Net electron energy gain from interaction with a chirped “plane-wave” laser pulse

► Analytic investigations of electron energy gain from laser fields. ► Interaction with chirped infinite and finite-duration plane-wave laser pulses. ► Aims to elucidate process of gain by symmetry breaking of the plane-wave fields through chirping. ► Physics has been discussed elsewhere, but analytic account is new and thorough here. ► Chirping circumvents conditions for no gain, as required by the Lawson-Woodward theorem.