Showing papers on "Femtosecond pulse shaping published in 2018"
SLAC National Accelerator Laboratory1, Max Planck Society2, Argonne National Laboratory3, Dublin City University4, Ohio State University5, Ludwig Maximilian University of Munich6, European XFEL7, Korea Research Institute of Standards and Science8, University of Hamburg9, National Science Foundation10
TL;DR: In this paper, a femtosecond-scale x-ray pulse pair is generated via electron bunch shaping and characterized using time-resolved photoelectron streaking spectroscopy.
Abstract: Arbitrary manipulation of the temporal and spectral properties of x-ray pulses at free-electron lasers would revolutionize many experimental applications. At the Linac Coherent Light Source at Stanford National Accelerator Laboratory, the momentum phase-space of the free-electron laser driving electron bunch can be tuned to emit a pair of x-ray pulses with independently variable photon energy and femtosecond delay. However, while accelerator parameters can easily be adjusted to tune the electron bunch phase-space, the final impact of these actuators on the x-ray pulse cannot be predicted with sufficient precision. Furthermore, shot-to-shot instabilities that distort the pulse shape unpredictably cannot be fully suppressed. Therefore, the ability to directly characterize the x-rays is essential to ensure precise and consistent control. In this work, we have generated x-ray pulse pairs via electron bunch shaping and characterized them on a single-shot basis with femtosecond resolution through time-resolved photoelectron streaking spectroscopy. This achievement completes an important step toward future x-ray pulse shaping techniques.
14 citations
TL;DR: In this paper, the authors used the temporal change of electron density induced by femtosecond laser pulse for generating high aspect ratio nanoholes, where secondary pulses are irradiated from 100 to 1000ps after the irradiation of first pulse.
14 citations
TL;DR: Three-dimensional microprocessing in glass is demonstrated with a nearly invariant spatial resolution for a large range of penetration depth between 250 μm and 9 mm without any aberration correction.
Abstract: We observe that focusing a femtosecond laser beam simultaneously chirped in time and space domains in glass can efficiently suppress the optical aberration caused by the refractive index mismatch at the interface of air and the glass sample. We then demonstrate three-dimensional microprocessing in glass with a nearly invariant spatial resolution for a large range of penetration depth between 250 μm and 9 mm without any aberration correction.
13 citations
TL;DR: In this article, the effects of the temporal intensity profile of the initial pulse on the nonlinear propagation spectral compression process arising from non-linear propagation in an optical fiber were theoretically studied.
Abstract: We theoretically study the effects of the temporal intensity profile of the initial pulse on the nonlinear propagation spectral compression process arising from nonlinear propagation in an optical fibre. Various linearly chirped input pulse profiles are considered, and their dynamics is explained with the aid of time-frequency representations. While initially parabolic-shaped pulses show enhanced spectral compression compared to Gaussian pulses, no significant spectral narrowing occurs when initially super-Gaussian pulses are used. Triangular pulses lead to a spectral interference phenomenon similar to the Fresnel bi-prism experiment.
11 citations
TL;DR: In this article, an ultra-thin reconfigurable localized surface plasmon (LSP) band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide was demonstrated.
Abstract: Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP) band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse's spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360 degrees. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.
10 citations
TL;DR: In this article, a femtosecond laser pulse shaping technique was proposed for improving the valence state conversion efficiency of rare-earth ions, and the authors demonstrated that the photoreduction efficiency from Sm3+ to Sm2+ using a π phase step modulation can be comparable to that using a transform-limited femtocond laser field, while the peak laser intensity is decreased by about 63%.
Abstract: The ability to manipulate the valence state conversion of rare-earth ions is crucial for their applications in color displays, optoelectronic devices, laser sources, and optical memory. The conventional femtosecond laser pulse has been shown to be a well-established tool for realizing the valence state conversion of rare-earth ions, although the valence state conversion efficiency is relatively low. Here, we first propose a femtosecond laser pulse shaping technique for improving the valence state conversion efficiency of rare-earth ions. Our experimental results demonstrate that the photoreduction efficiency from Sm3+ to Sm2+ in Sm3+-doped sodium aluminoborate glass using a π phase step modulation can be comparable to that using a transform-limited femtosecond laser field, while the peak laser intensity is decreased by about 63%, which is very beneficial for improving the valence state conversion efficiency under the laser-induced damage threshold of the glass sample. Furthermore, we also theoretically develop a (2+1) resonance-mediated three-photon absorption model to explain the modulation of the photoreduction efficiency from Sm3+ to Sm2+ under the π-shaped femtosecond laser field.
5 citations
TL;DR: Results show that the control effect on the population and vibrational coherence is highly dependent on the spectral detuning of the excitation spectrum, contrary to the popular belief in coherent control experiments.
Abstract: Mechanisms and optimal experimental conditions in coherent control still intensely stimulate debates. In this work, a phase-only control mechanism in an open quantum system is investigated experimentally and numerically. Several parameterizations for femtosecond pulse shaping (combination of chirp and multipulses) are exploited in transient absorption of a prototype organic molecule to control population and vibrational coherence in ground and excited states. Experimental results are further numerically simulated and corroborated with a four-level density-matrix model, which reveals a phase-only control mechanism based on the interaction between the tailored phase of the excitation pulse and the induced transient absorption. In spite of performing experiment and numerical simulations in the linear regime of excitation, the control effect amplitude depends non-linearly on the excitation energy and is explained as a pump-dump control mechanism. No evidence of single-photon control is observed with the model. Moreover, our results also show that the control effect on the population and vibrational coherence is highly dependent on the spectral detuning of the excitation spectrum. Contrary to the popular belief in coherent control experiments, spectrally resonant tailored excitation will lead to the control of the excited state only for very specific conditions.
4 citations
TL;DR: In this paper, a millijoule polarized fiber laser system was studied using polarization maintaining Ytterbium-fiber laser system as the seed, 10-μm core diameter Yb-doped fiber amplifier as the first-stage power amplifier, and 40-mm core diameter polarizing photonic crystal fiber (PCF) as the second-stage Power Amplifier.
3 citations
TL;DR: In this paper, the nonlinear process of pulse formation in mode-locked laser systems is analyzed, starting from a perturbation of a continuous wave, and it is shown that pulse growth is initially slow, dominated by a cascade of energy from low to high axial modes, followed by fast strongly nonlinear growth and finally relaxation to the stable pulse wave form.
Abstract: We analyze theoretically and numerically the nonlinear process of pulse formation in mode-locked lasers, starting from a perturbation of a continuous wave. Focusing on weak-to-moderate dispersion systems, we show that pulse growth is initially slow, dominated by a cascade of energy from low to high axial modes, followed by fast strongly nonlinear growth, and finally relaxation to the stable pulse wave form. The pulse grows initially by condensing a fixed amount of energy into a decreasing time interval, with peak power growing toward a finite-time singularity that is checked when the gain bandwidth is saturated by the pulse.
3 citations
Patent•
27 Jul 2018
TL;DR: In this paper, a super-resolution microimaging system and an imaging method based on femtosecond pulse shaping are presented. But the system and method overcome defects in methods in the prior art, has universality, is simple in optical path, allows wide-field observation, and is high in efficiency.
Abstract: The invention discloses a super-resolution microimaging system and an imaging method based on femtosecond pulse shaping. In the invention, a pulse shaping system is controlled by a computer control system so as to performing modulation in the aspects of phase position, intensity and polarization of light with different frequency components, so that femtosecond pulse laser becomes shaped pulse, ofwhich the intensity, polarization and frequency are related to time, as an exciting light; by using the exciting light for exciting a sample, particles, having different properties and types, in the sample have different response to the exciting light, so that responding intensity of a signal light relatively changes; when the pulse modulation changes, an signal light image is changed too; the computer control system, via a graphic processing algorithm, analyses and processes a plurality of the signal light images, thus acquiring a super-resolution image of the sample. The system and method overcome defects in methods in the prior art, has universality, is simple in optical path, allows wide-field observation, and is high in efficiency.
3 citations
TL;DR: In this paper, the spatial distribution in harmonic generation was investigated and a scheme to restrain the harmonic generation from the nucleus along the positive-x direction, and thus the interference is weaken in spatial.
TL;DR: In this article, the Auger effect in the presence of strong x-ray free-electron lasers (XFELs) propagating through resonant argon vapors by solving the Maxwell-Bloch equations numerically was studied.
Abstract: We study the Auger effect in the presence of strong x-ray free-electron lasers (XFELs) propagating through resonant argon vapors by solving the Maxwell-Bloch equations numerically. The simulations ...
13 May 2018
TL;DR: In this paper, a silicon-metasurface acting as both spectral amplitude and phase mask is used to shape <15 femtosecond ultrafast laser pulses using a silicon lattice.
Abstract: Metasurfaces provide extremely fine spatial control over the amplitude and phase of incident light. Here, we demonstrate shaping of <15 femtosecond ultrafast laser pulses using a silicon-metasurface acting as both spectral amplitude and phase mask.
TL;DR: In this article, a Taylor series system was used in conjunction with silicon metasurfaces for dynamic shaping of <15 femtosecond ultrafast laser pulses using a Taylor-series system.
Abstract: Metasurfaces offer the ability to shape optical pulses with unprecedented resolution. Here, we demonstrate dynamic shaping of <15 femtosecond ultrafast laser pulses using a Taylor series system in conjunction with silicon metasurfaces.
01 Jun 2018
TL;DR: In this paper, nonlinear spatiotemporal dynamics of femtosecond pulses in a hexagonal 7-core silica fiber pumped by a sub-uJ 370 fs Er:fiber CPA system was studied.
Abstract: Nonlinear spatiotemporal dynamics of femtosecond pulses in a hexagonal 7-core silica fiber pumped by a sub-uJ 370 fs Er:fiber CPA system was studied. Two orders of magnitude contrast enhancement of the pulses trapped in the central core of a multicore fiber was obtained. Further compression of pulses spectrally broadened in the multicore fiber down to 53 fs was demonstrated.