The Optical Design of CHARIS: An Exoplanet IFS for the Subaru Telescope

High-contrast imaging techniques now make possible both imaging and spectroscopy of planets around nearby stars. We present the optical design for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARTS), a lenslet-based, cryogenic integral field spectrograph (IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide spectral information for 138x138 spatial elements over a 2.07 arcsec x 2.07 arcsec field of view (FOV). CHARTS will operate in the near infrared (lambda = 1.15 2.5 mu m) and will feature two spectral resolution modes of R approximate to 18 (low-res mode) and R approximate to 73 (high-res mode). Taking advantage of the Subaru telescope adaptive optics systems and coronagraphs (AO188 and SCExAO), CHARTS will provide sufficient contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets. CHARTS will undergo CDR in October 2013 and is projected to have first light by the end of 2015. We report here on the current optical design of CHARTS and its unique innovations.