High-order phase-dependent asymmetry in the above-threshold ionization plateau

TL;DR

This paper investigates the complex phase-dependent asymmetry in above-threshold ionization spectra of cesium, revealing a high-order oscillation pattern linked to quantum orbit interference and time-domain holography.

Contribution

It demonstrates the high-order CEP dependence in ionization spectra and explains it through interference of quantum orbits using an improved strong-field approximation.

Findings

Asymmetry oscillates three times with CEP variation

Interference of quantum orbits causes high-order CEP dependence

Analogy with time-domain holography established

Abstract

Above-threshold ionization spectra from cesium are measured as a function of the carrier-envelope phase (CEP) using laser pulses centered at 3.1 $\mu$m wavelength. The directional asymmetry in the energy spectra of backscattered electrons oscillates three times, rather than once, as the CEP is changed from $0$ to $2\pi$. Using the improved strong-field approximation, we show that the unusual behavior arises from the interference of few quantum orbits. We discuss the conditions for observing the high-order CEP dependence, and draw an analogy with time-domain holography with electron wave packets.