Coupling Fluorophores Molecules to Nanophotonic Structures

Download or read book Coupling Fluorophores Molecules to Nanophotonic Structures written by Anika Amir Kinkhabwala and published by Stanford University. This book was released on 2010 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluorescence imaging and spectroscopy is an important tool in many areas of research. Biology has particularly benefitted from fluorescence techniques, since a single molecule's position, local environment, and even activity can be studied in real time by tagging it with a fluorescent label. It is, therefore, important to be able to understand and manipulate fluorescence. One way to control fluorescence is to shape the local electromagnetic fields that excite the fluorescent molecule. This thesis studies the interaction between fluorescent molecules and two nanophotonic structures that highly modify local electromagnetic fields: the bowtie nanoantenna and the photonic crystal cavity. The study of plasmons, or coherent excitations of free electrons in a metal, has led to the fabrication of antennas at optical frequencies. In particular, gold bowtie nanoantennas have been shown to concentrate light from the diffraction limit at 800 nm (~300 nm) down to ~20 nm, while also enhancing the local electric field intensity by a factor of 1,000. This huge change in the local field greatly alters the absorption and fluorescence emission of nearby molecules. This thesis will show that the fluorescence from an initially-poor single-molecule emitter can be enhanced by a factor of 1,300, allowing for the measurement of one highly enhanced molecule over a background of 1,000 unenhanced molecules. By extending this experiment to molecules in solution, dynamics of single molecules in concentrated solutions can also be measured. While bowtie nanoantennas act to concentrate light, light does not remain in the structure for long. The photonic crystal cavity can be used to trap and store light, which has interesting implications for molecular emitters located nearby. This thesis will show that molecules can be lithographically positioned onto a photonic crystal cavity and that the molecule's fluorescence emission is coupled to the cavity modes.