Optical coupling of semiconductor nanowires

The continued growth of computational demand has shifted performance and energy-efficiency bottlenecks from individual processors to data movement, where electronic interconnects are increasingly constrained by bandwidth and energy consumption. Photonic integrated circuits offer a promising solution by enabling high-bandwidth, low-energy optical interconnects. As integration density increases, optical functionality must be realized in confined volumes, leading to strong interactions between neighboring photonic elements. Semiconductor nanowires, combining subwavelength confinement with micrometer-scale propagation, have emerged as versatile building blocks for nanoscale photonics, including nanowire lasers. In densely integrated systems, optical coupling between nanowires becomes unavoidable and can significantly modify device behavior. This thesis investigates optical coupling between semiconductor nanowires experimentally and numerically, with a focus on the lasing regime. A bottom-up approach is employed using designed nanowire assemblies with controlled geometries, enabling systematic studies from single nanowires to pairs and clusters. Two platforms are examined: laterally arranged zinc oxide nanowires and vertically grown indium phosphide nanowires with defined positioning. Coupling effects are analyzed through emission spectra, far-field radiation patterns, and energy transfer under optical excitation, supported by simulations. In zinc oxide nanowire pairs, coupling induces frequency locking, master–slave behavior, and transitions between lasing states, with excitation density providing control over collective modes. In indium phosphide systems, coupled nanowires form supermodes with strongly directional emission, consistent with simulations. These results demonstrate that optical coupling enables controlled engineering of emission properties and establish semiconductor nanowires as key elements for directional nanoscale photonic devices and metasurfaces.