The promise of bolometers for CMB polarimetry

Bolometers currently offer the best sensitivity for measuring the anisotropy and polarization of the Cosmic Microwave Background (CMB). The next generation of CMB instruments intended to search for faint,curl-mode' polarization require bolometer focal plane arrays with significantly higher sensitivity than current temperature anisotropy receivers, and unprecedented control of systematic errors. Bolometers for the ESA/NASA Planck experiment, thermally optimized for the photon background from the sky and instrument, approach the fundamental photon noise from the CMB with defined allocations for systems level noise contributions. Ground-based CMB polarimeters will soon field focal planes with approximately the instantaneous sensitivity of Planck HE to deeply probe limited regions of sky. Future CMB polarimeters require large-format arrays of bolometers. Antenna-coupled bolometers with superconducting transition-edge readouts promise large-format arrays with well-controlled beam patterns and integral lithographed transmission-line filters.