A Tunable Blackbody Polarized Infrared Source for the B-BOP Camera

The B-BOP detector is composed of polarization sensitive bolometer arrays in the 70–350 µm spectral range with a goal sensitivity around one attoWatt/sqrt (Hz). A polarized infrared calibration set-up is required to evaluate its performances. The calibration source is based on 6-ring-shaped, concentric blackbody-like emitters that can be individually controlled. The total emitting surface is therefore tunable from 9 up to 1200 mm². The temperature is tunable from 1 to 40 K without disturbing the dilution cryostat and the working temperature of the detector arrays. The present paper describes the source, the rotating polarizer at low temperature, the modulation means, and the complete optical tube leading polarized infrared photons for characterizing detectors down to femtowatt level. Details of the design and realization are discussed.