Transfer-matrix analysis of optical bistability in DFB semiconductor laser amplifiers with nonuniform gratings

We present a transfer-matrix method capable of simulating the effects of nonuniform gratings on the filtering, amplification, and bistability characteristics of distributed feedback (DFB) semiconductor laser amplifiers. The linewidth enhancement factor is incorporated in a way that allows direct gain-tuning of the bistability hysteresis. As an example, we compare a /spl lambda//4 phase-shifted DFB amplifier with and without spatial chirp. For amplifiers driven to yield the same unsaturated peak amplifier gain, positive linear chirp widens the spectral range of low-threshold switching and increases the switching contrast.