Field Emission Tip as a Nanometer Source of Free Electron Femtosecond Pulses

Hommelhoff, Peter; Sortais, Yvan R. P.; Aghajani-Talesh, Anoush; Kasevich, Mark A.

doi:10.1103/physrevlett.96.077401

Cited by 438 publications

(409 citation statements)

References 29 publications

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“…Whereas the spatial resolution of current techniques for time-resolved nanoscale imaging of electric fields relies on the nearfield enhancement at nanostructures 5,6 , the high sensitivity of lowenergy electrons to electric fields further permits the investigation of weak field distributions in the vicinity of nanoscale objects 7 . Although the generation of few-femtosecond electron pulses is readily achieved by photoemission [8][9][10][11] , the biggest challenge in using low-energy electrons as ultrafast probe is to maintain femtosecond duration of the electron pulses during delivery to the sample.…”

mentioning

confidence: 99%

“…We developed a compact hybrid approach for femtosecond lowenergy electron diffraction (fsLEED) and femtosecond point projection microscopy (fsPPM) with electron energies in the range 20-1,000 eV. A laser-triggered metal nanotip provides a compact point-like source of coherent femtosecond electron wave packets [8][9][10][11] , optionally collimated for diffraction or spatially diverging for microscopy 7,19,20 . Employing the microscopy mode of operation, we investigate ultrafast currents in axially doped InP nanowires (NWs) with femtosecond temporal and nanometre spatial resolution.…”

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confidence: 99%

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Femtosecond electrons probing currents and atomic structure in nanomaterials

Müller¹,

Paarmann²,

Ernstorfer³

2014

Nat Commun

120

159

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The investigation of ultrafast electronic and structural dynamics in low-dimensional systems such as nanowires and two-dimensional materials requires femtosecond probes providing high spatial resolution and strong interaction with small volume samples. Low-energy electrons exhibit large scattering cross-sections and high sensitivity to electric fields, but their pronounced dispersion during propagation in vacuum so far prevented their use as femtosecond probe pulses in time-resolved experiments. Here, employing a laser-triggered point-like source of either divergent or collimated electron wave packets, we developed a hybrid approach for femtosecond point projection microscopy and femtosecond low-energy electron diffraction. We investigate ultrafast electric currents in nanowires with sub-100 femtosecond temporal and few 10 nm spatial resolutions, and demonstrate the potential of our approach for studying structural dynamics in crystalline single-layer materials.

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mentioning

confidence: 99%

mentioning

confidence: 99%

Femtosecond electrons probing currents and atomic structure in nanomaterials

Müller¹,

Paarmann²,

Ernstorfer³

2014

Nat Commun

120

159

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“…Fortunately, alternative ways to amplify coherent light using plasmons were explored. To cite only a couple of prominent examples, the production of high energy photoelectrons using plasmonic near enhanced fields from dielectric nanoparticles [29], metal nanoparticles [30][31][32] and metal nanotips [33][34][35][36][37] appears to be perfectly plausible. Besides the question of damage threshold of such nanotargets has been highlighted and indicates that new routes using initially low intensity laser field need to be considered [38].…”

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confidence: 99%

High-order-harmonic generation by enhanced plasmonic near-fields in metal nanoparticles

et al. 2013

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We present theoretical investigations of high-order harmonic generation (HHG) resulting from the interaction of noble gases with localized surface plasmons. These plasmonic fields are produced when a metal nanoparticle is subject to a few-cycle laser pulse. The enhanced field, which largely depends on the geometrical shape of the metallic structure, has a strong spatial dependency. We demonstrate that the strong non-homogeneity of this laser field plays an important role in the HHG process and leads to a significant increase of the harmonic cut-off energy. In order to understand and characterize this new feature, we include the functional form of the laser electric field obtained from recent attosecond streaking experiments [F. Süßmann and M. F. Kling, Proc. of SPIE, Vol. 8096, 80961C (2011)] in the time dependent Schrödinger equation (TDSE). By performing classical simulations of the HHG process we show consistency between them and the quantum mechanical predictions. These allow us to understand the origin of the extended harmonic spectra as a selection of particular trajectory sets. The use of metal nanoparticles shall pave a completely new way of generating coherent XUV light with a laser field which characteristics can be synthesized locally. When matter, i.e. atoms or molecules, is exposed to short and intense laser radiation, non-linear phenomena are triggered as a consequence of this interaction. Amongst these phenomena, high-order harmonics generation (HHG) process [1, 2] has attracted considerable interests, since it is one of the most reliable pathways to generate coherent light from the ultraviolet (UV) to extreme ultraviolet (XUV) spectral range. As a result, HHG has proven to be a robust source for the generation of a PHz attosecond pulses train [3], that can be temporally confined to a single XUV attosecond pulse, now with kHz repetition rates [4]. Thanks to its remarkable properties, HHG can be used as well to extract temporal and spatial information with both attosecond and subAngström resolution on the generating system [5]. Hence, HHG represents a considerable tool to enable scrutinizing the atomic world with its natural temporal and spatial scales [6][7][8][9][10][11].The intuitive physical mechanism behind HHG, for a single atom or molecule (referred to as 'single emitter'), has been well established in the so-called three steps or simple man's model [12][13][14]: in the first step, an electronic wave packet is released the continuum by tunnel ionization through the potential barrier as a consequence of the non-perturbative interaction of the single emitter with the laser field. In the second step, the emitted electronic wave packet propagates away from its ionic core in the continuum to be finally driven back when the laser electric field changes its sign. In the final step, upon its return, the electronic wave packet may recombine with the core and the system relaxes the excess kinetic energy acquired by radiating a high-harmonic photon.In order to experimentally control the high harmonic ...

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“…In recent years the coherent control of free electrons is gaining again importance for fundamental research and in a technical point of view. This can be observed in decoherence studies of electrons near semiconducting surfaces [5] and developments such as a field emission source for free electron femtosecond pulses [6,7], surface-electrode chips [8] or a biprism electron interferometer with a single atom tip source [9]. New quantum devices with coherent electrons are currently implemented like a recently proposed noninvasive quantum electron microscope [10].…”

Section: Introductionmentioning

confidence: 99%

Electron matter wave interferences at high vacuum pressures

Schütz¹,

Rembold²,

Pooch³

et al. 2015

Measurement

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The ability to trap and guide coherent electrons is gaining importance in fundamental as well as in applied physics. In this regard novel quantum devices are currently developed that may operate under low vacuum conditions. Here we study the loss of electron coherence with increasing background gas pressure. Thereby, optionally helium, hydrogen or nitrogen is introduced in a biprism interferometer where the interference contrast is a measure for the coherence of the electrons. The results indicate a constant contrast that is not decreasing in the examined pressure range between 10 −9 mbar and 10 −4 mbar. Therefore, no decoherence was observed even under poor vacuum conditions. Due to scattering of the electron beam with background H2-molecules a signal loss of 94 % was determined. The results may lower the vacuum requirements for novel quantum devices with free coherent electrons.

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Field Emission Tip as a Nanometer Source of Free Electron Femtosecond Pulses

Cited by 438 publications

References 29 publications

Femtosecond electrons probing currents and atomic structure in nanomaterials

Femtosecond electrons probing currents and atomic structure in nanomaterials

High-order-harmonic generation by enhanced plasmonic near-fields in metal nanoparticles

Electron matter wave interferences at high vacuum pressures

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