A detailed characterization of the Ini-xGaxAsyP1-j, quaternary material system lattice matched to GaAs, grown by gas source Molecular Beam Epitixy (MBE) has been performed. Photoluminescence, X-ray diffraction and Transmission Electron Microscopy (TEM) were used to study the lateral composition modulation (LCM) which was observed in this material system. Optimization of the growth process and the substrate orientation resulted in a significant reduction of the LCM. Additionally, a comprehensive analysis of the optical constants was performed which resulted in the first publication of wavelength and composition dependent index of refraction data for this material system. The combination of growth optimization and index of refraction data lead to the demonstration of efficient, low threshold operation of InGaAsP/GaAs based multiple quantum well lasers. In order to efficiently couple the above laser diodes to an external cavity to facilitate the generation of ultrashort pulses, antireflection facet coatings were required. As such, optical interference filters have been fabricated using a plasma enhanced chemical vapor deposition system, based on the SiOxNy material system. High quality antireflection facet coatings, suitable for application to the InGaAsP/GaAs diode lasers have been designed and fabricated, resulting in modal reflectivities of 1-2 x 10-4. Finally, an ultrashort-pulse external-cavity diode laser system was designed and manufactured which allowed the laser diode to be wavelength tuned and emit mode-locked ultrashort optical pulses. Pulses with sub 2 ps duration and greater than 1 mW average output power have been achieved. A study of the novel application of an asymmetric quantum well structure to the generation of ultrashort optical pulses has been proposed and initiated. / Thesis / Doctor of Philosophy (PhD)