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- ItemSimulation of microwave circuits and laser structures including PML by means of FIT(München : European Geopyhsical Union, 2004) Hebermehl, G.; Schefter, J.; Schlundt, R.; Tischler, Th.; Zscheile, H.; Heinrich, W.Field-oriented methods which describe the physical properties of microwave circuits and optical structures are an indispensable tool to avoid costly and time-consuming redesign cycles. Commonly the electromagnetic characteristics of the structures are described by the scattering matrix which is extracted from the orthogonal decomposition of the electric field. The electric field is the solution of an eigenvalue and a boundary value problem for Maxwell’s equations in the frequency domain. We discretize the equations with staggered orthogonal grids using the Finite Integration Technique (FIT). Maxwellian grid equations are formulated for staggered nonequidistant rectangular grids and for tetrahedral nets with corresponding dual Voronoi cells. The interesting modes of smallest attenuation are found solving a sequence of eigenvalue problems of modified matrices. To reduce the execution time for high-dimensional problems a coarse and a fine grid is used. The calculations are carried out, using two levels of parallelization. The discretized boundary value problem, a large-scale system of linear algebraic equations with different right-hand sides, is solved by a block Krylov subspace method with various preconditioning techniques. Special attention is paid to the Perfectly Matched Layer boundary condition (PML) which causes non physical modes and a significantly increased number of iterations in the iterative methods.
- ItemHochbitratige Schaltungen mit InP-HBTs : Schlussbericht(Hannover : Technische Informationsbibliothek (TIB), 2005) Heinrich, W.; Brunner, F.; Kurpas, P.; Meliani, C.; Rudolph, M.; Sidorov, V.; Würfl, J.[no abstract available]
- ItemTechnologie- und Epitaxieentwicklung von AlGaN/GaN HFETs: Materialgüte, innovative Prozesstechnologie und Zuverlässigkeit : Schlussbericht(Hannover : Technische Informationsbibliothek (TIB), 2007) Würfl, J.; Behtash, R.; Gesche, R.; Janke, B.; Klockenhoff, H.; Krüger, O.; Lossy, R.; Chaturvedi, N.; Heinrich, W.; Knigge, St.; Liero, A.; Mai, M.[no abstract available]
- ItemMehr-Sektions DBR-Laser mit einstellbarem sättigbarem Absorber zur Erzeugung kurzer Impulse mit hoher Leistung und geringem Chirp für die Frei-Raum Kommunikation : Abschlussbericht ; Berichtszeitraum: 15.4.2000 - 30.6.2004(Berlin : Ferdinand-Braun-Institut, 2004) Hasler, Karl Heinz; Wenzel, Hans; Klehr, Andreas; Knauer, Arne; Fricke, Jörg; Janke, Bernd; Erbert, Götz; Schwertfeger, Sven[no abstract available]
- ItemFörderschwerpunkt Laser 2000: Grundlegende Untersuchungen zur hochgenauen, berührungslosen laserinterferometrischen Messung großer Längen im Maschinenbau, Teilvorhaben: Grundlegende Untersuchungen leistungsstarker durchstimmbarer Halbleiterlaserdioden : Schlußbericht(Berlin : Ferdinand-Braun-Institut, 2000) Erbert, G.; Brugge, F.; Fechner, I.; Fredrich, D.; Gielow, M.; Hofmann, L.; Klehr, A.; Klein, A.; Krause, A.; Knauer, A.; Olschewsky, R.; Oster, A.; Rechenberg, I.; Ressel, P.; Sebastian, J.; Selent, R.; Smirnitzki, V.; Tessaro, T.; Thiemann, M.; Thies, A.; Vogel, K.; Wenzel, H.; Weyers, M.; Würfel, J.; Wochatz, P.[no abstract available]
- ItemFörderschwerpunkt: Wide Band Gap-Halbleiter, Teilvorhaben: GaN-Hochfrequenzelektronik : Abschlussbericht(Hannover : Technische Informationsbibliothek (TIB), 2003) Würfl, J.; Chaturvedi, N.; Heymann, P.; Janke, B.; Klockenhoff, H.; Lossy, R.; Schnieder, F.; Wolter, P.; Hamma, G.; Ickert, K.; John, W.; Liero, A.; Mai, M.; Wittrich, H.[no abstract available]
- ItemFörderschwerpunkt NOVALAS : Grundlegende Untersuchungen zur Technologie von Hochleistungsdiodenlasern, Teilvorhaben: Hochleistungsdiodenlaser auf der Basis von Al-freien Quantengräben und Wellenleitern im Wellenlängenbereich 800 - 1000 nm ; Schlussbericht(Berlin : Ferdinand-Braun-Institut, 2001) Erbert, G.; Beister, G.; Brade, P.; Fechner, I.; Fredrich, D.; Fricke, J.; Gielow, M.; Hülsewede, R.; Klein, A.; Krause, A.; Knauer, A.; Maege, J.; Pittroff, W.; Olschewsky, R.; Rechenberg, I.; Ressel, P.; Sebastian, J.; Selent, R.; Staske, R.; Schulze, H.; Sumpf, B; Tessaro, T.; Vogel, K.; Wenzel, H.; Wiechmann, S.; Weyers, M.; Würfel, J.; Wochatz, P.[no abstract available]
- ItemMode transitions in distributed-feedback tapered master-oscillator power-amplifier(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2008) Radziunas, Mindaugas; Tronciu, Vasile Z.; Bandelow, Uwe; Lichtner, Mark; Spreemann, Martin; Wenzel, HansTheoretical and experimental investigations have been carried out to study the spectral and spatial behavior of monolithically integrated distributed-feedback tapered master-oscillators power-amplifiers emitting around 973 nm. Introduction of self and cross heating effects and the analysis of longitudinal optical modes allows us to explain experimental results. The results show a good qualitative agreement between measured and calculated characteristics.
- ItemImproving the stability of distributed-feedback tapered master-oscillator power-amplifiers(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2009) Tronciu, Vasile Z.; Lichtner, Mark; Radziunas, Mindaugas; Bandelow, U.; Wenzel, H.We report theoretical results on the wavelength stabilization in distributed-feedback master-oscillator power-amplifiers which are compact semiconductor laser devices capable of emitting a high brilliance beam at an optical power of several Watts. Based on a traveling wave equation model we calculate emitted optical power and spectral maps in dependence on the pump of the power amplifier. We show that a proper choice of the Bragg grating type and coupling coefficient allows to optimize the laser operation, such that for a wide range of injection currents the laser emits a high intensity continuous wave beam.
- ItemVerbundvorhaben Femto-Diode, Teilvorhaben: Halbleiterkomponenten für kompakte Femtosekunden-Laserstrahlquellen : Projekt-Abschlussbericht ; Projekt FBH 9140, HaFemLas ; Abschlussbericht: 1.10.2004 - 30.09.2007(Hannover : Technische Informationsbibliothek (TIB), 2008) Klehr, Andreas; Zorn, Martin; Weyers, M.; Erbert, G.; Fricke, J.; Knauer, A.; Pittroff, W.; Staske, R.; Wenzel, H.; Zeimer, U.[no abstract available]