  We study the ionization dynamics in intense laser-droplet interaction using
three-dimensional, relativistic particle-in-cell simulations. Of particular
interest is the laser intensity and frequency regime for which initially
transparent, wavelength-sized targets are not homogeneously ionized. Instead,
the charge distribution changes both in space and in time on a sub-cycle scale.
One may call this the extreme nonlinear Mie-optics regime. We find that -
despite the fact that the plasma created at the droplet surface is overdense -
oscillating electric fields may penetrate into the droplet under a certain
angle, ionize, and propagate in the just generated plasma. This effect can be
attributed to the local field enhancements at the droplet surface predicted by
standard Mie theory. The penetration of the fields into the droplet leads to
the formation of a highly inhomogeneous charge density distribution in the
droplet interior, concentrated mostly in the polarization plane. We present a
self-similar, exponential fit of the fractional ionization degree which depends
only on a dimensionless combination of electric field amplitude, droplet
radius, and plasma frequency with only a weak dependence on the laser frequency
in the overdense regime.
