[di′strib·yəd·əd ə′mish·ən ‚fōd·ō‚dī‚ōd] (electronics) A broad-band photodiode proposed for detection of modulated laser beams at millimeter wavelengths; incident light falls on a photocathode strip that generates a traveling wave of photocurrent having the same wave velocity as the transmission line which the photodiode feeds.