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Tomographic reconstruction using multiple laser guide stars (MLGS) will be required by the next generation of extremely large (30 m class) telescopes (ELT). Modal decomposition of wavefront phase using Zernike polynomials is a widely used technique in adaptive optics (AO) research. However, this approach breaks down with the large number of degrees of freedom required by ELTs.This research proposes the use of an alternative basis, the disk harmonic functions, to overcome the disadvantages of the Zernike basis at high spatial resolution. A method of fast, analytic, modal tomographic modeling is developed and used for fast calculation of reconstruction matrices used on-sky at the MMT telescope.The specific reconstruction techniques of ground layer adaptive optics and laser tomography adaptive optics using MLGS are presented along with the results of on-sky experiments at the MMT. In addition to developing a laser AO instrument for the MMT, these experiments provide a test bed for validating the reconstruction techniques that will be critical to the success of ELTs.An approach to using real-time wavefront sensor and deformable mirror telemetry from the MLGS system to estimate the vertical distribution of turbulence in the atmosphere is also presented.

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The Er:YAG laser and the USPL are the most promising when considering the previous study results and their physical characteristics. This investigation compared the healing of various laser ablation units versus conventional mechanical cutting to explore the future applications for bone surgery and the effects when combined with rhBMP-7. A full-thickness circular defect was created on the parietal bones of mice for all the groups. Hard tissue healing was assessed using a microcomputerized tomography. Wound closure analyses suggested that the femtosecond laser created wounds displayed slightly healing delay in closure over the healing period when compared to mechanical instrumentation. The Er:YAG laser showed a healing rate similar to that of the mechanically ablated groups. In summary, femtosecond and Er:YAG lasers are two modalities suitable for bone ablation comparable to mechanical instrumentation.

Laser transmission welding of polymers is a relatively new joining technique. It is based on the fact that the majority of thermoplastics are transparent to infrared radiation. A laser beam passes through the transparent part, and is then absorbed by a part rendered absorbent by additives such as carbon black. Absorbed laser energy is transformed into heat that melts the polymer at the interface between two parts, thus forming a weld. Many industrial applications have quite a complex geometry. This may often make it impossible to irradiate small elements of the joint interface directly. One of the possible solutions for this problem is to employ an oblique mirror to redirect a laser beam to the desired direction. In present work, transparent nylon tubes were welded to absorbing nylon plaques using a conical mirror inserted in the tube. The effects of the laser power, the angular motion speed, and the number of cycles on the joint shear strength were examined. Additionally, a two–dimensional axi-symmetric transient finite element heat transfer model was developed and evaluated. It simulated the temperature developed in the specimen during the welding cycle; the model was validated with the welding and mechanical testing results. The experimental results demonstrated good joint strength, confirming the feasibility of this technique. It was also found that welding at a lower laser beam power and a higher rotational speed allowed higher maximum weld strengths to be achieved at the expense of longer cycle time and higher energy consumption. Simulation of the temperature demonstrated that varying of the rotational speed at constant laser power does not change the overall temperature rise trend. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-08-14 23:12:18.491

No description available.

No description available.

The Er:YAG laser and the USPL are the most promising when considering the previous study results and their physical characteristics. This investigation compared the healing of various laser ablation units versus conventional mechanical cutting to explore the future applications for bone surgery and the effects when combined with rhBMP-7. A full-thickness circular defect was created on the parietal bones of mice for all the groups. Hard tissue healing was assessed using a microcomputerized tomography. Wound closure analyses suggested that the femtosecond laser created wounds displayed slightly healing delay in closure over the healing period when compared to mechanical instrumentation. The Er:YAG laser showed a healing rate similar to that of the mechanically ablated groups. In summary, femtosecond and Er:YAG lasers are two modalities suitable for bone ablation comparable to mechanical instrumentation.