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.
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TL;DR: In this paper, the role of the relative thickness of the interaction region as dictated by the acousto-optic Q parameter was analyzed and it was shown that varying Q allows flexibility in choosing between diffraction efficiency and pixels of resolution.
Abstract: We focus theoretically and experimentally on the fundamental limitations of spectral pulse shaping using an acousto-optic modulator. We analyze the role of the relative thickness of the interaction region as dictated by the acousto-optic Q parameter and show that varying Q allows flexibility in choosing between diffraction efficiency and pixels of resolution. We model and experimentally demonstrate the effects of potential nonidealities such as nonlinear acoustic attenuation. In addition, we derive a simple and intuitive expression to predict the magnitude of the distortions in the spatial profile generated by an acousto-optic-modulator spectral light modulator. Finally, we demonstrate amplification of acousto-optic-modulator-generated shaped pulses for the first time.
188 citations
TL;DR: In this paper, the authors presented the first complete spatiotemporal experimental reconstruction of the field E(t,r) for a 100-TW peak-power laser, and revealed the spatio-temporal distortions that can affect such beams.
Abstract: Femtosecond lasers can now deliver ultrahigh intensities at focus, making it possible to induce relativistic motion of charged particles with light and opening the way to new generations of compact particle accelerators and X-ray sources. With diameters of up to tens of centimetres, ultra-intense laser beams tend to suffer from spatiotemporal distortions, that is, a spatial dependence of their temporal properties that can dramatically reduce their peak intensities. At present, however, these intense electromagnetic fields are characterized and optimized in space and time separately. Here, we present the first complete spatiotemporal experimental reconstruction of the field E(t,r) for a 100 TW peak-power laser, and reveal the spatiotemporal distortions that can affect such beams. This new measurement capability opens the way to in-depth characterization and optimization of ultra-intense lasers and ultimately to the advanced control of relativistic motion of matter with femtosecond laser beams structured in space–time. The complete spatiotemporal characterization of a 100-TW laser beam highlights distortions that must be taken into account for present and future generations of ultra-intense lasers.
188 citations
TL;DR: In this article, numerical results on femtosecond pulses in air including multiphoton ionization, group-velocity dispersion, space-time focusing, self-steepening, Raman response, and higher-order χ (5) defocusing are presented.
188 citations
TL;DR: Femtosecond transient reflectivity and absorption are used to measure the carrier lifetimes in α-Fe2O3 thin films and single crystals in this paper, and the results from the thin films show that initially excited hot electrons relax to the band edge within 300fs and then recombine with holes or trap within 5ps.
Abstract: Femtosecond transient reflectivity and absorption are used to measure the carrier lifetimes in α‐Fe2O3 thin films and single crystals. The results from the thin films show that initially excited hot electrons relax to the band edge within 300fs and then recombine with holes or trap within 5ps. The trapped electrons have a lifetime of hundreds of picoseconds. Transient reflectivity measurements from hematite (α‐Fe2O3) single crystals show similar but slightly faster dynamics leading to the conclusion that the short carrier lifetimes in these materials are due primarily to trapping to Fe d‐d states in the band gap. In the hematite single crystal, the transient reflectivity displays oscillations due to the formation of longitudinal acoustic phonons generated following absorption of the ultrashort excitation pulse.
187 citations
TL;DR: In this article, the anisotropies in ultrashort pulse pump-probe experiments were calculated and the original results, well known from the theory of resonance Raman, were recovered for zero delay times.
187 citations