bluuebunny/crossref_metadata_2025 huggingface dataset:
Coherent anti-Stokes Raman scattering microscopy with near-infrared ps pulses synchronized within 50 fs
Authors: Jones David J. , Potma Eric , Cheng Ji-Xin , Ye Jun , Xie X. Sunney
Published: February 2020

Coherent anti-Stokes Raman Scattering (CARS) microscopy [1] has enjoyed a resurgence following a series of recent improvements such as co-linear excitation geometry [2], and epi-direction detection [3]. An additional refinement has been the use of synchronized ps Ti:Sapphire lasers [4, 5]. Due to their wide tunability, ability of access the fingerprint region (1000 to 2000 cm
−
1) and near-infrared center wavelengths, these lasers are almost the ideal light source for CARS imaging. However, the relative timing jitter between the two lasers has remained a fundamental limitation. As CARS is inherently a multi-photon (four-wave mixing) microscopy technique, the presence of timing jitter is directly mapped to fluctuations in the CARS signal itself. In this work, we utilize a new locking method to reduce the timing jitter to below 50 fs. At this level of jitter, stability of the CARS signal is nearly shot-noise limited.
Femtosecond Si-Kα pulses from laser produced plasmas
Authors: Morak A. , Uschmann I. , Feurer T. , Förster E. , Sauerbrey R.
Published: February 2020

We have measured the strain induced by a fs laser in an InSb crystal temporally resolved using well characterized Si-Kα x-ray pulses. The generation of electron-hole-pairs is identified as the dominant strain inducing process.
Watching a protein as it functions: real-time observations at atomic resolution using picosecond x-ray crystallography
Authors: Schotte F. , Anfinrud P. A. , Wulff M.
Published: February 2020

The structural changes associated with ligand translocation in myoglobin have been investigated with picosecond time-resolved x-ray crystallography. These studies, conducted at the ESRF in Grenoble, France, unveil the protein’s structural evolution with atomic resolution.
Primary Processes of Ligand Dissociation in Heme Proteins
Authors: Armstrong M. , Ogilvie J. P. , Nagy A. M. , Miller R. J. D.
Published: February 2020

Amplified few cycle pulses were used to observe the initial dynamics of the pho todissociation process of carboxy myoglobin to specifically probe the issue of reaction driven modes in this system. Significant amplitude was observed at distinct modulation frequencies corresponding to deoxymyoglobin providing insight into the microscopic details of the reactive crossing.
Polar and non-polar solvation in the femtosecond evolution of 2D Fourier transform spectra
Authors: Yu Anchi , Hybl John D. , Farrow Darcie A. , Jonas David M.
Published: February 2020

A combination of magic angle pump-probe and femtosecond 2D Fourier transform spectra is used to probe polar and non-polar solvation in two structurally related molecules with and without a dipole moment change upon electronic excitation.
Photodissociation of ICN in polar solvents: evidence of long lived rotational excitation in real liquids
Authors: Germaine A. C. , Bradforth S. E.
Published: February 2020

Photodissociation dynamics in a liquid environment are of considerable complexity and interest. In liquids, effects such as caging and collisions with surrounding solvent molecules that cause dissipation of electronic, translational, rotational and vibrational energy to the surrounding solvent must be considered in addition to the often complex dissociation dynamics in the gas phase. The Ã band photodissociation of ICN is an excellent candidate to study the effects of the solvent on dissociation. This system has been studied extensively in the gas phase, both experimentally and theoretically. Three electronic states comprise this band and two product channels, ICN* I+CN and I*+CN, are observed [1]. In the I + CN channel, the CN is produced highly rotationally excited, N~50, making this system an excellent choice for the study of relaxation of a highly rotationally excited molecule in the liquid phase.
Reaction dynamics of hydrogen bonded aniline-ammonia clusters in intense laser fields by tandem mass spectroscopy
Authors: Itakura Ryuji , Watanabe Jun , Asano Taiki , Yamanouchi Kaoru
Published: February 2020

Mass-selected aniline cations and [aniline-(NH3)n]+ (n = 1 and 2) cluster ions are exposed to the femtosecond laser fields (λ ~ 395 nm, I ~ 4×1015 W/cm2) using a tandem type time-of-flight spectrometer. It is found that a bare aniline cation decomposes into the five-membered ring compound, cyclopentadienyl cation (C5H6+), while the decomposition is suppressed when one or two ammonia molecules are attached to the aniline cation. This suppression was interpreted in terms of an intermolecular energy flow through the hydrogen bonding.
Indole(NH3)n clusters: hydrogen atom transfer initiated by femtosecond laser pulses
Authors: Stert V. , Hesse L. , Lippert H. , Schulz C. P. , Radloff W.
Published: February 2020

The femtochemistry of the indole molecule which represents the chromophore of the amino acid trypophan is of particular interest because of its biological relevance. Recent studies (e.g. [1]) of indole in aqueous solution have shown that the photoexcitation leads to a fast charge separation process characterized by the formation of a solvated electron. The microscopic mechanism of the solvation process can be elucidated by gas phase studies of indole-solvent clusters with polar molecules like water or ammonia. Recent ab initio investigations of indolewater clusters have stressed the crucial role of the nonadiabatic coupling between the optically excited ππ* and a low-lying dark πσ* state for the electron transfer process [2]. In first pump-probe experiments on indole (NH3)n clusters with ns laser pulses a H atom transfer reaction has been stated [3].
Femtosecond Fluorescence Lifetimes Determined by an Intrinsic Raman Gate
Authors: An Q. , Zinth W. , Gilch P.
Published: February 2020

A technique to record fluorescence lifetimes in the femtosecond regime which relies on the inverse Raman effect is presented. This technique allows to use a conventional pump-probe set-up for the lifetime measurement.
How Fast is the Ultrafast Electron Transfer in Solute-Solvent Systems?
Authors: Gilch P. , Baigar E. , Zinth W. , Stöckl M. , Härter P. , von Feilitzsch T. , Michel-Beyerle M.E.
Published: February 2020

Comparison of the ultrafast electron transfer kinetics of a solute-solvent, system and its intramolecular analogue shows that the large solvent to solute rates are intrinsic and not due to accumulation of reaction probabilities.
Coherent valence fluctuation in photo-induced neutral-ionic transition of an one-dimensional charge transfer complex
Authors: Iwai S. , Tanaka S. , Fujinuma K. , Kishida H. , Okamoto H. , Tokura Y.
Published: February 2020

Optical excitation in low-dimensional electronic materials has exhibited various interesting excited state dynamics which is associated with the electron-electron and electron (spin)-lattice interactions. As a result of these interactions, macroscopic instabilities sometimes arise in the solid and leads to cause a photo-induced phase transition (PIPT) [1]. Recently, many efforts has been made to control those phase transitions and related macroscopic properties by optical excitations, since the controlling of the PIPT opens the way to high-speed switching of the various electronic properties. In addition, to found a new phenomena associated with the macroscopic instabilities and to reveal the mechanism of PIPT are the essential problem in solid state science relevant to the photo-excited state. Especially, the electronic and vibrational coherence in PIPT is of great interest.
Control of an electron transfer reaction using a sequence of femtosecond pulses
Authors: Martini Ignacio B , Barthel Erik R. , Schwartz Benjamin J.
Published: February 2020

A sequence of femtosecond laser pulses is used to control the electron transfer dynamics of sodide in solution. The electron recombination can be either enhanced or suppressed depending on the electron re-excitation delay time.
Watching and controlling intramolecular energy flow in solution: Effects of selective vibrational excitation and chemical substitution
Authors: Aßmann J. , Charvat A. , von Benten R. , Abel B.
Published: February 2020

Femtosecond transient absorption spectroscopy is used to excite CH- and OH-overtones in small organic molecules in solution and to monitor intramolecular energy flow for the case of different chemical substitutions or when different bonds are excited.
Photophysics of 9-Amino-6-chloro-2-methoxyacridine in aqueous solutions and selectively intercalated in duplex DNA
Authors: Ernsting N. P. , Kovalenko S. A. , Pérez Lustres J. L. , Senyushkina T. , Michel-Beyerle M. E. , Hess S. , Davis W. B. , Voityuk A. A. , Rösch N.
Published: February 2020

The photophysics of intercalated chromophores is an important tool in studies of DNA structure and dynamics. detection of DNA hybridization, the fluorescent imaging of DNA in gels, and fluorescent staining of chromosomal DNA.1,2 The transfer of a conjugated chromophore from aqueous solution to an intercalation site in the duplex often significantly affects the photophysics of that species.
Theory of THz-generation via optical rectification of fs-pulses in periodically poled nonlinear materials
Authors: Weiss C. , Torosyan G. , Wallenstein R. , Beigang R. , Avetisyan Y.
Published: February 2020

The generation of tunable THz-radiation via optical rectification of fs-pulses in periodically poled nonlinear materials is treated theoretically and compared with experimental results including generation in forward and backward direction, emission perpendicular to the surface and Cherenkov radiation.
Dynamics of the Carrier-Envelope-Offset Frequency of a modelocked Er: Fiber-Laser
Authors: Haverkamp Nils , Lipphardt Burghard , Stenger Joern , Telle Harald R. , Fallnich Carsten , Hundertmark Holger
Published: February 2020

In a periodic pulse train the carrier-envelope-offset frequency νCEO, that is the rate at which the phase of the carrier slips with respect to the pulse envelope, is of increasing interest for carrier phase dependent physics with few-cycle-pulses, e.g. higher harmonic generation. But also in the case of longer pulses, where single pulses contain many cycles of the optical field, characterization of νCEO offers new insights, for example into the dynamics within the laser. For measurements of νCEO various schemes have been proposed, e.g. in [1]. We present a novel scheme for determination of νCEO of a mode locked Er:fiber-laser emitting pulses of 80 fsec duration in the region spanning roughly 100 nm centered around 1560 nm [2]. For the purpose of this measurement the Er: fiber-laser is pulse-synchronized to a Kerr-lens-mode locked Ti: Sa-laser emitting 10 fsec pulses centered around 780 nm [3].
All-Optoelectronic CW THz-Imaging for Tumor Recognition
Authors: Siebert Karsten J. , Löffler Torsten , Quast Holger , Leonhardt Rainer , Thomson Mark , Bauer Tobias , Roskos Hartmut G. , Czasch Stephanie
Published: February 2020

Since its first demonstration by Nuss et al. [1] in 1995. optoelectronic THz imaging has become a rapidly- expanding field of research [2] with the potential for applications in package inspection and in the chemical and biomedical field. Typical optoelectronic THz measurement systems employ set-ups based on femtosecond laser systems which both are expensive and have problems to obtain narrow linewidth spectral data. For these reasons, there is an interest to find conceptual alternatives. We present a THz imaging system based on the coherent generation and detection of cw THz radiation by photomixing as demonstrated by Verghese et al. [3]. Our set up is given in Fig. 1.
Resonant-cavity magnetic-field probe for millimeter-wave frequency-domain spatial field mapping
Authors: Reano Ronald M. , Whitaker John F. , Katehi Linda P. B.
Published: February 2020

Probes based on electro-optic and magneto-optic effects can provide a complete characterization of electromagnetic behavior. Time-domain magneto-optic sampling has been investigated by Freeman et al. to examine spin relaxation and magnetic resonance effects, by Elazzabi et al. to measure picosecond current pulses, and by Riordan et al. to sample transient THz beams1-3. In the frequency domain, Wakana et al. have examined low-frequency RF circuits using a magneto-optic probe with a CW laser.4 The signal-to-noise ratio obtained from magneto-optic probes is typically far less than that obtained from electro-optic probes of similar physical dimensions. In this paper, a frequency-domain technique for sensitivity enhancement is presented. By tuning the probe dimensions to form a resonant cavity at the frequency of interest, the magnetic-field inside of the probe becomes a magnified representation of the sampled field, thereby improving the resulting signal-to-noise ratio. A short pulse laser is utilized to achieve millimeter-wave operation, thus providing the means to perform internal node diagnostics on high-frequency circuits and radiating structures.
THz Fresnel Lenses
Authors: Walsby E. D. , Wang S. , Ferguson B. , Xu J. , Yuan T. , Blaikie R. , Zhang X. -C.
Published: February 2020

Due to their flexibility of design and usage, Fresnel lenses are very attractive for THz applications. For example, Fresnel lenses could be used for maneuvering the THz wave front, fabricating THz diffraction optics or lens array for THz image application [1]. In general, Fresnel lenses are also more compact than conventional THz lenses.
Optical Modulator for Passive Synchronization and Active Modelocking of Lasers
Authors: Seitz W. , Ell R. , Schibli T. R. , Morgner U. , Kärtner F. X. , Lange C. H. , Richter W. , Braun B.
Published: February 2020

Modulation of intracavity losses is an important tool for controlling laser dynamics [1], for active mode-locking [2], and for synchronization of different lasers. In this paper, we present an optical device that allows for fast modulation of the intracavity losses by external illumination and its application as an intracavity device for active mode-locking and laser synchronization.
Programmable Two-dimensional fs Pulse Shaping Using an Optically Addressed Liquid Crystal Matrix
Authors: Vaughan Joshua C. , Feurer T. , Nelson Keith A.
Published: February 2020

Our interest in two-dimensional (2D) pulse shaping stems from efforts to control propagating excitations in crystals [1]. The difficulty in using conventional temporal-only (one-dimensional) pulse shaping for controlling propagating responses is that the material response quickly leaves the excitation region [2]. A 2D pulse shaper, which can produce independent temporally-shaped pulses along a transverse spatial coordinate, is able to irradiate a sample with different pulse shapes at different locations, thereby enabling the manipulation of propagating excitations. More generally, 2D pulse shaping enables multiplexed generation of complex optical signals and high-order time-resolved spectroscopy without beamsplitters or delay lines.
Laser induced microexplosions and applications in laser micromachining
Authors: Ashcom Jonathan B. , Gattass Rafael R. , Mazur Eric , Chay Yossi
Published: February 2020

The field of laser-induced damage in transparent materials has been under investigation since optical breakdown was first observed by Maker et al. in 1963 [1]. The nonlinear absorption mechanisms responsible for optical breakdown and damage in transparent materials are strongly intensity-dependent. The femtosecond laser is therefore an ideal tool to study these processes as the high intensity necessary to produce breakdown (on the order of 1017 W/m2) can be reached with very little energy (as little as 5 nJ per pulse with a 100-fs pulse). Femtosecond lasers have therefore revolutionized the field of laser micromachining as the low energy per pulse yields minimal collateral damage and hence high resolution in micromachining applications. Furthermore, focusing the pulse with high numerical aperture microscope objectives allows machining of the bulk without affecting the surface, because the intensity is only above the breakdown threshold in the focal volume.
Functional device fabrication by nonlinear material processing of glass with a femtosecond laser oscillator
Authors: Minoshima Kaoru , Kowalevicz Andrew M. , Ippen Erich P. , Fujimoto James G.
Published: February 2020

Photonic device fabrication using nonlinear material processing with near-IR femtosecond pulses can generate localized, clean, three-dimensional (3D) structures in many materials [1-3]. Recently, fabrication of glass waveguides using pulses directly from femtosecond lasers oscillators, without the need for amplification, has been reported [4-6]. Unamplified laser oscillators have several advantages over amplified systems for device fabrication including lower cost and complexity as well as greater control of exposure parameters. Because of their high repetition rates, multiple low intensity shots interact within the focal volume, leading to well controlled cumulative effects. Several photonic devices have been demonstrated including single-mode waveguides [5], X-couplers [6], and directional couplers [4]. Our group has developed a high-power femtosecond Ti:sapphire laser oscillator using a novel long cavity design [7]. Because of its high pulse energies and high repetition rate, this laser enables the versatile fabrication of a wide range of photonic devices.
Nanostructuring of transparent materials with femtosecond laser pulses
Authors: Korte F. , Nolte S. , Fallnich C. , Chichkov B.N.
Published: February 2020

Detailed investigations of possibilities to use femtosecond lasers for the fabrication of periodic structures in transparent materials with the scale length of the order of several hundreds nanometers are reported.
Gouy Phase Shift of Single-Cycle Picosecond Acoustic Pulses
Authors: Holme N.C.R. , Myaing M.T. , Norris T.B.
Published: February 2020

The generation of terahertz (THz) radiation via photoconductive switching or optical rectification with femtosecond optical pulses has enabled the investigation of diffractive effects with single-cycle pulses. The far-field diffraction of a broadband pulse from an aperture can be described by the time-domain Huygens-Fresnel integral.
Integrated THz technologies for femtomol sensitivity label-free detection of DNA
Authors: Nagel M. , Brucherseifer M. , Bolivar P. Haring , Kurz H. , Bosserhoff A. , Büttner R.
Published: February 2020

An integrated label-free approach for genetic analysis using time-domain femtosecond techniques for generating and electrooptically detecting THz signals is presented. Using planar THz resonators a femtomol sensitivity for DNA molecule detection is reached.
Adaptive femtosecond quantum control in the liquid phase
Authors: Brixner T. , Damrauer N. H. , Niklaus P. , Gerber G.
Published: February 2020

Despite the failure of single-parameter approaches (wavelength, intensity, or linear chirp control), adaptive femtosecond pulse shaping is able to discover complex laser fields to achieve chemically selective molecular excitation in the liquid phase.
Ultrafast relaxation dynamics of the solvated electron in liquid ammonia
Authors: Unterreiner Andreas N. , Lindner Jörg , Vöhringer Peter
Published: February 2020

We present what is to our knowledge the first femtosecond pump-probe studies on the solvated electron in liquid ammonia. Ultrafast near-infrared excitation of the electrons can be understood quantitatively in terms of a simple temperature jump which shifts within our time-resolution the electronic resonance by (5300 ± 500) cm−1 into the mid-infrared spectral region. A subsequent blue-shift of the time-dependent absorption spectrum indicates the dynamics of electron cooling and occurs on a time scale of (200 ± 50) fs. Both pump pulse-induced temperature jump and cooling occur under shape stability of the electron resonance.
Ultrafast electron transfer and solvation dynamics in amorphous ice layers on Cu(111)
Authors: Gahl C. , Bovensiepen U. , Frischkorn C. , Wolf M.
Published: February 2020

The solvation dynamics of excess electrons in water has attracted special interest due to its fundamental importance for charge transfer and solvation processes in chemistry and biology and the apparent simplicity of the hydrated electron as a model solute [1-3]. Upon photoinjection in liquid water at room temperature an excess electron localizes and relaxes on a timescale of ~1 ps via several precursor states to the equilibrated solvated ground state [3]. So far, most studies have focused on the solvation dynamics in the liquid phase, but very little is known about the initial stages of electron trapping in supercooled water and ice [4]. Electrons in precursor states to solvated electrons in ice are known to giantly enhance the dissociation of chlorfluorocarbons (CFCs) adsorbed on ice surfaces, a reaction which is of high relevance in the depletion of the ozone layer by released Cl atoms [5]. Photoinduced electron transfer into amorphous ice films leads also to molecular rearrangements and crystallization [6].
Hot-Electron-Driven Charge Transfer Processes on Surfaces
Authors: Lei Chi-Fong , Read Kendall , Tobey Ra’anan , Murnane Margaret M. , Kapteyn Henry C. , Bauer Michael
Published: February 2020

Chemistry driven by intense ultrafast pulses (femtochemistry) is distinguished from conventional phonon-mediated chemical reactions in that the product yield can be greatly enhanced and more importantly, new chemical reaction pathways can be accessed [1]. In a surface-adsorbate system, non-equilibrium or “hot” electrons created by a femtosecond pulse can drive these reactions[2]; however, direct, time-resolved observation of hot-electron-driven reactions has proven to be difficult. Here, we present time-resolved observations of a hot-electron driven change of adsorbate molecules (O2) on a metal surface (Pt) from one chemisorbed species to another. The process of time-resolved ultraviolet photoelectron spectroscopy makes it possible to observe both electronic energy relaxation, and structural changes in the surface/adsorbate, on their fundamental, femtosecond timescales.
Photoinduced electron transfer in dye/semiconductor systems on a sub-10-fs time scale
Authors: Huber Robert , Moser Jacques E. , Grätzel Michael , Wachtveitl Josef
Published: February 2020

Pump-probe investigation of alizarin adsorbed on the surface of TiO2 colloids reveals a 6 femtosecond electron transfer from the dye molecule to the semiconductor surface, allowing to identify the key factors for this ultrafast electron transfer.
Carrier relaxation dynamics in heavy fermion compounds
Authors: Demsar J. , Tracy L.A. , Averitt R.D. , Trugman S.A. , Sarrao J.L. , Taylor A.J.
Published: February 2020

Femtosecond time-resolved optical spectroscopy is an excellent experimental alternative to conventional spectroscopic methods that probe the low energy electronic structure in strongly correlated electron systems [1]. In particular, it has been shown that carrier relaxation dynamics are very sensitive to changes in the low energy density of states (e.g. associated with the formation of a low energy gap or pseudogap) providing new insights into the low energy electronic structure in these materials. In this report we present the first studies of carrier relaxation dynamics in heavy fermion (HF) systems by means of femtosecond time-resolved optical spectroscopy. Our results show that the carrier relaxation dynamics, below the Kondo temperature (TK), are extremely sensitive to the low energy density of states (DOS) near the Fermi level to which localized f-moments contribute. Specifically, we have performed measurements of the photoinduced reflectivity ∆R/R dynamics as a function of temperature and excitation intensity on the series of HF compounds YbXCu4 (X=Ag, Cd, In) [2] in comparison to their non-magnetic counterparts LuXCu4.
Low-density optical pump – THz probe analysis of high-temperature superconductors
Authors: Brucherseifer M. , Meltzow-Altmeyer A. , Bolivar P. Haring , Kurz H.
Published: February 2020

Using time-resolved THz probing we analyze the dynamics of low-density optically excited, optimally doped YBa2Cu3O7-δ. A previously unknown additional relaxation component is found, tentatively indicating the separate relaxation of charge and spin excitations.
Terahertz wave generation from multi-quantum well with transverse electric field
Authors: Morohashi I. , Komori K. , Shimura H. , Hidaka T. , Ikeda H. , Tujikura S. , Yamamoto M. , Okamoto Y.
Published: February 2020

Multi-quantum-well terahertz generator with a transverse electric field was proposed and investigated. The terahertz radiation characteristics including excitation wavelength dependence was investigated and high-power terahertz generation, which was 20-times higher than InAs references, was demonstrated.
Electronic charge transport in single-crystal Al2O3: Transient conductivity and its temperature dependence probed by THz time-domain spectroscopy
Authors: Shan J. , Wang F. , Knoesel E. , Bonn M. , Heinz T.F.
Published: February 2020

THz time-domain spectroscopy is applied to probe photo-induced charge transport in single-crystal Al2O3. The conductivity of the material and its temporal evolution yield carrier mobilities, excitation densities, and dynamics. The temperature dependence indicates that LO phonons are the dominant scattering mechanism.
T-ray diffraction tomography
Authors: Ferguson Bradley , Wang Shaohong , Gray Doug , Abbott Derek , Zhang X.-C.
Published: February 2020

T-ray computed tomography (T-ray CT) is an important new tomographic imaging modality utilizing ultrafast laser sources to probe the optical properties of 3 dimensional (3D) structures in the far-infrared [1]. It promises to have important applications in non-destructive mail and packaging inspection, semiconductor testing and manufacturing quality control. It provides sectional images of objects in an analogous manner to conventional computed tomography techniques such as X-ray CT.
Structural Dynamics in Water Probed by Heterodyne-Detected Photon Echo
Authors: Yeremenko Sergey , Pshenichnikov Maxim S. , Wiersma Douwe A.
Published: February 2020

Results of heterodyne-detected IR photon echo experiments on water at room temperature are reported. The measured time constants of 130 fs and 900 fs are attributed to dynamics of a single hydrogen bond and the hydrogen-bond network, respectively.
Ultrahigh resolution optical coherence tomography using novel femtosecond laser sources
Authors: Hartl I. , Kowalevicz A. , Hsiung P. , Ko T.H. , Schibli T. , Kärtner F. , Fujimoto J.G. , Birks T.A. , Wadsworth W.J. , Bünting U. , Kopf D.
Published: February 2020

Optical coherence tomography (OCT) is an emerging technology for micron-scale cross-sectional imaging of biological tissue and materials [1]. High resolution detection of reflected or backscattered light is performed using low coherence interferometry. One of the key problems in OCT has been the lack of compact, high performance, low coherence light sources with sufficient bandwidth and power to enable high resolution, real time imaging. A Ti:Al2O3 laser generating ~5fs pulses and bandwidths of 300 nm centered at 800 nm has been demonstrated for 1.5 µm axial resolution OCT imaging [2,3]. High nonlinearity, air-silica microstructure fibers [4] or tapered fibers [5] can generate a broadband continuum using low energy femtosecond pulses and have been used to achieve 2.5 µm imagie resolution at 1300 nm center wavelengths [6]. While these approaches achieve high resolutions in the important 800 nm and 1300 nm wavelength ranges, these lasers are relative expensive and bulky.
The Hall Current of Coherent Electron Wavepackets
Authors: Bauer T. , Hummel A. B. , Kolb J. S. , Roskos H. G. , Kosevich Yu. A. , Köhler K.
Published: February 2020

Terahertz-emission spectroscopy reveals two regimes of the Hall current of impulsively excited coherent charge-carrier wavepackets in a GaAs/AlGaAs superlattice as a function of the electric and magnetic bias fields.
Role of the absolute optical phase in carrier-wave Rabi flopping with two-cycle pulses
Authors: Mücke O. D. , Tritschler T. , Wegener M. , Morgner U. , Kärtner F. X.
Published: February 2020

When Rabi and light frequency become comparable, the Rabi doublets of the fundamental and the third harmonic meet around the second harmonic, giving rise to a signal which strongly depends on the absolute optical phase.
Passively mode-locked, self-frequency doubled, diode-pumped Yb: YAl3(BO3)4 laser
Authors: Taylor B. , Dawes J. , Dekker P. , Piper J. , Lederer M. J. , Hildebrandt M. , Kolev V. Z. , Luther-Davies B. , Tan H. H. , Jagadish C.
Published: February 2020

The broad fluorescence of Ytterbium doped lasers allows tunability and/or subpicosecond pulse generation at wavelengths around 1040nm. Also, the small quantum defect (<0.1) and high quantum efficiency reduce the thermal load. The simple energy level scheme of the Yb ion minimizes undesirable effects such as upconversion, excitedstate absorption and concentration quenching and is particularly suited to intracavity frequency-doubled lasers. As a result there is a growing range of mode-locked Yb3+-doped lasers, including the 40mW, 90fs pulses from a Yb3+:Ca4GdO(BO3)3 laser1 as well as the 200mW, 112fs pulses from a Yb3+:KGd(WO4)2 laser2. In particular, Yb:YAl3(BO3)4 (Yb: YAB) has a large second-order nonlinearity (deff >1.4pm/V) and favorable laser properties making it well suited to visible subpicosecond pulse generation. CW and Q-switched Yb:YAB lasers3,4 have previously been demonstrated with 1.1W of green output.
Experimental and theoretical studies on nonlinear propagation of a-few-optical-cycle pulses in a photoniccrystal fiber beyond the slowly-varying-envelope approximation
Authors: Fang Xiaojun , Hirasawa Masakatsu , Morita Ryuji , Yamashita Mikio , Windeler Robert S.
Published: February 2020

Photonic crystal fibers (PCFs) have attracted significant research attention in recent years for its zero-dispersion wavelength (ZDW) shifted into the visible range [1]. However, no study on the experimental and theoretical comparison of nonlinear propagation of a-few-cycle pulses covering the ZDW has been performed. In this paper, we clarified experimentally and theoretically the mechanism of the ultrabroad-band pulse generation for 4.5-cycle pulses during PCF propagation based on our derived nonlinear-propagation equation beyond the slowly-varying-envelope approximation (SVEA).
Size dependent photoconductivity in CdSe nanoparticles as measured by time-resolved THz spectroscopy
Authors: Beard Matthew C. , Turner Gordon M. , Schmuttenmaer Charles A.
Published: February 2020

The size dependent carrier dynamics in CdSe nanoparticles are consistent with carrier transport to their surface. In addition, a size dependent grouping of the photoconductivity is observed.
Polarizations of Raman sidebands generated in impulsively stimulated rotational Raman scattering
Authors: Kawano H. , Suda A. , Ishikawa K. , Midorikawa K.
Published: February 2020

Polarizations of high-order rotational Raman radiations are investigated via impulsively stimulated Raman scattering in hydrogen gas. Those polarizations are strongly dependent on the ellipticity of the polarization of a pump laser pulse.
Wavepacket interferometry for exciton transfer in molecular dimers
Authors: Kilin Dmitri S. , Cina Jeffrey A.
Published: February 2020

A detailed characterization of the pathways of photo-excitations in the coupled chromophores is needed to better characterize electronic energy transfer, a process important for photosynthetic-light harvesting and vision as well as photographic imaging and optical communication technologies. In order to motivate nonlinear wavepacket interferometry3 experiments on energy-transfer complexes in low-temperature media, we have carried out preliminary calculations on a model system comprising two coupled chromophores whose electronic transition dipole moments have specified (nonparallel) relative and lab-frame orientations. We represent Franck-Condon active nuclear modes by incorporating one internal molecular vibration in each monomer4. Because the energy-transfer matrix element, J, is nonzero selective ultrafast excitation of the donor moiety triggers surface-crossing to the acceptor-excited state yielding dynamical formation of an entangled one-exciton state.
Correlated vibrational dynamics in solution studied by two-dimensional Fourier transform infrared spectroscopy
Authors: Demirdöven N. , Khalil M. , Tokmakoff A.
Published: February 2020

We studied the ultrafast vibrational dynamics of a model system of two strongly coupled vibrations through characterization of the correlation between their transition energy fluctuations using two-dimensional Fourier transform infrared spectroscopy.
Nonlinear effects in microstructured fibers
Authors: Omenetto Fiorenzo G. , Efimov Anatoly , Taylor Antoinette J. , Knight Jonathan C. , Wadsworth William J. , Russell Philip St. J. , Arriaga Jesus
Published: February 2020

Control of nonlinear processes in optical fibers can provide the foundation for future all-optical signal processing applications which would impact a number of basic and applied fields. An ideal setting to study these phenomena is provided by microstructured optical fibers (or photonic crystal fibers –PCFs). The enhanced nonlinear effects in these structures has attracted considerable attention and has been the focus of intense research activity spanning a variety of applications [1,2]. We report here on a variety of effects which are observed experimentally by propagating 160 fs, λ=1550 nm pulses in a short segment of microstructured fiber. By operating at low average powers (up to 25 mW) and varying the input pulse polarization we can observe fundamental (N=1) soliton formation, higher order (N=2) formation in combination with a large self-frequency shift, visible harmonic generation and optical bistability in dependence of the input pulse polarization state.
Ultrafast dephasing of photoexcited polarons in primary doped polyaniline
Authors: Kim J. , Unterreiner A. -N. , Rane S. , Park S. , Jureller J. , Book L. , Liau Y. -H. , Scherer N. F.
Published: February 2020

Ultrashort pulse pump-probe and transient anisotropy methods are used to study polaron dynamics of primary doped conductive polyaniline in solution. Photoexcited carrier dynamics are identified on timescales of sub-100 fs up to >100 ps timescales.
Ultrafast intersystem crossing in a transition metal complex
Authors: Juban Eric A. , McCusker James K.
Published: February 2020

Intersystem crossing is an important aspect of virtually all photophysical and photochemical processes involving transition metals. One of the most extensively studied transition metal ions is chromium(III)[1,2]. A diagram of this ion’s electronic structure, depicting d-electrons under octahedral symmetry, is illustrated in Figure 1.
Sub-micrometer pulsetrain machining of diamond-like amorphous carbon films with a femtosecond pulse Ti:sapphire laser oscillator
Authors: Lakó S. , Apai P. , Pócsik I. , Szipcs R. , Wintner E.
Published: February 2020

Sub-micrometer holes on diamond-like amorphous carbon coatings on Si wafers were produced by ablation with femtosecond pulses. In contrast to earlier experiments with metallic coatings, even the damaged area does not exceed the sub-micrometer size.
Widely tunable femtosecond pulses from a tapered fiber for ultrafast microscopy and multiphoton applications
Authors: Jureller Justin E. , Scherer Norbert F. , Birks T.A. , Wadsworth W.J. , Russell P. St. J.
Published: February 2020

Approximately 100 femtosecond pulses centered at 690nm and 1000nm are produced by compressing sections of the ultrabroadband supercontinuum generated in a tapered fiber injected with pulses from a cavity dumped Titanium:sapphire laser. Biological and chemical applications are discussed.
Ultrafast Electron Optics: Propagation Dynamics of Femtosecond Electron Packets
Authors: Siwick Bradley J. , Dwyer Jason R. , Jordan Robert E. , Dwayne Miller R. J.
Published: February 2020

The recent interest in ultrafast diffraction has been stimulated by the potential of the technique to provide a complete, global picture of structural dynamics on the femtosecond time-scale with atomic level detail. X-rays have been the probe of choice in these early experiments as both plasma and synchrotron sources have been shown to be capable of producing femtosecond bursts of X-rays of sufficient brightness to perform useful investigations.
High-energy femtosecond stretched-pulse fiber faser with a nonlinear optical loop mirror
Authors: Ilday F. Ö. , Wise F. W.
Published: February 2020

A stretched-pulse fiber laser with a nonlinear optical loop mirror (NOLM) produces 125-fs pulses with 1-nJ energy. These are the best results obtained with a laser utilizing a NOLM, which can be the basis for environmentally-stable designs.
Complete Spatio-Temporal Characterization of Ultrashort Optical Pulses using Two-Dimensional Shearing Interferometry
Authors: Dorrer C. , Walmsley I. A.
Published: February 2020

We will present a novel technology for the complete spatio-temporal characterization of the electric field of an ultrashort light pulse, using an implementation of shearing interferometry in the spectral and spatial directions.
Indirect pulse shaping by parametric transfer
Authors: Tan Howe-Siang , Schreiber Elmar , Warren Warren S.
Published: February 2020

There has been much recent interest in generating mid-infrared (MIR) shaped pulses, useful for various applications such as extending ultrafast coherent control studies to vibrational systems of molecules of chemical and biological interests. Although high resolution pulse shaping capabilities exist for the visible and near-infrared (NIR) wavelengths [1, 2], direct phase and amplitude pulse shaping in the MIR has yet to be demonstrated. The main difficulty is the lack of appropriate materials for the usual direct methods of pulse shaping. Liquid crystal modulators absorb in the MIR; acousto-optic materials such as TeO2 and GaP, though transparent, have very low diffraction efficiency. One solution is to shape pulses in the visible or near-infrared wavelengths and transfer the shape to a pulse of another wavelength by a nonlinear optical process. There have been some recent successes in this approach[3]. However, in all these cases the shaped pulses are the result of nonlinear optical process between two pulses with similar bandwidth, and the resolution of the final pulse shape may be limited as it is a non-trivial convolution between the two input pulses. On the other hand, an OPA process pumped by a narrower spectral bandwidth pulse can effect a high fidelity transfer of a broadband pulse shape to another pulse of a different wavelength. We demonstrate this principle by generating complex high resolution shaped pulses with considerable pulse energy at NIR by a β-barium borate (BBO) based noncollinear optical parametric amplification (NOPA)[4] of visible shaped pulses [5]. We also demonstrate, for the first time to our knowledge, that with similar principles, a potassium niobate (KNB) based NOPA can amplify NIR shaped pulses with high fidelity and thereby obtaining MIR (3−4 µm) shaped pulses.
Diffractive optics based heterodyne detected six-wave mixing: “Dutch Cross” fifth-order Raman
Authors: Kubarych K. J. , Milne C. J. , Lin S. , Miller R. J. D.
Published: February 2020

A novel polarization configuration predicted to yield enhanced contrast of the direct fifth-order Raman signal is demonstrated in liquid carbon disulfide and shows a rapid decoherence in the liquid dynamics.
Femtosecond 2D Fourier transform study of electronic reorientation in silicon naphthalocyanine
Authors: Qian Wei , Ferro Allison Albrecht , Treglio Richard T. , Jonas David M.
Published: February 2020

26 fs excitation of a doubly degenerate transition in a molecule with square symmetry yielded a ~200 fs pump-probe anisotropy decay from 0.40(1) to 0.11(1). 2D spectra probe this rapid reorientation of the electronic wavefunction.
Coherent Femtosecond X-ray Raman Spectroscopy of Molecules
Authors: Tanaka Satoshi , Mukamel Shaul
Published: February 2020

By formulating the nonlinear response, in terms of correlation functions of charge and current densities we show that coherent x-ray Raman Spectroscopy provides an excellent local probe for the valence excitation dynamics in molecules.
Transition states in bacteriorhodopsin during retinal isomerization observed by sub-5-fs pulses
Authors: Kobayashi T. , Saito T. , Ohtani H.
Published: February 2020

We report the first direct observation of structural changes in a complex biological system, the chromophore of bacteriorhodopsin, as it undergoes the trans-cis photoisomerization by monitoring changes in the vibrational spectra of the transition state.
Far-Infrared Carrier Dynamics in Superconducting MgB2
Authors: Averitt R. D. , Demsar J. , Reagor D. W. , Taylor A. J. , Kang W. N. , Kim H. J. , Choi E. M. , Lee S. I.
Published: February 2020

The announcement in January 2001 of the discovery of bulk superconductivity in MgB2 at Tc ~ 39 K [1] has generated a great deal of excitement for several reasons. Most importantly, Tc is higher by nearly a factor of two in comparison to other previously known simple intermetallic superconductors (e.g. Nb3Ge, Tc ~ 23 K). This discovery has fueled the search for other simple metallic compounds that have a comparable or even higher transition temperature than MgB2 [2]. Indeed, an important fundamental issue that has resurfaced is determining the upper limit for Tc permitted by conventional phonon-mediated pairing (see also [3] in this regard). It is important in characterizing MgB2 to employ techniques that probe the bulk low energy electronic states. Far-infrared spectroscopy is especially useful since the gap can be directly observed. Recently, the superconducting gap in MgB2 has been studied using terahertz time-domain spectroscopy [4].
Nonlinear Optical Probes of Vibrational Motion at Interfaces.
Authors: Johansson T. , Kikteva T. , Star D. , Leach G.W.
Published: February 2020

New nonlinear methods sensitive to surface vibrational dynamics are presented. Femtosecond vibrational sum frequency generation allows for time-and frequency-domain vibrational spectroscopies and shows coherent nuclear motion (surface quantum beats) which dephases on a timescale dependent on surface inhomogeneity. A two-beam, equal pulse correlation technique has been used to examine low frequency intramolecular and intermolecular motions of organic molecules at the fused silica/air interface. The time-resolved parametric signals are modulated by adsorbate vibrational motion driven through stimulated Raman excitation. Frequency analysis of the temporal response of p-chloroaniline shows strong contributions at 80 and 120 cm−1, consistent with the excitation of low frequency Raman active lattice modes of crystalline p-chloroaniline.
Femtosecond fluorescence studies of two-dimensional dynamics of bridged and unbridged Michler’s ketones
Authors: van Veldhoven E. , Zhang H. , Glasbeek M.
Published: February 2020

For di- and triphenylmethane dye molecules in liquid solution it is well-known that the fluorescence quantum yield varies drastically with the viscosity of the solvent. Torsional motions of the phenyl rings of the dye molecules are believed to control the fluorescence quantum yield, i.e., if the solvent viscosity permits phenyl-group twisting the fluorescence is weakened. However, recent theoretical studies of photoexcited TICT states in liquid solution, have emphasized the importance of a two-dimensional reaction coordinate approach [1]. In the latter, the dynamics in the excited state is determined not only by the reaction coordinate (e.g., twisting), but also by the solvation coordinate. In this paper, we present results of femtosecond fluorescence upconversion experiments of two diphenyl methane dyes (Figure 1), Michler’s ketone (MK) and its bridged analog 3,6-bis(dimethylamino)-10,10-dimethylanthrone (BMK). For the unbridged MK in alcoholic solution very fast fluorescence decay kinetics of only a few picoseconds is reported, whereas its bridged counterpart BMK has a lifetime at least one order of magnitude longer. The molecules are identified as prototype examples of the slow and fast solvation limits in the model of Kim and Hynes.
Biexcitonic effects in coherently controlled six-wave-mixing experiments on ZnSe quantum wells
Authors: Breunig H. G. , Voss T. , Rückmann I. , Gutowski J.
Published: February 2020

Coherently controlled four-wave-mixing (FWM) measurements have turned out to be a very sensitive tool to investigate the microscopic origin of the nonlinear optical response of semiconductor quantum-well structures, in particular if excitons are excited [1-3]. The measured signal oscillates as a function of the phase difference of the two interferometric pulses and is modulated additionally by contributions that oscillate with integer multiples of the excitonic resonance frequency. The influence of these harmonics can be measured in background free directions, i.e., the first (FWM) or second (six-wave mixing, SWM) diffracted order in direction 2k2-k1 or 3k2-2k1, respectively. Their intensity is easily quantified by inspecting the corresponding Fourier transforms (FT). Here, we report on transient interferometric SWM measurements and the influence of biexcitons on the signal.
Diffractive optics-based heterodyne detected three-pulse photon echo
Authors: Ogilvie J. P. , Armstrong M. , Nagy A. , Miller R. J. D.
Published: February 2020

A novel diffractive optics-based method for performing three pulse photon echoes is demonstrated and extends the inherent passive phase stabilization of diffractive optics to this class of experiments for complete recovery of the signal field.
Electronic Excitation Oscillations in PPV – Femtosecond Luminescence Interferometry
Authors: Milota F. , Tortschanoff A. , Sperling J. , Szöcs V. , Kauffmann H. F.
Published: February 2020

Oscillatory relaxation of the conjugated polymer poly-(p-phenylenevinylene) (PPV) has been probed by fs-luminescence interferometry. Intersite polarization interference may account for the fast beating in the presence of strong damping and inhomogeneous site dephasing.
Vibrational energy relaxation in H2O
Authors: Lock A.J. , Bakker H. J.
Published: February 2020

Water is the most commonly used solvent for chemical reactions. Water molecules are believed to play an important role in the reaction dynamics by rearranging around the reactants and by lowering the energy barrier for the reaction. Detailed knowledge of the energy dynamics of liquid water can help us in understanding the role of water in reactions. In the past few years, extensive studies were performed on a dilute solution of HDO molecules in D2O [1,2,3]. It was found that the lifetime of the OH-stretch vibration T1 was 740 ± 20 fs [4]. Energy was shown to be transferred to a high overtone of the hydrogen bond stretch vibration [5]. Not much is known about the energy dynamics of “real” liquid water, i.e. H2O. Deàk et al. found that after excitation of the OH-stretch band of H2O population is transferred to the bending mode [3]. However, the time resolution of their experiment was not sufficient to determine the time constant of the relaxation. Here we present the first measurement of the timescale of the energy relaxation of H2O. We measured this time constant as a function of temperature. From the temperature dependence we conclude that the hydrogen bond strongly influences the relaxation behavior.
Ring opening reaction dynamics of a photochromic diarylethene derivative
Authors: Shim Sangdeok , Joo Taiha
Published: February 2020

Ring opening dynamics of a photochromic dye in solution has been studied by transient absorption and time-resolved fluorescence of the closed form. Reaction rate is determined and dynamics in the excited state is observed.