Nanofocused Plasmon-Driven Sub-10 fs Electron Point Source

Abstract

Progress in ultrafast electron microscopy relies on the development of efficient laser-driven electron sources delivering femtosecond electron pulses to the sample. In particular, recent advances employ photoemission from metal nanotips as coherent point-like femtosecond low-energy electron sources. We report the nonlinear emission of ultrashort electron wave packets from a gold nanotip generated by nonlocal excitation and nanofocusing of surface plasmon polaritons. We verify the nanoscale localization of plasmon-induced electron emission by its electrostatic collimation characteristics. With a plasmon polariton pulse duration below 8 fs at the apex, we identify multiphoton photoemission as the underlying emission process. The quantum efficiency of the plasmon-induced emission exceeds that of photoemission from direct apex illumination. We demonstrate the application for plasmon-triggered point-projection imaging of an individual semiconductor nanowire at 3 µm tip-sample distance. Based on numerical simulations we estimate an electron pulse duration at the sample below 10 fs for tip-sample distances up to few micrometers. Plasmon-driven nanolocalized electron emission thus enables femtosecond point-projection microscopy with unprecedented temporal and spatial resolution, femtosecond low-energy electron in-line holography, and opens a new route towards femtosecond scanning tunneling microscopy and spectroscopy.

Plasmonic nanofocusing – grey holes for light

“…Since our first implementation of such a plasmon nanofocusing electron source [87], related work has also been reported in Refs. [88,90].…”

“…When coupling ultrafast laser pulses to propagating SPPs at the shaft of those tapers, nanometre-localized light spots with pulse durations as short as 10 fs are created at the taper apex with high efficiency [42,76]. Consequently, the optical properties of such antennas have been studied in considerable detail, both experimentally and theoretically, during the past several years [42,63,64,70,[75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91].…”

Attosecond-controlled photoemission from metal nanowire tips in the few-electron regime

“…The progress in the field of nanophotonics has been fueled by advances in fabrication techniques such as lithography 1,2 and chemical synthesis, 3 where optical properties of nanomaterials are used to achieve functionality. 4,5 Collective electron motion as a result of the interaction of ultrashort light pulses with nanomaterials typically unfolds on attosecond to femtosecond time scales, where its properties depend on the waveform of the laser field, 6 and the material, composition, 7 shape, 8 and configuration 2 of nanomaterials, and their local environment.…”

“…16 The photoemission from metal nanotips is of particular interest offering the possibility to produce ultrashort electron pulses. These in turn can be used to seed electron accelerators, 17,18 and as an electron source for transmission 19 and diffraction imaging studies, 1 offering Angstrom spatial and down to attosecond temporal resolutions. It was recently found that the electron emission from metallic nanotips can be controlled with the carrier-envelope phase (CEP) of few-cycle laser pulses in the single-electron emission regime.…”

Nanoplasmonics Fundamentals and Surface-Enhanced Raman Scattering as a Physical Phenomenon

“…The ultrafast nature of the adiabatic concentration has been used to achieve simultaneously nanoscopic spatial resolution and femtosecond temporal resolution [19][20][21][82][83][84][85][86][87][88][89]. A unique application of the adiabatic nanofocusing is a new type of nanoscopy with chemical vision based on a highly efficient (with a quantum yield of 10%) hot electron generation [90].…”