Visar resultat 1 - 5 av 16 avhandlingar innehållade ordet laser-beams.
Sammanfattning : In this thesis, we investigate the propagation of some coherent and partially coherent laser beams, including a dark hollow beam (DHB), an elliptical Gaussian beam (EGB), a flat-topped beam and a twisted anisotropic Gaussian Schell-model (TAGSM) beam, through a paraxial optical system or a turbulent atmosphere. Several theoretical models are proposed to describe a DHB of circular or non-circular symmetry. LÄS MER
Sammanfattning : This thesis presents an investigation of the interaction mechanism involved in processing of different engineering materials using pulsed TEA CO2- and Nd:YAG lasers. Several methods were used. Digital Speckle Photography (DSP) or Speckle Correlation was used to detect micro-structural changes in the material surface during laser irradiation. LÄS MER
Sammanfattning : Two-photon-induced Degenerate Four-Wave Mixing, DFWM, was applied for the first time to the detection of CO, and NH3 molecules. Measurements were performed in a cell, and in atmospheric-pressure flames. In the cell measurements, the signal dependence on the pressure and on the laser beam intensity was studied. LÄS MER
Sammanfattning : Denna avhandling innefattar såväl experimentella som numeriska studier av laserkylda atomer i optiska kristallgitter. Bland annat har laserkylningsprocesser studerats, där atomers rörelser i optiska kristallgitter har uppvisat andra typer av bakomliggande mekanismer än de som tidigare förutsågs genom “Sisyfoskylningsmodellen”. LÄS MER
Sammanfattning : This dissertation describes the design, construction and characterization of a high energy chirped-pulse amplification Titanium-Sapphire laser system for the excitation of Extreme Ultraviolet (EUV) lasers. Compact EUV lasers have made possible nano-scale imaging, dense plasma diagnostics and photo-chemistry and photo-physics studies. LÄS MER