Interpretation of frequency self-modulation of semiconductor laser radiation

A physical model is used to explain deviation of the frequencies of longitudinal semiconductor laser modes observed in the case of amplitude self-modulation. The essence of the effect is that amplitude fluctuations are accompanied by synchronous fluctuations of the excess electron density and the latter influence the optical length of the resonator and longitudinal mode frequencies. It is shown that fluctuations of the electron density by 10–20% can give rise to a deviation comparable with the intermode separation in the radiation emitted from AlGaAs heterolasers at room temperature.