| Ultrashort ultrahigh intensity laser systems could generate the highest peak power laser pulses. These systems have numerous applications in spectroscopy, material processing, secondary radiation generation, high-energy particle acceleration, advanced attosecond science, and high energy laboratory astrophysics. However, it's difficult to increase the peak power greatly for a single channel laser system further. In order to achieve higher peak-power laser pulses, coherent beam combining (CBC) has been proposed as an alternative method. With CBC technology, we could generate a laser beam with the peak power greater than the limit of a single laser channel, while maintaining good beam quality. However, the large aperture ultrashort ultrahigh intensity CBC, which could generate the most powerful laser pulses, has not been realized experimentally and the theoretical analysis is still minimal.In this thesis, the phase effects of the large aperture ultrashort ultrahigh intensity CBC are investigated. Numerical simulations are made based on the modified physical models. Through the simulations, we try to answer the questions, "what's the requirements for wavefront error for large aperture ultrashort ultrahigh intensity CBC" and "what's the requirements for laser amplification system for these systems".To answer the first question, the requirements for each beam's own wavefront error and the requirements for the difference among beam's wavefronts are calculated. The influence of duration and number of combining beams on the wavefront error requirements is discussed too. In this section, we draw the conclusion as follows:1) The performance of CBC increases rapidly if we make wavefront parameters better than certain values.2) For different pulse durations and different number of combining beams, the relationships are nearly same. Combining more than two ultrashort pulses should be a good choice from the point of requirements for wavefront error.3) Piston and tip/tilt errors affects the performance of combining considerably for the case of small wavefront error, but have little influence on the performance of combining for the case of large wavefront error.To answer the second question, a numerical simulation for the OPA process of an assumed 10PW class large aperture OPCPA ultrashort ultrahigh intensity laser system are made. The amplification and wavefront degeneration of signal in these systems are reviewed. In this section, we draw the conclusion as follows:1) The nonlinear interaction distance to achieve highest efficiency is small for these systems.2) The effects of diffraction, walk-off and group velocity mismatch are small and signal can maintain good wavefront.3) The wavefront parameters of pump and signal is uncorrelated.4) When increase the energy of pump, the amplitude of wavefront error of amplified signal becomes greater, the focusing property becomes poorer and the scattering property becomes worse.5) The positive non-conlinear angle is preferred from the point of wavefront.Moreover, available methods for sensing and correcting wavefront errors in large aperture ultrashort ultrahigh intensity CBC laser systems are reviewed. Based on the simulation results and the knowledge about adaptive optical systems in large scale laser facilities, the thesis proposed a possible scheme for sensing and correcting wavefront errors. We find that quadri-wave lateral shearing interferometer (SID4) and Shack-Hartmann wavefront sensing are available for combining two large aperture ultrashort ultrahigh intensity laser. And if we need to combine more than two laser pulses, SID4 is a better way. In order to correcting wavefront error with high precision, high dynamic range, low-cost, low complexity, we should combine many different wavefront correction technologies and correct different order of wavefront error independently.These works may be benefited for the research of large aperture ultrashort ultrahigh intensity CBC, and valuable for practical large aperture ultrashort ultrahigh intensity CBC laser systems. |
PDF Full Text Request