Studies of Passive and Active Plasmonic Core-Shell Nanoparticles and their Applications

• Main Author: Campbell, Sawyer Duane
• Other Authors: Ziolkowski, Richard W.
• Language: en
• Published: The University of Arizona. 2013
• Subjects: metamaterials; Mie theory; nanoparticles; plasmon; resonance; Optical Sciences; active
• Online Access: http://hdl.handle.net/10150/293420

Coated nanoparticles (CNP) are core-shell particles consisting of differing layers of epsilon positive (EP) and epsilon negative (ENG) materials. The juxtaposition of these EP and ENG materials can lead to the possibility of coupling incident plane waves to surface plasmon resonances (SPR) for particles even highly subwavelength in size. We introduce standard models of the permittivities of the noble metals used in these CNPs, and propose corrections to them based on experimental data when their sizes are extremely small. Mie theory is the solution to plane wave scattering by spheres and we extend the solution here to spheres consisting of an arbitrary number of layers. We discuss the resonance behaviors of passive CNPs with an emphasis on how the Coated nanoparticles (CNP) are core-shell particles consisting of differing layers of epsilon positive (EP) and epsilon negative (ENG) materials. The juxtaposition of these EP and ENG materials can lead to the possibility of coupling incident plane waves to surface plasmon resonances (SPR) for particles even highly subwavelength in size. We introduce standard models of the permittivities of the noble metals used in these CNPs, and propose corrections to them based on experimental data when their sizes are extremely small. Mie theory is the solution to plane wave scattering by spheres and we extend the solution here to spheres consisting of an arbitrary number of layers. We discuss the resonance behaviors of passive CNPs with an emphasis on how the resonance wavelength can be tuned by controlling the material properties and radii of the various layers in the configuration. It is demonstrated that these passive CNPs have scattering cross sections much larger than their geometrical size, but their resonance strengths are attenuated because of the inherent losses in the metals. To overcome this limitation, we show how the introduction of active material into the CNPs can not only overcome these losses, but can actually lead to an amplification of the scattering of the incident field. We report several optimized active CNP designs, including ones based on quantum dot gain media and study their performance characteristics with particular attention to the effect of the location of the gain material on the performance of these designs. We investigate the ability to control the scattered field directivity of the CNPs in both their far- and near-field regions and propose designs with minimal backscattering and those emulating macroscopic nanojets. We compare data generated by initial efforts to experimentally prepare CNPs and compare against analytical and numerical simulation results. Finally, we suggest a variety of interesting future research directions. resonance wavelength can be tuned by controlling the material properties and radii of the various layers in the configuration. It is demonstrated that these passive CNPs have scattering cross sections much larger than their geometrical size, but their resonance strengths are attenuated because of the inherent losses in the metals. To overcome this limitation, we show how the introduction of active material into the CNPs can not only overcome these losses, but can actually lead to an amplification of the scattering of the incident field. We report several optimized active CNP designs, including ones based on quantum dot gain media and study their performance characteristics with particular attention to the effect of the location of the gain material on the performance of these designs. We investigate the ability to control the scattered field directivity of the CNPs in both their far- and near-field regions and propose designs with minimal backscattering and those emulating macroscopic nanojets. We compare data generated by initial efforts to experimentally prepare CNPs and compare against analytical and numerical simulation results. Finally, we suggest a variety of interesting future research directions