UC Berkeley

Semiconductor lasers based on microcavities have attracted a large amount of interest owing to their potential as highly integrated components in photonic circuits as well as diverse applications. Microcavity having a small modal volume is now one of the most essential components in the modern photonics, and its form has been extensively diversified thanks to recent improvements in nanofabrication. However, it has still been challenging for different types of cavities to operate under single mode and to lase in a preselected mode. This dissertation proposed three different techniques used to preselect and maintain single-mode lasing in cavities of different dimensionalities.Chapter 2 presents zero-dimensional microdisk resonators self-suspended by connecting bridges. The bridges offer mechanical support to suspend microdisks, and more importantly, can be used to enhance or reduce wave confinement in the whispering gallery mode depending on the azimuthal of modes and symmetry of bridge configurations. By tuning the quality factor of modes in microdisks, we have demonstrated single-mode lasing devices that exploit the arbitrary order whispering gallery mode. Chapter 3 demonstrates single-mode lasing of valley-Hall ring cavities using the interface (1D) between two topologically distinct photonic crystals. We present that the degree of asymmetry governs four photon confinement regimes at the interface of topologically distinct valley-Hall domains, and, controls an interplay between the width of the topological bandgap and the quality factor of ring-like modes for single-mode operation. Chapter 4 describes a single-mode lasing cavity based on the 2D photonic crystal array. It is shown that a carefully designed photonic crystal based on Dirac point scales infinitely while operating under single mode. Near the singularity, competing higher order modes are efficiently suppressed when the bands are mixed with more lossy ones, and the fundamental mode having a flat envelope makes all unit-cells in the same phase. We also discuss the experimental details on fabrications and characterizations of large-scale photonic crystal arrays.