Laser-solid interaction:

The invention of ultra-short pulsed lasers has paved the way towards creating stellar conditions on the tabletop. Otherwise called laboratory astrophysics, this emerging area of science deals with behavior of matter in extreme conditions. Huge intensities (~ 10¹⁶ W/cm²) are created by tightly focussing short pulsed laser light on solid targets placed in vacuum chambers. Ionization of the target atoms occurs as the binding Coulomb force is overcome by the external field. Thus, matter exists in the form of plasma in the focal volume.

The laser-produced plasmas are known to be bright sources of radiation, which ranges almost from one end to the other of the electromagnetic spectrum. Particularly, these plasmas are good emitters of x-rays with their energy varying from few eVs to few MeVs. The growing interest in these x-ray radiations is because of their pulsed nature that could be of immense use in lithography and biological studies.

The study is of laser-produced plasmas are important in basic physics point of view and in an angle of applications as well. Though the interest emerged with an eye on inertial confinement fusion, several other interesting pathways came up as and when the field matured. We are mainly concentrated on studying different absorption mechanisms of the laser light inside the plasma and their dependence on the Polarization State of the incident light field. One major tool to study the absorption is the analysis of the x-ray spectrum. Further, the bremsstrahlung curve gives the information about the temperatures of the electrons, which emit the radiation. Many valuable ideas about the Plasma State can be obtained by monitoring the reflected light from the plasma.

It is known that roughness of the order of few nanometers increases the x-ray yields by orders of magnitude. The most recent works include engineering the targets so as to enhance the laser absorption. Time resolved studies are also being done to estimate density scale length, expansion velocity, magnetic field generation etc. which would enable one to couple the light in a better way to the plasma.

Molecular Dynamics in intense laser field

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Last modified: July 29, 2004