Alouini, Mehdi
Overview
| Works: | 11 works in 13 publications in 2 languages and 10 library holdings |
|---|---|
| Roles: | Other, Opponent, Thesis advisor, Author |
Publication Timeline
.
Most widely held works by
Mehdi Alouini
Acquisition et extraction d'information des images polarimétriques actives by
Arnaud Bénière(
Book
)
2 editions published in 2009 in French and held by 2 WorldCat member libraries worldwide
Orthogonal State Contrast (OSC) imaging is an active polarimetric imaging mode which consists in illuminating the scene with a totally polarized light beam and analysing the backscattered light in two orthogonal states of polarization. This type of imaging provides additional contrast compared to classic intensity imaging systems. It arises a great interest in several domains such as remote sensing, biomedical imaging or vision through scattering medium. The goal of this thesis was to design a system and to characterize its performance in terms of acquisition capabilities and signal processing. We designed and tested a simple robust setup, which is able to acquire simultaneously both states of polarization. Thanks to this architecture the noise reaches fundamental limits set by detector noise, photon shot noise or spatial/temporal non-uniformity of the illumination. We demonstrated experimentally its benefit for imaging through turbulent medium. ln order to investigate the capabilities of the imaging mode, we proposed estimation algorithms depending on the predominant type of noise and characterized their performances thanks the Cramer-Rao lower bound. Then we addressed the performances of the system for target detection taking into account the non-uniformity of the illumination. Finally, we studied the maximization of the contrast in a polarimetric scalar imaging system. We proposed a method to optimize simultaneously the state of polarization of the illumination and the state of polarization of the analysis. It presents promising perspectives for the optimization of Mueller imaging systems
2 editions published in 2009 in French and held by 2 WorldCat member libraries worldwide
Orthogonal State Contrast (OSC) imaging is an active polarimetric imaging mode which consists in illuminating the scene with a totally polarized light beam and analysing the backscattered light in two orthogonal states of polarization. This type of imaging provides additional contrast compared to classic intensity imaging systems. It arises a great interest in several domains such as remote sensing, biomedical imaging or vision through scattering medium. The goal of this thesis was to design a system and to characterize its performance in terms of acquisition capabilities and signal processing. We designed and tested a simple robust setup, which is able to acquire simultaneously both states of polarization. Thanks to this architecture the noise reaches fundamental limits set by detector noise, photon shot noise or spatial/temporal non-uniformity of the illumination. We demonstrated experimentally its benefit for imaging through turbulent medium. ln order to investigate the capabilities of the imaging mode, we proposed estimation algorithms depending on the predominant type of noise and characterized their performances thanks the Cramer-Rao lower bound. Then we addressed the performances of the system for target detection taking into account the non-uniformity of the illumination. Finally, we studied the maximization of the contrast in a polarimetric scalar imaging system. We proposed a method to optimize simultaneously the state of polarization of the illumination and the state of polarization of the analysis. It presents promising perspectives for the optimization of Mueller imaging systems
Nouvelle stratégie de mesure d'ondes acoustiques par capteur à fibre optique distribué by
Guillaume Arpison(
)
1 edition published in 2021 in French and held by 1 WorldCat member library worldwide
For more than two decades, there has been growing interest for distributed acoustic sensing (DAS) using fiber optics, driven by the tempting prospect of exploiting the preexisting telecommunication fiber network in order to meet numerous applications (seismology, structural health monitoring, roadway, etc.). The major technological issue of this field is the achievement of a coherent and synchronized measurement between each virtual sensors of a same fiber. This should allow to identify and to classify several dynamic perturbations according to their vibrational signature along the cable. In this thesis, we are interested in the built of a DAS interrogator that is capable of addressing relatively high frequency acoustic applications compared to the state of art of the domain and with better spatial resolutions (less than a meter or even a centimeter).To do this, we develop a phase-sensitive optical frequency domain reflectometry (OFDR) system. This technology is based on the interference between a rapidly, linearly and continuously modulated optical wave and this same wave resulting from its global backscattering along the fiber length. The analysis of the radiofrequency spectrum obtained in phase and amplitude then allows going back to the signal seen at all the sensor positions. Spatial and time resolutions of the measurement are both conditioned by the quality of the modulated waveform that must be a priori as linear and stable as possible. However, we show in this work that stability and linearity of the frequency modulation can be digitally managed to some extent. Our DAS system combines three main building blocks: a laboratory solid-state laser, highly accordable and with reduced intrinsic nonlinearity (< 1%), an optoelectronic interferometric system and a numerical processing allowing both the correction of the frequency modulation and the obtaining of the sensor signals.We achieved to a DAS measurement spatially and temporally resolved over a fiber length of several kilometers where phase and frequency of the disturbance are detected. We finally quantify a sensitivity level for our interrogator and we propose a compared analysis of these interrogator performances for different tunable laser sources in order to identify limiting noise sources.To do this, we develop a phase-sensitive optical frequency domain reflectometry (OFDR) system. This technology is based on the interference between a rapidly, linearly and continuously modulated optical wave and this same wave resulting from its global backscattering along the fiber length. The analysis of the radiofrequency spectrum obtained in phase and amplitude then allows going back to the signal seen at all the sensor positions. Spatial and time resolutions of the measurement are both conditioned by the quality of the modulated waveform that must be a priori as linear and stable as possible. However, we show in this work that stability and linearity of the frequency modulation can be digitally managed to some extent. Our DAS system combines three main building blocks: a laboratory solid-state laser, highly accordable and with reduced intrinsic nonlinearity (< 1%), an optoelectronic interferometric system and a numerical processing allowing both the correction of the frequency modulation and the obtaining of the sensor signals.We achieved to a DAS measurement spatially and temporally resolved over a fiber length of several kilometers where phase and frequency of the disturbance are detected. We finally quantify a sensitivity level for our interrogator and we propose a compared analysis of these interrogator performances for different tunable laser sources in order to identify limiting noise sources
1 edition published in 2021 in French and held by 1 WorldCat member library worldwide
For more than two decades, there has been growing interest for distributed acoustic sensing (DAS) using fiber optics, driven by the tempting prospect of exploiting the preexisting telecommunication fiber network in order to meet numerous applications (seismology, structural health monitoring, roadway, etc.). The major technological issue of this field is the achievement of a coherent and synchronized measurement between each virtual sensors of a same fiber. This should allow to identify and to classify several dynamic perturbations according to their vibrational signature along the cable. In this thesis, we are interested in the built of a DAS interrogator that is capable of addressing relatively high frequency acoustic applications compared to the state of art of the domain and with better spatial resolutions (less than a meter or even a centimeter).To do this, we develop a phase-sensitive optical frequency domain reflectometry (OFDR) system. This technology is based on the interference between a rapidly, linearly and continuously modulated optical wave and this same wave resulting from its global backscattering along the fiber length. The analysis of the radiofrequency spectrum obtained in phase and amplitude then allows going back to the signal seen at all the sensor positions. Spatial and time resolutions of the measurement are both conditioned by the quality of the modulated waveform that must be a priori as linear and stable as possible. However, we show in this work that stability and linearity of the frequency modulation can be digitally managed to some extent. Our DAS system combines three main building blocks: a laboratory solid-state laser, highly accordable and with reduced intrinsic nonlinearity (< 1%), an optoelectronic interferometric system and a numerical processing allowing both the correction of the frequency modulation and the obtaining of the sensor signals.We achieved to a DAS measurement spatially and temporally resolved over a fiber length of several kilometers where phase and frequency of the disturbance are detected. We finally quantify a sensitivity level for our interrogator and we propose a compared analysis of these interrogator performances for different tunable laser sources in order to identify limiting noise sources.To do this, we develop a phase-sensitive optical frequency domain reflectometry (OFDR) system. This technology is based on the interference between a rapidly, linearly and continuously modulated optical wave and this same wave resulting from its global backscattering along the fiber length. The analysis of the radiofrequency spectrum obtained in phase and amplitude then allows going back to the signal seen at all the sensor positions. Spatial and time resolutions of the measurement are both conditioned by the quality of the modulated waveform that must be a priori as linear and stable as possible. However, we show in this work that stability and linearity of the frequency modulation can be digitally managed to some extent. Our DAS system combines three main building blocks: a laboratory solid-state laser, highly accordable and with reduced intrinsic nonlinearity (< 1%), an optoelectronic interferometric system and a numerical processing allowing both the correction of the frequency modulation and the obtaining of the sensor signals.We achieved to a DAS measurement spatially and temporally resolved over a fiber length of several kilometers where phase and frequency of the disturbance are detected. We finally quantify a sensitivity level for our interrogator and we propose a compared analysis of these interrogator performances for different tunable laser sources in order to identify limiting noise sources
Conception, mise en oeuvre et caractérisation d'un nouveau dispositif d'imagerie polarimétrique par fibre optique pour l'aide
au diagnostic médical in vivo in situ by
Jérôme Desroches(
)
1 edition published in 2010 in French and held by 1 WorldCat member library worldwide
The aim of this PhD thesis was to conceive and characterize a new fiber optic device for in vivo in situ endoscopic polarization imaging. The association of an endoscopic imaging technique with a polarization analysis process was made possible thanks to the use of a miniaturized Faraday rotator real-time comensates the birefringence of the optical fiber. This device allows to extract useful polarization parameters such as the phase delay induced by a target of interest of the degree of polarization of the light relected by this target. For the first time, polarization images were obtained through a flexible optical guide, in particular those of biological samples containing type I collagen (pork's tendon). These images allow to clearly discriminate healthy regions from spoiled ones, wich could potentially be pathological regions
1 edition published in 2010 in French and held by 1 WorldCat member library worldwide
The aim of this PhD thesis was to conceive and characterize a new fiber optic device for in vivo in situ endoscopic polarization imaging. The association of an endoscopic imaging technique with a polarization analysis process was made possible thanks to the use of a miniaturized Faraday rotator real-time comensates the birefringence of the optical fiber. This device allows to extract useful polarization parameters such as the phase delay induced by a target of interest of the degree of polarization of the light relected by this target. For the first time, polarization images were obtained through a flexible optical guide, in particular those of biological samples containing type I collagen (pork's tendon). These images allow to clearly discriminate healthy regions from spoiled ones, wich could potentially be pathological regions
Interférométrie hétérodyne moyen-infrarouge pour l'imagerie des environnements protoplanétaires by
Guillaume Bourdarot(
)
1 edition published in 2021 in English and held by 1 WorldCat member library worldwide
1 edition published in 2021 in English and held by 1 WorldCat member library worldwide
ETUDE THEORIQUE ET EXPERIMENTALE DES LASERS SOLIDES ER 3 + ET ND 3 + : APPLICATIONS DES LASERS BI-FREQUENCES AUX TELECOMMUNICATIONS
OPTIQUES ET HYPERFREQUENCES by
Mehdi Alouini(
Book
)
2 editions published in 2001 in French and held by 1 WorldCat member library worldwide
Nous explorons quelques aspects nouveaux des lasers solides mono-frequences et bi-frequences dopes aux terres rares. Nous nous interessons notamment a l'erbium dans les systemes complexes que sont les verres, mais qui presentent l'interet d'offrir une grande plage spectrale de gain. Tout d'abord, dans ce type de laser tout faisceau gaussien tem 0 0 induit un effet de lentille resonnant qui, associe a la diffraction, provoque des pertes resonnantes. Ceci conduit a des anomalies dans les caracteristiques de base d'un laser, comme la puissance de sortie d'un laser monomode ou le spectre d'un microlaser multimode. Grace a des montages originaux, nous avons pu explorer le caractere homogene de la raie de ce type de laser en mesurant le couplage non-lineaire entre deux modes. Ce couplage se revele constant et particulierement eleve pour l'erbium dans un verre : c = 0,85. En revanche, les termes de saturations croisees varient fortement avec la localisation spectrale des deux modes, mettant en evidence des structures spectrales inaccessibles par les methodes de spectroscopie usuelles. Nous mettons au point un laser bi-frequence mono-axe dont la qualite spectrale du battement, de l'ordre de 1 hz, est parfaitement adaptee pour realiser un oscillateur local dans la gamme des ghz. En outre, la separation spatiale des etats propres d'un laser er : yb : verre permet desormais d'atteindre des frequences de battement accordables dans la gamme des thz. Nous montrons, par ailleurs, que l'architecture bi-axe d'un tel laser peut mener au concept de frequence absolue-accordable. Le comportement dynamique des lasers a terres rares a deux etats propres est egalement explore. Parmi les nouveaux regimes predits puis observes, un regime impulsionnel
2 editions published in 2001 in French and held by 1 WorldCat member library worldwide
Nous explorons quelques aspects nouveaux des lasers solides mono-frequences et bi-frequences dopes aux terres rares. Nous nous interessons notamment a l'erbium dans les systemes complexes que sont les verres, mais qui presentent l'interet d'offrir une grande plage spectrale de gain. Tout d'abord, dans ce type de laser tout faisceau gaussien tem 0 0 induit un effet de lentille resonnant qui, associe a la diffraction, provoque des pertes resonnantes. Ceci conduit a des anomalies dans les caracteristiques de base d'un laser, comme la puissance de sortie d'un laser monomode ou le spectre d'un microlaser multimode. Grace a des montages originaux, nous avons pu explorer le caractere homogene de la raie de ce type de laser en mesurant le couplage non-lineaire entre deux modes. Ce couplage se revele constant et particulierement eleve pour l'erbium dans un verre : c = 0,85. En revanche, les termes de saturations croisees varient fortement avec la localisation spectrale des deux modes, mettant en evidence des structures spectrales inaccessibles par les methodes de spectroscopie usuelles. Nous mettons au point un laser bi-frequence mono-axe dont la qualite spectrale du battement, de l'ordre de 1 hz, est parfaitement adaptee pour realiser un oscillateur local dans la gamme des ghz. En outre, la separation spatiale des etats propres d'un laser er : yb : verre permet desormais d'atteindre des frequences de battement accordables dans la gamme des thz. Nous montrons, par ailleurs, que l'architecture bi-axe d'un tel laser peut mener au concept de frequence absolue-accordable. Le comportement dynamique des lasers a terres rares a deux etats propres est egalement explore. Parmi les nouveaux regimes predits puis observes, un regime impulsionnel
Analyse de la précision d'estimation de deux systèmes d'imagerie polarimétrique by
Valentine Wasik(
)
1 edition published in 2016 in French and held by 1 WorldCat member library worldwide
Polarimetric imaging allows one to estimate some characteristics of a medium which might not be revealed by standard intensity imaging. However, the measurements can be strongly perturbed by fluctuations that are inherent in the physical acquisition processes. These fluctuations are difficult to attenuate, for instance because of the fragility of the observed media or because of the inhomogeneity of the obtained images. It is then useful to characterize the estimation precision that can be reached. In this thesis, this question is addressed through two polarimetric imaging applications: polarized-resolved second-harmonic generation non-linear microscopy (PSHG) for the analysis of the structural organization of biomolecular objects, and polarimetric interferometric synthetic aperture radar imaging (PolInSAR) for the estimation of vegetation parameters. For the first application, the estimation precision in the presence of Poisson noise is characterized for any molecular assembly that presents a cylindrical symmetry. This study results in particular in a procedure to detect the measurements that do not lead to a required precision. For PolInSAR imaging, we analyze an acquisition system that is interesting for future spatial missions. In particular, the estimation precision of the vegetation height is studied in this context in the presence of speckle noise by relying on the analysis of the polarimetric contrast. A simple interpretation of the behavior of this acquisition system is obtained in the Poincaré sphere
1 edition published in 2016 in French and held by 1 WorldCat member library worldwide
Polarimetric imaging allows one to estimate some characteristics of a medium which might not be revealed by standard intensity imaging. However, the measurements can be strongly perturbed by fluctuations that are inherent in the physical acquisition processes. These fluctuations are difficult to attenuate, for instance because of the fragility of the observed media or because of the inhomogeneity of the obtained images. It is then useful to characterize the estimation precision that can be reached. In this thesis, this question is addressed through two polarimetric imaging applications: polarized-resolved second-harmonic generation non-linear microscopy (PSHG) for the analysis of the structural organization of biomolecular objects, and polarimetric interferometric synthetic aperture radar imaging (PolInSAR) for the estimation of vegetation parameters. For the first application, the estimation precision in the presence of Poisson noise is characterized for any molecular assembly that presents a cylindrical symmetry. This study results in particular in a procedure to detect the measurements that do not lead to a required precision. For PolInSAR imaging, we analyze an acquisition system that is interesting for future spatial missions. In particular, the estimation precision of the vegetation height is studied in this context in the presence of speckle noise by relying on the analysis of the polarimetric contrast. A simple interpretation of the behavior of this acquisition system is obtained in the Poincaré sphere
Conception et réalisation d'un endomicroscope polarimétrique de Mueller à fibre en vue d'une application à l'aide au diagnostic
médical in vivo by
Colman Buckley(
)
1 edition published in 2020 in French and held by 1 WorldCat member library worldwide
1 edition published in 2020 in French and held by 1 WorldCat member library worldwide
Noise in dual-frequency semiconductor and solid-state lasers by
Syamsundar De(
)
1 edition published in 2015 in English and held by 1 WorldCat member library worldwide
Les sources cohérentes de lumière émettant deux fréquences optiques avec une différence largement accordable dans le domaine radiofréquence et un fort degré de corrélation entre leurs fluctuations respectives peuvent être d'un grand intérêt pour de nombreuses applications telles que la photonique micro-onde, les horloges atomiques ultra stables, la physique atomique, la métrologie, etc. C'est le cas des lasers bifréquences émettant deux modes de polarisations linéaires croisées avec une différence de fréquence dans le domaine radiofréquence. Nous comparons les caractéristiques de telles sources bifréquences basées sur des lasers à semiconducteurs (VECSEL: vertical-external-cavity surface-emitting laser) ou des lasers à solide (notamment les solides dopés Nd3+ ou Er3+). Au-delà de la différence évidente entre les mécanismes de gain dans les lasers à semiconducteurs et dans les lasers à solide, le VECSEL bifréquence et le laser Nd:YAG bifréquence ne présentent pas la même dynamique. Le VECSEL bifréquence, comme pour un laser de classe A, a une dynamique dénuée d'oscillations de relaxation puisque la durée de vie des photons dans la cavité est beaucoup plus longue que celle de l'inversion de population. A l'opposé, le laser Nd:YAG bifréquence possède une dynamique présentant des oscillations de relaxation comme pour un laser de classe B, en vertu du fait que la durée de vie des photons dans la cavité est plus courte que celle de l'inversion de population. Dans cette thèse, nous explorons les mécanismes par lesquels cette dynamique, en plus du couplage non linéaire entre les deux modes, gouverne le bruit dans les lasers bifréquences. En particulier, nous analysons à la fois expérimentalement et théoriquement les propriétés spectrales des différents bruits (intensité, phase) ainsi que leurs corrélations dans le cas d'un VECSEL bifréquence de classe A et d'un laser Nd:YAG bifréquence de classe B. Enfin, un modèle de réponse linéaire de deux oscillateurs amortis couplés permet d'interpréter les résultats obtenus sur la corrélation entre ces différents bruits
1 edition published in 2015 in English and held by 1 WorldCat member library worldwide
Les sources cohérentes de lumière émettant deux fréquences optiques avec une différence largement accordable dans le domaine radiofréquence et un fort degré de corrélation entre leurs fluctuations respectives peuvent être d'un grand intérêt pour de nombreuses applications telles que la photonique micro-onde, les horloges atomiques ultra stables, la physique atomique, la métrologie, etc. C'est le cas des lasers bifréquences émettant deux modes de polarisations linéaires croisées avec une différence de fréquence dans le domaine radiofréquence. Nous comparons les caractéristiques de telles sources bifréquences basées sur des lasers à semiconducteurs (VECSEL: vertical-external-cavity surface-emitting laser) ou des lasers à solide (notamment les solides dopés Nd3+ ou Er3+). Au-delà de la différence évidente entre les mécanismes de gain dans les lasers à semiconducteurs et dans les lasers à solide, le VECSEL bifréquence et le laser Nd:YAG bifréquence ne présentent pas la même dynamique. Le VECSEL bifréquence, comme pour un laser de classe A, a une dynamique dénuée d'oscillations de relaxation puisque la durée de vie des photons dans la cavité est beaucoup plus longue que celle de l'inversion de population. A l'opposé, le laser Nd:YAG bifréquence possède une dynamique présentant des oscillations de relaxation comme pour un laser de classe B, en vertu du fait que la durée de vie des photons dans la cavité est plus courte que celle de l'inversion de population. Dans cette thèse, nous explorons les mécanismes par lesquels cette dynamique, en plus du couplage non linéaire entre les deux modes, gouverne le bruit dans les lasers bifréquences. En particulier, nous analysons à la fois expérimentalement et théoriquement les propriétés spectrales des différents bruits (intensité, phase) ainsi que leurs corrélations dans le cas d'un VECSEL bifréquence de classe A et d'un laser Nd:YAG bifréquence de classe B. Enfin, un modèle de réponse linéaire de deux oscillateurs amortis couplés permet d'interpréter les résultats obtenus sur la corrélation entre ces différents bruits
Diode laser 1.5 micron de puissance et faible bruit pour l'optique hyperfréquence. by
Mickael Faugeron(
)
1 edition published in 2012 in French and held by 1 WorldCat member library worldwide
This work focuses on the design, realization and characterization of high power, low noise 1.5 µm diode lasers for microwave applications and more particularly for high dynamic optical analog link for radar systems. The first part of this study deals with modeling and design of low internal losses DFB laser structures. These specific structures are called slab-coupled optical waveguide lasers, and are composed of a thick layer between the active layer and the substrate. The aim of this waveguide is to enlarge the optical eigenmode and to move the optical mode away from p-doped layers. The main difficulty was to find the good trade-off between laser static performances (optical power, efficiency) and dynamic performances (RIN and modulation bandwidth). We have succeeded in developing high efficiency (0.4 W/A), low noise (RIN ≈ 160 dB/Hz) DFB lasers with more than 150 mW and a 3 dB modulation bandwidth up to 7.5 GHz. We have then characterized our components on wide band and narrow band analog links. We have demonstrated state of the art gain links, dynamic and 1 dB compression power. In the L band (1-2 GHz) for example, we have obtained an optical link with a gain of 0.5 dB, a compression power of 21 dBm and a dynamic (SFDR) of 122 dB.Hz2/3.Finally we have applied the methodology and the design of slab-coupled optical waveguide structures to develop high power mode-locked lasers for ultra-short pulses generation and for optical and electrical comb generation. We have demonstrated narrow RF linewidth (550 Hz) lasers with very high power (continuous power > 400 mW and peak power > 18 W)
1 edition published in 2012 in French and held by 1 WorldCat member library worldwide
This work focuses on the design, realization and characterization of high power, low noise 1.5 µm diode lasers for microwave applications and more particularly for high dynamic optical analog link for radar systems. The first part of this study deals with modeling and design of low internal losses DFB laser structures. These specific structures are called slab-coupled optical waveguide lasers, and are composed of a thick layer between the active layer and the substrate. The aim of this waveguide is to enlarge the optical eigenmode and to move the optical mode away from p-doped layers. The main difficulty was to find the good trade-off between laser static performances (optical power, efficiency) and dynamic performances (RIN and modulation bandwidth). We have succeeded in developing high efficiency (0.4 W/A), low noise (RIN ≈ 160 dB/Hz) DFB lasers with more than 150 mW and a 3 dB modulation bandwidth up to 7.5 GHz. We have then characterized our components on wide band and narrow band analog links. We have demonstrated state of the art gain links, dynamic and 1 dB compression power. In the L band (1-2 GHz) for example, we have obtained an optical link with a gain of 0.5 dB, a compression power of 21 dBm and a dynamic (SFDR) of 122 dB.Hz2/3.Finally we have applied the methodology and the design of slab-coupled optical waveguide structures to develop high power mode-locked lasers for ultra-short pulses generation and for optical and electrical comb generation. We have demonstrated narrow RF linewidth (550 Hz) lasers with very high power (continuous power > 400 mW and peak power > 18 W)
Real-time imaging through fog over long distance by
Swapnesh Panigrahi(
)
1 edition published in 2016 in French and held by 0 WorldCat member libraries worldwide
L'imagerie à travers les milieux turbides comme le brouillard, les tissus, les colloïdes, etc. répond à plusieurs besoins de la vie courante. L'imagerie à travers de tels milieux diffusants est un défi auquel peuvent répondre les nouveaux systèmes d'imagerie, la théorie de l'information et l'étude des lois de transport de la lumière dans les milieux aléatoires. La thèse est divisée en deux parties adressant deux modalités d'imagerie différentes, à savoir : l'imagerie de contraste polarimétrique et l'imagerie modulée en intensité. Dans les deux cas, des systèmes d'imagerie en temps réel sont proposés et mis au point. Leurs performances sont évaluées à la fois théoriquement et expérimentalement. Dans la première partie de la thèse, une caméra polarimétrique à deux canaux instantanés conçue autour d'un prisme de Wollaston est utilisée pour imager de manière optimale une source de lumière polarisée noyée dans un brouillard. Une expérience en situation réelle a été mise en place à proximité du campus de Beaulieu à Rennes. La source est placée sur une tour de télécommunication située à plus d'un kilomètre du système imageant. Les données acquises dans diverses conditions météorologiques montrent que l'efficacité de cette caméra polarimétrique dépend de la corrélation du bruit de fond dans les deux images initiales. Ceci a été confirmé grâce à une analyse fondée sur la théorie de l'information qui montre que le contraste polarimétriques maximal est obtenu par une combinaison linéaire des deux canaux polarimétriques dont la pondération dépendant de la corrélation du bruit de fond dans les deux canaux. Un système de détection, intégrant cette représentation polarimétrique optimale, a été développé pour explorer de bout en bout les capacités offertes par l'imagerie polarimétrique à deux canaux à travers le brouillard. Ces études trouvent des applications directes dans le transport par temps dégradé, y compris pour l'aide à l'atterrissage d'aéronefs. Dans la même logique, la deuxième partie de la thèse porte sur l'apport de la modulation d'intensité plein champ pour imager les photons balistiques dans les milieux diffusants. En utilisant de concert la théorie de la diffusion et la théorie de l'information, nous avons pu montrer que, pour un budget de photons donné, il existait une fréquence de modulation minimale pour laquelle le filtrage de photons balistique devient efficace. Cette fréquence dépend des propriétés de diffusion du milieu intermédiaire et se trouve être dans la gamme du MHz en situation réelle. L'imagerie en temps réel à de telles fréquences étant un vrai défi, nous avons proposé un système de démodulation plein champ inédit basé sur l'utilisation d'un cristal électro-optique. Ce système d'imagerie, dont nous avons breveté le principe, est en mesure de démoduler avec une caméra standard une scène en temps réel et en plein champ à des fréquences de plusieurs MHz (voire GHz) sans synchronisation de phase. Un prototype de ce système a été développé permettant de confirmer qu'il était robuste, portable et rentable. Le travail présenté dans cette thèse ouvre la voie à la mise en œuvre de systèmes d'imagerie de pointe fonctionnant dans des situations réelles, allant de l'imagerie biomédicale, à la sécurité
1 edition published in 2016 in French and held by 0 WorldCat member libraries worldwide
L'imagerie à travers les milieux turbides comme le brouillard, les tissus, les colloïdes, etc. répond à plusieurs besoins de la vie courante. L'imagerie à travers de tels milieux diffusants est un défi auquel peuvent répondre les nouveaux systèmes d'imagerie, la théorie de l'information et l'étude des lois de transport de la lumière dans les milieux aléatoires. La thèse est divisée en deux parties adressant deux modalités d'imagerie différentes, à savoir : l'imagerie de contraste polarimétrique et l'imagerie modulée en intensité. Dans les deux cas, des systèmes d'imagerie en temps réel sont proposés et mis au point. Leurs performances sont évaluées à la fois théoriquement et expérimentalement. Dans la première partie de la thèse, une caméra polarimétrique à deux canaux instantanés conçue autour d'un prisme de Wollaston est utilisée pour imager de manière optimale une source de lumière polarisée noyée dans un brouillard. Une expérience en situation réelle a été mise en place à proximité du campus de Beaulieu à Rennes. La source est placée sur une tour de télécommunication située à plus d'un kilomètre du système imageant. Les données acquises dans diverses conditions météorologiques montrent que l'efficacité de cette caméra polarimétrique dépend de la corrélation du bruit de fond dans les deux images initiales. Ceci a été confirmé grâce à une analyse fondée sur la théorie de l'information qui montre que le contraste polarimétriques maximal est obtenu par une combinaison linéaire des deux canaux polarimétriques dont la pondération dépendant de la corrélation du bruit de fond dans les deux canaux. Un système de détection, intégrant cette représentation polarimétrique optimale, a été développé pour explorer de bout en bout les capacités offertes par l'imagerie polarimétrique à deux canaux à travers le brouillard. Ces études trouvent des applications directes dans le transport par temps dégradé, y compris pour l'aide à l'atterrissage d'aéronefs. Dans la même logique, la deuxième partie de la thèse porte sur l'apport de la modulation d'intensité plein champ pour imager les photons balistiques dans les milieux diffusants. En utilisant de concert la théorie de la diffusion et la théorie de l'information, nous avons pu montrer que, pour un budget de photons donné, il existait une fréquence de modulation minimale pour laquelle le filtrage de photons balistique devient efficace. Cette fréquence dépend des propriétés de diffusion du milieu intermédiaire et se trouve être dans la gamme du MHz en situation réelle. L'imagerie en temps réel à de telles fréquences étant un vrai défi, nous avons proposé un système de démodulation plein champ inédit basé sur l'utilisation d'un cristal électro-optique. Ce système d'imagerie, dont nous avons breveté le principe, est en mesure de démoduler avec une caméra standard une scène en temps réel et en plein champ à des fréquences de plusieurs MHz (voire GHz) sans synchronisation de phase. Un prototype de ce système a été développé permettant de confirmer qu'il était robuste, portable et rentable. Le travail présenté dans cette thèse ouvre la voie à la mise en œuvre de systèmes d'imagerie de pointe fonctionnant dans des situations réelles, allant de l'imagerie biomédicale, à la sécurité
Circuits intégrés photoniques sur InP pour la génération de signaux hyperfréquences by
Gaël Kervella(
)
1 edition published in 2016 in French and held by 0 WorldCat member libraries worldwide
This thesis deals with the microwave photonics context. We have implemented various opto- electronic solutions in order to realize a monolithically integrated microwave synthesizer which has a low noise and a wide tunability until millimeter-wave frequencies. The synthesizer is based on the integration of two InP DFB lasers, an optical coupler and a fast photodiode. In addition, an electro-optic modulator is also implemented on the chip in order to transmit data on the generated carrier. The performances obtained in terms of tunability and wireless data transmission proved consistent with the objectives. Thus, a tuning range of 0-110 GHz and a short distance wireless data transmission rate of 1 Gbit /s have been demonstrated, establishing our system to the state of the art for this type of fully integrated component. Phase noise and linewidth performances have however been disappointing. To solve this problem affecting the data rate we have investigated two ways of stabilizing the carrier frequency. The first, based on an electronic feedback loop (OPLL) has yet proved unsuccessful but allowed us to further explore the related issues. However, the second solution, based on a new system of optical cross injection and stabilization to an external electronic oscillator has filled our wishes. Indeed, the stabilization of the carrier frequency by this technique has demonstrated linewidth less than 30 Hz and a reduced phase noise to -90 dBc / Hz at 10 kHz for a given carrier at 90 GHz. Next to the first generation components, a second generation was developed to improve the intrinsic performances of the chip by remedying the limitations previously observed. Thus, a new cavity configuration was designed including longer lasers and high reflectivity integrated mirrors made by materials deep etching. Moreover, optimization of the photodiode structure was carried out to further improve the bandwidth. Such a source allows to consider the generation and modulation of low phase noise and widely tunable microwave signals on monolithically integrated components matching the compactness, reproducibility and high speed performances required by the telecom, defense and space industries
1 edition published in 2016 in French and held by 0 WorldCat member libraries worldwide
This thesis deals with the microwave photonics context. We have implemented various opto- electronic solutions in order to realize a monolithically integrated microwave synthesizer which has a low noise and a wide tunability until millimeter-wave frequencies. The synthesizer is based on the integration of two InP DFB lasers, an optical coupler and a fast photodiode. In addition, an electro-optic modulator is also implemented on the chip in order to transmit data on the generated carrier. The performances obtained in terms of tunability and wireless data transmission proved consistent with the objectives. Thus, a tuning range of 0-110 GHz and a short distance wireless data transmission rate of 1 Gbit /s have been demonstrated, establishing our system to the state of the art for this type of fully integrated component. Phase noise and linewidth performances have however been disappointing. To solve this problem affecting the data rate we have investigated two ways of stabilizing the carrier frequency. The first, based on an electronic feedback loop (OPLL) has yet proved unsuccessful but allowed us to further explore the related issues. However, the second solution, based on a new system of optical cross injection and stabilization to an external electronic oscillator has filled our wishes. Indeed, the stabilization of the carrier frequency by this technique has demonstrated linewidth less than 30 Hz and a reduced phase noise to -90 dBc / Hz at 10 kHz for a given carrier at 90 GHz. Next to the first generation components, a second generation was developed to improve the intrinsic performances of the chip by remedying the limitations previously observed. Thus, a new cavity configuration was designed including longer lasers and high reflectivity integrated mirrors made by materials deep etching. Moreover, optimization of the photodiode structure was carried out to further improve the bandwidth. Such a source allows to consider the generation and modulation of low phase noise and widely tunable microwave signals on monolithically integrated components matching the compactness, reproducibility and high speed performances required by the telecom, defense and space industries
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Related Identities
- Université Paris-Sud (1970-2019) Degree grantor
- Laboratoire Interdisciplinaire de Physique (Grenoble) Other
- Université de Limoges Degree grantor
- Goudail, François (1970-....). Thesis advisor
- Université Grenoble Alpes (2020-....). Degree grantor
- Pagnoux, Dominique (1960-....). Opponent Thesis advisor
- Bénière, Arnaud (1982-....). Author
- Université de Paris-Sud Faculté des sciences d'Orsay (Essonne) Other
- XLIM Other
- Perchoux, Julien (19..-....). Other