High-order corrected fields of ultrashort, tightly focused laser pulses

Abstract

High-order correction to the fields of ultrashort, tightly focused laser pulses expressed in power series of ε=1∕(ω0t0) and s=1∕(k0w00) (ω0=ck0 the central oscillatory frequency, t0 the pulse duration for half period, w00 the beam waist radius at the central frequency ω0), are derived. These expressions can be used to describe accurately the fields of laser pulses, and are suitable for practical calculations. The first-order correction terms to the fields based on paraxial approximation are explicitly given. They are applied to a simulation study of electron dynamics in laser pulse field with special attention given to the vacuum laser acceleration scheme. We found that as long as ω0t0>20, the zeroth-order approximation (long pulse approximation) is adequate for describing the interaction. For ω0t0<20, higher-order corrections have to be taken into account.