bluuebunny/crossref_metadata_2025 huggingface dataset:
Photon correlation: a fast new digital processor for optical measurements
Authors: Mayo W. T. , Smart A. E.
Published: February 2020

Correlation is a powerful mathematical technique which extracts coherent features from signals and noise. It can also be used to measure system transfer functions and frequency spectra. Single-bit processing is adequate for many practical applications when used with pulse or level crossing detection.
Simple mode-locked YAG laser
Authors: Zhang Wang Fu
Published: February 2020

The characteristics of a simple mode-locked YAG laser are described. They consist of two optical cavity mirrors, a condenser including a YAG rod and a linear Xe flashlamp, and an acoustooptical mode-locking device.
Active interferometry of flashlamp-pumped Nd:YAG lasers
Authors: Ricks Douglas W. , Teppo Edward
Published: February 2020

If a flashlamp-pumped Nd:YAG laser is placed in one arm of an interferometer and a videotape recording is made of the interference fringes, much useful information about the system can be obtained.
Microwave-pumped excimer lasers
Authors: Young J. F. , Wisoff P. J. K. , Mendelsohn A. J. , Harris S. E.
Published: February 2020

Microwave excitation is a simple practical method of pumping high-pressure rare-gas-halide laser systems which avoids the discharge instabilities of typical avalanche discharges. Thus long pulse high-repetition rate operation is possible. In addition, the device can be easily constructed with high-vacuum halogen compatible materials and is free from electrode sputtering problems.
Electrodeless UV laser
Authors: Butcher Robert , Erickson George
Published: February 2020

Laser action has been observed in XeCI in a novel longitudinal discharge device operating without internal electrodes. The all-glass system utilizes displacement current through the walls to excite the laser gas. The discharge is driven by an air core transformer connected as a Tesla coil. The absence of metal electrodes in contact with the gas is expected to increase the gas lifetime and perhaps lead to a seated excimer laser.
Injection-locking techniques for excimer lasers
Authors: Bigio Irving H. , Slatkine Michael
Published: February 2020

It is by now well recognized that the simplest way to control the spectral bandwidth and beam divergence of high-gain excimer lasers is by the combined implementation of an unstable resonator and injection locking. The technique is attractive because near-diffraction-limited output and an ultra-narrow linewidth can be achieved with no loss of laser efficiency. Moreover the attractiveness of the technique is enhanced by the fact that very little reference oscillator power is required to achieve those parameters.
Switchless TE gas lasers
Authors: De Witte O. , Lacour B. , Vannier C.
Published: February 2020

Since the advent of CO2 TEA lasers,1 high-efficiency TE lasers have made important progress with respect to energy, repetition rate, and even wavelength with excimer lasers2 emitting in the UV. One important problem with the laser is to avoid arc formation in the discharge. This can be done by é-beams but using fragile toils that cannot work at high repetition rates. It can also be done by UV photoionization through spark boards associated with a fast discharge, but that requires reliably switching very high peak intensities at high voltages with a spark gap or a Thyratron.
Laser-enhanced chemical etching of solid surfaces
Authors: Chuang T. J. , Houle F. A.
Published: February 2020

The laser-enhanced chemical etching of Si and Ta with SF6, Si, SiO2, Ta, and Te films with XeF2 excited by a pulsed CO2 laser arid SiO2 with Cl2 by a cw Ar+ laser has been studied, and the etch rates as a function of the laser wavelength, laser intensity, and gas pressure have been determined.
Low-temperature growth of polycrystalline Si and Ge films by photolytic laser-induced CVD
Authors: Osmundsen J. F. , Lubben D. , C C. , Abele  , Greene J. E. , Eden J. G.
Published: February 2020

Laser-induced chemical vapor deposition (LCVD) of thin films is initiated by the pyrolysis or photodissociation of a polyatomic molecule near a gas-substrate interface. Photolytic LCVD is based upon the photodecomposition of the molecule which minimizes heating of the substrate. Recently, photodissociation of organometallic molecules with either a UV laser1,2 or a lamp3 has been used to deposit a variety of metal films. Also Hanabusa et al.
Computer-controlled laser scanning system for characterizing Hg1−xCdx Te crystals
Authors: Khan M. Asif , Ready John F. , Kruse Paul W.
Published: February 2020

Hg1−xCdx Te is an important material for IR detectors. The x value (fraction of Cd in the alloy) determines the forbidden energy gap and thus controls the semiconductor properties. Unfortunately, segregation during crystal growth gives rise to compositional nonuniformities; i.e., the x value varies spatially in a given sample. Thus an ability to measure the spatial variations of the x value and transmission is important for successful detector fabrication.
Phase and intensity characteristics of the Omega high-power glass laser
Authors: Hoose J. , Hopkins R. , Kumpan S. , Soures J. M. , Kelly J. , Iwan L. , Friedman W. D. , Reynolds J. , Lund L.
Published: February 2020

Laser-driven inertial confinement fusion utilizing direct drive techniques will require on-target intensity profiles which are carefully controlled. Current ignition target designs require that the intensity on target should depart by <5% from a predetermined profile. Experiments are described which measured the phase and intensity of the 24-beam Omega laser system.
Temporal shape analysis of mode-locked Q-switched Nd3+ laser pulses
Authors: Albrecht G. F.
Published: February 2020

Laser fusion experiments require laser pulses of well-known shape. Since the powers focused on target exceed those at which a plasma develops by factors of <106, laser pulse power diagnostics of a comparable dynamic range become desirable. We, therefore, developed a third-harmonic correlation scheme, which, depending on various parameters, has a dynamic range from some 106 to 1011 and a time resolution of about the FWHM pulse duration.
Characteristics of the 46-cm amplifier for Nova
Authors: Yarema S. M. , Bradley L. P. , Powell H. T.
Published: February 2020

The 46-cm amplifier1 is the largest amplifier in the Nova laser system. The total system performance is largely determined by its characteristics. Three of these amplifiers will be cascaded at the end of each amplifier chain. Each amplifier is designed to provide a small signal gain of 1.9 and to amplify saturating pulses of 1-10 nsee.
Principles of optical recording systems with AlGaAs lasers and pregrooved disks
Authors: Carasso Marino G. , Huijser Arie
Published: February 2020

Key factors for a compact optical recording system for filing applications (as demonstrated in 1978 at Philips Research Laboratories) are semiconductor lasers and pregrooved disks with sensitive stable materials. Three aspects of recent optical systems will be treated in more detail.
Ultraviolet generation enhanced by third harmonic generation of a synchronously mode-locked dye-laser system
Authors: Boggy Richard
Published: February 2020

The advantages of tunable SJV cw dye-laser radiation can best be extended to the UV range by frequency doubling the dye-laser output in an angle-tuned crystal such as KDP. The high peak powers provided by a synchronously mode-locked dye-laser system improve the efficiencies of such nonlinear processes, but UV power in excess of several milliwatts is difficult to achieve with conventional systems. However, by increasing the mode-locking frequency of such a dye-laser system by a factor of 3, we obtain higher peak powers and greatly improved frequency-doubling efficiency.
Sealed 100-Hz CO2 TEA laser using high CO2 concentrations and ambient-temperature catalysts
Authors: Stark D. S. , Crocker A. , Steward G. J.
Published: February 2020

There is a growing interest in the development of compact sealed CO2 TEA lasers emitting high peak output powers and capable of operating at high pulse repetition frequencies for long periods without need of gas replenishment. Although there has been sealed operation of CO2TEA lasers, it has not hitherto been possible to achieve this with high concentrations of CO2 (needed to produce maximum peak power output per unit discharge volume) without use of heated catalysts.
Scanning laser microscope for in-process inspection of semiconductor wafers
Authors: Schmitt R. L.
Published: February 2020

A laser scanning microscope has been developed which permits in-process inspection of patterned semiconductor wafers. In addition to its ability to produce images similar to those obtained using conventional microscopes, tine laser microscope can produce an image of the particulates contaminating the semiconductor surface without imaging the pattern itself. These separate images (in video format) can be combined through addition and subtraction to produce other useful images.
Laser deposition
Authors: Ibbs K. G.
Published: February 2020

Laser photochemical deposition (LPD) and laser chemical vapor deposition (LCVD) have been used to prepare delineated thin metallic films on a variety of substrates from organometallic vapors. Work elsewhere has shown the techniques to be suitable for semiconductor device fabrication.1,2 The organometallic species, with room temperature vapor pressures in the 10-100-Torr region, are flowed with a carrier gas into a stainless steel cell having a laser input window.
Comparison of pulsed Nd:YAG and pulsed CO2 lasers for hole rinsed circuit-board materials
Authors: Allen S. D. , Bass M. , Teisinger M. L.
Published: February 2020

Connections between conductive layers in printed wiring circuits are normally made by mechanically drilling and plating holes through the layers. As the packing densities of printed-circuit (PC) boards increase, mechanical drilling becomes more difficult. In addition, blind holes or vias to a buried layer are often necessary and are difficult to achieve mechanically.1
Laser scanning camera
Authors: Jagger M. , Lichnowski A. , Adrain R. S. , Armour I. A.
Published: February 2020

A camera has been developed for low-light level high-resolution viewing inside nuclear reactors. This camera uses an He-Ne laser beam raster scanned across the field of view. By detection of the reflected light using a photomultiplier, the subject viewed can be reconstructed in a video plane and viewed on a conventional TV monitor. Advantages of this system include large depth of field, electronic and/or optical zoom capability, long range (>10 m) in regions such as ducts which conventionally are impossible to illuminate adequately for normal TV work, and resolution to better than 200 µm in the near field.
New approach to fiber-optic sensors using fiber Fabry-Perot interferometers
Authors: Yoshino T. , Ose T. , Itoh K. , Kurosawa K.
Published: February 2020

For interferometric fiber sensors, the fiber Fabry-Perot interferometer (FFPI)1 has the simplest form and can be much more sensitive than the Mach-Zehnder arrangement, because the FFPI uses multiple-beam interference in a single fiber. We have developed new schemes for fiber sensors using these features of FFPI. Figure 1 shows the schematic diagram for a fiber-optic microphone system using FFPI. The FFPI consists of a 1-m long single-mode fiber with end surfaces which are dielectric coated at the surface reflectance of R = 80%. The input light is a frequency-stabilized single-mode He-Ne (λ= 633-nm) laser.
Nova and Novette alignment systems
Authors: Bliss E. S. , Boyd R. D. , Ozarski R. G. , Seppala L. G. , Swift C. D. , Dryden E. H. , Parker J.
Published: February 2020

The Nova and Novette alignment systems guide laser pulses through the separate amplifier chains to the target and ensure simultaneous arrival at the target. Alignment tasks accomplished prior to each target shot involve automatic or remote-manual adjustments of ~2000 stepper motors and other actuators for the full 20-beam 3-wavelength Nova system. The sensor packages and individual detectors used for gathering alignment and diagnostic data are modular to minimize the number of different design and fabrication efforts. For example, the output sensor1 comprises separate, but essentially identical, modules for each of the 3 operating wavelengths.
Optical head with a unique servomechanism for digital audio disk
Authors: Takiguchi Haruhisa , Matsui Sadayoshi , Kurata Yukio , Okada Osamu , Hijikata Toshiki
Published: February 2020

Simplification and miniaturization of an optical head are key points in making the digital audio disk player available. The development goals for the optical head are as follows.
Picosecond optical electronics: new approaches to high speed electronics instrumentation
Authors: Auston D. H. , Smith P. R.
Published: February 2020

We shall review recent progress toward the development of a complete electronics instrumentation system for precision measurements of electronic devices and materials with picosecond resolution. This approach is based on use of new high speed photoconductivity materials in novel circuit configurations, which, when illuminated by picosecond optical pulses, can be used to generate and sample picosecond electrical impulses. The specifications of a typical system operating at 82 MHz are.
Bilinear response in sub-100 psec InP:Fe optoelectronic switches
Authors: Wagner R. S. , Hammond R. B. , Paulter N. G. , Malone R. M.
Published: February 2020

Recent work has shown that Fe-doped InP is an efficient photoconductive material with sub-100 psec response.1 Optoelectronic switches fabricated from this material have potential applications in radiation detection, electronic gating, and high- voltage pulse generation. Many applications of the optoelectronic switch are possible because it is a simple photoconductor. Thus the important characteristics of a photoconductor are: (1) a response linear with applied voltage, (2) a response linear with excitation intensity, and (3) a speed of response independent of applied voltage. In this work we have investigated the transient response characteristics of InP:Fe optoelectronic switches to verify these basic properties. We have shown that these devices do in fact behave as photoconductors with the properties identified.
Picosecond electrical pulse generation
Authors: mourou Gerard , Knox W. , Williamson S.
Published: February 2020

Laser-induced photoconductivity in high resistivity semiconductors makes possible the control of high power electrical pulses with picosecond accuracy, which is frequently needed to drive fast electrooptic devices such as Pockels and Kerr cells as well as streak cameras. We will review the intrinsic properties of the picosecond photoconductive switching in terms of speed, optical energy requirements, and threshold. Applications to Pockels cells for optical pulse shaping and switch out as well as the jitter-free streak camera (Fig. 1), which leads to averaging capability in the picosecond time domain, will be presented.
Kramers–Kronig detection of four 20  Gbaud 16-QAM channels using Kerr combs for a shared phase estimation
Authors: Zou Kaiheng , Liao Peicheng , Cao Yinwen , Kordts Arne , Almaiman Ahmed , Karpov Maxim , Pfeiffer Martin Hubert Peter , Alishahi Fatemeh , Fallahpour Ahmad , Tur Moshe , Kippenberg Tobias J. , Willner Alan E.
Published: February 2020

We experimentally demonstrate Kramers–Kronig detection of four 20 Gbaud 16-quadrature-amplitude-modulated (QAM) channels after 50 km fiber transmission using two soliton Kerr combs as signal sources and local oscillators. The estimated carrier phase at the receiver for each of the channels is relatively similar due to the coherence between the frequency comb lines. The standard deviation of the estimated carrier phase difference of the channels is less than 0.08 rad after 50 km single-mode fiber (SMF) transmission. This enables the carrier phase recovery derived from one channel to be shared among multiple channels. In the back-to-back scenario, the bit error rate (BER) performance for shared carrier phase recovery shows an optical signal-to-noise ratio penalty of∼0.5dBcompared to the BER performance for carrier phase recovery when derived for each channel independently. BERs below the forward error correction threshold are achieved after 50 km SMF transmission with both independent and shared carrier phase recovery for four 20-Gbaud 16-QAM signals.
Ultrafast laser neutron sources
Authors: Schwoerer Heinrich , Ewald Friederike , Düsterer Stefan , Sauerbrey Roland , Karsch Stefan , Pretzler Georg
Published: February 2020

We describe the laser induced generation of neutrons by photodisintegration of beryllium and by fusion of deuterium from a heavy water jet. Applications of these new neutron sources in isotope transmutation technologies are discussed.
Properties of liquid silicon and carbon studied by ultrafast time-resolved x-ray absorption spectroscopy
Authors: Johnson S. L. , Lindenberg A. M. , MacPhee A. G. , Falcone R. W. , Heimann P. A. , Jeschke H. O. , Garcia M. , Rehr J. J. , Lee R. W. , Chang Z.
Published: February 2020

Time-resolved x-ray absorption spectroscopy is used to study the electronic structure of laser heated foils of silicon and carbon on time scales early enough to observe the liquid phase before break-up into droplets.
Larmor X-ray radiation from an intense and femtosecond laser pulse
Authors: Rousse A. , Phuoc K. Ta , Notebaert L. , Pittman M. , Rousseau J.P. , Sebban S. , Balcou P. , Hulin D. , Malka V. , Marquès J.R. , Fritzler S. , David P.G.
Published: February 2020

Electrons in an electromagnetic field of an intense femtosecond laser experience strong accelerations and produce elementary Larmor-type radiation (1). The emission generated by the strong interaction between electrons and photons is also called non linear Thomson scattering and was observed few years ago by the detection of the second and third harmonic light of the laser (2). The x-ray spectral range was anticipated at relativistic quiver energies provided by the strong laser fields.
Potential for biomolecular imaging with femtosecond X-ray pulses
Authors: Hajdu Janos
Published: February 2020

Summary not available at time of publication.
CARS Microscopy: 3D Vibrational Imaging of Proteins, DNA, and Lipids in Living Cells
Authors: Cheng Ji-Xin , Xie X. Sunney
Published: February 2020

Coherent anti-Stokes Raman scattering (CARS) microscopy offers a 3D imaging technique with inherent chemical selectivity based vibration spectra of molecules.[1] A major drawback of this technique is the presence of a large non-resonant background arising from the electronic contributions. We have demonstrated polarization CARS (P-CARS) microscopy that effectively suppresses the non-resonant background and improves the vibrational contrast.[2] P-CARS makes use of the polarization difference between the resonant signal and the non-resonant background. A polarization analyzer is used before the detector to reject the non-resonant background. With P-CARS microscopy, we are able to image protein distribution in living cells with a high contrast, as shown in Figure 1.
Directly measuring the coupling of solvent intermolecular modes to photoinduced chemical reaction
Authors: Park Sungnam , Kim Jeongho , Scherer Norbert F.
Published: February 2020

Resonant pump off-resonant probe OKE spectroscopy was performed to study the coupling of solvent molecular modes to the electronic excitation of the solute. The intermolecular solvent modes of a range of polar and polarizable solvent including chloroform and acetonitrile respond differently to the electronic excitation of Coumarin 153.
Direct Measurement of Vibrational Relaxation and Dephasing of Molecules by Spectrally Resolved Two-Colour Three-Pulse Photon Echoes
Authors: Van Dao Lap , Lincoln Craig , Lowe Martin , Hannaford Peter
Published: February 2020

The dynamics of vibrational relaxation and dephasing has been directly determined from the wavelength dependence of stimulated two-colour three-pulse photon echo signals. The influence of rotational motion of the N(C2H5)2 group on the echo intensity is discussed.
Ultrafast Dynamics of Molecular Wires based on Multiporphyrin Linear Arrays
Authors: Cho Hyun Sun , Kim Dongho , Osuka Atsuhiro
Published: February 2020

Ultrafast dynamics of directly linked orthogonal and fused Zn(II)porphyrin arrays were investigated to reveal and compare their exciton (or energy) relaxation mechanism by using various time-resolved spectroscopic techniques.
Generation of tunable THz radiation by femtosecond tilted-pulse-front excitation
Authors: Hebling János , Almási Gábor , Kozma Ida Z. , Kuhl Jürgen
Published: February 2020

Optical rectification and electro-optic sampling are the most frequently used methods for the generation and time-resolved detection of ultrashort THz pulses, respectively [1]. Both effects are efficient only if the group velocity
V
v
i
s

g
r
of the ultrashort light pulse is matched to the phase velocity
V
T
H
z

p
h
of the generated THz radiation [2]
Opto-electronic THz-pulse generation by non-linearities in air and air plasmas
Authors: Eden S. , Löffler T. , Thomson M. , Roskos H. G.
Published: February 2020

Focusing of high-energy laser pulses overlapped with its second harmonic into air leads to THz generation. We present a detailed study on the enlargement of this effect when a plasma is formed in the focus.
Temperature dependence of vibrational dephasing revealed by frequency-selected vibrational echoes
Authors: Xu Qing-Hua , Fayer M. D.
Published: February 2020

The vibrational echo experiment can have advantages in the study of solvation dynamics over its electronic and NMR analogs because it has high time resolution and it examines systems with relatively simple energy level structures. A limitation is that the broad width of a short pulse will cover both 0-1 and 1-2 vibrational transitions, which can complicate the data analysis. By frequency selecting the detection wavelength of the echo signal (frequency selected vibrational echoes), we can obtain information on dynamics from a true two-level system modulated by the solvent fluctuations [1]. Here using this method, we present a study of the temperature dependence of the vibrational dephasing of a metalloporphyrin-CO compound, RuTPPCOPy (TPP = 5,10,15,20-tetraphenylporphyrin, Py = pyridine), in a polymer glass, polymethylmethacrylate (PMMA), and a glass-forming liquid, 2-methyltetrahydrofuran (2-MTHF, glass transition temperature 86 K).
Two-dimensional visible-infrared Fourier transform spectroscopy
Authors: Belabas Nadia , Joffre Manuel
Published: February 2020

We demonstrate here two-dimensional spectroscopy of a phase-matched sample of known non-linear response by means of coherent measurement of the emitted infrared field after a visible double-pulse excitation.
Femtosecond optically induced rectification, shift and injection currents in GaAs
Authors: Laman N. , Côté D. , Sipe J.E. , van Driel H.M.
Published: February 2020

Investigations of ultrafast electrical transients generated in semiconductors using optical pulses have been carried out since the early development of ultrashort pulse lasers. The generation of THz radiation from picosecond and femtosecond transient electrical currents represents just one of the important offshoots of the field of ultrafast optoelectronics. However, the underlying physics, and scope of the various mechanisms which can lead to current generation by optical pules have not been well understood. Here we show how emitted THz radiation can be used as a probe to deduce the salient signatures of the three lowest order, physically distinct, processes that are associated with all-optical current generation in GaAs. We refer to these as rectification, shift and injection currents.
Joint Quantum Measurement Using Fourier-Transform Spectral Interferometry
Authors: Beck M. , Dorrer C. , Walmsley I.A.
Published: February 2020

We have measured the joint Q-function of a highly multimode field using unbalanced spectral heterodyne detection with a charge-coupled device array. We reconstruct the statistics of about 25 adjacent temporal modes each of about 100 fs duration.
Control of high-order harmonics by free electrons
Authors: Reinhardt C. , Chichkov B.N. , Wellegehausen B.
Published: February 2020

New possibilities for the manipulation of high-order harmonics by performing independent variation of the gas and electron densities are demonstrated. This technique allows to choose a desired harmonic generation process and to control its efficiency.
The Laser Electron Accelerator Project at Stanford University
Authors: Plettner Tomas , Byer R.L. , Wisdom J. , Colby E. , Cowan B. , Siemann R.L. , Spencer J.E. , Barnes C.
Published: February 2020

The Laser Electron Accelerator Project (LEAP) is a proof-of principle experiment for a novel particle acceleration technique that takes advantage of the high damage threshold of dielectric materials under ultra-short pulse laser radiation.
Liquid/Glass Solvent Dynamics: from 300 to 3 K
Authors: Lazonder Kees , Pshenichnikov Maxim S. , Wiersma Douwe A.
Published: February 2020

Temperature-dependent echo-peak shift and heterodyned-echo experiments in glass-forming liquids are discussed. Freezing out a large part of the bath fluctuations by varying the temperature from 300 K to 3 K allows for testing current solvation models.
Time-Resolved Resonance Raman Studies of Halooxide Photoisomerization Kinetics
Authors: Hayes Sophia C. , Cooksey Catherine C. , Reid Philip J.
Published: February 2020

The photochemistry of halooxides has been of interest due to the participation of these compounds in a variety of stratospheric photochemical processes.[1,2] The most studied member of this class of molecules is chlorine dioxide (OClO), which can undergo the following series of reactions following photoexcitation:
Two-photon polymerization of photosensitive resins with femtosecond pulses and fabrication of microoptical devices and photonic structures
Authors: Serbin J. , Fallnich C. , Chichkov B.N.
Published: February 2020

Investigations of two-photon polymerization of photosensitive resins initiated by femtosecond laser pulses are performed. Applications of this technique for the fabrication of three-dimensional microoptical devices, photonic structures and micro-models are demonstrated.
Cross-correlation frequency-resolved-optical-gating measurements of ultrabroadband continuum from microstructure optical fiber
Authors: Gu Xun , Kimmel Mark W. , Zeek Erik , O’Shea Patrick , Trebino Rick , Windeler Robert S.
Published: February 2020

Cross-correlation frequency-resolved optical gating (XFROG) using an angle-dithered nonlinear-optical crystal allows the measurement of the intensity and phase of ultrabroadband continuum generated using recently developed microstructure optical fiber. Our measurements reveal fine-scale structure in the continuum spectrum, which is confirmed by separate, single-shot measurements and simulations.
Self-Compression of Ultrafast Optical Pulses using Molecular Phase Modulation
Authors: Bartels Randy , Weinacht Tom , Baertschy Mark , Wagner Nick , Greene Chris , Murnane Margaret M. , Kapteyn Henry C.
Published: February 2020

Ultrafast optical pulses are useful for a range of scientific applications from spectroscopy to surface science. Since ultrafast lasers are limited in pulse duration to 5–7fs,1 and high-energy laser amplifiers are limited to ~15fs,2 shorter pulses must be created through external pulse compression techniques. The most common configuration is to use self-phase modulation to broaden the pulse spectrum, followed by a negative dispersion element to compress the pulse.3,4 However, these techniques are limited in obtainable pulse duration, particularly at short-wavelengths, by high-order dispersion aberrations. In recent years, molecular modulation of light has been considered as an alternative source of phase modulation.5, 6 In this work, we demonstrate a new technique that uses the time-dependent index modulation of quantum revivals of molecular rotational wave packets in a molecular gas (CO2). This technique has an inherent advantage over SPM techniques in that the spectral broadening can be induced with a negative chirp, allowing for simple pulse compression by propagating through a dispersive medium. This technique differs from Raman techniques previously demonstrated in that a wavepacket consisting of many rotational levels is used to obtain a single, self-compressed, pulse.
Time-to-space conversion of ultrafast optical pulses via spectral nonlinear optics in the communications band
Authors: Chung J.-H. , Weiner A. M.
Published: February 2020

In ultrahigh-speed optical communication networks, time-to-space conversion, which maps the serial time-domain ultrafast optical signal into its spatial replica, is important both for demultiplexing and to enable spatial or parallel processing for various higher-layer functionalities, such as header recognition and data encryption [1]. Time-to-space conversion is also interesting as a new approach for ultrafast optical waveform measurement. Several groups have reported recently on time-to-space converters [1-4]. From the viewpoint of applications for real-world optical communication networks, however, several requirements will have to be fulfilled simultaneously. For example, the operating wavelength must fall within the 1.55 µm lightwave communications band, the response time of the nonlinear medium must be fast, the efficiency must be high, and the temporal processing window must be large enough to accommodate parallel processing of many optical bits. In this paper we report the first spectral nonlinear optics time-to-space converter operating in the lightwave band. The use of second harmonic generation (SHG) as the spectral nonlinear optical process [1,3,5] provides ultrafast response. Furthermore, drawing on our analysis of the conversion efficiency of a SHG time-to-space converter [5], we have optimized the sensitivity of our converter to realize the first direct, single-shot measurements of a single laser pulse with no averaging.
Heterodyne detected fifth-order nonresonant Raman spectroscopy of CS2: Evidence for anharmonic coupling
Authors: Kaufman Laura J. , Saito Shinji , Ziegler Larry D. , Ohmine Iwao , Fleming Graham R.
Published: February 2020

We present actively phase-locked heterodyne detected fifth-order data. Nodal lines are found in several tensor elements, and these are also present in molecular dynamics simulations of the signal. The nodes are a result of anharmonic coupling between modes.
Real-time Observation of Conformational Dynamics in Peptide Folding
Authors: Zinth W. , Spörlein S. , Carstens H. , Renner C. , Behrendt R. , Moroder L. , Tavan P. , Wachtveitl J.
Published: February 2020

Proteins acquire their native structures through conformational dynamics proceeding on a nested hierarchy of temporal and spatial scales. The fastest processes occur within picoseconds while slower reactions involving large parts of a protein may proceed on the time scale of seconds. In some situations during the various steps of the protein folding process parts of the protein undergo transitions between structures of well defined geometries. Such conformational dynamics are addressed in the present studies where we use a cyclic chromo-peptide as a model system.
Polarized transient absorption studies of the initial isomerization dynamics of photoactive yellow protein, its E46Q derivative, and model chromophore compounds
Authors: Larsen Delmar S. , van Stokkum Ivo , Vengris Mikas , van Grondelle Rienk , van der Horst Michael , Hellingwerf Klaas J.
Published: February 2020

The initial isomerization reactions dynamics (<3ns) of the photoactive yellow protein with several mutants and hybrids along their corresponding isolated chromophores in aqueous solutions were studied with polarization dependent transient absorption spectroscopy (~100fs time resolution).
Investigating excited state dynamics in bacteriorhodopsin by impulsive stimulated emission pumping.
Authors: Ruhman Sanford , Hou Bixue , Ottolenghi Michael , Friedman Noga , Sheves Mudi
Published: February 2020

Femtosecond stimulated emission pumping experiments from bacteriorhodopsins fluorescent state show for the first time that it is a photocycle intermediate, with a constant nonisomerized structure throughout its 0.5 psec lifetime. Implications concerning internal conversion dynamics are discussed.
Vibrational Dynamics upon photoexcitation of native bacteriorhodopsin (bR) and of the all-trans - locked bR5.12
Authors: Diller Rolf , Herbst Johannes , Heyne Karsten , Ottolenghi Michael , Friedman Noga , Sheves Mudi
Published: February 2020

The all-trans to 13-cis photoisomerization of the retinal chromophore in bacteriorhodopsin (bR) acts as a strong steric and electronic perturbation for the protein environment, thereby driving the proton pump mechanism. Photoexcitation and torsional movement are expected to be paralleled by various intra- and intermolecular relaxation processes. According to femtosecond (fs) time-resolved optical absorption spectroscopy the electronic ground state is reached after about 500 fs (J) [1-4], which then relaxes on a 3 ps time-scale to the K-state with the chromophore in 13-cis configuration.
Spectroscopic investigation of macrocyclic poly (9,9-dimethyl-2-vinylfluorene) as an artificial light harvester
Authors: Johnson J. M. , Germaine A. C. , Chen X. , Alberty K. , Zang X. , Hogen-Esch T. E. , Bradforth S. E.
Published: February 2020

Three-dimensional crystal structures for the light harvesting antenna complexes of photosynthetic bacteria have recently been resolved [1]. This has led to a more profound understanding of how nature harvests sunlight in an efficient fashion. The antenna complex (LH2) is highly symmetric and the deployment of chromophores is cyclic. It is therefore of interest whether this architecture is important for the very rapid and efficient energy transfer - excitation hopping times at room temperature of ~100 fs have been reported [2]. In our investigations, the ring-like structure of LH2 is mimicked by novel two-dimensional macrocyclic polymers, which have recently been synthesized [3]. Such poly-vinyl aromatic polymers can be prepared with 10 – 50 chromophore groups (here the chromophore is 9,9 dimethylfluorene) that are pendent to the polymer backbone. In this report, the steady state and time-resolved spectroscopic properties of the macrocyclic polymers are compared with their linear analogs.
The role of nanoaggregate domains in the exciton dynamics of poly(p-phenylene vinylene)
Authors: Bardeen C. J. , Lim S. –H. , Bjorklund T. G. , Gaab K. M.
Published: February 2020

The photophysics of conjugated polymers have been intensely studied in the hope that they will provide insight into the electronic structure and dynamics of these materials. Conjugated polymers are often considered as an inhomogeneous collection of weakly-coupled chain segments, among which energy can be transferred via a Forster mechanism [1]. In this model, aggregation leads primarily to nonradiative traps for the luminescent Frenkel excitons. We have made a detailed study of the photodynamics of the prototypical conjugated polymer poly(p-phenylene vinylene) (PPV) and have found that the effects of aggregation are more complex, and not as detrimental as previously thought [2]. In the disordered environment of a polymer film, there is a mix of species, from amorphous regions of isolated molecules to aggregates consisting of hundreds of molecules. Both powder x-ray diffraction and transmission electron microscopy confirm the existence of these different domains in PPV. Our experimental data indicates that it is the nanocrystalline aggregates that are largely responsible for PPV’s luminescence properties.
Ultrafast dynamics of recombinative desorption of hydrogen from a Ru(001) surface: Evidence for a collective mechanism from isotope effects
Authors: Frischkorn Christian , Wolf Martin , Denzler Daniel N. , Hess Christian , Ertl Gerhard
Published: February 2020

The dynamics of the energy transfer processes at surfaces is of fundamental importance for a microscopic understanding of chemical reaction at solid surfaces, e.g. in heterogeneous catalysis. In conventional chemistry where phonons and electrons are always in thermal equilibrium, no detailed information can be obtained on the pathway of the energy flow between the substrate and the adsorbate. However, when a metal substrate is excited by an intense femtosecond laser pulse, a transient non-equilibrium of the electronic and phononic temperatures is created, which lasts on the order of the electron-phonon coupling time (for ruthenium ~1 ps) and allows to distinguish electron-mediated from phonon-mediated reactions [1]. The appropriate experimental approach is to measure the two-pulse correlation (2PC) of the respective reaction yield. To this end, the fundamental output of an amplified Ti:sapphire femtosecond laser system is split in two equally intense portions and then both beams are sent time-delayed onto the sample mounted in ultrahigh vacuum chamber. The yield of the desorbed product species is detected with a quadrupole mass spectrometer as a function of the pulse-pulse delay.
Two-Color Three Pulse Photon Echo Peak Shift Spectroscopy
Authors: Agarwal R. , Prall B. S. , Rizvi A. H. , Yang M. , Fleming G. R.
Published: February 2020

Two-color three pulse photon echo spectroscopy has been used to probe correlation in two different regions of the electronic spectrum of a chromophore in the condensed phase.
Ultrafast thermalization dynamics of water nanodroplets by infrared pump-probe spectroscopy
Authors: Seifert G. , Patzlaff T. , Graener H.
Published: February 2020

The ultrafast thermal relaxation of reversed micelles was investigated by time-resolved infrared pump-probe spectroscopy. Modeling this picosecond cooling process in terms of heat conduction provides a new, selective way to determine the water nanodroplet radii.
Chirp-controlled ground-state photodissociation of Cr(CO)6
Authors: Witte T. , Windhorn L. , Yeston J. , Motzkus M. , Proch D. , Kompa K.L.
Published: February 2020

A longstanding goal of laser chemistry in general, and of molecular control in particular, is selective scission of chemical bonds by laser light. Early attempts employing nanosecond IR laser pulses were hindered because the excitation time exceeded the timescale of intramolecular vibrational redistribution (IVR), precluding selectivity. With the advent of femtosecond infrared laser technology, however, novel concepts have been developed. Specifically, Chelkowski et al. [1] have proposed the use of properly chirped laser pulses to enhance vibrational excitation and dissociation. The concept is intuitively clear assuming a multiphoton ladder climbing progression up the vibrational manifold. A negatively chirped IR laser pulse should enhance excitation to higher levels in an anharmonic potential, since the level spacing decreases with increasing energy. Applying a positively chirped IR laser pulse should conversely inhibit excitation. Although not yet realized for molecular dissociation, this concept has been applied to control vibrational population transfer in gas-phase NO [2] as well as solution-phase W(CO)6 [3]. Recently, it was shown that even without any chirp, metal-carbonyls could be dissociated in the gas phase with intense mid-infrared fs laser pulses tuned to the C-O stretch resonance at 5µm (Fig. 1), which requires an excitation to at least v=7 [4]. We now go a step further and investigate the role of chirp on the dissociation yield of Cr(CO)6.
Multidimensional Infrared Spectroscopies of Peptides; Design and Control of Coherence
Authors: Mukamel Shaul , Scheurer Christoph
Published: February 2020

Design principles for multiple pulse infrared spectroscopies which draw upon the analogy with NMR are developed. Novel multicolor vibrational analogs of heteronuclear NMR and the COSY, NOESY and HMQC techniques are simulated and new resonances are predicted.
Coherent Oscillations in Photoisomerization Reaction Dynamics of Photoactive Yellow Protein (PYP) and Related Systems
Authors: Chosrowjan Haik , Taniguchi Seiji , Mataga Noboru , Hamada Norio , Tokunaga Fumio , Imamoto Yasushi , Kataoka Mikio
Published: February 2020

In photosensory or photoactive proteins with chromophores absorbing in the visible region, such as rhodopsin (Rh) for vision, bacteriorhodopsin (bR), photoactive yellow protein (PYP) etc., light absorption leads to ultrafast and highly efficient reactions. Interestingly, despite quite different chromophores of these proteins, their behavior concerning the photoinduced primary processes in the protein nanospace in the course of the relaxation and twisting, including coherent processes seems to be similar. For instance, the fluorescence dynamics in all three proteins is nonexponential, no dynamic Stokes shift but a slight narrowing of the fluorescence spectra within first few picoseconds of the reaction were observed [1-3]. The spectral narrowing effect is most probably due to damping of coherently coupled intrachromophore high frequency modes and/or low frequency vibrations of environmental protein interacting with chromophore along the twisting coordinate. If this is the case, oscillatory behavior in fluorescence dynamics of photosensory proteins should be observed. To our knowledge, no such observation has been reported yet.
Pulse dynamics in polarisation-maintaining photonic crystal fibers
Authors: Ortigosa-Blanch A. , Knight J.C. , Russell P.St.J.
Published: February 2020

Photonic crystal fiber (PCF) is a pure silica fiber in which waveguiding is due to the arrangement of a pattern of tiny air holes running down the fiber length. The massive nonlinearity and unusual group velocity dispersion characteristics that can be achieved in such fibers make them spectacular vehicles for nonlinear fiber optics. Anomalous group velocity dispersion at near infrared and visible wavelengths, [1], soliton propagation in the near infrared [2] and broadband supercontinuum generation [3] amply demonstrate the wide range of interesting effects which have been reported.
Ultrafast dynamics of coherent anharmonic phonons in bismuth
Authors: Hase Muneaki , Kitajima Masahiro , Nakashima Shin-ichi , Mizoguchi Kohji
Published: February 2020

We report on the femtosecond dynamics of coherent anharmonic phonons in bismuth. The large amplitude coherent phonon generated by high-density photoexcitation exhibits a time-dependent phonon frequency, which is attributed to the anharmonicity of the lattice potential.
Immunohistochemical study to detect glucagon and insulin hormones in pancreas of camel and buffalo
Authors: Bargooth Ali F. , Ali-Jebori Jafar G. A. , Al-Badri Ahmed M. , Al-Yasari Ali M. R. , Zegyer Esraa A.
Published: February 2020

Background and Aim: Glucagon plays a significant role in glucose homeostasis by controlling hepatic glucose output in terms of both hypoglycemic and normoglycemic conditions. This study aimed to determine the amount and intensity of insulin and glucagon in addition to estimating the relationship between α- and β-cells for two animals, camel and buffalo. Materials and Methods: Twenty fresh pancreas samples were collected from 10 buffalo and 10 camel adults immediately after slaughter from AL-Kut abattoir, Al- Kut, Iraq. Hematoxylin and eosin staining technique and the immunohistochemistry technique were used. Results: The histological results, for both animals, showed the cells of the pancreatic islet could be differentiated from the exocrine cells by their paler appearance. The pancreatic islets were round, oval, and irregular shaped. In the camel, the pancreatic islets had a larger diameter than that in the buffalo. The average diameter of β-cells and their percentage was higher than those of the α-cells in the camel. In the buffalo, glucagon-immunoreactive cells were found in abundance with high intensity, whereas insulin-immunoreactive cells were more prominent with high intensity in the camel. In both animals, the α-cells and glucagon-immunoreactive cells were distributed on the peripheries of the pancreatic islets, whereas the β-cells were distributed throughout the pancreatic islets. Conclusion: The study inferences that these differences may be due to the differences in the environment of the animals which affect the structures of body organs.
Adaptive Synchronization of Time-Delay Chaotic Systems with Intermittent Control
Authors: Wang Yuangan , Li Dong
Published: February 2020

Time delay is a common but not negligible phenomenon in nonlinear systems, which affects the performance of synchronization. Based on principles of intermittent control and Lyapunov stability theories, we establish the synchronization criteria of the time-delay chaotic systems via adaptive intermittent control. The proposed control scheme is under aperiodically intermittent control, which is also extended to periodically intermittent control to better realization. Finally, to verify the effectiveness of our results, we choose the Lorenz system to do simulation.
Intercultural and interpersonal communication failures: analyzing hostile interactions among British and Spanish university students on WhatsApp
Authors: García-Gómez Antonio
Published: February 2020

Although the use of the mobile application communication technology for interpersonal communication seems to be less physically threatening, building successful relationships has become more complex. Using both quantitative and qualitative analyses of the way(s) British and Spanish university students manage a hostile situation when disputing among each other on WhatsApp, the present study aims to shed light on conflict management by investigating the differentiated topic management strategies the participants in the study deploy. This, in turn, will add new empirical evidence to the expanding field of intercultural pragmatics. Through a detailed analysis of the hostile interactions, the results show a differentiated linguistic process by means of which participants initiate, maintain and escalate conflict talk that also relates to the speaker’s failed attempts to understand and negotiate each other’s intended meaning in interaction.
How to do things with images: the editor, the cartoonist, and the reader
Authors: Abdel-Raheem Ahmed
Published: February 2020

Depending on context: to depict soaring prices as fires is to perform the act ofcomplaining; to portray the perpetrator of a sex crime as a wolf is to accomplish the action ofcondemning; to draw the ship of state sailing toward catastrophe is simultaneously to perform the action ofwarningand to issue a prediction; etc. It follows that, if political cartooning is action, then having a cartoon spiked is failure to act. The discussion of silenced speech acts cannot fail to have already been noticed by other scholars. Yet, so far little attention has been paid to this phenomenon, especially in multimodal and intercultural pragmatics. Apart from substantiating the claim that it makes sense to study speech acts in political cartoons, this article investigates the situational factors that may affect the editorial decision-making of a given newspaper. Using a corpus of selected American, British, Egyptian, and Jordanian cartoons, it is argued that the appropriateness conditions of (verbo) visual speech acts (and of discourse generally) depend on the context models of the participants (cartoonists/viewers).