Searcharxiv⌕ Search

arXiv subjects

H. O. Moser

Publications and source records attributed to H. O. Moser.

9 recordsLinked to original sources
arXiv2009

THz meta-foil - a new photonic material

Seeing sharper or becoming invisible are visions strongly driving the development of THz metamaterials. Strings are a preferred architecture of metamaterials as they extend continuously along one dimension. Here, we demonstrate that laterally interconnecting strings by structural elements that are placed in oscillation nodes such as to not quench electromagnetic resonances enables manufacturing of self-supported free-standing all-metal metamaterials. Upright S-strings, interconnected by rods, form a space-grid which we call meta-foil. In this way, we introduce binding between the "atoms" of the metamaterial, thus doing away with conventional "frozen-in solutions" like matrix embedding or thin films on substrates. Meta-foils are locally stiff, yet globally flexible. Even bent to cylinders of 1 cm radius, they maintain their spectral response, thus becoming true metamaterials on curved surfaces. Exploiting UV/X-ray lithography and ultimately plastic moulding, meta-foils can be cost-effectively manufactured in large areas and quantities to serve as optical elements.

physics.optics↗
arXiv2008

Observation of a New Magnetic Response in 3-Dimensional Split Ring Resonators under Normal Incidence

So far, research in the field of metamaterials has been carried out largely with arrays of flat, 2-dimensional structures. Here, we report a newly identified magnetic resonance in Split Cylinder Resonators (SCRs), a 3-dimensional version of the Split Ring Resonator (SRR), which were fabricated with the Proton Beam Writing technique. Experimental and numerical results indicate a hitherto unobserved 3-dimensional resonance mode under normal incidence at about 26 THz, when the SCR depth is approximately half the free space wavelength. This mode is characterized by strong currents along the cylinder axis which are concentrated at the cylinder gaps. Due to their orientation, these axial currents give rise to a magnetic response under normal incidence, which is not possible in shallow SRRs. Our results reveal new behavior in the SRR structure which arises from a change in its aspect ratio. Such new resonances can have a significant influence on the quest for practical, 3-dimensional metamaterials.

cond-mat.mtrl-sci↗
arXiv2008

Freely-suspended matrix-free metamaterials showing THz left-handed pass bands

Featuring dense spatial distributions of engineered metallic particles, electromagnetic metamaterials exhibit simultaneously negative values of both, dielectric permittivity and magnetic permeability, within a resonance frequency band called left-handed passband. Unusual electromagnetic properties are found resulting in promising applications such as sub-wavelength resolution imaging. State-of-the-art micro/nanomanufacturing has led to resonance frequencies reaching the visible red. The common embedding of the metal particles in plastic matrices or deposition on dielectric substrates within a small area severely limits the usefulness of the materials. Here, we use UV or X-ray lithography to build comparably large areas and quantities of the first freely-suspended matrix-free metamaterials in which the metallic structures are S-string-like with their ends held by a window-frame. In vacuo spectral characterization combined with simulation reveals left-handed passbands from 1.6 to 2.2 THz. Owing to their size, the devices can be easily handled. They offer a straightforward way of making them tunable and two-dimensionally isotropic.

cond-mat.mtrl-sci↗
arXiv2001

Extreme Ultraviolet (EUV) Sources for Lithography based on Synchrotron Radiation

The study presented here was initiated by a discussion to investigate the possibility of using synchrotron radiation as a source for the Next Generation Lithography (NGL) based on the EUV-concept (Extreme Ultra-Violet; here 13.5 nm or 11.3 nm radiation, respectively). The requirements are: 50 W, 2% bandwidth and minimal power outside this bandwidth. Three options were investigated. The first two deal with radiation from bending magnets and undulators. The results confirm the earlier work by Oxfords Instrument and others that these light-sources lack in-band power while emitting excessive out-of-band radiation. The third approach is a FEL (Free Electron Laser) driven by a 500 MeV linear accelerator with a superconducting mini-undulator as radiation emitting device. Such a device would produce in-band EUV-power in excess of 50 W with negligible out-of-band power.

physics.acc-ph↗
arXiv1998

First experiments with a 100 period superconductive undulator with a period length of 3.8 mm

A prototype of a novel superconductive undulator with a period length of 3.8 mm is described. The undulator is 100 periods long. In the first tests described in this paper the undulator was cooled in a helium bath and it was shown that it can be operated as expected with a maximum current of 1400 A. Afterwards the undulator field was measured with a miniature Hall probe with an active area of (100x100)x10^-6 m^2. Calculated and measured field distributions are in good agreement. A cryostat for a beam test at Mainz microtron MAMI was built in which liquid helium cools indirectly the in-vacuum undulator. At the moment the cryostat is tested and optimized.

physics.acc-ph↗
arXiv1997

A superconductive undulator with period length of 3.8 mm

During the last years several attempts were undertaken to decrease the period length of undulators to the mm range. In this paper, a novel type of an in-vacuum undulator is described which is built with superconductive wires. The period length of this special device is 3.8 mm. In principle, it is possible to decrease this period length even further. A 100 period long undulator has been built and will be tested with beam in the near future.

physics.acc-ph↗