Modeling and characterization of quantum-dash lasers: Intrinsic dynamics and intermixing effects

The intrinsic dynamics and intermixing effects of quantum dash lasers are characterized and modeled to explore the possibility of achieving high-performance and low-cost photonic integrated circuits (PICs) based-on quantum dash structures. A pulse optical modulation setup is proposed as a new characterization technique to measure the intrinsic dynamics of semiconductor lasers with minimal self-heating effects. A new extraction method based-on the phase frequency response of an amplitude-modulated laser is presented, as an alternative to the conventional magnitude-based method.;The intrinsic dynamics of InAs/InAlGaAs quantum-dash lasers are investigated subjected to optical modulation at various temperatures. The differential gain of the quantum dash lasers is found to be in the same order as a QW laser, however, the gain compression factor are 2-3 times larger, which becomes the main factor that limits the intrinsic bandwidth. The dash size and inhomogeneity are found to be critical to the temperature sensitivity of the dynamic properties. The optical injection modulation of semiconductor lasers by intra-cavity stimulated Raman scattering is also reported for the quantum dash lasers. This mechanism manifests itself as sharply enhanced modulation bandwidth when the injected photons are 33+/-3 meV more energetic than the lasing photons. Raman scattering measurements and rate equation models strongly support the direct gain modulation by stimulated Raman scattering.;The fundamental and dynamic properties of intermixed InGaAs-InGaAsP QW lasers were first investigated to assess possible degradation by intermixing. The fundamental properties such as threshold current and slope efficiency were largely unchanged even after as much as 120 nm of wavelength shift. Meanwhile, the dynamic properties such as modulation efficiency and K factor were degraded after just a moderate degree of intermixing, but the degradation was not worsened by further intermixing. Furthermore, the gain, alpha factors and modulation characteristics were measured and compared on InAs/InAlGaAs quantum-dash lasers intermixed by different techniques. The material quality is well preserved by the dielectric-capping technique. The quantum dash lasers show obvious degraded dynamic characteristics after intermixing, similar with the observation in the QW lasers. It is found that the degradation does not vary much with changing temperature. Provided the finite degradation of dynamic properties is tolerable, the quantum dash intermixing technique will be very useful for the fabrication of PICs.