Theoretical Study of Semiconductor Laser Diodes

This dissertation presents a comprehensive theoretical investigation into the physics, architectural evolution, and modern applications of Semiconductor Laser Diodes (SLDs). The study begins with an analysis of fundamental quantum mechanical processes, specifically focusing on Einstein's transition probabilities and the Bernard-Duraffourg criteria required to achieve the necessary population inversion for optical gain. A significant portion of the research evaluates the transition from basic homojunction structures to advanced Double Heterostructure (DH) designs, illustrating how the combination of electrostatic carrier confinement and dielectric waveguiding revolutionized device efficiency. Furthermore, the study explores the impact of low-dimensional physics in Quantum Well (QW) topologies, demonstrating how the modification of the density of states minimizes threshold current densities. The final sections analyze high-precision cavity geometries, including Vertical-Cavity Surface-Emitting Lasers (VCSELs) and Distributed Feedback (DFB) lasers, which serve as the backbone of modern fiber-optic communication and Photonic Integrated Circuits (PICS). The research concludes by projecting the future of the field through Quantum Dot (QD) integration, offering a roadmap for thermally stable, ultra-high-speed optical computing.