Variation of the Gain Factor of GaAs Lasers with Photon and Current Densities

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Abstract
The variation of the gain factor with the threshold current was studied in two cases, viz., (1) a reflective film was applied on one end of a GaAs laser, and (2) antireflective films were applied on both ends of the laser. In (1) the threshold current is reduced to one third as compared with the case in which no film is applied. The gain factor increases 30%. In (2) the threshold current becomes eleven times greater and the gain factor is reduced to one fourth. These phenomena were analyzed in the light of spontaneous and stimulated lifetime of electrons in the p region. A formula was obtained giving the gain factor as a function of the density of photons and of current. When the current is constant, the gain factor is inversely proportional to (P+1), where P is the density of photons. At the threshold current the gain factor is inversely proportional to the sum of quasi‐Fermi levels, Fn and Fp. The saturation effect of a light amplifier at a fixed current observed by Crowe and Craig and also the variation of the gain factor with the threshold current can be calculated by this formula.