  (abridged) Debris disks around main sequence stars are produced by the
erosion and evaporation of unseen parent bodies. AU Microscopii (GJ 803) is a
compelling object to study in the context of disk evolution across different
spectral types, as it is an M dwarf whose near edge-on disk may be directly
compared to that of its A5V sibling beta Pic. We resolve the disk from 8-60 AU
in the near-IR JHK' bands at high resolution with the Keck II telescope and
adaptive optics, and develop a novel data reduction technique for the removal
of the stellar point spread function. The point source detection sensitivity in
the disk midplane is more than a magnitude less sensitive than regions away
from the disk for some radii. We measure a blue color across the near-IR bands,
and confirm the presence of substructure in the inner disk. Some of the
structural features exhibit wavelength-dependent positions. The disk
architecture and characteristics of grain composition are inferred through
modeling. We approach the modeling of the dust distribution in a manner that
complements previous work. Using a Monte Carlo radiative transfer code, we
compare a relatively simple model of the distribution of porous grains to a
broad data set, simultaneously fitting to midplane surface brightness profiles
and the spectral energy distribution. Our model confirms that the large-scale
architecture of the disk is consistent with detailed models of steady-state
grain dynamics. Here, a belt of parent bodies from 35-40 AU is responsible for
producing dust that is then swept outward by the stellar wind and radiation
pressures. We infer the presence of very small grains in the outer region, down
to sizes of ~0.05 micron. These sizes are consistent with stellar mass-loss
rates Mdot_* << 10^2 Mdot_sun.
