipaty N; Karpf, Andreas

    2010-09-10

    A trace gas sensor for the detection of nitrogen dioxide based on cavity ringdown spectroscopy (CRDS) and a continuous wave external cavity tunable quantum cascade laser operating at room temperature has been designed, and its features and performance characteristics are reported. By measuring the ringdown times of the cavity at different concentrations of NO(2), we report a sensitivity of 1.2 ppb for the detection of NO(2) in Zero Air.

  9. Demonstration of a fully integrated superconducting receiver with a 2.7 THz quantum cascade laser.

    Science.gov (United States)

    Miao, Wei; Lou, Zheng; Xu, Gang-Yi; Hu, Jie; Li, Shao-Liang; Zhang, Wen; Zhou, Kang-Min; Yao, Qi-Jun; Zhang, Kun; Duan, Wen-Ying; Shi, Sheng-Cai; Colombelli, Raffaele; Beere, Harvey E; Ritchie, David A

    2015-02-23

    We demonstrate for the first time the integration of a superconducting hot electron bolometer (HEB) mixer and a quantum cascade laser (QCL) on the same 4-K stage of a single cryostat, which is of particular interest for terahertz (THz) HEB/QCL integrated heterodyne receivers for practical applications. Two key issues are addressed. Firstly, a low power consumption QCL is adopted for preventing its heat dissipation from destroying the HEB's superconductivity. Secondly, a simple spherical lens located on the same 4-K stage is introduced to optimize the coupling between the HEB and the QCL, which has relatively limited output power owing to low input direct current (DC) power. Note that simulation techniques are used to design the HEB/QCL integrated heterodyne receiver to avoid the need for mechanical tuning. The integrated HEB/QCL receiver shows an uncorrected noise temperature of 1500 K at 2.7 THz, which is better than the performance of the same receiver with all the components not integrated.

  10. Power scaling and experimentally fitted model for broad area quantum cascade lasers in continuous wave operation

    Science.gov (United States)

    Suttinger, Matthew; Go, Rowel; Figueiredo, Pedro; Todi, Ankesh; Shu, Hong; Leshin, Jason; Lyakh, Arkadiy

    2018-01-01

    Experimental and model results for 15-stage broad area quantum cascade lasers (QCLs) are presented. Continuous wave (CW) power scaling from 1.62 to 2.34 W has been experimentally demonstrated for 3.15-mm long, high reflection-coated QCLs for an active region width increased from 10 to 20 μm. A semiempirical model for broad area devices operating in CW mode is presented. The model uses measured pulsed transparency current, injection efficiency, waveguide losses, and differential gain as input parameters. It also takes into account active region self-heating and sublinearity of pulsed power versus current laser characteristic. The model predicts that an 11% improvement in maximum CW power and increased wall-plug efficiency can be achieved from 3.15 mm×25 μm devices with 21 stages of the same design, but half doping in the active region. For a 16-stage design with a reduced stage thickness of 300 Å, pulsed rollover current density of 6 kA/cm2, and InGaAs waveguide layers, an optical power increase of 41% is projected. Finally, the model projects that power level can be increased to ˜4.5 W from 3.15 mm×31 μm devices with the baseline configuration with T0 increased from 140 K for the present design to 250 K.

  11. High-Resolution Infrared Spectroscopy of Imidazole Clusters in Helium Droplets Using Quantum Cascade Lasers

    Science.gov (United States)

    Mani, Devendra; Can, Cihad; Pal, Nitish; Schwaab, Gerhard; Havenith, Martina

    2017-06-01

    Imidazole ring is a part of many biologically important molecules and drugs. Imidazole monomer, dimer and its complexes with water have earlier been studied using infrared spectroscopy in helium droplets^{1,2} and molecular beams^{3}. These studies were focussed on the N-H and O-H stretch regions, covering the spectral region of 3200-3800 \\wn. We have extended the studies on imidazole clusters into the ring vibration region. The imidazole clusters were isolated in helium droplets and were probed using a combination of infrared spectroscopy and mass spectrometry. The spectra in the region of 1000-1100 \\wn and 1300-1460 \\wn were recorded using quantum cascade lasers. Some of the observed bands could be assigned to imidazole monomer and higher order imidazole clusters, using pickup curve analysis and ab initio calculations. Work is still in progress. The results will be discussed in detail in the talk. References: 1) M.Y. Choi and R.E. Miller, J. Phys. Chem. A, 110, 9344 (2006). 2) M.Y. Choi and R.E. Miller, Chem. Phys. Lett., 477, 276 (2009). 3) J. Zischang, J. J. Lee and M. Suhm, J. Chem. Phys., 135, 061102 (2011). Note: This work was supported by the Cluster of Excellence RESOLV (Ruhr-Universitat EXC1069) funded by the Deutsche Forschungsgemeinschaft.

  12. Towards a continuous glucose monitoring system using tunable quantum cascade lasers

    Science.gov (United States)

    Haase, Katharina; Müller, Niklas; Petrich, Wolfgang

    2018-02-01

    We present a reagent-free approach for long-term continuous glucose monitoring (cgm) of liquid samples using midinfrared absorption spectroscopy. This method could constitute an alternative to enzymatic glucose sensors in order to manage the widespread disease of Diabetes. In order to acquire spectra of the liquid specimen, we use a spectrally tunable external-cavity (EC-) quantum cascade laser (QCL) as radiation source in combination with a fiber-based in vitro sensor setup. Hereby we achieve a glucose sensitivity in pure glucose solutions of 3 mg/dL (RMSEP). Furthermore, the spectral tunability of the EC-QCL enables us to discriminate glucose from other molecules. We exemplify this by detecting glucose among other saccharides with an accuracy of 8 mg/dL (within other monosaccharides, RMSEVC) and 14 mg/dL (within other mono- and disaccharides, RMSECV). Moreover, we demonstrate a characterization of the significance of each wavenumber for an accurate prediction of glucose among other saccharides using an evolutionary algorithm. We show, that by picking 10 distinct wavenumbers we can achieve comparable accuracies to the use of a complete spectrum.

  13. Theoretical investigation of injection-locked high modulation bandwidth quantum cascade lasers.

    Science.gov (United States)

    Meng, Bo; Wang, Qi Jie

    2012-01-16

    In this study, we report for the first time to our knowledge theoretical investigation of modulation responses of injection-locked mid-infrared quantum cascade lasers (QCLs) at wavelengths of 4.6 μm and 9 μm, respectively. It is shown through a three-level rate equations model that the direct intensity modulation of QCLs gives the maximum modulation bandwidths of ~7 GHz at 4.6 μm and ~20 GHz at 9 μm. By applying the injection locking scheme, we find that the modulation bandwidths of up to ~30 GHz and ~70 GHz can be achieved for QCLs at 4.6 μm and 9 μm, respectively, with an injection ratio of 5 dB. The result also shows that an ultrawide modulation bandwidth of more than 200 GHz is possible with a 10 dB injection ratio for QCLs at 9 μm. An important characteristic of injection-locked QCLs is the nonexistence of unstable locking region in the locking map, in contrast to their diode laser counterparts. We attribute this to the ultra-short upper laser state lifetimes of QCLs.

  14. Cavity-enhanced quantum-cascade laser-based instrument for carbon monoxide measurements.

    Science.gov (United States)

    Provencal, Robert; Gupta, Manish; Owano, Thomas G; Baer, Douglas S; Ricci, Kenneth N; O'Keefe, Anthony; Podolske, James R

    2005-11-01

    An autonomous instrument based on off-axis integrated cavity output spectroscopy has been developed and successfully deployed for measurements of carbon monoxide in the troposphere and tropopause onboard a NASA DC-8 aircraft. The instrument (Carbon Monoxide Gas Analyzer) consists of a measurement cell comprised of two high-reflectivity mirrors, a continuous-wave quantum-cascade laser, gas sampling system, control and data-acquisition electronics, and data-analysis software. CO measurements were determined from high-resolution CO absorption line shapes obtained by tuning the laser wavelength over the R(7) transition of the fundamental vibration band near 2172.8 cm(-1). The instrument reports CO mixing ratio (mole fraction) at a 1-Hz rate based on measured absorption, gas temperature, and pressure using Beer's Law. During several flights in May-June 2004 and January 2005 that reached altitudes of 41,000 ft (12.5 km), the instrument recorded CO values with a precision of 0.2 ppbv (1-s averaging time) and an accuracy limited by the reference CO gas cylinder (uncertainty < 1.0%). Despite moderate turbulence and measurements of particulate-laden airflows, the instrument operated consistently and did not require any maintenance, mirror cleaning, or optical realignment during the flights.

  15. An experimental study of noise in mid-infrared quantum cascade lasers of different designs

    Science.gov (United States)

    Schilt, Stéphane; Tombez, Lionel; Tardy, Camille; Bismuto, Alfredo; Blaser, Stéphane; Maulini, Richard; Terazzi, Romain; Rochat, Michel; Südmeyer, Thomas

    2015-04-01

    We present an experimental study of noise in mid-infrared quantum cascade lasers (QCLs) of different designs. By quantifying the high degree of correlation occurring between fluctuations of the optical frequency and voltage between the QCL terminals, we show that electrical noise is a powerful and simple mean to study noise in QCLs. Based on this outcome, we investigated the electrical noise in a large set of 22 QCLs emitting in the range of 7.6-8 μm and consisting of both ridge-waveguide and buried-heterostructure (BH) lasers with different geometrical designs and operation parameters. From a statistical data processing based on an analysis of variance, we assessed that ridge-waveguide lasers have a lower noise than BH lasers. Our physical interpretation is that additional current leakages or spare injection channels occur at the interface between the active region and the lateral insulator in the BH geometry, which induces some extra noise. In addition, Schottky-type contacts occurring at the interface between the n-doped regions and the lateral insulator, i.e., iron-doped InP, are also believed to be a potential source of additional noise in some BH lasers, as observed from the slight reduction in the integrated voltage noise observed at the laser threshold in several BH-QCLs.

  16. Frequency stabilization of quantum cascade laser for spectroscopic CO2 isotope analysis

    Science.gov (United States)

    Han, Luo; Xia, Hua; Pang, Tao; Zhang, Zhirong; Wu, Bian; Liu, Shuo; Sun, Pengshuai; Cui, Xiaojuan; Wang, Yu; Sigrist, Markus W.; Dong, Fengzhong

    2018-06-01

    Using off-axis integrated cavity output spectroscopy, named OA-ICOS, the absorption spectrum of CO2 at 4.32 μm is recorded by using a quantum cascade laser (QCL). The concentration of the three isotopologues 16O12C16O, 16O13C16O and 16O12C18O is detected simultaneously. The isotope abundance ratio of 13C and 18O in CO2 gas can be obtained, which is most useful for ecological research. Since the ambient temperature has a serious influence on the output wavelength of the laser, even small temperature variations seriously affect the stability and sensitivity of the system. In this paper, a wavelength locking technique for QCL is proposed. The output of a digital potentiometer integrated in the laser current driver control is modified by software, resulting in a correction of the driving current of the laser and thus of its wavelength. This method strongly reduces the influence of external factors on the wavelength drift of lasers and thus substantially improves the stability and performance of OA-ICOS as is demonstrated with long-time measurements on CO2 in laboratory air.

  17. Dual-wavelength DFB quantum cascade lasers: sources for multi-species trace gas spectroscopy

    Science.gov (United States)

    Kapsalidis, Filippos; Shahmohammadi, Mehran; Süess, Martin J.; Wolf, Johanna M.; Gini, Emilio; Beck, Mattias; Hundt, Morten; Tuzson, Béla; Emmenegger, Lukas; Faist, Jérôme

    2018-06-01

    We report on the design, fabrication, and performance of dual-wavelength distributed-feedback (DFB) quantum cascade lasers (QCLs) emitting at several wavelengths in the mid-infrared (mid-IR) spectrum. In this work, two new designs are presented: for the first one, called "Neighbour" DFB, two single-mode DFB QCLs are fabricated next to each other, with minimal lateral distance, to allow efficient beam-coupling into multi-pass gas cells. In addition, the minimal distance allows either laser to be used as an integrated heater for the other, allowing to extend the tuning range of its neighbour without any electrical cross-talk. For the second design, the Vernier effect was used to realize a switchable DFB laser, with two target wavelengths which are distant by about 300 cm^{-1}. These devices are promising laser sources for Tunable Diode Laser Absorption Spectroscopy applications targeting simultaneous detection of multiple gasses, with distant spectral features, in compact and mobile setups.

  18. Electrically-driven pure amplitude and frequency modulation in a quantum cascade laser.

    Science.gov (United States)

    Shehzad, Atif; Brochard, Pierre; Matthey, Renaud; Blaser, Stéphane; Gresch, Tobias; Maulini, Richard; Muller, Antoine; Südmeyer, Thomas; Schilt, Stéphane

    2018-04-30

    We present pure amplitude modulation (AM) and frequency modulation (FM) achieved electrically in a quantum cascade laser (QCL) equipped with an integrated resistive heater (IH). The QCL output power scales linearly with the current applied to the active region (AR), but decreases with the IH current, while the emission frequency decreases with both currents. Hence, a simultaneous modulation applied to the current of the AR and IH sections with a proper relative amplitude and phase can suppress the AM, resulting in a pure FM, or vice-versa. The adequate modulation parameters depend on the applied modulation frequency. Therefore, they were first determined from the individual measurements of the AM and FM transfer functions obtained for a modulation applied to the current of the AR or IH section, respectively. By optimizing the parameters of the two modulations, we demonstrate a reduction of the spurious AM or FM by almost two orders of magnitude at characteristic frequencies of 1 and 10 kHz compared to the use of the AR current only.

  19. Homogeneous spectral broadening of pulsed terahertz quantum cascade lasers by radio frequency modulation.

    Science.gov (United States)

    Wan, W J; Li, H; Cao, J C

    2018-01-22

    The authors present an experimental investigation of radio frequency modulation on pulsed terahertz quantum cascade lasers (QCLs) emitting around 4.3 THz. The QCL chip used in this work is based on a resonant phonon design which is able to generate a 1.2 W peak power at 10 K from a 400-µm-wide and 4-mm-long laser with a single plasmon waveguide. To enhance the radio frequency modulation efficiency and significantly broaden the terahertz spectra, the QCLs are also processed into a double-metal waveguide geometry with a Silicon lens out-coupler to improve the far-field beam quality. The measured beam patterns of the double-metal QCL show a record low divergence of 2.6° in vertical direction and 2.4° in horizontal direction. Finally we perform the inter-mode beat note and terahertz spectra measurements for both single plasmon and double-metal QCLs working in pulsed mode. Since the double-metal waveguide is more suitable for microwave signal transmission, the radio frequency modulation shows stronger effects on the spectral broadening for the double-metal QCL. Although we are not able to achieve comb operation in this work for the pulsed lasers due to the large phase noise, the homogeneous spectral broadening resulted from the radio frequency modulation can be potentially used for spectroscopic applications.

  20. Development of a diamond waveguide sensor for sensitive protein analysis using IR quantum cascade lasers

    Science.gov (United States)

    Piron, P.; Vargas Catalan, E.; Haas, J.; Österlund, L.; Nikolajeff, F.; Andersson, P. O.; Bergström, J.; Mizaikoff, B.; Karlsson, M.

    2018-02-01

    Microfabricated diamond waveguides, between 5 and 20 μm thick, manufactured by chemical vapor deposition of diamond, followed by standard lithographic techniques and inductively coupled plasma etching of diamond, are used as bio-chemical sensors in the mid infrared domain: 5-11 μm. Infrared light, emitted from a broadly tunable quantum cascade laser with a wavelength resolution smaller than 20 nm, is coupled through the diamond waveguides for attenuated total reflection spectroscopy. The expected advantages of these waveguides are a high sensitivity due to the high number of internal reflections along the propagation direction, a high transmittance in the mid-IR domain, the bio-compatibility of diamond and the possibility of functionalizing the surface layer. The sensor will be used for analyzing different forms of proteins such as α-synuclein which is relevant in understanding the mechanism behind Parkinson's disease. The fabrication process of the waveguide, its characteristics and several geometries are introduced. The optical setup of the biosensor is described and our first measurements on two analytes to demonstrate the principle of the sensing method will be presented. Future use of this sensor includes the functionalization of the diamond waveguide sensor surface to be able to fish out alpha-synuclein from cerebrospinal fluid.

  1. Room temperature negative differential resistance in terahertz quantum cascade laser structures

    Energy Technology Data Exchange (ETDEWEB)

    Albo, Asaf, E-mail: asafalbo@gmail.com; Hu, Qing [Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Reno, John L. [Center for Integrated Nanotechnologies, Sandia National Laboratories, MS 1303, Albuquerque, New Mexico 87185-1303 (United States)

    2016-08-22

    The mechanisms that limit the temperature performance of GaAs/Al{sub 0.15}GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding, we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. This result is a strong evidence for the effective suppression of the aforementioned leakage channel.

  2. Sensitive detection of acrolein and acrylonitrile with a pulsed quantum-cascade laser

    Science.gov (United States)

    Manne, J.; Lim, A.; Tulip, J.; Jäger, W.

    2012-05-01

    We report on spectroscopic measurements of acrolein and acrylonitrile at atmospheric pressure using a pulsed distributed feedback quantum-cascade laser in combination with intra- and inter-pulse techniques and compare the results. The measurements were done in the frequency region around 957 cm-1. In the inter-pulse technique, the laser is excited with short current pulses (5-10 ns), and the pulse amplitude is modulated with an external current ramp resulting in a ˜2.3 cm-1 frequency scan. In the intra-pulse technique, a linear frequency down-chirp during the pulse is used for sweeping across the absorption line. Long current pulses up to 500 ns were used for these measurements which resulted in a spectral window of ˜2.2 cm-1 during the down-chirp. These comparatively wide spectral windows facilitated the measurements of the relatively broad absorption lines (˜1 cm-1) of acrolein and acrylonitrile. The use of a room-temperature mercury-cadmium-telluride detector resulted in a completely cryogen-free spectrometer. We demonstrate ppb level detection limits within a data acquisition time of ˜10 s with these methodologies.

  3. Multipurpose terahertz quantum cascade laser based system for industrial, environmental and meteorological applications

    International Nuclear Information System (INIS)

    Taslakov, M; Simeonov, V; Bergh, H van den

    2008-01-01

    A portable system, based on a pulsed quantum cascade laser (QCL) is developed. The QCL operates at near to ambient temperature in a pulsed mode with relatively long pulse duration in the range of 200 - 500 ns. The system design is flexible, allowing its use for a number of open path or cell-internal applications. Due to the so called fingerprint spectral region, high haze and turbulence immunity and low beam divergence, this system can be used in various applications. The first group includes environmental monitoring of a number of trace gases as CH 4 , NH 3 , CO, O 3 , CO 2 , HNO 3 , hydrocarbons and many others. The meteorological applications include measuring the average humidity and temperature. Industrial surveillance control is another important application. Remote measurement of some physical parameters, as temperature or pressure, as well as for interferometric measurements are also possible. Space resolved study of air turbulence even in fog is another promising application. Security, speed control, open path data transfer and remote readout of information are but a few other real applications of our QCL based portable system

  4. Standoff detection of turbulent chemical mixture plumes using a swept external cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C. [Pacific Northwest National Laboratory, Richland, Washington; Brumfield, Brian E. [Pacific Northwest National Laboratory, Richland, Washington

    2017-08-21

    We demonstrate standoff detection of turbulent mixed-chemical plumes using a broadly-tunable external cavity quantum cascade laser (ECQCL). The ECQCL was directed through plumes of mixed methanol/ethanol vapor to a partially-reflective surface located 10 m away. The reflected power was measured as the ECQCL was swept over its tuning range of 930-1065 cm-1 (9.4-10.8 µm) at rates up to 200 Hz. Analysis of the transmission spectra though the plume was performed to determine chemical concentrations with time resolution of 0.005 s. Comparison of multiple spectral sweep rates of 2 Hz, 20 Hz, and 200 Hz shows that higher sweep rates reduce effects of atmospheric and source turbulence, resulting in lower detection noise and more accurate measurement of the rapidly-changing chemical concentrations. Detection sensitivities of 0.13 ppm*m for MeOH and 1.2 ppm*m for EtOH are demonstrated for a 200 Hz spectral sweep rate, normalized to 1 s detection time.

  5. Study of the exhaled acetone in type 1 diabetes using quantum cascade laser spectroscopy.

    Science.gov (United States)

    Reyes-Reyes, Adonis; Horsten, Roland C; Urbach, H Paul; Bhattacharya, Nandini

    2015-01-06

    The acetone concentration exhaled in the breath of three type 1 diabetes patients (two minors and one adult) and one healthy volunteer is studied using a quantum cascade laser-based spectroscopic system. Using the acetone signature between 1150 and 1250 cm(-1) and a multiline fitting method, the concentration variations on the order of parts per billion by volume were measured. Blood glucose and ketone concentrations in blood measurements were performed simultaneously to study their relation with acetone in exhaled breath. We focus on personalized studies to better understand the role of acetone in diabetes. For each volunteer, we performed a series of measurements over a period of time, including overnight fastings of 11 ± 1 h and during ketosis-hyperglycemia events for the minors. Our results highlight the importance of performing personalized studies because the response of the minors to the presence of ketosis was consistent but unique for each individual. Also, our results emphasize the need for performing more studies with T1D minors, because the acetone concentration in the breath of the minors differs, with respect to those reported in the literature, which are based on adults.

  6. Widely tunable Sampled Grating Distributed Bragg Reflector Quantum Cascade laser for gas spectroscopy applications

    Science.gov (United States)

    Diba, Abdou Salam

    Since the advent of semiconductor lasers, the development of tunable laser sources has been subject of many efforts in industry and academia arenas. This interest towards broadly tunable lasers is mainly due to the great promise they have in many applications ranging from telecommunication, to environmental science and homeland security, just to name a few. After the first demonstration of quantum cascade laser (QCL) in the early nineties, QCL has experienced a rapid development, so much so that QCLs are now the most reliable and efficient laser source in the Mid-IR range covering between 3 microm to 30 microm region of the electromagnetic spectrum. QCLs have almost all the desirable characteristics of a laser for spectroscopy applications such as narrow spectral linewidth ideal for high selectivity measurement, high power enabling high sensitivity sensing and more importantly they emit in the finger-print region of most of the trace gases and large molecules. The need for widely tunable QCLs is now more pressing than ever before. A single mode quantum cascade laser (QCL) such as a distributed feedback (DFB) QCL, is an ideal light source for gas sensing in the MIR wavelength range. Despite their performance and reliability, DFB QCLs are limited by their relatively narrow wavelength tuning range determined by the thermal rollover of the laser. An external cavity (EC) QCL, on the other hand, is a widely tunable laser source, and so far is the choice mid-infrared single frequency light sources for detecting multiple species/large molecules. However, EC QCLs can be complex, bulky and expensive. In the quest for finding alternative broadly wavelength tunable sources in the mid-infrared, many monolithic tunable QCLs are recently proposed and fabricated, including SG-DBR, DFB-Arrays, Slot-hole etc. and they are all of potentially of interest as a candidate for multi-gas sensing and monitoring applications, due to their large tuning range (>50 cm-1), and potentially low

  7. Real time detection of exhaled human breath using quantum cascade laser based sensor technology

    Science.gov (United States)

    Tittel, Frank K.; Lewicki, Rafal; Dong, Lei; Liu, Kun; Risby, Terence H.; Solga, Steven; Schwartz, Tim

    2012-02-01

    The development and performance of a cw, TE-cooled DFB quantum cascade laser based sensor for quantitative measurements of ammonia (NH3) and nitric oxide (NO) concentrations present in exhaled breath will be reported. Human breath contains ~ 500 different chemical species, usually at ultra low concentration levels, which can serve as biomarkers for the identification and monitoring of human diseases or wellness states. By monitoring NH3 concentration levels in exhaled breath a fast, non-invasive diagnostic method for treatment of patients with liver and kidney disorders, is feasible. The NH3 concentration measurements were performed with a 2f wavelength modulation quartz enhanced photoacoustic spectroscopy (QEPAS) technique, which is suitable for real time breath measurements, due to the fast gas exchange inside a compact QEPAS gas cell. A Hamamatsu air-cooled high heat load (HHL) packaged CW DFB-QCL is operated at 17.5°C, targeting the optimum interference free NH3 absorption line at 967.35 cm-1 (λ~10.34 μm), with ~ 20 mW of optical power. The sensor architecture includes a reference cell, filled with a 2000 ppmv NH3 :N2 mixture at 130 Torr, which is used for absorption line-locking. A minimum detection limit (1σ) for the line locked NH3 sensor is ~ 6 ppbv (with a 1σ 1 sec time resolution of the control electronics). This NH3 sensor was installed in late 2010 and is being clinically tested at St. Luke's Hospital in Bethlehem, PA.

  8. Resonant tunneling diodes based on ZnO for quantum cascade structures (Conference Presentation)

    Science.gov (United States)

    Hinkov, Borislav; Schwarz, Benedikt; Harrer, Andreas; Ristanic, Daniela; Schrenk, Werner; Hugues, Maxime; Chauveau, Jean-Michel; Strasser, Gottfried

    2017-02-01

    The terahertz (THz) spectral range (lambda 30µm - 300µm) is also known as the "THz-gap" because of the lack of compact semiconductor devices. Various real-world applications would strongly benefit from such sources like trace-gas spectroscopy or security-screening. A crucial step is the operation of THz-emitting lasers at room temperature. But this seems out of reach with current devices, of which GaAs-based quantum cascade lasers (QCLs) seem to be the most promising ones. They are limited by the parasitic, non-optical LO-phonon transitions (36meV in GaAs), being on the same order as the thermal energy at room temperature (kT = 26meV). This can be solved by using larger LO-phonon materials like ZnO (E_LO = 72meV). But to master the fabrication of ZnO-based QC structures, a high quality epitaxial growth is crucial followed by a well-controlled fabrication process including ZnO/ZnMgO etching. We use devices grown on m-plane ZnO-substrate by molecular beam epitaxy. They are patterned by reactive ion etching in a CH4-based chemistry (CH4:H2:Ar/30:3:3 sccm) into 50μm to 150μm square mesas. Resonant tunneling diode structures are investigated in this geometry and are presented including different barrier- and well-configurations. We extract contact resistances of 8e-5 Omega cm^2 for un-annealed Ti/Au contacts and an electron mobility of above 130cm^2/Vs, both in good agreement with literature. Proving that resonant electron tunneling can be achieved in ZnO is one of the crucial building blocks of a QCL. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 665107.

  9. Applications of a Mid-IR Quantum Cascade Laser in Gas Sensing Research

    KAUST Repository

    Sajid, Muhammad Bilal

    2015-05-01

    Laser absorption based sensors are extensively used in a variety of gas sensing areas such as combustion, atmospheric research, human breath analysis, and high resolution infrared spectroscopy. Quantum cascade lasers have recently emerged as high resolution, high power laser sources operating in mid infrared region and can have wide tunability range. These devices provide an opportunity to access stronger fundamental and combination vibrational bands located in mid infrared region than previously accessible weaker overtone vibrational bands located in near infrared region. Spectroscopic region near 8 µm contains strong vibrational bands of methane, acetylene, hydrogen peroxide, water vapor and nitrous oxide. These molecules have important applications in a wide range of applications. This thesis presents studies pertaining to spectroscopy and combustion applications. Advancements in combustion research are imperative to achieve lower emissions and higher efficiency in practical combustion devices such as gas turbines and engines. Accurate chemical kinetic models are critical to achieve predictive models which contain several thousand reactions and hundreds of species. These models need highly reliable experimental data for validation and improvements. Shock tubes are ideal devices to obtain such information. A shock tube is a homogenous, nearly constant volume, constant pressure, adiabatic and 0-D reactor. In combination with laser absorption sensors, shock tubes can be used to measure reaction rates and species time histories of several intermediates and products formed during pyrolysis and oxidation of fuels. This work describes measurement of the decomposition rate of hydrogen peroxide which is an important intermediate species controlling reactivity of combustion system in the intermediate temperature range. Spectroscopic parameters (linestrengths, broadening coefficients and temperature dependent coefficients) are determined for various transitions of

  10. Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

    Directory of Open Access Journals (Sweden)

    K. Gerdel

    2017-09-01

    Full Text Available The trace gas carbonyl sulfide (COS has lately received growing interest from the eddy covariance (EC community due to its potential to serve as an independent approach for constraining gross primary production and canopy stomatal conductance. Thanks to recent developments of fast-response high-precision trace gas analysers (e.g. quantum cascade laser absorption spectrometers, QCLAS, a handful of EC COS flux measurements have been published since 2013. To date, however, a thorough methodological characterisation of QCLAS with regard to the requirements of the EC technique and the necessary processing steps has not been conducted. The objective of this study is to present a detailed characterisation of the COS measurement with the Aerodyne QCLAS in the context of the EC technique and to recommend best EC processing practices for those measurements. Data were collected from May to October 2015 at a temperate mountain grassland in Tyrol, Austria. Analysis of the Allan variance of high-frequency concentration measurements revealed the occurrence of sensor drift under field conditions after an averaging time of around 50 s. We thus explored the use of two high-pass filtering approaches (linear detrending and recursive filtering as opposed to block averaging and linear interpolation of regular background measurements for covariance computation. Experimental low-pass filtering correction factors were derived from a detailed cospectral analysis. The CO2 and H2O flux measurements obtained with the QCLAS were compared with those obtained with a closed-path infrared gas analyser. Overall, our results suggest small, but systematic differences between the various high-pass filtering scenarios with regard to the fraction of data retained in the quality control and flux magnitudes. When COS and CO2 fluxes are combined in the ecosystem relative uptake rate, systematic differences between the high-pass filtering scenarios largely cancel out, suggesting that

  11. Eddy covariance carbonyl sulphide flux measurements with a quantum cascade laser absorption spectrometer.

    Science.gov (United States)

    Gerdel, Katharina; Spielmann, Felix Maximilian; Hammerle, Albin; Wohlfahrt, Georg

    2017-09-26

    The trace gas carbonyl sulphide (COS) has lately received growing interest in the eddy covariance (EC) community due to its potential to serve as an independent approach for constraining gross primary production and canopy stomatal conductance. Thanks to recent developments of fast-response high-precision trace gas analysers (e.g. quantum cascade laser absorption spectrometers (QCLAS)), a handful of EC COS flux measurements have been published since 2013. To date, however, a thorough methodological characterisation of QCLAS with regard to the requirements of the EC technique and the necessary processing steps has not been conducted. The objective of this study is to present a detailed characterization of the COS measurement with the Aerodyne QCLAS in the context of the EC technique, and to recommend best EC processing practices for those measurements. Data were collected from May to October 2015 at a temperate mountain grassland in Tyrol, Austria. Analysis of the Allan variance of high-frequency concentration measurements revealed sensor drift to occur under field conditions after an averaging time of around 50 s. We thus explored the use of two high-pass filtering approaches (linear detrending and recursive filtering) as opposed to block averaging and linear interpolation of regular background measurements for covariance computation. Experimental low-pass filtering correction factors were derived from a detailed cospectral analysis. The CO 2 and H 2 O flux measurements obtained with the QCLAS were compared against those obtained with a closed-path infrared gas analyser. Overall, our results suggest small, but systematic differences between the various high-pass filtering scenarios with regard to the fraction of data retained in the quality control and flux magnitudes. When COS and CO 2 fluxes are combined in the so-called ecosystem relative uptake rate, systematic differences between the high-pass filtering scenarios largely cancel out, suggesting that this

  12. Mid-infrared studies of GaAs/AlGaAs quantum cascade structures

    International Nuclear Information System (INIS)

    Keightley, Peter Thomas

    2001-01-01

    This thesis describes an investigation of GaAs/AIGaAs Quantum Cascade (QC) structures. Mid-infrared spectroscopic techniques are employed to study several QC LED and laser structures, in order to investigate the fundamental principles underlying the operation of these state of the art devices. The results presented in this thesis include the demonstration of intersubband lasing in a GaAs/AIGaAs QC laser, which closely followed the first report of QC lasing using this materials system in 1998, and form a basis from which further research into QC lasers can be built upon. Initially, a spectroscopic investigation of several QC LEDs is presented, beginning with a comparison of the performance of two designs incorporating an active region based on a diagonal transition. These devices have single quantum well (SQW), or multi-quantum well (MQW) bridging regions and are investigated using intersubband electroluminescence (EL) spectroscopy. It is found that although growth and design are simplified by the use of a SQW bridging region, superior performance is obtained by the use of MQW bridging regions, intersubband EL and photocurrent (PC) spectroscopy are employed to study the operating characteristics of a QC LED incorporating a graded superlattice active region. EL is observed at 9 and 11μm arising from interminiband radiative transitions. Complementary intersubband and interband spectroscopic techniques have been employed to study the evolution of the electron distribution within a QC LED, with increasing bias. Below the device turn on, the transfer of electrons from the donors to the active region ground state is observed. As the bias is increased the redistribution of electrons through the bridging region is observed, in conjunction with an alignment of energy levels within the structure, close to the operating bias. Intersubband lasing has been demonstrated from a GaAs/AIGaAs QC laser at λ∼9μm. Reciprocal gain measurements have been performed to determine the

  13. Detection of benzene and toluene gases using a midinfrared continuous-wave external cavity quantum cascade laser at atmospheric pressure.

    Science.gov (United States)

    Sydoryk, Ihor; Lim, Alan; Jäger, Wolfgang; Tulip, John; Parsons, Matthew T

    2010-02-20

    We demonstrate the application of a commercially available widely tunable continuous-wave external cavity quantum cascade laser as a spectroscopic source for the simultaneous detection of multiple gases. We measured broad absorption features of benzene and toluene between 1012 and 1063 cm(-1) (9.88 and 9.41 microm) at atmospheric pressure using an astigmatic Herriott multipass cell. Our results show experimental detection limits of 0.26 and 0.41 ppm for benzene and toluene, respectively, with a 100 m path length for these two gases.

  14. Quantum cascade laser-based analyzer for hydrogen sulfide detection at sub-parts-per-million levels

    Science.gov (United States)

    Nikodem, Michal; Krzempek, Karol; Stachowiak, Dorota; Wysocki, Gerard

    2018-01-01

    Due to its high toxicity, monitoring of hydrogen sulfide (H2S) concentration is essential in many industrial sites (such as natural gas extraction sites, petroleum refineries, geothermal power plants, or waste water treatment facilities), which require sub-parts-per-million sensitivities. We report on a quantum cascade laser-based spectroscopic system for detection of H2S in the midinfrared at ˜7.2 μm. We present a sensor design utilizing Herriott multipass cell and a wavelength modulation spectroscopy to achieve a detection limit of 140 parts per billion for 1-s integration time.

  15. Non-equilibrium Green's function calculation for GaN-based terahertz-quantum cascade laser structures

    Science.gov (United States)

    Yasuda, H.; Kubis, T.; Hosako, I.; Hirakawa, K.

    2012-04-01

    We theoretically investigated GaN-based resonant phonon terahertz-quantum cascade laser (QCL) structures for possible high-temperature operation by using the non-equilibrium Green's function method. It was found that the GaN-based THz-QCL structures do not necessarily have a gain sufficient for lasing, even though the thermal backfilling and the thermally activated phonon scattering are effectively suppressed. The main reason for this is the broadening of the subband levels caused by a very strong interaction between electrons and longitudinal optical (LO) phonons in GaN.

  16. A Study of Residual Amplitude Modulation Suppression in Injection Locked Quantum Cascade Lasers Based on a Simplified Rate Equation Model

    International Nuclear Information System (INIS)

    Webb, J F; Yong, K S C; Haldar, M K

    2015-01-01

    Using results that come out of a simplified rate equation model, the suppression of residual amplitude modulation in injection locked quantum cascade lasers with the master laser modulated by its drive current is investigated. Quasi-static and dynamic expressions for intensity modulation are used. The suppression peaks at a specific value of the injection ratio for a given detuning and linewidth enhancement factor. The intensity modulation suppression remains constant over a range of frequencies. The effects of injection ratio, detuning, coupling efficiency and linewidth enhancement factor are considered. (paper)

  17. Reversible switching of quantum cascade laser-modes using a pH-responsive polymeric cladding as transducer.

    Science.gov (United States)

    Basnar, Bernhard; Schartner, Stephan; Austerer, Maximilian; Andrews, Aaron Maxwell; Roch, Tomas; Schrenk, Werner; Strasser, Gottfried

    2008-06-09

    We present a novel approach for the reversible switching of the emission wavelength of a quantum cascade laser (QCL) using a halochromic cladding. An air-waveguide laser ridge is coated with a thin layer of polyacrylic acid. This cladding introduces losses corresponding to the absorption spectrum of the polymer. By changing the state of the polymer, the absorption spectrum and losses change, inducing a shift of 7 cm(-1) in the emission wavelength. This change is induced by exposure to acidic or alkaline vapors under ambient conditions and is fully reversible. Such lasers can be used as multi-color light source and as sensor for atmospheric pH.

  18. A field-deployable compound-specific isotope analyzer based on quantum cascade laser and hollow waveguide

    Science.gov (United States)

    Wu, Sheng; Deev, Andrei

    2013-01-01

    A field deployable Compound Specific Isotope Analyzer (CSIA) coupled with capillary chromatogrpahy based on Quantum Cascade (QC) lasers and Hollow Waveguide (HWG) with precision and chemical resolution matching mature Mass Spectroscopy has been achieved in our laboratory. The system could realize 0.3 per mil accuracy for 12C/13C for a Gas Chromatography (GC) peak lasting as short as 5 seconds with carbon molar concentration in the GC peak less than 0.5%. Spectroscopic advantages of HWG when working with QC lasers, i.e. single mode transmission, noiseless measurement and small sample volume, are compared with traditional free space and multipass spectroscopy methods.

  19. First quantitative measurements by IR spectroscopy of dioxins and furans by means of broadly tunable quantum cascade lasers

    International Nuclear Information System (INIS)

    Siciliani de Cumis, M; D’Amato, F; Viciani, S; Patrizi, B; Foggi, P; Galea, C L

    2013-01-01

    We demonstrate the possibility of a quantitative analysis of the concentration of several dioxins and furans, among the most toxic ones, by only using infrared absorption laser spectroscopy. Two broadly tunable quantum cascade lasers, emitting in the mid-infrared, have been used to measure the absorption spectra of dioxins and furans, dissolved in CCl 4 , in direct absorption mode. The minimum detectable concentrations are inferred by analyzing diluted samples. A comparison between this technique and standard Fourier transform spectroscopy has been carried out and an analysis of future perspectives is reported. (paper)

  20. Implementation of an integrating sphere for the enhancement of noninvasive glucose detection using quantum cascade laser spectroscopy

    Science.gov (United States)

    Werth, Alexandra; Liakat, Sabbir; Dong, Anqi; Woods, Callie M.; Gmachl, Claire F.

    2018-05-01

    An integrating sphere is used to enhance the collection of backscattered light in a noninvasive glucose sensor based on quantum cascade laser spectroscopy. The sphere enhances signal stability by roughly an order of magnitude, allowing us to use a thermoelectrically (TE) cooled detector while maintaining comparable glucose prediction accuracy levels. Using a smaller TE-cooled detector reduces form factor, creating a mobile sensor. Principal component analysis has predicted principal components of spectra taken from human subjects that closely match the absorption peaks of glucose. These principal components are used as regressors in a linear regression algorithm to make glucose concentration predictions, over 75% of which are clinically accurate.

  1. Design, fabrication, and optimization of quantum cascade laser cavities and spectroscopy of the intersubband gain

    Science.gov (United States)

    Dirisu, Afusat Olayinka

    Quantum Cascade (QC) lasers are intersubband light sources operating in the wavelength range of ˜ 3 to 300 mum and are used in applications such as sensing (environmental, biological, and hazardous chemical), infrared countermeasures, and free-space infrared communications. The mid-infrared range (i.e. lambda ˜ 3-30 mum) is of particular importance in sensing because of the strong interaction of laser radiation with various chemical species, while in free space communications the atmospheric windows of 3-5 mum and 8-12 mum are highly desirable for low loss transmission. Some of the requirements of these applications include, (1) high output power for improved sensitivity; (2) high operating temperatures for compact and cost-effective systems; (3) wide tunability; (4) single mode operation for high selectivity. In the past, available mid-infrared sources, such as the lead-salt and solid-state lasers, were bulky, expensive, or emit low output power. In recent years, QC lasers have been explored as cost-effective and compact sources because of their potential to satisfy and exceed all the above requirements. Also, the ultrafast carrier lifetimes of intersubband transitions in QC lasers are promising for high bandwidth free-space infrared communication. This thesis was focused on the improvement of QC lasers through the design and optimization of the laser cavity and characterization of the laser gain medium. The optimization of the laser cavity included, (1) the design and fabrication of high reflection Bragg gratings and subwavelength antireflection gratings, by focused ion beam milling, to achieve tunable, single mode and high power QC lasers, and (2) modeling of slab-coupled optical waveguide QC lasers for high brightness output beams. The characterization of the QC laser gain medium was carried out using the single-pass transmission experiment, a sensitive measurement technique, for probing the intersubband transitions and the electron distribution of QC lasers

  2. Inter-subbandspectroscopy on silicon-germanium quantum cascade structures; Intersubband Spektroskopie an Silizium-Germanium-Quantenkaskadenstrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Bormann, I.

    2006-02-15

    This work refers to the design, the fabrication and the structural, electrical and optical characterization of light emitters based on SiGe quantum cascade structures (QCS). In a first step two Si/SiGe quantum cascade structures without waveguides were designed using a 6-band k x p calculation of the subband structure including Si/Ge segregation effects during molecular beam epitaxy (MBE) growth. After growth on (001) Si substrates they were characterized by transmission electron microscopy (TEM). Although the structures are strongly strained due to the average Ge content of 18%, they show no signs of strain relaxation. The interface roughness amounts to three monolayers in good agreement with the segregation model. Both structures show well resolved intersubband electroluminescence (EL) at 146 meV and 159 meV respectively in excellent agreement with the band structure calculations. The line width is 30 meV. The transversal magnetic polarization and photocurrent measurements prove that the intersubband transition is the source of the emitted luminescence. Numerical calculations of the upper state nonradiative hole lifetime determined by the deformation potential scattering of holes with optical phonons reveal a lifetime of about 400 fs for both structures. The feasibility to enhance the upper state lifetime in 'diagonal' transitions between heavy hole states in neighboring quantum wells is investigated. Therefore the Si barrier thickness between the quantum wells was varied and accordingly the wave function overlap using a second sample series. From EL measurements the lifetime of the 35 A barrier sample was found to be 17 times longer than for a 15 A barrier. It is possible to reduce the strong strain in Si/SiGe structures by using a virtual Si{sub 1-x}Ge{sub x} substrate. For this purpose a thin Si{sub 0.72}Ge{sub 0.28} relaxed buffer with a threading dislocation density of 10{sup 7} cm{sup -2} and a RMS surface roughness of 13 A was developed and

  3. Time-Resolved Quantum Cascade Laser Absorption Spectroscopy of Pulsed Plasma Assisted Chemical Vapor Deposition Processes Containing BCl3

    Science.gov (United States)

    Lang, Norbert; Hempel, Frank; Strämke, Siegfried; Röpcke, Jürgen

    2011-08-01

    In situ measurements are reported giving insight into the plasma chemical conversion of the precursor BCl3 in industrial applications of boriding plasmas. For the online monitoring of its ground state concentration, quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range was applied in a plasma assisted chemical vapor deposition (PACVD) reactor. A compact quantum cascade laser measurement and control system (Q-MACS) was developed to allow a flexible and completely dust-sealed optical coupling to the reactor chamber of an industrial plasma surface modification system. The process under the study was a pulsed DC plasma with periodically injected BCl3 at 200 Pa. A synchronization of the Q-MACS with the process control unit enabled an insight into individual process cycles with a sensitivity of 10-6 cm-1·Hz-1/2. Different fragmentation rates of the precursor were found during an individual process cycle. The detected BCl3 concentrations were in the order of 1014 molecules·cm-3. The reported results of in situ monitoring with QCLAS demonstrate the potential for effective optimization procedures in industrial PACVD processes.

  4. Quantum-cascade lasers in the 7-8 μm spectral range with full top metallization

    Science.gov (United States)

    Kurochkin, A. S.; Babichev, A. V.; Denisov, D. V.; Karachinsky, L. Ya; Novikov, I. I.; Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E.; Bousseksou, A.; Egorov, A. Yu

    2018-03-01

    The paper demonstrates the generation of multistage quantum-cascade lasers (QCL) in the 7-8 μm spectral range in the pulse generation mode. The active region structure we used is based on a two-phonon resonance scheme. The QCL heterostructure based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys was grown by molecular beam epitaxy and includes 50 identical stages. A waveguide geometry with top cladding with full top metallization (surface- plasmon quantum-cascade lasers) has been used. The developed QCLs have demonstrated multimodal generation in the 7-8 μm spectral range in the pulse mode in the 78-250 K temperature range. The threshold current density for a 1.6 mm long laser and a 20 μm ridge width amounted to ˜ 2.8 kA/cm2 at a temperature of 78 К. A temperature increase to 250 K causes a long-wave shift of the wavelength from 7.6 to 7.9 μm and a jth increase to 5.0 kA/cm2.

  5. Quantum Cascade Laser-Based Infrared Microscopy for Label-Free and Automated Cancer Classification in Tissue Sections.

    Science.gov (United States)

    Kuepper, Claus; Kallenbach-Thieltges, Angela; Juette, Hendrik; Tannapfel, Andrea; Großerueschkamp, Frederik; Gerwert, Klaus

    2018-05-16

    A feasibility study using a quantum cascade laser-based infrared microscope for the rapid and label-free classification of colorectal cancer tissues is presented. Infrared imaging is a reliable, robust, automated, and operator-independent tissue classification method that has been used for differential classification of tissue thin sections identifying tumorous regions. However, long acquisition time by the so far used FT-IR-based microscopes hampered the clinical translation of this technique. Here, the used quantum cascade laser-based microscope provides now infrared images for precise tissue classification within few minutes. We analyzed 110 patients with UICC-Stage II and III colorectal cancer, showing 96% sensitivity and 100% specificity of this label-free method as compared to histopathology, the gold standard in routine clinical diagnostics. The main hurdle for the clinical translation of IR-Imaging is overcome now by the short acquisition time for high quality diagnostic images, which is in the same time range as frozen sections by pathologists.

  6. A Quantum Cascade Laser-Based CO Sensor for Fire Warning, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Maxion Technologies, Inc. (Maxion) proposes to develop and field test a Carbon Monoxide (CO)-sensor prototype for post fire cleanup and CO detection. The sensor will...

  7. High performance 40-stage and 15-stage quantum cascade lasers based on two-material active region composition

    Science.gov (United States)

    Figueiredo, P.; Suttinger, M.; Go, R.; Todi, A.; Shu, Hong; Tsvid, E.; Patel, C. Kumar N.; Lyakh, A.

    2017-05-01

    5.6μm quantum cascade lasers based on Al0.78In0.22As/In0.69Ga0.31As active region composition with measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured by testing devices with variable cavity length. Threshold current density of 1.7kA/cm2 and slope efficiency of 4.9W/A were measured for uncoated 3.15mm x 9µm lasers. Threshold current density and slope efficiency dependence on temperature in the range from 288K to 348K can be described by characteristic temperatures T0 140K and T1 710K, respectively. Pulsed slope efficiency, threshold current density, and wallplug efficiency for a 2.1mm x 10.4µm 15-stage device with the same design and a high reflection-coated back facet were measured to be 1.45W/A, 3.1kA/cm2 , and 18%, respectively. Continuous wave values for the same parameters were measured to be 1.42W/A, 3.7kA/cm2 , and 12%. Continuous wave optical power levels exceeding 0.5W per millimeter of cavity length was demonstrated. When combined with the 40-stage device data, the inverse slope efficiency dependence on cavity length for 15-stage data allowed for separate evaluation of the losses originating from the active region and from the cladding layers of the laser structure. Specifically, the active region losses for the studied design were found to be 0.77cm-1, while cladding region losses - 0.33cm-1. The data demonstrate that active region losses in mid wave infrared quantum cascade lasers largely define total waveguide losses and that their reduction should be one of the main priorities in the quantum cascade laser design.

  8. Frequency Locking and Monitoring Based on Bi-directional Terahertz Radiation of a 3rd-Order Distributed Feedback Quantum Cascade Laser

    NARCIS (Netherlands)

    Van Marrewijk, N.; Mirzaei, B.; Hayton, D.; Gao, J.R.; Kao, T.Y.; Hu, Q.; Reno, J.L.

    2015-01-01

    We have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency

  9. Phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser using a room-temperature superlattice harmonic mixer

    NARCIS (Netherlands)

    Hayton, D. J.; Khudchencko, A.; Pavelyev, D. G.; Hovenier, J. N.; Baryshev, A.; Gao, J. R.; Kao, T. Y.; Hu, Q.; Reno, J. L.; Vaks, V.

    2013-01-01

    We report on the phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser (QCL) using a room temperature GaAs/AlAs superlattice diode as both a frequency multiplier and an internal harmonic mixer. A signal-to-noise level of 60 dB is observed in the intermediate frequency

  10. Phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser using a room-temperature superlattice harmonic mixer

    NARCIS (Netherlands)

    Hayton, D.J.; Khudchenko, A.; Pavelyev, D.G.; Hovenier, J.N.; Baryshev, A.; Gao, J.R.; Kao, T.Y.; Hu, Q.; Reno, J.L.; Vaks, V.

    2013-01-01

    We report on the phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser (QCL) using a room temperature GaAs/AlAs superlattice diode as both a frequency multiplier and an internal harmonic mixer. A signal-to-noise level of 60?dB is observed in the intermediate frequency

  11. Apertureless near-field terahertz imaging using the self-mixing effect in a quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Dean, Paul, E-mail: p.dean@leeds.ac.uk; Keeley, James; Kundu, Iman; Li, Lianhe; Linfield, Edmund H.; Giles Davies, A. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Mitrofanov, Oleg [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)

    2016-02-29

    We report two-dimensional apertureless near-field terahertz (THz) imaging using a quantum cascade laser (QCL) source and a scattering probe. A near-field enhancement of the scattered field amplitude is observed for small tip-sample separations, allowing image resolutions of ∼1 μm (∼λ/100) and ∼7 μm to be achieved along orthogonal directions on the sample surface. This represents the highest resolution demonstrated to date with a THz QCL. By employing a detection scheme based on self-mixing interferometry, our approach offers experimental simplicity by removing the need for an external detector and also provides sensitivity to the phase of the reinjected field.

  12. Mid infrared quantum cascade laser operating in pure amplitude modulation for background-free trace gas spectroscopy.

    Science.gov (United States)

    Bidaux, Yves; Bismuto, Alfredo; Patimisco, Pietro; Sampaolo, Angelo; Gresch, Tobias; Strubi, Gregory; Blaser, Stéphane; Tittel, Frank K; Spagnolo, Vincenzo; Muller, Antoine; Faist, Jérôme

    2016-11-14

    We present a single mode multi-section quantum cascade laser source composed of three different sections: master oscillator, gain and phase section. Non-uniform pumping of the QCL's gain reveals that the various laser sections are strongly coupled. Simulations of the electronic and optical properties of the laser (based on the density matrix and scattering matrix formalisms, respectively) were performed and a good agreement with measurements is obtained. In particular, a pure modulation of the laser output power can be achieved. This capability of the device is applied in tunable-laser spectroscopy of N2O where background-free quartz enhanced photo acoustic spectral scans with nearly perfect Voigt line shapes for the selected absorption line are obtained.

  13. Frequency locking of an extended-cavity quantum cascade laser to a frequency comb for precision mid infrared spectroscopy

    KAUST Repository

    Alsaif, Bidoor; Lamperti, Marco; Gatti, Davide; Laporta, Paolo; Fermann, Martin E.; Farooq, Aamir; Marangoni, Marco

    2017-01-01

    Extended-cavity quantum cascade lasers (EC-QCLs) enable mode-hope-free frequency sweeps in the mid-infrared region over ranges in excess of 100 cm−1, at speeds up to 1 THz/s and with a 100-mW optical power level. This makes them ideally suited for broadband absorption spectroscopy and for the simultaneous detection of multiple gases. On the other hand, their use for precision spectroscopy has been hampered so far by a large amount of frequency noise, resulting in an optical linewidth of about 30 MHz over 50 ms [1]. This is one of the reasons why neither their frequency nor their phase have been so far locked to a frequency comb. Their use in combination with frequency combs has been performed in an open loop regime only [2], which has the merit of preserving the inherently fast modulation speed of these lasers, yet not to afford high spectral resolution and accuracy.

  14. Room temperature continuous wave operation of quantum cascade laser at λ ~ 9.4 μm

    Science.gov (United States)

    Hou, Chuncai; Zhao, Yue; Zhang, Jinchuan; Zhai, Shenqiang; Zhuo, Ning; Liu, Junqi; Wang, Lijun; Liu, Shuman; Liu, Fengqi; Wang, Zhanguo

    2018-03-01

    Continuous wave (CW) operation of long wave infrared (LWIR) quantum cascade lasers (QCLs) is achieved up to a temperature of 303 K. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 2-mm-long and 10-μm-wide laser with high-reflectivity (HR) coating on the rear facet, CW output power of 45 mW at 283 K and 9 mW at 303 K is obtained. The lasing wavelength is around 9.4 μm locating in the LWIR spectrum range. Project supported by the National Key Research And Development Program (No. 2016YFB0402303), the National Natural Science Foundation of China (Nos. 61435014, 61627822, 61574136, 61774146, 61674144, 61404131), the Key Projects of Chinese Academy of Sciences (Nos. ZDRW-XH-2016-4, QYZDJ-SSW-JSC027), and the Beijing Natural Science Foundation (No. 4162060, 4172060).

  15. Gas spectroscopy with integrated frequency monitoring through self-mixing in a terahertz quantum-cascade laser.

    Science.gov (United States)

    Chhantyal-Pun, Rabi; Valavanis, Alexander; Keeley, James T; Rubino, Pierluigi; Kundu, Iman; Han, Yingjun; Dean, Paul; Li, Lianhe; Davies, A Giles; Linfield, Edmund H

    2018-05-15

    We demonstrate a gas spectroscopy technique, using self-mixing in a 3.4 terahertz quantum-cascade laser (QCL). All previous QCL spectroscopy techniques have required additional terahertz instrumentation (detectors, mixers, or spectrometers) for system pre-calibration or spectral analysis. By contrast, our system self-calibrates the laser frequency (i.e., with no external instrumentation) to a precision of 630 MHz (0.02%) by analyzing QCL voltage perturbations in response to optical feedback within a 0-800 mm round-trip delay line. We demonstrate methanol spectroscopy by introducing a gas cell into the feedback path and show that a limiting absorption coefficient of ∼1×10 -4   cm -1 is resolvable.

  16. Frequency locking of an extended-cavity quantum cascade laser to a frequency comb for precision mid infrared spectroscopy

    KAUST Repository

    Alsaif, Bidoor

    2017-11-02

    Extended-cavity quantum cascade lasers (EC-QCLs) enable mode-hope-free frequency sweeps in the mid-infrared region over ranges in excess of 100 cm−1, at speeds up to 1 THz/s and with a 100-mW optical power level. This makes them ideally suited for broadband absorption spectroscopy and for the simultaneous detection of multiple gases. On the other hand, their use for precision spectroscopy has been hampered so far by a large amount of frequency noise, resulting in an optical linewidth of about 30 MHz over 50 ms [1]. This is one of the reasons why neither their frequency nor their phase have been so far locked to a frequency comb. Their use in combination with frequency combs has been performed in an open loop regime only [2], which has the merit of preserving the inherently fast modulation speed of these lasers, yet not to afford high spectral resolution and accuracy.

  17. A calibration-free ammonia breath sensor using a quantum cascade laser with WMS 2f/1f

    KAUST Repository

    Owen, Kyle

    2013-12-22

    The amount of ammonia in exhaled breath has been linked to a variety of adverse medical conditions, including chronic kidney disease (CKD). The development of accurate, reliable breath sensors has the potential to improve medical care. Wavelength modulation spectroscopy with second harmonic normalized by the first harmonic (WMS 2f/1f) is a sensitive technique used in the development of calibration-free sensors. An ammonia gas sensor is designed and developed that uses a quantum cascade laser operating near 1,103.44 cm -1 and a multi-pass cell with an effective path length of 76.45 m. The sensor has a 7 ppbv detection limit and 5 % total uncertainty for breath measurements. The sensor was successfully used to detect ammonia in exhaled breath and compare healthy patients to patients diagnosed with CKD. © 2013 Springer-Verlag Berlin Heidelberg.

  18. Absolute spectroscopy near 7.8 {\\mu} m with a comb-locked extended-cavity quantum-cascade-laser

    KAUST Repository

    Lamperti, Marco

    2017-07-31

    We report the first experimental demonstration of frequency-locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locking scheme is applied to carry out absolute spectroscopy of N2O lines near 7.87 {\\\\mu}m with an accuracy of ~60 kHz. Thanks to a single mode operation over more than 100 cm^{-1}, the comb-locked EC-QCL shows great potential for the accurate retrieval of line center frequencies in a spectral region that is currently outside the reach of broadly tunable cw sources, either based on difference frequency generation or optical parametric oscillation. The approach described here can be straightforwardly extended up to 12 {\\\\mu}m, which is the current wavelength limit for commercial cw EC-QCLs.

  19. Exhaled breath profiling using broadband quantum cascade laser-based spectroscopy in healthy children and children with asthma and cystic fibrosis.

    Science.gov (United States)

    van Mastrigt, E; Reyes-Reyes, A; Brand, K; Bhattacharya, N; Urbach, H P; Stubbs, A P; de Jongste, J C; Pijnenburg, M W

    2016-04-08

    Exhaled breath analysis is a potential non-invasive tool for diagnosing and monitoring airway diseases. Gas chromatography-mass spectrometry and electrochemical sensor arrays are the main techniques to detect volatile organic compounds (VOC) in exhaled breath. We developed a broadband quantum cascade laser spectroscopy technique for VOC detection and identification. The objective of this study was to assess the repeatability of exhaled breath profiling with broadband quantum cascade laser-based spectroscopy and to explore the clinical applicability by comparing exhaled breath samples from healthy children with those from children with asthma or cystic fibrosis (CF). Healthy children and children with stable asthma or stable CF, aged 6-18 years, were included. Two to four exhaled breath samples were collected in Tedlar bags and analyzed by quantum cascade laser spectroscopy to detect VOCs with an absorption profile in the wavenumber region between 832 and 1262.55 cm(-1). We included 35 healthy children, 39 children with asthma and 15 with CF. Exhaled breath VOC profiles showed poor repeatability (Spearman's rho  =  0.36 to 0.46) and agreement of the complete profiles. However, we were able to discriminate healthy children from children with stable asthma or stable CF and identified VOCs that were responsible for this discrimination. Broadband quantum cascade laser-based spectroscopy detected differences in VOC profiles in exhaled breath samples between healthy children and children with asthma or CF. The combination of a relatively easy and fast method and the possibility of molecule identification makes broadband quantum cascade laser-based spectroscopy attractive to investigate the diagnostic and prognostic potential of volatiles in exhaled breath.

  20. Frequency-domain cascading microwave superconducting quantum interference device multiplexers; beyond limitations originating from room-temperature electronics

    Science.gov (United States)

    Kohjiro, Satoshi; Hirayama, Fuminori

    2018-07-01

    A novel approach, frequency-domain cascading microwave multiplexers (MW-Mux), has been proposed and its basic operation has been demonstrated to increase the number of pixels multiplexed in a readout line U of MW-Mux for superconducting detector arrays. This method is an alternative to the challenging development of wideband, large power, and spurious-free room-temperature (300 K) electronics. The readout system for U pixels consists of four main parts: (1) multiplexer chips connected in series those contain U superconducting resonators in total. (2) A cryogenic high-electron-mobility transistor amplifier (HEMT). (3) A 300 K microwave frequency comb generator based on N(≡U/M) parallel units of digital-to-analog converters (DAC). (4) N parallel units of 300 K analog-to-digital converters (ADC). Here, M is the number of tones each DAC produces and each ADC handles. The output signal of U detectors multiplexed at the cryogenic stage is transmitted through a cable to the room temperature and divided into N processors where each handles M pixels. Due to the reduction factor of 1/N, U is not anymore dominated by the 300 K electronics but can be increased up to the potential value determined by either the bandwidth or the spurious-free power of the HEMT. Based on experimental results on the prototype system with N = 2 and M = 3, neither excess inter-pixel crosstalk nor excess noise has been observed in comparison with conventional MW-Mux. This indicates that the frequency-domain cascading MW-Mux provides the full (100%) usage of the HEMT band by assigning N 300 K bands on the frequency axis without inter-band gaps.

  1. A cascadic monotonic time-discretized algorithm for finite-level quantum control computation

    Science.gov (United States)

    Ditz, P.; Borzi`, A.

    2008-03-01

    A computer package (CNMS) is presented aimed at the solution of finite-level quantum optimal control problems. This package is based on a recently developed computational strategy known as monotonic schemes. Quantum optimal control problems arise in particular in quantum optics where the optimization of a control representing laser pulses is required. The purpose of the external control field is to channel the system's wavefunction between given states in its most efficient way. Physically motivated constraints, such as limited laser resources, are accommodated through appropriately chosen cost functionals. Program summaryProgram title: CNMS Catalogue identifier: ADEB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADEB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 770 No. of bytes in distributed program, including test data, etc.: 7098 Distribution format: tar.gz Programming language: MATLAB 6 Computer: AMD Athlon 64 × 2 Dual, 2:21 GHz, 1:5 GB RAM Operating system: Microsoft Windows XP Word size: 32 Classification: 4.9 Nature of problem: Quantum control Solution method: Iterative Running time: 60-600 sec

  2. Molecular-beam epitaxy growth and characterization of 5-μm quantum cascade laser

    International Nuclear Information System (INIS)

    Mamutin, V V; Ustinov, V M; Ilyinskaya, N D; Baydakova, M V; Ber, B Ya; Kasantsev, D Yu

    2011-01-01

    Molecular-beam epitaxy growth of 5 μm emitting strain-compensated quantum semiconductor laser (QCL) is reported. The QCL structure is characterized by complementary techniques: high-resolution X-ray diffraction and dynamical secondary-ion mass-spectrometry, that reveal the high quality of QCL structure and in-depth distribution of chemical composition, respectively.

  3. Intersubband spectroscopy of ZnO/ZnMgO quantum wells grown on m-plane ZnO substrates for quantum cascade device applications (Conference Presentation)

    Science.gov (United States)

    Quach, Patrick; Jollivet, Arnaud; Isac, Nathalie; Bousseksou, Adel; Ariel, Frédéric; Tchernycheva, Maria; Julien, François H.; Montes Bajo, Miguel; Tamayo-Arriola, Julen; Hierro, Adrián.; Le Biavan, Nolwenn; Hugues, Maxime; Chauveau, Jean-Michel

    2017-03-01

    Quantum cascade (QC) lasers opens new prospects for powerful sources operating at THz frequencies. Up to now the best THz QC lasers are based on intersubband emission in GaAs/AlGaAs quantum well (QW) heterostructures. The maximum operating temperature is 200 K, which is too low for wide-spread applications. This is due to the rather low LO-phonon energy (36 meV) of GaAs-based materials. Indeed, thermal activation allows non-radiative path through electron-phonon interaction which destroys the population inversion. Wide band gap materials such as ZnO have been predicted to provide much higher operating temperatures because of the high value of their LO-phonon energy. However, despite some observations of intersubband absorption in c-plane ZnO/ZnMgO quantum wells, little is known on the fundamental parameters such as the conduction band offset in such heterostructures. In addition the internal field inherent to c-plane grown heterostuctures is an handicap for the design of QC lasers and detectors. In this talk, we will review a systematic investigation of ZnO/ZnMgO QW heterostructures with various Mg content and QW thicknesses grown by plasma molecular beam epitaxy on low-defect m-plane ZnO substrates. We will show that most samples exhibit TM-polarized intersubband absorption at room temperature linked either to bound-to-quasi bound inter-miniband absorption or to bound-to bound intersubband absorption depending on the Mg content of the barrier material. This systematic study allows for the first time to estimate the conduction band offset of ZnO/ZnMgO heterostructures, opening prospects for the design of QC devices operating at THz frequencies. This was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement #665107.

  4. An external-cavity quantum cascade laser operating near 5.2 µm combined with cavity ring-down spectroscopy for multi-component chemical sensing

    Science.gov (United States)

    Dutta Banik, Gourab; Maity, Abhijit; Som, Suman; Pal, Mithun; Pradhan, Manik

    2018-04-01

    We report on the performance of a widely tunable continuous wave mode-hop-free external-cavity quantum cascade laser operating at λ ~ 5.2 µm combined with cavity ring-down spectroscopy (CRDS) technique for high-resolution molecular spectroscopy. The CRDS system has been utilized for simultaneous and molecule-specific detection of several environmentally and bio-medically important trace molecular species such as nitric oxide, nitrous oxide, carbonyl sulphide and acetylene (C2H2) at ultra-low concentrations by probing numerous rotationally resolved ro-vibrational transitions in the mid-IR spectral region within a relatively small spectral range of ~0.035 cm-1. This continuous wave external-cavity quantum cascade laser-based multi-component CRDS sensor with high sensitivity and molecular specificity promises applications in environmental sensing as well as non-invasive medical diagnosis through human breath analysis.

  5. Phase-locking of a 2.5 THz quantum cascade laser to a frequency comb using a GaAs photomixer.

    Science.gov (United States)

    Ravaro, M; Manquest, C; Sirtori, C; Barbieri, S; Santarelli, G; Blary, K; Lampin, J-F; Khanna, S P; Linfield, E H

    2011-10-15

    We report the heterodyne detection and phase locking of a 2.5 THz quantum cascade laser (QCL) using a terahertz frequency comb generated in a GaAs photomixer using a femtosecond fiber laser. With 10 mW emitted by the QCL, the phase-locked signal at the intermediate frequency yields 80 dB of signal-to-noise ratio in a bandwidth of 1 Hz.

  6. Real time ammonia detection in exhaled human breath using a distributed feedback quantum cascade laser based sensor

    Science.gov (United States)

    Lewicki, Rafał; Kosterev, Anatoliy A.; Thomazy, David M.; Risby, Terence H.; Solga, Steven; Schwartz, Timothy B.; Tittel, Frank K.

    2011-01-01

    A continuous wave, thermoelectrically cooled, distributed feedback quantum cascade laser (DFB-QCL) based sensor platform for the quantitative detection of ammonia (NH3) concentrations present in exhaled human breath is reported. The NH3 concentration measurements are performed with a 2f wavelength modulation quartz enhanced photoacoustic spectroscopy (QEPAS) technique, which is very well suited for real time breath analysis, due to the fast gas exchange inside a compact QEPAS gas cell. An air-cooled DFB-QCL was designed to target the interference-free NH3 absorption line located at 967.35 cm-1 (λ~10.34 μm). The laser is operated at 17.5 °C, emitting ~ 24 mW of optical power at the selected wavelength. A 1σ minimum detectable concentration of ammonia for the line-locked NH3 sensor is ~ 6 ppb with 1 sec time resolution. The NH3 sensor, packaged in a 12"x14"x10" housing, is currently installed at a medical breath research center in Bethlehem, PA and tested as an instrument for non-invasive verification of liver and kidney disorders based on human breath samples.

  7. A photothermal Mach-Zehnder interferometer for measuring caffeine and proteins in aqueous solutions using external cavity quantum cascade lasers

    Science.gov (United States)

    Kristament, Christian; Schwaighofer, Andreas; Montemurro, Milagros; Lendl, Bernhard

    2018-02-01

    One of the advantages of mid-IR spectroscopy in biomedical research lies in its capability to provide direct information on the secondary structure of proteins in their natural, often aqueous, environment. One impediment of direct absorption measurements in the correspondent spectral region is the strong absorbance of the native solvent (H2O). In this regard, the advent of broadly-tunable external cavity quantum cascade lasers (EC-QCL) allowed to significantly increasing the optical path length employed in transmission measurements due to their high spectral power densities. Low measured S/N ratios were improved by elaborated data analysis protocols that corrected mechanical flaws in the tuning mechanism of ECQCLs and allow for S/N ratios comparable to research grade FTIR spectrometers. Recent development of new optical set-ups outpacing direct absorption measurements led to further advancements. We present a dedicated Mach-Zehnder interferometer for photothermal measurements in balanced detection mode. In this highly sensitive design, the interferometer is illuminated by a HeNe laser to detect the refractive index change induced by the heat insertion of the EC-QCL. Here, we present photothermal phase shift interferometry measurements of caffeine in ethanol as well as casein in water. Further, the dependency of the signal amplitude on varying modulation frequencies was investigated for different liquids.

  8. A quartz enhanced photo-acoustic gas sensor based on a custom tuning fork and a terahertz quantum cascade laser.

    Science.gov (United States)

    Patimisco, Pietro; Borri, Simone; Sampaolo, Angelo; Beere, Harvey E; Ritchie, David A; Vitiello, Miriam S; Scamarcio, Gaetano; Spagnolo, Vincenzo

    2014-05-07

    An innovative quartz enhanced photoacoustic (QEPAS) gas sensing system operating in the THz spectral range and employing a custom quartz tuning fork (QTF) is described. The QTF dimensions are 3.3 cm × 0.4 cm × 0.8 cm, with the two prongs spaced by ∼800 μm. To test our sensor we used a quantum cascade laser as the light source and selected a methanol rotational absorption line at 131.054 cm(-1) (∼3.93 THz), with line-strength S = 4.28 × 10(-21) cm mol(-1). The sensor was operated at 10 Torr pressure on the first flexion QTF resonance frequency of 4245 Hz. The corresponding Q-factor was 74 760. Stepwise concentration measurements were performed to verify the linearity of the QEPAS signal as a function of the methanol concentration. The achieved sensitivity of the system is 7 parts per million in 4 seconds, corresponding to a QEPAS normalized noise-equivalent absorption of 2 × 10(-10) W cm(-1) Hz(-1/2), comparable with the best result of mid-IR QEPAS systems.

  9. Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking

    Science.gov (United States)

    Columbo, L. L.; Barbieri, S.; Sirtori, C.; Brambilla, M.

    2018-02-01

    The dynamics of a multimode Quantum Cascade Laser, is studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiationmedium interaction such as an asymmetric, frequency dependent, gain and refractive index as well as the phase-amplitude coupling provided by the Henry factor. By considering the role of the free spectral range and Henry factor, we develop criteria suitable to identify the conditions which allow to destabilize, close to threshold, the traveling wave emitted by the laser and lead to chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help understanding the conditions for the generation of ultrashort pulses and comb operation in Mid-IR and THz spectral regions

  10. Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation.

    Science.gov (United States)

    Consolino, Luigi; Jung, Seungyong; Campa, Annamaria; De Regis, Michele; Pal, Shovon; Kim, Jae Hyun; Fujita, Kazuue; Ito, Akio; Hitaka, Masahiro; Bartalini, Saverio; De Natale, Paolo; Belkin, Mikhail A; Vitiello, Miriam Serena

    2017-09-01

    Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 × 10 -10 . The unveiled emission LW (400 kHz at 1-ms integration time) indicates that DFG-QCLs are well suited to operate as local oscillators and to be used for a variety of metrological, spectroscopic, communication, and imaging applications that require narrow-LW THz sources.

  11. Rapid and Sensitive Quantification of Isotopic Mixtures Using a Rapidly-Swept External Cavity Quantum Cascade Laser

    Directory of Open Access Journals (Sweden)

    Brian E. Brumfield

    2016-05-01

    Full Text Available A rapidly-swept external-cavity quantum cascade laser with an open-path Herriott cell is used to quantify gas-phase chemical mixtures of D2O and HDO at a rate of 40 Hz (25-ms measurement time. The chemical mixtures were generated by evaporating D2O liquid near the open-path Herriott cell, allowing the H/D exchange reaction with ambient H2O to produce HDO. Fluctuations in the ratio of D2O and HDO on timescales of <1 s due to the combined effects of plume transport and the H/D exchange chemical reaction are observed. Noise-equivalent concentrations (1σ (NEC of 147.0 ppbv and 151.6 ppbv in a 25-ms measurement time are determined for D2O and HDO, respectively, with a 127-m optical path. These NECs are improved to 23.0 and 24.0 ppbv with a 1-s averaging time for D2O and HDO, respectively. NECs <200 ppbv are also estimated for N2O, 1,1,1,2–tetrafluoroethane (F134A, CH4, acetone and SO2 for a 25-ms measurement time. The isotopic precision for measurement of the [D2O]/[HDO] concentration ratio of 33‰ and 5‰ is calculated for the current experimental conditions for measurement times of 25 ms and 1 s, respectively.

  12. Quantum cascade laser absorption spectroscopy with the amplitude-to-time conversion technique for atmospheric-pressure plasmas

    International Nuclear Information System (INIS)

    Yumii, Takayoshi; Kimura, Noriaki; Hamaguchi, Satoshi

    2013-01-01

    The NO 2 concentration, i.e., density, in a small plasma of a nitrogen oxide (NOx) treatment reactor has been measured by highly sensitive laser absorption spectroscopy. The absorption spectroscopy uses a single path of a quantum cascade laser beam passing through a plasma whose dimension is about 1 cm. The high sensitivity of spectroscopy is achieved by the amplitude-to-time conversion technique. Although the plasma reactor is designed to convert NO in the input gas to NO 2 , it has been demonstrated by this highly sensitive absorption spectroscopy that NO 2 in a simulated exhaust gas that enters the reactor is decomposed by the plasma first and then NO 2 is formed again, possibly more than it was decomposed, through a series of gas-phase reactions by the time the gas exits the reactor. The observation is consistent with that of an earlier study on NO decomposition by the same type of a plasma reactor [T. Yumii et al., J. Phys. D 46, 135202 (2013)], in which a high concentration of NO 2 was observed at the exit of the reactor.

  13. Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator.

    Science.gov (United States)

    Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H; Davies, A Giles; Vitiello, Miriam S

    2016-03-15

    Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

  14. Propene concentration sensing for combustion gases using quantum-cascade laser absorption near 11 μm

    KAUST Repository

    Chrystie, Robin

    2015-05-29

    We report on a strategy to measure, in situ, the concentration of propene (C3H6) in combustion gases using laser absorption spectroscopy. Pyrolysis of n-butane was conducted in a shock tube, in which the resultant gases were probed using an extended cavity quantum-cascade laser. A differential absorption approach using online and offline wavelengths near λ = 10.9 μm enabled discrimination of propene, cancelling the effects of spectral interference from the simultaneous presence of intermediate hydrocarbon species during combustion. Such interference-free measurements were facilitated by exploiting the =C–H bending mode characteristic to alkenes (olefins). It was confirmed, for intermediate species present during pyrolysis of n-butane, that their absorption cross sections were the same magnitude for both online and offline wavelengths. Hence, this allowed time profiles of propene concentration to be measured during pyrolysis of n-butane in a shock tube. Time profiles of propene subsequent to a passing shock wave exhibit trends similar to that predicted by the well-established JetSurF 1.0 chemical kinetic mechanism, albeit lower by a factor of two. Such a laser diagnostic is a first step to experimentally determining propene in real time with sufficient time resolution, thus aiding the refinement and development of chemical kinetic models for combustion. © 2015 Springer-Verlag Berlin Heidelberg

  15. Time-resolved temperature measurements in a rapid compression machine using quantum cascade laser absorption in the intrapulse mode

    KAUST Repository

    Nasir, Ehson Fawad

    2016-07-16

    A temperature sensor based on the intrapulse absorption spectroscopy technique has been developed to measure in situ temperature time-histories in a rapid compression machine (RCM). Two quantum-cascade lasers (QCLs) emitting near 4.55μm and 4.89μm were operated in pulsed mode, causing a frequency "down-chirp" across two ro-vibrational transitions of carbon monoxide. The down-chirp phenomenon resulted in large spectral tuning (δν ∼2.8cm-1) within a single pulse of each laser at a high pulse repetition frequency (100kHz). The wide tuning range allowed the application of the two-line thermometry technique, thus making the sensor quantitative and calibration-free. The sensor was first tested in non-reactive CO-N2 gas mixtures in the RCM and then applied to cases of n-pentane oxidation. Experiments were carried out for end of compression (EOC) pressures and temperatures ranging 9.21-15.32bar and 745-827K, respectively. Measured EOC temperatures agreed with isentropic calculations within 5%. Temperature rise measured during the first-stage ignition of n-pentane is over-predicted by zero-dimensional kinetic simulations. This work presents, for the first time, highly time-resolved temperature measurements in reactive and non-reactive rapid compression machine experiments. © 2016 Elsevier Ltd.

  16. Equivalent circuit-level model of quantum cascade lasers with integrated hot-electron and hot-phonon effects

    Science.gov (United States)

    Yousefvand, H. R.

    2017-12-01

    We report a study of the effects of hot-electron and hot-phonon dynamics on the output characteristics of quantum cascade lasers (QCLs) using an equivalent circuit-level model. The model is developed from the energy balance equation to adopt the electron temperature in the active region levels, the heat transfer equation to include the lattice temperature, the nonequilibrium phonon rate to account for the hot phonon dynamics and simplified two-level rate equations to incorporate the carrier and photon dynamics in the active region. This technique simplifies the description of the electron-phonon interaction in QCLs far from the equilibrium condition. Using the presented model, the steady and transient responses of the QCLs for a wide range of sink temperatures (80 to 320 K) are investigated and analysed. The model enables us to explain the operating characteristics found in QCLs. This predictive model is expected to be applicable to all QCL material systems operating in pulsed and cw regimes.

  17. Suitability of quantum cascade laser spectroscopy for CH4 and N2O eddy covariance flux measurements

    Directory of Open Access Journals (Sweden)

    A. T. Vermeulen

    2007-08-01

    Full Text Available A quantum cascade laser spectrometer was evaluated for eddy covariance flux measurements of CH4 and N2O using three months of continuous measurements at a field site. The required criteria for eddy covariance flux measurements including continuity, sampling frequency, precision and stationarity were examined. The system operated continuously at a dairy farm on peat grassland in the Netherlands from 17 August to 6 November 2006. An automatic liquid nitrogen filling system for the infrared detector was employed to provide unattended operation of the system. The electronic sampling frequency was 10 Hz, however, the flow response time was 0.08 s, which corresponds to a bandwidth of 2 Hz. A precision of 2.9 and 0.5 ppb Hz−1/2 was obtained for CH4 and N2O, respectively. Accuracy was assured by frequent calibrations using low and high standard additions. Drifts in the system were compensated by using a 120 s running mean filter. The average CH4 and N2O exchange was 512 ngC m−2 s−1 (2.46 mg m−2 hr−1 and 52 ngN m−2 s−1 (0.29 mg m−2 hr−1. Given that 40% of the total N2O emission was due to a fertilizing event.

  18. Wavelength modulation spectroscopy coupled with an external-cavity quantum cascade laser operating between 7.5 and 8 µm

    Science.gov (United States)

    Maity, Abhijit; Pal, Mithun; Maithani, Sanchi; Dutta Banik, Gourab; Pradhan, Manik

    2018-04-01

    We demonstrate a mid-infrared detection strategy with 1f-normalized 2f-wavelength modulation spectroscopy (WMS-2f/1f) using a continuous wave (CW) external-cavity quantum cascade laser (EC-QCL) operating between 7.5 and 8 µm. The detailed performance of the WMS-2f/1f detection method was evaluated by making rotationally resolved measurements in the (ν 4  +  ν 5) combination band of acetylene (C2H2) at 1311.7600 cm-1. A noise-limited detection limit of three parts per billion (ppb) with an integration time of 110 s was achieved for C2H2 detection. The present high-resolution CW-EC-QCL system coupled with the WMS-2f/1f strategy was further validated with an extended range of C2H2 concentration of 0.1-1000 ppm, which shows excellent promise for real-life practical sensing applications. Finally, we utilized the WMS-2f/1f technique to measure the C2H2 concentration in the exhaled breath of smokers.

  19. A Quantum Cascade Laser-Based Optical Sensor for Continuous Monitoring of Environmental Methane in Dunkirk (France

    Directory of Open Access Journals (Sweden)

    Rabih Maamary

    2016-02-01

    Full Text Available A room-temperature continuous-wave (CW quantum cascade laser (QCL-based methane (CH4 sensor operating in the mid-infrared near 8 μm was developed for continuous measurement of CH4 concentrations in ambient air. The well-isolated absorption line (7F2,4 ← 8F1,2 of the ν4 fundamental band of CH4 located at 1255.0004 cm−1 was used for optical measurement of CH4 concentration by direct absorption in a White-type multipass cell with an effective path-length of 175 m. A 1σ (SNR = 1 detection limit of 33.3 ppb in 218 s was achieved with a measurement precision of 1.13%. The developed sensor was deployed in a campaign of measurements of time series CH4 concentration on a site near a suburban traffic road in Dunkirk (France from 9th to 22nd January 2013. An episode of high CH4 concentration of up to ~3 ppm has been observed and analyzed with the help of meteorological parameters combined with back trajectory calculation using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT model of NOAA.

  20. Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl- attack on CH3Cl.

    Science.gov (United States)

    Kuechler, Erich R; York, Darrin M

    2014-02-07

    The nucleophilic attack of a chloride ion on methyl chloride is an important prototype SN2 reaction in organic chemistry that is known to be sensitive to the effects of the surrounding solvent. Herein, we develop a highly accurate Specific Reaction Parameter (SRP) model based on the Austin Model 1 Hamiltonian for chlorine to study the effects of solvation into an aqueous environment on the reaction mechanism. To accomplish this task, we apply high-level quantum mechanical calculations to study the reaction in the gas phase and combined quantum mechanical/molecular mechanical simulations with TIP3P and TIP4P-ew water models and the resulting free energy profiles are compared with those determined from simulations using other fast semi-empirical quantum models. Both gas phase and solution results with the SRP model agree very well with experiment and provide insight into the specific role of solvent on the reaction coordinate. Overall, the newly parameterized SRP Hamiltonian is able to reproduce both the gas phase and solution phase barriers, suggesting it is an accurate and robust model for simulations in the aqueous phase at greatly reduced computational cost relative to comparably accurate ab initio and density functional models.

  1. Long Path Quantum Cascade Laser Based Sensor for Environment Sensing/Ambient Detection of CH4 and N2O

    Science.gov (United States)

    Castillo, P. C.; Sydoryk, I.; Gross, B.; Moshary, F.

    2013-12-01

    Methane (CH4) and Nitrous Oxide (N2O) are long-lived greenhouse gases in the atmosphere with significant global warming effects. These gases also are known to be produced in a number of anthropogenic settings such as manure management systems, which releases substantial GHGs and is mandated by the EPA to provide continuous monitoring. In addition, natural gas leaks in urban areas is another source of strong spatially inhomogeneous methane emissions Most open path methods for quantitative detection of trace gases utilize either Fourier Transform Spectrometer (FTIR) or near-IR differential optical absorption spectroscopy (DOAS). Although, FTIR is suitable for ambient air monitoring measurement of more abundant gases such as CO2 and H20 etc., the lack of spectral resolution makes the retrieval of weaker absorbing features such as N20 more difficult. On the other hand, conventional DOAS systems can be large and impractical. As an alternative, we illustrate a robust portable quantum cascade laser (QCL) approach for simultaneous detection of CH4 and N2O. In particular, gas spectra were recorded by ultrafast pulse intensity (thermal) chirp tuning over the 1299 - 1300cm-1 spectral window. Etalon measurements insure stable tuning was obtained. To deal with multiple species, a LSQ spectral fitting approach was used which accounted for both the overlapping trace gases , background water vapor as well as detector drift and calibration. In summary, ambient concentrations of CH4 with and N2O with accuracy < 1% was obtained on the order of 5ms using optical paths of 500 m path length. In addition, unattended long term operation was demonstrated and validations using other sensors when possible were shown to be consistent. The system accuracy is limited by systemic errors, which are still being explored.

  2. Methodical study of nitrous oxide eddy covariance measurements using quantum cascade laser spectrometery over a Swiss forest

    Directory of Open Access Journals (Sweden)

    W. Eugster

    2007-10-01

    Full Text Available Nitrous oxide fluxes were measured at the Lägeren CarboEurope IP flux site over the multi-species mixed forest dominated by European beech and Norway spruce. Measurements were carried out during a four-week period in October–November 2005 during leaf senescence. Fluxes were measured with a standard ultrasonic anemometer in combination with a quantum cascade laser absorption spectrometer that measured N2O, CO2, and H2O mixing ratios simultaneously at 5 Hz time resolution. To distinguish insignificant fluxes from significant ones it is proposed to use a new approach based on the significance of the correlation coefficient between vertical wind speed and mixing ratio fluctuations. This procedure eliminated roughly 56% of our half-hourly fluxes. Based on the remaining, quality checked N2O fluxes we quantified the mean efflux at 0.8±0.4 μmol m−2 h−1 (mean ± standard error. Most of the contribution to the N2O flux occurred during a 6.5-h period starting 4.5 h before each precipitation event. No relation with precipitation amount could be found. Visibility data representing fog density and duration at the site indicate that wetting of the canopy may have as strong an effect on N2O effluxes as does below-ground microbial activity. It is speculated that above-ground N2O production from the senescing leaves at high moisture (fog, drizzle, onset of precipitation event may be responsible for part of the measured flux.

  3. A widely tunable 10-μm quantum cascade laser phase-locked to a state-of-the-art mid-infrared reference for precision molecular spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sow, P. L. T.; Mejri, S.; Tokunaga, S. K.; Lopez, O.; Argence, B.; Chardonnet, C.; Darquié, B., E-mail: benoit.darquie@univ-paris13.fr [CNRS, UMR 7538, LPL, 93430 Villetaneuse (France); Université Paris 13, Sorbonne Paris Cité, Laboratoire de Physique des Lasers, 93430 Villetaneuse (France); Goncharov, A.; Amy-Klein, A.; Daussy, C. [Université Paris 13, Sorbonne Paris Cité, Laboratoire de Physique des Lasers, 93430 Villetaneuse (France); CNRS, UMR 7538, LPL, 93430 Villetaneuse (France)

    2014-06-30

    We report the coherent phase-locking of a quantum cascade laser (QCL) at 10-μm to the secondary frequency standard of this spectral region, a CO{sub 2} laser stabilized on a saturated absorption line of OsO{sub 4}. The stability and accuracy of the standard are transferred to the QCL resulting in a line width of the order of 10 Hz, and leading to the narrowest QCL to date. The locked QCL is then used to perform absorption spectroscopy spanning 6 GHz of NH{sub 3} and methyltrioxorhenium, two species of interest for applications in precision measurements.

  4. Experimental observation of pulse delay and speed-up in cascaded quantum well gain and absorber media

    DEFF Research Database (Denmark)

    Hansen, Per Lunnemann; Poel, Mike van der; Yvind, Kresten

    2008-01-01

    Slow-down and speed-up of 180 fs pulses in semiconductor waveguides beyond the existing models is obseved. Cascaded gain and absorbing sections is shown to provide significant temporal pulse shifting at near constant output pulse energy.......Slow-down and speed-up of 180 fs pulses in semiconductor waveguides beyond the existing models is obseved. Cascaded gain and absorbing sections is shown to provide significant temporal pulse shifting at near constant output pulse energy....

  5. An off Axis Cavity Enhanced Absorption Spectrometer and a Rapid Scan Spectrometer with a Room-Temperature External Cavity Quantum Cascade Laser

    Science.gov (United States)

    Liu, Xunchen; Kang, Cheolhwa; Xu, Yunjie

    2009-06-01

    Quantum cascade laser (QCL) is a new type of mid-infrared tunable diode lasers with superior output power and mode quality. Recent developments, such as room temperature operation, wide frequency tunability, and narrow line width, make QCLs an ideal light source for high resolution spectroscopy. Two slit jet infrared spectrometers, namely an off-axis cavity enhanced absorption (CEA) spectrometer and a rapid scan spectrometer with an astigmatic multi-pass cell assembly, have been coupled with a newly purchased room temperature tunable mod-hop-free QCL with a frequency coverage from 1592 cm^{-1} to 1698 cm^{-1} and a scan rate of 0.1 cm^{-1}/ms. Our aim is to utilize these two sensitive spectrometers, that are equipped with a molecular jet expansion, to investigate the chiral molecules-(water)_n clusters. To demonstrate the resolution and sensitivity achieved, the rovibrational transitions of the static N_2O gas and the bending rovibrational transitions of the Ar-water complex, a test system, at 1634 cm^{-1} have been measured. D. Hofstetter and J. Faist in High performance quantum cascade lasers and their applications, Vol.89 Springer-Verlag Berlin & Heidelberg, 2003, pp. 61-98. Y. Xu, X. Liu, Z. Su, R. M. Kulkarni, W. S. Tam, C. Kang, I. Leonov and L. D'Agostino, Proc. Spie, 2009, 722208 (1-11). M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 1997, 106, 3078-3089.

  6. Active standoff detection of CH4 and N2O leaks using hard-target backscattered light using an open-path quantum cascade laser sensor

    Science.gov (United States)

    Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

    2016-05-01

    Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they contribute to the global increase of greenhouse gas concentrations. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents standoff detection of CH4 and N2O leaks using a quantum cascade laser open-path system that retrieves path-averaged concentrations by collecting the backscattered light from a remote hard target. It is a true standoff system and differs from other open-path systems that are deployed as point samplers or long-path transmission systems that use retroreflectors. The measured absorption spectra are obtained using a thermal intra-pulse frequency chirped DFB quantum cascade laser at ~7.7 µm wavelength range with ~200 ns pulse width. Making fast time resolved observations, the system simultaneously realizes high spectral resolution and range to the target, resulting in path-averaged concentration retrieval. The system performs measurements at high speed ~15 Hz and sufficient range (up to 45 m, ~148 feet) achieving an uncertainty of 3.1 % and normalized sensitivity of 3.3 ppm m Hz-1/2 for N2O and 9.3 % and normalized sensitivity of 30 ppm m Hz-1/2 for CH4 with a 0.31 mW average power QCL. Given these characteristics, this system is promising for mobile or multidirectional search and remote detection of gas leaks.

  7. Conjugation of cascades

    International Nuclear Information System (INIS)

    San Martin, Jesus; Rodriguez-Perez, Daniel

    2009-01-01

    Presented in this work are some results relative to sequences found in the logistic equation bifurcation diagram, which is the unimodal quadratic map prototype. All of the different saddle-node bifurcation cascades, associated with every last appearance p-periodic orbit (p=3,4,5,...), can also be generated from the very Feigenbaum cascade. In this way it is evidenced the relationship between both cascades. The orbits of every saddle-node bifurcation cascade, mentioned above, are located in different chaotic bands, and this determines a sequence of orbits converging to every band-merging Misiurewicz point. In turn, these accumulation points form a sequence whose accumulation point is the Myrberg-Feigenbaum point. It is also proven that the first appearance orbits in the n-chaotic band converge to the same point as the last appearance orbits of the (n + 1)-chaotic band. The symbolic sequences of band-merging Misiurewicz points are computed for any window.

  8. Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: An experimental study of a single-pixel prototype

    International Nuclear Information System (INIS)

    Mei, X.; Pang, G.

    2005-01-01

    Our overall goal is to develop a new generation of electronic portal imaging devices (EPIDs) with a quantum efficiency (QE) more than an order of magnitude higher and a spatial resolution equivalent to that of EPIDs currently used for portal imaging. A novel design of such a high QE flat-panel based EPID was introduced recently and its feasibility was investigated theoretically [see Pang and Rowlands, Med. Phys. 31, 3004 (2004)]. In this work, we constructed a prototype single-pixel detector based on the novel design. Some fundamental imaging properties including the QE, spatial resolution, and sensitivity of the prototype detector were measured with a 6 MV beam. It has been shown that the experimental results agree well with theoretical predictions and further development based on the novel design including the construction of a prototype area detector is warranted

  9. Solution-Processed Nanocrystal Quantum Dot Tandem Solar Cells

    KAUST Repository

    Choi, Joshua J.; Wenger, Whitney N.; Hoffman, Rachel S.; Lim, Yee-Fun; Luria, Justin; Jasieniak, Jacek; Marohn, John A.; Hanrath, Tobias

    2011-01-01

    Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected quantum dot layers of cascaded energy gaps exhibit IR sensitivity and an open circuit voltage, V oc, approaching 1 V. The tandem solar cell performance depends critically on the optical and electrical properties of the interlayer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Solution-Processed Nanocrystal Quantum Dot Tandem Solar Cells

    KAUST Repository

    Choi, Joshua J.

    2011-06-03

    Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected quantum dot layers of cascaded energy gaps exhibit IR sensitivity and an open circuit voltage, V oc, approaching 1 V. The tandem solar cell performance depends critically on the optical and electrical properties of the interlayer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Hadronic cascade processes

    International Nuclear Information System (INIS)

    Ilgenfritz, E.M.; Kripfganz, J.; Moehring, H.J.

    1977-01-01

    The analytical treatment of hadronic decay cascades within the framework of the statistical bootstrap model is demonstrated on the basis of a simple variant. Selected problems for a more comprehensive formulation of the model such as angular momentum conservation, quantum statistical effects, and the immediate applicability to particle production processes at high energies are discussed in detail

  12. Stable single-mode distributed feedback quantum cascade lasers at λ ∼ 4.25 μm with low power consumption

    Science.gov (United States)

    Jia, Zhiwei; Wang, Lijun; Zhang, Jinchuan; Liu, Fengqi; Zhuo, Ning; Zhai, Shenqiang; Liu, Junqi; Wang, Zhanguo

    2016-10-01

    Short-wavelength (4.25 μm) distributed-feedback quantum cascade laser operating in continuous wave (cw) mode at room temperature with low power consumption was presented. Stable single-mode operation with a side-mode-suppression-ratio above 25 dB was maintained for the whole measured current and temperature range by enlarging gain difference and strong grating coupling. Because of the strong coupling, very low threshold current and power consumption were achieved. For a device of 9-μm-wide and 2-mm-long, the cw threshold current and power consumption at 293 K were as low as 126 mA and 1.45 W, respectively. All results above were from the device without using buried heterostructure geometry.

  13. Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser

    KAUST Repository

    Lamperti, Marco; Alsaif, Bidoor; Gatti, Davide; Fermann, Martin; Laporta, Paolo; Farooq, Aamir; Marangoni, Marco

    2018-01-01

    We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz. The strength of the approach, in view of an accurate retrieval of line centre frequencies over a spectral range as large as 100 cm-1, is demonstrated on the P(40), P(18) and R(31) lines of the fundamental rovibrational band of N2O covering the centre and edges of the P and R branches. The spectrometer has the potential to be straightforwardly extended to other spectral ranges, till 12 μm, which is the current wavelength limit for commercial cw EC-QCLs.

  14. Electrical tuning of the oscillator strength in type II InAs/GaInSb quantum wells for active region of passively mode-locked interband cascade lasers

    Science.gov (United States)

    Dyksik, Mateusz; Motyka, Marcin; Kurka, Marcin; Ryczko, Krzysztof; Misiewicz, Jan; Schade, Anne; Kamp, Martin; Höfling, Sven; Sęk, Grzegorz

    2017-11-01

    Two designs of active region for an interband cascade laser, based on double or triple GaInSb/InAs type II quantum wells (QWs), were compared with respect to passive mode-locked operation in the mid-infrared range around 4 µm. The layer structure and electron and hole wavefunctions under external electric field were engineered to allow controlling the optical transition oscillator strength and the resulting lifetimes. As a result, the investigated structures can mimic absorber-like and gain-like sections of a mode-locked device when properly polarized with opposite bias. A significantly larger oscillator strength tuning range for triple QWs was experimentally verified by Fourier-transform photoreflectance.

  15. Passive mode-locking of 3.25μm GaSb-based type-I quantum-well cascade diode lasers

    Science.gov (United States)

    Feng, Tao; Shterengas, Leon; Kipshidze, Gela; Hosoda, Takashi; Wang, Meng; Belenky, Gregory

    2018-02-01

    Passively mode-locked type-I quantum well cascade diode lasers emitting in the methane absorption band near 3.25 μm were designed, fabricated and characterized. The deep etched 5.5-μm-wide single spatial mode ridge waveguide design utilizing split-contact architecture was implemented. The devices with absorber to gain section length ratios of 11% and 5.5% were studied. Lasers with the longer absorber section ( 300 μm) generated smooth bell-shape-like emission spectrum with about 30 lasing modes at full-width-at-half-maximum level. Devices with reverse biased absorber section demonstrated stable radio frequency beat with nearly perfect Lorentzian shape over four orders of magnitude of intensity. The estimated pulse-to-pulse timing jitter was about 110 fs/cycle. Laser generated average power of more than 1 mW in mode-locked regime.

  16. Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser.

    Science.gov (United States)

    Lamperti, Marco; AlSaif, Bidoor; Gatti, Davide; Fermann, Martin; Laporta, Paolo; Farooq, Aamir; Marangoni, Marco

    2018-01-22

    We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz. The strength of the approach, in view of an accurate retrieval of line centre frequencies over a spectral range as large as 100 cm -1 , is demonstrated on the P(40), P(18) and R(31) lines of the fundamental rovibrational band of N 2 O covering the centre and edges of the P and R branches. The spectrometer has the potential to be straightforwardly extended to other spectral ranges, till 12 μm, which is the current wavelength limit for commercial cw EC-QCLs.

  17. High power frequency comb based on mid-infrared quantum cascade laser at λ ∼ 9 μm

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Q. Y.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu; Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Zhou, W. J.; Chen, M.; Heydari, D.; Haddadi, A.; McClintock, R. [Center for Quantum Devices, Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, Illinois 60208 (United States); Amanti, M.; Sirtori, C. [Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot and CNRS, UMR7162, 75205 Paris (France)

    2015-02-02

    We investigate a frequency comb source based on a mid-infrared quantum cascade laser at λ ∼ 9 μm with high power output. A broad flat-top gain with near-zero group velocity dispersion has been engineered using a dual-core active region structure. This favors the locking of the dispersed Fabry-Pérot modes into equally spaced frequency lines via four wave mixing. A current range with a narrow intermode beating linewidth of 3 kHz is identified with a fast detector and spectrum analyzer. This range corresponds to a broad spectral coverage of 65 cm{sup −1} and a high power output of 180 mW for ∼176 comb modes.

  18. High power frequency comb based on mid-infrared quantum cascade laser at λ ∼ 9 μm

    International Nuclear Information System (INIS)

    Lu, Q. Y.; Razeghi, M.; Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Zhou, W. J.; Chen, M.; Heydari, D.; Haddadi, A.; McClintock, R.; Amanti, M.; Sirtori, C.

    2015-01-01

    We investigate a frequency comb source based on a mid-infrared quantum cascade laser at λ ∼ 9 μm with high power output. A broad flat-top gain with near-zero group velocity dispersion has been engineered using a dual-core active region structure. This favors the locking of the dispersed Fabry-Pérot modes into equally spaced frequency lines via four wave mixing. A current range with a narrow intermode beating linewidth of 3 kHz is identified with a fast detector and spectrum analyzer. This range corresponds to a broad spectral coverage of 65 cm −1 and a high power output of 180 mW for ∼176 comb modes

  19. Enhancing the sensitivity of mid-IR quantum cascade laser-based cavity-enhanced absorption spectroscopy using RF current perturbation.

    Science.gov (United States)

    Manfred, Katherine M; Kirkbride, James M R; Ciaffoni, Luca; Peverall, Robert; Ritchie, Grant A D

    2014-12-15

    The sensitivity of mid-IR quantum cascade laser (QCL) off-axis cavity-enhanced absorption spectroscopy (CEAS), often limited by cavity mode structure and diffraction losses, was enhanced by applying a broadband RF noise to the laser current. A pump-probe measurement demonstrated that the addition of bandwidth-limited white noise effectively increased the laser linewidth, thereby reducing mode structure associated with CEAS. The broadband noise source offers a more sensitive, more robust alternative to applying single-frequency noise to the laser. Analysis of CEAS measurements of a CO(2) absorption feature at 1890  cm(-1) averaged over 100 ms yielded a minimum detectable absorption of 5.5×10(-3)  Hz(-1/2) in the presence of broadband RF perturbation, nearly a tenfold improvement over the unperturbed regime. The short acquisition time makes this technique suitable for breath applications requiring breath-by-breath gas concentration information.

  20. A two-level model of rise time in quantum cascade laser materials applied to 5 micron, 9 micron and terahertz-range wavelengths

    International Nuclear Information System (INIS)

    Webb, J F; Yong, K S C; Haldar, M K

    2014-01-01

    An equivalent circuit simulation of a two-level rate equation model for quantum cascade laser (QCL) materials is used to study the turn on delay and rise time for three QCLs with 5 micron, 9 micron and terahertz-range wavelengths. In order to do this it is necessary that the model can deal with large signal responses and not be restricted to small signal responses; the model used here is capable of this. The effect of varying some of the characteristic times in the model is also investigated. The comparison of the terahertz wave QCL with the others is particularly important given the increased interest in terahertz sources which have a large range of important applications, such as in medical imaging

  1. Measurements of linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene in the ν4+ν5 combination band using a cw quantum cascade laser

    KAUST Repository

    Sajid, Muhammad Bilal

    2014-11-01

    Linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene have been measured at 296K in the P branch of the ν4+ν5 combination band for 25 rotational transitions. The effect of gas temperature is studied over 296-683K for five transitions to allow the determination of the temperature dependent exponent n for N2- and Ar-broadening coefficients. These measurements were performed using a continuous-wave quantum cascade laser (cw-QCL) operating over 1253-1310cm-1. Spectroscopic parameters were obtained by fitting absorption spectra using Voigt, Galatry and Rautian profiles. Linestrength and broadening results are compared with previous studies available in literature for the ν4+ν5 combination band and other vibrational bands of acetylene. © 2014 Elsevier Ltd.

  2. Phenomenological scattering-rate model for the simulation of the current density and emission power in mid-infrared quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Kurlov, S. S. [Department of Physics, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Institute of Semiconductor Physics, National Academy of Sciences, pr. Nauki 45, Kiev-03028 (Ukraine); Flores, Y. V.; Elagin, M.; Semtsiv, M. P.; Masselink, W. T. [Department of Physics, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Schrottke, L.; Grahn, H. T. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin (Germany); Tarasov, G. G. [Institute of Semiconductor Physics, National Academy of Sciences, pr. Nauki 45, Kiev-03028 (Ukraine)

    2016-04-07

    A phenomenological scattering-rate model introduced for terahertz quantum cascade lasers (QCLs) [Schrottke et al., Semicond. Sci. Technol. 25, 045025 (2010)] is extended to mid-infrared (MIR) QCLs by including the energy dependence of the intersubband scattering rates for energies higher than the longitudinal optical phonon energy. This energy dependence is obtained from a phenomenological fit of the intersubband scattering rates based on published lifetimes of a number of MIR QCLs. In our approach, the total intersubband scattering rate is written as the product of the exchange integral for the squared moduli of the envelope functions and a phenomenological factor that depends only on the transition energy. Using the model to calculate scattering rates and imposing periodical boundary conditions on the current density, we find a good agreement with low-temperature data for current-voltage, power-current, and energy-photon flux characteristics for a QCL emitting at 5.2 μm.

  3. Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser

    KAUST Repository

    Lamperti, Marco

    2018-01-16

    We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz. The strength of the approach, in view of an accurate retrieval of line centre frequencies over a spectral range as large as 100 cm-1, is demonstrated on the P(40), P(18) and R(31) lines of the fundamental rovibrational band of N2O covering the centre and edges of the P and R branches. The spectrometer has the potential to be straightforwardly extended to other spectral ranges, till 12 μm, which is the current wavelength limit for commercial cw EC-QCLs.

  4. Laterally coupled distributed feedback type-I quantum well cascade diode lasers emitting near 3.22  μm.

    Science.gov (United States)

    Feng, Tao; Hosoda, Takashi; Shterengas, Leon; Kipshidze, Gela; Stein, Aaron; Lu, Ming; Belenky, Gregory

    2017-11-01

    The laterally coupled distributed feedback (LC-DFB) GaSb-based type-I quantum well cascade diode lasers using the second- and the sixth-order gratings to stabilize the output spectrum near 3.22 μm were designed and fabricated. The laser heterostructure contained three cascades. The devices were manufactured using a single dry etching step defining the ∼5-μm-wide ridge with ∼5-μm-wide gratings sections adjacent to the ridge sides. The grating coupling coefficients were estimated to be about 1  cm -1 . The stability of the single-frequency operation was ensured by alignment of the DFB mode to the relatively wide gain peak. The 2-mm-long second-order LC-DFB lasers generated above 10 mW of continuous-wave (CW) output power at 20°C in epi-side-up configuration and demonstrated power conversion efficiency above 2%. The sixth-order LC-DFB lasers showed lower efficiency but still generated several milliwatts of CW output power. The devices demonstrated a CW current tuning range of about 3.5 nm at the temperature of 20°C.

  5. High-accuracy and high-sensitivity spectroscopic measurement of dinitrogen pentoxide (N2O5) in an atmospheric simulation chamber using a quantum cascade laser.

    Science.gov (United States)

    Yi, Hongming; Wu, Tao; Lauraguais, Amélie; Semenov, Vladimir; Coeur, Cecile; Cassez, Andy; Fertein, Eric; Gao, Xiaoming; Chen, Weidong

    2017-12-04

    A spectroscopic instrument based on a mid-infrared external cavity quantum cascade laser (EC-QCL) was developed for high-accuracy measurements of dinitrogen pentoxide (N 2 O 5 ) at the ppbv-level. A specific concentration retrieval algorithm was developed to remove, from the broadband absorption spectrum of N 2 O 5 , both etalon fringes resulting from the EC-QCL intrinsic structure and spectral interference lines of H 2 O vapour absorption, which led to a significant improvement in measurement accuracy and detection sensitivity (by a factor of 10), compared to using a traditional algorithm for gas concentration retrieval. The developed EC-QCL-based N 2 O 5 sensing platform was evaluated by real-time tracking N 2 O 5 concentration in its most important nocturnal tropospheric chemical reaction of NO 3 + NO 2 ↔ N 2 O 5 in an atmospheric simulation chamber. Based on an optical absorption path-length of L eff = 70 m, a minimum detection limit of 15 ppbv was achieved with a 25 s integration time and it was down to 3 ppbv in 400 s. The equilibrium rate constant K eq involved in the above chemical reaction was determined with direct concentration measurements using the developed EC-QCL sensing platform, which was in good agreement with the theoretical value deduced from a referenced empirical formula under well controlled experimental conditions. The present work demonstrates the potential and the unique advantage of the use of a modern external cavity quantum cascade laser for applications in direct quantitative measurement of broadband absorption of key molecular species involved in chemical kinetic and climate-change related tropospheric chemistry.

  6. 5.5 W near-diffraction-limited power from resonant leaky-wave coupled phase-locked arrays of quantum cascade lasers

    International Nuclear Information System (INIS)

    Kirch, J. D.; Chang, C.-C.; Boyle, C.; Mawst, L. J.; Botez, D.; Lindberg, D.; Earles, T.

    2015-01-01

    Five, 8.36 μm-emitting quantum-cascade lasers (QCLs) have been monolithically phase-locked in the in-phase array mode via resonant leaky-wave coupling. The structure is fabricated by etch and regrowth which provides large index steps (Δn = 0.10) between antiguided-array elements and interelement regions. Such high index contrast photonic-crystal (PC) lasers have more than an order of magnitude higher index contrast than PC-distributed feedback lasers previously used for coherent beam combining in QCLs. Absorption loss to metal layers inserted in the interelement regions provides a wide (∼1.0 μm) range in interelement width over which the resonant in-phase mode is strongly favored to lase. Room-temperature, in-phase-mode operation with ∼2.2 kA/cm 2 threshold-current density is obtained from 105 μm-wide aperture devices. The far-field beam pattern has lobewidths 1.65× diffraction limit (D.L.) and 82% of the light in the main lobe, up to 1.8× threshold. Peak pulsed near-D.L. power of 5.5 W is obtained, with 4.5 W emitted in the main lobe. Means of how to increase the device internal efficiency are discussed

  7. CO concentration and temperature sensor for combustion gases using quantum-cascade laser absorption near 4.7 μm

    KAUST Repository

    Ren, Wei

    2012-05-25

    A sensor for sensitive in situ measurements of carbon monoxide and temperature in combustion gases has been developed using absorption transitions in the (v′ = 1 ← v″ = 0) and (v′ = 2 ← v″ = 1) fundamental bands of CO. Recent availability of mid-infrared quantum-cascade (QC) lasers provides convenient access to the CO fundamental band near 4.7 μm, having approximately 104 and 102 times stronger absorption line-strengths compared to the overtone bands near 1.55 μm and 2.3 μm used previously to sense CO in combustion gases. Spectroscopic parameters of the selected transitions were determined via laboratory measurements in a shock tube over the 1100-2000 K range and also at room temperature. A single-laser absorption sensor was developed for accurate CO measurements in shock-heated gases by scanning the line pair v″ = 0, R(12) and v″ = 1, R(21) at 2.5 kHz. To capture the rapidly varying CO time-histories in chemical reactions, two different QC lasers were then used to probe the line-center absorbance of transitions v″ = 0, P(20) and v″ = 1, R(21) with a bandwidth of 1 MHz using fixed-wavelength direct absorption. The sensor was applied in successful shock tube measurements of temperature and CO time-histories during the pyrolysis and oxidation of methyl formate, illustrating the capability of this sensor for chemical kinetic studies. © 2012 Springer-Verlag.

  8. Direct determination of glucose, lactate and triglycerides in blood serum by a tunable quantum cascade laser-based mid-IR sensor

    Science.gov (United States)

    Brandstetter, M.; Volgger, L.; Genner, A.; Jungbauer, C.; Lendl, B.

    2013-02-01

    This work reports on a compact sensor for fast and reagent-free point-of-care determination of glucose, lactate and triglycerides in blood serum based on a tunable (1030-1230 cm-1) external-cavity quantum cascade laser (EC-QCL). For simple and robust operation a single beam set-up was designed and only thermoelectric cooling was used for the employed laser and detector. Full computer control of analysis including liquid handling and data analysis facilitated routine measurements. A high optical pathlength (>100 μm) is a prerequisite for robust measurements in clinical practice. Hence, the optimum optical pathlength for transmission measurements in aqueous solution was considered in theory and experiment. The experimentally determined maximum signal-to-noise ratio (SNR) was around 140 μm for the QCL blood sensor and around 50 μm for a standard FT-IR spectrometer employing a liquid nitrogen cooled mercury cadmium telluride (MCT) detector. A single absorption spectrum was used to calculate the analyte concentrations simultaneously by using a partial-least-squares (PLS) regression analysis. Glucose was determined in blood serum with a prediction error (RMSEP) of 6.9 mg/dl and triglycerides with an error of cross-validation (RMSECV) of 17.5 mg/dl in a set of 42 different patients. In spiked serum samples the lactate concentration could be determined with an RMSECV of 8.9 mg/dl.

  9. Cascade Pumping of 1.9–3.3 μm Type-I Quantum Well GaSb-Based Diode Lasers

    International Nuclear Information System (INIS)

    Shterengas, Leon; Kipshidze, Gela; Hosoda, Takashi; Liang, Rui; Feng, Tao

    2017-01-01

    Cascade pumping of type-I quantum well gain sections was utilized to increase output power and efficiency of GaSb-based diode lasers operating in spectral region from 1.9 to 3.3 μm. Coated devices with ~100-μm-wide aperture and 3-mm-long cavity demonstrated continuous wave (CW) output power of 1.96 W near 2 μm, 980 mW near 3 μm, 500 mW near 3.18 μm, and 360 mW near 3.25 μm at room temperature. The corresponding narrow ridge lasers with nearly diffraction limited beams operate in CW regime with tens of mW of output power up to 60 °C. Two step shallow/deep narrow/wide ridge waveguide devices showed lower threshold currents and higher slope efficiencies compared to single step narrow ridge lasers. Laterally coupled DFB lasers mounted epi-up generated above 10 mW of tunable single frequency CW power at 20 °C near 3.22 μm.

  10. CO concentration and temperature sensor for combustion gases using quantum-cascade laser absorption near 4.7 μm

    KAUST Repository

    Ren, Wei; Farooq, Aamir; Davidson, David Frank; Hanson, Ronald Kenneth

    2012-01-01

    A sensor for sensitive in situ measurements of carbon monoxide and temperature in combustion gases has been developed using absorption transitions in the (v′ = 1 ← v″ = 0) and (v′ = 2 ← v″ = 1) fundamental bands of CO. Recent availability of mid-infrared quantum-cascade (QC) lasers provides convenient access to the CO fundamental band near 4.7 μm, having approximately 104 and 102 times stronger absorption line-strengths compared to the overtone bands near 1.55 μm and 2.3 μm used previously to sense CO in combustion gases. Spectroscopic parameters of the selected transitions were determined via laboratory measurements in a shock tube over the 1100-2000 K range and also at room temperature. A single-laser absorption sensor was developed for accurate CO measurements in shock-heated gases by scanning the line pair v″ = 0, R(12) and v″ = 1, R(21) at 2.5 kHz. To capture the rapidly varying CO time-histories in chemical reactions, two different QC lasers were then used to probe the line-center absorbance of transitions v″ = 0, P(20) and v″ = 1, R(21) with a bandwidth of 1 MHz using fixed-wavelength direct absorption. The sensor was applied in successful shock tube measurements of temperature and CO time-histories during the pyrolysis and oxidation of methyl formate, illustrating the capability of this sensor for chemical kinetic studies. © 2012 Springer-Verlag.

  11. Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser

    Science.gov (United States)

    Chevalier, Paul; Piccardo, Marco; Anand, Sajant; Mejia, Enrique A.; Wang, Yongrui; Mansuripur, Tobias S.; Xie, Feng; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

    2018-02-01

    Free-running Fabry-Perot lasers normally operate in a single-mode regime until the pumping current is increased beyond the single-mode instability threshold, above which they evolve into a multimode state. As a result of this instability, the single-mode operation of these lasers is typically constrained to few percents of their output power range, this being an undesired limitation in spectroscopy applications. In order to expand the span of single-mode operation, we use an optical injection seed generated by an external-cavity single-mode laser source to force the Fabry-Perot quantum cascade laser into a single-mode state in the high current range, where it would otherwise operate in a multimode regime. Utilizing this approach, we achieve single-mode emission at room temperature with a tuning range of 36 cm-1 and stable continuous-wave output power exceeding 1 W at 4.5 μm. Far-field measurements show that a single transverse mode is emitted up to the highest optical power, indicating that the beam properties of the seeded Fabry-Perot laser remain unchanged as compared to free-running operation.

  12. Phase locking of a 1.5 Terahertz quantum cascade laser and use as a local oscillator in a heterodyne HEB receiver.

    Science.gov (United States)

    Rabanus, D; Graf, U U; Philipp, M; Ricken, O; Stutzki, J; Vowinkel, B; Wiedner, M C; Walther, C; Fischer, M; Faist, J

    2009-02-02

    We demonstrate for the first time the closure of an electronic phase lock loop for a continuous-wave quantum cascade laser (QCL) at 1.5 THz. The QCL is operated in a closed cycle cryo cooler. We achieved a frequency stability of better than 100 Hz, limited by the resolution bandwidth of the spectrum analyser. The PLL electronics make use of the intermediate frequency (IF) obtained from a hot electron bolometer (HEB) which is downconverted to a PLL IF of 125 MHz. The coarse selection of the longitudinal mode and the fine tuning is achieved via the bias voltage of the QCL. Within a QCL cavity mode, the free-running QCL shows frequency fluctuations of about 5 MHz, which the PLL circuit is able to control via the Stark-shift of the QCL gain material. Temperature dependent tuning is shown to be nonlinear, and of the order of -16 MHz/K. Additionally we have used the QCL as local oscillator (LO) to pump an HEB and perform, again for the first time at 1.5 THz, a heterodyne experiment, and obtain a receiver noise temperature of 1741 K.

  13. Compact and portable open-path sensor for simultaneous measurements of atmospheric N2O and CO using a quantum cascade laser.

    Science.gov (United States)

    Tao, Lei; Sun, Kang; Khan, M Amir; Miller, David J; Zondlo, Mark A

    2012-12-17

    A compact and portable open-path sensor for simultaneous detection of atmospheric N(2)O and CO has been developed with a 4.5 μm quantum cascade laser (QCL). An in-line acetylene (C(2)H(2)) gas reference cell allows for continuous monitoring of the sensor drift and calibration in rapidly changing field environments and thereby allows for open-path detection at high precision and stability. Wavelength modulation spectroscopy (WMS) is used to detect simultaneously both the second and fourth harmonic absorption spectra with an optimized dual modulation amplitude scheme. Multi-harmonic spectra containing atmospheric N(2)O, CO, and the reference C(2)H(2) signals are fit in real-time (10 Hz) by combining a software-based lock-in amplifier with a computationally fast numerical model for WMS. The sensor consumes ~50 W of power and has a mass of ~15 kg. Precision of 0.15 ppbv N(2)O and 0.36 ppbv CO at 10 Hz under laboratory conditions was demonstrated. The sensor has been deployed for extended periods in the field. Simultaneous N(2)O and CO measurements distinguished between natural and fossil fuel combustion sources of N(2)O, an important greenhouse gas with poorly quantified emissions in space and time.

  14. Comprehensive growth and characterization study on highly n-doped InGaAs as a contact layer for quantum cascade laser applications

    Science.gov (United States)

    Demir, Ilkay; Altuntas, Ismail; Bulut, Baris; Ezzedini, Maher; Ergun, Yuksel; Elagoz, Sezai

    2018-05-01

    We present growth and characterization studies of highly n-doped InGaAs epilayers on InP substrate by metal organic vapor phase epitaxy to use as an n-contact layer in quantum cascade laser applications. We have introduced quasi two-dimensional electrons between 10 s pulsed growth n-doped InGaAs epilayers to improve both carrier concentration and mobility of structure by applying pulsed growth and doping methods towards increasing the Si dopant concentration in InGaAs. Additionally, the V/III ratio optimization under fixed group III source flow has been investigated with this new method to understand the effects on both crystalline quality and electrical properties of n-InGaAs epilayers. Finally, we have obtained high crystalline quality of n-InGaAs epilayers grown by 10 s pulsed as a contact layer with 2.8 × 1019 cm‑3 carrier concentration and 1530 cm2 V‑1 s‑1 mobility.

  15. The determination of the chemical composition profile of the GaAs/AlGaAs heterostructures designed for quantum cascade lasers by means of synchrotron radiation

    International Nuclear Information System (INIS)

    Gaca, Jaroslaw; Wojcik, Marek; Bugajski, Maciej; Kosiel, Kamil

    2011-01-01

    The chemical composition profile of the GaAs/AlGaAs quantum cascade structures grown on (0 0 1) GaAs substrate by molecular beam epitaxy is studied by a synchrotron radiation high-resolution X-ray diffraction. The analysis is carried out for the whole structure as well for its parts. In order to determine some structural parameters, such as: the thickness and chemical composition of each layer making up the investigated structure, the profile of the interface between succeeding layers, and the preservation of the structure periodicity, the experimental X-ray diffraction profiles are compared with simulated ones calculated by means of Darwin dynamical theory of X-ray diffraction. It is shown that this method gives correct chemical composition profiles and allows for the evaluation of the deviations from the designed values of the structural parameters in most investigated cases. Limits of the method are discussed, especially by the determination of the chemical composition profile for thin heterostructures, such as those making active or injector regions.

  16. Design of three-well indirect pumping terahertz quantum cascade lasers for high optical gain based on nonequilibrium Green's function analysis

    Science.gov (United States)

    Liu, Tao; Kubis, Tillmann; Jie Wang, Qi; Klimeck, Gerhard

    2012-03-01

    The nonequilibrium Green's function approach is applied to the design of three-well indirect pumping terahertz (THz) quantum cascade lasers (QCLs) based on a resonant phonon depopulation scheme. The effects of the anticrossing of the injector states and the dipole matrix element of the laser levels on the optical gain of THz QCLs are studied. The results show that a design that results in a more pronounced anticrossing of the injector states will achieve a higher optical gain in the indirect pumping scheme compared to the traditional resonant-tunneling injection scheme. This offers in general a more efficient coherent resonant-tunneling transport of electrons in the indirect pumping scheme. It is also shown that, for operating temperatures below 200 K and low lasing frequencies, larger dipole matrix elements, i.e., vertical optical transitions, offer a higher optical gain. In contrast, in the case of high lasing frequencies, smaller dipole matrix elements, i.e., diagonal optical transitions are better for achieving a higher optical gain.

  17. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    Science.gov (United States)

    Pitt, Joseph; Le Breton, Michael; Allen, Grant; Percival, Carl; Gallagher, Martin; Bauguitte, Stephane; O'Shea, Sebastian; Muller, Jennifer; Zahniser, Mark; Pyle, John; Palmer, Paul

    2016-04-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We evaluate the performance of the mid-IR continuous wave Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. Test flight data demonstrating the sensitivity of the instrument to changes in cabin pressure is presented, and a new in-flight calibration procedure to account for this issue is described and assessed. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA).

  18. Active Stand-off Detection of Gas Leaks Using a Short Range Hard-target Backscatter Differential Optical Absorption System Based on a Quantum Cascade Laser Transmitter

    Science.gov (United States)

    Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

    2016-06-01

    Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they can contribute to the global increase of greenhouse gas concentration. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents gas concentration measurements using a quantum cascade laser open path system (QCLOPS). The system retrieves the pathaveraged concentration of N2O and CH4 by collecting the backscattered light from a scattering target. The gas concentration measurements have a high temporal resolution (68 ms) and are achieved at sufficient range (up to 40 m, ~ 130 feet) with a detection limit of 2.6 ppm CH4 and 0.4 ppm for N2O. Given these characteristics, this system is promising for mobile/multidirectional remote detection and evaluation of gas leaks. The instrument is monostatic with a tunable QCL emitting at ~ 7.7 μm wavelength range. The backscattered radiation is collected by a Newtonian telescope and focused on an infrared light detector. Puffs of N2O and CH4 are released along the optical path to simulate a gas leak. The measured absorption spectrum is obtained using the thermal intra-pulse frequency chirped DFB QCL and is analyzed to obtain path averaged gas concentrations.

  19. Wavefront measurement of single-mode quantum cascade laser beam for seed application in laser-produced plasma extreme ultraviolet system.

    Science.gov (United States)

    Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru

    2012-12-01

    Quantum cascade laser (QCL) is a very attractive seed source for a multikilowatt pulsed CO2 lasers applied for driving extreme ultraviolet emitting plasmas. In this Letter, we investigate output beam properties of a QCL designed to address P18 and P20 lines of 10.6 micron band of CO2 molecule. In particular, output beam quality and stability are investigated for the first time. A well-defined linear polarization and a single-mode operation enabled a use of phase retrieval method for full description of QCL output beam. A direct, multi-image numerical phase retrieval technique was developed and successfully applied to the measured intensity patterns of a QCL beam. Very good agreement between the measured and reconstructed beam profiles was observed at distances ranging from QCL aperture to infinity, proving a good understanding of the beam propagation. The results also confirm a high spatial coherence and high stability of the beam parameters, the features expected from an excellent seed source.

  20. Coagulation and ablation of biological soft tissue by quantum cascade laser with peak wavelength of 5.7 μm

    Directory of Open Access Journals (Sweden)

    Keisuke Hashimura

    2014-05-01

    Full Text Available Molecules such as water, proteins and lipids that are contained in biological tissue absorb mid-infrared (MIR light, which allows such light to be used in laser surgical treatment. Esters, amides and water exhibit strong absorption bands in the 5–7 μm wavelength range, but at present there are no lasers in clinical use that can emit in this range. Therefore, the present study focused on the quantum cascade laser (QCL, which is a new type of semiconductor laser that can emit at MIR wavelengths and has recently achieved high output power. A high-power QCL with a peak wavelength of 5.7 μm was evaluated for use as a laser scalpel for ablating biological soft tissue. The interaction of the laser beam with chicken breast tissue was compared to a conventional CO2 laser, based on surface and cross-sectional images. The QCL was found to have sufficient power to ablate soft tissue, and its coagulation, carbonization and ablation effects were similar to those for the CO2 laser. The QCL also induced comparable photothermal effects because it acted as a pseudo-continuous wave laser due to its low peak power. A QCL can therefore be used as an effective laser scalpel, and also offers the possibility of less invasive treatment by targeting specific absorption bands in the MIR region.

  1. Architectural prototyping

    DEFF Research Database (Denmark)

    Bardram, Jakob Eyvind; Christensen, Henrik Bærbak; Hansen, Klaus Marius

    2004-01-01

    A major part of software architecture design is learning how specific architectural designs balance the concerns of stakeholders. We explore the notion of "architectural prototypes", correspondingly architectural prototyping, as a means of using executable prototypes to investigate stakeholders...

  2. MATLAB-based program for optimization of quantum cascade laser active region parameters and calculation of output characteristics in magnetic field

    Science.gov (United States)

    Smiljanić, J.; Žeželj, M.; Milanović, V.; Radovanović, J.; Stanković, I.

    2014-03-01

    A strong magnetic field applied along the growth direction of a quantum cascade laser (QCL) active region gives rise to a spectrum of discrete energy states, the Landau levels. By combining quantum engineering of a QCL with a static magnetic field, we can selectively inhibit/enhance non-radiative electron relaxation process between the relevant Landau levels of a triple quantum well and realize a tunable surface emitting device. An efficient numerical algorithm implementation is presented of optimization of GaAs/AlGaAs QCL region parameters and calculation of output properties in the magnetic field. Both theoretical analysis and MATLAB implementation are given for LO-phonon and interface roughness scattering mechanisms on the operation of QCL. At elevated temperatures, electrons in the relevant laser states absorb/emit more LO-phonons which results in reduction of the optical gain. The decrease in the optical gain is moderated by the occurrence of interface roughness scattering, which remains unchanged with increasing temperature. Using the calculated scattering rates as input data, rate equations can be solved and population inversion and the optical gain obtained. Incorporation of the interface roughness scattering mechanism into the model did not create new resonant peaks of the optical gain. However, it resulted in shifting the existing peaks positions and overall reduction of the optical gain. Catalogue identifier: AERL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AERL_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 37763 No. of bytes in distributed program, including test data, etc.: 2757956 Distribution format: tar.gz Programming language: MATLAB. Computer: Any capable of running MATLAB version R2010a or higher. Operating system: Any platform

  3. ZnCdMgSe as a Materials Platform for Advanced Photonic Devices: Broadband Quantum Cascade Detectors and Green Semiconductor Disk Lasers

    Science.gov (United States)

    De Jesus, Joel

    The ZnCdMgSe family of II-VI materials has unique and promising characteristics that may be useful in practical applications. For example they can be grown lattice matched to InP substrates with lattice matched bandgaps that span from 2.1 to 3.5 eV, they can be successfully doped n-type, have a large conduction band offset (CBO) with no intervalley scattering present when strained, they have lower average phonon energies, and the InP lattice constant lies in the middle of the ZnSe and CdSe binaries compounds giving room to experiment with tensile and compressive stress. However they have not been studied in detail for use in practical devices. Here we have identified two types of devices that are being currently developed that benefit from the ZnCdMgSe-based material properties. These are the intersubband (ISB) quantum cascade (QC) detectors and optically pumped semiconductor lasers that emit in the visible range. The paucity for semiconductor lasers operating in the green-orange portion of the visible spectrum can be easily overcome with the ZnCdMgSe materials system developed in our research. The non-strain limited, large CBO available allows to expand the operating wavelength of ISB devices providing shorter and longer wavelengths than the currently commercially available devices. This property can also be exploited to develop broadband room temperature operation ISB detectors. The work presented here focused first on using the ZnCdMgSe-based material properties and parameter to understand and predict the interband and intersubband transitions of its heterostructures. We did this by studying an active region of a QC device by contactless electroreflectance, photoluminescence, FTIR transmittance and correlating the measurements to the quantum well structure by transfer matrix modeling. Then we worked on optimizing the ZnCdMgSe material heterostructures quality by studying the effects of growth interruptions on their optical and optoelectronic properties of

  4. Learning Cascading

    CERN Document Server

    Covert, Michael

    2015-01-01

    This book is intended for software developers, system architects and analysts, big data project managers, and data scientists who wish to deploy big data solutions using the Cascading framework. You must have a basic understanding of the big data paradigm and should be familiar with Java development techniques.

  5. Ammonia detection using hollow waveguide enhanced laser absorption spectroscopy based on a 9.56 μm quantum cascade laser

    Science.gov (United States)

    Li, Jinyi; Yang, Sen; Wang, Ruixue; Du, Zhenhui; Wei, Yingying

    2017-10-01

    Ammonia (NH3) is the most abundant alkalescency trace gas in the atmosphere having a foul odor, which is produced by both natural and anthropogenic sources. Chinese Emission Standard for Odor Pollutants has listed NH3 as one of the eight malodorous pollutants since 1993, specifying the emission concentration less than 1 mg/m3 (1.44ppmv). NH3 detection continuously from ppb to ppm levels is significant for protection of environmental atmosphere and safety of industrial and agricultural production. Tunable laser absorption spectroscopy (TLAS) is an increasingly important optical method for trace gas detection. TLAS do not require pretreatment and accumulation of the concentration of the analyzed sample, unlike, for example, more conventional methods such as mass spectrometry or gas chromatography. In addition, TLAS can provide high precision remote sensing capabilities, high sensitivities and fast response. Hollow waveguide (HWG) has recently emerged as a novel concept serving as an efficient optical waveguide and as a highly miniaturized gas cell. Among the main advantages of HWG gas cell compared with conventional multi-pass gas cells is the considerably decreased sample which facilitates gas exchanging. An ammonia sensor based on TLAS using a 5m HWG as the gas cell is report here. A 9.56μm, continuous-wave, distributed feed-back (DFB), room temperature quantum cascade laser (QCL), is employed as the optical source. The interference-free NH3 absorption line located at 1046.4cm-1 (λ 9556.6nm) is selected for detection by analyzing absorption spectrum from 1045-1047 cm-1 within the ν2 fundamental absorption band of ammonia. Direct absorption spectroscopy (DAS) technique is utilized and the measured spectral line is fitted by a simulation model by HITRAN database to obtain the NH3 concentration. The sensor performance is tested with standard gas and the result shows a 1σ minimum detectable concentration of ammonia is about 200 ppb with 1 sec time resolution

  6. Modelling, Design, Growth and Characterization of Strain Balanced Quantum Cascade Lasers (3-11mum), grown by Gas Source Molecular Beam Epitaxy

    Science.gov (United States)

    Bandyopadhyay, Neelanjan

    Quantum Cascade Laser (QCL) is a compact room temperature (RT) source of mid-infrared radiation, which can be used for spectroscopic detection of trace amount of chemicals. The mid-infrared spectral range between (3-11 microm), has a dense array of absorption lines of numerous molecules, due to the presence of fundamental vibrational modes. The goal of this thesis can be subdivided into two parts. Firstly, short wavelength QCLs, emitting below 4microm, perform poorly at RT, due to inter-valley Gamma --- L carrier scattering, carrier escape to the continuum, heat removal from the core region at high power density corresponding to short wavelength operation, and large interface scattering due to highly strained materials. Secondly, it is desirable to have a single QCL based source emitting between 6-10microm, which be used to detect multiple molecules having their peak absorptions far apart, inside this spectral range. However, gain bandwidth of a single core QCL is relatively small, so laser emission cannot be tuned over a wide spectral range. This thesis describes the working principle of a QCL based on superlattice transport, rate equations, scattering mechanism, and waveguide design. The choice of the material system for this work and the fundamentals of band structure engineering has been derived. Gas source molecular beam epitaxy - growth optimization and characterization is one of the most important features of this work, especially for short wavelength QCLs, and has been explained in depth. Different strategies for design of active region design of short wavelength QCL and heterogeneous broadband QCL has been explored. The major milestones, of this research was the world's first watt level continuous wave (CW), RT demonstration at 3.76 microm, which was followed by another milestone of the first CW, RT demonstration at 3.39microm and 3.55microm, and finally the elusive result of QCL emitting at CW, RT at a wavelength as short as lambda ~3microm, a record. In

  7. Collaborative Prototyping

    DEFF Research Database (Denmark)

    Bogers, Marcel; Horst, Willem

    2014-01-01

    of the prototyping process, the actual prototype was used as a tool for communication or development, thus serving as a platform for the cross-fertilization of knowledge. In this way, collaborative prototyping leads to a better balance between functionality and usability; it translates usability problems into design......This paper presents an inductive study that shows how collaborative prototyping across functional, hierarchical, and organizational boundaries can improve the overall prototyping process. Our combined action research and case study approach provides new insights into how collaborative prototyping...... can provide a platform for prototype-driven problem solving in early new product development (NPD). Our findings have important implications for how to facilitate multistakeholder collaboration in prototyping and problem solving, and more generally for how to organize collaborative and open innovation...

  8. Prototyping Practice

    DEFF Research Database (Denmark)

    Ramsgaard Thomsen, Mette; Tamke, Martin

    2015-01-01

    This paper examines the role of the prototyping in digital architecture. During the past decade, a new research field has emerged exploring the digital technology’s impact on the way we think, design and build our environment. In this practice the prototype, the pavilion, installation or demonstr......This paper examines the role of the prototyping in digital architecture. During the past decade, a new research field has emerged exploring the digital technology’s impact on the way we think, design and build our environment. In this practice the prototype, the pavilion, installation...

  9. Quantum

    CERN Document Server

    Al-Khalili, Jim

    2003-01-01

    In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.

  10. Direct phase-locking of a 8.6-μm quantum cascade laser to a mid-IR optical frequency comb: application to precision spectroscopy of N2O.

    Science.gov (United States)

    Gambetta, Alessio; Cassinerio, Marco; Coluccelli, Nicola; Fasci, Eugenio; Castrillo, Antonio; Gianfrani, Livio; Gatti, Davide; Marangoni, Marco; Laporta, Paolo; Galzerano, Gianluca

    2015-02-01

    We developed a high-precision spectroscopic system at 8.6 μm based on direct heterodyne detection and phase-locking of a room-temperature quantum-cascade-laser against an harmonic, 250-MHz mid-IR frequency comb obtained by difference-frequency generation. The ∼30  dB signal-to-noise ratio of the detected beat-note together with the achieved closed-loop locking bandwidth of ∼500  kHz allows for a residual integrated phase noise of 0.78 rad (1 Hz-5 MHz), for an ultimate resolution of ∼21  kHz, limited by the measured linewidth of the mid-IR comb. The system was used to perform absolute measurement of line-center frequencies for the rotational components of the ν2 vibrational band of N2O, with a relative precision of 3×10(-10).

  11. How High Local Charge Carrier Mobility and an Energy Cascade in a Three-Phase Bulk Heterojunction Enable >90% Quantum Efficiency

    KAUST Repository

    Burke, Timothy M.

    2013-12-27

    Charge generation in champion organic solar cells is highly efficient in spite of low bulk charge-carrier mobilities and short geminate-pair lifetimes. In this work, kinetic Monte Carlo simulations are used to understand efficient charge generation in terms of experimentally measured high local charge-carrier mobilities and energy cascades due to molecular mixing. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. How High Local Charge Carrier Mobility and an Energy Cascade in a Three-Phase Bulk Heterojunction Enable >90% Quantum Efficiency

    KAUST Repository

    Burke, Timothy M.; McGehee, Michael D.

    2013-01-01

    Charge generation in champion organic solar cells is highly efficient in spite of low bulk charge-carrier mobilities and short geminate-pair lifetimes. In this work, kinetic Monte Carlo simulations are used to understand efficient charge generation in terms of experimentally measured high local charge-carrier mobilities and energy cascades due to molecular mixing. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Unikabeton Prototype

    DEFF Research Database (Denmark)

    Søndergaard, Asbjørn; Dombernowsky, Per

    2011-01-01

    The Unikabeton prototype structure was developed as the finalization of the cross-disciplinary research project Unikabeton, exploring the architectural potential in linking the computational process of topology optimisation with robot fabrication of concrete casting moulds. The project was elabor......The Unikabeton prototype structure was developed as the finalization of the cross-disciplinary research project Unikabeton, exploring the architectural potential in linking the computational process of topology optimisation with robot fabrication of concrete casting moulds. The project...... of Architecture was to develop a series of optimisation experiments, concluding in the design and optimisation of a full scale prototype concrete structure....

  14. Solution Prototype

    DEFF Research Database (Denmark)

    Efeoglu, Arkin; Møller, Charles; Serie, Michel

    2013-01-01

    This paper outlines an artifact building and evaluation proposal. Design Science Research (DSR) studies usually consider encapsulated artifact that have relationships with other artifacts. The solution prototype as a composed artifact demands for a more comprehensive consideration in its systematic...... environment. The solution prototype that is composed from blending product and service prototype has particular impacts on the dualism of DSR’s “Build” and “Evaluate”. Since the mix between product and service prototyping can be varied, there is a demand for a more agile and iterative framework. Van de Ven......’s research framework seems to fit this purpose. Van de Ven allows for an iterative research approach to problem solving with flexible starting point. The research activity is the result between the iteration of two dimensions. This framework focuses on the natural evaluation, particularly on ex...

  15. Using prototyping in software development

    OpenAIRE

    Šinkovec, Miha

    2010-01-01

    Today the business system changers faster than the usual conventional cascade life cycle. Because of that, we can conclude, that today's programming system will no longer be presented as the answer to this topic in the developing age of ever changing user requirements. Neither increased performance or higher productivity will decrease the problem. The appropriate solution to this stated problem is prototyping. Instead of building and developing the whole system, we build a module that can...

  16. Software Prototyping

    Science.gov (United States)

    Del Fiol, Guilherme; Hanseler, Haley; Crouch, Barbara Insley; Cummins, Mollie R.

    2016-01-01

    Summary Background Health information exchange (HIE) between Poison Control Centers (PCCs) and Emergency Departments (EDs) could improve care of poisoned patients. However, PCC information systems are not designed to facilitate HIE with EDs; therefore, we are developing specialized software to support HIE within the normal workflow of the PCC using user-centered design and rapid prototyping. Objective To describe the design of an HIE dashboard and the refinement of user requirements through rapid prototyping. Methods Using previously elicited user requirements, we designed low-fidelity sketches of designs on paper with iterative refinement. Next, we designed an interactive high-fidelity prototype and conducted scenario-based usability tests with end users. Users were asked to think aloud while accomplishing tasks related to a case vignette. After testing, the users provided feedback and evaluated the prototype using the System Usability Scale (SUS). Results Survey results from three users provided useful feedback that was then incorporated into the design. After achieving a stable design, we used the prototype itself as the specification for development of the actual software. Benefits of prototyping included having 1) subject-matter experts heavily involved with the design; 2) flexibility to make rapid changes, 3) the ability to minimize software development efforts early in the design stage; 4) rapid finalization of requirements; 5) early visualization of designs; 6) and a powerful vehicle for communication of the design to the programmers. Challenges included 1) time and effort to develop the prototypes and case scenarios; 2) no simulation of system performance; 3) not having all proposed functionality available in the final product; and 4) missing needed data elements in the PCC information system. PMID:27081404

  17. Interband cascade lasers

    International Nuclear Information System (INIS)

    Vurgaftman, I; Meyer, J R; Canedy, C L; Kim, C S; Bewley, W W; Merritt, C D; Abell, J; Weih, R; Kamp, M; Kim, M; Höfling, S

    2015-01-01

    We review the current status of interband cascade lasers (ICLs) emitting in the midwave infrared (IR). The ICL may be considered the hybrid of a conventional diode laser that generates photons via electron–hole recombination, and an intersubband-based quantum cascade laser (QCL) that stacks multiple stages for enhanced current efficiency. Following a brief historical overview, we discuss theoretical aspects of the active region and core designs, growth by molecular beam epitaxy, and the processing of broad-area, narrow-ridge, and distributed feedback (DFB) devices. We then review the experimental performance of pulsed broad area ICLs, as well as the continuous-wave (cw) characteristics of narrow ridges having good beam quality and DFBs producing output in a single spectral mode. Because the threshold drive powers are far lower than those of QCLs throughout the λ = 3–6 µm spectral band, ICLs are increasingly viewed as the laser of choice for mid-IR laser spectroscopy applications that do not require high output power but need to be hand-portable and/or battery operated. Demonstrated ICL performance characteristics to date include threshold current densities as low as 106 A cm −2 at room temperature (RT), cw threshold drive powers as low as 29 mW at RT, maximum cw operating temperatures as high as 118 °C, maximum cw output powers exceeding 400 mW at RT, maximum cw wallplug efficiencies as high as 18% at RT, maximum cw single-mode output powers as high as 55 mW at RT, and single-mode output at λ = 5.2 µm with a cw drive power of only 138 mW at RT. (topical review)

  18. Cascade processes in kaonic and muonic atoms

    International Nuclear Information System (INIS)

    Faifman, M.P.; Men'shikov, L.I.

    2003-01-01

    Cascade processes in exotic (kaonic and muonic) hydrogen/deuterium have been studied with the quantum-classical Monte Carlo code (QCMC) developed for 'ab initio' - calculations. It has been shown that the majority of kaonic hydrogen atoms during cascade are accelerated to high energies E ∼ 100 eV, which leads to a much lower value for the calculated yields Y of x-rays than predicted by the 'standard cascade model'. The modified QCMC scheme has been applied to the study of the cascade in μp and μd muonic atoms. A comparison of the calculated yields for K-series x-rays with experimental data directly indicates that the molecular structure of the hydrogen target and new types of non-radiative transitions are essential for the light muonic atoms, while they are negligible for heavy (kaonic) atoms. These processes have been considered and estimates of their probabilities are presented. (author)

  19. Cascade annealing: an overview

    International Nuclear Information System (INIS)

    Doran, D.G.; Schiffgens, J.O.

    1976-04-01

    Concepts and an overview of radiation displacement damage modeling and annealing kinetics are presented. Short-term annealing methodology is described and results of annealing simulations performed on damage cascades generated using the Marlowe and Cascade programs are included. Observations concerning the inconsistencies and inadequacies of current methods are presented along with simulation of high energy cascades and simulation of longer-term annealing

  20. Quantum Cascade Laser Measurements of Line Intensities, N2-, O2- and Ar- Collisional Broadening Coefficients of N2O in the  3 Band Near 4.5  m

    KAUST Repository

    Es-sebbar, Et-touhami

    2016-04-19

    This study deals with precise measurements of absolute line intensities, N2-, O2- and Ar- collisional broadening coefficients of N2O in the P-branch of the ν3 vibrational band near 4.5 μm. Collisional broadening coefficients of N2O-air are derived from the N2- and O2- broadening contributions by considering an ideal atmospheric composition. Studies are performed at room temperature for 10 rotational transitions over 2190-2202 cm-1 spectral range using a distributed-feedback quantum cascade laser. To retrieve spectroscopic parameters for each individual transition, measured absorption line shape is simulated within Voigt and Galatry profiles. The obtained results compare well with previous experimental data available in the literature: the discrepancies being less than 4% for most of the probed transitions. The spectroscopic data reported here are very useful for the design of sensors used to monitor the abundance of N2O in earth\\'s atmosphere. © The Author(s) 2016.

  1. Optical Remote Sensing for Fence-Line Monitoring using Open-Path Quantum Cascade Laser (QCL) mono-static system for multiple target compounds in the Mid IR 7-13um (Fingerprint) region.

    Science.gov (United States)

    Zemek, P. G.

    2017-12-01

    Quantum Cascade Lasers (QCLs) are quickly replacing Tunable Diode Lasers (TDL) for multi-target species identification and quantification in both extractive and open-path (OP) Optical Remote Sensing (ORS) fence-line instrumentation. As was seen with TDL incorporation and pricing drops as the adoption by the telecommunications industry and its current scaling has improved robustness and pricing, the QCL is also, albiet more slowly, becoming a mature market. There are several advantages of QCLs over conventional TDLs such as improved brightness and beam density, high resolution, as well as the incorporation of external etalons or internal gratings to scan over wide spectral areas. QCLs typically operate in the Mid infra-red (MIR) as opposed to the Near-Infrared (NIR) region used with TDL. The MidIR is a target rich absorption band area where compounds have high absorbtivity coefficients resulting in better detection limits as compared to TDL instruments. The use of novel chemometrics and more sensitive non-cryo-cooled detectors has allowed some of the first QCL open-path instruments in both active and passive operation. Data and field studies of one of the newest QCL OP systems is presented that allows one system to measure multiple target compounds. Multiple QCL spectral regions may be stitched together to increase the capability of QCLs over TDL OP systems. A comparison of several ORS type systems will be presented.

  2. Quantum Cascade Laser Measurements of Line Intensities, N2-, O2- and Ar- Collisional Broadening Coefficients of N2O in the  3 Band Near 4.5  m

    KAUST Repository

    Es-sebbar, Et-touhami; Deli, Meriem; Farooq, Aamir

    2016-01-01

    This study deals with precise measurements of absolute line intensities, N2-, O2- and Ar- collisional broadening coefficients of N2O in the P-branch of the ν3 vibrational band near 4.5 μm. Collisional broadening coefficients of N2O-air are derived from the N2- and O2- broadening contributions by considering an ideal atmospheric composition. Studies are performed at room temperature for 10 rotational transitions over 2190-2202 cm-1 spectral range using a distributed-feedback quantum cascade laser. To retrieve spectroscopic parameters for each individual transition, measured absorption line shape is simulated within Voigt and Galatry profiles. The obtained results compare well with previous experimental data available in the literature: the discrepancies being less than 4% for most of the probed transitions. The spectroscopic data reported here are very useful for the design of sensors used to monitor the abundance of N2O in earth's atmosphere. © The Author(s) 2016.

  3. Impact of anti-charge sharing on the zero-frequency detective quantum efficiency of CdTe-based photon counting detector system: cascaded systems analysis and experimental validation

    Science.gov (United States)

    Ji, Xu; Zhang, Ran; Chen, Guang-Hong; Li, Ke

    2018-05-01

    Inter-pixel communication and anti-charge sharing (ACS) technologies have been introduced to photon counting detector (PCD) systems to address the undesirable charge sharing problem. In addition to improving the energy resolution of PCD, ACS may also influence other aspects of PCD performance such as detector multiplicity (i.e. the number of pixels triggered by each interacted photon) and detective quantum efficiency (DQE). In this work, a theoretical model was developed to address how ACS impacts the multiplicity and zero-frequency DQE [DQE(0)] of PCD systems. The work focused on cadmium telluride (CdTe)-based PCD that often involves the generation and transport of K-fluorescence photons. Under the parallel cascaded systems analysis framework, the theory takes both photoelectric and scattering effects into account, and it also considers both the reabsorption and escape of photons. In a new theoretical treatment of ACS, it was considered as a modified version of the conventional single pixel (i.e. non-ACS) mode, but with reduced charge spreading distance and K-fluorescence travel distance. The proposed theoretical model does not require prior knowledge of the detailed ACS implementation method for each specific PCD, and its parameters can be experimentally determined using a radioisotope without invoking any Monte-Carlo simulation. After determining the model parameters, independent validation experiments were performed using a diagnostic x-ray tube and four different polychromatic beams (from 50 to 120 kVp). Both the theoretical and experimental results demonstrate that ACS increased the first and second moments of multiplicity for a majority of the x-ray energy and threshold levels tested, except when the threshold level was much lower than the x-ray energy level. However, ACS always improved DQE(0) at all energy and threshold levels tested.

  4. Mechanisms of cascade collapse

    International Nuclear Information System (INIS)

    Diaz de la Rubia, T.; Smalinskas, K.; Averback, R.S.; Robertson, I.M.; Hseih, H.; Benedek, R.

    1988-12-01

    The spontaneous collapse of energetic displacement cascades in metals into vacancy dislocation loops has been investigated by molecular dynamics (MD) computer simulation and transmission electron microscopy (TEM). Simulations of 5 keV recoil events in Cu and Ni provide the following scenario of cascade collapse: atoms are ejected from the central region of the cascade by replacement collision sequences; the central region subsequently melts; vacancies are driven to the center of the cascade during resolidification where they may collapse into loops. Whether or not collapse occurs depends critically on the melting temperature of the metal and the energy density and total energy in the cascade. Results of TEM are presented in support of this mechanism. 14 refs., 4 figs., 1 tab

  5. Learning optimal embedded cascades.

    Science.gov (United States)

    Saberian, Mohammad Javad; Vasconcelos, Nuno

    2012-10-01

    The problem of automatic and optimal design of embedded object detector cascades is considered. Two main challenges are identified: optimization of the cascade configuration and optimization of individual cascade stages, so as to achieve the best tradeoff between classification accuracy and speed, under a detection rate constraint. Two novel boosting algorithms are proposed to address these problems. The first, RCBoost, formulates boosting as a constrained optimization problem which is solved with a barrier penalty method. The constraint is the target detection rate, which is met at all iterations of the boosting process. This enables the design of embedded cascades of known configuration without extensive cross validation or heuristics. The second, ECBoost, searches over cascade configurations to achieve the optimal tradeoff between classification risk and speed. The two algorithms are combined into an overall boosting procedure, RCECBoost, which optimizes both the cascade configuration and its stages under a detection rate constraint, in a fully automated manner. Extensive experiments in face, car, pedestrian, and panda detection show that the resulting detectors achieve an accuracy versus speed tradeoff superior to those of previous methods.

  6. Exploring Broad Area Quantum Cascade Lasers

    Science.gov (United States)

    2017-10-01

    Strong current spreading: Trenches etched deeper than the active region. Minimal current spreading: Laser cavity defined by the electrical contact ...refractive index Θ: the angle measured within the cavity. x θ High-Order Transverse Modes 7 Approved for public release. Distribution is...through image. 10 Approved for public release. Distribution is unlimited. 0 5 10 15 20 25 30 -50-40-30-20-10 0 10 20 30 40 50 Angle (degrees) De vic e

  7. Cascade Organic Solar Cells

    KAUST Repository

    Schlenker, Cody W.

    2011-09-27

    We demonstrate planar organic solar cells consisting of a series of complementary donor materials with cascading exciton energies, incorporated in the following structure: glass/indium-tin-oxide/donor cascade/C 60/bathocuproine/Al. Using a tetracene layer grown in a descending energy cascade on 5,6-diphenyl-tetracene and capped with 5,6,11,12-tetraphenyl- tetracene, where the accessibility of the π-system in each material is expected to influence the rate of parasitic carrier leakage and charge recombination at the donor/acceptor interface, we observe an increase in open circuit voltage (Voc) of approximately 40% (corresponding to a change of +200 mV) compared to that of a single tetracene donor. Little change is observed in other parameters such as fill factor and short circuit current density (FF = 0.50 ± 0.02 and Jsc = 2.55 ± 0.23 mA/cm2) compared to those of the control tetracene-C60 solar cells (FF = 0.54 ± 0.02 and Jsc = 2.86 ± 0.23 mA/cm2). We demonstrate that this cascade architecture is effective in reducing losses due to polaron pair recombination at donor-acceptor interfaces, while enhancing spectral coverage, resulting in a substantial increase in the power conversion efficiency for cascade organic photovoltaic cells compared to tetracene and pentacene based devices with a single donor layer. © 2011 American Chemical Society.

  8. Energy cascades in Canada

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, A. C.; Brown, T. D.

    1979-03-15

    Combining energy uses in a cascade can result in significant overall reductions in fuel requirements. The simplest applications for a cascade are in the recovery of waste heat from existing processes using special boilers or turbines. Specific applications of more-complex energy cascades for Canada are discussed. A combined-cycle plant at a chemical refinery in Ontario is world leader in energy efficiency. Total-energy systems for commercial buildings, such as one installed in a school in Western Canada, offer attractive energy and operating cost benefits. A cogeneration plant proposed for the National Capital Region, generating electricity as well as steam for district heating, allows the use of a low-grade fossil fuel (coal), greatly improves energy-transformation efficiency, and also utilizes an effectively renewable resource (municipal garbage). Despite the widespread availability of equipment and technology of energy cascades, the sale of steam and electricity across plant boundaries presents a barrier. More widespread use of cascades will require increased cooperation among industry, electric utilities and the various levels of government if Canada is to realize the high levels of energy efficiency potential available.

  9. Cascade Organic Solar Cells

    KAUST Repository

    Schlenker, Cody W.; Barlier, Vincent S.; Chin, Stephanie W.; Whited, Matthew T.; McAnally, R. Eric; Forrest, Stephen R.; Thompson, Mark E.

    2011-01-01

    We demonstrate planar organic solar cells consisting of a series of complementary donor materials with cascading exciton energies, incorporated in the following structure: glass/indium-tin-oxide/donor cascade/C 60/bathocuproine/Al. Using a tetracene layer grown in a descending energy cascade on 5,6-diphenyl-tetracene and capped with 5,6,11,12-tetraphenyl- tetracene, where the accessibility of the π-system in each material is expected to influence the rate of parasitic carrier leakage and charge recombination at the donor/acceptor interface, we observe an increase in open circuit voltage (Voc) of approximately 40% (corresponding to a change of +200 mV) compared to that of a single tetracene donor. Little change is observed in other parameters such as fill factor and short circuit current density (FF = 0.50 ± 0.02 and Jsc = 2.55 ± 0.23 mA/cm2) compared to those of the control tetracene-C60 solar cells (FF = 0.54 ± 0.02 and Jsc = 2.86 ± 0.23 mA/cm2). We demonstrate that this cascade architecture is effective in reducing losses due to polaron pair recombination at donor-acceptor interfaces, while enhancing spectral coverage, resulting in a substantial increase in the power conversion efficiency for cascade organic photovoltaic cells compared to tetracene and pentacene based devices with a single donor layer. © 2011 American Chemical Society.

  10. Hadron cascades produced by electromagnetic cascades

    International Nuclear Information System (INIS)

    Nelson, W.R.; Jenkins, T.M.; Ranft, J.

    1986-12-01

    A method for calculating high energy hadron cascades induced by multi-GeV electron and photon beams is described. Using the EGS4 computer program, high energy photons in the EM shower are allowed to interact hadronically according to the vector meson dominance (VMD) model, facilitated by a Monte Carlo version of the dual multistring fragmentation model which is used in the hadron cascade code FLUKA. The results of this calculation compare very favorably with experimental data on hadron production in photon-proton collisions and on the hadron production by electron beams on targets (i.e., yields in secondary particle beam lines). Electron beam induced hadron star density contours are also presented and are compared with those produced by proton beams. This FLUKA-EGS4 coupling technique could find use in the design of secondary beams, in the determination high energy hadron source terms for shielding purposes, and in the estimation of induced radioactivity in targets, collimators and beam dumps

  11. Effect of field quantization on Rabi oscillation of equidistant cascade ...

    Indian Academy of Sciences (India)

    acting with a single-mode radiation field both semiclassically and quantum ... the equidistant cascade four-level system modeled by the generators of the spin-3. 2 ... (1), hω0 is the equidistant energy gap between the levels, Ω is the frequency.

  12. Rethink! prototyping transdisciplinary concepts of prototyping

    CERN Document Server

    Nagy, Emilia; Stark, Rainer

    2016-01-01

    In this book, the authors describe the findings derived from interaction and cooperation between scientific actors employing diverse practices. They reflect on distinct prototyping concepts and examine the transformation of development culture in their fusion to hybrid approaches and solutions. The products of tomorrow are going to be multifunctional, interactive systems – and already are to some degree today. Collaboration across multiple disciplines is the only way to grasp their complexity in design concepts. This underscores the importance of reconsidering the prototyping process for the development of these systems, particularly in transdisciplinary research teams. “Rethinking Prototyping – new hybrid concepts for prototyping” was a transdisciplinary project that took up this challenge. The aim of this programmatic rethinking was to come up with a general concept of prototyping by combining innovative prototyping concepts, which had been researched and developed in three sub-projects: “Hybrid P...

  13. Architectures of prototypes and architectural prototyping

    DEFF Research Database (Denmark)

    Hansen, Klaus Marius; Christensen, Michael; Sandvad, Elmer

    1998-01-01

    together as a team, but developed a prototype that more than fulfilled the expectations of the shipping company. The prototype should: - complete the first major phase within 10 weeks, - be highly vertical illustrating future work practice, - continuously live up to new requirements from prototyping......This paper reports from experience obtained through development of a prototype of a global customer service system in a project involving a large shipping company and a university research group. The research group had no previous knowledge of the complex business of shipping and had never worked...... sessions with users, - evolve over a long period of time to contain more functionality - allow for 6-7 developers working intensively in parallel. Explicit focus on the software architecture and letting the architecture evolve with the prototype played a major role in resolving these conflicting...

  14. Cascade reactor: introduction

    International Nuclear Information System (INIS)

    Pitts, J.H.

    1985-01-01

    Cascade is a concept for an ultrasafe, highly efficient, easily built reactor to convert inertial-confinement fusion energy into electrical power. The Cascade design includes a rotating double-cone-shaped chamber in which a moving, 1-m-thick ceramic granular blanket is held against the reactor wall by centrifugal action. The granular material absorbs energy from the fusion reactions. Accomplishments this year associated with Cascade included improvements to simplify chamber design and lower activation. The authors switched from a steel chamber wall to one made from silicon-carbide (SiC) panels held in compression by SiC-fiber/Al-composite tendons that gird the chamber both circumferentially and axially. The authors studies a number of heat-exchanger designs and selected a gravity-flow cascade design with a vacuum on the primary side. This design allows granules leaving the chamber to be transported to the heat exchangers using their own peripheral speed. The granules transfer their thermal energy and return to the chamber gravitationally: no vacuum locks or conveyors are needed

  15. Stability of cascade search

    Energy Technology Data Exchange (ETDEWEB)

    Fomenko, Tatiana N [M. V. Lomonosov Moscow State University, Faculty of Computational Mathematics and Cybernetics, Moscow (Russian Federation)

    2010-10-22

    We find sufficient conditions on a searching multi-cascade for a modification of the set of limit points of the cascade that satisfy an assessing inequality for the distance from each of these points to the initial point to be small, provided that the modifications of the initial point and the initial set-valued functionals or maps used to construct the multi-cascade are small. Using this result, we prove the stability (in the above sense) of the cascade search for the set of common pre-images of a closed subspace under the action of n set-valued maps, n{>=}1 (in particular, for the set of common roots of these maps and for the set of their coincidences). For n=2 we obtain generalizations of some results of A. V. Arutyunov; the very statement of the problem comes from a recent paper of his devoted to the study of the stability of the subset of coincidences of a Lipschitz map and a covering map.

  16. A Novel Concept for Three-Phase Cascaded Multilevel Inverter Topologies

    Directory of Open Access Journals (Sweden)

    Md Mubashwar Hasan

    2018-01-01

    Full Text Available One of the key challenges in multilevel inverters (MLIs design is to reduce the number of components used in the implementation while maximising the number of output voltage levels. This paper proposes a new concept that facilitates a device count reduction technique of existing cascaded MLIs. Moreover, the proposed concept can be utilised to extend existing single phase cascaded MLI topologies to three-phase structure without tripling the number of semiconductor components and input dc-supplies as per the current practice. The new generalized concept involves two stages; namely, cascaded stage and phase generator stage. The phase generator stage is a combination of a conventional three-phase two level inverter and three bi-directional switches while the cascaded stage can employ any existing cascaded topology. A laboratory prototype model is built and extensive experimental analyses are conducted to validate the feasibility of the proposed cascaded MLI concept.

  17. From quantum coherence to quantum correlations

    Science.gov (United States)

    Sun, Yuan; Mao, Yuanyuan; Luo, Shunlong

    2017-06-01

    In quantum mechanics, quantum coherence of a state relative to a quantum measurement can be identified with the quantumness that has to be destroyed by the measurement. In particular, quantum coherence of a bipartite state relative to a local quantum measurement encodes quantum correlations in the state. If one takes minimization with respect to the local measurements, then one is led to quantifiers which capture quantum correlations from the perspective of coherence. In this vein, quantum discord, which quantifies the minimal correlations that have to be destroyed by quantum measurements, can be identified as the minimal coherence, with the coherence measured by the relative entropy of coherence. To advocate and formulate this idea in a general context, we first review coherence relative to Lüders measurements which extends the notion of coherence relative to von Neumann measurements (or equivalently, orthonomal bases), and highlight the observation that quantum discord arises as minimal coherence through two prototypical examples. Then, we introduce some novel measures of quantum correlations in terms of coherence, illustrate them through examples, investigate their fundamental properties and implications, and indicate their applications to quantum metrology.

  18. The molecular beam epitaxy growth and characterization of zinc cadmium selenide/zinc cadmium magnesium selenide-indium phosphide quantum cascade structures for operation in the 3 - 5 um range

    Science.gov (United States)

    Charles, William O.

    The quantum cascade (QC) laser has captured the interest of researchers for almost three decades. In the early stages, researchers were very interested in proving the QC concept1 proposed by Kazarinov and Suris in 1971. This new concept gave researchers hope that very bulky energy inefficient infra-red (IR) lasers would be replaced with ones that are very compact, tunable and portable. Since the proposal of the QC laser concept and its first demonstration by researchers at Bell Laboratories2 in 1994, this technology has progressed to the point where it is now finding commercial applications in a variety of areas such as military counter measures, free space telecommunications, infra-red imaging and chemical spectroscopy.3-5 The success of this technology can be attributed to the coming of age of the techniques of molecular beam epitaxy (MBE) semiconductor growth and bandgap engineering. 6,7 Using MBE technology, the temperature of the source material can be stabilized by making use of a combination of proportional integral derivative (PID) controllers and thermocouple feedbacks. As a result, the material flux from the effusion cells can achieve stability better than (+/-) 1%. This flux stability together with a well-developed computer controlled shuttering mechanism make it possible to grow multi-quantum well (MQW) structures with excellent layer thickness precision (mono-layer scale) and interface quality. This stringent control of material flux is also a tool that is used by MBE growers to vary the material compositions for the growth of lattice matched and strain compensated QC structures. Today, MBE stands out as one of the premier methods for growing high performing QC lasers. The first successful demonstration of a QC laser2 was done using the InGaAs/InAlAs-InP material system. This demonstration was then repeated a few years later using GaAs/AlGaAs-InP.8 These III-V material systems were extensively studied to establish their material parameters. Given that

  19. Cascade laser applications: trends and challenges

    Science.gov (United States)

    d'Humières, B.; Margoto, Éric; Fazilleau, Yves

    2016-03-01

    When analyses need rapid measurements, cost effective monitoring and miniaturization, tunable semiconductor lasers can be very good sources. Indeed, applications like on-field environmental gas analysis or in-line industrial process control are becoming available thanks to the advantage of tunable semiconductor lasers. Advances in cascade lasers (CL) are revolutionizing Mid-IR spectroscopy with two alternatives: interband cascade lasers (ICL) in the 3-6μm spectrum and quantum cascade lasers (QCL), with more power from 3 to 300μm. The market is getting mature with strong players for driving applications like industry, environment, life science or transports. CL are not the only Mid-IR laser source. In fact, a strong competition is now taking place with other technologies like: OPO, VCSEL, Solid State lasers, Gas, SC Infrared or fiber lasers. In other words, CL have to conquer a share of the Mid-IR application market. Our study is a market analysis of CL technologies and their applications. It shows that improvements of components performance, along with the progress of infrared laser spectroscopy will drive the CL market growth. We compare CL technologies with other Mid-IR sources and estimate their share in each application market.

  20. Information cascade on networks

    Science.gov (United States)

    Hisakado, Masato; Mori, Shintaro

    2016-05-01

    In this paper, we discuss a voting model by considering three different kinds of networks: a random graph, the Barabási-Albert (BA) model, and a fitness model. A voting model represents the way in which public perceptions are conveyed to voters. Our voting model is constructed by using two types of voters-herders and independents-and two candidates. Independents conduct voting based on their fundamental values; on the other hand, herders base their voting on the number of previous votes. Hence, herders vote for the majority candidates and obtain information relating to previous votes from their networks. We discuss the difference between the phases on which the networks depend. Two kinds of phase transitions, an information cascade transition and a super-normal transition, were identified. The first of these is a transition between a state in which most voters make the correct choices and a state in which most of them are wrong. The second is a transition of convergence speed. The information cascade transition prevails when herder effects are stronger than the super-normal transition. In the BA and fitness models, the critical point of the information cascade transition is the same as that of the random network model. However, the critical point of the super-normal transition disappears when these two models are used. In conclusion, the influence of networks is shown to only affect the convergence speed and not the information cascade transition. We are therefore able to conclude that the influence of hubs on voters' perceptions is limited.

  1. Cascade ICF power reactor

    International Nuclear Information System (INIS)

    Hogan, W.J.; Pitts, J.H.

    1986-01-01

    The double-cone-shaped Cascade reaction chamber rotates at 50 rpm to keep a blanket of ceramic granules in place against the wall as they slide from the poles to the exit slots at the equator. The 1 m-thick blanket consists of layers of carbon, beryllium oxide, and lithium aluminate granules about 1 mm in diameter. The x rays and debris are stopped in the carbon granules; the neutrons are multiplied and moderated in the BeO and breed tritium in the LiAlO 2 . The chamber wall is made up of SiO tiles held in compression by a network of composite SiC/Al tendons. Cascade operates at a 5 Hz pulse rate with 300 MJ in each pulse. The temperature in the blanket reaches 1600 K on the inner surface and 1350 K at the outer edge. The granules are automatically thrown into three separate vacuum heat exchangers where they give up their energy to high pressure helium. The helium is used in a Brayton cycle to obtain a thermal-to-electric conversion efficiency of 55%. Studies have been done on neutron activation, debris recovery, vaporization and recondensation of blanket material, tritium control and recovery, fire safety, and cost. These studies indicate that Cascade appears to be a promising ICF reactor candidate from all standpoints. At the 1000 MWe size, electricity could be made for about the same cost as in a future fission reactor

  2. Quantumness-generating capability of quantum dynamics

    Science.gov (United States)

    Li, Nan; Luo, Shunlong; Mao, Yuanyuan

    2018-04-01

    We study quantumness-generating capability of quantum dynamics, where quantumness refers to the noncommutativity between the initial state and the evolving state. In terms of the commutator of the square roots of the initial state and the evolving state, we define a measure to quantify the quantumness-generating capability of quantum dynamics with respect to initial states. Quantumness-generating capability is absent in classical dynamics and hence is a fundamental characteristic of quantum dynamics. For qubit systems, we present an analytical form for this measure, by virtue of which we analyze several prototypical dynamics such as unitary dynamics, phase damping dynamics, amplitude damping dynamics, and random unitary dynamics (Pauli channels). Necessary and sufficient conditions for the monotonicity of quantumness-generating capability are also identified. Finally, we compare these conditions for the monotonicity of quantumness-generating capability with those for various Markovianities and illustrate that quantumness-generating capability and quantum Markovianity are closely related, although they capture different aspects of quantum dynamics.

  3. Imagining the prototype

    OpenAIRE

    Brouwer, C. E.; Bhomer, ten, M.; Melkas, H.; Buur, J.

    2013-01-01

    This article reports on the analysis of a design session, employing conversation analysis. In the design session three experts and a designer discuss a prototype of a shirt, which has been developed with the input from these experts. The analysis focuses on the type of involvement of the participants with the prototype and how they explicate the points they make in the discussion with or without making use of the prototype. Three techniques for explicating design issues that exploit the proto...

  4. Rapid Prototyping Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The ARDEC Rapid Prototyping (RP) Laboratory was established in December 1992 to provide low cost RP capabilities to the ARDEC engineering community. The Stratasys,...

  5. Fabrication and Prototyping Lab

    Data.gov (United States)

    Federal Laboratory Consortium — Purpose: The Fabrication and Prototyping Lab for composite structures provides a wide variety of fabrication capabilities critical to enabling hands-on research and...

  6. Cascading Corruption News

    DEFF Research Database (Denmark)

    Damgaard, Mads

    2018-01-01

    Through a content analysis of 8,800 news items and six months of front pages in three Brazilian newspapers, all dealing with corruption and political transgression, this article documents the remarkable skew of media attention to corruption scandals. The bias is examined as an information...... phenomenon, arising from systemic and commercial factors of Brazil’s news media: An information cascade of news on corruption formed, destabilizing the governing coalition and legitimizing the impeachment process of Dilma Rousseff. As this process gained momentum, questions of accountability were disregarded...

  7. Cascading Corruption News

    DEFF Research Database (Denmark)

    Damgaard, Mads

    2018-01-01

    Through a content analysis of 8,800 news items and six months of front pages in three Brazilian newspapers, all dealing with corruption and political transgression, this article documents the remarkable skew of media attention to corruption scandals. The bias is examined as an information...... phenomenon, arising from systemic and commercial factors of Brazil’s news media: An information cascade of news on corruption formed, destabilizing the governing coalition and legitimizing the impeachment process of Dilma Rousseff. As this process gained momentum, questions of accountability were disregarded...... by the media, with harmful effects on democracy....

  8. Distributed dual-parameter optical fiber sensor based on cascaded microfiber Fabry-Pérot interferometers

    Science.gov (United States)

    Xiang, Yang; Luo, Yiyang; Zhang, Wei; Liu, Deming; Sun, Qizhen

    2017-04-01

    We propose and demonstrate a distributed fiber sensor based on cascaded microfiber Fabry-Perot interferometers (MFPI) for simultaneous refractive index (SRI) and temperature measurement. By employing MFPI which is fabricated by taper-drawing the center of a uniform fiber Bragg grating (FBG) on standard fiber into a section of microfiber, dual parameters including SRI and temperature can be detected through demodulating the reflection spectrum of the MFPI. Further, wavelength-division-multiplexing (WDM) is applied to realize distributed dual-parameter fiber sensor by using cascaded MFPIs with different Bragg wavelengths. A prototype sensor system with 5 cascaded MFPIs is constructed to experimentally demonstrate the sensing performance.

  9. Designing and testing prototypes

    NARCIS (Netherlands)

    Vereijken, P.; Wijnands, F.; Stol, W.

    1995-01-01

    This second progress report focuses on designing a theoretical prototype by linking parameters to methods and designing the methods in this context until they are ready for initial testing. The report focuses also on testing and improving the prototype in general and the methods in particular until

  10. EUCLID ARCHIVE SYSTEM PROTOTYPE

    NARCIS (Netherlands)

    Belikov, Andrey; Williams, Owen; Droge, Bob; Tsyganov, Andrey; Boxhoorn, Danny; McFarland, John; Verdoes Kleijn, Gijs; Valentijn, E; Altieri, Bruno; Dabin, Christophe; Pasian, F.; Osuna, Pedro; Soille, P.; Marchetti, P.G.

    2014-01-01

    The Euclid Archive System prototype is a functional information system which is used to address the numerous challenges in the development of fully functional data processing system for Euclid. The prototype must support the highly distributed nature of the Euclid Science Ground System, with Science

  11. Specifications in software prototyping

    OpenAIRE

    Luqi; Chang, Carl K.; Zhu, Hong

    1998-01-01

    We explore the use of software speci®cations for software prototyping. This paper describes a process model for software prototyping, and shows how specifications can be used to support such a process via a cellular mobile phone switch example.

  12. EPCiR prototype

    DEFF Research Database (Denmark)

    2003-01-01

    A prototype of a residential pervasive computing platform based on OSGi involving among other a mock-up of an health care bandage.......A prototype of a residential pervasive computing platform based on OSGi involving among other a mock-up of an health care bandage....

  13. Cooperative Prototyping Experiments

    DEFF Research Database (Denmark)

    Bødker, Susanne; Grønbæk, Kaj

    1989-01-01

    This paper describes experiments with a design technique that we denote cooperative prototyping. The experiments consider design of a patient case record system for municipal dental clinics in which we used HyperCard, an off the shelf programming environment for the Macintosh. In the ecperiments we...... tried to achieve a fluent work-like evaluation of prototypes where users envisioned future work with a computer tool, at the same time as we made on-line modifications of prototypes in cooperation with the users when breakdown occur in their work-like evaluation. The experiments showed...... that it was possible to make a number of direct manipulation changes of prototypes in cooperation with the users, in interplay with their fluent work-like evaluation of these. However, breakdown occurred in the prototyping process when we reached the limits of the direct manipulation support for modification. From...

  14. Cascade Distiller System Performance Testing Interim Results

    Science.gov (United States)

    Callahan, Michael R.; Pensinger, Stuart; Sargusingh, Miriam J.

    2014-01-01

    The Cascade Distillation System (CDS) is a rotary distillation system with potential for greater reliability and lower energy costs than existing distillation systems. Based upon the results of the 2009 distillation comparison test (DCT) and recommendations of the expert panel, the Advanced Exploration Systems (AES) Water Recovery Project (WRP) project advanced the technology by increasing reliability of the system through redesign of bearing assemblies and improved rotor dynamics. In addition, the project improved the CDS power efficiency by optimizing the thermoelectric heat pump (TeHP) and heat exchanger design. Testing at the NASA-JSC Advanced Exploration System Water Laboratory (AES Water Lab) using a prototype Cascade Distillation Subsystem (CDS) wastewater processor (Honeywell d International, Torrance, Calif.) with test support equipment and control system developed by Johnson Space Center was performed to evaluate performance of the system with the upgrades as compared to previous system performance. The system was challenged with Solution 1 from the NASA Exploration Life Support (ELS) distillation comparison testing performed in 2009. Solution 1 consisted of a mixed stream containing human-generated urine and humidity condensate. A secondary objective of this testing is to evaluate the performance of the CDS as compared to the state of the art Distillation Assembly (DA) used in the ISS Urine Processor Assembly (UPA). This was done by challenging the system with ISS analog waste streams. This paper details the results of the AES WRP CDS performance testing.

  15. Cascade Error Projection Learning Algorithm

    Science.gov (United States)

    Duong, T. A.; Stubberud, A. R.; Daud, T.

    1995-01-01

    A detailed mathematical analysis is presented for a new learning algorithm termed cascade error projection (CEP) and a general learning frame work. This frame work can be used to obtain the cascade correlation learning algorithm by choosing a particular set of parameters.

  16. Can hydroxylamine be a more potent nucleophile for the reactivation of tabun-inhibited AChE than prototype oxime drugs? An answer derived from quantum chemical and steered molecular dynamics studies.

    Science.gov (United States)

    Lo, Rabindranath; Ganguly, Bishwajit

    2014-07-29

    Organophosphorus nerve agents are highly toxic compounds which strongly inhibit acetylcholinesterase (AChE) in the blood and in the central nervous system (CNS). Tabun is one of the highly toxic organophosphorus (OP) compounds and is resistant to many oxime drugs formulated for the reactivation of AChE. The reactivation mechanism of tabun-conjugated AChE with various drugs has been examined with density functional theory and ab initio quantum chemical calculations. The presence of a lone-pair located on the amidic group resists the nucleophilic attack at the phosphorus center of the tabun-conjugated AChE. We have shown that the newly designed drug candidate N-(pyridin-2-yl)hydroxylamine, at the MP2/6-31+G*//M05-2X/6-31G* level in the aqueous phase with the polarizable continuum solvation model (PCM), is more effective in reactivating the tabun-conjugated AChE than typical oxime drugs. The rate determining activation barrier with N-(pyridin-2-yl)hydroxylamine was found to be ∼1.7 kcal mol(-1), which is 7.2 kcal mol(-1) lower than the charged oxime trimedoxime (one of the most efficient reactivators in tabun poisonings). The greater nucleophilicity index (ω(-)) and higher CHelpG charge of pyridinylhydroxylamine compared to TMB4 support this observation. Furthermore, we have also examined the reactivation process of tabun-inhibited AChE with some other bis-quaternary oxime drug candidates such as methoxime (MMB4) and obidoxime. The docking analysis suggests that charged bis-quaternary pyridinium oximes have greater binding affinity inside the active-site gorge of AChE compared to the neutral pyridinylhydroxylamine. The peripheral ligand attached to the neutral pyridinylhydroxylamine enhanced the binding with the aromatic residues in the active-site gorge of AChE through effective π-π interactions. Steered molecular dynamics (SMD) simulations have also been performed with the charged oxime (TMB4) and the neutral hydroxylamine. From protein-drug interaction

  17. PRMS Data Warehousing Prototype

    Science.gov (United States)

    Guruvadoo, Eranna K.

    2002-01-01

    Project and Resource Management System (PRMS) is a web-based, mid-level management tool developed at KSC to provide a unified enterprise framework for Project and Mission management. The addition of a data warehouse as a strategic component to the PRMS is investigated through the analysis, design and implementation processes of a data warehouse prototype. As a proof of concept, a demonstration of the prototype with its OLAP's technology for multidimensional data analysis is made. The results of the data analysis and the design constraints are discussed. The prototype can be used to motivate interest and support for an operational data warehouse.

  18. The effect of quantum memory on quantum games

    International Nuclear Information System (INIS)

    Ramzan, M; Nawaz, Ahmad; Toor, A H; Khan, M K

    2008-01-01

    We study quantum games with correlated noise through a generalized quantization scheme. We investigate the effects of memory on quantum games, such as Prisoner's Dilemma, Battle of the Sexes and Chicken, through three prototype quantum-correlated channels. It is shown that the quantum player enjoys an advantage over the classical player for all nine cases considered in this paper for the maximally entangled case. However, the quantum player can also outperform the classical player for subsequent cases that can be noted in the case of the Battle of the Sexes game. It can be seen that the Nash equilibria do not change for all the three games under the effect of memory

  19. Quantum Statistical Testing of a Quantum Random Number Generator

    Energy Technology Data Exchange (ETDEWEB)

    Humble, Travis S [ORNL

    2014-01-01

    The unobservable elements in a quantum technology, e.g., the quantum state, complicate system verification against promised behavior. Using model-based system engineering, we present methods for verifying the opera- tion of a prototypical quantum random number generator. We begin with the algorithmic design of the QRNG followed by the synthesis of its physical design requirements. We next discuss how quantum statistical testing can be used to verify device behavior as well as detect device bias. We conclude by highlighting how system design and verification methods must influence effort to certify future quantum technologies.

  20. Inferring network structure from cascades

    Science.gov (United States)

    Ghonge, Sushrut; Vural, Dervis Can

    2017-07-01

    Many physical, biological, and social phenomena can be described by cascades taking place on a network. Often, the activity can be empirically observed, but not the underlying network of interactions. In this paper we offer three topological methods to infer the structure of any directed network given a set of cascade arrival times. Our formulas hold for a very general class of models where the activation probability of a node is a generic function of its degree and the number of its active neighbors. We report high success rates for synthetic and real networks, for several different cascade models.

  1. Feedback control of superconducting quantum circuits

    NARCIS (Netherlands)

    Ristè, D.

    2014-01-01

    Superconducting circuits have recently risen to the forefront of the solid-state prototypes for quantum computing. Reaching the stage of robust quantum computing requires closing the loop between measurement and control of quantum bits (qubits). This thesis presents the realization of feedback

  2. Cascade energy amplifier

    International Nuclear Information System (INIS)

    Barzilov, A.P.; Gulevich, A.V.; Kukharchuk, O.F.

    2000-01-01

    The technical problem of long-life fission product and minor actinide incineration and production of plutonium fuel in the prospective nuclear systems will arise at significant scales of nuclear power industry development. Subcritical nuclear reactors driven by extemal neutron sources (energy amplifiers) are considered as incinerators of toxicity of complete nuclear industry. In the frames of this concept, the subcritical reactor part consisting of two coupled blanket regions (inner fast neutron spectrum core and outer thermal core) driven by extemal neutron source is discussed. Two types of source are studied: spallation target and 14-MeV fusion bum of micropellets. Liquid metal Pb-Bi is considered as target material and coolant of inner fast core. Thermal core is a heavy-water subcritical reactor of the Candu-type. The fast core is protected from thermal neutrons influence with the boron shield. All reactor technologies used in this concept are tested during years of operation and commercially available. Thus, the cascade energy amplifiers have a set of advantages in comparison with traditional concepts: in energy production, in transmutation efficiency, and in economics. (authors)

  3. Quantum prisoner dilemma under decoherence

    International Nuclear Information System (INIS)

    Chen, L.K.; Ang, Huiling; Kiang, D.; Kwek, L.C.; Lo, C.F.

    2003-01-01

    It has recently been established that quantum strategies are superior to classical ones for games such as the prisoner's dilemma. However, quantum states are subject to decoherence. In this Letter, we investigate the effects of decoherence on a quantum game, namely the prisoner dilemma, through three prototype decoherence channels. We show that in the case of prisoner dilemma, the Nash equilibria are not changed by the effects of decoherence for maximally entangled states

  4. Ultrarelativistic cascades and strangeness production

    Energy Technology Data Exchange (ETDEWEB)

    Kahana, D.E. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Physics; Kahana, S.H. [Brookhaven National Lab., Upton, NY (United States). Physics Dept.

    1998-08-24

    A two-phase cascade code, LUCIFER II, developed for the treatment of ultra high energy-ion-ion collisions is applied to the production of strangeness at SPS energies {radical}(s)=17-20. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy-ion experiments at the CERN SPS. (orig.) 26 refs.

  5. Ultrarelativistic cascades and strangeness production

    International Nuclear Information System (INIS)

    Kahana, D.E.; Kahana, S.H.

    1998-01-01

    A two-phase cascade code, LUCIFER II, developed for the treatment of ultra high energy-ion-ion collisions is applied to the production of strangeness at SPS energies √(s)=17-20. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy-ion experiments at the CERN SPS. (orig.)

  6. Ultrarelativistic cascades and strangeness production

    International Nuclear Information System (INIS)

    Kahana, D.E.; Kahana, S.H.

    1998-02-01

    A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy Ion-Ion collisions is applied to the production of strangeness at SPS energies. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS

  7. Cascade redox flow battery systems

    Science.gov (United States)

    Horne, Craig R.; Kinoshita, Kim; Hickey, Darren B.; Sha, Jay E.; Bose, Deepak

    2014-07-22

    A reduction/oxidation ("redox") flow battery system includes a series of electrochemical cells arranged in a cascade, whereby liquid electrolyte reacts in a first electrochemical cell (or group of cells) before being directed into a second cell (or group of cells) where it reacts before being directed to subsequent cells. The cascade includes 2 to n stages, each stage having one or more electrochemical cells. During a charge reaction, electrolyte entering a first stage will have a lower state-of-charge than electrolyte entering the nth stage. In some embodiments, cell components and/or characteristics may be configured based on a state-of-charge of electrolytes expected at each cascade stage. Such engineered cascades provide redox flow battery systems with higher energy efficiency over a broader range of current density than prior art arrangements.

  8. Directional phonon-assisted cascading of photoexcited carriers in stepped Inx(Al0.17Ga0.83)1-xAs/Al0.17Ga0.83As multiple quantum wells

    DEFF Research Database (Denmark)

    Machida, S.; Matsuo, M.; Fujiwara, K.

    2002-01-01

    Perpendicular motion of photoexcited electron and hole pairs assisted by phononscattering is investigated in a novel step-graded staircase heterostructure consisting of strained In-1(Al0.17Ga0.83)(1-x). As multiple quantum wells (QWs) with similar widths but five different x values by cw and time...... amplitude in the inter-mediate temperature range, These variations reveal that the photoexcited carriers directionally move from shallower to deeper QWs via phonon-assisted activation above the barrier hand edge state. The PL dynamics directly indicate the perpendicular flowing of photoexcited carriers...

  9. Stochastic background of atmospheric cascades

    International Nuclear Information System (INIS)

    Wilk, G.; Wlodarczyk, Z.

    1993-01-01

    Fluctuations in the atmospheric cascades developing during the propagation of very high energy cosmic rays through the atmosphere are investigated using stochastic branching model of pure birth process with immigration. In particular, we show that the multiplicity distributions of secondaries emerging from gamma families are much narrower than those resulting from hadronic families. We argue that the strong intermittent like behaviour found recently in atmospheric families results from the fluctuations in the cascades themselves and are insensitive to the details of elementary interactions

  10. Computation of inverse magnetic cascades

    International Nuclear Information System (INIS)

    Montgomery, D.

    1981-10-01

    Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed

  11. From prototype to product

    DEFF Research Database (Denmark)

    Andersen, Tariq Osman; Bansler, Jørgen P.; Kensing, Finn

    2017-01-01

    This paper delves into the challenges of engaging patients, clinicians and industry stakeholders in the participatory design of an mHealth platform for patient-clinician collaboration. It follows the process from the development of a research prototype to a commercial software product. In particu......This paper delves into the challenges of engaging patients, clinicians and industry stakeholders in the participatory design of an mHealth platform for patient-clinician collaboration. It follows the process from the development of a research prototype to a commercial software product....... In particular, we draw attention to four major challenges of (a) aligning the different concerns of patients and clinicians, (b) designing according to clinical accountability, (c) ensuring commercial interest, and (d) dealing with regulatory constraints when prototyping safety critical health Information...... Technology. Using four illustrative cases, we discuss what these challenges entail and the implications they pose to Participatory Design. We conclude the paper by presenting lessons learned....

  12. Introduction to quantum algebras

    International Nuclear Information System (INIS)

    Kibler, M.R.

    1992-09-01

    The concept of a quantum algebra is made easy through the investigation of the prototype algebras u qp (2), su q (2) and u qp (1,1). The latter quantum algebras are introduced as deformations of the corresponding Lie algebras; this is achieved in a simple way by means of qp-bosons. The Hopf algebraic structure of u qp (2) is also discussed. The basic ingredients for the representation theory of u qp (2) are given. Finally, in connection with the quantum algebra u qp (2), the qp-analogues of the harmonic oscillator are discussed and of the (spherical and hyperbolical) angular momenta. (author) 50 refs

  13. Quantum optics

    National Research Council Canada - National Science Library

    Agarwal, G. S

    2013-01-01

    .... Focusing on applications of quantum optics, the textbook covers recent developments such as engineering of quantum states, quantum optics on a chip, nano-mechanical mirrors, quantum entanglement...

  14. Quantum mechanics theory and experiment

    CERN Document Server

    Beck, Mark

    2012-01-01

    This textbook presents quantum mechanics at the junior/senior undergraduate level. It is unique in that it describes not only quantum theory, but also presents five laboratories that explore truly modern aspects of quantum mechanics. These laboratories include "proving" that light contains photons, single-photon interference, and tests of local realism. The text begins by presenting the classical theory of polarization, moving on to describe the quantum theory of polarization. Analogies between the two theories minimize conceptual difficulties that students typically have when first presented with quantum mechanics. Furthermore, because the laboratories involve studying photons, using photon polarization as a prototypical quantum system allows the laboratory work to be closely integrated with the coursework. Polarization represents a two-dimensional quantum system, so the introduction to quantum mechanics uses two-dimensional state vectors and operators. This allows students to become comfortable with the mat...

  15. PANDA Muon System Prototype

    Science.gov (United States)

    Abazov, Victor; Alexeev, Gennady; Alexeev, Maxim; Frolov, Vladimir; Golovanov, Georgy; Kutuzov, Sergey; Piskun, Alexei; Samartsev, Alexander; Tokmenin, Valeri; Verkheev, Alexander; Vertogradov, Leonid; Zhuravlev, Nikolai

    2018-04-01

    The PANDA Experiment will be one of the key experiments at the Facility for Antiproton and Ion Research (FAIR) which is under construction now in the territory of the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. PANDA is aimed to study hadron spectroscopy and various topics of the weak and strong forces. Muon System is chosen as the most suitable technology for detecting the muons. The Prototype of the PANDA Muon System is installed on the test beam line T9 at the Proton Synchrotron (PS) at CERN. Status of the PANDA Muon System prototype is presented with few preliminary results.

  16. Prototyping a Smart City

    DEFF Research Database (Denmark)

    Korsgaard, Henrik; Brynskov, Martin

    In this paper, we argue that by approaching the so-called Smart City as a design challenge, and an interaction design perspective, it is possible to both uncover existing challenges in the interplay between people, technology and society, as well as prototype possible futures. We present a case...... in which we exposed data about the online communication between the citizens and the municipality on a highly visible media facade, while at the same time prototyped a tool that enabled citizens to report ‘bugs’ within the city....

  17. PANDA Muon System Prototype

    Directory of Open Access Journals (Sweden)

    Abazov Victor

    2018-01-01

    Full Text Available The PANDA Experiment will be one of the key experiments at the Facility for Antiproton and Ion Research (FAIR which is under construction now in the territory of the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. PANDA is aimed to study hadron spectroscopy and various topics of the weak and strong forces. Muon System is chosen as the most suitable technology for detecting the muons. The Prototype of the PANDA Muon System is installed on the test beam line T9 at the Proton Synchrotron (PS at CERN. Status of the PANDA Muon System prototype is presented with few preliminary results.

  18. Cell-free synthetic biology for in vitro prototype engineering.

    Science.gov (United States)

    Moore, Simon J; MacDonald, James T; Freemont, Paul S

    2017-06-15

    Cell-free transcription-translation is an expanding field in synthetic biology as a rapid prototyping platform for blueprinting the design of synthetic biological devices. Exemplar efforts include translation of prototype designs into medical test kits for on-site identification of viruses (Zika and Ebola), while gene circuit cascades can be tested, debugged and re-designed within rapid turnover times. Coupled with mathematical modelling, this discipline lends itself towards the precision engineering of new synthetic life. The next stages of cell-free look set to unlock new microbial hosts that remain slow to engineer and unsuited to rapid iterative design cycles. It is hoped that the development of such systems will provide new tools to aid the transition from cell-free prototype designs to functioning synthetic genetic circuits and engineered natural product pathways in living cells. © 2017 The Author(s).

  19. LEP vacuum chamber, prototype

    CERN Multimedia

    CERN PhotoLab

    1983-01-01

    Final prototype for the LEP vacuum chamber, see 8305170 for more details. Here we see the strips of the NEG pump, providing "distributed pumping". The strips are made from a Zr-Ti-Fe alloy. By passing an electrical current, they were heated to 700 deg C.

  20. Imagining the prototype

    NARCIS (Netherlands)

    Brouwer, C. E.; Bhomer, ten M.; Melkas, H.; Buur, J.

    2013-01-01

    This article reports on the analysis of a design session, employing conversation analysis. In the design session three experts and a designer discuss a prototype of a shirt, which has been developed with the input from these experts. The analysis focuses on the type of involvement of the

  1. MIND performance and prototyping

    International Nuclear Information System (INIS)

    Cervera-Villanueva, A.

    2008-01-01

    The performance of MIND (Magnetised Iron Neutrino Detector) at a neutrino factory has been revisited in a new analysis. In particular, the low neutrino energy region is studied, obtaining an efficiency plateau around 5 GeV for a background level below 10 -3 . A first look has been given into the detector optimisation and prototyping

  2. The prototype fast reactor

    International Nuclear Information System (INIS)

    Broomfield, A.M.

    1985-01-01

    The paper concerns the Prototype Fast Reactor (PFR), which is a liquid metal cooled fast reactor power station, situated at Dounreay, Scotland. The principal design features of a Fast Reactor and the PFR are given, along with key points of operating history, and health and safety features. The role of the PFR in the development programme for commercial reactors is discussed. (U.K.)

  3. AGS Booster prototype magnets

    Energy Technology Data Exchange (ETDEWEB)

    Danby, G.; Jackson, J.; Lee, Y.Y.; Phillips, R.; Brodowski, J.; Jablonski, E.; Keohane, G.; McDowell, B.; Rodger, E.

    1987-03-19

    Prototype magnets have been designed and constructed for two half cells of the AGS Booster. The lattice requires 2.4m long dipoles, each curved by 10/sup 0/. The multi-use Booster injector requires several very different standard magnet cycles, capable of instantaneous interchange using computer control from dc up to 10 Hz.

  4. AGS booster prototype magnets

    International Nuclear Information System (INIS)

    Danby, G.; Jackson, J.; Lee, Y.Y.; Phillips, R.; Brodowski, J.; Jablonski, E.; Keohane, G.; McDowell, B.; Rodger, E.

    1987-01-01

    Prototype magnets have been designed and constructed for two half cells of the AGS Booster. The lattice requires 2.4m long dipoles, each curved by 10 0 . The multi-use Booster injector requires several very different standard magnet cycles, capable of instantaneous interchange using computer control from dc up to 10 Hz

  5. Cockroft Walton accelerator prototype

    International Nuclear Information System (INIS)

    Hutapea, Sumihar.

    1976-01-01

    Prototype of a Cockroft Walton generator using ceramic and plastic capacitors is discussed. Compared to the previous generator, the construction and components are much more improved. Pralon is used for the high voltage insulation column and plastic is used as a dielectric material for the high voltage capacitor. Cockroft Walton generator is used as a high tension supply for an accelerator. (author)

  6. Prompt and Precise Prototyping

    Science.gov (United States)

    2003-01-01

    For Sanders Design International, Inc., of Wilton, New Hampshire, every passing second between the concept and realization of a product is essential to succeed in the rapid prototyping industry where amongst heavy competition, faster time-to-market means more business. To separate itself from its rivals, Sanders Design aligned with NASA's Marshall Space Flight Center to develop what it considers to be the most accurate rapid prototyping machine for fabrication of extremely precise tooling prototypes. The company's Rapid ToolMaker System has revolutionized production of high quality, small-to-medium sized prototype patterns and tooling molds with an exactness that surpasses that of computer numerically-controlled (CNC) machining devices. Created with funding and support from Marshall under a Small Business Innovation Research (SBIR) contract, the Rapid ToolMaker is a dual-use technology with applications in both commercial and military aerospace fields. The advanced technology provides cost savings in the design and manufacturing of automotive, electronic, and medical parts, as well as in other areas of consumer interest, such as jewelry and toys. For aerospace applications, the Rapid ToolMaker enables fabrication of high-quality turbine and compressor blades for jet engines on unmanned air vehicles, aircraft, and missiles.

  7. Surrogates-based prototyping

    NARCIS (Netherlands)

    Du Bois, E.; Horvath, I.

    2014-01-01

    The research is situated in the system development phase of interactive software products. In this detailed design phase, we found a need for fast testable prototyping to achieve qualitative change proposals on the system design. In this paper, we discuss a literature study on current software

  8. Z Andromedae: the prototype

    International Nuclear Information System (INIS)

    Viotti, R.; Giangrande, A.; Ricciardi, O.; Cassatella, A.

    1982-01-01

    Z And is considered as the ''prototype'' of the symbiotic stars. Besides its symbiotic spectrum, the star is also known for its characteristic light curve (and for the related spectral variations). Since many theoretical speculations on Z And and similar objects have been based on the luminosity and spectral variations of this star, the authors critically analyse the observational data concerning it. (Auth.)

  9. Prototype ATLAS straw tracker

    CERN Multimedia

    Laurent Guiraud

    1998-01-01

    This is an early prototype of the straw tracking device for the ATLAS detector at CERN. This detector will be part of the LHC project, scheduled to start operation in 2008. The straw tracker will consist of thousands of gas-filled straws, each containing a wire, allowing the tracks of particles to be followed.

  10. Courthouse Prototype Building

    Energy Technology Data Exchange (ETDEWEB)

    Malhotra, Mini [ORNL; New, Joshua Ryan [ORNL; Im, Piljae [ORNL

    2018-02-01

    As part of DOE's support of ANSI/ASHRAE/IES Standard 90.1 and IECC, researchers at Pacific Northwest National Laboratory (PNNL) apply a suite of prototype buildings covering 80% of the commercial building floor area in the U.S. for new construction. Efforts have started on expanding the prototype building suite to cover 90% of the commercial building floor area in the U.S., by developing prototype models for additional building types including place of worship, public order and safety, public assembly. Courthouse is courthouse is a sub-category under the “Public Order and Safety" building type category; other sub-categories include police station, fire station, and jail, reformatory or penitentiary.ORNL used building design guides, databases, and documented courthouse projects, supplemented by personal communication with courthouse facility planning and design experts, to systematically conduct research on the courthouse building and system characteristics. This report documents the research conducted for the courthouse building type and proposes building and system characteristics for developing a prototype building energy model to be included in the Commercial Building Prototype Model suite. According to the 2012 CBECS, courthouses occupy a total of 436 million sqft of floor space or 0.5% of the total floor space in all commercial buildings in the US, next to fast food (0.35%), grocery store or food market (0.88%), and restaurant or cafeteria (1.2%) building types currently included in the Commercial Prototype Building Model suite. Considering aggregated average, courthouse falls among the larger with a mean floor area of 69,400 sqft smaller fuel consumption intensity building types and an average of 94.7 kBtu/sqft compared to 77.8 kBtu/sqft for office and 80 kBtu/sqft for all commercial buildings.Courthouses range in size from 1000 sqft to over a million square foot building gross square feet and 1 courtroom to over 100 courtrooms. Small courthouses

  11. Time structure of cascade showers

    International Nuclear Information System (INIS)

    Nakatsuka, Takao

    1984-01-01

    Interesting results have been reported on the time structure of the electromagnetic components of air showers which have been obtained by using recent fast electronic circuit technology. However, these analyses and explanations seem not very persuasive. One of the reasons is that there is not satisfactory theoretical calculation yet to explain the delay of electromagnetic components in cascade processes which are the object of direct observation. Therefore, Monte Carlo calculation was attempted for examining the relationship between the altitude at which high energy γ-ray is generated up in the air and the time structure of cascade showers at the level of observation. The investigation of a dominant factor over the delay of electromagnetic components indicated that the delay due to the multiple scattering of electrons was essential. The author used the analytical solution found by himself of C. N. Yang's equation for the study on the delay due to multiple scattering. The results were as follows: The average delay time and the spread of distribution of electromagnetic cascades were approximately in linear relationship with the mass of a material having passed in a thin uniform medium; the rise time of arrival time distribution for electromagnetic cascade showers was very steep under the condition that they were generated up in the air and observed on the ground; the subpeaks delayed by tens of ns in arrival time may sometimes appear due to the perturbation in electromagnetic cascade processes. (Wakatsuki, Y.)

  12. Rescuing Ecosystems from Extinction Cascades

    Science.gov (United States)

    Sahasrabudhe, Sagar; Motter, Adilson

    2010-03-01

    Food web perturbations stemming from climate change, overexploitation, invasive species, and natural disasters often cause an initial loss of species that results in a cascade of secondary extinctions. Using a predictive modeling framework, here we will present a systematic network-based approach to reduce the number of secondary extinctions. We will show that the extinction of one species can often be compensated by the concurrent removal of a second specific species, which is a counter-intuitive effect not previously tested in complex food webs. These compensatory perturbations frequently involve long-range interactions that are not a priori evident from local predator-prey relationships. Strikingly, in numerous cases even the early removal of a species that would eventually be extinct by the cascade is found to significantly reduce the number of cascading extinctions. Other nondestructive interventions based on partial removals and growth suppression and/or mortality increase are shown to sometimes prevent all secondary extinctions.

  13. Database Replication Prototype

    OpenAIRE

    Vandewall, R.

    2000-01-01

    This report describes the design of a Replication Framework that facilitates the implementation and com-parison of database replication techniques. Furthermore, it discusses the implementation of a Database Replication Prototype and compares the performance measurements of two replication techniques based on the Atomic Broadcast communication primitive: pessimistic active replication and optimistic active replication. The main contributions of this report can be split into four parts....

  14. Brachial Plexus Blocker Prototype

    OpenAIRE

    Stéphanie Coelho Monteiro

    2017-01-01

    Although the area of surgical simulation has been the subject of study in recent years, it is still necessary to develop artificial experimental models with a perspective to dismiss the use of biological models. Since this makes the simulators more real, transferring the environment of the health professional to a physical or virtual reality, an anesthetic prototype has been developed, where the motor response is replicated when the brachial plexus is subjected to a proximal nervous stimulus....

  15. Development of a novel cascading TPV and TE power generation system

    International Nuclear Information System (INIS)

    Qiu, K.; Hayden, A.C.S.

    2012-01-01

    Highlights: ► A novel cascading thermophotovoltaic (TPV) and thermoelectric (TE) power generation system is proposed and developed. ► The used heat stream is taken from the TPV and applied to the input of a TE converter in the system. ► A prototype was built and tested where GaSb TPV cells and PbSnTe-based TE converter were used. ► The TPV cells generate 123.5 We whereas the TE converter generates 306.2 We in the prototype. ► It is shown the cascading power generation is feasible in fuel-fired furnaces and can be applied to micro-CHP. -- Abstract: Thermophotovoltaic (TPV) cells can convert infrared radiation into electricity. They open up possibilities for silent and stand-alone power production in fuel-fired heating equipment. Similarly, thermoelectric (TE) devices convert thermal energy directly into electricity with no moving parts. However, TE devices have relatively low efficiency for electric power generation. In this study, the concept of cascading TPV and TE power generation was developed where the used heat stream is taken from the TPV and applied to the input of a TE converter. A prototype cascading TPV and TE generation system was built and tested. GaSb TPV cells and an integrated semiconductor TE converter were used in the cascading power system. The electric output characteristics of the TPV cells and the TE converter have been investigated in the power generation system at various operating conditions. Experimental results show that the cascading power generation is feasible and has the potential for certain applications.

  16. Prototyping real-time systems

    OpenAIRE

    Clynch, Gary

    1994-01-01

    The traditional software development paradigm, the waterfall life cycle model, is defective when used for developing real-time systems. This thesis puts forward an executable prototyping approach for the development of real-time systems. A prototyping system is proposed which uses ESML (Extended Systems Modelling Language) as a prototype specification language. The prototyping system advocates the translation of non-executable ESML specifications into executable LOOPN (Language of Object ...

  17. MITRE sensor layer prototype

    Science.gov (United States)

    Duff, Francis; McGarry, Donald; Zasada, David; Foote, Scott

    2009-05-01

    The MITRE Sensor Layer Prototype is an initial design effort to enable every sensor to help create new capabilities through collaborative data sharing. By making both upstream (raw) and downstream (processed) sensor data visible, users can access the specific level, type, and quantities of data needed to create new data products that were never anticipated by the original designers of the individual sensors. The major characteristic that sets sensor data services apart from typical enterprise services is the volume (on the order of multiple terabytes) of raw data that can be generated by most sensors. Traditional tightly coupled processing approaches extract pre-determined information from the incoming raw sensor data, format it, and send it to predetermined users. The community is rapidly reaching the conclusion that tightly coupled sensor processing loses too much potentially critical information.1 Hence upstream (raw and partially processed) data must be extracted, rapidly archived, and advertised to the enterprise for unanticipated uses. The authors believe layered sensing net-centric integration can be achieved through a standardize-encapsulate-syndicateaggregate- manipulate-process paradigm. The Sensor Layer Prototype's technical approach focuses on implementing this proof of concept framework to make sensor data visible, accessible and useful to the enterprise. To achieve this, a "raw" data tap between physical transducers associated with sensor arrays and the embedded sensor signal processing hardware and software has been exploited. Second, we encapsulate and expose both raw and partially processed data to the enterprise within the context of a service-oriented architecture. Third, we advertise the presence of multiple types, and multiple layers of data through geographic-enabled Really Simple Syndication (GeoRSS) services. These GeoRSS feeds are aggregated, manipulated, and filtered by a feed aggregator. After filtering these feeds to bring just the type

  18. A prototype analysis of vengeance

    NARCIS (Netherlands)

    Elshout, Maartje; Nelissen, Rob; van Beest, Ilja

    2015-01-01

    The authors examined the concept of vengeance from a prototype perspective. In 6 studies, the prototype structure of vengeance was mapped. Sixty-nine features of vengeance were identified (Study 1), and rated on centrality (Study 2). Further studies confirmed the prototype structure. Compared to

  19. Quantum Erasure: Quantum Interference Revisited

    OpenAIRE

    Walborn, Stephen P.; Cunha, Marcelo O. Terra; Pádua, Sebastião; Monken, Carlos H.

    2005-01-01

    Recent experiments in quantum optics have shed light on the foundations of quantum physics. Quantum erasers - modified quantum interference experiments - show that quantum entanglement is responsible for the complementarity principle.

  20. Multiplicity distributions in QCD cascades

    International Nuclear Information System (INIS)

    Gustafson, G.

    1992-03-01

    Multiplicity distributions for hadrons and for jets are studied in QCD parton cascades. The colour dipole formalism is used and earlier results in the double log approximation are generalized to include terms which are suppressed by colour factors or factors of ln s. The result is a set of coupled differential equations, together with appropriate boundary conditions

  1. A cascaded three-phase symmetrical multistage voltage multiplier

    International Nuclear Information System (INIS)

    Iqbal, Shahid; Singh, G K; Besar, R; Muhammad, G

    2006-01-01

    A cascaded three-phase symmetrical multistage Cockcroft-Walton voltage multiplier (CW-VM) is proposed in this report. It consists of three single-phase symmetrical voltage multipliers, which are connected in series at their smoothing columns like string of batteries and are driven by three-phase ac power source. The smoothing column of each voltage multiplier is charged twice every cycle independently by respective oscillating columns and discharged in series through load. The charging discharging process completes six times a cycle and therefore the output voltage ripple's frequency is of sixth order of the drive signal frequency. Thus the proposed approach eliminates the first five harmonic components of load generated voltage ripples and sixth harmonic is the major ripple component. The proposed cascaded three-phase symmetrical voltage multiplier has less than half the voltage ripple, and three times larger output voltage and output power than the conventional single-phase symmetrical CW-VM. Experimental and simulation results of the laboratory prototype are given to show the feasibility of proposed cascaded three-phase symmetrical CW-VM

  2. A comparison of methods for cascade prediction

    OpenAIRE

    Guo, Ruocheng; Shakarian, Paulo

    2016-01-01

    Information cascades exist in a wide variety of platforms on Internet. A very important real-world problem is to identify which information cascades can go viral. A system addressing this problem can be used in a variety of applications including public health, marketing and counter-terrorism. As a cascade can be considered as compound of the social network and the time series. However, in related literature where methods for solving the cascade prediction problem were proposed, the experimen...

  3. Computer simulation of displacement cascades in copper

    International Nuclear Information System (INIS)

    Heinisch, H.L.

    1983-06-01

    More than 500 displacement cascades in copper have been generated with the computer simulation code MARLOWE over an energy range pertinent to both fission and fusion neutron spectra. Three-dimensional graphical depictions of selected cascades, as well as quantitative analysis of cascade shapes and sizes and defect densities, illustrate cascade behavior as a function of energy. With increasing energy, the transition from production of single compact damage regions to widely spaced multiple damage regions is clearly demonstrated

  4. Dynamics robustness of cascading systems.

    Directory of Open Access Journals (Sweden)

    Jonathan T Young

    2017-03-01

    Full Text Available A most important property of biochemical systems is robustness. Static robustness, e.g., homeostasis, is the insensitivity of a state against perturbations, whereas dynamics robustness, e.g., homeorhesis, is the insensitivity of a dynamic process. In contrast to the extensively studied static robustness, dynamics robustness, i.e., how a system creates an invariant temporal profile against perturbations, is little explored despite transient dynamics being crucial for cellular fates and are reported to be robust experimentally. For example, the duration of a stimulus elicits different phenotypic responses, and signaling networks process and encode temporal information. Hence, robustness in time courses will be necessary for functional biochemical networks. Based on dynamical systems theory, we uncovered a general mechanism to achieve dynamics robustness. Using a three-stage linear signaling cascade as an example, we found that the temporal profiles and response duration post-stimulus is robust to perturbations against certain parameters. Then analyzing the linearized model, we elucidated the criteria of when signaling cascades will display dynamics robustness. We found that changes in the upstream modules are masked in the cascade, and that the response duration is mainly controlled by the rate-limiting module and organization of the cascade's kinetics. Specifically, we found two necessary conditions for dynamics robustness in signaling cascades: 1 Constraint on the rate-limiting process: The phosphatase activity in the perturbed module is not the slowest. 2 Constraints on the initial conditions: The kinase activity needs to be fast enough such that each module is saturated even with fast phosphatase activity and upstream changes are attenuated. We discussed the relevance of such robustness to several biological examples and the validity of the above conditions therein. Given the applicability of dynamics robustness to a variety of systems, it

  5. Cascaded Bragg scattering in fiber optics.

    Science.gov (United States)

    Xu, Y Q; Erkintalo, M; Genty, G; Murdoch, S G

    2013-01-15

    We report on a theoretical and experimental study of cascaded Bragg scattering in fiber optics. We show that the usual energy-momentum conservation of Bragg scattering can be considerably relaxed via cascade-induced phase-matching. Experimentally we demonstrate frequency translation over six- and 11-fold cascades, in excellent agreement with derived phase-matching conditions.

  6. OPAL Jet Chamber Prototype

    CERN Multimedia

    OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. OPAL's central tracking system consists of (in order of increasing radius) a silicon microvertex detector, a vertex detector, a jet chamber, and z-chambers. All the tracking detectors work by observing the ionization of atoms by charged particles passing by: when the atoms are ionized, electrons are knocked out of their atomic orbitals, and are then able to move freely in the detector. These ionization electrons are detected in the dirfferent parts of the tracking system. This piece is a prototype of the jet chambers

  7. Prototyping Augmented Reality

    CERN Document Server

    Mullen, Tony

    2011-01-01

    Learn to create augmented reality apps using Processing open-source programming language Augmented reality (AR) is used all over, and you may not even realize it. Smartphones overlay data onto live camera views to show homes for sale, restaurants, or historical sites. American football broadcasts use AR to show the invisible first-down line on the field to TV viewers. Nike and Budweiser, among others, have used AR in ads. Now, you can learn to create AR prototypes using 3D data, Processing open-source programming language, and other languages. This unique book is an easy-to-follow guide on how

  8. Nightshade Prototype Experiments (Silverleaf)

    Energy Technology Data Exchange (ETDEWEB)

    Danielson, Jeremy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bauer, Amy L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-12-23

    The Red Sage campaign is a series of subcritical dynamic plutonium experiments designed to measure ejecta. Nightshade, the first experiments in Red Sage scheduled for fiscal year 2019, will measure the amount of ejecta emission into vacuum from a double-­shocked plutonium surface. To address the major technical risks in Nightshade, a Level 2 milestone was developed for fiscal year 2016. Silverleaf, a series of four experiments, was executed at the Los Alamos National Laboratory in July and August 2016 to demonstrate a prototype of the Nightshade package and to satisfy this Level 2 milestone. This report is documentation that Red Sage Level 2 milestone requirements were successfully met.

  9. Autocompensating quantum cryptography

    International Nuclear Information System (INIS)

    Bethune, Donald S.; Risk, William P.

    2002-01-01

    Quantum cryptographic key distribution (QKD) uses extremely faint light pulses to carry quantum information between two parties (Alice and Bob), allowing them to generate a shared, secret cryptographic key. Autocompensating QKD systems automatically and passively compensate for uncontrolled time-dependent variations of the optical fibre properties by coding the information as a differential phase between orthogonally polarized components of a light pulse sent on a round trip through the fibre, reflected at mid-course using a Faraday mirror. We have built a prototype system based on standard telecom technology that achieves a privacy-amplified bit generation rate of ∼1000 bits s -1 over a 10 km optical fibre link. Quantum cryptography is an example of an application that, by using quantum states of individual particles to represent information, accomplishes a practical task that is impossible using classical means. (author)

  10. High power cascade diode lasers emitting near 2 μm

    Energy Technology Data Exchange (ETDEWEB)

    Hosoda, Takashi; Feng, Tao; Shterengas, Leon, E-mail: leon.shterengas@stonybrook.edu; Kipshidze, Gela; Belenky, Gregory [State University of New York at Stony Brook, Stony Brook, New York 11794 (United States)

    2016-03-28

    High-power two-stage cascade GaSb-based type-I quantum well diode lasers emitting near 2 μm were designed and fabricated. Coated devices with cavity length of 3 mm generated about 2 W of continuous wave power from 100-μm-wide aperture at the current of 6 A. The power conversion efficiency peaked at 20%. Carrier recycling between quantum well gain stages was realized using band-to-band tunneling in GaSb/AlSb/InAs heterostructure complemented with optimized electron and hole injector regions. Design optimization eliminated parasitic optical absorption and thermionic emission, and included modification of the InAs quantum wells of electron and composition and doping profile of hole injectors. Utilization of the cascade pumping scheme yielded 2 μm lasers with improved output power and efficiency compared to existing state-of-the-art diodes.

  11. DataCollection Prototyping

    CERN Multimedia

    Beck, H.P.

    DataCollection is a subsystem of the Trigger, DAQ & DCS project responsible for the movement of event data from the ROS to the High Level Triggers. This includes data from Regions of Interest (RoIs) for Level 2, building complete events for the Event Filter and finally transferring accepted events to Mass Storage. It also handles passing the LVL1 RoI pointers and the allocation of Level 2 processors and load balancing of Event Building. During the last 18 months DataCollection has developed a common architecture for the hardware and software required. This involved a radical redesign integrating ideas from separate parts of earlier TDAQ work. An important milestone for this work, now achieved, has been to demonstrate this subsystem in the so-called Phase 2A Integrated Prototype. This prototype comprises the various TDAQ hardware and software components (ROSs, LVL2, etc.) under the control of the TDAQ Online software. The basic functionality has been demonstrated on small testbeds (~8-10 processing nodes)...

  12. OMS FDIR: Initial prototyping

    Science.gov (United States)

    Taylor, Eric W.; Hanson, Matthew A.

    1990-01-01

    The Space Station Freedom Program (SSFP) Operations Management System (OMS) will automate major management functions which coordinate the operations of onboard systems, elements and payloads. The objectives of OMS are to improve safety, reliability and productivity while reducing maintenance and operations cost. This will be accomplished by using advanced automation techniques to automate much of the activity currently performed by the flight crew and ground personnel. OMS requirements have been organized into five task groups: (1) Planning, Execution and Replanning; (2) Data Gathering, Preprocessing and Storage; (3) Testing and Training; (4) Resource Management; and (5) Caution and Warning and Fault Management for onboard subsystems. The scope of this prototyping effort falls within the Fault Management requirements group. The prototyping will be performed in two phases. Phase 1 is the development of an onboard communications network fault detection, isolation, and reconfiguration (FDIR) system. Phase 2 will incorporate global FDIR for onboard systems. Research into the applicability of expert systems, object-oriented programming, fuzzy sets, neural networks and other advanced techniques will be conducted. The goals and technical approach for this new SSFP research project are discussed here.

  13. Live Piloting and Prototyping

    Directory of Open Access Journals (Sweden)

    Francesca Rizzo

    2013-07-01

    Full Text Available This paper presents current trends in service design research concerning large scale projects aimed at generating changes at a local scale. The strategy adopted to achieve this, is to co-design solutions including future users in the development process, prototyping and testing system of products and services before their actual implementation. On the basis of experience achieved in the European Project Life 2.0, this paper discusses which methods and competencies are applied in the development of these projects, eliciting the lessons learnt especially from the piloting phase in which the participatory design (PD approach plays a major role. In the first part, the topic is introduced jointly with the theoretical background where the user center design and participatory design methods are presented; then the Life 2.0 project development is described; finally the experience is discussed from a service design perspective, eliciting guidelines for piloting and prototyping services in a real context of use. The paper concludes reflecting on the designers’ role and competencies needed in this process.

  14. Fabrication of prototype imaging arrays for SCUBA-2

    International Nuclear Information System (INIS)

    Hilton, G.C.; Beall, J.A.; Doriese, W.B.; Duncan, W.D.; Ferreira, L.S.; Irwin, K.D.; Reintsema, C.D.; Ullom, J.N.; Vale, L.R.; Xu, Y.; Zink, B.L.; Parkes, W.; Bunting, A.S.; Dunare, C.C.; Gundlach, A.M.; Stevenson, J.T.M.; Walton, A.J.; Schulte, E.; Corrales, E.; Sienicki, J.P.; Bintley, Dan; Ade, P.A.R.; Sudiwala, Rashmi V.; Woodcraft, Adam L.; Halpern, Mark; Holland, W.; Audley, M.D.; MacIntosh, M.

    2006-01-01

    Prototype imaging subarrays for SCUBA-2 (the Submillimeter Common-User Bolometer Array) have been fabricated and tested. The pixel count (1280) of these wafer-scale imagers is significantly larger than any other low-temperature detectors produced to date, and represents a major step forward for the low-temperature detector community. These transition-edge-sensor (TES) based imagers utilize several innovations including in-focal-plane superconducting quantum intereference device (SQUID) multiplexers, micromachined Si block absorbers, and superconducting wafer hybridization. In this paper, we review the fabrication processes developed for these imagers and present recent optical data from a prototype imaging subarray

  15. Particles, fields, quanta. From quantum mechanics to the Standard Model of particle physics; Teilchen, Felder, Quanten. Von der Quantenmechanik zum Standardmodell der Teilchenphysik

    Energy Technology Data Exchange (ETDEWEB)

    Ecker, Gerhard [Wien Univ. (Austria). Fakultaet fuer Physik

    2017-07-01

    The following topics are dealt with: Physics around 1900, the way to quantum mechanics, quantum field theory with quantum electrodynamics as prototype, the crisis of quantum field theory, from the beta decay to the electroweak gauge theory, quantum chromodynamics as quantum field theory of the strong nuclear force, the standard model of the fundamental interactions, physics beyond the standard model. (HSI)

  16. Atom-atom collision cascades localization

    International Nuclear Information System (INIS)

    Kirsanov, V.V.

    1980-01-01

    The presence of an impurity and thermal vibration influence on the atom-atom collision cascade development is analysed by the computer simulation method (the modificated dynamic model). It is discovered that the relatively low energetic cascades are localized with the temperature increase of an irradiated crystal. On the basis of the given effect the mechanism of splitting of the high energetic cascades into subcascades is proposed. It accounts for two factors: the primary knocked atom energy and the irradiated crystal temperature. Introduction of an impurity also localizes the cascades independently from the impurity atom mass. The cascades localization leads to intensification of the process of annealing in the cascades and reduction of the post-cascade vacancy cluster sizes. (author)

  17. Cascade Chaotic System With Applications.

    Science.gov (United States)

    Zhou, Yicong; Hua, Zhongyun; Pun, Chi-Man; Chen, C L Philip

    2015-09-01

    Chaotic maps are widely used in different applications. Motivated by the cascade structure in electronic circuits, this paper introduces a general chaotic framework called the cascade chaotic system (CCS). Using two 1-D chaotic maps as seed maps, CCS is able to generate a huge number of new chaotic maps. Examples and evaluations show the CCS's robustness. Compared with corresponding seed maps, newly generated chaotic maps are more unpredictable and have better chaotic performance, more parameters, and complex chaotic properties. To investigate applications of CCS, we introduce a pseudo-random number generator (PRNG) and a data encryption system using a chaotic map generated by CCS. Simulation and analysis demonstrate that the proposed PRNG has high quality of randomness and that the data encryption system is able to protect different types of data with a high-security level.

  18. Cascade reactor: granule fabrication processes

    International Nuclear Information System (INIS)

    Erlandson, O.D.; Winkler, E.O.; Maya, I.; Pitts, J.H.

    1985-01-01

    A key feature of Cascade is the granular blanket. Of the many blanket material options open to Cascade, fabrication of Li 2 O granules was felt to offer the greatest challenge. The authors explored available methods for initial Li 2 O granule fabrication. They identified three cost-effective processes for fabricating Li 2 O granules: the VSM drop-melt furnace process, which is based on melting and spheroidizing irregularly shaped Li 2 O feed granules; the LiOH process, which spheroidizes liquefied LiOH and uses GA Technologies' sphere-forming procedures; and the Li 2 CO 3 sol-gel process, used for making spherical fuel particles for the high-temperature gas-cooled reactor (HTGR). Each process is described below

  19. Bankruptcy cascades in interbank markets.

    Directory of Open Access Journals (Sweden)

    Gabriele Tedeschi

    Full Text Available We study a credit network and, in particular, an interbank system with an agent-based model. To understand the relationship between business cycles and cascades of bankruptcies, we model a three-sector economy with goods, credit and interbank market. In the interbank market, the participating banks share the risk of bad debits, which may potentially spread a bank's liquidity problems through the network of banks. Our agent-based model sheds light on the correlation between bankruptcy cascades and the endogenous economic cycle of booms and recessions. It also demonstrates the serious trade-off between, on the one hand, reducing risks of individual banks by sharing them and, on the other hand, creating systemic risks through credit-related interlinkages of banks. As a result of our study, the dynamics underlying the meltdown of financial markets in 2008 becomes much better understandable.

  20. Quantum optics

    National Research Council Canada - National Science Library

    Agarwal, G. S

    2013-01-01

    ..., quantum metrology, spin squeezing, control of decoherence and many other key topics. Readers are guided through the principles of quantum optics and their uses in a wide variety of areas including quantum information science and quantum mechanics...

  1. Prototypes as Platforms for Participation

    DEFF Research Database (Denmark)

    Horst, Willem

    developers, and design it accordingly. Designing a flexible prototype in combination with supportive tools to be used by both interaction designers and non-designers during development is introduced as a way to open up the prototyping process to these users. Furthermore I demonstrate how such a flexible...... on prototyping, by bringing to attention that the prototype itself is an object of design, with its users and use context, which deserves further attention. Moreover, in this work I present concrete tools and methods that can be used by interaction designers in practice. As such this work addresses both......The development of interactive products in industry is an activity involving different disciplines – such as different kinds of designers, engineers, marketers and managers – in which prototypes play an important role. On the one hand, prototypes can be powerful boundary objects and an effective...

  2. Prototype Stilbene Neutron Collar

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, M. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shumaker, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Snyderman, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Verbeke, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wong, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-10-26

    A neutron collar using stilbene organic scintillator cells for fast neutron counting is described for the assay of fresh low enriched uranium (LEU) fuel assemblies. The prototype stilbene collar has a form factor similar to standard He-3 based collars and uses an AmLi interrogation neutron source. This report describes the simulation of list mode neutron correlation data on various fuel assemblies including some with neutron absorbers (burnable Gd poisons). Calibration curves (doubles vs 235U linear mass density) are presented for both thermal and fast (with Cd lining) modes of operation. It is shown that the stilbene collar meets or exceeds the current capabilities of He-3 based neutron collars. A self-consistent assay methodology, uniquely suited to the stilbene collar, using triples is described which complements traditional assay based on doubles calibration curves.

  3. Brachial Plexus Blocker Prototype

    Directory of Open Access Journals (Sweden)

    Stéphanie Coelho Monteiro

    2017-08-01

    Full Text Available Although the area of surgical simulation has been the subject of study in recent years, it is still necessary to develop artificial experimental models with a perspective to dismiss the use of biological models. Since this makes the simulators more real, transferring the environment of the health professional to a physical or virtual reality, an anesthetic prototype has been developed, where the motor response is replicated when the brachial plexus is subjected to a proximal nervous stimulus. Using action-research techniques, with this simulator it was possible to validate that the human nerve response can be replicated, which will aid the training of health professionals, reducing possible risks in a surgical environment.

  4. Naval Prototype Optical Interferometer (NPOI)

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Used for astrometry and astronomical imaging, the Naval Prototype Optical Interferometer (NPOI) is a distributed aperture optical telescope. It is operated...

  5. Mobile prototyping with Axure 7

    CERN Document Server

    Hacker, Will

    2013-01-01

    This book is a step-by-step tutorial which includes hands-on examples and downloadable Axure files to get you started with mobile prototyping immediately. You will learn how to develop an application from scratch, and will be guided through each and every step.If you are a mobile-centric developer/designer, or someone who would like to take their Axure prototyping skills to the next level and start designing and testing mobile prototypes, this book is ideal for you. You should be familiar with prototyping and Axure specifically, before you read this book.

  6. Quantum Turbulence ---Another da Vinci Code---

    Science.gov (United States)

    Tsubota, M.

    Quantum turbulence comprises a tangle of quantized vorticeswhich are stable topological defects created by Bose-Einstein condensation, being realized in superfluid helium and atomic Bose-Einstein condensates. In recent years there has been a growing interest in quantum turbulence. One of the important motivations is to understand the relation between quantum and classical turbulence. Quantum turbulence is expected to be much simpler than usual classical turbulence and give a prototype of turbulence. This article reviews shortly the recent research developments on quantum turbulence.

  7. Quantum Instantons and Quantum Chaos

    OpenAIRE

    Jirari, H.; Kröger, H.; Luo, X. Q.; Moriarty, K. J. M.; Rubin, S. G.

    1999-01-01

    Based on a closed form expression for the path integral of quantum transition amplitudes, we suggest rigorous definitions of both, quantum instantons and quantum chaos. As an example we compute the quantum instanton of the double well potential.

  8. Quantum metrology

    International Nuclear Information System (INIS)

    Xiang Guo-Yong; Guo Guang-Can

    2013-01-01

    The statistical error is ineluctable in any measurement. Quantum techniques, especially with the development of quantum information, can help us squeeze the statistical error and enhance the precision of measurement. In a quantum system, there are some quantum parameters, such as the quantum state, quantum operator, and quantum dimension, which have no classical counterparts. So quantum metrology deals with not only the traditional parameters, but also the quantum parameters. Quantum metrology includes two important parts: measuring the physical parameters with a precision beating the classical physics limit and measuring the quantum parameters precisely. In this review, we will introduce how quantum characters (e.g., squeezed state and quantum entanglement) yield a higher precision, what the research areas are scientists most interesting in, and what the development status of quantum metrology and its perspectives are. (topical review - quantum information)

  9. Development of principles of two-cascaded laser speckle-microscopy with implication to high-precision express diagnostics of chlamydial infection

    Science.gov (United States)

    Ulianova, Onega; Moiseeva, Yulia; Filonova, Nadezhda; Subbotina, Irina; Zaitsev, Sergey; Saltykov, Yury; Polyanina, Tatiana; Lyapina, Anna; Ulyanov, Sergey; Larionova, Olga; Utz, Sergey; Feodorova, Valentina

    2018-04-01

    Principles of two-cascaded laser speckle-microscopy prospect for application to express diagnostics of chlamydial infection are developed. Prototype of two-cascaded speckle-microscope is designed and tested. Specific case of illumination of bacterial cells by dynamic speckles is considered. Express method of detection of epithelial cells, containing defects, which are caused by Chlamydia trachomatis bacteria, is suggested. Results of improved recognition of C. trachomatis bacteria are discussed.

  10. Quantum Distinction: Quantum Distinctiones!

    OpenAIRE

    Zeps, Dainis

    2009-01-01

    10 pages; How many distinctions, in Latin, quantum distinctiones. We suggest approach of anthropic principle based on anthropic reference system which should be applied equally both in theoretical physics and in mathematics. We come to principle that within reference system of life subject of mathematics (that of thinking) should be equated with subject of physics (that of nature). For this reason we enter notions of series of distinctions, quantum distinction, and argue that quantum distinct...

  11. Experimental quantum multimeter and one-qubit fingerprinting

    International Nuclear Information System (INIS)

    Du Jiangfeng; Zou Ping; Peng Xinhua; Oi, Daniel K. L.; Ekert, Artur; Kwek, L. C.; Oh, C. H.

    2006-01-01

    There has been much recent effort to realize quantum devices in many different physical systems. Among them, nuclear magnetic resonance (NMR) has been the first to demonstrate nontrivial quantum algorithms with small numbers of qubits and hence is a prototype for the key ingredients needed to build quantum computers. An important building block in many quantum applications is the scattering circuit, which can be used as a quantum multimeter to perform various quantum information processing tasks directly without recourse to quantum tomography. We implement in NMR a three-qubit version of the multimeter and also demonstrate a single-qubit fingerprinting

  12. Quantum optics of optomechanical networks

    International Nuclear Information System (INIS)

    Stannigel, K.

    2012-01-01

    This thesis proposes various setups in which micro-mechanical resonators and optomechanical systems can be combined with other quantum systems, such as solid-state qubits or atomic ensembles, in a beneficial way. These hybrid systems open up new ways for quantum control, and several protocols and applications for quantum information processing and, in particular, for quantum networks are presented. Part I describes an optically mediated coupling between the vibrational modes of a semi-transparent dielectric membrane and the center-of-mass motion of an atomic ensemble. Using the sophisticated toolbox available for the control of atomic systems, this setting enables an indirect manipulation of the membrane, including, for example, cooling it to the vibrational ground state. A fully quantum mechanical treatment of this open system is given in terms of the quantum stochastic Schrödinger equation. In Part II we explore the potential of optomechanical systems for quantum information processing applications. First, we introduce the concept of an optomechanical transducer, where a micro-mechanical resonator mediates an interaction between a solid-state based qubit on the one hand, and photons in an optical cavity on the other hand. The resulting qubit-light interface is shown to enable quantum state transfers between two distant solid-state qubits, thereby making them available for quantum networking applications. Second, we study multi-mode optomechanical systems in the single-photon single-phonon strong coupling regime. We predict quantum signatures of this interaction, which could be observed in future experiments, and provide a route towards possible applications of these systems as quantum information processing units. Part III presents a dissipative state preparation scheme for cascaded quantum networks. In such networks excitations can only propagate along a single spatial direction and the optomechanical transducer represents one way of realizing them. We show, in

  13. Window prototypes during the project

    DEFF Research Database (Denmark)

    Schultz, Jørgen Munthe

    1996-01-01

    The conditions for the PASSYS test and the results of the measurements on one of the aerogel window prototypes are described.......The conditions for the PASSYS test and the results of the measurements on one of the aerogel window prototypes are described....

  14. Rapid prototyping: een veelbelovende methode

    NARCIS (Netherlands)

    Haverman, T.M.; Karagozoglu, K.H.; Prins, H.; Schulten, E.A.J.M.; Forouzanfar, T.

    2013-01-01

    Rapid prototyping is a method which makes it possible to produce a three-dimensional model based on two-dimensional imaging. Various rapid prototyping methods are available for modelling, such as stereolithography, selective laser sintering, direct laser metal sintering, two-photon polymerization,

  15. Role model and prototype matching

    DEFF Research Database (Denmark)

    Lykkegaard, Eva; Ulriksen, Lars

    2016-01-01

    ’ meetings with the role models affected their thoughts concerning STEM students and attending university. The regular self-to-prototype matching process was shown in real-life role-models meetings to be extended to a more complex three-way matching process between students’ self-perceptions, prototype...

  16. Abnormal cascading failure spreading on complex networks

    International Nuclear Information System (INIS)

    Wang, Jianwei; Sun, Enhui; Xu, Bo; Li, Peng; Ni, Chengzhang

    2016-01-01

    Applying the mechanism of the preferential selection of the flow destination, we develop a new method to quantify the initial load on an edge, of which the flow is transported along the path with the shortest edge weight between two nodes. Considering the node weight, we propose a cascading model on the edge and investigate cascading dynamics induced by the removal of the edge with the largest load. We perform simulated attacks on four types of constructed networks and two actual networks and observe an interesting and counterintuitive phenomenon of the cascading spreading, i.e., gradually improving the capacity of nodes does not lead to the monotonous increase in the robustness of these networks against cascading failures. The non monotonous behavior of cascading dynamics is well explained by the analysis on a simple graph. We additionally study the effect of the parameter of the node weight on cascading dynamics and evaluate the network robustness by a new metric.

  17. Virtual Prototyping at CERN

    Science.gov (United States)

    Gennaro, Silvano De

    The VENUS (Virtual Environment Navigation in the Underground Sites) project is probably the largest Virtual Reality application to Engineering design in the world. VENUS is just over one year old and offers a fully immersive and stereoscopic "flythru" of the LHC pits for the proposed experiments, including the experimental area equipment and the surface models that are being prepared for a territorial impact study. VENUS' Virtual Prototypes are an ideal replacement for the wooden models traditionally build for the past CERN machines, as they are generated directly from the EUCLID CAD files, therefore they are totally reliable, they can be updated in a matter of minutes, and they allow designers to explore them from inside, in a one-to-one scale. Navigation can be performed on the computer screen, on a stereoscopic large projection screen, or in immersive conditions, with an helmet and 3D mouse. By using specialised collision detection software, the computer can find optimal paths to lower each detector part into the pits and position it to destination, letting us visualize the whole assembly probess. During construction, these paths can be fed to a robot controller, which can operate the bridge cranes and build LHC almost without human intervention. VENUS is currently developing a multiplatform VR browser that will let the whole HEP community access LHC's Virtual Protoypes over the web. Many interesting things took place during the conference on Virtual Reality. For more information please refer to the Virtual Reality section.

  18. UA1 prototype detector

    CERN Multimedia

    1980-01-01

    Prototype of UA1 central detector inside a plexi tube. The UA1 experiment ran at CERN's Super Proton Synchrotron and made the Nobel Prize winning discovery of W and Z particles in 1983. The UA1 central detector was crucial to understanding the complex topology of proton-antiproton events. It played a most important role in identifying a handful of Ws and Zs among billions of collisions. The detector was essentially a wire chamber - a 6-chamber cylindrical assembly 5.8 m long and 2.3 m in diameter, the largest imaging drift chamber of its day. It recorded the tracks of charged particles curving in a 0.7 Tesla magnetic field, measuring their momentum, the sign of their electric charge and their rate of energy loss (dE/dx). Atoms in the argon-ethane gas mixture filling the chambers were ionised by the passage of charged particles. The electrons which were released drifted along an electric field shaped by field wires and were collected on sense wires. The geometrical arrangement of the 17000 field wires and 6...

  19. Disaster Mythology and Availability Cascades

    Directory of Open Access Journals (Sweden)

    Lisa Grow Sun

    2013-04-01

    Full Text Available Sociological research conducted in the aftermath of natural disasters has uncovered a number of “disaster myths” – widely shared misconceptions about typical post-disaster human behavior. This paper discusses the possibility that perpetuation of disaster mythology reflects an “availability cascade,” defined in prior scholarship as a “self-reinforcing process of collective belief formation by which an expressed perception triggers a chain reaction that gives the perception increasing plausibility through its rising availability in public discourse.” (Kuran and Sunstein 1999. Framing the spread of disaster mythology as an availability cascade suggests that certain tools may be useful in halting the myths’ continued perpetuation. These tools include changing the legal and social incentives of so-called “availability entrepreneurs” – those principally responsible for beginning and perpetuating the cascade, as well as insulating decision-makers from political pressures generated by the availability cascade. This paper evaluates the potential effectiveness of these and other solutions for countering disaster mythology. Las investigaciones sociológicas realizadas tras los desastres naturales han hecho evidentes una serie de “mitos del desastre”, conceptos erróneos ampliamente compartidos sobre el comportamiento humano típico tras un desastre. Este artículo analiza la posibilidad de que la perpetuación de los mitos del desastre refleje una “cascada de disponibilidad”, definida en estudios anteriores como un “proceso de auto-refuerzo de la formación de una creencia colectiva, a través del que una percepción expresada produce una reacción en cadena que hace que la percepción sea cada vez más verosímil, a través de una mayor presencia en el discurso público” (Kuran y Sunstein 1999. Enmarcar la propagación de los mitos del desastre como una cascada de disponibilidad sugiere que ciertas herramientas pueden ser

  20. Ion-implantation dense cascade data

    International Nuclear Information System (INIS)

    Winterbon, K.B.

    1983-04-01

    A tabulation is given of data useful in estimating various aspects of ion-implantation cascades in the nuclear stopping regime, particularly with respect to nonlinearity of the cascade at high energy densities. The tabulation is restricted to self-ion implantation. Besides power-cross-section cascade dimensions, various material properties are included. Scaling of derived quantities with input data is noted, so one is not limited to the values assumed by the author

  1. Characterization of Prototype LSST CCDs

    Energy Technology Data Exchange (ETDEWEB)

    OCONNOR,P.; FRANK, J.; GEARY, J.C.; GILMORE, D.K.; KOTOV, I.; RADEKA, V.; TAKACS, P.; TYSON, J.A.

    2008-06-23

    The ambitious science goals of the Large Synoptic Survey Telescope (LSST) will be achieved in part by a wide-field imager that will achieve a new level of performance in terms of area, speed, and sensitivity. The instrument performance is dominated by the focal plane sensors, which are now in development. These new-generation sensors will make use of advanced semiconductor technology and will be complemented by a highly integrated electronics package located inside the cryostat. A test laboratory has been set up at Brookhaven National Laboratory (BNL) to characterize prototype sensors and to develop test and assembly techniques for eventual integration of production sensors and electronics into modules that will form the final focal plane. As described in [1], the key requirements for LSST sensors are wideband quantum efficiency (QE) extending beyond lpm in the red, control of point spread function (PSF), and fast readout using multiple amplifiers per chip operated in parallel. In addition, LSST's fast optical system (f71.25) places severe constraints on focal plane flatness. At the chip level this involves packaging techniques to minimize warpage of the silicon die, and at the mosaic level careful assembly and metrology to achieve a high coplanarity of the sensor tiles. In view of the long lead time to develop the needed sensor technology, LSST undertook a study program with several vendors to fabricate and test devices which address the most critical performance features [2]. The remainder of this paper presents key results of this study program. Section 2 summarizes the sensor requirements and the results of design optimization studies, and Section 3 presents the sensor development plan. In Section 4 we describe the test bench at BNL. Section 5 reports measurement results obtained to date oh devices fabricated by several vendors. Section 6 presents a summary of the paper and an outlook for the future work. We present characterization methods and results on

  2. A non-conventional isotope separation cascade without any mixing: net cascade

    International Nuclear Information System (INIS)

    Zeng Shi; Jiang Dongjun; Ying Zhengen

    2012-01-01

    A component has different concentrations in the incoming flows at a confluent point in all existing isotope separations cascades for multi-component isotope separation and mixing is inevitable, which results in deterioration of separation performance of the separation cascade. However, realization of no-mixing at a confluent point is impossible with a conventional cascade. A non-conventional isotope separation cascade, net cascade, is found to be able to realize no mixings for all components at confluent points, and its concept is further developed here. No-mixing is fulfilled by requiring symmetrical separation of two specified key components at every stage, and the procedure of realizing no-mixing is presented in detail. Some properties of net cascade are investigated preliminarily, and the results demonstrated the no-mixing property is indeed realized. Net cascade is the only separation cascade that so far possesses the no-mixing property. (authors)

  3. Mid-Infrared Quantum Cascade Lasers | Edeagu | Nigerian Journal ...

    African Journals Online (AJOL)

    Nigerian Journal of Technology. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 31, No 3 (2012) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  4. Integration of Quantum Cascade Lasers and Passive Waveguides

    Science.gov (United States)

    2015-06-01

    convenience, we can de - fine an effective mirror loss eαmLA = R referenced to the active region such that αm = ln(R) LA . This definition al- lows us to...the waveguide loss. The current density threshold de - pendence in a QCL may be expressed in terms of a mirror loss αm and waveguide loss αw as in Jth...M. Licht - ensteiger, C. Gatos, and H. Gatos, J. Appl. Phys. 51, 2659 (1980). 15O. Kim and W. Bonner, J. Electron. Mater. 12, 827 (1983). 16J

  5. Hybrid Quantum Cascade Lasers on Silicon-on-Sapphire

    Science.gov (United States)

    2016-11-23

    platforms have undergone a tremendous expansion in recent years, driven initially by applications in fiber - optics communications and optical ...Figure 1. The epi-transfer procedure. (a) A fully-processed QCL on InP. (b) Supporting elements made of SU-8 photoresist epoxy are formed via optical ...removed via selective etching . (e) The QCL is bonded to a Si substrate with the SU-8 epoxy adhesive. (f) The glass slide and the Crystalbond glue is

  6. Sensitivity of Heterointerfaces on Emission Wavelength in Quantum Cascade Lasers

    Science.gov (United States)

    2016-10-31

    thickness. To correct the composition, a secondary flow of the Al precursor was added during MOVPE growth to increase Al content in QCLs. The resulting...diluted 200 ppm in H2) was used as the n-type dopant. The growth temperature was 625 °C as measured by emissivity corrected optical pyrometrey. AlInAs and...Muraki, S. Fukatsu, Y. Shiraki, and R. Ito , "Surface segregation of In atoms during molecular beam epitaxy and its influence on the energy levels in

  7. Contingency Analysis of Cascading Line Outage Events

    Energy Technology Data Exchange (ETDEWEB)

    Thomas L Baldwin; Magdy S Tawfik; Miles McQueen

    2011-03-01

    As the US power systems continue to increase in size and complexity, including the growth of smart grids, larger blackouts due to cascading outages become more likely. Grid congestion is often associated with a cascading collapse leading to a major blackout. Such a collapse is characterized by a self-sustaining sequence of line outages followed by a topology breakup of the network. This paper addresses the implementation and testing of a process for N-k contingency analysis and sequential cascading outage simulation in order to identify potential cascading modes. A modeling approach described in this paper offers a unique capability to identify initiating events that may lead to cascading outages. It predicts the development of cascading events by identifying and visualizing potential cascading tiers. The proposed approach was implemented using a 328-bus simplified SERC power system network. The results of the study indicate that initiating events and possible cascading chains may be identified, ranked and visualized. This approach may be used to improve the reliability of a transmission grid and reduce its vulnerability to cascading outages.

  8. Protective Controller against Cascade Outages with Selective Harmonic Compensation Function

    Science.gov (United States)

    Abramovich, B. N.; Kuznetsov, P. A.; Sychev, Yu A.

    2018-05-01

    The paper presents data on the power quality and development of protective devices for the power networks with distributed generation (DG).The research has shown that power quality requirements for DG networks differ from conventional ones. That is why main tendencies, protective equipment and filters should be modified. There isa developed algorithm for detection and prevention of cascade outages that can lead to the blackoutin DG networks and there was a proposed structural scheme for a new active power filter for selective harmonics compensation. Analysis of these theories and equipment led to the development of protective device that could monitor power balance and cut off non-important consumers. The last part of the article describes a microcontroller prototype developed for connection to the existing power station control center.

  9. The 40 Gbps cascaded bit-interleaving PON

    Science.gov (United States)

    Vyncke, A.; Torfs, G.; Van Praet, C.; Verbeke, M.; Duque, A.; Suvakovic, D.; Chow, H. K.; Yin, X.

    2015-12-01

    In this paper, a 40 Gbps cascaded bit-interleaving passive optical network (CBI-PON) is proposed to achieve power reduction in the network. The massive number of devices in the access network makes that power consumption reduction in this part of the network has a major impact on the total network power consumption. Starting from the proven BiPON technology, an extension to this concept is proposed to introduce multiple levels of bit-interleaving. The paper discusses the CBI protocol in detail, as well as an ASIC implementation of the required custom CBI Repeater and End-ONT. From the measurements of this first 40 Gbps ASIC prototype, power consumption reduction estimates are presented.

  10. A Semisupervised Cascade Classification Algorithm

    Directory of Open Access Journals (Sweden)

    Stamatis Karlos

    2016-01-01

    Full Text Available Classification is one of the most important tasks of data mining techniques, which have been adopted by several modern applications. The shortage of enough labeled data in the majority of these applications has shifted the interest towards using semisupervised methods. Under such schemes, the use of collected unlabeled data combined with a clearly smaller set of labeled examples leads to similar or even better classification accuracy against supervised algorithms, which use labeled examples exclusively during the training phase. A novel approach for increasing semisupervised classification using Cascade Classifier technique is presented in this paper. The main characteristic of Cascade Classifier strategy is the use of a base classifier for increasing the feature space by adding either the predicted class or the probability class distribution of the initial data. The classifier of the second level is supplied with the new dataset and extracts the decision for each instance. In this work, a self-trained NB∇C4.5 classifier algorithm is presented, which combines the characteristics of Naive Bayes as a base classifier and the speed of C4.5 for final classification. We performed an in-depth comparison with other well-known semisupervised classification methods on standard benchmark datasets and we finally reached to the point that the presented technique has better accuracy in most cases.

  11. Cascade of negative muons in atoms

    International Nuclear Information System (INIS)

    Akylas, V.R.

    1978-01-01

    A study is made of the evolution of a negative muon captured in an atom and the formalism of energy loss associated with the muonic atom. The principal goals are to calculate reliability the muon x-ray intensities, given the initial population of the muonic orbits, to invert the problem and deduce the initial distribution from the x-ray intensities, to provide a reasonably simple and convenient tool to correlate observations, and finally, to systematize some questions of theoretical interest. The early part of the history of the muon in matter, including the atomic capture and classical phase of the atomic cascade are reviewed. In the quantal treatment of the transition rates, both radiative and electron Auger transitions are considered. In general, multipolarities up to E3 and K, L, and M electronic shells are fully investigated. Multipole radiation is treated in the conventinal way and pesents no special problems. Magnetic type transitions between states with different principal quantum numbers are shown to be small. Auger electron ejection rates are more complicated and several approximations have been adopted. The basic results have been computed in terms of elemetary functions. In the Auger transitions we have shown that magnetic multipoles can be safety neglected. The relative sizes of the rates corresponding to different multipoles are systematically studied. A comparison of results is made with atomic photoelectric effect data and with the nuclear internal conversion coefficients. A general agreement is found, except around shell thresholds. The existing data of muonic x-ray intensities in iron and thallium are analyzed in a systematic way. It is found that for Fe the initial l-distribution is almost flat, whereas that for T1 is weighted towards the high l values, sharper than statistical. As a result of the investigations and in order to make our findings usable, a computer program has been developed. 36 references

  12. Quantum walks, quantum gates, and quantum computers

    International Nuclear Information System (INIS)

    Hines, Andrew P.; Stamp, P. C. E.

    2007-01-01

    The physics of quantum walks on graphs is formulated in Hamiltonian language, both for simple quantum walks and for composite walks, where extra discrete degrees of freedom live at each node of the graph. It is shown how to map between quantum walk Hamiltonians and Hamiltonians for qubit systems and quantum circuits; this is done for both single-excitation and multiexcitation encodings. Specific examples of spin chains, as well as static and dynamic systems of qubits, are mapped to quantum walks, and walks on hyperlattices and hypercubes are mapped to various gate systems. We also show how to map a quantum circuit performing the quantum Fourier transform, the key element of Shor's algorithm, to a quantum walk system doing the same. The results herein are an essential preliminary to a Hamiltonian formulation of quantum walks in which coupling to a dynamic quantum environment is included

  13. Honeywell Cascade Distiller System Performance Testing Interim Results

    Science.gov (United States)

    Callahan, Michael R.; Sargusingh, Miriam

    2014-01-01

    The ability to recover and purify water through physiochemical processes is crucial for realizing long-term human space missions, including both planetary habitation and space travel. Because of their robust nature, distillation systems have been actively pursued as one of the technologies for water recovery. The Cascade Distillation System (CDS) is a vacuum rotary distillation system with potential for greater reliability and lower energy costs than existing distillation systems. The CDS was previously under development through Honeywell and NASA. In 2009, an assessment was performed to collect data to support down-selection and development of a primary distillation technology for application in a lunar outpost water recovery system. Based on the results of this testing, an expert panel concluded that the CDS showed adequate development maturity, TRL-4, together with the best product water quality and competitive weight and power estimates to warrant further development. The Advanced Exploration Systems (AES) Water Recovery Project (WRP) worked to address weaknesses identified by The Panel; namely bearing design and heat pump power efficiency. Testing at the NASA-JSC Advanced Exploration System Water Laboratory (AES Water Lab) using a prototype Cascade Distillation Subsystem (CDS) wastewater processor (Honeywell International, Torrance, Calif.) with test support equipment and control system developed by Johnson Space Center was performed to evaluate performance of the system with the upgrades. The CDS will also have been challenged with ISS analog waste streams and a subset of those being considered for Exploration architectures. This paper details interim results of the AES WRP CDS performance testing.

  14. Prototype moving-ring reactor

    International Nuclear Information System (INIS)

    Smith, A.C. Jr.; Ashworth, C.P.; Abreu, K.E.

    1981-01-01

    The objective of this work was to design a prototype fusion reactor based on fusion plasmas confined as ''Compact Toruses.' Six major criteria guided the prototype design. The prototype must: (1) produce net electricity decisively (P/sub net/ >70% of P/sub gross/), with P/sub net/ approximately 100 MW(e); (2) have small physical size (low project cost) but commercial plant; (3) have all features required of commerical plants; (4) avoid unreasonable extrapolation of technology; (5) minimize nuclear issues substantially, i.e. accident and waste issues of public concern, and (6) be modular (to permit repetitive fabrication of parts) and be maintainable with low occupational radiological exposures

  15. Interband cascade lasers with >40% continuous-wave wallplug efficiency at cryogenic temperatures

    International Nuclear Information System (INIS)

    Canedy, C. L.; Kim, C. S.; Merritt, C. D.; Bewley, W. W.; Vurgaftman, I.; Meyer, J. R.; Kim, M.

    2015-01-01

    Broad-area 10-stage interband cascade lasers (ICLs) emitting at λ = 3.0–3.2 μm are shown to maintain continuous-wave (cw) wallplug efficiencies exceeding 40% at temperatures up to 125 K, despite having a design optimized for operation at ambient and above. The cw threshold current density at 80 K is only 11 A/cm 2 for a 2 mm cavity with anti-reflection/high-reflection coatings on the two facets. The external differential quantum efficiency for a 1-mm-long cavity with the same coatings is 70% per stage at 80 K, and still above 65% at 150 K. The results demonstrate that at cryogenic temperatures, where free carrier absorption losses are minimized, ICLs can convert electrical to optical energy nearly as efficiently as the best specially designed intersubband-based quantum cascade lasers

  16. Quantum memory Quantum memory

    Science.gov (United States)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  17. Design concept of Hydro cascade control system

    International Nuclear Information System (INIS)

    Fustik, Vangel; Kiteva, Nevenka

    2006-01-01

    In this paper a design concept of the comple hydro cascade scheme is presented with the design parameters of the main technical features. The cascade control system architecture is designed considering up-to-date communication and information technology. The control algorithm is based on Pond Level Control and Economic Load Allocation concepts.

  18. Centrifugal separator cascade connected in zigzag manner

    International Nuclear Information System (INIS)

    Kai, Tsunetoshi; Inoue, Yoshiya; Oya, Akio; Nagakura, Masaaki.

    1974-01-01

    Object: To effectively accommodate centrifugal separators of the entire cascade within the available space in a plant by freely selecting perpendicular direction of connection of the centrifugal separator. Structure: Centrifugal separators are connected in zigzag fashion by using a single header for each stage so that in a rectangular shape the entire cascade is arranged. (Kamimura, M.)

  19. Cascaded impedance networks for NPC inverter

    DEFF Research Database (Denmark)

    Li, Ding; Gao, Feng; Loh, Poh Chiang

    2010-01-01

    they are subject to the renewable sources. To date, three distinct types of impedance networks can be summarized for implementing a hybrid source impedance network, which can in principle be combined and cascaded before connected to a NPC inverter by proposed two ways. The resulting cascaded impedance network NPC...

  20. Cascading costs: an economic nitrogen cycle.

    Science.gov (United States)

    Moomaw, William R; Birch, Melissa B L

    2005-09-01

    The chemical nitrogen cycle is becoming better characterized in terms of fluxes and reservoirs on a variety of scales. Galloway has demonstrated that reactive nitrogen can cascade through multiple ecosystems causing environmental damage at each stage before being denitrified to N(2). We propose to construct a parallel economic nitrogen cascade (ENC) in which economic impacts of nitrogen fluxes can be estimated by the costs associated with each stage of the chemical cascade. Using economic data for the benefits of damage avoided and costs of mitigation in the Chesapeake Bay basin, we have constructed an economic nitrogen cascade for the region. Since a single ton of nitrogen can cascade through the system, the costs also cascade. Therefore evaluating the benefits of mitigating a ton of reactive nitrogen released needs to consider the damage avoided in all of the ecosystems through which that ton would cascade. The analysis reveals that it is most cost effective to remove a ton of nitrogen coming from combustion since it has the greatest impact on human health and creates cascading damage through the atmospheric, terrestrial, aquatic and coastal ecosystems. We will discuss the implications of this analysis for determining the most cost effective policy option for achieving environmental quality goals.

  1. Suppressing recombination in polymer photovoltaic devices via energy-level cascades.

    Science.gov (United States)

    Tan, Zhi-Kuang; Johnson, Kerr; Vaynzof, Yana; Bakulin, Artem A; Chua, Lay-Lay; Ho, Peter K H; Friend, Richard H

    2013-08-14

    An energy cascading structure is designed in a polymer photovoltaic device to suppress recombination and improve quantum yields. By the insertion of a thin polymer interlayer with intermediate energy levels, electrons and holes can effectively shuttle away from each other while being spatially separated from recombination. An increase in open-circuit voltage and short-circuit current are observed in modified devices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Quantum stochastics

    CERN Document Server

    Chang, Mou-Hsiung

    2015-01-01

    The classical probability theory initiated by Kolmogorov and its quantum counterpart, pioneered by von Neumann, were created at about the same time in the 1930s, but development of the quantum theory has trailed far behind. Although highly appealing, the quantum theory has a steep learning curve, requiring tools from both probability and analysis and a facility for combining the two viewpoints. This book is a systematic, self-contained account of the core of quantum probability and quantum stochastic processes for graduate students and researchers. The only assumed background is knowledge of the basic theory of Hilbert spaces, bounded linear operators, and classical Markov processes. From there, the book introduces additional tools from analysis, and then builds the quantum probability framework needed to support applications to quantum control and quantum information and communication. These include quantum noise, quantum stochastic calculus, stochastic quantum differential equations, quantum Markov semigrou...

  3. Learning Axure RP interactive prototypes

    CERN Document Server

    Krahenbuhl, John Henry

    2015-01-01

    If you are a user experience professional, designer, information architect, or business analyst who wants to gain interactive prototyping skills with Axure, then this book is ideal for you. Some familiarity with Axure is preferred but not essential.

  4. Architectural Prototyping in Industrial Practice

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak; Hansen, Klaus Marius

    2008-01-01

    Architectural prototyping is the process of using executable code to investigate stakeholders’ software architecture concerns with respect to a system under development. Previous work has established this as a useful and cost-effective way of exploration and learning of the design space of a system......, in addressing issues regarding quality attributes, in addressing architectural risks, and in addressing the problem of knowledge transfer and conformance. Little work has been reported so far on the actual industrial use of architectural prototyping. In this paper, we report from an ethnographical study...... and focus group involving architects from four companies in which we have focused on architectural prototypes. Our findings conclude that architectural prototypes play an important role in resolving problems experimentally, but less so in exploring alternative solutions. Furthermore, architectural...

  5. Experimentation with PEC channel prototype

    International Nuclear Information System (INIS)

    Caponetti, R.; Iacovelli, M.

    1984-01-01

    Experimentation on prototypes of PEC components is presently being carried out at Casaccia CRE. This report shows the results of the first cycle of experimentation of the central channel, concerning the aspects of sodium removal after experimentation

  6. MAPK cascades in guard cell signal transduction

    Directory of Open Access Journals (Sweden)

    Yuree eLee

    2016-02-01

    Full Text Available Guard cells form stomata on the epidermis and continuously respond to endogenous and environmental stimuli to fine-tune the gas exchange and transpirational water loss, processes which involve mitogen-activated protein kinase (MAPK cascades. MAPKs form three-tiered kinase cascades with MAPK kinases and MAPK kinase kinases, by which signals are transduced to the target proteins. MAPK cascade genes are highly conserved in all eukaryotes, and they play crucial roles in myriad developmental and physiological processes. MAPK cascades function during biotic and abiotic stress responses by linking extracellular signals received by receptors to cytosolic events and gene expression. In this review, we highlight recent findings and insights into MAPK-mediated guard cell signaling, including the specificity of MAPK cascades and the remaining questions.

  7. Cascade Error Projection: An Efficient Hardware Learning Algorithm

    Science.gov (United States)

    Duong, T. A.

    1995-01-01

    A new learning algorithm termed cascade error projection (CEP) is presented. CEP is an adaption of a constructive architecture from cascade correlation and the dynamical stepsize of A/D conversion from the cascade back propagation algorithm.

  8. Displacement cascades in diatomic materials

    International Nuclear Information System (INIS)

    Parkin, D.M.; Coulter, C.A.

    1981-01-01

    A new function, the specified-projectile displacement function p/sub ijk/ (E), is introduced to describe displacement cascades in polyatomic materials. This function describes the specific collision events that produce displacements and hence adds new information not previously available. Calculations of p/sub ijk/ (E) for MgO, Al 2 O 3 and TaO are presented and discussed. Results show that the parameters that have the largest effect on displacement collision events are the PKA energy and the mass ratio of the atom types in the material. It is further shown that the microscopic nature of the displacement events changes over the entire recoil energy range relevant to fusion neutron spectra and that these changes are different in materials whose mass ratio is near one than in those where it is far from one

  9. The Geant4 Bertini Cascade

    Energy Technology Data Exchange (ETDEWEB)

    Wright, D.H.; Kelsey, M.H.

    2015-12-21

    One of the medium energy hadron–nucleus interaction models in the GEANT4 simulation toolkit is based partly on the Bertini intranuclear cascade model. Since its initial appearance in the toolkit, this model has been largely re-written in order to extend its physics capabilities and to reduce its memory footprint. Physics improvements include extensions in applicable energy range and incident particle types, and improved hadron–nucleon cross-sections and angular distributions. Interfaces have also been developed which allow the model to be coupled with other GEANT4 models at lower and higher energies. The inevitable speed reductions due to enhanced physics have been mitigated by memory and CPU efficiency improvements. Details of these improvements, along with selected comparisons of the model to data, are discussed.

  10. Availability Cascades & the Sharing Economy

    DEFF Research Database (Denmark)

    Netter, Sarah

    2014-01-01

    attention. This conceptual paper attempts to explain the emergent focus on the sharing economy and associated business and consumption models by applying cascade theory. Risks associated with this behavior will be especially examined with regard to the sustainability claim of collaborative consumption......In search of a new concept that will provide answers to as to how modern societies should not only make sense but also resolve the social and environmental problems linked with our modes of production and consumption, collaborative consumption and the sharing economy are increasingly attracting....... With academics, practitioners, and civil society alike having a shared history in being rather fast in accepting new concepts that will not only provide business opportunities but also a good conscience, this study proposes a critical study of the implications of collaborative consumption, before engaging...

  11. Tangiplay: prototyping tangible electronic games

    OpenAIRE

    Boileau, Jason

    2010-01-01

    Tangible electronic games currently exist in research laboratories around the world but have yet to transition to the commercial sector. The development process of a tangible electronic game is one of the factors preventing progression, as it requires much time and money. Prototyping tools for tangible hardware and software development are becoming more available but are targeted to programmers and technically trained developers. Paper prototyping board and video games is a proven and rapid m...

  12. Quantum Computing

    OpenAIRE

    Scarani, Valerio

    1998-01-01

    The aim of this thesis was to explain what quantum computing is. The information for the thesis was gathered from books, scientific publications, and news articles. The analysis of the information revealed that quantum computing can be broken down to three areas: theories behind quantum computing explaining the structure of a quantum computer, known quantum algorithms, and the actual physical realizations of a quantum computer. The thesis reveals that moving from classical memor...

  13. Quantum Malware

    OpenAIRE

    Wu, Lian-Ao; Lidar, Daniel A.

    2005-01-01

    When quantum communication networks proliferate they will likely be subject to a new type of attack: by hackers, virus makers, and other malicious intruders. Here we introduce the concept of "quantum malware" to describe such human-made intrusions. We offer a simple solution for storage of quantum information in a manner which protects quantum networks from quantum malware. This solution involves swapping the quantum information at random times between the network and isolated, distributed an...

  14. Experimental study of flow through compressor Cascade

    Directory of Open Access Journals (Sweden)

    Satyam Panchal

    2017-09-01

    Full Text Available The objective of this research work is to study the behaviour of flow at the inlet, within the blade passage and at the exit of a compressor cascade. For this purpose, a cascade with six numbers of aerofoil blades was designed and constructed. The cascade was fitted on the cascade test tunnel. Out of six blades two were instrumented for measuring the pressure distribution on the pressure and suction surface. The blades had a parabolic camber line, with a maximum camber position at 40% of the chord from the leading edge of the blade. The profile of the blade was C4, height of the blade was 160 mm, chord length was 80 mm, camber angle was 45° and stagger angle was 30°. Similarly, the length of the cascade was 300 mm, span was 160 mm, pitch was 60 mm, the actual chord of the cascade was 80 mm, the axial chord of the cascade was 70 mm, the stagger angle of the cascade was 30° and the pitch-chord ratio was 0.75. The data was taken and analyzed at −500% of the axial chord before the cascade, −25% of the axial chord before the leading edge, 25%, 50%, 75% and 150% of the axial chord from the leading edge of the blade. The readings were taken from the cascade wall to the mid span position along the pitch wise direction. The angle of incidence was also changed during the experiment and varied from i=−50°, −30°, −10° to 5°.

  15. Fast-prototyping of VLSI

    International Nuclear Information System (INIS)

    Saucier, G.; Read, E.

    1987-01-01

    Fast-prototyping will be a reality in the very near future if both straightforward design methods and fast manufacturing facilities are available. This book focuses, first, on the motivation for fast-prototyping. Economic aspects and market considerations are analysed by European and Japanese companies. In the second chapter, new design methods are identified, mainly for full custom circuits. Of course, silicon compilers play a key role and the introduction of artificial intelligence techniques sheds a new light on the subject. At present, fast-prototyping on gate arrays or on standard cells is the most conventional technique and the third chapter updates the state-of-the art in this area. The fourth chapter concentrates specifically on the e-beam direct-writing for submicron IC technologies. In the fifth chapter, a strategic point in fast-prototyping, namely the test problem is addressed. The design for testability and the interface to the test equipment are mandatory to fulfill the test requirement for fast-prototyping. Finally, the last chapter deals with the subject of education when many people complain about the lack of use of fast-prototyping in higher education for VLSI

  16. Quantumness beyond quantum mechanics

    International Nuclear Information System (INIS)

    Sanz, Ángel S

    2012-01-01

    Bohmian mechanics allows us to understand quantum systems in the light of other quantum traits than the well-known ones (coherence, diffraction, interference, tunnelling, discreteness, entanglement, etc.). Here the discussion focusses precisely on two of these interesting aspects, which arise when quantum mechanics is thought within this theoretical framework: the non-crossing property, which allows for distinguishability without erasing interference patterns, and the possibility to define quantum probability tubes, along which the probability remains constant all the way. Furthermore, taking into account this hydrodynamic-like description as a link, it is also shown how this knowledge (concepts and ideas) can be straightforwardly transferred to other fields of physics (for example, the transmission of light along waveguides).

  17. Nonlinear Dynamics In Quantum Physics -- Quantum Chaos and Quantum Instantons

    OpenAIRE

    Kröger, H.

    2003-01-01

    We discuss the recently proposed quantum action - its interpretation, its motivation, its mathematical properties and its use in physics: quantum mechanical tunneling, quantum instantons and quantum chaos.

  18. Superconducting detectors for semiconductor quantum photonics

    International Nuclear Information System (INIS)

    Reithmaier, Guenther M.

    2015-01-01

    In this thesis we present the first successful on-chip detection of quantum light, thereby demonstrating the monolithic integration of superconducting single photon detectors with individually addressable semiconductor quantum dots in a prototypical quantum photonic circuit. Therefore, we optimized both the deposition of high quality superconducting NbN thin films on GaAs substrates and the fabrication of superconducting detectors and successfully integrated these novel devices with GaAs/AlGaAs ridge waveguides loaded with self-assembled InGaAs quantum dots.

  19. High-Speed Operation of Interband Cascade Lasers

    Science.gov (United States)

    Soibel, Alexander; Hill, Cory J.; Keo, Sam A.; Wright, Malcom W.; Farr, William H.; Yang, Rui Q.; Liu, H. C.

    2010-01-01

    Optical sources operating in the atmospheric window of 3-5 microns are of particular interest for the development of free-space optical communication link. It is more advantageous to operate the free-space optical communication link in 3-5-microns atmospheric transmission window than at the telecom wavelength of 1.5 m due to lower optical scattering, scintillation, and background radiation. However, the realization of optical communications at the longer wavelength has encountered significant difficulties due to lack of adequate optical sources and detectors operating in the desirable wavelength regions. Interband Cascade (IC) lasers are novel semiconductor lasers that have a great potential for the realization of high-power, room-temperature optical sources in the 3-5-microns wavelength region, yet no experimental work, until this one, was done on high-speed direct modulation of IC lasers. Here, highspeed interband cascade laser, operating at wavelength 3.0 m, has been developed and the first direct measurement of the laser modulation bandwidth has been performed using a unique, highspeed quantum well infrared photodetector (QWIP). The developed laser has modulation bandwidth exceeding 3 GHz. This constitutes a significant increase of the IC laser modulation bandwidth over currently existing devices. This result has demonstrated suitability of IC lasers as a mid-IR light source for multi-GHz free-space optical communications links

  20. Genetic algorithm based separation cascade optimization

    International Nuclear Information System (INIS)

    Mahendra, A.K.; Sanyal, A.; Gouthaman, G.; Bera, T.K.

    2008-01-01

    The conventional separation cascade design procedure does not give an optimum design because of squaring-off, variation of flow rates and separation factor of the element with respect to stage location. Multi-component isotope separation further complicates the design procedure. Cascade design can be stated as a constrained multi-objective optimization. Cascade's expectation from the separating element is multi-objective i.e. overall separation factor, cut, optimum feed and separative power. Decision maker may aspire for more comprehensive multi-objective goals where optimization of cascade is coupled with the exploration of separating element optimization vector space. In real life there are many issues which make it important to understand the decision maker's perception of cost-quality-speed trade-off and consistency of preferences. Genetic algorithm (GA) is one such evolutionary technique that can be used for cascade design optimization. This paper addresses various issues involved in the GA based multi-objective optimization of the separation cascade. Reference point based optimization methodology with GA based Pareto optimality concept for separation cascade was found pragmatic and promising. This method should be explored, tested, examined and further developed for binary as well as multi-component separations. (author)

  1. Quantum mechanics

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    The book is on quantum mechanics. The emphasis is on the basic concepts and the methodology. The chapters include: Breakdown of classical concepts; Quantum mechanical concepts; Basic postulates of quantum mechanics; solution of problems in quantum mechanics; Simple harmonic oscillator; and Angular Momentum

  2. Quantum matter

    International Nuclear Information System (INIS)

    Buechler, Hans Peter; Calcarco, Tommaso; Dressel, Martin

    2008-01-01

    The following topics are dealt with: Artificial atoms and molecules, tailored from solids, fractional flux quanta, molecular magnets, controlled interaction in quantum gases, the theory of quantum correlations in mott matter, cold gases, and mesoscopic systems, Bose-Einstein condensates on the chip, on the route to the quantum computer, a quantum computer in diamond. (HSI)

  3. Quantum fluctuations

    International Nuclear Information System (INIS)

    Reynaud, S.; Giacobino, S.; Zinn-Justin, J.

    1997-01-01

    This course is dedicated to present in a pedagogical manner the recent developments in peculiar fields concerned by quantum fluctuations: quantum noise in optics, light propagation through dielectric media, sub-Poissonian light generated by lasers and masers, quantum non-demolition measurements, quantum electrodynamics applied to cavities and electrical circuits involving superconducting tunnel junctions. (A.C.)

  4. Prototypes in engineering design: Definitions and strategies

    DEFF Research Database (Denmark)

    Jensen, Lasse Skovgaard; Özkil, Ali Gürcan; Mortensen, Niels Henrik

    2016-01-01

    By reviewing literature, we investigate types, purposes and definitions of prototypes. There is no overarching definition of a prototype, but we identify five categories of prototypes in litterature. We further synthesize and reference previous work to create an overview of aspects in prototyping...

  5. Prototyping in theory and in practice

    DEFF Research Database (Denmark)

    Yu, Fei; Brem, Alexander; Pasinell, Michele

    2018-01-01

    and functions of a prototype and needed to meet specific goals in order to push the process forward. Designers, on the other hand, used prototypes to investigate the design space for new possibilities, and were more open to a variety of prototyping materials and tools, especially for low-fidelity prototypes...

  6. Rapid Prototyping of Formally Modelled Distributed Systems

    OpenAIRE

    Buchs, Didier; Buffo, Mathieu; Titsworth, Frances M.

    1999-01-01

    This paper presents various kinds of prototypes, used in the prototyping of formally modelled distributed systems. It presents the notions of prototyping techniques and prototype evolution, and shows how to relate them to the software life-cycle. It is illustrated through the use of the formal modelling language for distributed systems CO-OPN/2.

  7. Towards an Operational Framework for Architectural Prototyping

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak

    2005-01-01

    We use a case study in architectural prototyping as input for presenting a first, tentative, framework describing key concepts and their relationships in architectural prototyping processes.......We use a case study in architectural prototyping as input for presenting a first, tentative, framework describing key concepts and their relationships in architectural prototyping processes....

  8. Quantum radar

    CERN Document Server

    Lanzagorta, Marco

    2011-01-01

    This book offers a concise review of quantum radar theory. Our approach is pedagogical, making emphasis on the physics behind the operation of a hypothetical quantum radar. We concentrate our discussion on the two major models proposed to date: interferometric quantum radar and quantum illumination. In addition, this book offers some new results, including an analytical study of quantum interferometry in the X-band radar region with a variety of atmospheric conditions, a derivation of a quantum radar equation, and a discussion of quantum radar jamming.This book assumes the reader is familiar w

  9. Engineering prototypes for theta-pinch devices

    International Nuclear Information System (INIS)

    Hansborough, L.D.; Hammer, C.F.; Hanks, K.W.; McDonald, T.E.; Nunnally, W.C.

    1975-01-01

    Past, present, and future engineering prototypes for theta-pinch plasma-physics devices at Los Alamos Scientific Laboratory are discussed. Engineering prototypes are designed to test and evaluate all components under system conditions expected on actual plasma-physics experimental devices. The importance of engineering prototype development increases as the size and complexity of the plasma-physics device increases. Past experiences with the Scyllac prototype and the Staged Theta-Pinch prototype are discussed and evaluated. The design of the proposed Staged Scyllac prototype and the Large Staged Scyllac implosion prototype assembly are discussed

  10. Aspects of the QCD cascade

    International Nuclear Information System (INIS)

    Olsson, Magnus.

    1993-02-01

    A model is proposed for the production of transverse jets from diffractively excited protons. We propose that transverse jets can be obtained from gluonic bremsstrahlung in a way similar to the emission in DIS. Qualitative agreement is obtained between the model and the uncorrected data published by the UA8 collaboration. Perturbative QCD in the MLLA approximation is applied to multiple jet production in e + e - -annihilation. We propose modified evolution equations for deriving the jet cross sections, defined in the 'k t ' or 'Durham' algorithm. The mean number of jets as a function of the jet resolution is studied, and analytical predictions are compared to the results of MC simulations. We also study a set of differential-difference equations for multiplicity distributions in e + e - -annihilations, supplemented with appropriate boundary conditions. These equations take into account nonsingular terms in the GLAP splitting functions as well as kinematical constraints related to recoil effects. The presence of retarded terms imply that the cascade develops more slowly and reduces the fluctuations. The solutions agree well with MC simulations and experimental data. (authors)

  11. Prototypical Rod Consolidation Demonstration Project

    International Nuclear Information System (INIS)

    1993-05-01

    The objective of Phase III of the Prototypical Rod Consolidation Demonstration Project (PRCDP) was to procure, fabricate, assemble, and test the Prototypical Rod Consolidation System as described in the NUS Phase II Final Design Report. This effort required providing the materials, components, and fabricated parts which makes up all of the system equipment. In addition, it included the assembly, installation, and setup of this equipment at the Cold Test Facility. During the Phase III effort the system was tested on a component, subsystem, and system level. Volume IV provides the Operating and Maintenance Manual for the Prototypical Rod Consolidation System that was installed at the Cold Test Facility. This document, Book 1 of Volume IV, discusses: Process overview functional descriptions; Control system descriptions; Support system descriptions; Maintenance system descriptions; and Process equipment descriptions

  12. Science with the ASTRI prototype

    International Nuclear Information System (INIS)

    Sartore, Nicola

    2013-01-01

    ASTRI (Astrofisica a Specchi con Tecnologia Replicante Italiana) is a “Flagship Project” financed by the Italian Ministry of Instruction, University and Research and led by the Italian National Institute of Astrophysics. It represents the Italian proposal for the development of the Small Size Telescope system of the Cherenkov Telescope Array, the next generation observatory for Very High Energy gamma-rays (20 GeV - 100 TeV). The ASTRI end-to-end prototype will be installed at Serra La Nave (Catania, Italy) and it will see the first light at the beginning of 2014. We describe the expected performance of the prototype on few selected test cases of the northern emisphere. The aim of the prototype is to probe the technological solutions and the nominal performance of the various telescope's subsystems

  13. Flight Telerobotic Servicer prototype simulator

    Science.gov (United States)

    Schein, Rob; Krauze, Linda; Hartley, Craig; Dickenson, Alan; Lavecchia, Tom; Working, Bob

    A prototype simulator for the Flight Telerobotic Servicer (FTS) system is described for use in the design development of the FTS, emphasizing the hand controller and user interface. The simulator utilizes a graphics workstation based on rapid prototyping tools for systems analyses of the use of the user interface and the hand controller. Kinematic modeling, manipulator-control algorithms, and communications programs are contained in the software for the simulator. The hardwired FTS panels and operator interface for use on the STS Orbiter are represented graphically, and the simulated controls function as the final FTS system configuration does. The robotic arm moves based on the user hand-controller interface, and the joint angles and other data are given on the prototype of the user interface. This graphics simulation tool provides the means for familiarizing crewmembers with the FTS system operation, displays, and controls.

  14. Prototypical Rod Consolidation Demonstration Project

    International Nuclear Information System (INIS)

    1993-05-01

    The objective of Phase III of the Prototypical Rod Consolidation Demonstration Project (PRCDP) was to procure, fabricate, assemble, and test the Prototypical Rod Consolidation System as described in the NUS Phase II Final Design Report. This effort required providing the materials, components, and fabricated parts which makes up all of the system equipment. In addition, it included the assembly, installation, and setup of this equipment at the Cold Test Facility. During the Phase III effort the system was tested on a component, subsystem, and system level. Volume IV provides the Operating and Maintenance Manual for the Prototypical Rod Consolidation System that was installed at the Cold Test Facility. This document, Book 4 of Volume IV, discusses: Off-normal operating and recovery procedures; Emergency response procedures; Troubleshooting procedures; and Preventive maintenance procedures

  15. Quantum information

    International Nuclear Information System (INIS)

    Kilin, Sergei Ya

    1999-01-01

    A new research direction known as quantum information is a multidisciplinary subject which involves quantum mechanics, optics, information theory, programming, discrete mathematics, laser physics and spectroscopy, and depends heavily on contributions from such areas as quantum computing, quantum teleportation and quantum cryptography, decoherence studies, and single-molecule and impurity spectroscopy. Some new results achieved in this rapidly growing field are discussed. (reviews of topical problems)

  16. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Kilin, Sergei Ya [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    1999-05-31

    A new research direction known as quantum information is a multidisciplinary subject which involves quantum mechanics, optics, information theory, programming, discrete mathematics, laser physics and spectroscopy, and depends heavily on contributions from such areas as quantum computing, quantum teleportation and quantum cryptography, decoherence studies, and single-molecule and impurity spectroscopy. Some new results achieved in this rapidly growing field are discussed. (reviews of topical problems)

  17. Quantum ontologies

    International Nuclear Information System (INIS)

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs

  18. Cascaded systems analysis of photon counting detectors.

    Science.gov (United States)

    Xu, J; Zbijewski, W; Gang, G; Stayman, J W; Taguchi, K; Lundqvist, M; Fredenberg, E; Carrino, J A; Siewerdsen, J H

    2014-10-01

    Photon counting detectors (PCDs) are an emerging technology with applications in spectral and low-dose radiographic and tomographic imaging. This paper develops an analytical model of PCD imaging performance, including the system gain, modulation transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). A cascaded systems analysis model describing the propagation of quanta through the imaging chain was developed. The model was validated in comparison to the physical performance of a silicon-strip PCD implemented on an experimental imaging bench. The signal response, MTF, and NPS were measured and compared to theory as a function of exposure conditions (70 kVp, 1-7 mA), detector threshold, and readout mode (i.e., the option for coincidence detection). The model sheds new light on the dependence of spatial resolution, charge sharing, and additive noise effects on threshold selection and was used to investigate the factors governing PCD performance, including the fundamental advantages and limitations of PCDs in comparison to energy-integrating detectors (EIDs) in the linear regime for which pulse pileup can be ignored. The detector exhibited highly linear mean signal response across the system operating range and agreed well with theoretical prediction, as did the system MTF and NPS. The DQE analyzed as a function of kilovolt (peak), exposure, detector threshold, and readout mode revealed important considerations for system optimization. The model also demonstrated the important implications of false counts from both additive electronic noise and charge sharing and highlighted the system design and operational parameters that most affect detector performance in the presence of such factors: for example, increasing the detector threshold from 0 to 100 (arbitrary units of pulse height threshold roughly equivalent to 0.5 and 6 keV energy threshold, respectively), increased the f50 (spatial-frequency at which the MTF falls to a value of

  19. Cascaded systems analysis of photon counting detectors

    International Nuclear Information System (INIS)

    Xu, J.; Zbijewski, W.; Gang, G.; Stayman, J. W.; Taguchi, K.; Carrino, J. A.; Lundqvist, M.; Fredenberg, E.; Siewerdsen, J. H.

    2014-01-01

    Purpose: Photon counting detectors (PCDs) are an emerging technology with applications in spectral and low-dose radiographic and tomographic imaging. This paper develops an analytical model of PCD imaging performance, including the system gain, modulation transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). Methods: A cascaded systems analysis model describing the propagation of quanta through the imaging chain was developed. The model was validated in comparison to the physical performance of a silicon-strip PCD implemented on an experimental imaging bench. The signal response, MTF, and NPS were measured and compared to theory as a function of exposure conditions (70 kVp, 1–7 mA), detector threshold, and readout mode (i.e., the option for coincidence detection). The model sheds new light on the dependence of spatial resolution, charge sharing, and additive noise effects on threshold selection and was used to investigate the factors governing PCD performance, including the fundamental advantages and limitations of PCDs in comparison to energy-integrating detectors (EIDs) in the linear regime for which pulse pileup can be ignored. Results: The detector exhibited highly linear mean signal response across the system operating range and agreed well with theoretical prediction, as did the system MTF and NPS. The DQE analyzed as a function of kilovolt (peak), exposure, detector threshold, and readout mode revealed important considerations for system optimization. The model also demonstrated the important implications of false counts from both additive electronic noise and charge sharing and highlighted the system design and operational parameters that most affect detector performance in the presence of such factors: for example, increasing the detector threshold from 0 to 100 (arbitrary units of pulse height threshold roughly equivalent to 0.5 and 6 keV energy threshold, respectively), increased the f 50 (spatial-frequency at

  20. Cascaded systems analysis of photon counting detectors

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J.; Zbijewski, W.; Gang, G.; Stayman, J. W. [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Taguchi, K.; Carrino, J. A. [Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Lundqvist, M.; Fredenberg, E. [Philips Healthcare, Solna 171 41 (Sweden); Siewerdsen, J. H., E-mail: jeff.siewerdsen@jhu.edu [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21205 (United States)

    2014-10-15

    Purpose: Photon counting detectors (PCDs) are an emerging technology with applications in spectral and low-dose radiographic and tomographic imaging. This paper develops an analytical model of PCD imaging performance, including the system gain, modulation transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). Methods: A cascaded systems analysis model describing the propagation of quanta through the imaging chain was developed. The model was validated in comparison to the physical performance of a silicon-strip PCD implemented on an experimental imaging bench. The signal response, MTF, and NPS were measured and compared to theory as a function of exposure conditions (70 kVp, 1–7 mA), detector threshold, and readout mode (i.e., the option for coincidence detection). The model sheds new light on the dependence of spatial resolution, charge sharing, and additive noise effects on threshold selection and was used to investigate the factors governing PCD performance, including the fundamental advantages and limitations of PCDs in comparison to energy-integrating detectors (EIDs) in the linear regime for which pulse pileup can be ignored. Results: The detector exhibited highly linear mean signal response across the system operating range and agreed well with theoretical prediction, as did the system MTF and NPS. The DQE analyzed as a function of kilovolt (peak), exposure, detector threshold, and readout mode revealed important considerations for system optimization. The model also demonstrated the important implications of false counts from both additive electronic noise and charge sharing and highlighted the system design and operational parameters that most affect detector performance in the presence of such factors: for example, increasing the detector threshold from 0 to 100 (arbitrary units of pulse height threshold roughly equivalent to 0.5 and 6 keV energy threshold, respectively), increased the f{sub 50} (spatial

  1. Sharing Sensor Data with SensorSA and Cascading Sensor Observation Service

    Directory of Open Access Journals (Sweden)

    Denis Havlik

    2009-07-01

    Full Text Available The SANY IP consortium (http://www.sany-ip.eu has recently developed several interesting service prototypes that extend the usability of the Open Geospatial Consortium “Sensor Web Enablement” (OGC SWE architecture. One such service prototype, developed by the Austrian Research Centers, is the “cascading SOS” (SOS-X. SOS-X is a client to the underlying OGC Sensor Observation service(s (SOS. It provides alternative access routes to users (or services interested in accessing data. In addition to a simple cascading, SOS-X can re-format, re-organize, and merge data from several sources into a single SOS offering. Thanks to the built-in “Formula 3” prototype, a kind of time series library, SOS-X will be enabled to derive new data sets on the fly executing arbitrary algebraic operations on one or more data input streams. This article will discuss the SOS-X development status (focusing at end of 2008, further development agenda in year 2009, and possibilities for using the SOS-X outside of the SANY IP.

  2. Axure RP 6 Prototyping Essentials

    CERN Document Server

    Schwartz, Ezra

    2012-01-01

    Axure RP 6 Prototyping Essentials is a detailed, practical primer on the leading rapid prototyping tool. Short on jargon and high on concepts, real-life scenarios and step-by-step guidance through hands-on examples, this book will show you how to integrate Axure into your UX workflow. This book is written for UX practitioners, business analysts, product managers, and anyone else who is involved in UX projects. The book assumes that you have no or very little familiarity with Axure. It will help you if you are evaluating the tool for an upcoming project or are required to quickly get up to spee

  3. Bursting behaviours in cascaded stimulated Brillouin scattering

    International Nuclear Information System (INIS)

    Liu Zhan-Jun; He Xian-Tu; Zheng Chun-Yang; Wang Yu-Gang

    2012-01-01

    Stimulated Brillouin scattering is studied by numerically solving the Vlasov—Maxwell system. A cascade of stimulated Brillouin scattering can occur when a linearly polarized laser pulse propagates in a plasma. It is found that a stimulated Brillouin scattering cascade can reduce the scattering and increase the transmission of light, as well as introduce a bursting behaviour in the evolution of the laser-plasma interaction. The bursting time in the reflectivity is found to be less than half the ion acoustic period. The ion temperature can affect the stimulated Brillouin scattering cascade, which can repeat several times at low ion temperatures and can be completely eliminated at high ion temperatures. For stimulated Brillouin scattering saturation, higher-harmonic generation and wave—wave interaction of the excited ion acoustic waves can restrict the amplitude of the latter. In addition, stimulated Brillouin scattering cascade can restrict the amplitude of the scattered light. (physics of gases, plasmas, and electric discharges)

  4. Defect accumulation under cascade damage conditions

    DEFF Research Database (Denmark)

    Trinkaus, H.; Singh, B.N.; Woo, C.H.

    1994-01-01

    in terms of this reaction kinetics taking into account cluster production, dissociation, migration and annihilation at extended sinks. Microstructural features which are characteristic of cascade damage and cannot be explained in terms of the conventional single defect reaction kinetics are emphasized......There is now ample evidence from both experimental and computer simulation studies that in displacement cascades not only intense recombination takes place but also efficient clustering of both self-interstitial atoms (SIAs) and vacancies. The size distributions of the two types of defects produced...... reactions kinetics associated with the specific features of cascade damage is described, with emphasis on asymmetries between SIA and vacancy type defects concerning their production, stability, mobility and interactions with other defects. Defect accumulation under cascade damage conditions is discussed...

  5. Cascade theory in isotopic separation processes

    International Nuclear Information System (INIS)

    Agostini, J.P.

    1994-06-01

    Three main areas are developed within the scope of this work: - the first one is devoted to fundamentals: separative power, value function, ideal cascade and square cascade. Applications to two main cases are carried out, namely: Study of binary isotopic mix, Study of processes with a small enrichment coefficient. - The second one is devoted to cascade coupling -high-flux coupling (more widely used and better known) as well as low-flux coupling are presented and compared to one another. - The third one is an outlook on problems linked to cascade transients. Those problem are somewhat intricate and their interest lies mainly into two areas: economics where the start-up time may have a large influence on the interests paid during the construction and start-up period, military productions where the start-up time has a direct bearing on the production schedule. (author). 50 figs. 3 annexes. 12 refs. 6 tabs

  6. τ polarization in SUSY cascade decays

    International Nuclear Information System (INIS)

    Choi, S.Y.; Hagiwara, K.; Kim, Y.G.

    2006-12-01

    τ leptons emitted in cascade decays of supersymmetric particles are polarized. The polarization may be exploited to determine spin and mixing properties of the neutralinos and stau particles involved. (orig.)

  7. MAP kinase cascades in Arabidopsis innate immunity

    DEFF Research Database (Denmark)

    Rasmussen, Magnus Wohlfahrt; Roux, Milena Edna; Petersen, Morten

    2012-01-01

    Plant mitogen-activated protein kinase (MAPK) cascades generally transduce extracellular stimuli into cellular responses. These stimuli include the perception of pathogen-associated molecular patterns (PAMPs) by host transmembrane pattern recognition receptors which trigger MAPK-dependent innate ...

  8. Cascade Error Projection: A New Learning Algorithm

    Science.gov (United States)

    Duong, T. A.; Stubberud, A. R.; Daud, T.; Thakoor, A. P.

    1995-01-01

    A new neural network architecture and a hardware implementable learning algorithm is proposed. The algorithm, called cascade error projection (CEP), handles lack of precision and circuit noise better than existing algorithms.

  9. Quantum Computer Games: Quantum Minesweeper

    Science.gov (United States)

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  10. Simulation of concentration spikes in cascades

    International Nuclear Information System (INIS)

    Wood, H.G.

    2006-01-01

    Research has been conducted to investigate the maximum possible enrichment that might be temporarily achieved in a facility that is producing enriched uranium for fuel for nuclear power reactors. The purpose is to provide information to evaluate if uranium enrichment facilities are producing 235 U enriched within declared limits appropriate for power reactors or if the facilities are actually producing more highly enriched uranium. The correlation between feed rate and separation factor in a gas centrifuge cascade shows that as flow decreases, the separation factor increases, thereby, creating small amounts of higher enriched uranium than would be found under optimum design operating conditions. The research uses a number of cascade enrichment programs to model the phenomenon and determine the maximum enrichment possible during the time transient of a gas centrifuge cascade. During cascade start-up, the flow through the centrifuges begins at lower than centrifuge design stage flow rates. Steady-state cascade models have been used to study the maximum 235 U concentrations that would be predicted in the cascade. These calculations should produce an upper bound of product concentrations expected during the transient phase of start-up. Due to the fact that there are different ways in which to start a cascade, several methods are used to determine the maximum enrichment during the time transient. Model cascades were created for gas centrifuges with several product to .feed assay separation factors. With this information, the models were defined and the equilibrium programs were used to determine the maximum enrichment level during the time transient. The calculations predict in a cascade with separation factor 1.254 designed to produce enriched uranium for the purpose of supplying reactor fuel, it would not be unreasonable to see some 235 U in the range of 12-15%. Higher assays produced during the start-up period might lead inspectors to believe the cascade is being

  11. Designing the Cascade inertial confinement fusion reactor

    International Nuclear Information System (INIS)

    Pitts, J.H.

    1987-01-01

    The primary goal in designing inertial confinement fusion (ICF) reactors is to produce electrical power as inexpensively as possible, with minimum activation and without compromising safety. This paper discusses a method for designing the Cascade rotating ceramic-granule-blanket reactor (Pitts, 1985) and its associated power plant (Pitts and Maya, 1985). Although focus is on the cascade reactor, the design method and issues presented are applicable to most other ICF reactors

  12. High energy evolution of soft gluon cascades

    International Nuclear Information System (INIS)

    Shuvaev, A.; Wallon, S.

    2006-01-01

    In this paper we derive an evolution equation for the gluon density in soft gluon cascades emitted from any colored source, in the leading logarithmic approximation of perturbative QCD. We show that this equation has the same form as the BFKL equation in the forward case. An explicit expression for the total cascade wavefunction involving an arbitrary number of soft gluons is obtained. Renormalization of the colored source wavefunction turns out to be responsible for the reggeization of the source. (orig.)

  13. High energy evolution of soft gluon cascades

    Energy Technology Data Exchange (ETDEWEB)

    Shuvaev, A. [St. Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg district (Russian Federation); Wallon, S. [Universite Paris XI, Laboratoire de Physique Theorique, Orsay Cedex (France)

    2006-04-15

    In this paper we derive an evolution equation for the gluon density in soft gluon cascades emitted from any colored source, in the leading logarithmic approximation of perturbative QCD. We show that this equation has the same form as the BFKL equation in the forward case. An explicit expression for the total cascade wavefunction involving an arbitrary number of soft gluons is obtained. Renormalization of the colored source wavefunction turns out to be responsible for the reggeization of the source. (orig.)

  14. Cascade of links in complex networks

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Yeqian; Sun, Bihui [Department of Management Science, School of Government, Beijing Normal University, 100875 Beijing (China); Zeng, An, E-mail: anzeng@bnu.edu.cn [School of Systems Science, Beijing Normal University, 100875 Beijing (China)

    2017-01-30

    Cascading failure is an important process which has been widely used to model catastrophic events such as blackouts and financial crisis in real systems. However, so far most of the studies in the literature focus on the cascading process on nodes, leaving the possibility of link cascade overlooked. In many real cases, the catastrophic events are actually formed by the successive disappearance of links. Examples exist in the financial systems where the firms and banks (i.e. nodes) still exist but many financial trades (i.e. links) are gone during the crisis, and the air transportation systems where the airports (i.e. nodes) are still functional but many airlines (i.e. links) stop operating during bad weather. In this letter, we develop a link cascade model in complex networks. With this model, we find that both artificial and real networks tend to collapse even if a few links are initially attacked. However, the link cascading process can be effectively terminated by setting a few strong nodes in the network which do not respond to any link reduction. Finally, a simulated annealing algorithm is used to optimize the location of these strong nodes, which significantly improves the robustness of the networks against the link cascade. - Highlights: • We propose a link cascade model in complex networks. • Both artificial and real networks tend to collapse even if a few links are initially attacked. • The link cascading process can be effectively terminated by setting a few strong nodes. • A simulated annealing algorithm is used to optimize the location of these strong nodes.

  15. Cascade of links in complex networks

    International Nuclear Information System (INIS)

    Feng, Yeqian; Sun, Bihui; Zeng, An

    2017-01-01

    Cascading failure is an important process which has been widely used to model catastrophic events such as blackouts and financial crisis in real systems. However, so far most of the studies in the literature focus on the cascading process on nodes, leaving the possibility of link cascade overlooked. In many real cases, the catastrophic events are actually formed by the successive disappearance of links. Examples exist in the financial systems where the firms and banks (i.e. nodes) still exist but many financial trades (i.e. links) are gone during the crisis, and the air transportation systems where the airports (i.e. nodes) are still functional but many airlines (i.e. links) stop operating during bad weather. In this letter, we develop a link cascade model in complex networks. With this model, we find that both artificial and real networks tend to collapse even if a few links are initially attacked. However, the link cascading process can be effectively terminated by setting a few strong nodes in the network which do not respond to any link reduction. Finally, a simulated annealing algorithm is used to optimize the location of these strong nodes, which significantly improves the robustness of the networks against the link cascade. - Highlights: • We propose a link cascade model in complex networks. • Both artificial and real networks tend to collapse even if a few links are initially attacked. • The link cascading process can be effectively terminated by setting a few strong nodes. • A simulated annealing algorithm is used to optimize the location of these strong nodes.

  16. Defect production in simulated cascades: Cascade quenching and short-term annealing

    International Nuclear Information System (INIS)

    Heinisch, H.L.

    1983-01-01

    Defect production in displacement cascades in copper has been modeled using the MARLOWE code to generate cascades and the stochastic annealing code ALSOME to simulate cascade quenching and short-term annealing of isolated cascades. Quenching is accomplished by using exaggerated values for defect mobilities and for critical reaction distances in ALSOME for a very short time. The quenched cascades are then short-term annealed with normal parameter values. The quenching parameter values were empirically determined by comparison with results of resistivity measurements. Throughout the collisional, quenching and short-term annealing phases of cascade development, the high energy cascades continue to behave as a collection of independent lower energy lobes. For recoils above about 30 keV the total number of defects and the numbers of free defects scale with the damage energy. As the energy decreases from 30 keV, defect production varies with the changing nature of the cascade configuration, resulting in more defects per unit damage energy. The simulated annealing of a low fluence of interacting cascades revealed an interstitial shielding effect on depleted zones during Stage I recovery. (orig.)

  17. Formalism of continual integrals for cascade processes with particle fusion

    International Nuclear Information System (INIS)

    Gedalin, Eh.V.

    1987-01-01

    Formalism of continuous integrals for description of cascade processes, in which besides cascade particle reproduction, their synthesis and coalescence take place, is used. Account of cascade particle coalescence leads to the fact that the development of some cascade branches cannot be independent and main equations of the cascade process become functional instead of integral. The method of continuous intagrals permits to construct in the closed form producing functionals for the cascade process and to obtain the rules of their calculation using diagrams. Analytical expressions in the form of continuous integrals for producing functionals describing cascade development are obtained

  18. Compact representations for the design of quantum logic

    CERN Document Server

    Niemann, Philipp

    2017-01-01

    This book discusses modern approaches and challenges of computer-aided design (CAD) of quantum circuits with a view to providing compact representations of quantum functionality. Focusing on the issue of quantum functionality, it presents Quantum Multiple-Valued Decision Diagrams (QMDDs – a means of compactly and efficiently representing and manipulating quantum logic. For future quantum computers, going well beyond the size of present-day prototypes, the manual design of quantum circuits that realize a given (quantum) functionality on these devices is no longer an option. In order to keep up with the technological advances, methods need to be provided which, similar to the design and synthesis of conventional circuits, automatically generate a circuit description of the desired functionality. To this end, an efficient representation of the desired quantum functionality is of the essence. While straightforward representations are restricted due to their (exponentially) large matrix descriptions and other de...

  19. NMS Prototype development final report

    International Nuclear Information System (INIS)

    Lepetich, J.E.

    1993-01-01

    Program for development of NMS prototype for LAMPF consisted of 5 tasks: crystal procurement specification, inspection/evaluation of CsI crystals, design/fabrication of crystal housing, design/fabrication of PMT shields, and packaging of crystals in the housing

  20. EUSO-TA prototype telescope

    Energy Technology Data Exchange (ETDEWEB)

    Bisconti, Francesca, E-mail: francesca.bisconti@kit.edu

    2016-07-11

    EUSO-TA is one of the prototypes developed for the JEM-EUSO project, a space-based large field-of-view telescope to observe the fluorescence light emitted by cosmic ray air showers in the atmosphere. EUSO-TA is a ground-based prototype located at the Telescope Array (TA) site in Utah, USA, where an Electron Light Source and a Central Laser Facility are installed. The purpose of the EUSO-TA project is to calibrate the prototype with the TA fluorescence detector in presence of well-known light sources and cosmic ray air showers. In 2015, the detector started the first measurements and tests using the mentioned light sources have been performed successfully. A first cosmic ray candidate has been observed, as well as stars of different magnitude and color index. Since Silicon Photo-Multipliers (SiPMs) are very promising for fluorescence telescopes of next generation, they are under consideration for the realization of a new prototype of EUSO Photo Detector Module (PDM). The response of this sensor type is under investigation through simulations and laboratory experimentation.

  1. The OPAL vertex detector prototype

    International Nuclear Information System (INIS)

    Roney, J.M.; Armitage, J.C.; Carnegie, R.K.; Giles, G.L.; Hemingway, R.J.; McPherson, A.C.; Pinfold, J.L.; Waterhouse, J.; Godfrey, L.; Hargrove, C.K.

    1989-01-01

    The prototype test results of a high resolution charged particle tracking detector are reported. The detector is designed to measure vertex topologies of particles produced in the e + e - collisions of the OPAL experiment at LEP. The OPAL vertex detector is a 1 m long, 0.46 m diameter cylindrical drift chamber consisting of an axial and stereo layer each of which is divided into 36 jet cells. A prototype chamber containing four axial and two stereo cells was studied using a pion test beam at CERN. The studies examined the prototype under a variety of operating conditions. An r-Φ resolution of 60 μm was obtained when the chamber was operated with argon (50%)-ethane (50%) at 3.75 bar, and when CO 2 (80%)-isobutane (20%) at 2.5 bar was used a 25 μm resolution was achieved. A z measurement using end-to-end time difference has a resolution of 3.5 cm. The details of these prototype studies are discussed in this paper. (orig.)

  2. Rapid Prototyping Enters Mainstream Manufacturing.

    Science.gov (United States)

    Winek, Gary

    1996-01-01

    Explains rapid prototyping, a process that uses computer-assisted design files to create a three-dimensional object automatically, speeding the industrial design process. Five commercially available systems and two emerging types--the 3-D printing process and repetitive masking and depositing--are described. (SK)

  3. Encapsulation of polymer photovoltaic prototypes

    DEFF Research Database (Denmark)

    Krebs, Frederik C

    2006-01-01

    A simple and efficient method for the encapsulation of polymer and organic photovoltaic prototypes is presented. The method employs device preparation on glass substrates with subsequent sealing using glass fiber reinforced thermosetting epoxy (prepreg) against a back plate. The method allows...

  4. EUSO-TA prototype telescope

    Science.gov (United States)

    Bisconti, Francesca; JEM-EUSO Collaboration

    2016-07-01

    EUSO-TA is one of the prototypes developed for the JEM-EUSO project, a space-based large field-of-view telescope to observe the fluorescence light emitted by cosmic ray air showers in the atmosphere. EUSO-TA is a ground-based prototype located at the Telescope Array (TA) site in Utah, USA, where an Electron Light Source and a Central Laser Facility are installed. The purpose of the EUSO-TA project is to calibrate the prototype with the TA fluorescence detector in presence of well-known light sources and cosmic ray air showers. In 2015, the detector started the first measurements and tests using the mentioned light sources have been performed successfully. A first cosmic ray candidate has been observed, as well as stars of different magnitude and color index. Since Silicon Photo-Multipliers (SiPMs) are very promising for fluorescence telescopes of next generation, they are under consideration for the realization of a new prototype of EUSO Photo Detector Module (PDM). The response of this sensor type is under investigation through simulations and laboratory experimentation.

  5. Facial Prototype Formation in Children.

    Science.gov (United States)

    Inn, Donald; And Others

    This study examined memory representation as it is exhibited in young children's formation of facial prototypes. In the first part of the study, researchers constructed images of faces using an Identikit that provided the features of hair, eyes, mouth, nose, and chin. Images were varied systematically. A series of these images, called exemplar…

  6. The potential of the quantum computer

    CERN Multimedia

    2006-01-01

    The Physics Section of the University of Geneva is continuing its series of lectures, open to the general public, on the most recent developments in the field of physics. The next lecture, given by Professor Michel Devoret of Yale University in the United States, will be on the potential of the quantum computer. The quantum computer is, as yet, a hypothetical machine which would operate on the basic principles of quantum mechanics. Compared to standard computers, it represents a significant gain in computing power for certain complex calculations. Quantum operations can simultaneously explore a very large number of possibilities. The correction of quantum errors, which until recently had been deemed impossible, has now become a well-established technique. Several prototypes for, as yet, very simple quantum processors have been developed. The lecture will begin with a demonstration in the auditorium of the detection of cosmic rays and, in collaboration with Professor E. Ellberger of the Conservatoire de M...

  7. Manipulating cold atoms for quantum information processing

    International Nuclear Information System (INIS)

    Knight, P.

    2005-01-01

    Full text: I will describe how cold atoms can be manipulated to realize arrays of addressable qbits as prototype quantum registers, focussing on how atom chips can be used in combination with cavity qed techniques to form such an array. I will discuss how the array can be generated and steered using optical lattices and the Mott transition, and describe the sources of noise and how these place limits on the use of such chips in quantum information processing. (author)

  8. Monte Carlo simulation of a prototype photodetector used in radiotherapy

    CERN Document Server

    Kausch, C; Albers, D; Schmidt, R; Schreiber, B

    2000-01-01

    The imaging performance of prototype electronic portal imaging devices (EPID) has been investigated. Monte Carlo simulations have been applied to calculate the modulation transfer function (MTF( f )), the noise power spectrum (NPS( f )) and the detective quantum efficiency (DQE( f )) for different new type of EPIDs, which consist of a detector combination of metal or polyethylene (PE), a phosphor layer of Gd sub 2 O sub 2 S and a flat array of photodiodes. The simulated results agree well with measurements. Based on simulated results, possible optimization of these devices is discussed.

  9. Prototype diagnosis of psychiatric syndromes

    Science.gov (United States)

    WESTEN, DREW

    2012-01-01

    The method of diagnosing patients used since the early 1980s in psychiatry, which involves evaluating each of several hundred symptoms for their presence or absence and then applying idiosyncratic rules for combining them for each of several hundred disorders, has led to great advances in research over the last 30 years. However, its problems have become increasingly apparent, particularly for clinical practice. An alternative approach, designed to maximize clinical utility, is prototype matching. Instead of counting symptoms of a disorder and determining whether they cross an arbitrary cutoff, the task of the diagnostician is to gauge the extent to which a patient’s clinical presentation matches a paragraph-length description of the disorder using a simple 5-point scale, from 1 (“little or no match”) to 5 (“very good match”). The result is both a dimensional diagnosis that captures the extent to which the patient “has” the disorder and a categorical diagnosis, with ratings of 4 and 5 corresponding to presence of the disorder and a rating of 3 indicating “subthreshold” or “clinically significant features”. The disorders and criteria woven into the prototypes can be identified empirically, so that the prototypes are both scientifically grounded and clinically useful. Prototype diagnosis has a number of advantages: it better captures the way humans naturally classify novel and complex stimuli; is clinically helpful, reliable, and easy to use in everyday practice; facilitates both dimensional and categorical diagnosis and dramatically reduces the number of categories required for classification; allows for clinically richer, empirically derived, and culturally relevant classification; reduces the gap between research criteria and clinical knowledge, by allowing clinicians in training to learn a small set of standardized prototypes and to develop richer mental representations of the disorders over time through clinical experience; and can help

  10. Prototype Effect and the Persuasiveness of Generalizations.

    Science.gov (United States)

    Dahlman, Christian; Sarwar, Farhan; Bååth, Rasmus; Wahlberg, Lena; Sikström, Sverker

    An argument that makes use of a generalization activates the prototype for the category used in the generalization. We conducted two experiments that investigated how the activation of the prototype affects the persuasiveness of the argument. The results of the experiments suggest that the features of the prototype overshadow and partly overwrite the actual facts of the case. The case is, to some extent, judged as if it had the features of the prototype instead of the features it actually has. This prototype effect increases the persuasiveness of the argument in situations where the audience finds the judgment more warranted for the prototype than for the actual case (positive prototype effect), but decreases persuasiveness in situations where the audience finds the judgment less warranted for the prototype than for the actual case (negative prototype effect).

  11. Supporting Active User Involvment in Prototyping

    DEFF Research Database (Denmark)

    Grønbæk, Kaj

    1990-01-01

    The term prototyping has in recent years become a buzzword in both research and practice of system design due to a number of claimed advantages of prototyping techniques over traditional specification techniques. In particular it is often stated that prototyping facilitates the users' involvement...... in the development process. But prototyping does not automatically imply active user involvement! Thus a cooperative prototyping approach aiming at involving users actively and creatively in system design is proposed in this paper. The key point of the approach is to involve users in activities that closely couple...... development of prototypes to early evaluation of prototypes in envisioned use situations. Having users involved in such activities creates new requirements for tool support. Tools that support direct manipulation of prototypes and simulation of behaviour have shown promise for cooperative prototyping...

  12. Prototyping of user interfaces for mobile applications

    CERN Document Server

    Bähr, Benjamin

    2017-01-01

    This book investigates processes for the prototyping of user interfaces for mobile apps, and describes the development of new concepts and tools that can improve the prototype driven app development in the early stages. It presents the development and evaluation of a new requirements catalogue for prototyping mobile app tools that identifies the most important criteria such tools should meet at different prototype-development stages. This catalogue is not just a good point of orientation for designing new prototyping approaches, but also provides a set of metrics for a comparing the performance of alternative prototyping tools. In addition, the book discusses the development of Blended Prototyping, a new approach for prototyping user interfaces for mobile applications in the early and middle development stages, and presents the results of an evaluation of its performance, showing that it provides a tool for teamwork-oriented, creative prototyping of mobile apps in the early design stages.

  13. First examination of CASCADE-X-ray-detector and measurement of neutron-mirrorneutron-oscillation; Erste Untersuchungen zum CASCADE-Roentgendetektor und Messung zur Neutron-Spiegelneutron-Oszillation

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, B.

    2007-02-07

    The detection of X-radiation is of utmost importance for both fundamental physics and medical diagnostics. This work investigates whether or not the CASCADE detector working principle, first developed for the detection of neutrons, can be adapted for the detection of X-rays. This modular detector concept combines the use of a solid neutron or X-ray converter with the advantages of a counting gas detector. Thus, it gives the possibility to optimize efficiency, dynamics and spatial resolution independently. Firstly, it is necessary to find a suitable converter material that allows for the best possible detector efficiency. In order to do so, a mathematical model of the complete detector system was developed that yields the total efficiency for any given material. Respecting technical constraints, gold and gadolinium showed to be favorable choices. Based on these theoretical considerations a prototype of a CASCADE X-ray detector was built, and measurements for the determination of this detector's efficiency were conducted. In the second part of this work a CASCADE neutron detector was used to conduct the first measurement the neutron-mirrorneutron oscillation time. Mirrormatter was proposed in 1956 by Lee and Yang to allow for symmetry in the description of the universe despite the existence of parity violation. By using neutrons it was possible to determine a lower limit for the oscillation time in this work. (orig.)

  14. Quantum optics

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, P D [University of Queensland, St. Lucia, QLD (Australia).Physics Department

    1999-07-01

    Full text: Quantum optics in Australia has been an active research field for some years. I shall focus on recent developments in quantum and atom optics. Generally, the field as a whole is becoming more and more diverse, as technological developments drive experiments into new areas, and theorists either attempt to explain the new features, or else develop models for even more exotic ideas. The recent developments include quantum solitons, quantum computing, Bose-Einstein condensation, atom lasers, quantum cryptography, and novel tests of quantum mechanics. The talk will briefly cover current progress and outstanding problems in each of these areas. Copyright (1999) Australian Optical Society.

  15. Quantum entanglement and quantum teleportation

    International Nuclear Information System (INIS)

    Shih, Y.H.

    2001-01-01

    One of the most surprising consequences of quantum mechanics is the entanglement of two or more distance particles. The ''ghost'' interference and the ''ghost'' image experiments demonstrated the astonishing nonlocal behavior of an entangled photon pair. Even though we still have questions in regard to fundamental issues of the entangled quantum systems, quantum entanglement has started to play important roles in quantum information and quantum computation. Quantum teleportation is one of the hot topics. We have demonstrated a quantum teleportation experiment recently. The experimental results proved the working principle of irreversibly teleporting an unknown arbitrary quantum state from one system to another distant system by disassembling into and then later reconstructing from purely classical information and nonclassical EPR correlations. The distinct feature of this experiment is that the complete set of Bell states can be distinguished in the Bell state measurement. Teleportation of a quantum state can thus occur with certainty in principle. (orig.)

  16. Design in action: From prototyping by demonstration to cooperative prototyping

    DEFF Research Database (Denmark)

    Bødker, Susanne; Grønbæk, Kaj

    1991-01-01

    ... the development of any computer-based system will have to proceed in a cycle from design to experience and back again. It is impossible to anticipate all of the relevant breakdown and their domains. They emerge gradually in practice. Winograd and Flores, 1986. p.171 Some time ago we worked wi...... with a group of dental assistants, designing a prototype case record system to explore the possibility of using computer support in public dental clinics. ...

  17. Defect production in simulated cascades: cascade quenching and short-term annealing

    International Nuclear Information System (INIS)

    Heinisch, H.L.

    1982-01-01

    Defect production in high energy displacement cascades has been modeled using the computer code MARLOWE to generate the cascades and the stochastic computer code ALSOME to simulate the cascade quenching and short-term annealing of isolated cascades. The quenching is accomplished by using ALSOME with exaggerated values for defect mobilities and critical reaction distanes for recombination and clustering, which are in effect until the number of defect pairs is equal to the value determined from resistivity experiments at 4K. Then normal mobilities and reaction distances are used during short-term annealing to a point representative of Stage III recovery. Effects of cascade interactions at low fluences are also being investigated. The quenching parameter values were empirically determined for 30 keV cascades. The results agree well with experimental information throughout the range from 1 keV to 100 keV. Even after quenching and short-term annealing the high energy cascades behave as a collection of lower energy subcascades and lobes. Cascades generated in a crystal having thermal displacements were found to be in better agreement with experiments after quenching and annealing than those generated in a non-thermal crystal

  18. Quantum robots and quantum computers

    Energy Technology Data Exchange (ETDEWEB)

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  19. Quantum computers and quantum computations

    International Nuclear Information System (INIS)

    Valiev, Kamil' A

    2005-01-01

    This review outlines the principles of operation of quantum computers and their elements. The theory of ideal computers that do not interact with the environment and are immune to quantum decohering processes is presented. Decohering processes in quantum computers are investigated. The review considers methods for correcting quantum computing errors arising from the decoherence of the state of the quantum computer, as well as possible methods for the suppression of the decohering processes. A brief enumeration of proposed quantum computer realizations concludes the review. (reviews of topical problems)

  20. Quantum mystery

    CERN Document Server

    Chanda, Rajat

    1997-01-01

    The book discusses the laws of quantum mechanics, several amazing quantum phenomena and some recent progress in understanding the connection between the quantum and the classical worlds. We show how paradoxes arise and how to resolve them. The significance of Bell's theorem and the remarkable experimental results on particle correlations are described in some detail. Finally, the current status of our understanding of quantum theory is summerised.