Controlling Light With Plasmonic Metal Nanostructures

Owing to the plasmonic resonances of metal nanostructures, their optical responses are quite different from those of bulk metal, which makes them have important applications in many scientific and engineering fields. This thesis focuses on the applications of plasmonic metal nanostructures in two research areas, which are metamaterials and nanophotonics. For applications on metamaterials, plasmonic metal nanostructures are used as unit cell building blocks of an artificial metametarial with controlled optical electromagnetic parameters; while for appplications on nanophotonics, plasmonic metal nanostructures are used as optical nanoantennas to control the emission of nanoemitters.Firstly, we proposed a novel double negative negative index metamaterial design based on coupled metal nanorings. This novel metamaterial works at visible and even down to ultraviolet wavelength range, with much higher figure of merit (FOM) than the existing visible negative index metamaterials at that time. This design fills the gap in the design of low loss double negative negative index metamaterials at green, blue, violet and near ultraviolet wavelength range, which may find applications for super-resolution imaging technology, etc.We also designed a novel dielctric-metal hybrid ring resonator (HRR) for magnetic response. By using HRRs as unit cell building blocks, homogenizable magnetic metamaterials can be realized at short visible wavelengths and near ultraviolet wavelengths. In this research, we proposed a nanoring resonator model, and classified all-dielectric magnetic resonators, conventional split-ring magnetic resonators (SRRs) and the proposed HRR magnetic resonators into three resonance cases in the nanoring resonator model. The proposed HRR magnetic resonator design as well as the nanoring resonator model is inspiring for magnetic resonator design.In the thesis, we also observed for the first time the antisymmetric plasmonic resonance mode at single metal nanostrips. We found that as long as the insulator-metal-insulator (IMI) nanosandwich structure is formed, a single metal nanostrip will be able to support an antisymmetric plasmonic resonance. Using numerical simulations and a waveguide resonator model, we clarified the important role by the sandwiching high index dielectric layers in the formation of the antisymmetric plasmonic resonance mode. The IMI nanosandwich structures were then used for construction of metamaterials with magnetic responses at a wavelength range from blue to nearviolet. The discovery of the antisymmetric plasmonic mode in the IMI nanosandwich structure as well as the analysis based on the waveguide resonator model is inspiring for plasmonic mode study; while the featured magnetic response of the IMI nanosandwich structure may find applications for magnetic metamaterials as well as for the manipulation of magnetic dipole transitions.In the research on emission control of nanoemitters, we developed a technique for quantitative measurement of the field enhancement spectra of optical nanoantennas based on single quantum dot fluorescent probes. The key of the experiment work is developing highly stable single quantum dot fluorescent probes and precisely coupling single quantum dot with optical nanoantennas. Single colloidal quantum dots with high quantum yield were encapsulated with silica shells to form highly stable single quantum dot fluorescent probes; single quantum dots were coupled to optical nanoantennas with high spatial precision by using the developed AFM manipulation based on tapping mode. This experimental technique for field enhancement spectra measurement is not only a characterization tool for fundamental and application research on optical nanoantennas, but also with the help of it and the experimental techniques involved, we may develop novel quantum light sources based on hybrid systems of single quantum dots coupled to optical nanoantennas.