International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In this work we study numerically, by means of Particle-in-Cell simulations, the formation of non-radiating configurations in a plasma, arising from the ionization of atomic gases by intense laser pulse Our simulation show that, after the release of a short terahertz pulse, a nearly non-radiating field and current configuration is formed, even though the charge and current distributions of plasma remain essentially time-dependent. In a plasma target emitting terahertz waves, such a non-radiating state is formed under the action of radiation. Our calculations suggest that formation of a non-radiating configuration occurs in a self-consistent way and can therefore affect the duration of the emitted terahertz pulse.

In this work we study numerically the generation of intense terahertz radiation in the interaction of two-color circularly polarized laser pulses of optical or infrared wavelength range with argon. The terahertz pulses obtained in such a scheme can be used to generate strong slowly changing electric and magnetic fields of a given configuration. To investigate the terahertz emission by a plasma source arising from the ionization of a gas medium by femtosecond laser field with a peak intensity of 10¹⁴-10¹⁵ W/cm² a fully kinetic plasma model consisting of the Vlasov equations for the plasma distribution function and the Maxwell equations for the self-consistent electromagnetic field has been used. Our numerical code is based on the particle-in-cell method and employs state-of-the-art widely used algorithms, such as finite difference time domain method for modeling the electromagnetic fields, Boris pusher to update the particle positions and velocities, and the charge conservation scheme to satisfy the continuity equation. The field ionization is implemented using the tunneling ionization rate formula. Our simulations have shown that at a sufficiently small interaction volume the plasma oscillations excited by asymmetric ionization are almost homogeneous in space and lead to an efficient conversion of electron energy into the energy of emitted terahertz radiation.