Plasma-wall-interaction in ECRIS II

In an ECR-discharge, where the plasma is confined inside a copper-resonator by a simple magnetic mirror, it could be shown that sputtering of wall material has an important influence upon the plasma [1]. Spectroscopic measurements in ECRIS II with a copper vessel confirmed this model. Evidence for the presence of copper atoms and ions in the plasma could be found by ion extraction as well as with VUV-spectrometry. In a nitrogen discharge by adding helium as a mixing-gas we found that the extracted current of Cu-ions decreased and measured line intensities of copper emission lines dropped down. [1] D. Meyer, "Einfluss der Plasmainstabilitaet auf die Produktion hochgeladener Ionen in einer ECR-Entladung", Dissertation, Bochum, 199

Magnon polaron formed by selectively coupled coherent magnon and phonon modes of a surface patterned ferromagnet

Strong coupling between two quanta of different excitations leads to the formation of a hybridized state which paves a way for exploiting new degrees of freedom to control phenomena with high efficiency and precision. A magnon polaron is the hybridized state of a phonon and a magnon, the elementary quanta of lattice vibrations and spin waves in a magnetically-ordered material. A magnon polaron can be formed at the intersection of the magnon and phonon dispersions, where their frequencies coincide. The observation of magnon polarons in the time domain has remained extremely challenging because the weak interaction of magnons and phonons and their short lifetimes jeopardize the strong coupling required for the formation of a hybridized state. Here, we overcome these limitations by spatial matching of magnons and phonons in a metallic ferromagnet with a nanoscale periodic surface pattern. The spatial overlap of the selected phonon and magnon modes formed in the periodic ferromagnetic structure results in a high coupling strength which, in combination with their long lifetimes allows us to find clear evidence of an optically excited magnon polaron. We show that the symmetries of the localized magnon and phonon states play a crucial role in the magnon polaron formation and its manifestation in the optically excited magnetic transients

Scalable non-volatile tuning of photonic computational memories by automated silicon ion implantation

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record Data Availability Statement: All data used in this study are available from the corresponding author upon reasonable requestPhotonic Integrated Circuits (PICs) are revolutionizing the realm of information technology, promising unprecedented speeds and efficiency in data processing and optical communication. However, the nanoscale precision required to fabricate these circuits at scale presents significant challenges, due to the need to maintain consistency across wavelength-selective components, which necessitates individualized adjustments after fabrication. Harnessing spectral alignment by automated silicon ion implantation, in this work scalable and non-volatile photonic computational memories are demonstrated in high quality resonant devices. Precise spectral trimming of large-scale photonic ensembles from few picometers to several nanometres is achieved with long-term stability and marginal loss penalty. Based on this approach spectrally aligned photonic memory and computing systems for general matrix multiplication are demonstrated, enabling wavelength multiplexed integrated architectures at large scales. This article is protected by copyright. All rights reserved.European Union’s Horizon 2020European Research CouncilDeutsche Forschungsgemeinschaft (DFG, German Research Foundation)Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)Volkswagen Foundatio

Protected Long-Distance Guiding of Hypersound Underneath a Nanocorrugated Surface

In nanoscale communications, high-frequency surface acoustic waves are becoming effective data carriers and encoders. On-chip communications require acoustic wave propagation along nanocorrugated surfaces which strongly scatter traditional Rayleigh waves. Here, we propose the delivery of information using subsurface acoustic waves with hypersound frequencies of ∼20 GHz, which is a nanoscale analogue of subsurface sound waves in the ocean. A bunch of subsurface hypersound modes are generated by pulsed optical excitation in a multilayer semiconductor structure with a metallic nanograting on top. The guided hypersound modes propagate coherently beneath the nanograting, retaining the surface imprinted information, at a distance of more than 50 μm which essentially exceeds the propagation length of Rayleigh waves. The concept is suitable for interfacing single photon emitters, such as buried quantum dots, carrying coherent spin excitations in magnonic devices and encoding the signals for optical communications at the nanoscale

Simon short circuit effect in ECRIS

The plasma confinement within an electron cyclotron resonance ion source significantly influences the charge state distribution and hence the performance of the source. The different axial and radial diffusion processes govern the confinement time. In many experiments it has been shown that negatively biasing the end plate in the injection region improves the charge state distribution. In a few x-ray and vacuum ultraviolet spectroscopy experiments to clarify the mechanism it is observed that the biasing improves the confinement of the plasma. It is estimated that the effect cannot be explained solely by secondary electron emission from the plate into the plasma. We propose that by biasing, the overall balance between radial ion losses and axial electron losses will change, resulting in a different diffusional mode of the entire plasma. Hence, the plasma potential and the average charge state of ions in the plasma are significantly influenced. Usually, the ion flux is dominating radial diffusion while the electron flux is dominating axial losses. This is possible due to compensating wall currents in the electrical conducting plasma chamber ("Simon short circuit"). Thus the usual approach of ambipolar diffusion does not hold in this situation. A similar effect takes place if the plasma chamber is coated with electrically insulating materials. The condition of overall flux balance to the walls is no longer fulfilled and has to be replaced by the local ambipolar particle movement. Again the entire diffusion profile of the plasma changes and the confinement improves. We examine the short circuit current as a measure for the diffusion mode in more detail and try to develop an approximate calculation on the influence of plasma potential and average charge ion state Z in the plasma. First results are presented and discussed. (C) 2002 American Institute of Physics