HARMONIC-GENERATION BY SUPERINTENSE LIGHT-SCATTERING FROM RELATIVISTIC ELECTRONS

Relativistic harmonic generation by the scattering of very-high-intens ity laser light from fast free electrons is investigated theoretically . A general solution for the trajectory of an electron, moving initial ly with an arbitrary velocity in a light pulse of arbitrary intensity and polarization, is presented. This solution generalizes the classica l analysis of Eberly [Progress in Optics, edited by E. Wolf (North-Hol land, Armsterdam, 1969), Vol. 7] and that of Sarachik and Schappert [P hys. Rev. D 1, 2738 (1970)] for the trajectory of an electron initiall y at rest. The result is then applied to the case of effective harmoni c generation in a monochromatic, circularly polarized field under thre e different initial conditions for the electron, namely, (a) electron initially at rest, (b) electron initially moving in the direction of l ight propagation (and opposite to it), and (c) electron initially cros sing the radiation beam at right angles. Angular distributions of the harmonics generated by the scattering process are presented in terms o f the power scattering cross section in each case. Effects of increasi ng the light intensity and/or the initial electron speed and/or direct ion on the angular distributions are discussed. It is found, among oth er results, that at laser intensities higher than, say 10(18) W/cm(2), the low-order harmonics are suppressed while the higher-order harmoni cs are enhanced.