Monolithic InAs/InGaAs quantum dot lasers Experimental sub-threshold characterization of single section, broad-area devices for different p-doping concentrations and active region lengths

Study and characterization of a new monolithic mode-locked edge-emitting semiconductor quantum dot lasers emitting at 1.26 um are ideal sources for the generation of optical frequency combs for short-reach inter- and intra-data center links. The modal dispersion and gain properties determine the suitability for ultra short optical pulse generation by mode-locking. In this elaborate, as a first step, the power vs. current characteristics, the modal gains and the dispersion properties on InAs/InGaAs single section quantum dot lasers with broad ridge waveguide are experimentally investigated. This analysis focuses on spectrally-resolved gain, temperature dependence and near field investigation, trying to highlight the influences of the different p-doping values, different active region lengths and broad area effects. In the first chapter, introductory topics are discussed, and a brief summary of the technological motivation which led us to the modern state of the art on QD laser and a further motivation of this work is given. Moreover, an overview of the modelling techniques of these devices is provided. In the second chapter, the description of how the experimental characterization was carried out and insights on the various set-up used, within the technical motivation, are showed. In the third chapter, the elaborate focuses on the analysis and interpretation of the obtained results. The post-processing techniques used in this thesis are widely described and segments of scripts, created ad hoc, are reported. Due to the large number of elaborated data, the appendix stores all the detailed plots and graphs inherent to the post-processing, whereas in the main chapters they are summarized in more general and explicative plot.