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CMO - AMO SEMINAR | Artificially Structured Materials for Tailored Optical Properties

Tuesday, March 31, 2015
4:00 AM
335 West Hall

Artificially structured materials on the nanoscale hold the promise to enable a new class of ultrafast optoelectronic devices such as LEDs and enhance the performance of photodetectors and photovoltaic devices as well as pave the way for quantum-based technologies. Plasmonic cavities and nanoantennas can strongly modify the excitation and decay rates of nearby emitters by altering the local density of states. Here, we demonstrate large enhancements of fluorescence and spontaneous emission rates of dye molecules embedded in plasmonic nanoantennas with sub-10-nm gap sizes. The nanoantennas consist of colloidally synthesized silver nanocubes coupled to a metallic film which is separated by a 5-15 nm self-assembled polymer spacer layer with embedded molecules. Each film-coupled nanocube resembles a nanoscale patch antenna whose plasmon resonance can be changed independent of its local field enhancement. By varying the size of the nanopatch, we tune the plasmon resonance by ~200 nm throughout the excitation, absorption, and emission spectra of the embedded molecules demonstrating giant fluorescence enhancement for antennas resonant with the excitation wavelength [1]. Next, we directly probe and control the nanoscale photonic environment of the embedded emitters including the local field enhancement, dipole orientation and spatial distribution of emitters. This enables the design and experimental demonstration of Purcell factors exceeding 1,000, while maintaining high quantum efficiency and directional emission [2]. Finally, progress on enhancing nonlinear effects [3] and coupling single colloidal quantum dots to the plasmonic nanopatch antennas [4] will be discussed.