Razi University

   This thesis presents a comprehensive physics-based modeling and optimization study of 1550 nm InP/InGaAsP multiple quantum well (MQW) ridge-waveguide laser diodes for performance enhancement. The primary objective was to develop an accurate multi-physics model using Silvaco ATLAS Technology Computer-Aided Design (TCAD) software and to integrate it with the Particle Swarm Optimization (PSO) algorithm for systematic structural optimization. A baseline laser diode structure consisting of three compressively strained InGaAsP quantum wells embedded in a Separate Confinement Heterostructure (SCH) was designed and thoroughly characterized. The TCAD model incorporated advanced physical mechanisms, including strain-dependent band structure, Auger recombination, free-carrier and intervalence band absorption, thermionic emission with tunneling, and self-heating effects. After calibration against published experimental data, detailed Light-Current-Voltage (L-I-V) characterization and parametric sensitivity analysis were performed to identify the most influential design parameters. The PSO algorithm was subsequently coupled with the TCAD simulator to perform multi-objective optimization aimed at minimizing threshold current while maximizing slope efficiency and wall-plug efficiency, subject to thermal and wavelength constraints. After 80 iterations with a swarm of 30 particles, the optimized structure demonstrated significant performance improvements compared to the baseline design. The threshold current was reduced by 26.4% (from 18.2 mA to 13.4 mA), the slope efficiency increased by 17.4% (from 0.46 W/A to 0.54 W/A), and the peak wall-plug efficiency improved by 17.8%. The optimized device also exhibited higher output power and better thermal stability. The results confirm that the integration of rigorous TCAD-based device simulation with intelligent optimization algorithms provides an effective methodology for accelerating the design of high-performance long-wavelength laser diodes. This approach not only reduces development time and cost but also offers valuable physical insight into the relationships between structural parameters and device performance, contributing to the advancement of laser sources for optical communication systems. Abstract This thesis presents a comprehensive physics-based modeling and optimization study of 1550 nm InP/InGaAsP multiple quantum well (MQW) ridge-waveguide laser diodes for performance enhancement. The primary objective was to develop an accurate multi-physics model using Silvaco ATLAS Technology Computer-Aided Design (TCAD) software and to integrate it with the Particle Swarm Optimization (PSO) algorithm for systematic structural optimization. A baseline laser diode structure consisting of three compressively strained InGaAsP quantum wells embedded in a Separate Confinement Heterostructure (SCH) was designed and thoroughly characterized. The TCAD model incorporated advanced physical mechanisms, including strain-dependent band structure, Auger recombination, free-carrier and intervalence band absorption, thermionic emission with tunneling, and self-heating effects. After calibration against published experimental data, detailed Light-Current-Voltage (L-I-V) characterization and parametric sensitivity analysis were performed to identify the most influential design parameters.