Simulation and Characterization of Cooled Silicon Bolometers for the B-BOP SPICA Polarimetric Camera Instrument

Abstract

In the frame of the space infrared telescope for cosmology and astrophysics (ESA/JAXA) telescope project, we investigated the feasibility of a polarimetric camera, the magnetic field [B] explorer with bolometric polarimeter instrument, designed to study the magnetic field at different scales in the universe in the far infrared band (50–500 μm). A polarimetric detector array prototype was developed to address the 100-μm band. It is made of 16 × 16 pixels with a pitch of 750 μm and is fabricated on top of a read out integrated circuit complementary metal-oxide-semiconductor (CMOS) wafer. Each pixel consists in four active and four reference bolometers arranged in a double Wheatstone bridge configuration. Two kinds of polarimetric pixels (0°/90° and −45°/+45°) were integrated into the array in order to retrieve the linear Stokes coefficients without the need for a rotating polarizer or half-wave plate. At a wavelength of 100 μm, the detectors exhibit strong electromagnetic absorption (>90%), high responsivity (1–3 × 1011 V/W), and a total measured noise equivalent power of 8 × 10−18 W/Hz0.5. The electrical cutoff frequency is approximately 2 Hz (−3 dB), measured under an optical load of a few femtowatts at an operating temperature of 50 mK.