Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 56 for “"gaussian beam"”.
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Gaussian beam scattering from a deterministic rough metal surface
… method to the more general and important case of beam wave scattering by a deterministic rough metal surface.
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Excitation of an Optical Fiber by a Gaussian Beam
Made available in DSpace on 2014-12-10T19:07:27Z (GMT). No. of bitstreams: 1 7514148.pdf: 2177216 bytes, checksum: ad8f923a42479c4f7dfd44465c7a6105 (MD5) Previous issue date: 1975
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Seismological applications of boundary integral and Gaussian beam methods
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.
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Rough surface scattering under Gaussian beam illumination and the Kirchhoff approximation
… conductor (PEC) surface under illumination by a Gaussian beam using the Kirchhoff approximation is presented. The analysis assumes a source distribution which yields a Gaussian beam solution as a radiated field. This field is used to excite a current density on the surface using the Kirchhoff …
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Microcomb fabrication for high accuracy foil x-ray telescope assembly and vector Gaussian beam modeling
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.
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The Scintillation Index In Moderate To Strong Turbulence For The Gaussian Beam Wave Along A Slant Path
… work, an expression governing scintillation of a Gaussian beam along an uplink slant path valid in all regimes of turbulence is presented, as well as results for the limiting cases of a plane wave and a spherical wave.
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Effects Of Atmospheric Turbulence On The Propagation Of Flattened Gaussian Optical Beams
… on the coherence of an optical (laser) beam, interest has recently been shown in changing the beam shape to determine if a different power distribution at the transmitter will reduce the effects of the random fluctuations in the refractive index. Here, a model is developed for the field …
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Propagation of Gaussian Beams Through a Modified von Karman Phase Screen
Gaussian beam propagation through discrete phase screens and an extended random media has been studied extensively over the last four decades. In this thesis, we numerically examine the effects of a discrete phase screen during Gaussian beam propagation on the scintillation index for a single beam …
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The Design and Optimisation of Quasioptical Telescopes
… used to determine the phase centre of the beam from lens antennas are described, and use is made of the same optimisation techniques as for the MBI and ALMA work. As the beams propagating in these systems can be analysed accurately using the paraxial approximation, Gaussian Beam Mode …
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Electromagnetic Analysis of Horn Antennas in the Terahertz region
… on a scattering matrix approach to describe beam propagation in both the forward and backward direction is applied to the analysis of conical and pyramidal horn antenna both single and multi-moded, in particular the multi-moded pyramidal horn antenna array of the SAFARI instrument - a far …
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Design and Analysis of Quasioptical Components for use in Astronomical Telescopes
This thesis describes the use of Gaussian beam modes (GBM) and physical optics (PO) to design and analyse astronomical telescope systems operating at millimetre and submillimetre wavelengths. The techniques are applied to a proposed re-design of the 3 mm channel of the 20 m Onsala Space Observatory …
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Optical Binding Phenomena: Observations and Mechanisms
… interpret experimental results in evanescent and Gaussian beam traps, and to develop simple, intuitive explanations for the observed phenomena. Novel trapped states are reported, that do not conform to the symmetry of the underlying trap. A common theme throughout this thesis is the "emergent'' …
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Experimental study of a high efficiency step-tunable MW gyrotron oscillator
… efficiency and provides a high quality output beam to minimize system size, maximize reliability and avoid additional losses in external systems. This thesis presents the experimental study of such a gyrotron designed to operate at MW power levels and whose initial 110 GHz operation was …
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Modal Analysis of Millimetre-wave and Terahertz Imaging Systems
… field calculation using orthogonal Gaussian beam modes within the context of far-infrared imaging systems. Laguerre and Hermite-Gaussian modes have been frequently reported in the analysis of paraxial millimetre-wave propagation in astronomical optical systems. Here the method of …
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Analysis of multifrequency interferometry in a cylindrical plasma
… project. Standard data analysis based on a thin beam model neglecting refraction yields inconsistent electron densities and density profiles for different frequencies. This work focuses on the development of a model for the wave propagation through cylindrical plasmas when the plasma radius is on …
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Design and Analysis of Quasioptical Components for use in Terahertz Optics and Future CMB Missions
… (Gradient Index) lens was analysed using GBM (Gaussian Beam Mode) theory and PO (Physical Optics). This thesis also includes the work the author did as part of an international team of 16 students to design a candidate ESA mission. The final chapter, therefore, concerns itself with “Geophysics …
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Confinement and Tracking of Brownian Particles in a Bessel Beam Standing Wave
… we used an axicon-generated, zeroth-order Bessel beam standing wave whose parameters were adjusted to allow tight axial confinement and loose transverse confinement of microscopic-sized particles in the central maximum of the Bessel beam. We chose a Bessel beam because its unique non-diffracting …
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Transonic thermal blooming
… for the density perturbations within a laser beam at a Mach number of precisely unity is given. For a Gaussian beam with an intensity of 3.333xl0^7 watts/m^2 and an atmospheric absorption of 8.0xlO^-7 cm^-l the maximum fractional density perturbation is 1.028xlO^-6. The transonic thermal …
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Compressible Hydrodynamics of Few Body Optical Vortices
… generated holograms for producing vortex beams. Procedures for generating effective holograms and efficiently measuring vortex beams include a novel colinear phase-shifting digital holography technique using composite holograms that enables both amplitude and phase measurement of optical …
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A novel wideband 140 GHz gyrotron amplifier
… confocal waveguide using a gyrating electron beam. The electromagnetic theory, interaction theory, design processes and experimental procedures have been described in detail. The experiment has produced over 820 W peak power, 34 dB linear gain, and a -3 dB bandwidth of over 1.5 GHz (1.1%) from …
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