Showing papers by "Franz R. Aussenegg published in 2006"

Dielectric stripes on gold as surface plasmon waveguides

Abstract: We report on surface plasmon polariton (SPP) waveguiding by SiO2 stripes on gold thin films. Compared to other SPP waveguide schemes, these systems provide relatively large effective refractive indices which can be described by the effective index method. By leakage radiation and near-field optical microscopy, we observe directly multimode and monomode behavior in straight SPP waveguides of different widths. Furthermore, we demonstrate waveguide bends and cross-talk free propagation across waveguide crossings.

How to erase surface plasmon fringes

Abstract: The authors report on the imaging of surface plasmon polaritons (SPPs) by leakage radiation microscopy in both direct and Fourier space. They show that manipulating the intensity distribution in the Fourier plane allows them to selectively image SPP beams propagating along specific directions. Thereby individual SPP beams are made accessible for direct quantitative analysis which is important in cases where the interaction between different SPP beams leads to interference fringes obscuring the individual components.

Organic diodes as monolithically integrated surface plasmon polariton detectors

Abstract: The authors show that organic p∕n heterojunction diodes enable the direct electric detection of surface plasmon polaritons (SPPs) The organic diodes are built from two organic semiconductor thin film layers with an area of 150×500μm2 deposited on an extended silver thin film Besides serving as the bottom electrode of the diode this silver thin film is as well a waveguide feeding SPPs to the diode area The authors visualize the direct SPP detection by a spatially resolved induced current map

Raman scattering images and spectra of gold ring arrays

Abstract: We analyze the optical properties of m-sized rings of gold nanoparticles by the combination of extinction spectroscopy, surface enhanced Raman scattering SERS spectroscopy and microscopic dark field imaging in two variants. The imaging process relies on either SERS from methylene blue dye molecules adsorbed on the nanoparticles or elastically scattered light. Whereas elastically scattered light images are governed by the coherence and intensity of the light scattered from the particles, SERS images reflect the optical near field of the particles averaged incoherently over a surface area corresponding to the point spread function of the microscope. From the analysis of the extinction spectra, scattered light and SERS images, we find that near field interaction of the single gold nanoparticles in the rings plays a minor role. Both scattered light and SERS images are well reproduced by simple model calculations. Due to the different signal generation and coherence properties, the combination of both imaging methods is a useful means in the characterization of optical properties of nanostructured metal surfaces.

Electrically actuated elastomers for electro–optical modulators

Abstract: By using an elastomer as dielectric medium in a parallel plate capacitor, the attractive forces between the differently charged electrodes strongly compress that layer, representing a special type of electrostrictive effect. With an optical interference technique at the metal-insulator-metal layer system we studied the temporal behaviour of this mechanical deformation. We show that the deformation can be enhanced when the capacitor is laterally structured in order to allow the elastomer volume between the electrodes to move laterally, resulting in typical response times below 1 ms. The elastomer together with the metal electrodes is a metal-insulator-metal optical waveguide, whose mode properties can be tuned by electrically controlled mechanical thickness changes, suggesting applications for low-price electro–optical modulators with response speeds comparable to thermo–optical polymer modulators but with much smaller size.

Surface Plasmon Polariton Mach–Zehnder Interferometer and Oscillation Fringes

Abstract: We present a quantitative experimental analysis of a surface plasmon polariton (SPP) interferometer relying on elliptical Bragg mirrors. By using a leakage radiation microscope, we observe oscillation fringes with unit visibility at the two interferometer exits. We study the properties of the SPP beam splitter and determine experimentally both the norm and phase of the SPP reflection and transmission coefficients.

Far-Field Raman Imaging of Short-Wavelength Particle Plasmons on Gold Nanorods

Abstract: The surface plasmon fields of gold nanorods with a diameter of 100 nm and lengths of 1–5 $$\mu$$ m are imaged by using far-field Raman scattering of methylene blue adsorbed on the rods. When optically exciting the nanorods under total internal reflection with wave vector and electric field vector orientations along the rod axis, the plasmon field intensity along this axis is observed to be periodically modulated. This modulation is attributable to a beating of the exciting light wave and the nanorod plasmon mode. The plasmon wavelength deduced from the beat frequency is 379 nm, which is considerably smaller than the exciting laser wavelength of 647 nm. In general, Raman imaging is shown to be a powerful technique to probe local plasmon fields using far-field spectroscopy.

Surface plasmon interference fringes in back-reflection

Abstract: We report the experimental observation of surface plasmon polariton (SPP) interference fringes with near-unity visibility and half-wavelength periodicity obtained in back reflection on a Bragg mirror The presented method based on leakage radiation microscopy (LRM) represents an alternative solution to optical near-field analysis and opens new ways for the quantitative analysis of SPP fringes With LRM we investigate various SPP interference patterns and analyze the high reflectivity of Bragg mirror in comparison with theoretical models

Plasmonen als Lichttransporter: Nanooptik

Abstract: Metallische Nanopartikel, Nanodrahte oder Filme konnen Licht in Oberflachen-Plasmonen einfangen. Dieses Phanomen spielt sich im optischen Nahfeld und im Subwellenlangenbereich ab. Dabei entsteht ein hybrider, optoelektronischer Anregungszustand aus Licht und oszillierenden Leitungselektronen. Metallische Nanopartikel konnen zum Beispiel als “Hilfsantennen” die Fluoreszenz von Biomolekulen erheblich verstarken. Das ist fur Fluoreszenzsensoren interessant. Experimente zeigen, dass metallische Nanodrahte in Oberflachen-Plasmonen Licht transportieren konnen. Auf zweidimensionalen, strukturierten Metallfilmen wurden Bauelemente bis hin zum Interferometer fur Plasmonen erfolgreich demonstriert. Das junge Feld der Plasmonik konnte wichtige Beitrage zu einer zukunftigen Nanooptik liefern.