instrumentation: adaptive optics

On-sky verification of Fast and Furious focal-plane wavefront sensing: Moving forward toward controlling the island effect at Subaru/SCExAO

Context. High-contrast imaging (HCI) observations of exoplanets can be limited by the island effect (IE). The IE occurs when the main wavefront sensor (WFS) cannot measure sharp phase discontinuities across the telescope's secondary mirror support …

Focal-plane wavefront sensing with the vector-Apodizing Phase Plate

Context. One of the key limitations of the direct imaging of exoplanets at small angular separations are quasi-static speckles that originate from evolving non-common path aberrations (NCPA) in the optical train downstream of the instrument's main …

SPHERE/ZIMPOL high resolution polarimetric imager. I. System overview, PSF parameters, coronagraphy, and polarimetry

Context. The SPHERE planet finder is an extreme adaptive optics (AO) instrument for high resolution and high contrast observations at the Very Large Telescope (VLT). We describe the Zurich Imaging Polarimeter (ZIMPOL), the visual focal plane …

Laboratory verification of Fast & Furious phase diversity: Towards controlling the low wind effect in the SPHERE instrument

Context. The low wind effect (LWE) refers to a characteristic set of quasi-static wavefront aberrations seen consistently by the SPHERE instrument when dome-level wind speeds drop below 3 ms$^-1$. The LWE produces bright low-order speckles in the …

The coronagraphic Modal Wavefront Sensor: a hybrid focal-plane sensor for the high-contrast imaging of circumstellar environments

The raw coronagraphic performance of current high-contrast imaging instruments is limited by the presence of a quasi-static speckle (QSS) background, resulting from instrumental Non-Common Path Errors (NCPEs). Rapid development of efficient speckle …