Abstract
The characterization of the temporal profile of plasmonic fields is important both from the fundamental point of view and for potential applications in ultrafast nanoplasmonics. It has been proposed by Stockman et al (2007 Nat. Photonics 1 539) that the plasmonic electric field can be directly measured by the attosecond streaking technique; however, streaking from nanoplasmonic fields differs from streaking in the gas phase because of the field localization on the nanoscale. To understand streaking in this new regime, we have performed numerical simulations of attosecond streaking from fields localized in nanoantennas. In this paper, we present simulated streaked spectra for realistic experimental conditions and discuss the plasmonic field reconstruction from these spectra. We show that under certain circumstances when spatial averaging is included, a robust electric field reconstruction is possible.
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GENERAL SCIENTIFIC SUMMARY Introduction and background. Surface plasmons are collective electron oscillations within metal nanostructures that can be excited by a laser pulse. The plasmonic field is enhanced with respect to the incident field and has a longer temporal duration. Characterizing the temporal profile of the plasmonic field is important to understand ultrafast nanoplasmonic phenomena. The oscillating laser electric field can be measured directly by the attosecond streaking technique, which has so far been demonstrated mostly in gas phase targets. It is proposed that by performing attosecond streaking experiments on nanoplasmonic structures, one can directly characterize the temporal profile of the nanoplasmonic field. We theoretically investigate attosecond streaking from nanoplasmonic fields for a realistic arrangement of gold nanoantennas on a sapphire substrate.
Main results. We first calculated the nanoplasmonic field excited by a laser pulse and then numerically simulated streaking in this field. By analysis of the simulated streaked spectra, we reconstructed the plasmonic field, which was then compared with the plasmonic field that had entered the streaking calculation. Our simulations showed that the plasmonic field can be reconstructed with high accuracy for realistic experimental conditions where spatial averaging is included.
Wider implications. Characterizing the temporal profile of the plasmonic field is important to understand ultrafast nanoplasmonic phenomena. Nanoplasmonic field enhancement can be employed for high harmonic generation using a focused low-power laser. This may enable development of laptop-size high repetition rate (1 MHz) sources of coherent vacuum ultraviolet radiation that can be used for high-resolution imaging and to probe ultrafast processes in matter.
Figure. (a) Simulated streaked spectra from gold nanoantennas. (b) Comparison of the reconstructed electric field (red) and the original field (black) that entered the streaking simulation. The plasmonic field can be reconstructed with high accuracy.