Investigation of power density absorption in rippled density plasma toward THz generation

Department of Physics, University of Isfahan - Isfahan, Iran

^(a) py.masoodsaeed@gmail.com
m.saeed@sci.ui.ac.ir

Received: 15 December 2018
Accepted: 14 February 2019

Abstract

In the present paper by applying a two-color linear polarized laser in rippled density plasma, the density of absorbed energy has been investigated using the two-dimensional particle-in-cell method and its role on THz generation in resonance and non-resonance schematic has been studied. Interplaying of time dependence of two lasers and plasma frequency on the one hand and, on the other hand, lasers wave number and rippled density wave number lead to significant absorbed energy comparing to the non-resonance schematic. Cross-focusing of two lasers among the plasma changes the absorption of energy distribution across the plasma and, as a consequence, of this redistribution, spatial emission pattern of THz changes based on this pattern. The present paper discussion is divided into two main parts, In the first part, the interaction under the Rayleigh length has been investigated. In this part, it has been shown that the density of absorbed energy and THz emission are in complete agreement and in the other part, it has been discussed that the interaction in the resonance regime over the Rayleigh length has no significant consistency with the emitted THz radiation. It was revealed that the emission pattern of the THz in resonance schematic is the function of the absorbed energy under the Rayleigh length and in the lengths over the Rayleigh limit mismatching of laser wave vector and rippled density wave number leads to semi-resonance emission. The position of semi-resonance emission is under the influence of three parameters: i) absorbed energy of plasma, ii) mismatching of laser wave vector and rippled density wave number and iii) phase mismatching of radiation across the plasma.