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Laser Nd3+:YVO4: dynamique et conduite optimale

Abstract : This work takes place within the general framework of the study of class B lasers dynamics. Three aspects are investigated: the generation of laser pulses with arbitrary shapes, the validation of laser models and the demonstration of "ratchet" effects in the laser dynamics.
First, we present two methods developed in order to generate pulses of arbitrary shape (symmetric triangle, gaussian, and camel-like pulse) in spite of the natural propensity of the laser to deliver the "secant-hyperbolic" pulses. In both cases Genetic Algorithms (GA) determines the optimal parameters of laser pumping. In the first method, this signal is built from elementary functions whereas for the second it results from a natural spline interpolation between collocation points given by GA.
The experimental and numerical tools developed (in particular the coupling of fast signal digitizing with real time processing) were used to determine the validity of the different models which are often proposed to describe the dynamics of class B lasers operating in monomode or biline regime. The temporal evolution of the laser intensity is compared with the calculated intensity given by the models by means of AG. This allows to identify the most relevant model and to determine the values of its parameter.
Our expertise in the laser behaviour permitted us to conduct a detailed study of a "surprising" dynamical effect due to the asymmetry of the pump modulation. Moreover, we have carried out the first experimental demonstration on a laser of a "ratchet" effect similar to that proposed by Feynman to extract energy from random motion.
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Submitted on : Wednesday, September 5, 2007 - 12:22:55 PM
Last modification on : Friday, March 26, 2021 - 10:30:03 AM
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Cristina-Elena Preda. Laser Nd3+:YVO4: dynamique et conduite optimale. Physique Atomique [physics.atom-ph]. Université des Sciences et Technologie de Lille - Lille I, 2007. Français. ⟨tel-00169859⟩

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