The Dynamics and Radiation of a Relativistic Electron in the Field of an Intense, Focused Laser Pulse

The effect of the field-induced broadening of harmonics radiated by an electron in the field of a high-intensity focused laser pulse was investigated. Broadening is caused by ponderomotive scattering, which continuously changes the average velocity of the electron and thus modulates the Doppler frequency shift of harmonics in the laboratory frame of reference. At relativistic intensities, broadened harmonics overlap, yielding a continuous radiation spectrum. This paper proposes a modification of the averaging procedure, which yields equations governing the averaged motion of an electron in the strong field of a focused pulse, with the dimensionless intensity parameter higher than, or of the order of, unity.