Nonuniform injection current induced unusual chirp behavior of a four-electrode bistable distributed Bragg reflector laser

A complete analysis of the chirp of a four-electrode bistable distributed Bragg reflector laser is given in theory and by experiment. Experimentally, the chirp investigation is realized by a Mach-Zehnder interferometer. In small-signal regime, the modulus and phase of 2β/m, frequency and amplitude modulation index ratio, is measured for different injection currents and shows an unusual behavior against the modulation frequency. A theoretical model including nonuniform injection current shows the same behavior of 2β/m against the modulation frequency and proves that the nonuniform carrier distribution inside the cavity is the origin of the specific behavior. The large-signal analysis provides a study of the instantaneous chirp behavior during optical switching