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II11.02 - Ultra-Narrow Band Absorbers Based on Surface Lattice Resonances in Nanostructured Metal Surfaces 
April 24, 2014   2:00pm - 2:15pm

Nanostructured metals received significant amount of attention in recent years due to exciting plasmonic and photonic properties such as strong-field localization, light concentration, and strong absorption and scattering at the localized or delocalized surface plasmon resonance frequencies. In particular, resonant absorption phenomenon in plasmonic nanostructures is widely studied for applications in photothermal therapy, thermophotovoltaics, heat assisted magnetic recording, hot-electron collection, and biosensing. However, it has proven to be challenging to realize very narrow absorption bands using plasmonic elements due to radiative and dissipative losses. Here, we theoretically and experimentally demonstrate an ultra-narrow band absorber (NBA) based on the surface lattice resonances in periodic nanowire and nanoring arrays fabricated on a reflecting metallic substrate. In experiments, we observe very sharp absorption resonance peaks with 12 nm bandwidth (Quality factor is 63) with over 90% total absorbance in visible frequencies. Simulated absorption bandwidths are as narrow as 3 nm. The resonance absorption wavelength, amplitude of the absorption peak and the bandwidth can be controlled by tuning the period of NBA arrays, as well as the metal thickness and grating width. Unlike conventional plasmonic absorbers that utilize metal-insulator-metal (MIM) multilayers, our NBA design consist of only metals, which enable strong interaction between the surface lattice resonance (SLR) of periodic nanostructures and underneath highly reflective film. The radiative losses are significantly reduced in our design enabling an ultra-sharp resonance peak. Furthermore, we studied the coupling between nanoring and nanowire gratings by controlling the position of the nanowire with respect to the nanoring. We observe SLR mode splitting facilitated by the coupling between two individual SLRs from nanoring and nanowire arrays. We calculate the figure of merit (FoM=(dλ/dn)/Δλ)for plasmonic sensor as high as 226, which is due to narrow resonance bandwidth and highly localized electric field surrounding nanoring/nanowire system. Designing such all-metallic nanostructure arrays is a promising route for achieving ultra-narrow band absorbers which can find use in absorption filters, narrow-band thermal emitters in thermophotovoltaics, and ultra-sensitive plasmonic biosensors.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis