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Version: publishedVersion × Subject: Optical constants ×

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Now showing 1 - 5 of 5
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    The role of substrate temperature and magnetic filtering for DLC by cathodic arc evaporation
    (Basel : MDPI, 2019) Lux, Helge; Edling, Matthias; Lucci, Massimiliano; Kitzmann, Julia; Villringer, Claus; Siemroth, Peter; De Matteis, Fabio; Schrader, Sigurd
    Diamond-like carbon (DLC) films were deposited using two different types of high current arc evaporation. The first process used a magnetic particle filter to remove droplets from the plasma. For the second process, the samples were put into a metallic cage which was placed directly above the plasma source. For both processes, we varied the substrate temperature from 21 to 350 °C in order to investigate the temperature effect. The samples were characterized using SEM, AFM, XPS, Raman Spectroscopy, Ellipsometry, Photometry, and Nano Indentation in order to compare both methods of deposition and provide a careful characterization of such DLC films. We found that the sp3 content and the hardness can be precisely adjusted by changing the substrate temperature. Furthermore, in the case of unfiltered deposition, the optical constants can be shifted in the direction of higher absorbance in order to produce black and hard carbon coatings. © 2019 by the authors.
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    Propagator operator for pulse propagation in resonant media
    (Washington, DC : Soc., 2021) Morales, Felipe; Richter, Maria; Olvo, Vlad; Husakou, Anton
    We show that, for the case of resonant media, the available models for unidirectional propagation of short pulses can face serious challenges with respect to numerical efficiency, accuracy, or numerical artifacts. We propose an alternative approach based on a propagator operator defined in the time domain. This approach enables precise simulations using short time windows even for resonant media and facilitates coupling of the propagation equation with first-principle methods such as the time-dependent Schödinger equation. Additionally, we develop a numerically efficient recipe to construct and apply such a propagator operator.
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    Spatially modulated broad-area lasers for narrow lateral far-field divergence
    (Washington, DC : Soc., 2021) Zeghuzi, Anissa; Koester, Jan-Philipp; Radziunas, Mindaugas; Christopher, Heike; Wenzel, Hans; Knigge, Andrea
    A novel laser design is presented that combines a longitudinal-lateral gain-loss modulation with an additional phase tailoring achieved by etching rectangular trenches. At 100 A pulsed operation, simulations predict a far-field profile with 0.3° full width at half maximum (ΘFWHM=0.3∘) where a 0.4°-wide main lobe contains 40% of the emitted optical output power (Θ40%=0.4∘). While far-field measurements of these structured lasers emitting 10 ns long pulses with 35 W peak power confirm a substantial enhancement of radiation within the central 1∘ angular range, the measured far-field intensity outside of the obtained central peak remains high.
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    Linear and nonlinear absorption of titanium dioxide films produced by plasma ion-assisted electron beam evaporation: Modeling and experiments
    (Basel : MDPI, 2019) Stenzel, Olaf; Wilbrandt, Steffen; Mühlig, Christian; Schröder, Sven
    Titanium dioxide films were prepared by plasma ion-assisted electron beam evaporation. Linear optical properties were investigated in terms of spectrophotometry using the beta-distributed oscillator (ss_do) model as a parametrized dispersion law. The nonlinear two-photon absorption coecient of titanium dioxide was determined by means of the laser-induced deflection technique at a wavelength of 800 nm. The obtained values of (2-5) x 10-11 cm/W were consistent with published experimental values for rutile as well as for simulations performed in the frames of the ss_do and Sheik-Bahae models. © 2020 by the authors.
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    Sub-7 fs radially-polarized pulses by post-compression in thin fused silica plates
    (Washington, DC : Soc., 2021) Cao, Huabao; Nagymihaly, Roland S.; Khodakovskiy, Nikita; Pajer, Viktor; Bohus, Janos; Lopez-Martens, Rodrigo; Borzsonyi, Adam; Kalashnikov, Mikhail
    We experimentally demonstrate the post-compression of radially polarized 25 fs pulses at 800 nm central wavelength in a multiple thin plate arrangement for the first time, to the best of our knowledge. Sub-7 fs pulses with 90 µJ energy were obtained after dispersion compensation, corresponding to a compression factor of more than 3.5. Preservation of radial polarization state was confirmed by polarized intensity distribution measurements. Linear projections of the radially polarized pulses were also fully characterized in the temporal domain.