Study Of Bidirectional Ring Amplifier With Twin Pulses For High-power Lasers

The high-power laser system has been widely used in the fields of plasma physics,laboratory astrophysics,and inertial confinement fusion.The multi-pass amplifier for second generation high power laser system,which is large in size and expensive in construction,has four features:square beam,single aperture,single pulse and unidirectional propagation.The gain and the extraction efficiency are limited in part by the number of passes that the beam can make through the amplifiers.The expensive and complex preamplifier systems are required to compensate for the limited gain of the main amplifiers.Besides,the laser system in the multi-pass amplifier should operate at much higher fluence to achieve high extraction efficiency,which results in a technical challenge in the damage of optical components under high-power lasers irradiationThe bidirectional ring amplifier with twin pulses for high-power lasers is proposed.Compared with the multi-pass amplifier,the bidirectional ring amplifier uses two pulses with opposite propagating directions to increase equivalent fluence and achieve higher extraction efficiency,which can greatly increase the reliability and reduce the cost of system.The experiment of bidirectional ring amplifier with twin pulses is also demonstrated.The output performance of bidirectional ring amplifier with slit spatial filter is also discussed.Besides,the experimental results show that the bidirectional ring amplifier with twin pulses can achieve higher extraction efficiency of stored energy at lower operation fluence.The main results and progresses in the thesis are as follows:1.The bidirectional ring amplifier with near-field injection and the bidirectional ring amplifier with far-field injection are proposed.The operational principles of proposed amplifying architectures are described and analyzed in detail.The switch sequence of plasma-electrode Pockels cells is also described.2.A theory model for twin pulses amplification and a method for precompensation of waveform are proposed with the combination of the rate equation and the multi-pass amplification.The output performances of bidirectional ring amplifier are comprehended with the detailed simulation,the best configuration for the number of amplifier slabs and the result for precompensation of waveform are also demonstrated.4.A simulation model for large aperture beam is proposed with the combination of the theories for optical propagation and lens transformation.The amplification process of bidirectional ring amplifier with slit spatial filters is also analyzed.With simulation,the results of slit spatial filters are in good agreement with the pinhole spatial filter on the spatial filtering,which is helpful for the future high-power lasers.3.The experiment of bidirectional ring amplifier with twin pulses is demonstrated.The experiment results show that the maximum extraction efficiency of stored energy with twin pulses increases by 87%compared with that of single pulse amplification under the same conditions.The simulation results agree well with the experiment results,which prove the accuracy of the theory model.The results in this dissertation provide a new idea for a new generation of high-power laser facility with low cost and high reliability.