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The heating and melting dynamics of a 20 nm thick gold film were studied using femtosecond electron diffraction. After heating to 30% above the melting point the gold film underwent a thermally-driven heterogeneous phase transition by melting front propagation. [ABSTRACT FROM AUTHOR]

We demonstrate a method for measuring the duration of high-number density femtosecond electron pulses as well as for determining the t=0 position for time resolved diffraction experiments using the laser ponderomotive force. The electron pulse duration of our experimental setup is shown to be just over 400 fs. [ABSTRACT FROM AUTHOR]

THz SHG is observed in a patterned MgO:LiNbO3 crystal using crossed THz polariton waves generated by spatiotemporally shaped optical pulses. The experiment foreshadows versatile nonlinear THz spectroscopy with integrated THz field shaping, guidance, and visualization. [ABSTRACT FROM AUTHOR]

We demonstrate the first femtosecond spectroscopy measurements in a microfluidic device. The microfluidic device is characterized using two-photon fluorescence and computer simulations, and pulse propagation through the high N.A. objective is characterized with spectral interferometry. [ABSTRACT FROM AUTHOR]

A power-scalable approach for high power THz generation is demonstrated using optical rectification in GaP pumped by an ultrafast Yb-doped parabolic pulse fiber amplifier. 6.5 µW THz radiation is obtained from 10 W optical power. [ABSTRACT FROM AUTHOR]

We demonstrate an ultrasimple, extremely broad band, alignment-free, and single-shot Transient-Grating Frequency-Resolved-Optical-Gating device using a mask that separates the input beam into three beams and a Fresnel biprism that crosses and delays them. Unlike previous ultrasimple ultrashort-pulse-measurement devices (i.e., GRENOUILLE), this device is also ambiguity-free and extremely broadband—it can measure UV, visible, and IR (amplified) pulses without change of optics. [ABSTRACT FROM AUTHOR]

We demonstrated two-photon imaging of biological tissues by employing a mode-locked semiconductor laser. Kilowatt-peak-power second-harmonic pulses were obtained from amplified 1.55 urn optical pulses, and were used for two-photon excitation. [ABSTRACT FROM AUTHOR]

Optically active sum-frequency generation microscopy was applied to imaging cells, utilizing the intrinsic chirality of biological macromolecules as the contrast mechanism. [ABSTRACT FROM AUTHOR]

A supercontinuum light source generated from a photonic crystal fiber has been used to obtain both multiplex coherent anti-Stokes Raman scattering (CARS) and two-photon excitation fluorescence images of a living cell simultaneously with high speed. [ABSTRACT FROM AUTHOR]

We report a single-laser time-resolved Fourier transform implementation of coherent anti-Stokes Raman scattering microscopy that provides high resolution spectrally-resolved images. We also demonstrate coherent-control-based two-photon fluorescence microscopy for selective fluorescence excitation in live organisms. [ABSTRACT FROM AUTHOR]

Optical coherence microscopy (OCM) uses coherence gating to achieve superior performance than confocal microscopy. A femtosecond Nd:Glass laser and nonlinear fiber light source achieve cellular imaging of cancer tissues in the pathology laboratory. [ABSTRACT FROM AUTHOR]

Photonic crystal fiber supercontinuum generated from a standard 100 fs Ti: Sapphire-oscillator is successfully compressed and phase-tailored in a fs-pulse shaper. Using this supercontinuum, we present a novel scheme for time-resolved single-beam CARS microscopy. [ABSTRACT FROM AUTHOR]

The use of phase shaped 13 fs pulses to selectively enhance fluorophore excitation in biological samples is shown. Images of a mouse kidney sample show high contrast without the use of filters or tuning the laser. [ABSTRACT FROM AUTHOR]

We developed two methods to access novel nonlinear functional contrast in tissue. Here we present three-dimensional, high-resolution data of two-photon absorption, sum-frequency absorption and self-phase modulation acquired in mounted melanoma cells. This fundamentally new contrast, combined with the technique's high sensitivity, promises to significantly advance optical methods for tissue characterization and diagnosis. [ABSTRACT FROM AUTHOR]

Terahertz polariton amplification is demonstrated via a discrete titled pulse front generated by a glass echelon structure. A conceptual scheme for very substantial further amplification is presented together with a preliminary experimental demonstration. [ABSTRACT FROM AUTHOR]

Excitation of a n-type GaAs layer with intense ultrashort THz pulses at room temperature causes coherent emission at 2 THz. Phase-resolved nonlinear propagation experiments show a picosecond decoherence time of the emitted field, despite the ultrafast carrier-carrier scattering at T = 300 K. While the linear response is in agreement with Drude theory, the nonlinear response is dominated by the superradiant decay of optically inverted impurity transitions. [ABSTRACT FROM AUTHOR]

We show that single-shot, high-resolution reconstruction of ultrafast THz fields is possible when using a characterized chirped probe pulse in an electro-optic mixing measurement. Here, we identify the field reconstruction as a phase-retrieval problem and present an alternative iterative reconstruction technique. [ABSTRACT FROM AUTHOR]

THz pulse emission is used to study demagnetization dynamics in single crystal iron and polycrystalline nickel films of thickness from 5 to 60 nm. Bulk and surface contributions each play a role, and their origins are discussed. [ABSTRACT FROM AUTHOR]

We have investigated the dynamical properties of intense terahertz waves from coherent longitudinal optical phonons in a GaAs/AlAs multiple quantum well, which is radiated in accordance with the group velocity of the phonon-polariton branch. [ABSTRACT FROM AUTHOR]

The 2 dimensional periodically poled lithium niobate (2D PPLN) crystal is proposed for narrow-band THz-wave generation by optical rectification of ultrashort pulses in surface emitting geometry. The high-energy and wide-aperture optical beam may be used due to opportunity of vector phase-matched interaction in 2D PPLN. The amplitude of electrical field over 10 kV/cm is estimated. [ABSTRACT FROM AUTHOR]

Unique THz phonon-polariton properties in LiNbO3 planar waveguides and photonic crystals are examined experimentally and compared to theoretical expectations. [ABSTRACT FROM AUTHOR]

Nanostructured metal surfaces were created by depositing a 30 nm layer of bulk gold onto a periodic fused silica transmission grating. By exciting this with a femtosecond laser beam, in air, results in terahertz radiation being produced. This emission is angle dependent. Furthermore, the emitted radiation has a third order power dependence ruling out the x(2) process, optical rectification. [ABSTRACT FROM AUTHOR]

Spatial and temporal properties of single-cycle THz pulses from a laser-plasma accelerator have been measured. Spatio-temporal coupling is observed that can impact pump-probe experiments: aberrations in the THz focusing system cause an apparent double-pulse structure. [ABSTRACT FROM AUTHOR]

Using ultrashort terahertz (THz) pulses we observe stimulated emission between internal energy levels of excitons. Emission occurs in Cu2O due to the 3p to 2s transition at 6.6 meV, with a cross section of 10−14 cm2. [ABSTRACT FROM AUTHOR]

A complete picture of different interfacial electron transfer dynamics has been obtained from transient absorption and two-photon photoemission data when inserting different anchor/bridge groups between the excited organic donor and the electrode surface. [ABSTRACT FROM AUTHOR]

The transient photoconductivity of ZnO nanowires and polycrystalline and nanoparticle films displays non-Drude behavior. Electron injection occurs on sub-picosecond time scales and decay kinetics indicate that surfaces and interfaces are the dominant sources of recombination. [ABSTRACT FROM AUTHOR]

By exploiting velocity mismatch, we show that optical rectification can generate radially polarized THz pulses. A compact system is implemented using <001> cut ZnTe pumped by an ultrafast Yb-doped parabolic fiber amplifier. [ABSTRACT FROM AUTHOR]

We have investigated the thermal expansion dynamics of metal films using femtosecond electron diffraction. We show that the electronic thermal expansion from the transient heating of conduction electrons contributes significantly in driving coherent acoustic phonons. [ABSTRACT FROM AUTHOR]

Cyclobutane pyrimidine dimers are the major photoproducts formed when DNA is exposed to UV light. Femtosecond time-resolved vibrational spectroscopy reveals that thymine dimers are formed in thymidine oligonucleotides in an ultrafast photoreaction. [ABSTRACT FROM AUTHOR]

Time resolved photoemission is employed to visualize directly an ultrafast insulator to metal transition and the excitation of a coherent phonon mode in the Mott insulator 1T-TaS2. [ABSTRACT FROM AUTHOR]

We simulate electron emission from a sharp tungsten tip induced by sub-8fs laser pulses and compare DC field and laser power dependence of the emission with experimental results. The simulation shows that with the correct choice of carrier-envelope phase of the exciting laser pulse, a single 700 attosecond electron pulse can be generated. We also discuss the applicability of such a system as a carrier-envelope phase detector. [ABSTRACT FROM AUTHOR]

Results are presented of initial experiments on the interaction of ultrashort high intensity XUV pulses with solids, carried out at the XUV free electron laser facility FLASH at DESY (Hamburg). [ABSTRACT FROM AUTHOR]

We observe multiphoton electron emission from ultrasharp metallic tips illuminated with 7-fs-light pulses. Local field enhancement confines this emission to the tip apex, demonstrating the potential of this source for ultrafast electron imaging with nanometer-resolution. [ABSTRACT FROM AUTHOR]

DNA strand breaks studied with a laser-driven electron x-ray source (LEXS) suggest that ultrafast electrons and x-rays were emitted from this source, and that high energy electrons were mainly responsible for the DNA damage. [ABSTRACT FROM AUTHOR]

Coherent optical phonon of CdTe with a frequency of 5-THz is excited by femtosecond laser pulses and detected successfully with femtosecond time-resolved X-ray diffraction as well as with optical reflection measurements. [ABSTRACT FROM AUTHOR]

Results on plume dynamics of laser ablation of metal films in helium at ambient pressure studied with ultrafast hard x-ray imaging are presented. The speed of the x-ray absorbing plume was measured at 1×102 m/sec. [ABSTRACT FROM AUTHOR]

Structure sensitive methods like time-resolved X-ray diffraction and transient absorption in the mid-IR are combined with UV7VIS transient absorption spectroscopy to probe the charge transfer photo-reaction in single crystals of an aminobenzonitrile derivative. [ABSTRACT FROM AUTHOR]

A photoinduced FeII spin crossover reaction in solution is studied with ultrafast x-ray absorption spectroscopy. The iron-nitrogen bond lengthens by 0.21±0.03 A in the high-spin transient excited state relative to the ground state. [ABSTRACT FROM AUTHOR]

Ultrafast laser pump-XAFS probe spectra of ironhexacyanide solvated in water have been measured using a laser-driven plasma x-ray source. A new x-ray source driven by a 15-W, 5-kHz laser system has been developed. [ABSTRACT FROM AUTHOR]

We use femtosecond x-ray diffraction to measure the coherent lattice displacements associated with the excitation and propagation of THz phonon polaritons in LiTaO3. [ABSTRACT FROM AUTHOR]

Propagating strain waves in SrTiO3, launched from PbZr0.2Ti0.8O3 films are measured by time-resolved x-ray diffraction. X-ray interference among contributions from differently strained regions allow to determine absolute transient strain amplitudes down to Δa/a = 2 · 10−5.. [ABSTRACT FROM AUTHOR]

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements have allowed us to characterize the atomic motion occurring during the initial stages of a photo-induced phase transition. [ABSTRACT FROM AUTHOR]

With an X-ray spectroscopic technique based on the use of the lifetime of a core excited state as an "internal clock" we investigate electron transfer between adsorbed atoms and metallic substrates on (sub)-femtosecond time scales. [ABSTRACT FROM AUTHOR]

An ultrafast transient polarization grating method is proposed as a means of measuring the dynamics of exciton spin relaxation in colloidal quantum dots. Measurement for CdSe quantum dots shows that spin relaxation is selectively probed. [ABSTRACT FROM AUTHOR]

The relaxation dynamics of photogenerated charge carriers in ZnSe-nanoparticles were examined via transient absorbance spectroscopy. Using an electron quencher we were able to assign observed dynamics to the relaxation of the electron in the conduction band. [ABSTRACT FROM AUTHOR]

Sub-10-fs visible pulses allow real time detection of coherent phonons in single-walled carbon nanotubes. Nonlinear coupling between radial breathing (250 cm−1) and the carbon-stretching (1600 cm−1) modes is experimentally observed and theoretically modeled. [ABSTRACT FROM AUTHOR]

In three-pulse four-wave mixing experiments of undoped GaAs quantum wells in large perpendicular magnetic fields, we see a small signal with unexpectedly long-lived beats. Using a microscopic many-body theory, we identify the beats as due to non-radiative Raman coherences, thereby extracting the dephasing time of the Raman coherence. [ABSTRACT FROM AUTHOR]

In extreme nonlinear optics the Rabi frequency is comparable to or even larger than the transition frequency. Numerical solutions of the semiconductor Bloch equations show that the response of semiconductor quantum wells and wires differs characteristically from that of a two-level system in this highly nonperturbative regime. The main reason for these differences is the continuous electronic dispersion, and, to a lesser degree, the Coulombic interaction effects. [ABSTRACT FROM AUTHOR]

Three-pulse photon echo peak shifts of single-walled carbon nanotubes were recorded at 975 nm, showing an initial value of 26 fs, a dominant decay time of 59 fs and an oscillatory frequency of 282 cm−1. [ABSTRACT FROM AUTHOR]

The dynamics of the excitons in semiconducting single-walled carbon nanotubes are investigated by time-resolved fluorescence measurements. Auger recombination of excitons on the picosecond timescale is observed and compared with theory. [ABSTRACT FROM AUTHOR]