Nonlinear Dynamics in Semiconductor Lasers - Abstract
Lüdge, Kathy
Quantum-dot (QD) laser devices are promising candidates for a variety of data communication applications. However, their theoretically predicted high modulation capabilities are still not realized. In contrast to quantum-well heterostructures, their discrete energy spectrum gives rise to their most prominent drawback: the slow carrier redistribution between these levels. Nonetheless, the slow scattering also gives rise to the unique phenomenon of two-state lasing, i.e., simultaneous emission at two wavelengths. Due to the strong nonequilibrium carrier distribution, and thus a semi-decoupling of the charge-carriers in the ground and excited state of the QD, reaching the lasing threshold is possible for ground and higher bound states, enabling two-state lasing [1]. Here, we focus on the data transmission capabilities of QD lasers with and without optical injection by using a microscopically-motivated multi-population rate-equation model. We present numerical results on the connection between two-state lasing and improved modulation properties of QD laser devices. Simulated large signal modulation eye diagrams also suggest dramatic improvements of the signal quality along with decreased frequency chirp upon excited state lasing, which might be exploited for innovative device applications. Optical injection of the two state lasing QD lasers is shown to induce hystereses and switching events that could be exploited for all-optical device implementations. [1] A. Röhm, B. Lingnau, K. Lüdge, Appl. Phys. Lett. 106,191102 (2015)