Characterization of lasers based on self-organized In(Ga)As quantum dots

In this thesis work, we characterize lasers based on self-organized In(Ga)As quantum dots (QDs). Intrinsic static and dynamic lasing properties of QD lasers are surveyed in high performance devices with a variety of device geometry, cavity loss and QD gain system. At first, the carrier and gain processes are analyzed that affect the temperature dependence of QD lasers. The characteristic temperature and spectral characteristics are correlated in the analysis to pin down the major processes that determine various temperature dependent behaviors in different temperature ranges and in devices with varied cavity losses. The laser design strategy for extended temperature stability in QD lasers are addressed. In the next, the waveguide effects in QD lasers are investigated. The spectral hole burning effects due to the cavity resonances modes are found to be responsible for the spectral intensity modulations in ridge waveguide QD lasers. High performance narrow stripe QD lasers with deep etched through waveguide are demonstrated. These results indicate that laser waveguide design is critical for both spectral and spatial mode control in QD lasers, and novel design elements can be incorporated in the active region without incurring deleterious effects to the laser performance, due to the strong carrier localization effect in QDs. Potentially a variety of QD devices can be realized in a cost-effective way by using novel fabrication techniques that are not suitable for the devices with conventional gain media. The spectral dynamics of QD lasers are surveyed in a wide range of devices with different QD systems and at various temperatures. Antiphase mode dynamics feature all the investigated QD lasers, no matter if the mode spectrum is modulated by the waveguide effect and in both singleand multi-longitudinal-mode cases. Other than the vanishing mode oscillation amplitude in the quantum well lasers with current, the QD lasers show persistent strong oscillation intensity and are characterized by the frequency damping effects. Both stable and chaotic mode oscillation regimes are observed without changing the former oscillation frequency and amplitude characteristics. These spectral dynamic features are related to the mode cross-saturation mechanism in Fabry-Perot lasers, i.e. the