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[en] STUDY OF POLARIZATION MODE DISPERSION COMPENSATION IN OPTICAL / [pt] ESTUDO DA COMPENSAÇÃO DA DISPERSÃO DOS MODOS DE POLARIZAÇÃO EM SISTEMAS ÓPTICOSLUIS CARLOS BLANCO LINARES 07 August 2003 (has links)
[pt] Neste trabalho é desenvolvido um modelamento matemático
para os elementos que compõem um sistema de compensação de
PMD de primeira ordem, visando obter alternativas de solução para
a metodologia de controle do sistema de compensação.
Um algoritmo de controle utilizando uma lógica
simplificada, diferente das encontradas em outros sistemas
de compensação, é desenvolvido.
Os resultados das simulações matemáticas, das diferentes
partes do sistema de compensação e do algoritmo de controle
desenvolvido, são comparados com resultados experimentais,
obtendo-se uma excelente concordância.
Um protótipo de um compensador de PMD de primeira ordem,
utilizando diferentes topologias de compensação, é
implementado e os resultados experimentais apresentados.
Os resultados experimentais obtidos demonstram que a
performance do protótipo desenvolvido é melhor que à obtida
com outros sistemas de compensação desenvolvidos por outros
grupos de pesquisa [22, 60]. / [en] In this work a mathematical model for the elements of the
first order compensation system is developed to obtain
alternative solutions of control methodology of the
compensator.
A control algorithm, using a simplified logic, different
from the ones found in other compensation systems, is
developed.
The mathematical simulations results of the implemented
model for different parts of the compensation system and of
the control algorithm are compared to the experimental
results showing good agreement.
A first order PMD compensation prototype is implemented,
using different compensation topologies. The experimental
results are presented, proving a better performance when
compared to the experimental results obtained by other
research groups [22, 60].
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"Phase-Correlation Based Displacemnt-Metrology" - Few InvestigationsDiwan, C Yogesh 07 1900 (has links) (PDF)
No description available.
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Extension du modèle de tracé de rayons vectoriels complexes et application à la caractérisation d'une particule non-sphérique / Extension of vectorial complex ray model and its application to the metrology of non-spherical particlesMa, Zelong 31 January 2018 (has links)
Cette thèse est dédiée à l'extension du Tracé de Rayons Vectoriels Complexes (TRVC) développé au laboratoire et son application à la caractérisation des particules non-sphériques. Dans divers domaines de recherche, tels que la mécanique des fluides et la combustion, nous devons mesurer les caractéristiques des particules. Parmi les différents types de techniques de mesure, la métrologie optique est largement utilisée grâce à sa précision et sa fiabilité. Cependant, la forme des particules est souvent considérée comme sphérique principalement à cause du manque de moyens pour prédire avec précision l'interaction de la lumière avec de grandes particules non-sphériques. TRVC a été développé pour répondre à ces besoins. Il est basé sur le modèle de rayons mais une amélioration radicale a été apportée dans ce nouveau modèle par l'introduction d'une nouvelle propriété dans la notion de rayons lumineux - la courbure de front d'onde. Dans cette thèse, le modèle est appliqué à réexaminer la théorie d'Airy. Il a été montré que TRVC prédit mieux les intensités et les positions des lobes secondaires dans les arcs-en-ciel d'une particule sphérique que la théorie d'Airy. Ensuite, TRVC est appliqué à l'étude des propriétés des arcs-en-ciel formés par les ellipsoïdes allongé et aplati. Il est montré que TRVC peut prédire analytiquement les positions et les intensités de lobes secondaires dans les arcs-en-ciel d’une particule sphéroïdale lorsqu’elle est éclairée par une onde plane dans le plan symétrique. Les pics dus à l'effet focal d'une particule sphéroïdale aplatie ont également été évalués analytiquement en utilisantle facteur de divergence de TRVC. Un système de mesure est aussi mis en place dans le laboratoire pour la diffusion de la lumière par des gouttes pendantes. Il a été montré que le rapport des intensités des deux premiers arcs-en-ciel est sensible à l'ellipticité d'un sphéroïde équivalent. Ceci ouvre un champ d'application potentiel pour caractériser la déformation d'une goutte pendante. / This thesis is dedicated to the extension of Vectorial Complex Ray Model (VCRM)developed in the laboratory and its application in the characterization of large nonspherical particles. In various research domains, such as the uid mechanics and the combustion field, we need to measure the characteristics of the particles. Among di_erent kinds of measurement techniques, the optical metrology is largely employed due to its advantage of being accurate, reliable and non-intrusive. However, in many optical techniques, the shape of the particles is assumed to be spherical. The main reason of this limit is due to the lack of theoretical model to describe with precision the interaction of light with large non-spherical particles. The Vectorial Complex Ray Model has been developed to reply this demand. It is based on the ray model but a radical improvement has been done by introducing a new property the wave front curvatures in the ray model. In this thesis, the model is firstly applied to reexamine the Airy theory. It is shown that even in the case of spherical particle VCRM predicts better the intensity and positions of supernumerary bows of rainbow than the Airy theory. Then VCRM is applied to investigate the properties of the rainbows formed by a spheroidal (prolate or oblate) particle. It is shown that VCRM can predict analytically the positions and the intensity of supernumerary bows and the peaks due to the focal effect when it is illuminated by a plane wave in the symmetrical plane.The theoretical research results have been also applied to the experimental characterization of a pendant drop. The intensity ratio of the two first orders of rainbow is shown sensible to the aspect ratio of the equivalent spheroid and it opens a potential to develop a measurement technique to characterize the deformation of pendant drop.
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Structural Color Production in Melanin-based Amorphous Colloidal AssembliesPatil, Anvay 05 June 2022 (has links)
No description available.
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Evaluation of the thermal stability of a low-coherence interferometer for precision surface profilometryTaudt, Ch., Baselt, T., Nelsen, B., Assmann, H., Greiner, A., Koch, E., Hartmann, P. 09 August 2019 (has links)
Manufacturing of precise structures in MEMS, semiconductors, optics and other fields requires high standards in manufacturing and quality control. Appropriate surface topography measurement technologies should therefore deliver nm accuracy in the axial dimension under typical industrial conditions. This work shows the characterization of a dispersion-encoded low-coherence interferometer for the purpose of fast and robust surface topography measurements. The key component of the interferometer is an element with known dispersion. This dispersive element delivers a controlled phase variation in relation to the surface height variation which can be detected in the spectral domain. A laboratory setup equipped with a broadband light source (200 - 1100 nm) was established. Experiments have been carried out on a silicon-based standard with height steps of 100 nm under different thermal conditions such as 293.15 K and 303.15 K. Additionally, the stability of the setup was studied over periods of 5 hours (with constant temperature) and 15 hours (with linear increasing temperature). The analyzed data showed that a height measurement of 97.99 ± 4:9nm for 293.15 K and of 101.43 ± 3:3nm for 303.15 K was possible. The time-resolved measurements revealed that the developed setup is highly stable against small thermal uctuations and shows a linear behaviour under increasing thermal load. Calibration data for the mathmatical corrections under different thermal conditions was obtained.
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Measurement of surface topographies in the nm-range for power chip technologies by a modified low-coherence interferometerTaudt, Ch., Baselt, T., Nelsen, B., Aßmann, H., Greiner, A., Koch, E., Hartmann, P. 29 August 2019 (has links)
This work introduces a modified low-coherence interferometry approach for nanometer surface-profilometry. The key component of the interferometer is an element with known dispersion which defines the measurement range as well as the resolution. This dispersive element delivers a controlled phase variation which can be detected in the spectral domain and used to reconstruct height differences on a sample. In the chosen setup, both axial resolution and measurement range are tunable by the choice of the dispersive element.
The basic working principle was demonstrated by a laboratory setup equipped with a supercontinuum light source (Δλ = 400 ̶ 1700 nm). Initial experiments were carried out to characterize steps of 101 nm on a silicon height standard. The results showed that the system delivers an accuracy of about 11.8 nm. These measurements also served as a calibration for the second set of measurements. The second experiment consisted of the measurement of the bevel of a silicon wafer. The modified low-coherence interferometer could be utilized to reproduce the slope on the edge within the previously estimated accuracy. The main advantage of the proposed measurement approach is the possibility to collect data without the need for mechanically moving parts.
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Two-dimensional low-coherence interferometry for the characterization of nanometer wafer topographiesTaudt, Ch., Baselt, T., Nelsen, B., Aßmann, H., Greiner, A., Koch, E., Hartmann, P. 30 August 2019 (has links)
Within this work a scan-free, low-coherence interferometry approach for surface profilometry with nm-precision is presented. The basic setup consist of a Michelson-type interferometer which is powered by a supercontinuum light-source (Δλ = 400 - 1700 nm). The introduction of an element with known dispersion delivers a controlled phase variation which can be detected in the spectral domain and used to reconstruct height differences on a sample. In order to enable scan-free measurements, the interference signal is spectrally decomposed with a grating and imaged onto a two-dimensional detector. One dimension of this detector records spectral, and therefore height information, while the other dimension stores the spatial position of the corresponding height values.
In experiments on a height standard, it could be shown that the setup is capable of recording multiple height steps of 101 nm over a range of 500 µm with an accuracy of about 11.5 nm. Further experiments on conductive paths of a micro-electro-mechanical systems (MEMS) pressure sensor demonstrated that the approach is also suitable to precisely characterize nanometer-sized structures on production-relevant components. The main advantage of the proposed measurement approach is the possibility to collect precise height information over a line on a surface without the need for scanning. This feature makes it interesting for a production-accompanying metrology.
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[en] CONTROL SYSTEM TO SUPPRESS GAIN DYNAMIC INSTABILITIES OF AN EDFA / [pt] SISTEMA DE CONTROLE PARA SUPRESSÃO DE INSTABILIDADES DINÂMICAS DE GANHO DE UM EDFADJEISSON HOFFMANN THOMAS 01 October 2003 (has links)
[pt] Objetivando suprimir as instabilidades dinâmicas de ganho
em um amplificador à fibra dopada com Érbio (EDFA), uma
nova configuração de laser em anel é apresentada e
demonstrada. Neste trabalho, analizamos os efeitos da
variação do nível de atenuação no laço de re-alimentação
sobre a resposta transitória do EDFA. Particularmente,
observamos as excursões de ganho experimentadas pelo canal
sobrevivente quando sete dentre oito canais da rede são
adicionados ou removidos, à exemplo do que ocorre em
sistemas WDM reais. Sob esta análise, avaliamos o
desempenho do sistema em suprimir as instabilidades
dinâmicas de ganho do EDFA. / [en] A new ring laser configuration to eliminate the gain
dynamic instabilities of an erbium doped fiber amplifier
(EDFA) is proposed and demonstrated. We examine the effect
of the attenuation level in the optical feedback path over
thetransient response of the EDFA. In particular, we look
at the transient gain excursions experienced by surviving
channel when seven of eight channels are added or dropped,
like in real WDM systems. Using this analysis as a guide, we
highlight the robustness of the approach and evaluate its
performance to EDFA gain stabilization.
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