Long term stabilization of the beam combination laser with a phase controlled stimulated Brillouin scattering phase conjugation mirrors for the laser fusion driver

Abstract

Laser fusion requires very high energy0power 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.

Conceptual design of the Kumgang laser: a high-power coherent beam combination laser using SC-SBS-PCMs towards a Dream laser

“…Since then, the results have improved and the method has been applied to four-beam coherent combination lasers with both the wavefront dividing method and the amplitude dividing method [23][24][25][26][27][28][29][30][31] . Figure 5 shows the experimental setup for verifying the principles of the SC-SBS-PCM [24] .…”

“…The feasibility of a beam combination laser using fluorocarbonate SBS-PCMs has been proved experimentally in the low power range of several W [23][24][25][26][27][28][29][30][31] . Currently we are working on experimental verification of this beam combination laser with an average output power in the kW range.…”

Stimulated Brillouin Scattering Phase Conjugate Mirror and its Application to Coherent Beam Combined Laser System Producing a High Energy, High Power, High Beam Quality, and High Repetition Rate Output

“…However, a thermally induced long-term phase fluctuation occurs when the number of laser shots increases (Kong et al, 2006 Count of shots Fig. 21.…”

“…For this reason, the self-phase control method was proposed and has been developed by Kong et al (2005aKong et al ( , 2005bKong et al ( , 2005c, which can control the phase of the SBS wave with the simplest composition as well as ease of alignment, no limitations on the number of combined beams, and excellent phase conjugation. Furthermore, the active phase control with a piezoelectric translator (PZT) enables long-term phase stabilization (Kong et al, 2006. In addition to a random phase characteristic, the distortion that generally occurs in a pulse waveform of an SBS wave is another negative characteristic in terms of the beam combination.…”

0.4 J/10 ns/10 kHz‐4 kW coherent beam combined laser using stimulated Brillouin scattering phase conjugation mirrors for industrial applications

“…Only one problem to utilize SBS-PCM is piston error compensation, because SBS is originated from the thermal noise [15]. But it was resolved by the selfphase-control technique developed by Kong et al [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”