PICOSECOND DYNAMICS IN GAIN-SWITCHED UNCOUPLED AND COUPLED QUANTUM-WELL LASERS

We experimentally demonstrate the importance of two-dimensional carrier confinement for picosecond dynamics in gain-switched quantum well lasers, measuring time-resolved spectra of gain-switched quantum well (QW) lasers with coupled QWs and uncoupled QWs. The result indicates that an extremely short pulse (< 2 ps) is generated in the uncoupled QW lasers. On the other hand, the pulse duration is about 10 ps in the coupled QW lasers in which the two-dimensional confinement effect is significantly reduced owing to the miniband formation. These results demonstrate the importance of the two-dimensional confinement of carriers for the short pulse generation in the semiconductor lasers. The measured dynamic spectral shift of the gain-switched QW lasers also confirm the significant role of the two-dimensional carrier confinement.