H. Raether

Bio: H. Raether is an academic researcher from University of Hamburg. The author has contributed to research in topics: Surface plasmon & Surface finish. The author has an hindex of 19, co-authored 33 publications receiving 7438 citations. Previous affiliations of H. Raether include Munich University of Applied Sciences.

Untersuchung von Elektronenlawinen mit einem mehrstufigen Bildverstärker

Abstract: Using a high-gain image intensifier and a pulsed discharge gap, electron avalanches are photographed by means of the light emitted as a result of excitation processes by electron impact accompanying ionisation. — Principle and sensitivity of the method are briefly discussed. Electron drift velocities in nitrogen are measured, and the range of mean energy of agitation of electrons is derived from the photographs taken. Preliminary data have also been obtained for argon.

Die Elektronenemission von Metalloberflächen nach mechanischer Bearbeitung

Abstract: Im Vakuum von 2·10−5 Torr wurde die vonKramer gefundene Elektronenemission von Metallen nach mechanischer Bearbeitung mit Hilfe eines Sekundarelektronenvervielfachers untersucht. Elemente aus den ersten Hauptgruppen des Periodischen Systems liefern zeitlich verschiedenartig abklingende Nachstrome, wahrend einige edlere Metalle keine Emission zeigen. Die Intensitaten der Nachstrome werden mit der chemischen Aktivitat der Elemente verglichen und deutliche Zusammenhange mit der Stellung im Periodischen System gefunden. Die Emission scheint somit eine Begleiterscheinung chemischer Reaktionen zu sein. Der Abklingvorgang wird durch das Aufwachsen von Oxydschichten gedeutet. Bei der Bearbeitung mit Schmirgelpapier werden die Ergebnisse durch die Emission des Schmirgels verfalscht.

Plasmonics for improved photovoltaic devices

Abstract: The emerging field of plasmonics has yielded methods for guiding and localizing light at the nanoscale, well below the scale of the wavelength of light in free space. Now plasmonics researchers are turning their attention to photovoltaics, where design approaches based on plasmonics can be used to improve absorption in photovoltaic devices, permitting a considerable reduction in the physical thickness of solar photovoltaic absorber layers, and yielding new options for solar-cell design. In this review, we survey recent advances at the intersection of plasmonics and photovoltaics and offer an outlook on the future of solar cells based on these principles.

Extraordinary optical transmission through sub-wavelength hole arrays

Abstract: The desire to use and control photons in a manner analogous to the control of electrons in solids has inspired great interest in such topics as the localization of light, microcavity quantum electrodynamics and near-field optics1,2,3,4,5,6. A fundamental constraint in manipulating light is the extremely low transmittivity of apertures smaller than the wavelength of the incident photon. While exploring the optical properties of submicrometre cylindrical cavities in metallic films, we have found that arrays of such holes display highly unusual zero-order transmission spectra (where the incident and detected light are collinear) at wavelengths larger than the array period, beyond which no diffraction occurs. In particular, sharp peaks in transmission are observed at wavelengths as large as ten times the diameter of the cylinders. At these maxima the transmission efficiency can exceed unity (when normalized to the area of the holes), which is orders of magnitude greater than predicted by standard aperture theory. Our experiments provide evidence that these unusual optical properties are due to the coupling of light with plasmons — electronic excitations — on the surface of the periodically patterned metal film. Measurements of transmission as a function of the incident light angle result in a photonic band diagram. These findings may find application in novel photonic devices.

Diamond-like amorphous carbon

Abstract: Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

Surface plasmon resonance sensors: review

Abstract: Since the first application of the surface plasmon resonance (SPR) phenomenon for sensing almost two decades ago, this method has made great strides both in terms of instrumentation development and applications. SPR sensor technology has been commercialized and SPR biosensors have become a central tool for characterizing and quantifying biomolecular interactions. This paper attempts to review the major developments in SPR technology. Main application areas are outlined and examples of applications of SPR sensor technology are presented. Future prospects of SPR sensor technology are discussed.

High-impedance electromagnetic surfaces with a forbidden frequency band

Abstract: A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. Although it is made of continuous metal, and conducts dc currents, it does not conduct ac currents within a forbidden frequency band. Unlike normal conductors, this new surface does not support propagating surface waves, and its image currents are not phase reversed. The geometry is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped-circuit elements, and distributed in a two-dimensional lattice. The surface can be described using solid-state band theory concepts, even though the periodicity is much less than the free-space wavelength. This unique material is applicable to a variety of electromagnetic problems, including new kinds of low-profile antennas.