In this thesis, we studied chirp response and slow light properties in strained saturable Bragg reflector (SSBR). In the part of chirp response studying, we simulated the chirp response of SSBR of pulses with different chirps, and verified the results of related work. The trend of simulation was consistent with experimental result. Therefore firmly believing the broadening or compression ability of chirped incident pulse in SSBR, the pulse compression ability facilitates the mode-locking in laser cavity and generates more narrow pulse. In the studying of slow light properties in SSBR, a home-made pulse shaper system and a cross-correlator system were demonstrated. We control the chirp of the pulse by pulse shaper, and then pulse enter SSBR and reflect from SSBR, and measure the signal distribution in time domain by cross-correlator, finally we can analyze the properties of slow light of SSBR. We have demonstrated the slow light phenomenon was observed as central wavelength of incident pulse approach to resonance absorption of SSBR. In the aspect of chirp control, contrast with negative chirped incident pulse, slower group velocity with larger group delay for positive chirped incident pulse was observed. This could be attributing to absorption increasing which result from more efficient for creating carrier and less-sensitive to the carrier-scattering effect. In addition, we further study power dependence of slow light properties in SSBR under various incident chirps. Increasing group delay with power of incident pulse was performed. In addition, more group delay under saturation was also characterized and analyzed.

Network performance metrics such as delay variations and packet loss influence the performance of the network. As a consequence, the performance of applications on the network is also affected as most of the networked applications existing today are very much sensitive to the network performance. Therefore it is of utmost importance to test the intensity of such network level disturbances on the performance of applications. A network traffic shaper/emulator shapes the network traffic in terms of these performance metrics to test such applications in a controlled environment. Most of the traffic shapers existing today give the instantaneous step transition in delay and packet loss on network. In this work, we present time-controlled network traffic shaper, a tool that facilitates testing and experimentation of network traffic through emulation. It focuses on time variant behavior of the traffic shaper. A linear transition of delay and packet loss that is varying with respect to time may fits much better to the real network scenarios instead of an instantaneous step transition in delay and packet loss. This work illustrates the emulation capabilities of time-controlled network traffic shaper and presents its design architecture. Several approaches are analyzed to do the task and one of them is followed to develop the desired architecture of the shaper. The shaper is implemented in a small scenario and is tested to see whether the desired output is achieved or not. The shortfalls in the design of the shaper are also discussed. Results are presented that show the output from the shaper in graphical form. Although the current implementation of the shaper does not provide linear or exponential output but this can be achieved by implementing a configuration setting that is comprised of small transition values that are varying with respect to very small step sizes of time e.g. transitions on milli seconds or micro seconds. The current implementation of the shaper configuration provides the output with a transition of one milli second on every next second. / kami1219@gmail.com

In this thesis, a novel method for multi-pulse with equal chirp characteristics and more efficient THz generation through two photon absorption (TPA) are investigated and demonstrated. These are all the first time, for our best knowledge, odd multi-pulses generation and innovative approach for efficient THz through TPA are proposed and studied. By modulating the amplitude and phase of the spatial light modulator with the pulse shaper, the number of multi-pulses can be adjustable without the limitation of even number only. Meanwhile, the chirp properties of the generated pulses are with the same characteristics and tunable also. For the case with bandwidth of 10nm, the generated multi-pulses with equal chirps varying from -20000fs^2 to 20000fs^2 are demonstrated and the results have a good agreement with the theoretical estimation. We also discuss the number of the multi-pulses and inequalities of the amplitude of the pulses are limited by the spectral resolution of SLM within the pulse shaper. Regarding to efficient THz radiation, it can be generated more efficiently from a low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) antenna by taking into account the TPA induced photo-carrier in the photoconductor. A rate-equation-based approach using the Drude-Lorentz model taking into account the band-diagram of LT-GaAs is used for the theoretical analysis. The super-linear power dependent photocurrent clarifies the role of TPA. Previously unnoticed THz pulse features and anomalously increasing THz radiation power rather than saturation were observed. These are in good agreement with the theoretical predictions.

This thesis utilize pulse shaping in characterization of ultra-broad bandwidth laser pulse and multi-pulse generation. Using angle-dithering technique, time-integrating phase-matching bandwidth can be increased significantly even with a thin crystal. We also characterize the pulse by angle-dithered MIIPS( intrapulse interference phase scan ) technique. An addition advantage of using a thick crystal is increased signal strength. In addition, we provide a method to generate multi-pulses and proceed Michelson interferometeric autocorrelator by controlling the spectral amplitude and phase of the pulse. To compare with the past method, the efficiency was obtained from 33% to 80% , and the stability and time resolution of delay time can be improved. We expect this method applied to narrow-band frequency-tunable THz wave genetration will be better.

No description available.

Oversampled digital-to-analog converters typically employ an array of unit elements to drive out the analog signal. Manufacturing defects can create errors due to mismatch between the unit elements, leading to a sharp reduction in the effective dynamic range through the converter. Mismatch noise shaping is an established technique for alleviating these effects, but usually anchors the signal band to a fixed frequency location. In order to extend these advantages to tunable applications, this work explores a series of techniques that allow the suppression band of the mismatch noise shaping function to have an adjustable center frequency. The proposed techniques are implemented in hardware and evaluated according to mismatch shaping performance, latency and hardware complexity. / text

In diesem Beitrag wird die IDEA-Box MC (Industrial Digitalization in Education of Automation – Motion Control) und die damit realisierbaren Anwendungsmöglichkeiten und vermittelbaren Lerninhalte vorgestellt. Neben dem mechanischen Aufbau werden die unterschiedlichen Möglichkeiten und Methoden im Bereich der Positioniertechnik von mechatronischen Systemen, die sich heutzutage mit speicherprogrammierbaren Steuerungen realisieren lassen, vorgestellt. Dabei werden neben einfachen Rast-in-Rast Bewegungen von Einzelachsen, vor allem das resonanzfreie Positionieren von schwingungsfähigen Systemen und synchronisierten Mehrachssystemen im Kurvenscheibenverbund (integrierte und synchronisierte Robotik) aufgezeigt und beschrieben. Außerdem wird aufgeführt, dass mithilfe eines digitalen Zwillings kollisionsfreie Telemanipulation realisiert werden kann.

The aim of this study was to evaluate the efficacy of heat-treated nickel-titanium reciprocating instruments and complementary techniques in retreatment of flattened canals. Material and methods: Twenty-six mandibular incisors were prepared up to size 25/.08 rotary file and filled using the single-cone technique. Subsequently, the teeth were divided into 3 groups (n=12) according to retreatment procedures: Reciproc Blue: R25 and R40; ProDesign R: PDR 25/.06 and PDR 35/.05; WaveOne Gold: WOG Primary and WOG Medium. The apically extruded material was collected in microtubes and the volume (mm³) was measured by Micro-CT. After this, the specimens received complementary cleaning with XP-Endo Shaper, PUI and 60° oscillatory instrumentation with #30 Hedströem file. Micro-CT scans were performed before and after removing filling material. After quantification of the volume of remaining filling material, the teeth were sectioned and scanning electron microscopy (SEM) images of the cervical, middle and apical thirds were obtained with a 700X magnification, and evaluated by scores based on the amount of filling material in the surface of dentine walls. Results: No reciprocating instrument promoted complete removal of filling material. All systems showed extrusion, however, WOG25 presented the higher extrusion of material (P<.05). XP-Endo Shaper significantly reduced the amount of filling material in the apical and middle thirds (P<.05). In the SEM analysis, there was no statistical difference among the cleaning methods (P> .05). Conclusions: The reciprocating instruments studied did not promote complete removal of root canal filling materials. XP-Endo Shaper, used as a complementary instrument in retreatment, improved removal of filling material. / O objetivo deste estudo foi avaliar a eficácia de instrumentos reciprocantes em níquel-titânio tratados termicamente e métodos complementares no retratamento de dentes com raízes achatadas. Materiais e métodos: Trinta e seis incisivos inferiores foram preparados com instrumentos rotatórios até o diâmetro 25./08 e obturados pela técnica do cone único. Em seguida, os dentes foram divididos em 3 grupos (n=12) de acordo com os sistemas utilizados para desobturação no retratamento: Reciproc Blue: R25 e R40; ProDesign R: PDR 25./06 e PDR 35/.05; WaveOne Gold: WOG Primary e WOG Medium. O material extruído apicalmente foi coletado em microtubos e o volume (mm³) foi mensurado com Micro-CT. Na sequência, os espécimes receberam limpeza complementar com XP-Endo Shaper ou com irrigação passiva ultrassônica (PUI) ou com instrumentação com lima #30 Hedströem em movimento oscilatório. Escaneamentos em Micro-CT foram realizados antes e após a remoção do material obturador. Após quantificação do volume de remanescente de material obturador, os dentes foram seccionados e imagens com microscópio eletrônico de varredura (MEV), dos terços cervical, médio e apical, foram obtidas com aumento de 700X, e avaliadas através de escores baseados na quantidade de material obturador remanescente nas paredes dentinárias. Resultados: Nenhum instrumento reciprocante promoveu remoção completa do material obturador. Todos os sistemas demonstraram extrusão, no entanto, WOG25 proporcionou maior extrusão (P<.05). XP-Endo Shaper reduziu significantemente a quantidade de material obturador nos terços médio e apical (P<.05). Na análise da limpeza das paredes dentinárias, em MEV, não houve diferença estatística entre os métodos de limpeza (P>.05). Os instrumentos reciprocantes estudados não promoveram a remoção completa do material obturador. XP-Shaper, utilizado como instrumento complementar no retratamento, aumentou a remoção de material obturador.

The problem was to design and construct the necessary equipment to cut and fasten short stock end to end using finger-joints. The study was divided into five chapters: I contained the introduction to the problem; II was concerned with the design and construction of the equipment; III detailed the operation of the equipment; IV contained the presentation of the data; and V covered the summary and findings. The study concluded that the equipment could be constructed inexpensively, and would perform a useful service. Also, a student using waste wood salvaged through use of this equipment could expect a smaller bill for materials than if he purchased new wood.

En vue de la capture de réearrangements électroniques au sein d’une molécule ou au cours de réactions chimiques il est indispensable de développer un dispositif dont la résolution temporelle est attoseconde (as 1 as = 10−18 s). La voie naturelle est de rechercher des impulsions lumineuses dans cette gamme de durée. Leur fréquence centrale doit alors être dans la gamme UVX et couvrir plusieurs dizaines d’eVs. De plus, ses composantes fréquencielles doivent être synchronisées. Le processus de génération d’harmoniques d’ordre élevé (GHE) dans les gaz remplit ces exigences. Pendant ce processus, une impulsion laser de haute intensité est focalisée dans un jet de gaz, où son champ électrique courbe la barrière de potentiel d’un atome et permet l’ionisation tunnel d’un paquet d’ondes électronique (POE). Entrainé par le champ électrique du laser, le POE accélére et acquiert une énergie cinétique élevée. Dans le cas où il repasse au voisinage du coeur ionique cette énergie cinétique peut être émise sous la forme d’un photon UVX. Ces POE explorent la structure et la dynamique de l’ion dans un schéma d’auto-sonde: le POE émis à un instant donné revient lui même ultérieurement sonder l’ion. Plus précisément ce processus d’autosonde donne accès à la valeur complexe du dipôle de recombinaison moléculaire (DRM), lui-même determiné par les structures nucléaire et électronique de l’ion. Le dipôle de recombinaison, en rayonnant des harmoniques, encode ces caractéristiques dans l’amplitude, la phase et l’état de polarisation de l’émission harmonique. Grâce à la nature cohérente de la GHE nous pouvons mesurer ces trois paramètres.L’objectif de ma thèse de doctorat était double. En mettant en oeuvre des techniques avancées de caractérisation de l’amplitude, de la phase et de la polarisation des harmoniques nous avons dans un premier temps étudié la structure électronique de N2 et l’ionisation tunnel multi-canaux induite par le laser. Nous avons montré les reconstructions des plusieurs orbitals moléculaires et révélé la vibration nucléaire ultra-rapide en fonction des canaux d’ionisations. Dans un deuxième temps nous avons étudié la réflectivité et la dispersion de miroirs UVX à compensation de dérive de fréquence, fabriqués sur mesure. Ces miroirs autorisent la mise en forme temporelle d’une impulsion attoseconde, compriment la durée de l’impulsions où introduisent un TOD. Nous avons aussi proposé un nouveau façonneur d’impulsions. / To capture electronic rearrangements inside a molecule or during chemical reactions, attosecond (as, 1 as =10−18 s) time resolution is needed. To create a light pulse with this duration, the central frequency has to be in the XUV range and cover several tens of eVs. Moreover, the frequency components have to be synchronized. The so called High Harmonic Generation (HHG) in gases well suits this task. During this process a high intensity laser pulse is focused in a gas jet, where its electric field bends the potential barrier of an atom allowing an electron wave packet (EWP) to tunnel ionize. Following the electric field of the laser the EWP gets accelerated, gaining a large kinetic energy that may be released as a high energy (XUV) photon in the event of a re-collision with the ionic core. These recolliding EWP probe the structure and dynamics of the core in a self-probing scheme: the EWP, that is emitted by the molecule at a certain time, probes itself later. More precisely, this ”self-probing” scheme gives access to the complex valued recombination dipole moment (RDM) of the molecule which is determined by both the nuclear and electronic structure. The recombination encodes these characteristics into the spectral amplitude, phase and polarization state of the harmonic radiation emitted by the dipole. Due to the coherent nature of HHG it is possible to measure all these three parameters. Moreover, it is in principle possible through a tomographic procedure to reconstruct the radiating orbital.The objective of my thesis was two-fold. By implementing advanced characterization techniques of the harmonic amplitude, phase and polarization we studied i) the electronic structure of N2 and laser induced multi-channel tunnel ionization. We presented the reconstruction of molecular orbitals and revealed the ionization channel dependent ultrafast nuclear vibration. We also studied ii) the reflectivity and dispersion of recently designed chirped XUV mirrors that can shape the temporal profile of attosecond pulses. With these mirrors we could control the spectral phase over 20 eV and compensate the GDD of the harmonics or introduce a TOD. We also proposed a novel attosecond pulse shaper.