Spatiotemporal steering of photoelectron emission in multiphoton above-threshold ionization

TL;DR

This paper demonstrates how the emission direction and energy of photoelectrons in multiphoton above-threshold ionization can be controlled in space and time using phase-controlled orthogonally polarized two-color laser pulses, revealing detailed electron dynamics.

Contribution

It introduces experimental and simulation methods to steer and analyze photoelectron emission in multiphoton ionization with phase-controlled laser fields, showing detailed spatiotemporal control.

Findings

Distinct spatiotemporal behaviors of slow and fast electrons identified.

Phase-of-phase oscillations observed for slow electrons depending on energy and direction.

Fast electrons exhibit a flat phase structure mainly influenced by emission direction.

Abstract

We experimentally demonstrate spatiotemporal steering of photoelectron emission in multiphoton above-threshold single ionization of atoms exposed to a phase-controlled orthogonally polarized two-color (OTC) laser pulse. Spatial and energy resolved photoelectron angular distributions are measured as a function of the laser phase, allowing us to look into the fine structures and emission dynamics. The slow and fast photoelectrons, distinguished by the energy larger or smaller than 2Up with Up being the ponderomotive energy of a free electron in the laser field, have distinct spatiotemporal dependences of the laser waveform. The phase-of-phase of the slow electron oscillates as functions of both the energy and emission direction, however, the fast electron present rather flat phase structure which merely depends on its emission direction. Three-dimensional generalized quantum trajectory Monte Carlo simulations are performed to explore the sub-cycle dynamics of the electron emission in the phase-controlled OTC pulse.