Electron energy analysis by phase-space shaping with THz field cycles

• Published in: Structural dynamics (Melville, N.Y.) Vol. 5; no. 4; p. 044303
• Main Authors: Ehberger, Dominik, Kealhofer, Catherine, Baum, Peter
• Format: Journal Article
• Language: English
• Published: United States American Institute of Physics, Inc 01.07.2018; American Crystallographic Association; AIP Publishing LLC and ACA
• Subjects: Aluminum; Electron energy; Electron pulses; Energy; Energy measurement; Energy resolution; Energy spectra; Experiments; Femtosecond pulses; Field strength; Lasers; Material properties; Microscopy; Optical properties; Signal strength; Spectrum analysis; Time measurement; Germany
• ISSN: 2329-7778; 2329-7778
• DOI: 10.1063/1.5045167

Time-resolved electron energy analysis and loss spectroscopy can reveal a wealth of information about material properties and dynamical light-matter interactions. Here, we report an all-optical concept for measuring energy spectra of femtosecond electron pulses with sub-eV resolution. Laser-generated terahertz radiation is used to measure arrival time differences within electron pulses with few-femtosecond precision. Controlled dispersion and subsequent compression of the electron pulses provide almost any desired compromise of energy resolution, signal strength, and time resolution. A proof-of-concept experiment on aluminum reveals an energy resolution of <3.5 eV (rms) at 70-keV after a drift distance of only 0.5 m. Simulations of a two-stage scheme reveal that pre-stretched pulses can be used to achieve <10 meV resolution, independent of the source's initial energy spread and limited only by the achievable THz field strength and measuring time.