Method of Laser-radiation Guiding in Plasma

PACS number(s): 52.40.Mj, 52.40.Nk The progress in the technology of high-intensity lasers opens new opportunities for use of lasers in many branches of science and industry. Last years the chirped-pulse amplification technique [1] permitted the production of subpicosecond laser pulses of multiterrawatt power with peak intensity up to 10W/cm [2]. With intensities as such we practically have to do with a new interaction range of laser radiation with matter, where the role played by the nonlinear effects is often essential. At present the interactions of high-power laser radiation with plasma are actively investigated in connection with different applications: the excitation of strong plasma wake waves for acceleration of charged particles with acceleration rates to tens of GeV/m [3]; generation, due to nonlinear interaction with plasma, of radiation at harmonics of carrier laser frequency [4]; the “photon acceleration” [5]; X-ray sources [6] etc. Note also such application ranges of laser radiation as the Compton scattering, laser cooling of charged particle beams, the inertial fusion. The diffraction broadening of laser radiation is one of the principal phenomena (and frequently the primary phenomenon) inhibiting the effective use of the energy of laser in many applications. In vacuum, the laser spot size rs grows with the longitudinal coordinate according to the formula rs = r0(1 + z /Z R) 1/2 , where ZR = πr 2 0 /λ is the Rayleigh length, r0 is the minimum spot size at the focal point and λ is the laser wavelength. Owing to that, the intensity of radiation quickly decreases as the laser beam propagates. For high-intensity laser pulses the value of ZR is usually of the order of several millimeters. For instance, in the Laser Wakefield Accelerator (LWFA) scheme the increment in the energy of electrons accelerated by the