We have developed a bolometric detector that is intrinsically sensitive to linear polarization which is optimized for making measurements of the polarization of the cosmic microwave background radiation .
The receiver consists of a pair of co-located silicon nitride micromesh absorbers which couple anisotropically to linearly polarized radiation through a corrugated waveguide structure .
This system allows simultaneous background limited measurements of the Stokes I and Q parameters over \sim 30 % bandwidths at frequencies from \sim 60 to 600 GHz .
Since both linear polarizations traverse identical optical paths from the sky to the point of detection , the susceptibility to systematic effects is minimized .
The amount of uncorrelated noise between the two polarization senses is limited to the quantum limit of thermal and photon shot noise , while drifts in the relative responsivity to orthogonal polarizations are limited to the effect of non-uniformity in the thin film deposition of the leads and the intrinsic thermistor properties .
Devices using NTD Ge thermistors have achieved NEPs of 2 \cdot 10 ^ { -17 } ~ { } \mathrm { W } / \sqrt { \mathrm { Hz } } with a 1 / f knee below 100 mHz at a base temperature of 270 mK .
Numerical modelling of the structures has been used to optimize the bolometer geometry and coupling to optics .
Comparisons of numerical results and experimental data are made .
A description of how the quantities measured by the device can be interpreted in terms of the Stokes parameters is presented .
The receiver developed for the Boomerang and Planck HFI focal planes is presented in detail .