Laser microhole drilling using radially and tangentially polarized Q-switched laser radiation has been analyzed comparatively. Tangential polarization exhibited a significantly higher drilling speed compared to radial polarization. Light attenuation through interaction with the walls of a microhole was found to be weaker in the case of tangential polarization than in the case of radial polarization, thus leading to the assumption that the observed higher drilling rates
utilizing tangential polarization are due to more energy being deposited at the bottom of a microhole. The required radiation has been generated using a Q-switched Nd:YAG laser resonator in a configuration that exploits thermally induced birefringence to render the laser resonator stable only for radial polarization.
Radially polarized radiation shows some very interesting properties and has therefore gained interest in recent years. An overview of the advantages and the various applications where radially polarized modes are beneficial is given. In addition the different known methods to generate radial polarization are reviewed. In our work we developed a method to generate radially polarized laser beams by means of a polarization selective resonant grating mirror. The undesired polarization is coupled to a mode of the dielectric multilayer of the resonator end mirror and experiences severe losses while the radial polarization is not affected and oscillates in the laser resonator. Fundamental and higher-order radially polarized modes of high polarization purity and powers of more than 100W have been demonstrated.
Nd:YAG has favorable material properties to minimize the thermally induced lenses in lasers at cryogenic temperatures. In the present work we measured a significant reduction of the thermal lens in a Nd:YAG rod cooled with liquid nitrogen. The power range for stable fundamental-mode laser oscillation was demonstrated to be significantly enlarged at low temperatures. The experimental results were compared to analytical models and finite-elements simulations.
Nd:YAG has favorable material properties to minimize the thermally induced lenses in lasers at cryogenic temperatures. In the present work we measured a significant reduction of the thermal lens in a Nd:YAG rod cooled with liquid nitrogen. The power range for stable fundamental-mode laser oscillation was demonstrated to be significantly enlarged at low temperatures. The experimental results were compared to analytical models and finite-element simulations.
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