UC Santa Barbara

The integration of active and passive optical components on-chip is critical for reducing size, weight and power, and realizing useful photonic integrated circuits (PICs). III-V substrates allow for monolithic integration of actives and passives, since both can be realized with the same material system. Indium phosphide (InP) PICs in particular have reached the highest level of maturity, owing to their utility in fiber-connected communication systems. However the lower wavelength limit is around 1.2 μm and InP substrates are costly. Silicon photonics (SiPh) has emerged in recent decades as the preferred PIC platform for high volume applications. Thanks to its compatibility with standard complimentary metal oxide semiconductor (CMOS) processing, SiPh can be manufactured at very low cost, compared to InP. PICs on silicon (Si) have demonstrated extremely low loss waveguides, and high performance passive devices. However, the lack of optical gain on Si limits its utility. Heterogeneous integration approaches, such as wafer bonding or die bonding, have sought to bridge this gap by incorporating InP gain blocks on SiPh to take advantage of the best of both. Direct heteroepitaxial growth of III-V materials on Si is the long-term goal and has the potential to create the most robust and cost effective active-passive integration solution. This technology is, however, still relatively immature compared to heterogeneous integration.In the first part of this thesis, a monolithic active-passive integration platform on gallium arsenide (GaAs) is proposed and demonstrated. This PIC platform extends the wavelength of monolithic PICs down to 1030 nm. Fabry-Perot (FP) and widely tunable lasers were both demonstrated on this platform. FP laser performance is consistent with state-of-the-art, demonstrating injection efficiency of 98%, and output power in excess of 240 mW for broad area lasers, with low threshold current density of 94 A/cm2. Tunable lasers demonstrated greater than 20 nm of continuous wavelength tuning, with over 30 mW of output power. In the second part of this thesis, GaAs quantum dot (QD) lasers are demonstrated on Si by direct metalorganic chemical vapor deposition (MOCVD) heteroepitaxy. MOCVD growth is advantageous for high volume applications, and this is the first demonstration of electrically pumped QD lasers grown entirely by MOCVD on Si. Notable progress is also demonstrated towards realizing electrically pumped lasers on patterned Si by MOCVD selective area heteroepitaxy (SAH). SAH lasers would enable efficient coupling from III-V to Si and provide the clearest long-term path towards process integration with SiPh.