Ponderomotive generation and detection of attosecond free-electron pulse trains

TL;DR

This paper presents a novel all-optical method to generate and detect trains of attosecond free-electron pulses, enabling ultrafast electron imaging with sub-femtosecond resolution.

Contribution

The authors demonstrate the creation of attosecond electron pulse trains through ponderomotive modulation and dispersive compression, a significant advancement in ultrafast electron pulse generation.

Findings

Attosecond electron pulses with durations less than 300 as were achieved.

The technique allows for initial characterization of sub-optical cycle free-electron pulses.

The method enables high-repetition-rate, sub-femtosecond time-resolved experiments.

Abstract

Atomic motion dynamics during structural changes or chemical reactions have been visualized by picosecond and femtosecond pulsed electron beams via ultrafast electron diffraction and microscopy. Imaging the even faster dynamics of electrons in atoms, molecules and solids requires electron pulses with sub-femtosecond durations. We demonstrate here the all-optical generation of trains of attosecond free-electron pulses. The concept is based on the periodic energy modulation of a pulsed electron beam via an inelastic interaction with the ponderomotive potential of an optical travelling wave generated by two femtosecond laser pulses at different frequencies in vacuum. The subsequent dispersive propagation leads to a compression of the electrons and the formation of ultrashort pulses. The longitudinal phase space evolution of the electrons after compression is mapped by a second phase-locked interaction. The comparison of measured and calculated spectrograms reveals the attosecond temporal structure of the compressed electron pulse trains with individual pulse durations of less than 300 as. This technique can be utilized for tailoring and initial characterization of sub-optical cycle free-electron pulses at high repetition rates for stroboscopic time-resolved experiments with sub-femtosecond time resolution.