Distortion in a semiconductor laser under quasi-sinusoidal current modulation

Both intensity modulation (IM) and frequency modulation (FM) of a directly-modulated semiconductor laser are considered. Harmonic and intermodulation distortions are evaluated with the aid of a nonlinear differential equation for the photon density. Theoretical results are obtained through the Bessel function and the perturbation methods. They allow one to compare FM and IM distortion levels, as well as the two calculation methods.