Laser-plasma interactions have many theoretical and technological applications. One is the use of coherently accelerated electrons to provide novel sources of THz radiation. Our research focuses on simulating the cross/self-interactions between two high intensity, ultra-short, counter propagating and detuned laser pulses and an initial neutral target for controlled ionization. Unlike our previous studies of laser-matter interaction over preformed plasma, we explore the injection and collision of laser pulses to induce background plasma driven by the self-guided laser wakefield mechanism, which is then used to perturb the plasma resulting in induced dipole oscillations leading to transverse radiation. Inducing a cylindrical spatial plasma column within the laser beam radius regime provides a stable, spatially localized plasma channel. The emitted radiation from the plasma dipole oscillation (PDO) will not be affected by surrounding plasma absorption, resulting in effective radiation distribution. Results include 3D EM-PIC simulations and a comparison of the self- ionizing plasma against the preformed plasma to assess the efficiency of the mechanisms.
It is well known that an infinite homogeneous Langmuir wave, formed by accelerating charged particles, it does not emit electromagnetic radiation because of its electrostatic nature, which is represented by the zero curl of the electric field. To realise emission, the plasma density must be tailored such that the Langmuir wave takes on a non-zero component of the curl of the electric field. The mechanisms of inverse mode conversion or travelling wave antennae leads to emission of radiation. In these mechanisms, the emphasis is on energy conversion of the Langmuir ‘wave’ to an electromagnetic wave. However, an interesting way to cause the plasma wave to emit radiation is to isolate a single ‘oscillator’ composed of a localized plasma block, i.e., a plasma dipole. An outstanding question in the realization of this idea is how to isolate the plasma oscillation from the Langmuir wave. To answer this question, we propose a novel idea of colliding detuned counter-propagating laser pulses in plasma. Simulation results show that radiation is emitted from the isolated plasma dipole.