PhD Oral Examination - Plasmonic Optical Antennas (Wed April 6, 3:30pm, CIS-X 101)

Plasmonic Optical Antennas

For Enhanced Light Detection and Emission

 

Edward S. Barnard

Stanford University

Department of Materials Science & Engineering

Advisor: Prof. Mark L. Brongersma

Wednesday April 6^th 2011

3:30 pm

(Refreshments at 3:15 pm) 

Location: Paul G. Allen Auditorium (CIS-X 101)

http://cis.stanford.edu/misc/directions.html 

Abstract:

        Antennas are used in a wide range of frequencies in the electromagnetic spectrum to concentrate wave energy into electronic circuits. The principles that govern RF antennas can be applied to much higher frequencies and be applied to produce nanoscale plasmonic antennas that act as "receivers" and "transmitters" for visible light. This near-field concentration makes them excellent candidates for light trapping in solar cells, light concentration in sub-wavelength photodetectors, or even localized heating for cancer therapies.  However the optical properties of metals at visible frequencies make it difficult to apply traditional antenna design rules. Using full-field electromagnetic simulations and analytical antenna models, we developed new design rules for producing optical antennas with a desired set of optical properties. We then applied these design rules to create antennas that resonantly enhance both absorption of thin silicon photodetectors and emission of cathodo-luminescence (CL) photons. Through spatial and spectral mapping of both photocurrent and CL we clearly show the fundamental and higher-order resonant modes of these antennas. With CL we are also able to map the spatial distribution of these resonant modes with nanometer resolution. In addition to these specific demonstrated applications, the results of this study enable optical engineers to more easily design a myriad of plasmonic devices that employ optical antenna structures, including nanoscale photodetectors, light sources, sensors, and modulators.