| This thesis focuses on understanding fundamental nano-photonic properties of single crystalline DNA nanoparticle superlattices. Here, the single crystalline DNA nanoparticle superlattices are studied, for the first time, in several important nano-photonic aspects such as strong light-surface plasmon coupling, crystal habit-driven light scattering and focusing, and exciton-surface plasmon interaction.;Chapter 1 introduces the optically relevant degrees of freedom in single crystalline DNA nanoparticle superlattices, after briefly reviewing the synthetic aspects of DNA nanoparticle superlattices. Then, the overview and significance of this work are discussed. Chapter 2 discusses strong light-surface plasmon coupling within gold nanoparticle superlattices. An unconventional photonic band gap (polaritonic gap) is established due to the strong coupling rather than the crystal translational symmetry (Bragg gap). Particularly, tunability of the coupling strength is demonstrated by controlling crystal configurations such as lattice constant. Chapter 3 further investigates the light-surface plasmon coupling via the superlattices made with anisotropic gold nanoparticles. Due to the polarization dependence of the anisotropic nanoparticles, two different surface plasmon modes can be excited at the individual nanoparticle level, and therefore, the superlattices exhibit two different plasmonic resonant modes. Chapter 4 shows crystal habit-driven microlens phenomena of the superlattices. Theoretically, such microlens behaviors are characterized in terms of light focusing profiles and microlens imaging. Then, the predicted phenomena are demonstrated experimentally showing a qualitative agreement with the theoretical results. Chapter 5 discusses surface plasmon enhanced exciton emission and crystal habit-induced directionality of the emission. At the nano-scale, the fine control over dye positions allows for tuning optical antenna effects of gold nanoparticles on the dye exciton emission, and therefore, decay rates are tuned. At the micron scale, the anisotropic microcavity geometry and the plasmonic nature of the superlattices induce a directional emission pattern that is drastically different from behavior of conventional dielectric spherical microcavities. This significant development demonstrates the potential of superlattices as an active 3D plasmonic microcavity for applications such as plasmon lasing. Chapter 6, as conclusions and future perspectives, discusses future challenges and opportunities for optical studies based on single crystalline DNA nanoparticle superlattices. Possible applications and further fundamental studies are considered, including: microcavity lasing, Whispering Gallery resonant mode analysis, epsilon-near-zero microlensing, and molecular sensing. |
