TY - JOUR A1 - Reiserer, Andreas A. A1 - Huang, Jer-Shing A1 - Hecht, Bert A1 - Brixner, Tobias T1 - Subwavelength broadband splitters and switches for femtosecond plasmonic signals JF - Optics Express N2 - Numerical simulations and an analytic approach based on transmission line theory are used to design splitters for nano-plasmonic signal processing that allow to arbitrarily adjust the ratio of transmission from an input into two different output arms. By adjusting the geometrical parameters of the structure, either a high bandwidth or a sharp transmission resonance is obtained. Switching between the two arms can be achieved by modulating the effective refractive index of the waveguide. Employing the instantaneous Kerr effect, switching rates in the THz regime are potentially feasible. The suggested devices are of interest for future applications in nanoplasmonic information processing. Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-85889 UR - http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-18-11-11810&id=199640 ER - TY - JOUR A1 - Rewitz, Christian A1 - Keitzl, Thomas A1 - Tuchscherer, Philip A1 - Goetz, Sebastian A1 - Geisler, Peter A1 - Razinskas, Gary A1 - Hecht, Bert A1 - Brixner, Tobias T1 - Spectral-interference microscopy for characterization of functional plasmonic elements JF - Optics Express N2 - Plasmonic modes supported by noble-metal nanostructures offer strong subwavelength electric-field confinement and promise the realization of nanometer-scale integrated optical circuits with well-defined functionality. In order to measure the spectral and spatial response functions of such plasmonic elements, we combine a confocal microscope setup with spectral interferometry detection. The setup, data acquisition, and data evaluation are discussed in detail by means of exemplary experiments involving propagating plasmons transmitted through silver nanowires. By considering and experimentally calibrating any setup-inherent signal delay with an accuracy of 1 fs, we are able to extract correct timing information of propagating plasmons. The method can be applied, e.g., to determine the dispersion and group velocity of propagating plasmons in nanostructures, and can be extended towards the investigation of nonlinear phenomena. Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-85922 UR - http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-20-13-14632&id=238393 ER - TY - JOUR A1 - Steinbacher, Andreas A1 - Buback, Johannes A1 - Nürnberger, Patrick A1 - Brixner, Tobias T1 - Precise and rapid detection of optical activity for accumulative femtosecond spectroscopy JF - Optics Express N2 - We present polarimetry, i.e. the detection of optical rotation of light polarization, in a configuration suitable for femtosecond spectroscopy. The polarimeter is based on common-path optical heterodyne interferometry and provides fast and highly sensitive detection of rotatory power. Femtosecond pump and polarimeter probe beams are integrated into a recently developed accumulative technique that further enhances sensitivity with respect to single-pulse methods. The high speed of the polarimeter affords optical rotation detection during the pump-pulse illumination period of a few seconds. We illustrate the concept on the photodissociation of the enantiomers of methyl p-tolyl sulfoxide. The sensitivity of rotatory detection, i.e. the minimum rotation angle that can be measured, is determined experimentally including all noise sources to be 0.10 milli-degrees for a measurement time of only one second and an interaction length of 250 μm. The suitability of the presented setup for femtosecond studies is demonstrated in a non-resonant two-photon photodissociation experiment. Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-85913 UR - http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-20-11-11838&id=233249 ER - TY - JOUR A1 - Aeschlimann, Martin A1 - Bauer, Michael A1 - Bayer, Daniela A1 - Brixner, Tobias A1 - Cunovic, Stefan A1 - Fischer, Alexander A1 - Melchior, Pascal A1 - Pfeiffer, Walter A1 - Rohmer, Martin A1 - Schneider, Christian A1 - Strüber, Christian A1 - Tuchscherer, Philip A1 - Voronine, Dimitri V. T1 - Optimal open-loop near-field control of plasmonic nanostructures N2 - Optimal open-loop control, i.e. the application of an analytically derived control rule, is demonstrated for nanooptical excitations using polarization-shaped laser pulses. Optimal spatial near-field localization in gold nanoprisms and excitation switching is realized by applying a shift to the relative phase of the two polarization components. The achieved near-field switching confirms theoretical predictions, proves the applicability of predefined control rules in nanooptical light–matter interaction and reveals local mode interference to be an important control mechanism. KW - Chemie Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-75256 ER - TY - JOUR A1 - Brixner, Tobias A1 - Koch, Federico A1 - Kullmann, Martin A1 - Selig, Ulrike A1 - Nuernberger, Patrick A1 - Götz, Daniel C. G. A1 - Bringmann, Gerhard T1 - Coherent two-dimensional electronic spectroscopy in the Soret band of a chiral porphyrin dimer JF - New Journal of Physics N2 - Using coherent two-dimensional (2D) electronic spectroscopy in fully noncollinear geometry, we observe the excitonic coupling of β,β'-linked bis[tetraphenylporphyrinato-zinc(II)] on an ultrafast timescale in the excited state. The results for two states in the Soret band originating from an excitonic splitting are explained by population transfer with approximately 100 fs from the energetically higher to the lower excitonic state. This interpretation is consistent with exemplary calculations of 2D spectra for a model four-level system with coupling. KW - optics KW - quantum optics KW - laser Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-96139 ER - TY - JOUR A1 - Kanal, Florian A1 - Keiber, Sabine A1 - Eck, Reiner A1 - Brixner, Tobias T1 - 100-kHz shot-to-shot broadband data acquisition for high-repetition-rate pump–probe spectroscopy N2 - Shot-to-shot broadband detection is common in ultrafast pump–probe spectroscopy. Taking advantage of the intensity correlation of subsequent laser pulses improves the signal-to-noise ratio. Finite data readout times of CCD chips in the employed spectrometer and the maximum available speed of mechanical pump-beam choppers typically limit this approach to lasers with repetition rates of a few kHz. For high-repetition (≥ 100 kHz) systems, one typically averages over a larger number of laser shots leading to inferior signal-to-noise ratios or longer measurement times. Here we demonstrate broadband shot-to-shot detection in transient absorption spectroscopy with a 100-kHz femtosecond laser system. This is made possible using a home-built high-speed chopper with external laser synchronization and a fast CCD line camera. Shot-to-shot detection can reduce the data acquisition time by two orders of magnitude compared to few-kHz lasers while keeping the same signal-to-noise ratio. KW - cameras KW - CCD KW - charge-coupled device KW - modulators KW - time-resolved spectroscopy KW - ultrafast spectroscopy KW - ultrafast measurements Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-112853 ER - TY - JOUR A1 - Brixner, Tobias A1 - Pawłowska, Monika A1 - Goetz, Sebastian A1 - Dreher, Christian A1 - Wurdack, Matthias A1 - Krauss, Enno A1 - Razinskas, Gary A1 - Geisler, Peter A1 - Hecht, Bert T1 - Shaping and spatiotemporal characterization of sub-10-fs pulses focused by a high-NA objective N2 - We describe a setup consisting of a 4 f pulse shaper and a microscope with a high-NA objective lens and discuss the spects most relevant for an undistorted spatiotemporal profile of the focused beam. We demonstrate shaper-assisted pulse compression in focus to a sub-10-fs duration using phase-resolved interferometric spectral modulation (PRISM). We introduce a nanostructure-based method for sub-diffraction spatiotemporal characterization of strongly focused pulses. The distortions caused by optical aberrations and space–time coupling from the shaper can be reduced by careful setup design and alignment to about 10 nm in space and 1 fs in time. KW - Interference microscopy KW - Scanning microscopy KW - Subwavelength structures KW - nanostructures KW - Pulse shaping KW - Ultrafast measurements Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-111120 ER - TY - INPR A1 - Lambert, Christoph A1 - Völker, Sebastian F. A1 - Koch, Federico A1 - Schmiedel, Alexander A1 - Holzapfel, Marco A1 - Humeniuk, Alexander A1 - Röhr, Merle I. S. A1 - Mitric, Roland A1 - Brixner, Tobias T1 - Energy Transfer Between Squaraine Polymer Sections: From helix to zig-zag and All the Way Back T2 - Journal of the American Chemical Society N2 - Joint experimental and theoretical study of the absorption spectra of squaraine polymers in solution provide evidence that two different conformations are present in solution: a helix and a zig-zag structure. This unique situation allows investigating ultrafast energy transfer processes between different structural segments within a single polymer chain in solution. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. We combine here femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy showing that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zig-zag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the density of states between donor and acceptor polymer segments because of very small reorganization energy in these cyanine-like chromophores. KW - energy transfer dynamics KW - squaraine polymer Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159607 UR - http://dx.doi.org/10.1021/jacs.5b03644 N1 - This document is the unedited Author's version of a Submitted Work that war subsequently accepted for publication in Journal of the American Chemical Society, copyright American Chemical Society after peer review. To access the final edited and published work see doi:10.1021/jacs.5b03644. ER - TY - JOUR A1 - Verma, Pramod Kumar A1 - Steinbacher, Andreas A1 - Schmiedel, Alexander A1 - Nuernberger, Patrick A1 - Brixner, Tobias T1 - Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy JF - Structural Dynamics N2 - We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs) to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps) followed by decay (≈390 ps) to the corresponding ground state. KW - time resolved spectroscopy KW - ground states KW - fluorescence spectra KW - absorption spectra KW - ultraviolet light KW - hydrogen bonding KW - excited states KW - reaction mechanisms KW - fluorescence KW - solvents Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-181301 VL - 3 ER - TY - JOUR A1 - Aeschlimann, Martin A1 - Brixner, Tobias A1 - Cinchetti, Mirko A1 - Frisch, Benjamin A1 - Hecht, Bert A1 - Hensen, Matthias A1 - Huber, Bernhard A1 - Kramer, Christian A1 - Krauss, Enno A1 - Loeber, Thomas H. A1 - Pfeiffer, Walter A1 - Piecuch, Martin A1 - Thielen, Philip T1 - Cavity-assisted ultrafast long-range periodic energy transfer between plasmonic nanoantennas JF - Light: Science & Applications N2 - Radiationless energy transfer is at the core of diverse phenomena, such as light harvesting in photosynthesis\(^1\), energy-transfer-based microspectroscopies\(^2\), nanoscale quantum entanglement\(^3\) and photonic-mode hybridization\(^4\). Typically, the transfer is efficient only for separations that are much shorter than the diffraction limit. This hampers its application in optical communication and quantum information processing, which require spatially selective addressing. Here, we demonstrate highly efficient radiationless coherent energy transfer over a distance of twice the excitation wavelength by combining localized and delocalized\(^5\) plasmonic modes. Analogous to the Tavis-Cummings model, two whispering-gallery-mode antennas\(^6\) placed in the foci of an elliptical plasmonic cavity\(^7\) fabricated from single-crystal gold plates act as a pair of oscillators coupled to a common cavity mode. Time-resolved two-photon photoemission electron microscopy (TR 2P-PEEM) reveals an ultrafast long-range periodic energy transfer in accordance with the simulations. Our observations open perspectives for the optimization and tailoring of mesoscopic energy transfer and long-range quantum emitter coupling. KW - chemistry KW - nanocavities KW - nanophotonics and plasmonics KW - photonic devices Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173265 VL - 6 ER -