No description available.

Raman biosensors are appealing for many biomedical applications, due to their accuracy and speed. In addition, Raman microscopy is a non-labeled imaging technique that offers chemical contrast based on Raman vibrational frequencies. However, the weak Raman signal represents a significant obstacle to using Raman in biological applications. The objective of my PhD research, presented in this thesis, is to enhance the Raman signal, thereby enabling it to be used in a wide variety of biomedical applications. More specifically, the research focuses on two different Raman signal enhancement techniques. The first is to improve the Raman signal using hollow-core photonic crystal fibers; this enhanced the Raman signal of ethanol 40 times. The second approach is by generating a coherent anti-Stokes Raman scattering (CARS) signal. We demonstrated CARS microscopy of myelin (lipid-rich) structures using a single femtosecond Ti:sapphire laser, and a photonic crystal fiber (PCF) with two closely lying zero dispersion wavelengths (ZDWs). Generating low noise supercontinuum (Stokes beam) out of two closely lying ZDW PCFs, enabled us to perform fast data acquisition (84 μs per pixel) CARS imaging using a homebuilt microscope. However, the application of this fiber is often limited to CARS imaging of molecular species with vibrations at wavenumbers ≥ 2000 cm−1 Raman shift. In addition, as it is not a polarization maintaining fiber, it cannot be used for polarization CARS microscopy. A polarization-maintaining PCF with two far-lying zero dispersion wavelengths offers important advantages for polarization CARS microscopy, and for CARS imaging in the fingerprint region. This PCF, though commercially available, has had limited use for CARS microscopy in the C-H bond region. The main problem is that the supercontinuum from this fiber is typically noisier than that from a standard PCF with two closely-lying zero dispersion wavelengths. To overcome this, we determined the optimum operating conditions for generating a low-noise supercontinuum out of a PCF with two far-lying zero dispersion wavelengths, in terms of the input parameters of the excitation pulse. We measured the relative intensity noise (RIN) of the Stokes and the corresponding CARS signal, as a function of the input laser parameters in this fiber. We demonstrated that the results of CARS imaging using this alternate fiber are comparable to those achieved using the standard fiber for input laser pulse conditions of low average power, narrow pulse width with a slightly positive chirp, and polarization direction parallel to the slow axis of the selected fiber. Finally, we demonstrated a novel fiber-delivered, portable, multimodal CARS exoscope, for minimally invasive in-vivo imaging of tissues. The device was based on a micro-electromechanical system-scanning mirror and miniaturized optics, and light delivery by photonic crystal fibre. A single Ti:sapphire femtosecond laser approach is used to produce CARS and two photon excitation fluorescent and second harmonic generation images of different samples using the new setup. The high resolution and distortion-free images achieved with various samples, particularly in the reverse direction (epi), successfully demonstrate proof of concept, and paves the way to minimally or non-invasive in vivo imaging. Moreover, combining this novel endoscope with a portable femtosecond fiber laser will accelerate delivering multimodal nonlinear imaging endoscopy/microscopy to clinical bed-side applications.

This work deals with the transmission of optical radiation modulated by a radio frequency signal through an optical fiber. Furthermore, it describes the principles of communication and area coverage. It points out the practical use of components located in the communication chain of this system. Explains the functionality of the properties and the division of individual components. It introduces the benefits and limitations of this system. It further describes the creation of a topology suitable for laboratory measurement of RoF technology. Provides experimental measurement of C-band parameters. Indicates the possible use of RoF technology using a wireless optical link. A part of the work is also a sample laboratory protocol.

L’objectif de ce travail de thèse est d’étudier des lasers semi-conducteur issus de la plateforme d’intégration III-V sur Si et présentant un faible bruit d’intensité relatif (RIN) pour le transport de signaux RADAR par voie optique. Nous cherchons à obtenir des lasers de comportement dynamique dit de «Classe A», i.e. avec une réponse dynamique sans oscillations de relaxation. Dans ce cas, il a été précédemment montré qu’un tel comportement dynamique présente un RIN limité au bruit de grenaille sur une large bande de fréquences et est obtenu quand la durée de vie des photons dans la cavité est grande devant la durée de vie des porteurs dans la zone active. La plateforme photonique sur silicium est alors intéressante car elle permet de réaliser des cavités longues grâce aux guides optiques offrant de faibles pertes de propagation, i.e. de l’ordre du dB/cm. En première approche, nous avons étudié des lasers dont la cavité de longueur centimétrique est composée d’une partie active fournissant le gain optique et d’une partie passive composée de guide en silicium à faibles pertes de propagation. Nous avons proposé différentes optimisations des pertes optiques intra-cavité ainsi que différentes solutions de filtrage spectral à grande finesse nécessaire à une oscillation laser monomode. La seconde approcheétudiée repose sur le filtrage du RIN d’un laser hybride de longueur millimétrique en exploitant les effets de saturation du gain optique dans un amplificateur optique à SC (SOA). Nous avons présenté un modèle décrivant les différents mécanismes altérant le bruit du laser amplifié par un SOA. Une étudeexpérimentale a permis de mettre en évidence la réduction du RIN d’un laser hybride III-V sur silicium, allant jusqu’à 15 dB pour des fréquences allant jusqu’à quelques GHz. La dernière approche explorée dans cette thèse repose sur la conception de lasers DFB hybride III-V sur silicium à très haut facteur de qualité. L’utilisation d’un réseau de Bragg à pas variable permet de réduire les pertes radiatives, usuellement importantes dans les lasers DFB, et d’obtenir une cavité de facteur de qualité de l’ordre de quelques millions. Un premier composant réalisé présente un facteur de qualité de 65 000. / The objective of the present thesis is to investigate new laser architectures with low Relative Intensity Noise (RIN) using the Silicon Photonics integration platform. We intend to reach “class-A” dynamics, in which relaxation oscillations are eliminated. In this conditions, lasers with class-A dynamics exhibit shot-noise limited RIN over a wide frequency bandwidth, typically from 100 MHz to 20 GHz. Such behaviour can be obtained with high-Q laser cavities, i.e with long cavities or with ultra-low losses cavities. The silicon photonics platform is a good candidate for the desired dynamical behaviour as it makes possible the implementation of long cavities (ten’s of cm) based on low losses silicon waveguides (dB/cm). Three different approaches have been considered in the present work. In the first approach, we have developed centimetre long lasers, consisting of an active section providing the optical gain coupled to a passive section made with low losses silicon waveguides. We proposed different approaches to optimize the intra-cavity optical losses, and different architectures of high finesse optical filters allowing simultaneously single-mode operation and high side mode suppression. The second approach consists on filtering the laser RIN by taking advantage of the coherent population oscillations effects in a SC Optical Amplifier (SOA). We proposed a model for describing the different mechanisms altering the RIN of the amplified laser. We demonstrated 15 dB RIN reduction for frequencies up to a few GHz, using a hybrid III-V on Si laser and a “classical” SOA. The last approach explored in the present thesis is based on the use of hybrid III-V on silicon DFB lasers with a high quality factor. Using Silicon Bragg grating with a variable pitch can reduce the radiative losses, usually important in DFB lasers. In this case, we can obtain optical cavities with few millions quality factor, leading to few ns photon lifetime. We realize a first design of Si Bragg grating with a Q factor of 65 000.

No description available.

Uma sessão de exercício aeróbio provoca queda da pressão arterial (PA) e aumento da freqüência cardíaca (FC) pós-exercício. Diversos fatores, como a massa muscular, a intensidade e o gasto energético total do exercício podem influenciar esta resposta. Este estudo verificou as respostas pós-exercício da PA, da FC e de seus mecanismos, avaliando a influência dos fatores citados. Vinte e quatro jovens submeteram-se a quatro sessões: controle(C); exercício com um membro inferior (mmii) em 50% do VO2pico(E1); exercício com dois mmii em 50% do VO2pico (E2); e exercício com dois mmii com a mesma potência de E1(E2/1). As PA sistólica (PAS), média (PAM) e diastólica (PAD), o débito cardíaco (DC), a resistência vascular periférica (RVP), o volume sistólico (VS), a FC e a modulação autonômica cardíaca foram medidos. Após o exercício, a PAS e o DC diminuíram e a RVP aumentou em E2. A PAD e PAM não se alteraram. A FC aumentou e o VS e o componente de alta freqüência da variabilidade da FC diminuíram em E1 e E2 (maior em E2). Concluindo: o exercício aeróbio promove hipotensão pós-exercício, devido à queda do DC pela redução do VS. O gasto energético total do exercício é o principal determinante desta resposta. A FC permanece elevada pós-exercício devido ao retardo da reativação vagal. A intensidade e o gasto energético do exercício são os principais determinantes desta resposta / A single bout of aerobic exercise reduces blood pressure (BP) and increases heart rate (HR) during the recovery period. Many factors, such as exercise intensity, muscle mass and total energy expenditure might influence this response. This study verified post-exercise responses of BP, HR and their mechanisms, evaluating the influence of previous factors. Twenty-four subjects underwent four sessions: control (C); exercise with one leg at 50% of VO2peak (E1); exercise with two legs at 50% of VO2peak (E2); and exercise with two legs and the same workload employed in E1 (E2/1). Systolic, mean, and diastolic BPs (SBP, MBP, DBP), systemic vascular resistance (SVR), cardiac output (CO), stroke volume (SV), HR, and cardiac autonomic modulations were measured before and after interventions. After exercise, SBP and CO decreased, while SVR increased in E2. DBP and MBP did not change. HR increased, while SV and the high frequency band of HR variability decreased in E1 and E2 (more in E2). In conclusion: aerobic exercise produced post-exercise hypotension by a decrease in CO, via a decrease in SV. This response is determined by the exercise total energy expenditure. HR is elevated after exercise due to a delay in the restoration of vagal activity to the heart. Exercise intensity and total energy expenditure influence this response. Key-words: aerobic exercise, muscle mass, total energy expenditure, relative intensity, blood pressure, heart rate, autonomic modulation

Uma sessão de exercício aeróbio provoca queda da pressão arterial (PA) e aumento da freqüência cardíaca (FC) pós-exercício. Diversos fatores, como a massa muscular, a intensidade e o gasto energético total do exercício podem influenciar esta resposta. Este estudo verificou as respostas pós-exercício da PA, da FC e de seus mecanismos, avaliando a influência dos fatores citados. Vinte e quatro jovens submeteram-se a quatro sessões: controle(C); exercício com um membro inferior (mmii) em 50% do VO2pico(E1); exercício com dois mmii em 50% do VO2pico (E2); e exercício com dois mmii com a mesma potência de E1(E2/1). As PA sistólica (PAS), média (PAM) e diastólica (PAD), o débito cardíaco (DC), a resistência vascular periférica (RVP), o volume sistólico (VS), a FC e a modulação autonômica cardíaca foram medidos. Após o exercício, a PAS e o DC diminuíram e a RVP aumentou em E2. A PAD e PAM não se alteraram. A FC aumentou e o VS e o componente de alta freqüência da variabilidade da FC diminuíram em E1 e E2 (maior em E2). Concluindo: o exercício aeróbio promove hipotensão pós-exercício, devido à queda do DC pela redução do VS. O gasto energético total do exercício é o principal determinante desta resposta. A FC permanece elevada pós-exercício devido ao retardo da reativação vagal. A intensidade e o gasto energético do exercício são os principais determinantes desta resposta / A single bout of aerobic exercise reduces blood pressure (BP) and increases heart rate (HR) during the recovery period. Many factors, such as exercise intensity, muscle mass and total energy expenditure might influence this response. This study verified post-exercise responses of BP, HR and their mechanisms, evaluating the influence of previous factors. Twenty-four subjects underwent four sessions: control (C); exercise with one leg at 50% of VO2peak (E1); exercise with two legs at 50% of VO2peak (E2); and exercise with two legs and the same workload employed in E1 (E2/1). Systolic, mean, and diastolic BPs (SBP, MBP, DBP), systemic vascular resistance (SVR), cardiac output (CO), stroke volume (SV), HR, and cardiac autonomic modulations were measured before and after interventions. After exercise, SBP and CO decreased, while SVR increased in E2. DBP and MBP did not change. HR increased, while SV and the high frequency band of HR variability decreased in E1 and E2 (more in E2). In conclusion: aerobic exercise produced post-exercise hypotension by a decrease in CO, via a decrease in SV. This response is determined by the exercise total energy expenditure. HR is elevated after exercise due to a delay in the restoration of vagal activity to the heart. Exercise intensity and total energy expenditure influence this response. Key-words: aerobic exercise, muscle mass, total energy expenditure, relative intensity, blood pressure, heart rate, autonomic modulation

Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.