Segmented Circular LD Arrays Side-pumped Nd:YAG-KGW Wave-Agility Raman Laser

This thesis focuses on a segmented circular LD arrays side-pumped all-solid-state Nd:YAG /KGd（WO₄）₂ Raman laser operating in wave-agility.Side-pumped geometry design of lasers concerns on how to solve the space conflict between pump and heat-removal device due to the demands for larger lateral surface of a laser rod. The thesis tries to provide a configuration of the segmented periodical side pumping to get rid of the complex liquid cooling system and balance the space conflict. It has probably potential to be used in compact and miniature laser systems, especially in low and medium power applications.The investigation of wavelength-agility lidar focuses on how to solve the quick wavelength-switch among multiwave. The thesis tries to provide a practical method of quick wavelength-switch to realize the wavelength-selective, output-modulated and coding operation in a solid-state Raman laser.First, segmented circular LD arrays side-pumped and the side-pumped structure with alternating compensated arrangement have been proposed to solve the space conflict between pump and heat-removal device. Design optimization and simulation on the temperature distribution and the thermo-optic effects of laser rods have been performed. Two experiments on segmented side-pumped Nd: YAG a laser rod have also been carried out to verify the availability of side-pumped geometry design. The results indicate the conflict can be balanced better by the segmented side-pumped geometry in a periodical arrangement between circular LD arrays and holders. This novel design has great potential to be used in compact and miniature laser systems.Next,the quick wavelength-switch among multiwave of Raman laser has been investigated. The three designs of T-shape folded cavity configuration, H-shape and Raman extended cavity configuration have been demonstrated. The investigation focuses on T-shape folded cavity configuration. Aλ/2 electro-optical switch SW was introduced in the configuration, by which we can conveniently control the linear polarization direction of fundamental beam. By virtue of the polarization-dependent property of KGd（WO₄）₂ crystal, the purpose of controlling and selecting Raman wavelengths can be finally reached. The related parameters in Raman laser have been calculated. The simulation on thermal loading in Raman crystal and the curvature optimization of Raman mirrors have also been performed.The experiment of segment-pumped Nd:YAG-KGW Raman laser operating in 1177nm validated that the fundamental resource employing segmental side-pumped Nd:YAG module is available in intracavity Raman laser. A maximum pulse energy of 126mJ and a peak power of 21MW are achieved, corresponding to an overall Diode-Stokes conversion efficiency of 18.2%. The experimental results support the validity of calcaulation and simulation in Raman laser.Finally, the experimental investigation on a segmented circular LD arrays side-pumped all-solid-state Nd: YAG /KGd（WO₄）₂ Raman laser operating in two colors modulation has been carred out. The output wavelength can be switched quickly between 1159nm and 1177nm and the Raman output modulated in spectra-time domains was achieved. Raman pulse energy up to 114mJ at 1177nm and 98mJ at 1159nm were obtained respectively, corresponding to an overall Diode-Stokes conversion efficiency of 15.3% at 1177nm and 13.2% at 1159nm. To our knowledge, these are the best performance reported to date for an EO Q-switched tunable folded cavity Nd:YAG-KGW Raman laser with conductive cooling and air exchanging.The investigation reveals that the segmented LD arrays side-pumped configuration provides a way to get rid of the complex liquid cooling system and the quick wavelength-switch among multiwave of Raman laser provides a solution to realize the output-modulated and coding operation in spectra-time domains.