Optical efficiency of far-infrared photoconductors.

We report an experimental and theoretical study to optimize the geometry of far-IR photoconductive detectors with diffraction-limited throughput. Factors considered in this optimization include internal optical path relative to measured absorption length, photoconductive gain, uniformity of illumination, cosmic ray cross section, and compatibility of the design with the requirements of 1and 2-D arrays. A rod-shaped detector geometry with square cross section, electrodes on the lateral faces, and a beveled backface to trap the radiation by total internal reflection was found to have nearly equal responsivity to the best detectors in