Semiconductor lasers are key devices for wide range of applications (e.g. fiberoptical communications, optical disk memory and laser printer) due to various attractive features such as small size, low power consumption, fast response etc. However, design and fabrication of laser diodes involve various complicated procedures. The process is expensive and time consuming. Efficient and accurate simulation tools are in great demand for the laser design and optimization. Moreover, the design considerations vary from each other greatly for different types of laser diodes. In this thesis, two types of laser diodes, Le., Distributed Feedback Laser Diodes (DFB LDs) and Vertical Cavity Surface Emitting Lasers (VCSELs) are studied and analyzed. The development and the challenges of DFB LDs and VCSELs are introduced in Chapter 1. In Chapter 2 we discuss the characteristics of the multiple phase shift distributed feedback laser diodes (MPS DFB LDs). In chapters 3 to 6, the design of VCSEL and VCSEL-based devices and the analysis of their characteristics are presented. Distributed feedback laser diodes (DFB LDs) play an important role in the longhaul and high-bit-rate optical-fiber transmission systems. However, the singlemode operation is difficult to be achieved with the uniform DFB LDs or the quarter-wave-shift DFB LDs. Multiple phase shift DFB LD is a promising device to provide single-mode operation with a high coupling coefficient. In the design of multiple-phase-shift DFB LDs, two important criteria were considered, Le., the requirement of a high longitudinal side-mode suppression ratio and the necessary VII