Determining Carrier-Envelope Phase of Relativistic Laser Pulses via Electron Momentum Distribution

TL;DR

This paper proposes a method to determine the carrier-envelope phase of relativistic laser pulses by analyzing the asymmetric electron momentum distribution resulting from electron reflection in a focused laser beam, applicable at high intensities.

Contribution

The study introduces a novel technique to measure CEP using electron angular distributions in relativistic laser-electron interactions, effective at ultraintense laser facilities.

Findings

CEP signatures are observable at intensities ≥ 10^{19} W/cm^2.

Detection resolution can reach approximately 0.1° with high electron density.

Method is compatible with current ultraintense laser systems.

Abstract

The impacts of the carrier-envelope phase (CEP) of a long relativistic tightly-focused laser pulse on the dynamics of a counter-propagating electron beam have been investigated in the, so-called, electron reflection regime, requiring the Lorentz factor of the electron $\gamma$ to be approximately two orders of magnitudes lower than the dimensionless laser field parameter $\xi$. The electrons are reflected at the rising edge of the laser pulse due to the ponderomotive force of the focused laser beam, and an asymmetric electron angular distribution emerges along the laser polarization direction, which sensitively depends on the CEP of the driving laser pulse for weak radiative stochastic effects. The CEP siganatures are observable at laser intensities of the order or larger than $10^{19}$ W/cm$^2$ and the pulse duration up to 10 cycles. The CEP detection resolution is proportional to the electron beam density and can achieve approximately $0.1^{\circ}$ at an electron density of about $10^{15}$ cm$^{-3}$. The method is applicable for currently available ultraintense laser facilities with the laser peak power from tens of terawatt to multi-petawatt region.