University PhD Dissertation Defense of John Liu

John Liu sqliu at stanford.edu
Mon Oct 18 09:36:54 PDT 2010


Department of Applied Physics
University PhD Dissertation Defense


Design and Implementation of Plasmonic Cavities in Thin Metallic Films


John Liu
Applied Physics PhD Candidate
Reseach Advisor: Professor Mark L. Brongersma


October 21, 2010 @ 10:00 A.M.
Allen Building (CIS-X) Room 101


ABSTRACT
Metals contain a sea of free electrons that are easily driven into collective oscillation by electromagnetic waves.  As a result, small metal objects can serve as antennas that strongly scatter light.  At the same time, extended metal surfaces have been shown to guide surface plasmons (photons bound to surface charge oscillations) that can confine light to deep sub-wavelength dimensions.  Patterned metallic films can combine both the scattering and guiding properties of metals to capture and concentrate light from free space into a photodetector or to control the emission of light from emitting media.

We first consider the wide range of functions that can be achieved in directing light emission with the help of smooth metallic films.  We then describe how light interacts with patterned metallic films and present a detailed study of the effect of a single metallic groove on the scattering and surface plasmon guiding processes.  This has lead to our discovery of new, exciting opportunities for dense optical functionality with non-periodically patterned metallic films.  We show that a micronscale structure consisting of just two grooves in a metal film can lead to directional light coupling and wavelength splitting with a contrast ratio of 3:1.  Our understanding is then generalized giving rise to a fast, simplified optimization of large non-periodic structures for a desired function.  Lastly we consider the efficiency and bandwidth limits of coupling light through sub-wavelength slits for photodetection.  We outline a path to efficient, spectrally selective detection which may find application in compact, polarization sensitive, multi-wavelength plasmonic detectors.
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