Typical aberration influence on laser mode properties for an asymmetric folded resonator

We demonstrate the influence on mode features with typical intracavity astigmatism perturbation and results of aberrated wavefront in a folded-type unstable resonator usually used in high energy lasers. The mode properties are illuminated by numerical iterative calculation, and Zernike aberration polynomial fitting. Subtle beam features such as the first 35 order Zernike aberration coefficient, PSF and circle energy distribution in the far-field, and Strehl ratio with the intracavity astigmatism perturbation have been further achieved. The results show that such perturbation has significant influence on out coupling beam properties, and the uniform and symmetry of the mode is rapidly disrupted even by a slight intracavity astigmatism perturbation for the small Fresnel number unstable resonator. Moreover, some relevant higher order aberrations such as Zernike coefficient A3, A5 and A10 will also increase in the wavefront profiles. Based on the analysis, suggestions for the practical design and further possible aberration improvement strategies are proposed.