Chirped imaging pulses in four-dimensional electron microscopy: femtosecond pulsed hole burning

Park, Sang Tae; Kwon, Oh‐Hoon; Zewail, Ahmed H.

doi:10.1088/1367-2630/14/5/053046

Cited by 32 publications

(32 citation statements)

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“…2 and 3 have temporal, spatial, and polarization dependencies that are in qualitative agreement with those reported in our previous experimental and theoretical studies of PINEM (1)(2)(3)(4)(5)(6)(7)(8). However, the geometry of the structure studied here with its unique graphene thickness regime has not been examined in any of our previous work.…”

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confidence: 88%

“…The experimental technique has been applied to a wide range of objects with differing material properties and different geometries, such as spheres, cylinders, triangular blocks, nanoparticles with irregular shapes, and for dimers of nanoparticles. The applications range from the visualization of the distribution of induced electric fields at the microscopic level to the enhancement of image contrast for biological structures (1)(2)(3)(4)(5)(6)(7)(8).Despite this progress, we did not expect to find that PINEM can be observed in a strip of carbon-based structures of only several atomic layers in thickness, a common materials structure studied by different variants of electron microscopy (9). Here, we report experimental and theoretical studies of graphene layered-step structures formed by the edges of strips of graphene multilayers lying on a continuous substrate of the same material, which give rise to an observed, strong PINEM intensity that is very strong when compared either with bright-field images in terms of relative contrast or with the PINEM intensity that could be obtained for a spherical or cylindrical geometry of the same thickness.…”

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Graphene-layered steps and their fields visualized by 4D electron microscopy

Park

Yurtsever

Baskin

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Enhanced image contrast has been seen at graphene-layered steps a few nanometers in height by means of photon-induced near-field electron microscopy (PINEM) using synchronous femtosecond pulses of light and electrons. The observed steps are formed by the edges of graphene strips lying on the surface of a graphene substrate, where the strips are hundreds of nanometers in width and many micrometers in length. PINEM measurements reflect the interaction of imaging electrons and induced (near) electric fields at the steps, and this leads to a much higher contrast than that achieved in bright-field transmission electron microscopy imaging of the same strips. Theory and numerical simulations support the experimental PINEM findings and elucidate the nature of the electric field at the steps formed by the graphene layers. These results extend the range of applications of the experimental PINEM methodology, which has previously been demonstrated for spherical, cylindrical, and triangular nanostructures, to shapes of high aspect ratio (rectangular strips), as well as into the regime of atomic layer thicknesses.atomic-scale steps | dark field imaging | photon-electron interaction | light scattering | discrete dipole approximation T he emerging field of photon-induced near-field electron microscopy (PINEM) relies on the interaction between the imaging electrons of an ultrafast electron microscope and the near-field components of scattered light pulses to reveal properties of nanoobjects and the induced optical fields surrounding them (1, 2). The experimental technique has been applied to a wide range of objects with differing material properties and different geometries, such as spheres, cylinders, triangular blocks, nanoparticles with irregular shapes, and for dimers of nanoparticles. The applications range from the visualization of the distribution of induced electric fields at the microscopic level to the enhancement of image contrast for biological structures (1)(2)(3)(4)(5)(6)(7)(8).Despite this progress, we did not expect to find that PINEM can be observed in a strip of carbon-based structures of only several atomic layers in thickness, a common materials structure studied by different variants of electron microscopy (9). Here, we report experimental and theoretical studies of graphene layered-step structures formed by the edges of strips of graphene multilayers lying on a continuous substrate of the same material, which give rise to an observed, strong PINEM intensity that is very strong when compared either with bright-field images in terms of relative contrast or with the PINEM intensity that could be obtained for a spherical or cylindrical geometry of the same thickness. This signal strength opens the door to the imaging of low-atomicnumber, nanoscale materials using the enhanced contrast of PINEM. These low-atomic-number materials, such as carbonbased strips or cells, are weak elastic scatterers, making it a real challenge to obtain high contrast in, e.g., bright-field transmission electron microcopy (TEM). Dark-f...

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confidence: 99%

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Graphene-layered steps and their fields visualized by 4D electron microscopy

Park

Yurtsever

Baskin

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…The interferometer is stabilized by a feedback loop (PID control). Electron pulse chirp is not included in the calculation, so that the experimentally observed tilt of the photon sidebands 55 is not reproduced.…”

Section: Application Of Rabbittmentioning

confidence: 99%

Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

et al. 2017

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We introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond pulse trains for electron microscopy. Specifically, we employ phaselocked single-color and two-color optical fields to coherently control the electron wave function along the beam direction. We establish a new variant of quantum state tomography -"SQUIRRELS" -to reconstruct the density matrices of freeelectron ensembles and their attosecond temporal structure. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and the development of new forms of ultrafast electron microscopy and spectroscopy down to the attosecond regime.Optical, electron and x-ray microscopy and spectroscopy reveal specimen properties via spatial and spectral signatures imprinted onto a beam of radiation or electrons. Leaving behind the traditional paradigm of idealized, simple probe beams, advanced optical techniques increasingly harness tailored probes, or even their quantum properties and probe-sample entanglement. The rise of structured illumination microscopy 1 , pulse shaping 2 , and multidimensional 3 and quantum-optical spectroscopy 4 exemplify this development. Similarly, electron microscopy explores the use of shaped electron beams exhibiting particular spatial symmetries 5 or angular momentum 6,7 , and novel measurement schemes involving quantum aspects of electron probes have been proposed 8,9 . Ultrafast imaging and spectroscopy with electrons and x-rays are the basis for an ongoing revolution in the understanding of dynamical processes in matter on atomic scales [10][11][12][13] . The underlying technology heavily rests on laser science for the 2 generation and characterization of ever-shorter femtosecond electron 10,14 and xray [15][16][17] probe pulses, with examples in optical pulse compression 18 and streaking spectroscopy [19][20][21] . The temporal structuring of electron probe beams is facilitated by time-dependent fields in the radio-frequency [22][23][24] , terahertz 18,25 or optical domains. Promising a further leap in temporal resolution, recent findings suggest that ultrafast electron diffraction and microscopy with optically phasecontrolled and sub-cycle, attosecond-structured wave functions may be feasible 8,[26][27][28][29][30] . Specifically, light-field control may translate the temporal resolution of ultrafast transmission electron microscopy (UTEM) 31,32 and electron diffraction (UED) 10,33 , currently at about 200 fs 34 and 20 fs 14,23 , respectively, to the range of attoseconds 26,27,35 . However, such future technologies call for means to both prepare and fully analyze the corresponding quantum states of free electrons.Here, we demonstrate the coherent control and attosecond density modulation of free-electron quantum states using multiple phase-locked optical interactions. Moreover, we introduce quantum state tomography for free electrons, providing crucial e...

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“…33 and utilized to characterize the temporal spread and the energy-time correlation of an electron pulse in Ref. 34.…”

Section: Photon-electron Couplingmentioning

confidence: 99%

Photon-induced near field electron microscopy

Park

Zewail

2013

SPIE Proceedings

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Ultrafast electron microscopy in the space and time domains utilizes a pulsed electron probe to directly map structural dynamics of nanomaterials initiated by an optical pump pulse, in imaging, diffraction, spectroscopy, and their combinations. It has demonstrated its capability in the studies of phase transitions, mechanical vibrations, and chemical reactions. Moreover, electrons can directly interact with photons via the near field component of light scattering by nanostructures, and either gain or lose light quanta discretely in energy. By energetically selecting those electrons that exchanged photon energies, we can map this photon-electron interaction, and the technique is termed photon-induced near field electron microscopy (PINEM). Here, we give an account of the theoretical understanding of PINEM. Experimentally, nanostructures such as a sphere, cylinder, strip, and triangle have been investigated. Theoretically, time-dependent Schrödinger and Dirac equations for an electron under light are directly solved to obtain analytical solutions. The interaction probability is expressed by the mechanical work done by an optical wave on a traveling electron, which can be evaluated analytically by the near field components of the Rayleigh scattering for small spheres and thin cylinders, and numerically by the discrete dipole approximation for other geometries. Application in visualization of plasmon fields is discussed.

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Chirped imaging pulses in four-dimensional electron microscopy: femtosecond pulsed hole burning

Cited by 32 publications

References 38 publications

Graphene-layered steps and their fields visualized by 4D electron microscopy

Graphene-layered steps and their fields visualized by 4D electron microscopy

Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

Photon-induced near field electron microscopy

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