الفهرس 
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Abstract
Self-assembled quantum dot (QD) semiconductor laser has been an appealing subject in academia and industry since its introduction in the late 80s. The three-dimensional confinement allows for the creation of discrete energy levels, resulting in a small lasing threshold current value, wide tunable range, and high-temperature stability compared to quantum well semiconductor lasers [1]–[3]. The strong potential is foreseen in applications such as quantum computing [4], optical sensing [5], and visible light communication [6], where a red wavelength laser is required. The red wavelength laser in the range of 650- 670 nm emission has been achieved using a combination of InP QDs as an active layer inside AlGaInP as a barrier.
This thesis aims to study the InP/AlGaInP self-assembled QD laser while subjected to weak feedback. First, an experimental investigation is presented to extract the key parameters of the InP/AlGaInP laser chip, such as threshold current, output power, and output spectrum for single and double layer InP QDs active regions. The additional layer increased the threshold value, and the output power. A red shift in the lasing wavelength was also observed, which comes in agreement with the previous studies [7]. The output spectrum of the double-layer InP/AlGaInP QD laser chip is modeled as the sum of two inhomogeneous curves (small and large) due to the manufacturing process. As the injected current increases, the dominant peak is shifted from the large QD group to the small QD group. The analysis of the output spectrum with different applied current densities showed the saturation of the large QD group due to the large radiative lifetime and verified the lasing behavior via small QD group only. Second, a rate equation model is used to describe the bimodal QD size distribution impact on the output spectrum of InP/AlGaInP QD laser. The simulation results and the experimental results are in a good match.
Finally, an extended rate equation model is presented for the theoretical study of the laser characteristics tunability using an external cavity configuration where a mirror is placed in front of one of the cavity facets. The model considers the Hermite Gaussian nature of the output laser beam profile that has been reported for the edge-emitting semiconductor QD lasers. Also, the geometry of (flat and cylindrical) mirrors and the external cavity length have been considered.
The thesis consists of six chapters described as follows:
Chapter 1:
A summary of the thesis motivation and objectives, underlining the main contributions alongside the thesis structure, is presented in chapter 1.
Chapter 2:
This chapter deliberates the fundamentals of the QD semiconductor laser in the matter of fabrication, the state-of-the-art, the basics of QD rate equation modeling, and the external cavity QD laser.
Chapter 3:
In chapter 3, the experimental examinations of single/double layer self-assembled InP/AlGaInP QD laser chip displaying the extracted threshold, output power, and beam profile are presented.
Chapter 4:
This chapter presents two models for the single and dual QD size distribution rate equation, discussing the effect of various parameters such as the inhomogeneous broadening, homogenous broadening and radiative lifetime for the single QD size distribution model, where the simulation results of the QD dual size distribution model are compared to the experimental results obtained in chapter 3 and show a good match.
Chapter 5:
Chapter 5 uses the Hermite Gaussian modes propagation through an ABCD matrix system. Under weak feedback assumption, an extended rate equation model is presented in this chapter for an external cavity QD laser.
Chapter 6:
A conclusion of the thesis is stated in this chapter and an introduction of several suggestions for future work is also found.