The Study of the Beam Combination Laser System with High Power/Energy and High Repetition Rate Using Stimulated Brillouin Scattering Phase Conjugate Mirrors (SBS-PCMS) for Laser Fusion Driver

Beam combining method with stimulated brillouin scattering phase conjugate mirrors (SBS-PCMs) is a promising technique for achieving a laser fusion driver with high-energy, high power, and high-repetition-rate of ∼10 Hz. The key techniques for the realization of the beam combination laser system, ''the self-phase-control technique'' and' 'the pre-pulse injection technique,'' were proposed by H. J. Kong et al. and have been developed. In this project, the further developments have been achieved for the practical application of the beam combination system.The active phase control has been performed to stabilize the thermally induced long-term phase fluctuation. And the four-beam combination systems with the amplitude dividing and the wave-front dividing schemes have been constructed and tested. In the four-beam combination systems, the active controls of the SBS-PCMs have made the phase fluctuations less than λ/30. Operating the amplifiers in the wave-front dividing scheme, the phase fluctuation stabilized less than λ/25. As a further study for the pre-pulse injection technique, the relationship between the pre-pulse energy and the delay time for the waveform preservation of the SBS wave has been also investigated experimentally. It has been shown that the minimum pre-pulse energies required for the waveform preservation are 10 mJ, 3 mJ, 2 mJ and 4 mJ for the delay times of 3 ns, 8 ns, 15 ns and 17 ns, respectively. (author)