Intracavity adaptive optics. 3: Hsuria performance.

An experimental study has been conducted on the ability of intracavity adaptive optics to improve the performance of a half-symmetric unstable resonator with intracavity axicon (HSURIA) by correcting for aberrations from misfigure or misalignment of the intracavity conical optics. When the deformable mirror had adequate spatial frequency correction capability, near diffraction limited far-field performance was achieved, but secondary maxima lock-on by the multidither servo control severely limited the fully adaptive correction capability. A key observation from these experiments was the extreme sensitivity of the HSURIA to perturbations near the resonator optic axis. Variations as small as lambda/140 had a significant effect. This perturbation sensitivity is the principal cause of the secondary maxima lock-on problem since the open loop deformable mirror figure must be extremely close to the ideal figure to assure global maximum lock-on by the multidither servo control.