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Electron acceleration driven by sub-cycle and single-cycle focused optical pulse with radially polarized electromagnetic field.

The space-time properties of the expressions of sub-cycle and single-cycle focused optical pulses with radially polarized electromagnetic field based on the Sink-Source model are studied. The self-induced blue shift of the center frequency of spectrum in the center of the pulse field is found to have an important impact on the electrons acceleration. When the electrons approach to the center of pulse, the electrons will obtain a large kinetic energy gain in a short time. The effect of radiation-reaction force can't be ignored if the net kinetic energy gain of electrons is more than GeVs. The electrons will deviate from the original acceleration channel and the gain of kinetic energy that electrons may gain will be greatly reduced if the radiation-reaction effect is considered. In contrast to the few-cycle laser pulse accelerating electrons, the gain of kinetic energy obtained by electrons is a few times higher and the corresponding peak optical power is one order of magnitude lower in the case of the sub-cycle laser pulses accelerating electrons. The maximal kinetic energy gain of electrons is robust against the variation of the incident angles.