Multimode dynamics of semiconductor quantum-dot lasers

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In this project, the dynamics of multi-mode lasers based on semiconductor quantum-dots will be investigated. Semiconductor quantum-dots are nanometre-sized semiconductor structures that can be grown epitaxially and tailored to specific requirements. Their small size leads to the formation of discrete electronic energy states, yielding atom-like optical transitions. In contrast to conventional semiconductor laser materials, quantum dots offer a high tunability of the emission wavelength, a broad gain spectrum, and high dynamical stability. Optoelectronic devices based on quantum dots are well suited for generation of entangled photon pairs, single-photon generation, and secure quantum communication. In traditional telecommunications, quantum-dot based optical amplifiers can be used for optical data communication with bit rates exceeding 100Gb/s, owing to the ultra-fast recovery of the optical gain.The localized nature of quantum dots makes them susceptible to spatial inhomogeneities, as they arise naturally in laser cavities due to the standing wave pattern of the optical field. The interaction of the quantum-dot medium with such inhomogeneities leads to the formation of multi-mode dynamics, i.e. the emission of several lasing wavelengths at once. This can lead to new dynamic effects, either in the free-running laser or when optical perturbations are present, such as optical feedback or external optical injection.The aim of the project is to investigate the multi-mode dynamics of semiconductor quantum-dot lasers under these conditions, both theoretically and experimentally. To this end, an efficient numerical model will be derived, describing the laser dynamics and the interplay of different laser modes, as well as the complex quantum-dot dynamics. This model will be applied to and compared with experimental data gathered from measurements performed during the project. The obtained results will be of great importance for future design of optoelectronics based on semiconductor quantum dots.