[labmembers] Reminder: AP PhD Defense of Aaswath Raman (Today, 2pm, Allen 101)

Department of Applied Physics

University PhD Dissertation Defense

Broadband Nanophotonics: Plasmonic Band Theory & Light Trapping in Solar Cells

 

Aaswath Raman

Advisor: Professor Shanhui Fan

 

Friday February 15, 2013 @ 2:00 PM (Refreshments: 1:45 PM)

Location: Allen Building (CIS-X), Room 101

ABSTRACT

Subwavelength photonic structures enable a remarkable degree of control over light propagation and absorption at nanoscale dimensions. From sensing and modulation, to on-chip communication and light trapping in solar cells, new device applications and opportunities now motivate the need for a richer understanding of the optical properties of plasmonic structures and metamaterials over a broad range of frequencies.

In this talk, I will first introduce a photonic band theory that rigorously models the broadband behavior of plasmonic nanostructures and metamaterials. The theory formulates plasmonic band structures as Hermitian eigenvalue equations, and offers an intuitive physical picture of modal material loss. An upper bound on the modal material loss rate is then derived, placing fundamental limits on device operation. Furthermore, I will present a perturbation theory that elucidates the effect of dielectric refractive index modulation and metallic plasma frequency variation in plasmonic nanostructures.

Next, I will present a nanophotonic light trapping theory for solar cells and show that, using a nanophotonic design, one can exceed conventional limits on light trapping for all absorption regimes of the active material. The theory's insights are then applied to organic solar cells to design a dielectric light trapping structure that provides 10-15% photocurrent enhancement relative to an optimized planar organic solar cell. Finally, I will use the plasmonic band theory to probe the role of parasitic loss in the metal on achievable absorption enhancement factors in plasmonic light trapping schemes.

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Aaswath P. Raman | aaswath@stanford.edu 
Ph.D. Candidate, Stanford University | http://www.stanford.edu/~aaswath