We are developing multi-chroic antenna-coupled TES detectors for CMB polarimetry. Multi-chroic detectors increase the mapping speed per focal plane area and provide greater discrimination of polarized galactic foregrounds with no increase in weight or cryogenic cost. In each pixel, a silicon lens-coupled dual polarized sinuous antenna collects light over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into several frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization. We will describe the design and performance of these devices and present optical data taken with prototype pixels. Our measurements show beams with percent level ellipticity, percent level cross-polarization leakage, and partitioned bands using banks of 2, 3, and 7 filters. We will also describe the development of broadband anti-reflection coatings for the high dielectric constant lens. The broadband anti-reflection coating has approximately 100% bandwidth and no detectable loss at cryogenic temperature. Finally, we will describe an upgrade for the Polarbear CMB experiment and installation for the LiteBIRD CMB satellite experiment both of which have focal planes with kilo-pixel of these detectors to achieve unprecedented mapping speed.

We have developed epoxy-based, broadband antireflection coatings for millimeter-wave astrophysics experiments with cryogenic optics. By using multiple-layer coatings where each layer steps in dielectric constant, we achieved low reflection over a wide bandwidth. We suppressed the reflection from an alumina disk to 10% over fractional bandwidths of 92% and 104% using two-layer and three-layer coatings, respectively. The dielectric constants of epoxies were tuned between 2.06 and 7.44 by mixing three types of epoxy and doping with strontium titanate powder required for the high dielectric mixtures. At 140 K, the band-integrated absorption loss in the coatings was suppressed to less than 1% for the two-layer coating, and below 10% for the three-layer coating.

We are developing multi-chroic antenna-coupled TES detectors for CMB polarimetry. Multi-chroic detectors increase the mapping speed per focal plane area and provide greater discrimination of polarized galactic foregrounds with no increase in weight or cryogenic cost. In each pixel, a silicon lens-coupled dual polarized sinuous antenna collects light over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into several frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization. We will describe the design and performance of these devices and present optical data taken with prototype pixels. Our measurements show beams with percent level ellipticity, percent level cross-polarization leakage, and partitioned bands using banks of 2, 3, and 7 filters. We will also describe the development of broadband anti-reflection coatings for the high dielectric constant lens. The broadband anti-reflection coating has approximately 100% bandwidth and no detectable loss at cryogenic temperature. Finally, we will describe an upgrade for the Polarbear CMB experiment and installation for the LiteBIRD CMB satellite experiment both of which have focal planes with kilo-pixel of these detectors to achieve unprecedented mapping speed.

POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment observing at Atacama plateau in Chile. PB-2 is designed to improve the sensitivity to measure the CMB B-mode polarization by upgrading the current POLARBEAR-1 receiver that is currently mounted on the Huan Tran telescope. The improvements in PB-2 include, i) the dual band observations at 95 GHz and 150 GHz in each pixel using an sinuous antenna, ii) the increase of the total number of detectors, 7588 Al-Ti bilayer transition-edge sensor (TES) bolometers, iii) the bath temperature of bolometers at 100 mK in the second phase of observation (300 mK in the first phase.) With the expected sensitivity of 5.7 µK √ s, PB-2 is sensitive to a tensor-to-scalar ratio, r, of 0.01 at 95 % confidence level (CL) and constrains the sum of neutrino masses as 90 meV by PB-2 alone and 40 meV by combining PB-2 and Planck at 68 % CL. We schedule to deploy in 2014.

POLARBEAR-2 is a ground based cosmic microwave background (CMB) radiation experiment observing from Atacama, Chile. The science goals of POLARBEAR-2 are to measure the CMB polarization signals originating from the inflationary gravity-wave background and weak gravitational lensing. In order to achieve these science goals, POLARBEAR-2 employs 7588 polarization sensitive transition edge sensor bolometers at observing frequencies of 95 and 150 GHz with 5.5 and 3.5 arcmin beam width, respectively. The telescope is the off-axis Gregorian, Huan Tran Telescope, on which the POLARBEAR-1 receiver is currently mounted. The polarimetry is based on modulation of the polarized signal using a rotating half-wave plate and the rotation of the sky. We present the developments of the optical and polarimeter designs including the cryogenically cooled refractive optics that achieve the overall 4 degrees field-of-view, the thermal filter design, the broadband anti-reflection coating, and the rotating half-wave plate.