Theoretical and Experimental Investigation of Quantum Dot Passively Mode Locked Lasers for Telecomm and Biomedical Applications

This thesis is focused on the experimental and theoretical study of novel quantum dot passively mode locked lasers. The motivation behind this endeavour was the fundamental need, of many scientific areas, for high power, ultra-short and time stabilized optical pulses, generated directly from highly integrated laser devices. Such devices could allow the study of ultra-fast chemical and physical effects, or alternatively could provide telecomm engineers and medical practitioners with hand-held lasers suitable for a variety of applications. The first step consists of a detailed mathematical investigation of the mode-locking mechanism so as to depict clearly the fundamental limitations associated with ultra-fast high power generation. Through numerical modelling a novel semiconductor material (quantum-dots) is successfully introduced, whereas the benefits of such an approach are presented. The major part of this thesis consists of a detailed experimental investigation of various quantum-dot based mode-locked semiconductor structures. Through this investigation various new effects were demonstrated, that allowed a deeper insight to new regimes of operation. These regimes that namely consist of multi-wavelength emission and mode locking, pulse-width narrowing with increasing current injection, Q-switching stabilization and feedback-free chaotic operation, unlock new areas of applications, present new design guidelines for highly integrated semiconductor lasers. Finally, these regimes originate from the unique properties of the quantum-dot material and were firstly observed and investigated during this thesis. Consequently, this thesis played a major role in the future development of this scientific field and led to more than 15 publications in peer-reviewed journals 4 conference papers and a book chapter.