Engineering Tunable Plasmonic Nanostructures To Enhance Upconversion Luminescence

Plasmonic nanostructures, which can confine and manipulate light below the diffraction limit, are becoming increasingly important in many areas of optical physics and devices. One of the areas that can greatly benefit from surface-plasmon mediated confinement of optical fields is the enhancement of emission in low quantum yield materials. The resonant wavelength for plasmonic structures used for emission enhancement is either the excitation or emission wavelengths of the luminescent material. Therefore, a key component in designing plasmonic structures used in luminescent enhancement applications is the ability to engineer and tune plasmonic building blocks to create structures resonant at the desired wavelength. In this thesis, we have used two approaches to build tunable structures for luminescent enhancement: 1) using already synthesized metallic nanocrystals resonant at the desired wavelengths as building blocks, we designed structures that would result in maximum emission enhancement. 2) Designing arrays of plasmonic nanostructures with the help of simulation software to be resonant at the desired wavelength and then fabricating them with top-down nanoscale fabrication techniques. In either approach, the resulting large area structures were macroscopically studied by steady state and time-resolved photoluminescence measurements to quantify the plasmonic effects on enhancement. We were able to achieve high enhancement factors in almost all of the structures and designs. Furthermore, we were able to identify and study various effects that play a role in plasmonic enhancement processes.