Coulomb potential determining terahertz polarization in two-color laser field

TL;DR

This paper introduces a Coulomb-corrected classical trajectory Monte Carlo method to explain how Coulomb potential influences terahertz polarization in two-color laser fields, revealing mechanisms for polarization control and generation.

Contribution

The paper develops a new CTMC method that accurately reproduces experimental THz polarization behaviors and uncovers Coulomb potential effects on electron trajectories in two-color fields.

Findings

Coulomb potential twists THz polarization by deflecting electron momentum

THz polarization in certain fields is independent of phase delay

Mid-infrared fields can generate circularly-polarized THz radiation

Abstract

The orientation and ellipticity of terahertz (THz) polarization generated by two-color strong field not only cast light on underlying mechanisms of laser-matter interaction, but also play an important role for various applications. We develop the Coulomb-corrected classical trajectory Monte Carlo (CTMC) method to well reproduce the joint measurements, that the THz polarization generated by the linearly-polarized 800 nm and circularly-polarized 400 nm fields is independent on two-color phase delay. The trajectory analysis shows that the Coulomb potential twists the THz polarization by deflecting the orientation of asymptotic momentum of electron trajectories. Further, the CTMC calculations predict that, the two-color mid-infrared field can effectively accelerate the electron rapidly away from the parent core to relieve the disturbance of Coulomb potential, and simultaneously create large transverse acceleration of trajectories, leading to the circularly-polarized THz radiation.