Multichroic dual-polarization bolometric detectors for studies of the cosmic microwave background

Abstract

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.

Development of Flat Silicon-Based Mesh Lens Arrays for Millimeter and Sub-millimeter Wave Astronomy

“…Lens-coupled antenna architecture has been used in millimeter and sub-millimeter applications such as POLARBEAR, SPT-3G, and DESHIMA [22]. Hyper-hemispherical, elliptical, or synthesized elliptical lenses are placed on the top of planar antennas to increase their forward gain and their optical coupling efficiency to the telescope.…”

Design and development of an ambient-temperature continuously-rotating achromatic half-wave plate for CMB polarization modulation on the POLARBEAR-2 experiment

“…21 Because atmospheric noise at the observation site is several orders of magnitude brighter than the B-mode signal and has a 1/f knee ∼ 1 s, 22 even a small level of polarization leakage is detrimental. Additionally, PB2 is susceptible to instrumental effects that cause mismatch between orthogonal detectors, such as the ellipticity of the sinuous antenna beam, 20,23 and to differential response induced by the lenses and mirrors. 24 Because PB2 will achieve excellent statistical error, even small levels of these systematic errors can have a negative impact on experimental performance.…”

Superconducting On-Chip Spectrometery for Millimeter-submillimeter Wave Astronomy

“…Traditionally, a spiral antenna in combination with a dielectric lens has been regarded as the prime candidate for such broad band coupling, though the spiral antenna has a linear polarization angle that rotates with frequency. A good alternative is the sinuous antenna [19], which suppresses the rotation of polarization to within ∼ ±5 degrees. Recently, there has been the advent of the superleaky antenna, which combines broadband radiation coupling with polarization stability [20].…”

“…The pixels on these chips have an antenna connected to superconducting broadband filters that separate the signal into multiple colors and deliver them into different detectors, which can be for example TESs [19] or MKIDs [22].…”