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 - 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 - 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 - 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 - TY - JOUR A1 - Mueller, Stefan A1 - Lüttig, Julian A1 - Malý, Pavel A1 - Ji, Lei A1 - Han, Jie A1 - Moos, Michael A1 - Marder, Todd B. A1 - Bunz, Uwe H. F. A1 - Dreuw, Andreas A1 - Lambert, Christoph A1 - Brixner, Tobias T1 - Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways JF - Nature Communications N2 - Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions. KW - Atomic and molecular interactions with photons KW - Optical spectroscopy Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202529 VL - 10 ER - TY - INPR A1 - Fersch, Daniel A1 - Malý, Pavel A1 - Rühe, Jessica A1 - Lisinetskii, Victor A1 - Hensen, Matthias A1 - Würthner, Frank A1 - Brixner, Tobias T1 - Single-Molecule Ultrafast Fluorescence-Detected Pump–Probe Microscopy N2 - We introduce fluorescence-detected pump–probe microscopy by combining a wavelength-tunable ultrafast laser with a confocal scanning fluorescence microscope, enabling access to the femtosecond time scale on the micrometer spatial scale. In addition, we obtain spectral information from Fourier transformation over excitation pulse-pair time delays. We demonstrate this new approach on a model system of a terrylene bisimide (TBI) dye embedded in a PMMA matrix and acquire the linear excitation spectrum as well as time-dependent pump–probe spectra simultaneously. We then push the technique towards single TBI molecules and analyze the statistical distribution of their excitation spectra. Furthermore, we demonstrate the ultrafast transient evolution of several individual molecules, highlighting their different behavior in contrast to the ensemble due to their individual local environment. By correlating the linear and nonlinear spectra, we assess the effect of the molecular environment on the excited-state energy. KW - Fluoreszenz KW - Ultrafast spectroscopy KW - Single-molecule microscopy Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313485 ER - TY - JOUR A1 - Roeding, Sebastian A1 - Brixner, Tobias T1 - Coherent two-dimensional electronic mass spectrometry JF - Nature Communications N2 - Coherent two-dimensional (2D) optical spectroscopy has revolutionized our ability to probe many types of couplings and ultrafast dynamics in complex quantum systems. The dynamics and function of any quantum system strongly depend on couplings to the environment. Thus, studying coherent interactions for different environments remains a topic of tremendous interest. Here we introduce coherent 2D electronic mass spectrometry that allows 2D measurements on effusive molecular beams and thus on quantum systems with minimum system-bath interaction and employ this to identify the major ionization pathway of 3d Rydberg states in NO2. Furthermore, we present 2D spectra of multiphoton ionization, disclosing distinct differences in the nonlinear response functions leading to the ionization products. We also realize the equivalent of spectrally resolved transient-absorption measurements without the necessity for acquiring weak absorption changes. Using time-of-flight detection introduces cations as an observable, enabling the 2D spectroscopic study on isolated systems of photophysical and photochemical reactions. KW - Atomic and molecular interactions with photons KW - Excited states KW - Reaction kinetics and dynamics KW - Optical spectroscopy Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-226458 VL - 9 IS - 2519 ER - TY - JOUR A1 - Malý, Pavel A1 - Brixner, Tobias T1 - Fluorescence‐Detected Pump–Probe Spectroscopy JF - Angewandte Chemie International Edition N2 - We introduce a new approach to transient spectroscopy, fluorescence‐detected pump–probe (F‐PP) spectroscopy, that overcomes several limitations of traditional PP. F‐PP suppresses excited‐state absorption, provides background‐free detection, removes artifacts resulting from pump–pulse scattering, from non‐resonant solvent response, or from coherent pulse overlap, and allows unique extraction of excited‐state dynamics under certain conditions. Despite incoherent detection, time resolution of F‐PP is given by the duration of the laser pulses, independent of the fluorescence lifetime. We describe the working principle of F‐PP and provide its theoretical description. Then we illustrate specific features of F‐PP by direct comparison with PP, theoretically and experimentally. For this purpose, we investigate, with both techniques, a molecular squaraine heterodimer, core–shell CdSe/ZnS quantum dots, and fluorescent protein mCherry. F‐PP is broadly applicable to chemical systems in various environments and in different spectral regimes. KW - femtochemistry KW - FL spectroscopy KW - time-resolved spectroscopy KW - transient absorption Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-244811 VL - 60 IS - 34 SP - 18867 EP - 18875 ER - TY - INPR A1 - Dietzsch, Julia A1 - Jayachandran, Ajay A1 - Mueller, Stefan A1 - Höbartner, Claudia A1 - Brixner, Tobias T1 - Excitonic coupling of RNA-templated merocyanine dimer studied by higher-order transient absorption spectroscopy T2 - Chemical Communications N2 - We report the synthesis and spectroscopic analysis of RNA containing the barbituric acid merocyanine rBAM2 as a nucleobase surrogate. Incorporation into RNA strands by solid-phase synthesis leads to fluorescence enhancement compared to the free chromophore. In addition, linear absorption studies show the formation of an excitonically coupled H-type dimer in the hybridized duplex. Ultrafast third- and fifth-order transient absorption spectroscopy of this non-fluorescent dimer suggests immediate (sub-200 fs) exciton transfer and annihilation due to the proximity of the rBAM2 units. KW - Barbituric Acid Merocyanines KW - Nucleobase Surrogate Incorporation KW - Higher-order Transient Absorption Spectroscopy KW - rBAM2-labeled RNA strands Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-327772 ET - submitted version ER - TY - JOUR A1 - Li, Donghai A1 - Shan, Hangyong A1 - Rupprecht, Christoph A1 - Knopf, Heiko A1 - Watanabe, Kenji A1 - Taniguchi, Takashi A1 - Qin, Ying A1 - Tongay, Sefaattin A1 - Nuß, Matthias A1 - Schröder, Sven A1 - Eilenberger, Falk A1 - Höfling, Sven A1 - Schneider, Christian A1 - Brixner, Tobias T1 - Hybridized exciton-photon-phonon states in a transition-metal-dichalcogenide van-der-Waals heterostructure microcavity JF - Physical Review Letters N2 - Excitons in atomically thin transition-metal dichalcogenides (TMDs) have been established as an attractive platform to explore polaritonic physics, owing to their enormous binding energies and giant oscillator strength. Basic spectral features of exciton polaritons in TMD microcavities, thus far, were conventionally explained via two-coupled-oscillator models. This ignores, however, the impact of phonons on the polariton energy structure. Here we establish and quantify the threefold coupling between excitons, cavity photons, and phonons. For this purpose, we employ energy-momentum-resolved photoluminescence and spatially resolved coherent two-dimensional spectroscopy to investigate the spectral properties of a high-quality-factor microcavity with an embedded WSe\(_2\) van-der-Waals heterostructure at room temperature. Our approach reveals a rich multi-branch structure which thus far has not been captured in previous experiments. Simulation of the data reveals hybridized exciton-photon-phonon states, providing new physical insight into the exciton polariton system based on layered TMDs. KW - strong coupling KW - laser spectroscopy KW - transition metal dichalcogenide KW - coherent multidimensional spectroscopy KW - exciton Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-351303 UR - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.087401 SN - 1079-7114 ET - accepted version ER - TY - JOUR A1 - Dostál, Jakub A1 - Fennel, Franziska A1 - Koch, Federico A1 - Herbst, Stefanie A1 - Würthner, Frank A1 - Brixner, Tobias T1 - Direct observation of exciton–exciton interactions JF - Nature Communications N2 - Natural light harvesting as well as optoelectronic and photovoltaic devices depend on efficient transport of energy following photoexcitation. Using common spectroscopic methods, however, it is challenging to discriminate one-exciton dynamics from multi-exciton interactions that arise when more than one excitation is present in the system. Here we introduce a coherent two-dimensional spectroscopic method that provides a signal only in case that the presence of one exciton influences the behavior of another one. Exemplarily, we monitor exciton diffusion by annihilation in a perylene bisimide-based J-aggregate. We determine quantitatively the exciton diffusion constant from exciton–exciton-interaction 2D spectra and reconstruct the annihilation-free dynamics for large pump powers. The latter enables for ultrafast spectroscopy at much higher intensities than conventionally possible and thus improves signal-to-noise ratios for multichromophore systems; the former recovers spatio–temporal dynamics for a broad range of phenomena in which exciton interactions are present. KW - energy transfer KW - self-assembly KW - optical spectroscopy Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-226271 VL - 9 ER -