Interference between Quantum Paths in Coherent Kapitza-Dirac Effect

TL;DR

This paper investigates how the inclination angle between two laser fields affects electron diffraction in the Kapitza-Dirac effect, revealing complex interference patterns and potential for ultrafast electron beam control.

Contribution

It provides a combined analytical and numerical analysis of the influence of laser field inclination on electron diffraction, highlighting new interference phenomena and control mechanisms.

Findings

Complex diffraction patterns depend on laser inclination and intensity.

Interferences involve both scattering and light absorption/emission processes.

Potential applications in ultrafast electron beam manipulation.

Abstract

In the Kapitza-Dirac effect, atoms, molecules, or swift electrons are diffracted off a standing wave grating of the light intensity created by two counter-propagating laser fields. In ultrafast electron optics, such a coherent beam splitter offers interesting perspectives for ultrafast beam shaping. Here, we study, both analytically and numerically, the effect of the inclination angle between two laser fields on the diffraction of pulsed, low-energy electron beams. For sufficiently high light intensities, we observe a rich variety of complex diffraction patterns. These do not only reflect interferences between electrons scattered off intensity gratings that are formed by different vector components of the laser field. They may also result, for certain light intensities and electron velocities, from interferences between these ponderomotive scattering and direct light absorption and stimulated emission processes, usually forbidden for far-field light. Our findings may open up perspectives for the coherent manipulation and control of ultrafast electron beams by free-space light.