Near-field imaging of dipole emission modulated by an optical grating

TL;DR

This paper demonstrates near-field imaging of dipole emission modulated by an optical grating, revealing detailed spectral phase information of attosecond pulses generated via multiphoton ionization.

Contribution

It introduces a method to visualize and analyze the spectral phase of attosecond pulses modulated by an optical grating using near-field imaging.

Findings

Spatially modulated attosecond pulses observed

Spectral phase information encoded in near-field images

Effective measurement of attosecond pulse duration

Abstract

Multiphoton-ionized electrons are born into a strong light field that will determine their short-term future. By controlling the infrared beam, we enable atoms or molecules to generate extreme ultraviolet (XUV) pulses and synthesize attosecond pulses - the shortest controlled events ever produced. Here we show that a weak obliquely incident beam imposes an optical grating on the fundamental beam, resulting in a spatially modulated attosecond pulse. We observe the modulation on a spectrally resolved near-field XUV image, encoding all information of the spectral phase of the recollision electron and, therefore, the attosecond pulse produced by structureless atoms. Near-field imaging is an efficient method for measuring the duration of attosecond pulses, especially important for soft X-ray pulses created in helium. For more complex systems, it includes auto ionization and giant plasmon resonances.