Conceptual Design Studies of a Laser Diode Pumped Solid State Laser System for the Laser Fusion Reactor Driver

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Abstract
We have developed a conceptual designing technique of a laser diode pumped solid state laser system having high peak power, high efficiency, good beam quality, and high repetition rate. Using this technique, we evaluated the feasibility of the systems with several solid state laser materials for the laser fusion reactor driver with 10 MJ blue output, 10% overall efficiency, and 10 Hz repetition rate. The systems with such as HAP4 glass, Nd:SiO2 glass, Nd:Y:CaF2 crystal, and Tm, Ho:YAG crystal are shown to be attractive candidates for the reactor driver while the systems with such as LHG8 glass, Nd:YAG crystal, and Tm:YAG crystal will not be selected as the candidates. For an economical laser fusion reactor driver, the solid state laser materials are required to have the following properties; \hbarω/σ∼10 J/cm2 (\hbarω: the laser photon energy, σ: the stimulated emission cross section), a thermal shock parameter of ≥3 W/cm, a nonlinear index of refraction smaller than ∼3×10-13 esu, and a fluorescence lifetime of ≥4 ms.