Analysis of defocus aberration characteristics on a typical passively confocal unstable resonator

The analytical treatment of typical defocus aberration and its impact on the mode wavefront properties of a confocal structural laser resonator is discussed. Numerical modeling of the system is deduced to predict the influence of defocus disturbation on mode intensity and phase distribution. In addition, an experimental method by combining Zernike aberration function and wavefront reconstruction to measure the dynamic wavefront aberration for such lasers has been developed. Beam mode characteristics, including the alignment state and defocus aberration perturbation have been presented. It is shown that the typical Zernike aberration such as A3, A5 and A10 caused by intracavity perturbation significantly affected the beam properties, PSF profiles and circle energy distribution in the far field. The experimental results show that defocus aberration characteristics can be used as an effective basis for dynamic compensation of typical aberration in such lasers. Furthermore, corresponding strategies are proposed to implement the active correction of typical optical aberration in such resonators.