Spectral self-action of THz emission from ionizing two-color laser pulses in gases

Eduardo Cabrera-Granado,Luc Bergé,Ihar Babushkin,Yxing Chen,Stefan Skupin

doi:10.1088/1367-2630/17/2/023060

Abstract

The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields. We show that produced THz signals interact with free electron trajectories and thus significantly influence further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action contributes to the observed strong spectral broadening of the generated THz field. We show that diffraction of the generated THz radiation is the limiting factor for the co-propagating low frequency amplitudes and thus for the self-action mechanism in 2D and 3D geometries.

Highlights

18 February 2015The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields
Research on intense terahertz (THz) electromagnetic sources has received an increasing amount of attention owing to their numerous applications, for example, in time-domain spectroscopy, biomedical imaging or security screening [1]
It was shown later that the plasma builtup by tunneling photoionization is necessary to explain the high amplitudes of the THz field [4,5,6], and a quasidc plasma current generated by the temporally asymmetric two-color field is responsible for THz emission [7, 8]

Summary

18 February 2015

The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields. We show that produced THz signals interact with free electron trajectories and significantly influence further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action contributes to the observed strong spectral broadening of the generated THz field. We show that diffraction of the generated THz radiation is the limiting factor for the co-propagating low frequency amplitudes and for the self-action mechanism in 2D and 3D geometries

Introduction

THz spectral self-action

Simulations

Conclusions