Bandwidth Reduction of UTC-TW Photo Detector at High Optical Power Levels

High speed photo detectors are very useful components for high capacity optical communication links, generation of MM and sub-MM wave signals and more. The most promising photo detector for speed is the UTC-TW PD, which was proposed a few years ago. Operation of such devices was reported at frequencies exceeding 300 GHz. Output power and efficiency improve as the optical power is increased, however, when the optical power exceeds the saturation level, substantial reduction is observed in bandwidth. In this paper we present experimental results demonstrating the bandwidth degradation at high optical power, and offer an explanation to this phenomenon, which is backed up by theoretical simulations.