Investigation On SBS Coherent Beam Combination With Tapered Waveguide Independent Cell Configuration

In the future, MJ grade nanosecond laser pulses at repetition rate to5~10Hz cansatisfying the requirement for fusion driver. However, due to the thermal effects ofdielectric materials in inertial confinement fusion driver system is difficult to achievere-frequency operation. The beam combination using SBS-PCM (Stimulated BrillouinScattering-Phase Conjugate Mirror) can reduce the thermal effects and compensate thephase distortion to achieve this goal. In this paper, the SBS produced with mediumdensity modulated to set a starting SBS acoustic, then the SBS phase can automaticstabilize. The use of piezoelectric ceramic can adjust the focus lens position, to achievean exact phase match between sub-beams.Theoretically, from Pervasive SBS coupled wave equations began to establishweak periodic density modulation SBS (retention second-order equation) physicalmodels and derived the numerical solution model. Written the program for simulatingdensity modulation SBS of self-phase control. From the equation of the standing waveexcited acoustic field, the pump pulses simplified Gaussian, sinusoidal, linear;meanwhile obtained the solution of equations, respectively. Forward propagation foracoustic standing wave excitation expressions discussed in detail, got the parameters onthe acoustic field intensity impact of the law.Discussed the standing wave exciting forward propagation of the acoustic wave indetails and compared with the density modulation of numerical simulation. The impacton SBS with pump intensity, pulse width, waveform and medium velocity, phononlifetime is obtained. Analysis of the acoustic initial phase on the impact Stokes phase.To achieve the best operating parameters of SBS self-phase control.Based on the low-threshold characteristics of tapered waveguide can reduce thedemand of balancing the energies between beams, an independent cell configurationSBS coherent combination is made out with two sub beams by amplitude dividingscheme and an optical experiment is built. Phase stabilities on different pump ratio,counter-propagating ratio and waveguide curvature is obtained experimentally.According to the experimental results verify the correctness of the proposed theory.