光纤激光器自成像腔相干组束研究

探讨了3种不同自成像腔，即Talbot腔、自傅里叶变换腔（SF）和傅里叶变换自成像腔实现相干组束的机理和技术难点。介绍了利用光纤激光器，采用傅里叶变换自成像方法，实现1维2路和2维4路激光相干组束的实验情况，功率分别达到122W以及26W。

复杂地质条件下高精度地震勘探技术研究与应用-以泌阳凹陷为例

In order to carry out high-precision three-dimensional "integration" for the characteristics of the secondary seismic exploration for Biyang Depression, in the implementation process, through a combination of scientific research and production, summed up high-precision seismic acquisition, processing and interpretation technologies suitable for the eastern part of the old liberated areas, achieved the following results: 1. high-precision complex three-dimensional seismic exploration technology series suitable for shallow depression Biyang block group. To highlight the shallow seismic signal, apply goal-based observing system design, trail from the small panel to receive and protect the shallow treatment of a range of technologies; to explain the use of three-dimensional visualization and coherent combination of full-body three-dimensional fine interpretation identification of the 50-100 m below the unconformity surface and its formation of about 10 meters of the distribution of small faults and improve the small block and stratigraphic unconformity traps recognition. 2. high-precision series of three-dimensional seismic exploration technology suitable for deep depression Biyang low signal to noise ratio of information. Binding model using forward and lighting technology, wide-angle observation system covering the design, multiple suppression and raise the energy of deep seismic reflection processing and interpretation of detailed, comprehensive reservoir description, such as research and technology, identified a number of different types of traps. 3. high-precision seismic exploration technology series for the southern Biyang Depression high steep three-dimensional structure. The use of new technology of seismic wave scattering theory and high-precision velocity model based on pre-stack time migration and depth migration imaging of seismic data and other high-precision processing technology, in order to identify the southern steep slope of the local structure prediction and analysis of sandstone bedrock surface patterns provide a wealth of information.

El muro como referencia arquitectónica

Esta investigación parte del interés particular por la manifestación arquitectónica, paisajística o urbanística de aquellos muros construidos que se han erigido para limitar, planteando un enfoque del muro en una vertiente conceptual. Se propone la formulación de distintas interpretaciones para un mismo elemento físico, logrando una propuesta arquitectónica de identificación para diferentes casos de estudio que consideramos paradigmáticos en su concepto. La hipótesis plantea la posibilidad de identificar un muro con la autonomía o identidad conceptual que le hace capaz de condicionar o dirigir la conformación de una obra de arquitectura, sirviendo como instrumento arquitectónico para las acciones de articulación, implantación, referenciación o conformación. El desarrollo de la investigación muestra la aptitud de individualizar el muro como elemento excepcional en el cumplimiento de la síntesis de distintas variables de proyecto. Se elaboran cinco conceptos diferentes del elemento en la función que cumple en el espacio que se basan en una definición compuesta de dos propiedades determinantes que se identifican con la categoría de la “justificación conceptual” combinando, además, valores de las categorías “Relación con el lugar”, “Función estética”, “Función de programa” y “Generación”. Se propone la identificación del muro que presenta las cualidades que lo hacen actuar de forma articuladora en el espacio y que, al cumplir esa función, condiciona y determina parte de la obra de arquitectura en que se encuentra. El muro articulador se entiende como un elemento que soluciona formal y espacialmente distintas situaciones de programa; no responde a un esquema formal predeterminado, sino que lo crea, en la unión coherente entre opuestos: ámbitos opuestos, esquemas formales opuestos, etc. Proponemos la identificación del muro que presenta determinadas cualidades que lo hacen actuar de forma implantadora en el espacio y que, al cumplir esa función, condiciona y determina parte de la obra en que se encuentra. Se considera el muro implantador como el punto de partida del proyecto en que se ha utilizado y como el elemento elegido para hacer la síntesis entre las variables del proyecto - sitio, función constructiva y estructural, estableciendo una regla formal y espacial coherente. Proponemos la identificación del muro referenciador, elemento que se destaca en la edificación como entidad elegida para hacer la síntesis entre las distintas variables del proyecto: significado, función estética y sitio. El muro referenciador se percibe como una entidad autónoma, particular al carácter o programa de la obra y al sitio en que se erige. Se considera el muro-recinto como el punto de partida del proyecto en que se ha utilizado, así como un elemento fundamental que se destaca en el conjunto de la obra - sea por su vertiente constructiva o de tratamiento estético – como entidad elegida para hacer la síntesis entre las variables del proyecto: forma y programa. Al utilizar un esquema formal predeterminado, permite generar espacio coherente con las demandas de un programa específico, entendiéndose como un elemento arquitectónico particular a la obra. Proponemos la identificación del muro habitable como el elemento que presenta las cualidades que lo hacen pasible de generar espacio en su interior, siendo un instrumento útil para cumplir con la variable del proyecto del programa. El concepto de muro habitable, como contrapunto a los otros cuatro tipos, se manifiesta como una entidad más elemental que traduce un instrumento de trabajo todavía más manejable que los restantes muros estudiados. De hecho, su utilización es incluso posible en aquellos muros que ya presentan el concepto de muro articulador, implantador, referenciador o muro-recinto. ABSTRACT This research is based on a particular interest in the architectural, landscape or urban manifestations of those walls that have been erected to limit, considering a conceptual approach. It suggests the formulation of diverse interpretations for the same physical element to achieve an architectural proposal of identification for different case studies that we consider paradigmatic in its concept. The hypothesis considers the possibility to identify a wall with the autonomy or conceptual identity that makes it able to influence or direct the form of an architecture work, serving as an instrument for the actions of articulation, emplacement, referencing or conformation. The development of the research shows the ability to individualize the wall as an outstanding element in the synthesis of different variables of architectural design. It elaborates five different concepts of the wall function in space, based on a definition with two determinant properties which combine values of the categories "Relation with the context", "Aesthetic function", "Program function" and "Generation". We propose the identification of the wall that has the qualities that make it act in an articulating way in space, conditioning and determining part of the architectural work. The “articulating wall” is understood as an element that formally and spatially solves different situations of functional program; it does not respond to a previous formal scheme, it creates it instead, through the coherent combination between opposites: opposing fields, opposing formal schemes, etc. We identify as well the wall that has the qualities that make it able to emplace on site, conditioning and determining part of the architecture work. The “wall that emplaces” is considered the starting point of the architectural design and the chosen element to make the synthesis between the architectural design variables - site, constructive function and structural function - establishing a formal and spatial coherent rule. We propose the identification of the “referencing wall”, element that stands out in the building as an entity chosen to make the synthesis between the project variables: meaning, aesthetic function and site. The referencing wall is perceived as an autonomous entity, particular to the character or the functional program and the site on which it sits. We consider the “precinct wall” as the departure point of the architectural design where it is used as well as a fundamental element that stands out in the whole of the architecture work - either by its constructive aspect or esthetic treatment - as the chosen entity to synthetize form and pro-gram. Since it uses a predetermined formal scheme it will allow to generate consistent space with-in the demands of a specific program, being understood as an element particular to the architectural work. As a fifth concept we identify the “inhabitable wall” as the element that has the qualities that make it predisposed to generate space inside its nucleus, being a useful instrument to comply with the variable of program in the architectural design. The concept of inhabitable wall, as a counterpoint to the other four types, manifests itself as a more elemental entity that translates itself as a more manageable working tool. In fact, its use is even possible in those walls that al-ready present the concept of articulating wall, emplacing wall, referencing wall or precinct wall.

High power coherent beam combination from two fiber lasers

Phase locking of two fiber lasers is demonstrated experimentally by the use of a self-imaging resonator with a spatial filter. The high-contrast interference strips of the coherent beam profile are observed. The coherent output power of the fiber array exceeds 12W and the efficiency of coherent power combination is 88% with pump power of 60W. The whole system operates quite stably and, for the spatial filter, no thermal effects have been observed, which means that we can increase the coherent output power further by this method. (c) 2006 Optical Society of America

Leveraging coherent distributed space-time codes for noncoherent communication in relay networks via training

For point to point multiple input multiple output systems, Dayal-Brehler-Varanasi have proved that training codes achieve the same diversity order as that of the underlying coherent space time block code (STBC) if a simple minimum mean squared error estimate of the channel formed using the training part is employed for coherent detection of the underlying STBC. In this letter, a similar strategy involving a combination of training, channel estimation and detection in conjunction with existing coherent distributed STBCs is proposed for noncoherent communication in Amplify-and-Forward (AF) relay networks. Simulation results show that the proposed simple strategy outperforms distributed differential space-time coding for AF relay networks. Finally, the proposed strategy is extended to asynchronous relay networks using orthogonal frequency division multiplexing.

Influence of two photon absorption induced free carriers on coherent polariton and phonon generation in ZnTe crystals

Combination of femtosecond Kerr, two photon absorption, and impulsive stimulated Raman scattering (ISRS) experiments have been carried out to investigate the effect of pulse energy and crystal temperature on the generation of coherent polaritons and phonons in 〈110〉 cut ZnTe single crystals of three different resistivities. We demonstrate that the effect of two photon induced free carriers on the creation of both the polaritons and phonons is largest at 4 K where the free carrier lifetime is enhanced. The temperature dependant ISRS on high and low purity ZnTe crystals allows us to unambiguously assign the phonon mode at 3.5 THz to the longitudinal acoustic mode at X-point in the Brillouin zone, LA(X).

Imaging properties of coherent anti-Stokes Raman scattering microscope

The coherent anti-Stokes Raman scattering (CARS) microscope with the combination of confocal and CARS techniques is a remarkable alternative for imaging chemical or biological specimens that neither fluoresce nor tolerate labelling. CARS is a nonlinear optical process, the imaging properties of CARS microscopy will be very different from the conventional confocal microscope. In this paper, the intensity distribution and the polarization property of the optical field near the focus was calculated. By using the Green function, the precise analytic solution to the wave equation of a Hertzian dipole source was obtained. We found that the intensity distributions vary considerably with the different experimental configurations and the different specimen shapes. So the conventional description of microscope (e.g. the point spread function) will fail to describe the imaging properties of the CARS microscope.

The optoelectronic swept-frequency laser and its applications in ranging, three-dimensional imaging, and coherent beam combining of chirped-seed amplifiers

This thesis explores the design, construction, and applications of the optoelectronic swept-frequency laser (SFL). The optoelectronic SFL is a feedback loop designed around a swept-frequency (chirped) semiconductor laser (SCL) to control its instantaneous optical frequency, such that the chirp characteristics are determined solely by a reference electronic oscillator. The resultant system generates precisely controlled optical frequency sweeps. In particular, we focus on linear chirps because of their numerous applications. We demonstrate optoelectronic SFLs based on vertical-cavity surface-emitting lasers (VCSELs) and distributed-feedback lasers (DFBs) at wavelengths of 1550 nm and 1060 nm. We develop an iterative bias current predistortion procedure that enables SFL operation at very high chirp rates, up to 10^16 Hz/sec. We describe commercialization efforts and implementation of the predistortion algorithm in a stand-alone embedded environment, undertaken as part of our collaboration with Telaris, Inc. We demonstrate frequency-modulated continuous-wave (FMCW) ranging and three-dimensional (3-D) imaging using a 1550 nm optoelectronic SFL.

We develop the technique of multiple source FMCW (MS-FMCW) reflectometry, in which the frequency sweeps of multiple SFLs are "stitched" together in order to increase the optical bandwidth, and hence improve the axial resolution, of an FMCW ranging measurement. We demonstrate computer-aided stitching of DFB and VCSEL sweeps at 1550 nm. We also develop and demonstrate hardware stitching, which enables MS-FMCW ranging without additional signal processing. The culmination of this work is the hardware stitching of four VCSELs at 1550 nm for a total optical bandwidth of 2 THz, and a free-space axial resolution of 75 microns.

We describe our work on the tomographic imaging camera (TomICam), a 3-D imaging system based on FMCW ranging that features non-mechanical acquisition of transverse pixels. Our approach uses a combination of electronically tuned optical sources and low-cost full-field detector arrays, completely eliminating the need for moving parts traditionally employed in 3-D imaging. We describe the basic TomICam principle, and demonstrate single-pixel TomICam ranging in a proof-of-concept experiment. We also discuss the application of compressive sensing (CS) to the TomICam platform, and perform a series of numerical simulations. These simulations show that tenfold compression is feasible in CS TomICam, which effectively improves the volume acquisition speed by a factor ten.

We develop chirped-wave phase-locking techniques, and apply them to coherent beam combining (CBC) of chirped-seed amplifiers (CSAs) in a master oscillator power amplifier configuration. The precise chirp linearity of the optoelectronic SFL enables non-mechanical compensation of optical delays using acousto-optic frequency shifters, and its high chirp rate simultaneously increases the stimulated Brillouin scattering (SBS) threshold of the active fiber. We characterize a 1550 nm chirped-seed amplifier coherent-combining system. We use a chirp rate of 5*10^14 Hz/sec to increase the amplifier SBS threshold threefold, when compared to a single-frequency seed. We demonstrate efficient phase-locking and electronic beam steering of two 3 W erbium-doped fiber amplifier channels, achieving temporal phase noise levels corresponding to interferometric fringe visibilities exceeding 98%.

Collective dynamics of glass-forming polymers at intermediate length scales: a synergetic combination of neutron scattering, atomistic simulations and theoretical modelling

Qens/wins 2014 - 11th International Conference on Quasielastic Neutron Scattering and 6th International Workshop on Inelastic Neutron Spectrometers / editado por:Frick, B; Koza, MM; Boehm, M; Mutka, H

Developing Single-Laser Sources for Multimodal Coherent Anti-Stokes Raman Scattering Microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy has developed rapidly and is opening the door to new types of experiments. This work describes the development of new laser sources for CARS microscopy and their use for different applications. It is specifically focused on multimodal nonlinear optical microscopy—the simultaneous combination of different imaging techniques. This allows us to address a diverse range of applications, such as the study of biomaterials, fluid inclusions, atherosclerosis, hepatitis C infection in cells, and ice formation in cells. For these applications new laser sources are developed that allow for practical multimodal imaging. For example, it is shown that using a single Ti:sapphire oscillator with a photonic crystal fiber, it is possible to develop a versatile multimodal imaging system using optimally chirped laser pulses. This system can perform simultaneous two photon excited fluorescence, second harmonic generation, and CARS microscopy. The versatility of the system is further demonstrated by showing that it is possible to probe different Raman modes using CARS microscopy simply by changing a time delay between the excitation beams. Using optimally chirped pulses also enables further simplification of the laser system required by using a single fiber laser combined with nonlinear optical fibers to perform effective multimodal imaging. While these sources are useful for practical multimodal imaging, it is believed that for further improvements in CARS microscopy sensitivity, new excitation schemes are necessary. This has led to the design of a new, high power, extended cavity oscillator that should be capable of implementing new excitation schemes for CARS microscopy as well as other techniques. Our interest in multimodal imaging has led us to other areas of research as well. For example, a fiber-coupling scheme for signal collection in the forward direction is demonstrated that allows for fluorescence lifetime imaging without significant temporal distortion. Also highlighted is an imaging artifact that is unique to CARS microscopy that can alter image interpretation, especially when using multimodal imaging. By combining expertise in nonlinear optics, laser development, fiber optics, and microscopy, we have developed systems and techniques that will be of benefit for multimodal CARS microscopy.

Vibrational coherent quantum computation

A long-lived coherent state and nonlinear interaction have been experimentally demonstrated for the vibrational mode of a trapped ion. We propose an implementation of quantum computation using coherent states of the vibrational modes of trapped ions. Differently from earlier experiments, we consider a far-off resonance for the interaction between external fields and the ion in a bidimensional trap. By appropriate choices of the detunings between the external fields, the adiabatic elimination of the ionic excited level from the Hamiltonian of the system allows for beam splitting between orthogonal vibrational modes, production of coherent states, and nonlinear interactions of various kinds. In particular, this model enables the generation of the four coherent Bell states. Furthermore, all the necessary operations for quantum computation, such as preparation of qubits and one-qubit and controlled two-qubit operations, are possible. The detection of the state of a vibrational mode in a Bell state is made possible by the combination of resonant and off-resonant interactions between the ion and some external fields. We show that our read-out scheme provides highly efficient discrimination between all the four Bell states. We extend this to a quantum register composed of many individually trapped ions. In this case, operations on two remote qubits are possible through a cavity mode. We emphasize that our remote-qubit operation scheme does not require a high-quality factor resonator: the cavity field acts as a catalyst for the gate operation.

Coherent and stochastic contributions of compound resonances in atomic processes: Electron recombination, photoionization, and scattering

In open-shell atoms and ions, processes such as photoionization, combination (Raman) scattering, electron scattering, and recombination are often mediated by many-electron compound resonances. We show that their interference (neglected in the independent-resonance approximation) leads to a coherent contribution, which determines the energy-averaged total cross sections of electron- and photon-induced reactions obtained using the optical theorem. In contrast, the partial cross sections (e.g., electron recombination or photon Raman scattering) are dominated by the stochastic contributions. Thus, the optical theorem provides a link between the stochastic and coherent contributions of the compound resonances. Similar conclusions are valid for reactions via compound states in molecules and nuclei.