Effect of nonlinear gain reduction on semiconductor laser wavelength chirping

A simple wavelength chirping formula is presented which includes small nonlinearities in the net gain such as spectral hole burning. The two dominant terms are a laser-structure-independent derivative or ‘‘transient’’ chirp and a structure-dependent ‘‘adiabatic’’ chirp, each with distinctly different lightwave system consequences. The two chirp contributions are indirectly related through their mutual association with relaxation oscillations. Time-resolved spectral measurements on a number of different laser structures support the results.