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Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres.

Süßmann F, Seiffert L, Zherebtsov S, Mondes V, Stierle J, Arbeiter M, Plenge J, Rupp P, Peltz C, Kessel A, Trushin SA, Ahn B, Kim D, Graf C, Rühl E, Kling MF, Fennel T - Nat Commun (2015)

Bottom Line: Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses.Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging.We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process.

View Article: PubMed Central - PubMed

Affiliation: 1] Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany [2] Physics Department, Ludwig-Maximilians-Universität München, D-85748 Garching, Germany.

ABSTRACT
Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.

No MeSH data available.


Related in: MedlinePlus

Size and intensity scaling of the electron yield.(a) Number of near-cutoff electrons emitted from a single nanosphere as function of laser intensity as predicted by M3C with (red curve) and without (black curve) Coulomb interaction and corresponding experimental results (circles) for I=3.0 × 1013 W cm−2. The inset compares the near-cutoff electron yield (solid curves) calculated with and without mean-field to the respective total yield (dashed curves)—note the logarithmic scale. Horizontal and vertical error bars indicate the standard deviation of the particle diameter, cf. Fig. 1, and the estimated detection efficiency (see text), respectively. (b) Same as (a) but as function of laser intensity for nanopsheres with d=400 nm. The experimental results were taken under comparable conditions. Note that only electrons with projected momenta above the threshold  where counted in the experiment. The horizontal error bar indicates the estimated ±15% uncertainty of the intensity; vertical error bars for the yield are defined as in (a). We checked via the M3C data that the differences between results using projected and full momenta are insignificant for this analysis.
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f6: Size and intensity scaling of the electron yield.(a) Number of near-cutoff electrons emitted from a single nanosphere as function of laser intensity as predicted by M3C with (red curve) and without (black curve) Coulomb interaction and corresponding experimental results (circles) for I=3.0 × 1013 W cm−2. The inset compares the near-cutoff electron yield (solid curves) calculated with and without mean-field to the respective total yield (dashed curves)—note the logarithmic scale. Horizontal and vertical error bars indicate the standard deviation of the particle diameter, cf. Fig. 1, and the estimated detection efficiency (see text), respectively. (b) Same as (a) but as function of laser intensity for nanopsheres with d=400 nm. The experimental results were taken under comparable conditions. Note that only electrons with projected momenta above the threshold where counted in the experiment. The horizontal error bar indicates the estimated ±15% uncertainty of the intensity; vertical error bars for the yield are defined as in (a). We checked via the M3C data that the differences between results using projected and full momenta are insignificant for this analysis.

Mentions: In the investigated range of laser intensities and particle sizes we find a strong impact of the Coulomb field on the electron emission. The yield predicted by simulations without the Coulomb interaction scales roughly exponentially with sphere diameter and laser intensity, reflecting the highly nonlinear tunnelling rate. Inclusion of Coulomb effects decreases the yield by up to two orders of magnitude (red versus black dashed curves in the insets of Fig. 6a,b). The reduction is a direct consequence of the trapping field, which quenches tunnel ionization at the surface and limits the number of electrons that can escape with a given initial kinetic energy. This pivotal influence of the Coulomb field on the actual ionization dynamics also explains why the M3C results are only weakly affected from changes of the (certainly approximate) tunnelling rate (for example, by slight variations of the effective ionization potential) as soon as a substantial trapping field develops. On the other hand, the reasonable description of the Coulomb effects in the model then requires quantitative agreement of experiment and theory. However, a quantitative comparison of the total yield is difficult because of the spurious signal contribution from residual gas in our experiment and the imprint of focal averaging. To define a photoemission yield specific to nanoparticles and free from background gas contributions, we counted only electrons with momenta beyond the threshold , which includes only signal well above the gas signal cutoff (see Fig. 1g). Further, focal averaging is circumvented by assigning most intense single-shot VMI images to the peak laser intensity. Because of the low particle density in the beam, such images reflect the emission from a single nanoparticle. Considering the estimated experimental electron detection efficiency of (30±20)%, the resulting measured near-cutoff electron yield as function of particle size and laser intensity is compatible with the corresponding M3C predictions with mean-field, see symbols and solid red lines in Fig. 6a,b. The remaining discrepancies for small particles and at low intensities are attributed to residual background signal. The agreement strongly supports the M3C prediction that the number of emitted electrons evolves nearly linearly with size and intensity in the presence of substantial Coulomb interaction.


Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres.

Süßmann F, Seiffert L, Zherebtsov S, Mondes V, Stierle J, Arbeiter M, Plenge J, Rupp P, Peltz C, Kessel A, Trushin SA, Ahn B, Kim D, Graf C, Rühl E, Kling MF, Fennel T - Nat Commun (2015)

Size and intensity scaling of the electron yield.(a) Number of near-cutoff electrons emitted from a single nanosphere as function of laser intensity as predicted by M3C with (red curve) and without (black curve) Coulomb interaction and corresponding experimental results (circles) for I=3.0 × 1013 W cm−2. The inset compares the near-cutoff electron yield (solid curves) calculated with and without mean-field to the respective total yield (dashed curves)—note the logarithmic scale. Horizontal and vertical error bars indicate the standard deviation of the particle diameter, cf. Fig. 1, and the estimated detection efficiency (see text), respectively. (b) Same as (a) but as function of laser intensity for nanopsheres with d=400 nm. The experimental results were taken under comparable conditions. Note that only electrons with projected momenta above the threshold  where counted in the experiment. The horizontal error bar indicates the estimated ±15% uncertainty of the intensity; vertical error bars for the yield are defined as in (a). We checked via the M3C data that the differences between results using projected and full momenta are insignificant for this analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557130&req=5

f6: Size and intensity scaling of the electron yield.(a) Number of near-cutoff electrons emitted from a single nanosphere as function of laser intensity as predicted by M3C with (red curve) and without (black curve) Coulomb interaction and corresponding experimental results (circles) for I=3.0 × 1013 W cm−2. The inset compares the near-cutoff electron yield (solid curves) calculated with and without mean-field to the respective total yield (dashed curves)—note the logarithmic scale. Horizontal and vertical error bars indicate the standard deviation of the particle diameter, cf. Fig. 1, and the estimated detection efficiency (see text), respectively. (b) Same as (a) but as function of laser intensity for nanopsheres with d=400 nm. The experimental results were taken under comparable conditions. Note that only electrons with projected momenta above the threshold where counted in the experiment. The horizontal error bar indicates the estimated ±15% uncertainty of the intensity; vertical error bars for the yield are defined as in (a). We checked via the M3C data that the differences between results using projected and full momenta are insignificant for this analysis.
Mentions: In the investigated range of laser intensities and particle sizes we find a strong impact of the Coulomb field on the electron emission. The yield predicted by simulations without the Coulomb interaction scales roughly exponentially with sphere diameter and laser intensity, reflecting the highly nonlinear tunnelling rate. Inclusion of Coulomb effects decreases the yield by up to two orders of magnitude (red versus black dashed curves in the insets of Fig. 6a,b). The reduction is a direct consequence of the trapping field, which quenches tunnel ionization at the surface and limits the number of electrons that can escape with a given initial kinetic energy. This pivotal influence of the Coulomb field on the actual ionization dynamics also explains why the M3C results are only weakly affected from changes of the (certainly approximate) tunnelling rate (for example, by slight variations of the effective ionization potential) as soon as a substantial trapping field develops. On the other hand, the reasonable description of the Coulomb effects in the model then requires quantitative agreement of experiment and theory. However, a quantitative comparison of the total yield is difficult because of the spurious signal contribution from residual gas in our experiment and the imprint of focal averaging. To define a photoemission yield specific to nanoparticles and free from background gas contributions, we counted only electrons with momenta beyond the threshold , which includes only signal well above the gas signal cutoff (see Fig. 1g). Further, focal averaging is circumvented by assigning most intense single-shot VMI images to the peak laser intensity. Because of the low particle density in the beam, such images reflect the emission from a single nanoparticle. Considering the estimated experimental electron detection efficiency of (30±20)%, the resulting measured near-cutoff electron yield as function of particle size and laser intensity is compatible with the corresponding M3C predictions with mean-field, see symbols and solid red lines in Fig. 6a,b. The remaining discrepancies for small particles and at low intensities are attributed to residual background signal. The agreement strongly supports the M3C prediction that the number of emitted electrons evolves nearly linearly with size and intensity in the presence of substantial Coulomb interaction.

Bottom Line: Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses.Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging.We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process.

View Article: PubMed Central - PubMed

Affiliation: 1] Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany [2] Physics Department, Ludwig-Maximilians-Universität München, D-85748 Garching, Germany.

ABSTRACT
Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.

No MeSH data available.


Related in: MedlinePlus