The extreme adaptive optics testbed at UCSC: current results and coronagraphic upgrade

TLDR: The Extreme Adaptive Optics (ExAO) Testbed at UCO/Lick is optimized for ultra-high contrast applications requiring high-order wavefront control as discussed by the authors.

Abstract: We present a summary of our current results from the Extreme Adaptive Optics (ExAO) Testbed and the design and status of its coronagraphic upgrade. The ExAO Testbed at the Laboratory for Adaptive Optics at UCO/Lick Observatory is optimized for ultra-high contrast applications requiring high-order wavefront control. It is being used to investigate and develop technologies for the Gemini Planet Imager (GPI). The testbed is equipped with a phase shifting diffraction interferometer (PSDI), which measures the wavefront with sub-nm precision and accuracy. The testbed also includes a 1024-actuator Micro Electro Mechanical Systems (MEMS) deformable mirror manufactured by Boston Micromachines. We present a summary of the current results with the testbed encompassing MEMS flattening via PSDI, MEMS flattening via a Shack-Hartmann wavefront sensor (with and without spatial filtering), the introduction of Kolmogorov phase screens, and contrast in the far-field. Upgrades in progress include adding additional focal and pupil planes to better control scattered light and allow alternative coronagraph architectures, the introduction and testing of high-quality reflecting optics, and a variety of input phase aberrations. Ultimately, the system will serve as a full prototype for GPI.