Frankfurt 2006 – scientific programme

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Q: Quantenoptik und Photonik

Q 23: Optische Meßtechnik

Q 23.3: Talk

Tuesday, March 14, 2006, 11:10–11:25, H14

Polarization dependent light transmission through nanoscopic holes and coaxial structures — •Jochen Mueller, P. Banzer, S. Quabis, and G. Leuchs — Max Planck Research Group, Institute of Optics, Information and Photonics, University Erlangen-Nuremberg, Guenther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen

A large number of experiments have been carried out to clarify the nature of enhanced transmission through nanoscopic holes with just as much contradictory explanations having come up. Investigating the polarization dependence is therefore a necessary approach.

We measure the transmission of longitudinal and transverse fields through holes and coaxial structures down to subwavelength dimensions written in Ag and Cr layers at 775 nm. We prepare radially and azimuthally polarized beams focused by an objective (NA 0.9), thus illuminating each structure separately.

Generally we observe a significantly higher transmission for radial polarization, especially for thick metal layers. In case of very thin layers small holes reduce the ordinary skin depth penetration.

We found the transmission through coaxial rings for radial polarization to be larger than through pure holes of the same outer diameter, reaching a maximum when the diameter comes close to the wavelength. Even if the metal coaxial core gets larger than the focal spot size, a high on-axis-transmission is obtained. We discuss the results against the background of a waveguide theory.