Self-focusing Of Intense Laser Pulse Research Articles

Effect of obliquely external magnetic field on the intense laser pulse propagating in plasma medium

In this paper, self-focusing of intense laser pulse propagating along the obliquely external magnetic field on the collisional magnetoactive plasma by using the perturbation theory have been studied. The wave equation describing the interaction of intense laser pulse with collisional magnetoactive plasma is derived. In addition, employing source-dependent expansion (SDE) method, the analysis of the laser spot-size is discussed. It is shown that with increasing of the angle in obliquely external magnetic field, the spot-size of laser pulse decreases and as a result laser pulse becomes more focused. Furthermore, it is concluded that the self-focusing quality of the laser pulse has been enhanced due to the presence of obliquely external magnetic field in the collisional magnetoactive plasma. Besides, it is seen that with increasing of [Formula: see text], the laser spot-size reduces and subsequently the self-focusing of the laser pulse in plasma enhances. Moreover, it is found that changing the collision effect in the magnetoactive plasma leads to increases of self-focusing properties.

Investigation of non-stationary self-focusing of intense laser pulse in cold quantum plasma using ramp density profile

The authors have investigated the non-stationary self-focusing of Gaussian laser pulse in cold quantum plasma. In case of high dense plasma, the nonlinearity in the dielectric constant is mainly due to relativistic high intense interactions and quantum effects. In this paper, we have introduced a ramp density profile for plasma and presented graphically the behavior of spot size oscillations of pulse at rear and front portions of the pulse. It is observed that the ramp density profile and quantum effects play a vital role in stronger and better focusing at the rear of the pulse than at the front in cold quantum plasmas.

Blast-wave diagnosis of self-focusing of an intense laser pulse in a cluster medium

Self-focusing of intense laser pulses in a gas of atomic clusters is diagnosed in both long (>700fs) and short (<100fs) pulse regimes. This investigation uses blast-wave analysis techniques, which are sensitive to deposited energy, as a tool to identify locations of self-focusing. The detection of highly energetic x rays from the interaction of the short pulse with the clusters suggests the activation of electron acceleration in the self-focused high-intensity channels produced. The self-focusing is attributed to the optical properties of the clusters since it occurs at moderate laser powers and the cluster parameters are critical to the extent of the channel that forms.

Self-focusing of ultra-intense short laser pulses in plasmas with various density distributions

Effects of plasma density distributions on self-focusing of intense laser pulses propagating in an underdense cold plasma are investigated, where the laser intensity has a Gaussian distribution and the initial plasma density is cylindrical-symmetrically distributed. An evaluation function is derived to judge which type of plasma density distribution is more beneficial for the occurrence of self-focusing. Through analyzing and calculating the evaluation function, it is found that for a given laser field and with fixed initial plasma density along the central axis, which coincides with the axis of the laser beam, increasing plasma density with the distance from the axis favors self-focusing. Furthermore, the greater the density gradient, the more favorable. It is also found that the combined action of both relativistic and ponderomotive effects is of more advantage to self-focusing than that of relativistic effect alone. Numerical simulation confirms that the evaluation function is capable of accurately predicting the favorable role of plasma density distribution in producing laser self-focusing.

Control of filamentation induced by femtosecond laser pulses propagating in air

Filamentation formed by self-focusing of intense laser pulses propagating in air is investigated. It is found that the position of filamentation can be controlled continuously by changing the laser power and divergence angle of the laser beam. An analytical model for the process is given.

Self-focusing of intense laser pulses in a clustered gas.

We report the self-focusing of intense laser pulses in gases composed of atomic clusters. This is in strong contrast to beam spreading owing to ionization-induced refraction commonly observed in nonclustered gases. The effect is explained in terms of the ensemble average transient polarizability of the heated clusters as they explode in response to the intense pulse.

Nonlinear Propagation of Intense Short Pulses Through Underdense Plasmas

Currently there is much interest in the interaction of high-intensity ultra-short laser pulses with plasmas. Applications include the recently proposed Fast Ignitor Concept for Inertial Confinement Fusion. In the present work we make an analytical investigation of nonlinear propagation of intense short pulses through underdense plasmas. When a laser beam is focused into a plasma, self-focusing and self-channeling can occur as a result of relativistic modification of electron mass in the laser field and the reduction of electron density on the focal region due to the expulsion of electrons by laser ponderomotive force. The paper presents a paraxial theory of self-focusing of intense laser pulses due to expulsion of plasma electrons produced by the extreme ponderomotive force of a focused laser pulse. The nonlinear dielectric constant, self-focusing equation relating the variation of beamwidth parameter with distance of propagation, self-trapping condition and critical power are evaluated. The results suggest a self-focusing of the laser pulse in the plasma.