The beam combination method using stimulated Brillouin scattering phase conjugate mirrors (SBS-PCMs) is a promising technique for a high energy and high power laser output operating with a high repetition rate. The two-beam combined system was previously demonstrated with an amplitude dividing method. A four-beam combined laser system with amplitude dividing method is demonstrated in this work, and the phase stabilization experiment of this system is performed using the self phase control and the long-term stabilization technique. The phase differences between the SBS waves are stabilized with λ/30 and the fluctuation of the four-beam combined output energy is 6.16% during 2000 shots (200 s).

Laser fusion requires very high energy/power output with high repetition rate over 10 Hz, which is very difficult with the current laser technologies. However, the recent research work on the phase controlling of the stimulated Brillouin scattering wave enables the realization of this kind of laser fusion driver. The recent progress of controlling the phase has been successfully demonstrated by the self-generated density modulation method proposed by one of the authors (Kong). Nevertheless, it showed a long-term fluctuation of the phase because of the long-term fluctuation of the density of the SBS medium due to the thermal fluctuation. This long-term thermal fluctuation is inevitable a fact in nature. The authors used a specially designed stabilizing system for the phase controlling system, which has the PZT control of the mirror for phase controlling SBS-PCM (the so-called feedback mirror). This system stabilizes the phase controlling system very well for more than 1 h. This technique will help the laser fusion driver to be realized sooner than expected. In addition, we propose a similar scheme to be applied to the ultra-fast pulse laser system, which must operate at high repetition rate for the laser fusion energy power plant.