K. G. Lee

3-dimensional local field polarization vector mapping of a focused radially polarized beam using gold nanoparticle functionalized tips.

We have measured local electric field polarization vectors in 3-dimensional space on the nanoscale. A radial polarized light is generated by using a radial polarization converter and focused by an objective lens. Gold nanoparticle functionalized tips are used to scatter the focused field into the far-field region. Two different methods, rotational analyzer ellipsometry and Stokes parameters, are used in determining the polarization state of the scattered light. Two methods give consistent results with each other. Three dimensional local polarization vectors could be reconstructed by applying back transformation of the fully characterized polarizability tensor of the tip.

Surface plasmon polariton generation on metal surface: From nano-optical to terahertz frequency regime

We investigate surface wave generation by a single slit, both in nano-optical and in terahertz regimes. The wave-front in optical regime separates itself into forward propagating wave and surface-bound 90-degree diffracted wave; while, no such clear separation of modes is not observed in terahertz regime. Excitation wavelength dependency is systematically studied.

Nano-optical and terahertz near-field studies of surface plasmon generation

We investigate sub-wavelength diffraction by a single slit, both in nano-optical and in terahertz regimes. The wave-front in optical regime separates itself into forward propagating beam and surface-bound 90-degree diffracted wave, i.e., surface plasmon polaritons.

Surface plasmon image dipole effect

Polarization resolved detection of the scattered light by a gold nano-particle functionalized tip, off a propagating surface plasmon polariton wave enables quantitative studies of the image dipole orientation effects on flat metal surface.

Near-field studies of surface plasmon generation: optical and terahertz studies

We study the dielectric constant dependent diffraction phenomena of single slit apertures, both theoretically and experimentally. We experimentally simulate perfect metal and real metal cases by investigating subwavelength diffraction by a single slit, both in nano-optical and in terahertz regimes, keeping the slit-width/wavelength ratio approximately the same for both of frequency regimes. The wave-front in optical regime separates itself into forward propagating beam and surface-bound 90-degree diffracted wave, i.e., surface plasmon polaritons; while the separation of modes is not observed in terahertz regime.

Surface plasmon polariton detection discriminating polarization-dependent image dipole effects

Image dipole effects are highly dependent on the polarization direction, constructive (destructive) for the vertical (horizontal) dipole with respect to the interface, respectively. Polarization resolved detection of light scattered off a gold nano particle functionalized tip on a flat gold surface enables the study of the image dipole orientation effects on the scattering type near field scanning optical microscope signal. A propagating surface plasmon polariton as an excitation source sufficiently reduced the large background by virtue of its evanescent nature capacitating the quantitative description of the image dipole. At large tip-to-sample distances, the Fabry-Perot like interference between the radiations from the GNP and from the image dipole induced at the flat gold surface, are evident. The horizontal- polarization and vertical-polarization Fabry-Perot oscillations, however, are out-of-phase with each other. As the tip approaches the surface, the vertical component get further enhanced while the horizontal one gets suppresses, demonstrating the polarization reversal of image dipole as predicted by theory.

Local Vector Field Detection with Gold Nanoparticle Functionalized Tips: the Tip-Independence

We report on the vector mapping of optical standing waves with gold nanoparticle-functionalized tips. We can map the long- and short-axes of general elliptical polarization by performing the polarization-analyzed detection of the scattered light. The local field vectors are successfully read out independent of the tips with different scattering tensors.

Vector Mapping of Local Electric Fields

We report on experimental vector mapping of optical standing waves generated in prism surface. The polarization characteristics of photons scattered by gold nanoparticle-functionalized tips are used to determine the orientation of a local electric field.

Vector Field Mapping of Evanescent Light: Nano Ellipsometry

We mapped the nano-scale elliptical polarizations of an evanescent standing wave by polarization-analysis, and also by ellipsometric analysis of the scattered light off gold-nanoparticle functionalized tips. Both methods give consistent measurements of the local fields.

Advanced SIL System with High NA and Large Tolerance

To achieve high NA and large tolerance, we designed a new SIL system (optimum SIL) which combines each advantages of the hyper SIL and the hemi SIL system. Also using micro-SIL system we can improve its performance. There are simulation results which support our works.