Charge caching CMOS detector for polarimetry (C$^3$Po)


C$^3$Po is a concept for a novel array detector concept that is optimized for highly sensitive and precise differential imaging such as needed for astrophysical polarimetry. Chopping between two or more independent image states (such as four linearly independent polarization states) can be performed at speeds in the kHz domain to provide virtually simultaneous images without the need to read out the array at kHz frame rates. This allows the technology to be applied to large arrays with precise, slow readouts. All independent image planes are observed with the same physical pixel on the detector, which renders normalized differences between image planes insensitive to the gain of individual pixels. The detector concept has 100% geometrical fill factor and a quantum efficiency approaching unity. The technology can be applied to silicon to cover the 200-1100 nm wavelength range, and to infrared-sensitive materials such as HgCdTe or InSb for the 1-20 ensuremathμm wavelength range. While the detector concept has a wide range of potential applications outside of astronomy, we focus here on its application to polarimetric observations of the Sun.