A Hybrid Wavefront Sensor: Combining Shack-Hartmann and Pyramid Wavefront Sensors to Enable High Dynamic Range and Sensitivity

We are developing a Hybrid Wavefront Sensor which combines the high dynamic range of a Shack-Hartmann wavefront sensor and the high sensitivity of an unmodulated pyramid wavefront sensor. In our prototype, composed primarily of commercially available optics and 3D printed mounts, light is focused at the center of a crossed roof prism to create four identical pupils that each pass through a lenslet array which allows us to simultaneously perform Shack-Hartmann and pyramid wavefront sensing analyses on aberrated wavefronts. By using this hybrid method, an adaptive optics wavefront sensing setup could continually perform wavefront corrections with a deformable mirror (DM) during turbulent events that would saturate an unmodulated pyramid wavefront sensor functioning on its own. To test our prototype, multiple low-order Zernike mode aberrations are applied simultaneously with a DM. Code we have developed performs two separate wavefront analyses corresponding to a highly robust (Shack-Hartmann) and highly sensitive (pyramid) mode and returns two sets of estimated amplitudes of the induced aberrations present. Our tests have experimentally confirmed the Hybrid Wavefront Sensor's lenslet array allows wavefront analysis past the saturation point of its pyramid wavefront sensing mode resulting in high sensitivity to relatively weak aberrations while maintaining a high robustness to much stronger aberrations.