Attosecond electron emission probes of ultrafast nano-localized fields

"We will discuss theoretical and ongoing experimental work on the characterization of nanolocalized plasmonic fields utilizing time-of-flight photoelectron emission microscopy (TOF-PEEM). Because of their broad spectral bandwidth, surface plasmons undergo ultrafast dynamics with timescales as short as a few hundred attoseconds. So far, the spatiotemporal dynamics of optical fields localized on the nanoscale has been hidden from direct access in the real space and time domain. Our ultimate goal is to characterize the nanoplasmonic fields not only on a nanometer spatial scale but also on ~100 attosecond temporal scale. In collaboration with colleagues from MPQ, LMU and GSU Atlanta we have proposed and developed an attosecond nanoplasmonic-field microscope [1,2]. The principle of this microscope is based on the photoemission of electrons by an XUV attosecond pulse that is synchronized with a waveform-stabilized driving optical field. Information about the nanoplasmonic fields is imprinted in the energy of the XUV-emitted electrons, which are recorded with high spatial resolution. In addition to our efforts into this direction, we will present recent results on the acceleration of electrons in nanolocalized fields near dielectric nanoparticles. A fivefold increase in the cut-off energy of the electron spectra as compared to rare gases and directional control of the emission by the waveform of the laser field are observed [3]. The observed near-field enhancement offers promising new routes for pushing the limits of strong-field phenomena relying on electron rescattering, such as high-harmonic generation or molecular imaging.
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[1] J. Lin et al., Time of flight-photoemission electron microscope for ultrahigh spatiotemporal probing of nanoplasmonic optical fields, J. Phys. Cond. Mat. 21, 314005 (2009).
[2] M. I. Stockman et al., Attosecond nanoplasmonic-field microscope, Nature Photonics 1, 539 (2007).
[3] S. Zherebtsov et al., in preparation (2010)."