Origin of low dynamic wavelength chirp in short optical pulses from absorptive-grating gain-coupled distributed feedback semiconductor lasers

The instantaneous wavelength shift in gain-switched short optical pulses from absorptive-grating gain-coupled distributed feedback semiconductor lasers showed unusual behaviour which resulted in much smaller chirping than that in conventional lasers. Measurements of spontaneous emission from the absorptive grating layer indicate carrier accumulation in that layer. The origin of the low chirping has been attributed to the fact that the index increase due to carrier depletion in the active layer is compensated for by an index decrease due to carrier accumulation in the grating layer