Nonlinear effects associated with the large-signal direct modulation of semiconductor laser diodes

The relationship between the optical signal response at the fundamental modulation frequency and the magnitude of the driving current is of particular importance to analog communication applications of semiconductor laser diodes. A closed-form analytical expression for the optical response of a laser diode under large-signal direct modulation conditions is presented. It was derived on the basis of the single-mode rate equations. The rate equations used in the analysis presented include the optical gain compression term. It was found that the magnitude of the gain compression ( in ) strongly affects the linearity of the large-signal modulation characteristic, particularly at higher modulation frequencies close to the frequency of the relaxation oscillation peak. The relaxation oscillation peak whose magnitude depends on the value of in exhibits a shift towards lower frequencies with the increase of electrical modulation depth.<
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