The current thrust towards developing silicon compatible integrated nanophotonic devices is driven by need to overcome critical challenges in electronic circuit technology related to information bandwidth and thermal management. Surface plasmon nanophotonics represents a hybrid technology at the interface of optics and electronics that could address several of the existing challenges. Surface plasmons are electronic charge density waves that can occur at a metal-dielectric interface at optical and infrared frequencies. Numerous plasmon based integrated optical devices such as waveguides, splitters, resonators and multimode interference devices have been developed, however no standard integrated device for coupling light into nanoscale optical circuits exists. In this thesis we experimentally and theoretically investigate the excitation of propagating surface plasmons via resonant metal nanoparticle arrays placed in close proximity to a metal surface. It is shown that this approach can lead to compact plasmon excitation devices. Full-field electromagnetic simulations of the optical illumination of metal nanoparticle arrays near a metal film reveal the presence of individual nanoparticle resonances and collective grating-like resonances related to propagating surface plasmons within the periodic array structure. Strong near-field coupling between the nanoparticle and grating resonances is observed, and is successfully described by a coupled oscillator model. Numerical simulations of the effect of nanoparticle size and shape on the excitation and dissipation of surface plasmons reveal that the optimum particle volume for efficient surface plasmon excitation depends sensitively on the particle shape. This observation is quantitatively explained in terms of the shape-dependent optical cross-section of the nanoparticles. iv Reflection measurements on nanoparticle arrays fabricated using electron-beam lithography confirm the predicted particle-grating interaction. An unexpected polarizationdependent splitting of the film-mediated collective resonance is successfully attributed to the existence of out-of plane polarization modes of the metal nanoparticles. In order to distinguish between the excitation of propagating surface plasmons and localized nanoparticle plasmons, spectrally resolved leakage radiation measurements are presented. Based on these measurements, a universally applicable method for measuring the wavelength dependent efficiency of coupling free-space radiation into guided surface plasmon modes on thin films is developed. Finally, it is shown that the resonantly enhanced near-field coupling the nanoparticles and the propagating surface plasmons can lead to optimized coupler device dimensions well below 10 m.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd-2526 |
| Date | 01 January 2010 |
| Creators | Ghoshal, Amitabh |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations |
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