Nanofocused Plasmon-Driven Sub-10 fs Electron Point Source

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• 作者：Melanie Müller ; Vasily Kravtsov ; Alexander Paarmann ; Markus B. Raschke ; Ralph Ernstorfer
• 刊名：ACS Photonics
• 出版年：2016
• 出版时间：April 20, 2016
• 年：2016
• 卷：3
• 期：4
• 页码：611-619
• 全文大小：642K
• 年卷期：0
• ISSN：2330-4022

文摘

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 less than 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. On the basis of numerical simulations we estimate an electron pulse duration at the sample less than 10 fs for tip–sample distances up to a 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 a new route toward femtosecond scanning tunneling microscopy and spectroscopy.