Anil Ghimire Thesis Defense 08/14/14

Thesis Defense

Anil Ghimire

Thursday, August 14, 2014
10:00AM (334 JFB)

Title: Manipulating Light Using Nanostructures

Optical antennas can be used to manipulate the direction and polarization of radiation from an emitter. Usually, these metallic nanostructures utilize localized plasmon resonances to generate highly directional and strongly polarized emission, which is determined predominantly by the antenna geometry alone, and is thus not easily tuned. In this work, we have demonstrated that the emission polarization and direction can be manipulated using a simple, nonresonant atomic force microscope (AFM) probe. The mechanism responsible for this control is the interference between light emitted directly into the far-field with that elastically scattered from the tip apex. Furthermore, due to the relatively weak emitter-tip coupling, the tip must be precisely positioned very close to the emitter, but this weak coupling also leads to highly tunable emission properties. Overall, the semi-infinite geometry of the tip yields superior polarization and directional control compared to either a metallic nanosphere or a resonant dipole antenna, and performs similarly to lithographically fabricated, highly-directional antennas. The ability to control the polarization together with the direction of emission could have important implications for the development of integrated nanophotonic devices and single photon sources.

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