Author: Ilaria Gianani
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Category :
Languages : en
Pages :

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Author: Matthew Murray Springer
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Languages : en
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The propagation of ultrashort femtosecond laser pulses in linear dielectric materials is determined in the time, space, and frequency domains by linear Maxwell optics through dispersion and diffraction. For intense pulses, pulse propagation is additionally modified by nonlinearities in the medium such as the optical Kerr effect, plasma generation, and self-phase modulation. In this work we report the results of several experiments on the propagation of ultrashort pulses. In the linear regime, we characterize the temporal evolution of an ultrashort pulse during propagation through a linear dielectric under anomalous dispersion. Under these conditions the pulse evolution departs from the group velocity and group delay dispersion approximations, which leads to the formation of optical precursors. We describe an experiment which observes the propagation of optical precursors in a bulk condensed-matter dielectric. We generate ultrashort laser pulses and propagate the pulses through a bulk dye with an absorption resonance turned to the center wavelength of the femotsecond pulse. The pulse is then characterized in the time domain before and after propagation. Through numerical simulation we verify that the behavior of the precursors in the temporal pulse profille corresponds with the classical model. Under very high intensity laser pulses, the nonlinearities induced by the propagation of the intense ultrashort pulse produce changes in the complex refractive index of the nonlinear material. We report the results of experiments involving time-resolved imaging of the propagation of ultrashort pulses in dielectric materials. We experimentally observe and characterize these effects through a weak-probe imaging effect which directly measures the nonlinearity in a time-resolved manner. In these experiments an intense femtosecond laser pulse is propagated in a nonlinear intensity regime while an unfocused low-intensity femtosecond pulse is used as to probe the nonlinear pulse. We use this technique to characterize femtosecond pulses in air and liquid, especially in the regime of optical filamentation. We subsequently calculate parameters such as the plasma density, the transverse extent, and the instantaneous refractive index within the femtosecond laser fillament under conditions which are not accessible through most standard pulse measurement techniqes. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151868

Author: Steven P. Jensen
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Category :
Languages : en
Pages : 230

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Author: Ming Liu
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Category :
Languages : en
Pages : 71

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Author: Ellen M. Kosik
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Category :
Languages : en
Pages : 262

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Author: Wouter Kornelis
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Category :
Languages : en
Pages : 123

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Author: Victor C. Wong
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Category :
Languages : en
Pages : 286

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Author: Aleksandr S. Radunsky
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Category :
Languages : en
Pages : 91

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"Over the past several decades ultrafast laser science and technology has evolved into an extensive and diverse yet still one of the most rapidly growing and developing areas of optics. This evolution has been one of mutual interdependence. Each current generation of technological innovations not only solves the specific problems it was designed for, but uncovers new application opportunities and enables the exploration of new basic research areas. In turn, these new challenges will give rise to the next generation of technological improvements born of the currently existing technologies and the advances in fundamental scientific knowledge and understanding. Ultrashort pulse characterization has always been an essential part of this ultrafast optics evolution. The thesis makes yet another contribution to it by describing the principle, design, construction, development and operation of a novel interferometric ultrashort pulse characterization device. It consists of a new implementation of spectral-shearing interferometry for reconstructing the electric field of ultrashort pulses, requiring only a single optical element to encode the temporal field of the pulse under test. The technique relies on an asymmetric group velocity matching type II sum frequency generation process in a single long nonlinear crystal. We analyze the performance of the device for a wide range of experimentally available input pulse parameters. The device - potential building block for the future generations of ultrashort diagnostics - proves a practical, elegant, compact, robust, and sensitive option for complete amplitude and phase ultrashort pulse characterization. As the femtosecond systems of increasingly larger bandwidth become a widespread reality, the detrimental effects of dispersion require careful consideration. Dispersive pulse distortion degrades longitudinal resolution of broadband interferometric imaging methods such as optical coherence tomography and lowcoherence interferometry. We address the issue with a novel signal processing dispersion compensation method. This numerical technique improves the axial resolution without a priori knowledge of the material dispersive properties of the sample under consideration. The dispersion compensation is based on the generalized temporal fourth order field autoconvolution function computed from the readily available experimental interferometric scans and has an intuitive depiction in the time-frequency phase-space via the Wigner distribution function formalism"--Page viii-ix.

Author: Christian Thomsen
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ISBN:
Category : Laser pulses, Ultrashort
Languages : en
Pages : 49

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Author: Chester Anthony Murley
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Languages : en
Pages :

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