Setup of a Beam Control System for High Power Laser Systems at DLR

Different types of high power or high energy lasers in the multi kW class are currently available or are under development with promising progress reports. A major challenge is to deliver as much as possible of the available power onto a small and fast moving target over a long distance through a disturbing atmosphere. High resolution imaging is a common way to identify the category of targets dedication and to determine the spatial position relative to the observer. By illuminating the target with a laser the imaging system becomes more resilient towards ambient light and the exposure time can be reduced drastically. Fast and deterministic control loops are demanding for the moving parts in order to maintain a high accuracy for the pointing of the turret and aiming of the laser countermeasure system. Here, we report on the progress of such a beam control system developed at the Institute of Technical Physics of DLR. In an overview we present the beam control system and explain different sub-systems. Performance tests were taken at our outdoor test range. We investigated various scenarios for probing the limits of the tracking and pointing accuracy with a target sample mounted on a fast moving linear stage. We present first results of the beam control system performance

Magnetic resonance investigation of magnetic-labeled baker's yeast cells

In this study, the interaction of DMSA-coated magnetite nanoparticles (5 and 10 nm core-size) with Saccharomyces cerevisae was investigated using magnetic resonance (MR) and transmission electron microscopy (TEM). The TEM micrographs revealed magnetite nanoparticles attached externally to the cell wall. The MR data support the strong interaction among the nanoparticles supported by the cells. A remarkable shift in the resonance field was used as signature of particle attachment to the cell wall

The RD-Connect Genome-Phenome Analysis Platform: Accelerating diagnosis, research, and gene discovery for rare diseases.

Rare disease patients are more likely to receive a rapid molecular diagnosis nowadays thanks to the wide adoption of next-generation sequencing. However, many cases remain undiagnosed even after exome or genome analysis, because the methods used missed the molecular cause in a known gene, or a novel causative gene could not be identified and/or confirmed. To address these challenges, the RD-Connect Genome-Phenome Analysis Platform (GPAP) facilitates the collation, discovery, sharing, and analysis of standardized genome-phenome data within a collaborative environment. Authorized clinicians and researchers submit pseudonymised phenotypic profiles encoded using the Human Phenotype Ontology, and raw genomic data which is processed through a standardized pipeline. After an optional embargo period, the data are shared with other platform users, with the objective that similar cases in the system and queries from peers may help diagnose the case. Additionally, the platform enables bidirectional discovery of similar cases in other databases from the Matchmaker Exchange network. To facilitate genome-phenome analysis and interpretation by clinical researchers, the RD-Connect GPAP provides a powerful user-friendly interface and leverages tens of information sources. As a result, the resource has already helped diagnose hundreds of rare disease patients and discover new disease causing genes

Aberrations of Nd:YAG high power laser and amplifier: Effects and correction with adaptive optics

Eine ausgezeichnete Strahlqualität und damit exzellente Fokussierbarkeit der Laserstrahlung ist in vielen Bereichen, wie der Mikromaterialbearbeitung, der Medizintechnik, der Messtechnik oder in der nichtlinearen Optik, die Grundlage für eine Vielzahl von Anwendungen. Die starke Wärmebelastung in Nd:YAG Laserkristallen führt zur Ausbildung einer thermischen Linse und spannungsinduzierter Doppelbrechung. Die Aberrationen der thermischen Linse verhindern einen effizienten Laserbetrieb bei hoher Ausgangsleistung und gleichzeitig guter Strahlqualität. Die Messungen der Aberrationen in einem lampengepumpten Nd:YAG Laserstab mit einem Shack-Hartmann Wellenfrontsensor ergaben einen ausgeprägten Astigmatismus, sphärische Aberrationen und Koma. Der Peak-to-Valley Wert beträgt 3,9 µm bei einer elektrischen Pumpleistung von 14,8 kW. Aberrationen höherer Ordnung können vernachlässigt werden. Numerische Berechnungen der Strahlausbreitung eines Laserstrahls mit Aberrationen ergaben sehr gute Übereinstimmungen mit experimentellen Messungen. In Resonatoren, die an der Grenze des Stabilitätsbereiches aufgebaut sind, bewirken Aberrationen starke Beugungsverluste und verhindern einen effizienten Laserbetrieb. Dabei wirken sich die verschiedenen Aberrationen unterschiedlich stark auf die Verluste aus. Die Genauigkeit, mit der die Aberrationen mit Hilfe eines adaptiven Spiegels korrigiert werden müssen, beträgt etwa λ/10. Mit der Entwicklung mikrosystemtechnisch hergestellter, adaptiver Membranspiegel ist es möglich geworden, adaptive Optik in cw-Laserverstärker zu integrieren. Der üblicherweise vorhandene Wellenfrontsensor wird im untersuchten Nd:YVO4/Nd:YAG Master-Oszillator Power-Amplifier (MOPA) System durch eine speziell auf die Ermittlung der Wellenfrontaberrationen abgestimmte Power-in-the-Bucket Messung ersetzt. Die Strahlqualitätsoptimierung erfolgt mittels eines evolutionären Optimierungsalgorithmus. Zur Steuerung der verwendeten adaptiven Membranspiegel wurde ein externer Hochspannungsverstärker entwickelt. Im aufgebauten adaptiven optischen System wird die Wellenfront eines polarisierten und nahezu beugungsbegrenzten (M² = 1,2) Nd:YVO4 Oszillators mit 14 W Ausgangsleistung durch einen adaptiven Membranspiegel vordeformiert, um anschließend bei der Propagation durch die doppelbrechungskompensierten Nd:YAG Verstärker die Aberrationen des Lasermediums zu kompensieren. Während der Optimierungsdauer von 20 bis 60 Sekunden erhöht sich die Fotospannung der Power-in-the-Bucket Messung um den Faktor 3. Bei einer Laserleistung von 54 W im Einfachdurchgang konnte eine Verbesserung der Strahlqualität um einen Faktor 2 von M² = 5 auf M² = 2,5 nachgewiesen werden.aberration, adaptive optics, Nd:YAG, laser, amplifier, optimization algorithm, beam quality, membrane mirro

A local area UAS detection system from an elevated observation position

We present a new approach to an opticalUAS detection system that confirms several requirements specified by the authorities. Our UAS detection system consists of a ground unit and a convex mirror located in the air. The ground based unit contains high resolution camera system mounted on a pantilt unit. Therefore, the lens of the camera system can be actively aligned to a convex mirror which is located in vertical distance over the ground unit on the lower side of a raised captive balloon.The focal length of the ground based lens, the altitude of the balloon and the curvature of the mirror define the field of view towards the ground.The recorded video streams are processed in a vision system using change detection and other algorithms to alert a UAS intrusion.We will outlinethe design parameters of the optical system, the requirements and the implementation of the mechanical system as well as the active alignment system and show first resultsof outdoor operation

Laser based observation of space debris: Taking benefits from the fundamental wave

After the successful experimental demonstration of the prior published concept on laser-based monitoring of space debris in early 2012, we will present further technological and conceptual advancements of this position sensing scheme. The laser based measurement of LEO space debris positions in general offers the potential of a very high accuracy on the order of 10 meters in 3D, which in turn is the input for orbit processing of objects which are seemingly on collisional course. We argue that it is beneficial for the photon budget to make use of the so called fundamental wave, which is present in frequency doubled laser systems anyway. Thus, the here proposed move to near infrared wavelength is technologically easy to achieve and promising towards an operational laser-based debris ranging and tracking system