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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 57 for “"beam quality"”.
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Theoretical Study of Laser Beam Quality and Pulse Shaping by Volume Bragg Gratings
… study theoretically various definitions of laser beam width in a given cross-section. Quality of the beam is characterized by the dimensionless beam propagation products (?x???_x)?? , which are different for each of the 21 definitions. We study six particular beams and introduce an …
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Enhanced beam quality and polarization stability in oxide-confined Vertical-Cavity Surface-Emitting Lasers via anti-phase optical coatings and disorder-defined apertures
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2027-05-01
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Non-uniform emission studies of a magnetron injection gun
… non-uniformity of the MIG gun; Simulation of the beam quality of the MIG gun using MICHELLE 3-D, the first simulation of a MIG electron beam with azimuthal non-uniformity; Benchmarking the MICHELLE 3-D code to other established gun optics codes; Evaluation of the effects on the velocity spread and …
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An overview of laser operation and modelocking of a vertical external cavity surface emitting laser (VECSEL)
… features are high power, diffraction limited beam quality, intra-cavity frequency doubling, tunability, and ultrashort pulses generated from passive mode-locking. In this work, we give a brief overview of the VECSEL structure, previous VECSEL literature, how lasing in a VECSEL works, and how …
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System characterisation of a full body slit scanning radiography machine : theory and experiment
… NPS were compared to measure values of the RQA7 beam quality described in IEC 6222-1. The effect on Detector DQE of various system parameters such as coupling efficiency, CCD noise and pixel binning was quantified. Also detector performance for varous thicknesses of Gd2O2S:Tb screens were …
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Electron Beam Diagnostic at the ELBE Free Electron Laser
… to generate electromagnetic radiation as well as beams of secondary particles. The figure below shows the layout of the facility. ELBE is based on a superconducting electron linac. The linac consists of two accelerating modules and uses TESLA type nine-cell niobium cavities, two cavities in each …
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Study of the physics of the power-scaling of end-pumped solid-state laser sources based on Nd:YVO<sub>4</sub>
… achieved with 5W of output achieved, with the beam remaining diffraction limited. The prospects for further power scaling are investigated and it was shown that the limit to power scaling via amplifiers is the eventual beam quality degradation that will be suffered as the signal beam passes …
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Coherent laser arrays from bottom-surface vertical-cavity surface-emitting lasers
… (VCSELs) are among the best choices for high beam quality semiconductor lasers. By designing a VCSEL array for uniform current injection and having the output coupler on the substrate side of the laser cavity, the laser will more easily operate in the fundamental Gaussian mode. This type of …
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A novel few-cycle optical source in the mid-infrared
… 100MW, at a 1kHz repetition rate, with excellent beam quality. The system was based on adiabatic difference frequency generation in an aperiodically polled lithium niobate crystal of an amplified, mode-locked Ti:Sapphire laser system.
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EXTRACTION AND DIAGNOSTIC LINES FOR A LINAC-BASED CARBON ION MEDICAL FACILITY
… of hadron therapy, capable of producing high quality, pulsed beams at high repetition rates. The application of linacs to carbon ion therapy could improve its reliability, efficiency, and compactness. Although a complete carbon ion linac is still conceptual, a carbon ion pre-injector is under …
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Room temperature and cryogenic Yb:YAG thin disk laser : single crystal and ceramic
… thin-disk laser system. We improve the thin-disk beam quality by eliminating thermally induced lensing and disk bowing. The characteristics and performance of a ceramic and single crystal Yb:YAG thin disk (TD) lasers are analyzed both experimentally and theoretically. We perform these experiments …
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Fabrication of novel geometry fibre lasers for high power applications
… pumped helical core fibre laser improved the beam from a 30µm core from an M2 of 3.3 to < 1.4, with a maximum output power of 64W and slope efficiency of 84%. A ribbon fibre with multiple laser emitting cores was fabricated. The difficulties in the fabrication of such a fibre required …
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Optical Performance and Prototyping of a Liquid Lens Laser Communications Transceiver
… Free-space optical communications systems' beams are typically narrower in divergence and require precise pointing, acquisition, and tracking (PAT) systems to establish and maintain links. Several technologies for beam steering exist, including MEMS fast-steering mirrors (FSMs), gimbals, and …
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Spatial Mode Filters for Control of Lateral Modes in High Power Semiconductor Lasers
… thus prevent them from lasing and degrading the beam quality. Several concepts for modifying the lateral waveguide to create filtering of the lateral modes are examined, including the use of waveguide bend loss, waveguide frustration, and the addition of scattering loss. Each of the concepts …
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Tailoring the emission of stripe-array diode lasers with external cavities to enable nonlinear frequency conversion
… with extraordinary spatial temporal and spectral quality is required to pump frequency conversion. Broad area (BA) diode lasers are reliable high power light sources in the near-infrared spectral range. They belong to the most efficient coherent light sources with electro-optical efficiencies of …
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Časově rozlišená laserová spektroskopie nanomateriálů
… theoretical part we describe the influence the quality of laser beam, quality and thickness of the sample on measurements. There are numerical simulations of the measurements influenced by these parameters. This theory is used for processing of the measured dates by a program, which is attached …
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BEAM COMBINING OF FIBER LASERS AND VERTICAL EXTERNAL CAVITY SURFACE EMITTING LASERS USING VOLUME BRAGG GRATINGS
… laser sources with near diffraction limited beam quality outputs have enabled wide range of applications. However, physical constraints such as material heating and nonlinear effects limit the maximum achievable power of these laser sources. In order to obtain higher power level, beam …
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Development of a Hybrid Alanine-calorimetry Absorbed-dose Standard for Linac Electron Beams
… dose to water in cobalt-60, linac photon beams and high-energy linac electron beams. However, for lower-energy electron beams, given the short range of electrons and the physical dimensions of the calorimeter, it is impossible to perform measurements at the reference depths in water. …
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