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

Abstract

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.

Two-color multiphoton emission for comprehensive reveal of ultrafast plasmonic field distribution

“…Moreover, the optimized ratio between the photoemission electron yields induced by one-color 400 and 800 nm laser pulse excitation for the effective opening of multicolor quantum channel in the case of our experiment is also discussed. Additionally, we have found there exist a large difference in the nonlinear order of the two-color photoemission under the plasmonic excitation within a nanostructure, which has not been reported in the previous investigations on the two-color photoemission electron generation [46,47].…”

All-optical spatio-temporal control of electron emission from SiO2 nanospheres with femtosecond two-color laser fields

“…These results demonstrate the feasibility of using two-color laser fields for the control of the emission direction of the most energetic electrons from nanoparticles. This observation goes beyond the recently shown two-color control of the cutoff in the electron emission from metallic nanotips [3,4,39].…”

“…Intense laser pulses with tailored waveforms have proven to be a powerful tool for the control of electron dynamics in atomic, molecular, and solid targets [1][2][3][4][5][6][7][8][9][10][11][12]. The laser electric field of such pulses exerts a force that varies on the attosecond time scale for visible light and enables the steering of electron motion on sub-cycle time scales and on nanometer spatial dimensions or even below [13][14][15][16][17].…”

Two-color multiphoton emission from nanotips

“…As polycrystalline tungsten nanotips were used in our experiment, it is likely that there was no such intermediate state, thus no interference was possible. Nevertheless, it is noteworthy that the model developed through our experiment is able to predict the shape of the observed fringe pattern and the periodicity in Hommelhoff's experiment, for which they stated '... fail to describe the sinusoidal shape observed in the experiment' [24].…”

“…During the review process of this paper, a similar work from Hommelhoff's group was published, where they observed interference fringes in the electron correlation spectrum [24]. In their experiment, a single crystalline W(310) nanotip with an effective work function 3.6 eV was irradiated with 1560 and 780 nm femtosecond pulses.…”