An improved beam waist formula for ultrashort, tightly-focused linearly, radially, and azimuthally polarized laser pulses in free space

摘要

We derive an asymptotically accurate formula for the beam waist ofultrashort, tightly-focused fundamental linearly-polarized, radially-polarized,and azimuthally-polarized modes in free space. We compute the exact beam waistvia numerical cubature to ascertain the accuracy with which our formulaapproximates the exact beam waist over a broad range of parameters of practicalinterest. Based on this, we describe a method of choosing parameters in themodel given the beam waist and pulse duration of a laser pulse.