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Broadening of mode-locking pulses in quantum-dot semiconductor lasers : simulation, analysis and experiments
We consider a mode-locked quantum-dot edge-emitting semiconductor laser consisting of a reverse biased saturable absorber and a forward biased amplifying section. To describe the dynamics of this laser we use the traveling wave model taking into account carrier exchange processes between a reservoir and the quantum dots. A comprehensive parameter study is presented and an analysis of mode-locking pulse broadening with an increase of injection current is performed. The results of our theoretical analysis are supported by experimental data demonstrating a strong pulse asymmetry in a monolithic two section quantum dot mode-locked laser
Dynamical regimes in a monolithic passively mode-locked quantum dot laser
Operation regimes of a two section monolithic quantum dot (QD) mode-locked laser are studied experimentally and theoretically, using a model that takes into account carrier exchange between QD ground state and 2D reservoir of a QD-in-a-well structure, and experimentally. It is shown analytically and numerically that, when the absorber section is long enough, the laser exhibits bistability between laser off state and different mode-locking regimes. The Q-switching instability leading to slow modulation of the mode-locked pulse peak intensity is completely eliminated in this case. When, on the contrary, the absorber length is rather short, in addition to usual Q-switched mode-locking, pure Q-switching regimes are predicted theoretically and observed experimentally.
Strong asymmetry of mode-locking pulses in quantum-dot semiconductor lasers
We describe the formation of a strong pulse asymmetry in mode-locked quantum-dot edge-emitting two-section semiconductor lasers. A mode decomposition technique reveals the role of the superposition of different modal groups. The results of theoretical analysis are supported by experimental data.