Photoemission Electron Microscopy for Ultrafast Nano-Optics: Femtoseconds to Attoseconds

Condensed Matter Seminars

Speaker: Erik Marsell, Lund University
Date & Time: February 26, 2016 2:00 - 3:00
Location: AMPEL 311
Local Contact: George Sawatzky
Intended Audience: Graduate

Nano-optics, the use of nanostructured surfaces for the concentration, manipulation, and application of light on a sub-wavelength scale, is a maturing technology capable of connecting the worlds of photonics and electronics. This opens up possibilities for devices combining the small size currently only found in electronics with the high operating speed offered by photonics. However, the simultaneous small and fast nature of the nano-optical excitations calls for characterization methods with extreme spatiotemporal resolution. Photoemission electron microscopy (PEEM) combines light excitation with electron detection, and can therefore work with a temporal resolution defined by light, while its spatial resolution is limited by electron optics. The combination of PEEM with femtosecond laser sources has during the past 15 years proven to be very powerful for the spatiotemporal imaging of nano-optical fields. In Lund, we have specialized in exploring the use of various state-of-the-art ultrafast light sources together with PEEM. Using multiphoton photoemission induced by few-cycle laser pulses from an ultra-broadband Ti:Sapphire oscillator, we studied differences in the local field dynamics at different positions within a single metallic nanostructure during the few cycles of maximum field amplitude [1]. Furthermore, PEEM in combination with high-order harmonic generation is currently being investigated by multiple research groups due to its possibility of direct imaging of the near-field with ~10 nm, ~100 attosecond resolution [2]. To approach this ultimate goal, we explored the use of extreme ultraviolet attosecond pulse trains from two different high-order harmonic setups together with PEEM, and found a large improvement in image quality when increasing the repetition rate of the light source [3].
E. Mårsell et al., Nano Lett. 15, 6601 (2015).
M. I. Stockman et al., Nat. Photon. 1, 539 (2007).
S. H. Chew et al., in “Attosecond Nanophysics: From Basic Science to Applications”, edited by Peter Hommelhoff and Mattias Kling, Wiley VCH, pp. 325–364 (2015).