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Статті в журналах з теми "Coherent drive":
1
Miao, Kevin C., Alexandre Bourassa, Christopher P. Anderson, Samuel J. Whiteley, Alexander L. Crook, Sam L. Bayliss, Gary Wolfowicz, et al. "Electrically driven optical interferometry with spins in silicon carbide." Science Advances 5, no. 11 (November 2019): eaay0527. http://dx.doi.org/10.1126/sciadv.aay0527.
Анотація:
Interfacing solid-state defect electron spins to other quantum systems is an ongoing challenge. The ground-state spin’s weak coupling to its environment not only bestows excellent coherence properties but also limits desired drive fields. The excited-state orbitals of these electrons, however, can exhibit stronger coupling to phononic and electric fields. Here, we demonstrate electrically driven coherent quantum interference in the optical transition of single, basally oriented divacancies in commercially available 4H silicon carbide. By applying microwave frequency electric fields, we coherently drive the divacancy’s excited-state orbitals and induce Landau-Zener-Stückelberg interference fringes in the resonant optical absorption spectrum. In addition, we find remarkably coherent optical and spin subsystems enabled by the basal divacancy’s symmetry. These properties establish divacancies as strong candidates for quantum communication and hybrid system applications, where simultaneous control over optical and spin degrees of freedom is paramount.
2
Kobayashi, Yuki, and Stephen R. Leone. "Characterizing coherences in chemical dynamics with attosecond time-resolved x-ray absorption spectroscopy." Journal of Chemical Physics 157, no. 18 (November 14, 2022): 180901. http://dx.doi.org/10.1063/5.0119942.
Анотація:
Coherence can drive wave-like motion of electrons and nuclei in photoexcited systems, which can yield fast and efficient ways to exert materials’ functionalities beyond the thermodynamic limit. The search for coherent phenomena has been a central topic in chemical physics although their direct characterization is often elusive. Here, we highlight recent advances in time-resolved x-ray absorption spectroscopy (tr-XAS) to investigate coherent phenomena, especially those that utilize the eminent light source of isolated attosecond pulses. The unparalleled time and state sensitivities of tr-XAS in tandem with the unique element specificity render the method suitable to study valence electronic dynamics in a wide variety of materials. The latest studies have demonstrated the capabilities of tr-XAS to characterize coupled electronic–structural coherence in small molecules and coherent light–matter interactions of core-excited excitons in solids. We address current opportunities and challenges in the exploration of coherent phenomena, with potential applications for energy- and bio-related systems, potential crossings, strongly driven solids, and quantum materials. With the ongoing developments in both theory and light sources, tr-XAS holds great promise for revealing the role of coherences in chemical dynamics.
3
Melrose, Don. "Maser Emission in Astrophysical Plasmas: 2003 Robert Ellery Lecture." Publications of the Astronomical Society of Australia 22, no. 2 (2005): 144–52. http://dx.doi.org/10.1071/as04061.
Анотація:
AbstractThere are three distinct types of ‘coherent emission’ in astrophysical plasmas: plasma emission (e.g. in solar radio bursts), electron cyclotron maser emission (e.g. in Jupiter's radio bursts), and pulsar radio emission. The development and current status of our understanding of coherent emission is reviewed, concentrating on plasma emission and electron cyclotron maser emission for which there is direct information on the distributions of electrons that produce the radiation. A generic model for a coherent emission process involves a maser generating radiation in a natural mode of the ambient plasma, and operating near marginal stability. A specific coherent emission mechanism involves the form of free energy to drive the maser, a pump that provides the free energy, and the plasma instability that leads to wave growth. The nature of coherence and its measurement through higher order intensity correlations are discussed.
4
Dann, Roie, and Ronnie Kosloff. "Quantum thermo-dynamical construction for driven open quantum systems." Quantum 5 (November 25, 2021): 590. http://dx.doi.org/10.22331/q-2021-11-25-590.
Анотація:
Quantum dynamics of driven open systems should be compatible with both quantum mechanic and thermodynamic principles. By formulating the thermodynamic principles in terms of a set of postulates we obtain a thermodynamically consistent master equation. Following an axiomatic approach, we base the analysis on an autonomous description, incorporating the drive as a large transient control quantum system. In the appropriate physical limit, we derive the semi-classical description, where the control is incorporated as a time-dependent term in the system Hamiltonian. The transition to the semi-classical description reflects the conservation of global coherence and highlights the crucial role of coherence in the initial control state. We demonstrate the theory by analyzing a qubit controlled by a single bosonic mode in a coherent state.
5
Yang, Kai, William Paul, Soo-Hyon Phark, Philip Willke, Yujeong Bae, Taeyoung Choi, Taner Esat, Arzhang Ardavan, Andreas J. Heinrich, and Christopher P. Lutz. "Coherent spin manipulation of individual atoms on a surface." Science 366, no. 6464 (October 24, 2019): 509–12. http://dx.doi.org/10.1126/science.aay6779.
Анотація:
Achieving time-domain control of quantum states with atomic-scale spatial resolution in nanostructures is a long-term goal in quantum nanoscience and spintronics. Here, we demonstrate coherent spin rotations of individual atoms on a surface at the nanosecond time scale, using an all-electric scheme in a scanning tunneling microscope (STM). By modulating the atomically confined magnetic interaction between the STM tip and surface atoms, we drive quantum Rabi oscillations between spin-up and spin-down states in as little as ~20 nanoseconds. Ramsey fringes and spin echo signals allow us to understand and improve quantum coherence. We further demonstrate coherent operations on engineered atomic dimers. The coherent control of spins arranged with atomic precision provides a solid-state platform for quantum-state engineering and simulation of many-body systems.
6
Alam, Jahrul M. "Wavelet Transforms and Machine Learning Methods for the Study of Turbulence." Fluids 8, no. 8 (August 3, 2023): 224. http://dx.doi.org/10.3390/fluids8080224.
Анотація:
This article investigates the applications of wavelet transforms and machine learning methods in studying turbulent flows. The wavelet-based hierarchical eddy-capturing framework is built upon first principle physical models. Specifically, the coherent vortex simulation method is based on the Taylor hypothesis, which suggests that the energy cascade occurs through vortex stretching. In contrast, the adaptive wavelet collocation method relies on the Richardson hypothesis, where the self-amplification of the strain field and a hierarchical breakdown of large eddies drive the energy cascade. Wavelet transforms are computational learning architectures that propagate the input data across a sequence of linear operators to learn the underlying nonlinearity and coherent structure. Machine learning offers a wealth of data-driven algorithms that can heavily use statistical concepts to extract valuable insights into turbulent flows. Supervised machine learning needs “perfect” turbulent flow data to train data-driven turbulence models. The current advancement of artificial intelligence in turbulence modeling primarily focuses on accelerating turbulent flow simulations by learning the underlying coherence over a low-dimensional manifold. Physics-informed neural networks offer a fertile ground for augmenting first principle physics to automate specific learning tasks, e.g., via wavelet transforms. Besides machine learning, there is room for developing a common computational framework to provide a rich cross-fertilization between learning the data coherence and the first principles of multiscale physics.
7
Ampadu Boateng, Derrick, Gennady L. Gutsev, Puru Jena, and Katharine Moore Tibbetts. "Ultrafast coherent vibrational dynamics in dimethyl methylphosphonate radical cation." Physical Chemistry Chemical Physics 20, no. 7 (2018): 4636–40. http://dx.doi.org/10.1039/c7cp07261a.
8
Shumin Zou, Shumin Zou, Yiguang Wang Yiguang Wang, Yufeng Shao Yufeng Shao, Junwen Zhang Junwen Zhang, Jianjun Yu Jianjun Yu, and Nan Chi Nan Chi. "Generation of coherent optical multi-carriers using concatenated, dual-drive Mach-Zehnder and phase modulators." Chinese Optics Letters 10, no. 7 (2012): 070605–70609. http://dx.doi.org/10.3788/col201210.070605.
9
Fast, Alexander, and Eric Olaf Potma. "Coherent Raman scattering with plasmonic antennas." Nanophotonics 8, no. 6 (May 21, 2019): 991–1021. http://dx.doi.org/10.1515/nanoph-2019-0097.
Анотація:
AbstractCoherent Raman scattering (CRS) techniques are recognized for their ability to induce and detect vibrational coherences in molecular samples. The generation of coherent light fields in CRS produces much stronger signals than what is common in incoherent Raman spectroscopy, while also enabling direct views of evolving molecular vibrations. Despite the attractive attributes of CRS spectroscopy, the technique’s sensitivity is insufficient for performing measurements on single molecules, thus precluding the ability to coherently drive, manipulate and observe individual vibrational quantum oscillators with light. The single-molecule sensitivity that has been achieved in surface-enhanced Raman scattering (SERS) with the aid of plasmonic antennas suggests that a similar approach may be used to push CRS techniques to the single-molecule detection limit. Compared with SERS, however, experimental successes in surface-enhanced coherent Raman scattering (SE-CRS) are few, and a theoretical understanding of surface-enhancement in CRS is still incomplete. In this review, we discuss some of the principles and challenges in SE-CRS and summarize the latest advances in the quest of performing routine CRS experiments on single molecules.
10
Farahat, Omar M. "A DEVOTIONAL THEORY OF LAW: EPISTEMOLOGY AND MORAL PURPOSE IN EARLY ISLAMIC JURISPRUDENCE." Journal of Law and Religion 31, no. 1 (March 2016): 42–69. http://dx.doi.org/10.1017/jlr.2016.2.
Анотація:
AbstractThe question of the sources of legal normativity continues to haunt legal theorists to this day. While it is largely uncontroversial that modern legal systems claim to produce normative propositions, whether or not there are independent reasons to obey the law remains a contested issue. Those views, as varied as they may be, appear to largely agree that the law is a social phenomenon of definite ontological presence. In this article, I argue, through an analysis of the theories of three prominent ninth- to eleventh-century Muslim jurists, that early Muslim theories of lawmaking did not incorporate any ontologically coherent concept of law. Rather, lawmaking was understood as the case-by-case formulation of legal opinions by individual jurists who were presumed to be driven by the same moral drive, and therefore occupy the same moral order, as all subjects of law. In spite of this ad hoc epistemological view, Islamic jurisprudence conceived of legal pronouncements as fully normative. The normativity of those unstructured ad hoc individual pronouncements, I maintain, is the result of the centrality of moral purpose to early Muslim theories of law. It was the presumption of a common moral drive that gave the legal system structural coherence and allowed the advancement of those pronouncements as normative claims. Whereas recent historical and anthropological work shows that moral motivation was central to the manner in which sharīʿa operated as a system of social regulation, this article argues, along the same lines, that the pietistic drive was both conceptually and structurally indispensable for the normative coherence of early Islamic jurisprudence.
Дисертації з теми "Coherent drive":
1
Slosser, John Jason. "Dynamics of a coherently driven micromaser." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185283.
Анотація:
This dissertation considers both a lossless and a dissipative micromaser in which a monoenergetic beam of two-level atoms in a coherent superposition of their upper and lower states is injected inside a single mode, high-Q cavity. In the lossless case, we find that under appropriate conditions a field initially in a mixed state will evolve to previously unknown pure states, which we call the tangent and cotangent states. In various limits, these states exhibit interesting properties such as sub-Poissonian photon statistics and squeezing, and most importantly they acquire the characteristics of "macroscopic" quantum superpositions. When dissipation of the cavity mode is incorporated into the model, we find that although the field no longer evolves to a pure state, the mixed steady-state field may still retain the properties of a macroscopic superposition under experimentally realizable damping rates. We then evaluate the experimental conditions necessary for the preparation and detection of such macroscopic superpositions.
2
Goldobin, Denis S. "Coherence and synchronization of noisy-driven oscillators." Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2007/1504/.
Анотація:
In the present dissertation paper we study problems related to synchronization phenomena in the presence of noise which unavoidably appears in real systems. One part of the work is aimed at investigation of utilizing delayed feedback to control properties of diverse chaotic dynamic and stochastic systems, with emphasis on the ones determining predisposition to synchronization. Other part deals with a constructive role of noise, i.e. its ability to synchronize identical self-sustained oscillators.
First, we demonstrate that the coherence of a noisy or chaotic self-sustained oscillator can be efficiently controlled by the delayed feedback. We develop the analytical theory of this effect, considering noisy systems in the Gaussian approximation. Possible applications of the effect for the synchronization control are also discussed.
Second, we consider synchrony of limit cycle systems (in other words, self-sustained oscillators) driven by identical noise. For weak noise and smooth systems we proof the purely synchronizing effect of noise. For slightly different oscillators and/or slightly nonidentical driving, synchrony becomes imperfect, and this subject is also studied. Then, with numerics we show moderate noise to be able to lead to desynchronization of some systems under certain circumstances. For neurons the last effect means “antireliability” (the “reliability” property of neurons is treated to be important from the viewpoint of information transmission functions), and we extend our investigation to neural oscillators which are not always limit cycle ones.
Third, we develop a weakly nonlinear theory of the Kuramoto transition (a transition to collective synchrony) in an ensemble of globally coupled oscillators in presence of additional time-delayed coupling terms. We show that a linear delayed feedback not only controls the transition point, but effectively changes the nonlinear terms near the transition. A purely nonlinear delayed coupling does not affect the transition point, but can reduce or enhance the amplitude of collective oscillations.In dieser Dissertation werden Synchronisationsphänomene im Vorhandensein von Rauschen studiert. Ein Ziel dieser Arbeit besteht in der Untersuchung der Anwendbarkeit verzögerter Rückkopplung zur Kontrolle von bestimmten Eigenschaften chaotischer oder stochastischer Systeme. Der andere Teil beschäftigt sich mit den konstruktiven Eigenschaften von Rauschen. Insbesondere wird die Möglichkeit, identische selbsterregte Oszillatoren zu synchronisieren untersucht. Als erstes wird gezeigt, dass Kohärenz verrauschter oder chaotischer Oszillatoren durch verzögertes Rückkoppeln kontrolliert werden kann. Es wird eine analytische Beschreibung dieses Phänomens in verrauschten Systemen entwickelt. Außerdem werden mögliche Anwendungen im Zusammenhang mit Synchronisationskontrolle vorgestellt und diskutiert. Als zweites werden Oszillatoren unter dem Einfluss von identischem Rauschen betrachtet. Für schwaches Rauschen und genügend glatte Systeme wird bewiesen, das Rauschen zu Synchronisation führt. Für leicht unterschiedliche Oszillatoren und leicht unterschiedliches Rauschen wird die Synchronisation unvollständig. Dieser Effekt wird auch untersucht. Dann wird mit Hilfe von Numerik gezeigt, dass moderates Rauschen zur Desynchronisierung von bestimmten Systemen führen kann. Dieser Effekt wird auch in neuronalen Oszillatoren untersucht, welche nicht unbedingt Grenzzyklen besitzen müssen. Im dritten Teil wird eine schwache nichtlineare Theorie des Kuramoto-Übergangs, dem Übergang zur kollektiven Synchronisation, in einem Ensemble von global gekoppelten Oszillatoren mit zusätzlichen zeitverzögerten Kopplungstermen entwickelt. Es wird gezeigt, dass lineare Rückkopplung nicht nur den Übergangspunkt bestimmt, sondern auch die nichtlinearen Terme in der Nähe des Übergangs entscheidend verändert. Eine rein nichtlineare Rückkopplung verändert den Übergang nicht, kann aber die Amplitude der kollektiven Oszillationen vergrößern oder verringern.
3
Thompson, William Frederick. "Stochastic phase dynamics of noise driven synchronization of uncoupled conditional coherent oscillators." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/28013.
Анотація:
We consider a pair of uncoupled conditional oscillators near a subcritical Hopf bifurcation that are driven by two weak white noise sources, one intrinsic and one common. The effect of the
competition between the common and intrinsic noise forcing on the synchronization behaviour of
the phases of these two oscillators is studied. Using a stochastic multiple scales method, we derive the envelope equations of the oscillators and then use the theory of linearized stochastic differential equations as well as an asymptotic analysis to study the probability density of the phase difference of the oscillators. It is found that common noise increases the degree of synchrony in the pair of oscillators and that it can be characterized by the ratio of intrinsic to common noise. Furthermore, the nonlinear dynamics of the oscillators can affect the character of this synchronization in terms of the average phase difference. The results are also related to the study of spike time reliability and possible implications are briefly discussed.
4
Wong, Liang Jie. "Compact laser-driven electron acceleration, bunch compression and coherent nonlinear Thomson scattering." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84900.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 189-195).
Coherent hard x-rays have many medical, commercial and academic research applications. To facilitate the design of a table-top coherent hard x-ray source, this thesis studies the linear acceleration of electrons by optical lasers in unbounded vacuum, the linear acceleration and compression of electron bunches by coherent terahertz pulses in cylindrical waveguides, and the generation of coherent hard x-ray radiation by nonlinear Thomson scattering of compressed electron bunches. The Lawson-Woodward theorem describes conditions prohibiting net electron acceleration in laser-electron interactions. We point out how the Lawson-Woodward theorem permits net linear acceleration of a relativistic electron in unbounded vacuum and verify this with electrodynamic simulations. By hypothesizing that substantial net linear acceleration is contingent on the field's ability to bring the particle to a relativistic energy in its initial rest frame, we derive a general formula for the acceleration threshold, which is useful as a practical guide to the laser intensities that linear vacuum acceleration requires. We characterize the scaling laws of linear acceleration by a pulsed radially-polarized beam in infinite vacuum, showing that greater energy gain is achievable with tighter focusing and the use of pre-accelerated electrons. We propose a two-color linear acceleration scheme that exploits changes in the interference pattern caused by the Gouy phase shift to achieve over 90% the one-color theoretical gain limit, more than twice the 40% achievable with a one-color paraxial beam. Interested in capitalizing on the larger wavelengths of coherent terahertz radiation to accelerate larger electron bunches, we study electron acceleration and bunch compression in a cylindrical metal-coated dielectric waveguide. We numerically predict an achievable acceleration gradient of about 450 MeV/m using a 20 mJ terahertz pulse, and separately achieve a 50 times compression to a few-femtosecond duration of a 1.6 pC relativistic electron bunch. Finally, we numerically study the production of coherent hard x-rays via nonlinear Thomson scattering for different degrees of laser focusing. We derive an approximate analytical formula for the optimal incident field intensity that maximizes the radiation intensity spectral peak for a given output and input frequency.
by Liang Jie Wong.
Ph.D.
5
Rohde, Hannah. "Coherence-driven effects in sentence and discourse processing." Diss., [La Jolla, Calif.] : University of California, San Diego, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3323581.
Анотація:
Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed Sept. 9, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 202-209).
6
Zhi, Miaochan. "Broadband coherent light generation in Raman-active crystals driven by femtosecond laser fields." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2578.
7
Almano, Ada. "Spatially coherent solutions of damped-driven nonlinear evolution equations and reaction-diffusion system." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/4744.
8
Fang, Yimai. "Proposition-based summarization with a coherence-driven incremental model." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287468.
Анотація:
Summarization models which operate on meaning representations of documents have been neglected in the past, although they are a very promising and interesting class of methods for summarization and text understanding. In this thesis, I present one such summarizer, which uses the proposition as its meaning representation. My summarizer is an implementation of Kintsch and van Dijk's model of comprehension, which uses a tree of propositions to represent the working memory. The input document is processed incrementally in iterations. In each iteration, new propositions are connected to the tree under the principle of local coherence, and then a forgetting mechanism is applied so that only a few important propositions are retained in the tree for the next iteration. A summary can be generated using the propositions which are frequently retained. Originally, this model was only played through by hand by its inventors using human-created propositions. In this work, I turned it into a fully automatic model using current NLP technologies. First, I create propositions by obtaining and then transforming a syntactic parse. Second, I have devised algorithms to numerically evaluate alternative ways of adding a new proposition, as well as to predict necessary changes in the tree. Third, I compared different methods of modelling local coherence, including coreference resolution, distributional similarity, and lexical chains. In the first group of experiments, my summarizer realizes summary propositions by sentence extraction. These experiments show that my summarizer outperforms several state-of-the-art summarizers. The second group of experiments concerns abstractive generation from propositions, which is a collaborative project. I have investigated the option of compressing extracted sentences, but generation from propositions has been shown to provide better information packaging.
9
Fournier, Clarisse. "Centres colorés contrôlés en position dans le nitrure de bore hexagonal pour l'émission de photons uniques cohérents." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST165.
Анотація:
Le traitement optique de l'information quantique nécessite des émetteurs de photons uniques indiscernables. Dans ce cadre, des émetteurs quantiques récemment découverts dans les matériaux 2D offrent de nouvelles perspectives en termes de dispositifs photoniques intégrés. Ainsi, dans le nitrure de bore hexagonal (hBN), une nouvelle famille de centres colorés a l'avantage de posséder une faible dispersion en longueur d'onde. Ces centres émettant dans le bleu (λ ≈ 435 nm) peuvent également être positionnés de manière déterministe. Ces deux qualités sont rares parmi les émetteurs quantiques dans l'état solide et s'ajoutent en outre à des propriétés photophysiques avantageuses. Cette famille d'émetteurs constitue l'objet d'étude principal de cette thèse.Dans un premier temps, nous détaillons les principales figures de mérite d'un émetteur de photons uniques : brillance, pureté, cohérence temporelle et indiscernabilité. Nous évoquerons également les principaux systèmes physiques émettant des photons uniques, afin de contextualiser la caractérisation à suivre des centres colorés bleus dans hBN.Nous décrivons, dans une deuxième partie, les méthodes expérimentales génériques employées au cours de la thèse en commençant par l'exfoliation mécanique permettant d'obtenir des cristaux de hBN et l'irradiation électronique pour la création des centres colorés. Ceux-ci sont ensuite caractérisés optiquement à l'échelle individuelle au moyen de techniques combinant microscopie confocale, cryogénie, comptage de photons et spectroscopie. Nous détaillons également le traitement des données utilisé pour calculer la fonction d'autocorrélation d'intensité. Le troisième chapitre est consacré aux mesures de différentes propriétés photophysiques des centres bleus à l'échelle de l'émetteur individuel, telles que le temps de vie, la pureté, la polarisation et la photostabilité. Nous nous intéressons également au processus de création des centres colorés bleus, en effectuant des mesures de cathodoluminescence in situ, complétées par des mesures optiques. La nature microscopique de cette famille de centres colorés est également évoquée.Nous traitons ensuite de l'excitation laser résonante d'un centre bleu. L'étude des corrélations de photons permet d'observer des oscillations de Rabi, et d'en extraire le temps de cohérence de l'émetteur. En outre, ces corrélations donnent accès à la dynamique de la diffusion spectrale prenant place à une échelle de temps de l'ordre de la dizaine de microsecondes. Enfin, nous étudions l'indiscernabilité des photons émis par un centre bleu en mesurant les corrélations de photons dans un interféromètre de Hong, Ou et Mandel. Nous mettons en évidence le phénomène d'interférence à deux photons témoignant de l'indiscernabilité partielle des photons émis par le centre coloré. Ce résultat prometteur pourra être améliorée grâce à l'intégration des émetteurs dans des structures photoniques visant à augmenter la collection et diminuer l'impact du déphasage.Les résultats détaillés dans cette thèse démontrent le potentiel de ces centres colorés bleus dans hBN pour des applications dans le domaine de l'information quantique. De futur développements permettront une meilleure compréhension et un meilleur contrôle de leur dynamique d'émission ainsi que leur intégration dans des dispositifs optoélectroniques. Ces travaux ouvrent de nouvelles perspectives en termes de photonique quantique avec des matériaux 2DOptical quantum information processing requires single and indistinguishable photon emitters. In this context, recently discovered quantum emitters in 2D materials offer new perspectives in terms of integrated photonic devices. In hexagonal boron nitride (hBN), a new family of color centers has the advantage of a low wavelength dispersion. These blue-emitting color centers (λ ≈ 435 nm) can also be positioned deterministically. These two qualities are rare among solid-state quantum emitters, and add up to advantageous photophysical properties. This family of emitters is the main focus of this thesis.First, we detail the main figures of merit of a single-photon emitter: brightness, purity, temporal coherence and indistinguishability. We also discuss the main physical systems emitting single photons, in order to contextualize the following characterization of blue color centers in hBN.In the second part, we describe the generic experimental methods used during the thesis: mechanical exfoliation to obtain hBN crystals and electron irradiation to create the color centers. The latter are then optically characterized on an individual scale using techniques combining confocal microscopy, cryogenics, photon counting and spectroscopy. Finally, we describe the data processing methods used to calculate the intensity autocorrelation function.The third chapter is devoted to measurements of various photophysical properties of blue centers at the scale of individual emitters, such as lifetime, purity, polarization and photostability. We also focus on the creation process of blue color centers, by carrying out in-situ cathodoluminescence measurements, complemented by optical measurements. The microscopic nature of this family of color centers is also discussed.We then address the resonant laser excitation of a blue center. The study of photon correlations allows us to observe Rabi oscillations, and to extract the coherence time of the emitter. In addition, these correlations give access to the dynamics of the spectral diffusion taking place on a time scale of a few tenths of microseconds. Finally, we study the indistinguishability of photons emitted by a blue center by measuring photon correlations in a Hong-Ou-Mandel interferometer. We demonstrate two-photon interference, indicating partial indistinguishability of photons emitted by the color center. This promising result could be improved by integrating the emitters into photonic structures designed to increase collection and reduce the impact of dephasing.The results detailed in this thesis show the potential of this family of blue color centers in hBN as quantum emitters for quantum information applications. With future developments aiming to understand and control their dynamics, as well as to integrate them into optoelectronic devices, our work opens new perspectives for optical quantum information with 2D materials
10
Kampschulte, Tobias [Verfasser]. "Coherently driven three-level atoms in an optical cavity / Tobias Kampschulte." Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/1043910786/34.
Книги з теми "Coherent drive":
1
Dryzek, John S., Richard B. Norgaard, and David Schlosberg. Climate-Challenged Society. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199660100.001.0001.
Анотація:
This book is an original, accessible, and thought-provoking introduction to the severe and broad-ranging challenges that climate change presents and how societies can respond. It synthesizes and deploys cutting-edge scholarship on the range of social, economic, political, and philosophical issues surrounding climate change. The treatment is introductory, but the book is written "with attitude", for nobody has yet charted in coherent, integrative, and effective fashion a way to move societies beyond their current paralysis as they face the challenges of climate change. The coverage begins with an examination of science, public opinion, and policy making, with special attention to organized climate change denial. The book then moves to economic analysis and its limits; different kinds of policies; climate justice; governance at all levels from the local to the global; and the challenge of an emerging "Anthropocene" in which the mostly unintended consequences of human action drive the earth system into a more chaotic and unstable era. The conclusion considers the prospects for fundamental transition in ideas, movements, economics, and governance.
2
Hildebrandt, Mireille. Law for Computer Scientists and Other Folk. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198860877.001.0001.
Анотація:
This book introduces law to computer scientists. Computer scientists develop, protect, and maintain computing systems in the broad sense of that term, whether hardware, software, or data. They may be focused on e.g. digital security, or on embedded systems, or on software science. The aim of this book is to convey the internal logic of legal practice, firmly grounded in legal theory. It attempts to bridge the gap between two scientific practices, and probe the middle ground to present a reasonably coherent picture of the grammar and vocabulary of law and the rule of law. This attempt is geared toward those with no wish to become lawyers but who are nevertheless forced to consider the salience of legal rights and obligations. Simultaneously, this book aims to help lawyers to review their own trade. It is a volume on law in an onlife world, presenting a coherent picture of how modern law operates, how it emerged in the context of printed text, and how it confronts its new, data-driven environment.
3
Rodogno, Davide. Fascism and War. Edited by R. J. B. Bosworth. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780199594788.013.0014.
Анотація:
This article explores Benito Mussolini's view on fascism and war. War had an essential place in Mussolini's worldview, even before he came to power in 1922. After this, Mussolini showed some realism and opportunism in domestic and foreign policy, but he was first and foremost driven by an ultranationalist, racist, militarist, and Social Darwinist worldview which rested on the fundamental assumption that life is a struggle and war the father of all things. Mussolini believed the twentieth century to be the century of Italy. He failed to assemble his ideas into an all-embracing intellectual system; however, he possessed a sufficiently articulated and coherent worldview, the essence of which was that the nation would be made through war and territorial expansion. Racism was the most radical part of the fascist project to transform Italians into a warrior race.
4
Lobban, Michael. The Law of Obligations. Edited by Heikki Pihlajamäki, Markus D. Dubber, and Mark Godfrey. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780198785521.013.45.
Анотація:
The Anglo-American law of obligations was profoundly reshaped in the two centuries after 1800, driven by social and economic changes, and changes in legal institutions and doctrines. In contract law, nineteenth-century jurists increasingly sought to put the rules of law into a coherent rational framework (inspired by continental models resting on will theory), though they soon found that this theory could not explain many contractual doctrines. In tort law, jurists were also divided over whether unifying principles underlying tort could be uncovered, with formalist efforts to find such principles being challenged by Realists who argued that tort was in effect ‘public law in disguise’. The quest for underlying principles was also pursued by scholars of unjust enrichment, first in the United States and subsequently in England; though as in the other areas of obligations, by the end of the twentieth century, there was no consensus on whether this was possible.
5
America, Carina, Nazeem Edwards, and Maureen Robinson, eds. Teacher Education for Transformative Agency: Critical perspectives on design, content and pedagogy. African Sun Media, 2020. http://dx.doi.org/10.18820/9781928480938.
Анотація:
Many teacher education programs globally are undergoing significant changes in response to government policy, imperatives driven by global competitiveness, as well as local conditions. This is particularly relevant in the South African context where teacher education seeks to navigate from the ravages of apartheid education towards addressing the developmental needs of the majority of its citizens. This book records and explores efforts by academic staff members within the Faculty of Education at Stellenbosch University, South Africa, responding to the demands of a new program in initial teacher education. It brings together diverse views seeking to present a coherent program in the Postgraduate Certificate in Education (PGCE). It examines how curriculum design unfolds across disciplines in the program, and crucially, the commonalities in the presentation of course material. Lecturers examine the purpose, structure and content of their teaching as they engage with putting democratic policy goals into practice in the core, as well as subject-specific modules of the program.
6
Schulkin, Jay. Radical Change. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780198793694.003.0004.
Анотація:
Chapter 4 talks about how CRF is involved in two quite striking processes: metamorphosis and parturition. Both of these processes revolve around the wondrously vital feature of radical change. In both instances, we are discussing the changing of form and the maturation of an organism. While one change is ancient and one more modern, both continue to be important features of life on this planet, and they represent the importance of development and its responsiveness to changing environments. Our story of metamorphosis, however, is about change and adaptation or preadaptation and the expansion of use and capability. CRF is fundamentally tied to the world in which animals are adapting to changes including the seasons, times of day, droughts, and breeding cycles. Cycles of stability and change set the conditions for adaptive viability; underlying such events is predictive coherence, where diverse information molecules drive physiological and behavioral adaptations.
7
Trencsényi, Balázs, Michal Kopeček, Luka Lisjak Gabrijelčič, Maria Falina, Mónika Baár, and Maciej Janowski. Political Thought in Exile. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198829607.003.0002.
Анотація:
The post-1945 exile from East Central Europe was characterized by extreme ideological pluralism and political fragmentation, ranging from post-fascist to radical leftist streams. Given this initial diversity and the permanent reconfiguration due to the arrival of new waves, it remained an extremely variegated phenomenon with limited ideological coherence. However the specific exile experience produced a certain type of political thought offering a choice between interventionist, gradualist, or passivist stances. Whereas in the first post-war decades the exile’s main drive was to preserve the “authentic” cultural and political traditions, in the course of the 1960s and the 1970s they became the transmitters of the local dissident discourses. These developments validated the ideas of the best strategic minds in emigration arguing that it was the pressure from the domestic public and opposition, not the émigré groups or Western powers, which could become a main catalyst of democratization.
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Wirtz, Kristina. “With Unity We Will Be Victorious!”. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780190652807.003.0006.
Анотація:
This chapter investigates the relationship between monologue and dialogue in Cuban revolutionary discourse. It proposes to attend to the “mono-logic”—the semiotic and ideological forces designed to compel alignments toward unity, coherence, and continuity, that are, asymptotically, never quite reached. Cuba’s political leaders have for decades insisted that citizens undergo a continual process of conscientization in which inner selves and outer displays jointly cultivate commitment to revolutionary principles. There are two semiotic calibrations of such discourse: (1) the charismatic, in which heroic figures such as José Martí and Fidel Castro speak with overwhelming authority; and (2) the nomic, in which slogans on banners and in graffiti present universalized Truths voiced by no one and therefore, potentially, by everyone. Inevitably, heteroglossic criticism of the mono-logic surfaces in irony, parody, and even silence. The chapter argues that the monologic drive for unity across psyche, self, society, and history co-constitutes and reframes the dialogic.
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Harter, Susan. Developmental and Prosocial Dimensions of Hypo-egoic Phenomena. Edited by Kirk Warren Brown and Mark R. Leary. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199328079.013.6.
Анотація:
This chapter provides a developmental perspective on phenomena that involve a hypo-egoic perspective—such as perspective taking, prosocial behavior, empathy, true-self behavior, and self-coherence—with a focus on whether hypo-egoic processes that have been described in adult populations also exist in childhood and adolescence. The chapter examines the extent to which children and adolescents have the cognitive skills to engage in various hypo-egoic behaviors and explores the motives that might underlie hypo-egoic phenomena at different developmental levels. Along the way, the development of skills and motives that promote self-absorbed and self-aggrandizing tendencies, such as egocentrism and narcissism, are also discussed. The role of cognitive-developmental changes, socially driven developmental transitions, developmentally salient needs, and individual differences in parenting and socialization practices on hypo-egoic perspectives and behaviors are also examined.
10
Harriss-White, Barbara. Innovation in the Informal Economy of Mofussil India. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199476084.003.0002.
Анотація:
This chapter explores innovation in the informal economy of small-town ‘mofussil’ India. Two-thirds of the urban population lives outside metropolitan cities in towns noted for their infrastructural backwardness. Ninety per cent of livelihoods and two-thirds of the economy, disproportionately in small-town India, are unregistered or unregulated and termed ‘informal’. It is the informal economy that drives growth and livelihoods. After reviewing innovation theories, a case study of the innovation activity of a small-town is developed through evidence from the presidents of the town’s many business associations. They supply an account of five types of innovation: invention, adaptive and adoptive innovation, incremental and disruptive innovation; innovation in products, process, services, contracts and information; and innovation by labour as well as capital. The chapter concludes that although innovations flourish, the intertwined and hybrid formal and informal institutions do not behave coherently enough to constitute an informal innovation system.
Частини книг з теми "Coherent drive":
1
Zillner, Sonja, Laure Le Bars, Nuria de Lama, Simon Scerri, Ana García Robles, Marie Claire Tonna, Jim Kenneally, et al. "A Roadmap to Drive Adoption of Data Ecosystems." In The Elements of Big Data Value, 41–62. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-68176-0_3.
Анотація:
AbstractTo support the adoption of big data value, it is essential to foster, strengthen, and support the development of big data value technologies, successful use cases and data-driven business models. At the same time, it is necessary to deal with many different aspects of an increasingly complex data ecosystem. Creating a productive ecosystem for big data and driving accelerated adoption requires an interdisciplinary approach addressing a wide range of challenges from access to data and infrastructure, to technical barriers, skills, and policy and regulation. In order to overcome the adoption challenges, collective action from all stakeholders in an effective, holistic and coherent manner is required. To this end, the Big Data Value Public-Private Partnership (BDV PPP) was established to develop the European data ecosystem and enable data-driven digital transformation, delivering maximum economic and societal benefit, and achieving and sustaining Europe’s leadership in the fields of big data value creation and Artificial Intelligence. This chapter describes the different steps that have been taken to address the big data value adoption challenges: first, the establishment of the BDV PPP to mobilise and create coherence with all stakeholders in the European data ecosystem; second, the introduction of five strategic mechanisms to encourage cooperation and coordination in the data ecosystem; third, a three-phase roadmap to guide the development of a healthy European data ecosystem; and fourth, a systematic and strategic approach towards actively engaging the key communities in the European Data Value Ecosystem.
2
Santini, P. M., and A. S. Fokas. "The Initial-Boundary Value Problem for the Davey-Stewartson 1 Equation; How to Generate and Drive Localized Coherent Structures in Multidimensions." In Partially Intergrable Evolution Equations in Physics, 223–59. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0591-7_7.
3
Kuenkel, Petra. "Collective Stewardship Towards Life Economies." In Transformation Literacy, 307–31. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-93254-1_21.
Анотація:
AbstractThis chapter explores how different actors, who drive an urgently needed economic systems change, can become part of a more coherent transformation system by focusing on a unifying future narrative: creating economiesin service to life. The understanding of what gives life to systems is an overarching guiding force of the manifold transformative efforts that already exist. Based on an extensive literature review of new economic approaches, the chapter introduces a combination of guiding principles for new economies that would safeguard planetary and human integrity, while allowing for different interpretations and manifestations. It shows that for most principles, implementation strategies already exist. However, the so urgent systems transformations require combined efforts and an approach of collective stewardship by multiple actors, across societal sectors, cultures and institutions. The chapter elaborates how the adoption of a systems aliveness approach informs collective stewardship. The conscious choice of a constellation of strategic drivers, if applied together, increases the leverage of transformative efforts. The chapter concludes with deliberations on how to use the guiding principles and strategic drivers as an entry point for creating pathways towards regenerative civilizations, in which planetary life-support systems are as much valued as the dignity of people.
4
Ravela, Sai. "Statistical Inference for Coherent Fluids." In Dynamic Data-Driven Environmental Systems Science, 121–33. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-25138-7_12.
5
Hellwagner, Hermann, and Alexander Reinefeld. "Device Driver Software and Low-Level APIs." In SCI: Scalable Coherent Interface, 177–78. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/10704208_12.
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Grauer, R., and Y. S. Kivshar. "Dynamics of Parametrically Driven Sine-Gordon Breathers." In Nonlinear Coherent Structures in Physics and Biology, 381–84. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4899-1343-2_59.
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Bologna, Roberto, and Giulio Hasanaj. "A Systematic Catalogue of Design Solutions for the Regeneration of Urban Environment Contrasting the Climate Change Impact." In The Urban Book Series, 601–16. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-29515-7_54.
Анотація:
AbstractThe article illustrates a research for the definition of a catalogue of design solutions for climate change adaptation in the process of urban regeneration, reducing the vulnerability to climate change impacts and increasing the city resilience. Based on the analysis of relevant case studies of architectural and urban projects in the main biogeographical regions of Europe, the paper describes the research methodology applied for the construction of a catalogue of spatial and technological adaptive design models mainly focusing on the category of “nature-based solutions” but also considering “artificial solutions”. In order to assess their effectiveness, different design alternatives are tested in a specific urban contest (a school courtyard in the City of Scandicci–Metropolitan City of Florence) prone to climate hazards of urban heat islands and pluvial flooding, simulating the impact on the more vulnerable user (children between 11 and 14 years old). For an adequate performance evaluation of multi-hazard effectiveness of the different adaptive design solutions, appropriate IT software and procedural models have been applied: ENVI-met microclimatic simulation software for thermal analysis and predictive method for hydraulic assessment. By comparing the results before and after the application, the climate-adaptive performance of alternative design solutions is measured through specific indicators. This approach is coherent to the design process management aiming to a predictive definition of performance evaluation through procedural models and digital instruments in order to properly address the complexity of architectural and urban project. The systematic catalogue of adaptive design solution offers useful tools and methods to designers and decision makers for the construction of climate change adaptation and mitigation plans in order to build a healthy and safe urban environment for citizens and drive an ecological and sustainable transition to green cities.
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van Tartwijk, Guido H. M., Alfred M. Levine, and Daan Lenstra. "Coherence Collapse and Maximum Gain Drive in Semiconductor Lasers." In Coherence and Quantum Optics VII, 511–12. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4757-9742-8_129.
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Ritsch, H., and P. Zoller. "Atomic Systems Driven by Colored Squeezed Light." In Coherence and Quantum Optics VI, 1013–17. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4613-0847-8_183.
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Ravela, Sai. "Tractable Non-Gaussian Representations in Dynamic Data Driven Coherent Fluid Mapping." In Handbook of Dynamic Data Driven Applications Systems, 29–46. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-95504-9_2.
Тези доповідей конференцій з теми "Coherent drive":
1
Purohit, Ankit, and Akhilesh Kumar Mishra. "Comparison of Coherent and Incoherent Drive in SPASER." In Frontiers in Optics. Washington, D.C.: OSA, 2021. http://dx.doi.org/10.1364/fio.2021.jw7a.93.
2
Solgaard, O., N. Tien, M. Daneman, M. Kiang, R. S. Muller, and K. Y. Lau. "Micro-external-cavity Semiconductor Laser on a Silicon Chip - a Miniaturized, Continuously Tunable, Narrow-linewidth Laser for Coherent Lidar." In Coherent Laser Radar. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/clr.1995.thd6.
Анотація:
Successful large-scale introduction of coherent-lidar/remote-sensing techniques in environmental monitoring is hindered currently by the relatively high cost of continuously tunable, narrow-linewidth laser sources, as well as their relative bulkiness that preclude their installations in confined spaces. While semiconductor lasers are currently massed-produced at low cost, the requirements of narrow-linewidth and continuously tunable necessitates coupling the laser diode to an external cavity grating which makes its cost very high. In this paper, we describe a new technology that has evolved in the past year, that uses silicon micromachining technology to implement a miniaturized, lost cost, continuously tunble, highly coherent, micro External- Cavity semiconductor Laser (micro-ECL). The entire optical system is built on a silicon chip measuring less than 0.3cm square, and on-chip micromotors are used to drive the grating reflector for continuous wavelength tuning. The semiconductor laser can also be made to emit very short, wavelength tunable pulses by simply electrically driving the laser diode. A schematic of the micro-ECL is shown in Fig. 1.
3
Fisher, D. S., and F. T. S. Yu. "Acoustooptic signal processing using partially coherent light." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.tue5.
Анотація:
An investigation into acoustooptic (AO) correlation and spectrum analysis using partially coherent light is presented. The salient feature of the processing architectures is the implementation of a white-light source to reduce coherent artifact noise at the detector plane. In all information processing operations the Bragg cell is amplitude modulated to perform linear processing of light in complex amplitude. Pure sinusoidal signals with no input noise were used to drive the AO cells to isolate the effects of the multiplicative phase noise. This phase noise arises from random thickness variations and refractive-index fluctuations. Two signal-to-noise ratio (SNR) measurements are used to compare partially coherent light and laser light for the same signal processing architectures. A theoretical treatment is given to quantify the effects of the spatial and temporal coherence on these SNR measurements. Finally, the effects of the temporal and spatial coherence on the correlation peak intensity for a space-integrating and a time-integrating architecture is described. Similarly these effects are studied in the spectral estimation peak for the spectrum analyzer.
4
Harris, M., G. N. Pearson, J. M. Vaughan, C. Karlsson, D. Letalick, and I. Renhorn. "Eye-Safe Semiconductor Lasers for Lidar: Experimental Studies of Coherence and Atmospheric Propagation." In Coherent Laser Radar. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/clr.1995.thd5.
Анотація:
Shorter-wavelength lasers (with λ of order 1.5-2.5 μm), both semiconductor and solid-state, are showing increasing promise for lidar applications, with improved power levels and frequency stability. Advantages over existing long-wavelength systems include: compactness and robustness, compatibility with cheap components and optical fibres from the telecommunications industry, and the lack of need for cooled detectors. It is thus becoming important to investigate the primary aspects of such lasers to establish their performance characteristics. The potential for semiconductor lasers in lidar/rangefinder systems is currently limited by their relatively low output power and short coherence length (or equivalently, their broad spectral bandwidth). This reduces the level of performance in range and velocity resolution, as well as leading to a degraded signal-to-noise ratio. In fact, the two considerations of power and linewidth are closely linked, because attempts to increase the output by turning up the laser drive current eventually lead to a significant increase in bandwidth. This "rebroadening" effect is poorly understood; it imposes a limit on the coherence performance of this type of laser, and hence also on its capabilities in laser radar applications. The work reported here could benefit understanding of the serious problem of rebroadening. Further limitations to the use of semiconductor lasers may result from the increased effects of atmospheric turbulence at these wavelengths.
5
Bright, G. A., R. E. Macior, and H. K. Schuman. "Coherent (I/Q) Detector Performance Under Extended Drive Signal Conditions." In 27th ARFTG Conference Digest. IEEE, 1986. http://dx.doi.org/10.1109/arftg.1986.323661.
6
Kapteyn, H. C., and M. M. Murnane. "Ultrafast Mid-IR Lasers for Soft X-ray High-Harmonic Generation and Applications." In CLEO: Applications and Technology. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_at.2022.jm2e.4.
Анотація:
Coherent soft x-rays can be generated on a tabletop by using mid-IR lasers to drive high harmonic generation. The high coherence of this source enables diffraction-limited x-ray functional microscopy of nano and bio systems.
7
Gacusan, L. Z., S. L. Kwiatkowski, B. J. Sullivan, and J. J. Snyder. "Coherent Heterodyne Scatterometer." In Optical Fabrication and Testing. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oft.1988.tha4.
Анотація:
An instrument has been developed that measures the magnitude of the Bidirectional Scattering Distribution Function (BSDF) employing coherent optical heterodyne detection at 633nm in a Mach-Zehnder interferometer configuration. In preliminary measurements, instrument performance agrees with theoretical predictions and is characterized by diffraction limited resolution, 15 decades of dynamic range and shot noise limited sensitivity. The scatterometer is constructed from readily available components and the instrument configuration can be adapted to measure scattering from objects in transmission or reflection. In the scatterometer, the beam from a commercially available stabilized 3mW He-Ne laser is split into two beams: a scattering beam and a local oscillator beam. The frequency of each beam is individually shifted by separate acousto-optic modulators operating at different drive frequencies. The scattering beam is directed to the target whose orientation is adjustable. The scattered light and the local oscillator beam are combined and directed onto a photodetector where the resulting heterodyne signal is the frequency difference between the two beams. The RF power of the heterodyne signal is proportional to the optical power that is scattered from the target and is polarization-and mode-matched to the local oscillator beam. The combination of shot-noise-limited sensitivity of a heterodyne detector and milliwatt saturation levels of typical photodetectors provides the large dynamic range necessary for accurate measurements of BSDF. Moreover, characteristics inherent to coherent detection systems permit measurements with diffraction limited angular resolution and yield information of the polarization content of the scattered light. Results of BSDF measurements of various surfaces and materials will be presented.
8
Deeney, C., J. Levine, T. Nash, P. D. LePell, and M. Krishnan. "X-Ray Laser Research at Physics International." In Short Wavelength Coherent Radiation: Generation and Applications. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/swcr.1988.swlos157.
Анотація:
Photopumped and recombination X-ray laser schemes are under investigation at Physics International, on the DNA/PITHON 3 TW facility. For the sodium-neon resonant photopumped scheme, DNA/PITHON is used to implode a sodium-bearing plasma, the pump, and a secondary capacitor bank is used to drive a neon gas puff Z-pinch, the lasant. The characterization of the pinched sodium plasma is reported in this paper, as are pump power measurements, which showed 65 GW in the Na X 1s2-1s2p 1P line. In earlier experiments, neon gas was imploded onto sodium-fluoride coated targets, on-axis, but insufficient sodium pump powers were obtained. However, some very interesting spectral features, which could be an indication of recombination pumping, were observed in the neon plasmas formed when neon was imploded onto aluminum targets. These results are also presented in this paper.
9
Zimmermann, Matthew, Y. Henry Wen, Mark Dong, Andrew J. Leenheer, Gerald Gilbert, Matt Eichenfield, Mikkel Heuck, and Dirk R. Englund. "Arbitrary Waveforms from a Resonant Modulator via Coherent Pre-Compensation." In Frontiers in Optics. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/fio.2023.fth3b.6.
Анотація:
We observe a highly structured complex frequency response of a piezo-actuated photonic crystal cavity due to optomechanical resonances. We demonstrate a scheme to coherently pre-compensate the drive signal to obtain high-fidelity arbitrary optical waveforms.
10
Surette, Marc, and Alan Rolf Mickelson. "Coherent guided-wave implementations for photonic control of phased-array radar systems." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.fee4.
Анотація:
Coherent guided-wave optical systems offer significant advantages for use with phased-array drive and readout schemes. Single-side-band modulation of received fields allows for optical mixing of the microwave signals through Butler-matrix techniques with the attendant low loss and high resolution of optics. Such methods obviate the need for adaptive antenna processing and also produce a baseband signal at the output of an optical detector. Coherent drive allows for phase shifting to be performed at optical, rather than microwave, wavelengths, thereby allowing for compact, high- bandwidth true-time-delay, integrated-optical phase shifting. Heterodyning at the antenna-element end allows one to use a high-power locked local oscillator, thereby minimizing any need for at-element microwave amplification. Many of the elements necessary to realize such photonic array control schemes already exist and, in the near future, should become monolithically integrable, allowing for fiber-compatible modular construction of various drive schemes. We will discussion the performance of the various system elements, including those fabricated and tested in our laboratory as well as others for which data is available, and thereby project eventual system performance in terms of the standard phased-array performance measures.
Звіти організацій з теми "Coherent drive":
1
Chiara Tornaghi, Chiara Tornaghi, and Michiel Dehaene Michiel Dehaene. AGROECOLOGICAL URBANISM: What is it, why we need it, and the role of UN-Habitat. Coventry University, June 2024. http://dx.doi.org/10.18552/cawr/2024/0001.
Анотація:
Current urbanisation approaches drive climate change, soil destruction, biodiversity loss, people’s alienation from nature, and unsustainable and unhealthy diets. To achieve sustainable urbanisation we need coherent and integrated urban and agricultural policies, that radically transform how we urbanise. Agroecological urbanism is a promising model, addressing simultaneously the challenges of climate change, soil regeneration, resource conservation and sustainable farming, while developing sustainable and socially just urban habitats and livelihoods. This brief suggests ways in which UN-Habitat, whose influence is key at the rural-urban interface, can adopt and promote this approach.
2
Kaffenberger, Michelle, and Marla Spivack. System Coherence for Learning: Applications of the RISE Education Systems Framework. Research on Improving Systems of Education (RISE), January 2022. http://dx.doi.org/10.35489/bsg-risewp_2022/086.
Анотація:
In recent decades, education systems in most low- and middle-income countries (LMICs) have rapidly expanded access to schooling, but learning has lagged behind. There are many reasons for low learning in LMICs. Proximate determinants (such as insufficient financing or poor school management) receive much attention, but focus on these often ignores underlying system drivers. In this chapter we use a systems approach to describe underlying system dynamics that drive learning outcomes. To do so, we first describe the RISE education systems framework and then apply it to two cases. In the case of Sobral, Brazil, the systems framework illustrates how a coherent package of reforms, improving upon multiple system components, produced positive outcomes. In the case of Indonesia, a reform that increased teacher pay, but did not change underlying system dynamics, had no impact on learning. The chapter shows how a systems approach can help to understand success, diagnose failure, and inform action to bring about improvements to children’s learning.
3
Blaskiewicz, Michael. Noise driven emittance growth with coherent forces. Office of Scientific and Technical Information (OSTI), August 2022. http://dx.doi.org/10.2172/1887548.
4
Oh, H. G., H. R. Lee, Thomas F. George, and C. I. Um. Exact Wave Functions and Coherent States of a Damped Driven Harmonic Oscillator. Fort Belvoir, VA: Defense Technical Information Center, February 1989. http://dx.doi.org/10.21236/ada205785.
5
Pan, Wei, John Reno, and Julien Tranchida. Enhance coherence time in intensely driven quantum systems. Office of Scientific and Technical Information (OSTI), September 2020. http://dx.doi.org/10.2172/1670245.
6
Lumplin, Alex. Coherent Optical Transition Radiation Imaging for Laser-Driven Plasma Accelerator Electron-Beam Diagnostics. Office of Scientific and Technical Information (OSTI), June 2019. http://dx.doi.org/10.2172/1599615.
7
Armas, Elvira G., Magaly Lavadenz, Natividad Rozsa, and Gisela O’Brien. English Learner Master Plan Playbook: Developing Equitable Local Policies for Multilingual and English Learners Students. Center for Equity for English Learners, 2021. http://dx.doi.org/10.15365/ceel.elmasterplan2021.
Анотація:
The education of English Learners (ELs) is informed by federal, state, and local policies, research and practice. The EL Master Plan is the Local Education Agency’s (LEA) policy document that has the potential to positively impact the educational programs, practices and experiences of ELs. Aligned and informed by California’s English Learner Roadmap policy as well as federal requirements, this playbook is a guide for educational partners to use to achieve four goals in their LEAs EL Master Plans: (1) equitable, coherent, and sustainable systems; (2) equity-driven processes to deliver research-based programs and practices; (3) effective family-community engagement; and (4) accountability models that ensure EL students’ success. The authors include a variety of tools and processes for LEA’s to use in the development of their EL Master Plan.
8
Revina, Shintia, Rezanti Putri Pramana, Rizki Fillaili, and Daniel Suryadarma. Systemic Constraints Facing Teacher Professional Development in a Middle-Income Country: Indonesia’s Experience Over Four Decades. Research on Improving Systems of Education (RISE), November 2020. http://dx.doi.org/10.35489/bsg-rise-wp_2020/054.
Анотація:
Despite government efforts to reform teacher professional development (TPD) in the past four decades, Indonesian teacher quality remains low. Why have the improvement efforts failed? In the present study we investigate what caused these reforms to fail from two angles. First, we examine the efficacy of the latest teacher professional development (TPD) initiative in Indonesia, Pengembangan Keprofesian Berkelanjutan or PKB (Continuing Professional Development), and identify the factors affecting its efficacy. We found that some essential features of effective TPD are missing in PKB. The PKB programme has not targeted teachers based on years of experience, has not followed up teachers with post-training activities, has not incorporated teaching practice through lesson enactment, and has not built upon teacher existing practice. Second, our analysis demonstrates that PKB's weaknesses have existed in Indonesia's previous TPD initiatives as far back as four decades ago. This indicates that the long-term problem of TPD’s ineffectiveness is driven by different elements of the education system beyond the TPD’s technical and operational aspects. Our system-level analysis points out that merely improving the technical aspects of TPD would be insufficient given the Indonesian education system’s lack of coherence surrounding teacher quality. The problems surrounding the provision of effective TPD is more complex than simply a matter of replacing the “old” with the “new” initiative. The change requires a reorientation of the education system to produce high-quality teachers.
9
Revina, Shintia, Rezanti Putri Pramana, Rizki Fillaili, and Daniel Suryadarma. Systemic Constraints Facing Teacher Professional Developmentin a Middle-Income Country: Indonesia’s Experience Over Four Decades. Research on Improving Systems of Education (RISE), November 2020. http://dx.doi.org/10.35489/bsgrisewp_2020/054.
Анотація:
Despite government efforts to reform teacher professional development (TPD) in the past four decades, Indonesian teacher quality remains low. Why have the improvement efforts failed? In the present study we investigate what caused these reforms to fail from two angles. First, we examine the efficacy of the latest teacher professional development (TPD) initiative in Indonesia, Pengembangan Keprofesian Berkelanjutan or PKB (Continuing Professional Development), and identify the factors affecting its efficacy. We found that some essential features of effective TPD are missing in PKB. The PKB programme has not targeted teachers based on years of experience, has not followed up teachers with post-training activities, has not incorporated teaching practice through lesson enactment, and has not built upon teacher existing practice. Second, our analysis demonstrates that PKB's weaknesses have existed in Indonesia's previous TPD initiatives as far back as four decades ago. This indicates that the long-term problem of TPD’s ineffectiveness is driven by different elements of the education system beyond the TPD’s technical and operational aspects. Our system-level analysis points out that merely improving the technical aspects of TPD would be insufficient given the Indonesian education system’s lack of coherence surrounding teacher quality. The problems surrounding the provision of effective TPD is more complex than simply a matter of replacing the “old” with the “new” initiative. The change requires a reorientation of the education system to produce high-quality teachers.
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Green technology and youth employment potential in Africa: a continental scoping report. APRI - Africa Policy Research Private Institute gUG (haftungsbeschränkt)., November 2023. http://dx.doi.org/10.59184/rp023.005.
Анотація:
This scoping report investigates some of the trends in green technology policies and programmes on the continent. It also points to several opportunities for improved policy coherence and programmatic focus to drive youth employment and entrepreneurship. The findings also identify gaps and opportunities for better-aligned and more impactful programmes in green technology, such that they benefit youth.