UC San Diego

The last two decades have witnessed the fruitful research on nanoscale semiconductor nanolasers due to their compact footprint, low energy consumption and fast modulation speed, that are advantageous merits for nanolasers serving as light sources in future ultra-dense photonic integrated circuits (PIC). Previously, most of the research focus on the demonstration of individual devices with improving performance. Recently, there has been escalating interest in investigating the interaction of dual nanolasers, aiming at exploring the behavior of larger-size laser arrays. Before applying nanolasers in future laser array systems, certain aspects require further investigation, where this dissertation aims to fill the blank. While most of the laser parameters that have impact on the phase-locking stability of coupled nanolasers are studied in previous literatures, spontaneous emission factor has not been explored. This can be justified by the fact that conventional semiconductor has negligible spontaneously emitted photons funneling into the lasing mode due to their comparably large dimension. The compact resonator size of nanoscale lasers leads to pronounced spontaneous emission factor and necessitates research effort in evaluating the phase-locking stability on such factor. In chapter 2, we have employed the bifurcation analysis based on the coupled laser rate equations and presented the theoretical impact of spontaneous emission factor on the nonlinear dynamics of coupled nanolasers. We show that the stability is enhanced with increasing spontaneous emission factor, which indicates the huge potential of nanolasers being applied in array forms. To experimentally access the requirement for such stability, we have engineered a novel coupling geometry in chapter 3. By controlling the coupling bridge that locates in between two nanolasers, we have shown that either an in-phase or out-of-phase mode can be selected, which is confirmed by the experimental results. In chapter 4, we have theoretically explained the broad linewidths in nanolasers, focusing on the thermal noise and intensity noise inside these nanoscale cavities. We have observed that the fundamental thermal fluctuation is a huge contribute towards the measured linewidth at room temperature, that is on the order of 1nm. In chapter 5, we have reviewed some recent progress that researchers have made in building dense nanolaser arrays with applications ranging from biosensing to long-haul communications. Chapter 6 concludes the thesis and discusses some future directions that remain to explore.