Frequency modulation of a semiconductor laser by injection current

The emission frequency of a continuous-wave GaAs laser was modulated by varying the injection current. The frequency dependence of the efficiency of the modulation (the ratio of the amplitude of the frequency oscillations to the amplitude of the current oscillations) was investigated by a new method. It was found that this efficiency decreased by a factor of 30 when the modulation frequency was increased from 5 to 200 kHz. The experimental results were in agreement with the calculation of the temperature dependence of the frequency and of the thermal conditions in the laser.