U Lemmer

Learn More
  • Stefan Riechel, Gutachter, Jochen Feldmann, Khaled Karrai, S Riechel, C Kallinger +12 others
  • 2002
Photograph of a mechanically flexible 2D-DFB laser made from the conjugated polymer MeLPPP. The laser is optically pumped well above the threshold for amplified spontaneous emission. The complex far-field emission pattern (blue-green) results from a large detuning between the resonance wavelength and the gain maximum. • A nearly diffraction limited surface(More)
The photo-Dember effect is a source of impulsive THz emission following femtosecond pulsed optical excitation. This emission results from the ultrafast spatial separation of electron-hole pairs in strong carrier gradients due to their different diffusion coefficients. The associated time dependent polarization is oriented perpendicular to the excited(More)
  • Carsten Sönnichsen, Carsten Sönnichsen, Gutachter, J Feldmann, Weitere H Gaub, Prüfungskommissionsmitglieder +38 others
  • 2001
Except where specific reference is made to the work of others, this work is original and has not been already submitted either wholly or in part to satisfy any degree requirement at this or any other university. The picture on the front page shows a true color image of a sample containing gold and silver nanospheres as well as gold nanorods photographed(More)
We demonstrate red-emitting silicon quantum dot (SiQD) phosphors as a low-cost and environment-friendly alternative to rare-earth element phosphors or CdSe quantum dots. After surface passivation, the SiQD-phosphors achieve high photoluminescence quantum yield = 51% with 365-nm excitation. The phosphors also have a peak photoluminescence wavelength at 630(More)
We have realized a 76 MHz white-light differential transmission spectroscopy system. The technique employs a Ti:sapphire laser oscillator and a tapered fiber to generate a white-light continuum spanning almost the full visible to near-infrared spectral range. Using acousto-optical modulation and subsequent lock-in detection, transient relative transmission(More)
We have investigated the broadband terahertz (THz) optical properties of nanoporous silicon samples with different porosities and the ultrafast carrier dynamics of photogenerated charge carriers in these materials. Following photoexcitation, we observe a fast carrier recovery time consisting of two dominant recombination processes with decay constants below(More)
  • K Forberich, A Gombert, S Pereira, J Crewett, U Lemmer, M Diem +51 others
  • 2011
Lasing mechanisms in organic photonic crystal lasers with two-dimensional distributed feedback, Lasing action in two-dimensional photonic crystal lasers with hexagonal symmetry, Shrinkage precompensation of holographic three-dimensional photonic-crystal templates, Transition between corrugated metal films and split-ring-resonator arrays, Appl. Fabrication(More)
  • Uli Lemmer, T Woggon, M Punke, M Bruendel, M Schelb, T Mappes +11 others
  • 2011
" Organic semiconductor lasers as integrated light sources for optical sensors " , in: 2.) U. Lemmer and E. O. Göbel, "Photoluminescence spectroscopy as a probe for disorder and excitonic effects in organic and inorganic semiconductors", in: Nature of the primary photoexcitation in conjugated polymers, N.
  • U Lemmer, H.-J Eisler, J Hetterich, G Bastian, N A Gippius, S G Tikhodeev +32 others
  • 2011
Optical data link employing organic light-emitting diodes and organic photodiodes as optoelectronic components, circuit board encapsulation and integration of high-speed polymer photodiodes, Influence of temperature-dependent mobilities on the nanosecond response of organic solar cells and photodetectors, Appl. Highly localized non-linear optical(More)