The IRCAL Polarimeter: Design, Calibration, and Data Reduction for an Adaptive Optics Imaging Polarimeter

摘要

We have upgraded IRCAL, the near-infrared science camera of the LickObservatory adaptive optics system, to add a dual-channel imaging polarimetrymode. This mode uses an optically contacted YLF (LiYF_4) Wollaston prism toprovide simultaneous images in perpendicular linear polarizations, providinghigh resolution, high dynamic range polarimetry in the near infrared. Wedescribe the design and construction of the polarimeter, discuss in detail thedata reduction algorithms adopted, and evaluate the instrument's on-the-skyperformance. The IRCAL polarimeter is capable of reducing the stellar PSF haloby about two orders of magnitude, thereby increasing contrast for studies offaint circumstellar dust-scattered light. We discuss the various factors thatlimit the achieved contrast, and present lessons applicable to future highcontrast imaging polarimeters.