Exact classical and quantum dynamics in background electromagnetic fields

Analytic results for (Q)ED processes in external fields are limited to a few special cases, such as plane waves. However, the strong focussing of intense laser fields implies a need to go beyond the plane wave model. By exploiting Poincar'e symmetry and superintegrability we show how to construct, and solve without approximation, new models of laser-particle interactions. We illustrate the method with a model of a radially polarised ™ laser beam, for which we exactly determine the classical orbits and quantum wave functions. Including in this way the effects of transverse field structure should improve predictions and analyses for experiments at intense laser facilities.