  We study ionization of atoms in strong two-dimensional (2D) laser fields with
various forms, numerically and analytically. We focus on the local
most-probable tunneling routes (some specific electron trajectories) which are
corresponding to the local maxima of photoelectron momentum distributions
(PMDs). By making classic-quantum correspondence, we obtain a condition for
these routes characterized by the electron position at the tunnel exit. With
comparing the identified routes with the classical limit and the
partial-decoupling approximation where it is assumed that tunneling is
dominated by the main component of the 2D field, some semiclassical properties
of 2D tunneling are addressed. The local maxima of PMD related to the local
most-probable routes can be used as one of the preferred observables in
ultrafast measurements.
