Mode aberration analysis of positive-branch confocal unstable resonators by use of wavefront reconstruction

The effect of intracavity aberrated perturbation on output mode structure properties of passive confocal unstable resonator is been experimentally researched by adopting Hartmann-Shack wavefront sensor and Zernike modal wavefront reconstruction on the basis of numerical simulation. Results show that intracavity perturbation such as mirror tilt and misadjustment in the vertical axis notablely affects outcoupled mode properties, and will also increase some high-order aberrations of beam phase properties. However, low-order Zernike tilt aberration is the main component when phase-tilted perturbation is introduced into the resonator. Defocus (Z(3)), astigmatism (Z(4) or Z(5)) and coma aberration (Z(6) or Z(7)) will all be brought, and also such high-order aberration included in wavefront will directly degrade output beam quality for larger Fresnel number unstable resonators. When wavefront corrector is used for intracavity aberrated compensation, low-order aberration should be considered preferentially.