Molecular Foundry Seminar

"Manipulating Light at the Nanometer Scale"

Dr. Alex Weber-Bargioni, Molecular Foundry Postdoctoral Fellow,
Tuesday, August 24 at 1:30 pm, Bldg. 67 - Room 3111

Abstract:

In radio/microwave science and engineering, the antenna constitutes a fundamental tool, since it allows the easy and well-controllable manipulation of electromagnetic fields, thanks to its function of interfacing propagating radiation and localized field. The capability of controlling light via optical antennae would allow one to manipulate light on the nm scale and would open an unprecedented variety of possibilities for the scientific and the technical community to surpass the diffraction limit and employ optics for optical/plasmonic circuitry.

However, metals do not conduct well at optical frequencies. But at optical frequencies, the free electrons gas can sustain surface and volume charge density oscillations, called plasmon-polaritons or plasmons, which enable the localization of light in the visible regime. Metal nanoparticles represent cavities for these plasmons and act as optical antennae.

In the presentation, I will give an overview on the efforts at the Lawrence Berkeley National Laboratory on manipulating light at the nm scale by employing surface plasmon polaritons via optical antennae. By employing E-beam lithography and Induced Deposition Mask Lithography, we fabricate a variety of geometric antenna structures and investigating their specific resonances, which were studied via Dark Field Spectroscopy and Two Photon Photo Luminescence. This work contributed substantially on the basic understanding of optical antennae (resonance, far-field and near-field radiation), which is crucial to design antennae for specific systems. Optical antennae can also been viewed as basic elements for plasmonic circuits, where we work towards controlling the resonance of optical antennae electronically to make electronic switches. Last but not least, these optical antennae have been implemented to scanning probe tips to employ the highly localized and enhanced optical near fields of optical antennae for tip-enhanced Raman spectroscopy on carbon nanotubes.