arXiv subjects

Zsuzsanna Pápa

Publications and source records attributed to Zsuzsanna Pápa.

3 recordsLinked to original sources

arXiv2026

Momentum microscopy of a holey nanostructure

Momentum microscopy records the three-dimensional momentum distribution of photoelectrons emitted from a solid sample and, by utilizing sufficiently high photon energies in the ultraviolet spectral range, offers direct access to the electronic band structure of a material. By employing a pump-probe scheme, this method provides a femtosecond view of light-matter interaction and the subsequent relaxation and transport dynamics in a broad range of material systems. However, momentum microscopy has so far been mostly limited to flat and spatially extended surfaces. Photoelectron emission from different three-dimensional facets, in combination with inhomogeneous electric fields around these structures, makes the analysis of the momentum distribution significantly more challenging. Here, we extend the state-of-the-art to a substantially more complex structure and show that a careful analysis of the electron distribution recorded with a momentum microscope provides rich information about both the spatial and momentum distributions on a few-nm and few-mÅ$^{-1}$ scale, respectively. Combined with prior knowledge of the three-dimensional structure, momentum-resolved photoelectrons can be assigned to nano-localized emission spots, permitting a new level of insight into spatio-temporal charge carrier dynamics.

physics.optics↗

arXiv2026

Momentum microscopy of ultrafast electron emission from a strongly driven optical nanoantenna

Metallic nanostructures in combination with femtosecond lasers are a well-suited platform for the control of photoelectrons by strong and nano-localized driving fields, with high relevance for ultrafast, coherent electron emitters and petahertz electronics. Photoelectron spectroscopy resolves such photoelectron dynamics, but lacks nanoscale spatial resolution, making it only suited for single emitters or homogeneous arrays. We report the first strong-field experiment combining both photoemission electron microscopy and momentum microscopy, two complementary techniques providing spatial and momentum resolution within the same instrument. We apply this new methodology to a double-hole nanoantenna with sub-10 nm apex radii, demonstrating the potential of this approach for the control of photoelectrons in heterogeneous nanostructured samples using few-cycle light fields. Our measurements reveal distinct signatures of two classes of electron trajectories in the near-field. Quiver trajectories result in directed, angularly more focused emission, whereas subcycle trajectories give rise to a broader transverse momentum distribution. Surprisingly, this observation disagrees with previously reported emission characteristics from nanotip emitters, which we classify as a special case of a broader class of curved emitter surfaces driven by ultrashort light fields. This demonstrates both the impact of sophisticated electron detection methods and the potential of strong-field control of electrons in nanoscale geometries.

physics.optics↗

arXiv2026

Transmissive extreme ultraviolet metagrating

Extreme ultraviolet (EUV) radiation is a key tool for attosecond physics and lithography. However, strong material absorption limits the availability of transmissive optical elements at these wavelengths. Metaoptics exploit geometry to control the wavefront of transmitted light on the nanoscale and, due to their minimal thickness, promise to fill this gap. Here, we demonstrate the first EUV metaoptics for broadband applications: we design, fabricate, and experimentally investigate a blazed transmissive EUV metagrating and compare it with a focused-ion-beam-milled sawtooth-blazed grating serving as an in-situ reference. The metagrating achieves an angular dispersion of 0.04°/nm with a directionality (the ratio of the +1st and -1st diffraction order efficiency) of up to 5.8. The device shows phase-based operation up to 50 eV photon energy (down to 25 nm vacuum wavelength) and an octave-spanning bandwidth of 25 eV, doubling the previous spectral window addressable by metasurfaces. Comparing both gratings' performance reveals that, when accounting for fabrication constraints, EUV metasurfaces are competitive with free-form optics while offering scalability to large apertures and arbitrary phase profiles. Broadband transmissive operation removes the need for grazing incidence optics, defeating a major source of aberrations, and allows polarization-insensitive spectral analysis, enabling energy-resolved ultrafast spectroscopy in compact experimental configurations.

physics.optics↗