Novel approach to the laser driver based on generation and amplification of radiation with controllable coherence was realized under construction of the laser facility module “KANAL-2”.
The performed studies have demonstrated that the laser based on such a principle has a number of advantages as compared to the conventional laser schemes:
- the decrease of coherence degree leads to the increase of the small-scaled self-focusing threshold and, due to this, to its suppression without the use of spatial filtration;
- the coherence control gives a possibility to smooth a speckle structure of the target field and to achieve very high level of irradiation homogeneity on a target without using traditional correcting systems (phase plates, adaptive optics and etc.);
- the absence of spatial filters between successive amplification cascades, the feasibility to use the elongated active elements with high gain, the absence of complex optical devices for a laser beam wavefront corrections allows a laser scheme to be significantly simplified as well as the total number of optical elements to be decreased.
Recent experimental results obtained at the KANAL-2 facility (Nd-laser, the pulse energy of up to 300 J, the output aperture of 60 mm, the pulse duration of 2.5 ns, the average laser intensity on target of up to 5x1014 W/cm2) are presented and discussed; the main attention is paid to the following important laser-target interaction phenomena:
- absorption and scattering of laser radiation;
- laser radiation harmonics generation;
- X-ray generation;
- crater formation and plasma expansion under laser pulse;
- conversion of laser radiation by means nonlinear crystals;
- influence of coherence degree on the processes mentioned above.
Metal foils and volume-structured materials were used as targets. The present work has been partially supported by the Program of the Physical Sciences Division of the Russian Academy of Sciences “Nonlinear optics of the unique laser systems” and by the Russian Foundation of Basic Researches (Grant No. 07-02-01407).