  We report the measurement of a large optical reflection matrix (RM) of a
highly disordered medium. Incident optical fields onto a turbid sample are
controlled by a spatial light modulator, and the corresponding fields reflected
from the sample are measured using full-field Michelson interferometry. The
number of modes in the measured RM is set to exceed the number of resolvable
modes in the scattering media. We successfully study the subtle intrinsic
correlations in the RM which agrees with the theoretical prediction by
random-matrix theory when the effect of the limited numerical aperture on the
eigenvalue distribution of the RM is taken into account. The possibility of the
enhanced delivery of incident energy into scattering media is also examined
from the eigenvalue distribution which promises efficient light therapeutic
applications.
