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Abstract

The theoretical framework for describing the emission by free charged particles, scattered from highly intense laser fields, is extended to arbitrary temporal shapes of the scattering laser field. This work is motivated by the recent trend of laser technology, to achieve highest laser intensities by a tight temporal compression of the laser energy, down to only a few cycles of the carrying electromagnetic wave. Since modern laser fields are inaccessible to the perturbative treatment of usual QED, they are described as unquantized external fields and taken into account exactly. The emission of one or two photons are particularly studied. For both processes a powerful analytical approximation is formulated, valid in the experimentally relevant regime of high laser intensities and electron energies. This technique foreshadows possible applications, such as a viable way of determining the absolute phase of a highly intense few-cycle laser pulses, which was an unresolved problem so far. Furthermore it is demonstrated how the usually strongly suppressed signal from two photon emission can be reliably discriminated from the dominant single photon emission signal. Finally analytical solutions for two hitherto unresolved issues are presented: Describing the spatial focusing of a fewcycle laser pulse and solving the Dirac equation in the presence of a focused laser beam.