Unique lasing mechanism of localized dispersive nanostructures in InAs/InGaAlAs quantum dash broad interband laser

The authors report on the nanowires-like and nanodots-like lasing behaviors in addition to multiple-wavelength interband transitions from InAs/InAlGaAs quantum dash (Qdash) lasers in the range of ~1550 nm. The presence of lasing actions simultaneously from two different dash ensembles, after postgrowth intermixing for crystalline quality improvement, indicate the absence of optical phonon emission due to the small variation in quantized interband transition energies. This effect is reproducible and shows different lasing characteristics from its quantum dot and quantum wire laser counterparts. Furthermore, the small energy spacing of only 25 nm (at center lasing wavelength of ~1550 nm) and the subsequent quenching of higher energy transition states at higher bias level in Qdash lasers suggest the absence of excited-state transition in highly inhomogeneous self-assembled Qdash structures. However, the appearance of a second lasing line in a certain range of high injection level, which is due to the presence of different sizes of dash assembles, corresponds to the transition from smaller size of Qdash ensembles in different planar active medium. This unique transition mechanism will affect the carrier dynamics, relaxation process in particular and further indicates localized finite carrier lifetime in all sizes of Qdash ensembles. These phenomena will lead to important consequences for the ground-state lasing efficiency and frequency modulation response of Qdash devices. In addition, these imply that proper manipulation of the Qdash ensembles will potentially result in localized nanolasers from individual ensemble and thus contributing towards enormously large envelope lasing coverage from semiconductor devices.