This research investigates the impact of different device architectures on the frequency response of long-cavity multi-section quantum-dot lasers. This work focused on a novel 8.3-mm multi-section quantum-dot device which possessed the flexibility to be configured either as a single- or multi-section device having gain-to-modulation section ratios of 14:2 and 15:1. The long-cavity device design facilitated the testing of increased gain-to-modulation section length ratios previously unexplored in the context of the gain-lever effect. The investigation of the gain-lever effect showed improvements to both the modulation efficiency and modulation bandwidth of the device under test. The modulation efficiency and modulation bandwidth were found to vary as the modulation section length was increased, leading to the conclusion of an ideal gain-to-modulation section ratio. In addition to providing a means to investigate the gain-lever effect, the long-cavity quantum-dot device exhibited passive mode locking both with and without a saturable absorber present. While the predictable gain-lever effects were observed, long-cavity and mode-locking effects were also present in the response; these effects presented unexpected characteristics that are not captured by current published models
