Polarization-sensitive reconstruction of transient local THz fields at dielectric interfaces

Kay Waltar,Luca Castiglioni,Michael Weinl,Jeroen A Van Bokhoven,Nikola Stojanovic,Pavel Kliuiev,Torsten Golz,Matthias Hengsberger,Saša Bajt,Johannes Haase,Rui Pan,Jürg Osterwalder,Matthias Schreck

doi:10.1364/optica.6.001431

Abstract

Intense THz fields can be used to excite specific low-frequency modes in condensed matter or drive confined currents in nano-structured arrays, paving the way for a new class of optoelectronic devices. The long wavelength enables spatially confined field enhancement due to interaction with metallic structures and interference effects at dielectric interfaces. We use THz photoelectron streaking for the polarization-sensitive reconstruction of all electric field components at dielectric and metallic interfaces. This is realized in a THz/x-ray pump–probe experiment where x-ray emitted photoelectrons probe the effective THz field in close surface proximity. We observe distinct differences in the THz response of a nano-structured Pt thin film and a Pt(111) bulk crystal, in particular for the parallel field component. Simulations of the nanoscale spatial field modulation at metallic islands on the thin film provide design parameters for different sensitivity regimes with respect to local fields.

Highlights

The increasing availability of sources of strong ultrashort THz pulses in recent years has enabled new types of experiments where the electric field is used to drive and control dynamic processes [1,2]
Large field amplitudes and/or narrow-bandwidth radiation are required which can, for instance, be generated in free-electron-laser (FEL) undulators [6]. Another approach to locally increase the field amplitude is through the application of metamaterial array structures in which localized charge carriers can resonate with the incoming radiation and increase the electric field in surface plasmon polaritons [7,8,9]
We address the question of how photoelectron streaking [17,18,19,20] can be used for spatiotemporal characterization of effective THz fields near solid–vacuum interfaces at different length scales

Summary

Introduction

The increasing availability of sources of strong ultrashort THz pulses in recent years has enabled new types of experiments where the electric field is used to drive and control dynamic processes [1,2]. THz fields can be used to induce lightwave-driven currents in a topological surface band [3]; to stimulate atomic motion in adsorbed molecules, thereby controlling their reactivity [4]; or to electrically write antiferromagnetic memory devices [5]. Large field amplitudes and/or narrow-bandwidth radiation are required which can, for instance, be generated in free-electron-laser (FEL) undulators [6]. Another approach to locally increase the field amplitude is through the application of metamaterial array structures in which localized charge carriers can resonate with the incoming radiation and increase the electric field in surface plasmon polaritons [7,8,9]. Atoms and molecules placed in close vicinity to these nanostructures can be studied under the influence of the enhanced fields, given a suitable probing technique

Methods

Results

Conclusion