Topic
Femtosecond
About: Femtosecond is a research topic. Over the lifetime, 35106 publications have been published within this topic receiving 691405 citations. The topic is also known as: 1 E-15 s & fs.
Papers published on a yearly basis
Papers
More filters
TL;DR: The transmission of 100-fs ultrafast laser pulses through biological tissues was measured by using femtosecond and picosecond time-resolved detection techniques and the broadening of transmitted pulses was found to increase as the thickness of the biological tissue increases.
Abstract: The transmission of 100-fs ultrafast laser pulses through biological tissues was measured by using femtosecond and picosecond time-resolved detection techniques. The broadening of transmitted pulses was found to increase as the thickness of the biological tissue increases. The absence of a distinct ballistic pulse transmitted through a relatively thin tissue is in sharp contrast with the pulse transmission through a random medium of discrete scatterers. Because of the continuous variation of the dielectric constant in tissue, the photons undergo scattering through the tissue, travel in various small zigzag least optical paths, and form a broadened early-arriving portion of the transmitted pulse. Even in the absence of a well-defined ballistic pulse, we can image an opaque object hidden inside a tissue as thick as 6.5 mm with submillimeter resolution by selecting the early-arriving portion of the transmitted pulse.
134 citations
TL;DR: Experiments on ultrashort pulses that maintain their strong lateral and longitudinal localization in a bulk linear highly dispersive medium and can be applied in femtosecond laser optics are reported.
Abstract: We report experiments on ultrashort pulses that maintain their strong lateral and longitudinal localization in a bulk linear highly dispersive medium. The diameter of the central peak and the temporal width of the field autocorrelation function of the pulses were 20 µm and 210 fs, respectively, and the spatiotemporal structure was preserved in the course of 7-cm propagation in the sample. The pulses were obtained with a computer hologram designed for generating the Bessel beam and can be applied in femtosecond laser optics.
134 citations
TL;DR: These measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances and establish that mediation through electronically excited molecular states is a key mechanistic feature.
Abstract: Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor-acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined.
134 citations
TL;DR: In this paper, the temporal pro le of relativistic laser-plasma-accelerated electron bunches has been characterized using electro-optic sampling, which demonstrates both shot-to-shot stability of the laserplasma accelerator and femtosecond synchronization between bunch and probe beam.
Abstract: The temporal pro le of relativistic laser-plasma-acceleratedelectron bunches has been characterized. Coherent transition radiation atTHz frequencies, emitted at the plasma-vacuum boundary, is measuredthrough electro-optic sampling. The data indicates that THz radiation isemitted by a skewed bunch with a sub-50 fs rise time and a ~; 600 fs tail(half-width-at-half-maximum), consistent with ballistic debunching of 100percent-energy-spread beams. The measurement demonstrates bothshot-to-shot stability of the laser-plasma accelerator and femtosecondsynchronization between bunch and probe beam.
133 citations
AT&T1
TL;DR: In this paper, a new approach to far-infrared spectroscopy is described that uses extremely short farinfrared pulses to measure the dielectric properties of materials, which is equivalent to having a tunable laser in the spectral range from 0.1 to 2 THz.
Abstract: A new approach to far-infrared spectroscopy is described that uses extremely short far-infrared pulses to measure the dielectric properties of materials. Optical rectification of femtosecond optical pulses is used to produce a Cerenkov cone of pulsed far-infrared radiation of approximately one cycle in duration in the terahertz spectral range. The coherent detection of the electric field of these far-infrared pulses by electro-optic sampling provides a capability for measuring precise changes in the shape of the waveform following reflection or transmission from materials. This method, which is equivalent to having a tunable laser in the spectral range from 0.1 to 2 THz, is illustrated by the measurement of the dielectric response of a solid-state plasma in n-type germanium and a GaAs/GaAlAs multi-quantum-well superlattice.
133 citations