Highly sensitive and wide dynamic range polarimetric detectors arrays in the submillimeter domain

One of the main goals of the canceled Space Infrared Telescope for Cosmology and Astrophysics (SPICA), was to reveal the evidence of the influence of magnetic field in the structuration of different astrophysical objects, as for example the filamentary structure of star-forming regions. For this purpose, “instrument-in-pixel” detector arrays were developed under ESA, CNES and FOCUS contracts, to propose sensitive, compact and easy to integrate detection solutions for a Space Observatory. Magnetic field influences the light emission or absorption of small grains and molecules imprinting its characteristics in the received electromagnetic message in terms of polarization, degree, angle and intensity. Each pixel of the developed detectors absorb the radiation through two orthogonal dipole networks. The detector array is organized like a chessboard with every other pixel having absorbers rotated by 45° in order to unveil simultaneously the linear Stokes parameters without any optical loss. A very large absorption efficiency is obtained, as usual since PACS detectors, by a backshort-under-grid scheme. To obtain the goal sensitivity of 1 attoW/√Hz, detectors are cooled to 50 mK and linked to an Above IC CMOS readout circuit. For each pixel, four interleaved spiral silicon sensors gather the absorber power. They are organized in a Wheatstone bridge configuration that allows fully differential outputs: total power and polarization unbalanced intensity.