Argonne National Laboratory

Upcoming Events

Antenna-load Interactions at Optical Frequencies: Impedance Matching to Quantum Systems

CNM Nanoscience Colloquium
Markus Raschke, University of Colorado at Boulder
December 12, 2012 4:00PM to 5:00PM
Building 440, Room A105-106
Refreshments will be available at 3:30 p.m.

Abstract The goal of antenna design at optical frequencies is to deliver optical electromagnetic energy to loads in the form of, e.g., atoms, molecules, or nano-structures, or to enhance the radiativeemission from such structures, or both. A true optical antenna would, on a qualitatively new level, control the light-matter interaction on the nano-scale for controlled optical signal transduction, radiative decay engineering, quantum coherent control, super-resolution microscopy, and provide unprecedented sensitivity in spectroscopy.

However, in contrast to the RF, where exact design rules for antennas, waveguides, and antenna-load matching in terms of their impedances are well established, substantial physical differences limit the simple extension of the RF concepts of antenna design to the optical regime. I will discuss the generalization of the ideal antenna-load interaction at optical frequencies, characterized by far-field transformation from a propagating mode into an antenna resonance, the subsequent transformation of that mode into a nanoscale localization, and the free space transformation via an enhanced local density of states to a quantum load.

These steps define the goal of efficient transformation of incident radiation into a quantum excitation in an impedance matched fashion. I willreview the physical basis of the light-matter interaction at the transitionfrom the rf to optical regime, discuss extension of antenna theory as needed for the design of impedance-matched optical antenna-load coupled systems, and provide several examples of the state of the art in design strategies and suggest future extensions. I will discuss new measurable performance metrics based on electric vector field, measurement, field enhancement, and capture cross section to aid the comparison between different antenna designs.