Transmission trap detectors.

Polarization-independent trap detectors, in which light is strongly absorbed through multiple reflections, are generically described in terms of the symmetry planes of a cube. The detailed design of a four-element transmission trap with coaxial input and output beams is presented. It is shown that such a trap retains polarization-dependent loss and that six detectors are required for a polarizationindependent transmission trap with coaxial beams.