Abstract
The detection of injected carriers by their absorption and by emission due to their recombination with majority carriers is discussed. Two new components are proposed: (1) the "photo-modulator," which permits modulation of a light beam by the change in absorption due to injected carriers (the photomodulator in connection with a phototransistor, or some other type of photocell, may be useful as an amplifier); and (2) the "graded seal junction," which permits the light to be transmitted to and from a p-n-junction without substantial absorption in the bulk semiconductor.