Biomolecules and nanostructures
The Optical Sciences group studies the interaction of light and matter. Our current focus is on detection and sensing/imaging with an emphasis on the development of integrated photonics. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.
A Monopole Antenna at Optical Frequencies: Single-Molecule Near-Field Measurements(full pdf)
Tim H. Taminiau, Frans B. Segerink, and Niek F. van Hulst
IEEE Transactions on Antennas and Propagation
vol 55 no 11 november 2007 p3010-3017
We present a monopole antenna for optical frequencies ( ~600 THz) and discuss near-field measurements with single fluorescent molecules as a technique to characterize such antennas. The similarities and differences between near-field antenna measurements at optical and radio frequencies are discussed in detail. Two typical antenna properties, polarization selectivity and resonances, are studied for the optical monopole by direct near-field measurements and finite integration technique calculations. The antenna is driven by the local field of a sub-wavelength aperture. This gives rise to a dependence of the antenna response on the orientation of the local field vector, in an analogous way to the polarization selectivity of linear wire antennas. The antenna resonances are studied by varying the antenna length. Typical monopole resonances are demonstrated. The finite conductivity of metals at optical frequencies (in combination with the antenna radius) causes the wavelength of the surface charge density oscillation (surface plasmon polariton) along the antenna to be shortened in comparison to the free space wavelength. As a result, resonances for the optical monopole antenna occur at much shorter relative lengths than for conventional radio monopole antennas.