Direct optical measurements of the evolving spatio-temporal charge density in ultrashort electron pulses

Morrison, Vance R.; Chatelain, Robert P.; Godbout, Chris; Siwick, Bradley J.

doi:10.1364/oe.21.000021

Cited by 17 publications

(11 citation statements)

References 22 publications

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“…A radio-frequency cavity is used to compress electron bunches to ≈ 150 fs at the sample, as measured by a home-built photoactivated streak camera 24 . More detailed descriptions of this instrument are given elsewhere [25][26][27] The interrogated film area covers 500 µm × 500 µm, with a pump spot of 1 mm × 1 mm full-width half-max (FWHM) ensuring nearly uniform illumination of the probed volume.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Time- and momentum-resolved phonon population dynamics with ultrafast electron diffuse scattering

et al. 2019

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Interactions between the lattice and charge carriers can drive the formation of phases and ordering phenomena that give rise to conventional superconductivity, insulator-to-metal transitions, and charge-density waves. These couplings also play a determining role in properties that include electric and thermal conductivity. Ultrafast electron diffuse scattering (UEDS) has recently become a viable laboratory-scale tool to track energy flow into and within the lattice system across the entire Brillouin zone, and to deconvolve interactions in the time domain. Here, we present a detailed quantitative framework for the interpretation of UEDS signals, ultimately extracting the phonon mode occupancies across the entire Brillouin zone. These transient populations are then used to extract momentum-and mode-dependent electron-phonon and phonon-phonon coupling constants. Results of this analysis are presented for graphite, which provides complete information on the phonon-branch occupations and a determination of the A 1 phonon mode-projected electronphonon coupling strength g 2 e,A 1 = 0.035 ± 0.001 eV 2 that is in agreement with other measurement techniques and simulations.

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Section: Experimental and Computational Methodsmentioning

confidence: 99%

Time- and momentum-resolved phonon population dynamics with ultrafast electron diffuse scattering

et al. 2019

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“…[29,48,77,78]. In our UED setup we have characterized electron pulse durations by grating enhanced ponderomotive scattering according to [30,31,48,79]. This cross-correlation method uses the ponderomotive interaction of the electron bunches with two counter-propagating laser pulses in a standingwave enhanced geometry (see figure 9(b)).…”

Section: Transverse Coherence Lengthmentioning

confidence: 99%

Spatio-temporal resolution studies on a highly compact ultrafast electron diffractometer

et al. 2015

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Keywords: ultrafast electron diffraction, electron pulse characterization, femtosecond electron pulses, spatial coherence, brightness, structural dynamics, multilayer graphene Abstract Time-resolved diffraction with femtosecond electron pulses has become a promising technique to directly provide insights into photo induced primary dynamics at the atomic level in molecules and solids. Ultrashort pulse duration as well as extensive spatial coherence are desired, however, space charge effects complicate the bunching of multiple electrons in a single pulse. We experimentally investigate the interplay between spatial and temporal aspects of resolution limits in ultrafast electron diffraction (UED) on our highly compact transmission electron diffractometer. To that end, the initial source size and charge density of electron bunches are systematically manipulated and the resulting bunch properties at the sample position are fully characterized in terms of lateral coherence, temporal width and diffracted intensity. We obtain a so far not reported measured overall temporal resolution of 130 fs (full width at half maximum) corresponding to 60 fs (root mean square) and transversal coherence lengths up to 20 nm. Instrumental impacts on the effective signal yield in diffraction and electron pulse brightness are discussed as well. The performance of our compact UED setup at selected electron pulse conditions is finally demonstrated in a time-resolved study of lattice heating in multilayer graphene after optical excitation.

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“…Dielectric particles are also subject to this phenomenon, and applications of electromagnetic ponderomotive forces have included atomic cooling, optical manipulation of living organisms, plasma confinement, and electron acceleration [26][27][28]. The optical ponderomotive force has also been used in the characterization of ultrashort electron pulses [29][30][31][32].…”

Section: Overviewmentioning

confidence: 99%

All-optical three-dimensional electron pulse compression

et al. 2015

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We propose an all-optical, three-dimensional electron pulse compression scheme in which Hermite-Gaussian optical modes are used to fashion a three-dimensional optical trap in the electron pulse's rest frame. We show that the correct choices of optical incidence angles are necessary for optimal compression. We obtain analytical expressions for the net impulse imparted by Hermite-Gaussian freespace modes of arbitrary order. Although we focus on electrons, our theory applies to any charged particle and any particle with non-zero polarizability in the Rayleigh regime. We verify our theory numerically using exact solutions to Maxwell's equations for first-order Hermite-Gaussian beams, demonstrating single-electron pulse compression factors of >10 2 in both longitudinal and transverse dimensions with experimentally realizable optical pulses. The proposed scheme is useful in ultrafast electron imaging for both single-and multi-electron pulse compression, and as a means of circumventing temporal distortions in magnetic lenses when focusing ultrashort electron pulses. Other applications include the creation of flat electron beams and ultrashort electron bunches for coherent terahertz emission.

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Direct optical measurements of the evolving spatio-temporal charge density in ultrashort electron pulses

Cited by 17 publications

References 22 publications

Time- and momentum-resolved phonon population dynamics with ultrafast electron diffuse scattering

Time- and momentum-resolved phonon population dynamics with ultrafast electron diffuse scattering

Spatio-temporal resolution studies on a highly compact ultrafast electron diffractometer

All-optical three-dimensional electron pulse compression

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