The infrared integrated optics technology for use in the ten micrometer region of the spectrum has been developed as reported herein, comprising a traveling-wave photoconductive heterodyne detector as may be applied to CO2 laser receiver systems. The effort reported herein specifically addresses extrinsic photoconduction in gold-doped, antimony-compensated germanium at 77K in a rectangular waveguide structure and using a gallium- arsenide substrate. A traveling-wave structure is employed wherein the input infrared waveguide is phase matched with the output electrical signal transmission line which also serves as the bias electrodes. Both the slot and strip configuration of the output signal transmission line were investigated. An analysis of the traveling-wave heterodyne detector structure includes the waveguides and phase matching; carrier excitation, lifetime, and diffusion; and detector operation and performance. The analysis of the traveling-wave structure shows that its intrinsic circuit bandwidth extends through the microwave range.