Shaping And Stability Of Amplified Spontaneous Emission Pulse Of High Power KrF Excimer For Inertial Confinement Fusion

In this thesis, obtaining short pulse width, shaping and stability of stack shaping of amplified spontaneous emission(ASE) at 248 nm from Kr F excimer laser have been studied. It provides the theoretic and technological for obtaining high stability ASE pulse with nanosecond pulse width and shaping of ASE pulse. Potential amplification of such pulses could be used for the Inertial Confinement Fusion(ICF) in the future.A theoretical model based on timeshare quenching of ASE pulse of Kr F excimer is established for obtaining short pulse width. The mechanism for generating short ASE pulse based on timeshare quenching is studied. The approximate expression of relative delay and relative intensity have been achived respectively. The effect for getting ASE pulse with short pulse width could be prejudged from simulation. Both feasibility and practicality of ASE pulse with short pulse width theory based on timeshare quenching are investigated. By analysing the results of simulation, experimental parameters could be optimized for improving the obtaining rate of ASE pulse with short pulse.Experimentally, the ASE pulse with short pulse width based on timeshare quenching is designed, implemented and optimized. The position of full-reflective mirror, the mirrors relative to the deviation from main optic axis, the longitudinal deflection angle relative to the main optic axis are investigated to obtain ASE pulse width short pulse width respectively. Compared to the initial ASE pulse with a duration of 16.06±0.42, pulse width as short as 2.59±0.05 ns which is 6 times less than initial pulse width are achieved under optimal condition. The absolute value of pulse width variation is reduced from ±0.42 ns to ±0.05 ns, which is reduced as much as 8.4-fold. The relative value is reduced from 2.5% to 1.9%. It proves that the method can obtain ASE pulse with short pulse width effectively and enhance the stability of output.The theoretical model of ASE pulse stacking and stability of results are established. By use of this model, the number of seed pulse, pulse width, flat-top widths, flatness, and stability of flat-top are calculated respectively. Based on the incoherent beam combination, the scheme for obtaining flat-top or approximate flat-top by using ASE pulse stacking is designed. Both the stability of ASE pulse stacking and the ability to get the expected flat-top are improved.The ASE pulse shaping based on pulse stacking is designed and optimized. The pulse width of 5.29 ns, flat-top widths of 2.35 ns, flatness of 3.26% and the stability of flatness 1.17% are achieved. In the simulation results, the pulse width of 5.21±0.04 ns, flat-top widths of 2.41±0.05 ns, and flatness of 4.69±0.60% and the stability of flatness of 1.45±0.20% are obtained. The experimental results confirms the validity of theoretical model. This result shows the ability of acquiring stable ASE pulse with duration of ns and flat-top approximatly.