Electron acceleration in vacuum induced by a tightly focused chirped laser pulse

Electron acceleration in vacuum induced by a tightly focused chirped laser pulse has been studied. For a fixed laser output power, the tightly focused chirped laser pulse can accelerate electrons to much higher energies. Focusing laser down to the order of wavelength requires inclusion of terms of third order at least in the diffraction angle ε in the description of the associated field. Retained electron energy depends strongly on frequency chirp parameter and initial position of the electron. Besides, retained energy increases with laser intensity, pulse duration, and initial velocity of electron, and varies periodically with laser constant phase.