The Research On LD End-pumped Nd:YVO₄ Slab Laser Amplifiers

Laser diode partially end-pumped slab amplifier is a novel all- solid-state laser that have been developed over the past 20 years, it combines the very best of partially end-pumped slab laser and master oscillator power-amplifier, including high efficiency, compact configuration and excellent heat management. The dissertation is focused on this kind of technique, the main content and innovations are as follows: 1. The thermal effects in partially end-pumped slab were studied. Temperature profiles in a Nd:YVO₄ slab were numerically investigated by the heat conduction equation. Also the simulation values of thermal induced stress and thermal lensing focal length were achieved through analytic expressions. We compared the impact of pumping at 808 nm to thermal effects with that of direct pumping into the upper laser level from the above aspects, demonstrating the superiority of the latter. 2. Utilizing the laser diode stack with the central wavelength of 880 nm as pumping source and one Nd:YVO₄ slab as gain medium, we achieved eight-pass amplification based on a plane-planar resonator. At the repetition rate of 30 k Hz, a maximum amplified output power 92 W was achieved when the seed had an average output power of 6W. The corresponding extraction efficiency was 29.5%. At the output power of 82 W, the beam quality factors in the two orthogonal directions were 1.89 and 1.38, respectively. 3. Theory research on the uniform side-pumping using ceramic slab with gradient doping was devoted. The continuously changed concentration profile was acquired through the condition of uniform pumping. The flat temperature profile in a dual-side-pumped Nd:YAG slab was proved. For approximations, we adopted bonded multiple uniform doping slabs. Temperature uniformity and high absorption efficiencies were achieved simultaneously in the two cases. Further optimizations can be realized though more and thinner slabs.