Absorption of the S-polarized short laser pulse in underdense plasma by considering the electrons ohmic heating and the laser pulse ponderomotive force effects

Abstract

With the advent of ultrashort high intensity laser pulses, laser absorption during laser-plasma interactions has received significant attention during the past two decades since it is related to a variety of applications of high intensity lasers, including the hot electron production for fast ignition of fusion targets, bright X-ray and gamma-ray sources, ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Although some absorption mechanisms appear for short laser pulses with nanosecond duration time, they usually appear for some nonlinear phenomena as electron ohmic heating and laser pulse ponderomotive force are not considered. In this paper, the absorption of the S-polarized laser pulse through an interaction with an underdense plasma in attendance of electron ohmic heating and ponderomotive nonlinearities is analyzed. It is shown that, due to the effect of the ponderomotive force in both isothermal and non-isothermal plasmas, the increasing laser radiation angle leads to the increasing electric field wavelength. Also, since the ponderomotive force modifies the electron density and temperature distribution, it is shown that the decreasing radiation angle leads to the steepening of the electron density profile and the narrowing of electron bunching. Furthermore, by increasing the radiation angle, the absorption coefficient is decreased strongly. It is found that due to the heat of the plasma at the expanse of the wave energy in the case of a non-thermal plasma, the absorption coefficient is increased intensively in comparison to a collisional plasma.

Influence of plasma inhomogeneity and ohmic heating on the nonlinear absorption of intense laser pulse in collisional magnetized plasma

“…Then, it can lead to an increase in the wavelength of the oscillations. This behavior is expected based on Equation (22). Figure 4d indicates the effects of the magnitude of the external magnetic field and initial laser electric field on the absorption coefficient.…”

“…The nonlinear interaction of intense laser pulse with plasma has attracted a lot of interest due to the number of important applications, such as the charged particles acceleration, [1][2][3][4][5][6][7][8] intense magnetic field generation, [9] shock generation, [10] X-ray lasers, [11,12] resonance absorption, [13] and optical harmonic generation. [14] In addition, some nonlinear effects appear such as Raman scattering, [15] ponderomotive and ohmic heating nonlinearities, [16][17][18] and inverse bremsstrahlung absorption (IBA) [19][20][21][22] during this interaction. A series of mechanisms such as collisional absorption or IBA, resonant absorption, and vacuum heating is proposed to explain the absorption observed under different laser pulse and plasma conditions.…”