Imaging Localized Surface Plasmons by Femtosecond to Attosecond Time‐Resolved Photoelectron Emission Microscopy – “ATTO‐PEEM”

Abstract

The direct detection of the spatiotemporal dynamics of nanolocalized optical near-fields on nanostructured metal surfaces, for example, imaging of localized surface plasmons (cf. Chapter 1) on rough or nanostructured metal films or the imaging of propagating surface plasmon polaritons at a vacuum-metal or metal-dielectric interface is a prerequisite to further control and optimize surface-plasmon based ultrafast nanooptics for future device development and applications [1][2][3][4].While free electrons in metals collectively respond to excitation from a light pulse, which is resonant to the surface plasmon frequency of the system, and squeeze and amplify the field intensity of the incoming plane light field into a subwavelength spatial volume, the typically broad frequency bandwidth of surface plasmon resonances supports an ultrafast response of these fields with rapid field changes on sub-femtosecond time scales [5].The sub-wavelength nanoscaled localization of optical fields in the vicinity of metal nanostructures and the ultrafast temporal evolution of such fields on a 0.1-100 fs time scale require the invention and development of new experimental methodologies, which combine nanometer (sub-optical) spatial resolution, sub-femtosecond temporal resolution, and optionally further nanospectroscopic information.Resolving the spatial distribution of such fields requires a microscopic technique with sub-optical spatial resolution, for example, in the 10-100 nm range. Scanning near-field optical microscopy (SNOM) techniques have been successfully applied with spatial resolutions of about ∼100 nm; however, the combination with ultrashort light pulses is still very difficult. Photoemission electron microscopy (PEEM) is a technique capable of resolving the spatial emission distribution of photoelectrons with an ultimate resolution of ∼10 nm.

Spatio-spectral structures in high harmonic generation driven by tightly focused high repetition rate lasers

“…This opens the route to the investigation of, e.g., time delays in molecular photoionization [35]. The same applies to solid-state applications, such as, for instance, the attosecond PhotoElectron Emission microscope, which promises the dynamical imaging of localized nanoscale structures, e.g., surface plasmons [36,37]. Also, femtosecond Angularly Resolved PhotoEmission Spectroscopy (FemtoArpes) [38][39][40][41] will benefit from these emerging sources with high photon fluxes but low photon number per pulse.…”

A high-repetition rate attosecond light source for time-resolved coincidence spectroscopy

“…Our setup includes the possibility to add a second end station in order to perform time-resolved surface science experiments (Figure 1). As in coincidence spectroscopy, these experiments strongly benefit from high-repetition rate in order to avoid space charge-related blurring effects in spectroscopy and imaging applications [21]. As the setup is designed for the two end stations to be used simultaneously, the gas phase experiments can serve as a benchmark for simultaneous time-resolved studies on nanostructured surfaces.…”

“…The XUV pump and IR probe are then focused by a toroidal mirror (B), yellow, into the sensitive region of the 3D momentum spectrometer (C), red. A refocusing chamber (D), purple, contains a second toroidal mirror for reimaging to the second interaction region, (E), where different end stations for surface science, usually a photoemission electron microscope, can be installed [20][21][22]. The beamline is designed for simultaneous operation of both end stations.…”

The 2021 ultrafast spectroscopic probes of condensed matter roadmap

“…In recent years, the concept of so-called atto-PEEM that probes the ultrafast near-field oscillations on their native attosecond time scale has gained great interest [156] as it promises new insights into the physics of plasmonic eigenmodes. The proposal is based on attosecond streaking spectroscopy, where a few-cycle near-infrared femtosecond pump pulse excites LSPs and the temporal evolution of the plasmonic field is subsequently probed by a single XUV attosecond pulse that is created via HHG (see section 7 by M Murnane et al).…”