Strong quantum interferences in frequency up-conversion towards short vacuum-ultraviolet radiation pulses

Ackermann, Patric; Scharf, A.; Halfmann, Thomas

doi:10.1103/physreva.89.063804

Cited by 6 publications

(3 citation statements)

References 11 publications

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“…Of importance appear the pronounced peaks in the vicinity of E F + 2 ω and in particular In summary, we have demonstrated quantum-pathway interference in multiphoton and above-threshold photoemission at a tungsten tip on femtosecond time scales with two-color femtosecond driving fields. Despite the solid-state nature of the emitter, the maximum mod- ulation depth of 94% is, to the best of our knowledge, the highest reported value for two-color photoemission experiments, including those for isolated atoms in the gas phase [42]. This high visibility is closely related to the nanometer-sized interaction volume, preventing the influence of focal averaging effects and inhomogeneous broadening.…”

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confidence: 77%

Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip

et al. 2016

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We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission.

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confidence: 77%

Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip

et al. 2016

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“…Despite the solidstate nature of the emitter, the maximum modulation depth of 94% is, to the best of our knowledge, the highest reported value for two-color photoemission experiments, including those for isolated atoms in the gas phase [42]. This high visibility is closely related to the nanometer-sized interaction volume, preventing the influence of focal averaging effects and inhomogeneous broadening.…”

Section: Prl 117 217601 (2016) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 73%

An Ultrafast Switch for Electron Emission

Kealhofer

2016

Physics

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We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solidstate nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission. DOI: 10.1103/PhysRevLett.117.217601 Ionization by two-color laser fields with well-defined relative phase allows one to tune and control electronic dynamics on the (sub)femtosecond time scale. By virtue of the synthesized laser field, the energy and angular distributions of emitted electrons can be manipulated. Two-color pulses have been used in investigations of above-threshold ionization of atoms [1][2][3], controlled dissociative ionization [4][5][6], dichroism in ionization [7,8], and orientation of molecules [9]. Recently, they have also been applied to control interference fringes in the momentum distribution of electron emission [10][11][12]. In this Letter we demonstrate exquisite coherent emission control by simultaneous interaction of fundamental (ω) and second harmonic (2ω) femtosecond laser pulses with condensed matter. Specifically, we control photoemission from an individual nanotip.While nanotips are nowadays routinely used as electron sources in high-resolution electron microscopes [13], their superb transverse coherence known from dc field emission has only recently been observed in photoemission [14]. Field enhancement at the apex of nanotips [15] confines and enhances electron emission, thus enabling the study of strong-field physics with moderate laser intensities well below the damage threshold [16][17][18][19][20][21]. Laser-induced photoemission from tips (for extensive reviews, see Ref.[22]) has already been employed in pulsed electron guns for electron diffraction experiments [23,24], while arrays of nanotips have been fabricated and explored as electron sources for compact coherent x-ray production [25][26][27]. Recently, a ω − 2ω experiment was performed on a silicon tip array, but no phase-resolved signal indicative of coherent control was reported [27].In our experiment, atomic-scale in situ control over the sample surface results in a well-defined nanoemitter that surpasses the limitations of focal averaging and inhomogeneous broadening. We show that electron emission induced by a strong fundamental pulse can be enhanced or suppressed with a contrast of up to 94% when superimposing a weak second harmonic pulse. This scheme thereby allows efficient coherent control of the nanotip photocurrent utilizing the metal-vacuum interface to suppress emission in one direction. Accompanying simulations suggest that the strong modulation can be explained in te...

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“…In this article we demonstrated coherently controlled two-color above-threshold photoemission from a metal nanotip. Optimizing fundamental and second harmonic intensities, as well as the static field at the tip, an optimized visibility of 97.5% was obtained, which is amongst the highest values for two-color experiments [ 22 ]. Given the solid-state nature of the nanotip the degree of control of the total electron emission is surprisingly high.…”

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confidence: 99%

High visibility in two-color above-threshold photoemission from tungsten nanotips in a coherent control scheme

Paschen

Förster

Krüger

et al. 2017

Journal of Modern Optics

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In this article, we present coherent control of above-threshold photoemission from a tungsten nanotip achieving nearly perfect modulation. Depending on the pulse delay between fundamental () and second harmonic () pulses of a femtosecond fiber laser at the nanotip, electron emission is significantly enhanced or depressed during temporal overlap. Electron emission is studied as a function of pulse delay, optical near-field intensities, DC bias field and final photoelectron energy. Under optimized conditions modulation amplitudes of the electron emission of 97.5% are achieved. Experimental observations are discussed in the framework of quantum-pathway interference supported by local density of states simulations.

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Strong quantum interferences in frequency up-conversion towards short vacuum-ultraviolet radiation pulses

Cited by 6 publications

References 11 publications

Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip

Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip

An Ultrafast Switch for Electron Emission

High visibility in two-color above-threshold photoemission from tungsten nanotips in a coherent control scheme

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