Terahertz radiation driven by two-color laser pulses at near-relativistic intensities: Competition between photoionization and wakefield effects.

ABSTRACT: We numerically investigate terahertz (THz) pulse generation by linearly-polarized, two-color femtosecond laser pulses in highly-ionized argon. Major processes consist of tunneling photoionization and ponderomotive forces associated with transverse and longitudinal field excitations. By means of two-dimensional particle-in-cell (PIC) simulations, we reveal the importance of photocurrent mechanisms besides transverse and longitudinal plasma waves for laser intensities >10(15) W/cm(2). We demonstrate the following. (i) With two-color pulses, photoionization prevails in the generation of GV/m THz fields up to 10(17) W/cm(2) laser intensities and suddenly loses efficiency near the relativistic threshold, as the outermost electron shell of ionized Ar atoms has been fully depleted. (ii) PIC resul

SUBMITTER: Gonzalez de Alaiza Martinez P 

PROVIDER: S-EPMC4891721 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature