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Duparre A.,Fraunhofer Institute for Applied Optics and Precision Engineering | Ristau D.,Laser Zentrum Hannover e.V.
Applied Optics | Year: 2011

The 2010 Measurement Problem comprised the determination of the reflectance of high-reflective dielectric mirrors at 1064 nm. © 2010 Optical Society of America. Source


Jauregui C.,Friedrich - Schiller University of Jena | Eidam T.,Friedrich - Schiller University of Jena | Limpert J.,Friedrich - Schiller University of Jena | Tunnermann A.,Friedrich - Schiller University of Jena | Tunnermann A.,Fraunhofer Institute for Applied Optics and Precision Engineering
Optics Express | Year: 2011

Recent work on high-power fiber amplifiers report on a degradation of the output beam quality or even on the appearance of mode instabilities. By combining the transversally resolved rate equations with a 3D Beam propagation method we have managed to create a model able to provide an explanation of what we believe is at the root of this effect. Even though this beam quality degradation is conventionally linked to transversal hole burning, our simulations show that this alone cannot explain the effect in very large mode area fibers. According to the model presented in this paper, the most likely cause for the beam quality degradation is an inversion-induced grating created by the interplay between modal interference along the fiber and transversal hole burning. © 2011 Optical Society of America. Source


Gather M.C.,University of Iceland | Gather M.C.,Harvard University | Meerholz K.,University of Cologne | Danz N.,Fraunhofer Institute for Applied Optics and Precision Engineering | Leosson K.,University of Iceland
Nature Photonics | Year: 2010

Plasmonicsthe study of the interaction between electromagnetic waves and electron plasmas on metal surfaces and in metallic nanostructureshas received much attention in recent years, with potential new applications ranging from subwavelength photonic circuits to photothermal cancer therapy. In many cases, however, the substantial attenuation of the electromagnetic wave due to absorption (ohmic loss) in the metal is of serious concern. Introduction of optical gain into the dielectric material adjacent to the metal surface has been identified as a means of compensating for the absorption loss, but the experimental realization of lossless propagation or optical gain in plasmonic waveguides has proven elusive. Here, we demonstrate direct proof of plasmonic propagation with net positive gain over macroscopic distances. The gain is provided by an optically pumped layer of fluorescent conjugated polymer adjacent to the metal surface in a dielectric-metal-dielectric plasmonic waveguide. © 2010 Macmillan Publishers Limited. All rights reserved. Source


Herzog C.,University of Leipzig | Beckert E.,Fraunhofer Institute for Applied Optics and Precision Engineering | Nagl S.,University of Leipzig
Analytical Chemistry | Year: 2014

Herein, the fabrication, characterization, calibration, and application of integrated microfluidic platforms for fast isoelectric point (pI) determinations via free-flow electrophoresis with integrated inkjet-printed fluorescent pH sensor microstructures are presented. These devices allow one to determine the pI of a biomolecule from a sample mixture with moderately good precision and without addition of markers in typically less than 10 s total separation and analysis time. Polyhydroxyethyl methacrylate (pHEMA) hydrogels were covalently coupled with fluorescein and hydroxypyrene trisulfonic acid (HPTS)-based pH probes. These were piezoelectrically jet-dispensed onto acrylate-modified glass as pH sensor microarrays with a diameter of 300-600 μm and thicknesses of 0.4-2.4 μm with high spatial accuracy. Microchip fabrication and integration of these pH sensor arrays was realized by multistep liquid-phase photolithography from oligoethylene glycol precursors resulting in glass-based microfluidic free-flow isoelectric focusing (μFFIEF) chips with integrated pH observation capabilities. The microchips were characterized with regard to pH sensitivity, response times, photo-, and flow stability. Depending on the sensor matrix, they allowed IEF within a pH range of roughly 5.5-10.5 with good sensitivity and fast response times. These microchips were used for FFIEF of small molecule markers and several protein mixtures with simultaneous monitoring of local pH. This allowed the determination of their pI via multispectral imaging of protein and pH sensor fluorescence without addition of external markers. Obtained pI's were generally in good agreement with known data, demonstrating the applicability of the method for pI determination in micropreparative procedures within a time frame of a few seconds only. © 2014 American Chemical Society. Source


Jauregui C.,Friedrich - Schiller University of Jena | Limpert J.,Friedrich - Schiller University of Jena | Limpert J.,Helmholtz Center for Heavy Ion Research | Limpert J.,Fraunhofer Institute for Applied Optics and Precision Engineering | And 3 more authors.
Nature Photonics | Year: 2013

Fibre lasers are now associated with high average powers and very high beam qualities. Both these characteristics are required by many industrial, defence and scientific applications, which explains why fibre lasers have become one of the most popular laser technologies. However, this success, which is largely founded on the outstanding characteristics of fibres as an active medium, has only been achieved through researchers around the world striving to overcome many of the limitations imposed by the fibre architecture. This Review focuses on these limitations, both past and current, and the creative solutions that have been proposed for overcoming them. These solutions have enabled fibre lasers to generate the highest diffraction-limited average power achieved to date by solid-state lasers. © 2013 Macmillan Publishers Limited. All rights reserved. Source

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