Nnanoscale light-matter interactions: fundamentals and applications

Novel phenomena and promising applications have been emerging from nanoscience and nanotechnology research over recent decades. Particularly, people pursue a better understanding of how light and matter interact with each other at the nanoscale. This dissertation will present our work on the relevant topics, including ultrafast optical generation and manipulation of nanoscale phonons, metamaterials for thermal management, and cooperative chirality in inorganic nano-systems. Through an acoustically mismatched nanoscale interface, interfacial phonon coupling may lead to a coherently modulated phonon spectrum, which however has been less studied. We have demonstrated unambiguous experimental evidences of coherent interfacial phonon coupling between the core and shell constituents by employing a well-designed nanoscale core-shell structure with a precisely tunable interface as a model system. Furthermore, the observed phonon modes can be selectively tailored in a highly controllable manner by different ultrafast pulse control schemes. This study represents an important step towards nanoscale phonon engineering with rationally tailored nanostructures as building blocks. Metamaterials, which are artificially patterned micro/nano-structures, are studied for thermal management. For this purpose, we propose patterned arrays in different forms, including micropillar arrays and fiber arrays. We have discovered the structural dependence of the arrays’ characteristic resonance and emission properties, and how the properties are impacted in imperfect patterns which are common in real life. This study provides new perspectives on metamaterials for thermal management and the textile industry. Lastly, chiral light-matter interaction is studied in a novel type of inorganic nanocrystals, consisting of both crystallographic and geometric chirality. We build up a general model for simulating electromagnetic response of chiral objects and extract the materials parameters from experimental data of the achiral-shape nanocrystals. By simulating nanocrystal of different geometries and comparing with experimental circular dichroism spectra, the unique spectral features from the nanocrystals’ intrinsic crystallographic chirality, geometric chirality and their interplay are identified. Besides, an excellent agreement is achieved between the simulation and the experiment. This result opens up the opportunities for new chiroptical devices and chiral discrimination technology