Auto-alignment in four-pass amplifier with wavefront correction system

In order to solve the interaction problem between the wavefront distortion correction and optical alignment in a high-power laser system, especially in a multi-pass amplification system, based on fresnel diffraction integral theory, the beam propagation model of 310 mm×310 mm aperture beam in four-pass amplifier is built by analyzing the properties of this system. The problem of excessive amount of calculation, caused by high resolution in traditional calculation, is solved by coordinate transformation method, Using this model, the differences of far-field accuracy among centroid method, circle fitting and pure phase matching filter in beam with wavefront distortion are discussed; what influence the wavefront correction has on focal spot position is analyzed. This article provides an important basis for optimizing collimation adjustment programs in four-pass amplifier.