Ultralow chirping short optical pulse (16 ps) generation in gain-coupled distributed feedback semiconductor lasers

We describe optical short pulse generation in novel gain-coupled distributed feedback (GC-DFB) semiconductor lasers by using a simple electrically pumped gain switching method. An optical pulse as short as 16 ps has been obtained from a 130 ps current pulse. The most exciting result is that the lasers keep single longitudinal mode oscillation with very low wavelength chirping (∼0.12 nm) during the gain switching operation. From the optical pulse width and the amount of the wavelength chirping, we have estimated the α parameter of the GC-DFB laser to be less than 1.6.