Chirp minimization and optimum biasing for current-modulated coupled-cavity semiconductor lasers

Dynamic line broadening (chirping) of a single-frequency coupled-cavity semiconductor laser under direct current modulation is analyzed theoretically using a set of generalized rate equations. When the controller section is biased below threshold in a three-terminal device, the chirp is not significantly affected by the intercavity coupling. By contrast, when both sections are biased above threshold, the chirpcan be reduced by a proper combination of the bias levels. The present analysis is in qualitative agreement with the reported experimental observations and should be useful for device optimization.