New NIR spectro-polarimetric modes for the SCExAO instrument

Julien Lozi, Olivier Guyon, Nemanja Jovanovic, Barnaby Norris, Tyler D. Groff, Jeffrey Chilcote, Jeremy Kasdin, Tomoyuki Kudo, Motohide Tamura, Jin Zhang, Steven Bos, Frans Snik, David Doelman, Ben Mazin, Alex Walter, Sebastien Vievard, Ananya Sahoo, Frantz Martinache

Research output: Contribution to conferencePaperpeer-review

1 Scopus citations


The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is equipped with a fast visible dual-camera polarimetric module, VAMPIRES, already producing valuable scientific observations of protoplanetary disks and dust shells. We present two new polarimetric modules that were recently implemented,. using the NIR light from y- to K-band and identical Wollaston prisms to split the polarizations. The fast polarization module follows a design similar to VAMPIRES, with a fast IR camera either the First Light C-RED 2 or a Leonardo SAPHIRA detector that can run at kilohertz frame rates, and a Ferroelectric Liquid Crystal (FLC) device modulating the polarization in a synchronized way with the acquisition. The fast frame rate coupled with the FLC allows to freeze atmospheric speckles and to calibrate more precisely the degree of polarization of the target, as already demonstrated by VAMPIRES. For the second module, we perform spectro-polarimetric measurements at a slower rate, using the CHARIS Integral Field Spectrograph (IFS). The field-of-view is reduced by a factor 2 in one direction to 2x1 arcsec, to accommodate for the imaging of both polarizations on the same detector without sacrificing the spectral resolution of the instrument. This is the first demonstration of a high-contrast spectro-polarimeter using an IFS. We present on-sky results of the new polarimetric capabilities taken during the commissioning phase, on strongly polarized targets. In addition, we show future capabilities that are already scheduled to increase the performance of these modules, especially the addition of non-redundant masks, as well as a polarimetric vector Apodizing Phase Plate (vAPP) coronagraph.

Original languageEnglish (US)
StatePublished - 2019
Event6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019 - Quebec City, Canada
Duration: Jun 9 2019Jun 14 2019


Conference6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019
CityQuebec City


  • Adaptive optics
  • High-contrast imaging
  • Polarimetry
  • Spectro-polarimetry

ASJC Scopus subject areas

  • Space and Planetary Science
  • Control and Systems Engineering
  • Mechanical Engineering
  • Electronic, Optical and Magnetic Materials
  • Astronomy and Astrophysics
  • Instrumentation


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