  We have upgraded IRCAL, the near-infrared science camera of the Lick
Observatory adaptive optics system, to add a dual-channel imaging polarimetry
mode. This mode uses an optically contacted YLF (LiYF_4) Wollaston prism to
provide simultaneous images in perpendicular linear polarizations, providing
high resolution, high dynamic range polarimetry in the near infrared. We
describe the design and construction of the polarimeter, discuss in detail the
data reduction algorithms adopted, and evaluate the instrument's on-the-sky
performance. The IRCAL polarimeter is capable of reducing the stellar PSF halo
by about two orders of magnitude, thereby increasing contrast for studies of
faint circumstellar dust-scattered light. We discuss the various factors that
limit the achieved contrast, and present lessons applicable to future high
contrast imaging polarimeters.
